Algal Biofouling (Studies in Environmental Science)

ALGAL BIOFOULING

Other volumes in this series

1 Atmospheric Pollution 1978 edited by M.M. Benarie 2 Air Pollution Reference Measurement Methods and Systems edited by T. Schneider, H.W. de Koning and L.J. Brasser 3 Biogeochemical Cycling of Mineral-FormingElements edited by P.A. Trudinger and D.J. Swaine 4 Potential Industrial Carcinogens and Mutagens by L. Fishbein

5 Industrial Waste Water Management by S.E. Jgjrgensen 6 Trade and Environment: A Theoretical Enquiry by H. Siebert, J. Eichberger, R. Gronych and R. Pethig 7 Field Worker Exposure during Pesticide Application edited by W.F. Tordoir and E .A. H. van Heems t ra- Lequin 8 Atmospheric Pollution 1980 edited by M.M. Benarie 9 Energetics and Technology of Biological Elimination of Wastes edited by G. Milazzo 10 Bioengineering, Thermal Physiology and Comfort edited by K. Cena and J.A. Clark

11 Atmospheric Chemistry. Fundamental Aspects by E. MBszhros 12 Water Supply and Health edited by H. van Lelyveld and B.C.J. Zoeteman 13 Man under Vibration. Suffering and Protection edited by G. Bianchi, K.V. Frolov and A. Oledzki 14 Principles of EnvironmentalScience and Technology by S.E. Jgrgensen and I. Johnsen 15 Disposal of Radioactive.Wastesby 2. Dlouht. 16 Mankind and Energy edited by A. Blanc-Lapierre 17 Quality of Groundwater edited by W. van Duijvenbooden, P. Glasbergen and H. van Lelyveld 18 Educationand Safe Handling in Pesticide Application edited by E.A.H. van HeemstraLequin and W.F. Tordoir 19 Physicochemical Methods for Water and Wastewater Treatment edited by L. Pawlowski 20 Atmospheric Pollution 1982 edited by M.M. Benarie 21 Air Pollution by Nitrogen Oxides edited by T. Schneider and L. Grant 22 Environmental Radioanalysis by H.A. Das, A. Faanhof and H.A. van der Sloot

23 Chemistry for Protection of the Environment edited by L. Pawlowski, A.J. Verdier and W.J. Lacy

24 Determinationand Assessment of Pesticide Exposure edited by M. Siewierski 25 The Biosphere: Problems and Solutions edited by T.N. Vezirog'lu 26 Chemical Events in the Atmosphere and their Impact on the Environment edited by G.B. Marini-Betthlo 27 Fluoride Research 1985 edited by H. Tsunoda and M.-H. Yu

Studies in Environmental Science 28

ALGAL BIOFOULING Edited by

L.V. Evans Dept. of Plant Sciences, The University of Leeds, Baines Wing, Leeds LS2 9 J T , U.K.

K.D. Hoagland Dept. of Biology, Texas Christian University, P.O. Box 32916, Fort Worth, TX 76129, U.S.A.

ELSEVl E R Amsterdam - New York

1986

- Oxford - Tokyo

ELSEVIER SCIENCE PUBLISHERS B.V. Sara Burgerhartstraat 25 P.O. Box 211, 1000 AE Amsterdam, The Netherlands Distributors for the United States and Canada:

ELSEVIER SCIENCE PUBLISHING COMPANY INC. 52, Vanderbilt Avenue New York, NY 10017, U.S.A.

Lihrary of Conpre5s C~taloginginPubliutionDaln

Algal biofouling. (Studies i n environmental scierlce , 2 8 ; Papers from a symposium sponsored by the Phycological Society of America a t a rceeting organized i n conjunction with the American I n s t i t u t e of Biological Sciences a t the University o f F l a . , Cainesville, Aug. 1985. Bibliography: p. Includes index. 1. Aleae--Congresses. L. Fouling organism-4. Fouling Congresses. 3. Algae--Control--Congresses. organisms--Control--Congresses. I. Evans, L. V . 11. IIoagland, K . D . 111. Phycological Society of America. IV. American I n s t i t u t e of Biological Sciences. V . Series.

QK5Lb.3.A56 198b ISBN 0-444-42705-0

539.3’5

C.6-24132

ISBN 0-444-42705a (VOI. 28) ISBN 044441696-X (Series)

0 Elsevier Science Publishers B.V. , 1986 All rights resewed. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher, Elsevier Science Publishers B.V. /Science & Technology Division, P.O. Box 330,1000 AH Amsterdam, The Netherlands. Special regulations for readers in the USA - This publication has been registered with the Copyright Clearance Center Inc. (CCC), Salem, Massachusetts. Information can be obtained from the CCC about conditions under which photocopies of parts of this publication may be made in the USA. All other copyright questions, including photocopying outside of the USA, should be referred t o the publisher. Copyright of pages 65-78,79-100 and 115-127 hes not been transferred t o Elsevier. Printed in The Netherlands

V

CONTENTS L I S T OF CONTRIBUTORS

1.

2.

3.

4.

5.

6. 7.

a. 9.

10. 11.

12.

13.

A WORLD-WIDE SURVEY OF S L I M E F O R M A T I O N I N A N T I FOULING PAINTS M.E. C a l l o w

1

THE SOURCE O F A L G A L C O L O N I Z E R S ON ROCK S U B S T R A T E S I N A FRESHWATER IMPOUNDMENT K . D . H o a g l a n d , A . Z l o t s k y a n d C.G. P e t e r s o n

21

A D H E S I O N O F F O U L I N G D I A T O M S TO S U R F A C E S : SOME BIOCHEMISTRY K.E. C o o k s e y a n d B. C o o k s e y

41

S Y N E R G I S M BETWEEN A N T I F O U L I N G B I O C I D E S L.V. E v a n s , M . E . C a l l o w a n d K . R . Wood

55

CELL ATTACHMENT MECHANISMS I N THE FLAGELLATE. COLACIUM (EUGLENOPHYCEAE) R.L. W i l l e y and J.G. G i a n c a r l o

65

F O U L I N G ON P A I N T S C O N T A I N I N G COPPER AND Z I N C M.S. F r e n c h a n d L . V . E v a n s

79

D I A T O M C O M M U N I T I E S ON N O N - T O X I C S U B S T R A T A AND TWO C O N V E N T I O N A L A N T I F O U L I N G S U R F A C E S I M M E R S E D I N L A N G S T O N E HARBOUR, SOUTH COAST O F ENGLAND S. P y n e , R . L . F l e t c h e r a n d E . B . G . Jones

101

THE P H Y S I O L O G I C A L ECOLOGY OF N U I S A N C E ALGAE I N AN OLIGOTROPHIC LAKE J . E . R e u t e r , S.L. L o e b a n d C . R . G o l d m a n

115

P H Y S I C O - C H E M I C A L PROCESSES A F F E C T I N G COPPER, T I N AN0 Z I N C T O X I C I T Y TO ALGAE : A REVIEW J.S. Kuwabara

129

THE CONTROL OF F O U L I N G BY N O N - B I O C I O A L SYSTEMS M.E. C a l l o w , R.A. P i t c h e r s a n d A . M i l n e

145

A L G A L B I O F O U L I N G OF O L I G O T R O P H I C L A K E T A H O E : CAUSAL FACTORS AFFECTING PRODUCTION S.L. Loeb

159

G R O W T H OF T H E F O U L I N G A L G A C L A D O P H O R A GLOMERATA ( L . ) KUTZ. AT V A T C O " T R A T 1 O N S OF COPPER De V r i e s H. H i l l e b r a n d and P.J.R.

175

A L G A L F O U L I N G I N THE NORTH S E A L . A . T e r r y and G.B. P i c k e n

179

VI

14.

15.

16.

17.

18.

IMPORTANCE OF V A R I A T I O N I N A L G A L I M M I G R A T I O N AND GROWTH R A T E S E S T I M A T E D BY MODELLING BENTHIC ALGAL COLONIZATION R.J. S t e v e n s o n

193

RECENT I N V E S T I G A T I O N S I N T O THE E F F E C T S OF ALGAE ON CORROSION L.A. T e r r y and R.G.J. Edyvean

211

D I A T O M C O M M U N I T I E S ON S T E E L P R O T E C T E D FROM CORROSION I N SEAWATER R.G.J. Edyvean

231

STRUCTURAL MORPHOLOGY O F D I A T O M - D O M I N A T E D STREAM B I O F I L M C O M M U N I T I E S UNDER THE I M P A C T OF S O I L E R O S I O N J . R . R o s o w s k i , K.D. H o a g l a n d , S.C. R o e m e r and J.H. P a l m e r

247

MEASUREMENTS B A L T I C FUCUS C O N T R I B m T. K a i r e s a l o

301

OF M E T A B O L I C A C T I V I T I E S W I T H I N A VESICULOSUS COMMUNITY: THE OF F O U L I N G M I C R O A L G A E AND G R A Z E R S and E . L e s k i n e n

VII

PREFACE This

volume

convened

by

Society

of

with at

the the

i s

America

for

lesser

of

on and

additional editors,

exchange

.

important

understanding

reference (The the of

in

Algae, as

as

eutrophication.

further

to

Periphyton

the

benefit were

at were

field from

eleven

the

field

a

oral

symposium;

invited

by t h e

n o t c o v e r e d by

m e e t i n g was t o a c h i e v e some terminologies like

are

the

i n

term

difficult

Cambridge

algal

volume,

the

(and t o

use.

For

t o r e a l i z e t h a t t h e words " f o u l i n g " ,

plants,

"weed"

t o define.

University

g r o w t h o n man-made

Press,

with Round

1981)

structures.

w e l l a s i n t h e symposium,

a b r o a d e r sense,

organisms

the

"periphyton",

of

"fouling"

present

used

of

necessary

higher

Ecology

defined

respective

within

There

the

provided

workers

to

given

of

aim

the

and

volume

areas

initial

and

to

i n

the

of i s

it

"biofouling",

front

(AIBS)

A u g u s t 1985.

macroalgae) t o gain

activities

ideas.

to

in

marine and

conjunction

Sciences

symposium

and

posters

contributions particularly

example,

of

five

Phycological

in

organized

micro-

broad

the

Biological this

research a

and

on

on A l g a l B i o f o u l i n g by

Gainesville,

time

workers

s y m p o s ium p a r t ic ip a n t s An

of

freshwater

on

presentations

meeting

first

current

biofouling

synthesis

a

symposium sponsored

Florida,

both

extent,

update

of

at

the

for

a

and

Institute

University

opportunity a

result of editors

American

Probably

an

a

the

In

t h e t e r m was

f o r example " f o u l i n g " as a consequence

Moreover,

useage

c o u l d be broadened s t i l l

i n c l u d e t h e s e t t l e m e n t and growth o f m i c r o - o r macroon has

any

man-made

been

or

natural

submerged

similarly

defined

in

the

substratum. l i t e r a t u r e on

fresh waters. The

problems

the

context

rather

of

different.

ecological to

presented

approach

community

by

fouling In

freshwater would

t h e case

versus

superficially of

marine algae i n appear

freshwater fouling,

to

be

a basic

i s applied t o a myriad o f questions related

structure.

Marine

fouling

s t u d i e s on t h e o t h e r

VIII

hand comprise a focused, economic

importance,

successful kinds

development

immersed

to

both.

include:(i) the

of

attachment

or

f o u l i n g organisms on s u r f a c e s o f a l l

seawater.

However

i n

general

terms,

and t h e processes and mechanisms i n v o l v e d

More

surfaces); aspects

specifically,

substratum

boundary

microdiffusion,

principles

of

p h y s io 1 o g ic a 1 ,

film,

organic

adhesion (chemical s t r u c t u r e o f

include

incubations, Future

research

understanding fouling

i s

bacteria,

invertebrate; secretion

the

of

constituent increasing

artificial

bacterial,

phenomena,

constituents

i n r e l a t i o n t o d i f f u s i o n and

and

fouling

of

( i i i )

be

we

would

"first

encounter"

disciplines

having

not

possible

but

tremendous

important

area

to

say

benefit i n

systems,

researchers

bacterial would

future

or

i n

particular

the

based f o r example on

u t i1 iz in g n a t u r a l 1y -

compounds.

biofouling

include

and

fouling,

was a m o s t e n j o y a b l e a n d r e w a r d i n g

between algal

marine

on r e s e a r c h aimed towards

m a t e r ia 1 s ,

this

colonization i n

prevention,

anti-fouling

i n particular the

ecology o f the diatom i.e.

addition, placed

fouling

( " n o n - s t ic k " )

non-toxic

the

sequence,

In .

w i l l

emphasis

Finally

i n situ

a l g a l ( e s p e c i a l l y m i c r o a l g a l ) and

development o f environmentally-safe produced,

substrata,

whole-community

the

methods

n o n - b i o c ida 1

Common

l i k e l y t o f o c u s l a r g e l y on g a i n i n g a b e t t e r

development.

improving

of

macroalgae;

etc.).

and e l e c t r o n microscopy.

mucilages; of

community

-

( i i )

of

use

microalgae,

phenomena

( i )t h e p h y s i c s a n d c h e m i s t r y o f b i o d h e s i o n i n

of:

organisms

metabolism

the

bioassays,

u 1t r a s t r u c t u r a 1

and

and ( i i i ) ecology (sequence

colonization/immigration;dispersal techniques

similarities

c h e m i s t r y o f submerged

b io c h e m i c a 1

o f synthesis and secretion);

events-

underlying

phenomena(physica1chemistry

surface

layer,

( i i )

a d h e s iv e s , of

prevention

attachment and growth on an i n d i v i d u a l o r community b a s i s a r e

common of

the

of

i n

c o l o n i z a t i o n sequences, in

a p p l i e d approach t o a problem o f g l a r i n g viz.

be

symposia

from

a

variety

a s common g r o u n d . studies

gained on

of

I t was

on t h i s occasion,

by i n c l u s i o n o f t h i s t h i s topic.

It i s our

IX

sincere

wish

to

exchange

that

has

provoking water

body

and

workers

mutual

of

i n

fouling

the It

point benefit

the

here.

literature

marine

awareness. starting

continue begun

other

i s for of

type

inter-disciplinary

exists i n respect t o both fresh-

organisms,

area

hoped

of

It i s apparent t h a t a thought-

the

presumably

that

this

one r a r e l y c i t e d by because

of

w i l l

volume

lack

of

provide

a

t h e d e v e l o p m e n t o f such an awareness t o t h e workers

i n

all

areas

of

the

field

of

biofouling. We

would

of on

America this

l i k e t o thank the o f f i c e r s o f the Phycological Society f o r g i v i n g u s t h e o p p o r t u n i t y t o convene a symposium

topic,

arrangements computerising anonymous

Or

for

L V Evans K D Hoagland

Hodgson

for

participants, the

colleagues

volume.

Lynn

Index, who

reviewed

making Or

and the

all

the

local

Maureen

Callow

for

especially

the

many

contributions

i n this

This Page Intentionally Left Blank

1

CHAPTER I A WORLD-WIDE SURVEY OF SLIME FORMATION ON ANTI-FGULING PAINTS MAUREEN E. CALLOW

Department of Plant Biology, University of Birmingham, Birmingham B15 2Tp, U.K.

1.1 INIROEUCI'ION Fouling results from the settlement and growth of a variety of plant and animal forms. Fouling on the hulls of ships results in an increase in frictional resistance leading to loss of speed and increased use of fuel (Townsin & &, 1981). In the past, acorn barnacles were the most troublesome fouling forms (see Southward & Crisp, 1963) but the trading patterns of modern ocean-going ships with quick turn-round periods and rapid transition between tropical and temperate waters favours the settlement of algae rather than barnacles and other animals (Christie, 1973). However, recent studies on the attachment of barnacle larvae under flowing conditions led Dalley and Crisp (1981) to conclude that the paucity of barnacles on ships with a quick turnround was due to the short period spent in larvae-rich coastal waters rather than the inability of the cyprids to attach on moving ships. The most common fouling algae on ships are species of the green alga m o m o m h a and the brown alga ECtOCarDUs. The dominance of !&.teromorDha results from its cosmopolitan distribution, its enormous reproductive potential and its ability to withstand widespread fluctuations in environmental conditions such as desiccation and salinity (Biebl, 1962; Christie & Shaw, 1968). mteromorpb is commonly found to be the dominant alga on traditional copper-containing anti-fouling paints (Banfield 1980, Evans 1981). Following the introduction of organometallic biocides particularly tr iorganotin compounds into paints, was largely g as the major cosmopolitan fouling alga on ships (Evans, replaced by 1970). Ectochas been shown to be more resistant to triorganotin compounds than (Mearns, lS73). grows as a dense mat, rapidly covering a surface by means of its horizontal creeping system of filaments combined with rapid reproduction and establishment of new plants (e.g. Clitheroe and Evans, 1975; Fletcher and Chamberlain, 1975). Following the introduction of self-polishing copolymer (SFC) anti-fouling paints in the early 1970's weed fouling became less important. In SPC systems, the copolymer of tributyltin methacrylate and methyl methacrylate hydrolyses at

2

the paint/seawater interface releasing the biocide tributyl tin in a controlled manner. Other biocides such as cuprous thiocyanate and cuprous oxide are incorporated into the polymer matrix and these are also released as the polymer hydrolyses. The rate of hydrolysis, known as the "polishing rate", depends on a number of factors including the speed of water movement, pH and temperature. As the paint "polishes", thereby becoming smoother, the skin frictional resistance of the vessel decreases providing it remains free of fouling. Cm ships operating under optimal conditions the rate of biocide release should be sufficient to control all types of fouling. However, this is rarely the case and the copolymer paints become fouled by diatom slimes (Christiefi &, 1976; Daniel .& d., 1980) and occasionally by macroalgae and/or barnacles. Microbial slime films have been shown to increase significantly the drag of objects in contact with moving seawater (Fischer fi al., 1984; Haderlie, 1984; Loeb, 1981; Gucinski, & & 1984). A recent study by Lewthwaite & id. (1985)has quantified the drag imposed by slime on a ship's hull. A slime layer of one millimeter thickness caused an 80% increase in skin friction together with a 15% loss in ship speed compared with values obtained for the clean hull. The voyaging patterns of ships are very complex and the geographical location of the onset of fouling is rarely known. The present study was initiated to provide data on the fouling communities throughout the world particularly with respect to the distribution of slime organisms on three types of anti-fouling composition. 1.2 MATERIALS AND MFIHODS 1.2.1 &.&m r .Each test kit consisted of three plastic strips, 8 x 3cm attached to a wooden holder. Half of one strip was untreated thereby serving as a non-toxic surface whilst the other half was painted with a continuous contact vinyl-rosin conventional antifouling paint containing cuprous oxide as the only biocide. A second strip was painted with a clear varnish composed of 60% tributyl tin methacrylate and 40% methyl methacrylate and thus containing tributyl tin as the sole biocide. The third strip was painted with a self-polishing tributyl tin methacrylate/methyl methacrylate copolymer containing cuprous oxide and thus having both tributyl tin and copper as biocides. These four surfaces are referred to throughout this paper as non-toxic, copper, organotin and organotin/copper respectively. The plastic strips used were either black or white plastic so that the non-toxic and those coated with the organotin varnish appear either black or white on photographs.

~

3

Immersion. Sets of test plnels were immersed for 2 months at a depth 1.2.2 of approximately one metre below the water surface. On removal from the water, each holder with panels was preserved by immersing overnight in 4% (v/v) formaldehyde in seawater. Excess formaldehyde was poured away and the holder sealed in a plastic box which was sent to Birmingham for examination. Fifteen sites around the world were used in the survey. The 1.2.3 geographic co-ordinates are listed in Table 1.1. Panels were immersed and returned on a regular basis from sites 1-7 and continuous data from January 1983 - December 1984 is presented for these sites. Panels from sites 8-15 were returned intermittently and a full set of data is not available.

m.

TABLE 1.1 co-ordinates af k.&sikzi Site No.

1 2 3 4 5 6* 7* 8 9 10 11 12 13 14 15

site/ Country

..

Miami/U S A. Rio-de-Janeiro/Brazil Newton Ferrers/England Burnham/England Dubai/United Arab hirates Tamano/Japan Aioi/Japan San Francisc0fl.S.A. La Spezia/Italy Bratton/Sweden Djuro/Sweden Singapre Hong Kong Kaosiungfl'aiwan Sydney/Australia

Geographical Lat

Co-ordinates Long.

Number of Samples

25'45" 22'53's 50°18'N 51'31" 24'59" 39 2 ' 4 'N 34'44" 37'48" 44'07" 57'55" 59'29 'N 1'24" 22'22 ' N 22'36" 16O4O'S

80'15 'W 41'17 'W 4'02'W 9 4 ' 0 'E 5S000'E 133'56 'E 134'23 ' E 122022'w 9'48'E 11'45'E 1E040'E 103'59 ' E 114'15 ' E 120'17 'E 139'30 ' E

13 14 18 16 14 15 15 8 7 9 6 8 2 4 9

.

*Taman0 and Aioi are both located on the Inland Sea, approximately 80km apart.

1.3

RESULTS

The panels from sites 1-7 between January 1983 and December 1984 are shown in figures 1.1-1.7. Preliminary data from January-December 1983 were reported in Callow (1984).

4

Niimi: The panels from Miami are shown in Fig.l.1; the May-June 1984 panels were lost. All panels were covered by a fine deposit of silt (as evidenced by the poor contrast of Fig.l.1). The mean surface seawater temperatures recorded at the exposure site were 22OC over the winter months (Dec-Feb) and 27OC over the summer months (June-August). Barnacle (B. . . amphitr 1te) settlement occurred throughout the year, peak settlement being during September and October. Macroalgae grew vigorously on all non-toxic panels but were not found on any of the anti-fouling formulations. The most . u.l o s u s , abundant macroalgae were Cladophora sericea, Ectocarpus u c lthamnion and Enteromorpha intestin- i The anti-fouling surfaces supported only light diatom slimes. The organotin/copper paint bore only patches of Amphora slime (E. coffeaeformis, & veneta and & biaibbd whilst on the copper paints more substantial slimes of & w h o r a w . mixed with BmRhiDrora and Stauroneis were found. Slimes of Achnanthes w s t a t a occurred on the organotin varnish panels during the winter months. U-de-JaneirQ: The panels from Rio-de-Janeiro are shown in Fig.1.2; the July-August 1984 samples were lost. Water temperatures range between 2loC (June-August) and 27OC (November-January). Heavy animal fouling occurred on all the non-toxic panels. The major types in order of abundance were . . barnacles (B. amphitrite and B. tintinnabulum), the hydrozoan Bbelia aeniculata, the polyzoan Bugula neritina, the serpulid worm Hvdroida norveaica, and the amphipod Jassa falcata. Algae were not found on the nontoxic control with the exception of a microscopic growth of Ylothrh and filamentous blue-green algae (Cyanobacteria). All three anti-fouling surfaces allowed settlement and growth of both species of barnacle although in reduced numbers compared to the controls. All antifouling surfaces bore diatom slimes together with substantial growths of the protozoan Vorticelb Both the copper and organotin/copper paints had slimes dominated by BmDhora (A. coffeaeformis and A. veneta) and Bmphiprora The sole diatom found on the organotin varnish was &hnant hes longices. The panels from Newton Ferrers are shown in Fig.1.3. Newton :F Mean surface water temperatures are 8OC for December-February and 16OC for June-August. Growth on the control surfaces was negligible during the winter (November-February)and was unusually light during the whole of 1983. The non-toxic panels predominently bore ectocarpacean algae (Ectocarpus si1icu10sus and Giffordiaaanulosa) during the summer months. These were . . intermixed with the hydrozoan Tubularia indivisa between July and October. . . Other algae present in lesser numbers included mtero momha , Ulothrix flacca. UBh & u a Polvsiphonia&mg&aandCeramlum ' rubrum as well as small numbers of a mixed population of diatoms. During 1984 patches

=.

.

.

.

5

7

8

of W h o r a (A. veneta and A. coffeaeformls ' ) colonized the organotin/copper hvalina grew on the copper paint. Small paint and these plus . . . . . found on the organotin varnishes and during growths of Tubularla ~ 1 V l S a were 1984 patches of m e s s i l. l.s were also present. m n h a m : The panels from Burnham are shown in Fig.l.4. There is considerable variation in water temperature between the winter months with a mean of 6OC during November-February and summer months with a mean of 2OoC during June-August. This rapid increase in water temperature during spring and summer is due to large areas of mud and sand being exposed to the sun at . . low tide. The seasonal settlement of the Australian barnacle, Elmlnlus modestus typically occurred during July-August followed by settlement of the . . . . hydrozoan Tubular- rndivisa Both of these organisms were found in the presence of the amphipod aand a l l were able to colonize and grow on the organotin varnish. Small amounts of algal fouling occurred throughout the summer on the non-toxic and organotin surfaces. The most frequently

.

. .

encountered algae were EnteromorDha intestlnalls . . I iL&xaUsUculosus. Ulothrix flacca, Ceram ium rubrum, PolvS i D ' U s.and the tube-dwelling . . 1 ramoslSSlma and B. Beudocomoides Various diatoms N a v i c U (Schizonema fouling organisms were found on the copper and organotin/copper antifouling paints but in reduced numbers including Navicub ramosissima. &&sa falcata and a mixed venet$/BmphiDru byalina slime. The panels from Dubai are shown in Fig.1.5: the March-April 1983 panels were lost. The water temperature ranged from 23OC (mean for DecemberFebruary) to 37OC (mean for June-August). No obvious seasonal settlement occurred. The major fouling organisms on all the non-toxic control panels were blue green algae (Cyanobacteria). The following genera were . . represented:- U a t o r i a , Ueotrichu, M o t h r is and SDirulina Other , ascidians and the green algae common fouling forms were Balanus P e r c u r e percursa, mteromorDb flexuoa and E. l h z a and Derbesia sg.. The latter and blue green algae were found in reduced growth forms on the organotin varnish. The copper and organotin/copper paints supported the growth of diatom slimes principally composed of &a&xxa veneta and &a&&uxa

.

.

se.. Bmano: The panels from Tamano are shown in Fig.1.6. This site is characterised by heavy algal fouling. The mean winter water temperature is ll°C (December-February) and the mean summer water temperature is 24OC (JuneAugust). On the non-toxic surface algae are abundant throughout the year often tightly bound with the mud-binding amphipd falcata and these were intermixed during January-February with a growth of hydrozoans. The most abundant macroalgae were

fasciculatusI-

.

.

9

10

11

and Ch&&xa =rice a. A spcies-rich diatom slime was also present . . including members of the genera Navicula. Stauroneis. Fraallarla. . . , occone&, Achnanthes and Thick diatom slimes were formed on all the anti-fouling surfaces. On the copper and organotin/copper paints slimes were chiefly composed of Amgkxa (a veneta, A. coffeaefo m i sr A. m.1 and AmDhiDrOra w.with lesser amounts of a t z s c h h w. On the organotin varnish slimes of Achnanthesformed, sometimes in conjunction with afalcata. The mud associated with the latter could form a substrate for attachment of macroalgae as shown in the May-June 1984 sample where W e r o m o r D b j.ntestinalis is attached to mud deposited on the surface of the organotin varnish. The p e l s from Aioi are shown in Fig.l.7. Water temperatures are similar to those found at Tamano although other conditions are different. At Aioi the water is deep, clear and still in comparison to the shallow, turbid, fast flowing conditions at Tamano. Aioi is characterised by its heavy settlement of barnacles between May and October. During winter and spring (November-April) fouling was chiefly due to the amphipod w f a l c a t a and

E.

.-

r L!hZ w.,E 0 - e macro-algae including E c t o c a w fascic. . U e s tinalis, E. flexuosa PolvsiDhonia SEE., ildQhXaruwstrls, . c. sericea. minima, and filamentous blue-green algae (Cyanobacteria). Throughout the year a diversity of benthic and planktonic diatoms were also found on the non-toxic surfaces. Members of the genera m, m, Stauroneis and Hitzschia formed slimes on the copper and organotin/copper paints. Admanthes was always found in abundance on the organotin varnishes and on some samples barnacles, EctocarDusfascicuW , and the diatoms veneb and Stauroneis m. also occurred. Sari m c i s c o : Growth on the non-toxic surface was approximately constant throughout the year. The major growth was a thick and floristically rich diatom slime intermixed with Fctocarw w c u l o s u s and Ulothrlx ' flacca. The , Navicula most common types of diatom in order of abundance were -

(Sch i zonema1 ximosissim, Achnanthes lonQiDeS, Navicuh (Schizonema Nitzschia OValiS, COccOneiS, W D h o r a , ,Prasilaria. QanmatoDhora and &a&ua. A thin diatom slime covered the three grew as an almost pure stand anti-fouling compositions. Achnanthes on the organotin varnish. Although only small numbers of AmDhora SEE. were found on the non-toxic surface, A. coffeaeform var. coffeaeformls ' and A. veneta formed a slime on the organotin/copper pint and these plus SEE. and small numbers of those types identified on the non-toxic surface were found on the copper paint. La SDezia: Most of the non-toxic panels bore a substantial growth of the

13

14

serpulid worms Bvdroides and in lesser numbers

-.

Small numbers of

Balanus m h i t r k were found throughout the year. All samples of non-toxic surfaces had macroalgae present including R c t o c w b s c i c u w inalis and ChaetomorDha l h m . The copper paint ' sg. intermixed with small developed slimes of veneta and Stauronels . . plants of ECtOCarDUS u c i c w and B t e r o w intestlnalls The organotin/copper paint supported little growth other than a few patches of . . BmDhiDrOra m.. Substantial Achnanthes slimes (& subsessllls and A. )mixed with small plants of E. fasciculatus developed on the organotin varnish. Bratton/DjurQ: The sea is mostly frozen around the coast of both West (Bratton) and East (Djuro) Sweden from December until March. At Bratton Ectocarrxls W C U l O S ~and Ulothrlx ' flacca grew on the non-toxic surface from April to October. During June-July a heavy settlement and rapid growth of Balanus improvisus and the protozoan V o r t i c e u occurred. There was no significant growth on any of the anti-fouling surfaces examined except for a few patches of (a veneta and A. coffeaeformis var. ' in the spring on the copper and the orgnotin/copper surfaces. At Djuro growth was confined to the non-toxic surface during the summer months when a diatom slime mixed with was recorded. Diatoms were from the genera . . cinodiscus and Dore: Heavy animal setlement and growth occurred on all the nontoxic samples. The major animals were Balanus @trite , colonial ascidians and serpulid worms. This fouling pattern is typical of the tropical waters around the equator where the mean seawater temperature at lm depth is approximately 29OC throughout the year. Some barnacles, usually of smaller size than those on the non-toxic surface were also able to grow on both the copper and the organotin surfaces. A thick &slime developed on the A. a.)as well as on former paint (A. veneta, A. coffeaeforrnisI A. &.&b, . . the organotin/copper paint. A light slime of Achnanthes subsessllls grew on the organtin varnish. Hono-Kona: Massive animal fouling of the control surfaces contrasted with the diatom slimes formed on the anti-fouling paints. slimes covered sE.1 -btest

.

-.

the copper and organotin/copper paints (A. veneta, A. c o f f e a e f o dI A. biaibba) whilst a unialgal stand of Achnanthes covered the organotin varnish. I(aohsiuns: Non-toxic samples bore a substantial growth of Balanus . . . m Slimes of veneb and Stauronels ' were found on the copper and organotin/copper surfaces whereas on the organotin varnish there was a slime of Am.Dhiwora. Stauroneis. Navicuh and &&a&bes

-.

15

-. Moderate fouling occurred throughout the year on the non-toxic panels. Serpulid worms from the genera H~&Q&s ' and were present throughout as were the algae ECtOCarDW siliculosus and EnteromorDha . . A mixed population of diatoms was also found on all samples including Stauroneis0AmPhora coffeaeformis, BmEhiDrora and N a v i c o SEE. Thick diatom slimes developed on all the anti-fouling surfaces throughout the year. The copper and organotin/copper paints had slimes of m D r o r a , Stauroneis. veneta and Navicula whilst on the organotin varnish slimes of Achnanthes (A. lonalDes and A. gnaustata) sometimes intermixed with m a n d m were most commonly found.

.-

1.4

DISCUSSION Fouling growth on non-toxic submerged surfaces can be immense even within two months as seen at certain sites in the present study.. Although the test areas employed were very small, fouling developnent was consistent from one year to the next and followed the same pattern as that observed on large test areas immersed at certain sites. At sites where the spore inoculum is low, the use of small panels may lead to an underestimate of the potential fouling community (see Brecka, 1983). 'Ihe pattern of colonization and growth appears to be related more to local conditions rather than geographical location. For example, large differences were Seen between Newton Ferrers and Burnham, and Tamano and Aioi even though these sites are geographically relatively close. Many surveys of fouling organisms have been undertaken around the world over the last 30 years (seeAnon, 1952; Fletcher, 1974; Costlow and Tipper, 1984) and the present survey has underlined the widespread occurrence and abundance of the most common macrofoulers viz. -, and Ectocarsas. At the majority of sites, all three antifouling compositions were effective in preventing settlement and growth of these organisms. In cases where colonization was not prevented, it must be concluded that the leaching rate of biocides from the paints was not sufficiently great. The paints tested here contained either copper or organotin or both organotin and copper. Copper leaching rates of 10 and 20ug/cm2/day are required to prevent settlement of barnacles and diatom slime respectively (Banfield, 1980). It is generally accepted that for triorganotins about half of these values are effective and the combined leaching rates of 10 and 4ug/cm2/day for copper and organotin respectively should prevent settlement of all organisms (Milne, personal communication). The leaching rates of paints used in this study are not precisely known and will vary at different exposure sites since leaching rate is temperature, pH and salinity dependent as well as being related to the speed of water movement in the case of copolymer paints.

16

During the first two months after immersion and under dynamic conditions at 25OC the following leaching rates are expected: >10ug/cm2/day copper from the copper paint; approximately 2.5ug/cm2/day tributyltin from the organotin varnish and 10 plus 2.5 ug/cm2/day of copper and tributyltin respectively from the organotin/coper paint (Milne, prs. comm.). French & &., (1985) quote copper leaching rates of 20-30 ug/cm2/day from a copolymer paint after two months immersion on a raft but tributyltin leaching rate was not determined. Therefore, it would be expected that sufficient copper and tributyltin would leach from the copolymer paint used in this study to prevent all macrofouling. Furthermore, any organisms able to colonize this surface will be highly resistant to copper and triorganotin. The occurrence of the major fouling organisms found on the three antifouling formulations are listed in W l e 1.2. The majority of cases of animal fouling occurred at Ride-Janeiro and here, even the organotin/copper paint allowed settlement of barnacles. Local conditions such as high pollution may result in reduced rates of biocide leaching at this site. There is a high incidence of diatom slimes on all antifouling surfaces but with a restricted species composition (see Robinson & &, 1985). AmDhora and to a lesser extent were found on the majority of p e l s containing copper or organotin/copper, and a proportion of pnels at every site bore slimes of one or both diatoms. The dominance of slimes of m Daludosa and z!ahQra coffeaeformis on panels of SPC paints containing cuprous oxide was also noted by Robinson & a.,(1985). Species of both (Daniel and Chamberlain, 1981; French, 1985) and(French, 1985; Sanders & 1981) are known to be highly resistant to copper. Daniel and Chamberlain showed that veneta was due to immobilization of c o m r within copper resistance in intracellular membrane+ound bodies thereby keeping cytoplasmic levels low. Although mand mwere found on the organotin/copper paint they were rarely found on the organotin varnish whilstslimes were found on 50% of the latter panels. Three species of Achnanthes were found viz. A . . ' is reported to be lonaiws,A. subsessllls and A. anaustata. A. lonolDes resistant to copper (Hendey, 1951; Blunn, 1982). In laboratory measurements of LC50 values for tributyltin oxide, A. was found to be only slightly * (Wood, pers. (20%) more resistant than mcoffeaeformis var. wrrxlsllla . . comm.). &bx&hes subsessllls on the other hand is known to be highly resistant to organotins (Callow and Evans, 1981) and the IC50 value is fifteen The differences seen in species times higher than that for & composition of slimes between the organotin and organotin/copper surfaces cannot be explained solely in terms of current data on resistance to copper and organotin.

&.,

.

17 TABLE 1.2

Incidence nf major foulina organisms on mti-foulinssurfaces ORGANISM

Barnacles Other animals Enteromorr,ha EctocarDus Other macro-algae

AmDhora Bmphiprora

Stauroneis Nitzschia Achnanthes Other diatans

ORGANOTIN

OIEGANOTIN/COPPER

COPPER

8 0 0 0

13 18 5

4 0 101 67 33 14 11 0

107 47 17 14

6

0

24 17 8 18 4 5 7 12

0

9

2 81 6

9 0

A total of 158 p e l s of each surface were examined.

Barnacles Enter-

Ectocarws Other macro-algae

AmDhora Other diatans

8 11 5 5

5 10

1 4

6 2 18 12

*Fouling samples from a total of 34 ship were examined ' 1 ships were coated with a conventional copper antifouling paint ++23 ships were coated with a self-polishing copolymer paint containing organotin and copper

18

Patches of the three antifouling paints used in this survey are currently being tested on bilge keel panels attached to an in-service ship. It will be of interest to discover whetiier the organotin varnish becomes slimed with W t h e s under ship-operating conditions. Both the copper and organotin/copper paints are widely used on ships. Results from a survey of paint flakes taken from in-service ships (Callow, in preparation) is summarised in Table 1.3. The organisms identified on the conventional copper paints are predominantly macrofouling types whilst the majority of copolymer paints bear only diatom slimes. A m p h a is the most common slime diatom and the three most commonly occurring species are the same as those found on the panels in the present study viz. A. veneta, A. coffeaeformls ' , A . However, AmDhiDrora. Stauronels. Achnanthes.Navicula and Nitzschla ' have all been found as major ship-fouling diatoms. Thus, the composition of slimes which develop on static panels and on in-service ships appear to be similar. Further laboratory studies on biocide resistance (particularly using mixed combinations of biocides) are needed on those diatoms found to flourish on antifouling paint surfaces. Such data combined with analysis of paint leachates will improve our understanding of the biology of fouling organisms.

u.

'

1.5

ACKNOWLEIX;m I am grateful to International Paint plc for providing financial support and test facilities. I thank all those people who have been involved in handling the test samples particularly Dr R Dalley who co-ordinated this project.

i.6 REFERENCES Anon. 1952. Marine fouling and its prevention. U.S. Naval Institute, Annapolis. 368p. Banfield, T.A. 1980. OCCA Monograph No.1, Marine Finishes. Part 11. J.0il Col. Chem. Assoc. 69, 93-100 Biebl, R. 1962. Seaweeds. In: R.A. Lewin (ed.) , Physiology and Biochemistry of Algae. pp. 799-815 Bishop, J.H. and Silva, S.R. 1969. The examination of the structure of antifouling coatings by scanning electron microscopy. J. Oil Col. Chem. Assoc. 52, 353-362 Ph.D. Blunn, G.W. 1982. Studies of the ship-fouling diatom w . thesis, Univ. of Leeds. Brecka, A.M. 1983. Improved analysis of static panel immersion testing results. J. of Coatings Technology. 55, 51-54 Callow, M.E. 1984. A world-wide survey of fouling on non-toxic and three anti- fouling paint surfaces. In: 6th International Congress on Marine Corrosion and Fouling. Marine Biology, Athens 5-8 September, 1984. m. 325346 Callow, M.E. and Evans, . . L.V. 1981. Some effects of triphenyltin chloride on Achnanthessubsessllls. Bot. Mar. ;Le 201-205 Callow, M.E., Wood, K.R. and Evans, L.V. 1978. The biology of slime films. Part 3. Shipping World & Shipbuilder, NQ. EEQ, 133

19

.-

Christie, 24.0. 1973. spore settlement in relation to fouling by Proceedings of the 3rd International Congress on Marine Corrosion and Fouling, Gaithersburg, M.D., U.S.A. 2-7 October, 1972. pp. 674-681 Northwestern Univ. Press Christie, A.O. and Shaw, M. 1968. Settlement experiments with zoospores of -intestlnalls * ' (L.) Link. Br. Phycol. Bull. 3, 529-534 Christie, A.O., Evans, L.V. and Callow, M.E. 1976. A new look at Marine Fouling. Part 4. Shipping World and Shipbuilder. ElI.3, 121 Clitheroe, S.B. and Evans, L.V. 1975. A new look at marine fouling, Part 3. Shipping World and Shipbuilder, Dec. 1975 Costlow, J.D. and Tipper, R.C. (Editors) 1984. Marine Biodeterioration: An interdisciplinary study. Naval Institute Press. Annapolis, M.D. Dalley, R. and Crisp, D.J. 1981. Conchoderma: A fouling hazard to ships underway. Mar. Biol. Lett. 2, 141-152 Daniel, G.F. and Chamberlain, A.H.L. 1981. Copper immobilization in fouling diatoms. Bot. Mar. J& 229-243 Daniel, G.F., Chamberlain, A.H.L. and Jones, E.B.G. 1980. Ultrastructural observations on the marine fouling diatom &g.Axxa. Helgolander wiss Meeresunters. 34, 123-149 Evans, C.J. 1970. The development of organotin-based anti-fouling paints. Tin and its uses, 85: 3-7 Evans, L.V. 1981. Marine algae and fouling: A review with particular reference to ship-fouling. Bot. Mar. J& 167-171 Fischer, E.C., Castelli, V.J., Rogers, S.D. and Bleile, H.R. 1984. Technology for control of marine biofouling. In: Marine Biodeterioration: An interdisciplinary study. J.D. Costlow and R.C. Tipper, eds. Naval Institute Press. Annapolis, M.D. Fletcher, R.L. 1974. Results of an international research programme on the fouling of non-toxic panels by marine algae. Travaux du Centre de Recherches et d'Etudes Oceanographiques U, 7-24 Fletcher, R.L. and Chamberlain, A.H.L. 1975. Marine fouling algae. In: Microbial Aspects of the Deterioration of materials. pp. 59-81 (D.W. Lovelock & R.J. Gilbert, eds). Academic Press. Society f o r Applied Bacteriology, Technical Series No.9 French, M.S. 1985. Copper and zinc in anti-fouling paint and their effects upon the diatoms mphora and m D r o r a Ph.D. thesis. University of Leeds French, M.S., Evans, L.V. and Dalley, R. 1985. Raft Trial Experiment on leaching from anti-fouling paints. In: Polymers in a marine environment. The Institute of Marine Engineers. London. 229-233 Gucinski, H., Baier, R.E., Meyer, A.E., Fornalik, M.S. and King, R.W. 1984. Surface Microlayer Properties affecting drag phenomena in seawater. 6th Int. Congress on Marine Corrosion and Fouling. Marine Biology. Athens 5-8 September, 1984. 585-604 Haderlie, E.S. 1984. A brief overview of the effects of macrofouling. In: Marine Biodeterioration: An interdisciplinary study. J.D. Costlow and RC. Tipper, eds. Naval Institute Press. Annapolis, M.D. Hendey, N.I. 1951. Littoral diatoms of Chichester harbour with special reference to fouling. J.R. Microsc. Soc. Z L 1-86 Lewthwaite, J.C., Molland, A.F. and Thomas, K.W. (1985). An investigation into the variation of ship skin frictional resistance with fouling Trans. R.I.N.A. 127, 269-284 Loeb, G.T. 1981. The influence of microbial fouling films on hydrodynamic drag of rotating discs. Symp. Marine Biodeterioration, Office of Naval Research, Methesda, M.D. April 20-23, 1981 Mearns, RD. 1973. Vinyl weed-resistant antifouling: a practical approach to laboratory formulations. J.0il Col. Chem. Assoc. 50, 201-208 Robinson, M.G, Hall, B.D. and Voltolina, D. 1985. Slime Films on antifouling paints. Short-term indicators of long-term effectiveness. J. of Coatings Te~hn010gy. 57, 35-41

.

.

20

Sanders, J.G., Batchelder, J.H., and Ryther, J.H. Dominance of a stressed marine phytoplankton assemblage by a copper-tolerant pennate diatom. Pot. Mar. 24, 39-41 Southward, A.J. and Crisp, D.J. 1963. Catalogue of main marine fouling organisms. Vol.1. Barnacles. Published by O.D.E.M.A., Brussels Townsin, R.L., Byrne, D., Milne, A. and Svensen, T. 1981. Speed, Power and Roughness: The economics of outer bottom maintenance. Trans. R1.N.A. 123.

21 Chapter 2

THE SOURCE OF ALGAL COLONIZERS ON ROCK SUBSTRATES I N A FRESHWATER IMPOUNDMENT. KYLE D. HOAGLAND, AMY ZLOTSKY'and

CHRISTOPHER G. PETERSON'

Department o f Biology, Texas C h r i s t i a n U n i v e r s i t y ,

F o r t Worth, TX 76129 U.S.A.

' P r e s e n t a d d r e s s : F r e e s e and N i c h o l s , I n c . 8 1 1 Lamar St.,

F o r t Worth, TX 76102

U.S.A.

2Department o f Biology, U n i v e r s i t y o f L o u i s v i l l e ,

Louisville,

KY 40292 U.S.A.

ABSTRACT The source o f a l g a l c o l o n i z e r s onto rock substrates i n a e u t r o p h i c r e s e r v o i r was a n a l y z e d d u r i n g t h e s p r i n g d i a t o m p u l s e by p l a c i n g s e d i m e n t t r a p s i n and beyond t h e p e r i p h y t o n growth zone and by scraping i n t a c t surfaces o f known age. I m p i n g e m e n t o r " r a i n i n g " o f d i a t o m c e l l s f r o m t h e w a t e r c o l u m n was more i m p o r t a n t i n t h e r e c o l o n i z a t i o n o f rock surfaces than d i r e c t encroachment f r o m the adjacent attached community. Re1a t i ve t o substrate-associ a t e d standing crops (R = 2.16 X l o 4 c e l l s mm-z), h i g h d e n s i t i e s o f p l a n k t o n i c and p e r i p h y t i c diatoms impinged f r o m t h e water column (K = 5.03 X 10 3 c e l l s mm-2 d - l ) , p a r t i c u l a r l y i n t h e upper (surge) zone. D i r e c t encroachment f r o m i m m e d i a t e l y adjacent populati ons c o n t r i b u t e d very 1ittl e q u a n t i t a t i v e l y (none detected) o r qua1 it a t i v e l y ( 6 r a r e t a x a o f 67 t o t a l d i a t o m t a x a f o u n d ) t o t h e r e c o l o n i z a t i o n o f denuded surfaces. Storm-i nduced turbulence reduced n a t u r a l p e r i p h y t o n d e n s i t i e s by up t o 47%, w i t h p s e u d o p e r i p h y t i c s p e c i e s (e.g., F r a g i l a r i a v a u c h e r i a e ) e x h i b i t i n g greater losses than attached forms. The percentage of n o n l i v i n g diatoms on rock substrates increased d u r i n g c a l m periods, p r i o r t o storm events. 2.1

INTRODUCTION O b j e c t s submerged i n m a r i n e o r f r e s h w a t e r s a r e r e a d i l y c o l o n i z e d by

microalgae and b a c t e r i a i n a b r i e f p e r i o d o f time.

Bacteria colonize natural

and a r t i f i c i a l surfaces w i t h i n a few hours (Gerchakov e t al., al.,

1976; Zachary e t

1978; F l e t c h e r , 1980; Dempsey, 19811, w h i l e d i a t o m s and o t h e r m i c r o b e s

i m m i g r a t e onto s u b s t r a t e s w i t h i n a day t o several weeks (Cundell and M i t c h e l l , 1977; C o l w e l l e t al.,

1980; Hudon and B o u r g e t ,

1981; Hoagland e t al.,

1982).

Diatoms and o t h e r microorganisms have a l s o been shown t o a t t a c h t o a v a r i e t y o f

,

s u b s t r a t e s u n d e r l a b o r a t o r y o r e x p e r i m e n t a l f i e l d c o n d i t i o n s (Rosemarin and Gelin,

1978; Marszalek e t al.,

1979; Tuchman and Stevenson,

1980; B l i n n e t al.,

19801, i n c l u d i n g surfaces coated w i t h t o x i c p a i n t s (Callow e t al., and Evans,

1981; Daniel and Chamberlain,

1981).

1976; Callow

Rapid c o l o n i z a t i o n occurs n o t

o n l y on i n s h o r e rocks, p i l i n g s , aquatic vegetation, etc.,

b u t a l s o i n open water

on o i l p l a t f o r m s , s h i p h u l l s , and buoys (Evans, 1981; C h a r a c k l i s and Cooksey, 1983; Terry and Edyvean,

1984; Roemer e t al.,

1984).

22 D e s p i t e t h e u n i v e r s a l i t y o f t h e c o l o n i z a t i o n o r f o u l i n g phenomenon, v e r y l i t t l e i s known a b o u t t h e source o f m i c r o a l g a l i m m i g r a n t s o n t o m a r i n e o r f r e s h water substrates.

S t r u c t u r e s l o c a t e d i n t h e p e l a g i c zone a r e p r e s u m a b l y

c o l o n i z e d by t y c h o p l a n k t o n i c s p e c i e s w h i c h c o m p r i s e a l o w p r o p o r t i o n o f t h e p e l a g i c assemblage,

a l t h o u g h t h i s assumption a w a i t s t e s t i n g .

P e r i p h y t i c algae

i m m i g r a t i n g onto substrates i n the l i t t o r a l zone p o t e n t i a l l y e m i g r a t e f r o m a number o f sources,

i n c l u d i n g t h e w a t e r column, a d j a c e n t s u r f a c e s , sand and

s e d i m e n t s i n deeper w a t e r ,

etc.

Brown and A u s t i n (1973) d e m o n s t r a t e d an

exchange o f c e l l s between t h e p h y t o p l a n k t o n and p e r i p h y t o n ( a t t a c h e d a l g a e ) , p a r t i c u l a r l y f o l l o w i n g f a l l turnover.

As t h e p l a n k t o n i c d i a t o m F r a g i l a r i a

c r o t o n e n s i s s e t t l e d o u t o f open w a t e r , i t a p p e a r e d on a r t i f i c i a l s u b s t r a t e s , c o n s t i t u t i n g as much a s f o r t y p e r c e n t o r m o r e o f t h e p e r i p h y t o n r e l a t i v e abundance ( p e r h a p s a d y i n g p o p u l a t i o n , a l t h o u g h v i a b l e c e l l n u m b e r s w e r e n o t reported).

O t h e r s t u d i e s have r e v e a l e d a s i m i l a r i n v e r s e r e l a t i o n s h i p between

f r e e - f l o a t i n g and a t t a c h e d c o m m u n i t i e s ( K a i r e s a l o , 1976; Moss, 1981; Oleksowicz, 1982). P r e v i o u s r e p o r t s i n o u r s t u d y r e s e r v o i r h a v e shown t h a t p o r t i o n s o f a t t a c h e d c o m m u n i t i e s on r o c k s u b s t r a t e s c a n p e e l o r s l o u g h o f f u n d e r c e r t a i n c o n d i t i o n s ( R o e n e r e t al.,

1984).

S i m i l a r f i n d i n g s have been r e p o r t e d f o r a

v a r i e t y o f o t h e r a q u a t i c h a b i t a t s (Castenholz, Hoagland, 1983).

1961; K i n g a n d B a l l ,

1966;

The p r e s e n t s t u d y was designed t o i n v e s t i g a t e t h e s i m p l e model

i l l u s t r a t e d i n F i g . 1. ble p o s t u l a t e d t h a t c o l o n i z e r s on denuded p o r t i o n s o f s u b s t r a t e s c o u l d e m i g r a t e f r o m t h e community i m m e d i a t e l y s u r r o u n d i n g t h e c l e a r e d area and/or i m p i n g e from t h e w a t e r column above.

D i r e c t encroachment w o u l d be

a t t r i b u t a b l e t o m o t i l e d i a t o m s a s s o c i a t e d w i t h t h e substrate adjacent t o t h e denuded area,

whereas impingement c o u l d i n c l u d e p e r i p h y t i c o r t y c h o p l a n k t o n i c

members r e g a r d l e s s of t h e i r o r i g i n . addressed was:

The s p e c i f i c q u e s t i o n t h a t t h i s s t u d y

what i s t h e r e l a t i v e i m p o r t a n c e o f t h e s e t w o p r i n c i p a l sources

t o recolonization?

E x p e r i m e n t a l f i e l d m a n i p u l a t i o n s were conducted d u r i n g t h e

s p r i n g d i a t o m g r o w t h p u l s e i n an e x t e n s i v e e p i l i t h i c community ( a t t a c h e d t o rock),

2.2

t o e v a l u a t e t h e c o n t r i b u t i o n o f each o f t h e s e m a j o r sources. MATERIALS AND METHODS

2.2.1

Study s i t e -McConaughy r e s e r v o i r i s a l a r g e , e u t r o p h i c impoundment c o n s t r u c t e d f o r f l o o d

c o n t r o l , r e c r e a t i o n a l use, a n d h y d r o e l e c t r i c p o w e r g e n e r a t i o n ( T a b l e 1). r e s e r v o i r i s l o c a t e d on t h e N o r t h P l a t t e R i v e r i n w e s t e r n Nebraska, U.S.A., t h e f o o t o f t h e S a n d h i l l s r e g i o n i n K e i t h C o u n t y (T.14N, R.38-42\41. periphyton.

R.38,39W

The near

a n d T.15N,

S p r i n g and autumn d i a t o m blooms o c c u r a n n u a l l y i n t h e p l a n k t o n and D e s p i t e i t s p r o d u c t i v e t r o p h i c s t a t u s , t h e deeper e a s t e r n end o f

t h e r e s e r v o i r i s r e l a t i v e l y c l e a r , a l l o w i n g development o f dense e p i l i t h i c a l g a l

23 Water Column IMFINGEMENT

Fig. 2.1. Model f o r p o s s i b l e source(s) o f immigrants i n r e c o l o n i z a t i o n o f denuded area o f rock s u b s t r a t e (dark c i r c l e ) . stands down t o 6 m o r more on t h e rocky dam.

Quantum i r r a d i a n c e values, as w e l l

as a d d i t i o n a l morphometri c, p h y s i c a l and chemical data have been pub1 i s h e d f o r t h i s r e s e r v o i r (Roemer and Hoagland,

1979).

Due t o t h e r e s e r v o i r ' s b a s i c east-

w e s t o r i e n t a t i o n , f e t c h , and t h e p r e v a l e n c e o f W - S W w i n d s d u r i n g t h e g r o w i n g season, t h e rocky dam i s p e r i o d i c a l l y subjected t o severe wave action. 2.2.2

Field collections

A1 g a l c e l l s " r a i n i n g " f r o m t h e w a t e r c o l u m n w e r e c o l l e c t e d u s i n g s e d i ment traps,

c o n s i s t i n g o f 21.2 cm l e n g t h s o f 4.1 cm d i a m e t e r PVC p l a s t i c tubes,

darkened on t h e i n n e r s u r f a c e t o reduce l i g h t r e f l e c t i o n .

The height:diameter

r a t i o o f ca. 5, t h e wide spacing between tubes (34 cm) and between t h e tubes and t h e c e n t e r support p o l e (35 cm),

and t h e s i m p l e tube design,

f o l l o w t h e design

suggestions o f Hargrave and Burns (1979) and reviews by Bloesch and Burns (1980) and B l o m q u i s t and HSkanson (1981).

Tubes were occluded on one end w i t h a rubber

stopper t o f a c i 1 i t a t e l a t e r removal o f sedi mented m a t e r i a l .

The c e n t e r support

and base were c o n s t r u c t e d f r o m a PVC p i p e anchored i n a concrete block (combined tube and support h e i g h t = 1.39 m).

A sediment t r a p apparatus was l o c a t e d i n 3 m

o f water ( t o t o p o f t r a p ) , adjacent t o rock s u b s t r a t e s described below, and i n 6.7 m o f w a t e r , beyond t h e r o c k dam and b e n e a t h open w a t e r , ca. 25 m f r o m t h e

shallow trap.

Based on underwater observations f o l l o w i n g s t o r m events,

i n d u c e d wave a c t i o n does n o t t r a n s l a t e t o t h e l o v e r depth. p l a c e d i n t h e f i e l d on 22 June 1984. J u l y 1984.

storm-

A l l t r a p s were

One t u b e was c o l l e c t e d e v e r y 4d u n t i l 12

On each sampling date, a new t r a p was a l s o i n t r o d u c e d and c o l l e c t e d

f o u r days l a t e r , t o p r o v i d e 4d " i n s t a n t a n e o u s " i n f o r m a t i o n i n a d d i t i o n t o t h e c u m u l a t i v e t r a p data.

A l l s a m p l e s w e r e c o l l e c t e d w i t h t h e a i d o f SCUBA by

s t o p p e r i n g t h e open upper end o f t h e trap, r e t u r n i n g i t t o t h e boat, and p l a c i n g

24

TABLE 2.1 Selected physico-chemical properties of McConaughy reservoir.

Maximum depth (m) Mean depth ( m ) Maximum length (km) Maximum width Volume (x10 6 Surface area (hectares) Alkalinity (mg/l CaC03)* Siiica (mg/l) PH

mjp)

50 .O 16.9 35.0 5.6 2,400 .O 14,164.0 176 .O 24 .O 8.6

*mean values, from Roemer and Hoagland (1979).

i t i n an i c e c h e s t f o r t r a n s p o r t t o t h e l a b . T r a p s were then e m p t i e d , rinsed, and the s e d i mented m a t e r i a l was f i x e d w i t h 6:3:1 ( w a t e r : e t h a n o l : f o r m a l i n ) p r e s e r v a t i v e ( P r e s c o t t , 1970). The r e l a t i v e contribution of d i r e c t encroachment t o recolonization was t e s t e d by brushing clean p a i r s of c i r c u l a r a r e a s (9 cm i n diameter) on l a r g e horizontal rock s u r f a c e s a l o n g t h e f a c e of t h e dam. A PVC r i n g (8.8 cm dia., 1.8 cm h e i g h t ) was cemented around one of each p a i r u s i n g m a r i n e epoxy p u t t y ( P e r m a l i t e P l a s t i c s Corp., Neuport Beach, CA ) t o prevent d i r e c t encroachment f r o m t h e periphyton surrounding the denuded a r e a . Three r e p l i c a t e p a i r s of r i n g e d and unringed samples were c o l l e c t e d every 4d concurrent w i t h sediment t r a p samples, using a modified syringe apparatus s i m i l a r t o t h a t described by Loeb (1981). In a d d i t i o n , semi - q u a n t i t a t i v e samples were t a k e n from t h r e e nearby a r e a s of unscraped rock, by brushing material from s i m i l a r areas (with respect t o locat i o n and s u r f a c e a r e a ) i n t o a p l a s t i c c o l l e c t i o n j a r . A l l s a m p l e s were taken using SCUBA and f i x e d i n t h e f i e l d with 6:3:1. Laboratory methods All s e d i m e n t t r a p and e p i l i t h i c s a m p l e s were d i v i d e d i n t o two equal portions; one portion was boiled i n concentrated HC1 f o r ca. 2 hr. t o remove a l l organic matter. After several rinses with d i s t i l l e d water, a measured portion of the concentrate was a i r dried onto a 22 mm2 c o v e r s l i p and permanently mounted i n Hyrax. A t o t a l o f 500 d i a t o m v a l v e s were c o u n t e d from e a c h s l i d e u s i n g an Olympus microscope equipped w i t h a l O O X planachromat o b j e c t i v e (N.A.=1.30). The r e m a i n i n g p o r t i o n of each f i x e d sample was used f o r nondiatom a l g a e counts and t o determine t h e percentage of l i v i n g versus nonliving diatom cells (by t h e p r e s e n c e o r a b s e n c e of i n t a c t c h l o r o p l a s t s ) . Nondiatom a l g a e were t a b u l a t e d from 30 random Whipple f i e l d s a t 200X from each of two SedgewickR a f t e r c e l l s . McAlice (1971) i n d i c a t e d t h a t c o u n t i n g 30 random f i e l d s y i e l d s 2.2.3

25

X

Cn

w

4. 40-

0

-

0

-

IX

A ringed

TlME (d)

Fig. 2.2. Mean diatom c e l l densities (min-' x 103 ) on ringed and unringed rock substrates. P >> 0.05; n = 30 5 1 SD.

90-95% of a l l species present. Approximately 100 c e l l s of the dominant diatom genera were counted from a total of three Whipple f i e l d s a t 400X using a Palmer cell. I f 100 c e l l s of a given genus were encountered before three f i e l d s were scanned, counts were continued u n t i 1 three f i el ds had been completed. Diatom habitat preferences were based principally on information contained i n Lowe (19741, P a t r i c k and Reimer (1966; 19751, Beaver (19811, a n d on d i r e c t observations of growth habits. 2.3 RESULTS Eighty-four d i a t o m taxa representing 21 genera were found among the 31,500 valves t a b u l a t e d from 63 samples. In a d d i t i o n , 24 nondiatom a l g a e were identified from preserved samples. The substrate occurrences of each taxon, i t s h a b i t a t preference (excluding nondiatom a l g a e ) , and t h e t o t a l number of t a x a found i n each c o l l e c t i o n type a r e l i s t e d i n Table 2. The most a b u n d a n t taxa encountered were Fragil a r i a vaucheriae, Achnanthes m i n u t i ssima, Cymbell a af fi n i s , F. c r o t o n e n s i s , a n d A s t e r i o n e l l a formosa. A t o t a l of 16 d i a t o m t a x a were unique t o sediment t r a p ( 1 0 unique t a x a ) , ringed (31, unringed (21, o r unscraped (1) rock samples. 2.3.1 Encroachment Diatom c e l l densities from ringed and unringed substrates are i l l u s t r a t e d i n Fig. 2. The two curves coincided closely, as mean densities for both increased t h r o u g h day 1 2 , then decreased u n t i l day 20. No s t a t i s t i c a l l y s i g n i f i c a n t difference between the two populations of means was detected ( t - t e s t ; p >> 0.05,

26

TABLE 2.2 Occurrences of algal taxa by sample type (based on its presence in at least one sample) and the growth habit of each diatom taxa. STPsediment trap, RG=ringed rock, URG=unringed rock, RK=unscraped rock.

BACILLARIOPHYCEAE

Growth Habit1

ST -

RG URG -

x x x x X x

x x x x X x

x x x X x

X

X

X

X P L PL2 X P X P L X PL X P X PL

X X X X

X

X

x

X X

X X

X X

X

X

X X

X X

x x

CENTRICS Aulacosira ambigua (Grun.) Simonsen Cyclotella atomus Hust. C. stelligera P.T. C1. ex Grun. E. granulata (Ehr.) Ralfs E . granulata var. angustissima Mull. E. varians Ag. Stephanodiscus minutula (Kutz.)Round PENNATES Achnanthes deflexa Reim.

A. linearis (Wm. Smith) Grun. A. minutissima Kutz Amphora ovalis var. pediculus (Kiitz. Grun. A. perpusilla (Grun.)Grun. A. -veneta Katz. Asterionella formosa Hass. Caloneis bacillum (Grun.) C1. Cocconeis diminuta Pant. C. pediculus Ehr. C. placentula var. euglypta (Ehr.)Cl Cymatopleura solea (BrBb.)Wm. Smith Cymbella affinis Kfltz. C. amphicephala Naeg. C. cesatii (Rabh .)Grun. C. cistula (Ehr.)Kirchn. C. cymbiformis Ag. C. -laevis Naeg. ex Kutz. C. mexicana (EhrTC1. C. microcephala Grun. C. -minuta Hilse ex Rabh. C. muelleri Hust. Denticula elegans Kutz. Diatoma tenue var. elongatum Lyngb. D. vulgare Bory Diploneis pseudovalis Hust. Fragilaria brevistriata(Grun.) Hust F. brevistriata var. inflata (Pant.) F. capucina Desm. F. capucina var. mesolepta Rabh. F. construens (Ehr.)Grun. F. crotonensis Kitton F. pinnata Ehr. F. vaucheriae (Ehr.) Petersen Gomphoneis eriense (Grun)Skv. & Meye!r G. herculeana var. robusta (Grun.IC1..?

.

X

X

X X X X X X X X X X

X

X X

X X X

X X X X X X X X X X

X X X X X X X X X

X

X

X

x

x

X

x X x X

(P) (P) P P (P) P PL P P P P P P P P P P P P P P P P (PI P (PI P (PL) P PL P (PL)3 P P

27

ST Gomphonema accuminatum Ehr. intricatum Kfitz. olivaceum (Lyngb )Kut z parvulum (KOtz.)Grun. truncatum Ehr. Navicula arvensis Hust. N. biconica Patr N. capitata Ehr. N. capitata var. hungarica ( Grun.)Ross tote hala Kutz. - EEk&Eup -N. menisculus var. upsaliens (Grun. Grun. N. -minima Grun. N. -mutica Kutz. N. -mutica var. cohnii (HilseIGrun. N. pupula Kiitz N. radiosa var. tenella (Breb. ex Kutz. )Grun. N. reinhardtii (Grun.)Grun. N. salinarum var. intermedia (Grun1 . )C1. N. tripunctata (O.F. Miill.)Bory Nitzschia acicularioides Hust. N. amphibia Grun. N. angustata (Wm. Smith)Grun. N. apiculata (Greg.)Grun. N. denticula Grun. N. dissipata (Kutz. )Grun. N. fonticola Grun. N. frustuluii KutZ. N. ~. linearis Wm. Smith N. microcephala Grun. N. palea (Kiitz.) Wm. Smith N. sigmoidea (Ehr.) Wm. Smith Rhoicosphenia curvata (Kiitz.)Grun. Surirella ovata Kutz. S angustata-t z Synedra ~iitz. S. filiformis var. exilis ~1 S. radians Kutz. S. rumpens var. familiaris ( Kutz. Hust. S. -socia Wallace S. -ulna (Nitz.)Ehr. Total Taxa/Sample Type __ Total Unique Taxa Total Diatom Taxa

G. G. G. G.

.

.

2

~~

-

.

.

..

OTHER ALGAE Ankistrodesmus sp. Aphanocapsa sp. Closterium sp. Cosmarium sp. Glenodinium sp. Lyngbya sp. Merismopedia sp. Mougeot ia sp Oocystis sp.

.

Growth

g Habit1

X

.

.

RG URG X X

X X

X

X X

X

X

X X

X X X

X X X X

x

x X

X X X

x X X X X X X X X X X X X X X X X X X

X

X

X

X X

X X

X

X X X X X X X X X X X X

X X X X X X X X X X X X X X X

X X

X X X X X X

X X X X X X 51 1

X 70 10 84

X 61

X

X

X X

X X

X X

X X X

X

X

X X X X

X X X

X X X

X X X

3

50

2

P PL PL P P

P PL4 P2

(PI (P) (P) P P P P P P P P (P) P P PL P (P) PL

28 ST RG URG -

x x

Oscillatoria sp. Pediastrum Boryanum (Turp.)Menegh. P. duplex Meyen P. integrum Naeg. P. obtusum Lucks Phacotus cf. lendneri Chod. Phacotus sp. Phacus sp. Phormidium sp. Scenedesmus falcatus Chod. Scenedesmus sp. Spirogyra sp. Staurastrum sp. Stigeoclonium sp. Trachelomonas sp. Ulothrix sp. Total Nondiatom Taxa = 25

IP = periphytic

PL = planktonic 2Hustedt (1938) 30ccurred in long chains lHustedt (1959

(

x x

X

x x x

X

x x x X

,X

x x x x x x x x x )

x x x x x x x x x

x x

x x

x x x x x X x

x x x x x x X

= assigned growth habit

n=30). In t h e s e as well as a l l o t h e r samples, t h e nondiatom a l g a e comprised less than 10%of t h e t o t a l c e l l density. Two s p e c i e s of Phacotus (Chlorophyceae) were the most frequently encountered of these algae. The overall mean percentages of planktonic diatoms tabulated i n ringed and unringed substrate samples were 48.2% and 45.02 respectively. A comparison of a l l c e l l count values upon which t h e s e percentages were based i n d i c a t e d t h a t t h e r e was no s i g n i f i c a n t d i f f e r e n c e between t h e two t r e a t m e n t s ( t - t e s t ; p > 0.05, n=30; Table 3). L i t t l e qualitative difference was found between ringed and unringed samples. Of the 57 d i a t o m t a x a identified from these substrates (Table 21, 6 were found only i n samples from ringed surfaces and 6 from unringed. All of these unique taxa were uncommon, many o c c u r r i n g as a s i n g l e valve in j u s t one count. The most abundant and only planktonic form of t h e 13 unique taxa was F r a g i l a r i a capucina, which occurred i n three counts from ringed substrates, w i t h a maximum of 442 c e l l s mm-' (4.9% of t o t a l ) i n one day 9 sample. 2.3.2 Impingement from water column tlased on 4d (instantaneous) sediment trap samples, daily impingement rates ranged from 0.84 X lo3 t o 8.80 X lo3 c e l l s mm-' (I-' i n the upper growth zone and 0.46 X l o 3 t o 3.70 X l o 3 c e l l s mm-?dml i n t h e lower zone (Table 4). Further a n a l y s i s i n d i c a t e d t h a t accumulation d e n s i t i e s i n t h e t w o g r o w t h zones were significantly different ( t - t e s t ; p < 0.05); additional direct observations using SCUBA showed a s t r i k i n g d i f f e r e n c e . The mean d a i l y impingement r a t e i n t h e

29

TABLE 2.3 Mean percent planktonic diatoms from ringed and unringed substrates1.

Date -

Ringed

Unringed

6/26 6/30 7/1 7/8 1/12

49.3 60.2 37.1 50.3 44 .o

51.5 52.2 40.3 41.8 39.3

48.2 13.8

45 .O 8.6

X S (%

basis)

lthree replicates.

TABLE 2.4 Instantaneous (4d) sediment trap accumulation rates in the upper ( U ) and lower ( L ) zones from June 22-July 12, 1984.

Date

Zone

6/26

U L

6/30

U L

U

7/4

L

U

7/8

L

7/12

U L

-

Diatom Accumulation Rate (cells mm-2 d-l x lo3) 0.84 0.46 3.85 1.11 8.80 1.22 5.28

*

6.40 3.70 3.52 2.90

X

S

*Not available

upper zone 4d t r a p s ,

a d j a c e n t t o r o c k s u b s t r a t e s , was 5.03 X l o 3 c e l l s mm-'

d-'.

T h i s v a l u e c o n s t i t u t e d 48.8% o f day 20 d e n s i t i e s f r o m u n r i n g e d r o c k s u r f a c e s (Fig. 2) and 23.35:

mm-'1.

o f t h e o v e r a l l mean u n r i n g e d sample d e n s i t y (2.16 X l o 4 c e l l s

The i n i t i a l 4d s e d i m e n t t r a p ( 2 6 J u n e ) d e n s i t y o f 3.36 X 10' d i a t o m

c e l l s mm-'

was g r e a t e r t h a n t h e day 4 u n r i n g e d d e n s i t y (2.90 X lo3 c e l l s mm-')

and 23.5% o f t h e day 4 r i n g e d d e n s i t y , a l l c o l l e c t e d on t h e same date.

Qualita-

30 TABLE 2.5

Percentage of nonliving diatom cells in ringed (RG), unringed (URG), and unscraped rock ( R K ) samples. (mean of three replicates

.

% Nonliving Diatoms

Date -

RG -

URG

RK -

6/26 ( 4 d ) 6/30 ( 8 d ) 7/4 ( 1 2 d ) 7/8 ( 1 6 d ) 7/12 ( 2 0 d )

22 23 25 32 12

26 31 23 28 20

26 28 25 32 25

tively,

o n l y 13 o f t h e 84 d i a t o m t a x a i d e n t i f i e d i n a l l c o u n t s d i d n o t o c c u r i n see Table 2).

sediment t r a p s ( i n c l u d i n g c u m u l a t i v e t r a p s ;

The r e s u l t s of l i v i n g versus n o n l i v i n g d i a t o m c e l l c o u n t s a r e l i s t e d i n Table 5.

I n a d d i t i o n , f i v e 4d s e d i m e n t t r a p s a m p l e s w e r e s e l e c t e d a t r a n d o m a n d The percentage o f n o n l i v i n g d i a t o m c e l l s i n

counted f o r c o m p a r a t i v e purposes.

these counts ranged f r o m 18-34?; (X=26%). from rinqed,

Comparison o f these v a l u e s w i t h those

u n r i n g e d , and u n s c r a p e d r o c k s a m p l e s r e v e a l e d n o s i g n i f i c a n t

difference (t-test;

p>0.05,

n=50).

D i a t o m c e l l d e n s i t i e s f r o m c u m u l a t i v e sediment t r a p s a r e p l o t t e d i n Fig.

3.

T r a p s f r o m t h e u p p e r g r o w t h zone r a n g e d f r o m 3.36 X l o 3 c e l l s m n - 2 on day 4 t o 4.50 X 1 0 4 on day 2fi = 2.36 X l o 4 ) , w h e r e a s l o w e r t r a p s r a n g e d f r o m 1.85 X

(x

650{ N

0 upper zone

A I(3wer zone

I

'c 0

w

-

30

0

2 ; 20 I

d 111

I

lo=

.............

/ ,-.- _*.-

p= .083

__-. *_*.*.............................. P=,O18 __*............... __-. _. A ...................... A ...................

I

a E

0

4

8

12

16

20

TIME (d)

F i g . 2.3. 22 June-12 v a l u e ; --comparison

3 Cumulative sediment t r a p d i a t o m c e l l d e n s i t i e s (mm-2 x 10 ) , J u l y , 1984, from upper ( 0 ) and l o w e r ( A ;--- e x c l u d i n g 20d i n c l u d i n g 20d v a l u e ) g r o w t h zones. P-values i n d i c a t e t h e o f s l o p e s between t h e two zones.

31

TABLE 2.6 Percent planktonic diatoms in 4d instantaneous and cumulative sediment traps in the upper ( U ) and lower ( L ) growth zones. Cumulative Traps L U -

4d Traps L U -

Date 6/2 6 6/30 7/4 7/8 7/12

X

65.2 34.4 56.2 35.6 63.2

59.4 46.2 49.2

50.9

53.8

-

60.4

S

lo3

c e l l s mm-* on day 4 t o 2.56 X

l o 4 on

65.2 71.8 60 .O 56.8 66.8

59.4 57 .O 54.8 60 .O 56.4

64.1 29 .4

57.5 10.8

day 16

(x = 1.15

X. l o 4 ) .

A comparison

o f t h e s l o p e s o f r e g r e s s i o n l i n e s o f d e n s i t i e s f r o m each zone demonstrated t h a t sediment t r a p a c c u m u l a t i o n r a t e s (impingement r a t e s ) i n t h e upper g r o w t h zone w e r e g r e a t e r t h a n i n t h e l o w e r z o n e ( p = 0.018, s e e F i g . 3 l e g e n d ) . A s i g n i f i c a n t l y g r e a t e r percentage o f p l a n k t o n i c d i a t o m s was f o u n d i n upper

(64%) v e r s u s l o w e r ( 5 8 % ) g r o w t h z o n e t r a p s ( T a b l e 61, impingement samples ( t - t e s t ;

p < 0.05,

n=10).

b a s e d on c u m u l a t i v e

No s t a t i s t i c a l l y s i g n i f i c a n t

d i f f e r e n c e was e v i d e n t based on 4d t r a p s however. 2.3.3

Storm e f f e c t s --

Storm-induced

wave a c t i o n a n d b e l o w

surface

s i g n i f i c a n t losses o f e p i l i t h i c diatom cells.

turbulence

resulted i n

Reductions i n unscraped rock

d e n s i t i e s were p a r t i c u l a r l y d r a m a t i c , r e s u l t i n g i n a 47% d e c l i n e a f t e r t h e f i r s t s t o r m and a 10% d e c l i n e f o l l o w i n g a s e r i e s o f l e s s e r s t o r m s b e g i n n i n g on day 16 (Fig. 4).

A l t h o u g h unscraped r o c k samples were semi - q u a n t i t a t i v e ,

t h e standard

d e v i a t i o n a b o u t t h e mean o f t h r e e r e p l i c a t e s was l e s s t h a n t h o s e f r o m r i n g e d s a m p l e s c o l l e c t e d on t h e same d a t e s ( c f . F i g . 2).

Comparison o f t h e o v e r a l l

mean o f u n s c r a p e d r o c k d e n s i t i e s b e f o r e s t o r m s (1.45 X n=9) versus a f t e r s t o r m s (1.05 X

lo5

d i a t o m c e l l s mm-2,

f i c a n t d i f f e r e n c e between t h e t w o ( t - t e s t ; effects

p<0.05).

l o 5 diatom

c e l l s mm-2,

n=6) i n d i c a t e d a s i g n i Due t o t h e c o n f o u n d i n g

o f c o l o n i z a t i o n a n d m i c r o s u c c e s s i o n on r i n g e d a n d u n r i n g e d r o c k

s u r f a c e s , b e g i n n i n g w i t h n e a r z e r o d e n s i t i e s , b e f o r e v e r s u s a f t e r s t o r m mean comparisons were n o t performed. The percentages o f p l a n k t o n i c d i a t o m s f o u n d on unscraped rock, u n r i n g e d rock, and i n 4d s e d i m e n t t r a p s a r e l i s t e d i n T a b l e 7.

Planktonic diatom densities

( p a r t i c u l a r l y F r a g i l a r i a v a u c h e r i a e ) were s i g n i f i c a n t l y h i g h e r on r o c k s u r f a c e s p r i o r t o storms, p a r t i c u l a r l y t h o s e s u p p o r t i n g " a m b i e n t " c o m m u n i t y d e n s i t i e s .

32

I

h

*? X N

'E

.5g

GS= &=

14.5 XI$ 10.5 xl0'

PC .05

20-

W O

wa tn

15-

W W

zn W<

n c T

10-

rO,

2s

5-

n h< 0'

20

4

TIME (d)

Fig. 2.4. Unscraped rock mean diatom d e n s i t i e s (mn-2 X lO4), demonstrating t h e e f f e c t s of storm-induced turbulence (arrows i n d i c a t e storm events, with l a r g e r arrow p r i o r t o 12d sample indicating a major storm; 16d samples'collected a t 1500hr, p r i o r t o evening storm designated by PM). Upper l e f t : mean before and a f t e r storm values; *P < 0.05; n = 3; + 1 SD. Before t he f i r s t s t o r m , 78% of t h e d i a t o m s from unscraped rock samples were p l a n k t o n i c a s compared t o 48% a f t e r t h e storm. S i m i l a r l y , unringed rock communities were 64% planktonic before and 33% a f t e r t h e f i r s t storm. I n c o n t r a s t , 4d sediment t r a p p l a n k t o n p e r c e n t a g e s were n u m e r i c a l l y l o w e r before than a f t e r storms i n the upper growth zone. Although the difference was n o t s t a t i s t i c a l l y s i g n i f i c a n t a t the 0.05 l e v e l , t h i s was l i k e l y due t o a low number o f samples (n=5). P r i o r t o the f i r s t storm, 34% of the 4d t r a p material

TABLE 2.7 Mean percent planktonic diatoms in unscraped rock, unringed rock, and 4d sediment trap samples before and after storms1. Collection Unscraped Rock3 Unringed Rock3 Sediment Trap(4d)

Before Storms 64 49 45

After Storms

Comparison2

42 40 60

lBefore storm dates: 6/26, 6/30, 7/8; After: 7/4, 7/12 2t-test *Indicates significant difference 3Upper growth zone

p0.05

33

was comprised of planktonic diatoms, whereas 56% were planktonic a f t e r t h e f i r s t storm. The p e r c e n t a g e of n o n l i v i n g d i a t o m s on rock s u r f a c e s tended t o i n c r e a s e during calm p e r i o d s p r i o r t o s t o r m s . The mean p e r c e n t a g e on unringed rock s u b s t r a t e s was 25% b e f o r e v e r s u s 21% a f t e r s t o r m d i s t u r b a n c e s ; t h e o v e r a l l d i f f e r e n c e was s i g n i f i c a n t a t t h e 0.05 l e v e l . Comparable p e r c e n t a g e s of 29% before and 25% a f t e r storms were found on unscraped rock surfaces, however the means were n o t s t a t i s t i c a l l y s i g n i f i c a n t a t t h e a f o r e m e n t i o n e d l e v e l (O.lO>p>O.O5). 2.4

DISCUSSION

2.4.1 Recolonization Refering back t o t h e simple model i n Figure 1 , i t i s c l e a r t h a t impingement of c e l l s from t h e w a t e r column was more i m p o r t a n t i n t h e r e c o l o n i z a t i o n of denuded rock s u r f a c e s than was d i r e c t encroachment from adjacent populations. If encroachment had c o n t r i b u t e d s i g n i f i c a n t l y t o r e c o l o n i z a t i o n , then ( 1 ) unringed s u b s t r a t e c e l l d e n s i t i e s s h o u l d have exceeded r i n g e d s u b s t r a t e densities, since the l a t t e r treatment precluded d i r e c t encroachment, and/or (2) community composition should have d i f f e r e d s i g n i f i c a n t l y between t h e two t r e a t ments. The' r e s u l t s do n o t s u p p o r t e i t h e r c o n t e n t i o n . Data i n Fig. 2 d e m o n s t r a t e t h a t t h e r e was no q u a n t i t a t i v e d i f f e r e n c e between unringed and ringed s u b s t r a t e samples throughout the study period. Moreover, l i t t l e o r no q u a l i t a t i v e d i f f e r e n c e was found between t h e two treatments. Taxa t h a t were unique t o e i t h e r sample type were r a r e i n occurrence and exhibited no recognizable growth h a b i t pattern. Furthermore, an overall comparison of general growth habits revealed no significance difference between ringed and unringed samples (Table 3). Impingement of c e l l s from t h e water column appeared t o contribute s i g n i f i cantly t o the recolonization of denuded rock areas. Diatom accumulation r a t e s were high in sediment t r a p s when compared t o rock surfaces being recolonized, p a r t i c u l a r l y when v a l u e s from t h e upper growth zone t r a p s were used i n t h e comparison (Table 4). T h i s was e x e m p l i f i e d by t h e f a c t t h a t t h e 4d s e d i m e n t trap density was a c t u a l l y g r e a t e r than the 4d unringed s u b s t r a t e density over the same time increment. That i s , recolonization of denuded rock surfaces could be accounted f o r on the b a s i s of d a i l y impingement r a t e s alone. In a d d i t i o n , f l o r i s t i c d i f f e r e n c e s between s u r f a c e s undergoing recolonization and sediment t r a p samples were not s t r i k i n g . Fewer than 20% o f the 67 diatom taxa i d e n t i f i e d from ringed and unringed samples did not occur i n sediment t r a p samples. Again, those taxa were t y p i c a l l y r a r e i n abundance and encountered a s s i n g l e valves i n only one count. C o n s i d e r i n g the v a r i a b i l i t y among r e p l i c a t e samples w i t h r e s p e c t t o the diatom t a x a found, t h e 20% v a l u e would seem of even l e s s e r

34 importance. Not s u r p r i s i n g l y , unequivocal d i f f e r e n c e s were found between impingement r a t e s i n t r a p s f r o m t h e upper ( e p i l i t h i c ) zone versus t h e l o w e r ( p e l a g i c ) zone. One would presumably f i n d r a t e d i f f e r e n c e s based on t h e i n f l u e n c e o f t h e " l o c a l " f l o r a i n each zone, h o w e v e r t h e p r e c i s e n a t u r e o f t h e d i s i i m i l a r i t y i s n o t intuitive.

Two b a s i c d i f f e r e n c e s were observed.

F i r s t , t h e r a t e o f impingement

was g r e a t e r i n t h e upper versus the l o w e r zone (Fig. 3).

I n contrast,

Reynolds

(1976) f o u n d r e l a t i v e l y l a r g e numbers o f c e l l s i n t r a p s suspended i n d e e p e r waters.

The p r e s e n t f i n d i n g s c o u l d n o t be a t t r i b u t e d t o a d i s p r o p o r t i o n a t e

number o f resuspended, o r the other,

n o n l i v i n g diatom f r u s t u l e s being r e d e p o s i t e d i n one zone

s i n c e t h e percentage o f n o n l i v i n g c e l l s remained r a t h e r constant

among a l l samples (ca. 25%; Table 5). Second,

t h e percentages o f p l a n k t o n i c diatoms were g r e a t e r i n upper versus

l o w e r growth zone c u m u l a t i v e samples (Table 6).

(Although n o t a l l sediment t r a p

c o l l e c t i o n s w e r e a n a l y z e d f o r n o n l i v i n g d i a t o m s , no c o n s i s t e n t d i f f e r e n c e between t h e two zones was e v i d e n t on t h a t basis).

Interestingly,

t h e dominant

p l a n k t o n i c d i a t o m i n v o l v e d was F r a g i l a r i a v a u c h e r i a e , a t a x o n w h i c h has a l s o i n the periphyton i n colonial rosettes attached t o the substrate

been f o u n d

(Hoagland e t al.,

1982).

The v a r i a b i l i t y i n i t s growth h a b i t has i n p a r t l e d t o

i t s u n c e r t a i n taxonomic s t a t u s (Petersen,

1938).

Although such d i f f e r e n c e s between zones i n a l a k e o r r e s e r v o i r have n o t been reported,

t h e exchange o f i n d i v i d u a l s between t h e p l a n k t o n and p e r i p h y t o n has

been d e s c r i b e d .

Brown and A u s t i n (1973) f o u n d a d e c l i . n e i n t h e p l a n k t o n i c

d i a t o m F r a g i l a r i a c r o t o n e n s i s w i t h a c o i n c i d e n t r i s e i n i t s abundance i n t h e periphyton,

suggesting a s e t t l i n g .

"...particularly

Similarly,

Moss (1981) r e p o r t e d t h a t ,

i n t h e cases o f D i a t o m a e l o n g a t u m and Synedra sp.,

i t appears

t h a t species which are n u m e r i c a l l y predominant i n t h e p l a n k t o n a t c e r t a i n t i m e s o f t h e y e a r a r e a l s o n u m e r i c a l l y a b u n d a n t o r p r e d o m i n a n t a t t h e same o r o t h e r t i m e s i n t h e periphyton."

K a i r e s a l o (1976) a l s o described an i n v e r s e r e l a t i o n -

s h i p between the l i t t o r a l phytoplankton and t h e e p i l i t h o n i n o l i g o t r o p h i c Lake Paajarvi.

The disappearance o f l o o s e l y attached species,

t h e i r resuspension i n

t h e water column and subsequent r e s e t t l i n g onto c o l o n i z e d surfaces was proposed by Hudon and B o u r g e t (19831, i n a model based on o b s e r v a t i o n s f r o m p l a s t i c p a n e l s p l a c e d i n an e s t u a r y .

A p a r t f r o m t h e s e s t u d i e s , l i t t l e e l s e has been

r e p o r t e d concerning t h e p o t e n t i a l source o f c o l o n i z e r s on l i t t o r a l substrates, d e s p i t e t h e v o l u m i n o u s s t u d i e s on p e r i p h y t o n c o m m u n i t y c o m p o s i t i o n and t h e c l a s s i c a l papers on t h e source o f t h e s p r i n g p l a n k t o n p u l s e (Lund, 1954; 1955). A p e r t i n e n t q u e s t i o n t o p o s e i n l i g h t o f t h e s e r e s u l t s i s do such denuded

areas on rocks represent an e c o l o g i c a l l y r e a l i s t i c s i t u a t i o n ?

I n addition t o

s t u d i e s t h a t have noted t h e occurrence o f p e e l i n g o r sloughing o f t h e p e r i p h y t o n i n o t h e r h a b i t a t s ( K i n g and B a l l , 1966; C a s t e n h o l z , 19611, p a r t i c u l a r l y as a

35 r e s g l t o f wave a c t i o n (Young, 1945; K a i r e s a l o , 1976; Hoagland, 19831, t h i s s u b s t a n t i a l l o s s o f t h e a t t a c h e d b i o f i l m has a l s o been r e p o r t e d f o r McConaughy r e s e r v o i r (Roemer e t al.,

1984).

O b s e r v a t i o n s u s i n g SCUBA i n d i c a t e d t h a t

s l o u g h i n g occurs i n a p a t c h y manner under c o n d i t i o n s o f l o w turbulence.

This

k i n d o f b i o m a s s r e m o v a l h a s b e e n d i s c u s s e d f o r m a r i n e h a b i t a t s as w e l l (e.g., Yodzis,

1978; S o u s a , 1979).

By b r u s h i n g r e l a t i v e l y s m a l l a r e a s c l e a r o f

p e r i p h y t o n biomass, t h e methods employed i n t h i s s t u d y have presumably removed p o r t i o n s o f t h e community i n a s i m i l a r ,

p a t c h y manner.

The s i z e , d i s t r i b u t i o n ,

and temporal frequency o f n a t u r a l patches have n o t been examined i n f r e s h w a t e r a t t a c h e d communities. The use o f i n t a c t , n a t u r a l s u b s t r a t e s a l s o s u p p o r t s t h e e c o l o g i c a l r e a l i s m o f t h e p r e s e n t s t u d y methods.

The s u b s t r a t e s were c l e a r l y l o c a t e d i n an e c o l o g i -

c a l l y r e l e v a n t p o s i t i o n and were i d e n t i c a l i n c o m p o s i t i o n t o s u r r o u n d i n g s u r f a c e s , b o t h c o n d i t i o n s o f c o n c e r n i n s t u d i e s o f t h i s n a t u r e ( W e t z e l , 1965; 1953).

M o r e o v e r , t h e i n t r o d u c t i o n o f " g a p s " i n t h e a t t a c h e d c o m m u n i t y may be

more p e r t i n e n t i n m a r i n e and f r e s h w a t e r s t u d i e s t h a n t h e use o f c l e a n a r t i f i c i a l s u b s t r a t e s f o r i n v e s t i g a t i n g c o l o n i z a t i o n and succession phenomena.

A r t i f i c i a1

surfaces, p a r t i c u l a r l y when suspended f r o m buoys o r o t h e r openwater s t r u c t u r e s , l i k e l y f u n c t i o n as e c o l o g i c a l i s l a n d s ( H e n e b r y a n d C a i r n s , 1980; Osman, 1982; see however S t e w a r t e t al.,

19851, whereas denuded areas on e x i s t i n g s u b s t r a t e s

may be, f o r example, more analogous t o t r e e gaps (e.g., d i s t u r b a n c e s ( P l a t t , 1975).

Denslow, 1980) o r badger

S e c o n d a r y s u c c e s s i o n s a r e 1 i k e l y a more common

occurrence i n t h e p e r i p h y t o n than p r i m a r y successions,

g i v e n t h e area o f

s u b s t r a t e s u r f a c e a v a i l a b l e f o r a t t a c h m e n t t h r o u g h o u t t h e g r o w i n g season.

At

present, o u r l a c k o f u n d e r s t a n d i n g o f t h e s c a l e s i n v o l v e d w h i c h s e p a r a t e c o l o n i zers from p o t e n t i a l sites,

b o t h t e m p o r a l l y and s p a t i a l l y ,

p r e c l u d e s any

c o n c l u s i o n s c o n c e r n i n g t h e s u i t a b i l i t y o f a p a r t i c u l a r e x p e r i m e n t a l design i n the field.

The r e s u l t s p r e s e n t e d h e r e a r g u e f o r t h e s i m i l a r i t y b e t w e e n t h e

"gap" and " i s l a n d " approach, s i n c e impingement c o n t r i b u t e d f a r more t o r e c o l o n i z a t i o n t h a n encroachment, however f i n a l d e t e r m i n a t i o n o f t h e e x t e n t t o w h i c h these f i n d i n g s a p p l y t o o t h e r a q u a t i c systems a w a i t s f u r t h e r research. 2.4.2

Storm e f f e c_ ts _

~

Wind-induced t u r b u l e n c e had a d r a m a t i c e f f e c t on t h e s t r u c t u r e and dynamics o f t h e unscraped e p i l i t h i c community (Fig.

4).

D i r e c t underwater o b s e r v a t i o n s

c o n f i r m e d t h a t t u r b u l e n c e r e s u l t e d i n a v i s i b l y reduced b i o f i l m t h i c k n e s s on a l l rock s u r f a c e s down t o ca. 3.5m,

c o i n c i d e n t w i t h an i n c r e a s e i n w a t e r t u r b i d i t y

due t o suspended c e l l s and d e t r i t u s .

It i s i n t e r e s t i n g t o n o t e t h a t t h e younger

communities (4-12d) f r o m r i n g e d and u n r i n g e d s u b s t r a t e s were a p p a r e n t l y u n a f f e c t e d by t u r b u l e n c e , whereas t h e r e l a t i v e l y o l d e r c o m m u n i t i e s (16-2Od) were s i g n i f i c a n t l y i m p a c t e d ( F i g . 2).

These r e s u l t s a r e c o n s i s t e n t w i t h p r e v i o u s

36 o b s e r v a t i o n s made on communities of a s i m i l a r c o m p o s i t i o n from a e u t r o p h i c r e s e r v o i r (Hoagland, 1983). Presumably when diatom c e l l d e n s i t i e s and t h e v e r t i c a l s t a t u r e of t h e community a r e r e l a t i v e l y great, t h e biofilm i s physicall y more susceptible t o dislodging depending upon the degree of turbulence. The i m p o r t a n c e of

disturbance

i n t h e marine rocky i n t e r t i d a l zone i s w e l l

e s t a b l i s h e d ( L e w i s , 1 9 7 7 ; Sousa, 1984; D e t h i e r , 19841, b u t has n o t been adequately addressed i n f r e s h waters. Of equal importance perhaps i s the d i f f e r e n t i a l e f f e c t t h a t storm a c t i v i t y had on planktonic versus periphytic diatoms.

The proportion of planktonic diatoms

on unscraped and unringed surfaces was s i g n i f i c a n t l y g r e a t e r before storms than

a f t e r and v i c e v e r s a f o r s e d i m e n t t r a p samples t o a l e s s e r degree ( T a b l e 7). This s t r o n g l y s u g g e s t s t h a t t h e p l a n k t o n i c members of t h e p e r i p h y t o n , o r t h e tychoplankton (Round, 19811, were more g r e a t l y a f f e c t e d by t u r b u l e n c e d u r i n g storm events than t h e t r u e periphytic forms which produce permanent attachment s t r u c t u r e s ( s t a l k s , pads, etc.). That i s , the f r e e - f l o a t i n g members of t h e attached community were dislodged from t h e s u b s t r a t e and subsequently deposited i n t h e 4d s e d i m e n t t r a p s d u r i n g each s t o r m e v e n t , t o a g r e a t e r e x t e n t than s e s s i l e forms. This reduction was p r e f e r e n t i a l and therefore not random among species i n the community as indicated by Peterson (1977) i n h i s model t o examine the r e l a t i o n s h i p between perturbations and d i v e r s i t y , or equal a s suggested by Robinson and Sandgren (1983) i n t h e i r e x p e r i m e n t a l m a n i p u l a t i o n s of p l a n k t o n microcosms. T h e s e r e s u l t s a r e c o n s i s t e n t w i t h t h o s e of K u h n e t a l . (1981) who hypothesized t h a t planktonic populations i n t h e periphyton a r e maintained primarily by invasion pressure. Similarly, Jones (1978) found t h a t t h e a b i l i t y of planktonic forms t o e s t a b l i s h on polyurethane foam "islands" determined t h e pattern of e a r l y colonization. I n addition, t h i s type of l a r g e s c a l e upwelling and subsequent s e t t l i n g of pseudoplanktonic and p s e u d o p e r i p h y t i c d i a t o m s f o l l o w i n g t u r b u l e n c e e v e n t s may i n p a r t e x p l a i n t h e i n c r e a s e s i n s e d i m e n t t r a p d e n s i t i e s seen by Reynolds (1976) during calm periods, r a t h e r than turbulencer e l a t e d differences i n trapping efficiences. A1 though diatom colonization i s probably the most poorly understood process of t h e f o u l i n g sequence i n marine s y s t e m s ( s e e Callow and Evans, 1951), i t i s even l e s s known i n f r e s h w a t e r s . Aside from t h e p r o c e s s of r e c o l o n i z a t i o n of s u b s t r a t e s during the growing season, the actual source of t h e i n i t i a l spring diatom bloom common in many bodies of fresh water remains basically unknown. As Yodzis (1978) pointed out, "...dispersal i s a dynamic element of competition f o r space," a n o t i o n t h a t c e r t a i n l y w a r r a n t s f u r t h e r r e s e a r c h i n s e s s i l e systems.

37 ACKNOWLEDGEMENTS The a u t h o r s t h a n k R. Wheeler a n d J.R. Rosowski f o r t h e i r a s s i s t a n c e i n t h e f i e l d . We a r e a l s o g r a t e f u l t o t h e U n i v e r s i t y o f Nebraska, Cedar P o i n t B i o l o g i cal S t a t i o n f o r p r o v i d i n g l a b o r a t o r y space and f a c i l i t i e s . This research was supported by a g r a n t f r o m t h e Texas C h r i s t i a n U n i v e r s i t y Research Fund t o K.D.H. and by a g r a n t f r o m t h e Nebraska W a t e r Resources C e n t e r t o J.R. Rosowski and K.D.H. REFERENCES Beaver, J., 1981. Apparent e c o l o g i c a l c h a r a c t e r i s t i c s o f some common f r e s h w a t e r diatoms. O n t a r i o M i n i s t r y o f t h e Environment, 517 pp. B l i n n , D.W., F r e d e r i c k s e n , A., and K o r t e , V., 1980. C o l o n i z a t i o n r a t e s and community s t r u c t u r e o f diatoms on t h r e e d i f f e r e n t rock s u b s t r a t a i n a l o t i c system. B r i t . Phycol. J., 15: 303-310. Bloesch, J. and Burns, N.M., 1980. A c r i t i c a l r e v i e w o f s e d i m e n t a t i o n t r a p t e c h n i q u e . Schweiz. Z. Hydrol., 42: 15-55. B l o m q v i s t , S. and Hakanson, L., 1981. A r e v i e w on s e d i m e n t t r a p s i n a q u a t i c environments. Arch. Hydrobiol., 91: 101-132. Brown, S.D. and A u s t i n , A.P., 1973. D i a t o m s u c c e s s i o n and i n t e r a c t i o n i n l i t t o r a l p e r i p h y t o n and plankton. Hydrobiologia, 43: 333-356. C a l l o w , M.E. and Evans, L.V., 1981. Some e f f e c t s o f t r i p h e n y l t i n c h l o r i d e on Achnanthes subsessil i s . Bot. Mar., 24: 201-205. C a l l o w , M.t., t v a n s , L.V. and C h r i s t i e , A.O., 1976. The b i o l o g y o f s l i m e f i l m s . P a r t 2. Shipping World & S h i p b u i l d e r 3923: 949-951. Castenholz, R.W., 1961. Seasonal changes i n t h e attached algae o f f r e s h w a t e r and s a l i n e l a k e s i n t h e l o w e r Grand Coulee, Washington. Limnol. Oceanogr., 5: 128. C h a r a c k l i s , W.G. and Cooksey, K.E., 1983. B i o f i l m s and b i o f o u l i n g . Adv. Appl. Microbiol., 29: 93-138. C o l w e l l , R.R., Belas, M.R., Zachary, A., A u s t i n , B. and A l l e n , D., 1980. A t t a c h ment o f microorganisms t o surfaces i n t h e a q u a t i c environment. Devel. Indust. Microbiol., 21: 169-178. C u n d e l l , A.M. and M i t c h e l l , R., 1977. M i c r o b i a l s u c c e s s i o n on a wooden s u r f a c e exposed t o t h e sea. I n t . B i o d e t e r . B u l l . , 13: 67-73. D a n i e l , G.F. and C h a m b e r l a i n , A.H.L., 1981. Copper i m m o b i l i z a t i o n i n f o u l i n g d i a t o m s . Bot. Mar., 24: 229-243. Dempsey, M.J., 1981. M a r i n e b a c t e r i a l f o u l i n g : a s c a n n i n g e l e c t r o n m i c r o s c o p e study. Mar. B i o l . , 61: 305-315. 1980. Gap p a r t i t i o n i n g among t r o p i c a l r a i n f o r e s t t r e e s . Denslow, J.S., B i o t r o p i c a (Suppl.), 12: 47-55. Dethier, M.N., 1984. Disturbance and recovery i n i n t e r t i d a l pools: maintenance o f mosaic patterns. Ecol. Monogr., 54: 99-118. Evans, L.V., 1981. Marine algae and f o u l i n g : a review, w i t h p a r t i c u l a r reference t o s h i p - f o u l i n g . Bot. Mar., 24: 157-171. Fletcher, M., 1980. Adherence o f marine micro-organisms t o smooth surfaces. In: E.H. Beachey ( E d i t o r ) , B a c t e r i a l Adherence. Receptors and R e c w n i t i o n , Series B, Vol. 6. Chapman and H a l l , London, pp. 347-374. Gerchakov, M., M a r s z a l e k , D.S., Koth, F.J. and Udey, L.R., 1976. S u c c e s s i o n o f p e r i p h y t i c microorganisms on metal and glass surfaces i n n a t u r a l seawater. Proc. 4 t h I n t . Cong. Mar. C o r r . F o u l i n g , A n t i b e s , France, pp. 203-211. Hargrave, B.T. and Burns, N.M., 1979. Assessment o f s e d i m e n t t r a p c o l l e c t i o n e f f i c i e n c y . L i mnol. Oceanogr., 24: 1124-1136. Henebry, M.S. and C a i r n s , J.Jr., 1980. The e f f e c t o f i s l a n d s i z e , d i s t a n c e and epicenter m a t u r i t y on c o l o n i z a t i o n i n f r e s h w a t e r protozoan communities. Amer. Midland Nat., 104: 80-92. Hoagland, K.D., 1983. S h o r t - t e r m s t a n d i n g c r o p and d i v e r s i t y o f p e r i p h y t i c

38 diatoms i n a e u t r o p h i c r e s e r v o i r . J. Phycol., 19: 30-38. Roemer, S.C. and Rosowski, J.R., 1982. C o l o n i z a t i o n and communiHoagland, K.D., t y s t r u c t u r e o f t w o p e r i p h y t o n assemblages, w i t h e m p h a s i s on t h e d i a t o m s (Bacillariophyceae). Amer. J. Bot., 69: 188-213. Hudon, C. and B o u r g e t , E., 1981. I n i t i a l c o l o n i z a t i o n o f a r t i f i c i a l s u b s t r a t e : community development and s t r u c t u r e s t u d i e d by scanning e l e c t r o n microscopy. Can. J. F i s h . Aquat. Sci., 38: 1371-1384. Hudon, C. and B o u r g e t , E., 1983. The e f f e c t o f l i g h t on t h e v e r t i c a l s t r u c t u r e o f e p i b e n t h i c d i atom communi ti es. Bot. Mar., 26: 317-330. Hustedt, F., 1938. Systematische and Bkoloqische Untersuchungen uber d i e D i a t o meenflora von Java, B a l i und Sumatra. Arch. Hydrobiol. (Suppl.), 15: 131-177, 16: 187-295. 16: 393-506. H u s t e d t , F., 1?_59. D i e D i a t o m e e n f l o r a des Neudiedler Sees i m 6 s t e r r e i c h i s c h e n Burgenland. Osterreich. Bot. Z., 106: 390-430. Jones, R.C., 1978. A l g a l b i o m a s s d y n a m i c s d u r i n g c o l o n i z a t i o n o f a r t i f i c i a l i s l a n d s : experimental r e s u l t s and a model. Hydrobiologia, 59: 165-180. Kairesalo, T., 1976. Measurements o f p r o d u c t i o n o f e p i l i t h i p h y t o n and 1 i t t o r a l p l a n k t o n i n Lake PB'dj'drvi, southern Finland. Ann. Bot. Fennici, 13: 114-118. K i n g , D.L. and B a l l , R.C., 1966. A q u a l i t a t i v e a n d q u a n t i t a t i v e measure of Aufwuchs production. Trans. Amer. Microsc. SOC., 85: 232-240. 1981. Q u a l i t a t i v e Kuhn, D.L., P l a f k i n , J.L., C a i r n s , Jr.,J. and Lowe, R.L., c h a r a c t e r i z a t i o n o f a q u a t i c environments u s i n g diatom l i f e - f o r m s t r a t e g i e s . Trans. Amer. M i c r o s c . SOC., 100: 165-152. Lewis, J.R., 1977. The r o l e o f p h y s i c a l and b i o l o g i c a l f a c t o r s i n t h e d i s t r i b u t i o n and s t a b i l i t y o f r o c k y s h o r e c o m m u n i t i e s . I n : B.F. Keegan, P. O c e i d i g h and P.J.S. Boaden ( E d i t o r s ) , B i o l o g y o f B e n t h i c Organisms. Pergamon Press, New York. pp. 417-424. Loeb, S.L., 1981. An i n s i t u m e t h o d f o r m e a s u r i n g t h e p r i m a r y p r o d u c t i v i t y and s t a n d i n g c r o p o f t h e e p i l i t h i c p e r i p h y t o n c o m m u n i t y i n l e n t i c systems. L i mnol. Oceanogr., 26: 394-399. Lowe, R.L., 1974. Environmental requirements and p o l l u t i o n t o l e r a n c e o f f r e s h 334 p. water diatoms. U.S. Environmental P r o t e c t i o n Agency, EPA-670/4-74-005. Lund, J.W.G., 1954. The s e a s o n a l c y c l e o f t h e p l a n k t o n d i a t o m M e l o s i r a i t a l i c a (Ehr.) Kiitz. subsp. s u b a r c t i c a 0. M i i l l . J. Ecol., 42: 151-179. Lund, J.W.G., 1955. F u r t h e r o b s e r v a t i o n s on t h e s e a s o n a l c y c l e o f M e l o s i r a i t a l i c a (Ehr.) Kiltz. subsp. s u b a r c t i c a 0. M l i l l . J. Ecol., 43: 90-102. M a r s z a l e k , D.S., Gerchakov, S.R. and Udey, L.R., 1979. I n f l u e n c e o f s u b s t r a t e composition on marine m i c r o f o u l i n g . Appl. Environ. Microbiol., 38: 987-995. M c A l i c e , B.J., 1971. P h y t o p l a n k t o n s a m p l i n g w i t h t h e S e d g w i c k - R a f t e r c e l l . L i nnol. Oceanogr., 16: 19-25. Moss, B., 1981. The composition and ecology of p e r i p h y t o n communities i n f r e s h w a t e r s . 11. I n t e r - r e l a t i o n s h i p s b e t w e e n w a t e r c h e m i s t r y , p h y t o p l a n k t o n p o p u l a t i o n s and p e r i p h y t o n p o p u l a t i o n s i n a s h a l l o w l a k e and a s s o c i a t e d experimental r e s e r v o i r s ('Lund tubes'). B r i t . Phycol. J., 16: 59-76. Oleksowicz, A.J., 1982. I n t e r a c t i o n s among a l g a l communities i n t h r e e l a k e s o f t h e T u c h o l a F o r e s t s a r e a ( N o r t h e r n Poland). Arch. H y d r o b i o l . (Suppl.), 63: 77-90. Osman, R.W., 1982. A r t i f i c i a l s u b s t r a t e s as e c o l o g i c a l i s l a n d s . I n : J. C a i r n s J r . ( E d i t o r ) , A r t i f i c i a l S u b s t r a t e s . Ann A r b o r Publ., Ann A r b o r , M i c h i g a n , U.S.A., pp. 71-114. P a t r i c k , R. and Reimer, C.W., 1966. The D i a t o m s o f t h e U n i t e d S t a t e s . Vol.1. Academy o f N a t u r a l Sciences o f Phi l a d e l p h i a, Monogr. No. 13., Phi l a d e l p h i a, 688 pp. P e n n s y l v a n i a , U.S.A., 1975. The D i a t o m s o f t h e U n i t e d S t a t e s . Vol.11. P a t r i c k , R. and Reimer, C.W., pt.1. Academy o f N a t u r a l Sciences o f Phi l a d e l p h i a, Monogr. No.13., P h i l a d e l p h i a , P e n n s y l v a n i a , U.S.A., 213 pp. Petersen, J.B., 1938. F r a g i l a r i a i n t e r m e d i a - Synedra Vaucheriae? Bot. Not., 1938, pp. 164-170. 1977. Species d i v e r s i t y and p e r t u r b a t i o n s : p r e d i c t i o n s o f a nonPeterson, C.H.,

39 i n t e r a c t i v e model. Oikos, 29: 239-244. P l a t t , W.J., 1975. The c o l o n i z a t i o n and f o r n a t i o n o f e q u i l i b r i u m p l a n t species a s s o c i a t i o n s on badger d i s t u r b a n c e s i n a t a l l -grass p r a i r i e . Ecol. Monogr., 45~285-305. 1970. How t o Know t h e F r e s h w a t e r Algae. Wm. C. Brown P u b l i s h e r s , Prescott, G.W., Dubuque, I o w a , U.S.A., 348 pp. 1976. S i n k i n g movements o f p h y t o p l a n k t o n i n d i c a t e d by a s i m p l e Reynolds, C.S., t r a p p i n g method. I. A F r a g i l a r i a p o p u l a t i o n . B r i t . Phycol. J., 11: 279-291. Robinson, J.V. a n d Sandgren, C.D., 1983. The e f f e c t o f t e m p o r a l e n v i r o n m e n t a l h e t e r o g e n e i t y on c o m m u n i t y s t r u c t u r e : a r e p 1 i c a t e d e x p e r i m e n t a l s t u d y . Oecologia, 57: 98-102. Roemer, S.C. a n d Hoagland, K.D., 1979. S e a s o n a l a t t e n u a t i o n o f q u a n t u m i r r a d i ance (400-700 nm) i n t h r e e Nebraska r e s e r v o i r s . H y d r o b i o l o g i a , 63: 81-92. H o a g l a n d , K.D. a n d R o s o w s k i , J.R., 1984. D e v e l o p m e n t o f a f r e s h Roener, S.C., w a t e r p e r i p h y t o n community as i n f l u e n c e d by d i a t o m mucilages. Can. J. Bot., 62: 1799-1813. Rosemarin, A.S. and Gelin, C., 1978. E p i l i t h i c a l g a l presence and p i g m e n t compos i t i o n on n a t u r a l l y o c c u r r i n g and a r t i f i c i a l s u b s t r a t e s i n Lakes Trummen and F i o l e n , Sweden. Verh. I n t e r n a t . Verei n. Limnol., 20: 808-813. Round, F.E., 1981. The Ecology o f Algae. Cambridge U n i v e r s i t y Press, Cambridge, Great B r i t i a n , 653 pp. Sousa, W.P., 1979. E x p e r i m e n t a l i n v e s t i g a t i o n s o f d i s t u r b a n c e a n d e c o l o g i c a l succession i n a r o c k y i n t e r t i d a l a l g a l community. Ecol. Monogr., 49: 227-254. Sousa, W.P., 1984. The r o l e o f d i s t u r b a n c e i n n a t u r a l c o m m u n i t i e s . Ann. Rev. E c o l . Syst., 15: 353-391. P r a t t , J.R., C a i r n s , Jr., J. a n d Lowe, R.L., 1985. D i a t o m and S t e w a r t , P.M., p r o t o z o a n s p e c i e s a c c r u a l on a r t i f i c i a l s u b s t r a t e s i n l e n t i c h a b i t a t s . Trans. Amer. M i c r o s c . SOC., 104: 369-377. T e r r y , L.A. a n d Edyvean, R.G.J., 1984. I n f l u e n c e s o f m i c r o a l gae on c o r r o s i o n o f s t r u c t u r a l s t e e l . In: J.R. L e w i s a n d A.D. M e r c e r ( E d i t o r s ) , C o r r o s i o n a n d M a r i n e G r o w t h on O f f s h o r e S t r u c t u r e s . S o c i e t y o f C h e m i c a l I n d u s t r y , E l l i s Horwood Ltd., pp. 38-44. Tuchman, M.L. a n d S t e v e n s o n , R.J., 1980. C o m p a r i s o n o f c l a y t i l e , s t e r i l i z e d rock, and n a t u r a l s u b s t r a t e d i a t o m c o m m u n i t i e s i n a s m a l l s t r e a m i n southe a s t e r n Michigan, USA. H y d r o b i o l o g i a , 75: 73-79. Wetzel, R.G., 1965. Techniques and problems o f p r i m a r y p r o d u c t i v i t y measurements i n h i g h e r a q u a t i c p l a n t s and p e r i p h y t o n . Proceedings o f t h e I.B.P. Symposium on P r i m a r y P r o d u c t i v i t y i n A q u a t i c Environments, P a l l a n z a , I t a l y , 1965. Mem. I s t . I t a 1 . I d r o b i o l . ( S u p p l . ) , 18: 249-267. 1983. Limnology, 2nd E d i t i o n . Saunders C o l l e g e Pub., P h i l a d e l p h i a , Wetzel, R.G., P e n n s y l v a n i a , U.S.A., 767 pp. Yodzis, P., 1978. C o m p e t i t i o n f o r space and t h e s t r u c t u r e o f e c o l o g i c a l communit i e s . L e c t u r e N o t e s i n B i o m a t h e m a t i c s , V o l . 25, S p r i n g e r - V e r l a g , New York, 1 9 1 pp. 1945. A l i m n o l o g i c a l i n v e s t i g a t i o n o f p e r i p h y t o n i n Douglas Lake, Young, O.W., M i c h i g a n . T r a n s . Amer. M i c r o s c . SOC., 64: 1-20. 1978. A m e t h o d f o r Z a c h a r y , A., T a y l o r , M.E., S c o t t , F.E. a n d C o l w e l l , R.R., r a p i d evaluation o f m a t e r i a l s f o r s u s c e p t i b i l i t y t o marine biofouling. Int. B i o d e t e r i o r . Bull., 14: 111-118.

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41 Chapter 3

ADHESION OF FOULING DIATOMS TO SURFACES: SOME BIOCHEMISTRY

K. E. COOKSEY AND BARBARA COOKSEY Department o f U.S.A., 59717

3.1

M i c r o b io 1ogy , Montana

State

U n i v e r s i t y , Bozeman,

Montana,

INTRODUCTION I n s p i t e o f t h e f a c t t h a t most s t u d i e s o f m i c r o b i o l o g i c a l f o u l i n g show t h e

presence o f diatoms on f o u l e d s u r f a c e s , l i t t l e i s known o f t h e c o n t r i b u t i o n o f these organisms t o t h e e c o l o g y o f t h e b i o f i l m .

A c u r s o r y assessment o f t h e

m i c r o f o u l i n g l i t e r a t u r e may suggest t h a t b a c t e r i a r e p r e s e n t t h e o n l y f o u l i n g problem.

While t h a t may be t r u e f o r s u r f a c e s t h a t a r e d a r k , i t c e r t a i n l y does

not apply t o t h e l i g h t e d surface.

A l l s u b s t r a t a t h a t a r e wet and i l l u m i n a t e d

u l t i m a t e l y w i l l s u p p o r t t h e g r o w t h o f an a l g a l p o p u l a t i o n . algae w i l l be diatoms.

I n many cases these

Diatoms may p l a y a c o n s i d e r a b l e r o l e i n t h e n u t r i e n t

dynamics o f t h e b i o f i l m ( C h a r a c k l i s and Cooksey, 1983; Escher and C h a r a c k l i s , 1982) t h r o u g h s y n t r o p h i c i n t e r a c t i o n s . t h e w a t e r column ( B e l l and Sakshaug,

Such i n t e r a c t i o n s a r e w e l l known f o r 1980; Brock and C l i n e , 1984) where t h e

s y n t r o p h i c p a r t n e r s a r e much f u r t h e r a p a r t and d i f f u s i o n p a t h s much l o n g e r t h a n i n a biofilm.

C r o s s - f e e d i n g i n b i o f i l m s may i n v o l v e much more t h a n exchange o f It could, f o r instance,

o r g a n i c molecules. b i o f i l m environment

by b a c t e r i a l

involve the detoxification o f the

r e s p i r a t i o n o f photosynthetically-produced

oxygen. B e f o r e d i a t o m attachment t a k e s p l a c e , t h e c e l l s must be t r a n s p o r t e d t o a surface.

In all

b u t t o t a l l y quiescent

hydrodynamic means (Breznak e t a l . ,

situations

this

process occurs by

1985).

I t i s t h e purpose o f t h i s paper t o t h r o w some l i g h t on some o f t h e

m e t a b o l i c e v e n t s which t a k e p l a c e i m m e d i a t e l y f o l l o w i n g t h e a r r i v a l o f a raphe-bearing d i a t o m on a s u r f a c e . 3.2

METHODS

3.2.1

Choice o f organism Except where s t a t e d o t h e r w i s e ,

t h e e x p e r i m e n t a l organism used i n t h i s

study was Amphora c o f f e a e f o r m i s (Agardh)

Kutz ( F i g .

3.3).

A.

coffeaeformis

grows h e t e r o t r o p h i c a l l y and m i x o t r o p h i c a l l y on g l u c o s e (Cooksey and Chansang,

1976).

42 3.2.2

E l e c t r o n microscopy T h i s has been d e s c r i b e d (Webster e t a l . ,

3.2.3

1985).

Video r e c o r d i n g Video r e c o r d i n g s were made i n t h e 6-111 mode on a Toshiba r e c o r d e r (Model

V8500T).

Images were o b t a i n e d f r o m a R e i c h e r t phase-contrast-microscope

w i t h an RCA v i d e o camera (Model TC2011).

fitted

The v i d e o image was m o d i f i e d t o

c o n t a i n a t i m e / d a t e s i g n a l (RCA Model TC1440B).

The o v e r a l l m a g n i f i c a t i o n was

330x (microscope 16x, e l e c t r o n i c a p p r o x i m a t e l y 20x1. 3.2.4

Chemotaxis Experiments Two methods were used.

I n the f i r s t ,

s t e r i l e 90 mm P e t r i d i s h e s were

f i l l e d w i t h a r t i f i c i a l seawater medium ( P r o v a s o l i e t a l . ,

1957), m o d i f i e d t o

c o n t a i n 5 mM Ca2+ and 2% a g a r (Cooksey and Chansang, 1976) t o a d e p t h of 4 mm. A w e l l was c u t i n t h e a g a r which was t h e n f i l l e d w i t h s t e r i l e 10 mM g l u c o s e i n t h e same medium.

A f t e r i n c u b a t i o n a t 28°C o v e r n i g h t ,

diatoms were a p p l i e d t o

t h e s u r f a c e o f t h e agar i n a l i n e 20 m f r o m t h e g l u c o s e - c o n t a i n i n g w e l l .

A

f i n e , s t e r i l e p a i n t b r u s h which had been d i p p e d i n an a x e n i c d i a t o m suspension was used f o r t h i s o p e r a t i o n .

N i n e t e e n hours f r o m t h e a d d i t i o n o f t h e g l u c o s e

t o t h e agar, 'the p l a t e s were observed as d e s c r i b e d above.

C e l l s moving up o r

down t h e g l u c o s e g r a d i e n t were i d e n t i f i e d by means o f t h e t r a c k s l e f t i n t h e agar s u r f a c e and counted.

I n some experiments,

t r a c i n g s o f t h e t r a c k s were

made and used f o r measurements o f changes i n d i r e c t i o n i n response t o t h e g l u c o s e g r a d i e n t i n t h e agar.

A second method f o r t h e d e t e c t i o n o f chemosensing o f g l u c o s e was based on t h a t o f Zigmond (1977).

I n t h i s procedure diatoms a t t a c h e d t o a g l a s s m i c r o -

scope c o v e r - g l a s s were exposed t o a chemical g r a d i e n t e s t a b l i s h e d between two w e l l s i n an a c r y l i c p l a s t i c microscope s l i d e .

Again c e l l s moving up o r down

t h e g r a d i e n t and t r a v e l l i n g a t an a n g l e o f no more t h a n 45" t o t h e g r a d i e n t were counted. tion.

T h i s r e p r e s e n t e d a h i g h l y c o n s e r v a t i v e assessment o f o r i e n t a -

R e s u l t s were c a l c u l a t e d w i t h r e s p e c t t o a normal a p p r o x i m a t i o n o f a

b i n o m i a l d i s t r i b u t i o n w i t h P<0.05 and compared t o a t h e o r e t i c a l d i s t r i b u t i o n o f

50% p o s i t i v e o r i e n t a t i o n . 3.2.5

Incorporation o f r a d i o - l a b e l l e d substrates D e t a i l s a r e g i v e n i n each experiment.

p u b l i s h e d (Cooksey,

1978).

The g e n e r a l procedure has been

Where drugs were used,

c o n t r o l i n c u b a t i o n s con-

t a i n e d t h e same c o n c e n t r a t i o n o f s o l v e n t as t h e d r u g - c o n t a i n i n g i n c u b a t i o n s .

43 3.2.6

Adhesion assays These were c a r r i e d o u t as d e s c r i b e d e a r l i e r (Cooksey, 1981).

3.2.7

Preparation o f diatom footpads C e l l s were

attached

to

glass

microscope

cover

glasses

as

described

The c o v e r g l a s s e s were r i n s e d t o remove u n a t t a c h e d c e l l s and

(Cooksey, 1981).

placed i n 10 mM e t h y l e n e g l y c o l b i s ( B - a m i n o e t h y l e t h e r )

N,NI-tetraacetic

acid

(EGTA) i n minimal media l e s s c a l c i u m a t pH 7.7 f o r 20 min. a t room temperature. They were t h e n r i n s e d f u r t h e r w i t h minimal medium and observed m i c r o s c o p i c a l l y using phase-contrast o p t i c s . 3.2.8

Drugs, i n h i b i t o r s , r a d i o c h e m i c a l s and c o u n t i n g procedures

3-(3,4-dichlorophenyl)-l,lLaboratories

Inc.,

and

dimethylurea

r e c r y s t a l 1i z e d

(DCMU) was

from

aqueous

a - i s o p r o p y l - a - [ (N-methyl-N-homoveratryl )-a-amino

propyl]

p h e n y l a c e t o n i t r i l e (D-600) was a g i f t f r o m K n o l l A. G., cyanide - 3 - c h l o r o p h e n y l

obtained from

ethanol

before

K&K

use.

-3,4,5- t r i m e t h o x y -

West Germany.

Carbonyl

hydrazone (CCCP) , c y c l o h e x i m i d e (CH) and t u n i c a m y c i n

USA, and used w i t h o u t f u r t h e r p u r i f i c a A l l d r u g s o l u t i o n s were made i n d i m e t h y l s u l f o x i d e o r 70% (V/V) ethanol

were o b t a i n e d f r o m Sigma Chemical Co., tion.

1% o f t h e s o l v e n t i n t h e

a t such a c o n c e n t r a t i o n t o a l l o w no more t h a n incubation mixture.

3H-glucose was o b t a i n e d f r o m I C N C o r p o r a t i o n , USA.

Radio-

a c t i v i t y was determined i n c e l l s a f t e r s o l u b i l i z a t i o n i n P r o t o s o l and c o u n t i n g i n Aquasol I 1 (New England N u c l e a r C o r p o r a t i o n , USA). 3.2.9

Cell counts Diatom c e l l s were counted i n a haemocytometer.

V i a b l e c e l l s were counted

a f t e r t r e a t i n g w i t h Trypan b l u e ( f i n a l c o n c e n t r a t i o n ,

0.5%).

Unstained c e l l s

were c o n s i d e r e d v i a b l e . 3.3

RESULTS AND DISCUSSION

A. c o f f e a e f o r m i s has been shown t o respond t o a g l u c o s e g r a d i e n t i n agar by moving up t h e c o n c e n t r a t i o n g r a d i e n t ( T a b l e 3.1). I n t h e absence o f g l u cose, c e l l s move i n a s e r i e s o f random e l l i p s e s .

The cause o f t h e e l l i p t i c a l

movement i s p r o b a b l y t h e geometry o f t h e raphe systems. possesses

two

raphes

on t h e v e n t r a l

suggested (Cooksey and Cooksey,

side o f

A.

t h e organism.

coffeaeformis I t has been

1986) t h a t one o f t h e raphes i s i n c l o s e r

c o n t a c t w i t h t h e s u b s t r a t u m t h a n t h e o t h e r and t h u s t r a n s m i t s t h e 'dominant' d r i v i n g force.

When i n a g r a d i e n t , however,

A.

c o f f e a e f o r m i s moved i n a s e r i e s

o f separate s l i g h t l y c u r v e d l i n e s , each o f which f o l l o w e d a d i r e c t i o n change so

44 TABLE 3.1 Chemosensing i n a g l u c o s e g r a d i e n t i n agar. Expt. No.

T o t a l c e l l s counted

Percent moving towards g l u c o s e ? (S.E.)a

31 38 50 82 74 48

90 92 92 77

i f

85

i f

71

(66 (74 (77

? 2

(63 (72 (51

-

-

99) 99) 99)

- 88) - 94) - 86)

a R e s u l t s s i g n i f i c a n t a t Pc0.01.

as t o m a i n t a i n movement a l o n g t h e g r a d i e n t

(Fig.

3.1).

It i s possible t o

r e g a r d u n d i r e c t e d movement as a s e r i e s o f e r r o r accumulations w i t h r e s p e c t t o an i m a g i n a r y s t r a i g h t l i n e .

On t h e o t h e r hand, d i r e c t e d movement as a r e s u l t

o f t h e r e p e a t e d s e n s i n g o f a chemical g r a d i e n t , c c r r e c t i o n and i m p l i e s

that

at

least

in this

results

i n constant e r r o r

organism d i f f e r e n t i a l

raphe

control i s possible.

CHEM0SENSING:DlRECTlONAL CHANGE

_-

_ -- -

glucose

constructed track

mean directional change 37t 3 degrees

F i g . 3.1. D i r e c t i o n a l Changes i n Response t o a Glucose G r a d i e n t . ( i ) The (ii) t r a c k s o f a d i a t o m on an a g a r s u r f a c e were t r a c e d f r o m t h e v i d e o m o n i t o r . The s e r i e s o f c u r v e s i n ( i ) were s t r a i g h t e n e d i n o r d e r t o measure t h e a n g l e changes made by t h e diatom. The mean a n g l e change (a - h ) was 37" ? 3".

45 Although t h e a g a r p l a t e method was p a r t i c u l a r l y s u i t a b l e f o r t h e observat i o n o f t h e b e h a v i o r a l responses o f t h e c e l l t o a g l u c o s e g r a d i e n t , i t was l e s s S O f o r t h e q u a n t i f i c a t i o n o f t h e c o n c e n t r a t i o n s o f c h e m o a t t r a c t a n t necessary t o

e l i c i t a response.

F o r t h i s work we chose t o use a Zigmond chamber

apparatus v e r y c o n v e n i e n t f o r t h e o b s e r v a t i o n o f slow-moving organisms those t h a t move a t a few vm/sec. w i t h 0.5 mM glucose.

After

-

an

i.e.

F i g . 3.2a shows t h e r e s u l t s o f a time-course

random movement a t f i r s t ,

a f t e r 20 min so t h a t 70% a r e moving up t h e g r a d i e n t .

c e l l s become o r i e n t e d

A t p r e s e n t we do n o t know

whether t h e l a g i n response t o g l u c o s e i s caused by t h e t i m e needed f o r t h e g r a d i e n t t o be e s t a b l i s h e d , response t o glucose.

o r t h e time

necessary

to

induce a m e t a b o l i c

Glucose u p t a k e and metabolism i s an i n d u c i b l e p r o p e r t y o f

t h i s organism t h a t n o r m a l l y t a k e s 25 min t o develop

(Cooksey,

unpublished

I t w i l l be i n f o r m a t i v e t o d i s c o v e r whether glucose-induced c e l l s

observation).

Should such an i n d u c t i o n p e r i o d be

a l s o show t h i s l a g i n o r i e n t a t i o n response.

necessary t o sense a l l e x t r a c e l l u l a r chemical s i g n a l s ,

i t would i m p l y t h a t a

t i m e o f t h i s o r d e r would be necessary f o r t h e c e l l t o adhere as a r e s u l t o f such a s i g n a l .

T h i s seems u n l i k e l y t o us.

The minimal

glucose g r a d i e n t

d e t e c t e d was 0-0.1 mM g l u c o s e which was e s t a b l i s h e d o v e r 2.5 mm d i s t a n c e .

This

I n control

t r a n s l a t e s t o an approximate g r a d i e n t of 0.04 uM/pm o f c e l l l e n g t h .

experiments, where no g l u c o s e i s p r e s e n t c e l l s moved randomly ( F i g . 3.2b),

i.e.

o r i e n t a t i o n was n o t d i f f e r e n t f r o m 50%.

TIME-COURSE: 0.5mY GLUCOSE

sm

T

UI

2 YI 0

50

I

/

0

\/

8

I

g30

$ '

-

42

25

53

38

n:w

10

0

10

50

80

F i g . 3.2. ( a ) Time-course f o r t h e Development o f C e l l O r i e n t a t i o n i n a Glucose Gradient. Diatom c e l l s on a microscope c o v e r - g l a s s were exposed t o a 0-0.5 mM glucose g r a d i e n t i n a Zigmond d i f f u s i o n chamber. T o t a l , number o f c e l l s ( n ) moving up t h e g l u c o s e g r a d i e n t (pos.) a r e expressed as a f u n c t i o n o f t h e t o t a l number o f c e l l s moving up and down t h e glucose g r a d i e n t , t o g e t h e r w i t h t h e 95% confidence i n t e r v a l s (P<0.05), ( b ) a s i m i l a r t i m e - c o u r s e i n t h e absence o f a glucose g r a d i e n t .

46 The p h y s i o l o g i c a l

r e q u i r e m e n t s f o r t h e adhesion o f

A.

coffeaeformis

g l a s s were i n v e s t i g a t e d by means o f t h e q u a n t i t a t i v e adhesion assay.

to

We f o u n d

t h a t Ca2+ o r Sr2+ were necessary w i t h no o t h e r i o n t e s t e d b e i n g a b l e t o subs t i t u t e ( T a b l e 3.2).

It s h o u l d be n o t e d t h a t a l t h o u g h c e l l s would adhere i n

t h e presence o f Sr2+, t h e y were n o t a b l e t o move, whereas c e l l s t h a t adhered i n t h e presence o f Ca2+ were m o t i l e ( F i g . 3.3b).

F u r t h e r , c e l l s adhered i n Sr2+

c o u l d be d i s t i n g u i s h e d f r o m t h o s e i n Ca2+ by t h e morphology o f t h e adhesive polymer (Webster and Cooksey, u n p u b l i s h e d o b s e r v a t i o n ) . can s u b s t i t u t e f o r Ca2+ s t r u c t u r a l l y , e t al.,

1984).

T h i s i m p l i e s t h a t Sr2+

b u t n o t i n t h e s e c r e t i o n process (Cooksey

The response t o Ca2+ was n o t an i s o l a t e d one and was found w i t h

s e v e r a l o t h e r pennate f o u l i n g diatoms ( T a b l e 3.3).

Adhesion t o o k p l a c e i n t h e

l i g h t o r d a r k and was n o t i n h i b i t e d by t h e photosystem I 1 i n h i b i t o r DCMU.

TABLE 3.2 Adhesive Response o f

c o f f e a e f o r m i s t o t h e Presence o f D i v a l e n t C a t i o n s

Ion

Percent o f Controla

C o n t r o l , 0.25 mM Ca2+ 5 mM CaZt 5 mM S r Z + 10 mM Sr2+ 5 m M MnZ+ 5 mFI Ba2+

100 ( 3 6 ) 354 t 69 ( 1 2 ) 193 f 4 ( 6 ) 427 f 14 ( 6 ) 60 f 27 ( 6 ) 0 (6)

a Adhesion of d i a t o m c e l l s t o a g l a s s s u r f a c e was measured by t h e method o f Cooksey (1981). F i g u r e s a r e means + 1 s t a n d a r d d e v i a t i o n (no. o f determinat i o n s ) . Data f r o m Cooksey, 1981.

TABLE 3.3 Adhesion t o Glass b y Marine F o u l i n g Diatoms Grown i n A r t i f i c i a l Seawater Medium a t V a r i o u s C o n c e n t r a t i o n s o f Calcium O r g a n i s n number Genus C e l l l e n g t h (urn) Adhesion i n ASP-2 medium + 0.75 mM Ca 2.5 mM Ca 10.0 mM Ca

4 Navi c u l a 10

6 Nitzschia 13

25 Tropidoneis 23

27 Nitzschia 50

+ ++

+/-

-

+/-

t

+t

+ + ++

-, no adhesion; +/-, g e n t l e a g i t a t i o n suspends c e l l s ; +, s h a k i n g suspends c e l l s ; ++, s h a k i n g does n o t remove c e l l s f r o m g l a s s . Experiment c a r r i e d o u t i n 5 m l p o r t i o n s o f ASP-2 medium ( P r o v a s o l i e t a l . , 1957) a t t h e Ca c o n c e n t r a t i o n s shown.

47

F i g . 3.3. (a) SEM Photomicrograph o f Cleaned F r u s t u l e o f A. coffeaeformis. Ventral view showing raphe openings. Bar = lum. (b) A. coffeaeformis adhered t o glass surface. Note p o s i t i o n and s i z e o f adhesive appendages. Bar = lpm. ( c ) Phase-Contrast Micrograph o f Raphe Imprints o f A. coffeaeformis. Bar = 5um.

48 I t was

i n h i b i t e d by an energy

uncoupler

(CCCP),

an

inhibitor of

protein

s y n t h e s i s ( c y c l o h e x i m i d e ) and a Ca2+ t r a n s p o r t i n h i b i t o r (D-600)

( T a b l e 3.4).

These r e s u l t s i m p l y t h a t energy i s r e q u i r e d f o r adhesion,

i t i s not a

p a s s i v e process and t h e c e l l s a r e n o t i n h e r e n t l y s t i c k y .

i.e.

Further,

protein

s y n t h e s i s i s necessary.

We a r e aware t h a t CH has s e v e r a l o t h e r modes o f a c t i o n

( d i s c u s s e d i n Cooksey,

1981 and McMahon,

1975),

system t h e same v e r y l o w l e v e l o f d r u g (3.6

but the fact that

in this

uM) causes an 84% i n h i b i t i o n o f

leucine incorporation i n t o the hot trichloroacetic acid insoluble f r a c t i o n o f t h e c e l l ( p r o t e i n and g l y c o p r o t e i n ) tends t o s u p p o r t t h i s o b s e r v a t i o n ( T a b l e 3.5). al.,

D-600 a c t s o u t s i d e t h e c e l l membrane (Mayer e t a l . ,

1972; M e i s h e r i e t

1981) and p r e v e n t s Ca2+ e n t r y , t h u s s u g g e s t i n g an i n t r a c e l l u l a r r o l e f o r

Ca2+.

Such a r o l e c o u l d be i n t h e s e c r e t o r y ,

e x o c y t o t i c process known t o be

i n v o l v e d i n t r a n s p o r t o f t h e a d h e s i v e t o t h e raphe c a n a l 1985).

(Webster e t a l . ,

The p r o p o s a l t h a t Ca2+ a c t s i n t e r n a l l y does n o t r u l e o u t an e x t e r n a l

r o l e f o r Ca2+ a l s o . external role.

I n f a c t , t h e r e s u l t s f r o m t h e EGTA e x p e r i m e n t s do i m p l y an

Footpads o r raphe i m p r i n t s were o b t a i n e d a f t e r removal o f Ca2+

w i t h EGTA, a Ca2+ c h e l a t o t - ( F i g .

A s u g g e s t i o n o f how t h e s e i m p r i n t s

3.3~).

c o u l d be made when a c o h e s i v e b r e a k i n t h i s adhesive m a t e r i a l o c c u r s as ir r e s u l t o f t h e removal o f C a Z t these

i s g i v e n i n F i g . 3.4.

have a l s o been f o u n d by G a n i e l

e t al.

Raphe i m p r i n t s such as

(1980)

u s i n g t h e SEM a f t e r

mechanical removal o f t h e d i a t o m c e l l s f r o m t h e substratum.

TABLE 3.4 I n h i b i t i o n o f Adhesion of

A. c o f f e a e f o r m i s . % o f C o n t r o l -e S.D.

Trea tmen t

(No. o f D e t e r m i n a t i o n s ) C o n t r o l , 0.25 5 mM 5 mM 5 mM 5 mM 5 mM 5 mM

mM Ca, l i g h t Ca, l i g h t Ca, d a r k Ca, l i g h t , + Ca, l i g h t , + Ca, l i g h t , + Ca, l i g h t , +

2 UM DCMU 5 pM CCCP 3.6 pM CH 25 DM D-600

100 478 i 168 ( 1 C ) 543 I- 156 ( 6 ) 549 i 122 ( 6 ) 76 f 4 ( 6 ) 39 It 13 ( 6 ) 55 -t 50 ( 9 )

Washed c e l l s were suspended i n minimal medium and p r e i n c u b a t e d f o r 15 niin. (CCCP, DCMU, D-600) o r 30 min. (CH), b e f o r e Ca was added a t t h e c o n c e n t r a t i o n s shown. Adhered c e l l s were q u a n t i f i e d as d e s c r i b e d (Cooksey, 1981). Data f r o m Cooksey, 1981.

49

b

F i g . 3.4. surface.

P o s s i b l e mode o f a c t i o n o f EGTA i n c a u s i n g d i a t o m removal f r o m a E F F E C T OF T U N I C A M V C I N O N M O T I L I T Y

I

E f f e c t o f Tunicamycin on M o t i l i t y o f A. c o f f e a e f o r m i s . Tunicamycin F i g . 3.5. (0.5 g/ml) was added t o a suspension o f diatoms i n m i n i m a l media c o n t a i n i n g 5 mM Ca!+. Speed o f m o t i l i t y was measured f r o m a v i d e o t a p e .

50 TABLE 3.5 I n h i b i t i o n o f Adhesion and L a b e l i n g o f H o t T r i c h l o r o a c e t i c A c i d Fraction o f coffeaeformis.

Insoluble

Percent I n h i b i t i o n Incorporation Treatment Tunicamycin, 5 dm1 Cycloheximide, 3.6 UM

N.D.

Adhesion

Leucine

G1 ucose

98 92

0

88

84

N.D.

= n o t determined.

The f a c t t h a t t h e cytochernical work o f D a n i e l e t a l .

(1980) showed t h e

d i a t o m adhesive polymer t o be an a c i d p o l y s a c c h a r i d e and o u r subsequent f i n d i n g t h a t an i n h i b i t o r of p r o t e i n s y n t h e s i s p r e v e n t e d adhesion,

suggested t h a t we

i n v e s t i g a t e t h e e f f e c t o f an i n h i b i t o r o f g l y c o p r o t e i n s y n t h e s i s (Tamura, 1982)

on adhesion. Tunicamycin (TM) p r e v e n t e d t h e adhesion o f d i a t o m c e l l s ( T a b l e 3.6) and a l s o a t a l o w c o n c e n t r a t i o n slowed m o t i l i t y ( F i g . 3.5). I t was n o t e w o r t h y t h a t even h i g h l e v e l s o f TM d i d n o t a f f e c t c e l l v i a b i l i t y ( T a b l e 3.6). That TM was a f f e c t i n g g l y c o p r o t e i n s y n t h e s i s r a t h e r t h a n p r o t e i n s y n t h e s i s i s shown by Table 3.5.

Here TM i n h i b i t s t h e i n c o r p o r a t i o n o f g l u c o s e b u t n o t

l e u c i n e i n t o t h e p r o t e i n and g l y c o p r o t e i n f r a c t i o n o f t h e c e l l .

TABLE 3.6 E f f e c t o f Tunicamycin on t h e Adhesion and V i a b i l i t y o f

coffeaeformis.

Treatment

Adhesion Viabilitya (Percent Control Value)

C o n t r o l , no d r u g 0.5 g/ml t u n i c aI,m y c i n b 1.0 g/ml I, 5.0 g/ml 10.0 g/ml "

100

79+9 (4)

5 (2) 81+12 (16) 52239 (14) 6+1 ( 7 )

N. D.

a V i a b i l i t y as measured by t h e Trypan b l u e method. 24 h p r e i n c u b a t i o n . N.D. = n o t determined.

83k5 (4) 83+2 (4) N.D.

M o t i 1 it y a1 1 jerky few none none

51

controlled by (chemical?) signals

adhesive/trail substance SUBSTRATUM A Conceptual Model o f Pennate Diatom Adhesion.

Fig. 3.6.

The r e s u l t s presented here, t o g e t h e r w i t h t h e work o f Chamberlain's group (Daniel e t al.,

1980; Daniel and Chamberlain, 1981) suggest a conceptual model

for

i n diatom adhesion

the

steps

(Fig.

3.6).

Vesicles

produced

in

the

dictysome o f t h e G o l g i apparatus c o n t a i n polysaccharide-1 i k e m a t e r i a l (Daniel e t al.,

1980).

These v e s i c l e s a r e t r a n s p o r t e d t o t h e c e l l membrane near t o t h e

raphe canal by some as y e t unknown means, b u t m i c r o t u b u l e s may be i m p l i c a t e d (Webster e t a l . , secretion o f

1985).

their

Fusion o f t h e v e s i c l e s w i t h t h e c e l l membrane a l l o w s

contents.

This

material

(Fig.

3.3b),

which

is

still

associated w i t h t h e c e l l membrane, a l l o w s t h e c e l l t o adhere t o t h e substratum (Webster e t al., adhesion

1985;

Edgar and Pickett-Heaps,

by TM and t h e

possible secretion o f

1983).

The i n h i b i t i o n o f

a molecule w i t h

different

r h e o l o g i c a l p r o p e r t i e s a t low TM c o n c e n t r a t i o n s suggest t h e involvement o f a g l y c o p r o t e i n i n t h e s y n t h e s i s o f t h e adhesive.

It has been suggested t h a t

c e l l u l o s e i s synthesized on a g l y c o p r o t e i n p r i m e r (MacLachlan, 1982). a s i m i l a r s i t u a t i o n e x i s t s w i t h r e s p e c t t o t h e diatom adhesive. obviously

i n v o l v e d a t an

intracellular

and e x t r a c e l l u l a r

Perhaps

Calcium i s

site(s).

Intra-

c e l l u l a r l y i t may be i n v o l v e d i n t h e s e c r e t o r y process and t r a n s p o r t

of

vesicles; e x t r a c e l l u l a r l y i t c o u l d be i n v o l v e d as a c r o s s - l i n k i n g agent between

52 l o c a l i z e d n e g a t i v e charges.

Which o f t h e p r e v i o u s steps i s c o n t r o l l e d by

sensing o f an e x t e r n a l chemical s i g n a l i s n o t y e t known, b u t i t seems c l e a r t h a t such a c o n t r o l phenomenon i s p o s s i b l e .

Whether t h e p o t e n t i a l chemical

s i g n a l i s processed d i r e c t l y o r a f t e r i n t r a c e l l u l a r metabolic conversion o f t h e chemical i s n o t known. process.

Also unknown i s t h e r o l e o f t h e c y c l o h e x i m i d e - s e n s i t i v e

Perhaps t h i s c o u l d i n v o l v e t h e induced s y n t h e s i s o f a p r o t e i n as a

r e s u l t o f a chemosensory event.

These aspects o f t h e work w i l l form t h e b a s i s

o f f u r t h e r investigations. ACKNOWLEDGEMENTS We would l i k e t o thank t h e U n i t e d States O f f i c e o f Naval Research Oceanic B i o l o g y Program f o r t h e i r support o f t h i s work. REFERENCES B e l l , W.H., and Sakshaug, E., 1980. B a c t e r i a l U t i l i z a t i o n of A l g a l Extrac e l l u l a r Products, 2. A K i n e t i c Study o f N a t u r a l Populations. Limnol. Oceanogr. 25:1021-1033. Cooksey, K.E., Eckhardt, F.E.W., F i l i p , Z., F l e t c h e r , M., Breznak, J.A., Gibbons, R.J., Gude, H., Hamilton, W.A., Hatton, T., Hoppe, H.-G., Matthysse, A.G., Savage, D.C. and S h i l o , M. A c t i v i t y on Surfaces. I n : K.C. Marshall ( E d i t o r ) , M i c r o b i a l Aggregation and Adhesion. Springer Verlag, B e r l i n , pp. 203-221. Brock, T.D. and C l i n e , J., 1984. S i g n i f i c a n c e o f a l g a l e x c r e t o r y products f o r growth o f e p i l i m n e t i c b a c t e r i a . Appl. Environ. M i c r o b i o l . , 47:731-734. 1983. B i o f i l m s and m i c r o b i a l f o u l i n g . Adv. C h a r a c k l i s , W.G. and Cooksey, K.E., Appl. M i c r o b i o l . , 29:93-138. Paul, J.H., Rubin, R.W. and Webster, Cooksey, B., Cooksey, K.E., M i l l e r , C.A., D., 1984. The attachment o f m i c r o f o u l i n g diatoms. I n : J.D. Costlow and R.C. T i p p e r ( E d i t o r s ) , Marine B i o d e t e r i o r a t i o n : An I n t e r d i s c i p l i n a r y Study. Naval I n s t i t u t e Press, Annapolis, MD, USA, pp. 167-171. Cooksev, B. and Cooksev, K.E.. 1980. Calcium i s necessarv f o r m o t i l i t v i n t h e diatom Am hora c o f f i a e f o r m i s . P l a n t P h y s i o l . , 653129-131. Cooksey, B. an Cooksey, K.E., 1986. Studies on Chemosensing i n a T r o p i c a l Marine F o u l i n a Diatom. Proc. I n t . Conf. on Marine B i o d e t e r i o r a t i o n . Goa. I n d i a . January 1986. Oxford and IBH P u b l i s h e r s ( i n press). 1978. R e s p i r a t o r y A s s i m i l a t i o n o f 14C-labeled Substrates by a Cooksey, K.E., Microalqa. I n : J.A. H e l l e b u s t and J.S. C r a i a i e ( E d i t o r s ) . Handbook o f Phycological Methods. Vol 2. Cambridge U n j v e r s j t y Press, Cambridge, DD. 317-337. Cookkey, K.E., 1981. Requirement f o r c a l c i u m i n adhesion o f a f o u l i n g diatom t o glass. Appl. Env. M i c r o b i o l . , 41:1378-1382. Cooksey, K.E. and Chansang, H., 1976. I s o l a t i o n and p h y s i o l o g i c a l s t u d i e s on t h r e e i s o l a t e s o f Am hora (Bacillarcophyceae). J. Phycol., 12:455-460. Chambe&A.H.L. and Jones, E.B.G. , 1980. U l t r a s t r u c t u r a l Daniel , G.F., observations on t h e marine f o u l i n g diatom Amphora. Helgolander Wiss. Meeresunters, 34: 123-149. 1981. Copper i m m o b i l i z a t i o n i n f o u l i n g Daniel , G.F. and Chamberlain, A.H.L., diatoms. Botan. Marina, 24:229-243. Edgar, L.A. and Pickett-Heaps, J.D., 1983. The mechanism o f diatom locomotion. I. An u l t r a s t r u c t u r a l study o f t h e m o t i l i t y apparatus. Proc. Roy. SOC. London ( B i o l . ) , 218:331-343.

-%-

.

53 1982. A l g a l - b a c t e r i a l i n t e r a c t i o n s w i t h i n Escher, A. and C h a r a c k l i s , W.G., aggregates. B i o t e c h . Bioeng., 24:2283-2290. Mayer, C.J., van Breeman, C. and C a s t e l l o , R., 1972. The a c t i o n o f lanthanum and D-600 on t h e c a l c i u m exchange i n t h e smooth muscle c e l l s o f t h e guinea p i g Taenia c o l i . P f l u e g e r s Arch., 337:333-350. MacLachm.A.,1982. Does B-glucan s y n t h e s i s need a p r i m e r ? I n : R.M. Brown ( E d i t o r ) . C e l l u l o s e and O t h e r N a t u r a l Polymer Systems: Biogenesis, S t r u c t u r e and Degradation. Plenum Press, New York, pp. 327-339. 1975. Cycloheximide i s n o t a s p e c i f i c i n h i b i t o r o f p r o t e i n McMahon, D., s y n t h e s i s i n v i v o . P l a n t P h y s i o l . , 55:815-821. M e i s h e r i , K., Kwang, 0. and van Breeman, C., 1981. Evidence f o r two s e p a r a t e Ca2+ pathways i n smooth muscle plasmalemma. J. Membrane B i o l . , 59:19-25. P r o v a s o l i , L., McLaughlin, J.J.A. and Droop, M.R., 1957. The development of a r t i f i c i a l media f o r m a r i n e algae. Arch. M i k r o b i o l . , 25:392-428. Tamura, G. ( E d i t o r ) , 1982. Tunicarnycin. Japan S c i e n t i f i c S o c i e t i e s Press, Tokyo, 220 pp. Cooksey, K.E. and Rubin, R.W., 1985. An i n v e s t i g a t i o n of t h e Webster, D.R., involvement o f cytochernical s t r u c t u r e s and s e c r e t i o n i n g l i d i n g m o t i l i t y o f t h e marine d i a t o m Amphora c o f f e a e f o r m i s . C e l l M o t i l i t y , 5:103-122. Zigmond, S . , 1977. A b i l i t y o f polymorphonuclear l e u k o c y t e s t o o r i e n t t o g r a d i e n t s o f c h e m o t a c t i c f a c t o r s . J . C e l l B i o l . 75:606-616.

This Page Intentionally Left Blank

55 Chapter 4

S Y N E R G I S M BETWEEN ANTIFOULING B I O C I D E S

L.V.

M A U R E E N E. CALLOW'

EVANS1,

a n d K.R.

WOOD3

' D e p a r t m e n t o f P l a n t S c i e n c e s , U n i v e r s i t y o f L e e d s , L e e d s LS2 9 J T ' D e p a r t m e n t o f P l a n t B i o l o g y , B i r m i n g h a m U n i v e r s i t y , PO Box 363, B i r m i n g h a m 8 1 5 ZTT, UK 3 T e c h n i c a l D e p a r t m e n t , H o e c h s t A n i m a l H e a l t h , W a l t o n Manor, W a l t o n , M i l t o n K e y n e s , B u c k s MK7 7 A J . U K . 4.1

INTRODUCTION m a j o r a d v a n c e i n t h e c o n t r o l o f f o u l i n g b y m a r i n e a l g a e on

A

t h e u n d e r w a t e r p a r t s o f s h i p s w a s made i n t h e e a r l y s e v e n t i e s w i t h the

development

copolymer which

of

system

a

type

of

( s e e Evans,

antifouling

p a i n t known a s t h e

1981). U n l i k e c o n v e n t i o n a l systems,

a r e p h y s i c a l mixes r e l e a s i n g t o x i n (eg.

cuprous oxide) a t a

diminishing r a t e and t h e r e f o r e a t reduced e f f e c t i v e n e s s w i t h time, t h e c o p o l y m e r s y s t e m i s a c h e m i c a l m i x o f t w o monomers. forming

paint-resin

copolymerisation methacrylate. toxic

of

moieties,

(Evans,

as the

cuprous oxide,

addition,

the

roughness of

A filmthe

and

vinyl

tributyltin

by e s t e r bonds t o t h e polymer

manner.

a t r i o r g a n o t i n such as t r i b u t y l t i n Other

biocides

(pigments)

and

are

released

as h y d r o l y s i s occurs.

surface i n i t s e l f i s self-polishing,

decreases i s

such

may a l s o b e i n c o r p o r a t e d a s p h y s i c a l m i x e s i n t o

matrix

composition

by

copolymer h y d r o l y s e s i n seawater t o

biocide,

i n a controlled

polymer

made

methacrylate

linked

1 9 7 0 ) . The

release the principle oxide,

methyl

i s

T h i s copolymer c o n t a i n s a h i g h molar p r o p o r t i o n o f

organotin

backbone

("binder")

as

the

polymer i s eroded,

i.e. so

In

surface that

the

known a s s e l f - p o l i s h i n g c o p o l y m e r (SPC). The r a t e

polishing

i s

dependent

upon

polymer

( p r o p o r t i o n s o f t h e monomers), v e s s e l speed,

composition

water temperature,

pH

and s a l i n i t y . Although algae,

they

forming

SPC

are

systems e f f e c t i v e l y c o n t r o l t h e l a r g e r f o u l i n g n o t e f f e c t i v e i n t h e complete c o n t r o l o f slime-

organisms

(French,

Evans and O a l l e y ,

1 9 8 5 ) . Movement o f

the ship through the water i s essential f o r optimal self-polishing and

when

the

biological slimes

polishing occur

rate which

i s

not

optimal,

microscopical

although

visually

insignificant

56 contribute

markedly

(Lewthwaite natural

e t

for

which

addition,

slime

hence

slime

1985). Slime-covered surfaces a l s o provide a

al.,

substrate

Ectocarpus, and

t o t h e f r i c t i o n a l r e s i s t a n c e o f a moving s h i p

films are and

retard

composed

under

w i l l

which

may

and

be

into

the

or

acetate;

1986;

combinations

Here the

and

w i l l

be

at

slime films

d e v e l o p o n SPC finding

( 1 ) new

we

which i n a c t i n g together

permit

report

effects

of

acetate;

the

on

use

the

of

reduced

results

tributyltin

of

oxide

an

(TBTO),

1-dodecylguanidine acetate

trade

2-dodecylguanidine

guanidine,

Amphora

added t o such p a i n t s t o g i v e b e t t e r s l i m e control

names

acetdte

dodine,

cyprex,

(2-guanidinododecane

(I-methylundecy1)-monoacetate 1 on t h e

diatom

I n t h e i n t e r e s t s o f b r e v i t y t h e two l a t t e r

coffeaeformis.

compounds

The

(Callow,

conditions,

aimed

w i t h two c a t i o n i c s u r f a c t a n t s ,

melprex)

mucilage.

Navicula

diatom

undertaken

biocide

(1-guanidinododecane

Amphora

semi-rigid

ship-operating by

been

levels.

investigation together

has

improved

triorganotin

a

Stauroneis

average

(2)

give

i n

p a i n t s b e l o n g t o t h e g e n e r a Amphora,

SPC

particular

and,

of

1986).

paints,research biocides

on

rate

o f an aggregation o f organisms, c h i e f l y held

Achnanthes,

control

the

I n

Biological

Amphiprora,

i n

eg.

release (leaching) from t h e paint.

diatoms

Since

spores,

hydrolysis

predominant

dominated

macroalgal copolymer

diatoms,

French and Evans,

of

may g e r m i n a t e a n d g r o w i n t e r m i x e d w i t h i t .

may

biocide

bacteria

settlement

r e f e r r e d t o as 1-OGA

a n d 2-DGA

respectively i n

t h i s communication. 4.2

MATERIALS AN0 METHODS Axenic

stock

perpusilla

(Grunnow)

described 2dm3 as

by

Blunn

cultures

o f

Amphora

Cleve

derived

from

and Evans (1981) were

a

clonal

maintained

f l a s k s o f G u i l l a r d ' s F2 medium ( G u i l l a r d described

by C a l l o w and Evans (1981).

w i t h I n s t a n t Ocean ( A q u a r i u m S y s t e m s , The

effects

determined sterile

as F2

r p m ) a t 20°C 130

of

biocides,

follows: medium

10 were

cm3

log

culture

as

a t 20°C

Ryther,

i n

19621,

T h e m e d i u m was p r e p a r e d

U.S.A.1

singly

and

var.

artificial

or

i n

phase

transferred

seawater.

combination, culture

aseptically

and

were 90cm3

t o 250cm3

f l a s k s w h i c h w e r e m a i n t a i n e d on an o r b i t a l s h a k e r (180

Ehrlenmeyer of

coffeaeformis

uE

under continuous irradiance a t m-*s-'

.

After

24h,

a

biocidal

photon f l u x density solutions

were

57 added

to

give

the

desired concentrations.

Four r e p l i c a t e s per

treatment were used. Stock made

up

4OC.

solutions at

xl000

o f TBTO ( A l d r i c h C h e m i c a l s ) i n e t h a n o l w e r e f i n a l c o n c e n t r a t i o n and s t o r e d i n t h e dark a t

C o n t r o l s c o n t a i n e d 0.1% e t h a n o l .

(Cyanamid)

and

Chesterfield,

2-DGA

(synthesised

Derbyshire)

concentration

i n

were

ethanol.

Stock by

freshly

Controls

solutions

the

o f 1-DGA

C o a l i t e Group p l c ,

uy a t X l O O O f i n a l

made

contained

0.1%

ethanol,

a l t h o u g h t h i s h a d no e f f e c t o n g r o w t h . Chlorophyll,

concentrations

addition o f biocides. cultures pore

were

size

tubes

filtered

uM,

1.2

sulphoxide

(DMSO)

a

the

cell-free

onto

determined adhering

a

after 10cm3 o f

w h i c h w e r e t h e n i m m e r s e d i n 5 cm3 d i m e t h y l

the

dissolved

1976).

A f t e r l h ( i n darkness)

filters

were v o r t e x e d and l e f t

f u r t h e r 30min t o a l l o w c e l l s t o s e t t l e .

using

96h

cells,

c e l l u l o s e n i t r a t e membrane f i l t e r s

(Shoaf and Lium,

containing

for

were

After dislodging

The absorbances o f

s u p e r n a t a n t s w e r e t h e n d e t e r m i n e d a t 6 3 0 a n d 664nm

LKB U l t r o s p e c

4050

spectrophotometer,

and c h l o r o p h y l l a

concentration determined u s i n g t h e equation o f Holden (1976). means

of

the

The

r e p l i c a t e s were c a l c u l a t e d and t h e standard e r r o r s

a r e shown i n t h e f i g u r e s . 4.3

RESULTS TBTO

diatom

exhibits

A.

coffeaeformis

concentration (Fig.4.la) by

of

i.e.

reduction

relative

pronounced a

total

concentration)

controls.

order

uM ( F i g . 4 . l b ) to

and

1-DGA

s i g n i f i c a n t a l g i c i d a l a c t i o n a g a i n s t A. In

k i l l

i s

against achieved

the at a

I t s L C - 5 0 v a l u e i s a p p r o x i m a t e l y lOOnM

chlorophyll

the

v a l u e s o f 1.25

activity

a t t h i s c o n c e n t r a t i o n t h e gr,owth r a t e ( d e t e r m i n e d i n

to

-and

250nM.

algicidal

a n d 13.0

i s r e d u c e d by 50%, 2-DGA

also

coff.eaeformis,

showed

g i v i n g LC50

uM ( F i g . 4 . l ~ ) r e s p e c t i v e l y .

determine whether synergism i s occurring,

i.e.

whether two b i o c i d e s used t o g e t h e r g i v e an e f f e c t g r e a t e r t h a n t h e sum

of

their

individual effects,

concentrations approximately 1-DGA

25%

(Fig.4.ld)

synergistic giving

which

inhibition. and

i t i s necessary t o use b i o c i d e

individually 2-DGA

cause

not

more

Used a t such c o n c e n t r a t i o n s , (Fig.4.le)

showed

a

e f f e c t w h e n u s e d i n c o m b i n a t i o n w i t h TBTO,

t h e more marked response.

Thus,

f o r example,

than both

pronounced the latter

inhibition of

g r o w t h b y l O n M TBTO o n i t s own i s n o t s i g n i f i c a n t l y d i f f e r e n t f r o m the

control

and

inhibition

by

1.3uM

1-DGA

used

singly i s

58

8 E

9

Y

0

TO

0.

._ 0

76

60

26

DTOl

125

100

150

(nW)

1.5

(b)

r)

E 9

Y

0

-

0.00

h

7

E

1

2

3

4

__. I 5

59

1.4

0.8-

0

10

20

30

40

50

40

50

ITSTO1 (nH)

rr)

E IT

u 0

0

10

20

30

Fig.4.1. The e f f e c t s o f v a r i o u s b i o c i d e s o n c h l o r o p h y l l , l e v e l s in coffeaeformis. ( a ) t r i b u t y l t i n o x i d e (LC 104nM1, ( b ) 1d o d e c y l g u a n i d i n e a c e t a t e (LC 1.25uM), ( c ) 2 5 i o d e c y l g u a n i d i n e a c e t a t e (LC 13.0uM), ( d ) ' ? r i b u t y l t i n o x i d e (A), t r i b u t y l t i n o x i d e + 1.%M 1 - d o d e c y l g u a n i d i n e a c e t a t e (01, ( e l t r i b u t y l t i n o x i d e ( A ) , t r i b u t y l t i n o x i d e + 8.0uM 2 - d o d e c y l g u a n i d i n e a c e t a t e ( 0 ). To= c h l o r o p h y l l c o n c e n t r a t i o n when b i o c i de added. Ethanol c o n t r o l = same a s z e r o TBTO.

60 approximately when

used

some

65%

effect

40%

compared

together

at

(Fig.4.ld).

Using

is

even

more

inhibition

and

used

(Fig.4.le).

However,

two

compounds

(Fig.4.le).

With

the c o n t r o l (Fig.4.ld),

2-DGA

and

singly,

lOnM

used together

at

on

the

2-DGA gave

TBTO

was

of

TBTO t h e s y n e r g i s t i c

8uM

100% i n h i b i t i o n

1-DGA

but

c o n c e n t r a t i o n s t h e y i n h i b i t by

pronounced.

were

concentration

TBTO

with

these

gave

no i n h i b i t i o n

observed these

other

when

the

concentrations

hand

50nM was r e q u i r e d ,

25%

(Fig.4.ld),

with

a

1.3uM 1 - D G A ,

to

g i v e 100% i n h i b i t i o n . 4.4

DISCUSSION

Although

on i t s own ( L C 5 0 1.25uM)

1-DGA

coffeaeformis

than

2-DGA

(LC50

13.0uM),

i s more t o x i c t o A.

the

demonstrate t h a t i n l a b o r a t o r y experiments,

results

i n T B T O c o n c e n t r a t i o n c a n be made ( a b o u t 5 0 - f o l d ) , algicidal and

if

activity,

clearly

the greatest reduction

2-DGA i s p r e s e n t .

without loss o f

I f t h e f l u x o f TBTO

2-DGA c o u l d be m a i n t a i n e d a t s y n e r g i s t i c a l l y e f f e c t i v e l e v e l s t h e b o u n d a r y l a y e r o f an S P C a n t i f o u l i n g p a i n t s y s t e m ,

within tin

level

reduced,

of

the

whilst

paint

still

respect

to

the

control

of

this

could

retaining

fouling

diatom

and/or

in

very

effective

control

coffeaeformis.

A.

the

t h e o r y be c o n s i d e r a b l y with

Whether such

o t h e r f o u l i n g d i a t o m s on p a i n t s u r f a c e s

w o u l d o c c u r i n p r a c t i c e i s n o t known. i s a fungicide w i t h c a t i o n i c surface a c t i v e properties

1-DGA

which

has

pear

since

result

been

from

cell, amines

cell

scab

of

permeability electron

and

apple and

I t s t o x i c i t y appears t o

Sisler

and

transfer.

(1960)

on In

found t h a t

o f v i t a l c e l l u l a r constituents,

vital

enzymes.

and by

Amongst a r a n g e o f o l i g o -

and o l i g o g u a n i d i n e s t e s t e d by S r i v a s t a v a and S m i t h (19821, on

including

higher

betacyanin Hassall

from (1982)

disrupting being

on

Brown

loss

i n

1956.

e f f e c t by a l t e r i n g t h e p e r m e a b i l i t y o f t h e

certain

monoguanidines, effect

toxic

resulting

against

i n

chloroplastic

pastorianus

its

inactivating

effects

and/or

Saccharomyces exerts

particularly

introduction its

mitochondria1 it

used

its

cell

suggested

hydrophobic

plant

1-DGA,

beetroot also

the

causing

most t o x i c i n t h e i r massive

efflux of

d i s c s a n d i o n e f f l u x f r o m swede d i s c s .

reported

membranes, to

were

membranes,

dissolve

that

1-DGA

acts

p r i m a r i l y by

the hydrophilic p a r t o f the molecule in

the

membrane

lipid

and

p a r t t o a l t e r t h e a t t a c h m e n t o f membrane p r o t e i n s .

the In

61

addition

to

altering

guanidines, mitochondria1

systems

also

good

found

octylguanidine) electron

cell

including

permeability,

energy

i n v i t r o (Pressman, evidence

affected

transport

there i s evidence t h a t

inhibit

1-DGA,

in

that

state pea

transfer

1963).

n-dodecylguanidine

3

(ADP

stimulated)

chloroplasts,

and

in

M o t t l e y (1978) (and

n-

non c y c l i c

inhibited

Ca2+-

d e p e n d e n t ATPase a c t i v i t y i n i s o l a t e d c h l o r o p l a s t f r a g m e n t s o f t h e unicellular

green

chloroplasts,

alga

energy

concentrations,

transfer

uncoupling

photophosphorylation inhibition

of

at

electron

The

first

seeds

168,

24

Brit.

Ltd.

pea

at

transport

low from

c o n c e n t r a t i o n s , and d i r e c t

transport

at

relatively

high

1978).

and

1973)

In

occurred

electron

r e c o r d e d u s e o f 2-DGA was i n 1 9 7 3 ,

(Reckitt August

Products

reinhardi.

inhibition of

intermediate

concentrations (Mottley, for

Chlamydomonas

Colman P r o d u c t s L t d .

as a f u n g i c i d e

Brit.

Appl.

73/40,

a n d wood p r e s e r v a t i o n ( R e c k i t t and Colman Appl.

73/40,

169,

24

August 1973).

The

g u a n i d i n e s a l t 2 - g u a n i d i n o d o d e c a n e p h o s p h a t e h a s a 1 s o been u s e d a s a seed f u n g i c i d e ( B r i t . Appl.

73/40,

168 a b o v e ) ,

a s w e l l as i n t h e

c o n t r o l o f f u n g i on p o t a t o a n d t o m a t o ( R e c k i t t and Colman P r o d u c t s Ltd. B r i t . Appl. of

fungal

growth

(Springle, 1973).

(Cl.

activity

D.F.,

recently,

have

been

fungicides 82/29,

relating

to

this

fungi, 73/40,

b a c t e r i a and l i c h e n s

W h e a t l e y C h e m i c a l Co.

S.,

growth

(Fig.lc)

suggest metabolic

1,475,073

so

L t d . GB Appl.

The l i t e r a t u r e i s t h u s c o n f i n e d t o

investigations and

compound.

without

Brit.

137, 24 August 1973).

such as g u a n i d i n o d o d e c a n e a c e t a t e

on

2-DGA a s a f u n g i c i d e i n

t h e r e i s a s y e t no w o r k on t h e mode o f However,

i t i s considered l i k e l y t h a t

effects are not dis-similar of

24 A u g u s t

f o r m u l a t i o n and i m p r o v i n g t h e i r e f f i c i e n c y as

patents,

cellular

p a i n t composition

a l s o recorded as having a wide

against algae,

14 October 1982).

of

stimulation

a

40,305/73,

s o l u b l e by c o m b i n i n g w i t h m e t a l c h e l a t e s ,

their

respect

of

into

B r i t . Appl.

was

guanidinoalkanes

reports action

salt

(Everest-Todd,

425,

D.F.

1 J u n e 1977, A p p l .

rendered

facilitating

incorporated

R e c k i t t a n d Colman P r o d u c t s L t d .

C07 C1 2 9 / 1 2 )

More

its

when

phosphate

of

(Rushman,

166, 24 A u g u s t 1 9 7 3 ) a n d i n t h e i n h i b i t i o n

a n d Rushman,

W.R.

The

spectrum

73/40,

caused

by

low

t o t h o s e o f 1-DGA. concentrations

The

o f 2-DGA

an i n i t i a l i n c r e a s e d p e r m e a b i l i t y t o n u t r i e n t s , damage.

However,

t h e i n h i b i t o r y response on

g r o w t h a b o v e 7 u M c l e a r l y s u g g e s t s c e l l u l a r damage.

62 The the

biocidal

algae,

effects

Mottley

inhibited

o f organotins are well-documented.

(1978)

reported

Ca2+-dependent

chloroplasts,

and

intestinalis

ATPase

activity

i n the multicellular

and

Ulothrix

In

t h a t several t r i o r g a n o t i n s i n

C.

reinhardi

green algae Enteromorpha

p s e u d o f l a c c a M i l l n e r a n d Evans ( 1 9 8 0 )

showed t h a t t r i p h e n y l t i n c h l o r i d e (TPTC) a c t s a s a e n e r g y t r a n s f e r i n h i b i t o r o f both r e s p i r a t i o n and photosynthesis. There

are

many

examples

o f s y n e r g i s m between b i o c i d e s a n d

t h i s has been u s e d t o enhance t h e a c t i o n o f drugs, fungicides 1985). i n

(e.g.

Albert,

1980).

As

use o f a

of

far

a s i s known,

seen

Uptake

essentially

i n of

that

the the

presence

the

to

1978;

Lloyd,

may

present

TPTC

pronounced

the

TPTC

has

concentration.

of

2-DGA

been

of the

energy

to

be

I t c a n t h e r e f o r e be

concentration transfer

Alternatively,

even

w i l l

result

i n

a t ' l o w exogenous

or i n addition to this,

2-

a f f i n i t y f o r TBTO o f t h e s p e c i f i c b i n d i n g

t h y l a k o i d membranes,

possibilities.

of

found

19811, t h e r a t e

a l l o w s m o r e TBTO t o e n t e r t h e c e l l ,

C a 2 + - d e p e n d e n t ATPase a c t i v i t y . these

synergistic

i n v e s t i g a t i o n c a n be s p e c u l a t e d

intracellular

o f TBTO.

increase

i n

the

i n c r e a s e i n membrane p e r m e a b i l i t y r e s u l t i n g

inhibition

concentrations

uptake

Rusch,

t h e r e h a s b e e n no b a s i c s t u d y o n t h e

underlying

the

elevated

enhanced

test

p a i n t s (e.g.

radio-labelled

proportional

sites

a n t i b i o t i c s and

Goss a n d M a r s h a l l ,

a p a s s i v e p r o c e s s ( N i l l n e r a n d Evans,

postulated

OGA

antifungal

mechanisms

responses upon.

from

1977;

t r i o r g a n o t i n a n d 1- o r 2-DGA t o g e t h e r .

The

and

Shadomy,

S y n e r g i s m between b i o c i d e s has a l s o been u s e d t o a d v a n t a g e

formulations

being

1973;

radio-labelled

These TBTO

o r i t s e l f i n h i b i t f o r example

E x p e r i m e n t s a r e now would

by A.

necessary t o

include monitoring the

coffeaeformis c e l l s i n the

p r e s e n c e o f 2-DGA a t d i f f e r e n t c o n c e n t r a t i o n s , a n d i n i t s a b s e n c e ; measurements DGA,

and

leakage o f i o n s from c e l l s i n t h e presence o f 2-

of

d e t a i l e d m e t a b o l i c s t u d y o f t h e e f f e c t s o f 2-DGA + / -

a

TBTO o n t h e r e s p i r a t o r y a n d p h o t o s y n t h e t i c p a t h w a y s . ACKNOWLEDGEMENTS Thanks

are

investigation,

due to

Drs

t o International Paint p l c f o r funding t h i s W.

Harpur,

t h e Company f o r h e l p f u l d i s c u s s i o n s , D r P.

C.

A n d e r s o n a n d R.

Dalley from

leading t o t h i s study,

and t o

N i g h t i n g a l e o f t h e C o a l i t e Group p l c f o r h i s i n v o l v e m e n t a n d

f o r p r o v i d i n g u s w i t h 2-DGA.

63 REFERENCES Albert, A., 1973. S e l e c t i v e t o x i c i t y o f t h e r a p y . Chapman a n d H a l l .

-

the physico-chemical

basis

Blunn, G.W. a n d E v a n s , L.V., 1981. M i c r o s c o p i c a l o b s e r v a t i o n s on Achnanthes s u b s e s s i l i s , with particular reference t o stalk formation. B o t . Mar., 24: 193-199. Brown, I.F. and S i s l e r , H.D.,1960. Mechanisms o f f u n g i t o x i c a c t i o n o f N-Dodecylguanidine acetate. P h y t o p a t h o l o g y , 50: 830-839. Callow, M.E., 1986. A w o r l d - w i d e s u r v e y o f s l i m e f o r m a t i o n on antifouling paints. In: L.V. Evans a n d K.D. Hoagland (Editors), Algal Biofouling. E l s e v i e r , Amsterdam. Callow, M.E. a n d E v a n s , L.V., 1981. Some e f f e c t s o f t r i p h e n y l t i n c h l o r i d e on Achnanthes s u b s e s s i l i s . B o t . Mar., 24: 201-205. Th e d e v e l o p m e n t o f o r g a n o t i n - b a s e d a n t i f o u l i n g E v a n s , C.J., 1 9 7 0 . paints. T i n a n d i t s Uses, 85: 3-7. Evans, L.V., 1981. Marine algae and f o u l i n g : a review w i t h particular reference t o ship-fouling. B o t . Mar., 24: 167171. French, M . S . a n d E v a n s , L.V., 1986. F o u l i n g on p a i n t s c o n t a i n i n g t r i b u t y l t i n w i t h cuprous and z i n c oxides. I n : L.V. E v a n s a n d K.D. Hoagland (Editors), Algal Biofouling. Elsevier, Amsterdam. French, M.S., Evans, L.V. and Dalley, R., 1985. Raft t r i a l In: experiment on leaching from a n t i - f o u l i n g paints. Polymers i n a Marine Environment. T r a n s I Mar E ( C ) , 97, 127-130. and Marshall, W.D., 1985. Synergistic antifungal Goss, V . i n t e r a c t i o n s o f zinc o r copper w i t h anilazine. P e s t i c . Sci., 16: 163-171. Guillard, R.R.L. and Ryther, J.H., 1962. Studies o f marine p l a n k t o n i c d i a t o m s . I. C y c l o t e l l a n a n a H u s t e d t a n d D e t o n u l a c o n f e r v a c e a ( C l e v e ) Gran. Can. J . M i c r o b i o l . , 8 : 2 2 9 - 2 3 9 . 1982. The C h e m i s t r y o f P e s t i c i d e s their H a s s a v Metabolism, Mode o f A c t i o n a n d U s e s i n C r o p P r o t e c t i o n . Macmillan. Holden, M., 1976. In: T.W. Goodwin ( E d i t o r ) , C h e m i s t r y and B i o c h e m i s t r y o f P l a n t P i g m e n t s , V o l . 2, Academic P r e s s . Lewthwaite, J.C., Molland, A.F. a n d Thomas, K.W., 1985. An investigation into the variation o f ship skin frictional resistance with fouling. R o y a l I n s t . N a v a 1 A r c h i t e c t s , 127, 269-284. Lloyd, G., 1980. The n e e d f o r biocides i n aqueous based p a i n t polymer. P a i n t C o l o u r J o u r n a l , 24: 919-920. Millner, P.A. a n d E v a n s , L.V., 1980. ThePffects of triphenyltin c h l o r i d e on r e s p i r a t i o n a n d p h o t o s y n t h e s i s i n t h e green a l g a e Enteromorpha i n t e s t i n a l i s and U l o t h r i x pseudoflacca. Plant, C e l l a n d E n v i r o n m e n t , 3: 3 3 9 - 3 4 8 . L.V., 1981. Uptake o f t r i p h e n y l t i n Millner, P.A. a n d Evans, chloride by Enteromorpha intestinalis and Ulothrix seudoflacca. P l a n t , Ce an E n v i r o n m e n t , 4: 383-38 Mottl-978. S t u d i e l ’ o n d t h e ’ modes o f a c t i o n 9 o f n alkylguanidines a n d t r i o r g a n o t i n s on p h o t o s y n t h e t i c energy conservation i n the pea and the u n i c e l l u l a r alga Chlamydomonas r e i n h a r d i Dangeard. P e s t i c i d e Biochem. and P h y s l o l . , 9: 340-350.

. .,

-

.

64 Pressman, B.C., 1963. The e f f e c t s o f g u a n i d i n e a n d a l k y l g u a n i d i n e on t h e e n e r g y t r a n s f e r r e a c t i o n s o f m i t o c h o n d r i a . J. Biol. Chem., 2 3 8 : 4 0 1 - 4 0 9 . Rusch, T.E., 1978. Improving antimicrobial protection w i t h the co-biocide technique. American P a i n t and Coatings J o u r n a l C o n v e n t i o n D a i l y , p. 3435. Shadomy, S., 1977. I n v i t r o a n d i n v i v o s t u d i e s on s y n g e r g i s t i c C o n t r i b . M i c r o b i o l . Immunol., 4 : 147a n t i funga 1 a c t i v j ty. 157. T.W. and Lium, B.S., 1976. Improved e x t r a c t i o n o f Shoaf, chlorophyll a and b from algae u s i n g dimethyl sulphoxide. L i m n o l . Oceanogr., 21: 926-928. S.K. and Smith, T.A., 1982. T h e e f f e c t o f some Srivastava, o l i g o a m i n e s a n d g u a n i d i n e s on membrane p e r m e a b i l i t y i n h i g h e r plants. P h y t o c h e m i s t r y , 21: 997-1008.

65

5

Chapter

CELL ATTACHMENT M E C H A N I S M S I N THE FLAGELLATE,

RUTH L. WILLEY AND JENNIFER

G.

C O L A C I U M (EUGLENOPHYCEAE)

GIANCARLO

Department o f B i o l o g i c a l Sciences (m/c 066). PO Box 4348, Chicago. I L 60680

5.1

U n i v e r s i t y o f I l l i n o i s a t Chicago,

INTRODUCTION Fouling

i s the o p p o r t u n i s t i c

colonization

systems o f a man-made o r man-provided man's

resulting

determined

be

w i l l

economic

substrate,

and

the

biotic/abiotic

d u r i n g and a f t e r c o l o n i s t focus

involved

in

the

attachment.

study

of

interests.

by

a v a i l a b i l i t y and d i v e r s i t y o f c o l o n i s t s , the

s e s s i l e organisms

in

aquatic

s u b s t r a t e w i t h subsequent succession i n t o

a c o r n u n i t y which may a f f e c t cornunity

by

the

The c h a r a c t e r

nature

of

the

of

the

substrate,

the

the e f f i c i e n c y o f t h e i r events

attachment t o

( o f t e n man-directed)

occurring

I f we can s e t a s i d e t h e a n t h r o p o c e n t r i c

fouling,

we

w i l l

see

that

the

process

and

problems i n v o l v e d a r e n o t u n l i k e t h o s e e x p e r i e n c e d b y a s u b s t r a t e organism r e l a t i o n t o an e p i b i o n t . is

the

fouling

The h o s t p r o v i d e s a s u b s t r a t e s u r f a c e and t h e e p i b i o n t

colonist.

The

organisms,

such

predator

avoidance,

maintenance

interests.

and

just

nutrients

and

simpler

aquatic

and

another the

mutual ism

or of

or may

parasitism). a ship

epibiosis can

in

position

of

will

one

attachment

be

it

may

In

be

the

-

movements

into

epibiosis. a wharf

to

small,

severe

motile

i n terms o f

water

colunn

namely t h e i r

(for

economic

t h e s u b s t r a t e organism may

r e p r e s e n t , an

coevolve

bottom o r

represented by a s i n g l e species.

dispersal,

of

respiratory

surface,

association

than t h a t

cornunity

of

arthropods,

From t h e p o i n t o f v i e w o f t h e e p i b i o n t .

represent

(e.g.,

feeding

as

consequences

substrate

zooplankton),

in

a

important

highly

source o f

integrated

the

resulting

piling.

In

system

cornunity

fact,

it

may

is be

However, we can assume t h a t even t h i s reduced

controlled

mechanisms,

by

the

maintenance,

same

parameters

of

colonist

r e p r o d u c t i o n and e x t i n c t i o n ,

as

p e r t a i n s t o f o u l ing conmunities. Euglenoid f l a g e l l a t e s o f t h e genus Colacium Ehrenberg a r e t y p i c a l l y e p i b i o n t s on freshwater

arthropods.

as a determinant

o f attachment

--

Colacium l i b e l l a e Rosowski larvae,

readily

We have become i n t e r e s t e d

respond,

success as w e l l

C Willey.

in

as h o s t

n o r m a l l y found

culture,

to

i n t h e attachment selectivity.

process Cells of

i n t h e h i n d g u t s o f odonate

artificial

substrate

surfaces.

L a b o r a t o r y o b s e r v a t i o n s have determined t h a t t h e y have e f f i c i e n t a d a p t a t i o n s f o r establishing,

maintaining,

and b r e a k i n g c o n t a c t w i t h t h e i r

s u b s t r a t e organisms

66

( K i l l e n e t al.. Colacium

1984).

and

involved.

an

Studies

understanding

of

We p r e s e n t t h e b e h a v i o r a l sequence o f c e l l attachment

histochemical of

the

analysis

Colacium

attachment

of

should

the

several

contribute

mechanisms o f

bridging

significantly

flagellated

in

polymers to

organisms.

the

some o f

w h i c h a r e found as e a r l y stages i n t h e development o f f o u l i n g c o m n u n i t i e s .

5.2

MATERIALS

5.2.1

AND METHODS

C u l t u r e o f algae

Monoalgal c u l t u r e s o f Colacium l i b e l l a e (Rosowski c l o n e number glass

Petri

Alga-Gro

1 5 (W-15)

and

Peshtigo clone

dishes

containing

(Carolina

Biological

nmber

soil-water-pea Supply,

and W i l l e y .

1 (P-1).

extract

B u r l ington.

1964)

Carolina,

on a

were o r i g i n a l l y

14:lO

hr

(day:night)

cycle.

f r o m ponds a t t h e Warren Dunes S t a t e Park, Warren, damselfly

1983 f r o m a Peshtigo.

U.S.A..

L i g h t microscope p r e p a r a t i o n s

Whole mount p r e p a r a t i o n s were made b y p l a c i n g a d r o p o f clean

coverslip

for

o l d ( n e a r t h e end o f

used were:

7.2:

or

Warrington.

c u l t u r e on a

1984).

The c u l t u r e s used were

6

to

7

days

l o g phase g r o w t h ) and t h e p r e p a r a t i o n s were t i m e d so t h a t

t h e c e l l s would be observed o r Fixatives

cell

30 m i n u t e s t o e n s u r e t h e presence o f a l l

approximately

a t t a c h m e n t stages ( s e e K i l l e n e t a l . .

and

U.S.A.).

larvae obtained

M i c h i g a n . and i n

l a r v a o b t a i n e d from a sand q u a r r y on t h e s o u t h e r n edge o f

Wisconsin,

5.2.2

in 10%

Specimens used i n t h i s s t u d y

i n 1972 f r o m t h e h i n d g u t o f d a m s e l f l y

isolated

with

under a 1000

C u l t u r e s were m a i n t a i n e d a t room t e m p e r a t u r e ( a p p r o x i m a t e l y 25'C) lux Gro-light

Warren

were m a i n t a i n e d

(Starr, North

1975).

fixed

at

approximately

1400 h o u r s (0800

CT).

4% g l u t a r a l d e h y d e (GA) i n 0.1M c a c o d y l a t e b u f f e r , pH 6.5

a mixture

GA

of

Pennsylvania,

plus

U.S.A.)

1% a l c i a n after

blue

Edgar

8GX

and

(AB)

(Polysciences.

Pickett-Heaps

(1982).

P r e p a r a t i o n s were s t a i n e d

i n v a r i o u s combinations w i t h t h e p e r i o d i c a c i d - S c h i f f

procedure

et

1968). agents However.

(PAS)

(Willey

al..

1977) and 1% AB

A c e t i c - a n i l i n e and sodium b o r o h y d r i d e for

t h e PAS r e a c t i o n

since non-specific

t h e s e b l o c k i n g agents

were

t o mask aldehydes staining

turned

was d i s c o n t i n u e d .

in

3 % a c e t i c a c i d (Pearse.

used

mounting

in

r e s i n caused a severe

t o be n e g l i g i b l e ,

Control

reduction

p r e p a r a t i o n s were r o u t i n e l y mounted d i r e c t l y w i t h Dow-Corning o f 1.533

Silicone O i l

( Z u g i b e and F i n k .

#7lO.

1966).

as b l o c k i n g

r e s u l t i n g from f i x a t i o n

out

slides

s u b s t i t u t e d d i s t i l l e d water f o r t h e p e r i o d a t e o x i d a t i o n . and

initially

after

i n A6

for

the

i n GA. use o f

t h e PAS r e a c t i o n

Dehydration i n ethanol staining.

washing

Therefore,

i n d i s t i l l e d water

a n o n o r g a n i c medium w i t h a r e f r a c t i v e index C e l l s were p r e p a r e d b o t h a t room t e m p e r a t u r e

and a f t e r b e i n g c h i l l e d i n an i c e b a t h .

67 5.2.3

Enzyme e x t r a c t i o n

Protein content

of

the

attachment

s t r u c t u r e s was assessed by r e d u c t i o n

in

s t a i n a b i l i t y and l o s s o f s t r u c t u r e a f t e r t r e a t m e n t , up t o

36 h o u r s , w i t h t r y p s i n

(Sigma.

and 10 mg/ml)

St.Louis,

tris-maleate Louis,

Missouri.

temperature

A.

Missouri.

buffer

U.S.A.) and

repeatedly.

arrangement,

and

U.S.A.)(O.l in

1.0

pH 8.0 the

mg/ml

in a grid

Hanging

drop

condition

same b u f f e r

pattern

at

and

made,

The c u l t u r e medium was d r a i n e d o f f , and

cell

individual

b u f f e r s o l u t i o n and t h e n w i t h t h e r e q u i s i t e enzyme-buffer

5.2.4

at

St. roan

w i t h approximately

were

recorded

were photographed a t 15 min, 30 min. and 1, 24.

pH 7.0.

60

so i n d i v i d u a l c e l l s c o u l d be

preparations were

i n 0.1M

and w i t h pronase (Sigma,

Covers1 i p s were s p u t t e r - c o a t e d

scored

general

p o s i t i o n s were noted.

mg/ml.

1 mM CaC12 a t (10 mg/ml)

and a t 37°C.

gold/palladium

located

with

nunber,

attachment

replaced f i r s t w i t h solution.

The c e l l s

36 h r i n t e r v a l s .

Scanning e l e c t r o n microscope (SEM) p r e p a r a t i o n s

Drops o f c e l l s were p l a c e d on c o v e r s l i p s c o a t e d w i t h

60 A.

gold/palladiun.

5. 10. 15 and 30 min, most o f t h e c o v e r s l i p s were f l o o d e d w i t h t h e 1% AB 4% G A i n c a c o d y l a t e b u f f e r a t pH 6.5 a t room t e m p e r a t u r e o r a t 4°C. and then i m n e d i a t e l y f l o o d e d w i t h 1% OsO,, i n t h e same b u f f e r f o r 30 m i n i n t h e d a r k

After in

(Edgar and Pickett-Heaps.

1982).

Some c o v e r s l i p

preparations

m i x t u r e o f 2%GA and 0.5% osmium t e t r o x i d e i n 0.05M (Willey,

1984).

point-dried

After

(Bomar

Humner J r . ) .

dehydration

SPC-SO/LX)

Individual

and

cells

in

ethanol,

sputter

were

the

coated

examined

with

were f i x e d

in a

c a c o d y l a t e b u f f e r a t pH 7.2 covers1 i p s

with an

were

12 nm g o l d

IS1

DS-130

critical (Technics

SEM a t

an

a c c e l e r a t i n g v o l t a g e o f 10-20 kV.

5.2.5

T r a n s m i s s i o n e l e c t r o n m i c r o s c o p e (TEM) p r e p a r a t i o n s

C e l l s f o r TEM e x a m i n a t i o n were f i x e d i n e i t h e r o f t h e two f i x a t i v e s f o r SEM. p e l l e t i z e d by c e n t r i f u g a t i o n . embedded i n BSA,

and processed a c c o r d i n g t o W i l l e y

(1984).

5.3

RESULTS C e l l s o f Colacium l i b e l l a e f o l l o w a b a s i c a t t a c h m e n t p r o c e s s i n v o l v i n g : ( 1 ) a

l o n g range t r a n s l o c a t i o n ( m i g r a t i o n i n t o t h e immediate v i c i n i t y o f t h e s u b s t r a t e organism).

( 2 ) a subsequent

short

subsequent o r i e n t a t i o n t o t h e h o s t

range t r a n s l o c a t i o n surface).

to

and

( 3 ) i n i t i a l surface contact,

(swimming c l o s e

and

( 4 ) a permanent (more t h a n 24 h r s ) a t t a c h m e n t m e d i a t e d b y a f l e x i b l e s t a l k ( F i g . 5.1).

Our

observations

presented

here

focus

on

the

last

two

parts o f

the

process which a r e s p e c i f i c a l l y a s s o c i a t e d w i t h b r i d g i n g polymer f o r m a t i o n . C e l l s undergoing

attachment,

when c l o s e t o t h e s u b s t r a t e ,

t h e i r swimming p a t t e r n s so t h a t t h e y s p i r a l end v e r y c l o s e t o t h e s u r f a c e .

rapidly

a b r u p t l y change

i n place with the anterior

The f l a g e l l u n appears t o b e c o i l e d

c e l l , and g e n e r a t e s a s p i n n i n g movement w h i c h may l a s t s e v e r a l seconds. c o n t a c t o c c u r s when t h e s p i r a l maneuver a b r u p t l y ceases.

about t h e Initial

The flagellun.becomes

F i g . 5.1. Diagrammatic r e p r e s e n t a t i o n o f t h e b a s i c attachment process o f Colacium i n v o l v i n g : ( 1 ) s h o r t range t r a n s l o c a t i o n , ( 2 ) o r i e n t a t i o n and i n i t i a l c o n t a c t w i t h t h e f o r m a t i o n o f t h e AD, ( 3 ) o r i e n t a t i o n o f t h e a n t e r i o r p o l e o f t h e a t t a c h e d c e l l s towards t h e s u b s t r a t e accompanied by u n c o o r d i n a t e d movements o f the flagellum, ( 4 ) resorption o f the flagellum, and ( 5 ) f o r m a t i o n and elongation o f the stalk. D u r i n g i n i t i a l c o n t a c t , c e l l s may o r i e n t normal t o t h e s u r f a c e w i t h a c h a r a c t e r i s t i c , s p i r a l l i n g swimming movement j u s t b e f o r e i n i t i a l c o n t a c t ( 2 a ) o r may swim i n a t an a n g l e t o t h e s u r f a c e and make i n i t i a l c o n t a c t a l o n g t h e s i d e o f t h e c e l l w i t h t h e l a t e r a l AD ( 2 b ) . I n t h e l a t t e r case, t h e c e l l must e s t a b l i s h a second c o n t a c t by i t s a n t e r i o r p o l e w i t h a t e r m i n a l AD b e f o r e t h e subsequent f l a g e l l a r r e s o r p t i o n ( 3 . 4 ) can o c c u r .

u n c o o r d i n a t e d and, over t h e succeeding 20 t o 30 min,

i s resorbed i n t o t h e c e l l .

F u r t h e r d e t a i l s o f t h i s p r o c e s s have been p u b l i s h e d by K i l l e n e t a l .

(1984).

E a r l y s t u d i e s w i t h t h e SEM had d i f f i c u l t y d e m o n s t r a t i n g t h e e x t e n t o f polymer involvement

(see

Killen

p h t h a l o c y a n i n dye. Heaps,

1982)

et

al..

1984).

a l c i a n b l u e 8GX,

provided

excellent

However,

the

images o f ,

b r a n c h and s u b s e q u e n t l y s u p p o r t many c e l l s ( F i g . The AD appears t o be formed by s m a l l pole o f the c e l l .

the p e l l i c u l a r granules

(Fig.

preparations

of

strips. 5.3) chilled

the

w i t h t h e f i x a t i v e ( a f t e r Edgar and P i c k e t t SEM

first,

an adhesion

b r i d g i n g t h e space between t h e c e l l and s u b s t r a t e and,

anterior

incorporation o f

disc

(AD)

next,

a s t a l k which may

polymer

extruded from t h e

5.2).

strands

of

The p o i n t s o f e x t r u s i o n c o i n c i d e w i t h p o r e s between

These p o r e s a r e which

are

cells

for

the

secretion

specialized the

channels

mucocysts.

1 i g h t microscope.

In all

for

biphasic

alcian

stages

of

blue the

e x t r u s i o n p r o c e s s a r e c l e a r l y d e l i n e a t e d f r o m t h e qppearance o f b l u e p r o d u c t i n f o c a l s p o t s ( a t t h e p o r e s ) t o t h e f u l l y formed AD ( F i g . The above d e s c r i b e d p r o c e s s o f c e l l attachment i s t y p i c a l o f a l l populations o f

5.

5.4).

5.1;

(Fig.

l i b e l l a e observed.

s t e p s 1.

However,

v a r i a t i o n o f t h e normal p r o c e d u r e was comnonly observed.

2a.

3-5)

i n c l o n e P-1.

a

The c e l l s f r e q u e n t l y

69

Fig. 5.2. Scanning e l e c t r o n micrographs o f selected stages I n t h e attachment ( a ) I n i t i a l c o n t a c t i s accompanied by t h e e x t r u s i o n o f process o f C. l i b e l l a e . an AD (arrow) which mediates c o n t a c t between t h e a n t e r i o r p o l e o f t h e c e l l and the substrate. Flagellum ( F ) . Scale = 5 pm. ( b ) The f l a g e l l u m ( F ) i s resorbed ( c ) A t t h e end o f t h e r e s o r p t i o n step, a f t e r i n i t i a l contact. Scale = 5 pm. the emergent f l a g e l l u m has been shortened so t h a t i t occurs o n l y i n the ( d ) After f l a g e l l a r resorption, a s t a l k ( S ) i s r e s e r v o i r . Scale = 5 pm. extruded from t h e a n t e r i o r end o f t h e c e l l . When t h e c e l l d i v i d e s . each daughter c e l l continues t o secrete s t a l k m a t e r i a l c r e a t i n g a colony h e l d together by a branched s t a l k system. Scale = 5 pm. ( e ) The AD (arrow) e x h i b i t s strong cohesion and adhesion t o t h e substrate. Adhesive f a i l u r e occurs r e l a t i v e l y e a s i l y a t t h e cell-adhesive i n t e r f a c e . The f l a g e l l u m ( F ) . i n t h i s preparation. maintains c o n t a c t o f t h e c e l l w i t h t h e AD. Scale = 5 pm. ( f ) During processing, c e l l s f r e q u e n t l y break f r e e from t h e AD l e a v i n g f l a g e l l u m ( F ) and AD attached t o t h e substrate. Scale = 2 pm.

swim s t r a i g h t toward t h e s u b s t r a t e surface a t a low angle w i t h o u t u t i l i z i n g the s p i r a l maneuver ( F i g . the side.

rather

5.1;

steps 1. 2b,

than the a n t e r i o r end,

3-5).

They make i n i t i a l attachment by

o f the c e l l

-

a "pancake"

landing.

Observations w i t h t h e SEM revealed pores located over t h e p e l l i c u l a r surface i n

70

F i g . 5.3. The AD i s e x t r u d e d from t h e a n t e r i o r end o f t h e c e l l . ( a ) Strands o f polymer ( a r r o w s ) extend from t h e p e l l i c u l a r s u r f a c e t o t h e AD i n t h i s p r e p a r a t i o n i n which t h e c e l l i s o n l y s l i g h t l y d i s t u r b e d b y p r o c e s s i n g . C e l l (C). f l a g e l l u m ( F ) . Scale = 2 vm. ( b ) Pores i n t h e p e l l i c l e o f t h e a n t e r i o r end o f t h e c e l l appear t o s e c r e t e polymer ( a r r o w ) w h i c h w i l l form t h e AD. S c a l e = 0.5 pm. ( c ) B i p h a s i c g r a n u l e s ( G ) l i e d i r e c t l y under t h e p e l l i c l e ( P ) a t t h e a n t e r i o r pole o f the c e l l . T u b u l a r e x t e n s i o n s from t h e g r a n u l e s c o i n c i d e w i t h t h e p e l l i c u l a r p o r e s ( a r r o w ) . Scale = 0.5 pm.

ADHESION DISC FORMING

F i g . 5.4. The A D ( a r r o w s ) i s formed by a l c i a n b l u e - s t a i n i n g f r o m t h e a n t e r i o r p e l 1 i c u l a r pores.

addition t o the anterior pores are the

somewhat

same c e l l

different

(Fig.

end.

different

5.5).

Subpell i c u l a r

mucocysts

ultrastructurally

The p r o d u c t

p a t t e r n and c h a r a c t e r i s t i c a l l y

within

from the

m a t e r i a l extruded

associated

w i t h these

t h e biphasic granules

in

g r a n u l e has a

distinctly

i s much more o s m i o p h i l i c .

In c l o n e s

71 TABLE 5.1 Qualitative results of - = negative reaction).

histochemical

(+

reactions

=

positive

reaction;

S t a i n Reaction AB PAS

B r i d g i n g Polymer

Source

AD ( a n t e r i o r ) AD (lateral) s t a l k - core - periphery

biphasic granules p e l 1 i c u l a r mucocysts reservoir b i p h a s i c granules

+++ +++

-

- (?I +++ +

+ +++

F i g . 5.5. C e l l s i n c l o n e P-1 o f 5. l i b e l l a e can make t h e i n i t i a l c o n t a c t b y t h e side o f the c e l l . ( a ) The c e l l on t h e l e f t ( C l ) has a t t a c h e d by a l a t e r a l AD. The s p h e r i c a l mass o f a n t e r i o r AD m a t e r i a l ( a r r o w ) may have been e x t r u d e d i n response t o t h e f i x a t i v e . Each c e l l must, however, e s t a b l i s h c o n t a c t b y t h e a n t e r i o r AD b e f o r e t h e attachment p r o c e s s can proceed (C2). S c a l e = 10 pm. ( b ) C e l l s which a r e c a p a b l e o f l a t e r a l i n i t i a l c o n t a c t e x h i b i t p e l l i c u l a r p o r e s ( a r r o w ) a l o n g t h e s i d e as w e l l as t h e a n t e r i o r end o f t h e c e l l . The image on t h e r i g h t i s a 5 X m a g n i f i e d v i e w o f t h e a r e a boxed i n t h e c e l l image on t h e ( c ) M u c o c y s t - l i k e g r a n u l e s (M) l i e under t h e l a t e r a l l e f t . S c a l e = 10 pm. p e l l i c u l a r p o r e s ( a r r o w ) and, l i k e t h e b i p h a s i c g r a n u l e s , a r e a t t a c h e d by t u b u l a r e x t e n s i o n s ( a r r o w ) . S c a l e = 1 pm.

i n which

the

cells

primarily

mucocysts a r e r a r e l y observed. t h e c e l l s have t o , cell

and

its

AD

3

the

spiral

maneuver,

the

pellicular

Regardless o f t h e t y p e o f approach ( 2 a o r b ) .

ultimately. (step

utilize

in

e s t a b l i s h contact by t h e a n t e r i o r Fig.

5.1).

Only

then

do

the

pole o f

cells

the

initiate

f l a g e l l a r r e s o r p t i o n and complete t h e attachment process. The AD and t h e s t a l k e x h i b i t e d s t a i n s ( T a b l e 5.1).

The adhesion

dark b l u e w i t h a l c i a n b l u e i f Fixation without

alcian

a strong

discs,

r e a c t i o n s w i t h the histochemical

f r o m b o t h t y p e s o f mucocyst.

it i s incorporated

i n the f i x a t i v e

(Fig.

stain 5.6).

b l u e d i d n o t r e t a i n s u f f i c i e n t polymer t o r e a c t w i t h

subsequent s t a i n procedures. gives

different

Alcian blue also reacts with the stalk,

reaction w i t h the peripheral

part

but only

( t h e I t c o r t e x t ' o f Ward and

72

F i g . 5.6. Attachment b y C. l i b e l l a e i n v o l v e s two d i f f e r e n t polymers. ( a ) The adhesion d i s c s (a rro ws) s t a i n i n t e n s e l y w i t h a l c i a n blue. These c e l l s were exposed f o r 36 h r s t o t h e t r i s - m a l e a t e b u f f e r used as a c o n t r o l f o r t h e t r y p s i n ( b ) The s t a l k r e a c t s s t r o n g l y w i t h a l c i a n b l u e on extraction. S c a l e = 10 pm. i t s p e r i p h e r y ( a r r o w h e a d s ) and w i t h PAS i n i t s c e n t r a l c o r e ( a r r o w s ) . The alcianophilic material ( A ) around t h e c e l l c a n a l p r o b a b l y r e p r e s e n t s AD m a t e r i a l w h i c h c o n t i n u e s t o be s e c r e t e d d u r i n g s t a l k f o r m a t i o n . Note t h a t t h e A B - s t a i n i n g p a t c h e s o f t h e s t a l k p e r i p h e r y a r e l a r g e s t c l o s e s t t o t h e c e l l and a r e s m a l l e r ( o l d e r ) f a r t h e r away f r o m t h e c e l l . The A B - s t a i n i n g m a t e r i a l appears t o d i s s o l v e more r a p i d l y t h a n t h a t o f t h e s t a l k c o r e . S c a l e = 10 p m . ( c ) C r o s s - s e c t i o n o f a s t a l k f i x e d w i t h 1% AB i n GA f o l l o w e d by OsOb d e l i n e a t e s t h e p e r i p h e r a l a l c i a n o p h i l i a ( a r r o w ) and t h e c o r e p a r t w h i c h r e a c t s w i t h PAS (C). Note t h e r a d i a t i n g p a t t e r n o f dense f i b r i l l a r m a t e r i a l i n t h e c o r e w h i c h c o r r e s p o n d s t o t h e p a t t e r n o f s t r i p s f o r m i n g t h e p e l l i c l e around t h e c a n a l . ( d ) The s t a l k s t a i n e d w i t h P A S r e a c t s most i n t e n s e l y i n t h e c o r e S c a l e = 1 pm. ( a r r o w ) whereas t h e p e r i p h e r a l p o r t i o n ( a r r o w h e a d ) r e a c t s o n l y s l i g h t l y . The a l s o c o n t a i n s PAS-reacting m a t e r i a l . S c a l e = 10 pm. r e s e r v o i r (::)

73

Fig. 5.7. Graphic r e p r e s e n t a t i o n o f the response o f c e l l body, AD, enzyme degradation w i t h t r y p s i n . Pronase gives s i m i l a r r e s u l t s .

and s t a l k t o

1981) and w i t h f r e s h l y formed s t a l k d i r e c t l y around t h e canal opening.

Willey.

The peripheral

p a r t i s s t r u c t u r a l l y d i s t i n c t from t h e r e s t o f t h e s t a l k .

c e n t r a l p o r t i o n o f the s t a l k c h a r a c t e r i s t i c a l l y r e a c t s w i t h PAS ( F i g . 5.6). observed

no

reaction

staining material

of

the

AD w i t h PAS,

b u t we

f r e q u e n t l y observed

i s summarized

The r e s u l t s w i t h pronase a r e e s s e n t i a l l y t h e same.

resistant

to

We red

i n the r e s e r v o i r .

E x t r a c t i o n o f whole mount preparations w i t h t r y p s i n

5.7.

The

these

digested away ( F i g .

proteases

5.8).

under

conditions

i n which

i n Fig.

The AD and s t a l k are t h e whole

cell

is

74

F i g . 5.8. The s t a l k and AD a r e r e s i s t a n t t o p r o t e a s e d i g e s t i o n . ( a ) A f t e r 36 h r exposure t o 10 mg/ml t r y p s i n . t h e c e l l s have d i s i n t e g r a t e d l e a v i n g b e h i n d o n l y t h e s t a l k ( s t a i n e d w i t h AB) w i t h i t s p e r i p h e r y ( a r r o w h e a d ) and c o r e ( b ) A f t e r 3 3 h r exposure t o 10 ( a r r o w ) s t r u c t u r a l l y i n t a c t . S c a l e = 10 urn. mg/ml pronase. t h e A D ( a r r o w h e a d ) and s t a l k ( a r r o w ) a r e s t r u c t u r a l l y i n t a c t . C o n t r o l c e l l s a r e i l l u s t r a t e d i n F i g . 5.6. S c a l e = 20'pm.

5.4

DISCUSSION The g e n e r a l p a t t e r n o f a t t a c h m e n t b y c e l l s o f Colacium i s n o t unique.

same

general

patterns of attachment Christie. of

steps

have been o u t l i n e d

parasites (Whitfield, by

Characium

and

1970: Lee and Bold,

attachment

the

for

1979)

as

the association-specific

behavior

in

zoospore

well

ship-foul ing

1974).

The

as.

alga,

part,

for

Enteromorpha (Evans and

Perhaps t h e most c o m p l e t e i n v e s t i g a t i o n s

have focussed on b a c t e r i a ( s e e M a r s h a l l ,

1984) and most o f t h e

t h e o r e t i c a l work has been c a r r i e d o u t on t h i s l a t t e r system. Organisms as s m a l l as Colacium have a v e r y s m a l l Reynolds number ( G i t t e l s o n . 1974).

They w i l l

be a f f e c t e d by hydrodynamic and e l e c t r o s t a t i c

s u b s t r a t e ' s boundary l a y e r .

R e l a t i v e l y l i t t l e i s known o f t h e e f f e c t o f t h e s e

f o r c e s on e u k a r y o t i c

flagellates

(see Charters e t al..

1973).

spiralling

and/or

pancake

Colacium

behavior

response t o a t u r b u l e n t organism.

forces a t the

the

landings

of

Presumably t h e are

both

in

boundary l a y e r on t h e s u r f a c e o f an a c t i v e s u b s t r a t e

Why some c l o n e s s h o u l d e x h i b i t two methods o f p e n e t r a t i n g t h i s l a y e r

and o t h e r c l o n e s have o n l y one c a n n o t be e x p l a i n e d w i t h t h e e x i s t i n g d a t a . The c e l l s o f C o l a c i u m make i n i t i a l c o n t a c t w i t h t h e p e l l i c u l a r the anterior located. with

the

surface a t

p o l e o f t h e c e l l even though t h e emergent f l a g e l l u m i s a n t e r i o r l y

This behavior d i f f e r s from f l a g e l l a t e d c e l l s which i n i t i a t e c o n t a c t flagellum

substrate

surface

tomentosa;

Toth.

itself.

These

during

flagellar

1976).

remain

latter

cells

resorption

attached

by

may

(e.g.. the

then

be

drawn

zoospores

flagellum

of

itself

to

the

Chorda (e.g..

75 Trypanosoma flagellar 1984).

%: Vickerrnan, 1973).

surface

However,

glycoprotein

on t h e o t h e r hand, clear

However,

how

poles.

the

fouling

Evans and C h r i s t i e .

alga,

Enteromorpha.

a1 so

which

makes

undergo

It i s

1974).

initial

attachment.

i t appears l i k e l y t h a t t h e

s p i r a l 1 ing

the

well

known

approach

(see

c o n t a c t by one o r more t y p e s o f b r i d g i n g

i n microbial

systems

(Sutherland.

t y p e s o f polymers appear t o m e d i a t e t h e attachment

1972).

attach

1970). a l s o a t t a c h d i r e c t l y b y t h e a n t e r i o r c e l l surface.

The maintenance o f c e l l - s u b s t r a t e

viscosity

l i k e Colacium.

The zoospores o f Pseudocharacium americanurn.

and n o t of Pseudocharacium,

Enteromorpha.

is

t h e zoospores,

and Workman,

swirming which i s o r i e n t e d p e r p e n d i c u l a r t o t h e surface

i s t y p i c a l o f Characium,

polymers

Bloodgood

a t t a c h b y t h e i r f l a g e l l a r t i p s ( L e e and Bold,

since s p i r a l

zoospores of

Chlamydornonas;

i n s p e c i e s o f Characium,

d i r e c t l y by t h e i r a n t e r i o r

not

o r g l i d e a l o n g t h e s u r f a c e mediated b y a

(e.g..

1983).

-

process

an

TWO b a s i c initial.

low

( S t e f a n ) a d h e s i v e and a subsequent, more permanent a d h e s i v e ( C r i s p ,

In algal cells,

polysaccharide-protein character o f the

t h e a d h e s i v e polymers have been shown g e n e r a l l y t o be complexes ( C h a m b e r l a i n ,

polymer

at

different

1976).

stages

Differences

i n t h e attachment

i n physical p r o c e s s have

been a t t r i b u t e d t o t h e chemical t r a n s f o r m a t i o n o f t h e e x t e r n a l i z e d polymer over t i m e (e.g.. two

Enteromorpha zoospores:

separate

Colacium

polymers

appear

separately.

to

have

AD

The

C h r i s t i e e t al.,

(e.g.,

zygotes;

the

secreted

ability by

the

to

1970). o r t h e s e c r e t i o n o f

Rrsten.

1975).

externalize

biphasic

The

different

granules

is

cells

of

compounds

histochemically

d i s t i n c t from t h e c o r e o f t h e s t a l k which appears t o be e x t r u d e d t h r o u g h t h e canal from t h e r e s e r v o i r ( s e e F i g .

5.6).

The l a t e r a l AD a s s o c i a t e d w i t h t h e p e l l i c u l a r mucocysts o f c l o n e P-1 strongly

AB

with

just

as

does

the

u l t r a s t r u c t u r a l l y and p o s i t i o n a l l y d i s t i n c t the

possibility

distinct, often

that

polymer.

associated

they

and,

The

therefore,

slime

i n general,

trails

and

also

reacts

granules

we cannot

a l s o may p r o v e t o e x t r u d e a t h i r d ,

Euglenoids, with

AD.

anterior

ignore

biochemically

s e c r e t e a m u c i l a g e which

euglenoid

movement

channels o f t h e ER - t h e m u c i f e r o u s b o d i e s ( L e e d a l e ,

1967).

are

is

from s p e c i a l i z e d M u c i f e r o u s body

p r o d u c t does n o t y e t appear t o have a r o l e i n attachment o f Colacium.

However,

i t s p o s s i b l e r o l e i n attachment, p a r t i c u l a r l y i n r e l a t i o n t o g l i d i n g behavior, cannot be t o t a l l y

disregarded

the

producing

potential

organellar

of

routes.

Such

either.

four

Therefore,

separate

biosynthetic

t h e c e l l s o f Colacium have

compounds

d i v e r s i t y may

through

four

different

have c o n t r i b u t e d t o t h e

success o f t h e s e c e l l s i n a t t a c h i n g t o a c t i v e , moving s u b s t r a t e organisms such as f r e s h w a t e r a r t h r o p o d s . The r e a c t i o n s o f t h e A D and s t a l k w i t h AB and PAS s t r o n g l y polysaccharide

component

(Pearse,

1968).

6.5 because i t had t o be i n c o r p o r a t e d

However,

i n the

i n d i c a t e a major

t h e AB was b u f f e r e d a t pH

fixative.

Polyanions

reacting

76 w i t h AB a t t h i s pH c o u l d be s u l f a t e o r c a r b o x y l a t e f o r m s o f a c i d p o l y s a c c h a r i d e or

could

be

Therefore,

t h e carboxyl

enzymatic

pronase was but

also

the

of

aminoacids the

i n determining

polysaccharide

Both

of

extraction

important

polymers.

groups

trypsin

or

and

(Behnke and Z e l a n d e r .

bridging

polymers

n o t o n l y t h e general

proteinaceous'

pronase

had

if

trypsin

of

the

any,

AB-reacting

effect

on

structural

i n t e g r i t y o r s t a i n r e a c t i v i t y o f t h e s t a l k o r t h e AD ( s e e F i g s .

5.8).

therefore,

We,

polysaccharide

in

presume t h a t t h e s e two polymers,

composition.

We

have

no

and

presence o f p r o t e i n

identity

little.

with

1970).

the

5.7.

a t least, are primarily

comparable

observations

on

the

l a t e r a l A D o r t h e m u c i f e r o u s body p r o d u c t . We propose t h a t t h e p o l y a n i o n i c AD ( e i t h e r a n t e r i o r o r l a t e r a l ) r e p r e s e n t s a rapidly

extruded

which "tacks"

polymer

of

relatively

effectively

high

solubility

the c e l l t o i t s substrate during the

The m a j o r s t a l k m a t e r i a l of

relatively

high

i s primarily a neutral

flexibility.

maintains

tensile

adhesion

of

initial

cell

step

adhesive)

i n attachment.

polysaccharide (PAS-reactive)

strength

the

( a Stefan

and

to

low

actively

solubility. moving

It

substrate

The c o r t i c a l s t a l k m a t e r i a l which r e a c t s s t r o n g l y w i t h A B p r o b a b l y

organisms.

r e p r e s e n t s A D m a t e r i a l which c o n t i n u e s t o be s e c r e t e d b y t h e b i p h a s i c g r a n u l e s during

s t a l k elongation.

Whether

these

polyanions

contribute

i n any way t o

s t a l k c h a r a c t e r i s t i c s i s unknown. Most a l g a l

adhesives s t u d i e d

complexes

of

considerable

channeled

through

- -calvum.

I n C.

1976).

o r i g i n (Willey. by

the

Golgi

Golgi

shown t o be p o l y s a c c h a r i d e - p r o t e i n

with

apparatus

some

(Christie

t h e b i p h a s i c granules,

1984).

vesicles

have been

variability

also,

part et

(unpublished

observations).

The G o l g i

two

o f polymer appear

steps

of

relatively

-

diverse

of

diverse

orientation,

u t i l i z i n g a b r i d g i n g polymer. are

with

However,

there

different initial

appear

to

even w i t h i n

be:

(1)

two

i n i t i a l a d h e s i v e systems,

and permanent c o n t a c t .

attached,

to

diversity

of

the

active.

approaches

r i g o r o u s circumstances

under

cells

are

the

same c e l l

system.

Colacium r e f l e c t s different

and

approach

The a t t a c h m e n t

this versatility mechanisms.

in

( 2 ) two

( 3 ) two d i f f e r e n t t y p e s o f a d h e s i v e f o r

surfaces

polymers which

probably

i n i t i a l and permanent attachment

The c e l l s o f C o l a c i u m must a t t a c h ,

moving and

flagellated

t h e mechanisms f o r each o f t h e s e s t e p s

mechanisms o f t h e f l a g e l l a t e d c e l l s o f that

Colacium c e l l s ,

Components o f a t l e a s t

1973).

attachment

- approach,

similar

of

in part,

t o be produced a t d i f f e r e n t t i m e s o r by s e p a r a t e

i n E c t o c a r p u s ( B a k e r and Evans,

quite

Chamberlain.

A s i m i l a r v e r s a t i l i t y has been suggested f o r G o l g i f u n c t i o n

Golgi organelles.

basic

biosynthesis

have been a t t r i b u t e d a G o l g i

e x h i b i t s considerable synthetic v e r s a t i l i t y .

The

their 1970;

The l a t e r a l mucocysts may p r o v e t o be formed,

therefore, types

of

al.,

of

may

their reflect

attachment

must

substrate the be

and remain

organisms.

adaptations achieved.

The

to

The

the

basic

77 b e h a v i o r p a t t e r n appears t o be p r e d i c t a b l e , that

it

(biotic Colacium that

can

manipulated.

and

abiotic)

which

Therefore,

l i b e l l a e by d e t e r m i n i n g what

some o f

our

findings

we

contribute

w i l l

however, are

to

and we have some e v i d e n c e

exploring

attachment

the

various

success

of

f a c t o r s a l t e r t h e i r behavior.

contribute

to

the

understanding

factors

cells

of

of

We hope fouling

systems.

REFERENCES Baker, J.R.J. and Evans, L.V.. 1973. The s h i p f o u l i n g a l g a E c t o c a r p u s . I . U l t r a s t r u c t u r e and c y t o c h e m i s t r y o f p l u r i l o c u l a r r e p r o d u c t i v e stages. P r o t o p l asma, 77: 1-1 3. Behnke, 0. and Z e l a n d e r . 0.. 1970. P r e s e r v a t i o n o f i n t e r c e l l u l a r substances b y t h e c a t i o n i c dye a l c i a n b l u e i n p r e p a r a t i v e p r o c e d u r e s f o r e l e c t r o n m i c r o s c o p y . J. U l t r a s t r . Res.. 31: 424-438. Bloodgood. R.A. and Workman, L.J., 1984. A f l a g e l l a r s u r f a c e g l y c o p r o t e i n mediating c e l l - s u b s t r a t e i n t e r a c t i o n i n Chlamydomonas. C e l l M o t i l i t y , 4:

77-87.

B r s t e n , T., 1975. O b s e r v a t i o n s on mechanisms o f a t t a c h m e n t i n t h e green a l g a U l v a m u t a b i l i s Foyn. P r o t o p l a s m a , 84: 161-173. Chamberlain, A.H.L., 1976. A l g a l s e t t l e m e n t and s e c r e t i o n o f a d h e s i v e Kaplan ( E d i t o r s ) . Proc. Third materials. In: J.M. S h a r p l e y and A.M. I n t e r n a t i o n a l B i o d e g r a d a t i o n Symposium. A p p l i e d S c i e n c e P u b l i s h e r s L t d . . London, pp. 417-432. C h a r t e r s , A.C., Neushul, M. and Coon, D.. 1973. The e f f e c t o f water m o t i o n on a l g a l s p o r e adhesion. L i m n o l . Oceanogr.. l e : 844-896. C h r i s t i e , A.O., Evans, L.V. and Shaw, M.. 1970. S t u d i e s on t h e s h i p - f o u l i n g I I . The e f f e c t o f c e r t a i n enzymes on t h e adhesion o f a l g a Enteromorpha. zoospores. Ann. Bot.. 34: 467-482. C r i s p , D.J.. 1972. Mechanisms o f adhesion o f f o u l i n g organisms. Proc. 3 r d I n t e r n a t i o n a l Congress o f M a r i n e C o r r o s i o n and F o u l i n g . N a t i o n a l Bureau o f 691-699. Standards, G a i t h e r s b u r g , MD, U.S.A.: Edgar, L.A. and P i c k e t t - H e a p s , J.D., 1982. U l t r a s t r u c t u r a l l o c a l i z a t i o n o f polysaccharides i n the m o t i l e diatom Navicula cuspidata. Protoplasma. 113:

10-22. Evans, L.V. and C h r i s t i e . A.O.. 1970. S t u d i e s on t h e s h i p - f o u l i n g a l g a Enteromorpha. I . Aspects o f t h e f i n e - s t r u c t u r e and b i o c h e m i s t r y o f swimming and n e w l y s e t t l e d zoospores. Ann. Bot., 34: 451-466. G i t t e l s o n , S.M., 1974. F l a g e l l a r a c t i v i t y and Reynolds number. Trans. Am. M i c r o s c . SOC., 93: 272-276. K i l l e n , R.P.. W i l l e y . R . L . and Durum, F.A., 1984. Docking b e h a v i o r o f Colacium l i b e l l a e (Euglenophyceae): C e l l - s u b s t r a t e adhesion and f l a g e l l a r r e s o r p t i o n . 103: 67-73. Trans. Am. M i c r o s c . SOC., Lee, K.W. and B o l d , H.C., 1974. P h y c o l o g i c a l s t u d i e s . X I I . Characium and some C h a r a c i u r w l i k e a l g a e . Univ. o f Texas P u b l i c a t i o n No. 7403, A u s t i n , Texas. 1967. E u g l e n o i d F l a g e l l a t e s . P r e n t i c e - H a l l . Inc., Englewood L e e d a l e , G.F., C l i f f s , EIJ. 242 pp. (Editor). 1984. M i c r o b i a l Adhesion and A g g r e g a t i o n . Dahlem M a r s h a l l , K.C. 31. S p r i n g e r - V e r l a g , Berlin/ Workshop Life Sciences Research R e p o r t , Heidelberg/Hew York/Tokyo. 423 pp. 1968. H i s t o c h e m i s t r y : T h e o r e t i c a l and A p p l i e d . W i l l i a m s and Pearse. A.G.E.. W i l k i n s , B a l t i m o r e , 759 pp. 1975. C o l a c i u m l i b e l l a e sp. nov. Rosowski. J.R. and Willey. R.L., (Euglenophyceae), a photosynthetic inhabitant o f t h e l a r v a l damselfly 11: 310-315. r e c t u m . J. Phycol.. S t a r r . R.C.. 1964. The c u l t u r e c o l l e c t i o n o f a l g a e a t I n d i a n a U n i v e r s i t y . Amer. J . Bot.. 51: 1013-1044.

S u t h e r l a n d , I.W., 1983. M i c r o b i a l e x o p o l y s a c c h a r i d e s - t h e i r r o l e i n m i c r o b i a l adhesion i n aqueous systems. CRC C r i t i c a l Reviews i n M i c r o b i o l o g y , 10: 173201. T o t h , R.. 1976. The r e l e a s e , s e t t l e m e n t and g e r m i n a t i o n o f zoospores i n Chorda tomentosa (Phaeophyceae. L a m i n a r i a l e s ) . J. Phycol.. 12: 222-233. Vickerman, K., 1973. The mode o f a t t a c h m e n t o f Trypanosoma i n the p r o b o s c i s o f t h e t s e t s e f l y G l o s s i n a f u s c i p e s : an u l t r a s t r u c t u r a l s t u d y of t h e e p i m a s t i g o t e s t a g e o f t h e trypanosomes. J. P r o t o z o o l . , 20: 394-404. Ward, K.A. and W i l l e y , R.L., 1981. The development o f a c e l l - s u b s t r a t e a t t a c h m e n t system i n a e u g l e n o i d f l a g e l l a t e . J. U l t r a s t r . Res., 74: 165-174. W h i t f i e l d , P.J., 1979. The B i o l o g y o f P a r a s i t i s m : An I n t r o d u c t i o n t o t h e Study o f A s s o c i a t i n g Organisms. U n i v e r s i t y Park Press, B a l t i m o r e . 277 pp. R.L.. 1984. F i n e s t r u c t u r e o f t h e mucocysts o f Colaciurn calvum Willey. (Euglenophyceae). J. Phycol., 2 0 : 426-430. Ward, K.. Russin. W. and W i h e l . R., 1977. H i s t o c h e m i c a l s t u d i e s W i l l e y , R.L., o f t h e e x t r a c e l l u l a r c a r b o h y d r a t e o f Colacium mucronatum (Euglenophyceae). J . Phycol., 13: 349-353. Zugibe, F.T. and F i n k , M.L., 1966. A new i o n a s s o c i a t i o n f r a c t i o n a t i o n t e c h n i q u e f o r d e m o n s t r a t i n g p o l y a n i o n s i n t i s s u e s e c t i o n s . J. Histochem. 153-158. Cytochem.. 14: 147-152,

+

79

Chapter 6 Fouling on Paints Containing Copper and Zinc

M.S. FRENCH and L.V. EVANS

Department of Plant Sciences, University of Leeds, Leeds LS2 9JT.

6.1

INTRODUCTION Fouling

on ships

causes hull

roughness

leading to

increased

frictional resistance and an increase in fuel consumption if the service speed of a vessel is to be maintained. Removal of fouling necessitates expensive dry-docking and therefore periods out of service.

Self-polishing copolymer (SPC) antifouling paints control

most animal and weed fouling, but the slime-forming organisms, notably bacteria and diatoms, persist. In SPC systems, triorganotins are a major toxic component polymerised with unsaturated monomers to produce film-forming polymers with a high concentration of organotin groups. Other toxic components may include cuprous oxide and sometimes a small amount of zinc oxide. SPC paints hydrolyse and dissolve in seawater releasing the biocides at a contrblled rate during service. Polymer dissolution takes place at a higher rate where there is greater turbulence, e.g. in areas of hull roughness, and erosion of the coating is faster in these areas resulting in a progressive polishing of the hull surface with time. Cuprous and zinc oxides were compared as additional biocides in a SPC paint, i.e the antifouling performance of different combinations of cuprous and zinc oxides in such paint was tested. Fouling organisms found on the zinc- and copper-containing SPC paints were compared with those on non-toxic panels to determine the selective action of the biocides on the local population of fouling organisms. In addition, a comparison was made of the relative influences of seasonal variation and extended periods of

80

exposure on fouling levels on the test paints. MATERIALS AND METHODS The antifouling efficiency

6.2

of cuprous

and

zinc

oxides

was

evaluated by exposing test panels coated with SPC antifouling paint incorporating these biocides on experimental rafts. Two raft trials were run concurrently over a period of fifteen months (August 1982-November 1983) to test five paints all based on the

/ methyl methacrylate SPC system (Table 1). Cuprous oxide and zinc oxide were used singly and in two different combinations and non-toxic calcium sulphate was used as a

tributyltin methacrylate

substitute in a control paint. Two coats of each test paint were applied by weight to 100cm2 Formica panels to achieve a dry-film thickness of 100pm. The panels were attached in groups of twenty five to both sides of wooden plates, which were vertically suspended to a depth of 1.5m from a raft in the Yealm estuary, Newton Ferrers, Devon. In order to remove any variation that may occur due to the position of the panels on the raft, the arrangement and sampling of the wooden plates was randomised. They were placed 0.8m apart on the central area

of the

raft to

avoid any

currents or

turbulence near

the

edges. It was assumed that any variation caused by panel position on the wooden plates would be mainly the result of differences in TABLE 6.1 Composition of self-polishing copolymer test paints

Paint

Components

A B C D

tributyltin tributyltin tributyltin tributyltin

+ + +

E

tributyltin

+

The pigments cuprous present at approx. approx. 30% weight.

+

cuprous oxide zinc oxide calcium sulphate cuprous oxide + zinc oxide 2 : l cuprous oxide + zinc oxide 1 : 2

oxide, zinc oxide and calcium sulphate were 50% weight, and tributyltin was included at

81

depth (irradiance level) rather than horizontal position. A randomised block design was used for the arrangement of the panels on the wooden plates. There were five replicates of each test paint on one side of a plate with one replicate at each depth. -6.2.1 Raft trial 1 Three hundred and seventy five panels were immersed in August 1982. Five replicates of each paint (i.e. one side of a wooden plate) were randomly sampled at monthly intervals following increasing exposure periods up to fifteen months. Each successive set had been exposed for one month longer than the previous set. This trial tested variation in fouling between the test paints and the pattern of fouling over increasing exposure periods. 6.2.2 -

Raft trial 2 Five replicate panels of each

paint were immersed

monthly and

removed after three months exposure. These monthly immersions were continued for twelve months (August 1982-July 1983). Three hundred panels were exposed in all. This trial tested variation in fouling between the test paints and seasonal fouling variation. A plate of non-toxic, uncoated, black Formica panels was also immersed. There was one panel for every twenty five test panels sampled,

immersed at the same time and

for the same period as the

test panels. 2exposed panels 6.2.2 Assessment of fouling 0 Fouled panels were examined visually and microscopically

to

determine the main organisms present and the percentage of the panel surface covered by these organisms. Fouling was then measured by chlorophyll a concentration and dry weight throughout both trials and ashed weight was also measured for panels sampled on February 22nd 1983 and thereafter. Panel surfaces were divided into five strips. Two strips per panel were used for chlorophyll determination and a further two strips were used for dry and ashed weight determinations.

Total fouling levels

for each

panel were

calculated from measurement of these strips. Fouling material was removed from the panel surface using cotton wool buds and suspended in filtered seawater (Whatman GF/A). The suspension was centrifuged at 15009 in a Beckman T-J6 centrifuge for lOmin and the supernatant discarded. Successive extractions in dimethyl sulphoxide were carried out following the method of Shoaf and Lium (1976) and the chlorophyll a concentration determined spectrophotometrically using the equation: [chlorophyll a g

m3]

= 11.47 A664

-

0 . 4 A630

(Holden, 1976)

(1)

82 where A664 and A630 are absorbances at 664nm and 630nm respectively. For dry weight determination, the pellet of fouling material was obtained as above and then washed three times in distilled water to remove salts. These crystallise out on drying the sample and interfere with weight measurements. The samples were transferred to tared porcelain crucibles and dried to constant weight at 80%. They were than placed in a furnace at 400: for 16h after which they were removed to a desiccator until cool and the ashed weights measured. Temperature,

pH and

salinity were

monitored throughout the

exposure period of both trials. 6.3 RESULTS During the raft trials, a study was made of the selective action of copper and zinc on the seasonal populations of fouling diatoms. The results of the visual and microscopic examination of the fouling organisms on both the non-toxic, uncoated panels and the five SPC test paints were very similar in the two raft trials, so the data for trial 1 are presented here (Figs6.1-6) and any differences recorded for trial 2 will be indicated. A much wider range of algal species was found on paint C, where tributyltin was the only biocide, than on those paints containing cuprous and/or zinc oxide. Several species of macroalgae were found on paint C , together with a greater number of diatom species, and hydroids were also present. The filamentous green alga Ulothrix was found on paint C between May and August. It was also found on paints B, D and E, but was absent on paint A. Enteromorpha was found on paint C between May and December and also on paints B, D and E between July and December, but again it was not found on paint A. The diatoms Achnanthes longipes and Achnanthes subsessilis were found on paint C , but not on any of the copper- or zinc-containing paints (A, B, D or E). In addition to Enteromorpha and Ulothrix, Ectocarpus was found on paint B. Amphiprora hyalina was the predominant diatom for most of the year on all the cuprous and zinc oxide-containing paints. On paint C , this species was only found during January to February and between September and October. Stauroneis amphoroides was also found on all five test paints for most of the year. Amphora coffeaeformis was again found on all five test paints and like 9. hyalina, it was present in lower numbers and for a more limited period on paint C . Amphora veneta

--

was found on paints A and C between September and October, on paint B in February and on paints D and E in July and October. A. exigua

Diatoms Achnanthes longipes Achnanthes subsessilis AmDhiDrora hvalina Amphoia coffeaeformis Amphora exigua Amphora veneta LicmoDhora SDD.

Stauroneisamphoroides Macroalgae

Ulothrix 9 .

I

1 S

2 O

3 4 5 6 7 N D , J F M Length of exposure

1

8 9 1 0 1 1 1 2 1 3 1 4 1 5 A M J J A S O N (months)

Fig. 6.1. Speciation and percentage of the panel Surface covered by fouling organisms on SPC test paint A in raft trial 1. Bars represent the mean Visual estimation of five replicate panels at each exposure time.

W

w

Diatoms Achnanthes longipes Achnanthes subsessilis AmDhiDrora hvalina Amphora coffeaeformis Amphora exigua Amphora veneta LicmoDhora SDD. Melosira .ps Navicula e p . Nitzschia spp. Stauroneisxphoroides Macroalgae Cladophora spp. Ectocaruus SDD. Enterombrphaspp. ulothrix 2 . I

~

L

I I

I

I

0

1 S

-

I = I

1

2 O

3 4 5 6 7 N D J F M Length of exposure

8 9 1 0 1 1 1 2 1 3 1 4 1 5 A M J J A S O N (months)

Fig. 6.2. Speciation and percentage of the panel surface covered by fouling organisms on SPC test paint B in raft trial 1. B a r s represent the mean Visual estimation of five replicate panels at each exposure time.

Diatoms Achnanthes lonaioes

Amphora veneta Licmophora spp. Melosira sp. Navicula Nitzschia spp. Stauroneis amphoroides Macroalgae Cladophora spp. Ectocarpus spp. Enteromorpha spp Ulothrix 2.

G.

L

I

0

1 S

1

2 O

3 4 5 6 7 N D J F M Length of exposure

8 A

9 1 0 1 1 M J J

1

1 2 1 3 1 4 A S O

-

15 N

(months)

Fig. 6.3. Speciation and percentage of the panel surface covered by fouling organisms on S P C test paint c in raft trial 1. Bars represent t h e mean Visual estimation Of five replicate panels at each exposure time.

03 vl

Diatoms Achnan _ _ _ -hes lonsiDes Achnan hes subsessilis AmphiF _era hyal ina Amphora coffeaeformis Amphora exigua Amphora veneta Licmophora spp. Melosira SD. <

-

Stauroneis amphoroides Macroalgae Cladophora spp. Ectocarpus spp. Enteromorpha spp. Ulothrix 2 .

I I

1

I

Fig. 6.4. Speciation and percentage of the panel surface covered by fouling organisms on spc test paint D in raft trial 1. Bars represent the mean visual estimation of five replicate panels at each exposure time.

Diatoms Achnanthes l o n g i p e s Achnanthes s u b s e s s i l i s Amphiprora h y a l i n a Amphora c o f f e a e f o r m i s Amphora exigua Amphora Licmophora spp. Melosira p s. Navicula F p . Nitzschia-p. Stauroneisxphoroides Macroalaae Cladophora spp. Ectocarpus spp. Enteromorphapp. U l o t h r i x so. 0

1

2

S

O

3

4

5

6

7

N D J F M Length of exposure

8

9

A M (months)

1 0 1 1

1 2 1 3 1 4 1 I5

J

A

J

S

O

N

Fig. 6.5. S p e c i a t i o n and p e r c e n t a g e of t h e p a n e l s u r f a c e covered by f o u l i n g organisms on S P C t e s t p a i n t E i n r a f t t r i a l 1 . Bars r e p r e s e n t t h e mean v i s u a l e s t i m a t i o n of f i v e r e p l i c a t e p a n e l s a t each exposure t i m e .

03 U

W 03

Animals Ascidians Balanus balanoides Balanus perforatus Bryozoans Mussels Serpulids Sponges Tubularia indivisa Macroalgae Cladophora s p p . Ectocarpus s p p . Enteromorpha spp. Giffordia 7 Laminaria saccharina Polysiphonia s p p . Ulva lactuca Diatoms Achnanthes s p p . Licmophora s p p . Navicula spp. Melosira Tabellaria s p p .

-- m- uI

-

*.

i S

2 0

N

Length

4 D. Of

;

4 J

F

exposure

M

b A M (months)

1

,

10

11 J

J

.

1'2 A

1'3

14

s

0

I

15 N

Fig. 6 . 6 . Speciation and percentage of the panel surface covered by fouling organisms on uncoated, non-toxic Formica panels in raft trial 1. Bars represent the visual estimation of one panel at each exposure time.

89

was found on paints B, D and E. Licmophora species were found on all the test paints for a large part of the year, but in relatively low numbers. Other commonly found species were of the genera Nitzschia and Navicula. Non-toxic uncoated panels were more heavily fouled than the test paints and also were fouled by a more diverse range of organisms. This included extensive fouling by macroalgae from February until August with highest algal fouling in June and July mainly of Ectocarpus and Giffordia species. During the period September to February, there was very little algal fouling on the panels, but Ectocarpus and Enteromorpha were present. In March to May, Cladophora species were found together with Ectocarpus and a little Polysiphonia. They provided a thin algal covering over about 00% of the panel surface. Ulva lactuca was found in both trials in September to November, trial 1, in August.

but Laminaria saccharina was found only in From August onwards the algal cover became

reduced and animal fouling increased. Diatoms were mainly epiphytic on the macroalgae and were therefore present in highest numbers during the summer. They included Tabellaria, Licmophora, Navicula, Achnanthes and Melosira species. Heavy silt deposits were found on the non-toxic uncoated panels throughout the year and this was the major constituent on these panels during the winter. Animal fouling occurred mainly consisted of hydroids, barnacles,

during June to November and serpulids and bryozoan colonies.

Hydroids, mainly Tubularia indivisa, were found throughout the year, the dead stalks persisting after the colonies had developed. The barnacles were mainly of Balanus perforatus was in trial 1. High numbers November following ten to

Balanus balanoides, although one specimen found following thirteen months exposure of large barnacles were found in June to fifteen months exposure (trial 1). while

they were present in much lower numbers over this period on those panels exposed for three months (trial 2). Barnacles covered 50-80% of November.

the surface of panels in trial 1 during September to A high proportion of the serpulid worms were Spirorbis

species and non-toxic

panels of

trial

1 continued

to show

the

broken calcareous serpulid tubes until December, although none were found in trial 2 after September. Large bryozoan colonies were also found in trial 1 in June to November, covering up to 40% of the panel surface and often covering silt, barnacles and other fouling organisms. Only occasional small colonies of bryozoans were found on non-toxic panels of trial 2 exposed for three month periods.

90

Large numbers of a variety of sponge species were found on the nontoxic uncoated panels throughout the year and shellfish were occasionally found. Ascidians were also found during the summer. The variables used to assess fouling levels on exposed raft panels (chlorophyll a concentration, dry weight and ashed weight) were found to show high and significant correlation, at the 95% confidence level, for most of the exposure periods of both trials (Figs 7-16), i.e. from February 1983- November 1983 in raft trial 1 and from the fourth three month exposure period (December 1982) in trial 2 until the end of the trial. All the test paints follow a similar fouling pattern in both trials. The figures show a large peak of fouling in January to May with a smaller peak in August to November. A small peak was also found in June and in trial 1. another small peak occurred in December to February. The fouling levels on each test paint were found to vary significantly, at the 95% confidence level, with the final month of exposure (trial 1) and with the month of immersion (trial 2). In trial 1, where the panels were exposed for increasing periods up to fifteen months, it appears from the figures that the significant fouling variation which occurs with time is due to seasonal variation and not to increasing exposure time of the test paints. This was confirmed by the results of trial 2, where the panels were exposed for a constant period of three months with immersions throughout the year. It is apparent that the time of year that the test panels were immersed had a greater effect on fouling levels than the total length of the exposure period. Differences in fouling between the test paints and between the five depths of panel immersion, corresponding to the five vertical positions on the wooden plates, were considered in a two-way analysis of variance test on the In transformed data for each exposure period, i.e. for each month in trial 1 and for each three month period in trial 2 (see French, 1985 f o r tables of data and statistical analysis). Since seasonal variation in fouling was greater than that between the test paints, the entire fifteen month exposure period could not be considered. For those sample times where the test paints were found to have significantly different fouling levels at the 95% confidence level, t-tests were used to compare individual paints. From these a general ranking order relating to antifouling performance emerged. Paints A , D and E had the lowest fouling levels and the relative order of their antifouling activity varied with the particular fouling variable

r

s

': -20I1

Fig. 6.7

1200{

1000-

4

800-

= 800

m

a 0

Fig. 6.10

.;loo0

600,

Length of exposure (months

Length of exposure (months)

Fig. 6.8

7

Fig. 6.11

1000.

-4

h

800-

a m

600-

m

400-

E

Length of exposure (months

c .rl

4

200.

I

0 [..

0-5 0

3

6

4

12

1'5

Length of exposure (months)

9

12

15

Length of exposure (months)

Figs 6.7-11. Fouling on the SPC test Paints A €3 ( a ) , C ( 0 1 , D ( 0 ) and E ( A ) in raft trial 1. Chlorophyll a x lCr3 (-1 and dry weight (---IPoints are means of five replicate panels.

10 4

W N

A2000

Fig 6.12

r I

Fig. 6.15

4

;lsoo d

a m1000 E

-

n

zrn 800 -4

$

400

x 0

Fig. 6.14

0

E s p o s 11re p e r i od

Exposure p e r i o d

$'-(j

Fig. 6.13

rn

800

Fig. 6.16

1

d

d

3 400

% O L -

a

Cl

Exposure period

Exposure period

n

Exposure period

Fias 6.12-16. Foulina on the SPC test paints ( A , B, C, D and E respectively) i n esGimated by dry weigGt. Bars represent t h e mean dry weight of five replicate panels.

raft trial 2

93 and with the exposure period considered. Significant differences, at the 95% confidence level, between these three paints were rare'ly found. Paints B and C both had significantly higher fouling levels, within 95% confidence limits, than paints A , D and E and paint C was often found to be significantly more fouled than paint B, at the 95% confidence level. To test the ranking order of paints indicated by t-tests for each sample time over the entire exposure period of each trial, a weighted mean for each test paint was calculated and these are shown in Table 2 for raft trial 2. Taking each variable in turn viz. chlorophyll a concentration, dry weight and ashed weight, the fouling means of each paint for each month in trial 1 and for each three month exposure period in trial 2 were then compared to the corresponding weighted means by computation of the correlation coefficient by a least squares regression. The three variables generally showed high and significant correlation, at the 95% confidence level, between the fouling means for each sample time and the ranking order of paints given by the weighted means. It can be seen from Table 2 that the three variables do not indicate the same order of ranking for paints A, D and E , but the overall impression gained is very similar to that formed from ttests. Therefore in both trials, the overall trend was that there was very little difference in the antifouling performance of paints A, D and E. Paint C, the control paint, had poor antifouling activity compared to these three paints and paint B had intermediate antifouling activity.

TABLE 6.2

Weighted means for the SPC test paints in raft trial 2

Paint

A

B C D E

Chlorophyll a content

2.827 3.827 5.024 2.614 2.955

Dry weight

Ashed weight

4.128 5.652 6.269 4.104 4.085

3.029 3.671 4.876 2.986 2.805

94

Depth was also

considered as an influence on

fouling levels on

the test paints. Fouling variation with depth was found to be significant, within 95% confidence limits, for some months in trial 1 and for some the case,

for 5 months

estimated by dry weight in trial of fouling

2.

three month exposure periods in trial

for example,

1.

However no consistent pattern

variation with depth was

panels exposed between

This was

out of 15 for fouling levels found,

although in

1.3 and 1.5m did show

trial 2 ,

heavier fouling more

often than those between 1.0 and 1.3m. 6.4

DISCUSSION Raft trials are

formulations

a good

with

method of

replication.

testing a

They

are

large number

rigorous

of

tests

of

antifouling activity as they are performed at sites rich in fouling organisms similar to the situation of a ship in harbour which is where most fouling occurs. No anticorrosive coating was used on the Formica panels as would be the case there is

some evidence that the

the amount of

fouling or the speciation of

(C. Anderson, persona Electron

on a ship in service,

type of anticorrosive

microscopy

because

may affect

organisms that develop

communication, 1985; Robinson et al., 1985). has

shown

that

anticorrosives

retard

the

polishing rate of SPC paints and this may influence the antifouling performance. Comparison between non-toxic, with the

uncoated panels and panels coated

SPC test pa nts exposed

for the same

period illustrated

the effectiveness of the-antifouling biocides tested. The biocidecontaining SPC paints had considerably reduced total fouling levels compared

to the

non-toxic panels

organisms was also restricted. biocides

could also

be

seen in

particular of diatoms, on paints contain tributyltin, possess

some

resistance to

of

exception

speciation of

fouling

selective action of particular

the

variation

of species,

in

the test paints. All five SPC test so all the organisms encountered must this

tributyltin only as in paint C, the

and th;!

The

the hydroid

biocide.

In the

presence

of

animal fouling was prevented with Tubularia

fouling was also reduced compared to

indivisa.

the non-toxic

Macroalgal

panels and was

species.

zinc oxide in addition to tributyltin,

no animal fouling was found

and

macroalgal

fouling

was

further

restricted.

Enteromorpha and Ectocarpus occurred on the

paint B ,

but

On paint B ,

with

restricted to relatively few resistant

Ulothrix,

control paint C and on

were absent when copper was present

instead of zinc

35

(paint A). Taylor and Evans (1976) and Millner and Evans (1980) have previously shown Ulothrix to be resistant to organotin paints and this is confirmed in these trials. It must also have some tolerence of zinc oxide. Enteromorpha has been found to be more sensitive to organotins than Ulothrix (Millner and Evans, 1980), but it was found on all the SPC test paints except paint A , which suggests that it has some resistance to all three biocides. Ectocarpus has

been found to

be resistant to

organotins (Millner

and Evans, 1980) and has also been found to develop resistance to heavy metals (Clitheroe and Evans, 1975). In this study Ectocarpus was found only on paint B indicating tolerance to tributyltin and zinc oxide. Its absence on paint C suggests that it does not compete successfully with Enteromorpha and Ulothrix when tributyltin is the only bioci.de present. The use of zinc and/or cuprous oxide in paints A ,

B,

D and E resulted in a smaller range

of diatom species. Only those able to compete successfully under the selective pressure of these metal oxides and tributyltin were able to grow in the slime-film. Achnanthes longipes were found only

Achnanthes on paint C,

subsessilis and indicating that

these diatom species are tolerant to

tributyltin but not to copper

or zinc. This is contrary to the findings of Hendey (1951) who found that both these species and particularly 4. longipes showed resistance to copper-containing paints. However, Callow et al. (1976) found that Achnanthes species could form up to 80% of the fouling organisms following 20 weeks exposure of paints coated with an organotin antifouling paint and both these species were found on paints with tributyltin as the only biocide at various sites around the world by Callow amphoroides were the

(1986). Amphiprora hyalina and Stauroneis predominant diatoms on the five test paints.

They appear to be able to compete successfully under the influence of all three biocides. Hendey (1951) and Harris (1946) found E . hyalina to

be strongly resistant to copper-containing paints and

Callow (1986) found Amphiprora species on a copper- and tributyltin-containing paint exposed on the east coast of England. Stauroneis has also been found in large numbers on a tributyltin paint (Blunn, 1982) and this diatom has been found to be resistant to both copper and tributyltin at several sites around the world (Callow, 1986). Various species of the genus Amphora were found on the SPC test paints. 4. coffeaeformis perpusilla and 4. veneta were found on all five test paints, suggesting resistance to all three biocides. 4. exigua was found on paints B, D and E. This

x.

96

Species appears to compete successfully when both zinc and tributyltin are present as biocides. These three Amphora species hatre previously been found to be resistant to copper-containing paints together with Licmophora species (Hendey, 1951). Licmophora was found on all five test paints in this study. Hendey (1951) also found that several Nitzschia species showed slight resistance to copper-containing paints, and particularly resistant was 2. closterium. Diatoms of this genus were found in limited numbers on all the paints, but mainly on paint C. Animal and weed fouling were prevalent on the non-toxic uncoated panels particularly during the summer. B . balanoides and bryozoan colonies were the major animal foulers, increasing in numbers in late summer to replace heavy algal fouling mainly by Ectocarpus and Giffordia which occurred in June and July. Fletcher (1974) also noticed the presence of Balanus species on non-toxic panels in September following the development of

the algal climax community.

Serpulid worms, bryozoans, sponges and mussels were also found during the summer. Harris (1946) found mussels to be very sensitive to antifouling paints and a good indication of the lack of toxicity of a surface. The diatom species were mainly epiphytic on the fouling algae and few of the species found in high numbers on the SPC test paints were found on the non-toxic panels. No diatoms were found on non-toxic panels exposed in the Yealm estuary by Callow (1986), but Navicula,

Stauroneis and Amphora species were found at

various sites around the world. Fletcher (1974) found colonial naviculoid diatoms on non-toxic panels at a U.K. site in January, March and June. The quantitative method of fouling assessment employed in these trials provided a regular profile of fouling on each test paint. High and significant correlation between the fouling variables was attained indicating that they are accurate representations of fouling levels. The test paints in these trials were all of similar formulation and similar fouling organisms with variable fouling levels were expected. Therefore variables such as chlorophyll a concentration, and dry and ashed weights were a suitable measure of fouling.

However, when different test paints are to be tested or a

wider range of fouling organisms (which may include animal foulers and macroalgae in addition to the slime-film) is anticipated, then an alternative fouling assessment system may be a ranking system for different organisms which relates organism size or weight to coverage of the panel surface (Fry, 1975). The data could then be

97

summed to form a fouling total. Alternatively a means of comparing paints by species diversity could be used as effective antifouling paints

reduce the

number

of fouling

species

(Robinson et

al.,

1985). Both raft trials showed the variation in antifouling performance of the test paints. Data analysis showed that there were no significant differences in the antifouling performances of the cuprous oxide-containing paints A, D and E, even though D and E contained lower levels of cuprous oxide. Zinc oxide was used as a substitute for cuprous oxide in paint B and this paint was shown to have significantly higher fouling levels, at the 95% confidence level, than all the copper-containing paints. Therefore it seems that zinc oxide cannot be used effectively as a complete replacement for cuprous oxide in this paint formulation, but it can be used to partly replace cuprous oxide, as in paints D and E, with no significant loss in antifouling performance compared to paint A, which did not contain zinc oxide. The control paint ( C ) showed significantly higher fouling levels than all the other test paints. All five test paints were composed of a copolymer matrix and contained tributyltin as the principal biocide. Therefore the addition of either cuprous oxide or zinc oxide (as in paints A , B, D or E) considerably improved the antifouling performance compared Such high to that when tributyltin was the only biocide (paint C ) . levels of zinc oxide as used in paints B, D and E are not in current commercial use. Antifouling activity was similar when a combination of cuprous and zinc oxide was used (paints D and E )

as

Therefore it in the presence of cuprous oxide alone (paint A ) . appears that zinc oxide does not improve the antifouling performance of the paint system but it does allow cost reduction without significant loss of antifouling activity. The cost of cuprous oxide in December 1984 was zinc oxide was €805 per tonne.

El553 per tonne, while that of Therefore complete or partial

replacement of cuprous oxide by zinc oxide in a SPC paint would be financially desirable. Izral'yants et al. (1982) also found that a vinyl-matrix paint containing cuprous and zinc oxides at 26.6 and 13.4 percentage volumes respectively showed good antifouling activity. In an epoxy-base enamel containing -tributyltin oxide, Frost et al. (1975) found that 25% of the cuprous oxide could be replaced with zinc oxide with no resulting change in the enamel properties and this enamel resisted fouling in the Barents sea for three years. The similar antifouling performances shown by paints

98 A, D and E, even though the last two paints contained proportionally less cuprous oxide, may be the result of a synergistic toxic action between copper and zinc as found in laboratory growth experiments on axenic cultures of Amphora and Amphiprora (French, 1985). In addition, or alternatively, since the presence of zinc oxide in paints D and E has been found from leaching tests to result in increased copper leaching rates from the test paints (French, 1985 and French et al., 1985), it may be due to this. Raft trials 1 and 2 also compared the relative influences of increasing exposure period (trial 1) and of seasonal variation (trial 2 ) on the fouling levels on the five test paints. The dominant effect of season was apparent. The main fouling peaks were January to May and August to November. At these times fouling differences

between

the

test

paints were

most

clear

and

the

greatest diversity of diatom species was found. The results suggest that a better test of the antifouling properties of paints could be made under conditions of peak fouling. Raft exposure times could perhaps be reduced by immersion over periods of peak fouling which may facilitate the use of more than one test site to allow paint testing under different fouling conditions at sites with different indigenous populations. Peak fouling periods at the different test locations would need to be established and physical features of the paints which may vary with length of exposure could be determined by other means, such as immersion on a rotor apparatus for biocide leaching tests (French, 1985). A high proportion of the fouling organisms on the SPC test paints were diatoms and they must compete under the influence of seasonal changes as well as in response to the presence of antifouling biocides. Irradiance levels vary with season and will influence the growth of fouling organisms. Growth levels may also follow the seasonal temperature variation. Low temperatures and low irradiance levels could account for the higher levels of fouling found on the SPC test paints during the months November to January. Reduction in fouling in summer may partly be a result of grazing by zooplankton. Salinity and pH also vary with season and the fouling peaks corresponded to pH values lying in the range 7.8-8.0 and salinity values in the range 32.5-34.5% (French, 1985). Seasonal changes in river outflow may also influence seasonal production (Kirk, 1983) and this may have some effect on panels exposed in the Y e a h estuary.

fouling levels on

09

Five

replicate

test

panels

of

each

SPC

test

paint

were

sufficient to distinguish the cuprous oxide-containing paints, A, D and E from paints B and C. They also diffferentiated between paint B containing tributyltin and zinc oxide as biocides and paint C with only tributyltin. However, had a greater number of replicates been used, significant differences in fouling levels on the coppercontaining paints may have been found, but when a study was made of the occasional times when significant differences between these three paints was found,

no consistent

order of fouling levels was

apparent. Therefore, it is unlikely that these paints could be shown to differ significantly and consistently in antifouling performance with higher replication. 6.5

ACKNOWLEDGEMENTS This work was carried out during tenure by M . S . French of a SERC CASE studentship in conjunction with International Paint plc. The authors wish to thank both organisations. 6.6

REFERENCES

Blunn, G.W., 1982. Studies on the ship-fouling alga Achnanthes. Ph.D. Thesis, University of Leeds. Callow, M.E., 1986. A world-wide survey of slime formation on antifouling paints. In: L.V. Evans and K.D. Hoagland (Editors), Algal Biofouling. Elsevier, Amsterdam. Callow, M.E., Evans, L.V. and Christie, A . O . , 1976. The biology of slime films, Part 2. Shipp. Wld., 169 (3923): 949-951. Clitheroe, S.B. and Evans, L.V., 1975. A new look at marine fouling, Part 3. Shipp. Wld., 168 (3912): 1123-1124. Fletcher, R.L., 1974. Results of an international cooperative research programme on the fouling of non-toxic panels by marine algae. Trav. Cent. Rech. Etud. Oceanogr., 14: 7-24. French, M . S . , 1985. Copper and zinc in antifouling paint and their effect upon the diatoms Amphora and Amphiprora. Ph.D. Thesis, University of Leeds. French, M.S., Evans, L.V. and Dalley, R., 1985. Raft trial experiment on leaching from antifouling paints. Trans. I. Mar. Eng., 97: 127-130. Frost, E.I., Sinel'nikova, N.R., Gennik, N.M., Rozhkov, Yv. P. and Nazarova, E.V., 1975. Use of zinc oxide in non-fouling coatings. Lakokras. Mater. Ikh. Primen., 1975 (4): 4-5. Fry, W.G., 1975. Raft fouling in the Menai Strait 1963-1971. Hyrobiologia, 47: 52-528. Harris, J.E., 1946. Report on antifouling research. J. Iron Steel Inst., 154: 296-333. Hendey, N.I., 1951. Littoral diatoms of Chichester Harbour with special reference to fouling. J. R. Microsc. S O C . , 71: 1-96. Holden, M., 1.976. Chlorophylls. In: T.W. Goodwin (Editor). Chemistry and Biochemistry of Plant Pigments, Vol. 2. Academic Press, London, pp. Izral'yants, E.D., Tikhonovich, L.I., Prazdnova, A.I. and Frost, A.M., 1982. Effect of zinc oxide on weather resistance and

100

protective properties of antifouling coatings containing copper (I) oxide. Lakokras. Mater. Ikh. Primen., 1982 (5): 34-35. Kirk, J.T.O., 1983. Light and Photosynthesis in Aquatic Ecosystems. Cambridge University Press, Cambridge, 401 pp. Millner, P.A. and Evans, L.V., 1980. The effects of triphenyltin chloride on respiration and photosynthesis in the green algae Enteromorpha intestinalis and IJlothrix pseudoflacca. Plant Cell Environ., 3 : 339-348. Robinson, M.G., Hall, B.D. and Voltolina, D., 1985. Slime films on antifouling paints, short-term indications of long-term effectiveness. J. Coatings Technol., 57: 35-41. Shoaf, W.T. and Lium, B.W., 1976. Improved extraction of chlorophyll a and b from algae using dimethylsulphoxide. Limnol. Oceanogr., 21: 926-928. Taylor, G . E . and Evans, L.V., 1916. The biology of slime films, Part 1. Shipp. Wld., 169 (3922): 857-859.

101 Chapter 7

DIATOM COMMUNITIES ON

NON-TOXIC

SUBSTRATA AND TWO

CONVENTIONAL ANTIFOULING

SURFACES IMMERSED I N LANGSTONE HARBOUR, SOUTH COAST OF ENGLAND.

S. PYNE1, R.L.

FLETCHER1 and E.B.G.

JONES2

Department of B i o l o g i c a l S c i e n c e s , P o r t s m o u t h P o l y t e c h n i c , Marine L a b o r a t o r y , F e r r y Road, H a y l i n g I s l a n d , Hampshire, U.K. Department

of

Biological

S t r e e t , P o r t s m o u t h , U.K.

7.1

Sciences,

P o l l ODG.

Portsmouth

Polytechnic,

King Henry

1

PO1 2DY.

INTRODUCTION T h e r e have been a number of r e p o r t s of d i a t o m f o u l i n g on b o t h n o n t o x i c

( B a s t i d a e t a l . , 1974; Bacon and T a y l o r , 1976; K a r e n t z and M c I n t i r e , 1977) and t o x i c test p a n e l s (Hendey, 1951; Kingcome, 1959; Callow, 1984) on a w o r l d wide basis.

I n g e n e r a l a d i v e r s e and r i c h d i a t o m f l o r a h a s been d e s c r i b e d on t h e

non-toxic

test panels.

For example Bacon and T a y l o r

g e n e r a , t h e dominant

species

Achnanthes l o n g i p e s .

I n comparison t o t h i s

of

examined diatom

being

Synedra f a s c i c u l a t a ,

Paralia

s u l c a t a and

t h e a n t i f o u l e d / t o x i c test p a n e l s

t o s u p p o r t a much more r e s t r i c t e d f o u l i n g community w i t h

have been r e p o r t e d fewer numbers

(1976)

s u r f a c e s and r e c o r d e d a t o t a l of 1 8 3 s p e c i e s i n 50

communities on n o n - t o x i c

g e n e r a and s p e c i e s i d e n t i f i e d .

P r o b a b l y t h e most d e t a i l e d

i n v e s t i g a t i o n o f f o u l i n g d i a t o m s on t o x i c p a n e l s w a s t h a t of Hendey (1951) who r e c o r d e d 97

species distributed

in

27

genera

copper

on

based

c o a t i n g s immersed in C h i c h e s t e r Harbour,

S o u t h C o a s t of England.

g e n e r a r e c o r d e d by Hendey were Amphora,

Achnanthes,

which are

often

adpressed t o

referred

the

The p r e s e n t

paper

as

to

surface

and

is

'true

form

concerned

a

slime' sheet with

f o u l i n g d i a t o m communities on b o t h n o n - t o x i c

N a v i c u l a and S t a u r o n e i s ,

formers or

an

film

as

they

over

the

investigation

of

lie

closely

substratum. the

marine

and t o x i c t e s t p $ n e l s suspended

from a r a f t i n Langstone Harbour, S o u t h Coast o f England.

is made between t h e f l o r i s t i c c o m p o s i t i o n of

antifouling The dominant

A g e n e r a l comparison

t h e s e two s u r f a c e t y p e s ,

which

is f u r t h e r r e l a t e d t o a s p e c t s s u c h a s t h e q u a l i t y and q u a n t i t y of i n c o r p o r a t e d antifouling biocide immersion of

the

and v a r i o u s e n v i r o n m e n t a l p a r a m e t e r s ,

panels

and w a t e r t e m p e r a t u r e .

s u c h a s d e p t h of

Using a weighted d i v e r s i t y

i n d e x a s e m i - q u a n t i t a t i v e a n a l y s i s of t h e f o u l i n g d i a t o m s is a l s o c a r r i e d o u t .

7.2

Materials and Methods

7.2.1.

P a n e l Exposure S i t e

-

Langstone Harbour

The t e s t p a n e l s were immersed from t e s t r a f t s moored i n Langstone Harbour, n o r t h - e a s t s o l e n t r e g i o n on t h e s o u t h c o a s t of England ( g r i d r e f .

SU 615015).

I t is a f u l l y marine h a r b o u r system b e i n g t h e c e n t r a l one of t h r e e interconnecting harbours (see

fig.

7.1).

The h a r b o u r

is almost completely

l a n d locked w i t h two narrow c h a n n e l s c o n n e c t i n g i t t o Portsmouth Harbour i n t h e w e s t and C h i c h e s t e r Harbour i n t h e east.

I t i s s h a l l o w ( d o e s n o t exceed

10m i n d e p t h ) and has a n area of a p p r o x i m a t e l y 19.4km2.

T i d a l range v a r i e s

between 1.5m ( n e a p s ) and 4.5m ( s p r i n g s ) , w i t h a t i d a l stream c u r r e n t r e v e r s i n g w i t h t h e t i d e r a n g i n g from 2.5km/hr 1959). to a

( n e a p s ) t o 4.54km/hr

( s p r i n g s ) (Hdughton,

The s u r f a c e water t e m p e r a t u r e s ranged from a minimum of 2.lOC ( J a n u a r y ) maximum

of

v a r i a t i o n s from 30.7% r a n g i n g between 1-3m, does r e c e i v e

about

Fig.7.1

(August)

22.1OC

to

34%

.

for

1982

whilst

Water c l a r i t y

salinities

show

is g e n e r a l l y poor,

slight usually

and i n d u s t r i a l p o l l u t i o n is l i g h t a l t h o u g h t h e h a r b o u r

40000

litres

of

treated

sewage

per

day

(Anon,

Map t o show l o c a t i o n o f Langstone Harbour and r a f t s i t e . (P.H. Portsmouth Harbour; L.H. Langstone Harbour; C.H. C h i c h e s t e r Harbour; y T e s t R a f t s )

1976).

103 7.2.2

Non t o x i c panel exposure The t e s t panels were made of polypropylene and measured 15cm x 8cm.

They were attached t o t h e frame by means of nylon n u t s and b o l t s a t depths of

0, 75 and 180 cms below t h e water-line. observation.

Duplicate panels were set up f o r each

The frame was immersed i n t h e harbour i n January 1982 and t h e

panels examined a t weekly i n t e r v a l s f o r a 1 2 month period.

Panels were removed

from the 0 and 75cm l e v e l every week and f r a n t h e 180cm l e v e l every two weeks and replaced with cleaned panels. 7.2.3.

Toxic panel exposure

A series of t o x i c panels comprising two commonly used biocides (copper

oxide and organo-tin) were a l s o immersed from t h e t e s t r a f t from March 1982 onwards.

Each panel, measuring 15cm x 8cm, was.constructed of polyethylene

onto which w a s sprayed two c o a t s (approximately 100 m and 150 m t h i c k respectively) of t h e r e l e v a n t a n t i - f o u l i n g formulation.

Three d i f f e r e n t

loadings were used f o r both toxin types ( s e e t a b l e 7.1).

TABLE 7.1.

Loading value f o r both t h e copper and organo-tin formulations

(i)

Low loadings

(ii)

Medium loadings

( i i i ) High loadings

-

10%weight/volume

30% weight/volume 50% weight/volume

A t o t a l of 1 2 panels were immersed ( t h r e e loadings of both copper and organo-tin

i n d u p l i c a t e ) and examined each month over a 2 year period.

A l l panels were

immersed a t t h e water l i n e l e v e l . 7.2.4

Sampling procedure The non-toxic panels were brushed with a hard-haired brush t o remove a l l

attached diatom c e l l s .

These samples were then t r a n s f e r r e d t o a v i a l containing

a 4% formal s a l i n e s o l u t i o n .

The t o x i c panels were, however sampled l i g h t l y

by brushing and removing a l l a t t a c h e d diatoms with a f i n e h a i r e d brush i n order not t o remove any excess t o x i n from the surface.

These diatom cells

were then placed i n t o a 4% formal s a l i n e s o l u t i o n . 7.2.5

Preparation of permanant diatom s l i d e s from sampled m a t e r i a l

The diatom supernatant, in formal s a l i n e , was decanted and 20ml of concentrated hydrochloric a c i d added.

The mixture was heated f o r about 15

minutes u n t i l effervescence ceased and t h e s o l u t i o n then cooled. d i l u t e d i n d i s t i l l e d water and l e f t t o s e t t l e .

This was

The clear l i q u i d w a s decanted

104 and the diatoms repeatedly

washed with d i s t i l l e d

water t o remove any acid.

A f t e r the t h i r d wash t h e supernatant was decanted and 20mls of

concentrated

s u l p h u r i c a c i d was added and the mixture b o i l e d f o r 15 minutes.

The s o l u t i o n

was l e f t

t o stand

f o r approximately 60 minutes

potassium permanganate

(KMn04)

was

a f t e r which

added drop by drop u n t i l

ceased ( a l l organic m a t t e r has been oxidised).

cleaned f r u s t u l e s

were

washed

100% e t h a n o l t o

in

distilled

allow

saturated

effervescence

The s o l u t i o n was l e f t t o stand

and cool a f t e r which o x a l i c acid was added t o decolourise

dehydrated i n

time

water

the liquid.

several

easy attachment

to

times

cover

The

and

then

slips.

The

m a t e r i a l was mounted i n a medium of high r e f r a c t i v e index i n o r d e r t o i n c r e a s e c l a r i t y of

the f r u s t u l es

R.I.

(Naphrax:

=

1.62,

Fleming,

1954).

Permanent

diatom s l i d e s were produced f o r each sampling t i m e , i n d u p l i c a t e and f o r a l l depths.

I d e n t i f i c a t i o n was

carried

out using the taxonomic nomenclature of

van Heurck (1896) and Hendey (1951). 7.2.6

%mi-Quantitative

a n a l y s i s of b i o f o u l i n g (numerical d i v e r s i t y index)

For each permanent s l i d e , twenty f i e l d s of view were examined, using a Wild M20 microscope with x15 eye piece and x40 objective.

were i d e n t i f i e d and given a

c e r t a i n numerical weighting,

Dominant s p e c i e s depending on t h e i r

estimated abundance; these were:

Percentage occurrence i n population

Diversity Index

(i)

g r e a t e r than 50% (dominant)

3

(ii)

25-50% (sub-dominant)

2

(iii)

12-25% (common)

1

The a n a l y s i s was repeated f o r a l l types

of

t o x i c loading formulations

and non-toxic panels.

7.3

RESULTS

7.3.1.

Non-toxic panel a n a l y s i s A t o t a l of 187 s p e c i e s d i s t r i b u t e d i n 37 genera were i d e n t i f i e d on

a l l t h e non t o x i c panels.

Table 7.2

shows the number of

recorded on t h e panels a t t h e t h r e e depths of immersion.

genera and s p e c i e s There was generally

a decrease i n number of both genera and s p e c i e s with depth, ranging from 146 s p e c i e s i n 34 genera a t t h e water-line immersion depth.

t o 99 s p e c i e s i n 20 genera a t 180 cms

The most abundant s p e c i e s recorded on t h e non-toxic

were Achnanthes l o n g i p e s , Amphora coffeaeformis, scutellum, Grammatophora A l l of

oceanica,

Navicula

Biddulphia a u r i t a ,

c i n c t a and

panels

Cocconeis

Synedra f a s c i c u l a t a .

t h e s e s p e c i e s possess a d i s t i n c t mode of attachment which allows t h e

c e l l t o adhere d i r e c t l y t o t h e surface.

The m a j o r i t y of diatom s p e c i e s recorded

105 on the t e s t panels in Langstone Harbour, however were more obviously motile on the surface and w i t h i n the biofilm.

TABLE 7.2.

Number of s p e c i e s and genera on non-toxic panels

Number of s p e c i e s

Number of genera

1.

Total

187

37

2.

Water-line

146

34

3.

75 cms below water-line

140

34

4.

180 cms below water-line

99

20

(i)

Water-line panel

The genera with t h e g r e a t e s t number of s p e c i e s a t t h i s depth were Navicula (25 s p e c i e s ) , N i t z s c h i a (18 s p e c i e s ) , Amphora (10 s p e c i e s ) , Diploneis (9 species) and Cocconeis ( 6 s p e c i e s ) . (ii)

75cms below w a t e r l i n e

The genera with most s p e c i e s a t t h i s depth were Navicula (29 species) and Nitzschia

(14 s p e c i e s ) while o t h e r

population were Amphora (10 s p e c i e s ) ,

genera prevalent

within t h e fouling

Cocconeis (10 s p e c i e s ) and Synedra ( 5

species). ( i i i ) 18Ocms below water-line The genera with t h e h i g h e s t number of s p e c i e s a t t h i s depth were Navicula (19 species) and Nitzschia (10 s p e c i e s ) , data f o r t h e o t h e r depths. were Cocconeis

s l i g h t l y lower f i g u r e s than f o r the

Other genera which were common w i t h i n t h e population

(6 species),

Diploneis

(4 s p e c i e s ) and

Synedra ( 4 species).

Using t h e weighted values of t h e d i v e r s i t y index ( 3 , 2 and 1 ) and summing these f o r i n d i v i d u a l s p e c i e s , t h e dominant diatom s p e c i e s a t the t h r e e immersion depths was estimated.

The most common diatom s p e c i e s a t t h e water-line

and

18Ocms depth was Cocconeis scutellum ( h a s t h e h i g h e s t d i v e r s i t y index) while a t 75cms Amphora coffeaeformis was the dominant species.

Other species which

had a r e l a t i v e l y h i g h d i v e r s i t y index were Synedra f a s c i c u l t a (180 depth) and Grammatophora oceanica ( a l l t h r e e depths). Table 7.3

7.3.2.

sumarises the

results

for

all

t h r e e depths

of

immersion:

Copper and organo-tin a n t i - f o u l i n g panels The dominant genus on both a n t i - f o u l i n g formulations was Amphora,

comprising A.

coffeaeformis var. coffeaeformis and A. coffeaeformis var.

106 perpusilla.

In a g e n e r a l comparison with t h e non-toxic panels t h e numbers of

s p e c i e s and genera were 50% l e s s on t h e copper formulation and approximately

40% l e s s on t h e organo-tin matrix.

A summary of the numbers of s p e c i e s and

genera recorded on both the copper and organo-tin a n t i - f o u l i n g panels is given

in Table 7.4.

TABLE 7.3.

Dominant diatom s p e c i e s on non-toxic panels

Depth

Water-line

Species

D i v e r s i t y Index

Cocconeis scutellum

75

Amphora coffeaeformis

66

Grammatophora oceanica

(ii)

75cms

18Ocms

(iii)

63

Amphora coffeaeformis

71

Cocconeis scutellum

65

Grammatophora oceanica

60

Cocconeis scutellum

30

Syndera f a s c i c u l a t a

21

Grammatophora oceanica

20

The monthly average number of genera and s p e c i e s (over a 1 2 month immersion period) on both a n t i - f o u l i n g compositions was estimated.

I t was

found t h a t copper p a n e l s had a lower s p e c i e s d i v e r s i t y throughout t h e y e a r , having 2 1 s p e c i e s in 1 4 genera while t h e organo-tin formulation supported on average, 26 s p e c i e s in 15 genera.

The dominant genus, on both compositions,

throughout the immersion period, was Amphora, although o t h e r genera such a s Cocconeis and Navicula were a l s o present.

The dominant s p e c i e s , estimated

using the d i v e r s i t y index, a r e shown in Table 7.5. The d i s t r i b u t i o n of t h e monthly mean number of genera and species on both formulations from October 1982 t o September 1983 a r e shown in f i g s . 7.2 and 7.3.

Both graphs i n d i c a t e t h a t t h e r e was a f l u c t u a t i o n in d i v e r s i t y

throughout t h e year.

P a r t i c u l a r a t t e n t i o n was given t o examining the temporal

d i s t r i b u t i o n of t h e two most common genera, Amphora and Navicula. Calculating t h e cumulative d i v e r s i t y index f o r both these genera i t was shown t h a t t h e r e was a ' c y c l i c a l ' p a t t e r n in t h e i r appearance on t h e panels (Fig. 7.4).

Amphora spp. were dominant during November and December 1983 while

107

TABLE 7.4

Total number of species and genera on copper and organo-tin panels

A.

Copper t r e a t e d panels Number of s p e c i e s

Number of genera

Total

91

35

low

66

28

Medium

73

28

High

71

30

Toxin l o a d i n g

B.

Organo-tin t r e a t e d panels Toxin l o a d i n g

Number of s p e c i e s

111

Total

35

low

85

32

Medium

78

30

High

81

28

TABLE 7.5.

Prevalant diatom s p e c i e s on t h e biocide compositions

Species

Amphora c o f f e a e f o m i s var p e r p u s i l l a A.

Number of genera

coffeaefonnis var c o f f e a e f o n n i s

D i v e r s i t y Index

106

32

Navicula b i s k a n t e r i

24

Cocconeis scutellum

11

Navicula g r e v i l l e a n a

11

Navicula ramosissima

9

Cocconeis speciosa

8

108

v)

30

H W

U

w

a

(0

8

20

dw

5 8

u

10

a w a

3z 8

9

10

11

12

13

14

15

16

18

17

19

SEPT. ' 8 3

OCT '82

LENGTH OF IMMERSION (MONTHS)

Fig. 7.2.

Distribution of mean number of genera and species for organotin-based antifouled panels over a 12 month period.

30 v)

z

U

w

a

v)

8

=O

d w z 8

lo

a

0

a

w m

5

z

8

9

10

11

12

13

14

15

16

17

18

19

SEPT. '83

OCT '82 LENGTH OF IMMERSION (MONTHS)

Fig. 7.3.

Distribution of mean number of genera and species for copper-based antifouled panels over a 12 month period.

109

m

3

Ba

0

AMPHORA - 13spp ( 3 Dom)

8

l4

x w n

R

NAVICULi

14

- 2Ospp ( 3 Dom)

$I

E

8

10

H

n

w

6

2;

3

3

2

BU 8

9

10

11

12

13

14

15

16

17

18

19 SEPT ' 8 3

OCT '82 LENGTH OF IMMERSION (MONTHS)

Fig. 7 . 4 .

Graph t o show t o t a l cumulative d i v e r s i t y i n d i c e s f o r two common genera p r e s e n t on a l l t o x i c panels.

Total no of s p e c i e s and (general f o r

50 COPPER

ORGANO-TIN

1.

2. 3.

X

w

Copper - 91 ( 3 1 ) Organo-tin - 1 1 1 ( 3 5 ) Overall - 1 2 2 ( 3 6 )

n

H

Em

4c

a w

2; n w

2;

2

3

I

3i

I

Bu

HIGH

Fig. 7.5.

MEDIUM

LOW

HIGH

MEDIUM

LOW

T o t a l cumulative i n d i c e s for i n d i v i d u a l panels with various t o x i n loadings.

110 becaiiic abundant l a t e r d u r i n g March/April 1983; f i n a l l y Amphora

Navicula spp.

was a g a i n

prevaient

within

the

population

during

August/

September

1983.

The s p e c i q s d i v e r s i t y on both t h e copper and o r g a n o - t i n f o r m u l a t i o n s was a l s o examined i n r e l a t i o n t o t h e t o x i n l o a d i n g s and t h e r e s u l t s p r e s e n t e d i n F i g u r e 7.5.

The p a i n t s w i t h t h e h i g h l o a d i n g s of

-

cumulative index (copper

33; organo-tin

-

b o t h t o x i n s had t h e lowest

4 2 ) while,

i n comparison, t h e low

l o a d i n g p a i n t s had t h e h i g h e s t c u m u l a t i v e i n d e x ( c o p p e r 41;

7.4

-

organotin

50).

DISCUSSION a primary f i l m and b i o f o u l i n g l a y e r s on a s u r f a c e i s

The f o r m a t i o n of

f a c t o r s i n c l u d i n g sea-water

i n f l u e n c e d by a number of

chemistry, turbulence,

t e m p e r a t u r e , l i g h t and i n c o r p o r a t e d a n t i f o u l i n g b i o c i d e s .

In t h i s d i s c u s s i o n

s e v e r a l p h y s i c a l f a c t o r s w i l l be h i g h l i g h t e d and how they a r e t h o u g h t t o a f f e c t diatom d i s t r i b u t i o n . Several reports

have drawn

development of

benthic

diatom

e t al.,

McClean

et

1976;

increase i n depth

were

found

to

the

depth

on t h e

and TaylQK, 1976;

Stupak

effect

and

of

Bourget,

corresponding decrease

a

in

1983).

light

With

s u r v i v e a d e q u a t e l y on

the deeper

an

availability

I n t h i s s t u d y t h e r e are a number of

mainly due t o w a t e r t u r b u l e n c e . d i a t o m s which

to

(Bacon

1981; Hundon

al.,

is

there

attention

communities

common

panels while

o t h e r s p e c i e s could dominate t h e p o p u l a t i o n o n l y on t h e more s h a l l o w s u b s t r a t a . The former group a r e c l a s s e d as ' l i g h t t o l e r a n t '

diatoms and t h e l a t t e r group

classed a s ' l i g h t s e n s i t i v e ' species. Bacon and T a y l o r (1976)

and

Stupak e t

al.

(1976)

i n c r e a s e i n d e p t h (below 75cms from t h e w a t e r - l i n e )

found t h a t w i t h an

t h e number of Achnanthes

c e l l s a t t a c h e d t o t h e t e s t s u b s t r a t u m was g r e a t l y reduced and t h i s genus was v i r t u a l l y a b s e n t below 2 metres.

In Langstone Harbour Achnanthes l o n g i p e s was

r e c o r d e d on t h e 180 c m s p a n e l s o n l y s e v e n t i m e s i n twenty f i v e sampling p e r i o d s , s u g g e s t i n g t h a t l i g h t p e n e t r a t i o n h a s a n i m p o r t a n t i n f l u e n c e on t h e v e r t i c a l d i s t r i b u t i o n of t h i s s p e c i e s . n o t considered

a

fouling

A common c h a i n forming g e n u s , MeloSiKa, a l t h o u g h

species

occurs

quite

abundantly

in

the

biofilm.

During t h e summer months when l i g h t i n t e n s i t y ( p e n e t r a t i o n ) w a s h i g h , M e l o s i r a moniliformis

OCCUKS

on

the

surface panels

while

!&

nummuloides

a b u n d a n t l y on t h e d e e p e r p a n e l s (180 crns).

McClean e t a l .

t h a t these

requirements.

two

s p e c i e s had

different light

was

(1981) They

found

suggested

reported

M.

nummuloides w a s a b l e t o s u r v i v e i n deep water ( h i g h growth r a t e a t low l i g h t i n t e n s i t i e s ) while

g.

m o n i l i f o r m i s c o u l d o n l y s u r v i v e on t h e s h a l l o w e r s u b s t r a t a

(low growth r a t e in low l i g h t i n t e n s i t i e s ) . t h o s e of

C a s t e n h o l z (1964)

and Hudon and

These o b s e r v a t i o n s a r e s i m i l a r t o Bourget (1983)

nummuloides o c c u r r e d on t h e d e e p e r p a n e l s w h i l e

g.

who found t h a t

E.

m o n i l i f o r m i s was p r e s e n t on

111 the shallower

panels.

These

findings

strongly

suggest

that

the

vertical

d i s t r i b u t i o n of t h e g e n u s , and in p a r t i c u l a r t h e s e two s p e c i e s , i s governed by light availability. One p h y s i c a l f a c t o r t h a t h a s a profound e f f e c t on f o u l i n g and t h e b u i l d up of

the

fouling

t h a t Synedra

community i s t e m p e r a t u r e .

fasciculata

appeared

s p e c i e s , t h r o u g h o u t May and June.

test

on

Bacon and T a y l o r ( 1 9 7 6 ) n o t e d panels,

as t h e dominant

usually

However, when t h e t e m p e r a t u r e exceeded 10°C

t h e r e w a s a d r a m a t i c r e d u c t i o n i n numbers.

S i m i l a r l y Synedra f a s c i c u l a t a was

recorded in t h e p r e s e n t s t u d y a t t h e s t a r t of t h e i m e r s i o n p e r i o d s f r e q u e n t l y sub-dominant,

when t h e t e m p e r a t u r e was a p p r o x i m a t e l y 7%; above t h i s t e m p e r a t u r e

t h e s p e c i e s c o n t i n u e s t o be p r e s e n t b u t n o t i n such h i g h numbers,

suggesting

t h a t 7-8OC i s t h e optimum t e m p e r a t u r e f o r growth of t h i s s p e c i e s i n Langstone be a g r e a t d e a l

There w i l l

harbour.

of

variability

in t e m p e r a t u r e r e l a t e d

growth w i t h i n a genus b u t R e i s e n and S p e n c e r ( 1 9 7 0 ) n o t e d t h a t a n o t h e r Synedra sp. had a n optimum growth r a t e a t 6.5% t o that reported here f o r

2.

i n l a b o r a t o r y c u l t u r e , which i s s i m i l a r

fasciculata. show a marked r e a c t i o n

S e v e r a l workers have n o t e d t h a t Achnanthes spp. t o v a r i a t i o n i n temperature.

A. l o n g i p e s

w a s dominant

However, a t

temperatures

Stupak e t a l . (1976) r e c o r d e d t h a t between 8-15OC

on most greater

test than

panels

a l a r g e percentage

and r a r e l y c o n s t i t u t e d

-

from 0.5

15oC t h i s

species

of t h e p o p u l a t i o n .

A.

were r e c o r d e d by Bacon and T a y l o r ( 1 9 7 6 ) who n o t e d t h a t

on t e s t p a n e l s more higher than t h i s . do n o t

frequently

at

2 metres depth.

w a s merely p r e s e n t

temperatures

below

Similar trends

longipes occurred

15oC t h a n a t

values

The r e s u l t s p r e s e n t e d in t h i s p a p e r from Langstone Harbour

show any t r e n d s

i n d i s t r i b u t i o n in Achnanthes

spp.

when r e l a t e d t o

temperature f l u c t u a t i o n s .

One of t h e few chain-forming was B i d d u l p h i a a u r i t a

d i a t o m s commonly found on t h e t e s t p a n e l s

( d i s t r i b u t i o n shown i n f i g .

continuously recorded

this

species

at

3).

temperatures

Stupak e t a l .

8-ll°C;

between

s p e c i e s f r e q u e n c y was i n t e r m i t t e n t .

these temperatures,

(1976) above

S i m i l a r l y , Bacon and

Taylor (1976) n o t e d J. a u r i t a on t e s t p a n e l s when t h e t e m p e r a t u r e was between 5-13oC;

a t higher

t e m p e r a t u r e s i t was no l o n g e r p r e s e n t .

similar t o t h o s e o b t a i n e d i n t h e p r e s e n t p a n e l s in

Langstone

Harbour

which i t had a ' p a t c h y '

when

appearance.

the

study.

temperature

2.

These r e s u l t s are

aurita

range

was r e c o r d e d on

w a s 4-12OC.

above

I t is e v i d e n t t h a t t e m p e r a t u r e p l a y s a n

i m p o r t a n t r o l e i n t h e f r e q u e n c y of o c c u r r e n c e of t h i s s p e c i e s .

One of t h e most i m p o r t a n t p a r a m e t e r s which w i l l a f f e c t d i a t o m communities on a t e s t

surface

substratum matrix.

is t h e p r e s e n c e

of

an

anti-fouling

biocide

within

the

T h e r e have been many r e p o r t s on t h e c o l o n i s a t i o n of copper

based p a i n t f o r m u l a t i o n s

( H a r r i s , 1946; Hendey, 1951; Lu e t a l . ,

1979; Callow,

112 1984) but

o n l y a few p a p e r s

(Blunn, 1982;

Callow,

on t h e d i a t o m s c o l o n i s i n g organo-tin

1984).

The

results

of

Hendey's

(1951)

compounds

s t u d y of

the

b i o f i l m s on copper based p a i n t s , i n which 97 species ( r e p r e s e n t e d i n 2 9 g e n e r a )

were r e p o r t e d , i s s u p p o r t e d by t h e p r e s e n t i n v e s t i g a t i o n s i n Langstone Harbour ( 9 1 species

in

35

genera).

Also

in

agreement

with

Hendey,

Amphora

was

by f a r t h e most abundant genus t o be i d e n t i f i e d . Callow (1984)

examined

based f o r m u l a t i o n s

the

biofouling

world-wide

a

on

copper

on

Amphora

basis.

c o n s t i t u e n t s of t h e slime a l o n g w i t h Achnanthes.

identified

(1981) a l s o examined

a

on only

number

of

the

major

The r e s u l t s a g r e e w i t h t h o s e

a few o c c a s i o n s .

Daniel and

commercially

paint

noted on some t h a t Amphora formed a u n i - a l g a l surface.

organottn

were

3 and 4 i n which Amphora i s t h e dominant genus a l t h o u g h

presented i n f i g s . Achnanthes w a s

based and spp.

The numerical d i v e r s i t y index adopted

used

Chamberlain

formulations

and

s l i m e adhering c l o s e l y t o t h e i n t h i s paper a l s o r e v e a l e d

Amphora t o be a n i m p o r t a n t f o u l i n g genus; Amphora c o f f e a e f o r m i s v a r . p e r p u s i l l a had a n i n d e x of 106 and A.

c o f f e a e f o r m i s var.

i t is evident

In c o n c l u s i o n ,

that

c o f f e a e f o r m i s a n i n d e x of 32.

t h e r e are a l a r g e number of diatoms

which a r e a s s o c i a t e d w i t h t h e b i o f i l m on non-toxic

surfaces.

However, only a

few of t h e s e a t t a c h d i r e c t l y t o t h e s u r f a c e and c a n be c l a s s e d as t r u e ' s l i m e formers'.

Amphora w a s by f a r t h e most abundant genus w i t h i n t h e bio-

fouling layer,

o t h e r prominent genera b e i n g Navicula,

Cocconeis and Synedra.

The d i v e r s i t y i n d e x method allowed comparison of diatom communities from month t o month and i t w a s e v i d e n t t h a t Amphora c o f f e a e f o r m i s var. p e r p u s i l l a w a s t h e dominant diatom s p e c i e s i n most samples. ( 1 9 8 2 ) , i t w a s shown t h a t Achnanthes

had

In c o n t r a s t t o t h e r e p o r t of Blunn no p r e f e r e n c e f o r

the

organo-tin

based f o r m u l a t i o n s and r a r e l y o c c u r r e d w i t h i n t h e f o u l i n g p o p u l a t i o n .

7.5

ACKNOWLEDGEMENTS

This work w a s sponsored by t h e Research O r g a n i z a t i o n of S h i p ' s Compositions N a n u f a c t u r e r s Limited.

We are p a r t i c u l a r l y g r a t e f u l t o D r s P.

M o r r i s and K.

Borer f o r u s e f u l d i s c u s s i o n s .

7.6

REFERENCES

Anon (1976). Harbour. Bacon, G.R.

The e f f e c t s of sewage e f f l u e n t on t h e ecology of Langstone Portsmouth P o l y t e c h n i c . & Taylor,

A.R.A.

(1976).

Succession and s t r a t i f i c a t i o n i n

b e n t h i c diatom communities c o l o n i s i n g p l a s t i c c o l l e c t o r s . 19: 231-240.

Bot. Mar.,

113 B a s t i d a , R.,

Mandri, M.T.,

B a s t i d a , V.L.

& Stupak, M.

(1974).

Ecological

a s p e c t s of marine f o u l i n g a t t h e p o r t of Mar d e l P l a t a (Argentina). Cide-pint-Anales, Blunn, G.W. Ph.D.

11: 119-202.

(1982).

S t u d i e s on t h e

ship

f o u l i n g diatom

Achnanthes.

Thesis, U n i v e r s i t y of Leeds.

Callow, M.E.

(1984).

A world wide survey of

three antifouling paint surfaces.

f o u l i n g on non-toxic

In: Proc.

and

of t h e 6 t h I n t e r n a t i o n a l

Congress on Marine Corrosion and F o u l i n g , Athens, Greece, pp. 325-346. Castenholz, R.W.

(1964).

An experimental s t u d y on t h e d i s t r i b u t i o n of

marine l i t t o r a l diatoms. Daniel, G.F.

Limnol. Oceanogr.,

Chamberlain,

&

f o u l i n g diatoms. Bot. Mar., Fleming, W.D.

(1954).

(1981).

A.H.L.

Copper

immobilisation

in

24: 229-243.

Naphrax:

r e f r a c t i v e index.

8: 458-462.

a

synthetic

mounting

medium

of

N e w and improved methods of p r e p a r a t i o n .

high

J1.

R.

micro. SOC. 74: 42-44. H a r r i s , J.E.

(1946).

and S t e e l I n s t . , Hendey, N . I .

Report on a n t i f o u l i n g r e s e a r c h , 1942-44. 154: 296-333.

(1951).

L i t t o r a l diatoms of C h i c h e s t e r Harbour, with s p e c i a l

reference t o fouling. Heurck, H.van Baxter).

(1896).

J1. R. micro. A treatise

Soc.,

71: 1-86.

on t h e Diatomaceae ( t r a n s l a t e d by W.

Wesley & Son. London.

Houghton, D.R.

(1959). T i d a l measurements in Langstone Harbour,

Hampshire. Hudon, C.

J. I r o n

Dock Harb. Author.,

& Bourget,

(1983).

E.

40: 172-179. The e f f e c t

s t r u c t u r e of e p i b e n t h i c diatom communities. Karentz, D.

McIntire,

&

E.

(1977).

(1959).

l i g h t on t h e v e r t i c a l Bot.

Distribution

phytoplankton of Yaquina E s t u a r y , Oregon. Kingcome, J.C.

of

mar., of

J. Phycol.

R a f t t r i a l s of underwater p a i n t s .

26: 317-330.

diatoms

in t h e

13: 379-388. 2.

Paint Mf.,

January: 5-8. Lu, Q.,

Wang, Q.,

Xiong, Y & Huang, T. (1979).

S t u d i e s on microfouling

organisms on t h e s u r f a c e s of a n t i f o u l i n g p a i n t s .

Oceanologica Limnol.

sin., 10: 152-156. McLean, R.O.,

C o r r i g a n , J. & Webster, J. (1981).

i n Melosira nummuloides,

in t h e Clyde Estuary. Reisen, W.K.

&

Spencer,

Heterotrophic n u t r i t i o n

a p o s s i b l e r o l e in a f f e c t i n g d i s t r i b u t i o n

Br.

Phycol.

D.J.

(1970).

J., 16: 95-106.

Succession

and

current

demand

r e l a t i o n s h i p s of diatoms on a r t i f i c i a l s u b s t r a t e s in P r a t e r ' s Creek, South Carolina. Stupak, M.E.,

J. Phycol.,

6: 117-121.

B a s t i d a , R. & A r i a s , P.J.

(1976).

The b i o l o g i c a l

i n c r u s t a t i o n s of t h e P o r t of Mar d e l P l a t a (1976-1977).

h a l e s , 2: 175-232.

Cide-pint-

This Page Intentionally Left Blank

115 Chapter

8

THE PHYSIOLOGICAL ECOLOGY OF NUISANCE ALGAE I N AN OLIGOTROPHIC LAKE

JOHN E. REUTER~, STANFORD L. L O E B ~ , CHARLES R.

GOLD MAN^

' I n s t i t u t e o f Ecology, U n i v e r s i t y o f Cal t f o r n i a , Davis, CA 95616, USA 2Div. of Environmental Studies, U n i v e r s i t y o f Cal i f o r n i a , Davis, CA 95616, USA ABSTRACT P e r i p h y t o n Growth i n o l i g o t r o p h t c L a k e Tahoe appears t o be r e g u l a t e d by n u t r i e n t i n p u t and p r o v i d e s a d d i t i o n a l evtdence o f c u l t u r a l eutrophication. A s t a l k e d diatom CommunftYt h @ M d s herculeana, dominates t h e biomass i n t h e e u l i t t o r a l (splash) zone. and i t is t h e l u x u r i a n t growth o f t h i s a l g a which has caused a l g a l b i o f o u l t n g problems i n t h i s p r t s t i n e lake. 15N-labelled n i t r a t e and ammonium u p t a k e e x p e r i m e n t s showed t h a t t h i s community had a g r e a t e r a f f i n i t y f o r these n u t r i e n t s than d t d t h e s u b l i t t o r a l periphyton community whlch depended on n i t r o g e n f i x a t i o n t o meet i t s c e l l u l a r demands. The r a t e s o f n i t r o g e n u p t a k e a t n a t u r a l s u b s t r a t e 1e v e 1 s, measured under no f 1ow ( s t a t i c ) c o n d i t i o n s were t o o l o w t o a c c o u n t f o r t h i s community's N-demand. We s u g g e s t t h a t water movement (e.g., wave a c t i o n ) i s an i m p o r t a n t mechanism which acts t o increase t h e b l o - a v a i l a b i l i t y o f n u t r i e n t s and t h e r e f o r e a1 lows these a l g a e t o achieve h i g h r a t e s o f growth even though ambient s u b s t r a t e concentrations are low. 8.1

INTRODUCTION Long t e r m measurements

(Cal ifornta-Nevada)

o f productivity

i n oligotrophic

Lake Tahoe

have c l e a r l y demonstrated t h a t t h e r a t e o f p e l a g i c a l g a l

growth has more than doubled o v e r t h e l a s t two decades (Goldman 1985).

Nutrient

1 imitation, p a r t i c u l a r l y n i t r o g e n , appears t o b e t h e most i m p o r t a n t f a c t o r r e g u l a t i n g p h y t o p l a n k t o n g r o w t h (Arneson 1979; Go1 dman 1974, 1981).

Further

evidence whtch supports t h e o b s e r v a t i o n t h a t t h e o v e r a l l f e r t i l t t y o f t h e l a k e i s increasing comes from s t u d i e s o f nearshore periphyton (Goldman and de Amezaga 1975;

Goldman e t a l .

1982;

Loeb and R e u t e r 1984).

The r e s u l t s o f t h e s e

i n v e s t i g a t i o n s i n d l c a t e t h a t t h e amount o f g r o w t h o f a t t a c h e d a l g a e 1s w e l l c o r r e l a t e d w i t h l a n d d i s t u r b a n c e i n t h e a d j a c e n t w a t e r s h e d and t h e r e f o r e ,

is

most l i k e l y r e g u l a t e d by n u t r i e n t a v a i l a b i l t t y ( s e e Loeb m a n u s c r t p t i n t h i s symposium).

The i m p o r t a n c e of n u t r t e n t a v a i l a b i l i t y t o p e r i p h y t o n g r o w t h I n

Lake Tahoe has been e x p e r t m e n t a l l y v e r i f i e d using a l g a l bioassay techniques. Dissolved inorgantc n i t r o g e n (DIN) as b o t h n i t r a t e and ammonium, and t o a l e s s e r e x t e n t ortho-phosphorus,

s i g n i f i c a n t l y stimul ated t h e a s s i m i l a t i o n o f l4C-

l a b e l l e d i n o r g a n i c carbon, and i n c r e a s e d t h e c h l o r o p h y l l a c o n t e n t p e r u n i t biomass and t h e percentage c h l o r o p h y l l 1986).

a t o t o t a l ptgments ( E l o r a n t a 1983; Loeb

116 The c o n t r i b u t i o n o f a l l o c h t h o n o u s sources ( s u r f a c e w a t e r and ground-water) t o t h e n u t r i e n t budget o f Lake Tahoe i s c o n s i d e r e d s i g n i f i c a n t ,

and t h e r e f o r e i t

i s n o t uncommon t o f i n d t h a t t h e w a t e r s o f t h e l i t t o r a l z o n e c o n t a i n h i g h e r c o n c e n t r a t i o n s o f n u t r i e n t s r e 1 a t i v e t o t h e open w a t e r (Go1 dman 1974; e t al.

1982).

Go1 dman

S i n c e t h e a t t a c h e d a l g a l and 1 i t t o r a l p h y t o p l a n k t o n communities

occupy t h i s n e a r s h o r e r e g i o n , t h e y h a v e t h e f i r s t o p p o r t u n i t y ( v i s - a - v i s p e l a g i c p h y t o p l a n k t o n ) t o use n u t r i e n t s d e r i v e d f r o m t h e watershed.

Indeed,

the in

L a k e Tahoe t h e p e r i p h y t o n c o m m u n i t y h a s p r o v i d e d t h e m o s t v i s u a l l y s t r i k i n g evidence o f c u l t u r a l eutrophication. community i n t h e e u l i t t o r a l ,

The l u x u r i a n t growth o f an a t t a c h e d diatom

o r s p l a s h zone o f t h i s l a k e i s c o n s i d e r e d a

nuisance f r o m b o t h an a e s t h e t i c p o i n t o f view and a water q u a l i t y p e r s p e c t i v e . T h e s e o r g a n i s m s o c c u p y a u n i q u e n i c h e i n t h e l a k e ecosystem; l i v i n g i n a region o f higher n u t r i e n t loading,

i n addition t o

t h e y i n h a b i t an area o f t h e l a k e

w h i c h i s c o n s t a n t l y u n d e r t h e i n f l u e n c e o f t u r b u l e n t w a t e r niovements (i.e. b r e a k i n g waves).

These t w o f a c t o r s a p p e a r t o b e c r i t i c a l i n d e t e r m i n i n g t h e

a v a i l a b i l i t y o f n u t r i e n t s f o r t h i s community. I n t h i s paper we w i l l f i r s t ,

examine t h e p h y s i o l o g i c a l c h a r a c t e r i s t i c s o f

n i t r o g e n uptake by t h e s p l a s h zone diatom community, second, e x p l a i n why biomass accumulations i n t h i s r e g i o n a r e so h i g h d e s p i t e t h e f a c t t h a t t h e s e organisms l i v e i n a n u t r i e n t d e f i c i e n t system andJ t h i r d , r e s t r i c t e d t o t h e e u l i t t o r a l zone. i n part,

h y p o t h e s i z e why t h e s e a l g a e a r e

We would 1 i k e t o s t r e s s t h a t t h i s paper is.,

an o v e r v i e w o f p r e v i o u s and ongoing p e r i p h y t o n r e s e a r c h a t Lake Tahoe.

I n a d d i t i o n , we c o n s i d e r some o f o u r c o n c l u s i o n s r e g a r d i n g t h e i m p o r t a n c e o f water movement t o n u t r i e n t uptake and growth o f t h i s community as p r e l iminary. However, g i v e n t h e o v e r a l l l a c k o f i n f o r m a t i o n c o n c e r n i n g t h e f u n c t i o n a l r o l e o f freshwater p e r i p h y t o n communities i n n u t r i e n t c y c l i n g ,

we hope t h a t o t h e r

researchers w i l l be encouraged t o t e s t t h e hypotheses we p r e s e n t here. 8.2

METHODS K i t r a t e and

ammonium ( D I N )

u p t a k e w e r e d e t e r m i n e d i n d e p e n d e n t 1 y by

measuring t h e r a t e o f i n c o r p o r a t i o n o f t h e s t a b l e i s o t o p e I 5 N periphyton p a r t i c u l a t e fraction. s p r i n g o f 1980,

into the

These experiments were conducted d u r i n g t h e

a p e r i o d o f a c t i v e biomass a c c r u a l a p p r o x i m a t e l y midway between

t h e minimum and maximum annual p r o d u c t i o n f o r t h a t year.

S i n c e senescence anti

t h e t y p i c a l summer s l o u g h i n g o f f o f biomass d i d n o t occur u n t i l l a t e August we assumed t h a t t h e e x p e r i m e n t a l r e s u l t s o b t a i n e d were r e p r e s e n t a t i v e o f t h e p e r i o d o f a c t i v e growth. P e r i p h y t o n was removed f r o m n a t u r a l rock s u r f a c e s a t a depth o f 0.5 rn a t a l o c a t i o n a d j a c e n t t o a f e r t i l i z e d lawn. laboratory,

The b i o m a s s was r e t u r n e d t o t h e

and t r a n s f e r r e d t o f l a s k s c o n t a i n i n g 100 m l o f l a k e w a t e r .

measure DIN uptake,

To

a k i n e t i c s approach was used i n which each s e t o f t r e a t m e n t

117 f l a s k s (n=3)

was

Btomedlcals Inc.) 10-2,000

i n o c u l a t e d w t t h 15NH4C1

ug N 1 tter'l.

condtttons

of

200-250 uE m-'

o r Na15N03 (99.5

atom-%,

ICN

t o achteve a f t n a l s u b s t r a t e c o n c e n t r a t t o n which ranged from Samples were tncubated t n t h e l a b o r a t o r y f o r 6 '

ambtent sec-l.

temperature

(10-1500

and a

1tght

h under

Intensity

of

Studies on D I N uptake by o t h e r pertphyton communttles i n

Lake Tahoe have shown t h a t s u b s t r a t e d e p l e t i o n is 1 tnear o v e r t i m e (2-8 h) and that non-biological

u p t a k e ts t n s t g n t f t c a n t ( R e u t e r 1983).

Following the

tncubatton, t h e pertphyton btomass was removed from t h e treatment f l a s k s , rtnsed

6-8 t i m e s w t t h l a k e water,

o v e n d r t e d (6OoC),

A mass

and f r o z e n (-20°C).

spectrometer (Consoltdated Engtneertng Systems) was used t o determine t h e f t n a l l 5 N enrtchment and samples were prepared f o r ana.lysts ustng a K j e l d a h l d i g e s t i o n

and steam d t s t t l l a t t o n procedure ( F t e d l e r and Proksch 1975).

The f r a c t t o n o f

15N I n t h e gas phase was c a l c u l a t e d accordtng t o Neess e t a l .

(1962) and P a v l o u

e t a l . (1974).

F i n a l e n r t c h m e n t v a l u e s ranged f r o m 0.1-6.0

atom-% 1 5 N w t t h

substrate d e p l e t i o n g e n e r a l l y l e s s than 25%. The Mtchaelts-Menten equation was used t o model t h e k t n e t t c s o f D I N uptake (Dugdale 1967):

where V N Is t h e r a t e o f uptake,

S i s t h e e x t e r n a l s u b s t r a t e concentratton, Vmax a t s a t u r a t t o n l e v e l s o f S), and K t Is t h e

Is t h e maxtmum r a t e o f u p t a k e (t.e.

ha1 f - s a t u r a t t o n c o n s t a n t ( a t w h i c h V=Vma,/2).

Vmax,

The k t n e t t c p a r a m e t e r s K t and

a l o n g w t t h t h e i r s t a n d a r d d e v i a t i o n s , were c a l c u l a t e d d t r e c t l y f r o m a

r e c t a n g u l a r h y p e r b o l a f l t t e d t o t h e d a t a p o t n t s by a l e a s t s q u a r e s a n a l y s t s (Cleland 1967). Rates o f n i t r o g e n f t x a t t o n were measured u s t n g t h e a c e t y l e n e r e d u c t t o n t e c h n t q u e ( S t e w a r t e t a l . 1967; F l e t t e t a l . 1976).

The f a c t o r 4.6,

used t o

c o n v e r t moles o f e t h y l e n e t o moles o f n i t r o g e n was expertmental l y determined using 15N2 (Reuter e t a l .

1983).

P a r t i c u l a t e n i t r o g e n was used as an e s t t m a t e o f s t a n d i n g c r o p f o r t h e k t n e t l c s e x p e r l m e n t s and was measured

tmmedtately

followtng

t h e steam

d t s t t l l a t t o n p r o c e d u r e u s t n g 1.04N H2S04 a s t h e t t t r a n t (APHA 1 9 8 1 ) . C h l o r o p h y l l B ( c o r r e c t e d f o r phaeophyttn) was a l s o used as a biomass I n d i c a t o r and was measured accordtng t o S t r t c k l a n d and Parsons (1972) ustng 90% acetone as the

extracttng solvent.

ln d-tu

and expertmental

concentrattons o f

nitrate

(NOS+NOZ) were d e t e r m i n e d u s t n g t h e h y d r a z t n e r e d u c t t o n method d e s c r i b e d by M u l l t n and R t l e y (1955) and Kamphake e t a l . accordt ng t o Sol orzano (1969).

(1967) w h i l e ammonium was measured

118 Water movement was measured u s t n g an

in SUJ current

IU2WA240) equtpped w t t h an electro-mechantcal, chosen because It d e t e c t s t w o - d t r e c t t o n a l

d t g l t a l counter.

meter ( K a h l s t c o This meter was

f l o w (180°) and t h e r e f o r e measurements

were more r e p r e s e n t a t t v e o f t h e surge-type f l o w whtch occurs I n t h e s p l a s h zone. Measurements were taken on t h e bottom a l o n g a t r a n s e c t away from t h e shoreltne. The f t n a l readtngs a r e presented as a percent o f s u r f a c e f l o w and n o t as a c t u a l v e l oc t t t es.

F t g u r e 8.1. L u x u r t a n t g r o w t h o f t h e s t a l k e d diatom hm&&meb henxkmu i n t h e e u l t t t o r a l zone. Btomass a c c u m u l a t t o n r e p r e s e n t s a s t n g l e y e a r ' s growth. Productton begtns as e a r l y as January and by m t d - l a t e summer t h t s communtty has sloughed o f f t h e rocks. This unattached biomass may accumulate I n t h e l t t t o r a l zone. b e washed up on t h e beaches, o r b e t r a n s p o r t e d away f r o m s h o r e by l a k e Photograph was taken a t t h e study s i t e a t a depth o f 'lm currents.

119 8.3

RESULTS AND DISCUSSION I n Lake Tahoe,

attachment.

n a t u r a l rock surfaces p r o v t d e t h e major substratum f o r a l g a l

The v e r t t c a l ( d e p t h ) d t s t r t b u t t o n o f p e r t p h y t o n can be b r o a d l y

d t v i d e d I n t o two zones d e l tneated p r t m a r t l y by t h e annual changes t n l a k e l e v e l and by wave a c t i o n .

Each o f t h e s e zones i s c h a r a c t e r t z e d by a s e p a r a t e a l g a l The e u l t t t o r a l or

f l o r a w t t h d t s t t n c t taxonomtc and p h y s i o l o g t c a l differences.

splash zone is r e s t r i c t e d t o t h e area l o c a t e d between annual pertods of low and h t g h w a t e r l e v e l s (t.e.

0-2 m) and i s t h e most a f f e c t e d by w a t e r movement.

S u b s t r a t a w i t h i n t h t s r e g i o n d e s s t c a t e d u r i n g t h e summer p e r t o d o f reduced p r e c t p t t a t t o n (June-September) and each year,

pertphyton btomass must r e c o l o n t z e

when t h e l a k e - l e v e l r i s e s agatn I n t h e s p r i n g (February-June).

The biomass o f

t h t s communtty i s t o t a l l y domtnated by t h e s t a l k e d diatom Gmq&mMs The l u x u r t a n t g r o w t h o f t h t s s p e c i e s can b e seen I n F t g u r e t h e second,

8.1.

hejxulaana.

I n contrast,

deeper s u b l i t t o r a l zone r e m a i n s c o n s t a n t l y submerged and extends

from 2 t o o v e r 150 m t n depth. domtnated by heterocystous,

0

0.2

The a l g a e i n t h e upper s u b l t t t o r a l (2-80 m) a r e

ftlamentous blue-green algae.

I

I

I

I

I

-I I

0.4 h

F t g u r e 8.2. Verttcal p r o f t l e o f pertphyton nttrogen f t x a t t o n t n the e u l t t t o r a l zone o f Lake Tahoe. A t t h e t t m e o f sampl t n g t h e t r a n s t t t o n d e p t h between t h e e u l t t t o r a l dtatom communtty and t h e s u b l t t t o r a l blue-green a l g a l communtty was v t s u a l l y apparent a t approxtmately 0.5 m F o r each depth n=3.

120 The v e r t t c a l d t s t r t b u t t o n o f b e n t h i c nttrogenase a c t t v i t y was measured from

0-1 m and c l e a r l y showed t h a t n t t r o g e n f t x a t i o n was v i r t u a l l y non-extstent

in

t h e e u l i t t o r a l zone r e l a t i v e to t h e s u b l i t t o r a l zoner and was n o t Important as a s o u r c e o f n t t r o g e n f o r t h e s p l a s h zone community ( F i g .

8.2).

T h i s was n o t

unexpected s i n c e t h e a l g a l btomass i n t h t s regton was dominated by dtatoms. t h e t t m e t h e s a m p l e s were t a k e n ( J u l y ) ,

At

t h e l a k e l e v e l was d e c l i n t n g and t h e

t r a n s i t t o n between t h e e u l i t t o r a l and sub1 t t t o r a l was l o c a t e d between 0.4

and

0.6 m. A t and b e l o w t h t s d e p t h h e t e r o c y s t o u s b l u e - g r e e n a l g a e (i.e. IQJ.~,QQLUX, Ilalo and Nostoc) th dominated rlx t h, e btomass and s t u d t e s have shown t h a t t h i s communtty depends on n t t r o g e n f i x a t i o n as t h e m a j o r pathway o f n t t r o g e n a s s t m t l a t i o n ( R e u t e r e t a l . 1986).

Occastonal, i s o l a t e d patches o f

n t t r o g e n f t x t n g species e x i s t e d beneath t h e f o r the positive,

communtty and accounted

a l b e t t minimalr r a t e s o f n t t r o g e n f i x a t t o n observed a t Or 0.15

and 0.30 m. R a t e s of n i t r a t e and ammontum u p t a k e were d e p e n d e n t on t h e e x t e r n a l s u b s t r a t e c o n c e n t r a t i o n and these data agreed w e l l w t t h t h e c u r v e s generated by t h e Mtchael is-Menten model (Fig.

8.3).

The h a l f - s a t u r a t i o n constants were very

10000

NH$

2om 400

800

1200

1600 JUN 1980 2000

OO

D I N Concentration (tLg

~.d-')

F t g u r e 8.3. Ammonium and n i t r a t e u p t a k e as a f u n c t i o n o f s u b s t r a t e c o n c e n t r a t i o n f o r e u l i t t o r a l ( s p l a s h zone) e p t l i t h t c p e r t p h y t o n . These expertrnents were conducted d u r t n g t h e p e r i o d o f a c t i v e s p r t n g growth.

121 high

relative

t o ambient

levels

These

o f DIN.

113226 ug N l i t e r - l (X+SD) and 634+158 ug N l i t e r ’ ’ respectively.

i.e.

values

were

f o r n i t r a t e and ammonium,

The a m b i e n t l a k e c o n c e n t r a t i o n s o f NO;

these experiments were l e s s than 5 ug N 1 iter’l;

kt

and NHa a t t h e t i m e of

near t h e a n a l y t i c a l l i m i t

o f detection. The maximum r a t e o f ammonium u p t a k e was c a l c u l a t e d t o be 954021047 ug N g-lPN h’l w h i c h was more t h a n f i v e t i m e s g r e a t e r t h a n t h e Vmax f o r n i t r a t e u p t a k e (18642108 ug N g’lPN c o n c e n t r a t i o n s (125 ug N 1 i t e r ’ l ) ,

A t ecological l y relevant DIN

h”).

however, t h e r a t e s o f u p t a k e f o r t h e s e two

forms o f n i t r o g e n were s i m i l a r (V-ammonium/V-nitrate

= 1.6).

These r e s u l t s

suggest t h a t when D I N l e v e l s are low t h e organisms i n t h i s e u l i t t o r a l periphyton community appear t o be adapted t o use e i t h e r s u b s t r a t e equally. i s supported by f i e l d s t u d i e s of Reuter e t al. Lake,

California,

This conclusion

(1985) who found t h a t i n C a s t l e

a t ammonium c o n c e n t r a t i o n s l e s s t h a n 45 ug N 1 i t e r ’ l D

e p i l i t h i c p e r i p h y t o n was a b l e t o use NH4+ and NO3’ s i m u l t a n e o u s l y w i t h o u t an apparent p r e f e r e n c e f o r e i t h e r s u b s t r a t e .

I n addition, evidence from batch

c u l t u r e s t u d i e s has shown t h a t i f e x t e r n a l ammonium l e v e l s a r e i n s u f f i c i e n t t o saturate i n t e r n a l - N ~ O O ~ s simultaneous D NH4+ and NO3- uptake i s 1 i k e l y (McCarthy 1981). The magnitude o f t h e k i n e t i c s parameter, KtD

i s o f t e n i n t e r p r e t e d as an

i n d i c a t i o n o f an organism’s a b i l i t y t o use a n u t r i e n t when a v a i l a b l e i n low concentrations.

A low Kt v a l u e i m p l i e s t h a t an organism has a h i g h b i o l o g i c a l

a f f i n i t y f o r a specific nutrient,

p r e s u m a b l y an a d a p t i v e advantage i n

environments where t h a t n u t r i e n t was s c a r c e ( D u g d a l e 1976;

Raymont 1980).

P r e v i o u s s t u d i e s o f m a r i n e and f r e s h w a t e r p h y t o p l a n k t o n have shown t h a t t h e magnitude o f ha1 f - s a t u r a t i o n constants o f these n a t u r a l a l g a l communities f o r n i t r a t e and ammonium uptake are o f t e n d i r e c t l y r e l a t e d t o s u b s t r a t e a v a i l a b i l i t y (e.g.

MacIsaac and D u g d a l e 1969; E p p l e y e t a l . 1969; Murphy 1980; A x l e r e t a l .

1982, 1983;

P r l s c u and P r i s c u 1984).

Therefore,

we h y p o t h e s i z e d t h a t t h e

e u l i t t o r a l perlphyton community would have a low Kt (5 20 ug N liter’’)

i n order

t o s u r v i v e i n a n u t r i e n t d e f l c i e n t system Since t h e measured k t v a l u e was much greater, k i n e t i c s d a t a by e x a m i n i n g t h e r a t i o o f Vmax/Kt‘

we r e e v a l u a t e d t h e uptake This value represents the

i n i t l a 1 s l o p e o f t h e M i c h a e l is-Menten e q u a t i o n (dV/dS),

and p r o v i d e s a more

r e a l i s t i c i n t e r p r e t a t i o n o f b i o l o g i c a l a f f i n i t y i n cases where, , V d i f f e r e n t ( H e a l e y 1980; Zevenboom 1980). amOUnt o f c h l o r o p h y l l il (1.e. f o r NO;

and NH;

values are

When u p t a k e was normal i z e d t o t h e

m e t a b o l i c a l l y a c t i v e algae),

were n e a r l y I d e n t i c a l , 3.8 and 3.4

t h e Vm K/t,

respectively.

values

These Vmw/Kt

values f o r e u l i t t o r a l algae were 20 times g r e a t e r than those r a t i o s c a l c u l a t e d f o r t h e s u b l i t t o r a l community which depends on n i t r o g e n f i x a t i o n and n o t D I N f o r n i t r o g e n ( R e u t e r unpubl. data).

T h i s suggested t h a t t h e

community

had a g r e a t e r a f f i n i t y f o r D I N than t h e cyanophycean s u b l i t t o r a l community even

122 though t h e Kt

v a l u e s f o r each community were s i m i l a r (Reuter 1983).

r e 1 a t l o n s h i p between t h e Vmax/Kt

A similar

r a t i o s has a l s o been d e m o n s t r a t e d f o r t h e

w e m i l dominated e u l i t t o r a l p e r i p h y t o n and t h e n i t r o g e n - f i x i n g cyanophycean

sub1 i t t o r a l c o r n u n i t i e s i n N - d e f i c i e n t C a s t l e Lake, C a l i f o r n i a (Reuter and A x l e r i n press). E s t i m a t e s o f n e t c a r b o n p r o d u c t l o n were used t o c a l c u l a t e t h e n i t r o g e n demand o f t h i s community.

E u l i t t o r a l a l g a l p r o d u c t i v i t y was t a k e n as t h e

d i f f e r e n c e between t h e s e a s o n a l minlmum and maximum l e v e l s o f s t a n d i n g c r o p t o t a l carbon.

D u r i n g t h e p e r i o d o f s p r i n g maximum g r o w t h f r o m 1981-1983 t h i s

r a t e was 122+29 mg C m-’

day’’

(X+SD).

T h i s v a l u e represents n e t carbon

p r o d u c t i v i t y and w l l l underestlmate t h e a c t u a l d a l l y n i t r o g e n demand o f t h i s communlty t o t h e e x t e n t t h a t metabol i c and mechanical l o s s e s occur (i.e.

release

o f n i t r o g e n o u s e x t r a c e l 1u l a r p r o d u c t s , d e a t h and d e c o m p o s i t i o n , g r a z i n g and s l o u g h i n g due t o wave a c t i o n ) .

The maximum,

p r o d u c t i o n was c a l c u l a t e d t o b e 231+47 mg C m-’

s h o r t t e r m ( 3 0 day) r a t e o f day’’.

Since t h e r a t e o f

blomass accumulatlon d u r i n g s h o r t t l m e p e r i o d s . I s more l i k e l y t o r e f l e c t gross p r o d u c t i o n , t h e 30-day r a t e was used t o e s t l m a t e n l t r o g e n demand. C/N uptake o f 8 : l

Assuming a

( a v a l u e w h l c h was a l w a y s g r e a t e r t h a n t h e C / N biomass

c o m p c s i t i o n r a t l o ) and t h a t N-uptake o c c u r r e d a t e q u a l r a t e s o v e r t h e e n t i r e day, ’1200

t h e e s t i m a t e d n i t r o g e n demand o f t h i s community was ug N m”

h-l.

c a l c u l a t e d t o be

T h l s v a l u e i s be1 i e v e d t o be an underestimate o f t h e a c t u a l

n i t r o g e n demand because o f t h e two assumptlons made above.

Based on t h e r a t e s

o f N-uptake measured d u r i n g t h e k i n e t i c s experlments, t h e c o n c e n t r a t i o n o f t o t a l D I N t h a t would be necessary t o s u p p o r t e u l i t t o r a l a l g a l growth would be

’70 ug N l l t e r - ’ .

Since t h e maxlmum c o n c e n t r a t i o n s o f n l t r a t e I n t h e euphotic

r e g l o n o f Lake Tahoe n e v e r exceed 15-20 ug N l i t e r - ’ concentrations o f ammonium r a r e l y exceed 5 ug N 1 I t e r - l ,

( P a e r l e t a l . 1975) and t h e maximum a v a l l a b l e

c o n c e n t r a t l o n o f D I N cannot be g r e a t e r than 20-25 ug N l l t e r - ’ . Based on these c a l c u l a t l o n s , o t h e r n i t r o g e n sources and/or mechanisms which enhance t h e b l o a v a i l a b i l i t y o f t h i s n u t r i e n t must e x i s t t o enable these a l g a e t o meet t h e i r n l t r o g e n demand d u r i n g p e r i o d s o f maximum growth.

Groundwater

seepage and o v e r l a n d r u n o f f c o u l d b e i m p o r t a n t s o u r c e s o f n i t r o g e n t o t h e

1 I t t o r a l zone.

P r e l imlnary data on t h e c h e m i c a l c o m p o s i t l o n o f i n t e r s t i t i a l

water sampled from t h e e u l l t t o r a l

z o n e i n L a k e T a h o e shows t h a t D I N

c o n c e n t r a t i o n s a r e h i g h (general l y g r e a t e r than 100 ug N 1 i t e r ’ l )

relatlve t o

t h e v a l u e s r o u t i n e l y measured i n t h e o v e r l y i n g water (Loeb and Palmer 1985).

It

i s t h e r e f o r e p o s s l b l e t h a t t h e p e r i p h y t o n communlty I s a l s o exposed t o t h e s e e l e v a t e d DIN l e v e l s .

We b e l l e v e t h a t a more i m p o r t a n t f a c t o r w h t c h may

r e g u l a t e t h e r a t e o f D I N uptake by t h e . e u l l t t o r a 1 communlty I s r e l a t e d t o t h e p h y s i c a l r i g o r o f t h e h a b i t a t o f these organlsms.

The s p l a s h zone I s a r e g l o n

123 o f the l a k e where t h e r e i s constant water movement and water movement per se can enhance n u t r i e n t t r a n s p o r t i n t o c e l l s .

W h i t f o r d (1960) p r e s e n t e d t h e o r e t i c a l

evidence t o suggest t h a t a t v e l o c i t i e s g r e a t e r than

15 cm sec'l

the rate o f

periphyton growth c o u l d be i n c r e a s e d by m a i n t a i n i n g a s t e e p n u t r i e n t c o n c e n t r a t i o n g r a d i e n t a t t h e c e l 1 boundary w h i c h w o u l d i n t u r n f a c i l i t a t e d i f f u s i o n from t h e surrounding water.

Lock and John (1979) observed t h a t even a

minimal f l o w v e l o c l t y s t i m u l a t e d phosphorus uptake by r i v e r periphyton.

Wheeler

(1982) examined n i t r a t e and ammonium u p t a k e by m a t u r e b l a d e s o f t h e m a r i n e macroalga W o c y t b

as a f u n c t i o n o f c u r r e n t speed and showed t h a t a t

v e l o c i t i e s g r e a t e r than 5 cm sec-l t h e uptake r a t e s were 5-10 times g r e a t e r than those measured under s t a t i c conditions.

We hypothesize t h a t t h e n i t r o g e n demand

o f t h e ' n a t u r a l e u l i t t o r a l a l g a l community can be accounted f o r a t low ambient substrate l e v e l s because water f l o w w i 1 1 augment n u t r i e n t uptake rates. The v e l o c i t i e s o f breaking waves i n l a k e s range from 50-500 cm sec'l

(Boyce

1974) and t h e r e f o r e s h o u l d b e more t h a n s u f f i c i e n t t o m a i n t a i n an e l e v a t e d nutrient concentration gradient a t the c e l l

boundary.

The w a t e r f l o w

measurements t a k e n i n t h e e u l i t t o r a l zone a t Lake Tahoe showed t h a t w a t e r movement a t t h e r o c k - w a t e r boundary decreased e x p o n e n t i a l l y w i t h d e p t h on a t r a n s e c t away from t h e shoreline,

and a t a depth o f 2 m t h e c u r r e n t was reduced

t o 7% o f t h a t measured a t t h e s u r f a c e a t t h e l a k e s h o r e boundary.

We s u g g e s t

t h a t t h e l u x u r i a n t growth o f e u l i t t o r a l p e r i p h y t o n community i s r e s t r i c t e d t o the upper 2-3 meters o f t h e l i t t o r a l zone because below t h i s depth wave f l o w i s i n s u f f i c i e n t t o s u s t a i n t h e r e q u i r e d r a t e s o f n u t r i e n t uptake. data) found t h a t

Loeb (unpubl.

lh@um& 14C prtmary p r o d u c t i v t t y was reduced a t t h e surface

r e l a t i v e t o more i n t e r m e d i a t e d e p t h s (2-30 m).

T h i s suggests t h a t t h i s

community i s n o t r e s t r i c t e d t o t h e e u l i t t o r a l zone on t h e b a s i s o f i t s l i g h t requirements.

As s u g g e s t e d l o n g ago b y R u t t n e r (1926), t h e movement o f w a t e r

a1 l o w s a t t a c h e d a l g a e t o 1 i v e i n a * * p h y s i o l o g i c a l l y r i c h " e n v i r o n m e n t even though t h e n u t r i e n t c o n c e n t r a t i o n i n t h e surrounding water may be low.

8.4

CONCLUSIONS P e r i p h y t o n biomass a c c u m u l a t i o n i n t h e e u l i t t o r a l zone i n Lake Tahoe i s

much g r e a t e r than t h a t measured for t h e sub1 i t t o r a l community.

We be1 i e v e t h a t

t h e l u x u r i a n t g r o w t h o f t h i s n u i s a n c e a l g a l community i s r e l a t e d t o t h e f o l 1ow 1ng:

1.

The

G a q h n d s community has a g r e a t e r b i o l o g i c a l a f f i n i t y f o r

n i t r o g e n as compared t o t h e s u b l i t t o r a l algae.

2.

I n c r e a s e d w a t e r movement i n t h i s zone p r o b a b l y enhances t h e r a t e o f

3.

A d d i t i o n a l sources o f n u t r i e n t s a r e g r e a t e r a t t h e lakeshore boundary,

uptake o f DIN,

as w e l l as o t h e r i m p o r t a n t n u t r i e n t s .

p a r t i c u l a r l y from groundwater seepage and o v e r 1 and runoff.

124 F u r t h e r m o r e , we h y p o t h e s i z e t h a t t h e v e r t i c a l d i s t r i b u t i o n o f t h e e u l i t t o r a l a l g a e i s a l s o r e l a t e d t o n u t r i e n t a v a i l a b i l i t y as r e g u l a t e d by water movement. 8.5

ACKNOWLEDGMENTS Research support was p r o v i d e d by NSF g r a n t DEB80-19918 t o Dr.

C.R.

Goldman

and by t h e C a l i f o r n i a S t a t e Water Resources C o n t r o l B o a r d u s i n g C l e a n Lakes g r a n t funds made a v a i l a b l e by t h e Environmental P r o t e c t i o n Agency.

This support

from t h e CSWRCB and EPA does n o t s i g n i f y t h a t t h e contents n e c e s s a r i l y r e f l e c t t h e v i e w s o f t h e s e agencies.

We t h a n k S. H a c k l e y , T. Dunn, J. A l o i r G. Z u n i g a

and S. R e u t e r and D. Dogge f o r t h e i r v a r i o u s c o n t r i b u t i o n s t o t h i s p r o j e c t . s p e c i a l acknowledgment i s g i v e n t o Dr.

R.P.

A

A x l e r f o r h i s support and c r e a t i v e

discussion. REFERENCES APHA (American Pub1 i c H e a l t h A s s o c i a t i o n ) . 1981. S t a n d a r d methods f o r t h e examination o f water and wastewater. 1 5 t h ed. WHAD New York. A r n e s o n r P.A.r 1979. E f f e c t s o f n u t r i e n t e n r i c h m e n t on t h e n a t u r a l M.S. theSiSr U n i v e r s i t y o f phytoplankton o f Lake Tahoer Cal ifornia-Nevada. C a l i f o r n i a r Davis. 150 pp. A x l e r r R.P.8 Gersberg, R.M. and Goldmanr C.R.1 1982. a s s i m i l a t i o n i n a s u b a l p i n e lake. Limnol. Oceanogr.r

Inorganic nitrogen 27: 53-65.

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&:I

W.W.r F.F.

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Dugdaler R.C.r 1967. N u t r i e n t 1 i m i t a t i o n . i n t h e sea: Dynamicsr i d e n t i f i c a t i o n , and significance. Limnol. Oceanogr., 12: 685-695. Dugdale, R.C.D (Editors),

1976. N u t r i e n t cycles. Ecology o f t h e seas. WB ..

h: D.H. Saunders.

C u s h i n g and J.J.

Walsh

E l oranta,

P.V.r 1983. P e r i p h y t o n p i g m e n t analyses using paper chromatography. P e r l p h y t o n o f F r e s h w a t e r Ecosystems. R.G. Wetzel ( E d i t o r ) Developments i n Hydrobiology 17. Pp. 161-167.

In:

Eppl ey, R.W.r Rogers, J.N., and McCarthy, J.J., 1969. Hal f - s a t u r a t i o n constants f o r u p t a k e o f n i t r a t e and ammonium by m a r i n e p h y t o p l a n k t o n . Limnol. Oceanogr.r 14: 912-920.

125 F t e d l e r , R., and PrOkSCh. J.. 1975. The d e t e r m t n a t t o n o f n t t r o g e n - 1 5 by emtsston and mass spectrometry i n biochemical analysts: A revtew. Anal. Chem. Acta, 78: 1-62. F l e t t , R.J., Hami 1ton. R.D., and Campbel 1, N.E.R., 1976. A q u a t t c a c e t y l e n e reductton techntques: S o l u t i o n s t o s e v e r a l problems. Can. J. Microbio1.r 22: 43-51. Goldman. C.R.8 1974. E u t r o p h t c a t t o n o f Lake Tahoe Emphastztng Water Qua1 t t y . U.S. WA-660/3-74-034. Gov. P r t n t t n g Offtce, Washtngton. D.C. 408 pp. Goldman, C.R.1 1981. Lake Tahoe: Two decades o f change I n a n t t r o g e n d e f t c t e n t o l t g o t r o p h i c lake. I n t . Ver. Theor. Angew. Ltmnol. Verh., 21: 45-70. Goldman, C.R. 1985. Lake Tahoe: A mtcrocosm f o r t h e s t u d y o f change. Nat. H t s t . Sur. B u l l . V o l . 33: 247-260.

I 1 1.

and deAmezagar E.D 1975. P r l m a r y p r o d u c t t v t t y t n t h e 1 t t t o r a l Goldman, C.R. zone o f Lake Tahoe. C a l tfornta-Nevada. Symp. B l o l . Hungary 15: 49-62. Goldman, C.R., Leonard. R.L., A x l e r , R.P., Reuter. J.E., and Loebr S.L.. 1982. I n t e r a g e n c y Tahoe M o n t t o r t n g Program: Second Annual Report, Water Year 1981. I n s t i t u t e o f Ecology, U n t v e r s t t y o f Cal t f o r n t a . Davts. 193 pp. Healey, F.P. 1980. Slope o f t h e Monod equation as an t n d t c a t o r o f advantage i n n u t r t e n t competttlon. Mtcrob, Ecol. 5: 281-286. 1967. Automated a n a l y s t s f o r Kamphake, L.J., Hannah. S.A.D and Cohen. J.M.. n i t r a t e determlnatton by hydrazlne reductlcn. Water Res., 1: 205-216. and John, P.M.8 1979. The e f f e c t o f f l o w p a t t e r n s on u p t a k e o f Lock. M.A., phosphorus by r t v e r pertphyton. Ltmnol. Oceanogr.. 24: 376-383. Loeb, S.L., 1980. The productton o f t h e e p t l t t h l c p e r l p h y t o n community I n Lake Tahoe, Cal tfornta-Nevada. Ph.D. Thests. Unt v e r s t t y o f Cal i f o r n i a , Davts. 165 pp. Loeb. S.L., 1986. A l g a l b t o f o u l tng o f 01 t g o t r o p h l c Lake Tahoe: (Thts symposium Chapter 11). a f f e c t i n g productton.

Causal f a c t o r s

Loeb. S.L., and Reuter, J.E., 1984. L i t t o r a l zone t n v e s t t g a t t o n s , Lake Tahoe 1982. Pertphyton. I n s t i t u t e o f Ecology. U n i v e r s i t y o f Cal t f o r n t a , Davts. 66 PP. Loeb, S.L., Reuter, J.E., and Eloranta, P.V. 1984. The u t t l t t y o f the l i t t o r a l zone p h y t o p l a n k t o n t n e v a l u a t l n g t h e e f f e c t s o f n u t r i e n t l o a d t n g . 1. Prlmary p r o d u c t t v i t y . I n t . Ver. Theor. Angew. Ltmnol. Verh.. 22: 605-611. Loeb, S.L., and Palmer, J., 1985. L i t t o r a l zone I n v e s t l g a t l o n s , Lake Tahoe 1983. pertphyton. I n s t i t u t e o f Ecology, U n i v e r s i t y o f Cal t f o r n l a , Davts. 106 pp. MacIsaac, J.J., and Dugdale, R.C., 1969. The k i n e t t c s o f n t t r a t e and ammonium uptake by n a t u r a l popul a t t o n s o f marlne phytoplankton. Deep-sea Res., 16: 445-457. Mccarthy. J.J., 1981. The k i n e t i c s o f n u t r i e n t u t i l i z a t i o n . In: T. P l a t t ( E d t t o r ) , P h y s i o l o g t c a l Bases o f P h y t o p l a n k t o n E c o l o g y . Can. B u l l . o f F t s h and Aquatic Scl., B u l l . 2101 Ottawa, Canada. pp.211-233.

126 Mu1 1 in. J.B., and Rt l e y , J.P.8 1955. The s p e c t r o p h o t o m e t r i c d e t e r m t n a t t o n o f Anal. n i t r a t e I n n a t u r a l waters, w t t h p a r t i c u l a r r e f e r e n c e t o seawater. Chim. A c t a t 12: 464-480. Murphy, T.P., 1980. Ammonia and n t t r a t e u p t a k e I n t h e Lower G r e a t Lakes. J. F i s h . Aquat. sct.D 37: 1365-1372.

Can.

DUgdalet V.A., and Goertng, J.J.t 1962. N t t r o g e n Neess, J.C., Dugdale, R.C., I. Measurement o f n t t r o g e n f i x a t i o n w t t h 15-N. metabolism t n lakes. Ltmnol. Oceanogr., 7: 163-169.

,

P a e r l HW . ,. R i c h a r d s , R.C., Leonard, R.L., and Go1 dman, C.R.1 1975. Seasonal n t t r a t e c y c l i n g as e v t d e n c e f o r c o m p l e t e v e r t i c a l m t x t n g i n Lake Tahoe, C a l tfornia-Nevada. Limnol. Oceanogr., 20: 1-8. P a v l out S.P., F r t e d e r i c h , G.E., and MacIsaac, J.J., 1974. Q u a n t i t a t t ve d e t e r m t n a t i o n o f t o t a l o r g a n i c n i t r o g e n and Isotope enrtchment i n marine phytoplankton. Analyt. Btochm, 61: 16-24. Prtscu, J.C. and Prlscu, L.R., Lake Taupo, New Zealand.

1984. I n o r g a n i c n i t r o g e n uptake i n o l i g o t r o p h i c ~ 1436-1445. Can. J. F i s h . Aquat. S C ~ .41:

1985. N t t r o g e n m e t a b o l i s m o f t h e P r t s c u , J.C., A x l e r , R.P., and Goldman, C.R., s h a l l o w and deep-water phytoplankton i n a subalptne lake. OIkOS, 45: 137147. Raymont, J.E.G., 1980. P l a n k t o n and p r o d u c t i v i t y i n t h e oceans, 2nd ed.r 1. Phytoplankton. 489 pp. Oxford, Pergamn Press.

Vol.

Reuter, J.E.t 1983. I n o r g a n i c n i t r o g e n metabol ism i n t h e p e r i p h y t o n communities o f N - d e f t c t e n t o l i g o t r o p h i c lakes. Ph.D. thesis, U n i v e r s i t y o f Cal i f o r n i a , D a v i s . 220 pp. Reuter, J.E., Loeb, S.L., and Goldman, C.R. 1983. Nitrogen f i x a t i o n i n In: R.G. Wetzel p e r i p h y t o n o f l o t g o t r o p h i c Lake Tahoe, pp. 101-109. (Edttor), Periphyton o f freshwater ecosystems. Develop. Hydrobtol.D 17. Reuter, J.E., Loeb, S.L.1 A x l e r , R.P., C a r l t o n , R.G., and Goldman, C.R., 1985. T r a n s f o r m a t i o n s o f n i t r o g e n f o l l o w i n g an e p i l i m n e t t c n t t r o g e n f e r t i l t z a t t o n i n C a s t l e Lake. CA. 1. P e r t p h y t o n responses. Arch. Hydrobtol., 102:425-433. 1986. I n o r g a n i c n i t r o g e n u p t a k e by Reuter, J.E., LOebr S.L., and Goldman, C.R., e p t l i t h i c pertphyton t n an N - d e f t c i e n t lake. Ltmnol. Oceanogr., 31: 149160. Reuter, J.E., and A x l e r , R.P., I n press. P h y s i o l o g t c a l c h a r a c t e r t s t i c s o f i n o r g a n i c n i t r o g e n uptake by s p a t i a l l y separate a l g a l communittes i n a Nd e f i c i e n t lake. Freshwater B i o l . R u t t n e r , F., 1926. Bermerkungen u b e r d e r S a u e r s t o f f g e h a l t d e r Gewasser und Dessen Respt r a t o r i s c h e n Wert. Naturwtss 14. D e t e r m t n a t i o n o f ammonia i n n a t u r a l w a t e r s by t h e S o l o r z a n o , L., 1969. phenol h y p o c h l o r i t e method. Ltmnol. Oceanogr., 14: 799-801. S t e w a r t , W.D.P.9 F i t z g e r a l d , G.P., and B u r r t s , R.H.1 1967. h SiU s t u d i e s on n i t r o g e n f i x a t i o n u s i n g t h e a c e t y l e n e r e d u c t i o n technique. Proc. Nat. Acad. Sci., U.S.1 58: 2071-2078.

127 S t r i c k l a n d , J.D.H., and ParsonsI T.R.? 1972. A P r a c t i c a l Handbook o f Seawater A n a l y s i s . B u l l . F l s h . Res. Bd. Canada, 1967. 3 1 0 pp.

m.

Wheeler, WN .,. 1982. N i t r o g e n n u t r l t i o n of h: L.M. S r i v e s t a v a ( E d i t o r ) # S y n t h e t i c and d e g r a t i v e process i n marine macrophytes? pp. 121137. W a l t e r de GrUytert B e r l in. Whitford, L.A.# 1960. The c u r r e n t e f f e c t and g r o w t h o f f r e s h - w a t e r Trans. Amer. M i c r o . Sot., 79: 302-309.

algae.

1980. G r o w t h and n u t r i e n t u p t a k e k i n e t i c s o f PSrlllatPrin comparative i n v e s t i g a t i o n o f continuous c u l t u r e s and n a t u r a l p o p u l a t i o n s o f a cyanobacteriurn. Ph.D. t h e s i s . U n i v e r s i t y o f Amsterdam 178 pp.

Zevenboom,

W.,

m:a

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129

Chapter 9 PHYSICO-CHEMICALPROCESSES AFFECTING COPPER, TIN AND ZINC TOXICITY TO ALGAE: A REVIEW JAMES S . KUWABARA, U.S. California, 94025, U.S.A. 9.1

Geological Survey,

Menlo

Park,

INTRODUCTION

Algal biofouling results from uncontrolled and undesirable algal growth on a surface that has usually been

created by and for humans. A comprehensive

understanding of this phenomenon requires the ability to quantify nutrient and toxicant interactions among that surface, the algae and the surrounding solution.

This

goal is complicated by the fact that highly interdependent chemi-

cal, biological and physical processes are involved. The discussion presented herein represents a brief review of how various chemical processes, listed as topic headings, affect and

are affected by

biological processes. These

processes, which may interactively affect the availability and hence toxicity of

solutes,

include:

precipitation-dissolution, adsorption-desorption,

complexation-dissociation, oxidation-reduction and photoactivation. Each will be discussed with an emphasis on quantifying process effects on algal response. Examples from the literature involving copper (Cu) and zinc been chosen, because

of

algicidal applications of antifouling agent used discussed.

(Zn) toxicity have

the well-documented inhibitory effects and common these two

in

the

elements.

form of

Toxicity

of

tin (Sn), an

organic complexes, is also briefly

Some background information is initially given on the relationship

between chemical speciation. and establish the

algal

toxicological response

in order to

importance of discussing the topics in this chapter. Temporal

and light effects

are mentioned in terms of adaptation mechanisms, reaction

kinetics and photochemistry.

However, physical processes, which

may

be

important, are not addressed (e.g.,effects of temperature and flow regime.) The reader

is directed

to

reviews by Mauersberger (1983) and Bowie et al.

(1985) on this topic. Both Cu and Zn are essential algal micronutrients (Wiessner, 1962; Brand et al., 1983),

cofactors in numerous biochemical processes (Lehninger, 1975).

Yet, submicromolar activities growth

of

these essential elements may inhibit algal

(Petersen, 1982; Kuwabara, 1985; Brand et al., 1986).

(1981) presented

Gavis et al.

results of an extensive Cu toxicity study using 24 clones of

11 marine phytoplankton species. They reported pCu (negative logarithm of free 2+

Cu

activity) threshold values of typically 8.7 and 11.5. For both Cu and Zn

the uncomplexed metal

ion seems most readily available to algae (Manahan and

Smith, 1973; Sunda and Guillard, 1976; Anderson et al., 1978; Petersen, 1982).

130 Rueter

2+

et

al. (1981) suggested a toxicity mechanism for diatoms in which Cu

inactivates the

silicic

inhibits diatom

growth, resulting

though

acid (Si(OH),)

transport site. Intracellular Cu also

in accumulation of intracelluar Si even

Si uptake is inhibited. Cu also adversely affects growth of algae in

general by increases

affecting cell membrane

permeability

as

demonstrated by large

in cell volume and accelerated cell potassium release (McBrien and

Hassall, 1965; Riisgard et al., 1980; Rai et al., 1981; Kuwabara and Leland, 1986).

Evidence

from

interferes with

Zn toxicity experiments indicates that uncomplexed Zn

efficient intracellular phosphate utilization (Bates et al.,

1982; Kuwabara, 1985). Bates et al. (1982) hypothesized that Zn accumulates intracellular

polyphosphate

bodies until reaching some

threshold level, at

which point phosphate metabolism ceases. Zn generally appears to be effective

algicide than Cu, although

considerably

among

in

a

less

sensitivity to these elements varies

species (Gavis et

al., 1981; Petersen, 1982; Kuwabara,

1985). Under pH

conditions typical of most natural waters (pH 6.5-8.5), chemical

speciation of Cu(I1)

is

usually

carbonate complexes. Although unpolluted Leland

magnitude lower

-11

(10

hydrolysis products

or

1978; Kremling et

free

ion activites are three or more orders of

-lO-l3N). When high concentrations of dissolved organic

(DOC) are present

bioavailability may

be

(> 10 mg/L),

Cu

free ion activities and hence

further decreased due to chelation (Mantoura et al.,

al., 1981; Wood, 1983; Wood

nanomolar dissolved concentrations are waters.

by

marine and freshwaters are in the nanomolar range (Brewer, 1975;

and Kuwabara, 1985),

carbon

dominated

total dissolved Cu concentrations reported for

et

al., 1983).

Like Cu,

typical for background Zn in natural

However, uncomplexed Zn(I1) can be the predominant species in water

+

with low DOC. Other important inorganic complexes include ZnOH , ZnCO,',

ZnCl',

0

0

ZnC1,

and

ZnSO, .

A

comprehensive

review of Zn cycling in the coastal

environment has been presented by Young et al. (1980). It

is

ability

clear from

to provide

the

toxicological mechanisms

an accurate

description of

discussed above that an

Cu and

Zn speciation and

distribution in natural waters enables improved predictions for responses to algal

inhibitory

chemical

The

discussion presented below of physico-

processes that regulate solute speciation and distribution is

sectionalized by this

treatments.

process to enhance readability. It is hoped, however, that

format does not cause one to lose sight of the fact that these processes

operate interactively in nature and should be modeled accordingly.

131 9.2

PHYSICO-CHEMICALPROCESSES

9.2.1

PreciDitation-dissolution

The availability of a nutrient or toxic substance can be significantly affected by

precipitation (Anderson and Morel, 1982; De Haan et al., 1985).

Furthermore, formation of precipitates tions of other

can then affect dissolved concentra-

solutes by adsorption, a subject which will be discussed in a

later section of this paper.

Precipitation-dissolutionreactions are generally

quantified by a solubility product (Kso) as shown below:

Me.L.(s)

+

i(Me)

+

j(L)

(dissolution reaction) (1)

1 J

Kso

=

(solubility product) (2)

(7Me[Mel)i(7L[Ll)j

Equation 1 represents the dissolution of a solid composed Me and j moles of ligand L. when controlled by the metal

of i moles of metal

Equation 2 defines the activities of Me and L ions

the dissolution of the

(yMe) and the ligand

solid. Activity coefficients for

(7 )

may be determined by the Davies Equation

for ionic strengths less than 0.5

(Stumm and Morgan, 1981) or by Pitzer

Equations 1975). more

for

ionic

L

strengths equivalent to seawater and higher (Whitman,

The simple case described above may be extended for a solid composed of than one metal or

(Cu,(OH),CO,(s))

ligand.

For example, the dissolution of malachite

under acidic conditions, is defined by:

(Schindler,l967) ( 3 ) It has been noted

that

inorganic tin (Sn) is not an effective algicide

relative to

organotin complexes that are commonly used in antifouling paints

(Hallas and

Cooney,

1981; Wong et al., 1982). This result may be due to the

low solubility of Sn(1V) predicted

in

water. A

pSn(1V)

from solubility data (Hogfeldt, 1982)

of approximately 20 is

for a system controlled by

Sn oxide at pH 7. Chelation, photochemical and redox processes, to be discussed in later sections, appear to be more important in controlling Sn toxicity. Numerous

computer programs

(Westall et al., 1976; Felmy et al., 1983) are

available to determine whether a solubility product is exceeded (i.e.,whether formation of a precipitate is thermodynamically favorable.)

The applicability

of such equilibrium computations is dependent on the accuracy of the thermodynamic data base, the validity

of the analytical measurements, and the

importance of reaction kinetics over the time scales of interest (Pankow and Morgan, 1981).

132 9.2.2

Adsorption-desorption

Like precipitation-dissolution reactions, adsorption-desorptionreactions affect solute bioavailability through interactions of solid and aqueous phases. Kuwabara et al. (1986) demonstrated a dramatic difference between availability of dissolved and particulate-bound forms of both Zn and orthophosphate to a freshwater chlorophyte. studies to

Partitioning coefficients are often used in field

quantify solute distribution between dissolved and particulate

phases (Ambrose et al., 1983). to

the

Yet recent research has pointed out limitations

applicability of a partitioning coefficient approach for determining

solute availability to desorption,

and

algae.

hence

Many

factors affect

solute adsorption and

tend to make partitioning coefficient data site

specific. These factors include: 1. Surface minerology - Oxide and clay surfaces react very differently with different solutes (Hart, 1982; Wauchope and McDowell, 1984), 2. Sediment particle size - Smaller particles generally have a higher adsorption site density

(i.e., sites per unit mass) (Onishi et al.,

1982), 3. Reactions involving particulate and dissolved organic matter

-

Dissolved organic material may form strong chelates with the solute or form reactive organic films around inorganic particles (Toledo et al., 1982; Luoma and Davis, 1983),

4. Chemical speciation - Factors like pH and ionic strength affect chemical speciation and the reactivity of an adsorbent. If adsorption sites are limited, competition between adsorbates can occur (Benjamin and Leckie, 1980), 5. Reaction kinetics - Rapid desorption as a result of changing chemical environment can effectively buffer

dissolved solute concentrations

and

thus enhance bioavailability (Kuwabara et al., 1986).

may

also be

Kinetics

dependent on physical processes like diffusive mass

transfer rates (i.e. solute velocity to surface reaction sites). 6. Interdependence with biological processes - Some photosynthesizing algae can create a high pH microenvironment (> 2 pH units above the bulk

solution)

that can decrease availability of metals like Cu and

Zn while increasing anion (e.g., phosphate) availability (Revsbech et al., 1984; Kuwabara et al., 1986). The

algal cell surface has been recently studied as a trace metal adsorbent

(Grist, 1981).

Fisher et al. (1984) found that uptake of

marine phytoplankton was studies

trace metals by

initially a passive sorption process. Our recent

(unpublished) indicate that active uptake of Zn and orthophosphate by

the chlorophyte Selenastrum capricornutum is not significant over the first

133 24 h.

While uptake of orthophosphate (10 @ total P) by heat-

of exposure.

killed Selenastrum cells after 24 h. was nearly 100% efficient over a pH range of 6.5 to 8.5, Zn uptake (1 @ total Zn) increased from 30 to 70% over the same pH

range

(Fig. 1).

results suggest that the algal cell surface can

These

successfully compete with inorganic surfaces for dissolved nutrients and toxic substances within this environmentally significant pH range. Methods

for modeling the effects of adsorption-desorption reactions have

been previously

reviewed (Onishi et al., 1982; Kuwabara and Helliker, 1986).

Operational methods for determining biological availability of particulatebound metals have

also been presented

and reviewed (Luoma and Jenne, 1976;

Tessier et al., 1984).

. I

I

1

I

I

Orthophosphate

100-

0

.

B

eg

0

0 .

0

3

-

80-

-0

a

0

B 603 0

v)

ap

O O

40 0

I

-

1 pM total Zn 1 0 p M total P 1.1 ? 0.1 Mcells/mL

0

20 -

0

Zn ( 1 1 )

I

I

-

1

Fig. 9.1.Effects of culturing media pH on Zn(I1) and orthophosphate adsorption 0

by heat-killed Selenastrum cells. A 1.1+0.1 x 10 cells/mL concentration was used for both experiments with 1 @ and 10 @ total Zn or orthophosphate, respectively.

9.2.3 Comulexation-dissociation It was previously noted that the free ion forms of Cu and Zn appear to be most available

to

algae.

Complexation and dissociation reactions therefore

represent an important process regulating availability of these solutes. An equilibrium constant (K),

analogous to

the precipitation-dissolutionKs o '

describes the association of i moles of metal (Me) and j moles of ligand (L) that form complex MeiLj.

134

+

i(Me)

The

j(L)

Me.L.

+

1 J

activity

coefficients ( 7

Me' 'L'

)

'complex

may be estimated from the same

equations cited previously for precipitation reactions.

Though chemical

equilibrium programs can be helpful in modeling speciation of solutes (Westall al.,

et

1976; Felmy et al., 1983), field applicability of such computations

is highly

dependent

on:

(1) the accuracy of equilibrium constants used to

model

the particular environment, ( 2 ) the extent to which the sample repre-

sents

the

in-situ conditions, (3) and the degree to which kinetics of these

reactions affects the departure from assumed equilibrium conditions. Consider for example, the discharge of inorganic Cu into an environment with dissolved organic matter. tion of

Though formation of strong Cu chelates and subsequent reduc-

Cu availability to algae is thermodynamically favorable, Cu chelation

may be suppressed by slow dissociation of existing metal-organic chelates. This kinetic effect, which

enhances Cu availability, has been observed in several

laboratory experiments (Anderson and Morel, 1978; Kuwabara and Leland, 1986). and hence potential algal toxicity of Cu and Zn, may also be

Availability, dependent on Si(OH),

the

transport

previously

availability of other sites in marine

discussed.

solutes. The competition of Cu for

diatoms

Button et al. (1973) noted that manganese (Mn) contam-

ination of phosphate stock solutions used sensitivity of proposed by

(Rueter et al., 1981) has been

in culture media reduced copper

the marine yeast Rhodotorula m. Sunda et al. (1981) later

that for marine phytoplankton Cu interferes with manganese metabolism

competing with Mn for nutritional sites. Another type of interaction was

reported by

Rana

and Kumar

(1974)

in which Zn toxicity was ameliorated by

increasing orthophosphate concentrations. with

The mechanism of Zn interference

intracellular phosphate utilization has been mentioned earlier (Bates et

al., 1982; Kuwabara, 1985). reduces Zn

toxicity, but

Increased availability of

cadmium (Cd) also

total Cd concentrations orders of magnitude above

typical background concentrations were needed to induce this interaction (Braek et al., 1980).

While response and

algae may to

be

inhibited, they may also show adaptive mechanisms in

elevated Cu and Zn ion activities.

These include intracellular

cell wall exclusion mechanisms (Silverberg et al., 1976; Rai et al., 1981;

Reed and Moffat, 1983) that may dramatically increase tolerance to these metals (Wikfors and Ukeles, 1982). history

of

It

is clear therefore that the environmental

an algal population is an important consideration in analysis or

prediction of

algal growth

(Bates et al, 1983, Kuwabara and Leland, 1986).

135 One would also expect that under field conditions, algal community composition would

change over the long term to adapt to changes in metal ion activity (Say

and Whitton, 1980).

Metal

resistant algal strains have often been isolated

from natural waters known or suspected to be impacted by heavy metal pollution (Gavis et al. 1981; Murphy et al., 1982). to

the

It should be noted that in contrast

above reports of algal adaptation to Cu and Zn, marine diatoms do not

appear to adapt to organotin biocides (Walsh et al., 1985). Although the format of this paper focuses on interacting chemical processes that affect biological response, it should again be mentioned that biological processes

in turn affect the chemistry of natural waters. Useful predictions

of algal response require an understanding of the relative importance of these interactions shown that cantly

For example, it has been

decrease biologically available Cu (McKnight and Morel, 1979; Van den

Berg et (1978)

(both magnitude and time dependence).

certain algal species release organic molecules that may signifi-

al.

1979; Lumsden and Florence, 1983).

In contrast, Swallow et al.

found only one of nine test phytoplankton species that produced suffi-

cient exudate to significantly complex Cu in a defined medium.

However, it is

not clear from these experiments of Swallow et al. (1978) if exudate production is stimulated in response to elevated toxicant concentration, because the algae were not directly exposed to Cu. By

solute uptake and release, algae can also affect water chemistry. Algal

blooms

represent the extreme example of this phenomenon. Button and Hostetter

(1977)

observed that both Cu uptake and release by algae are rapid, although

uptake

is considerably more rapid than the rate of Cu release (estimated first -4

order rate coefficents of approximately 10 s

-1

-5

and 10

-1

s

,

respectively).

Similar results have been determined for marine algae by Mandelli (1969) and for periphyton in a mountain stream by Kuwabara et al. (1984). 9.2.4

Oxidation-reduction

Reactions

involving electron transfer from an oxidant to a reductant are of

significance to phycologists and aquatic toxicologists, because these reactions are often biologically mediated. Because redox reactions can be written in a manner

similar to other chemical reactions, chemical speciation programs may

be useful in estimating results of redox equilibria (Westall et al., 1976). Full reactions represent the

combination of redox couples containing an

electron acceptor and an electron donor as shown in the example below for the oxidation of ferrous to ferric Fe (Sillen and Martell, 1971; Hogfeldt, 1982):

3+

Fez+ + Fe

+

e

-

; equilibrium constant KO

-

-13.0

10

(6)

136

+

(1/4)02(aq)

H+

+ 2+

+

Full reaction: Fe equilibrium

It may

- 10

20 . a

e-

+

(1/2)H20; equilibrium constant K

+

(l/')02(aq)

constant K

H+

3+

Fe

-+

+

(1/2)H20;

- KoKr -

is again stressed, however, that an assumption of thermodynamic equilibrium be

a distinct limitation for certain solutes. Reactions like the one

above or biologically-mediated redox processes may be kinetically controlled. For example, the' fact that the photic zone in most aquatic environments is usually well oxygenated might lead one to assume that reduced states of solutes would not be

present at significant concentrations. In the case of Cu, this

assumption is

generally

true; Cu exists primarily in the divalent state in

oxidizing environments. Zn does not participate in redox processes under these 2+

conditions and

always is present as Zn

aerobic environments in both

Tin exists primarily as Sn (IV) in -10

species are typically in the ng/L (of the order of 10

these Sn(IV)

(Braman and Tompkins, 1978). explanation environment

.

inorganic and organic forms. Concentrations of

for the ubiquitous presence (Ridley et

B)

range

Biological methylation has been proposed as an of

methyltin compounds in the

al, 1977; Braman and Tompkins, 1978; Maguire et al.,

1982).

In contrast to Cu, Zn and Sn, there are a number of elements for

which

the above assumption may be misleading. Through photosynthesis, organic

molecules

(reduced states)

involved in the

are produced from oxidized nutrients. Algae are

reduction of inorganic arsenic (As) species to methylated A s

complexes (Andreae, 1978).

Immobilization reactions involving the reduction of

toxic

selenate and selenite species can also be biologically mediated (Doran,

1982).

Consequently, deviation from redox equilibrium may partially be related

to

the rates of these biological processes. Ambrose et al. (1983) modeled the

concentrations of reactants and product for a solute oxidation reaction in the following manner: dloxidized uroductl dt where 9.2.5

Kredox

=

-

Kredox[~xidant](reductant]

(10)

a second order rate constant that is process dependent

Photoactivation

Photochemical reactions represent a biologically significant subset of redox processes

that affect trace metal availability by the conversion of light to

137 chemical energy.

Methods for including photochemical reactions in solute

transport equations have been reviewed (Jorgensen, 1983). are primarily detailed

Cu(I1) complexes

photosensitive to radiation in the ultraviolet wavelengths. A

review of Cu photooxidation-reduction reactions involving various

ligands has been presented by

Balzani and Carassiti (1970).

The effect of

photochemical reactions on Cu bioavailability in aquatic systems has not yet Cu may exist in water in forms other than the divalent state.

been determined.

In moderately reducing environments, Cu,O can control Cu solubility at pH 7 and

in reduced low-sulfur environments, metallic Cu is stable (Garrels and

Christ, 1965). Monovalent Cu

The unstable Cu'

2 i

ion disproportionates into Cu

species could possibly be

stabilized by

0

and Cu

.

complexation with

organic ligands, although photochemical processes would more likely degrade the organic ligands. out a much

In their review, Balzani and Carassiti (1970) also pointed

lack of photochemical information for Zn complexes. In that Zn has a

lower susceptibility toward redox processes, Zn(I1) is the only stable

oxidation state in the water domain. Photoreduction and

dissolution of Mn oxides by dissolved humic substances

has been proposed as an important factor regulating dissolved Mn distribution in seawater (Sunda et

al., 1983).

observed surface maximum

The authors suggest that the typically-

in dissolved Mn concentrations in the sea is due to

riverine and aeolean inputs and photoactivated reduction of Mn(1V) oxides to Mn

2 i

.

Both these processes are worth consideration when assessing Cu toxicity

to coastal algal populations because of the proposed Cu-Mn interaction on algal growth mentioned previously (Sunda et al., 1981) and because adsorbed Cu and Zn may

be

released into solution upon dissolution of Mn oxides. Availability of

Cu and Zn may

therefore bk

indirectly affected by photochemical and redox

processes. Photodegradation of Anderson

iron

a chemically-defined medium presence

(Fe) chelates also inhances Fe uptake by algae.

et al. (1982) observed that Fe uptake by Thalassiosira weissflopii in

of

dominated by FeEDTA complexation doubled in the

light (cool white

spectrum, 95 uE m

-2

-1

s

).

This photodegradation

of the FeEDTA complex is contrasted by the insensitivity of the CuEDTA complex to photochemical reactions (Hill-Cottingham,1955).

Organotin compounds are

also photosensitive, but Walsh et al. (1985) noted that the kinetics of the degradation reactions appear to be slow (of the order of months). products of

Degradation

trialkyl tin compounds have been detected in an area of heavy

industrial and antifouling paint use (Hodge et al. 1979; Maguire et al., 1982). In contrast to the enhancement of Fe availability by photodegradation, degradation of organotin compounds would Recent

probably

decrease Sn toxicity to algae.

algal studies (Laughlin and French, 1980; Wong et al., 1982; Walsh et

138

al., 1985)

found

that

toxicity of alkyltin compounds increased with carbon

chain length; with butyl was

also

directly

compounds generally being the most toxic. Toxicity

related to solubility of the Sn compound in octanol and to

its molar surface area (Laughlin et al., 1984). bility

Therefore, unlike the availa-

of Cu and Zn free ion forms, the mechanism for Sn toxicity appears to

reflect the strong partitioning in algal tissue of certain organic compounds. 9.3

ACKNOWLEDGEMENTS

C.C.Y.

Chang

is gratefully acknowledged for her help in the Zn and phos-

phate uptake experiments reported herein. Editorial comments by Drs. J.D Hem, H.V. Leland and A.S. Maest, and by C.C.Y. Chang and M. A. Tompkins are also deeply appreciated. REFERENCES Ambrose,

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145

Chapter 10 THE

OF FOULING BY NON-BICCIDAL SYSTEPlS

MAUREEN E. CALcOw, R.A. PITCHERS AND A. M I W * Department of Plant Biology, University of Birmingham B15 2TT, U.K. *International Paint plc, R & D Laboratories, Stoneygate Lane, Felling-onTyne, NElO QIY, U.K. 10.1 1mDucr10N Fouling results in the loss of efficiency of ships, buoys, pilings, offshore platforms, sonar domes and a variety of piping systems (Haderlie, 1984). Fouling has been controlled traditionally by antifouling paints which prevent settlement of organisms through the release of biocides, chiefly metallic e.g. copper, or organometallic compounds e.g. triorganotins (Evans, 1981; Fischer -&&, 1984). Recent studies on the environmental impact of antifouling paints (Alzieu -&&, 1980; Waldock & Miller, 1983; Waldock & Thain, 1983) have led to renewed interest in the development of non-biccidal antifouling systems (see Milne & Callow, 1985; Gucinski & d ., 1984; Meyer a&.,1984). Non-biocidal antifoulings aim to utilize surface effects which result in non-adhesion of organisms or at worst, in weak adhesion so that fouling organisms are easily removed, for example, during passage of ships through the water or in the case of small yachts, by hosing. The first event on exposure of a 'clean' surface to any natural aqueous environment (salt or fresh wated is the spontaneous adsorption of an organic layer principally of glycoproteins producing a modified substrate which, irrespective of the original surface characters becomes hydrophilic and negatively charged. This is then rapidly colonized by pioneer bacteria whose exudates in turn further modify the surface (Baier 1980, 1984; Baier & &, 1983). Larvae of macrofouling forms as well as members of the microfouling slime community (principallydiatoms) attach to what has quickly become, a heterogenous substrate (Mitchell and Kirchman, 1984; Cmksey & &, 1984). The adhesives produced by marine fouling algae range from various types of glycoprotein e.g. Enterom(Callow & Evans, 1974), (Braten, 1975), ' (Chamberlain & EGtocaeus (Faker & Evans, 1973; Clitheroe, 1977), and Ceramlum Evans, 1973; 1981) to the various types of substituted acidic plysaccharides produced by diatoms (e.g. Chamberlain, 1976, Blunn & Evans, 1981). The diatom mucilages are more closely related to those of marine bacteria (Fletcher, 1980) than to the adhesives of spores of macroalgae. The range of chemical

146

types of cell mucilages and adhesives is thus very diverse. The physical chemistry of bioadhesion has been extensively reported in the literature, particularly with respect to microbial systems (see Beachey, 1980; Berkeley & d.,1980; Allen, 1982). Bioadhesion is dependent on three major components, viz. the cell surface, the separating medium, and the substrate. Since it is not possible to alter either of the two former parameters, any attempts at non-adhesion of cells depend on modification of the substrate. Several approaches to surface modification have been investigated including surface charge (Marshall & &. , 1971) and surface energy (Bier, 1980) Three principle types of low energy surface have been investigated for use as non-biocidal anti-fouling systems. The development of fluoropolymers (Bultman& d., 1984; Griffiths, 1985) and the "tethering" of drag-reducing molecules such as polyox (polyoxyethylene)(Gucinski& d., 1984) are two systems being studied in the United States of America. ..Thethird system is that described in this paper viz. silicone elastomers (Milne,1977; Milne & Callow, 1985). The silicone liTv polymers are based on a backbone of repeating (-Si-0-) units with the non-backbone valencies of the silicone attached to organic radicals (see Threadgold, 1985). The silicone polymers can be variously modified e.g. by inclusion of phenyl-methyl silicone fluid. Results of experiments on adhesion of the diatom Amphora to a range of silicone elastomers, in particular RTV elastomers and raft exposure trials of these substrates are described in this paper.

.

10.2 MATERIALS AND METHODS 10.2.1. Surfaces. Three groups of silicone elastomer were tested (A) Room temperature vulcanizing (Kl!V) silicone elastomers cured by the addition of tin catalysts referred to as RTV(i)-(iv). RTV(i) corresponds to the silicone elastomer described in Milne & Callow (1985). (B) platinum cured silicone elastomers referred to as PC(i)-(iii). (C) moisture cured acetyl tipped silicone elastomers referred to MC(i)-(iv). Modification of the elastomers was achieved by the addition of phenyl methyl silicone fluid (PMS) in the ratio of 100:5 (w/w) before curing. Elastomers were brush-applied to 10cm2 formica panels. Glass microscope slides (75mm x 39mm) were coated using an applicator which produced a band of elastomer 18mm wide down the middle of the slide. Thus each experimental surface had an area of 13.5cm2. Control surfaces were acid washed glass and P.T.F.E. (teflon). Raft trials were carried out at Newton Ferrers, South Devon, England during 1985. 10.2.2.

Q=JJ

culture. Axenic stock cultures of AmPhora mffeaeformis var

.

PerPusilla were maintained under static conditions inGuillards F2 medium

147

(Guillard & Ryther, 1962) in 2 dm3 Ehrlenmeyer flasks. Instant Ocean artificial seawater was used to prepare the medium. Flasks were maintained at 2OoC with continuous irradiance at a photon flux density of 15umol m-2s-1 and were subcultured weekly. For cell attachment experiments log phase cultures were shaken by hand and then filtered through nylon mesh, pore size 30um to remove c l u m ~of ~ cells. 10.2.3. Attachment exDermerit s. Elastomer coated slides were randomized in white plastic trays to which a standard volume of log phase culture was added. The trays were incubated under the conditions described for cell culture for 8-16h Slides were carefully washed using a standard procedure to remove unattached cells. The biomass of attached cells was then estimated by measurement of chlorophyll, or adenosine triphosphate (ATP) content. Previous experiments (Pitchers and Callow, in preparation) have established that a direct relationship exists between cell numbers, chlorophyll content and ATP content for log phase cultures of AmPhora. 10.2.4. aloroDhvfia. Cells were removed from the polymer surface on each slide (13.5cm2) using a cotton wool bud which was immersed in l m 3 dimethyl sulphoxide (DMSO) to extract chlorophyll (Shoaf & Lium, 1976). Microscopical examination of surfaces after swabbing showed that >99% of cells were removed. After 1.5h in darkness at room temperature, tubes containing cotton wool buds were agitated and the absorbance of the DMSO extract determined at 630 and 664nm. Chlorophyll, was calculated following Holden (1976). 10.2.5. BTE: Cells were removed from the polymer surface as described above. The cotton bud was placed in lcm3 of extractant (0.2% v/v Triton X-100 containing 0.15% w/v disodium E D l l in distilled water) and gently agitated for 5 min. For luminometry 100mm3 of extract were transferred to a reaction cwette containing 700mm3 0.1 M tris acetate buffer, pH 7.75 containing 0.075% w/v disodium EDTA and 200mm3 luciferin - luciferase monitoring reagent (LKB). Readings were taken immediately after a ten second integration period using an LKB 1250 Luminometer. Readings are expressed as relative light units (R.L.U.) per standard area of surface. 10.3 RESULTS The attachment of Ampima (measured as chlorophyll,) to a range of silicone elastomers is shown in Fig.lO.1. A one-way analysis of variance produced an F-ratio that was highly significant thus, the Least Significance Difference (L.S.D.) test (Parker 1979) was applied (Table 10.1).

148

Fig. 10.1. Histoqram showinq attachment of Amphora to a ranqe of silicone elastomers.

L.S.D.

RTV = Room Temperature Vulcanising ; MC PC = Platinum Cured

= Moisture Cured ;

Biomass is measured as chlorophyll a

Table 10.1. Summary of the analysis of variance for data presented in Fig.lO.1

Variance

Degrees of

due to

freedom

Polymer Error

Sum of squares

Mean square

5

23.13

4.63

24

2.98

0.12

(L.S.D.

= 0.46)

F-ratio

37.29(***)

149

Means found to differ by more than the L.S.D. i.e. 0.46 can be considered significantly different. Thus, from the data expressed in Fig.lO.1 three distinct groups appear to emerge in descending order of efficacy viz. m ( i ) : RTV(iii)/lFv(iv) : MC(i)/MC( ii)/PC( i) An expanded range of silicone elastomers was tested for adhesion of Arrghxa using ATP measurement as an indicator of cell biomass. Two separate experiments were performed so a two-way analysis of variance was applied to the combined data (Table 10.2). A highly significant F-ratio for the batch effect coupled with a nonsignificant difference for the interaction indicated that although a difference existed in absolute values between both experiments differences in ranked order between two experiments could be accounted for by random variation alone. Therefore, the pooled means of the two experiments were used and are shown (Fig.10.2). From the L.S.D. (i.e. 30.3) polymer RTV(i) is significantly different from all the other elastomers. Groups could be derived but there was considerable overlap between members of a group. However, it appeared that the tin - catalysed RTV elastomers exhibited a greater efficacy than either the MC or FC elastomers and application of a oneway analysis of variance showed this hypothesis to be correct (Table 10.3). The effect of addition of PMS to RTV(i) was tested using glass and PTFE (teflon) as controls. Fig.lO.3 shows the ranking of surfaces with respect to adhesion of &@bra cells. From a one-way analysis of variance (Table 10.4) there is no effect resulting from the addition of PMS although the RTV elastomers (+ or - PMS) are both highly significantly different from glass and teflon However, slides coated with m ( i ) with and without Ebddition of PMS showed differences in anti-fouling performance when exposed in the marine environment for periods of 3 months or longer. Fig.10.4 shows typical slides after 16 weeks immersion. The W C control is overgrown by macroalgal fouling, chiefly Ectocarws ~ c u l o s y s W(i) bore a mixed diatom slime whilst m(i) + PMS is essentially free of all fouling organisms. Addition of PMS improves the antifouling performance of other silicone elastomers immersed for 16 weeks (Figs.lO.5 and 10.6). Polymer RTV(ii) (Fig.lO.5) had approximately 60% and 20% cover of slime and macroalgae respectively. The addition of PMS reduced the slime cover to 20% and no attachment of macroalgae occurred. Polymer MC(i) (Fig.10.6) had approximately 80% slime and 5% macroalgal cover whilst the addition of PMS resulted in 30% slime cover and no detectable attachment of macroalgae.

.

.

.

150

Table 10.2

Surranary of two-way analysis of variance

Variance due to

Degrees of freedom

Sum of squares

Mean square

F-ratio

Polymer

10

137704.0

13770.O

9.8

(***)

1

65901.O

65901.0

47.0

(***)

10

22507.0

2251.0

1.6

110

154382.0

1403.O

Batch Interaction Error

(L.S.D.

=

30.3)

Table 10.3 Surranary of one-way analysis of variance to test the performance of tin catalysed W elastomers

Variance due to Catalyst Error

Sum of squares

Mean square

F-ratio

1

93418.3

93418.0

42.3

130

287074.5

2208.3

Degrees of freedom

(***)

151

Fig 10.2. Histogram showing attachment of Amphora to a range of silicone elastomers 200

L.S.D. 150

2

4 [r

I

100

a t-

a

50

0

1

2

3

4

5

6

7

8

9

RTV = Room Temperature Vutcanising ; MC PC = Platinum Cured

1

6-MC 7-MC 8-MC 9-PC 10-PC 11-MC

iv i

ii ii i iii

1

1

= Moisture Cured;

Biomass is measured as ATP and expressed as relative light units - R.L.U.

Legend 1-RTV i 2-RTV iv 3-RTV iii 4-RTV ii 5-PC iii

0

152 Fig 10.3. Histogram showinq attachment of Amphora to various surfaces

100

3:

d I

a k-

Q

{

L.S.D.

8ol lYi 0-

., % Q

@'

RTV = Room Temperature Vulcanising ; prns = phenylmethylsilicone fluid. Biomass is measured 0 s ATP ond expressed as relative light units - R.L.U.

Table 10.4

Summary of one-way analysis of variance for data presented in Fiq. 10.3

Variance

Degrees of

due to

freedom

Surface

3

31987.2

1066 2.4

Error

29

5141.4

177.3

Sum of squares

(L.S.D.

= 13.6)

Mean square

F-ratio

60.1 (***)

153

10.4. DISCUSSION AmDhora was chosen for laboratory studies because of its importance in shipfouling (Callow, 1986) and for its ease of culturing an3 rapid attachment to surfaces (Cooksey, 1981). In spite of being derived from a clonal culture, differences in the adhesive capacity of cells between cultures occurs. However, it has proved possible to pool data from separate experiments as shown in Fig.lO.2 and Tables 10.2 and 10.3. The rapid attachment process and the continuing motility of cells after attaching led Cooksey (1981) to regard the type of adhesion displayed by AmDhora as "temporary" as defined by Marshall and Bitton (1980). The greatest reduction in adhesion of AmBhora occurred on the tincatalysed RTV silicone elastomers and RTV(i) was best overall. The addition of PMS to W ( i ) in the experiments reported here did not influence adhesion of AmDhora although large visual differences in performance were apparent after 16 weeks immersion in the sea. Results previously reported (Milne and Callow, 1985) showed significantly fewer cells attached to RTV(i) whn PMS was added. It is not known whether these differences are due to cell variability or variability between batches of RTV polymer. Analytical studies on polymers are in progress. The techniques used here do not allow small differences in cell adhesion to be determined due to variability between replicates within any one treatment nor do they take any account of surface shear forces. The raft panels are exposed to surface shear stress caused by tidal flow (approximately 2 knots) and this may account for the differences in accumulated fouling between elastomers with and without the addition of PMS. Laboratory experiments where attached &whora cells were subjected to shear in a radial flow chamber (Milne'and Callow, 1985) suggested that the addition of PMS to W(i) resulted in enhanced cell detachment under conditions of shear. This line of investigation is beinq persued usidg a redesigned radial flow apparatus. The silicone elastomers tested here are hydrophobic and possess low surface energy properties although to date these'have not been quantitatively determined. Attachment and growth of macroalgal sporelings to silane-based coatings of low surface energy (Fletcher & &, 1984) resulted in altered morphology of the attaching rhizoids. In EnteromorDha, compact rhizoidal discs were strongly adherent on high energy surfaces in contrast to the loose filamentous rhizoids which only adhered poorly to the low energy surfaces. However, this response was not typical of all the algae studied (Fletcher & &, 1984). Macroalgae were not found attached to the best silicone elastomer viz. RTV(i) (Fig.10.4), although the WC control was overgrown by Ectocams. It is also interesting to note that when exposed on rafts, those silicone

154

Fig. 10.4. Photograph of slides exposed on test raft for 16 weeks. Note that only the middle strip was exposed thus each side is free from fouling. A = control of PVC bearing a dense growth of ECtOCarDUS siliculosus and a few plants of ulva. Dteromorpha and ylothrix. B = W ( i ) bearing a thick diatom slime. C = W ( i ) + PMS bearing only traces of a diatom slime. Figs. 10.5 and 10.6. Photographs of panels exposed on raft for 16 weeks. Fig.10.5 (top) A = RTV(ii) bearing a mixed macroalgal fouling growth of . . FnteromorDha intestinalis, lactuca, Ectocarpus siliculosus and polvsiDhonia a.and a mixed diatom slime. B = Rnr(ii) + PMS bearing a diatom slime. Note - some of the slime has been removed by "brushing" caused by macroalgae attached to the wooden support holding the panels. Fig. 10.6 (bottom) A = MC(i); B = MC(i) + PMS. Description as for Fig.10.5.

156

elastomers which performed less well than RTV(i) in the laboratory allowed growth and settlement of some macroalgae (see Figs.10.5 and 10.6). Furthermore, macroalgae were absent from the polymers containing PMS. Reduced adhesion of mussels. barnacles, (Young and Crisp, 1980; Crisp & 1984)., ArnDhora (present communication; Characklis and Cooksey, 1983) and bacteria (Dexter, 1979) to a variety of low energy surfaces supports their potential use for fouling control. However, there are exceptions to this general pattern and some bacteria attach preferentially to low energy surfaces (Fletcher and Marshall, 1982). The results to date with RTV silicone elastomers indicate them to be worthy of further study as non-biocidal anti-fouling systems. However, their physical properties of poor abrasion resistance and tear strength limit the range of possible applications to situations where such characteristics are not of primary importance e.g. aquaculture, offshore structures, piping systems and power station water intakes.

&.,

10.5 ACKNU&EM;EME”S We thank International Paint plc for financial support and Ms H Denny for discussion of statistical methods. 10.6 REFERENCES Allen, K.W. (ed.) 1982. Adhesion. Applied Science Publishers Ltd., London. Alzieu, C., Thibaud, Y., Heral, M. and Boutier, B. 1980. Evaluation des risques dus a l’emploi de peintures anti-salissures dans les zones condylicoles. Rev. Trav. Inst. Peches Marit. 44: 301-348. Baier, R.E. 1980. Substrate influences on adhesion of microorganisms and their resultant new surface properties. In: Adsorption of microorganisms to surfaces (G. Bitton & K.C. Marshall, eds.) Wiley - Interscience, New York, pp. 59-104. Baier, R.E. 1984. Initial events in Microbial Film Formation. In: Marine Biodeterioration: An interdisciplinary study (J.D. Costlow and RC. Tipper, eds.). U.S. Naval Institute,Annapolis, 57-62. Baier, R.E., Meyer, A.E., de Palma, V.A., King, R.W. and Fornalik, M.S. 1983. Surface Microfouling during the Induction Period. J. Heat Transfer. 105: 618-624. Baker, J.R.J. and Evans, L.V. 1973. The ship-fouling alga ECtOCarDUS I. Ultrastructure and cytochemistry of plurilocular reproductive stages. Protoplasma. 77: 1-13. Beachey, E.H. 1980. Bacterial Adherence. Receptors and Recognition Series, B. Volume 6. Chapman & Hall, London and New York. Berkeley, R.C.W., Lynch, J.M., Melling, J., Rutter, P.R. and Vincent, B. (eds.). 1980 Microbial Adhesion to Surfaces. Ellis Horwood, Chichester. Blunn, G.W.. and Evans, L.V. 1981. Microscopical observations on Achnanthes . with special reference to stalk formation. Bot. Mar., 24: 193199. Braten, T. 1975. . . observations on mechanisms of attachment in the green alga ULBmutabllls Foyn. Protoplasma. 84: 161-173. Bultman, J.D., Griffith, J.R and Field, D.E. 1984. Fluoropolymer coatings for the marine environment. In: Marine Biodeterioration, an interdisciplinary study. (J.D. Costlow and R.C. Tipper, eds.). U.S. Naval Institute, Annapolis. 237-243.

157

Callow, M.E. 1986. A world-wide survey of slime formation on anti-fouling paints. In: Algal Biofouling. (L.V. Evans and K.D. Hoagland, eds.). Callow, M.E. and Evans, L.V. 1974. Studies on the ship-fouling alga Enteromorpba Cytochemistry and Autoradiography of Adhesive Production. Protoplasma. 80: 15-27. Chamberlain, A.H.L. 1976. Algal settlement and secretion of adhesive materials. In: Proceedings of the 3rd International Biodegradation Symposium (J.M. Sharpley and A.M. Kaplan, eds.). Applied Science, London. 417-432. Chamberlain, A.H.L. and Evans, L.V. 1973. Aspects of spore production in the red alga Ceranu' ~ m . Protoplasma. 76: 139-159. Chamberlain, A.H.L. and Evans, L.V. 1981. Chemical and histochemical studies In: Proceedings of the VIIIth on the spore adhesive of m a m i u m International Seaweed Symposium, Bangor, 18-23 August 1974. (G.E. Fogg and W.E. Jones, eds). 539-542. Clitheroe, S.B. 1977. Fine structural and cytochemical studies on the brown seaweed EctocarpuS. Ph.D. thesis. University of Leeds. Characklis, W.G. and Cooksey, K.E. 1983. Biofilms and Microbial Fouling. Adv. App. Microbiol. 29: 93-138. Cooksey, K.E. 1981. Requirement for calcium in adhesion of a fouling diatom to glass. Applied and Environ. Biol. 41: 1378-1382. Cooksey, B., Cooksey, K.E., Miller, C.A., Paul, J.H., Rubin, R.W. and Webster, D. 1984. The attachment of microfouling diatoms. In: Marine Biodeterioration, an interdisciplinary study (J.D. Costlow and RC. Tipper, eds.). U.S. Naval Institute, Annapolis. 167-171. Crisp, D.T., Walker, G., Young, G.A. and Yule, A.B. 1985. Adhesion and substrate choice in mussels and barnacles. J. Coll. Interface Sci. 104: 4050. Dexter, S.C. 1979. Influence of substratum critical surface tension on bacterial adhesion - in s.&u studies. J. Coll. Interface Sci. 70: 346-354. Evans, L.V. 1981. Marine algae and fouling : A review with particular reference to shipfouling. Bot. Mar. 14: 167-171. Fischer, EX., Castelli, V.J., Rodgers, S.D. and Bleile, H.R. 1984. Technology for control of marine biofouling - A Review. In: Marine Biodeterioration: An Interdisciplinary Study (J.D. Costlow and RC. Tipper, eds.). U.S. Naval Institute, Annapolis. 261-299. Fletcher, R.L., Baier, R.E. and Fornalik, M.S. 1984. The influence of surface energy on spore development in some common marine fouling algae. In: 6th International Congress on Marine Corrosion and Fouling, 5-8 August 1984, Athens. Fletcher, M. 1980. Adherence of marine micro-organisms to smooth surfaces. In: Bacterial Adherence (E.H. Beachey, ed.) Receptors and Recognition. Series B. Vo1.6. Chapman & Hall, London and New York. pp 347-374. Fletcher, M. and Marshall, K.C. 1982. Are solid surfaces of ecological significance to aquatic bacteria? Adv. Microb. Ecol. 6. (K.C. Marshall, ed.). Plenum. 199-236. Griffiths, J J L 1985. The fouling-release concept: A viable alternative antifouling coating? In: Polymers in a marine environment (R Smith, ed.). The Institute of Marine Engineers, London. 235-236. Gucinski, H., Baier, R.E., Meyer, A.E., Fornalik, M.S. and King, R.W. 1984. Surface microlayer properties affecting drag phenomena in seawater. In: 6th International Congress on Marine Corrosion and Fouling, 5-18 August 1984, Athens. 585-604. Guillard, RRL. and Ryther, J.H. 1962. Studies of marine planktonic diatoms. I. Q z l c L d h naIAa Hustedt and Detonula confervacea (Cleve) Gran., Can. J. Microbiol. 8: 229-239. Haderlie, E.C. 1984. A brief overview of the effects of macrofouling. In: Marine Biodeterioration, an Interdisciplinary study. (J.D. Costlow and RC. Tipper, eds.). U.S. Naval Institute, Annapolis. 163-166.

.

.

158

Holden, M. 1976. Chlorophylls. In: Chemistry and Biochemistry of plant pigments. (T.W. Goodwin, ed.). Vol. 2. Academic Press. Marshall, K.C. and Bitton, G. 1980. Microbial adhesion in perspective. In: Adsorption of microorganisms to surfaces (G. Bitton and K.C. Marshall, eds.). John Wiley, New York. 1-5. Marshall, K.C., Stout, R. and Mitchell, R. 1971. Mechanism of the initial events in the sorption of marine bacteria to surfaces. J. Gen. Microbiol. 68: 337-348. Meyer, A.E., Fornalik, M.S., Baier, R.E., King, R.W., Zarnbon, J.J., Huber, P.S., Wattle, B.J. and Gucinski,H. 1984. Microfouling survey of Atlantic ocean waters. In: 6th International Congress on Marine Corrosion and Fouling, 5-8 August 1984, Athens. 605-621 pp. Milne, A. 1977. British Patent 1, 470, 465. Milne, A. and Callow, M.E. 1985. Non-biocidal antifouling processes. In: Polymers in a marine environment. The Institute of Marine Engineers, London. pp. 229-233. Mitchell, R and Kirchman, D. 1984. The Microbial Ecology of Marine Surfaces. In: Marine Biodeterioration: An Interdisciplinary study (J.D. Costlow and R.C. Tipper, eds.). U.S. Naval Institute, Annapolis. 49-56. Parker, RE. 1979. Introductory Statistics for Biology. Studies in Biology No.43. Edward Arnold. Shoaf, T.W. and Lium, B.S. 1976. Improved extraction of chlorophyll a and b from algae using dimethyl sulphoxide. Limnol. Cceanogr. 21: 926-928. Threadgold, R.C. 1985. Organosilicones in Biological Systems. In: Biotechnology: Applications and Research (P.N. Cheremisinoff and R.P. Cuellette, eds.). Technomic Publishing Co. Inc. 643-650. Waldock, M.J. and Miller, D. 1983. The determination of total and tributyl tin in seawater and oysters in areas of high pleasure craft activity. ICES Paper CM 1983/E12. International Council for the Exploration of the Sea, Copenhagen. Waldock, M.J. and Thain, J.E. 1983. Shell thickening in Crassastrea gigas, organotin antifouling or sediment induced? Mar. Poll. Bull. 14: 411-415. Young, G.A. and Crisp, D.J. 1982. In: Adhesion (K.W. Allen, ed.). Applied Science Publishers Ltd., London. 19-39.

159 Chapter 11

ALGAL BIOFOULING OF OLIGOTROPHIC LAKE TAHOE:

CAUSAL FACTORS AFFECTING

PROOUCTION STANFORD L. LOEB D i v i s i o n o f Environmental Studiesr U n i v e r s i t y o f Cal i f o r n i a r Davis, CA 95616 ABSTRACT The a l g a l b i o f o u l i n g o f 01 i g o t r o p h i c Lake Tahoe r e f e r s t o t h e increased growth o f a t t a c h e d a l g a e r p e r i p h y t o n r on n a t u r a l l y o c c u r r i n g r o c k s u b s t r a t a a l o n g t h e s h o r e l ine. P e r s i s t e n t p a t t e r n s o f periphyton production have been observed and a s s o c i a t e d w i t h l a n d d i s t u r b a n c e ti.&, development) w i t h i n t h e watershed. N u t r i e n t bioassays demonstrated p r o d u c t i v i t y can be stimulated with increased a v a i l a b i l i t y o f nitrogen alone o r phosphorus and nitrogen together. Both stream and ground waters have been i d e n t i f i e d as n u t r i e n t loading pathways from t h e watershed t o t h e lake. P a r t i c u l a r a c t i v i t i e s a s s o c i a t e d w i t h l a n d d i s t u r b a n c e i n c r e a s e n u t r i e n t m o b i l i t y and subsequent l o a d i n g t o Lake Tahoe. These a c t i v i t i e s are b e l i e v e d t o be causal f a c t o r s a f f e c t i n g the d i f f e r e n t i a l accural o f periphyton biomass (Chl I) along the shoreline. 11.1 INTRODUCTION The t e r m " a l g a l b i o f o u l ing" g e n e r a l l y r e f e r s t o t h e attachment o f a l g a e o n t o man-made s t r u c t u r e s p l a c e d i n waters (e.g.r p l a t f o r m s r etc.).

boatsr piers, o i l d r i l l i n g

I n t h i s paperr t h e t e r m i s used t o r e f e r t o t h e growth o f

attached a l g a e r periphyton. on n a t u r a l l y o c c u r r i n g r o c k s u r f a c e s a l o n g t h e shorel i n e o f an 01 igotrophic laker Lake Tahoe (Cal ifornia-Nevada). Lake Tahoe (39'

N Lat.;

120'

W Long.Ir

which l i e s a t an e l e v a t i o n o f

1,898 m amid mountains o f g r a n i t e and volcanic composition i n the Sierra Nevada mountainsr i s t h e t h i r d deepest l a k e i n N o r t h American h a v i n g a mean depth o f 313 m and a maximum d e p t h o f 501 m (Fig.

11.1).

The r a t i o o f t h e lake's

watershed (807 km2) t o i t s s u r f a c e area (499 km2) i s v e r y s m a l l r 1.62. small watershed area and acidic.

The

n u t r i e n t poor s o i l s o f i t s drainage basin have

c o n t r i b u t e d t o t h e o l i g o t r o p h i c c o n d i t i o n s o f t h i s s u b a l p i n e lake.

Overthe

p a s t 17 yearsr a steady i n c r e a s e i n t h e t o t a l annual p r i m a r y p r o d u c t i v i t y o f p e l a g i a l phytoplankton has been accompanied by a steady d e c l i n e i n the lake's transparency (Goldmanr 1981).

The most v i s i b l e e v i d e n c e o f t h e a c c e l e r a t i n g

eutrophication has been the increased amounts o f p e r i p h y t o n p r o d u c t i o n w i t h i n the l i t t o r a l zone o f Lake Tahoe (Goldman and de Amezagar 1975).

These observed

changes have been a t t r i b u t e d t o an increased n u t r i e n t l o a d i n g t o t h e l a k e r e s u l t i n g from 1and disturbances w i t h i n the watershed.

160

CALIFORNIA , -1

.-.I I

LAKE

TAHOE

F i g u r e 11.1. Land use map o f t h e Lake Tahoe watershed i n d i c a t i n g areas which h a v e been d i s t u r b e d ( d e v e l o p e d a r e a s a r e b l a c k e n e d ; u n d e v e l o p e d a r e a s a r e white). Periphyton sampl ing l o c a t i o n s (P=Pinel and, DP=Deadman Point, I C = I n c l i n e Condominium, I W = I n c l i n e West) a r e indicated.

161 The o v e r a l l hypothesis o f t h i s study i s t h a t t h e r e i s a d i r e c t a s s o c i a t i o n between l a n d d i s t u r b a n c e and t h e p r o d u c t i o n o f p e r i p h y t o n along t h e shore1 i n e o f Lake Tahoe.

The o b j e c t i v e s o f t h i s paper a r e t o document t h e long-term s p a t i a l

d i s t r i b u t i o n p a t t e r n s o f periphyton biomass (Chl a), demonstrate t h e a s s o c i a t i o n between w a t e r s h e d d i s t u r b a n c e and p e r i p h y t o n biomass a c c u r a l , d e t e r m i n e t h e r e l a t i o n s h i p between n u t r i e n t a v a i l a b i l i t y and p e r i p h y t o n p r o d u c t i v i t y , and finally,

d i s c u s s those f a c t o r s which a f f e c t n u t r i e n t mobilization within the

watershed as they may a f f e c t

t h e growth o f

periphyton.

This paper i s meant t o

p r o v i d e an o v e r v i e w o f t h e s i t u a t i o n a t Lake Tahoe r e v i e w i n g t h e f n t e r a c t i o n s between v a r i o u s l a n d use a c t i v i t i e s and t h e b i o l o g i c a l p r o c e s s e s p o t e n t i a l a f f e c t e d by such a c t i v i t i e s . 11.2 METHODS F o u r l o c a t i o n s were sampled on n e a r l y a m o n t h l y b a s i s f o r t h r e e y e a r s (1982-1984):

two l o c a t i o n s a d j a c e n t t o d e v e l o p e d a r e a s and t w o a d j a c e n t t o

u n d e v e l o p e d a r e a s (Fig. 11.1).

S t a t i o n P i n e l a n d ( P I was chosen t o b e a d j a c e n t

t o Ward V a l l e y w i t h i n w h i c h an i n t e n s i v e h y d r o l o g y i n v e s t i g a t i o n has been c o n d u c t e d ( L e o n a r d e t al., Goldman, 1979).

1979) i n c l u d i n g a g r o u n d w a t e r s t u d y (Loeb and

This s t a t i o n was adjacent t o a h e a v i l y developed area.

Station

I n c l i n e Condo ( I C ) and I n c l i n e West ( I W ) were e s t a b l i s h e d 200 m a p a r t :

IC

adjacent to a l a k e f r o n t condominium having a h e a v i l y f e r t i l i z e d area o f lawn and a s e w e r l i n e l e s s t h a n 20 m away f r o m t h e shore; u n d e v e l o p e d area.

d i f f e r e n c e s i n p e r i p h y t o n biomass. an u n d i s t u r b e d area, drainage towards DP,

I W . a d j a c e n t t o an

These t w o s i t e s were used t o examine smal 1 s c a l e (meters) S t a t i o n Deadman P o i n t (DP) was adjancent t o

t h e n e a r e s t d e v e l o p m e n t a p p r o x i m a t e l y 1 km away. however,

The

was undisturbed.

Sampling l o c a t i o n s were e s t a b l i s h e d adjacent t o areas representing a range i n t h e degree o f watershed disturbance (i.e.,

development) I n order t o e v a l u a t e

whether p e r i p h y t o n p r o d u c t i o n and 1and d i s t u r b a n c e were associated.

Disturbed

l a n d s w i t h i n t h e Tahoe b a s i n t o t a l 1 4 1 km2 o r 17% o f t h e t o t a l watershed a r e a (Fig.

11.1).

S t a t i o n s I C ( d e v e l o p e d ) and I W ( u n d e v e l o p e d ) were chosen t o

determine i f d i f f e r e n c e s I n amounts o f p e r i p h y t o n biomass c o u l d be detected on a s m a l l s c a l e b a s i s (meters);

s t a t i o n s P ( d e v e l o p e d ) and DP ( u n d e v e l o p e d )

e v a l u a t e d l a r g e s c a l e d i f f e r e n c e s i n p e r i p h y t o n biomass (kilometers). P e r i p h y t o n biomass was sampled

In siiu

f r o m r o c k s u r f a c e s (0.5 m d e p t h )

(Loeb. 1981); t h r e e samples were c o l l e c t e d w i t h i n a 0.5 each s i t e on each date.

These samples were centrifuged,

f o r c h l o r o p h y l l A determination.

m2 a r e a o f b e n t h o s a t

weighed and subsampled

Subsamples were p l a c e d i n 5-10 m l o f 100%

b o i l i n g methanol f o r 2-3 m i n t c e n t r i f u g e d t o clear,

then read a t 666nm and 653nm

on a d u a l beam s p e c t r o p h o t o m e t e r u s i n g a r e f e r e n c e c e l l o f 100% methanol.

162 T u r b i d i t y was measured a t 720nm and c o n c e n t r a t i o n s o f c h l o r o p h y l l 4 were c a l c u l a t e d using t h e equation o f Iwamura e t al.D 1970.

A n a l y s i s f o r phaeophytfn

p i g m e n t s u s i n g paper c h r o m a t o g r a p h y on t h e s e s a m p l e s i n d i c a t e d t h e r e were no s i g n i f i c a n t amounts present (Eloranta,

1983).

The e f f e c t s o f n u t r i e n t e n r i c h m e n t s on t h e p r i m a r y p r o d u c t i v i t y o f p e r i p h y t o n were examined i n t h e laboratory.

Periphyton was c o l l e c t e d from rock

surfaces (0.5 m depth) a t s t a t i o n P (Pineland) d u r i n g t h e maximum s p r i n g growth p e r i o d (May 24D 1982).

The community composition was almost e n t i r e l y

h e r c u l w a t a l l 0.5 m depth s t a t i o n s around t h e lake.

Nine treatments were

prepared c o n s i s t i n g o f 1000 m l o f l a k e water i n 1500 m l f l a s k s : water only),

control (lake

( 6 0 0 ug N'1 i t e r - l l D a m m o n i u m - n i t r o g e n

nitrate-nitrogen

(600 ug N ' l i t e r - l D n i t r a t e p l u s ammonium (300 ug " l i t e r - '

e a c h I D phosphorus

phosphous p l u s n i t r a t e (100 and 600 ug o f P

(orthophosphate) (100 ug P'1 iter-l)D and

GomDhoneis

N r e s p e c t i v e l y I D phosphorus p l u s ammonium (100 and 600 u g * l i t e r - l ) D and

p h o s p h o r u s D n i t r a t e and ammonium t o g e t h e r (100, 300D 300 u g ' l i t e r - ' ) . ambient l a k e water concentrations o f n i t r a t e ,

N

*

1iter-lD

<2 ug P'1 i t e r - I

below

level

respectively;

of

The

ammonium and phosphorus were 3 ug

d e t e c t i o n ((2

ug N ' l i t e r ' l ) ,

and

a m b i e n t w a t e r t e m p e r a t u r e was l l ° C .

n u t r i e n t c o n c e n t r a t i o n s were chosen f i r s t ,

These

t o make c e r t a i n no s i g n i f i c a n t

d e p l e t i o n o f t h e n u t r i e n t s occurred d u r i n g t h e 3-day

i n c u b a t i o n and second,

to

b e t t e r determine a p o t e n t i a l response t o t h e a v a i l a b i l i t y o f t h e s p e c i f i c nutrient(s1. A p p r o x i m a t e l y 5 g wet w e i g h t o f p e r i p h y t o n were added t o each t r e a t m e n t f l a s k D p l a c e d i n a l i g h t (ca. 200 E i n s t . m-2s-1) i n c u b a t o r and s w i r l e d t w i c e a day.

and t e m p e r a t u r e c o n t r o l l e d

A f t e r t h r e e days, a p p r o x i m a t e l y 50 mg o f

a l g a e was t r a n s f e r r e d i n t o 125 m l f l a s k s c o n t a i n i n g the same s o l u t i o n from which t h e a l g a e were taken.

Three r e p l i c a t e s were made f o r each treatment.

f l a s k s were t h e n i n n o c u l a t e d w i t h 2.85

The s m a l l

uCi o f 14C-bicarbonate b e f o r e b e i n g

returned t o t h e incubators f o r t h r e e hours.

A f t e r t h e i n c u b a t i o n t h e a l g a e were

removed and prepared f o r combustion i n a C a r l o Erba CHN elemental analyzer f o r determination o f carbon biomass and t h e amount o f 14C incorporated (LoebD 1981). Because t h e amount o f a v a i l a b l e d i s s o l v e d i n o r g a n i c c a r b o n ( D I C ) v a r i e d between t r e a t m e n t s f l a s k s a f t e r t h e t h r e e - d a y i n c u b a t i o n 'and,

since these

r e s u l t s were going t o be presented as primary p r o d u c t i v i t y r a t e s ( r a t e s o f uptakeID D I C concentrations were determined.

D I C c o n c e n t r a t i o n s were analyzed

by i n j e c t i n g 0.2 m l o f s a m p l e i n t o 5 m l o f 3N H2S04.

T h i s a c i d s o l u t i o n was

sparged w i t h n i t r o g e n gas and t h e amount o f C02 e v o l v e d measured by i n f r a r e d a n a l y s i s a g a i n s t s o l u t i o n s o f known concentrations o f sodium bicarbonate. Seepage f l u x t h r o u g h l a k e s e d i m e n t ( 2 m e t e r d e p t h ) was measured using seepage meters (LeeD 1977). o f a 208 1 i t e r m e t a l drum.

ia sl.tu

The seepage meter consisted o f t h e t o p 20 cm

The drum 1 i d was pushed i n t o t h e b o t t o m s e d i m e n t s

163

m2 o f l a k e sedtments.

c o v e r i n g a p p r o x i m a t e l y 0.25 sedtments

t n t o t h e seepage meter,

an e q u a l

As w a t e r seeped o u t o f t h e

v o l u m e was d t s p l a c e d I n t o a

c o l l e c t i o n bag t h r o u g h a s m a l l h o l e d r i l l e d f n t h e t o p o f t h e l t d .

These

seepage meters were used t o determine t h e d t r e c t t o n o f groundwater f l u x (t.e., i n t o o r o u t o f t h e l a k e ) and n o t t h e t o t a l n u t r i e n t l o a d t n g v t a groundwater. These data supported a p r e v t o u s groundwater f l o w study which used hydraul t c and we1 1 w a t e r c h e m t s t r y d a t a t o detetritne t h e t o t a l groundwater n u t r l e n t l o a d l n g f r o m Ward V a l l e y t o Lake Tahoe ( a d j a c e n t t o S t a t t o n PI Goldman, 1984,

1979).

however,

therefore,

F i g . 11.1) (Loeb and

Two seepage r a t e samples were c o l l e c t e d between A p r t l and J u l y c o l l e c t i o n bags were l o s t o r t o r n on s e v e r a l occasions,

reducing t h e sample s t z e t o one on those dates.

I n t e r s t i t t a l water qua1 i t y was c o l l e c t e d adjacent to, t h e seepage meter.

b u t separate from,

Porous T e f l o n R s o i l m o t s t u r e e x t r a c t o r s were p l a c e d 1978), and w a t e r was

a p p r o x i m a t e l y 10 cm t n t o t h e s e d t m e n t (Ztmmerman e t al.,

e x t r a c t e d from t h e sampling tube which extended t n t o t h e l a k e using a hand pump ( s a m p l i n g done u s i n g SCUBA). n i t r o g e n (Mu1 1 t n and R i l e y ,

These w a t e r s were t h e n a n a l y z e d f o r n t t r a t e -

1955;

Kamphake e t al.,

19671,

ammontum (Solorzano,

19691, and s o l u b l e r e a c t i v e phosphorus ( S t r i c k l a n d and Parsons, 1972; Murphy and R i 1ey,

1962).

Land use d i s t r i b u t i o n and area mapping was provtded by t h e Tahoe Regional Planning Agency (TRPA).

The TRPA a l s o provtded data from a survey o f 200 homes

from 23 houstng areas around t h e l a k e which were reduced t o p r o v i d e an estimate o f t h e area o f developed l a n d on which grass lawns were being grown (7.05 kn?). T h i s g r a s s l a w n a r e a was t h e n m u l t t p l t e d by t h e a v e r a g e a n n u a l f e r t i l i z e r appl t c a t t o n r a t e (TFPA,

unpubl tshed) t o g e t a t o t a l amount.

The l a r g e s t s i n g l e

user o f f e r t t l t z e r s w i t h i n t h e Tahoe basin is b e l t e v e d t o be g o l f courses which cover 4.01 km2. N u t r i e n t tnputs t o t h e watershed o f Lake Tahoe from p r e c t p i t a t i o n have been c o n t i n u o u s l y measured s i n c e 1973 (Leonard e t al., 19851,

1979; B y r o n and Goldman,

i n c l u d i n g one s y n o p t i c e v a l u a t i o n ( A x l e r e t al.,

1983).

These data were

used t o d e t e r m t n e t h e a v e r a g e a n n u a l n u t r i e n t t n p u t s t o t h e watershed o f n t t r o g e n and phosphorus from t h i s source. 11.3 RESULTS AND DISCUSSION 11.3.1

S

s bi-

The species composttton o f t h e e u l t t t o r a l p e r i p h y t o n community was n e a r l y e n t t r e l y one s p e c t e s o f t h e s t a l k e d diatom, pennate d t a t o m s were common (e.g., t h e s e were n e v e r dominant. l o c a t i o n s sampled.

hnmgmeb w l m n .

S y n d m sp. and

sp.),

Other

however,

T h i s community c o m p o s t t t o n was s h a r e d by a l l

164

Dp

1

IW

1

40 20

0

I40 I 20 I00

80 60

40 20 40

-

20

I

0

80 60

40

20 0

JFMAMJJASONDJFMAMJJASONDJ

I982

I983

I984

Figure 11.2. P a t t e r n s o f p e r i p h y t o n biomass ( c h l o r o p h y l l sampled from rock s u r f a c e s a t 0.5 m depth from t h e f o u r sampling s t a t i o n s between 1982 and 1984. Error bars represent f SE (h=3); no e r r o r bars a r e present when the e r r o r term i s l e s s than diameter o f the open c i r c l e mark.

165 O v e r a l l , p e r i p h y t o n biomass ( c h l o r o p h y l l a) c o l l e c t e d between 1982 and 1984 11 l u s t r a t e d a s t r o n g s e a s o n a l p a t t e r n o f growth.

Maximum amounts o f biomass

usual l y occurred d u r i n g s p r i n g (March-June) a t a1 1 f o u r s t a t i o n s (Fig. 11.2).

A

v e r y pronounced s p a t i a l p a t t e r n i n t h e amounts o f biomass was a l s o e v i d e n t . Greater amounts o f p e r i p h y t o n biomass were found a t t h e developed stations,

P

and I C , t h a n a t t h e t w o u n d e v e l o p e d s t a t i o n s (DP and I W ) .

The r a t i o s between

t h e maximum amount o f biomass a t each l o c a t i o n (DP:IW:IC:P)

d u r i n g each o f t h e

t h r e e years i l l u s t r a t e d t h e p e r s i s t e n c e o f t h i s s p a t i a l d i s t r i b u t i o n : 1:3:8:8;

1983

-

1:1:6:10;

1984

-

1:2:4:13.

1982

-

Annual d i f f e r e n c e s i n p e r i p h y t o n

biomass were b e l i e v e d t o b e t h e r e s u l t o f h y d r o l o g i c f a c t o r s w h i c h a f f e c t n u t r i e n t loading.

S i m i l a r s p a t i a l d i f f e r e n c e s i n amounts o f periphyton biomass

i n t h e l i t t o r a l zone o f Lake Tahoe h a v e been r e p o r t e d by o t h e r s (Goldman and deAmezaga, 1975; Loeb and Reuter,

1984; Loeb and Palmer,

1985).

These data e s t a b l i s h t h a t m r e periphyton biomass accrued i n t h e l i t t o r a l zone a d j a c e n t t o a r e a s o f undeveloped.

t h e w a t e r s h e d t h a t had been d e v e l o p e d t h a n

The p e r s i s t e n t c h a r a c t e r i s t i c o f t h i s s p a t i a l d i s t r i b u t i o n

suggested t h a t some f a c t o r ( s ) which enhance t h e p r o d u c t i o n o f periphtyon must be a f f e c t e d by l a n d development.

The e f f e c t s o f development were a l s o d e t e c t a b l e

on b o t h a s m a l l (meters) and l a r g e ( k i l o m e t e r s ) scale, causal f a c t o r s c o u l d be e l i m i n t e d .

For example,

therefore,

some p o s s i b l e

a v a i l a b l e l i g h t energy,

water

t e m p e r a t u r e , and n u t r i e n t p o o l s i n t h e l a k e w a t e r d i d n o t v a r y s i g n i f i c a n t l y enough t o e x p l a i n t h e s p a t i a l d i f f e r e n c e s i n p e r i p h y t o n biomass between s i t e s , e s p e c i a l l y between I C and Loeb and Palmer, 1985).

IW which were o n l y 200 m a p a r t (Loeb and Reuter, 1984;

The most l i k e l y d i f f e r e n c e between s t a t i o n s which would

cause such g r e a t d i f f e r e n c e s I n t h e amount o f p e r i p h y t o n biomass was n u t r i e n t availability. 11.3.2 B i o l o g i c a l assays were designed t o examine whether n u t r i e n t a v a i l a b i l i t y affected periphyton productivity.

The r e s u l t s o f t h e b i o a s s a y s d e m o n s t r a t e d

t h a t t h e p r o d u c t i v i t y o f t h i s a l g a l community was s t i m u l a t e d by a d d i t i o n s o f n i t r a t e and ammonium e i t h e r a l o n e o r i n combination o r phosphorus i n combination w i t h n i t r o g e n ( F i g . 11.3).

T r e a t m e n t c o m p a r i s o n s v e r s u s t h e c o n t r o l showed

s i g n i f i c a n t increases i n p r o d u c t i v i t y except f o r phosphorus a l o n e (NO3,

(0.01;

a1 1 n i t r o g e n and phosphorus c o m b i n a t i o n s , NH4, a (0.05; NO3 t NH4, a(0.005; a (0.001). A d d i t i o n s o f n i t r a t e - n i t r o g e n a l o n e enhanced p r o d u c t i v i t y 200% compared t o t h e c o n t r o l s .

The s y n e r g i s t i c e f f e c t o f n i t r o g e n (as ammonium and

n i t r a t e ) and phosphorus added t o g e t h e r r e s u l t e d i n t h e most s t i m u l a t i o n , 370%.

These and o t h e r d a t a ( E l o r a n t a ,

279-

1983) s u p p o r t t h e h y p o t h e s i s t h a t

increased n u t r i e n t a v a i l a b i l i t y can be t h e causal f a c t o r a f f e c t i n g t h e observed s p a t i a l heterogeneity i n p e r i p h y t o n biomass.

166 T h i s bioassay was conducted on p e r i p h y t o n sampled d u r i n g May 1982, from s t a t i o n P,

a developed area.

The s p e c i e s c o m p o s l t l o n o f t h e p e r i p h y t o n

comnunity was the same a t a l l stations, o n l y biomass was d i f f e r e n t .

The r e s u l t s

o f t h i s bioassay were s l m p l y t h a t increased n u t r i e n t a v a i l a b i l i t y i n c r e a s e d periphyton p r o d u c t i v i t y .

I n Lake Tahoe, an extremely n u t r i e n t d e f i c i e n t system,

t h e r e s u l t s o f t h i s bioassay were n o t s u r p r i s i n g .

I f t h e r e was d l f f e r e n t i a l

n u t r i e n t loading t o the l i t t o r a l zone from the surrounding watershed, the r e s u l t would very l i k e l y be manifested i n d i f f e r e n t i a l amounts o f perlphyton biomass. 11.3.3

&cdpLUlon.

strenm and

gmu&abr

sour=

P r e c i p i t a t i o n n u t r i e n t inputs to the watershed, stream n u t r i e n t loading t o the lake, and o v e r a l l l a k e l i n n o l o g y have been continuously investigated a t Lake Tahoe since 1968 (see review, Go1dman, 1981).

E a r l y i n v e s t i g a t i o n s demonstrated

T T

0 !&

0 W

a v)

0

CONTROL

1

NO - N

NH4-N

(680)

(600)

N03-N NH4-N

11 PO4-P

PO4-P

PO4-P

(100)

NO3-N

NH4-N

(300) ( 300)

(100) (600)

(100) (600)

W4-pb NOS-N NH4-N

(100)

T R EATM ENT Figure 11.3. N u t r i e n t b i o l o g i c a l assay o f periphyton primary p r o d u c t i v i t y using t r e a t m e n t s o f n i t r o g e n (nitrate=N03-N and ammonium=NH -N) and phosphorus (orthophosphate=PO -P). U n i t s f o r amounts added t o ambient l a k e water o f each The c o n t r o l eriphyton i n ambient 1 ke n u t r i e n t are I n m?crograms per l i t e r . NH4-N (2 ug N ' l i t r-f, PO P ( 2 ug Politer-'). water (N03-N=3 ug * l i t e r - ' , E r r o r bars Units o f s p e c l f i c productions are i n ug Cliter-'h-'/ug &iomass. r e p r e s e n t & 1 SE (n-3). Treatment comparisons v e r s u s t h e c o n t r o l showed s i g n l f l c a n t increases i n p r o d u c t i v i t y except f o r phosphorus alone a (0.01; NH4, ~(0.05 NO3 + NH4, a(0.005; a1 1 N + P treatments, a(0.001).

"4,

167 t h a t g r e a t e r amounts o f pertphyton grew on a r t i f i c i a l s u b s t r a t a placed t n t h e l a k e adjacent t o streams d r a i n i n g developed areas compared t o undeveloped areas P e r t p h y t o n growth, however, was a l s o e v t d e n t

(Go1 dman and deAmezaga, 1975).

along t h e s h o r e l i n e away from stream water inputs. pathway,

groundwater,

Another p o s s i b l e n u t r t e n t

was then constdered.

I n v e s t i g a t i o n s o f groundwater w i t h i n t h e Tahoe b a s i n have been 1 tmtted.

A

study o f groundwater n u t r i e n t tnputs from Ward V a l l e y (adjacent t o s t a t t o n P, Fig. 11.1) t o Lake Tahoe estimated t h a t n i t r a t e - n i t r o g e n l o a d l n g o f t h e l a k e v t a g r o u n d w a t e r was e q u a l t o t h a t o f Ward Creek (Loeb and Goldman,

1979).

Ward

Creek i s t h e f o u r t h l a r g e s t stream t n p u t source o f n t t r a t e t o Lake Tahoe i n the basin (Byron and Goldman,

1985).

I n t h e present study,

d i r e c t measurements o f

seepage t h r o u g h t h e sedtments i n t o t h e l a k e a t s t a t t o n P ( 2 m d e p t h ) demonstrated

I 800 I600 I400

a net

posttive

f l u x o f groundwater

T

i n t o Lake Tahoe (Fig. 11.4).

INTERSTITIAL WATER CHEMISTRY nutrient mean conc.(pg* I-'~ s . E . NO-, N NH4-N P04-PS~

101 2 2 1 ( n = 3 ) 3 2 0 (n.2) 27+3 (n=3)

I200 I000

SEEPAGE FLUX - 2 meter depth

800 600 400 200

0 F i g u r e 11.4. Mean r a t e o f seepage f l u x t h r o u g h s e d i m e n t s t n t o Lake Tahoe (Pineland s t a t i o n ) a t 2 m, d u r i n g 1984. E r r o r b a r s = +1 SE (n=2) and (n=l) when n o t present. I n s e r t v a l u e s a r e t h e mean i n t e r s t l t i a l water chemistry.

168 Furthermore,

n u t r i e n t c o n c e n t r a t i o n s o f these seepage waters were h i g h i n b o t h

n i t r a t e and orthophosphate.

The hypothesis t h a t groundwater may be an i n p o r t a n t

s o u r c e o f n u t r i e n t s a f f e c t i n g t h e a l g a l b i o f o u l i n g o f t h e s h o r e 1 i n e o f Lake Tahoe, therefore,

appeared p l a u s i b l e .

N u t r i e n t l o a d i n g t o t h e watershed v l a r a i n and snow was reviewed i n order t o e s t i m a t e t h e a v e r a g e a n n u a l n i t r o g e n and phosphorus i n p u t s ( T a b l e 11.1) ( L e o n a r d e t al.,

1979; A x l e r e t al.,

1983; B y r o n a n d Goldman,

A p p r o x i m a t e l y 147.7 MT o f n i t r o g e n (1.83 k g Noha'')

(0.044 kg Pha'l) data.

1985).

and 3.5 MT o f phosphorus

a r e loaded i n t o t h e watershed annually.

based on n i n e years o f

These n u t r i e n t s i n p u t s a r e g e n e r a l l y processed w i t h i n t h e watershed by

t h e v e g e t a t i o n and s o i l b i o t a (Coat e t al.,

1975). F o r example.

8% o f t h e i n o r g a n i c n i t r o g e n e n t e r i n g t h e Ward

approximately

V a l l e y watershed from

p r e c i p i t a t i o n flowed i n t o Lake Tahoe v i a Ward Creek i n 1984. N i t r o g e n and Phosphorus i n p u t s t o t h e w a t e r s h e d o f Lake Tahoe T a b l e 11.1. from p r e c i p i t a t i o n and f e r t l l i z e r sources. ( U n i t = m e t r i c t o n s p e r year.) Nitrogen (MT-N) Precipitation

147.7

Fertilizers

79.3

TOTAL

227.0

% Fert. o f Total

11.3.4

Phosphorus (MT-P 1

34

3.5

- 84.6

26.4

- 232.3

29.9

- 28.2

- 31.7 83 - 94%

- 37%

Watershed a c t i v i t i e s affectSol1 disturbance w i t h i n t h e 'watershed through v a r i o u s a c t i v i t i e s tends t o

e n r i c h t h e waters w i t h i n t h e system w i t h n u t r i e n t s .

Topical applications o f

f e r t i l i z e r w i t h i n t h e Lake Tahoe watershed g r e a t l y increases t h e n u t r i e n t load. MT o f n i t r o g e n and 26.4-28.2

A p p r o x i m a t e l y 79.3-84.6

MT o f phosphorus a r e

a p p l i e d t o b a s i n s o i l s as f e r t i l i z e r each year by g o l f courses, o t h e r p r o p e r t y owners o r u s e r s ( T a b l e 11.1). most r e c e n t l a n d use data.

home owners and

These e s t i m a t e s , made f r o m t h e

a r e s i m i l a r t o p r o j e c t e d v a l u e s made i n an e a r l i e r

study o f f e r t i l i z e r use i n t h e Tahoe b a s i n ( M i t c h e l l and Relsenaur,

1973).

F e r t i l i z e r n u t r i e n t i n p u t s c u r r e n t l y a c c o u n t f o r a t l e a s t 34-37% o f t h e t o t a l n i t r o g e n l o a d i n g and 83-94% of t h e t o t a l phosphorus l o a d i n g t o t h e watershed ( T a b l e 11.1).

Increased n u t r i e n t i n p u t s t o t h e watershed Increase t h e

l o a d i n g of n i t r o g e n and phosphorus t o t h e groundwaters and p o s s i b l y i n t o s u r f a c e r u n o f f (Table 11.2).

I n c r e a s i n g t h e n a t u r a l l o a d i n g of n i t r o g e n by o v e r 50% and

169 T a b l e 11.2. A c t i v i t i e s A s s o c i a t e d w i t h Land D i s t u r b a n c e and t h e P o t e n t i a l R e s u l t A f f e c t i n g N u t r i e n t M o b i l i z a t i o n and Loading o f Lake T a k e

f!au!m

RESULT

1.

la.

Increased n i t r t t i c a t i o n r e s u l t i n g i n t h e r e l e a s e of NO3-N i n t o groundwaters.

b.

I n c r e a s e d e r o s i o n r e l e a s i n g Nt PI Fe and t r a c e m e t a l s I n t o s u r f a c e runoff.

Impervious s u r f a c e ( b u i l d i n g s , roads, p a r k i n g l o t s , etc.).

2.

F e r t i l i z e r application.

2.

3.

Road cuts.

3.

Leaching o f N g r o u n d waters.

and P

into

Increased erosion release o f N, PI Fe and t r a c e m e t a l s i n t o

surface runoff. 4.

E x f i l t r a t i o n from sewer l i n e s .

4.

L e a c h i n g o f N, g r o u n d waters.

5.

Maintaining high lake level v i a t h e dam.

5.

Increased s h o r e 1 i n e bank e r o s i o n a d d i n g N, PI Fe and trace metals i n t o l i t t o r a l waters o f t h e lake.

6.

Septic leach f i e l d s (no longer allowed i n t h e Tahoe b a s i n discontinued f i e l d s probably s t i l l leaching).

6.

L e a c h i n g o f N, g r o u n d water.

7.

Sewage disposal w i t h i n watershed .. (two discontinued s i t e s w i t h i n t h e Tahoe basin).

7a.

Inc r eased

8.

9.

--

Unpaved roads and t r a i l s (compacted s o i l s ) .

I r r i g a t i o n o f soils.

P,

PI

etc.

etc.

into

into

n 1 t r if ic a t Io n r e s u l t i n g i n NO3-N r e l e a s e i n t o t h e ground waters.

b.

L e a c h i n g o f P and o t h e r n u t r i e n t s i n t o t h e ground waters.

8a.

Increased erosion r e l e a s i n g Nt P, Fe and t r a c e m e t a l s i n t o surface runoff.

b.

Increased n i t r ification r e s u l t i n g i n the release o f NO3-N i n t o ground waters.

9.

I n c r e a s e d m i n e r a l i z a t i o n and increased mobil i z a t i o n o f s o l u b l e n u t r i e n t s i n t o ground waters p l u s p o s s i b l e r u n o f f o f n u t r i e n t s and s e d i m e n t s i n t o s u r f a c e waters.

170 o f phosphorus by 700 t o 800% tends t o Increase n u t r t e n t l o a d t n g t o Lake Tahoe. I n an ecosystem w h i c h has e v o l v e d u n d e r c o n d t t t o n s o f e x t r e m e n u t r i e n ‘ t d e f i c i e n c y , a c c e l e r a t e d e u t r o p h l c a t l o n w o u l d b e an u n a v o f d a b l e r e s p o n s e t o

t ncreased n u t r t e n t 1oad t ng. F e r t t l t z e r usage a f f e c t s pertphyton production, I C and I W .

S e p a r a t e d by o n l y 200

mr

as was e v t d e n t a t s t a t t o n s

s t a t t o n I C was a d j a c e n t t o a condominlum

development w l t h approxtmately 0.1 ha o f f e r t t l t z e d lawn,

w h t l e I W was adjacent

t o an u n d e v e l o p e d area.

Each year, 1.3 t o 1.6 MT o f f e r t t l l z e r a r e a p p l l e d t o

t h t s area,

MT o f n t t r o g e n and 0.10-0.13

t.e.,

0.13-0.16

MT o f phosphorus.

These

a r e a l l o a d i n g r a t e s were 700 t o 800 times and 23,000-29r000 times g r e a t e r than t h e average annual

areal

p r e c t p t t a t t o n sources,

l o a d t n g r a t e s o f n t t r o g e n and phosphorus f r o m

respectively.

F e r t t l t z e r d e r i v e d n u t r t e n t s leached i n t o

t h e groundwater and i n t o t h e l a k e were b e l f e v e d t o be t h e cause o f t h e observed d i f f e r e n c e s i n t h e amounts o f p e r t p h y t o n biomass between t h e s e t w o s t a t t o n s (Ftg.

11.2). Other

acttvtttes

also

i n c r e a s e n u t r t e n t m o b t l t z a t i o n ( T a b l e 11.2).

C r e a t i o n o f tmpervtous surfaces ( b u i l d i n g s ,

roads,

parking l o t s ,

t h e n a t u r a l v e g e t a t t o n w h i c h absorb n u t r i e n t s f o r t h e i r growth. services, therefore,

etc.)

removes

Impervious

t n d l r e c t l y enhance t h e b a c t e r i a l mediated t r a n s f o r m a t t o n o f

ammonium t o n i t r a t e , n l t r t f t c a t t o n , as m l n e r t z a t t o n o f r e s t d u a l organic m a t e r i a l i n t h e soils p r o d u c e s ammontum.

N t t r a t e can t h e n move r e a d i l y i n t o t h e

g r o u n d w a t e r s because no p l a n t s a r e p r e s e n t t o u t t l tze t h e n u t r i e n t . f i n d i n g s have been reported i n o t h e r s t u d i e s (Ltkens e t al., 1976).

Furthermore,

1969;

Stmtlar

Coats e t al.,

tmpervtous surfaces increase t h e v e l c c t t y o f r u n o f f waters

thereby I n c r e a s i n g t h e e r o s i o n p o t e n t t a l o f t h e surroundtng s o i l s which r e s u l t s t n added nitrogen,

phosphorus,

t r o n and t r a c e metals t o s u r f a c e runoff.

Road c u t s a r e sources o f eroston r e l e a s i n g n u t r t e n t s t n t o s u r f a c e waters. Unpaved roads and t r a i l s cause t h e compaction o f t h e sotls r e s u l t t n g i n e f f e c t s s t m t l a r t o those o f tmpervtous servtces: potenttals.

increased eroston and n t t r t f t c a t t o n

I n c r e a s e d s h o r e 1 i n e bank e r o s t o n r e s u l t i n g from htgh l a k e water

l e v e l s matntatned by t h e 2 m dam on t h e o u t l e t t o Lake Tahoe r e l e a s e n u t r t e n t s t n t o t h e 1 t t t o r a l zone o f t h e l a k e .

This practice o f matntaintng a htgh l a k e

water l e v e l t o use as storage water has become more common a s ’ a g r t c u l t u r a l and o t h e r needs f o r water down stream o f t h e o u t f l o w have increased. The p r o b l e m o f t n f t l t r a t t o n o f f r e s h w a t e r t n t o sewer l i n e s has been a problem w i t h t n t h e Tahoe bastn.

The r e v e r s e o f t h t s problem,

exftltration of

sewage i n t o t h e s o t l s has a s t r o n g p o t e n t i a l stnce t h e pipes a r e g e n e r a l l y above t h e water t a b l e l e v e l .

The r e s u l t w o u l d b e i n c r e a s e d l e a c h i n g o f n t t r o g e n ,

phosphorus and o t h e r m a t e r l a l s t n t o t h e groundwaters. ftelds,

used throughout t h e basin u n t i l 1970,

Old s e p t t c tank leach

probably s t t l l continue t o l e a c h

n u t r t e n t s i n t o t h e groundwaters as s t o r e s o f organtc m a t e r t a l continue t o decay.

171 S e v e r a l l a n d sewage d t s p o s a l areas, now d t s c o n t t n u e d w t t h t n t h e bastn, a l s o conttnue t o leach nutrlents.

I n c r e a s e d n t t r l f l c a t t o n a s s o c t a t e d w t t h one o f

t h e s e a r e a s has r e s u l t e d I n e l e v a t e d n t t r a t e concentrattons I n s p r i n g waters d r a t n t n g t h e area (1-2 mg'l t t e r ' l )

(Perktns e t al.,

19751,

concentrattons whtch

s t l l 1 p e r s t s t 15 y e a r s a f t e r t h e s y s t e m was d t s c o n t t n u e d (Loeb u n p u b l l s h e d data). Finally,

i r r i g a t i o n o f t h e Tahoe s o t l s enhances m t n e r a l t z a t t o n and

mobtl t z a t t o n o f s o l u b l e n u t r l e n t s I n t o t h e groundwaters and p o s s l b l y n u t r t e n t s and sedtments i n t o s u r f a c e runoff.

Under n a t u r a l condltlons,

T a k e s o l l s are

dry from June u n t t l September due t o t h e l a c k o f p r e c t p t t a t t o n . stablltzed

Nutrlents are

i n t h e v e g e t a t t o n and sotl b t o t a d u r t n g t h t s summer p e r t o d .

I r r l g a t t o n tends t o Increase t h e b a c t e r l a l a c t l v t t y responstble f o r m i n e r a l i z a t i o n durtng t h e summer when s o t l temperatures a r e a t t h e l r highest and t o enhance b a c t e r t a l n t t r t f t c a t i o n , a1 l o w t n g n t t r a t e t o b e l e a c h e d I n t o t h e groundwaters.

Most i r r i g a t e d s o t l s are a l s o most o f t e n those s o t l s whlch have

been f e r t t l t z e d whlch f u r t h e r compounds t h e p r o b l e m These a c t t v l t t e s a s s o c l a t e d w t t h d l s t u r b e d a r e a s add t o t h e n u t r l e n t l o a d i n g o f Lake Tahoe.

Stream and g r o u n d w a t e r s a r e b e l t e v e d t o b e t h e

p r t n c t p a l pathways through which these n u t r t e n t s e n t e r from t h e l a k e from t h e watershed.

The p e r t p h y t o n communtty, s t t u a t e d a t t h e I n t e r f a c e between t h e

watershed and t h e lake,

a c t s t o i n t e r c e p t these n u t r t e n t s b e f o r e they reach t h e

open waters o f t h e lake.

Whether these n u t r l e n t s a r e tmmoblllzed permanently I n

t h e b e n t h o s o r o n l y t e m p o r a r t l y h e l d b e f o r e b e i n g r e l e a s e d t n t h e summer as these a l g a e decompose f o l l o w t n g t h e s p r i n g bloom Is n o t known.

The perlphyton

communtty p r o v i d e s v t s t b l e e v i d e n c e o f change w h l c h d i r e c t s o u r a t t e n t i o n towards a need t o b e t t e r understand t h e r e 1 a t t ve tmportance o f those processes a f f e c t t n g t h e water q u a l l t y o f Lake Tahoe. 11.4 CONCLUSIONS The growth of attached algae,

pertphyton, along t h e s h o r e l l n e o f Lake Tahoe

shows p e r s l s t e n t s p a t t a l patterns.

These p a t t e r n s .were d t r e c t l y associated w l t h

l a n d disturbance such t h a t g r e a t e r amounts o f pertphyton btomass (Chl 1) were p r e s e n t a d j a c e n t t o a r e a s o f t h e w a t e r s h e d w h l c h h a v e been d i s t u r b e d (t.e., d e v e l o p e d ) compared t o l o c a t t o n s a d j a c e n t t o u n d t s t u r b e d areas.

Pertphyton

p r o d u c t t v l t y showed s t l m u l a t t o n as n u t r t e n t a v a t l a b l l t t y was increased, s p e c t f l c a l l y , n l t r o g e n a l o n e o r phosphorus and n i t r o g e n I n comblnatlon.

Vartous

types o f a c t i v i t i e s assoctated w t t h l a n d d e v e l o p m e n t a f f e c t n u t r i e n t mobtl I z a t t o n and subsequent l o a d i n g t o t h e lake.

F e r t t l t z e r usage,

f o r example,

has increased l o a d i n g o f n i t r o g e n by o v e r 50% and o f phosphorus by 700-800% t o t h e watershed o f Lake Tahoe.

Other a c t i v t t t e s a f f e c t t n g

nutrient

mob11 t z a t t o n

172 i n c l u d e impervious surfaces, road cuts, s o l 1 compaction, a r t i f i c i a l l y maintained h i g h l a k e water l e v e l s , fields,

e x f i l t r a t i o n from sewer l i n e s ,

abandoned sewage disposal s i t e s ,

o l d s e p t i c tank l e a c h

and t h e I r r i g a t i o n o f s o i l s .

The two

major pathways by whlch watershed d e r i v e d n u t r i e n t s e n t e r t h e l a k e are stream and ground waters. This paper o u t l i n e s those processes which appear t o have c o n t r i b u t e d t o t h e a l g a l b l o f o u l i n g o f t h e s h o r e l i n e o f Lake Tahoe.

The periphyton community has

p r o v e n I t s u t i l f t y as a s i t e s p e c i f i c b i o l o g i c a l i n d i c a t o r o f t h e i n c r e a s e d nutrient a v a i l a b i l ity.

The s e n s i t i v i t y o f t h e watershed which s u r r o u n d s t h e

l a k e must b e t h o r o u g h l y u n d e r s t o o d i n o r d e r t o r e a c h a b a l a n c e between u t i l i z a t i o n and p r e s e r v a t i o n o f t h e a r e a and t o s l o w t h e r a t e o f a l g a l b i o f o u l i n g and e u t r o p h i c a t i o n o f Lake Tahoe.

11.5 ACKNOWLEDGMENTS This study was funded by t h e Cal i f o r n i a S t a t e Water Resources C o n t r o l Board using Clean Lakes g r a n t funds made a v a i l a b l e by t h e Environmental P r o t e c t i o n Agency.

This support does n o t s i g n i f y t h a t t h e contents n e c e s s a r i l y r e f l e c t t h e

v i e w s o f t h e s e agencies. individuals.

The o p e r a t i o n o f t h i s program i n v o l v e d many

My a p p r e c i a t i o n i s extended t o J. A l o i , S. Hackley, and T. Dunn

f o r t h e i r activ.e

participation.

Drs. J. Reuter, R. A x l e r and C. Goldman were

h e l p f u l w i t h t h e i r a d v i c e and c r i t i c i s m s . were h e l p f u l i n c l a r i f y i n g some s e c t i o n s .

Comments o f an anonymous r e v i e w e r Thanks a r e a l s o extended t o t h e

Lahontan Water Q u a l i t y C o n t r o l Board f o r t h e i r support and t o t h e Tahoe Regional Plannlng Agency f o r p r o v i d i n g needed information. REFERENCES Leonard, R.L. and Goldman, C.R., 1983. A t m o s p h e r i c A x l e r , R.P., Byron, E.R., d e p o s i t i o n o f n u t r i e n t s i n t h e Lake Tahoe basin. I n t e r a g e n c y Tahoe M o n i t o r i n g Program, Water Year 1982. I n s t i t u t e o f Ecology, Univ. o f C a l if., D a v i s , 53 pp.

1985. F i f t h Annual Report, Lake Byron, E.R., A x l e r , R.P. and Goldman, C.R., Tahoe I n t e r a g e n c y M o n i t o r i n g Program, Water Year 1984. I n s t i t u t e o f Ecology, Unlv. o f Calif., Davis, 122 pp. 1975. Removal o f n i t r o g e n f r o m Coats, RN . ,. Leonard, R.L. and Loeb, S.L., snowmelt water by t h e s o i l - v e g e t a t i o n system, Lake Tahoe Basin, Cal I f o r n i a . P r o c e e d i n g s o f Western Snow Conference, San Diego, CAI A p r i l 22-25, 98100 pp. Coats,

RN . ,. Leonard, R.L. and Goldman, CR . ,. 1976. Nitrogen uptake and r e l e a s e i n a f o r e s t e d watershed, Lake Tahoe Basin, C a l i f o r n i a , Ecology, 57: 995-

1004. E l o r a n t a , P.V., 1983. P e r i p h y t o n pigment a n a l y s i s using paper chromatography. In: R.G. W e t z e l ( E d i t o r ) , P e r i p h y t o n o f F r e s h w a t e r Ecosystems. Developments I n Hydrobiology 17: 291-298.

173 Goldman, CR . ,. 1981. Lake Tahoe: two decades o f change i n a n i t r o g e n d e f i c i e n t o l i g o t r o p h i c lake. Verh. I n t e r n a t . Verein. Limnol., 21: 45-70. Goldman, C.R. and deAmezaga, E., 1975. P r i m a r y p r o d u c t i v i t y i n t h e l i t t o r a l zone o f Lake Tahoe, Cal ifornia-Nevada. Symp. B i o l . Hungary, 15: 49-62. Iwamura, T., Nagai, H. and Ichimura, S., 1970. Improved methods f o r determining contents o f c h l o r o p h y l l , protein, r i b o n u c l e i c acid, and desoxyribonucleic a c i d i n p l a n k t o n populations. I n k Revue ges. Hydrobiol., 55: 131-147. Kamphake, L.J., Hannah, S.A. and Cohen, J.M., 1967. Automated a n a l y s i s f o r n i t r a t e determination by hydrazine reduction. Water Res., 1: 205-216. Lee, D.R., 1977. A d e v i c e f o r m e a s u r i n g seepage f l u x i n l a k e s and e s t u a r i e s . Limnol. Oceanogr., 22: 140-147. Leonard, R.L., K a p l a n , L.A., E l d e r , J.F., Coats, R.N. and Goldman, C.R., 1979. N u t r i e n t t r a n s p o r t i n s u r f a c e r u n o f f from a s u b a l p i n e watershed, Lake Tahoe Basin, Cal i f o r n i a . Ecolo. Moncgr., 49(3): 281-310. Likens, G.E., Bormann, F.H. and Johnson, N.M., 1969. N i t r i f i c a t i o n : t o n u t r i e n t l o s s e s from a c u t o v e r f o r e s t e d ecosystem. Science,

Importance

163: 1205-

1206. Loeb, S.L., 1981. An In method f o r measuring t h e primary p r o d u c t i v i t y and s t a n d i n g c r o p o f t h e e p i l i t h i c p e r i p h y t o n community i n l e n t i c systems. Limnol. and Oceanogr., 26: 394-399. Loeb, S.L. a n d Goldman, C.R., 1979. W a t e r and n u t r i e n t t r a n s p o r t v i a groundwater from Ward V a l l e y i n t o Lake Tahoe. Limol., Oceanogr., 24: 1146-

1154. Loeb, S.L.

and Palmer, J.E., 1985. L i t t o r a l zone i n v e s t i g a t i o n s , Lake Tahoe I n s t i t u t e o f Ecology, Univ. o f Calif., Davis, 106 pp.

1983, periphyton. Loeb, S.L.

1982:

1984. L i t t o r a l zone i n v e s t i g a t i o n s , Lake Tahoe and Reuter, J.E., Periphyton. I n s t i t u t e o f Ecology, Univ. o f Calif., Davis, 66 pp.

and Reisenauer, H.M., 1973. Lake Tahoe b a s i n f e r t i l I z e r use M i t c h e l l , C.R. s t u d y , 1972. Univ. o f C a l i f . , D a v i s , 20 pp. Mu1 1 in, J.B. and R i l e y , J.P., 1955. The s p e c t r o p h o t o m e t r i c d e t e r m i n a t i o n o f n i t r a t e I n n a t u r a l waters, w i t h p a r t i c u l a r r e f e r e n c e t o seawater. Anal. Chim. Acta, 12: 464-480. Murphy, J. and R i l e y , J.P., 1962. A m o d i f i e d s i n g l e s o l u t i o n method f o r t h e determination o f phosphate i n n a t u r a l waters. Anal. Chlm Acta, 27: 31-36. P e r k i n s , M.S., Goldman, C.R. and Leonard, R.L., 1975. R e s i d u a l n u t r i e n t discharge i n streamwaters i n f l u e n c e d by sewage e f f l u e n t spraying. Ecology,

56: 453-460. S o l o r z a n o , L., 1969. D e t e r m i n a t i o n o f ammonia I n n a t u r a l w a t e r s by t h e phenol h y p o c h l o r i t e method. Limnol. Oceanogr., 14: 799-801. S t r i c k l a n d , J.D.H. and Parsons, T.R., 1972. A P r a c t i c a l Handbook o f Seawater A n a l y s i s . F i s h . Res. Board Can. B u l l . 167 (2nd ed.), 310 p.

1978. Comparison o f c e r a m i c Zimmerman, C.F., P r i c e , M.T. and Montgomery, J.R., and t e f l o n In sLiu s a m p l e r s f o r n u t r i e n t p o r e w a t e r d e t e r m l n a t l o n s .

This Page Intentionally Left Blank

175

Chapter 12 GROWTH OF THE FOULING ALGA CLADOPHORA GLOMERATA (L.) Kirtz. AT VARIOUS CONCENTRATIONS OF COPPER. H. HILLEBRAND AND P.J.R. DE VRlES Biologisch Laboratorium, Vrije Universiteit, P.O. Box 7161, 1007 MC Amsterdam, The Netherlands

12.1 INTRODUCTION

Trace amounts of copper are essential for metabolic processes of algae (Sorentino, 1978) whereas higher concentrations inhibit growth or kill the algae (Francke and Hillebrand. 1980). Copper sulphate has widely been used as an algicide to control or prevent considerable algal growth (Whittaker et al., 1978). For instance, copper-based paints are used as antifouling coatings on ships. The effectivity of such paints is restricted, after a few months algae will start to settle on the treated surface. This may be due to the loss of algicide properties of the paint and/or settlement of highly tolerant algae. Hall et al. (1979) observed that strains of the marine alga Ectocarpus siliculosus (Dillw.) Lyngb. collected from panels coated with antifouling paint were tolerant to high concentrations of copper. In this study preliminary results are presented from a survey for copper tolerant strains of the freshwater alga Cladophora glomerata (L.) Kirtz.. 12.2 MATERIALS AND METHODS

The algae were collected from two antifouling coated shipwalls at the yacht harbor at the lake Nieuwe Meer, Amsterdam. A strain isolated from a sheet piling in a ditch at the University campus served as a reference. Unialgal filaments of Cladophora glomerata were isolated and transferred into a synthetic medium, Woods Hole slightly modified (Table 12.1). The strains were identifiedaccording to the classifiiation of Van den Hoek (1963). Aggregations of algae were fragmented and 5-cell filaments were inoculated in Petri dishes, containing 20 ml of the synthetic medium in 0.5% agar. Copper (CuSO4 .5H20) was added in a series containing 0.002, 0.16, 0.33, 0.48, and 0.58 mg . I-1 ,including the copper in the standard medium. The experiments were run in a climate room at 20 f 2 'C. Light was provided with TL 32 fluorescent tubes in a 16 - 8 hr lightdark regime at 90 pEinsteins m 2 . s 1 , measured with the LI-COR LI-185A Quantum meter. The cell numbers of the filaments were

counted under the microscope, at 400 x. Specific growth rate was calculated as doublings per day with the formula :

where x2 and x1 represent the number of cells per filament at day 12 and 11, respectkery.

176 Table 12.1. Components of the synthetic growth medium Component concentration mg.r1

Concentration of the elementdions mg.1-1

CaC1.2H20 MgS04.7H20 NaHC03.7H20 NaN03 K2HP04 Na2EDTA.2H20 FeC13.6H20 MnC12.4H20 ZnS04.7H20 NaMo04.2H20 CoC12.6H20 CuS04.5H20 H3BO3

36.8 37.0 100.0 85.0 8.7 4.4 1.5 0.2 0.02 0.006 0.01 0.01 0.5

HEPES Thiamine Biotine Cyanobalamine (vit. 612)

500 0.1 0.0005

Ca 10.0 Mg 3.6 Na 27.4 Na 23.0 K 4.2 Na 0.53 Fe 0.30 Mn 0.055 Zn 0.0046 Mo 0.0026 Co 0.0024 Cu 0.0025 0 0.09

CI 17.7 SO4 14.4 HCO3 72.6 N 14.0 P 1.75

NO3 62.0 HPO4 4.8

CI 0.6 CI 0.07 SO4 0.007

0.0005

12.3 RESULTS AND DISCUSSION The growth responses to the various concentrations of copper are presented in Fig. 12.1. The amounts of cells are more or less the same for the three tested strains at low concentrations of 0.002 mg.1-l Cu, but afler addition of 0.1 6 rng.1-l , the amount of cells was less for strain 3 (reference) than for strains 1 and 2. Filaments of a relatively larger number of cells were observed with strain 2 in comparison with strains 1 and 3 at 0.48 and 0.58 mg.1-l Cu. Specific growth rates (p)of the filaments at different concentrations of copper, expressed as doublings per day, are presented in Table 12.2. The growth of the strains is identical at 0.002 mg.l-lCu, but at increasing concentrations the responses deviate. Growth slightly diminished for strain 2, whereas specific growth rates dropped drastically for the filaments of strains 1 and 3 (reference). So strains 1 and 3 are less tolerant to copper than strain 2. Although strains 1 and 2 were both collected from surfaces treated with an antifouling substance, only strain 2 showed a higher tolerance for copper. This indicates that Cu-intolerant as well as Cu-tolerant strains of Cladophora glomerata are found on such substrates. Several examples have been reported of marked differences in metal resistance within a single species. These include planktonic species, e.g. Ni-tolerant Scenedesmus species (Stokes et at.. 1973) and Cutolerant Scenedesmus species (Mierle and Stokes, 1976) and Chlorella vulgaris Beyerinck (Foster, 1977)

177

4c

40

Ib)

P 30

30

Y 20

r

u u

u

-

10

20

10

1

1

2

3

4

5

Days

0

1

2

3

4

3

Days

Fig. 12.1. Number of Cells per filament at various concentrations of copper ( A - 0.002 mg. 1-1, A 0.16 mg. I-1 , - 0.33 mg. 1 - l , m - 0.48 mg. 1-1 , 0 0.58 mg. 1 - l ),versus time, of three strains of Cladophora glornerata . Strains 1 (a) and 2 (b) are isolated from antifouling-coated shipwalls; Strain 3 (c) serves as a reference. ~

-

0

1

2

3 Days

4

5

178

Table 12.2. Growth rate (p)for filaments of Cladophora glomerata at different concentrations of copper; p in doublings per day. Concentration mg.rlcu 0.002 0.16 0.33 0.48 0.58

Strain 1

Strain 2

Strain3

0.37 0.39 0.32 0.25 0.18

0.37 0.40 0.38 0.34 0.34

0.39 0.34 0.19 0.15

as well as Zn-tolerant strains of filamentous algae , e.g. Hormidium species (Say et al., 1977) and

Stigeoclonium tenue Kutz. (Harding and Whitton, 1976). The presence of Cu-tolerant strains from antifouling coated surfaces as described in this study agrees with the observations of Hall et al. (1979). They isolated a Cu-tolerant strain of the marine brown alga

Ectocarpus siliculosus . Although Cladophora glomerata is regarded as sensitive to heavy metals (Whitton, 1970) it was, besides the dominant alga Oedogonium , present on the antifouling-coatedshipwall. As the coating will steadily lose its algicide properties it can be expected that more tolerant strains settle in an early stage; with diminishing toxicity more tolerant strains may survive. This phenomenon can be responsible for the presence of Cu-tolerant and Cu-intolerant strains on the coatings. 12.4 ACKNOWLEDGEMENTS We wish to thank Wim Verhoog for assistance in the experiments and Joske Bunders for stimulating comments. REFERENCES Foster, P.L., 1977. Copper exclusion as a mechanism of heavy metal tolerance in a green alga. Nature, 269: 322-323. Francke, J.A. and Hillebrand, H., 1980. Effects of copper on filamentous Chlorophyta. Aq. Bot., 8: 285;289. Hall, A,, Fielding, A.H. and Butler, M., 1979. Mechanisms of copper tolerance in the marine fouling alga Ecfocarpus siliculosus- evidence of an exclusion mechanism. Mar. Biol.. 54: 195;199. Harding, J.P.C. and Whitton, B.A., 1976. Resistance to zinc of Stigeoclonium tenue in the field and the laboratory. Br. Phycol., 11: 417;426. Mierle, G. and Stokes, P.M., 1976. Heavy metal tolerance and metal accumulation by planktonic algae. In: D.D. Hamphill (Editor), Trace Substacnes in Environmental Health, X. University of Missouri, Columbia, pp. 113-122. Say, P.J., Diaz, B.M. and Whitton, B.A.. 1977. Influence of zinc on lotic plants. Tolerance of Hormidium species to zinc. Freshw. Biol., 7: 357-376. Stokes, P.M., Hutchinson, T.C. and Krauter, H., 1973. Heavy metal tolerance in algae isolated from contaminated lakes near Sudbury, Ontario. Can. J. Bot., 51: 2155;2168. Sorentino, C., 1978. The effects of heavy metals on phytoplankton - a review. Phykos, 18: 149-161. Van den Hoek, C., 1963. Revision of the European species of Cladophora. Doctoral thesis, Leiden, The Netherlands, 258 pp. Whittaker. J., Barica. J., King, H. and Buckley, M., 1978. Efficacy of copper sulphate in the suppression of Aphanizomenon flos-aquae blooms in prairie lakes. Environm. Poll., 15: 185-194. Whitton, B.A., 1970. Toxicity of heavy metals to algae: a review. Phykos. 9: 116-125.

179

Chapter 13

ALGAL FOULING I N THE NORTH SEA

TERRY a n d G.B.

L.A.

Aberdeen

PICKEN

University

Marine

Studies

Ltd.,

Department

of

Z o o l o g y , U n i v e r s i t y o f A b e r d e e n , A b e r d e e n , AB9 2TN, U . K .

1 3 . 1 INTRODUCTION O f f s h o r e g a s e x t r a c t i o n i n t h e U.K. 1960's

in

produced

the

southern

North

Sea

and

s t a r t e d i n t h e mid f i r s t oil

the

T h e r e a r e now

from t h e c e n t r a l North Sea i n 1975.

o v e r 100 i n s t a l l a t i o n s i n t h e t h r e e areas o f northern,

-

c e n t r a l and southern

was

t h e North Sea

-

The t o a maximum d e p t h o f 30m, t h o s e i n t h e c e n t r a l N o r t h S e a f r o m 45m t o 142m a n d t h e d e e p e s t p l a t f o r m s , f r o m 117m t o 187m, a r e f o u n d i n t h e installations

i n the southern

n o r t h e r n North Sea.

i n d i c a t e d i n F i g u r e 1.

North

Sea e x t e n d

Throughout t h i s paper,

r e l a t i v e t o Lowest Astronomical Tide, A l l

d e p t h s are g i v e n

(L.A.T.)

i n s t a l l a t i o n s are r a p i d l y c o l o n i s e d by f o u l i n g

organisms w i t h f o u l i n g communities extending zone t o t h e seabed.

from t h e s p l a s h

The c o m p o s i t i o n , e x t e n t a n d t h i c k n e s s o f

f o u l i n g i n a l l t h r e e areas o f t h e North Sea is b r o a d l y similar b u t t h e r e are d i f f e r e n c e s i n d e t a i l between t h e

r e g i o n s and

also

in

sometimes

quite

striking

differences

composition between

adjacent platforms.

have been d e s c r i b e d

for several

(e.g.

Fouling

structures

G o l d i e , 1 9 8 1 ; Goodman a n d R a l p h ,

Forteath et al., Picken,

1982;

1983;

1984;

t h e North Sea

1981; Hardy,

1981;

et al.,

1983;

Picken

in press). L i c e n s i n g r e g u l a t i o n s f o r t h e U.K.

r e q u i r e t h a t annual surveys of and

in

species

communities

that

such

surveys

s e c t o r (HMSO, 1 9 7 7 )

f i x e d i n s t a l l a t i o n s a r e made

s h o u l d make

an

assessment of

the

t h i c k n e s s o f m a r i n e g r o w t h o n t y p i c a l members or areas o f t h e structure.

There are no d e t a i l e d g u i d e l i n e s , however, a s t o

how o p e r a t o r s s h o u l d make t h i s a s s e s s m e n t .

S i n c e 1 9 8 1 , AUMS

(Aberdeen U n i v e r s i t y Marine S t u d i e s Ltd.)

has provided an

a n a l y s i s s e r v i c e t o h e l p e n g i n e e r s t o assess t h e c u r r e n t s t a t e of

marine

growth

and

t o p r e d i c t i t s f u t u r e c o m p o s i t i o n and

180

Fig. 13.1.Map of North Sea showing location of ( a ) offshore structures from which data on algal fouling has been obtained and ( b ) t h e b u o y s in t h e a p p r o a c h channel to the Cromarty Firth

.

181

t h i c k n e s s on e x i s t i n g s t r u c t u r e s and on f u t u r e i n s t a l l a t i o n s . The

time

allocated

to

i n s p e c t i o n is s h o r t and c o l l e c t i o n of c o v e r and

marine it

relevant data

growth

assessment

during

is i m p o r t a n t t o maximise ( s p e c i e s composition,

t h i c k n e s s ) which w i l l b e o f

the

percentage

importance t o t h e

e n g i n e e r s who h a v e t o make d e c i s i o n s on c l e a n i n g programmes t o relieve s t r u c t u r a l loading. T h i s p a p e r o u t l i n e s t h e methods o f d a t a a n a l y s i s adopted

t o p r o v i d e s u c h i n f o r m a t i o n t o meet e n g i n e e r i n g r e q u i r e m e n t s and d e s c r i b e s t h e d i s t r i b u t i o n o f a l g a e on o f f s h o r e s t r u c t u r e s i n t h e North Sea.

The o f f s h o r e a l g a l c o m m u n i t i e s a r e compared

w i t h t h e a l g a l f o u l i n g on n a v i g a t i o n buoys f r o m i n s h o r e waters i n t h e I n n e r Moray F i r t h i n n o r t h - e a s t

Scotland.

13.2 METHODS 13.2.1.

Data c o l l e c t i o n from o f f s h o r e s t r u c t u r e s

The l o c a t i o n s o f i n s t a l l a t i o n s from which d a t a on a l g a l f o u l i n g h a v e b e e n o b t a i n e d a r e shown i n F i g u r e 1.

Marine were c o l l e c t e d by commercial d i v e r s who f o l l o w e d a s a m p l i n g programme d e s i g n e d i n c o n s u l t a t i o n w i t h t h e operator. The d i v e r s l o c a t e d a number o f p r e - s e l e c t e d s a m p l i n g p o i n t s on t h e s t r u c t u r e and p e r f o r m e d t h e f o l l o w i n g sequence of tasks:(1) t h e attachment of a site i d e n t i f i c a t i o n l a b e l ; ( 2 ) t h e attachment of a q u a d r a t or scale m a r k e r a t e a c h l o c a t i o n ; ( 3 ) t h e t a k i n g o f s t a n d - o f f and c l o s e - u p c o l o u r p h o t o g r a p h s o f t h e s i t e s ; ( 4 ) t h e measurement o f t h e c i r c u m f e r e n c e o f s p e c i f i e d members u s i n g a s p e c i a l l y designed t a p e measure; ( 5 ) t h e c o l l e c t i o n of t h e marine growth w i t h i n t h e q u a d r a t by s c r a p i n g i t i n t o a l a b e l l e d p l a s t i c sampling jar. I n d u s t r i a l m e t h y l a t e d s p i r i t (IMS) was added a s a p r e s e r v a t i v e t o t h e s a m p l e s on r e t u r n t o t h e s u r f a c e .

growth

13.2.2.

samples

Data a n a l y s i s

The r a t i o n a l e g o v e r n i n g t h e m e t h o d s u s e d b y AUMS t o a n a l y s e marine growth d a t a from o f f s h o r e s t r u c t u r e s h a s been described

and

discussed

by

Picken

(1984).

The

information

r e q u i r e d by e n g i n e e r s and t h e s o u r c e o f t h i s i n f o r m a t i o n from t h e m a r i n e g r o w t h i n s p e c t i o n d a t a a r e summarised i n T a b l e 1.

182

TABLE 13.1. Sources o f d a t a f o r m a r i n e g r o w t h a n a l y s i s Information required 1. I d e n t i t y o f s p e c i e s present 2.

% c o v e r o f t h e major

fouling types 3 . Average s i z e ( l e n g t h o r height) of each species or fouling type

Scource of d a t a Samples c o l l e c t e d by d i v e r s A n a l y s i s of t h e c l o s e - u p photog r a ph s E s t i m a t i o n from photographs w h i c h i n c l u d e a q u a d r a t or scale E s t i m a t i o n from p h o t o g r a p h s which i n c l u d e a s c a l e Range o f s i z e p o s s i b l e o b t a i n e d from t h e l i t e r a t u r e

Upper part of buoy

Lower part of buoy

Anchor chain

F i g . 13.2.

The s t r u c t u r e of a n i n s h o r e buoy.

183

13.2.3.

Fouling communities on i n s h o r e buoys

D u r i n g May 1 9 8 4 AUMS was a b l e t o e x a m i n e t h e f o u l i n g on s i x n a v i g a t i o n b u o y s , s i t u a t e d i n t h e I n n e r Moray F i r t h i n t h e a p p r o a c h c h a n n e l t o t h e C r o m a r t y F i r t h ( s e e F i g u r e l . ) , when they were taken aboard a lighthouse s h i p f o r annual maintenance work.

The s t r u c t u r e and d i m e n s i o n s o f t h e s e b u o y s

a r e shown i n F i g u r e 2 . When e a c h buoy was l i f t e d c l e a r of t h e water o n t o t h e v e s s e l p h o t o g r a p h s were t a k e n o f t h e f o u l i n g a n d s a m p l e s of t h e f i l a m e n t o u s and m i c r o - a l g a e were t a k e n f o r laboratory identification. During t h i s a n n u a l maintenance t h e f o u l i n g on t h e u p p e r and lower p a r t s o f t h e b u o y s w a s removed u s i n g s c r a p e r s , t h e u p p e r p a r t s c l e a n e d w i t h c l o t h s and c o a t e d w i t h an a n t i f o u l i n g p a i n t . The lower p a r t was n o t a n t i f o u l e d and t h e f o u l i n g on t h e c h a i n was n o t removed.

13.3.

RESULTS An e x a m p l e of t y p i c a l r e s u l t s f r o m t h e a n a l y s i s o f

m a r i n e g r o w t h o n a s t r u c t u r e i n t h e c e n t r a l N o r t h Sea s t a n d i n g in

130m o f

water

i s shown

in

Figure

3.

This

type

of

p r e s e n t a t i o n h a s b e e n a d o p t e d t o summarise i n f o r m a t i o n on m a r i n e g r o w t h c o m p o s i t i o n and t h i c k n e s s f o r e n g i n e e r i n g identity

of

is

purposes.

The

particularly

important i n t h i s context b u t division i n t o t h e

individual

m a j o r f o u l i n g g r o u p s is u s e f u l .

species

I n t h e example i l l u s t r a t e d ,

a l g a e were f o u n d i n t h e d e p t h r a n g e L.A.T.

t o -15m where t h e

c o m p e t i t o r s f o r s p a c e were m u s s e l s and h y d r o i d s . a n d h y d r o i d s were

not

f r e q u e n t l y found overgrowing

Both a l g a e t h e mussels.

M u s s e l b e d s formed t h e d o m i n a n t h a r d g r o w t h s from L.A.T.

to

-45m b u t a t g r e a t e r d e p t h s t h e d o m i n a n t h a r d f o u l i n g c o n s i s t e d

of s o l i t a r y tubeworms.

H y d r o i d s were p r e s e n t t h r o u g h o u t t h e

d e p t h r a n g e w i t h o t h e r s o f t g r o w t h s , i n c l u d i n g s o f t c o r a l s and anemones, p r e s e n t f r o m -15m t o a d e p t h o f a p p r o x i m a t e l y 100m. T h e d e p t h r a n g e o f a l g a e on o f f s h o r e s t r u c t u r e s i n t h e N o r t h S e a i s d e t e r m i n e d by t h e c l a r i t y o f geometry of the structure.

t h e water and t h e

T h e r e a r e many r e g i o n s i n t h e

p h o t i c z o n e o n s t e e l p l a t f o r m s which a r e s o s h a d e d t h a t a l g a e

a r e a b s e n t ; on s t e e l s t r u c t u r e s a l g a e a r e p r e d o m i n a n t l y f o u n d o n t h e o u t e r f a c e s o f l e g s a n d on t h e u p p e r s u r f a c e s o f h o r i z o n t a l a n d v e r t i c a l d i a g o n a l members. In the shallow

184

t u r b i d waters of t h e s o u t h e r n N o r t h Sea a l g a e a r e t h e r e f o r e c o n f i n e d t o a r e a s s h a l l o w e r t h a n -5m w h e r e a s i n t h e c e n t r a l and n o r t h e r n s e c t o r s p l a n t s h a v e b e e n f o u n d a s d e e p a s -40m.

0

n

E W

50

5

Q

a,

n

100

Seabed

I

0

I

I

I

I

I

10

20

30

40

50

60

Thickness (mm) Mussels

m Fig.

13.3.

Solitary Tubeworms

a Seaweeds Hydroids a Soft Corals: ...... Hydroids

Anemones on tops of members Hydroids

rq

Depth z o n a t i o n and a v e r a g e t h i c k n e s s of t h e major c o m p o n e n t s of t h e f o u l i n g community on a s t e e l s t r u c t u r e 5 y e a r s a f t e r placement i n t h e c e n t r a l N o r t h Sea.

185

TABLE 13.2.

S p e c i e s l i s t o f a l g a e r e c o r d e d on o f f s h o r e i n s t a l l a t i o n s i n t h e North Sea. Taxonomic n o m e n c l a t u r e f o l l o w s t h a t of P a r k e and Dixon ( 1 9 7 6 ) . _Chlorophyceae

I

Rhodophyceae

.

Znteromorpha s p p ( i n c l u d e s E. i n t e s t i n a l i s i (SrCrN) E. l i n z a , E. t o r t a and Enteromorpha s p . 1 lactuca and sp. 'haetomorpha s p . 'ladophora s p . Spongomorpha s p .

Xanthophyceae ilaucheria s p . Phaeophyceae

&laria esculenta Laminaria d i g it a t a Laminar i a hype r b o r e a ~

Erythrotrichia carnea (C Bangia a t r o p u p u r e a (S Porphyra sp. (C,N Audou i n e l l a concr e s c e n s (S Audouinella sp. (SICIN Gelidium l a t i f o l i u m (.~ N and G e l i d i u m SD. Bonnemaisonia h a m i f e r a "Trailliella" phase (N Palmaria almata (C,N Lome n t a r i b 1 l o s a ( c ,N Lomentaria o r c a d e n s i s ( C , N Antithamnion (C.N f loccosum Ccramium rubrum (C;N Plumaria elegans (N Delessaria s a n g u i n e a (N Hypoglossum woodwardi i ( N Polysiphonia brodiaei (C,N P o l v s iDhon i a macrocarpa (C Polysiphonia nigrescens P o l y s i ph on i a ureolata (SIC Rhodomela c o n f e r v o i d e s - L

S = Southern North Sea

:= C e n t r a l N o r t h S e a N =

N o r t h e r n North S e a

Data f r o m G o l d i e , 1 9 8 1 ; Hardy, 1981, 1983; 1 9 8 4 ; and u n p u b l i s h e d s o u r c e s .

Forteath et al.,

1982;

A s p e c i e s list of

t h e a l g a e which h a v e b e e n i d e n t i f i e d

from o f f s h o r e s i t u a t i o n s i n t h e N o r t h S e a is g i v e n i n T a b l e 2 . Few

recognisable

trends

in

algal

distribution

have

been

o b s e r v e d b e t w e e n d i f f e r e n t s t r u c t u r e s 'or r e g i o n s of t h e N o r t h Sea. Kelps, however, are n o t widespread i n t h e s o u t h e r n North Sea and a l t h o u g h t h e y o c c u r on many p l a t f o r m s i n t h e o t h e r t w o

s e c t o r s t h e y a r e a s e r i o u s problem on o n l y t w o o f t h e i n st a l l a t ions. The u p p e r r e g i o n s of some s t r u c t u r e s , p a r t i c u l a r l y those i n t h e southern sector, can be t o t a l l y d o m i n a t e d by t h e m u s s e l M y t i l u s e d u l i s , b u t a l g a e may o v e r g r o w such a c o v e r i f l i g h t l e v e l s are s u f f i c i e n t . A common f o u l i n g p a t t e r n was found on a l l s i x n a v i g a t i o n b u o y s i n t h e Moray F i r t h . The u p p e r p a r t was f o u l e d from t h e w a t e r l i n e r e g i o n t o i t s j u n c t i o n w i t h t h e lower p a r t - a d e p t h o f 0.8m. T h r e e z o n e s were d i s t i n g u i s h e d on t h i s u p p e r p a r t : a s p l a s h z o n e a p p r o x i m a t e l y 15cm d e e p a b o v e t h e w a t e r l i n e , a l a r g e mid z o n e and a l o w z o n e c o v e r i n g t h e b a s a l 1 0 t o 15cm o f The a l g a e i n t h e s p l a s h z o n e were t h e u p p e r p a r t of t h e buoy. Ulothrix sp. , Enteromorpha sp. , Chaetomorpha linum, u n i d e n t i f i e d s m a l l s t a g e s of g r e e n a l g a e , a n d b l u e - g r e e n algae. The mid zone was d o m i n a t e d by E c t o c a r p u s s p . , w i t h S c y t o s i p h o n l o m e n t a r i a , P o l y s i p h o n i a f i b r a t a and sp. a l s o present. On some o f t h e b u o y s t h e c o v e r of E c t o c a r p u s extended above t h e w a t e r l i n e . Laminarians, principally L a m i n a r i a s a c c h a r i n a , were p r e s e n t i n t h e low z o n e , w i t h some Ectocarpus sp. The m u s s e l , M y t i l u s e d u l i s , d o m i n a t e d t h e lower p a r t o f t h e buoy w i t h some L a m i n a r i a d i g i t a t a a n d , t o a lesser e x t e n t , L . s a c c h a r i n a a l s o p r e s e n t .

13.4 DISCUSSION The f o u l i n g on o f f s h o r e i n s t a l l a t i o n s i n t h e N o r t h S e a has

necessitated

a

regular

monitoring

of

the

species

c o m p o s i t i o n , e x t e n t o f c o v e r and m a r i n e g r o w t h t h i c k n e s s .

The

are

for

thickness

measurements

particularly

important

e s t i m a t i n g t h e e f f e c t s o f m a r i n e g r o w t h on hydrodynamic loading. A l t h o u g h t h e s a m p l i n g methods c a r r i e d o u t o f f s h o r e f a l l s h o r t o f a n i d e a l b i o l o g i c a l programme, t h e y have e n a b l e d data

on

providing

t h e s e o f f s h o r e communities operators with

information

t o be obtained while to

answer

engineering

187

problems. Algal

f o u l i n g can a f f e c t

number o f ways:and

impairs

the

offshore

installations

in a

(1) it o b s c u r e s t h e u n d e r l y i n g s u b s t r a t u m inspection

of

a structure.

d e s t r u c t i v e t e s t i n g r e q u i r e s t h e pre-removal

i t i n c r e a s e s dynamic and hydrodynamic

Some

of

non-

fouling;

loading;

(2)

( 3 ) it can

p r o v i d e environments f o r b a c t e r i a l a c t i v i t y (see, f o r example, T e r r y and Edyvean,

1986).

Sulphate reducing b a c t e r i a

(SRB)

a r e a c t i v e i n a n a e r o b i c p o c k e t s u n d e r m a c r o f o u l i n g and t h e y can enhance c o r r o s i o n o f s t r u c t u r a l steels. b a c t e r i a , which c a n promote d i s s o l u t i o n

Sulphur oxidising and s p a l l i n g o f

c o n c r e t e , can be a c t i v e i n a e r o b i c pockets under macrofouling; (4)

i t c a n a f f e c t c o r r o s i o n and c o r r o s i o n p r o t e c t i o n o f f s h o r e

.

( s e e , f o r example , T e r r y and Edyvean , 1986 ) The m o s t s i g n i f i c a n t e f f e c t o f a l g a l f o u l i n g i s i t s c o n t r i b u t i o n t o hydrodynamic l o a d i n g , and i t now a p p e a r s t h a t t h e c o n t r i b u t i o n of s o f t g r o w t h t o hydrodynamic l o a d i n g h a s been shown

underestimated. that

the

Recent

effect

laboratory

of

kelps

i n v e s t i g a t i o n s have

on

drag

and

inertia

c o e f f i c i e n t s may b e n e a r l y t w i c e t h e g e n e r a l l y assumed v a l u e and t h e r e f o r e g r e a t e r t h a n t h o s e f o r h a r d g r o w t h s (Wolfram and Theophanatos, 1985). T h e r e h a s b e e n much d e b a t e a b o u t which m e a s u r e o f s i z e , p a r t i c u l a r l y f o r s o f t frond growths, is a p p r o p r i a t e f o r use i n hydrodynamic l o a d i n g c a l c u l a t i o n s . t h i c k n e s s of h a r d g r o w t h s c a n b e determined

Although t h e average reasonably accurately

from p h o t o g r a p h i c a n a l y s i s , c i r c u m f e r e n t i a l

tape

m e a s u r e m e n t s o r p r o b e r e a d i n g s , s u c h m e a s u r e m e n t s may n o t accurately

reflect

the

roughness

factor

(Wolfram

and

T h e o p h a n a t o s , 1 9 8 5 ) and measurement p r o c e d u r e s may have t o b e modified

in

the

future.

It

i s e v e n more d i f f i c u l t

to

i s a n a p p r o p r i a t e t h i c k n e s s measurement f o r , s o f t c o m p r e s s i b l e g r o w t h s s u c h a s a l g a e . To d a t e , t h e maximum l e n g t h o f t h e a l g a l f r o n d s a s d e t e r m i n e d by p h o t o g r a p h i c a n a l y s i s h a s been used. This g i v e s the "worst p o s s i b l e case"

d e t e r m i n e what

f o r e n g i n e e r s t o c o n s i d e r i n t h e i r c a l c u l a t i o n s b u t t h e u s e of t h i s measurement may a l s o h a v e t o b e r e v i e w e d i n t h e l i g h t of any f u r t h e r e x p e r i m e n t a l d a t a on t h e e f f e c t s of s o f t g r o w t h on loading. Collating data

from a

number

of

sources,

w e have

188

recorded a total of

35 s p e c i e s and/or

offshore s t r u c t u r e s over

the p e r i o d

algae on

genera of

1 9 7 7 t o 1 9 8 4 ( T a b l e 2).

T h i s a p p e a r s a p p e a r s l o w when c o m p a r e d w i t h v a l u e s o f 1 2 0

major g r o u p s i n p e r m a n e n t i n t e r t i d a l i n the north-east of

a l g a l species and/or

monitoring q u a d r a t s on rocky shores Scotland

i n p r e s s ) a n d 55 a l g a l f o u l i n g

( T e r r y and S e l l ,

s p e c i e s on f l o a t i n g s t r u c t u r e s i n Sullom Voe ( T i t t l e y and Fletcher,

1984).

A l t h o u g h t h i s l i s t is p r o b a b l y a n u n d e r e s t i m a t e o f t h e

t o t a l s p e c i e s p r e s e n t , i t is p o s s i b l e t h a t o f f s h o r e a l g a l are

communities The

in

combination of obtaining depth

less d i v e r s e

fact

factors:-

samples

those

nearshore.

(1) t h e d i f f i c u l t i e s encountered i n

from o f f s h o r e

t o -15m.

r a n g e L.A.T.

than

t h e o f f s h o r e f l o r a may b e d u e t o a

relative paucity of

and

in

particular

from

the

Wave a c t i o n i s most p r o n o u n c e d

h e r e a n d w o r k i n g c o n d i t i o n s a r e d i f f i c u l t ; d i v e r s may loose o r o v e r l o o k s m a l l s p e c i e s ; e v e n when d i v e r s c a n w o r k

most

region

intertidal

and

splash

zone

species

in this will

be

excluded a s s u r v e y s c o n c e n t r a t e on s u b l i t t o r a l r e g i o n s below ( 2 ) t h e p o o r q u a l i t y o f many a l g a e w h i c h a r e r e t u r n e d

L.A.T.;

I t i s rare t o o b t a i n a n e n t i r e p l a n t i n a

from offshore.

r e a s o n a b l e c o n d i t i o n and t h e u s e o f

IMS a s a p r e s e r v a t i v e

f u r t h e r h i n d e r s i d e n t i f i c a t i o n to s p e c i e s . specimens,

I n t h e absence of

i d e n t i f i c a t i o n f r o m p h o t o g r a p h s is u s u a l l y o n l y t o

g r o u p or g e n u s l e v e l ; ( 3 ) t h e d i f f i c u l t i e s which a l g a e have i n r e a c h i n g o f f s h o r e sites.

It

i s n o t c l e a r by w h i c h method or

m e t h o d s a l g a e are a b l e t o s e e d p a r t i c u l a r p l a t f o r m s .

Spores

may a r r i v e a t a s i t e t h r o u g h n a t u r a l d i s p e r d a l i n c u r r e n t s , t h e y may a t t a c h t o t h e i n s t a l l a t i o n i f submerged during

inshore

tow-out

during

it h a s been p a r t i a l l y

construction,

they

may

colonise

o r t h e y may e v e n r e a c h t h e o f f s h o r e s i t e o n

ships' hulls. C o m p e t i t i o n f o r s p a c e on o f f s h o r e which

are n o t

cleaned

regularly

often

fixed structures

results

in

the

algae

overgrowing hard organisms, u s u a l l y mussels, as t h e r e s u l t s i n F i g u r e 3 f r o m t h e c e n t r a l N o r t h S e a i n s t a l l a t i o n show. algal

communities

are

particularly species of sp.

and

structures in

sp. the

often

have been North

dominated

Polysiphonia. Sea,

recorded records

by

Although frequently

red

Such algae,

Enteromorpha on o f f s h o r e

f o r other green

algae

189

h a v e b e e n l e s s common.

This is probably because

i s r a r e l y sampled o n o f f s h o r e s t r u c t u r e s ;

s p l a s h zone

h i g h e s t s a m p l e s a r e o b t a i n e d f r o m L.A.T. d i f f i c u l t i e s o f w o r k i n g a t Om, may

be

t h e upper

lacking.

s a m p l e s from e v e n t h i s d e p t h

splash

A

the

and, because of t h e

zone

community

dominated

filamentous green a l g a e probably e x i s t s o f f s h o r e b u t ,

by

unlike

t h e n a v i g a t i o n buoys, it is n e v e r a d e q u a t e l y sampled. Given t h e d i f f i c u l t i e s i n sampling t h e a l g a l dominated o f f s h o r e s t r u c t u r e s i t is perhaps

r e g i o n s of

not surprising

t h a t few g e n e r a l i s a t i o n s c a n b e made a b o u t a l g a l d i s t r i b u t i o n , b o t h v e r t i c a l y on i n d i v i d u a l p l a t f o r m s o r between d i f f e r e n t D i f f e r e n t f a c e s of a s t r u c t u r e

s t r u c t u r e s i n t h e North Sea.

may b e s a m p l e d i n s u c c e s s i v e y e a r s and t h e s e f a c e s may r e c e i v e different

patterns

of

wave

action;

samples

may

also

be

I t is

o b t a i n e d f r o m d i f f e r e n t d e p t h s on d i f f e r e n t o c c a s i o n s .

r a r e t o a d e q u a t e l y s a m p l e t h e e n t i r e a l g a l - c o v e r e d r e g i o n on I t i s s t i l l n o t c l e a r , f o r e x a m p l e , how any one v i s i t . p r e c i s e a l g a l z o n a t i o n is o f f s h o r e . Although photographs of entire

structures

frequently

show a n

Enteromorpha-dominated

s p l a s h zone,

t h i s g e n u s h a s a l s o been f o u n d w e l l below t h e

L.A.T.

U s u a l l y s a m p l e s a r e t a k e n f r o m l e v e l s a t which

mark.

t h e r e i s a h o r i z o n t a l member r a t h e r t h a n b e t w e e n e l e v a t i o n s . Consequently,

a

disjointed

sampling

procedure

has

to

be

a d o p t e d which r e s u l t s i n d i f f e r e n t d e p t h s b e i n g sampled on d i f f e r e n t s t r u c t u r e s and n o c o m p l e t e p i c t u r e a v a i l a b l e f o r any one.

Most of t h e a l g a e r e c o r d e d i n T a b l e 2 ,

t h e r e f o r e , have

b e e n found a t a v a r i e t y of d e p t h s s i n c e t h e r e is c o n s i d e r a b l e variation i n the depth of the photic d i f f e r e n t r e g i o n s o f t h e North Sea.

zone

between

the

R e c o r d s o b t a i n e d from f l o a t i n g s t r u c t u r e s e l s e w h e r e i n the

British

Isles,

e.g.

the

Firth

of

Clyde

( G r i e v e and

R o b e t s o n , 1 8 6 4 ) , t h e I s l e o f Man ( L o d g e , 1 9 4 9 ) , t h e S o l e n t r e g i o n ( F l e t c h e r , 1 9 8 0 ) and S u l l o m Voe ( T i t t l e y and F l e t c h e r , 1 9 8 4 ) , c o n t a i n e d more a l g a l s p e c i e s t h a n were f o u n d on t h e s i x Moray

Firth

n a v i g a t i o n buoys.

The Moray

Firth

communities

were, h o w e v e r , o n l y o n e y e a r o l d a n d were g r o w i n g o n a n a n t i - f o u l e d s u r f a c e which would b e e x p e c t e d t o r e s t r i c t t h e s p e c i e s c o l o n i s i n g t h e buoys.

A l t h o u g h t h e a l g a l f o u l i n g on

t h e e i g h t b u o y s i n t h e C l y d e ( G r i e v e and R o b e r t s o n , 1 8 6 4 ) was

a l s o o n l y o n e y e a r o l d , t h e g r e a t e r number of s p e c i e s r e c o r d e d

190

i n t h e C l y d e compared w i t h t h e Moray F i r t h b u o y s i s p r o b a b l y

.

due t o t h e a n t i - f o u l i n g I n p a r t i c u l a r , more Rhodophyceae were o b s e r v e d i n t h e C l y d e , e s p e c i a l l y some l u x u r i a n t g r o w t h s of

Polysiphonia

most widespread North

Sea.

brodiaei.

T h i s s p e c i e s h a s been one of

a l g a l f o u l e r s of

Like

offshore structures i n the

t h e s t r u c t u r e s i n S u l l o m Voe

F i r t h Buoys were d o m i n a t e d by Phaeophyceae. extensive

growths

of

the

early

s a c c h a r i n a were f o u n d on t h e buoys. not

( T i t t l e y and

1 9 8 4 ) , t h e a l g a l f o u l i n g c o m m u n i t i e s on t h e Moray

Fletcher,

is

the

generally

found

on

kelp

In particular

coloniser

,

Laminaria

This s p e c i e s of Laminaria

offshore

installations

where

L . d i g i t a t a and A l a r i a e s c u l e n t a a r e t h e m o s t f r e q u e n t l y found A l l t h r e e s p e c i e s were found o n a t h r e e y e a r o l d

laminarians.

j e t t y i n t h e Cromarty F i r t h (Picken, i n p r e s s ) . p o s s i b l e t h a t t h e g r e a t e r e x p o s u r e o f f s h o r e may l i m i t

It

is

L. s a c c h a r i n a H o r i z o n t a l b a n d i n g o f a l g a e on f l o a t i n g s t r u c t u r e s h a s been r e p o r t e d p r e v i o u s l y ( e . g .

M i l n e , 1 9 4 0 ; F l e t c h e r , 1980 and

T i t t l e y and F l e t c h e r , 1 9 8 4 ) . Six d i f f e r e n t a l g a l zones e x t e n d i n g upwards from t h e w a t e r l i n e were r e c o g n i s e d on structures

in

Langstone

and

Portsmouth

harbours

(Fletcher,

Only t w o s u c h z o n e s c o u l d b e f o u n d , h o w e v e r , from t h e

1980).

c o r r e s p o n d i n g r e g i o n o n t h e Moray F i r t h b u o y s .

There w a s a

n a r r o w E c t o c a r p u s d o m i n a t e d band a t t h e w a t e r l i n e and above this

a

filamentous

green

algal

band

of

maximum

depth

a p p r o x i m a t e l y 15cm. B o t h F l e t c h e r ( 1 9 8 4 ) a n d M i l n e ( 1 9 4 0 ) r e p o r t e d t h e p r e s e n c e o f r e d a l g a e i n t h e lowest z o n e i . e . a t the waterline,

and t h e a b s e n c e t h i s zone on t h e Moray F i r t h

buoys is probably a t t r i b u t a b l e t o a combination of t h e s h o r t period of

immersion and t h e t o x i c i t y o f

the anti-fouling

paint. 13.5.

ACKNOWLEDGEMENTS One o f u s ( L . A . T e r r y )

would l i k e t o t h a n k t h e Royal

S o c i e t y f o r a t r a v e l g r a n t t o a t t e n d t h e 3 6 t h A n n u a l AIBS meeting

i n Gainesville.

Thanks are d u e t o t h e C a p t a i n and

crew o f MV P h a r o s f o r t h e i r h o s p i t a l i t y d u r i n g t h e i n s p e c t i o n o f t h e n a v i g a t i o n b u o y s i n t h e Cromarty F i r t h and t o N o r t h e r n The L i g h t Vessels f o r a r r a n g i n g p a r t i c i p a t i o n i n t h e c r u i s e . d a t a f r o m t h e b u o y s was c o l l e c t e d by M r . A.R. Milne.

191 1 3 . 6 REFERENCES F l e t c h e r , R.L., 1980. The a l g a l c o m m u n i t i e s o n f l o a t i n g s t r u c t u r e s i n Portsmouth and Langstone Harbours (South coast of England). I n J . H . P r i c e , D.E.G. I r v i n e a n d W.F. Farnham (Editors), The Shore Environment Volume 2: Ecosystems, Academic P r e s s , London a n d N e w Y o r k , pp 8 43-8 7 4. F o r t e a t h , G.N.R., P i c k e n , G.B., R a l p h , R. a n d W i l l i a m s , J . 1982. Marine growth s t u d i e s on t h e North Sea o i l p l a t f o r m M o n t r o s e A l p h a . M a r i n e E c o l o g y P r o g r e s s S e r i e s , 8 : 61-68. F o r t e a t h , G.N.R., P i c k e n , G.B. a n d R a l p h , R. 1 9 8 3 . I n t e r a c t i o n a n d c o m p e t i t i o n f o r s p a c e between f o u l i n g o r g a n i s m s on t h e Beatrice o i l p l a t f o r m i n t h e Moray F i r t h , N o r t h S e a . I n t e r n a t i o n a l B i o d e t e r i o r a t i o n B u l l e t i n , 1 9 : 45-52. F o r t e a t h , G.N.R., P i c k e n , G.B. a n d R a l p h , R. 1 9 8 4 . P a t t e r n s o f m a c r o f o u l i n g o n steel p l a t f o r m s i n t h e c e n t r a l and n o r t h e r n North Sea. I n J.R.Lewis and A.D. Mercer ( E d i t o r s ) , C o r r o s i o n and Marine Growth on O f f s h o r e S t r u c t u r e s . E l l i s Horwood, C h i c h e s t e r , p p . 1 0 - 2 2 . G o l d i e , B.P.F. 1981. Assessment o f marine f o u l i n g on g a s p l a t f o r m "WE". I n : M a r i n e F o u l i n g o f O f f s h o r e P l a t f o r m s V o l 11, S o c i e t y f o r U n d e r w a t e r T e c h n o l o g y , L o n d o n , 19-20 May. G o o d m a n , K.S. a n d R a l p h , R. 1 9 8 1 . A n i m a l f o u l i n g o n t h e Forties platforms. In: Marine Fouling on Offshore Vol I. S o c i e t y f o r Underwater Technology, Structures, London. G r i e v e , J . a n d R o b e r t s o n , D. 1 8 6 4 . On t h e d i s t r i b u t i o n of m a r i n e a l g a e o n t h e C.L.T. Buoys i n t h e C l y d e . Proceedings o f t h e P h i l o s o p h i c a l S o c i e t y o f G l a s g o w , 5: 121-126. H a r d y , F.G. 1981. Fouling on North Sea p l a t f o r m s . B o t a n i c a M a r i n a , 24: 173-176. HMSO 1 9 7 7 . O f f s h o r e I n s t a l l a t i o n s : G u i d a n c e o n D e s i g n a n d C o n s t r u c t i o n . D e p a r t m e n t o f E n e r g y D o c u m e n t , HMSO. L o d g e , S.M. 1 9 4 9 . Notes o n t h e f l o r a o f P o r t E r i n b u o y s . R e p o r t o f t h e Marine B i o l o g i c a l S t a t i o n P o r t E r i n , 61: 32-33. M i l n e , A. 1 9 4 0 . T h e E c o l o g y o f t h e Tamar E s t u a r y I V . The d i s t r i b u t i o n of t h e f a u n a and f l o r a on buoys. Journal of 2 4 : 69-87. t h e Marine B i o l o g i c a l A s s o c i a t i o n U.K., P i c k e n , G.B. 1 9 8 4 . The o p e r a t i o n a l a s s e s s m e n t o f marine g r o w t h o n o f f s h o r e s t r u c t u r e s . I n : P r o c e e d i n g s o f t h e 5 t h IRM C o n f e r e n c e , 5 - 6 t h November 1 9 8 4 , A b e r d e e n . P i c k e n , G.B. i n press. Moray F i r t h m a r i n e f o u l i n g c o m m u n i t i e s . Paper p r e s e n t e d a t "The M a r i n e E n v i r o n m e n t o f t h e Moray F i r t h " . Symposium h e l d i n A b e r d e e n , 2 6 - 2 7 t h M a r c h , 1 9 8 4 a n d t o b e p u b l i s h e d i n t h e P r o c e e d i n g s o f t h e Royal S o c i e t y o f Edinburgh. P i c k e n . G.B.. F o r t e a t h , G.N.R., R a l p h , R. a n d S w a i n , G. 1 9 8 3 . Fouiing below lOOm o n t h e European C o n t i n e n t a l S h e l f . I n : Progress i n Underwater Technology, P r o c e e d i n g s of the Subsea Challenge Conference, Amsterdam. Society f o r U n d e r w a t e r T e c h n o l o g y , London. P a p e r C14. T e r r y , L.A. and Edyvean, R.G.J. (1986). Recent i n v e s t i g a t ons i n t o t h e e f f e c t s o f a l g a e o n c o r r o s i o n . I n : L.V. E v a n s a n d K.D. Hoagland (Editors), Algal Biofouling. Elsev e r r Amsterdam. C h a p t e r 1 5 .

192 T e r r y , L.A. a n d S e l l , D. i n p r e s s ) . Rocky S h o r e s i n t h e Moray F i r t h . P a p e r p r e s e n t e d a t "The M a r i n e E n v i r o n m e n t o f t h e Moray F i r t h " Symposium h e l d o n 2 7 - 2 8 t h M a r c h 1 9 8 5 , A b e r d e e n a n d t o b e p u b l i s h e d i n P r o c e e d i n g s o f t h e Royal S o c i e t y o f Ed i n b u r g h T i t t l e y , I . a n d F l e t c h e r , R.L. 1 9 8 4 . S u l l o m V o e O i l T e r m i n a l , Shetland: b e n t h i c marine a l g a l f o u l i n g communities. In: Proceedings of 6th I n t e r n a t i o n a l Congress on Marine C o r r o s i o n a n d F o u l i n g , M a r i n e B i o l o g y , A t h e n s , p p . 65-79. W o l f r a m , J. a n d T h e o p h a n a t o s , A. 1 9 8 5 . The e f f e c t s o f m a r i n e some fouling on the f l u i d loading of cylinders: e x p e r i m e n t a l r e s u l t s . I n : P r o c e e d i n g s o f t h e 1 7 t h Annual OTC, H o u s t o n , T e x a s , P a p e r 4954.

.

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Chapter 14

IMPORTANCE OF VARIATION I N ALGAL IMMIGRATION AND GROWTH RATES ESTIMATED BY MODELLING BENTHIC ALGAL COLONIZATION R. JAN STEVENSON Dept. B i o l o g y , Univ. L o u i s v i l l e , L o u i s v i l l e , Kentucky

40292 (USA)

ABSTRACT

A s i m p l e mathematical model o f i m m i g r a t i o n and growth was used t o s t u d y diatom accumulation, s p e c i e s c o m p o s i t i o n , and d i v e r s i t y p a t t e r n s d u r i n g c o l o n i z a t i o n on c l a y t i l e s . Accumulation p a t t e r n s o f dominant species and t h e e n t i r e assemblage were a c c u r a t e l y p r e d i c t e d by t h e model when i m m i g r a t i o n parameters were i t e r a t i v e l y v a r i e d t o t h e b e s t f i t . The species t h a t were f a s t i m m i g r a t o r s d u r i n g e a r l y stages o f c o l o n i z a t i o n were d i f f e r e n t t h a n those species w i t h h i g h g r o w t h r a t e s . However, m o d e l l e d e s t i m a t e s o f maximum i m m i g r a t i o n r a t e s d u r i n g c o l o n i z a t i o n i n d i c a t e d t h a t t h e f a s t e s t reproducers a l s o had t h e f a s t e s t i m m i g r a t i o n r a t e s d u r i n g l a t e r stages o f c o l o n i z a t i o n . F i e l d procedures f o r e s t i m a t i n g i m m i g r a t i o n r a t e s were p r o b a b l y n o t as a c c u r a t e as e s t i m a t e s made w i t h t h e model. P a t t e r n s o f s p e c i e s c o m p o s i t i o n and d i v e r s i t y were shown t o be s t r o n g l y i n f l u e n c e d by t h e balance c r e a t e d when d i f f e r e n t s p e c i e s were f a s t i m m i g r a t o r s and f a s t r e p r o d u c e r s . 14.1

INTRODUCTION

I n t e r e s t i n t h e m o d e l l i n g approach t o s t u d y i n g b e n t h i c a l g a l c o l o n i z a t i o n has been s t i m u l a t e d by a need t o q u a n t i t a t i v e l y e s t i m a t e a l g a l ' i m m i g r a t i o n and reproduction r a t e s from short-term,

temporal a c c u m u l a t i o n p a t t e r n s .

Since

I v l e v ' s (1933) s t u d y o f p e r i p h y t o n a c c u m u l a t i o n p a t t e r n s on s l i d e s i n d i f f e r e n t c u r r e n t v e l o c i t i e s , t h e i n t e r p r e t a t i o n o f a c c u m u l a t i o n p a t t e r n s has r e c e n t l y been used t o i n v e s t i g a t e a l g a l c o l o n i z a t i o n i n r e s e r v o i r s (Hoagland, 1983), i n an e s t u a r y (Hudon and Bourget, 1981), i n t e m p e r a t e - c l i m a t e streams (eg. K o r t e and B l i n n , 1983; Stevenson, 1984), and i n b o r e a l streams ( H a m i l t o n and D u t h i e , 1984).

I n many o f t h e s e s t u d i e s , t h e i n t e r p r e t a t i o n o f how a l g a l

i m m i g r a t i o n and r e p r o d u c t i o n r a t e s v a r i e d i n d i f f e r e n t environments and c o n t r o l l e d a c c u m u l a t i o n p a t t e r n s was i m p o r t a n t f o r e x p l a i n i n g i n t e r a c t i o n s between t h e environment and a l g a l assemblages. I n t e r p r e t a t i o n o f a l g a l assemblage dynamics has o f t e n been d e r i v e d from e s t i m a t e s o f a l g a l s t a n d i n g c r o p s on s u b s t r a t e s f r o m o n l y one date. D i f f e r e n c e s i n a c c u m u l a t i o n among h a b i t a t s a r e o f t e n assumed t o be t h e r e s u l t o f d i f f e r e n c e s i n growth r a t e s ( r e p r o d u c t i o n

-

death).

However, growth o f

algae on s u b s t r a t e s i s n o t t h e o n l y i m p o r t a n t mechanism c o n t r o l l i n g accumulation.

V a r i a t i o n i n i m m i g r a t i o n r a t e s w i t h c u r r e n t v e l o c i t y has been

shown t o be a p r o b a b l e cause o f d i f f e r e n c e s i n a l g a l a c c u m u l a t i o n around

194

s u b s t r a t e s i n streams (Stevenson, 1984).

G r a z i n g can a l s o a f f e c t a l g a l

a c c u m u l a t i o n (eg. Sumner and M c I n t i r e , 1982).

Thus, a v a r i e t y o f mechanisms

d e t e r m i n i n g a l g a l a c c u m u l a t i o n may v a r y among h a b i t a t s and i n t e r a c t t o a f f e c t accumulation. I n a d d i t i o n t o v a r i a t i o n s among h a b i t a t s , e v i d e n c e a l s o suggests t h a t a l g a l i m m i g r a t i o n and r e p r o d u c t i o n r a t e s a r e somewhat density-dependent and v a r y during colonization.

F i e l d estimates o f a l g a l immigration r a t e s i n d i c a t e t h a t

o r g a n i c s b e i n g adsorbed, s e c r e t e d , and e x c r e t e d o n t o s u b s t r a t e s i n c r e a s e s immigration rates.

Algae, i n v e r t e b r a t e s , and aggregates o f f u n g i , b a c t e r i a ,

and d e t r i t u s on s u b s t r a t e s a l s o enhance i m m i g r a t i o n by i n t e r r u p t i n g c u r r e n t s and r e d u c i n g shear s t r e s s (Stevenson, 1983).

Dec.reases i n a l g a l p r o d u c t i v i t y

w i t h s t a n d i n g c r o p ( L a m b e r t i and Resh, 1983) and growth h a b i t s o f a l g a e t h a t m a i n t a i n them a t t h e s u r f a c e o f d e v e l o p i n g p e r i p h y t o n mats have suggested t h a t a l g a e compete f o r l i g h t and n u t r i e n t s (Hoagland e t a l . ,

1982; Hudon and

Bourget, 1983). A complete model o f a l g a l a c c u m u l a t i o n s h o u l d i n c l u d e t h e s e complex

c o m p e t i t i v e and p r e d a t o r - p r e y i n t e r a c t i o n s as w e l l as r e s o u r c e l i m i t a t i o n w i t h i n t h e environment.

However, i m p o r t a n t i n s i g h t s i n t o t h e dynamics o f

b e n t h i c a l g a l assemblages can be g a i n e d by usincj s i m p l e models w h i l e r e c o g n i z i n g t h e l i m i t a t i o n s and assumptions i n h e r e n t i n t h e model.

Such a

model was developed f o r two reasons: f i r s t , t o s t u d y t h e s e n s i t i v i t y o f a l g a l a c c u m u l a t i o n p a t t e r n s t o v a r i a t i o n s i n i m m i g r a t i o n and growth r a t e s and second, t o p r o v i d e a q u a n t i t a t i v e b a s i s t o compare a l t e r n a t i v e hypotheses f o r e x p l a i n i n g d i f f e r e n t a c c u m u l a t i o n p a t t e r n s i n d i f f e r e n t stream c u r r e n t s (Stevenson, 1984; Stevenson, i n p r e s s ) .

Nt and Nt+l

I n t h e model e q u a t i o n

were a l g a l abundances on s u b s t r a t e s on c o n s e c u t i v e days o f

colonization,

I. was t h e i n i t i a l i m m i g r a t i o n r a t e o n t o newly exposed

was t h e maximum enhancement of i m m i g r a t i o n as s u b s t r a t e s became s u b s t r a t e s , I,,, c o l o n i z e d , K was a c o n s t a n t t h a t r e l a t e d enhancement o f i m m i g r a t i o n t o a l g a l abundance on s u b s t r a t e s , and r was t h e a l g a l growth r a t e .

The maximum

enhancement o f i m m i g r a t i o n r e f e r s t o t h e d i f f e r e n c e i n minimum i m m i g r a t i o n r a t e s on newly exposed s u b s t r a t e s and maximum i m m i g r a t i o n r a t e s on s u b s t r a t e s which have been c o n d i t i o n e d by c o l o n i z i n g organisms. c o m p e t i t i o n among algae, a l g a l e m i g r a t ' ,n

Density-dependent

(detachment f r o m t h e s u b s t r a t e ) , and

h e r b i v o r y were assumed t o be n e g l i g i b l e f o r purposes o f m o d e l l i n g . P r e d i c t i o n s o f a l g a l a c c u m u l a t i o n p a t t e r n s by t h e model p r o v i d e d a s i g n i f i c a n t l y good f i t t o d a t a (Stevenson, i n p r e s s ) .

I. was e s t i m a t e d f r o m

195 f i e l d c o l l e c t i o n s as 90% o f t h e number o f a l g a e c o l o n i z i n g t i l e s u b s t r a t e s d u r i n g a 24-h p e r i o d (Stevenson, 1983).

I,,, was e s t i m a t e d as t h e d i f f e r e n c e i n

24-h a l g a l accumulations on t i l e s u b s t r a t e s and s u b s t r a t e s t h a t had been coated w i t h agar and w i t h s u r f a c e f l o w s i n t e r r u p t e d t o s i m u l a t e c o l o n i z e d substrates.

K was e s t i m a t e d t o be 2000 c e l l s / c m * ( a p p r o x i m a t e abundance o f

diatoms a f t e r one week).

A l g a l g r o w t h r a t e s were e s t i m a t e d d u r i n g t h e l a s t 16

days o f t h e 32-day c o l o n i z a t i o n p e r i o d , when i t was assumed t h a t accumulation due t o i m m i g r a t i o n would be n e g l i g i b l e compared t o a c c u m u l a t i o n due t o reproduction.

A l g a l growth r a t e s were e s t i m a t e d as

which was t h e d i f f e r e n c e i n n a t u r a l l o g - t r a n s f o r m e d abundances between day 32 and 16, d i v i d e d by T, t h e l e n g t h o f t i m e between dates. P r e d i c t i o n s o f t h i s model, p a r t i c u l a r l y f o r c o l o n i z a t i o n p e r i o d s g r e a t e r than 14 days, were a f f e c t e d more by p r o p o r t i o n a l l y equal changes i n r e p r o d u c t i o n r a t e s , t h a n i m m i g r a t i o n r a t e s (Stevenson, i n p r e s s ) .

An a n a l y s i s

o f model s e n s i t i v i t y was done by c a l c u l a t i n g changes i n a c c u m u l a t i o n p a t t e r n s when o n l y one f a c t o r i n t h e model was changed a t a t i m e .

Increasing

r e p r o d u c t i o n r a t e s by 50% caused a s i x - f o l d i n c r e a s e i n a c c u m u l a t i o n a f t e r 32 days.

Changing maximum i m m i g r a t i o n r a t e s was a l s o i m p o r t a n t because 50%

increases caused 55% i n c r e a s e s i n a c c u m u l a t i o n a f t e r 32 days.

The same 50%

changes i n i n i t i a l i m m i g r a t i o n r a t e s and t h e h a l f - s a t u r a t i o n c o n s t a n t ( K ) caused r e s p e c t i v e i n c r e a s e s and decreases of o n l y 15% i n accumulation a f t e r 32 days.

Changes became more i m p o r t a n t i n maximum i m m i g r a t i o n t h a n r e p r o d u c t i o n

i f c o l o n i z a t i o n p e r i o d s were s h o r t .

These r e s u l t s i n d i c a t e t h a t a c c u r a t e

e s t i m a t i o n o f i m m i g r a t i o n and r e p r o d u c t i o n r a t e s a r e i m p o r t a n t f o r p r e d i c t i n g c o l o n i z a t i o n , because v a r i a t i o n i n b o t h s t r o n g l y a f f e c t a l g a l c o l o n i z a t i o n . The o b j e c t i v e o f t h i s m o d e l l i n g s t u d y of a b e n t h i c a l g a l assemblage was t o assess t h e s e n s i t i v i t y o f a c c u m u l a t i o n r a t e s and community s t r u c t u r e t o changes i n i m m i g r a t i o n and growth r a t e s of species.

Estimates o f a l g a l

i m m i g r a t i o n r a t e s o b t a i n e d by f i e l d methods and by f i t t i n g model p r e d i c t i o n s t o n a t u r a l a c c u m u l a t i o n p a t t e r n s were compared t o s t u d y t h e r e l i a b i l i t y o f estimating immigration.

The d i f f e r e n c e s i n a l g a l i m m i g r a t i o n and growth r a t e s

among dominant s p e c i e s i n a b e n t h i c a l g a l assemblage were s t u d i e d .

Then, f a s t

growth r a t e s o f l a t e c o l o n i s t s and s l o w growth r a t e s o f r a p i d l y i m m i g r a t i n g p i o n e e r s p e c i e s were exchanged t o s t u d y changes i n a c c u m u l a t i o n r a t e s , species composition, and d i v e r s i t y o f assemblages t h a t c o u l d r e s u l t i f species were n o t s p e c i a l i z e d as f a s t i m m i g r a t o r s o r f a s t reproducers.

196

Research p r e s e n t e d i n t h i s paper was based on m o d e l l i n g a c c u m u l a t i o n p a t t e r n s o f i n d i v i d u a l d i a t o m s p e c i e s and a d d i n g them t o g e t h e r t o s t u d y t h e e n t i r e assemblage, whereas o n l y t o t a l assemblage abundances were m o d e l l e d p r e v i o u s l y (Stevenson, 1984; i n p r e s s ) .

Results i n d i c a t e considerable

i n t e r s p e c i f i c v a r i a t i o n i n a l g a l i m m i g r a t i o n and r e p r o d u c t i o n r a t e s , t h e p o s s i b i l i t y o f a l g a l s p e c i a l i z a t i o n as i m m i g r a t o r s o r r e p r o d u c e r s , and t h a t e m i g r a t i o n and d e n s i t y - d e p e n d e n t c o m p e t i t i o n f o r n u t r i e n t s may be i m p o r t a n t . 14.2

METHODS

A l g a l abundances on c l a y t i l e s were e s t i m a t e d a f t e r 1, 2, 4, 8, 16, 24, and 32 days i n c u b a t i o n i n a s t r e a m d u r i n g t h e w i n t e r when w a t e r temperatures were about 2" C (Stevenson, 1983; 1984).

Fifteen t i l e s , i n current velocities

r a n g i n g f r o m 27 t o 33 cm/s, were c o l l e c t e d on each sampling d a t e . Q

scraped f r o m t i l e s and mounted i n HYRAX

Algae were

medium by u s i n g v a p o r - s u b s t i t u t i o n

t e c h n i q u e s (Stevenson and Stoermer, 1981).

A t l e a s t 500 c e l l s o f l i v e diatoms

were counted w i t h a N i k o n l i g h t microscope a t 1OOOX. Cliatoms dominated t h e assemblage.

The t e n d i a t o m s p e c i e s w i t h h i g h e s t

r e l a t i v e abundances were chosen f o r s t u d y .

Mean abundance on each sampling

day was c a l c u l a t e d and used t o g e n e r a t e a temporal a c c u m u l a t i o n p a t t e r n w i t h which p r e d i c t i o n s o f a model were compared.

F i e l d estimates o f i n i t i a l a l g a l

i m m i g r a t i o n r a t e s ( I ) were equal t o mean abundances o f a l g a e on t i l e s t h a t 0

had been p l a c e d i n t h e stream f o r 24-h.

F i e l d e s t i m a t e s o f maximum

enhancement o f a l g a l i m m i g r a t i o n r a t e s ( I t ) were equal t o t h e sums o f b o t h t h e d i f f e r e n c e between 24-h abundances on t i l e s t h a t had been c o a t e d w i t h agar and t h e d i f f e r e n c e between 24-h a l g a l abundances on t i l e s w i t h s u r f a c e f l o w s i n t e r r u p t e d and I.

( s e e Stevenson;

1983 f o r d e t a i l s ) .

Growth r a t e s were

c a l c u l a t e d w i t h n a t u r a l l o g - t r a n s f o r m e d abundances d u r i n g t h e l a s t 16 days of c o l o n i z a t i o n (equation 2). F i e l d and model e s t i m a t e s o f a l g a l i m m i g r a t i o n r a t e s were compared t o s t u d y t h e accuracy o f e s t i m a t i n g i m m i g r a t i o n r a t e s .

F i e l d e s t i m a t e s o f I.

and r

were used i n a FORTRAN computer program t o e s t i m a t e I,,, and K w i t h t h e model by i t e r a t i v e l y v a r y i n g Im and K u n t i l t h e b e s t f i t w i t h a c t u a l a c c u m u l a t i o n p a t t e r n s was found.

B e s t f i t o f model p r e d i c t i o n (Nt p r e d i c t e d ) w i t h a c t u a l

a c c u m u l a t i o n p a t t e r n s (Nt observed) was c a l c u l a t e d w i t h a Chi-squared t e s t ( Z a r , 1974) u s i n g n a t u r a l l o g - t r a n s f o r m e d abundances o f algae. The s i m i l a r i t i e s between f i e l d and m o d e l l e d assemblage abundance, s p e c i e s c o m p o s i t i o n , and d i v e r s i t y ( c a l c u l a t e d w i t h t h e Shannon formula; P i e l o u , 1977) d u r i n g c o l o n i z a t i o n were s t u d i e d f o r accuracy o f model p r e d i c t i o n s of assemblage c h a r a c t e r i s t i c s .

Subsequently, growth r a t e s were exchanged between

species t h a t were f a s t and s l o w i m m i g r a t o r s d u r i n g e a r l y stages o f

197

c o l o n i z a t i o n t o s t u d y s e n s i t i v i t y of assemblage c h a r a c t e r i s t i c s (abundance, species c o m p o s i t i o n , and d i v e r s i t y ) t o changes i n p o p u l a t i o n c h a r a c t e r i s t i c s . The two s p e c i e s t h a t were dominant d u r i n g e a r l y stages o f c o l o n i z a t i o n and t h e two species w i t h t h e h i g h e s t growth r a t e s were i d e n t i f i e d .

Growth r a t e s o f

f a s t r e p r o d u c e r s were exchanged w i t h t h e s l o w e r growth r a t e s o f t h e species dominant d u r i n g e a r l y c o l o n i z a t i o n .

14.3

RESULTS

Ten diatoms comprised most o f t h e d i a t o m assemblage on t i l e s i n t h e stream, r a n g i n g f r o m 70% on day 1, t o 90% a f t e r o n l y 8 days, t o 98% b y day 32.

When

FLEMING CREEK

80-

-8

W

60-

Y dz

3

40-

GOOLIVAC

5 W

FRVAUCHE

W

a 20-

DITENUE

0 1 2

4

8

16

24

32

TIME I d ] F i g . 14.1. R e l a t i v e abundances o f d i a t o m species found on t i l e s i n t h e stream d u r i n g t h e c o l o n i z a t i o n p e r i o d . The assemblage has been s i m p l i f i e d t o t h e t e n most dominant species. DITENUE=Diatoma tenue, FRVAUCHE=Fra i l a r i a vaucheriae, GOOLIVAC=Gomphonema o l ivaceum, NAPELLIC=Navicul a p e l 1 i c u h M P E N = S y n e d r a rumpens, SYULNA=Synedra u l n a .

t h e assemblage was s i m p l i f i e d t o i n c l u d e o n l y these t a x a ( F i g . 14.1),

diatoms

c o u l d be c l a s s i f i e d i n one o f t h r e e groups: 1) p i o n e e r s , w i t h r e l a t i v e abundances d e c r e a s i n g d u r i n g t h e c o l o n i z a t i o n p e r i o d ; 2 ) l a t e c o l o n i s t s , w i t h r e l a t i v e abundances i n c r e a s i n g d u r i n g c o l o n i z a t i o n ; and 3) i n t e r m e d i a t e s , w i t h more s t a b l e r e l a t i v e abundances t h a n o t h e r t a x a d u r i n g c o l o n i z a t i o n . Decreases i n r e l a t i v e abundances o f Synedra u l n a and F r a g i l a r i a v a u c h e r i a e f r o m h i g h l e v e l s d u r i n g t h e f i r s t week o f c o l o n i z a t i o n ( F i g . 14.1) i n d i c a t e d t h a t t h e i r i m m i g r a t i o n r a t e s were f a s t e r and t h e i r growth r a t e s were s l o w e r than other taxa.

W i t h growth r a t e s o f a l l t a x a r a n g i n g between 0.079 and

0.206 ( T a b l e 14.1), t h e two l o w e s t . r a t e s , about 0.2,

g r o w t h r a t e s o f t h e s e p i o n e e r t a x a , l e s s t h a n 0.1, were

The r a p i d l y i n c r e a s i n g r e l a t i v e abundances and h i g h growth o f N a v i c u l a p e l l i c u l o s a and Gomphonema o l i v a c e u m i n d i c a t e d

t h a t t h e y were l a t e c o l o n i s t s and t h e b e s t r e p r o d u c e r s .

R e l a t i v e abundances

o f Synedra rumpens and Diatoma tenue were more c o n s t a n t t h a n o t h e r t a x a . E s t i m a t e d growth r a t e s o f t h e s e two i n t e r m e d i a t e t a x a were between t h o s e of i m m i g r a t o r s and r e p r o d u c e r s . C o n s i d e r a b l e v a r i a t i o n e x i s t e d among f i e l d and m o d e l l e d e s t i m a t e s o f maximum i m m i g r a t i o n r a t e s and e s t i m a t e s based on c l a s s i f i c a t i o n o f t h e diatoms as e i t h e r p i o n e e r s , i n t e r m e d i a t e s , o r l a t e c o l o n i s t s ( T a b l e 14.1).

Field

e s t i m a t e s o f maximum i m m i g r a t i o n r a t e s o f l a t e c o l o n i s t s were low, as would be expected f r o m t h e i r l o w r e l a t i v e abundances d u r i n g t h e f i r s t days o f TABLE 14.1 E s t i m a t e s o f maximum enhancement o f i m m i g r a t i o n r a t e s f o r s i x d i a t o m s p e c i e s ( I . c e l ls-cm-2.d-1) u s i n g f i e l d and m o d e l l i n g procedures. Chi-squared goodness o f m f i t ( X 2 , d f = 4 ) s t a t i s t i c s f o r model p r e d i c t i o n s o f t h e a c c u m u l a t i o n p a t t e r n s g e n e r a t e d by u s i n g m o d e l l e d and f i e l d e s t i m a t e d i m m i g r a t i o n r a t e s a r e r e p o r t e d w i t h t h e g r o w t h r a t e s ( r ) , i n i t i a l i m m i g r a t i o n r a t e s ( I o ) , and h a l f s a t u r a t i o n c o n s t a n t s ( K ) used i n t h e m o d e l l i n g . Field Estimated Diatom Species Pioneers Synedra u l n a F r a g i l a r i a vaucheriae I nt e rmed iat e s Synedra rumpens Diatoma tenue Late Colonists Navicula e l l i c u l o s a

m

m

b

Model Estimated

K

Xz

262. 39.

2000 2000

0.53 2.80

118. 193.

2.2 7.9

31. 108.

2000 2000

2.23 1.93

176. 656.

0.1 3.3

2. 42.

2000 2000

160. 2.67

1312. 1060.

I*

I0

Im

0.079 0.095

10.5 9.0

0.164 0.128 0.206 0.193

Im

K

200 250

X2 0.26 0.23

950 0.27 1950 0.33 4300 4150

0.69 0.18

199 c o l o n i z a t i o n , however u n e x p e c t e d l y l o w f i e l d e s t i m a t e s were a l s o observed o f a p i o n e e r and i n t e r m e d i a t e s p e c i e s ( T a b l e 14.1). M o d e l l e d e s t i m a t e s o f maximum i m m i g r a t i o n r a t e s i n d i c a t e d t h a t p i o n e e r s were t h e f a s t e s t i m m i g r a t o r s o n l y d u r i n g e a r l y stages o f c o l o n i z a t i o n ( F i g . 14.2) and t h a t l a t e c o l o n i s t s were a c t u a l l y t h e f a s t e s t i m m i g r a t o r s , as we1 1 as t h e f a s t e s t r e p r o d u c e r s , d u r i n g l a t e r stages o f c o l o n i z a t i o n .

Although

l a t e c o l o n i s t s had h i g h e r Im t h a n p i o n e e r s , t h e e s t i m a t e s o f a l g a l abundances

( K ) needed t o i n c r e a s e i m m i g r a t i o n t o maximum r a t e s were a l s o h i g h e r f o r l a t e c o l o n i s t s than pioneers.

Thus, i m m i g r a t i o n o f l a t e c o l o n i s t s i n c r e a s e d most

NAPELLIC

DITENUE

FRVAUCHE

W

5 GOOLIVAC

SYRUMPEN SYULNA

TIME Id1

I m n i g r a t i o n r a t e s e s t i m a t e d by m o d e l l i n g o f s i x d i a t o m species F i g . 14.2. d u r i n g t h e c o l o n i z a t i o n p e r i o d . See F i g . 14.1 f o r s p e c i e s a b b r e v i a t i o n s .

200 r a p i d l y d u r i n g l a t e r s t a g e s o f c o l o n i z a t i o n and immigrat.ion r a t e s o f p i o n e e r s were enhanced r a p i d l y d u r i n g e a r l y stages o f c o l o n i z a t i o n . Comparison o f observed a c c u m u l a t i o n p a t t e r n s and t h o s e generated when u s i n g f i e l d and m o d e l l e d e s t i m a t e s o f maximum i m m i g r a t i o n r a t e s i n d i c a t e d t h a t f i e l d e s t i m a t e s p r o b a b l y u n d e r e s t i m a t e d maximum i m m i g r a t i o n r a t e s ( F i g . 14.3). S i g n i f i c a n t l y good f i t s of observed a c c u m u l a t i o n p a t t e r n s were generated by u s i n g b o t h f i e l d and m o d e l l e d e s t i m a t e s o f i m m i g r a t i o n ( T a b l e 14.1),

DITENUE

FRVAUCHE

I ,

w

0

z

8 z

3

m

a

however

NAPELLIC

,

-/ SYRUMPEN

1.

...'

*

i TIME Id1

F i g . 14.3. Log-transformed abundances o f s i x diatoms t h a t were p r e d i c t e d by modelling accumulation patterns w i t h estimates o f immigration r a t e s obtained w i t h f i e l d procedures ( d o t t e d l i n e ) and w i t h m o d e l l i n g procedures ( s o l i d l i n e ) . Abundances o f a l g a e on t i l e s i n t h e stream a r e marked w i t h an " X " . See F i g . 14.1 f o r s p e c i e s a b b r e v i a t i o n s .

201 lower X 2 v a l u e s i n d i c a t e d t h a t a c c u m u l a t i o n p a t t e r n s were b e t t e r f i t by modelled t h a n f i e l d e s t i m a t e s . P r e d i c t i o n s o f assemblage accumulation, s p e c i e s c o m p o s i t i o n , and d i v e r s i t y p a t t e r n s when u s i n g m o d e l l e d e s t i m a t e s o f maximum i m m i g r a t i o n f i t a c t u a l assemblage accumulation, s p e c i e s c o m p o s i t i o n , and d i v e r s i t y p a t t e r n s observed i n t h e stream.

Small d e v i a t i o n s between m o d e l l e d and observed accumulation

p a t t e r n s were e v i d e n t among p o p u l a t i o n and assemblage p a t t e r n s ( F i g s . 14.3 and 14.4).

M o d e l l e d a c c u m u l a t i o n p a t t e r n s were i n t e r m e d i a t e between h i g h and l o w

stream abundances on days 4 and 8 r e s p e c t i v e l y .

I n a d d i t i o n , model

p r e d i c t i o n s f o r abundances were l o w e r on day 16 t h a n t h o s e observed.

However,

t h e model was u s u a l l y q u i t e a c c u r a t e i n p r e d i c t i n g d i a t o m abundances on day 32 w i t h a v e r y good f i t f o r t o t a l assemblage abundances ( X 2 = 0.1856) and p o p u l a t i o n abundances ( T a b l e 14.1).

Shannon d i v e r s i t y o f s i m p l i f i e d

assemblages (i. e . , evenness, because s p e c i e s r i c h n e s s was c o n s t a n t l y 10) from t h e stream was g e n e r a l l y l o w e r d u r i n g t h e f i r s t two weeks o

c o l o n i z a t i o n than

A d i v e r s t y peak i n t h e stream assemblage on day 2 was n o t observed i n t h e m o d e l l e d assemblage and d i v e r s i t y was m a i n t a i n e d l o n g e r i n t h e stream assemblage. n b o t h assemblages

d i v e r s i t y o f t h e m o d e l l e d assemblage ( F i g . 14.5).

14-

12108-

6-

-

0

1 4

16

32

TIME [ d l

F i g . 14.4. Log-transformed abundances o f t h e t e n - s p e c i e s assemblages t h a t were p r e d i c t e d by t h e model w i t h i m m i g r a t i o n r a t e s o f t h e s p e c i e s e s t i m a t e d u s i n g m o d e l l i n g procedures.

202 t h e r e was a s l i g h t i n c r e a s e i n d i v e r s i t y between day 8 and 16, w h i c h was f o l l o w e d b y a decrease. R e s u l t s o f a l t e r i n g p o p u l a t i o n c h a r a c t e r i s t i c s t o make p i o n e e r s i n t o f a s t reproducers i n d i c a t e d t h a t t h e h i g h i m m i g r a t i o ' n r a t e s o f

5,

o l i v a c e u m and

p e l l i c u l o s a d u r i n g l a t e r stages o f c o l o n i z a t i o n were i m p o r t a n t .

y.

When t h e f a s t

growth r a t e s o f t h e s e two t a x a were s w i t c h e d w i t h t h o s e o f t h e p i o n e e r s

(2.

E. v a u c h e r i a e ) ,

f i n a l a c c u m u l a t i o n a f t e r 32 days was s l i g h t l y l o w e r 5 i n t h e a l t e r e d assemblage (6.61 X 10 c e l l s / c m 2 ) t h a n i n t h e u n a l t e r e d

u l n a and

5 c e l l s / c m 2 ; F i g . 14.6).

assemblage (6.79 X 10

Abundance o f t h e a l t e r e d

assemblage i n c r e a s e d more r a p i d l y t h a n f o r t h e u n a l t e r e d assemblage d u r ng t h e f i r s t week o f c o l o n i z a t i o n , b u t more s l o w l y d u r i n g t h e second week when l a t e i m m i g r a t i o n became more i m p o r t a n t . D e v i a t i o n s i n d i v e r s i t y p a t t e r n s between a l t e r e d and m o d e l l e d assemb ages c o r r e l a t e d w i t h t h e change i n p o p u l a t i o n c h a r a c t e r i s t i c s .

Diversity of the

a l t e r e d assemblage decreased more r a p i d l y d u r i n g t h e f i r s t week o f c o l o n i z a t i o n and i n c r e a s e d more r a p i d l y d u r i n g t h e second and t h i r d weeks of c o l o n i z a t i o n t h a n t h e u n a l t e r e d assemblage ( F i g . 14.5).

The more r a p i d e a r l y

decrease i n d i v e r s i t y o f t h e a l t e r e d assemblage was due t o t h e enhanced g r o w t h

2.1

I

>

t u) K

w

g

1.9

P

z a

I

u)

1.i

7 s

I

12 4

8

16

24

32

TIME Id1

F i g . 14.5. Shannon d i v e r s i t y o f t e n - s p e c i e s assemblages on t i l e s i n t h e stream ( s o l i d l i n e c o n n e c t i n g "X'ls), when m o d e l l e d w i t h u n a l t e r e d ( s o l i d l i n e ) and a l t e r e d ( d o t t e d l i n e ) p o p u l a t i o n c h a r a c t e r i s t i c s .

203 r a t e s o f p i o n e e r s , which i n c r e a s e d t h e unevenness o f p o p u l a t i o n abundances t h a t had been balanced by f a s t e r growth o f l a t e c o l o n i s t s i n t h e u n a l t e r e d m o d e l l e d assemblage.

The subsequent m i d - t e r m i n c r e a s e i n d i v e r s i t y , which was

g r e a t e r i n a l t e r e d t h a n u n a l t e r e d assemblages, was caused by evenness i n c r e a s i n g as f a s t , l a t e - i m m i g r a t i o n r a t e s o f l a t e c o l o n i s t s s t a r t e d t o S i m i l a r l y , h i g h d i v e r s i t y was s u s t a i n e d l o n g e r i n t h e

increase r a p i d l y .

a l t e r e d assemblage t h a n i n t h e u n a l t e r e d and stream assemblages, because t h e species w i t h t h e f a s t , l a t e - i m m i g r a t i o n r a t e s no l o n g e r had f a s t growth r a t e s . U n l i k e s p e c i e s c o m p o s i t i o n p a t t e r n s i n m o d e l l e d and s t r e a m assemblages, r e l a t i v e abundances were r e l a t i v e l y c o n s t a n t t h r o u g h o u t t h e c o l o n i z a t i o n Pioneers i n t h e a l t e r e d assemblage p e r i o d i n a l t e r e d assemblages ( F i g . 14.7). d i d n o t comprise s u b s t ' a n t i a l l y s m a l l e r p r o p o r t i o n s o f assemblages a t t h e end t h a n a t t h e b e g i n n i n g o f t h e c o l o n i z a t i o n p e r i o d , because t h e y now had f a s t 1oc

80

GOOLIVAC W

$

FRVAUCHE

J

W

K

20

DITENUE

(

I

1 2

I

4

I

8

I

16

I

24

$2

TIME [dl F i a . 14.6. R e l a t i v e abundances o f d i a t o m sDecies d u r i n q t h e c o l o n i z a t i o n p e h o d when t h e assemblage was m o d e l l e d w i t h u n a l t e r e d e s t i m a t e s of p o p u l a t i o n c h a r a c t e r i s t i c s . See F i g . 14.1 f o r s p e c i e s a b b r e v i a t i o n s . U n l a b e l e d spaces a r e same s p e c i e s as t h o s e i n r e s p e c t i v e l o c a t i o n s i n F i g . 14.1.

204 growth r a t e s .

R e l a t i v e abundances o f l a t e c o l o n i s t s , now w i t h t h e s l o w e s t

growth r a t e s , d i d n o t d e c l i n e d u r i n g l a t e r stages o f c o l o n i z a t i o n as r e l a t i v e abundances o f o t h e r s p e c i e s w i t h slow r e p r o d u c t i o n r a t e s had i n m o d e l l e d and stream assemblages.

The f a s t l a t e - i m m i g r a t i o n r a t e s o f l a t e c o l o n i s t s were

a b l e t o s u s t a i n t h e i r r e l a t i v e abundances, even though p i o n e e r s were growing faster. 14.4

DISCUSSION

The range o f i m m i g r a t i o n and growth r a t e s among common diatoms was considerable.

D i f f e r e n c e s among i m m i g r a t i o n r a t e s o f s p e c i e s were g r e a t e r

t h a n d i f f e r e n c e s among g r o w t h r a t e s .

That d i d n o t mean t h a t i m m i g r a t i o n was a

more i m p o r t a n t f a c t o r t h a n g r o w t h i n a c c u m u l a t i o n .

According t o

e x t r a p o l a t i o n s o f a s e n s i t i v i t y a n a l y s i s , when 50% changes i n g r o w t h and

SYULNA

FRVAUCHE

>

I

1 2

I

4

I

8

I

16

I

24

I

32

TIME Id1

F i g . 14.7. R e l a t i v e abundances of d i a t o m s p e c i e s d u r i n g t h e c o l o n i z a t i o n p e r i o d when t h e assemblage was m o d e l l e d w i t h a l t e r e d e s t i m a t e s o f p o p u l a t i o n U n l a b e l e d spaces c h a r a c t e r i s t i c s . See F i g . 14.1 f o r s p e c i e s a b b r e v i a t i o n s . a r e same s p e c i e s as t h o s e occupying r e s p e c t i v e l o c a t i o n s i n F i g . 14.1.

205 i m m i g r a t i o n r e s p e c t i v e l y caused s i x - f o l d and 50% changes i n a c c u m u l a t i o n (Stevenson, i n p r e s s ) , t h e t w o - f o l d d i f f e r e n c e s among growth r a t e s and t h i r t e e n - f o l d d i f f e r e n c e s among i m m i g r a t i o n r a t e s p r o b a b l y accounted f o r s i m i l a r changes i n a c c u m u l a t i o n on s u b s t r a t e s a f t e r a 32-day c o l o n i z a t i o n . The g r e a t d i f f e r e n c e s among d i a t o m i m m i g r a t i o n r a t e s i n d i c a t e s t h a t i m m i g r a t i o n , as w e l l as r e p r o d u c t i o n , can be an i m p o r t a n t f a c t o r i n a l g a l c o l o n i z a t i o n and s u c c e s s i o n on s u b s t r a t e s . D i f f e r e n c e s i n i m m i g r a t i o n and growth r a t e s among d i a t o m s p e c i e s i n d i c a t e d t h a t some diatoms, i n c e r t a i n h a b i t a t c o n d i t i o n s , may be s p e c i a l l y adapted as pioneer species o r l a t e c o l o n i s t s .

P i o n e e r s p e c i e s i m m i g r a t e d most r a p i d l y

d u r i n g e a r l y stages o f c o l o n i z a t i o n b u t had t h e l o w e s t growth r a t e s .

I f the

common s u g g e s t i o n i s c o r r e c t , t h a t n u t r i e n t a v a i l a b i l i t y t o c e l l s decreases w i t h assemblage d e n s i t y , t h e n p i o n e e r s may g a i n a c o m p e t i t i v e advantage by i m m i g r a t i n g r a p i d l y and s e q u e s t e r i n g n i t r o g e n and phosphorus r e s e r v e s t o s u s t a i n l o w growth r a t e s d u r i n g l a t e r stages o f c o l o n i z a t i o n .

Late c o l o n i s t s ,

w i t h f a s t growth r a t e s and r a p i d i m m i g r a t i o n r a t e s d u r i n g l a t e r stages o f c o l o n i z a t i o n , may be a b l e t o absorb n u t r i e n t s a t l o w e r c o n c e n t r a t i o n s ( l o w e r K s ) t h a n p i o n e e r s p e c i e s d u r i n g l a t e c o l o n i z a t i o n when mats and,

t h e o r e t i c a l l y , n u t r i e n t d i f f u s i o n g r a d i e n t s develop. There a r e a l t e r n a t i v e hypotheses f o r s p e c i e s b e i n g e i t h e r f a s t e a r l y i m m i g r a t o r s o r f a s t r e p r o d u c e r s and l a t e - i m m i g r a t o r s .

A l t e r n a t i v e hypotheses

s t a t e t h a t i m m i g r a t i o n r a t e s a r e more c l o s e l y r e l a t e d t o d e n s i t i e s o f a l g a e i n t h e p l a n k t o n t h a n t o i n t e r a c t i o n s w i t h b e n t h i c organisms and t h e i r modifications o f substrate conditions.

One a l t e r n a t i v e h y p o t h e s i s s t a t e s t h a t

i m m i g r a t i o n r a t e s o f l a t e c o l o n i s t s i n c r e a s e d o n l y d u r i n g l a t e stages o f c o l o n i z a t i o n because o f e p i s o d i c changes i n abundances o f a l g a e i n t h e water. S l i g h t i n c r e a s e s i n d i s c h a r g e c o u l d cause such sudden changes i n a l g a l d r i f t as more l o o s e l y a t t a c h e d a l g a e d r i f t f r o m s u b s t r a t e s .

I have observed t h a t

wind d i s t u r b a n c e o f submerged macrophytes can d i s t u r b m a c r o p h y t i c s u b s t r a t e s and cause i n c r e a s e s i n a l g a l d r i f t .

However, d i s c h a r g e d u r i n g c o l o n i z a t i o n

decreased i n Fleming Creek and macrophytes were n o t p r e s e n t d u r i n g t h e w i n t e r . Another a l t e r n a t i v e h y p o t h e s i s i s t h a t i m m i g r a t i o n and p l a n k t o n abundances changed w i t h seasonal v a r i a t i o n i n h a b i t a t c o n d i t i o n s and w i t h a s h i f t i n s p e c i e s b e s t adapted f o r f a s t r e p r o d u c t i o n d u r i n g s u c c e s s i v e c o l o n i z a t i o n periods.

Thus, p i o n e e r s w i t h f a s t e a r l y - i m m i g r a t i o n r a t e s had

h i g h d e n s i t i e s i n t h e w a t e r because o f h i g h abundances on s u b s t r a t e s and h i g h abundances on s u b s t r a t e s because t h e i r r e p r o d u c t i v e r a t e s were f a s t i n t h e past; d e n s i t i e s on s u b s t r a t e s and i n t h e w a t e r decreased because t h e i r r e p r o d u c t i v e r a t e s d e c l i n e d w i t h r e c e n t c l i m a t i c changes.

The s p e c i e s t h a t

a r e f a s t r e p r o d u c e r s a r e b e s t adapted t o t h e new ambient c o n d i t i o n s o f t h e

206 present c o l o n i z a t i o n period.

Consequently, t h e i r abundances on s u b s t r a t e s and

i n t h e w a t e r i n c r e a s e and cause an i n c r e a s e i n t h e i r i m m i g r a t i o n r a t e s . E x p l a n a t i o n s f o r changes i n i m m i g r a t i o n r a t e s t h a t i n v o l v e changes i n plankton o r b i o t i c i n t e r a c t i o n s w i t h previous colonizers are n o t mutually e x c l u s i v e , b u t a r e complementary.

A l t h o u g h p l a n k t o n abundances were n o t

e s t i m a t e d d u r i n g c o l o n i z a t i o n i n t h i s study, t h e y s h o u l d be c o n s i d e r e d i n f u t u r e research; then, i m m i g r a t i o n r a t e s i n t h e model o f a c c u m u l a t i o n c o u l d be r e l a t e d t o p l a n k t o n abundances.

It i s a l s o probable t h a t

i m m i g r a t i o n r a t e s were r e l a t e d t o b e n t h i c a l g a l abundance.

Other

i m m i g r a t i o n s t u d i e s have shown t h a t t h e r e a r e d i f f e r e n c e s i n d i a t o m immigration a b i l i t i e s , t h a t diatom immigration r a t e s increase d u r i n g the c o l o n i z a t i o n p e r i o d , and t h a t i m m i g r a t i o n o f some diatoms p r o b a b l y i n c r e a s e more t h a n o t h e r s d u r i n g t h e c o l o n i z a t i o n p e r i o d (Stevenson, 1983).

B o t h w e l l (1983!,

however, d i d n o t observe i n c r e a s e s i n i m m i g r a t i o n

r a t e s d u r i n g c o l o n i z a t i o n o f a l g a e on o p e n - c e l l styrofoam.

Actually,

Bothwell's observation f u r t h e r substantiates previous observations t h a t development o f s u r f a c e i r r e g u l a r i t i e s (aggregates o f algae, d e t r i t u s , b a c t e r i a , and f u n g i ) on smooth s u b s t r a t e s enhances i m m i g r a t i o n r a t e s more t h a n o r g a n i c c o a t i n g s (Stevenson, 1983).

The s u r f a c e i r r e g u l a r i t i e s o f B o t h w e l l ' s

s u b s t r a t e s p r o b a b l y i n t e r r u p t e d f l o w , and consequently, a d d i t i o n a l s u r f a c e i r r e g u l a r i t y and c o a t i n g o f s u b s t r a t e s w i t h s e c r e t e d mucopolysaccharides had l i t t l e e f f e c t on i m m i g r a t i o n . A l g a l a c c u m u l a t i o n r a t e s and community s t r u c t u r e were s e n s i t i v e t o changes i n b o t h i m m i g r a t i o n and g r o w t h r a t e s .

The importance o f h i g h i m m i g r a t i o n

r a t e s by l a t e c o l o n i s t s d u r i n g l a t e r s t a g e s o f c o l o n i z a t i o n was e v i d e n t a f t e r exchanging growth r a t e s between p i o n e e r s and l a t e c o l o n i s t s .

F i r s t , t h e r e was

no i n c r e a s e i n assemblage a c c u m u l a t i o n when p i o n e e r s grew f a s t e r t h a n l a t e colonists.

Assemblage a c c u m u l a t i o n was expected t o be g r e a t e r i f p i o n e e r s

were a l s o f a s t r e p r o d u c e r s because p i o n e e r s would have l o n g e r t o reproduce on substrates than l a t e reproducers.

P r e v i o u s s t u d y w i t h t h e a c c u m u l a t i o n model

(Stevenson, i n p r e s s ) had shown t h a t i m m i g r a t i o n accounts f o r most o f a c c u m u l a t i o n d u r i n g t h e f i r s t week o f c o l o n i z a t i o n , and growth i s most important t h e r e a f t e r .

The l a t e c o l o n i s t s i n t h a t s t u d y d i d n o t have f a s t

l a t e - i m m i g r a t i o n r a t e s , as were d e t e c t e d i n t h i s s t u d y .

F a s t e r i m m i g r a t i o n by

l a t e c o l o n i s t s t h a n p i o n e e r s was g r e a t enough t o compensate f o r t h e t i m e l o s t d u r i n g w h i c h g r o w t h on s u b s t r a t e s d i d n o t occur.

The importance o f l a t e

i m m i g r a t i o n was a l s o e v i d e n t when l a t e c o l o n i s t s were a b l e t o m a i n t a i n c o n s t a n t p r o p o r t i o n s o f t h e assemblage.

Pioneers comprised s u c c e s s i v e l y s m a l l

p r o p o r t i o n s o f t h e assemblage when t h e y were s l o w growers.

Again, i m m i g r a t i o n

207

o f l a t e c o l o n i s t s b e i n g f a s t e r t h a n p i o n e e r s was i m p o r t a n t f o r g e n e r a t i o n o f these r e s u l t s . The importance o f v a r i a t i o n s i n i m m i g r a t i o n and growth r a t e s i n c o n t r o l l i n g species c o m p o s i t i o n and d i v e r s i t y was e v i d e n t i n d i f f e r e n c e s f o r modelled and a l t e r e d assemblages.

Evenness o f abundances o f f a s t i m m i g r a t o r s and f a s t

r e p r o d u c e r s s u s t a i n e d h i g h d i v e r s i t y d u r i n g t h e c o l o n i z a t i o n p e r i o d , whereas d i v e r s i t y decreased when t h e same s p e c i e s were f a s t i m m i g r a t o r s and f a s t reproducers.

E v e n t u a l l y , when abundances a r e h i g h and r e p r o d u c t i o n accounts

f o r most o f accumulation, uneven r e p r o d u c t i o n r a t e s among s p e c i e s caused a decrease i n evenness and d i v e r s i t y .

The importance o f f a s t l a t e - i m m i g r a t i o n

r a t e s was a g a i n e v i d e n t i n a h i g h e r m i d - c o l o n i z a t i o n d i v e r s i t y i n c r e a s e and i n d i v e r s i t y b e i n g s u s t a i n e d l o n g e r d u r i n g c o l o n i z a t i o n i n a l t e r e d t h a n modelled assemblages. The accuracy o f r e s u l t s o f t h i s s t u d y i s d i f f i c u l t t o address directly.

F u t u r e r e s e a r c h i s b e i n g done t o s t u d y hypotheses t h a t

developed d u r i n g t h i s m o d e l l i n g work.

Accuracy o f r e s u l t s can be

addressed h e r e by examining r e s u l t s o f o t h e r s t u d i e s and by examining model assumptions. Results o f o t h e r f i e l d studies i n d i c a t e t h a t estimates o f immigration and growth r a t e s a r e c l o s e t o t h o s e observed i n o t h e r s t u d i e s . C o l o n i z a t i o n s s t u d i e d by I v l e v (1933) and by K o r t e and B l i n n (1983) a r e p a r t i c u l a r l y w e l l s u i t e d f o r comparison because t h e y i n c l u d e e a r l y ( l e s s t h a n 7 d ) samples and t h e l a c k o f sudden decreases i n a c c u m u l a t i o n i n d i c a t e t h a t s l o u g h i n g d i d n o t occur.

T h e i r a c c u m u l a t i o n p a t t e r n s were shaped

s i m i l a r l y t o t h o s e i n Fleming Creek.

Curves o f l o g - t r a n s f o r m e d abundances

tended t o be s t r a i g h t d u r i n g t h e l a s t two weeks o f c o l o n i z a t i o n , which i n d i c a t e d t h a t growth was t h e predominant a c c u m u l a t i o n process.

Slopes o f

t h e s e c u r v e s , e s t i m a t e s o f growth r a t e s , ranged between 0.1 and 0.3 ( e x c l u d i n g h i g h e s t and l o w e s t c u r r e n t c o n d i t i o n s i n I v l e v ' s s t u d y ) , which a r e s i m i l a r t o growth r a t e s e s t i m a t e d i n t h i s study. evident i n both data sets.

S t r o n g e f f e c t s of i m m i g r a t i o n a r e

Given growth r a t e s above, i n c r e a s e s f r o m 150 t o

10,000 c e l l s / c m 2 on days 1 and 3 ( I v l e v , 1933) and a t l e a s t 13,000

cells/cm2

on day 3 ( K o r t e and B l i n n , 1983) were p r o b a b l y t h e r e s u l t of h i g h i m m i g r a t i o n rates.

I m m i g r a t i o n r a t e s h i g h e r and l o w e r t h a n f i e l d o r m o d e l l e d e s t i m a t e s

f o r Fleming Creek have been observed (Stevenson, u n p u b l i s h e d d a t a ) . Among o t h e r assumptions, t h e model assumed t h a t t h e r e l a t i o n s h i p between i m m i g r a t i o n r a t e s c o u l d be r e l a t e d t o abundances on s u b s t r a t e s by a h a l f - s a t u r a t i o n constant.

Thus, i m m i g r a t i o n r a t e s i n c r e a s e d a s y m p t o t i c a l l y

n o t l i n e a r l y w i t h abundances on s u b s t r a t e s .

I m m i g r a t i o n c o u l d have been

r e l a t e d m a t h e m a t i c a l l y t o t h e number o f a l g a e on s u b s t r a t e s i n a v a r i e t y o f

208 ways. An a s y m p t o t i c r e l a t i o n s h i p was chosen because o f a c o m b i n a t i o n o f factors.

The most r a p i d enhancement o f i m m i g r a t i o n was expected d u r i n g e a r l y

stages o f c o l o n i z a t i o n as f i l m s o f adsorbed o r g a n i c molecules and b a c t e r i a l s e c r e t i o n s developed r a p i d l y , c o n s i d e r a b l y f a s t e r t h a n a l g a l accumulations. The r a t e o f i m m i g r a t i o n enhancement f r o m a t t a c h e d a l g a e , d e b r i s , and o t h e r organisms i n t e r r u p t i n g f l o w s h o u l d decrease because t h e p r o p o r t i o n o f t h e s u r f a c e where c u r r e n t s were i n t e r r u p t e d by organisms would decrease as a d d i t i o n a l organisms c o l o n i z e t h e s u b s t r a t e .

Assume, f o r example, t h a t t h e

area o f t h e s u r f a c e around an a t t a c h e d organism, where c u r r e n t s a r e a l t e r e d The

and i m m i g r a t i o n i s enhanced, i s a f r a c t i o n o f a c i r c l e ( a ) around i t .

c i r c l e has t h e r a d i u s o f t h e organism ( r ) p l u s a c o n s t a n t d i s t a n c e ( c ) around t h e organism ( r + c ) .

The area a f f e c t e d around organisms, a ( I I ( r + c ) z

i s g r e a t e r t h a n o n e - f o u r t h t h e a r e a around f o u r organisms, a ( n ( Z r + c ) ' n(2r)2).

-

nr2),

-

E v e n t u a l l y , i n t e r r u p t i o n o f f l o w , and c o n c o m m i t t e n t l y , r e l a t e d

i m m i g r a t i o n r a t e s , would decrease as areas o f s u b s t r a t e a f f e c t e d by aggregates o f organisms and d e b r i s s t a r t e d t o o v e r l a p .

However, h i g h i m m i g r a t i o n r a t e s

would p r o b a b l y c o n t i n u e t o be s u s t a i n e d as d r i f t i n g a l g a e became e n t a n g l e d i n t h e o v e r g r o w t h o f s t a l k e d and f i l a m e n t o u s forms.

Although immigration r a t e s

a r e n o t d i r e c t l y and r e a l i s t i c a l l y r e l a t e d a s y m p t o t i c a l l y t o abundances of a l g a e on s u b s t r a t e s , i t was j u d g e d t o be t h e s i m p l e s t and most a c c u r a t e way t o Relating

generate t h e immigration p a t t e r n hypothesized f o r colonization.

i m m i g r a t i o n r a t e s t o abundances o f diatoms on s u b s t r a t e s by u s i n g a h a l f - s a t u r a t i o n c o n s t a n t was j u d g e d p r a c t i c a l and i n f o r m a t i v e . V i o l a t i o n o f model assumptions c o u l d cause o v e r e s t i m a t i o n o f maximum immigration rates.

I f e m i g r a t i o n and n u t r i e n t c o m p e t i t i o n were d e n s i t y -

dependent, t h e n maximum g r o w t h r a t e s may have been u n d e r e s t i m a t e d w i t h d a t a from t h e l a s t 16 days o f c o l o n i z a t i o n .

There was some evidence f o r and

a g a i n s t n e g a t i v e density-dependent i n t e r a c t i o n s .

I f the negative e f f e c t s o f

e m i g r a t i o n and/or n u t r i e n t c o m p e t i t i o n developed b e f o r e day 16, maximum growth r a t e s and abundance on day 16 would have been underestimated. day 16 was u n d e r e s t i m a t e d d u r i n g m o d e l l i n g .

Abundance on

However, s i m i l a r i t y o f e s t i m a t e s

o f growth r a t e s between days 16 and 24 and r a t e s between days 24 and 32 i n d i c a t e d t h a t growth r a t e s d i d n o t decrease d u r i n g c o l o n i z a t i o n (Stevenson, 1984).

I f d e n s i t y - d e p e n d e n t e m i g r a t i o n o r growth i n h i b i t i o n occurred, growth

r a t e s c a l c u l a t e d f o r t h e p e r i o d between days 16 and 24, when abundances were low, s h o u l d be g r e a t e r t h a n t h e growth r a t e between days 24 and 32, when abundances were h i g h e r .

So t h e assumptions t h a t e m i g r a t i o n and

density-dependent g r o w t h were n o t i m p o r t a n t i n h i s h a b i t a t seem j u s t i f i a b l e . V i o l a t i o n o f o t h e r assumptions c o u l d cause u n d e r e s t i m a t i o n o f maximum immigration rates.

Low model p r e d i c t i o n s o f abundances on day 16 c o u l d

209 be e x p l a i n e d by o v e r e s t i m a t i n g growth r a t e s and u n d e r e s t i m a t i n g maximum immigration rates.

T h i s would have a l s o enhanced e a r l y a c c u m u l a t i o n r a t e s ,

slowed l a t e a c c u m u l a t i o n r a t e s , and produced an a l m o s t p e r f e c t f i t between model p r e d i c t i o n s and observed a c c u m u l a t i o n p a t t e r n s .

I t has been shown t h a t

i m m i g r a t i o n accounts f o r about 15% and 5% o f t h e a c c u m u l a t i o n on days 16 and 24, r e s p e c t i v e l y when i m m i g r a t i o n and growth r a t e s a r e c l o s e t o t h o s e i n t h i s s t u d y (Stevenson, 1981).

Thus, i t seems l i k e l y t h a t a modest o v e r e s t i m a t i o n

o f g r o w t h r a t e s and u n d e r e s t i m a t i o n o f maximum i m m i g r a t i o n r a t e s i s t h e b e s t founded e x p l a n a t i o n f o r p r e d i c t i o n s o f l o w abundances on day 16. The accuracy o f e s t i m a t i n g i m m i g r a t i o n and growth r a t e s w i t h t h e m o d e l l i n g and f i e l d procedures used can be j u d g e d by comparing model p r e d i c t i o n s and a c t u a l a c c u m u l a t i o n p a t t e r n s and comparing model e s t i m a t e s and independent f i e l d e s t i m a t e s o f maximum i m m i g r a t i o n r a t e s .

Despite s l i g h t differences,

f i t between m o d e l l e d and a c t u a l c o l o n i z a t i o n was good.

the

T h e r e f o r e , modelled

e s t i m a t e s o f i m m i g r a t i o n and g r o w t h r a t e s must have been a c c u r a t e enough t o be i n f o r m a t i v e , and e r r o r s due t o density-dependent i n t e r a c t i o n s were p r o b a b l y not important i n t h i s h a b i t a t .

I t i s d i f f i c u l t t o j u d g e whether m o d e l l i n g o r

f i e l d e s t i m a t e s o f i m m i g r a t i o n were most a c c u r a t e .

F i e l d estimates o f

i m m i g r a t i o n were p r o b a b l y l e s s a c c u r a t e t h a n m o d e l l e d e s t i m a t e s because i m m i g r a t i o n samples were o n l y c o l l e c t e d on t h e f i r s t day o f c o l o n i z a t i o n .

In

a d d i t i o n , s i m u l a t e d f l o w i n t e r r u p t i o n , which enhanced i m m i g r a t i o n g r e a t l y (Stevenson, 1983), d i d n o t c o v e r t h e e n t i r e s u b s t r a t e as would o c c u r during colonization.

Thus, low f i e l d e s t i m a t e s can be e x p l a i n e d and h i g h

m o d e l l e d e s t i m a t e s o f i m m i g r a t i o n a r e w i t h i n i m m i g r a t i o n r a t e s t h a t have been measured w i t h f i e l d procedures i n o t h e r h a b i t a t s .

Further evaluation o f the

accuracy o f t h e m o d e l l i n g and f i e l d procedures f o r e s t i m a t i n g i m m i g r a t i o n and growth w i l l r e q u i r e use o f more c o n t r o l l e d f i e l d procedures.

ACKNOWLEDGEMENTS

I would l i k e t o thank Mrs. Leah Kohn, A d m i n i s t r a t i v e A s s i s t a n t , Department o f B i o l o g y , U n i v e r s i t y o f L o u i s v i l l e , f o r e d i t i n g and preparing t h i s manuscript. r e v i e w e r s were a1 so he1 p f u l

Reviews by K y l e Hoagland and two anonymous

.

REFERENCES

B o t h w e l l , M.L., 1983. A l l - w e a t h e r t r o u g h s f o r p e r i p h y t o n s t u d i e s . Water Res., 17: 1735-1741. 1984. P e r i p h y t o n c o l o n i z a t i o n o f r o c k H a m i l t o n , P.B. and D u t h i e , H.C., s u r f a c e s i n a b o r e a l f o r e s t stream s t u d i e d by scanning e l e c t r o n microscopy and t r a c k a u t o r a d i o g r a p h y . J . Phycol., 20: 525-532.

21 0 Hoagland, K.D., 1983. Short-term s t a n d i n g crop and d i v e r s i t y o f p e r i p h y t i c diatoms i n an e u t r o p h i c r e s e r v o i r . J. Phycol., 19: 30-38. Hoagland, K.D., Roemer, S.C., and Rosowski, J.R., 1982. C o l o n i z a t i o n and community s t r u c t u r e o f two p e r i p h y t o n assemblages, w i t h emphasis on t h e diatoms ( B a c i l l a r i o p h y c e a e ) . Amer. J. Bot.., 69: 188-213. Hudon, C. and Bourget, E., 1981. I n i t i a l c o l o n i z a t i o n o f a r t i f i c i a l substrate: community development and s t r u c t u r e s t u d i e d by scanning e l e c t r o n microscopy. Can. J. Fish. Aquat. Sci., 38: 1371-1384. Hudon, C. and Bourget, E., 1983. The e f f e c t o f l i g h t on t h e v e r t i c a l s t r u c t u r e o f e p i b e n t h i c diatom communities. Bot. Mar., 26: 317-330. 1933. E i n Versuch z u r e x p e r i m e n t e l l e n Erforschung der Okologie I v l e v , V.S., der Wasserbioconosen. Arch. Hydrobiol., 25: 177-191. Korte, V.L. and B l i n n , D.W., 1983. Diatom c o l o n i z a t i o n on a r t i f i c i a l s u b s t r a t a i n pool and r i f f l e zones s t u d i e d by l i g h t and scanning e l e c t r o n microscopy. J. Phycol., 19: 332-341. Lamberti, G.A. and Resh, V.H., 1983. Stream p e r i p h y t o n and i n s e c t herbivores: an experimental study o f g r a z i n g by a c a d d i s f l y population. Ecology, 64: 1124-1135. 1977. Mathematical Ecology. John Wiley & Sons, I n c . New York. Pielou, E.C., 385 pp. Stevenson, R.J., 1981. Microphytobenthos accumulation and c u r r e n t . Ph.D. D i s s e r t a t i o n . The U n i v e r s i t y o f Michigan, Ann Arbor, Michigan, USA, 172 PP. Stevenson, R.J. 1983. E f f e c t s o f c u r r e n t and c o n d i t i o n s s i m u l a t i n g a u t o g e n i c a l l y changing m i c r o h a b i t a t s on b e n t h i c diatom immigration. Ecology, 64: 1514-1524. Stevenson, R.J., 1984. How c u r r e n t s on d i f f e r e n t sides o f s u b s t r a t e s i n streams a f f e c t mechanisms o f b e n t h i c a l g a l accumulation. I n t e r n a t . Revue ges. Hydrobiol 69: 241-262. Stevenson, R. J. , * ! i n press). Mathematical model o f e p i l i t h i c diatom accumulation. I n : M. R i c a r d ( E d i t o r ) , Proceedings o f t h e V I I I t h I n t e r n a t i o n a l Symposium o f Recent and F o s s i l Diatoms. Stevenson, R.J. and Stoermer, E.F., 1981. Q u a n t i t a t i v e d i f f e r e n c e s between b e n t h i c a l g a l communities along a depth g r a d i e n t i n Lake Michigan. J. Phycol., 17: 29-36. Sumner, W. T. and M c I n t i r e , C.D., 1982. Grazer-periphyton i n t e r a c t i o n s i n l a b o r a t o r y streams. Arch. Hydrobiol., 93: 135-157. Z a r , J.H., 1974. B i o s t a t i s t i c a l Analysis. P r e n t i c e - H a l l , I n c . Englewood C l i f f s , New Jersey, USA. 620 pp.

CHAPTER 15

RECENT INVESTIGATIONS INTO THE EFFECTS OF ALGAE ON CORROSION L.A.

TERRY'

and R.G.J.

1 Aberdeen

EDYVEAN

2

U n i v e r s i t y Marine S t u d i e s Ltd.

,

Department

Zoology, U n i v e r s i t y o f A b e r d e e n , T i l l y d r o n e Avenue

of

, ABERDEEN,

AB9 2TN, U . K . 2

Department

of

Metallurgy,

University of

Sheffield,

Mappin

S t r e e t , SHEFFIELD, S 1 3JD, U . K .

15.1.

INTRODUCTION The

the

development of

1970's

stimulated

e f f e c t s which

fouling

t h e North

interest

in

growing

on

Sea o i l

industry during in the

t h e U.K. fixed

offshore

P r i o r to

could have on t h e c o r r o s i o n o f t h e u n d e r l y i n g steel. t h i s most

interest

in biologically

possible

structures

i n d u c e d c o r r o s i o n had

c o n c e n t r a t e d o n m i c r o b i a l c o r r o s i o n o f b u r i e d p i p e l i n e s and i n a i r c r a f t f u e l systems. The e l e c t r o c h e m i c a l n a t u r e o f c o r r o s i o n is i l l u s t r a t e d T h e m e t a l c a n b e c o n s i d e r e d a s h a v i n g a n o d i c and

i n F i g u r e 1.

c a t h o d i c sites.

Metal

ions go

into solution

at

t h e anode,

e l e c t r o n s p a s s t h r o u g h t h e metal to t h e c a t h o d e and a c u r r e n t p a s s e s t o t h e c a t h o d e t h r o u g h t h e seawater e l e c t r o l y t e . form

of

a v a i l a b i 1i t y

the

.

cathodic

Water

reaction dissociates

depends and

upon

under

The

oxygen anaerobic

c o n d i t i o n s h y d r o g e n atoms a n d m o l e c u l a r h y d r o g e n a c c u m u l a t e t o polarize the

cathode thus preventing corrosion.

c a t h o d i c hydrogen

i s removed

If

this

c o r r o s i o n c o n t i n u e s and

c a t h o d e is s a i d to b e d e p o l a r i z e d .

the

Under a e r o b i c c o n d i t i o n s

h y d r o x y l i o n s are formed a n d t h e s e r e a c t w i t h t h e f e r r o u s i o n s f r o m t h e a n o d i c r e a c t i o n t o form c o r r o s i o n p r o d u c t s which c a n b e complex

in nature.

In a

freely corroding

system the

i n i t i a l c o r r o s i o n r a t e may b e h i g h b u t t h e r e s u l t i n g c o r r o s i o n products can

form a b a r r i e r p r e v e n t i n g

oxygen from r e a c h i n g

t h e metal s u r f a c e and so r e t a r d t h e c o r r o s i o n r a t e . Many f i x e d s t r u c t u r e s i n t h e N o r t h S e a h a v e a n t i c i p a t e d working l i v e s of

2 0 y e a r s o r more a n d t h e m e t h o d s u s e d

to

m a i n t a i n s t r u c t u r a l i n t e g r i t y o v e r s u c h a time p e r i o d a r e

21 2

ELECTROLYTE

H+

OH-

CATHODE

ELECTRON FLOW

CATHODE

............

ee-

OH-@

................

ANODE

1

H

ANODE

-

e-e-

Fe

@ OH-

I\

HYDROGEN ACCUMULATION (Cathodic p o l a r i z a t i o n )

CORROSION PRODUCTS

02+4e-+W20+40HOXYGEN CONCENTRATION

Can promote and m a i n t a i n the c a t h o d i c r e a c t i o n .

Fig. 15.1. The electrochemical corrosion reactions.

21 3

from t h o s e u s e d o n s h i p p i n g w h i c h

different

i n t o dry-dock with

f o r maintenance.

t h e p o s i t i o n on

1977; Hodgkiess, with

can be

The p r o t e c t i o n d e p l o y e d v a r i e s

structure (Bartlett,

the

brought

1977;

Ridler,

Above t h e w a t e r l i n e s t e e l i s c o a t e d

1978).

a n i n o r g a n i c z i n c p r i m e r o v e r l a i n by p a i n t s c o n t a i n i n g

corrosion

inhibitive

compounds.

The

splash-zone,

where

the

waters and g r e a t e s t

c o m b i n a t i o n o f water movement, o x y g e n - r i c h

hydrodynamic l o a d i n g p r e s e n t s a p a r t i c u l a r l y d i f f i c u l t r e g i o n

t o p r o t e c t , o f t e n h a s t h e added p r o t e c t i o n o f a s h e a t h i n g o f a c o r r o s i o n r e s t i s t a n t c o p p e r n i c k e l a l l o y s u c h a s Monel 400 o r Kunifer.

is p r o t e c t e d by a c a t h o d i c

The submerged p o r t i o n

p r o t e c t i o n s y s t e m , sometimes a u g m e n t e d b y a c o a l - t a r e p o x y o r chlorinated

rubber paint

system.

Two d i f f e r e n t c a t h o d i c

e i t h e r impressed c u r r e n t or s a c r i f i c i a l anode. Commonly u s e d s a c r i f i c i a l a n o d e m a t e r i a l s are zinc, aluminium and magnesium all of which are

p r o t e c t i o n s y s t e m s c a n be used:

s u b s t a n t i a l l y anodic to steel. which

results

engineered

in

the

system,

impressed current

steel

the

is f o r m e d

A galvanic cell

anode corroding w h i l s t , remains

in

a properly

intact.

system a d i r e c t c u r r e n t

With

the

is d r i v e n t h r o u g h

t h e s t r u c t u r e by a g e n e r a t o r w i t h a n i n e r t o r e x p e n d a b l e anode

remote f r o m t h e p l a t f o r m c o m p l e t i n g t h e c i r c u i t t h r o u g h a seawater e l e c t r o l y t e . A g a i n , t h e a i m is t o e n s u r e t h a t t h e s t e e l e f f e c t i v e l y becomes a c a t h o d e o v e r its e n t i r e s u r f a c e and is p r o t e c t e d from c o r r o s i o n . pH

Both s y s t e m s g e n e r a t e a h i g h

a t t h e metal s u r f a c e and t h i s promotes t h e d e p o s i t i o n o f

calcereous deposits of

c a l c i u m a n d magnesium c a r b o n a t e s ,

the

t h i c k n e s s of which is r e l a t e d t o c u r r e n t d e n s i t y and exposure

t i m e (Wolfson and Hartt, 1 9 8 1 ) . Anti-fouling

are

situation,

paints,

rarely

used

i n contrast to the shipping on

fixed

structures.

Their

i n f r e q u e n t use h a s been l i m i t e d t o l o c a l i s e d areas such as on s i g n s which a i d d i v e r s i n l o c a t i n g t h e i r p o s i t i o n on t h e strucure.

Consequently, e x t e n s i v e f o u l i n g communities develop

from t h e splash-zone

t o t h e sea-bed.

The f o u l i n g c o m m u n i t i e s

o n some N o r t h S e a s t r u c t u r e s h a v e b e e n d e s c r i b e d ( e . g . G o l d i e , 1981; et

Hardy,

al.,

1981; F o r t e a t h e t a l . ,

1983)

docummented

and

the

1982; 1983;

distibution

( T e r r y and P i c k e n ,

of

in press).

1984; Picken

algae

has

been

Algae h a v e b e e n

21 4

f o u n d t o a maximum d e p t h o f

-40m

on i n s t a l l a t i o n s i n t h e

c e n t r a l a n d n o r t h e r n N o r t h S e a a n d t o -5m i n t h e s o u t h e r n s e c t o r . The most w i d e s p r e a d a l g a e a r e E n t e r o m r p h a s p p . i n t h e splash-zone, ligulata,

Ulva

P.urceolata

Desmarestia v i r i d i s , Desmarestia p a r t i c u l a r l y P.brodiaei and

sp.,

Polysiphonia

spp.,

and i n t h e c e n t r a l and n o r t h e r n sectors L a m i n a r i a

d i g i t a t a and A l a r i a e s c u l e n t a . The e f f e c t s of f o u l i n g o n North Sea i n s t a l l a t i o n s have recently

been

reviewed

(Edyvean

et

al.,

1985a).

The

impairment of v i s u a l inspection is p a r t i c u l a r l y important around welds.

The

loading,

i s most

which

structure

where

increase

i n dynamic and hydrodynamic

noticable

algae

and

i n t h e upper

mussels

are

n e c e s s i t a t e c o s t l y cleaning f o r s a f e t y reasons. c o n c e n t r a t e s on t h e d i r e c t and

20m o f

dominant,

a

can

This paper

i n d i r e c t e f f e c t s which a l g a l

f o u l i n g c a n have on c o r r o s i o n and on c o r r o s i o n p r o t e c t i o n s y stens.

15.2.

DIRECT EFFECTS OF ALGAE ON CORROSION A l g a e may t h e m s e l v e s i n f l u e n c e c o r r o s i o n t h r o u g h t h e i r

m o d i f i c a t i o n o f t h e environment,

i.e.

the e l e c t r o l y t e , through

d i r e c t involvement i n t h e e l e c t r o c h e m i c a l c o r r o s i o n r e a c t i o n s

or

through

an

i n f l u e n c e on mechanically

A l t h o u g h some o f a c t i o n of

these effects

bacteria

they

are

linked

induced

corrosion.

closely with

the

are d i s c u s s e d h e r e under d i r e c t

effects. 15.2.1.

Modification of t h e environment A l g a e c a n m o d i f y t h e l o c a l e n v i r o n m e n t o f t h e s t e e l by

i n f l u e n c i n g o x y g e n c o n c e n t r a t i o n , c h a n g i n g t h e pH a n d t h r o u g h t h e p r o d u c t i o n o f m e t a b o l i t e s w h i c h c r e a t e a more a g g r e s s i v e electrolyte.

The

basic

electrochemical nature of

corrosion

s u g g e s t s t h a t a r e d u c t i o n i n t h e oxygen c o n c e n t r a t i o n would r e d u c e t h e c a t h o d i c r e a c t i o n r a t e a nd l e a d t o a r e d u c t i o n i n corrosion.

The p r e s e n c e o f

a n a l g a e f o u l i n g cover might

be

e x p e c t e d t o produce such a r e d u c t i o n i n t h e local oxygen c o n c e n t r a t i o n a n d s t u d i e s u s i n g steel p a n e l s immersed a t

s i t e s h a v e shown t h a t , i n i t i a l l y , c o r r o s i o n r a t e s were r e d u c e d b y f o u l i n g , w i t h a t h i n c o v e r o f E n t e r o m o r p h a s p .

offshore

21 5

a particularly effective barrier

providing

(Bultman e t a l .

,

1977).

Once t h e c o n d i t i o n s u n d e r s u c h f o u l i n g a l t e r e d so t h a t

oxygen

was

excluded

an d

sulphate-reducing

bacteria

(SRB)

became a c t i v e t h e n t h e b e n e f i c i a l e f f e c t s o f t h e f o u l i n g c o v e r were

l o s t a s SRB m e d i a t e d c o r r o s i o n d o m i n a t e d .

Polarization

studies, ( E d y v e a n an d T e r r y , 1 9 8 3 b ) , h a v e shown a n o d i c p o l a r i z a t i o n ( i . e . r e d u c t i o n i n c o r r o s i o n ) o f 50D s t e e l u n d e r c u l t u r e s of

b o t h Enteromorpha

sp.

and a primary

film of

b a c t e r i a a n d d i a t o m s t h u s s u p p o r t i n g t h e i d e a t h a t u n d e r some c o n d i t i o n s a f o u l i n g c o v e r may b e b e n e f i c i a l . Algae,

especially microalgae,

produce

c o p i o u s amounts

m u c i l a g e and release o r g a n i c compounds

i n t o seawater. seawater c o n t a i n i n g biologically derived components p r o d u c e s very d i f f e r e n t s u r f a c e f i l m s and c o r r o s i o n p r o d u c t s on metal s u r f a c e s t h a n of

Recent

has

work

shown

that

natural

d o e s a r t i f i c i a l seawater w i t h o u t o r g a n i c components. u s i n g a 9 0 / 10

cupro-nickel

a l l o y (Castle et al.,

A

study

1 9 8 3 ) found

v e r y d i f f e r e n t s u r f a c e f i l m s o n t h e metal i n n a t u r a l seawater containing

organic

co mp o u n d s

derived

from

bacteria

and

m i c r o a l g a e t h a n o n metal e x p o s e d t o s o d i u m c h l o r i d e s o l u t i o n . The p r e s e n c e o f t h e o r g a n i c f i l m r e n d e r e d t h e metal l i a b l e t o a loss o f c a t h o d i c i n h i b i t i o n and t h e release o f a g g r e s s i v e p r o d u c t s i n t h e a b s e n c e o f oxygen. L a b o r a t o r y s t u d i e s h a v e s h o w n t h a t t h e mode o f a t t a c h m e n t o f d i a t o m s c a n a f f e c t c o r r o s i o n (McDonnell e t a l . , 1984).

S t e e l o n t o w h i c h A c h n a n t h e s d i a t o m s were a t t a c h e d by

m e a n s o f a s t a l k were f r e e l y c o r r o d i n g a f t e r t w o w e e k s i n c u l t u r e w h e r e a s s p e c i m e n s w i t h Amphora a t t a c h e d c l o s e t o t h e s u r f a c e p r o d u c e d l i t t l e loose c o r r o s i o n p r o d u c t s . Attachment i n t h i s c a s e was e f f e c t e d b y m e a n s o f a m u c i l a g e p a d o v e r t h e s u r f a c e of t h e diatom.

S u c h a mode o f a t t a c h m e n t w ould h a v e

b r o u g h t a b o u t a greater r e d u c t i o n i n oxygen c o n c e n t r a t i o n a t the metal surface Subsequent s t u d i e s , 1985),

have

Polarization

than wo u l d attachment (E.A.McDonnel1, personal

further

confirmed

experiments have

the

shown

role

by a stalk. communication, of

mucilage.

t h e diatom Nitzchia

to

(i.e. reduction i n t h a n t h e diatoms Nitzchia did not N a v i c u l a , C o c c o n e i s , Amphora o r A c h n a n t h e s .

produce

greater

cathodic

c o r r o s i o n compared attach

polarization

w i t h c o n t r o l specimens)

t o t h e s t e e l b u t moved

across t h e s u r f a c e s p r e a d i n g

21 6

F i g . 15.2.

S.E.M. showing c o r r o s i o n p r o d u c t s on u n p r o t e c t e d m i l d s t e e l exposed t o flowing s e a w a t e r f o r 105 d a y s and c o v e r e d by a m u c i l a g e bound mat o f f i l a m e n t o u s Reproduced b l u e - g r e e n a l g a e and a p e n n a t e d i a t o m . w i t h p e r m i s s i o n f r o m T e r r y , L.A. a n d Edyvean, R . G . J . 1981. B o t a n i c a M a r i n a , 24: 177-183.

m u c i l a g e . C a t h o d i c d e p o l a r i z a t i o n was o b s e r v e d w i t h A c h n a n t h e s s u g g e s t i n g t h a t its i r r e g u l a r covering of t h e s u r f a c e w a s enhancing corrosion.

Figure

2 shows a c o v e r o f

a l g a e and d i a t o m s on u n p r o t e c t e d s t e e l . produced

by

blue-green

The r o l e o f m u c i l a g e

t h e a l g a e i n c o v e r i n g and c o n s o l i d a t i n g t h e

underlying c o r r o s i o n p r o d u c t s can be seen. Over t h e

normal r a n g e o f

pH v a l u e s e n c o u n t e r e d

in

s e a w a t e r t h e a v a i l a b i l i t y of oxygen h a s a g r e a t e r i n f l u e n c e on c o r r o s i o n t h a n d o a n y c h a n g e s i n t h e pH p e r se (LaQue, 1 9 7 5 ) . I n d e c a y i n g a l g a l c u l t u r e s , however, pH v a l u e s a s low a s pH 1 . 8 h a v e b e e n r e c o r d e d (Edyvean a n d T e r r y , 1 9 8 3 a ) . I f s u c h l o w v a l u e s were f o u n d o f f s h o r e t h e c o u l d be e x p e c t e d t o accelerate

21 7

c o r r o s i o n a n d / o r a l t e r any n a t u r a l p a s s i v a t i o n of t h e metal or d i s r u p t p r o t e c t i v e c a r b o n a t e scales. Local d i f f e r e n c e s i n pH may g i v e r i s e t o l o c a l c o n c e n t r a t i o n c e l l s ( s e e b e l o w ) . 15.2.2.

E f f e c t s o f a l g a e on e l e c t r o c h e m i c a l c o r r o s i o n D i f f e r e n t i a l concentration cells

15.2.2.1.

D i f f e r e n t i a l a e r a t i o n cells are widespread forms of corrosion offshore. formed under macro-fouling. by

all

types fouling, bacteria, diatoms and A d i f f e r e n t i a l a e r a t i o n c e l l is b r o u g h t a b o u t

lower

the

p r o b a b l y t h e most S u c h c e l l s may b e

concentration

of

oxygen

under

the

fouling

c o m p a r e d w i t h a d j a c e n t u n f o u l e d o r more l i g h t l y f o u l e d a r e a s . T h e a r e a u n d e r t h e f o u l i n g b eco mes a n o d i c t o t h e s u r r o u n d i n g , c a t h o d i c areas where t h e h i g h e r oxygen c o n c e n t r a t i o n promotes t h e aerobic cathodic reaction.

The e n d r e s u l t is a c c e l e r a t e d

corrosion under t h e fouling.

m e t a l i o n a n d pH T h e pH c o n c e n t r a t i o n c e l l s , o p e r a t e i n a s i m i l a r manner. algal fouling varies due to the photosynthetic under Other

activities. recorded blue-green

concentration

cells,

D a i l y pH c h a n g e s o f u p t o 2 u n i t s h a v e b e e n

under

cultures of

Enteromorpha

sp.,

a

filamentous

a l g a and c o l o n i a l d i a t o m s ( T e r r y and Edyvean, 1981;

1984; Edyvean a n d T e r r y , 1 9 8 3 a ) . Algal photosynthesis can p u s h pH v a l u e s a b o v e pH 1 0 ( T e r r y a n d E d y v e a n , 1 9 8 1 ) w h e r e a s u n d e r d e c a y i n g a l g a e t h e pH v a l u e s f a l l w e l l b e l o w t h a t of t h e a m b i e n t s e a w a t e r . T h e p o t e n t i a l f o r t h e c r e a t i o n o f l o c a l pH c o n c e n t r a t i o n c e l l s e x i s t s a l t h o u g h t h e r e is no d i r e c t evidence confirming the operation of

s u c h a mechanism o n

offshore structures. 15.2.2.2.

P i t t i n g corrosion (Active-passive cells)

T h i s i s a l o c a l i s e d c o r r o s i o n b r o u g h t a b o u t by t h e b r e a k d o w n of

natural

p a s s i v i t y or by t h e p r e v e n t i o n o f

the

formation of passive films. D i f f e r e n t i a l aeration, reducing t h e oxygen a t t h e metal s u r f a c e , c a n c a u s e c o n s i d e r a b l e p i t t i n g corrosion on a l l o y s ,

s u c h as s t a i n l e s s s t e e l , which

r e l y on passive films for t h e i r corrosion resistance.

There

i s a l a r g e b o d y of wo r k d e s c r i b i n g t h e e f f e c t s of seawater o n the

corrosion of

various

s t a i n l e s s steels

and o t h e r a l l o y s

21 8 (e.g.

c o p p e r n i c k e l a n d o t h e r copper a l l o y s ) .

work

on the

e f f e c t s of

c o r r o s i o n and p i t t i n g

of

T h e r e is some

d i f f e r e n t i a l aeration on crevice s t a i n l e s s steel

(e.g.

Krougman a n d

I j s s e u n g , 1 9 8 4 ) i n c l u d i n g t h e a c t i o n o f b a c t e r i a ( e . g . Mollica e t a l . , 1 9 8 4 ) b u t t h e r e are no d e t a i l s o f a n y a l g a l e f f e c t s . P i t t i n g c o r r o s i o n h a s been found o f f s h o r e and p i t s are known t o o c c u r u n d e r b a r n a c l e s ( P i p e , 1 9 8 1 ) . sulphides

i n c r e a s e s p i t t i n g and

sulphides

during

their

The p r e s e n c e o f

h e n c e SRB w h i c h p r o d u c e

metabolism

can

enhance

pitting

A FeS l a t t i c e i s f o r m e d o n t h e s t e e l a n d h y d r o g e n

corrosion.

formed d u r i n g t h e a n a e r o b i c c a t h o d i c r e a c t i o n is bonded w i t h i n t h i s lattice thus reducing corrosion. are

generated

corrosion

When f u r t h e r s u l p h i d e s

increases

and

SRB

preferentially

remove t h e h y d r o g e n f r o m t h e s u l p h i d e l a t t i c e r a t h e r t h a n f r o m t h e s t e e l and b r i n g a b o u t i n c r e a s e d c a t h o d i c d e p o l a r i z a t i o n by i n c r e a s i n g t h i s rate l i m i t i n g s t e p of

the corrosion reaction

(Sanders, 1984). 15.2.3.

Mechanically induced c o r r o s i o n

15.2.3.1.

Hydrogen e m b r i t t l e m e n t

This reaction.

form of

corrosion

also

involves the

cathodic

A t o m i c hydrogen generated i n t h e c a t h o d i c r e a c t i o n

steel r e s u l t i n g

penetrates the

in

the

loss o f

ductility.

A

number of d e t a i l e d mechanisms have been p o s t u l a t e d t o a c c o u n t f o r t h e e m b r i t t l e m e n t e f f e c t ( H i n t h and J o h n s o n , 1 9 7 6 ) which, when combined w i t h t h e p r e s e n c e of

l o c a l r e g i o n s of h i g h

stress, c a n r e s u l t i n s e v e r e c r a c k i n g of t h e metal (see below). Hydrogen e m b r i t t l e m e n t is e n h a n c e d by t h e h i g h l e v e l s o f h y d r o g e n w h i c h c a n b e g e n e r a t e d b y SRB u n d e r c e r t a i n

is g e n e r a t e d by t h e o v e r - p r o t e c t i o n

c o n d i t i o n s and which

c a t h o d i c p r o t e c t i o n s y s t e m s (Gooch,

1984).

If

by

t h e l e v e l s of

c a t h o d i c p r o t e c t i o n a r e i n c r e a s e d too h i g h i n o r d e r t o combat SRB c o r r o s i o n t h e r e may b e e n h a n c e d .

is a danger t h a t hydrogen embrittlement

T h e p r e s e n c e of H2S, w h i c h c a n be p r o d u c e d

by SRB, i s known t o r e t a r d t h e f o r m a t i o n of m o l e c u l a r h y d r o g e n on t h e metal s u r f a c e and t o enhance t h e pick-up h y d r o g e n by t h e m e t a l .

o f atomic

Whenever a l g a e p r o v i d e c o n d i t i o n s f o r

SRB t h e y may c o n s e q u e n t l y e n h a n c e h y d r o g e n e m b r i t t l e m e n t . evolution of

h y d r o g e n by

t h e a l g a e t h e m s e l v e s would

Any

also

219

A l t h o u g h some w o r k h a s b e e n

a f f e c t hydrogen embrittlement. carried

(e.9.

out

Healey,

1970)

the

possibilty

of

this

o c c u r r i n g h a s n o t been f u l l y i n v e s t i g a t e d . 15.2.3.2.

Corrosion fatigue

i s a form o f d e t e r i o r a t i o n i n v o l v i n g t h e i n i t i a t i o n and s u b s e q u e n t slow g r o w t h o f cracks u n d e r t h e The p r e s e n c e of a c o r r o s i v e i n f l u e n c e o f c y c l i c stress. Fatigue

environment, s u c h a s seawater, usually causes an acceleration and

crack-propagation

rates

O f f s h o r e stresses c a n a r i s e high

frequency

machinary

c o n t a i n i n g hydrogen sulphide i n both the crack-initiation producing

corrosion

from hydrodynamic

v i b r a t i o n s and

from

fatigue.

loading,

low

from

frequency

t r a n s i e n t stresses g e n e r a t e d b y wind a n d c a r g o movement. Algae c a n c o n t i b u t e d i r e c t l y t o t h e f i r s t o f t h e s e stresses hydrodynamic

loading.

Until

recently

very

l i t t l e work

-

has

b e e n c a r r i e d o u t on t h i s e f f e c t of s o f t f o u l i n g on o f f s h o r e structures. Th e e f f e c t o f 1 0 0 % c o v e r o f k e l p s o n t h e i n e r t i a h a s b e e n shown t o b e n e a r l y d o u b l e t h a t o f a 1 0 0 %

co-efficient mussel

cover

Theophantos, contribute thought.

in

laboratory

experiments

(Wolfram

a nd

1 9 8 5 ) a n d i t i s r e c o g n i s e d t h a t s o f t g r o w t h s may more t o h y d r o d y n a m i c l o a d i n g t h a n p r e v i o u s 1 y

M e t a b o l i t e s , s u c h a s H2S, h a v e l o n g b e e n r e c o g n i s e d t o enhance c r a c k growth r a t e s d u e t o hydrogen e m b r i t t l e m e n t and u s u a l l y H2S is a d d e d t o s e a w a t e r i n l a b o r a t o r y t e s t s o n c r a c k growth rates.

R e c e n t l y , wo r k u s i n g b i o g e n i c H 2 S d e r i v e d f r o m

a d e c a y i n g Enteromorpha s p .

c u l t u r e (Edyvean e t a l . ,

1985b;

Thomas e t a l . , 1 9 8 6 ) s u g g e s t e d t h a t t h e r e i s a t h r e s h o l d l e v e l f o r s u c h e n h a n c e m e n t a s s i m i l a r r a t e s were p r o d u c e d f r o m l e v e l s o f 600ppm b i o g e n i c H2S a s were p r o d u c e d w i t h s e a w a t e r s a t u r a t e d w i t h 3100ppm H 2 S .

15.3.

INDIRECT EFFECTS OF ALGAE ON CORROSION Even a t h i n a l g a l c o v e r may p r o v i d e c o n d i t i o n s e n a b l i n g

b a c t e r i a l g r o w t h . Th e c o r r o s i o n p r o c e s s c a n b e a f f e c t e d b y t h e a c t i v i t i e s o f some b a c t e r i a , b o t h a e r o b e s a n d a n e a r o b e s .

220 15.3.1.

Aerobic b a c t e r i a Two g r o u p s

The

of

aerobic

sulphur-oxidising

bacteria

bacteria,

can a f f e c t

Thiobacilli

spp.,

i n o r g a n i c s u l p h u r and produce s u l p h u r i c a c i d , w h i c h is c o r r o s i v e t o s t e e l .

,

Pseudomonas s p .

corrosion. oxidise

( I v e r s o n , 19721,

The n i t r a t e - r e d u c i n g

bacterium,

h a s b e e n shown e x p e r i m e n t a l l y t o b r i n g a b o u t

anodic depolarization (an increase i n the anodic reaction) of F e r r i c compounds m i l d s t e e l (Obuekwe e t a l . , 1 9 8 1 a ; 1 9 8 1 b ) . were r e d u c e d t o f e r r o u s o n e s e i t h e r r e m o v i n g o r p r e v e n t i n g t h e f o r m a t i o n of p r o t e c t i v e f e r r i c coatings. A s i m i l a r mechanism was s u g g e s t e d t o a c c o u n t f o r t h e a n o d i c d e p o l a r i z a t i o n o f 50D steel observed with cultures of the blue-green alga

Oscillatoria

sp.

(Edyvean and

Terry,

1983b).

Although

the

c h e m i s t r y i n v o l v e d i n s u c h r e a c t i o n s h a s b e e n docummented ( e . g . C r a g n o l i n o and Touvinen, 19841, t h e e x t e n t t o which t h e y are a n i n f l u e n c e o f f s h o r e h a s n o t been d e t e r m i n e d . 15.3.2.

Anaerobic b a c t e r i a

role o f

The

the

sulphate-reducing

bacteria

c o n s i d e r a b l e a t t e n t i o n as t h e y a r e known

received

many o f f s h o r e o p e r a t i o n s ( S a n d e r s ,

(SRB) h a s to affect

Although t h e y are

1984).

p r e s e n t i n a e r a t e d s e a w a t e r a t low l e v e l s a n d may b e f o u n d i n t h e primary film within active

only

under

2 t o 20 d a y ' s e x p o s u r e ,

anaerobic

conditions

they are

(Sanders,

1983;

Hamilton and S a n d e r s , 1 9 8 4 ) . T h e c l a s s i c a l t h e o r y o f SRB-mediated of

cathodic depolarization

Vlugt,

1934).

SRB

c o r r o s i o n is t h a t

( v o n Wolzogen Kuhr and van d e r

stimulate

the

normal

c o r r o s i o n m e c h a n i s m s by t h e r e m o v a l o f

electrochemical

t h e hydrogen produced

i n t h e a n a e r o b i c c a t h o d i c r e a c t i o n and t h e f o r m a t i o n of a corrosion

t o steel. h o w e v e r , d o u b t s h a v e b e e n e x p r e s s e d a s ,to how t h e

product,

Recently,

FeS,

which

is

itself

cathodic

c a t h o d i c d e p o l a r i z a t i o n mechanism c a n w o r k discussion recognition

see has

Cragnolino been g i v e n

and

Touvinen,

to the

in

practice

1984)

role o f

the

and

(for

more

products,

p a r t i c u l a r l y F e S , a n d H2S w h i c h a r e p r o d u c e d d u r i n g b a c t e r i a l metabolism.

act

Iron sulphides, although cathodic to iron, cannot

a s permanent

SRB b r i n g s

fresh

c a t h o d e s b u t t h e i r c o n t i n u e d p r o d u c t i o n by

steel and P o l a r i z a t i o n s t u d i e s h a v e shown t h a t

sulphides into contact with

promotes corrosion.

the

221 bacterial

activity

bring

about

both

steel

with

the

i n decaying anodic

and

cultures of

Enteromorpha can

cathodic depolarization

conclusion

that

both

the

of

ulilization

50D of

c a t h o d i c hydrogen and t h e a c t i o n of b i o g e n i c s u l p h i d e s c a n be involved

(Edyvean and T e r r y ,

involved,

whenever

algae

W h a t e v e r m e c h a n i s m is

1983b). provide

micro-environments

for

b a c t e r i a l c o r r o s i o n they can enhance c o r r o s i o n i n d i r e c t l y . The

hydrogenase

enzyme

to

SRB

and

nodosum,

been

found

in

responsible

for

lactuca,

Ascophyllum

P o r p h y r i d i u m c r e u e n t u m a n d some

Porphyra umbicalis,

blue-green

15.4.

has

is

system

T h i s enzyme is n o t r e s t r i c t e d

c a t h o d i c d e p o l a r i z a t i o n b y SRB.

a l g a e ( F r e n k e l and R i e g e r , 1 9 5 1 ) .

EFFECTS O F ALGAE ON CORROSION PROTECTION SYSTEMS

15.4.1.

Disruption of c o a t i n g s Although

applications, protection.

antifouling coal-tar

coatings

have

little

are used

epoxy p a i n t s

offshore

for

corrosion

Algal r h i z o i d s can p e n e t r a t e weaknesses

c o a t i n g s and

the

removal of

i n such

f o u l i n g may a c c e n t u a t e t h i s .

U n p r o t e c t e d s t e e l may d e v e l o p n a t u r a l p a s s i v a t i n g f i l m s .

The

r e m o v a l o f f o u l i n g c a n d i s r u p t s u c h f i l m s a n d h a s b e e n known

t o r e s u l t i n t h e removal o f metal ( F o r t e a t h e t a l . , 15.4.2.

1984).

I n t e r a c t i o n with cathodic protection systems settle readily

Algae

(see Figure 3 ) .

on

cathodically

protected

steel

Both i m p r e s s e d c u r r e n t and s a c r i f i c i a l anode

cathodic protection

systems generate a p r o t e c t i v e calcareous

s c a l e a t t h e metal s u r f a c e .

The p r o p e r t i e s o f t h i s s c a l e a r e

i n f l u e n c e d by s e v e r a l f a c t o r s i n c l u d i n g t h e b u l k seawater chemistry, organics

particularly

present,

local

the

oxygen

profiles

concentration

(e.g.

pH)

of

the

and

the

seawater

a d j a c e n t t o t h e m e t a l s u r f a c e , t e m p e r a t u r e and c u r r e n t d e n s i t y (Hartt et al.,

1984).

The h i g h pH g e n e r a t e d by a l g a e d u r i n g

p h o t o s y n t h e s i s may e n h a n c e s c a l e f o r m a t i o n ( E d y v e a n a n d T e r r y , 1983a).

F o u l i n g c a n become e n t r a p p e d i n t h e s c a l e w h i c h

continues

to

be

deposited

around

the

organisms

and

the

p r e s e n c e o f s u c h f o u l i n g may a l t e r t h e p r o p e r t i e s o f t h e s c a l e (Edyvean,

1984).

Removal

of

embedded

fouling

can

result

in

222

Fig.

15.3.

S.E.M. showing a d e n s e c o v e r i n g o f d i a t o m s and blue-green algae on cathodically protected , u n p a i n t e d s t e e l a f t e r 100 d a y s immersion i n f l o w i n g seawater. F r o m E d y v e a n , R.G.J. a n d T e r r y , L.A. 1983. In: B i o d e t e r i o r a t i o n 5 , O x l e y , T.A. and B a r r y , S. ( e d s . ) . Reproduced by p e r m i s s i o n o f J o h n Wiley and S o n s L t d .

damage t o t h e s c a l e and c a n e x p o s e s t e e l which becomes a n o d i c t o t h e s c a l e - p r o t e c t e d s t e e l ( T e r r y and Edyvean, 1 9 8 4 ) . The possibility

of

l o c a l i s e d c o r r o s i o n is t h e r e f o r e enhanced

t h e c a t h o d i c p r o t e c t i o n i s s h u t down, d e s i g n e d t o cope with

the

if

if

i t has not been

i n c r e a s e d c u r r e n t demand a t s u c h

l o c a t i o n s o f exposed steel or i f t h e p r e - e x i s t i n g a d j a c e n t f o u l i n g organisms i n t e r f e r e with t h e cathodic process.

223

UNPROTECTED AND INTERMITTENTLY PROTECTED STEEL

1 Uniform a l g a l c o v e r

b-.

2 Aerobic b a c t e r i a

--)I

Limited p r o t e c t i o n

+2

Provides corrosive environment 6

generate acids

r e d u c e s (021

3 Cathodic A

depolarisation

+4

Pitting corrosion

3 Anaerobic pockets SRB

4 Macro- 6 m i c r o - a l g a e

b-~

c h a n g e s in 5 Trapped water

+ [Q],

pH 6

i o n i c balance

-4

+5

Differential aeration cell

+6

Corrosive electrolyte

7 D i s r u p t i o n of

6 Removal of f o u l i n g 3

+

protective oxide films

Fig. 15.4.

I n t e r a c t i o n s b e t w e e n a l g a e and c o r r o s i o n w h i c h c a n o c c u r on u n p r o t e c t e d and i n t e r m i t t e n t l y p r o t e c t e d steel.

224

PROTECTED AND UNPROTECTED STEEL

1 Removal of

1 Removal of A metal

\2

2 Drag by

macro-algae

3 Bacteria i n decaying a l g a l

Corrosion fatigue

-

+3

Hydrogen embr i t t lemen t

turf

Fig- 15.5.

I n t e r a c t i o n s between a l g a e and c o r r o s i o n which c a n o c c u r o n b o t h p r o t e c t e d and u n p r o t e c t e d s t e e l .

225

1 5 . 5 THE EXTENT OF CORROSION ON OFFSHORE INSTALLATIONS The e x t e n t t o w h i c h f o u l i n g is a p r o b l e m o f f s h o r e

is

n o t e a s y t o assess s i n c e i f a l l t h e p r o t e c t i o n systems work p r o p e r l y c o r r o s i o n should n o t happen a t a l l . despite

some i n i t i a l

problems

on c e r t a i n

Generally,

structures

(e.g.

Tischuck, 1984) , c o r r o s i o n p r o t e c t i o n s y s t e m s have performed w e l l i n t h e North Sea. An i m p r e s s e d c u r r e n t s y s t e m , h o w e v e r , may n o t b e i n s t a l l e d u n t i l s e v e r a l m o n t h s a f t e r t h e p l a t f o r m and

both

cathodic

protection

modification a f t e r installation.

systems

often

require

During p e r i o d s of i n a d e q u a t e

p r o t e c t i o n s t r u c t u r a l steel is v u l n e r a b l e t o g e n e r a l c o r r o s i o n and t h e b i o l o g i c a l l y

induced c o r r o s i o n d e p i c t e d i n Figures 4

a n d 5. Some m i n o r s t r u c t u r a l f a i l u r e s h a v e b e e n r e p o r t e d ( S k r e b o w s k i , 1 9 7 8 ; V e n n e t t , 1 9 7 9 ) o f risers w h i c h c a r r y h o t

o i l from t h e seabed t o t h e p l a t f o r m and v u l n e r a b l e areas s u c h as w e l d s r e q u i r e f r e q u e n t s t r u c t u r a l i n t e g r i t y m o n i t o r i n g . Corrosion p r o d u c t s have been found i n samples o f marine growth collected offshore f o r onshore analysis (Forteath et al., 1 9 8 4 ) a n d SRB c o r r o s i o n c a n a f f e c t a v a r i e t y o f o f f s h o r e o p e r a t i o n s i n a d d i t i o n t o e f f e c t s on t h e s t r u c t u r a l i n t e g r i t y of i n s t a l l a t i o n s (Sanders, 1984).

1 5 . 6 SUMMARY OF ALGAL/CORROSION INTERACTIONS A n u mb er o f a l g a l / c o r r o s i o n s c e n a r i o s c a n b e f o r m u l a t e d

f o r d i f f e r e n t s i t u a t i o n s depending on t h e t y p e of protection adopted. a n d 6.

corrosion

T h e s e s c e n a r i o s a r e shown i n F i g u r e s 4 , 5

These i n t e r a c t i o n s have been d e r i v e d l a r g e l y from

l a b o r a t o r y s t u d i e s and t h e o r e t i c a l c o n s i d e r a t i o n s s i n c e d i r e c t

are l i m i t e d . Some o f the i n t e r a c t i o n s a r e known t o d e p e n d u p o n b a c t e r i a l a c t i v i t y a n d it i s n o t clear to what e x t e n t a l g a e c o n t r i b u t e to processes such as p i t t i n g c o r r o s i o n i n t h e a b s e n c e o f b a c t e r i a .

observations

from

offshore

226

PROTECTED STEEL

1 Breaks down

1 P r e s e n c e of

protective

algae

c o a t i ngs

2 Disruption /

2 Algae embedded i n calcereous

a l t e r a t i o n of

scale

Fig.

15.6.

scale

I n t e r a c t i o n s between algae and c o r r o s i o n which c a n o c c u r on p r o t e c t e d steel.

15.7 ACKNOWLEDGEMENTS

R.G.J.E. Fellowship

of

is t h e the

current holder of

Royal

Society

Metallurgy, Sheff ield University.

at

L.A.

t h e Sorby Research the

Department

of

Terry wishes t o thank

t h e Royal S o c i e t y f o r a t r a v e l g r a n t t o a t t e n d t h e 3 6 t h Annual AIBS M e e t i n g i n G a i n e s v i l l e .

227

15.8 REFERENCES Bartlett, A., 1977. Marine corrosion. Dock and Harbour Authority, 58: 154-157. Bultman, J.D., Southwell, C.R. and Hummer, C.W. 1977. Biocorrosion of structural steels in seawater. Reviews in Coatings and Corrosion, 2 : 187-214. Castle, J.E., Parvisi, M.S. and Chamberlain, A.H.L. 1983. Interaction of marine biofouling and corrosion on copper based alloys. In: Microbial Corrosion Book 303. The Metals Society, London, pp. 36-45. 1984. The role of Cragnolino, G. and Tuovinen, O . H . , sulphate-reducing and sulphur-oxidizing bacteria in the localised corrosion of iron-base alloys - a review. International Biodeterioration, 20: 9-27. Edyvean, R.G.J., 1984. Interactions between microfouling and the calcareous deposit formed on cathodically protected steel in seawater. In: Proceedings of the 6th International Congress on Marine Corrosion and Fouling Marine Biology, Athens, pp. 469-483. Edyvean, R.G.J. and Terry, L.A., 1983a. The influence of micro-algae on the corrosion of structural steels used in the North Sea. In: T.A. Oxley and S. Barry (Editors), Biodeterioration 5, John Wiley and Sons, pp.336-347. Edyvean, R.G.J. and Terry, L.A. , 1983b. Polarization studies of 50D steel in cultures of marine algae. International Biodeterioration Bulletin, 19: 1-11. Edyvean, R.G.J., Terry, L.A. and Picken, G.B., 1985a. Marine fouling and its effects on offshore structures in the North International Biodeterioration, 21: Sea - A review. 277-284. Edyvean, R.G.J., Thomas, C.J., Brook, R. and Austin, I.M. 1985b. The use of biologically active environments for testing corrosion fatigue properties of offshore structural steels. Paper presented at the International Conference on Biologically Induced Corrosion (NACE), Washington, June 1985 and to be published in the Proceedings. Forteath, G.N.R., Picken, G.B., Ralph, R. and Williams, J. 1982. Marine growth studies on the North Sea oil platform Montrose Alpha. Marine Ecology Progress Series, 8: 61-68. Forteath, G.N.R., Picken, G.B. and Ralph, R. 1983. Interaction and competition for space between fouling organisms on the Beatrice oil platform in the Moray Firth, North Sea. International Biodeterioration Bulletin, 19: 45-52. Forteath, G.N.R., Picken, G.B. and Ralph, R. 1984. Patterns of macrofouling on steel platforms in the central and northern North Sea. In J.R.Lewis and A.D. Mercer (Editors), Corrosion and Marine Growth on Offshore Structures. Ellis Horwood, Chichester, pp. 10-22. Frenkel, A.W. and Rieger, C. 1951. Photoreduction in algae. Nature, 167: 1030. Goldie, B.P.F. 1981. Assessment of marine fouling on gas platform 'I WE " In: Marine Fouling of Offshore Platforms Vol 11, Society for Underwater Technology, London, 19-20 May.

.

228

Gooch, T.G. 1984. Cathodic protection and steel properties. In: J.R. Lewis and A.D. Mercer (Editors), Corrosion and Marine Growth on Offshore Structures. Ellis Horwood, Chichester , pp 81-94. Hamilton, W.A. and Sanders, P.F. 19,84. Sulphate-reducing bacteria and anaerobic corrosion. In: J.R. Lewis and A.D. Mercer (Editors), Corrosion and Marine Growth on Offshore Structures. Ellis Horwood, Chichester, pp.23-30. Hardy, F.G. 1981. Fouling on North Sea platforms. Botanica Marina, 24: 173-176. Hartt, W.H., Culberson, C.H. and Smith, S.W. 1984. Calcareous deposits on metal surfaces in seawater - a critical review. Corrosion, 40: 609-618. Healey, S.P. 1970. Hydrogen evolution by several algae. Planta, 91: 220-226. Hinth, J.P. and Johnson, H.H. 1976. Hydrogen problems in energy related technology. Corrosion, 32: 3-25. Hodgkeiss, T. 1978. The effects of seawater on the integrity of offshore structures. Proceedings of the Royal Society of Edinburgh, 76 (B): 95-114. Iverson, W.P. 1972. Biological corrosion. In: M.G. Fontana and R.W. Staehle (Editors), Advances in Corrosion Science and Technology, Plenum Press, New York, V o l . 2: 1-42. Krougman, J.M. and Ijsseung, F.P. 1984. Crevice corrosion testing of stainless alloys in seawater. In: Proceedings of the 6th International Congress on Marine Corrosion and Fouling - Marine Corrosion, Athens, pp.75-96. LaQue, F.L. 1975. Marine Corrosion. John Wiley and Sons, New York, London, Sydney and Toronto, 332p. McDonnell, E.A., Mulder, J., Hodgkiess, T. and Boney, A.D. 1984. Some corrosion effects of marine micro-organisms. I n : U.K. Corrosion 1984. The international exhibition and conference of the Institution of Corrosion Science and Technology and Corrosion Control Engineering joint venture with NACE. 12-14th November 1984, Wembley, London. Mollica, A., Trevis, A., Traverso, E . , Ventura, G., Scotto, V., Alabiso, G., Marcenaro, G., Montini, U., De Carlos, G. and Dellepiane, R. 1984. Interaction between biofouling and oxygen reduction rate on stainless steel in seawater. In: Proceedings of the 6th International Congress on Marine - Marine Corrosion, Athens, Corrosion and Fouling pp.269-281. Obuekwe, C.0 , Westlake, D.W.S., Plambeck, J.A. and Cook, F.D. 1981a. Corrosion of mild steel in cultures of ferric iron reducing bacterium isolated from crude oil. 1. Polarization characteristics. Corrosion, 37: 461-467. Obuewke, C.O., Westlake, D.W.S., Plambeck,.J.A. and Cook, F.D. 1981b. Corrosion of mild steel in cultures of ferric iron reducing bcterium isolated from crude oil. 11. Mechanism of anodic depolarization. Corrosion, 37: 632-638. Picken, G.B., Forteath, G.N.R., Ralph, R. and Swain, G. 1983. Fouling below lOOm on the European Continental Shelf. In: Progress in Underwater Technology, Proceedings of the Subsea Challenge Conference, Amsterdam. Society for Underwater Technology, London. Paper C14. Pipe, A. 1981. North Sea fouling organisms and their potential effects on the corrosion of North Sea structures. In: Marine Corrosion on Offshore Structures. Society of Chemical Industry, London.

229

Ridler, K. 1977. Protecting offshore structures. Civil Engineering, October 1977, 31-35. Sanders, P.F. 1983. Biological aspects of marine corrosion. Metals World, December, 13-14. Sanders, P.F. 1984. Assessment of bacterial activity and corrosion in offshore environments. In: Proceedings of IRM Conference, 5-6th November, 1984, Aberdeen. Skrebowski, C. 1978. "Trust the rust busters." Petroleum Review, June, 32-33. Terry, L.A. and Edyvean, R.G.J. 1981. Microalgae and corrosion. Botanica Marina, 24: 177-183. Terry, L.A. and Edyvean, R.G.J. 1984. Influences of microalgae on the corrosion of structural steel. In: J.R. Lewis and A.D. Mercer (Editors), Corrosion and Marine Growth on Offshore Structures. Ellis Horwood, Chichester, pp. 38-44. Terry, L.A. and Picken, G.B. (in press). Algal fouling in the North Sea. In: L.V. Evans and K.D. Hoagland (Editors), Algal Biofouling. Elsevier, Amsterdam. Chapter 13. Tischuck, J.L. 1984. Operation and maintenance of impressed current cathodic protection systems. In J.R. Lewis and A.D. Mercer (Editors), Corrosion and Marine Growth on Offshore Structures. Ellis Horwood, Chichester, pp. 61-80. Vennett, R.M. 1979. Cathodic protection of a hot riser in cold seawater. Materials performance, 18: 26-33. von Wolzogen Kuhr, C.A.H. and van der Vlugt, I.S. 1934. The graphitization of cast iron as an electochemical process in anaerobic soils. Water, 18: 147-165. Wolfram, J. and Thoephanatos, A. 1985. The effects of marine fouling on the fluid loading of cylinders: some experimental results. In: Proceedings of the 17th Annual OTC, Houston, Texas, Paper 4954. Wolfson, S.L. and Hartt, W.H. 1981. An initial investigation of calcareous deposits upon cathodic steel surfaces in seawater. Corrosion, 37: 70-76.

This Page Intentionally Left Blank

231

Chapter 1 6

DIATOM COMMUNITIES ON STEEL PROTECTED FROM CORROSION IN SEAWATER R.G.J.EDYVEAN. DEPARTMENT OF METALLURGY UNIVERSITY OF SHEFFIELD, SHEFFIELD U.K. S1 3JD.

16.1 INTRODUCTION There is a large body of work comparing micro-algal settlement (especially diatoms) on different substrata in freshwater (Blinn et a1.,1980; Moore, 1976; Brown, 19761, however,only recently has this quantitative and qualitative work been extended to marine habitats (Neushul et.a1.,1976; Santelices et.a1.,1981; Edyvean et.a1.,1985). The development of oil and gas production in the seas around Britain has led to a renewed interest in the effects of marine fouling of steel structures in seawater, especially the influence of microfouling upon subsequent macrofouling, and in the relationship between fouling organisms and the corrosion of steel (Houghton, 1978; Ralph & Troake. 1980; Terry & Edyvean, 1984). A surface placed in the sea immediately undergoes complex physical and chemical interactions, resulting in d ssolved organic material being absorbed/adsorbed onto the surface and changing the electrostatic and other characteristics of the substratum (Loeb & Neihof, 1977). Following these interactions, bacteria, diatoms and other microorganisms begin to colonise the substratum (Floodgate, 1971; Cuba & Blake, 983). Diatoms usually comprise the greatest percentage of microalgal colonisation and can be present in large numbers within a few days of immersion (Cuba & Blake, 1983). This colonisation, known as the primary film, can considerably influence the physical and chemical conditions at the surface (Terry & Edyvean, 1984; Edyvean, 1984) and may influence macrofouling settlement and development, by chemical, nutrient (Young & Mitchell, 1973) o r surface tension changes (Fletcher et al., 1984). The methods used to protect steel structures from corrosion in seawater are barrier paints, cathodic protection, or a combination of both. Anti-corrosion barrier paint systems are usually coal-tar epoxy coatings used in conjunction with cathodic protection. Cathodic protection counteracts the normal electrochemical corrosion reaction by forcing the steel to become cathodic with respect to a sacrificial or inert anode. Sacrificial anodes are pieces of metal, such as Magnesium, Aluminium or Zinc alloys which, when in electrical connection with the structure, will corrode in preference to the steel. Inert dnOdeS are used with a DC electrical current which is driven through the structure in the opposite direction to the normal corrosion current. The relative surface area and distance between the anode and the structure to be protected is dependant on

232 the

properties

of t h e e l e c t r o l y t e ( t h e seawater). P r o t e c t i o n w i l l cease i f the

e l e c t r o l y t e is removed ( e g . by a receding t i d e ) a s t h e is

broken.

Both

electrochemical

circuit

systems generate a high pH a t t h e metal s u r f a c e caused by the

reduction of oxygen t o form hydroxyl i o n s ( t h e cathodic r e a c t i o n ) and s i n c e solubility

of

most

inorganic

compounds,

carbonates, decreases w i t h i n c r e a s i n g pH, form

on

especially calcareous

calcium

and

deposits

the

magnesium

("scale")

will

t h e protected s t e e l . This s c a l e is i n s o l u b l e a t normal seawater pH and

can be an a i d t o corrosion prevention. Many o f f s h o r e o i l and gas platforms i n t h e North combination

three possible calcareous

substrata

scale

formed

for on

colonisation cathodically

by

marine

protected

s u r f a c e , and a combination of t h e two systems i n which any these

Sea

are

protected

by

a

of c o a l - t a r epoxy p a i n t s and z i n c s a c r i f i c i a l anodes. This presents fouling steel,

a

calcareous

organisms,

a

painted s t e e l scale

fills

cracks i n t h e p a i n t . The study presented here a s s e s s e s diatom settlement on surfaces

together

with

Perspex

as

a

control

at

continuously submerged and t h e o t h e r i n t h e i n t e r t i d a l zone.

Fig. 16.1. S i t e of s u b s t r a t a exposure.

two

sites,

one

233 16.2 MATERIALS AND METHODS 16.2.1 P r e p a r a t i o n of s u b s t r a t a Perspex

and

substrata

steel

were

t o a s t a n d a r d s i z e (8cm.x 2.5cm.x

cut

0.3cm) w i t h lcm. h o l e s d r i l l e d a t one end f o r s u s p e n d i n g on onto

exposure

panels.

The

or

racks

mounting

s t e e l , t o BS 4360/43A s p e c i f i c a t i o n was abraded t o

b r i g h t metal and p r o t e c t e d from c o r r o s i o n by: ( a ) c o n n e c t i o n t o Z i n c s a c r i f i c i a l anodes, ( b ) c o a t i n g w i t h an combination

epoxy

coal

tar

or

paint,

(c)

protected

by

a

of b o t h systems. When used, anodes were p o s i t i o n e d i n s u c h a way as

t o e n s u r e even p r o t e c t i o n (even c u r r e n t d e n s i t y ) over a l l steel

specimens.

All

s u b s t r a t a were c l e a n e d b e f o r e u s e by immersion i n c o n c e n t r a t e d s u r f a c t a n t (Decon 90)

for

ten

minutes,

washed

in

h o t r u n n i n g water, r i n s e d i n two changes of

a b s o l u t e e t h a n o l , a i r d r i e d and s t o r e d i n a d e s i c c a t o r u n t i l r e q u i r e d . 16.2.2 Exposure s it e s S u b s t r a t a were exposed a t two s i t e s : On r a c k s i n

50

cm.

continuously

deep

flowing s e a w a t e r t a n k s a t t h e Dove Marine L a b o r a t o r y , C u l l e r c o a t s , Tyne and Wear ( G r i d Ref.

or

NZ366717)

bolted

to

Perspex

panels

fixed

to

rocks i n t h e

i n t e r t j d a l zone a t St.Mary's I s l a n d ( G r i d Ref. NZ353755). Both s i t e s are on

the

n o r t h - e a s t c o a s t of England ( F i g . 1 6 . 1 ) . S u b s t r a t a were exposed f o r s e q u e n t i a l 25 day

between J u n e 1980 and J a n u a r y 1982, f o r t h e c o n t i n u o u s l y submerged

periods

s i t e , and f o r f o u r 25 day p e r i o d s d u r i n g 1981 a t t h e i n t e r t i d a l s i t e . These were t h e 25 days ending 8 t h . J a n u a r y , 1 9 t h . May, 3 r d . August and 10th. December 1981. 16.2.3 Assesment of s e t t l e m e n t Total algal counts composition

was

were

assessed

1981 f o r t h e submerged exposed

made

substrata.

for

throughout

scanning

and

sites.

throughout

1981

for

intertidally

the

microscopy.

Jones

Replicate

(1979)

plates

and

qualitatively

of t h e f o u r s u b s t r a t a

( t h r e e a t t h e i n t e r t i d a l s i t e ) , were removed a t each sample d a t e and 0.45pm

stored

nylon

bristle

brush

into

known

quantities

diameter

slides,

air

and made

cleared for

50

with

cedarwood

fields

microscope and t h e number of organisms on t h e samples

13

f i l t e r s . The f i l t e r s were p l a c e d on microscope

0 . 4 5 ~ Millipore dried

i d e n t i f i c a t i o n were Sub

of

f i l t e r e d seawater c o n t a i n i n g L u g o l ' s i o d i n e . The r e s u l t i n g s u s p e n s i o n s

were d i l u t e d as n e c e s s a r y , and t h r e e r e p l i c a t e 5 m l . samples passed through

mm.

in

membrane-filtered seawater c o n t a i n i n g L u g o l ' s i o d i n e . Algae were removed

from each p l a t e w i t h a small membrane

Community

s e t t l e m e n t was a s s e s s e d q u a n t i t a t i v e l y by u s i n g

Microalgal

electron

both

e a c h exposure p e r i o d between J u n e 1980 and J u n e

substrata

t h e d i r e c t count on membrane f i l t e r method of using

at

1981

oil.

Algal

counts

and

of view a t X400 u s i n g a V i c k e r s M17 original

substratum

calculated.

were washed i n a 20% s o l u t i o n of e t h a n o l c o n t a i n i n g 2% s u r f a c t a n t ,

f i l t e r e d o n t o 0.2pm p o r e s i z e 'qNucleopore'l p o l y c a r b o n a t e

filters,

air

dried,

234

2 x U v l

0

z

FE B

APRIL

JUNE

AUG

OC T

FEB

APRIL

JUNE

A UG

OCT

DEC

B

~~

DEC

235 gold

coated

and

the

algae

identified

using

a J E O L JSM 1 Scanning E l e c t r o n

Microscope. Diatoms were i d e n t i f i e d t o g e n e r a , and t o s p e c i e s whenever p o s s i b l e , and a l l i n d i v i d u a l s were counted whether s o l i t a r y o r c o l o n i a l . Other u n i c e l l u l a r a l g a e ( g r e e n , blue-green and a l g a l s p o r e s ) were

counted

as

individuals

while

each p i e c e of a f i l a m e n t o u s a l g a o r macroalgal g e r m l i n g was counted as one u n i t . 16.3 RESULTS 16.3.1 T o t a l m i c r o a l g a l c o u n t s Microalgal

communities

developed

to

a

or

greater

lesser

e x t e n t on a l l

s u b s t r a t a , depending on t h e time of y e a r , b u t no m a c r o f o u l i n g was 25

the

day

exposure

periods.

Colonisation

layering process taking place, i n

which

the

was

rapid

initial

found

during

a t both s i t e s with a

colonising

species

are

overgrown by d i f f e r e n t s p e c i e s . I t was n o t i c e d t h a t w h i l e c o l o n i s a t i o n tended t o be

uniform

clumped

on

the

continuously

submerged

c o l o n i s a t i o n was more

substrata,

and p a t c h y on t h e i n t e r t i d a l l y exposed s u b s t r a t a .

T o t a l numbers of m i c r o a l g a e p r e s e n t on t h e c o n t i n u o u s l y

are shown i n Figure.16.2 day

period

submerged

p r i o r t o t h e 16th.May 1981 on c a t h o d i c a l l y p r o t e c t e d p a i n t e d s t e e l .

The l o w e s t v a l u e of

1,200

14th.August

on

1981

per the

sq.cm.

was

for

same s u b s t r a t u m .

the There

25

days

were

prior

typical

f l u c t u a t i o n s i n m i c r o a l g a e on a l l s u b s t r a t a , w i t h peaks i n t h e l a t e late

autumn.

Counts

of

microalgae

to

the

seasonal

spring

and

on t h e i n t e r t i d a l l y exposed s u b s t r a t a are

shown i n F i g u r e 16.2 (B). Counts were h i g h e s t (41,800 p e r sq.cm.) period p r i o r t o t h e 1 9 t h . May 1981 on Perspex and l o w e s t (817 the

substrata

Counts were h i g h e s t (98,400 p e r sq.cm.1 f o r t h e 25

(A).

f o r t h e 25 day

per

sq.cm.)

for

25 day p e r i o d p r i o r t o 3 r d . August 1981 o n c a t h o d i c a l l y p r o t e c t e d s t e e l . On

t h e s e i n t e r t i d a l s u b s t r a t a , s e a s o n a l f l u c t u a t i o n s were o n l y found on perspex. The c o u n t s were a n a l y s e d t o d e t e r m i n e any

significance

in

the

differences

between s u b s t r a t a (One way a n a l y s i s of v a r i a n c e on p a i r s of s u b s t r a t a , Sokal and Rohlf,

1969).

On

t h e c o n t i n u o u s l y submerged s u b s t r a t a , c a t h o d i c a l l y p r o t e c t e d

steel had s i g n i f i c a n t l y lower l e v e l s of a l g a e t h a n t h e o t h e r s u b s t r a t a for

perspex,

P<0.02

for

cathodically

p a i n t e d s t e e l ) b u t there were substrata.

At

the

no

intertidally

protected

significant

differences

between

the

other

exposed s i t e a l g a l numbers were s i g n i f i c a n t l y

g r e a t e r on Perspex t h a n t h e o t h e r s u b s t r a t a d u r i n g t h e summer but

(P
p a i n t e d steel and P
months

(P
n o t when compared over a l l exposure p e r i o d s , nor were there any s i g n i f i c a n t

d i f f e r e n c e s between t h e o t h e r s u b s t r a t a .

Fig.16.2. ( O p p o s i t e ) . M i c r o a l g a l numbers on s u b s t r a t a exposed d u r i n g 1981, (A) . c o n t i n u o u s l y submerged and (B) exposed i n t e r t i d a l l y . 0 0 Perspex. A- A Painted steel. A---A C a t h o d i c a l l y p r o t e c t e d p a i n t e d s t e e l . 0-0 C a t h o d i c a l l y p r o t e c t e d steel.

- ---

--

236 A

B

O/O

80 PERSPEX

60 40

20

80

PAINTED UNPROTECTED STEEL

60 40 20

80

PAINTED CATHUDICALLY PROTECTED STEEL

60

n

Itr 80 60

J J A 5 0 N D J FMAM J 1980 1981

Fig. 16.3. R e l a t i v e s e a s o n a l abunaance of' non-diatom a l g a e a s a p e r c e n t a g e of t o t a l m i c r o a l g a l c o l o n i z a t i o n on s u b s t r a t a A ) C o n t i n u o u s l y submerged and B) exposed i n t e r t i d a l l y .

237 16.3.2 Community c o m p o s i t i o n The

proportion

of

the

communities made up of diatoms and o t h e r m i c r o a l g a e

averaged over a l l exposure p e r i o d s a r z g i v e n i n T a b l e 16.1.

TABLE 16.1

Average p e r c e n t a g e of m i c r o a l g a l groups on A . C o n t i n u o u s l y and

B.

I n t e r t i d a l l y exposed s u b s t r a t a .

PX

C a t h o d i c a l l y p r o t e c t e d p a i n t e d s t e e l , CS

=

=

P e r s p e x , PU

submerged

substrata

P a i n t e d s t e e l , PP

=

=

Cathodically protected s t e e l .

PX

PU

PP

cs

DIATOMS

64.4

53.7

56.3

46.4

OTHER UNICELLULAR ALGAE

34.9

44.9

42.4

52.2

0.7

1.4

A

MULTICELLULAR ALGAE

1-3

1.4

B

DIATOMS

66.8

-

51 .O

49.2

OTHER UNICELLULAR ALGAE

28.6

-

36.6

44.1

12.4

6.7

4.6

MULTICELLULAR ALGAE

A t b o t h s i t e s diatoms a r e i n g r e a t e s t abundance on Perspex and l e a s t abundant

on c a t h o d i c a l l y p r o t e c t e d s t e e l , making up between.468 algal

communities.

other

algae

filamentous

There

(unicellular green

and

however,

is,

green

red

and

algae

67% of

may

algae,

or

may

certain

total

algal

spores

and

n o t have been a c t i v e l y

a t t a c h i n g t o t h e s u b s t r a t a ) making up very h i g h p r o p o r t i o n s of at

the

considerable seasonal v a r i a t i o n , with

blue-green

which

and

the

communities

times of t h e y e a r , e s p e c i a l l y on t h e i n t e r t i d a l l y exposed s u b s t r a t a

(Figure 16.3). The a v e r a g e composition of diatom communities is shown i n T a b l e 16.2 f o r continuously

the

submerged s u b s t r a t a and i n T a b l e 1 6 . 3 f o r t h e i n t e r t i d a l l y exposed

s u b s t r a t a . 18 g e n e r a of diatoms were found, 17 on t h e submerged s u b s t r a t a and 1 1 on t h e i n t e r t i d a l l y exposed s u b s t r a t a . 1 0 were common t o b o t h s i t e s , b u t only

6

averaged more t h a n 5% on any of t h e s u b s t r a t a communities. The

most

prominent

diatoms

were N a v i c u l a spp. ( p a r t i c u l a r l y N . R r e v i l l e i

(Agardh) C l e v e found b o t h a s i n d i v i d u a l s and i n c o l o n i a l c h a i n s ) which between

averaged

55% and 67% of t h e diatom t o t a l on t h e c o n t i n u o u s l y submerged s u b s t r a t a

and between 80% and 86% of diatoms on t h e i n t e r t i d a l l y exposed s u b s t r a t a . diatoms

which

formed

55

or

more

of

diatom

communities

Other

are C s p y l o d i s c u s

f a s t u o s u s Ehrenb., P a r a l i a s u l c a t a (Ehrenb.) C l e v e . and G y l i n d r o t h e c a c l o s t e r i u m (Ehrenb.) Reiman and Lewin

on c o n t i n u o u s l y submerged

substrata

and

Cocconeis

TABLE 16.2

Average

percentage

s u b s t r a t a . PX

s t e e l , CS

c o m p o s i t i o n of d i a t o m communities on c o n t i n u o u s l y submerged-

P e r s p e x , PU

=

P a i n t e d s t e e l , PP

=

C a t h o d i c a l l y p r o t e c t e d steel.

=

*

Cathodically protected painted

=

Planktonic

=

t o Hendey

according

(1974).

PX

PU

PP

cs

54.953

62.106

59.244

66.847

Cocconeis s p p

3.097

2.561

3.499

3.991

Melosira s p p .

0.943

1.139

0.944

0.777

2.323

4.698

4.923

4.549

Navicula spp.

Campylodiscus D i ploneis sp.

fastuosus

1.190

1.038

1.078

1.143

4.788

6.087

4.507

4.873

*

0.071

0.233

0.263

0.593

0.808

1.391

0.699

1.31 1

-C y l i n d r o t h e c a clos t e r i um

24.002

12.843

18.173

9.393

Paralia sulcata

Act i n o p l y c h u s s e n a r i us. Pleurosigmn spp.

-Biddulphia regih.*

0.036

0.208

0 033

0 * 033

L m p h r a SPP.

0.915

1.074

0.747

0.838

Nitzschia spp.

1.038

2.508

2.513

2.051

-Amphiprora _

alata

0.049

0.029

0

0

Achnanthes s p p .

0.987

0.466

0.828

0.131

-Licmophora s p .

0

0

0

0

Rhizosol e n i a sp. *

0

0.029

0

0.065

Chaetdceros sp.*

0.345

0.600

0.130

0

Unknown

4.455

2.990

2.419

3.406

spp.,

Melosira

s p p . and A c h n a n t h e s s p p . o n t h e i n t e r t i d a l l y exposed s u b s t r a t a .

Some diatoms showed d i s t i n c t s i t e p r e f e r e n c e s . Both C y l i n d r o t h e c a closterium and m p y l o d i s c u s f a s t u o s u s were a l m o s t submerged

substrata

where

they

entirely occurred

restricted in

quite

a b u n d a n t d i a t o m s s u c h a s Amphora s p p . , N i t z s c h i a s p p . ,

-sole

nia

to

the

continuously

h i g h numbers. O t h e r less A_mphiprora

alata

Kutz,

and maet ocerm s p . were a l s o r e s t r i c t e d t o t h e c o n t i n u o u s l y

sp.,

submerged s u b s t r a t a . Some d i a t o m s show s e a s o n a l p e a k s i n abundance ( F i g s . 16.4 a n d 16.5). spp.

are

more

Campylodiscus

dominant fastuosus

in (Fig.

the

summer

16.4).

as

Navicula

are C y l i n d r o t h e c a c l o s t e r i u m and

Cocconeis

spp.,

Paralia

sulcata

and

Melosira s p p . show w i n t e r p e a k s a t b o t h s i t e s ( F i g 16.4 and 16.5). Some

species

show

a

substratum

p r e f e r e n c e ; On t h e c o n t i n u o u s l y submerged

239 TABLE 16.3 Average p e r c e n t a g e c o m p o s i t i o n of d i a t o m substrata.

PX

=

PP

Perspex,

Cathodically protected steel.

*

=

communities

Cathodically

=

on

intertidally

protected

cs

PP

Navicula spp.

86.120

Cocconeis spp

3.450

79.689 6.591

80.034 4.315

Melosira spp.

0.'704

7.869

3.659

mpylodiscus fastuosus

0

0

Diploneis sp.

0

0.769 1.270

4.762

Paralia sulcata

0

0

0.769 0.385 1.154

Cylindrotheca closterium

0

0

0

-B i d d u l p h i a reg&.*

0

0.253

0

Amphora spp.

0

0

0

N i t z s c h i a spp.

0

0

0

0

0

0

5.634 0.038

1.247

4.849

0

0

0

P 1e u r 0 s i gmna spp

_ Amphiprora _

3.378 0.674

*

.

alata

Achnanthes s p p .

-Licmophora

sp.

0

2.381

Rhizosolenia sp.*

0

0

Chaetoceros sp.*

0

0

0

Unknown

0

0

0

s u b s t r a t a C a m p y l o d i s c u s f a s t u o s u s c o m p r i s e s a h i g h p r o p o r t i o n of t h e d i a t o m s

all

abundant

on

substrata

Nitzschia

sp.

is

also

o t h e r t h a n perspex, b u t t h e s e d i f f e r e n c e s are not

s i g n i f i c a n t . C y l i n d r o t h e c a c l o s t e r i u m however, i s more a b u n d a n t o n p e r s p e x the

on

s u b s t r a t a e x c e p t p e r s p e x t o t h e 20% s i g n i f i c a n c e l e v e l o v e r a l l (P<0.2), b u t

w i t h g r e a t e r d i f f e r e n c e s a t c e r t a i n times of t h e y e a r . more

=

P l a n k t o n i c a c c o r d i n g t o Hendey (1974). PX

Acti nopJychus s e n a r i us.

exposed

p a i n t e d s t e e l , CS

than

o t h e r s u b s t r a t a (P<0.05 f o r c a t h o d i c a l l y p r o t e c t e d s t e e l , P
steel, not s i g n i f i c a n t f o r cathodically protected painted steel).

Cylindrotheca

c l o s t e r i u m i s a l s o more a b u n d a n t o n c a t h o d i c a l l y p r o t e c t e d p a i n t e d s t e e l t h a n o n cathodically

protected

steel

(Pc0.02). On I n t e r t i d a l l y e x p o s e d s u b s t r a t a b o t h

P a r a l i a s u l c a t a and Achnanthes spp. protected

painted

steel

than

are

lower

in

abundance

on

cathodically

o n t h e o t h e r s u b s t r a t a w h i l e C o c c o n e i s s p p . and

Melosira s p p . a r e h i g h e s t o n t h i s S u b s t r a t u m . S e v e r a l diatoms were o n l y f o u n d o n

cathodically protected painted steel, these

were

Biddulphia

Ostenfeld., DiDloneis sp., and C s p y l o d i s c u s r a s t u o s u s .

regia

(Schultze)

240

a

a

3

a

x a

o m

w

m

a,

0.-

55

m

m N

I

m

1

m

”

1

a

m I

N

a Q m

I

m

z

rl

0

m

. . i

L

c

I

I

0 0 0

3

m

m0

cl

rl

m m . . i

L

rl

n

.rl

z

a

I i

a

0

m . . i I:

2, u 2 o m

m

Ill

n

= U

a

a m

L L

. . i

rl

0 4 0

m

4 0 .A 0

UI 0

xzl

Pa,

acr

>

cJ2

m

N c,

z

I

I -

I

a 7

LL

z

0

0

m a 7

I -

-

0

m

93

0

m

4)

z

6

0 a)

m

L

7

c

m

W

-m

8

0

24 1 16.5 DISCUSSION 1 6.5.1 M i c r o a l g a l c o u n t s

Microalgal

colonisation

varies

being 817 a l g a e per s q . cm. and t h e results

for

the

continuously

f l u c t u a t i o n i n numbers e x p e c t e d springlsummer

"bloom"

c o n s i d e r a b l y w i t h s e a s o n . The l o w e s t c o u n t s greatest

submerged of

98,400

temperate

(Fig.16.2A).

at

and

cathodically

per

cm.

sq.

The

show t h e t y p i c a l s e a s o n a l

microalgal

However,

s e a s o n a l d i f f e r e n c e s were found o n l y on perspex protected

algae

substrata the

communities

intertidal

(Fig.16.2B).

The

a

with

s i t e , these cathodically

p r o t e c t e d p a i n t e d s t e e l s d i d n o t show any s e a s o n a l

i n c r e a s e s , and t h e r e was even a tendancy t o d e c r e a s e i n numbers o v e r t h e summer. These d i f f e r e n c e s may be due t o t h e e l e c t r o c h e m i s t r y of steel,

painted

whether

or

a f f e c t t h e performance of t h e c a t h o d i c p r o t e c t i o n . lost

cathodically

protected

n o t , where a l t e r n a t i n g immersion and exposure w i l l Electrical

conductivity

is

when t h e s u b s t r a t a are uncovered by t h e r e c e d i n g t i d e and t h i s w i l l r e s u l t

i n l a r g e changes i n pH, e l e c t r i c a l c h a r g e and o t h e r chemical surfaces. explain

significantly

cathodically

protected

at

the

changes t h a t occur on c a t h o d i c a l l y p r o t e c t e d s t e e l may

chemical

The

the

reactions

lower

steel

colonisation

than

on

continuously

submerged

on o t h e r c o n t i n u o u s l y submerged s u b s t r a t a ,

e s p e c i a l l y perspex ( P < O . O O l ) . High pH v a l u e s and p r e c i p i t a t i n g calcium c a r b o n a t e c r e a t e u n f a v o u r a b l e c o n d i t i o n s f o r a l g a l s e t t l e m e n t and t r a p i n i t i a l l y

settling

a l g a e (Edyvean, 1 9 8 4 ) . T h i s w i l l a f f e c t b o t h r e c r u i t m e n t and r e p r o d u c t i o n . 16.5.2 Diatom communities Diatoms

are

t h e main c o n s t i t u e n t s of t h e m i c r o a l g a l communities, a v e r a g i n g

j u s t over 50% of t o t a l a l g a e . A t b o t h cathodically

protected

sites

diatoms

were

least

g r e a t e r a b i l i t y of diatoms t o a c t i v e l y choose a s u b s t r a t u m . Diatoms reported

as

abundant

on

and most abundant on p e r s p e x . T h i s may r e f l e c t a

steel

are

widely

t h e dominant f i r s t a l g a l c o l o n i s e r s , b o t h on n a t u r a l (Scheer,1945,

S a n t e l i c e s e t . a l . 1 9 8 1 , ) and a r t i f i c i a l s u b s t r a t a (Neushul e t a 1 . ( 1 9 7 6 ) ,

however

t h e numbers and r o l e of o t h e r a l g a e t e n d s t o be o v e r l o o k e d i n e a r l y c o l o n i s a t i o n studies.

Despite

the

general

preponderance

of

u n i c e l l u l a r a l g a e , a l g a l s p o r e s and m i c r o s c o p i c very

high

proportion

of

the

communities

1 6 . 3 ) . These i n c r e a s e s t e n d e d t o occur colonisation

is

low.

An

diatoms a t both s i t e s , o t h e r

mu1 t i c e l l u l a r

algae

formed

during

the

winter

months

when

total

spring

and

colonisation

which

autumn "blooms"

total

e x c e p t i o n t o t h i s was f o r t h e c o n t i n u o u s l y submerged

s u b s t r a t a i n m i d summer ( J u n e ) 1980. Again t h i s may have c o i n c i d e d w i t h in

a

a t c e r t a i n times of t h e y e a r ( F i g .

is

often

( T h e r e was

a

drop

e n c o u n t e r e d i n mid summer, s e p a r a t i n g no

marked m i d

summer f a l l i n

total

F i g . 16.4. ( O p p o s i t e ) R e l a t i v e abundance of diatoms on c o n t i n u o u s l y submerged s u b s t r a t a . PX = p e r s p e x , PU = p a i n t e d s t e e l , PP = c a t h o d i c a l l y p r o t e c t e d p a i n t e d s t e e l , CS = c a t h o d i c a l l y p r o t e c t e d s t e e l .

-

PX

O/O

1;: -7 5

Navicula s p p .

4l-

-25 Cocconeis s p p .

n

Paralia sulcata

-25 Achnanthes s p p .

-15

. . . . n

Pleurosigmn s p p .

Melosira s p p .

Others

JAN .MAY AUG 1981

2 N

--

DEC

JAN

MAY AUG 1981

DEC

--*JAN

MAY AUG 1981

DEC

-15

243 c o l o n i s a t i o n i n 1981 1. t o t a l of 18 d i a t o m t a x a were f o u n d a t 0 0 t h s i t e s , however o n l y s e v e n g r o u p s

A

(Navicula

spp.

Cylindrotheca

Campylodiscus

fastuosus,

closteriug,

Paralia

Cocconeis

sulcnta

and

spp.,

Achnanthes

s i g n i f i c a n t c o n t r i b u t i o n t o t h e communities, and t h e s e are

spp.)

spp.,

make

almostly

any

completely

by N a v i c u l a s p p . . The d i v e r s i t y i s lower f o r t h e i n t e r t i d a l s i t e t h a n

dominated

f o r t h e c o n t i n u o u s l y submerged s u b s t r a t a (Tables

Melosira

16.2

(Figs.16.4

and

16.3).

Most

with higher l e v e l s

of

Navicula

spp.

d i a t o m s show some s e a s o n a l p r e f e r e n c e

the

of

and 1 6 . 5 ) , C y l i n d r o t h e c a c l o s t e r i u m

most

is

prominent

during

the

summer months r e a c h i n g 62.5% of d i a t o m s ( 4 9 . 6 % of t o t a l a l g a e ) i n t h e 25 d a y s t o 16th

May

1981

c o n t i n u o u s l y submerged p e r s p e x . C s p y l o d i s c u s f a s t u o s u s 1s

on

also most p r o m i n e n t i n t h e summer w h i l e C o c c o n e i s s p p . , N i t z s c h i a s p p . , sulcata,

Achnanthes

spp.

Pleurosigma

Paralia

and M e l o s i r a s p p . t e n d t o b e more

spp.

prominent d u r i n g t h e w i n t e r . The number of t a x a f o u n d i n t h i s work i s c o n s i d e r a b l y lower communities

reported

from

freshwater

and

than

for

diatom

s a l t marsh e n v i r o n m e n t s ( S u l l i v a n ,

1977; C z a r n e c k i , 1 9 7 9 ) . However, S u l l i v a n (1977) f o u n d t h a t t h e number of diatom taxa decreases a s s a l i n i t y increases (1984)

has

found

15

genera

of

and

in

diatoms

the on

marine

environment,

Callow

n o n - t o x i c p a n e l s exposed a t S a n

F r a n s i s c o , of which 5 g e n e r a were dominant. S i m i l a r r e s u l t s were f o u n d f o r J a p a n and A u s t r a l i a , w h i l e o n t h e s o u t h c o a s t

of

England

two

species

of

Navicula

dominated n o n - t o x i c s u r f a c e s (Callow, 1 9 8 4 ) . T h e r e a p p e a r s t o b e l i t t l e d i f f e r e n c e i n d i a t o m community c o m p o s i t i o n between the

substrata,

due

largely

agreement w i t h t h e f i n d i n g s (Tuchman

and

the

dominance

Edyvean

and

various

diatom

of

Moss

B l i n n , 1979., B l i n n e t . a 1 . , 1 9 8 0 . ,

S i m i l a r i t y I n d e x t o compare between

to of

communities

spp. T h i s i s i n

Navicula (1986)

and

other

authors

S u l l i v a n , 1975) who have u s e d a and

found

high

correlations

n o n - t o x i c s u b s t r a t a . B o t h Wetzel & Westlake ( 1 9 6 9 ) and Neushul

e t a 1 . ( 1 9 7 6 ) p o i n t o u t t h a t t h e r e can b e l a r g e d i f f e r e n c e s

in

the

numbers

of

o r g a n i s m s o n d i f f e r e n t s u b s t r a t a , b u t s p e c i e s c o m p o s i t i o n is o f t e n s i m i l a r . Although

the

comnunities

are

v e r y similar o v e r a l l , some diatom s p e c i e s do

show s i t e and s u b s t r a t u m p r e f e r e n c e s . C s p y l o d i s c u s f a s t u o s u s and closterium

are

two

i n t e r t i d a l l y exposed submerged

substrata.

species substrata

but

reach

Cylindrotheca

perspex than t h e o t h e r s u b s t r a t a w h i l e perspex.

Such

substratum

Cylindrotheca

which show b o t h . They are v i r t u a l l y a b s e n t o n t h e high

closterium

levels shows

Cspylodiscus

on

the

continuously

a marked p r e f e r e n c e f o r fastuosus

is l o w e s t

on

p r e f e r e n c e s i n d i c a t e e i t h e r an a c t i v e c h o i c e by some

d i a t o m s s p e c i e s , o r t h a t t h e p h y s i c a l and

chemical

c o n d i t i o n s of t h e s u b s t r a t a

F i g . 16.5. ( O p p o s i t e ) R e l a t i v e abundance of d i a t o m s on s u b s t r a t a exposed intertidally. PX = p e r s p e x , PU = p a i n t e d s t e e l , PP = c a t h o d i c a l l y p r o t e c t e d p a i n t e d s t e e l , CS = c a t h o d i c a l l y p r o t e c t e d s t e e l .

244 or

discourage

settlement

Cylindrotheca

encourage

closterium

forms

or

entrapment

certain

of

species.

a d h e r e n t c o l o n i e s and seems t o f a v o u r

closely

smooth s u b s t r a t a s u c h as p e r s p e x w h i l e @ p y l o d i s c u s

f a s t u o s u s does

not

appear

t o a c t i v e l y a t t a c h t o a s u b s t r a t u m . b u t becomes enmeshed o n r o u g h s u r f a c e s , s u c h as

are

found

on

cathodically

protected

While

steel.

selective

community

development o n t o x i c s u r f a c e s is w e l l known, ( D a n i e l and C h a m b e r l a i n , 1 9 8 1 ) , a n y s u b s t r a t u m p r e f e r e n c e shown by i n d i v i d u a l s p e c i e s on n o n - t o x i c s u r f a c e s a r e

more

to

subtle

environmental

due

i n f l u e n c e s , such a s topography, s u r f a c e charge,

s u r f a c e t e n s i o n o r n u t r i e n t a v a i l a b i l i t y . I n t h e 25 d a y e x p o s u r e p e r i o d s u s e d i n t h i s work, m i c r o a l g a e substrata

from

and

other

organisms

not

will

only

settle

onto

the

t h e water but a l s o reproduce i n s i t u . These w i l l produce copious

amounts of m u c i l a g e , t r a p p i n g o t h e r o r g a n i s m s , a s well as d y i n g and b e i n g washed o f f . Once an i n i t i a l c o l o n i s a t i o n h a s e s t a b l i s h e d new s p e c i e s develop

on

top

work and i t s e r v e s t o r a p i d l y d i m i n i s h a n y d i f f e r e n c e s producing

et

and

between

substrata,

the

a s u r f a c e more p h y s i c a l l y and c h e m i c a l l y s u i t a b l e f o r c o l o n i s a t i o n by

o t h e r o r g a n i s m s ( B i s h o p e t a 1 . , 1 9 7 4 ; Neushul Blinn

settle

will

e a r l i e r o n e s . Such a l a y e r i n g p r o c e s s was o b s e r v e d i n t h i s

of

a1.,1980).

et

a1.,1976;

et

Paul

a1.,1977;

is l i k e l y t h a t o n t h e s u b s t r a t a u s e d i n t h i s work a n y

It

d i f f e r e n c e s i n t h e numbers of

algae

or

choice

of

substratum

by

individual

s p e c i e s would d i s a p p e a r w i t h l o n g e r immersion p e r i o d s . 16.6 CONCLUSIONS (i)

The

differences

i n numbers of a l g a e f o u n d a t b o t h s i t e s . a r e m a i n l y t h o s e

between c a t h o d i c a l l y p r o t e c t e d s t e e l and t h e

other

substrata,

particularly

p e r s p e x , f o r t h e c o n t i n u o u s l y submerged s u b s t r a t a and between p e r s p e x a n d t h e other

substrata

a t t h e i n t e r t i d a l site. T h i s reinforces t h e conclusion t h a t

differences i n substratum s t a b i l i t y shown

affects

colonisation.

The

differences

by p e r s p e x r e i n f o r c e p r e v i o u s f i n d i n g s t h a t e x t r a p o l a t i o n of d a t a from

p e r s p e x a n d g l a s s t o o t h e r s u b s t r a t a may b e m i s l e a d i n g (Edyvean e t a l . 1 9 8 5 ) . ( i i ) There are

no

overall

differences

in

community

structure

between

the

s u b s t r a t a , a n d i t i s u n l i k e l y t h a t t h e r e w i l l b e any d i f f e r e n c e s i n i n f l u e n c e on subsequent f o u l i n g . ( i i i ) S p e c i e s of N a v i c u l a d o m i n a t e t h e communities a t b o t h s i t e s .

(iv)

Some s p e c i e s , n o t a b l y C y l i n d r o t h e c a closterium and C s p y l o d i s c u s f a s t u o s u s

show marked s i t e , s u b s t r a t u m and s e a s o n a l p r e f e r e n c e s . ( v ) S p e c i e s d i v e r s i t y is l e s s o n t h e s e a r t i f i c i a l s u b s t r a t a i n s e a w a t e r t h a n f o r r e p o r t s of a r t i f i c i a l and n a t u r a l s u b s t r a t a i n freshwater. ACKNOWLEDGEMENTS T h i s work was c a r r i e d o u t d u r i n g t h e t e n u r e of an SERC CASE award, s p o n s o r e d British

Petroleum,

at

Newcastle

University.

The

by

a u t h o r would l i k e t o t h a n k

245 Dr.B.L.Moss f o r her h e l p and s u p p o r t d u r i n g t h e work. R . G . J . E .

i s t h e holder

of

t h e Sorby R e s e a r c h F e l l o w s h i p of t h e Royal S o c i e t y a t S h e f f i e l d U n i v e r s i t y . REFERENCES S i l v a , S.R. and S l i v a , V.M., 1974. A s t u d y of m i c r o f o u l i n g on Bishop, J . H . , a n t i f o u l i n g c o a t i n g s u s i n g e l e c t r o n microscopy. J o u r n a l of t h e O i l and Colour Chemists A s s o c i a t i o n , 57: 30-35. 1980. C o l o n i s a t i o n r a t e s and B l i n n , D.W., F r e d e r i c k s e n , A. and K o r t e , V . , community s t r u c t u r e of diatoms on t h r e e d i f f e r e n t rock s u b s t r a t a i n a l o t i c system. B r i t i s h P h y c o l o g i c a l J o u r n a l , 15: 303-310. Brown, H . D . , 1976. A comparison of t h e a t t a c h e d a l g a l communities of a n a t u r a l and an a r t i f i c i a l s u b s t r a t e . J o u r n a l of Phycology, 12: 301-306. Callow, M.E., 1984. A world-wide s u r v e y of f o u l i n g on non-toxic and t h r e e a n t i f o u l i n g p a i n t s u r f a c e s . Proceedings of t h e . 6 t h I n t e r n a t i o n a l Congress on Marine C o r r o s i o n and F o u l i n g , Athens. 325-346. and B l a k e , N . J . , 1983. The i n i t i a l development of a marine f o u l i n g Cuba, T.R. assemblage on a n a t u r a l s u b s t r a t e i n a s u b t r o p i c a l e s t u a r y . B o t a n i c a Marina, 26: 259-264. 1979. E p i p e l i c and e p i l i t h i c diatom assemblages i n Montezuma C z a r n e c k i , D.B., w e l l N a t i o n a l Monument, Arizona. J o u r n a l of P h y c o l o g y , l 5 : 346-352. 1981. Copper i m m o b i l i z a t i o n i n F o u l i n g D a n i e l , G.F. and Chamberlain, A . H . L . , Diatoms. B o t a n i c a Marina,24: 185-191. 1984. I n t e r a c t i o n s between m i c r o f o u l i n g and t h e c a l c a r e o u s Edyvean, R . G . J . , d e p o s i t formed on c a t h o d i c a l l y p r o t e c t e d s t e e l i n s e a w a t e r . Proceedings of t h e 6 t h . I n t e r n a t i o n a l c o n g r e s s on marine c o r r o s i o n and f o u l i n g , Athens. 469-483. Rands, G . A . and Moss, B . L . , 1985. A comparison of diatom Edyvean, R . G . J . , c o l o n i s a t i o n on n a t u r a l and a r t i f i c i a l s u b s t r a t a i n s e a w a t e r . E s t u a r i n e , C o a s t a l and S h e l f S c i e n c e , 2 0 : 233-238. Edyvean, R . G . J . and Moss, B . L . , 1986. M i c r o a l g a l communities on p r o t e c t e d s t e e l s u b s t r a t a i n s e a w a t e r . E s t u a r i n e , C o a s t a l and S h e l f S c i e n c e ( i n press). Fletcher, R.L., B a i e r , R . E . and Formalik, M.S.,.1984. The i n f l u e n c e of s u r f a c e energy on s p o r e development i n some common marine f o u l i n g a l g a e . Proceedings of t h e 6 t h . I n t e r n a t i o n a l c o n g r e s s on marine c o r r o s i o n and f o u l i n g , Athens. 129-1 4 4 . and F l o o d g a t e , G . D . , 1971. Primary f o u l i n g by b a c t e r i a . I n : J o n e s , E . B . G . E l t r i n g h a m , S.K. ( e d s ) Marine B o r e r s , Fungi and F o u l i n g organisms of wood. O r g a n i s a t i o n de C o o p e r a t i o n e t de Development Economiques, 117-123. Hendey, N . I . , 1974. A r e v i s e d c h e c k l i s t of B r i t i s h marine diatoms. J o u r n a l of t h e Marine B i o l o g i c a l A s s o c i a t i o n , 54: 277-300. Houghton, D . R . , 1978. Marine f o u l i n g and o f f s h o r e s t r u c t u r e s . Ocean Management, 4 : 347-352. J o n e s , J . G . , 1979. A g u i d e t o methods f o r e s t i m a t i n g m i c r o b i a l numbers and biomass in f r e s h water. Freshwater Biological Association S c i e n t i f i c Publication 3 9 , 1 1 2 ~ ~ . 1977. Adsorption of an o r g a n i c f i l m a t t h e Loeb, G . I . and N e i h o f , R . A . , platinum-seawater i n t e r f a c e . J o u r n a l of Marine Research, 35: 283-291. Moore, J.W., 1976. S e a s o n a l s u c c e s s i o n of a l g a e i n r i v e r s 1 . Examples from t h e Avon, a l a r g e slow-flowing r i v e r . J o u r n a l of Phycology, 12: 342-3119. 1976. Neushul, M . , F o s t e r , M.S., Coon, D . A . , Woessner, J.W. and H a r g e r , B.W.W., An i n s i t u s t u d y of r e c r u i t m e n t , growth and s u r v i v a l of s u b t i d a l marine a l g a e . Techniques and p r e l i m i n a r y r e s u l t s . J o u r n a l of Phycology, 12: 397-408. 1977. Paul, R.W., Kuhn, D.L., P l a f k i n , J . L . , C a i r n s , J . and Croxdale, J.G., E v a l u a t i o n of n a t u r a l and a r t i f i c i a l s u b s t r a t e c o l o n i z a t i o n by scanning e l e c t r o n microscopy. T r a n s a c t i o n s of t h e American M i c r o s c o p i c a l S o c i e t y , 96: 506-51 9. 1980. Marine growth on N o r t h S e a o i l and gas Ralph, R. and Troake, R . P . , p l a t f o r m s . Paper OTC 3860. I n : P r o c e e d i n g s of t h e 1 2 t h Annual O f f s h o r e Technology Conference, Houston,Texas, Vo1.4.49-52.

246 S a n t e l i c e s , B., Montalva, S. and O l i g e r , P . , 1981. C o m p e t i t i v e a l g a l community. o r g a n i s a t i o n i n exposed i n t e r t i d a l h a b i t a t s from c e n t r a l C h i l e . Marine Ecology P r o g r e s s S e r i e s , 6: 267-276. S c h e e r , B.T., 1945. The development of marine f o u l i n g communities. B i o l o g i c a l B u l l e t i n , 89: 103-121. S o k a l , R.R. and R o h l f , F . J . , 1969. Biometry, t h e P r i n c i p l e s and p r a c t i c e of S t a t i s t i c s i n B i o l o g i c a l Research. W.H.Freeman, San F r a n s i s c o , 776 pp. S u l l i v a n , M.J., 1975. Diatom communities from a Delaware s a l t m a r s h . J o u r n a l of Phycology, 1 1 : 384-390. 1977. Edaphic diatom communities a s s o c i a t e d w i t h S p a r t i n a S u l l i v a n , M.J., a l t e r n i f l o r a and S . p a t e n s i n N e w J e r s e y . H y d r o b i o l o g i a , 52: 207-211. T e r r y , L.A. and Edyvean, R . G . J . , 1984. I n f l u e n c e s of m i c r o a l g a e on t h e c o r r o s i o n of s t r u c t u r a l s t e e l . I n : Lewis, J.R. and Mercer, A.D. C o r r o s i o n and Marine Growth o n O f f s h o r e S t r u c t u r e s . E l l i s Horwood l t d . C h i c h e s t e r . 38-45. Tuchman, M . and B l i n n , D . W . , 1979. Comparison of a t t a c h e d a l g a l communities on natural and artificial s u b s t r a t a a l o n g a thermal g r a d i e n t . B r i t i s h P h y c o l o g i c a l J o u r n a l , 1 4 : 243-254. (ed). Wetzel, R.G. and Westlake, D.F., 1969. P e r i p h y t o n . I n : V o l l e n w e i d e r , R.A. A manual on methods f o r primary p r o d u c t i o n i n a q u a t i c environments. I P B Handbook No.12, Blackwell S c i e n t i f i c P u b l i s h e r s , Oxford. 33-40. Young, L.Y. and M i t c h e l l , R., 1973. T h e r o l e of microorganisms i n marine f o u l i n g I n t e r n a t i o n a l B i o d e t e r i o r a t i o n Bull e t i n , 9 : 1 05-1 09.

.

247 Chapter 17

STRUCTURAL MORPHOLOGY OF DIATOM-DOMINATED STREAM BIOFILM COMMUNITIES UNDER THE IMPACT OF SOIL EROSION

J .R.

ROSOWSKI~, K.D.

H O A G L A N D ~ ~ AND ~ , J .E.

~ ~ 0 1 1 ~ 3

lSchoo1 o f B l o l o g l c a l Sciences, U n i v e r s i t y o f Nebraska, Lincoln, NE 68588 U. S.A. 2Present address: Department of Blology, Texas C h r i s t i a n U n i v e r s i t y , F o r t Worth, TX 76129, U.S.A. 3Present address: D i v i s i o n o f Environmental Studies, U n i v e r s i t y o f C a l i f o r n i a , Davis, CA 95616, U.S.A. ABSTRACT Dlatomdomlnated b l o f i l m communities which developed i n one-month periods over two years were monitored i n t r i b u t a r i e s o f a small e u t r o p h i c p r a l r l e stream w l t h a g r i c u l t u r a l watershed s u b j e c t t o e x t e n s i v e s o i l erosion. S i t e A, whlch was s p r i n g fed, had a yeat-round flow, t h e h l g h e s t s i l i c a and n i t r a t e - n i t r o g e n levels, and a d i s t i n c t dlatom community regardless o f t h e season w l t h g e n e r a l l y l e s s trapped sediments i n t h e e a r l y s p r i n g t h a n s i t e s downstream. All communities ( S i t e s A-E) had a t l e a s t two t i e r s e x l s t l n g s i d e by s l d e on t h e primary g l a s s substrates: a p r o s t r a t e t l e r o f pennate diatoms, attached o r motile, w i t h t h e i r v a l v e surfaces p a r a l l e l t o t h e substrate; and a second t l e r o f pennate species attached by a proximal a p i c a l p o l e perpendlcular t o t h e primary substrate. A t a l l s i t e s , b u t p a r t i c u l a r l y t h e downstream s l t e s , t h e communltles were surrounded and/or covered by sedlments h e l d by mucilages o f domlnant and codominant diatom specles and b a c t e r i a o f t h e f i r s t two t l e r s . Second t l e r (perpendicular) l l f e - f o r m s included r o s e t t e s o f Surlrel'la i n d l v i d u a l Navicula clumps o r rows o f Gonlohonema rosettes o f &&&a clumps o r r o s e t t e s o f m,and fan-1 1ke aggregates o f Merldion clrculare formlng hemispherical colonies. Some diatoms o f t h i s t i e r were n o t attached d l r e c t l y t o t h e a r t i f i c l a l s u b s t r a t e b u t t o o t h e r dlatoms o r t o bound p a r t i c u l a t e s . Filamentous b a c t e r i a were p a r t i c u l a r l y important I n t y l n g together clumps o f organisms and sediments I n t l e r s 1 and 2, a t s i t e s C and D. A t h i r d t l e r consisted of filamentous organisms, e.g. &&QQ&RI sp. (Chlorophyceae) , a s t a l k e d diatom sp., and protozoans i n c l u d i n g s t a l k e d p e r i t r i c h s , whlch developed i n t e r m i n g l e d w l t h t h e f i r s t two t l e r s and d i r e c t l y attached t o t h e g l a s s substrate. Secondary attachment o f h@uma and -to f i l a m e n t s o f t h e t h i r d t l e r occurred, b u t t h i s t i e r was never s u f f l c i e n t l y populated o r s t a b l e enough t o t r a p and h o l d a l a y e r o f sediments. A species o f dlatom c o u l d occupy o n l y one t l e r (Achnanthes , t l e r 1; ,Q&.ca U,Svnedra t i e r 21, o r more than one t i e r I f i t s growth h a b i t included s t r u c t u r a l and/or f u n c t i o n a l heteromorphy. Diatom l i f e - f o r m s a r e i l l u s t r a t e d , as a r e b a c t e r i a i n t h e i r a s s o c l a t i o n s w l t h t h e diatomdominated communit Ies.

m,

17.1 17.1.1

m,

m,

e,

INTRODUCTION

General

I n studies o f mlcrobial biofilms,

an understanding o f a l g a l attachment i s now

recognlzed as a p r e r e q u l s i t e f o r developlng e f f e c t i v e

means t o

control

these

248 growths where they have s e r i o u s economic consequences (Characklis

i t appears u s e f u l i n both b a s i c

1983). Regardless o f t h e approach,

s t u d i e s t o know what s t r a t e g i e s attached algae employ t o perturbations,

and

Cooksey,

and

survive

applied

environmental

t h a t i s , what s t r u c t u r a l and perhaps behavioral adaptations

they

have evolved i n response t o n a t u r a l s e l e c t i o n w i t h i n t h e b i o f i l m . A t present, i s d i f f i c u l t t o assess such adaptations

in

freshwater

periphyton

it

communities

from t h e i n f o r m a t i o n a v a i l a b l e . Reviews on t h e suggest,

from

ecology

the

paucity

of

attached

of

freshwater

references

algae

(algal

1980;

(MOSS,

periphyton)

Round,

1981),

that

freshwater a l g a l p e r i p h y t o n has i n t h e p a s t received scant a t t e n t i o n o r has been ignored ( K a l f f and Hoagland, 1982) i n which

has

received

considerable

comparison

attention

f o r m / f u n c t i o n s t r a t e g i e s (Margalef,

to

with

phytoplankton

to

life

1978; Reynolds, 1984a1, n u t r i e n t

and c o m p e t i t i o n i n s t r u c t u r i n g communities (Tilman Sterner,

freshwater respect

et

al.,

1982;

history limitation

Tilman

and

1984; Kilham and Kilham, 19841, and has a depth and breadth o f research

i n o t h e r areas which has provided t h e b a s i s f o r book-length reviews (Fogg, 1975; Morris, 1980; Reynolds, 1984b). Indeed, attached e u k a r y o t i c photosynthesizers o f t h e a q u a t i c mileau have n o t received

attention

by

terrestrial

ecologists

developing e c o l o g i c a l t h e o r y on h e r b i v o r y and a n t i h e r b i v o r e defenses and Janzen, 19791, perhaps because u n t i l major a l g a l / h e r b i v o r e studies, Vadas,

recently

and mostly from

1977, 1986; Emerson and

Zedler,

1978;

Cubit,

1984; Dayton e t al.,

were

marine

1981a;

relatively

environment

Lubchenco,

L i t t l e r and L i t t l e r , 1980; Underwood, 1980; Hay, 1981; Underwood and Jernakoff,

there

the

1978; Menge

1981; Robles, 1982; L i t t l e r

et

and

is

changing

rapidly

with

,

1979;

Lubchenco,

al.,

1983a,

1985;

the

few

(e.g.

Sousa,

1984; Underwood, 1984a, b, c; Gaines,

and Reed, 1985). T h i s s i t u a t i o n

in

(Rosenthal

b;

Harrold

stimulus

for

c u r r e n t work on attached algae coming from several d i r e c t i o n s . 17.1.2

Macroaloae

Among t h e macroalgae, an a r r a y o f morphologies ( L i t t l e r

and

L ttler,

1980)

and l i f e h i s t o r y s t r a t e g i e s (Hay, 1981b; L i t t l e r and L i t t l e r , 1983; L i t t l e r Kauker,

1984) e x i s t

to

increase

disturbances such as p e r i o d i c temperature stresses,

fitness

in

the

presence

desiccation

at

low

tides,

1983, 1984) and L i t t l e r e t al.

(1983a,

l e a s t s i x f u n c t i o n a l - f o r m groups t h a t d i f f e r i n anatomy, and t e x t u r e .

They

range,

perhaps

Littler b)

external

in

a

winter

and

and

summer

currents,

(19801,

Littler

and

have

identified

at

morphology,

continuum,

h e r b i v o r e r e s i s t a n t stony o r tough c r u s t o s e group t o t h e

and

environmental

hydrodynamic shear f o r c e s created by waves

sand-scouring abrasion o r b u r i a l , and herbivory. L i t t l e r (1980,

of

soft,

internal

from

the

more

herbivore

most

s u s c e p t i b l t sheet o r filamentous groups. These morphological groups have shown a range i n r e s i s t a n c e t o g r a z i n g from f i s h and

sea

urchins

depending

on

their

249 t e x t u r e and a c c e s s i b i l i t y ( L i t t l e r e t t e x t u r e o r a c c e s s l b i l i t y does

I)ictvota-,

not

al.,

1983b).

predict

the

L i t t l e r and L i t t l e r , 19841,

t t s s u e s may e x p l a i n h e r b i v o r e

avoidance.

In

specific

secondary

For

cases

where

of h e r b i v o r y

outcome example,

(e.g.,

metabolites

where

in

the

vegetatlve

and

s p o r o p h y l l i c t i s s u e s a r e o n l y s l i g h t l y d t f f e r e n t i n toughness, t h e i n c o r p o r a t i o n o f secondary m e t a b o l t t e s such as phenoltc t a n n i n s i n s p o r o p h y l l t c t i s s u e s may be o f tmportance as a defense a g a i n s t g r a z i n g o f these high h e r b i v o r e d e n s i t y

(Stelnberg,

1984,

(Rhodophyceae), n o n f e r t t l e fronds,

reproducttve

1985).

However,

but not

fertile

Idotea

c u t t c l e which d e t e r s t h e h e r b i v o r e

fronds

i n the

red

fronds,

(an

under alga

possess

isopod)

a

although

o t h e r herbtvores a r e n o t d e t e r r e d from e i t h e r o f these fronds (Gaines, 1985). 17.1.3

Microalaae

A l l e n (1977) suggests t h e use o f microalgae f o r developtng theory and s t a t e s t h a t

for

studies

b l o l o g i c a l system o f choice.l! freshwater suggest

of

Primary

succession, algal

similarittes t o certain

p l a n t communittes (Hoagland e t al.,

colonizatton sequenttal to

and

in

terrestrtal

interval years

between

for

plant

1982; Roemer e t al.,

1984)

thus making p o s s i b l e more r a p t d assessment o f t h e bastc

or

the

successton in

time

months

communittes (Brown and Austin, 1973; Hoagland e t al.,

ecologlcal

often offer

events

1982). However, t h e

events I s days o r weeks f o r algae t n c o n t r a s t

basic

"algae

attributes

of

primary

s u b s t r a t e events. Microalgae

of

the

martne

envtronment

have

(Castenholz, 1961; N i c o t r t , 1977; Hunter and 1984a, b, c; Varela and Penas, 19851, g e n e r a l l y r e a l i z e d . As epiphytes,for

but

received

Russell-Hunter, they

may

example, t h e y

may

equal

and have a s e t

seek them o u t even when they a r e

abundance

low

B i o f o u l t n g I s an area where t h e marine

mtcroalgae

Underwood,

important the

of

et

al.,

recetved

than

btomass

herbivores

(Kittlng have

attention

1983;

be more

seagrass blades on which they a r e growing, In

sporatlc

of

which 1984).

considerable

a t t e n t i o n i n t h e p a s t decade (Evans, 1981; C h a r a c k l i s and Cooksey, 1983). Among t h e mtcroalgae, diatoms (Bacillartophyceae) appear t o be t h e f i r s t e u k a r y o t i c algae

which

colontze

and

mtcrocommunittes I n martne, b r a c k i s h and f r e s h waters 1978; Gale e t al.,

19841,

although

diatoms

misstng from t u r b u l e n t martne waters ( S i e b u r t h e t al., stature

of

developing

pertphyton f l u f f ,

(Amspoker

1979; Lowe and Gale, 1980; Hudon and

Hoagland, 1983; Roemer e t al.,

btoftlms,

i.e.,

has been suggested as

the

and in

universally

substrates and

Bourget,

1974).

Increase

reflecttng

almost

dominate

McInttre,

1981,

bacteria The

1983; may

Increase

thlckness

competttton

for

of

of

be tn the

substrate

surface, where t h i c k communtttes may a r t s e I n response t o g r a d t e n t s o f COz,

02,

nutrtents,

and

o r l i g h t (Hudon and b u r g e t , 1981; Hoagland e t al.,

McInttre, 1982). Hoagland e t al.

(1982) and Roemer e t al.

1982; Sumner

(1984) have speculated

250 t h a t t h e formatton o f l o n g s t a l k s by dtatoms

may

competitton by e l e v a t i n g t h e t r f r u s t u l e s away load, and t h a t mucilaginous m a t e r i a l

of

enable

from

biofilms

them

the

to

avoid

accumulattng

also

stabtltzes

this

sedtment developing

communittes by aggregattng p o t e n t t a l l y abrastve d e t r i t a l p a r t i c u l a t e s . It Is t h e s t r u c t u r i n g o f communtttes

by

dtatoms

and

sediments

considered here, on a morphological basts, ustng

will

that

be

scanning

electron

provided

the

further

mtcroscopy

(SEM). 17.1.4

Spactftc

QLQ&&

The Maple Creek Model Implementatton P r o j e c t

opportunity

examine seasonally t h e p e r i p h y t o n o f a stream system w l t h i n a watershed from c u l t i v a t e d a g r i c u l t u r a l l a n d w t t h extenstve s o t l term, t h t s p r o j e c t was destgned t o demonstrate ways p o l l u t t o n , s p e c i f i c a l l y s o t l eroston, encouraged t o c o n t r o l s o i l permanent

vegetatlve

dtverstons,

wtndbreaks,

sedimentation

wtth

erosion

cover

could by

through

such

s t r u c t u r e s (ACP, 1979; Schepers e t al.,

and

as

longer source

to

of and

otherwtse

eroston

22 tons/acre/year

were

waterways or

1985). The p r o j e c t area

reduce

water-control

33,000

totaled

acres, w t t h 85% p l a n t e d t o crops. Annual s o t l losses i n t h e area p r o j e c t exceeded 100 tons/acre/year

owners

establishment

sod

and

other

the

nonpotnt Land

the

systems,

tillage,

tmpoundments

In

which

controlled.

means

terrace

conservation

water

be

eroston. in

to

derived

prtor

on 3% o f t h e land, w i t h an average

(Anonymous, 1982). The study s t t e s f o r o u r work were

by watershed o u t s i d e o f t h e p r o j e c t area where implementation o f t h e

to

the

loss

of

tmpinged best

soil

conservation p r a c t i c e s would be slow, as w e l l as watershed i n t h e p r o j e c t

study

area where 140 o f 280 o w n e r o p e r a t o r s o f cropland e s t a b l t s h e d one o r

more

soil

conservation p r a c t t c e s over a 3-year pertod

the

short

(Anonymous,

1982).

In

term, our p a r t i c u l a r t n t e r e s t was i n compartng t h e a l g a l p e r i p h y t o n community o f t h e headwaters o f a stream w t t h o u t t h e f u l l impact o f

sotl

w t t h downstream communtties where extenstve s o t l e r o s i o n

erosion

was

(Stte

occurring

A),

(Sttes

6-E). 17.2 17.2.1

MATERIALS AND METHODS m v sites

The study s t t e s (Fig. U.S.A.

1) were

in

Stanton

and

Colfax

counttes,

Nebraska,

S i t e s were chosen along t h e t r i b u t a r i e s o f Maple Creek t o r e f l e c t a range

o f a g r t c u l t u r a l t i l l a g e practtces. None o f t h e s t t e s had rock s u b s t r a t e s and t h e stream bottom was mostly c l a y and s t l t . S i t e A i s near t h e o r t g t n o f t h e t r i b u t a r y (Fig.

1) and ts s p r t n g fed. The s p r t n g f l o w s

continuously

mtddle

throughout

t h e year a t t h t s s i t e , which g e n e r a l l y had t h e lowest t u r b i d i t y f o r it does r e f l e c t t h e Impact o f extensive s o t l eroston e v t d e n t downstream. S t t e 10 k i l o m e t e r s downstream from S t t e A,

and is

located

below

areas

not

B Is about

where

sotl

251

LOCATION M A P MODEL IMPLEMENTATION PROJECT AREA COLFAX. PLATTE. AND S T A N T O N C O U N T I E S , N E B R A S K A

Fig. 1. Periphyton sampling sites A-E along tributaries of Maple Creek, in Stanton and Colfax counties, Nebraska. U.S.A.

252 conservation p r a c t i c e s were t o be implemented. Low f l o w and h i g h s i l t a t i o n r a t e s are t y p i c a l o f t h i s s i t e , which i s h i g h l y accessible t o

cattle.

C

Site

is

a

p o t e n t l a l f u t u r e c o n t r o l s i n c e i t i s an e a s t e r n t r i b u t a r y which e n t e r s t h e creek below S i t e B, w i t h watershed

for

this

tributary

located

outside

the

Implementation P r o j e c t area. Water f l o w a t S i t e C was constant and shading occurred. join,

S i t e D i s below t h e p o i n t where t h e water from S i t e s B

near t h e town o f Clarkson, b u t above t h e sewage o u t f l o w

T h l s s l t e would show t h e e f f e c t s o f d i l u t i o n and a d d i t i o n water from S i t e s B, C,

and E. S i t e E was added t h e

from

from

second

implemented. However, t h i s s i t e was f r e q u e n t l y d r y

and

only

the were

three

C

town.

mixing

of

s i n c e i t was below t h e watershed where s o i l conservation p r a c t i c e s

and

this

the

year

Model

intermittent

of

study to

be

periphyton

samples were c o l l e c t e d . Samples i n t h e w i n t e r months were n o t o f t e n c o l l e c t e d a t S i t e s 6-D because t h e samplers became encased i n o r covered w i t h ice. 17.2.2 The a l g a l samplers (Design A l l i a n c e , C i n c i n a t t i , Ohio) were suspended i n

the

creek between two 1.5 m long, 3.2 cm diameter galvanized pipes, d r i v e n 1 m t h e creek bottom. F i v e microscope s l i d e s ,

i n c l u d i n g one spare,

were

t h e samplers i n a v e r t i c a l p o s i t i o n , w i t h t h e l o n g a x i s o f t h e

placed

slides

mid-afternoon.

daylight

hours9

19811, noon

to

Three s l i d e s were placed i n Whirl-Pak bags; t h e f o u r t h s l i d e ,

a p l a s t i c s l i d e mailer, was f i x e d i n

2% glutaraldehyde

medium ( C a r o l i n a

Co.).

Blological

Supply

New

prepared

microscope

replaced i n t h e sampler, which was immersed i n t h e

creek,

in

The glutaraldehyde-fixed

samples

were

dehydration, c r i t i c a l - p o i n t drying, Some s l i d e s were photographed i n

stored

in

a

were

then

be

removed

the

finger

laboratory.

refrigerator

and thermal c o a t i n g w i t h Au/Pd, large

bowls,

In

Alga-Gro

slides

to

f o l l o w i n g month. A l l samples were placed on i c e and returned t o t h e

comparisons;

in

parallel

t o t h e water flow. For most months over a two-year p e r i o d (May, 1979-May, f o u r s l i d e s were removed from t h e sampler d u r i n g t h e

into

for

for

later

f o r SEM.

overall

growth

examples a r e shown i n F i g u r e 2. Three s l i d e s from each sampler were

processed t o remove and

clean

the

diatom

frustules

for

identification

enumeration. Permanent s l i d e s were made f o r examination w i t h l i g h t and e l e c t r o n microscopy. The s p e c i f i c procedures were as l i g h t microscopy were scraped and

the

frustules

peroxide and potassfurn dichrornate (van d e r Werff,

follows,

were

The

treated

slides

with

mn?

slides

coverslips

and known q u a n t l t i e s o f t h e diatom sample. A t o t a l o f 600 valves per s l l d e counted and d i f f e r e n t i a t e d i n t o t h e dominant

and

codominant

specles

for

hydrogen

1955). Permanent Hyrax

were made t o f a c i l i t a t e q u a n t i t a t i v e a n a l y s i s u s i n g standard 22

and

scanning

were

and

all

others. The samples i n glutaraldehyde were dehydrated

in

a

10% graded

series

of

acetone and c r i t i c a l - p o i n t d r i e d usfng l i q u l d carbon d i o x i d e as t h e t r a n s i t i o n a l

253

May 23

-

July 18 - August 1 5

June 20 1979

Maple Creek Model Implementation Project Fig. 2. Glass microscope slides with periphyton, actual size.

254 f l u i d . The d r i e d speclmens were then coated by thermal evaporatlon

wlth

and o c c a s l o n a l l y w l t h a d d l t l o n a l c o a t i n g by diode s p u t t e r l n g D uslng

Au/PdD

procedures

which best s t a b l l z e t h e speclmens and p r o t e c t them from thermal damage t o mucllage (Rosowskl and G l l d e r D 1977; Rosowskl

et

al.D

examlned w l t h a Cambrldge S4-10 SEMI operated a t ZOkV.

their

1981). Samples were Photographs were

made

w l t h P o l a r o i d 55 P/N o r Kodak 4127 c u t f i l m .

17.2.3 Water samples were c o l l e c t e d I n 1-1 I t e r polypropylene b o t t l e s and transported t o t h e l a b o r a t o r y packed i n i c e and

tn

the

A

dark.

sample

of

150 ml

was

bottle

for

preserved w l t h 2 m l o f h y d r o c h l o r l c a c l d and transported I n a g l a s s analysls

of

unf 11t e r e d

ferrous water

Iron.

Ferrous

(APHAD

1976).

Iron

analyses

were

performed

Nltrate-nltrogenD

on

thls

amnonl umnltrogen.

orthophosphate and s i l i c a were analyzed from f i l t e r e d water

samples

(Mllllpore

f l l t e r t y p e HAD 0.45 pm p o r o s l t y ) D f o l l o w l n g t h e procedures o f APHA (1976).

17.2.4 I n dlscusslng t h e o r l e n t a t i o n o f diatoms and o t h e r

organlsms

on

substrates we have chosen terms which do n o t depend on t h e o r l g l n a l

the

glass

orlentatlon

o f t h e a r t l f l c l a l substratesD which was v e r t l c a l . We d i s t i n g u i s h t h r e e t i e r s

community s t r u c t u r e b u t do n o t mean t o Imply t h a t It 1s always p o s s i b l e t o these t l e r s , f o r

I n many cases sediments obscure t h e

relative

posltlon

communlty members. The terms p r o s t r a t e o r low p r o f i l e are used f o r

of

view

of

the

1 and

tier

perpendicular o r u p r l g h t f o r t l e r 2 r a t h e r than lowerstorey and upperstoreyD o r v e r t i c a l and h o r l z o n t a l . T I e r s 1 and 2

develop

alongside

each

other

on

the

prlmary s u b s t r a t e as does t l e r 3. T i e r 3 may develop over t i e r s 1 and 2

because

o f I t s g r e a t e r p o t e n t i a l s l z e and fllamentous nature. TherefOrer by t h e

use

another. Organlsms

which

attach

to

members o f

the

three

of

on t o p o f

t h e term t l e r we do n o t Imply t h a t one t i e r develops attached t o o r

tlers

would

be

eplphytesD n o t a d d l t i o n a l t l e r s . The o r l g l n a l p o s l t l o n o f t h e communltles i s how they appear when t h e p l a t e s o f vertlcally. respect

to

thls

paper

Second t l e r communftles thus the

orlentation

of

the

are

vlewed

develop

In

substrate

wlth

a

the

lateral

durlng

pages

held

fashlon

wlth

imnersionD

l.e.D

perpendlcular t o t h e v e r t l c a l l y o r i e n t e d substrate.

17.3

RESULTS

The domlnant and codomlnant dlatoms f o r t h e s p r i n g and summer months f l r s t year o f t h e study (1979) are presented i n Table genera f o r a l l s i t e s was 9.2 and t h e range was perlodD 17 specles occurred

as

domlnants

or

3-15.

1.

The

I n the

codomlnants

mean

of

two-year

(Tables

the

number

1-51.

of

study For

purposes o f I l l u s t r a t i n g t h e t h r e e dlmenslonallty o f t h e communltles a t S l t e s A D

255 TABLE 1 Spring and summer dtatom pertphyton o f Maple Creek, on g l a s s substrates? 1979.

*

~~~

~

Total Dtatoms/mm

Doml nant Spectes/mm

Codomlnant2 Specles/mm

Other Diatoms/mm

Stte A June July August

1,500 100 7

630a 68a 4a

270g 16b lb

600 23 2

Stte 0 June August

lr500 470

900; 180

380b 180b

290 160

Stte C June July August

1,200 3 ,700 5r600

450b 2~300: 4,300

77; 820b 880

600 550 360

Slte D June July August

720 2 ? 800 1,600

1, OOOd 500

190c agoe 590f

280 900 510

**

*A l l numbers rounded **Immersion periods:

230d d

t o two s l g n i f t c a n t figures.

June = May 23-June 20; J u l y = June 20-July 18; August = J u l y 18-August 15. Key: a. = -J&gxd&a (Bre'b.) Grun., b. = intrlcatum Kutz., c. = 6. Darvulum (Kutz.) Grun., d. = Naulcula (Ag. 1 Kiitz., e. = Nitrschia xu@dhh Grun. , f. = Nitzschia ~ p p D. g. = Svnedra ylnn (Nitz. 1 Ehr. B, C,*and D. these

are

morphologically

photographs from a s t n g l e (May/June,

as

b u t t o l i m t t t h e number o f e l e c t r o n micrographs

cmunittes

collection

characterlzed

p e r i o d which

with

documentatton?

a

selection

developed

I n the

of

spring

1979, Figs. 3-28).

Ftgure 2 i l l u s t r a t e s t h e r e l a t l v e d e n s i t y and low p r o f l l e o f t h e whtch develop I n one month. Midge f l y (Chironomtdae) pupal e v l d e n t a t S i t e s B and D I n t h e s p r i n g b u t n o t t n t h e

cases

summer.

communities were

The

clearly

only

other

obvlous d e t a i l d i s c e r n i b l e w t t h o u t m a g n l f l c a t t o n 1s t h a t t h e community a t S l t e A was l e s s dense i n t h e s p r i n g than summer. T h i s

was

because

angtosperm

along t h e banks o f t h e stream screened o u t a s l g n l f t c a n t p o r t t o n durtng t h e t r a n s i t i o n from s p r i n g t o summer. During t h e p l a s t t c was used e f f e c t t v e l y

to

Inhtbtt

angtosperm

of

following growth.

growth

the

light

year,

Shadtng

black due

vascular p l a n t growth a t t h e o t h e r s t t e s was apparently n o t as s l g n l f t c a n t t o t a l numbers o f c e l l s are compared f o r both years o f t h e study ( c f . 3 ? 4). T h i s was perhaps due t o t h e grazing and t r a m p l i n g by c a t t l e , t h e stream was much wlder a t these sttes, reduced t h e l l k e l t h o o d o f shading.

placlng

of

samplers

In

to

when

Tables

1,

and, because the

mtddle

256 TABLE 2 F a l l and w i n t e r diatom p e r i p h y t o n o f Maple Creek, 1979/1980. Total D i atoms/mm’ Site A September December February

27 4,499 83

Site B September

1,041

Site C September October November December

16,336 10,302 10,989

801

Site D September October November

8,771 7 ,765 537

Dominant Speci es/mm

on g l a s s substrates,

Codominant2 Species/m

7d 2~677~ 52a

Other D iatoms/mm

15

5a 872a

950 20

llC

410

24ae

383d

3s56gfd

5,733; 3,538 5,101; 3 09 2,477bd

,

2,965d 1, 706d 172

7 034 3,799 4,182 320

2,2497 1 945 20OC

4,045 2,100 120

,

3,721 217h

* Immersion

periods: September = August 15-September 11; October = September 11-October 9; November = October 9-November 8; December = November 8-December 4 ; February = December 4, 1979-February 23, 1980. Key: a. = Achnanthes (Bre’b.) Grun., b. = Gomohonema intricatum Kutz. c. = G. (KUtz. 1 Grun, d. = Navlcula U c e o l a (Ag.) Kutz., e. = ’ Grun., f. = fontlcola Grun., g. = fh%ljan clrculare (Grev.) Ag. , h. = M&. U i c u l a (Greg.) Grun.

,

17.3.1

m.

S D r i n a o w t h ’ (19791

I n t h e f i r s t t h r e e months o f t h i s study

we

found

diatoms; o n l y those which were dominant o r codominant

17

different

were

species l e v e l . These dominant and codominant diatoms were with the

exception

-,

of

Cvmatooleura

(Bre’b.)

found

at

Smith

Wm.

to

all

were was

of the

sites

. .

and

which occurred o n l y a t S i t e A. S i x species o f diatoms

o r codominant. A t S i t e A, t h e dominant diatom i n June and J u l y

ku&sd&&,

genera

identified

dominant

Achnanthe+

a species n o t found a t t h e o t h e r s i t e s and one known t o c o l o n i z e new

streams and t o disappear under c o n d i t i o n s

of

hish

organic

1974). It i s perhaps s i g n i f i c a n t t h a t Gomohonema

did

enrichment not

(Lowe,

occur

as

a

dominant a t S i t e A whereas i t occurred a t a l l o t h e r s i t e s . T h i s species has been suggested as an i n d i c a t o r o f o r g a n i c water p o l l u t i o n (Lowe, Reimer, 1975). The dominant diatoms a t

Site

L ~ ~ ~ Q intricatum, w M species g e n e r a l l y (Lowe, 1974; P a t r i c k and Reimer, 1975).

C

1974;

were

characteristic

of

Patrick

and

lanceolata

and

eutrophic

waters

257 TABLE 3 Spring diatom periphyton o f Maple Creek, on g l a s s substrates, Total Diatoms/mm

1980.

Dominant Species/mm

Codominant2 Specles/mm

Other Dlatoms/mn

1,512:

53; 743 208

32 263 110 55 154 45 5

2,518 Site B March April May June

644 1,087 306 32

3779 563; 221d

22

212c 380g 4 Oe 5e

Site C March April May June

99 829 84 9 307

389 Slog 441e 210h

33c 225' 161' 51'

28 94 248 46

Site D March Aprll May

229 995 383

106g 665 124'

105' 157'

lloe

18 123 149

713; 600

70: 169

219 120

S t t e E*** May June

1,002 889

* Immersion

periods: March = February 23-March 22; A p r i l = March 22A p r i l 19; May = A p r l l 19-May 19; June = May 19-June 18. Key: a. = Achnanthes lanceolata (Br8b.I Grun. , b. = &QW vaucheriae (Kutz.) Peter., c. = GomDhonema Intrlcatum Kutz., d. = L. oarvulum (Kutz.) Grun., e. = Navicula lanceolata (Ag.) Kutz.. f. = circulare (Grev.) Ag., g. = u r e l l a Kutz., h. = m&ci.Ma Grun.

**On A p r l l

1 9 sheets o f heavy black p l a s t i c were placed along t h e stream banks t o i n h i b i t anglosperm growth which had caused severe sampler shading.

***Added

on A p r i l 19, since s o i l conservatlon p r a c t i c e s were t o be implemented upstream from t h i s l o c a t i o n .

SEM has provided

a

useful

perspective

of

the

organisms

p a r t l c u l a t e s which developed i n t h e creek periphyton.

The

and

o f s o i l p a r t i c l e build-up i s i l l u s t r a t e d by comparing S l t e s A and B 3-7 8 8-14). (lr500/d;

Although t h e t o t a l number o f see Table 1, footnote*),

diatoms

at

each

t h e dominant species

associated

morphological (cf.

s i t e was

were

effect Figs. similar

different,

and

whereas diatoms were c l e a r l y e v i d e n t a t S i t e A (Fig. 3 ) and were s t i l l

trapping

considerable q u a n t i t i e s o f p a r t i c u l a t e s (Figs. 4-71,

obscured

they were

almost

2 58 TABLE 4 Summer and f a l l diatom p e r i p h y t o n o f Maple Creek, on g l a s s substrates, Total Dtatorns/mm Site A * July August September October November Site B July August

948 55

Stte C July August September October November Site D July September October November Site E Auaust

613 131 693 4,220 8,932

1,006 1,692 92 0 6,990 3,898 1,631

185 2,315 5,227

Codomtnant2 Spectes/mm

Dominant Spectes/mm 459;: 58 392: 2~844~ 6,457

74 21 148 a44 1,447

387d 17e

152 12

26 410f 804: 403 3 ~ 6 9 1 ~ 1,902

323: 614 294: 28146 896'

273 274 223 1t 063 1,099

388; 4 7. 25ge 1,531g

415 39 475 706

94e

109

841f 98; 1 ~ 5 8 1 ~ 2,990

301

Other D i atoms/mm

7gb 52: 153 532e 1,027"

4OOff

9gf

1980.

*

Immersion periods: J u l y = June 18-July 23; August = J u l y 23-August 21; September = August 21-September 22; October = September 22-October 20; November = October 20-November 20. Key: a. = Achnanthes (Br6b.l Grun., b. = curvata (Kutz. 1 Lagerst., c. = GomDhonema KitZ. (Klitz. 1 Grun., e. = Navirula (Ag.) Kutz., d. = G. f. = Nitzschla ' Grun., g. = (Wm. Smtth) Grun., h. = U. Wm. Smith, t . = Surlrella K h .

w.

a

by p a r t t c u l a t e s a t S i t e B (Figs. 8 B 9). SEM a l s o shows t h e r e l a t t v e

o f t h e s t z e o f vartous diatoms.

For

t

example,

although

( t t e r 1) was t h e numerical domtnant f o r S t t e A I n June,

importance

&bm$bi lanceolata It was Sycmka U l M

( t t e r 2 ) which was t h e biovolume domtnant when scanntng e l e c t r o n micrographs are examtned (cf. Ftgs. 3 8 4). The s t r t k t n g f e a t u r e o f S t t e B ( c f . Ftgs. 6 8 10, a t t h e same was t h e d t f f t c u l t y t n f i n d i n g any diatoms because o f t h e them. Some s p h e r t c a l c e l l s ( u n t d e n t l f l e d , distance,

debris

magntficatton) which

perhaps from sltme which t h e y secrete, which t h e n

I n spectmen p r e p a r a t t o n l e a v t n g a space around them.

This

s h r i n k s o r Is flocculant

n o t o n l y c o l l e c t s between t h e dtatoms (Figs. 9-11) b u t may a l s o occur surface (Ftgs. 13 B 14). It was n o t determined matertal

covered

Ftg. 12) were a b l e t o keep d e b r l s a t a

if

the

dtatoms

on

secreted

or t f It was depostted on t h e dtatoms from t h e stream water.

lost

material thetr this

259 TABLE 5 Spring diatom p e r i p h y t o n o f Maple Creek, on g l a s s substrates, Total Diatoms/mm

Dominant Species/mm

*

Site A March April May

9,917 1,279 7 ,582

Site B April

1,462

Site C March April May Site D March April May

Codominant2 Species/mm

6~50 d5~

1981. Other Diatoms/mn

lt388f 409: 30

2 t 023 3 02 16

619'

483f

361

260 5,810 908

93 2t034e 218g

36; 843 87 a

130 2,934 603

10,447 13,939 3 ,833

6,456b 7,318; 1t 782

568 7#537a

2t633bd

-

1,358 3,485 623

3~136~ 1, 428

*

Immersion periods: March = November 20-March 14; A p r i l = March 14A p r i l 14; May = A p r l l 14-May 12. Key: a. = Achnanthes (Breb.) Grun., b. = GomDhonema D a r v u l w (Kutz.) Grun., c. = JamxhLa (Ag.) Kutz., d. = Nitzschla Grun., e. = Wm. Smith, f. = w i t e l m Hustedt, g. = curvata (Kutz.) Grun.

m.

u.

A comparison o f S i t e s B and C a t t h e same m a g n i f i c a t i o n shows (Fig. 15) a l s o trapped a dense s l l t load, b u t it was

possible

i n d i v i d u a l diatoms i n t h i s community (Figs. 15 8 16))

unlike

that

Slte

C

to

distinguish

Site

B i n most

specimen areas. On many o f t h e diatoms a t t h i s s i t e , an o r g a n i c s k i n

was

noted

(Figs. 18 8 19). be

The s i l t l o a d t h a t t h e s u b s t r a t e s c o u l d h o l d a t S i t e s B and C appeared t o t h a t which occurred between t h e perpendicular diatoms

of

meant t h a t t h e p r o s t r a t e forms were mostly buried, i.e.,

A t h i r d t i e r developed i n c e r t a i n filaments

of

unknown

identity

areas (Fig.

of 17))

the

the

community

which

n o t observed w i t h

substrate

initiated

and

SEM.

consisted

perpendicular

to

of the

s u b s t r a t e b u t which t h e n developed over t h e adjacent sediment-loaded double t i e r paralleling

the

surface;

these

fllaments

were

not

stalks

of

peritrichs

( V o r t i c e l l i d a e ) which were r e a d i l y i d e n t i f i a b l e (Flg. 19) because they

extended

away from t h e second t i e r by t h e i r c o i l e d s t a l k s . The most i n t e r e s t i n g t i e r o f t h e one-month (Figs. 20

a

old

21). As a t S i t e s B and C, t h e two-tlered

b u r i e d w i t h sediments (Figs. 25-28),

substrates communlty

was

at

was

and c e r t a i n diatoms were noted t o

Site

0

completely have

an

260

26 1 t n t r t c a t e organic coating community,

(Figs.

loricate perttrtchs

t w o - t t e r l e v e l o f t h e community b u t a r e t h i r d t t e r a l s o developed,

certain

22-24);

(Vagintcol tdae), not

nondiatom

were

members

conspicuous

tllustrated

here.

of

the

wtthin

the

filamentous

A

attached t o t h e g l a s s b u t w i t h t h e b u l k o f t h i s

composed o f f i l a m e n t s p a r a l l e l t o t h e b u r i e d s u b s t r a t e and colonized by 1t k e

Svnedra U

and

GomDhonema

tter

diatoms

(Figs. 20 8 21). Because o f t h e

network o f t h i s t h t r d t t e r o f filaments,

loose

and t h e a b t l t t y o f t h e P e r t t r t c h i d a

expand and c o n t r a c t i n and o u t o f t h e second and t h i r d t i e r 25, 281, t h i s t h i r d - t i e r communtty d i d n o t

appear

levels

sufftctently

to

(Figs.

stable

20,

to

be

Important I n h o l d i n g seston. 17.3.2

F a l l and wtn-

1979.

The f a l l c o l l e c t t o n s g e n e r a l l y showed an Increase i n c e l l d e n s i t y over I n t h e summer (Table 2 ) . S i t e D showed a f o u r - f o l d

increase I n c e l l

those

numbers

in

w h i l e a t S i t e C d e n s t t i e s were two t o t h r e e

monthly c o l l e c t i o n s from Sept.-Nov.,

times g r e a t e r t h a n i n t h e summer pertod. Overgrowth o f Iyphn a t S i t e A prevented development o f a dtatom pertphyton. and sedtment was w i t h i n 5 cm o f

A t S t t e B (Oct. 9 t h ) t h e stream had d r i e d up

the

top

of

the

pipe

holding

the

sampler,

suggesttng a d e p o s t t t o n o f sedtment over t h e preceeding months t o a depth o f cm

30

.

A new domtnant, -iu@iLj~,

along w i t h M a y i c u l a

ir&&&um

and

occurred a t S i t e s C and D t n

early

fall

lanceol. These t a x a were l a t e r replaced by !im&mma fonticola, f o l l o w e d by G. p a r v u l u q and H. lanceolata a t

Stte C i n the late fall. s i r c u l u e was an e a r l y w i n t e r dominant, (water temp. 3"C), I n l a t e winter.

lanceolata were

At

f o l l o w e d by Site

C

occurring only

at

Stte

A

Achnanthes lanceolata and GomDhonema l&ckaLw (Dec.

4th.1,

Nitzschia &&aikLa

codominants. An i c e cover o r encasement o f t h e

i c e prevented t h e development and/or c o l l e c t i o n o f samples

at

and fhduh sampler Sites

In B

the

and

d u r i n g t h e w i n t e r months. Figures 3-7 of pertphyton communittes a t S t t e A, Fig. 3. L t g h t sediment l o a d w t t h second t t e r o f area o f t h e substrate. 130 X.

immersed May 23-June 20, 1979.

Svnedra u l . dominant ~

Fig. 4. F i r s t t i e r w i t h b a c t e r i a e v i d e n t a t whtte arrow; second t t e r w t t h p a r t t c u l a t e s clumped near t h e i r apices. 260 X.

U

i n this

Svnedra

Fig. 5. T i e r 1 w i t h Achnanthes lanceolata and Navlcula lanceolata I n center. Sediment p a r t t c u l a t e s aggregated and attached t o t t e r 1. 260 X. Fig. 6. Mixed diatom spectes of g r e a t range i n stze, and several n o t attached d i r e c t l y t o t h e g l a s s substrate. 650 X. Ftg. 7. P a r t i c l e s trapped w i t h t n t h e perpendicular colony o f 1,300 X.

m u h i i .

D

26 2

17.3.3 R e l a t t v e l y low l e v e l s o f growth developed (Table 31, w t t h t h e

highest

A t S i t e s B-D,

cells/&).

denstty

at

occurrtng

a was

W r e l l a

c h a r a c t e r t s t t c o f c o o l runntng water (Lowe,

narvulum

and

all

stations

at

Site

A

the

spring

I n April

domtnant in e a r l y spring,

(2,518 a

taxon

GomDhonema I n t r f c a t u m r 8.

1974).

c o n s t i t u t e d most o f t h e o t h e r I n l a t e s p r t n g a t S t t e A, E c a g t l a r t a

I n the sprtng flora.

in

dtatoms

present

xu&baAe . appeared as

a new codomihant; t h t s taxon ts t n d i c a t t v e o f e u t r o p h i c waters (Lowe, 1974).

17.3.4 Data f o r t h t s p e r i o d ts found t n Table 4. The

heavy

rains

and

which occurred on June 14 a l t e r e d t h e e n t i r e stream morphometry

high

as

bank was eroded and t h e bank v e g e t a t t o n destroyed. Consequently, a l l S i t e s A and D were l o s t

and

those

at

the

remaining

sttes

wtnds

the

stream

sltdes

had

at

undoubtedly

undergone extreme abrasion. Although June was a month o f dense a l g a l growth previous year, t h e growth f o r samples from S i t e s B, C, and

E

fell

well

the

below

those o f t h e previous year. Stte

Water f l o w was down s u b s t a n t t a l l y by midsummer a t a l l s t t e s except A. was dominated by

A. lanceolata and

a new codomtnant-curvata,

B, C, and D were again domtnated mainly by Nitzschia

A

whtle Sttes

m.The

water

level

a t S t t e E was n e g l i g i b l e and t h e sampler was destroyed (presumably by c a t t l e ) .

At

By l a t e summer, water l e v e l s as w e l l as dtatom d e n s t t t e s were low a t S i t e s B, and E. Samplers a t S i t e s B and

mud, w h t l e

at

Stte

D

the

E were densely shaded and p a r t i a l l y encased i n

sampler

was

destroyed.

Only

C

Stte

and Nitzschia appreciable diatom growth, w t t h Qxuhmem h.t~&&~

exhtbtted

mgtdLa

t h e dominant spectes. I n t h e e a r l y f a l l , S i t e s B and E (Sept. 22) were d r y and water flow was low a t

S i t e s C and D.

Achnanthes lanceolata and Eunotla curvata were

S i t e A and Navlcula

m

and Nitzschia

were

agatn domtnant the

at

domtnants

S t t e s C and D. By l a t e f a l l t h e sampler a t S t t e A was damanged b u t i n t a c t ,

at

wtth

evtdence o f heavy s i l t i n g . Low water f l o w occurred a t S i t e s C and D, w t t h t u r b i d and/or

statned

Nitzschia

waters.

Maxtmum c e l l

I n t h e l a t e r f a l l , a new

Unaxk,

occurred

at

Stte

wtth

C,

diatom

domtnant

for

Site

A

occurred,

Nitzschla 1974).

g e n e r a l l y t n d t c a t t v e o f oxygen r t c h sprtngs and streams (Lowe,

Lower d e n s t t t e s were found a t S i t e s extremely low water flow),

iugu&La.

denstttes

domtnant.

Interesttngly, t h i s

standtng water (Lowe, 1974).

dtatom

D

and

C

tncludtng

a

new is

beneath domtnant

noted

as

1-2 cm o f at betng

Site

D,

ice

(wtth

Nltzschia

characteristtc

of

26 3 17.3.5 S l t d e s imnersed on Nov. 20, 1980, were harvested on March 14 should be noted t h a t t h i s sample represented almost a 4-month unl t k e most o t h e r samples which period. S t t e A was domtnated by

were

such as Navicula

after

Nitzschia

w t t h many o f t h e subdomtnants betng length),

harvested

-,

and

large

diatoms

a

(Table 5). tmrston

one-month

period,

tmnerston

w,

Nltzschia

(greater

It

than

Stauroneis , -

100 JMI

in

and

~QKW&(Donk.) C1. T h i s domtnance by l a r g e spectes o f dtatoms was n o t observed a t any sampl t n g s t t e p r i o r t o t h i s sample.

A s p r t n g sample a t S i t e C (Table 5) was domtnated by

GomDhonema m,b o t h

1974). The s l i d e s a t S t t e A (May 12th) populatton o f

and

species i n d t c a t o r s o f v e r y h i g h n t t r o g e n l e v e l s (Lowe, were

Achnanthas m. Pure

covered

wtth

stands o f one

a

nearly

spectes

untalgal

had

not

been

encountered a t any s i t e up t o t h t s ttme. 17.3.6

-itv

- + r w

Seasonal d t f f e r e n c e s were e v i d e n t I n (Figs. 29-32).

the

periphyton

communtty

at

Stte

spring,

A d t s t t n c t two-ttered community developed I n l a t e

Achnanthes s u b s t r a t e ) Svnedra lilnn

1979, and

c o n s t s t t n g o f a dense growth o f p r o s t r a t e l y attached p e r p e n d t c u l a r l y o r i e n t e d ( i n respect t o t h e w t t h sediment p a r t t c u l a t e s . I n contrast, t h e

early

fall,

A

assoctated

1979, sample

showed

sparse development o f dtatoms ( o n l y 10 f r u s t u l e s observed a f t e r scanning most o f a 1c d

glass

chip),

but

bacteria

muctlaglnous s t r a n d s on t h e substrate. overlaid

the

glass

surface.

predominated, In

It should

forming

addition, noted

be

angiosperms causing shading probably favored t h i s

small

clumps

some

parttculate

that

the

development

of

matter

overgrowth of

of

heterotrophs

over autotrophs. The pertphyton communtty c o l l e c t e d a t S t t e A i n e a r l y spring, o f many clumps o f dtatoms w t t h l i t t l e

accumulatton

of

1980, conststed

sediment

parttculates.

P o r t t o n s o f t h e g l a s s s u b s t r a t e between t h e clumps were uncolontzed by

diatoms,

b u t h i g h e r m a g n t f t c a t t o n showed t h e s u b s t r a t e t o

ftlm

be

covered

with

b a c t e r i a and t h e t r associated muctlage strands. The e a r l y f a l l , consisted o f a heavy accumulatton o f sedtment p a r t t c u l a t e s , o c c a s t o n a l l y viewed w i t h i n t h i s m a t e r i a l (Ftg. 32). On areas where

sedtment

lanceolata were

butld-up

was

not

evident,

found. Although t h e p r o s t r a t e

domtnant a t S t t e A on Oct. 20, 1980 (Table 4 ) . (Ftg. 32),

t.e.,

Isolated

1980,

wtth of

patches

A. lanceolata

a

was

of

community

dtatoms

only

the

substrate

of

Achnanthes

the

numertcal

It was mostly b u r l e d by sedtments

n o t observed w t t h SEM except i n t s o l a t e d patches.

placement o f t h e b l a c k p l a s t t c along t h e banks o f t h e stream,

i n the

1980, t o c o n t r o l shadtng o f t h e sampler from vegetatton, c o n t r i b u t e d and sedtmentatton I n t h e imnedtate area o f S t t e A.

Perhaps sprtng to

the of

runoff

264 I n communities from S i t e s Br Cr and Dr where e x t e n s i v e sediment build-up

was

e v i d e n t r diatoms were o f t e n found attached t o and d i v i d i n g w i t h i n t h e sedimentsr on

thus l i k e l y contributing t o the s t a b i l i z a t i o n o f t h e p a r t i c u l a t e matter a r t i f i c i a l substrate. partially or

fully

I n a d d i t i o n , s e s s i l e diatoms were buried

in

the

sediments

commonly

33-34)D

(Figs.

found

the

either

evidence

that

p a r t i c u l a t e s were c o n t i n u o u s l y accumulating i n t h e p e r i p h y t o n stream community. F u r t h e r increase i n t h e t h i c k n e s s o f t h e

periphyton

beyond

created by p r o s t r a t e and perpendicular forms was observed i n from S i t e s C and

the

two

samples

D. Large e r e c t a l g a l f i l a m e n t s (Qedoaonlum sp.)

tiers

collected

were

basally

attachedr forming a p a r t i a l canopy over t h e s u b s t r a t e r w i t h t h e g r e a t e s t d e n s i t y a t t h e edge o f t h e g l a s s s l i d e (Fig. 3 6 ) . B a c t e r i a l mucilages a r e important i n t h e b i n d i n g o f sediment p a r t i c l e s i n t h e periphyton

of

Maple

Creek.

Unicellular

and

colonial

bacteria

were

found

attachedr v i a mucilage s e c r e t i o n s r d i r e c t l y t o t h e g l a s s s u b s t r a t e (Figs.

10 8

42Ir t o surfaces o f i n o r g a n i c and o r g a n i c p a r t i c l e s (Figs. 37-41)r and t o diatom f r u s t u l e s (Figs. 39 8 4 0 ) . B a c t e r i a

and

their

mucilages

were

found

in

all

communities sampledr regardless o f t h e season. Clumps o f b a c t e r i a l mucilage were o c c a s i o n a l l y found c o v e r i n g t h e g l a s s surface (Fig. 3 7 ) . A more common bacterial

mucilage

was

sheet-like

webs

(Fig.

38) which

often

p a r t i c u l a t e s . I n Fig. 44, b a c t e r i a beneath t h e mucilage are

visualized

e l e c t r o n beam o f t h e SEM penetrated t h e

webs.

diatoms on t h e

substrate

surface

or

delicate elevated

mucilage away

sometimes found e i t h e r p a r t i a l l y o f f u l l y overgrown w i t h

from

the

strands

form

of

collected as

the

Furthermore# surface of

were

bacterial

mucilage (Fig. 4 0 ) . I n a d d i t i o n t o t h e b a c t e r i a r protozoa and f u n g i were commonr although t h e y never were dominants i n t h e community. Figures 8-14 of p e r i p h y t o n communities a t S i t e Br immersed May 23-June 201 1979. Fig. 8. Substrate densely packed w i t h sediments e n t i r e l y obscuring t i e r 1 and t i e r 2 communities. 260 X. Fig. 9. A few diatoms b a r e l y v i s i b l e ; diatom a t b l a c k arrow n o t attached t o t h e g l a s s and w i t h f r u s t u l e damage. 650 X. Fig. 10. Two p r o k a r y o t i c f i l a m e n t s attached t o diatom o f t i e r 2 w i t h f l o c c u l a n t d e b r i s i n t h e v i c i n i t y . 2,600 X. Fig. 11. Higher m a g n i f i c a t i o n o f t h e f l o c c u l a n t d e b r i s shown i n Fig. 10. 61000 X. Fig. 12. Some s p h e r i c a l c e l l s o f t i e r 1 surrounded by debris. The c l e a r areas may represent where h i g h l y hydrated mucilage occurred and c o l l a p s e d t o t h e s u b s t r a t e w i t h c r i t i c a l - p o i n t drying. 1,300 X. Fig. 13. Surlrella

m on c e l l s

and d e b r i s o f t i e r 2.

m

2,600 X.

Fig. 14. F l a k y p a r t i c l e s bound t o Surlrella of Fig. 13 resemble t h e small p a r t i c l e s found on t h e g l a s s s u b s t r a t e i n Fig. 11; raphe on edge i s evident. 13r000 X.

265

266 Occasionally,

rod-shaped b a c t e r i a adhered d i r e c t l y t o t h e g l a s s s u r f a c e

few attachment s t r a n d s (Fig. 42). Generally,

t h e g l a s s s u b s t r a t e v i a many e x t r a c e l l u l a r mucilage s t r a n d s (Figs. Figures

43-48

illustrate

bacteria

with

their

associated

their

cell

surface

i n t e r c o n n e c t i o n s (Figs. 43 8 471, whereas o t h e r b a c t e r i a fine,

formed

densely woven s l i m e threads (Fig. 44). B a c t e r i a were

t o t h e valves o f

bacteria

only

a

colonies

commonly

w i t h t h e surfaces o f diatoms. Rod-shaped b a c t e r i a were found

strands

Some

with

to

43).

37-40,

mucilage

attached t o t h e s u r f a c e o f t h e p e r i p h y t o n o r t h e g l a s s substrate. secreted l a r g e numbers o f s t r a n d s from

with

however, b a c t e r i a were attached

few with

associated

attached

apically

GomDhonema intricatum (Fig. 45). and were i n t h e process o f

budding a t t h e f r e e end (Fig.

46).

Other

rod-shaped

threads were seen p r o s t r a t e l y attached t o t h e g i r d l e

bacteria region

with

mucilage

Nltzschla sp.

of

(Fig. 47) and t o t h e valves and g i r d l e bands o f Merldlon circulare (Fig. 48). The most i m p o r t a n t organisms associated sediments were filamentous types, These presumptive

bacteria

with

similiar t o

were

present

important a t S i t e s C and D. Indeed,

these

the

surface

those

at

of

illustrated

Sites

A-D,

filaments,

f i l a m e n t s developed, f i l a m e n t s were micrometers,

about

f o r example.

in

but

occasionally

in

diameter

but

Fig.

55. most

branching,

communities

I n a l l communities,

connecting aggregates o f organisms together.

1 micrometer

trapped

appeared

were t h e conspicuous f e a t u r e o f t h e o u t e r s u r f a c e o f t h e t i e r 2 S i t e C (10/20/80) and D (8/11/79),

the

others

at

similar thin Most

were

of up

the

4

to

i n d i s t i n g u i s h a b l e as b a c t e r i a based on t h e i r morphology.

Diatoms were t h e most conspicuous e u k a r y o t i c members

of

the

one-month

periphyton. A v a r i e t y o f growth h a b i t s and attachment mechanisms were by t h e diatoms.

Achnanthas

s u r f a c e a t S i t e A,

colonized

and was p r o s t r a t e l y attached

large by

an

expanses

of

adhesive

between t h e r a p h i d v a l v e and t h e substrate. The attachment was

so

even t h e r a p h i d valves o f dead c e l l s remained attached (Fig. 49). s t r u c t u r e s were l e s s e v i d e n t i n

AmDhora ovalis var.

pediculyg

old

exhibited the

pad

glass

produced

secure

that

The attachment

(Kutz).

V.H.

su

Figures15-19 o f p e r i p h y t o n communities o f S i t e C, immersed May 23-June 20, 1979. Fig. 15. D e b r i s n o t t i g h t l y packed and diatoms evident. 260 X. Fig. 16. Diatom a p i c a l l y attached t o t h e g l a s s s u b s t r a t e and surrounded by debris; another diatom, lower l e f t on t i e r 2. 1,300 X. Fig. 17. U n i d e n t i f i e d f i l a m e n t s o f t i e r 3 community. Filaments o r i g i n a t e d from t h e g l a s s surface. 260 X. Fig. 18. Nitzschia sp. on t h e t i e r 2 community w i t h mucilage adhering t o t h e v a l v e f a c e and g i r d l e regions. 2,600 X. Fig. 19. Diatom w i t h mucilage strands on v a l v e face and g i r d l e regions; c o i l e d s t a l k o f p e r i t r i c h e v i d e n t a t lower r i g h t . 2,600 X.

268 DeT. (Fig. 50) embedded

in

and k i c u l a detrltal

Unmdxta

particulates.

~JXUIJS~ UuUdcurvata.

(Fig.

In

Svnedra

contrast,

Surlrella u & a

species

52),

and GomDhonema

perpendicular c o l o n l e s which were attached t o t h e s u b s t r a t e The attachment pad o f

by

commonly

found

u, Merfdlon oarvulurn formed adhesive

pads.

Eunotla curvata was connected t o t h e proxlmal c e l l

near t h e v e s t i g i a l raphe (Fig. 5 6 ) . whereas

-m

produced a s h o r t

mucllaglnous s t a l k (Fig. 5 8 ) . Long-stalked diatoms were,

however.

uncommon

t h e Maple Creek p e r l p h y t o n although t h e e a r l y s p r i n g 1980 community showed several patches o f

apex

at

In

Site

B

GomDhonema sp. w i t h v e r y l o n g s t a l k s forming a t h i r d

t i e r (Fig. 5 9 ) .

17.3.7 The water chemistry data I s presented I n Tables 6 and 7. n u t r i e n t I n p u t p r l m a r l l y from ground water

while

the

Site A

downstream

i n c l u d e c o n t r l b u t l o n s from s o i l r u n o f f . The h i g h e s t

nitrate

mg/l) was a t S i t e A, w i t h l e v e l s reduced downstream

(means

A m o n l a on t h e o t h e r hand was l o w e s t a t S l t e A; c a t t l e and The

hlghest

mean

concentratlon

for

WE)

sites

level below

(mean 1.43 mg/l).

0.58

wildlife

t h e stream watershed presumably account f o r t h e h i g h ammonla f o r S i t e s C-E.

represents

levels

active

In

determlned

orthophosphate,

a

form

associated w i t h s o l 1 p a r t i c u l a t e s I n r u n o f f s i t u a t i o n s , occurred a t S i t e C, be

impacted

crash

of

planktonic

diatom

communltles i n c e r t a l n s i t u a t i o n s (Bringmann and Kuhn, 1971; Lund e t al.,

1975)r

wlth

watershed

that

will

be

least

conservation p r a c t i c e s . Iron, I m p l i c a t e d

likely

the

to

site

I n the

remalned a t h i g h l e v e l s f o r every c o l l e c t l o n p e r i o d when a t low l e v e l s t o cause t h e wane o f diatoms,

(Table

by

soil

6). S i l i c a ,

shown

p a r t l c u l a r l y p l a n k t o n i c species

(Jorgensen, 1957; Heron, 1961; Kilham. 1971), was found a t very h i g h mean l e v e l s

(9.21-27.51 mg/l) and would n o t have been l i m i t i n g t o growth on any o f t h e Figures 20-24 of p e r l p h y t o n communities o f S l t e D, 1979.

days

incubated May 23-June 20,

Fig. 20. Svnedra vlnn ( r i g h t w h t t e arrow) and sp. c o l o n i e s ( t h e clumps o f c e l l s ) on u n i d e n t i f i e d f i l a m e n t s o f t i e r 3; s t a l k e d p e r l t r i c h s e v i d e n t a t t h e l e f t w h i t e arrow and above. T i e r s 1 and 2 b u r i e d I n sediments, lower right. 132 X. Fig. 21. C l u s t e r o f GomDhonema sp. on f i l a m e n t s o f t l e r 3; a few diatoms e v i d e n t I n t h e d e b r l s o f t i e r s 1 and 2. 330 X. Fig. 22. Valve ( V ) and g i r d l e view (GI o f showing a few clumps o f mucilage. 2,650 X.

s p . on surface o f t i e r 2

Fig. 23. Mantle edge o f specimen i n Fig. 22; v a l v e f a c e ( r g h t ) and g r d l e ( l e f t ) r e g i o n w l t h mucllage strands. 13,300 X. Fig. 24. G l r d l e o f specimen I n Flg. 22 showing minute papi l a e o f muc l a g e o f unknown o r i g i n . 26,500 X.

270 TABLE 6

Maple Creek water chemistry (mg/l) N03-N

PO4-P

sio2

Fet+

A B

0.28 0.86 C 0.47 D 1.24 E 0.75

1.29 0.90 0.73 0.75 0.87

0.05 0.05 0.22 0.22 0.12

24.16 14.48 15.92 16.08 18.72

0.22 ,0.28 0.26 0.28 0.34

A 0.30 B 0.62

1.35 0.65 1.40 0.91 0.67

0.05 0.51 0.16 0.08

27.94 23.17 24.33 19.28 23.56

0.26 0.68 0.72 0.56 1.04

A B

0.04 0.08 C 0.38 D 0.10 E 0.19

2.03 0.05 0.98 0.32 0.01

0.07 0.06 0.15 0.09 0.07

26.50 2.13 16.10 12.10 7.90

0.15 0.30 0.15 0.45 0.41

A B

0.17 0.15 C 1.39 D 1.48 E 0.87

1.15 0.24 0.45 0.52

0.07 0.18 0.43 0.24 0.08

46.53 10.25 39.35 12.36 6.60

0.09 0.32 1.10 0.49 0.24

BLD

1.42 0.05 BLD

0.52 0.15 0.02

30.55 20.04 1.93

0.35 0.23 0.36

2.04 0.62 0.95

0.03 1.60 0.29

28.72 24.61 15.12

0.32 1.25 0.83

A

0.05 0.20 D 0.08

1.44 1.31 0.65

0.08 0.23 0.22

21.90 18.67 7.90

0.30 0.15 0.13

A 0.07 B BLD

1.25

C 0.06 0.63

0.13 0.61

0.03 0.02 0.02 0.12

21.67 0.96 7.49 2.37

1.14 0.12 0.20 0.15

A 0.04 B 0.02

1.31

0.04 0.05 0.17 0.16

17.11 4.25 1.93 0.14

0.23 0.68 0.43 0.47

0.04 0.19 0.58

30.04 14.32 3.45

0.20 0.28 0.41

NH4-N Site 5/19 1980

6/18

C 0.57 0.57 0.80

D E

7/23

8/21

A

9/22

C 0.06 D 0.50

A 0.03 10/20 C 5.92 D 0.32

11/20

3/14 1981

4/14

5/12

c

D

BLD

BLD

BLD BLD

C 0.08 D 0.02

0.05

A

BLD

0.98

C 0.09 D 0.83

BLD

0.75

BLD = below level o f detection

0.05

271 TABLE 7 Mean and range values o f the water chemistry o f Maple Creek (mg/l) May, 1980 t o May. 1981. Slte

A

B

C

D

E

NH4-N

1ow mean hlgh

BLD 0.10 0.30

BLD 0.29 0.86

0.06 0.92 5.92

0.02 0.58 1.48

0.19 0.65 0.87

N03-N

1ow mean high

0.98 1.43 2.04

0.05 0.38 0.90

BLD 0.58 1.40

BLD 0.55 0.95

BLD 0.39 0.87

PO4-P

1ow mean hlgh

0.03 0.10 0.52

0.02 0.07 0.18

0.02 0.33 1.60

0.02 0.21 0.58

0.07 0.09 0.12

sio,

1ow mean high

17.11 27.51 46.53

0.96 9.21 23.17

1.93 18.28 39.35

0.14 9.08 19.28

6.60 14.20 23.56

Fe++

1ow mean high

0.09 0.33 1.14

0.12 0.40 0.68

0.15 0.48 1.25

0.13 0.41 0.83

0.24 0.51 1.04

water

samples

BLD = below l e v e l o f detectlon water samples were taken. The l i m l t e d number o f

(10)

d i f f i c u l t t o determine any seasonal trends (Table 61, although

makes

it

regeneration o f

c e r t a i n n u t r i e n t s over t h e one-month span between samples i s suggested from the data. 17.4

DISCUSSION

17.4.1 The data from the water chemical analyses (Tables 6 and 7) make it c l e a r t h a t Maple Creek I s h i g h l y eutrophic, based on

inorganic

nitrogen

and

phosphorus

concentrations. S l l i c a was always 10-100 times more abundant t h a t necessary diatom growth. w i t h other macronutrients a t s u f f l c i e n t l e v e l s t o support

for

active

growth. 17.4.2 Studies which assess a removing and

minimally

particular

dlsturbing

production (Rodgers e t al.,

aspect the

of

periphyton

substrate,

for

without

example,

1978; Pennak and LaVelle, 1979; Loeb,

for

carbon

19811,

would

appear t o l e a s t i n t e r f e r e w i t h the functioning o f natural communltles measuring apparatus i s i n place

(although

container

effects

must

once the be

always

considered). Studies which vary a physical parameter o f natural communities, f o r example such as l l g h t by shading h a l f o f stream channels w i t h

a

plastic

cover

272 (Rountck and WtnterbournD 1983)D leave t h e parameters (e.g.D

water

itself

unaltered

and

other

wtndD i n s e c t s D d e b r i s ) a r e mtntmally affected. (Vadas,

D i r e c t observatton o f some community aspects a r e p o s s i b l e underwater 1977; PrOtaSOV e t al.,

1982). HoweverD d i r e c t study o f freshwater microcommunity

s t r u c t u r a l morphology o r development

In SLLUu s u a l l y

ts n o t p o s s i b l e because o f

t h e minute StZe of many o f t h e members; such communities must their

environment

for

mtcroscopic

observattons

of

be

removed

detailed

from

community

o r g a n i z a t i o n and morphological f e a t u r e s ( b u t see Kennelly and Underwood, 1984). The removal of a r t i f i c i a l o r n a t u r a l ltmited

appltcattons

In

assessing

substrates

community

may

dynamics

componentsD f o r t h e f o l l o w i n g reasons. F i r s t D t h e grazers,

result and

in

data

total

by d e f t n i t t o n species

which move over and through t h e communityD a r e n o t

ltkely

when s u b s t r a t e s a r e removed. I f t h e y are sometimes

to

remain

attachedD t h e i r

attached

attachment as

may be tenuous o r s h o r t t n d u r a t t o n so t h a t they a r e dislodged o r leave sample i s c o l l e c t e d . O r D mtcroscale (e.g.D

they

may

be

fast

movers

in

low

abundance

I n s e c t l a r v a e o r gastropods)D and perhaps nocturnal

a c t i v i t i e s as w e l l D and t h u s would be ( s e c t i o n s o f mtcroscope s l t d e s )

unobserved

if

with

community

the

samples

the

on

a

in

their

were

small

or i f t h e c o l l e c t t o n s were made i n d a y l t g h t

hours (as i n t h i s study). Even approaching an a q u a t i c s t t e f o r c o l l e c t t o n

purposes

may

c e r t a t n grazers j u s t as It would i n a t e r r e s t r i a l community. It

frighten is

well

off known

t h a t zooplankters may avoid n e t s t h a t a r e used t o c o l l e c t themD i f t h e n e t s

are

n o t moved r a p t d l y enough. C l e a r l y thenD t h e herbivores o f a

are

n o t l i k e l y t o be d t r e c t l y assessed by SEM

of

substrates

mtcrocommunity since

they

permanently attached and/or abundant components o f such substrates.

are

I n 10

not years

o f s t u d y i n g p e r i p h y t o n mtcrocommuntties we have y e t t o f t n d any t y p t c a l l y m o t i l e herbivores on SEM s u b s t r a t e s from

stream

or

reservotr

a r t i f t c i a l s u b s t r a t e s I n t h e daytime (HoaglandD Rosowskt.

samples RO9Inerr

collected

Figures 25-28 o f p e r i p h y t o n communittes o f S t t e DD tmmersed May 23-June 20D 1979. Cracks t n F i g u r e s 25-27 a r e belteved t o be a r t t f a c t s from specimen preparattonD t a eD s h r t nkage from c r t t i c a l - p o i n t drying. Ftg. 25. Dtatoms obscured by sediments; two p e r i t r t c h s ( P e r i t r i c h i d a ) attached t o g l a s s s u b s t r a t e and feeding a t t h e l e v e l o f t t e r 3. 265 X. Flg. 26. Lone a p t c a l l y attached debrts. l D 3 5 0 X. Ftg. 27. 660 X.

Gomohonema p a r v u l w

on

unpublished

o f t t e r 2 surrounded by

( r i g h t ) on d e b r t s whtch has b u r i e d t t e r s 1 and 2.

Fig. 28. Same spectmen and m a g n t f t c a t t o n as t n Fig. 27, b u t t n an area w t t h diatoms and p e r i t r i c h s o f t h e f a m i l y V o r t t c e l l idae. Several dtatoms dtspersed w t t h t n t h e second t l e r r a t h e r t h a n attached d i r e c t l y t o t h e g l a s s substrate. 660 X.

273

274 observattons).

Thus,

aware t h a t we a r e

I n constdertng t h e data o f t h e present stream study, we are

not

herbivores, and t h a t t h e

observing

a

domtnant

major dtatom

component

of

the

community,

the

ltfe-forms

of

the

communtty

have

developed under s e l e c t i o n pressure from t h t s component. SEM

studies

whtch u t t l t z e c o l l e c t t o n s from a r t t f t c t a l o r n a t u r a l substrates.

nevertheless

Those

members

o f t h e community whtch a r e f t r m l y attached,

algae,

fungt,

I n face o f these l t m i t a t t o n s r t h e r e is

tncludtng

value

in

bacteria,

and protozoans, u s u a l l y do s u r v i v e c o l l e c t i o n and processing w t t h o u t betng moved from t h e l r o r t g t n a l p o i n t o f attachment. S t l l l ,

t h e r e a r e problems which must be

addressed. Once a sample Is c o l l e c t e d f o r SEM, many changes o f f l u t d s

are

used

t o f t x and dehydrate t h e samples. These changes o f f l u t d s tend t o dtslodge loose components (e.g., addition,

community.

In

c o a t t n g procedures t o make d r t e d spectmens e l e c t r t c a l l y conducttve

pseudoperiphyttc o r

mottle

members)

to

reduce specimen charging so t h a t t h e y can be vtewed

of

wtth

a l t e r o r destroy p a r t t c u l a r l y del t c a t e mucilaginous and c e l l s (Rosowski and Gltder,

SEM

may

drasttcally

flagellar

1977). The h i g h l y hydrated muctlage o f

b a c t e r i a ts l a r g e l y a r t l f a c t u a l s t r a n d diameters,

the

wtth

s u r f a c e features,

respect

to

specific

and interconnections), result

l o o s e l y assoctated community members (Rosowski e t al.,

In

of and

morphology

although

t h a t t h e s t t e s o f attachment ( o r i g i n ) a r e representative. and o u t o f t h e vacuum system o f t h e SEM can

features dtatoms

Movtng gross

1981),

we

(e.g., belteve

spectmens

In

displacement even

of

though

the

sample has supposedly been s t r u c t u r a l l y s t a b t l t z e d w t t h a metal coattng. F i n a l l y t h e r e i s t h e problem t h a t i n pertphyton (Roemer e t al.,

communttles

that

are

well

19841, samples may be d t f f t c u l t t o view i n t e r n a l l y

evenly w t t h a heavy metal s i n c e t h e communtttes a r e so dense

developed

or

(Rosowskt

to

coat

et

al.

19811. On t h e p o s t t i v e side, c r t t t c a l - p o i n t d r y i n g procedures

have

been

developed

(Cohen,

1979

which mtnimtze t h e a r t i f a c t s o f specimen p r e p a r a t l o n

for

SEM

Rosowskt e t al.,

and

Tamartn,

1981; Hoagland e t a l .

1982;

Boyde

1984);

;

and

Figures 29-32 o f seasonal d i f f e r e n c e s I n community s t r u c t u r e a t S t t e A. Fig. 29. L a t e sprtng,

Achnaothes Svnedra m. May

1979, two-tiered commmuntty showing p r o s t r a t e l a y e r of (small arrows), and l a t e r a l l y attached second s t o r e y o f 23-June 20, 1979. 140 X.

Fig. 30. E a r l y f a l l , 1979, mtcrocommuntty w t t h numerous clumps o f b a c t e r t a l mucilage (small arrows) and one dtatom ( l a r g e arrow). Severe shadtng o f sampler by tracheophytes a t t h t s time. Sept. 11-Oct. 9, 1979. 280 X. Ftg. 31. E a r l y sprtng, 1980, f o u r - c e l l e d chatns o f GomDhonema sp. and o t h e r dtatoms on t h e g l a s s substrate, w t t h sparse accumulation o f sediments; before placement o f b l a c k p l a s t t c on t h e stream banks. March 22-April 19, 1980. 280 X. Ftg. 32. E a r l y f a l l , 1980, a l a r g e dtatom surrounded by sediments and smaller dtatoms (arrow). Sept 22-0ct. 20, 1980. 290 X.

276 f r a c t u r e d w a l l s o f diatoms

observed

in

a t t r i b u t e d t o damage which occurred p r i o r

SEM

samples

to

the

9)

sampling.

s t u d i e s have shown t h a t p a r t i c u l a t e s which impinge on t h a t a r e bound t o i t by b a c t e r i a and algae can. be

(Fig.

1982; Roemer e t al., 17.4.3

-iod.

visually

-ate

and

et

al.,

methods

in

which

communities s t a b l e i n c e l l d e n s i t y except as

four

weeks

sloughing

s u i t a b l e p e r i o d i n streams and r i v e r s (Cattaneo and

our

appeared occurred

1982; Roemer e t a l . 1984). Others have a l s o found

that

produce

(Hoagland

four

Ghittori,

previous

to weeks

1975;

as noted i n two o f o u r samples t h a t were immersed more

(Tables 3 8 5). Brown and A u s t i n (1973)

found

that

station

l e a s t between s t a t i o n s f o r s u b s t r a t e s t h a t were immersed f o r

et

is

Blinn

19801, b u t perhaps more complex o r d i v e r s e communities develop w i t h

periods,

very 1980;

1984).

experience i n l e n t i c environments

al.,

SEM

and

and al.,

1983; Hoagland

The choice o f t h e immersion p e r i o d o f t h e samples was based on

al.,

be

communities

i n f o r m a t i v e l y i n a q u a l i t a t i v e manner (Chamberlain, 1976; Daniel e t Hudon and Bourget, 1981, 1983; Rounick and Winterbourn,

thus

Furthermore,

aquatic

assessed

can

than

longer

3

months

differences monthly

a et

were

intervals

and g r e a t e s t f o r those immersed f o r a four-month period. Clay t i l e s a r e considered by several i n v e s t i g a t o r s t o be

superior

to

rocks

w i t h r e p e c t t o reduced sample v a r i a b i l i t y (Tuchman and Stevenson, 1980; Lamberti and Resh, 19851, and although g l a s s s l i d e s have

not

accurately

reflected

the

p e r i p h y t o n o f some communities i n biomass accural 'or species composition (Siver, 1977), they apparently have i n o t h e r s (Cattaneo and G h i t t o r i , o u r use o f g l a s s because o f i t s h i g h l y u n i f o r m

and

1975).

chemically

We

inert

defend surface,

which reduces w i t h i n - and between-sample v a r i a t i o n . Methods f o r sampling p e r i p h y t o n have (Weitzel, 1979; A u s t i n e t al.,

been

the

focus

1981). Glass rods were

of

used

specific to

studies

s i m u l a t e Lvphp

Figures 33-36 of s p e c i a l s t r u c t u r a l f e a t u r e s o f t h e p e r i p h y t o n o f communities o f S i t e s B, C, and D. Fig. 33. Dense accumulation o f sediments a t S i t e B associated w i t h diatoms. Note (small arrow). Mar. 22-Apr. 19, 1980. 290 X.

$ymka YLnn ( l a r g e arrow) and Surirella QY&L

Fig. 34. Diatom (arrow) attached a p i c a l l y t o t h e g l a s s s u r f a c e and surrounded by sediments; upper r i g h t a diatom w i t h a cracked f r u s t u l e attached on t h e second t i e r ; lower l e f t o f diatoms secondarily attached t o sediments o f t i e r 2. May 22-June 21, 1979. S i t e B. 2,800 X. Fig. 35. Basal attachment t o g l a s s s u b s t r a t e o f component o f t i e r 3. Oct. 9-Nov. 8, 1980. S i t e D. 145 X.

sp. which becomes a

Fig. 36. Filaments o f Oedooonlum sp. concentrated on edge o f t h e g l a s s substrate. June 20-July 18, 1979. S i t e C. 29 X.

277

278 stems i n a study o f

chironomid

grazing

p e r i p h y t i c algae grew w e l l on t h e d i v e r s i t y as on

the

0.5

(Mason and

cm

u, chironomids

glass did

Bryant,

rods,

not

1975).

with

occur

presumably because they could not f i n d a s u i t a b l e surface

similar

on on

Although

glass

which

to glass

(Mason and Bryant, 1975). The higher density o f periphyton

on

the

than on t h e Ivphp was suggested t o

of

feeding

be

due

to

the

c h i r o n m i d s on t h e periphyton o f t h e glass-rods.

lack

On our

glass-slide

chironomid pupal cases d i d develop (Fig. 2, S i t e s B and D, spring). layer

for

rods attach rods

by

the

substrates Perhaps

l a r g e r f l a t surface o f the 2 cm wide s l i d e oriented i n t h e d i r e c t i o n flow provided a broader and more p r o t e c t i v e boundary

species

the

of

the

stream

attachment

occur i n which l o c a l shear forces would be reduced s u f f i c i e n t l y

below

to

that

of

the main stream ( S i l v e s t e r and Sleigh, 1985). Although there are

many

examples

of

interesting

and

diverse

attachment

structures i l l u s t r a t e d f o r b a c t e r i a associated w i t h diatom dominated communitles (Hoagland e t al.,

1982; Roemer e t al.,

* * d e f i n i t i v e evidence f o r

permanent

19841, Marshall (1980) has suggested t h a t adhesion

of

microorganisms

sediment p a r t i c u l a t e s i s lacking,** w i t h evidence f o r

permanent

demonstration o f polymer bridges between t h e microorganisms and

soil

and

attachment

to

the

the

substrate,

so t h a t they would not be dislodged **when substantial shear forces are applied.*'

Marshall (1980) cautions t h a t **especially w i t h SEMI t h a t a l l microorganisms seen on s o l i d

surfaces

it i s

were

dangerous

firmly

surfaces p r i o r t o specimen drying. Many o f t h e organisms may have bulk aquaeous phase o r

superficially

deposited on t h e surfaces during t h e

attracted drying

to

the

process.**

been

surfaces This

to

adhering and

statement

assume to

the

in

the

merely bears

cons'i derat ion. Figures 37-42 o f e x t r a c e l l u l a r b a c t e r i a l mucilages and/or o f b a c t e r i a l attachment modes. Fig. 37. Clumps o f b a c t e r i a l mucilage ( w i t h b a c t e r i a beneath) from a sample w i t h sparse autotrophic growth. Sept. 11-Oct. 9, 1979. S i t e A. 1,400 X. Flg. 38. Sheet-like webs o f b a c t e r i a l mucilage adhering t o t h e glass substrate from a sample w i t h sparse autotrophic growth. June 18-July 23, 1979. S i t e A. 2,800 x. Fig. 39. B a c t e r i a l mucilage strands p a r t i a l l y covering a c e l l o f extending from the pseudoraphe valve face t o t h e substrate surface ( r i g h t ) . June 20-July 18, 1979. S i t e A. 2,850 X. Fig. 40. B a c t e r i a l mucilage strands i n a loose network over c e l l s o f sp. Mar. 22-Apr. 19. 1980. S i t e A. 1,400 X.

GomDhonema

Fig. 41. A p i c a l l y attached b a c t e r i a w i t h mucilage strands adhering them t o t h e glass substrate. June 20-July 18, 1979. S i t e A. 7,200 X. Fig. 42. P r o s t r a t e l y attached b a c t e r i a l a c k i n g conspicuous mucilage attachment strands. Mar. 22-April 19, 1980. S i t e D. 1,400 X.

280 It was o u r procedure I n prevlous s t u d l e s (Hoagland e t al., al.,

1982;

Roemer

et

1984) t o f l x n a t u r a l c o l l e c t l o n s I n f l x a t l v e made up I n r e s e r v o l r water

so

t h a t t h e c o n c e n t r a t i o n of t h e suspended organisms o f these samples were those o f I n t h e present study our f l x a t l v e was made

t h e o r l g l n a l r e s e r v o l r water.

Alga-Gro medium from t a p water whlch was forced

from

a

squeeze

up

bottle

In

under

pressure i n t o open s l l d e contalners; t h e d e n s i t y o f suspended c e l l s I n t h i s case would be l e s s t h a n o r l g l n a l l y occurred I n t h e stream samples. The purpose o f p o s i t l o n l n g s l l d e s v e r t l c a l l y when Immersed I n t h e so t h a t organisms t h a t

appear

are

more

llkely

to

have

Sedlments t h a t a r e present a r e f i r m l y attached o r they removal

for

fixation

or

In

transfer

of

llqulds

would In

stream

actlvely come

Is

attached. off

subsequent

durlng speclmen

dehydration. And although c l e a n g l a s s s l l d e s which a r e f i x e d w l t h one-month communftles on s l l d e s

do

not

collect

organisms

during

fixation

old

(Rosowski, aquaeous

unpublished), It cannot be denied t h a t suspended organlsms o f t h e b u l k

phase c o u l d become entangled I n t h e p e r i p h y t o n o f w e l l developed communltles, undoubtably occurs I n t h e

natural

s p e c l f l c l t y o f attachment s i t e s

of

envlronment the

as

bacterla

well. (Figs.

However, 37-42;

s p e c i f i c s i t e s o f o r l g l n o f attachment s t r a n d s on t h e b a c t e r i a

(Figs.

attached

41, 43, 45-48), attached,

and t h e p a u c i t y o f b a c t e r i a t h a t

we b e l l e v e t h a t c o n t r l b u t l o n s

of

appear

unattached

column which would f l r m l y adhere t o t h e s u b s t r a t e d u r i n g

to cells

be

only from

fixatlon

i n s l g n i f l c a n t component o f t h e communlties we have observed i n t h i s low d e n s l t y o f

bacterla

on

one-week

old

samples

during

the

45-47),

47).

t h e s p e c l f l c o r l e n t a t l o n o f c e r t a i n b a c t e r i a specles when

as

glven

the

41,

43,

(Flgs. casually

the

water

comprlse

an

study.

The

colonization

also

Figures 43-48 o f e x t r a c e l l u l a r b a c t e r l a l mucllages and/or o f attachment modes and b a c t e r l a l morphology. Fig. 43. B a c t e r i a l mucllages w i t h strands r a d i a t i n g a p l c a l l y and l a t e r a l l y from t h e a p l c a l l y attached b a c t e r l a l c e l l s . May 23-June 22, 1979. S l t e A. 14,200 X. Fig. 44. Fused mucllage s t r a n d s forming webs over t h e b a c t e r i a attached t o t h e g l a s s substrate. Sept. 11-Oct. 9, 1979. S l t e A. 7,200 X. Flg. 45. B a c t e r l a a p l c a l l y attached t o t h e -Intrlcatum. buddlng (arrows). May 12-June Zl., 1979. S l t e C. 2,900 X.

Note

Fig. 46. D e t a l l o f Flg. 45--bacteria showlng p a p l l l a e o f c e l l s u r f a c e (arrow). May 12-June 21, 1979. S l t e C. 14,500 X. Flg. 47. Fuslform bacteria, one I n t h e process o f d l v l s l o n b u t n o t separated ( l e f t ) , attached t o g i r d l e band surfaces o f sp. Mar. 22-Apr. 19, 1980. S i t e C. 14,250 X. Flg. 48. Rod-shaped b a c t e r l a p r o s t r a t e l y attached and Interconnected w l t h Note sparsely produced mucilage strands, on b r l d l q n sp. attached a t g i r d l e band s u t u r e (see mlnute arrow). Mar. 22-Apr. 19, 1980. 7,100 X.

w.

282 suggests

that

arttfactual

(Hoagland e t al.,

settltng

1982; Hoagland,

on

substrates

durtng

1983; Roemer, e t al.,

fixatton

1984).

could be Important I n bodtes o f water where t h e r e are many

is

low

Sttll,

settltng

suspended

organtsms

a t t h e ttme o f sample f i x a t t o n .

17.4.4

l l f e f o r m--Structural

and f u n c t t onal heteromo rphy

How attached diatoms cope w i t h physfcal and b i o l o g i c a l disturbances i s mostly conjecture

based

on

vtewed

forms

macroalgae. Expertmental work has

as

analogous

vertfted

the

defenses o f c e r t a i n morphologtes and/or l i f e L i t t l e r , 1984). As yet,

functtonal-fcrm

dtatoms o r f o r attached

mtcroalgae.

morphologtcal aspects o f

Achnanthes

hydrodynamic forces, al.,

A

adhered

to

the

substrate

whereas being

periphyttc, the

are

or

anttherbtvore

strategtes

(Littler

growth

of

for

adapttve

study

considers

dtscusston,

tn

sesstle,

adapttve

and

small

the

and

not

of

dtatoms

considering

the

and

and

for

a

et

stream

(Kondratteff were

velocity other

Benson-Evans,

adapttve

stream

(Rosowskt

dtatoms

tychoplanktontc,

1981). The water c u r r e n t

and

the

and p a r t t c u l a r l y w e l l

features are

ltfe-form strategtes

pertphyttc

and

recent

Important

pertphyttc

benthic

models have n o t been proposed

documented f o r a number o f species (Antotne following

the

the

I n r e s t s t t n g graztng

free-ltvtng

p a r t t c u l a r spectes (Kuhn e t al., best support

of

of

based on m a t e r t a l from S t t e A i n Maple Creek

StmmOns, 1985). I n another study, strtctly

those

extent

htstory

1986). I n t h t s case, belng small, prostrate.

env!ronment,

to

whtch

and were

noted

for

whtch

wtll

algae 1982).

potenttalttles

has

been

I n the of

the

Ftgures 49-54 o f growth h a b i t s and attachment modes o f selected dtatom taxa. attached p r o s t r a t e l y t o g l a s s surface. Raphe Ftg. 49. Achnanthes valves o f dead c e l l s rematn attached (arrows). May 23-June 20, 1979. S i t e A. 720 X. Ftg. 50. AmDhora var. attached t o t h e g l a s s s u b s t r a t e (below arrow) and above t h t s s u b s t r a t e (arrow) on sediment. May 23-June 20, 1979. S t t e C. 725 X. Ftg. 51. A c t r c u l a r n t n e - c e l l e d colony of ~ r i r e l b attached a p i c a l l y a t t h e tapered end by a confluent pad o f mucilage. Mar. 22-Apr. 19, 1980. S i t e D. 1,400 X. Ftg. 52. surrounded toward 23-June 20, 1979. S t t e A. 2,800 X.

t h e base by p a r t t c u l a t e s . May

Ftg. 53. Rosettes o f Svnedra xu Kutz. ( l a r g e arrow) attached t o glass surface; note small r o s e t t e o f ucy&a (small arrow). Note f i n e f i l a m e n t s on substrate. Mar. 22-Apr. 19, 1980. S i t e D. 140 X. Fig. 54. Fan-shaped arrays o f MerldlonMar. 22-Apr. 19, 1980. S t t e D. 280 X.

f o m t n g hemtsphertcal colonies.

284 pertphyttc mtcroalgae, i t ts useful t o keep i n mind the l t f e h i s t o r y elucidated f o r c e r t a i n macrobenthtc marine algae:

e.g.,

strategies

heterotrtchy

(Littler

and Kauker, 1984) and heteromorphy ( L i t t l e r and L i t t l e r , 1983). Hoagland e t al. (1982) and Roemer e t al.

(1984) showed a range t n s t a t u r e

of

l e n t l c pertphyton, w t t h e a r l y Invading p r o s t r a t e forms havtng the l e a s t stature. However, both monoraphtd and btraphtd dtatoms which h i s t o r y t n a p r o s t r a t e mode may tncrease

thetr

community by secreting an aptcal attachment

have

part

stature wtth

pad

and

of

elevating

1982; Korte

and

Diatoms which take t h e best advantage longest aptcal axis,

such as

Bltnn,

of

1983;

thts

strategy

m.Such genera,

passtvely a t the substrate surface where they except t o adjust t h e t r angle o f attachment.

Roemer

Bourget, et

are

al.,

those

are

the on

1981, 1984).

wtth

which have no raphes,

presumably

ltfe

to

themselves

t h e t r proxtmal end a t r t g h t angles t o t h e substrate (Hudon and 1983; Hoagland e t al.,

thetr

respect

unable

the

arrlve to

move

However, c e r t a i n smaller species may

a t t a i n even greater perpendtcular s t a t u r e by secrettng s t a l k s o f muctlage

whtch

elevate them i n the canopy several orders o f magnttude htgher than they would be t f they could only elevate t h e t r sesstle f r u s t u l e on t h e t r

proxtmal

end,

from

heteromorphy

stnce

p r o s t r a t e t o perpendtcular. These changes i n l t f e - f o r m may be vtewed

as

there is no tncrease i n t h e btovolume o f t h e

functional

organtsm

when

a

prostrate

elevates t t s e l f on i t s proxtmal apex and tncreases t h e dtstance from I t s apex t o t h e substrate without a c e l l - s t z e increase and without (e.g.,

araphtd r o s e t t e formers such as

m). Structural

Merldion

m w,

-,

which

distal

formation

stalk

heteromorphy would be when such an

Is followed by the development o f a stalk,

may

become

c o n t i n u t t y (as I n many monoraphtd and btraphtd spectes). btovolume

of

the

organtsm,

elevation

I n t h t s case wtth

the

and

colony

there

stalks

al.,

heterotrtchy,

1984).

Such

an

increase

In

size

ts not vtewed the

1963;

here

stnce t h e p a r t t c u l a r dtatoms which form t h e perpendtcular

growth form are no longer p r o s t r a t e and thus are not members o f

1s

often

occupytng a much greater volume than the c e l l s which produced them (Drum, Roemer e t

and

dichotomous

extenstve I f s t b l t n g progeny conttnue t o produce s t a l k s and maintain t h e also an tncrease i n t h e

cell

as

tter

2

prostrate

t t e r 1 communtty. The two-ttered nature o f stream pertphyton was not discussed (Hynes, 1970) or I n a more recent review (MOSS, 1980); It has, been mentioned b r i e f l y f o r streams. Patrtck and

Roberts

tn

an

tn

fact.

(1979)

earlter

described

only the

mature stream periphyton as a "mtntature complex forest."

It has been

thatftlamentousovergrowth which creates an upperstorey

Is brought about by

n u t r t e n t deftctency a t t h e

substrate

level

I n the

understorey

suggested

(Sumner

McIntire, 1982). Other studies suggest t h a t n u t r l e n t s may a f f e c t development s p e c t f t c dtatom communlties I n t h e face o f equal sources o f

prtmary

and of

colonlzers

285

b u t unequal n u t r i e n t a v a i l a b i l i t y .

For example,

i n a study o f l e n t i c

periphyton

Eolthemla danata

on a r t i f i c i a l substrates which released s i n g l e n u t r i e n t s .

and

&&@ahLk g l h h were found t o be stimulated i n growth w i t h phosphate addition, w h i l e growth o f

Achnanthes

was

slightly

depressed

Lowe. 1984). I n another study, substrates w i t h n i t r a t e favored n a v i c u l o i d diatoms ( F a i r c h i l d e t al..

1985).

and In

(Fairchild

phosphate

a

lotic

sand/agar substrates which released n i t r a t e and phosphate, s i n g l y i t was found t h a t phosphate alone o r n i t r a t e and phosphate

t h e growth of-

and

Nitzschia whereas

and

together

study or

together

using

together, stimulated

control

t h e substrates o f t h e

and

and Achnanthes

n i t r a t e treatments alone were dominated by Cocconeis ( P r l n g l e and Bowers, 1984). It has been proposed ( B l i n n et al.,

1980)

that

periphyton

streams i s i n f l u e n c e d by microsurface features and s u b s t r a t e t h e f i r s t week i n p a r t i c u l a r ,

development

in

solubilization

in

b u t t h a t a f t e r two weeks aggregated organic matter

i s s u f f i c i e n t l y dense t o mask t h e i n f l u e n c e o f t h e o r i g i n a l

substrate

The evidence i n support o f t h i s hypothesis was t h e

fatlure

of

d i f f e r e n t diatom communities i n t h e

on

same

stream

Verde

surface.

development limestone,

of

Supai

sandstone and A n d e s i t i c b a s a l t substrata a f t e r t h r e e weeks, t h e p e r i o d i n which maximum diatom d e n s i t i e s developed.

I n a study o f

b a c t e r i a l colonization,

and Maubrey (1981) found t h a t b a c t e r i a more h e a v i l y colonized analog o f sandstone) than c a l c i t e

artificial

substrates

(chemical

limestone) a t two d i f f e r e n t s i t e s a t 10 and 20 day periods; more b a c t e r i a than t h e o t h e r two, b u t

there

was

no

quartz a

analog

of

site

had

third

difference

Mills

(chemical

in

bacterial

numbers on t h e two d i f f e r e n t substrates suggesting t h a t Ifthe composition o f

the

mineral substrate,

the

i n concert

with

the

imnersion

environment,

controls

formation o f primary s l i m e l a y e r s in aquatic systems.gt D i f f e r e n t i a l c o l o n i z a t i o n i n t o microzones occurs as a r e s u l t o f c u r r e n t d i r e c t i o n ,

as

conceptualized

in

models i l l u s t r a t e d by K o r t e and B l i n n (1983). 17.4.5

Herbivorv

It has been suggested by Kesler (1981a) t h a t "the impact o f grazer

upon freshwater periphyton communities has been assumed by most

organisms

workers

i n s i g n i f i c a n t . However, w i t h o u t q u a n t i f l c a t i o n o f m a t e r i a l removed by

to

be

grazers,

and comparison o f t h i s amount t o t h e periphyton standing crop, these assumptions are unfounded."

Perhaps such an assumption could e x p l a i n why

1978) found g r a z i n g i n streams t o have

l t t t l e effect

Moore

on t h e

whereas o t h e r s t u d i e s o f streams show a decrease i n abundance of t a x a w i t h grazing (Dickman,

1968;

Elwood

Harman, 1977; Hunter, 1980; Mulholland e t al.,

and

(1977a,

standing and/or

diversity

Nelson,

1972;

Doremus

19831, o r a

slight

decrease

abundance w i t h no e f f e c t on species d i v e r s i t y (Kehde and Wilhm,

1972).

case, a f a c t o r i n obscuring t h e importance o r r o l e o f herbivory would

br

crop, and in

I n any be

rapid

286 turnover r a t e s o f t h e periphyton ( M c I n t i r e and Colby, 1978). Even the r e l a t i v e l y low standing crops we r e p o r t here i n respect t o those f o r r e s e r v o i r (Hoagland e t al.,

1982; Hoagland, 1983; Roemer e t al.,

communities

1984) might be supporting

a high consumer biomass w i t h a rapid turnover o f t h e a l g a l periphyton and Resh, 1983). And, I n diverse aquatic

systems,

high

nutrient

rates from grazlng and other a c t i v i t i e s have been shown t o

be

(Lamberti

regeneration

responsible

for

1976; Granel i, increased a1gal (Cooper, 1973; F1 in t and Go1dman, 1975; Porter, 1979; Robles and Cubit, 1981; Osborne and McLachlan, 1985; Power e t al., 1985) and b a c t e r i a l production (Lopez

et

However, r e c y c l i n g can be so t i g h t

al., as

1977; Sierszen to

occur

within

themselves without t r a n s f e r i n t o the water (Haack

and

and the

Brooks,

1982).

microcommunities

McFeters,

1982; Cuker,

1983) and thus t h i s exchange could e a s i l y go undetected. I n enclosure-exclosure experiments, Kesler (1981b) showed a reduction i n t h e

limosa was

periphyton standing crop when t h e gastropod Cattaneo (1983) showed t h a t a sudden decline i n intense

grazlng

from

oligochaetes

and

epiphyte

chironomids.

included,

biomass

There

while

was

is

due

to

apparently

discriminatory herbivory w i t h respect t o t h e microalgae (Bowker e t

al.,

1983,

1985)r w i t h an example o f removal o f unwanted species t o perhaps provide room f o r growth o f desired species (Hart, 1985). We do not here consider t h e invertebrate fauna o f Maple Creek, some features o f which have been studied

by

P i t c a i r n (1981) and Shadle (1984).

17.4.6

dev-

It has been suggested t h a t a primary sera1 stage i n aquatic h a b i t a t s

establishment o f o r g a n i c r i c h d e t r i t a l materials on surfaces f u r t h e r i f they f a i l t o receive l i g h t , e.g.,

which

is

the

develop

t h e undersides o f submerged

no

stones

o r i n shaded areas (Calow, 1975). Such organic f i l m s may develop i n only a few hours (Korte and Blinn, 1983). The accumulatlon o f organic carbon on reach i t s peak i n the dark a f t e r one month and malntain t h a t three mo'nths (Rounick and Winterbourn,

level

1983). Surface organic

layers

substrata are p o t e n t i a l s i t e s f o r t h e uptake of dissolved organic could be t r a n s f e r r e d t o t h e benthos

(Wlnterbourn

et

al.,

rocks may for of

matter

1985).

m l c r o c m u n i t i e s i n l o t i c and l e n t i c systems usually are

dominated

by

dominance

for

f o u r f l v e weeks (Hoagland e t al.,

and

maintain

that

to

hard which

Illuminated

w i t h i n the f i r s t week o f

immersion

up

1982, Hoagland, 1983; Roemer e t al.,

diatoms up

to

19841,

w i t h more diverse diatom c m u n i t l e s r e q u i r l n g months f o r development (Brown and

1973) and even years i n t h e case o f long-lived macroalgae o f t h e marine envi ronment (Kay and Butler, 1983).

Austin,

We found a great reductlon i n t h e standing crop o f diatoms when was shaded (1,500 diatoms/&

a community

t o 7 / d , Table 1). Similarly, Moore (1977b) found

t h a t "the f l o r a developed a t o n l y 1-2% o f

the

rate

exhlbited

by

a

similar

287 community i n unshaded condittonstt; r e d u c t i o n t n

gross

prtrnary

productton

a l s o noted by Sumner and M c I n t t r e (1982) i n shaded l a b o r a t o r y streams. t t was shown t h a t c e r t a i n n u t r t e n t requtrements and

species

a r e a f f e c t e d by l t g h t which b r i n g about these e f f e c t s by

was

Recently

interrelattonshtps

altertng

the

opttmum

c e l l u l a r N:P r a t t o s (Wynne and Rhee, 1986). We found t h e h t g h e s t c e l l d e n s i t y i n a n e a r l y 4-month o l d community,

N. subcaDitellata

w i t h Nitzschia

a domtnant a t S i t e C and

as a c o d m l n a n t a t t h r e e d i f f e r e n t s i t e s

(Table

51,

species

which d l d n o t occur as t h e domtnant o r codomtnant spectes t n any o f 15 one-month immersion p e r i o d s over 2 years ( c f . Tables 1-51, 17.4.7

and

Prevtous revtews have d e a l t w i t h t h e t n t e r a c t t o n s o f and sediments (Corpe,

microorganisms,

1980; Paerl, 1980). S t a b t l t z a t t o n o f sedtments

mucilages i s known (Holland e t al.,

sotls,

by

diatom

1974). There i s accumulattng evtdence

algae and b a c t e r t a i n t e r a c t I n s t t m u l a t o r y and t n h t b t t o r y manners (Cole, It ts now appreciated t h a t b a c t e r t a are tmportant as

uttltztng

dissolved

organtc

carbon

and

that

major

graztng

producer by

that

1982).

organtsms

bactertovores

Is

s t g n i f i c a n t i n t h e r e l e a s e o f bacterial-bound n u t r i e n t s t h a t c o n t r t b u t e t o a l g a l growth

(Ducklow,

1983).

In

eplltthic

stream

communtttes,

r e l a t t o n s h t p between algae and b a c t e r i a may r e s u l t i n algal

products

to

the

bactertal

population,

wtth

u t t l t z a t i o n o f d i s s o l v e d organics from t h e o v e r l y i n g

the

nutrtttonal

dtrect flux o f 1I t t l e

steam

soluble

heterotrophic

watert1

(Haack

and

McFeters, 1982). T h l s s t i m u l a t i o n o f b a c t e r t a by algae appears to occur b e s t d a y l t g h t hours i n some s t t u a t t o n s (Nalewajko e t al., There ts

a

close

association

of

unicellular,

b a c t e r t a w t t h dtatoms and sedtments t n t h e

stream

colonial communtty

and of

fllamentous

Maple

C e r t a t n b a c t e r t a a t t a c h w t t h f t b r o u s webs near and sometimes over

Creek.

dtatoms

a p i c a l o r p r o s t r a t e attachment a t s p e c t f t c s t t e s on t h e valves o r g i r d l e These s i t e s a r e presumably where t h e

diatoms

are

secrettng

these a s s o c l a t t o n s p r o v i d e morphological evtdence o f t h e might be necessary f o r n u t r i e n t exchanges t o

occur

water column (Haack and McFeters, 1982; Cuker, 1983).

close

without

prtmary s u b s t r a t e where

most

unicellular

and

bands. and

proxtmtty

detectton

Although

colonial

wtth

metabol ttes,

we

bacterta

that

in

have

b a c t e r i a I n t h e t i e r 2 communtties attached t o diatoms (Ftgs. 45-48], onemonth o l d s u b s t r a t e s a r e examined (Figs. 37-42).

tn

1984).

the

found

it i s

occur

Wtth sedtment trapping,

the when It

is tmposstble t o vtew t h e diatoms o r b a c t e r t a regardless o f t h e m a g n t f t c a t i o n because t h e y appear ttcoveredtt w t t h r e f l e c t e d t y p e o f vtewtng (SEMI although

the

t r a n s m i t t e d l t g h t of t h e

for

natural

comunlty

is

probably

sttll

adequate

photosynthesis a t t h e t t e r 1 s u b s t r a t e l e v e l . Paerl (1980),

I n reviewing t h e

literature,

has

noted

that

bacterta w t l l

c o l o n i z e I n e r t s u b s t r a t e s as w e l l as those which provtde n u t r t e n t s , and t h a t t h e

288 even i f i n e r t , allows f o r microbial

mere presence o f a surface f o r colonization,

growth. Glass s l i d e substrates are i n i t i a l l y i n e r t , but it t h a t c o l o n i z a t i o n by

bacteria

b a c t e r i a l events as well,

quickly

follows,

f o r example w i t h

is

widely

reported

and there may be successional

nonbranching

bacteria

followed

by

branching b a c t e r i a (Aumen, 1980). The evidence presented by Hamilton and Duthie

film

(1984) f o r t h e absence o f a preconditioning organic bacteria i n e a r l y c o l o n i z a t i o n

of

a

boreal

forest

e l e c t r o n micrographs o f substrates o f t h e f i r s t

and

stream

five

days

a

is at

six

ca.

magnification a t which b a c t e r i a and t i g h t organic f i l m s would be d i s t i n g u i s h even when t h e substrate colonizers are sparse

paucity

at

scanning

140 X,

53).

Fig.

1,300 X )

reveals

o n l y t h e upper t i e r o f a nine-day o l d community, as evidence t h a t bacteria Itnoticeably

absent

and were

not

important

i n i t i a t i o n . @ ' A t t h i s magnification i t

is

components

difficult

to

b a c t e r i a by SEM (see our Fig. 42). Similarly, Perkins reported t h a t SEM f a i l e d t o reveal a

"heterotrophic

of

and

were

colonization

definitively Kaplan

biomass"

a

impossible t o

(see our

Their highest magnification e l e c t r o n micrograph (Fig. 11

of

identify

(1978) also

in

a

subalpine

stream. However, since o n l y extant e p i l i t h i c samples were examined i n which

the

periphyton was already w e l l developed i t might be

(as

difficult

to

determine

t h e i r e l e c t r o n micrographs suggest) i f b a c t e r i a attached d i r e c t l y t o t h e natural substrates. We would expect o l i g o t r o p h i c bacterial

density

than

eutrophic,

stream

substrates

particularly

when

(Hamilton and Duthie, 1984). However, although t h e i r Kaplan, 1978; Hamilton and

Duthie,

to

the

have

water

conclusions

1984) may be correct,

a is

lower acidic

(Perkins

failure

and

to

show

bacteria w i t h SEM i n these cases i s not nearly so convincing as would have

been

t h e i r demonstration.

1 and t i e r 2

It i s t h e period during and a f t e r t h e appearance o f t h e t i e r

diatoms t h a t most o f t h e s i l t and d e t r i t u s i s

trapped.

However,

where only heterotrophic growth was s i g n i f i c a n t (shaded accumulated b u t d i d not develop beyond about t h e appear t o be essentlal

i n the

Maple Creek

tier

i n the

samples),

particulates

1 level.

community

for

case

Diatoms

the

thus

trapping

sediments t h a t compose t h e t i e r 2 l e v e l which then buries t h e t i e r 1 level.

of The

p a r t i c l e s provide p o t e n t i a l l y new sources o f n u t r i e n t s f o r t h e microcommunities, b u t they do not appear t o provide a p a r t i c u l a r l y s u i t a b l e attachment o f diatoms. We noted high d e n s i t i e s

of

surface

dlatoms

within

comnunities, b u t these diatoms appeared t o be l a r g e l y attached

to

for

further

silt the

substrate ( t h e glass s l i d e s ) presumably a t t a i n i n g t h a t p o s i t i o n before

laden primary

most

of

the p a r t i c u l a t e s accumulated over and around them. But some diatoms do manage t o

or on debris

attach w i t h i n t h e i r own developing clumps,

m,Nltrschia sp., attachment t o observations

the on

Svnedra ulna), and

primary the

substrate

attachment

(e.g.,

t h i s a b i l i t y t o e x i s t without

may

habit o f

be

a

species

specific

attribute.

species

in

silt

direct Further laden

289 communities i s needed. process

Although diatom buildup on substrates has been considered a l a y e r i n g (Pryfogle and Lowe, 19791, we must emphasize t h a t t h e increase i n periphyton i n one-month o l d c m u n i t i e s i s p r i m a r i l y due t o t h e the

build

up

of

one

(Hoagland

community by

attachment on t h e top o f another. Although the accumulation o f debris t i e r 1 and around t h e t i e r 2 communities would f a c t o r and p r o t e c t the members o f these communities may s t i l l be

sufficiently

appear

communities unstable

f u r t h e r c o l o n i z a t i o n by diatoms. Alternatively, n o t have been o l d enough f o r other sediment

to

have

from

a

over

dislodgement,

these

or otherwise unsuitable f o r one-month

colonizing

old

tier

substrates species

substrate)

epiphytes

its

own

diatom

epiphytes.

These

the

i n d i r e c t l y , u n l i k e the diatoms o f t i e r s 1 and 2, as t h e filaments o f

may

to

to

develop

the

stabilizing

invaded. The t h i r d t i e r community ( l a r g e s t life-forms attached does

of

progression o f

substrate

t h e comnunity t o l a r g e r l i f e - f o r m s attached t o t h e primary e t al. 1982; Roemer e t al. 19841, not t o

thickness

have

primary move

the

third

We have assumed i n t h e present study, and i n t h e past (Hoagland e t al.,

1982;

t i e r w i t h t h e i r epiphytes s h i f t p o s i t i o n w i t h changing currents. Roemer e t al.,

19841, t h a t the material which binds sediments i s

mucilage

from

diatoms and bacteria. Such material i s destroyed by organic acids (cf. Rosowski, 1980 and Rosowski e t al.,

1983). However, Lewin e t al.

(1980)

have

noted material

a f t e r prolonged hot acid treatment which suggests t h a t t h e binding t h i s diatom i s not a t y p i c a l

mucilage.

mucilage o f diatoms i s responsible

Therefore,

for

that

mnaium remain attached

c l a y p a r t i c l e s bound t o t h e marine diatom

the

the

binding

assumption

of

here

sediments

of that

should

considered tentative. Diatom mucilage could have the opposite effect,of

be

course,

t h a t o f keeping o f f t h e r a i n o f particulates; evidence f o r t h i s i n our study was i n t h e 10/20/80 sample, S i t e C, i n which clumps

of

Gomohonema

had

copious q u a n t i t i e s o f surface mucilage (fuzzy surfaces) w i t h no attached debris. Does t h e s i l t o f

these

silt-laden

communities

affect

tiering

structure?

Unfortunately, we had no way o f separating the e f f e c t s o f stream flow f r o m o f t h e s i l t load c a r r i e d by t h a t flow, which had reported ranges i n o f 0.23-12.72 e t al.,

in

1980,

and

0.42-121.40

that

weight

g/l

i n 1982

1985). Compared w i t h shallow reservoirs i n Nebraska

(Hoagland

g / l i n 1979, 0.38-8.08

(Schepers e t al.,

dry

1982; Hoagland, 1983)r the Maple Creek periphyton

t h i c k o f a l a y e r i n one month, b u t binding o f

sediments

not

develop

as

[quantity

did

trapped

as

judged by apparent density) appeared w i t h SEM t o be greater. The Maple Creek d i d not destroy the

periphyton

by

scouring

as

silt

might

expected, b u t It would take experimental work a t erosion prone s i t e s

load have

of been

(B through

E ) t o demonstrate community s t r u c t u r e without the impact o f p a r t i c l e s from

this

erosion-prone watershed.

It should

be

noted

that

i n our

bright-field

microscopy

assessment o f

290 d i v e r s i t y and dominance we d i d n o t d i s t i n g u i s h between l i v i n g

and

dead

cells,

which were d i s t i n g u i s h a b l e w i t h SEM t o t h e e x t e n t t h a t i n t a c t f r u s t u l e s c o u l d be distinguished

from

damaged

frustules;

inclusion

of

dead

enumerations may have e i t h e r increased o r decreased sample and Lowe, 1979). A study o f hourly,

cells

in

diversity

d a i l y and weekly development o f

cell

(Pryfogle silt

communities which e v e n t u a l l y slough would be a l o g i c a l e x t e n s i o n o f t h e

laden present

work, which was c o n f i n e d p r i m a r i l y t o a comparison o f one-month o l d communities. A t t e n t i o n i n f u t u r e s t u d i e s c o u l d t h e n be d i r e c t e d

to

s t r u c t u r e o f mature communities, perhaps d e f i n e d as mass sloughing,

defining

diversity

communities

which

and

exhibit

r a t h e r than s t u d y i n g communities o f a s p e c i f i c age which may

or

may n o t be mature depending on t h e season and p e r i o d o f immersion. 17.4.8

m l i c a t i o n s o f + o i l BCpsion t o t h e

q b i o f i l m

The h i g h l y erosion-prone watershed o f t h e t r i b u t a r i e s o f t h e o f the

present

study

(Sites

B-D)

dominance by diatoms a t one month

showed

that

immersion

substrate

intervals

prairie

stream

colonization

was

not

and

prevented

by

scouring from t h e s i l t load. Indeed, t i e r 1 and t i e r 2 diatom l i f e - f o r m s trapped and h e l d sediments.

These two t i e r s were present i n a l l one month samples over a

two-year period, w i t h t h e e x c e p t i o n o f a shaded sample which had mostly b a c t e r i a and had trapped o n l y a modicum o f debris. Thus t h e

diatoms

f o r t h e accumulation and increase i n t h e t h i c k n e s s o f t h e

themselves sediment

provide

layer.

The

f i n a l t h l c k n e s s o f attached d e b r i s was determined l a r g e l y by t h e

level

of

the

d i s t a l apices o f t h e diatoms forming t h e second t i e r ,

generally

not

the debris

extending beyond t h i s l e v e l . The occurrence o f t i e r 2 diatoms appears t o p r o v i d e t h e means by which p r o s t r a t e diatom species o f sediments.

1 are

These b u r i e d species may be dominant or codominant

t h e case f o r the other

tier

Achnanthas lanceolata

sites

(5D)

during

often

covered

species,

as

by was

a t S i t e A i n t h e summer and f a l l . However, a t

most

seasons,

much

higher

diatom

densities

Figures 55-59 o f growth h a b i t s and o f attachment p r o f i l e s o f selected diatom taxa. Fig. 55. Rosette o f Eunotla curvata w i t h assoclatea p r o k a r y o t i c filaments. 22-0ct. 20, 1980. S i t e A. 1,350 X.

Sept.

Fig. 56. C e l l s o f curvata produce mucilage ( l a r g e arrow) a t t h e c e l l apex near t h e v e s t i g i a l raphe (small arrow). Mar. 22-Apr. 19, 1980. S i t e A. 14,000 X. Fig. 57. T i e r 2 r o s e t t e s o f Gomohonema oarvulum surrounded by debris. Oct. 9-Nov. 8, 1979. S i t e D. 725 X. Fig. 58. Short mucilaginous s t a l k (arrow) o f 20, 1980. S i t e A. 2,800 X.

GomDhonema parvuLum. Sept. 22-Oct.

Fig. 59. Long mucilaginous s t a l k s o f Gomohonema sp. forming a t h l r d t i e r community. Mar. 22-Apr. 19, 1980. S i t e B. 280 X.

291 occurred. Here the dominant o r codominant species was one t h a t

perhaps

as a t i e r 1 species b u t u l t i m a t e l y became a member o f a t i e r 2

community.

established as t i e r 2 members, many o f

appear

these

colony

formers

m u l t i p l y and t o add t h e l r o f f s p r i n g d i r e c t l y t o t h i s t i e r without going

arrived Once

able

to

through

t h e t i e r 1 phase. through perpendicular colony formation (Figs. 51, 53, 54).

292 Since s t a l k and colony forming diatoms u s u a l l y e x h i b i t

their

typical

life-

form morphologies i n c u l t u r e s where impingement o f s i l t from moving water i s not t a k i n g place (Roemer, Hoagland, Rosowski.

unpublished),

the

tiering

here i s probably not the ontogenetlc r e s u l t o f a t u r b i d environment.

reported

Rather, the

s i l t p a r t i c l e s appear t o be passively c o l l e c t e d by t h e diatoms and bacteria, l i f e f o r m s t h a t would have presented themselves anyway. The s p e c i f i c role, any, o f t h e s i l t

in

structuring or

even

s t a b i l i z i n g microcommunities

remains undocumented. It i s c l e a r however t h a t s o i l erosion from the does not i n h i b i t b i o f i l m formation eutrophic stream. Through microspecies,

a

stable

the

on

artificial

interactions

sediment

laden

of

substrates diatoms,

periphyton

thus

watershed

i n thls

bacteria

by if

and

highly other

community develops

and

persists, trapping debris t h a t would be l i k e l y absent without t h l s community.

ACKNOWLEDGEMENTS We thank Dave Mazour and Mike Brogan f o r t h e water chemical analyses, and Mike Pitcairn, J e n n i f e r Carr and John Schnagl f o r occasional assistance w i t h the f i e l d work. We also thank Barbara Ang f o r processing some o f t h e samples f o r SEM. We are very g r a t e f u l t o Dr. Roger E. Gold, Environmental Programs, I n s t i t u t e o f A g r i c u l t u r e and Natural Resources, U n i v e r s i t y o f Nebraska-Lincoln, f o r h i s coordination o f t h e b i o l o g i c a l monitoring o f t h e Maple Creek Model Implementation Project. The Nebraska Natural Resources Commission administered Environmental the funding f o r t h i s study which was provided i n p a r t by t h e U.S. Protection Agency, Region V I I . REFERENCES ACP, 1979. Handbook: P l a t t e r Stanton and Colfax Counties, f o r t h e Maple Creek Model Implementation Project. 32 pp. Allen, T.F.H., 1977. Scale i n mlcroscopic a l g a l ecology: a neglected dimension. Phycologia, 16: 253-257. Amspoker, M.C. and McIntire, C.D., 1978. D i s t r i b u t i o n o f i n t e r t i d a l dlatoms associated w i t h sediments i n Yaquina Estuary, Oregon. J. Phycol, 14:

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Rosenthal, G.A. and Janzen, D.H., 1979. Herbivores, t h e i r i n t e r a c t i o n w i t h secondary p l a n t metabolites. Academic Press, N.Y.r 718 pp. Rosowski, J.R., 1980. Valve and band morphology o f some freshwater diatoms. 11. I n t e g r a t i o n o f valves and bands i n confervacea var. confervacea. J. PhyC0l.r 16: 88-101. 1977. Comparative e f f e c t s o f metal coating by Rosowski, J.R. and Glider, W.V., s p u t t e r i n g and by vacuum evaporation on d e l i c a t e featurs o f euglenoid flagellates. In: Om. Johari (Editor), Proc. 10th Ann. SEM. Symposium, VOl.1, pp. 471-480. Rosowski, J.R., Hoagland, K.D., Roemer, S.C. and Lee, K.W., 1981. Improving the image o f d e l i c a t e and complex b i o l o g i c a l surfaces. ka.ndn&

4: 181-187. Rosowski, J.R., Hoagland, K.D. and Roemer, S.C., 1983. Valve and band morphology of some freshwater diatoms. I V . Outer surface mucilage o f confervacea var. confervacea. J. Phycol., 19: 342-347. Rosowski, J.R., Roemer, S.C., Palmer, J. and Hoagland, K.D., 1986. E x t r a c e l l u l a r association and adaptive s i g n i f i c a n c e o f the bas-relief mucilage pad of Achnanthes (Bacillariophyceae). Diatom Research, 1: i n press. Round, F.E., 1981. The Ecology of Algae. Cambridge U n i v e r s i t y Press, Cambridge, CB2 lRP, 653 pp. 1983. The formation, s t r u c t u r e and Rounick, J.S. and Winterbourn, M.J., u t i l i z a t i o n o f stone surface organic layers i n two New Zealand streams.

298 Fresh. Biol., 13: 57-72. Schepers, J.S. Francis, D.D. and Mielke, L.N., 1985. Water q u a l i t y e r o s i o n c o n t r o l s t r u c t u r e s i n Nebraska. J. Environ, Qual., 14: 186-190. Shadle, J.J., 1984. A study o f t h e c r a y f i s h O r c o n e c t e s m t n an i n t e r m i t t e n t Nebraska stream. M.S. thesis, u n i v e r s i t y o f Nebraska, Lincoln, Nebraska 68588, 32 pp. Sieburth, J. McN., Brooks, R.D., Gessner, R.V., Thomas, C.D. and T o t t l e , 1974. M i c r o b i a l c o l o n t z a t i o n of marine p l a n t surfaces as observed by J.L., scanning e l e c t r o n microscopy. I n : R.R. Colwell and R.Y. M o r i t z ( E d i t o r s ) , E f f e c t o f t h e Ocean Environment on M i c r o b i a l A c t i v i t i e s . U n i v e r s i t y Park Place, Baltimore, pp. 416-432. 1982. The r e l e a s e o f d i s s o l v e d o r g a n i c Sierszen, M.E. and Brooks, A.S., carbon as a r e s u l t o f diatom fragmentation d u r i n g feeding by && 1985. The f o r c e s on microorganisms a t S i l v e s t e r , N.R. and Sleigh, M.A., surfaces i n f l o w l n g water. Fresh. Biol., 15: 433-448. 1977. Comparison of attached diatom communities on n a t u r a l and Siver, P.A., a r t i f i c a l substrates. J. Phycol, 13: 402-406. 1979. Experimental i n v e s t i g a t t o n s o f disturbance and e c o l o g t c a l Sousa, W.P.9 succession i n a rocky i n t e r t i d a l a l g a l community. Ecol. Monogr.,

m.

49: 227-254. Steinberg, P.D., 1984. A l g a l chemical defense a g a i n s t herbivores: a l l o c a t t o n of p h e n o l i c compounds i n t h e k e l p Science, 223:

405-407.

-.

Steinberg, P.D., 1985. Feeding preferences of T e o u l a m and chemical defenses o f marine brown algae. Ecol. t h o , , 55: 333-349. Sumner, W.T. and M c I n t i r e , C.D., 1982. Grazer-periphyton i n t e r a c t i o n s i n l a b o r a t o r y streams. Arch. Hydrobiol., 93: 135-157. Tilman, D., Kilham, S.S. and Kilham, P., 1982. Phytoplankton community ecology: t h e r o l e of l i m i t i n g n u t r i e n t s . Ann. Rev. Ecol. Syst., 13:

349-372. Ttlman, D. and Sterner, R.W., 1984. Invasions o f e q u t l i b r i a : t e s t s o f resource c o m p e t i t i o n u s i n g two species o f algae. Oecologia, 61: 197-200. Tuchrnan, M.L. and Stevenson, R.J., 1980. Cornpartson o f c l a y t i l e , s t e r t l i z e d rock, and n a t u r a l s u b s t r a t e diatom communities i n a small stream i n southeastern Michigan, USA. Hydrobiologta, 75: 73-79. Underwood, A.J., 1980. The e f f e c t s o f g r a z i n g by gastropods and p h y s i c a l f a c t o r s on t h e upper l i m i t s o f d i s t r i b u t i o n o f I n t e r t i d a l macroalgae. Oecologia, 46: 201-213. 1984a. The v e r t i c a l d i s t r i b u t i o n and seasonal abundance o f Underwood, A.J., i n t e r t t d a l microalgae on a rocky shore i n New South Wales. J. Exp. Mar. B i o l . Ec0l.r 78: 199-220. Underwood, A.J., 1984b. M i c r o a l g a l food and t h e growth of t h e i n t e r t i d a l (Lamarck) a t f o u r gastropods Nerlta atramentosa Reeve and h e i g h t s on a shore. J. Exp. Mar. B i o l . Ecol., 79: 277-291. Underwood, A.J., 1984~.V e r t i c a l and seasonal p a t t e r n s i n c o m p e t i t i o n f o r microalgae between i n t e r t i d a l gastropods. Oecologia, 64: 211-222. Underwood, A.J. and Jernakoff. P., 1981. E f f e c t s o f I n t e r a c t i o n s between algae and g r a z i n g gastropods on t h e s t r u c t u r e o f a low-shore i n t e r t i d a l a l g a l community. Oecologta, 48: 221-233. Vadas, R.L., 1977. P r e f e r e n t i a l feeding: an o p t i m i z a t i o n s t r a t e g y i n sea urchins. E c o l o g i c a l Monographs, 47: 337-371. Vadas, R.L., 1986. Herbivory. I n : M.M. L i t t l e r and D.S. L i t t l e r ( E d i t o r s ) , Handbook o f Phycological Methods. Ecologlcal F i e l d Methods: Macroalgae. Cambrldge U n i v e r s i t y Press, pp. 531-572. Varela, M. and Penas, E., 1985. Primary p r o d u c t l o n o f b e n t h i c microalgae i n an i n t e r t i d a l sand f l a t of t h e R i a de Arosa, NW Spain. Mar. Ecol. Progress. Ser., 25: 111-119. Weitzel, R.L. ( E d t t o r ) , 1979. Methods and Measurements o f Perlphyton Communlties: A Review. American Society f o r T e s t i n g and Materials. Philadelphia, PA., U.S.A., 183 pp.

299 Werff, A. van der, 1955. A new method o f concentrattng and c l e a n i n g diatoms and o t h e r organisms. I n t . Ver. Theor. Angew. Ltmnol. Verh., 12: 276-7. Winterbourn, M.J., Hildrew. A.G. and Box, A., 1985. S t r u c t u r e and graztng o f stone surface organic l a y e r s i n some a c i d steams o f southern England. Fresh. Btol., 15: 363-374. Wynne, D. and Rhee, G-Y. 1986. E f f e c t s o f l i g h t t n t e n s i t y and q u a l i t y on t h e r e l a t i v e N and P requtrements ( t h e opttmum N:P r a t t o ) o f martne planktontc algae. 3 . Plank. Res., 8: 91-103.

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301 CHAPTER 18

MEASUREMENTS OF METABOLIC ACTIVITIES WITHIN A BALTIC FUCUS VESICULOSUS COMMUNITY: THE CONTRIBUTION OF FOULING MICROALGAE AND GRAZERS T. KAIRESALO' and E. LESKINEN2

'Lammi Biological S t a t i o n , Univ. of Helsinki, SF-16900 Lammi (Finland) 'Tvarminne Zoological S t a t i o n , U n j v . of Helsinki, SF-10900 Hanko (Finland)

18.1

INTRODUCTION

Fucus vesiculosus L . , t h e bladder-wrack, i s widely d s t r i b u t e d throughout the B a l t i c l i t t o r a l forming dense stands between d e p t h s of . 5 and 5.5 m (Luther e t a l . 1975, Wallentinus 1979). The Fucus b e l t c o n s t i t u t e s a r i c h and diverse system f o r plant-animal i n t e r a c t i o n s i n t h e B a l t i c Proper (Jan son 1977, Jansson e t a l . 1982). However, in brackish water, Fucus vesiculosus i s highly suscepticle t o changes in hydrography, microalgal colonization, grazing pressure by herbivores and sedimentation. Pulses of North Sea water i n t o t h e B a l t i c Sea change t h e sal i ni t y and n u t r i e n t level s of t h e water, and enhanced mi croal gal production may seriously d i s t u r b the growth of E . An extensive decline and disappearance of Fucus from Finnish coastal areas i n t h e l a t e 1970's and e a r l y 1980's (Kangas e t a l . 1982) revealed t h a t t h e community dynamicswithin t h e dominant macroalgal b e l t a r e s t i l l too poorly known f o r valid predictions. More d e t a i l e d measurements of community metabolism and foodweb i n t e r a c t i o n s within stands a r e necessary f o r better understanding and possible management. To accomplish t h i s , methodological problems must be solved. The purpose o f the present study was t o develop and t e s t methods f o r the simultaneous i n s i t u measurement of ( 1 ) community metabolism within stands, ( 2 ) t h e contribution of d i f f e r e n t subsystems of t h e community ( i .e., t h e macroalga, epiphyton, plankton and benthos) t o t h e t o t a l metabolism, and ( 3 ) grazing a c t i v i t i e s o f dominant herbivores on t h e algal communities. 18.2

MATERIALS AND METHODS

The study area was located close t o Tvarminne Zoological Station on t h e SW coast of Finland (Fig. 1 ) . The average s a l i n i t y i s 6% and t i d a l range i s n e g l i g i b l e there. During t h e f i r s t experiment (14-14 June) the s k i e s were sunny and water temperature was 10.8-11.3 "C. During t h e second experiment (20-21 July) t h e sky was overcast and water temperature was 11.5-12.5 "C. During both experiments t h e water pH was near 7.9. A d e t a i l e d description of conditions i n t h e Tvarminne area i s given by Niemi (1973).

302

Gulf of Finland

23.5

Fig. 1 . Location of t h e study s i t e i n the Tvarminne area in t h e northern B a l t i c Sea. The sampling area was on a southfacing shore of Halsholmen island. Measurements were c a r r i e d out on a r e l a t i v e l y hard, sandy bottom a t a depth of 1.5-2 m where t h e Fucus stand (permanently submerged) consisted mainly of l a r g e , separate specimens, which were densely covered by epiphytic m a t e r i a l . The f i e l d work was done using SCUBA. One t a l l (50-60 cm), healthy-looking individual from t h e Fucus stand was selected f o r t h e measurement of community metabolism. A transparent a c r y l i c p l a s t i c chamber (volume 106 1 , height 70 cm) was s l i d over t h e macroalga, taking care not t o detach i t from i t s stone substratum or t o d i s t u r b i t s epiphytic f l o r a and fauna. The chamber was constructed of two p a r t s , which were bound together with strong rubber bands (Fig. 2 ) . The j o i n t s were sealed with s i l i c o n rubber. I n t h e upper p a r t t h e r e was a l a r g e ( 6 cm d i a . ) hole f o r t h e probe and t h e s t i r r e r of a YSI oxygen meter (model 5 8 ) . Neoprene was used t o t i g h t l y hold t h e probe and t h e s t i r r e r in position. During t h e f i r s t measurement, more e f f i c i e n t water mixing within t h e chamber was achieved by manual s t i r r i n g with a p r o p e l l e r , since t h e s t i r r e r connected t o t h e oxygen probe proved inadequate. During t h e second measurement, a supplementary b a t t e r y powered s t i r r e r ran continuously i n s i d e the chamber (Fig. 2 ) . A two blade propeller ( t o t a l length 24 cm, speed 8 rpm) was s u f f i c i e n t t o keep t h e water thoroughly mixed throughout the experiment. Variation (S.D./mean * 100) among 4-6 subsamples o f dissolved inorganic carbon

(DIC), taken from d i f f e r e n t p a r t s of t h e chamber,

was f 1 %, compared t o * 0.5 % f o r t h e d i s t i l l e d water standard (15 mg C 1-’1. Water samples f o r DIC were taken from t h e measuring chamber with 4-6 10 ml

303

70 cm

Fig. 2 . A schematic representation of t h e measuring chamber ( s e e t e x t f o r d e t a i l s ) . syringes by i n s e r t i n g t h e needles through s i l i c o n stoppers on t h e walls and t h e roof of t h e chamber (Fig. 2 ) . The samples were transported t o t h e laboratory in a dark cool-box. DIC was analysed as C02 using a Unicarb-carbon analyser ( e l e c t r o Dynamo) a f t e r t h e method of Salonen (1981). When r e s p i r a t i o n of t h e Fucus community was measured, t h e chamber was covered with an opaque p l a s t i c bag. The bag was removed while measurements of photosynthetic a c t i v i t y of t h e community was taken. A t t h e i n i t i a t i o n of t h e photosynthetic measuremants a NaH 14C03 solution was injected and mixed i n t o t h e chamber water (290 pCi on 14-15 June and 90 VCi on 20-21 J u l y ) . The sampling procedure a f t e r an incubation time of 5-5.5 hours was as follows: ( 1 ) a water sample o f 500 ml was taken from i n s i d e t h e chamber; ( 2 ) t h e upper p a r t of t h e chamber was gently removed and 6 ends of t h e Fucus t h a l l u s (with t h e i r epiphytes) were clipped off and p u t separately i n t o 100 ml p l a s t i c enclosures; ( 3 ) t h e r e s t of t h e Fucus t h a l l u s with i t s epiphytes was harvested and placed in a l a r g e p l a s t i c bag; ( 4 ) 3 sediments samples from inside t h e lower p a r t of t h e chamber were taken with a c r y l i c p l a s t i c c o r e s . ( 4 . 5 cm d i a . ) . All samples were transported t o t h e laboratory in cool-boxes under an opaque sheet. I n t h e laboratory t h e samples were prepared f o r analysis by a CHN-analyser connected t o a l i q u i d s c i n t i l l a t i o n system as follows: ( 1 ) water samples were f i l t e r e d through Whatman GF/C f i l t e r s , acidified with 1 N HC1 t o l i b e r a t e inorganic 14C and then dried a t room temperature; ( 2 ) epiphytes from the ends of the Fucus t h a l l u s were removed with the help of a s o f t p l a s t i c b r u s h and vigorous

304

shaking; (3) Surface l a y e r s (0.5-1 cm) of the sediment cores were c u t off f o r f u r t h e r treatment; (41 Attached material on t h e r e s t of t h e t h a l l u s was removed as thoroughly as possible with strong water j e t s and a p l a s t i c b r u s h . The water containing t h e detached epiphytic material was gathered separately i n t o p l a s t i c containers and concentrated t o a smaller volume of water ( 500 ml by l e t t i n g t h e suspension s e t t l e overnight in a dark, cold room ( 2 Water over t h e concentrated suspension was siphoned away, with t h e exception of a 500 ml subsample which was f i l t e r e d and subsequently t r e a t e d in t h e same manner as t h e plankton sample ( f o r checking t h e sedimentation e f f i c i e n c y of t h e epiphytic O C ) .

m a t e r i a l ) . After c o l l e c t i o n of t h e most common invertebrates (Table 3) from t h e epiphytic suspension, the r e s t of t h e suspension was dried a t 60 "C as well as t h e other 14C-saaples ( i . e . Fucus t h a l l u s , 6 ends of the t h a l l u s , epiphytic materials, sediment samples and i n v e r t e b r a t e s ) . All samples were a c i d i f i e d with 1 N HC1 before drying. Before drying, t h e = t h a l l u s was divided i n t o four p a r t s : remaining ends, upper p a r t , middle p a r t and lower p a r t ( c f . Fig. 4 ) . All p a r t s were then t r e a t e d separately. After drying a l l t h e p a r t s , epiphytic materials and sediment samples were homogenized and weighed. Then 2-5 small subsamples ( 10 mg) were combusted in a CHN-analyser (Hewlett Packard) f o r analysis of t o t a l carbon and nitrogen and fixed 14C. The radiocarbon was trapped as 14C02 from t h e outflow gas in a gas-liquid exchange column and t h e absorbent (Carbo-Sorb 11, Lumac) was run d i r e c t l y i n t o a s c i n t i l l a t i o n vial attached t o t h e column. The l a r g e r animals were combusted separately, whereas f o r t h e smaller species 3-5 individuals were analysed together. Radioactivities were measured i n a xylene based s c i n t i l l a t i o n c o c t a i l (Carbo-Luma, Lumac) using a Wallac Rackbeta l i q u i d s c i n t i l l a t i o n counter. TABLE 1

Comparison of primary production and darkrespiration r a t e s of e n t i r e comnunity measured by 14C and O2 methods.

14-15 June 14c 14c 14c l4C P.Q. P.Q. R.Q.

/ / / /

net o2 gross o2 net CO, gross to2

net gross

a not measured

1.08 0.71 -a

20-21 July 0.69 0.46 0.70

0.49 1.02 1.06 0.87

Fucus

305

A

20-21 July

14-15 June

mg m2h-'

1 600

- 600

c

- LOO - 200 -

o2 co2 '4~0,

OL, 21

. 2L

6

12

0

.

18 21

2L

6

12

18

Fig. 3. ( A ) Primary production (white) and dark r e s p i r a t i o n ( s t i p p e d ) measured by d i f f e r e n t methods. ( B ) Changes i n oxygen (closed c i r c l e s ) and di.ssolved inorganic carbon ( D I C ) (open c i r c l e s ) concentrations i n t h e chamber. Dark period i s marked with a shaded bar and l i g h t period with white. 18.3

RESULTS

For the metabolic a c t i v i t y of t h e whole Fucus communtiy, t h e r e s u l t s from t h e 14C method and net O2 changes i n t h e l i g h t produced comparable r e s u l t s in t h e f i r s t experiment (14-15 June) (Fig. 3A, Table 1 ) . Dark r e s p i r a t i o n contributed 33 % of the gross O2 change and 30 % of the gross C02 change, respectively. Both t h e dissolved inorganic carbon (DIC) and t h e oxygen concentrations showed l i n e a r changes during t h e measuring periods (Fig. 3B). The gas exchange r a t e s t h u s seemed t o be only s l i g h t l y affected by the changing concentrations. The photosynthetic quotient ( P . Q . ) f o r evolved O2 and assimilated C02 on 20-21 July was near unity (1.02 f o r the net r e s u l t s and 1.06 f o r t h e gross r e s u l t s , Table 1 ) . The r e s p i r a t o r y quotient ( R . Q . 1 f o r evolved C02 and consumed O2 remained below unity (0.87, Table 1 1 , indicating t h a t t h e f r e s h l y synthesized carbohydrates were hardly used as s u b s t r a t e s f o r r e s p i r a t o r y processes ( c f . Fogg 1969). 14C incorporation in t h e l i g h t revealed t h e s i t e s and d i s t r i b u t i o n of photosynthetic a c t i v i t y within the & community. The r e s u l t s indicated t h a t t h e macroalga had much g r e a t e r photosynthetic a c t i v i t y than other producers i n t h e

306

TABLE 2 Percent contributions o f d i f f e r e n t subsystems of t h e FucUs community t o t o t a l 14C f i x a t i o n ( P ) and t o t a l carbon content ( B ) together with s p e c i f i c photosynthetic r a t e s ( P / B ; mg C/g C hr-’) f o r each. subsystem.

14-15 June

Fucus vesi cul osus Epi phyton Phytoplankton Mi crobenthos a

P

B

%

%

89.1 9.7 1.1 0.1

82.2

17.1 0.6 0.1

20-21 July P/B

mg C/g C h r - ’ 0.57 0.30 1.00 0.72

P

B

%

%

90.5

7.7 1.8 -a

P/B

mg C/g C h r - ’

87.7 11.8 0.5

0.43 0.27 1.59

-

not measured

chamber (Table 21, even though i t was shaded by a thick epiphytic cover. The as a whole was responsible f o r about 90 % of t h e t o t a l 14C fixation. The most a c t i v e photosynthetic s i t e was t h e upper p a r t of t h e & t h a l l u s (Fig. 4 ) . The Fucus P/B-ratio was a l s o higher than t h a t f o r t h e epiphytic communities (Table 2 ) . Microscopic analysis revealed t h a t t h e epiphytic mass consisted l a r g e l y o f d e t r i t a l material. Surrounding plankton and microbenthos made only minor contributions ( 2 % ) t o t h e photosynthetic a c t i v i t y o f t h e whole

Fucus t h a l l u s

14-15 J u n e

20-21 July

P

B

P

B

31.2

16.7

19.8

13.7

44.9

28.9

54.2

41.5

19.9

45.6

22.5

36.6

4.0

8.8

3.5

8.2

Fig. 4. Percent contributions of d i f f e r e n t p a r t s o f incorporation ( P ) and carbon content ( B ) .

FucUs t h a l l u s

t o total 14C

307 TABLE 3

Range of absolute (dpm) and r e l a t i v e (dpm/mg C ) r a d i o a c t i v i t y of d i f f e r e n t invertebrates l i v i n g i n epiphyton on Fucus vesiculosus. Number of animals combusted e i t h e r separately or 3-5 animals together " 1 i s given in parenthesis. 14 (On 14-15 June t h e amount of Na C03 injected was 290 p C i and on 20-21 July, 90 VCi. CaCO was ignored as a carbon source.) 3 ( ' I

14-15 June Gammarus spp. ( 1 0 ) Idotea b a l t i c a ( 3 ) Jaera a l b i f r o n s ( " 5 " ) Theodoxus f l u v i a t i l i s ( 4 ) Lymnaea spp. ( 3 ) Chironomidae 20-21 July Gammarus spp. ( 4 ) Jaera a l b i f r o n s ( " 3 " ) Neomysi s integer ( 1 1 Bal anus improvi sus ( 4 ) Theodoxus f l u v i a t i l i s ( 3 ) Chi ronomi dae ( 1 ) Electra c r u s t u l e n t a ( 1 )

dPm

dpm/mg C

89-1 20 1106- 1463

164-1 74 142-186

42 119-417 280-496 25

81 15-62 83-1 1 2

dPm

dpm/mg C

43-92 10 11 50-82

16-34 19

119-182

17-34 390

44 61

18

6 12-22

264

Fucus community (Table 2 ) . The s p e c i f i c photosynthetic r a t e o f phytoplankton,

however, was higher than those of other primary producers (Table 2 ) . Table 3 shows the absolute and r e l a t i v e r a d i o a c t i v i t i e s of d i f f e r e n t herbivorous invertebrates feeding e i t h e r on t h e macroalga o r on i t s epiphyton. I n June, t h e isopod Idotea b a l t i c a was q u a n t i t a t i v e l y t h e most a c t i v e herbivore, although high s p e c i f i c a c t i v i t i e s were a l s o measured f o r small amphipod< (Gammarus s p p . ) . I n July, t h e highest feeding r a t e s were measured f o r t h e gastropod Theodoxus f l u v i a t i l i s , whereas t h e bryozoan Electra c r u s t u l e n t a and a chironomid larva showed t h e highest s p e c i f i c a c t i v i t i e s . The high s p e c i f i c a c t i v i t y of Electra c r u s t u l e n t a may, however be a t t r i b u t a b l e t o some t i g h t l y attached algae growing on t h e surface of t h e animal. C : N r a t i o s may be used as a measure of r e l a t i v e protein content (McMahon e t al. 1974). On t h e average, proteins a r e comprised of 50 % carbon and 16 % nitrogen, with a C : N r a t i o by weight of ca. 3 . 1 : l . The C : N r a t i o was d i s t i n c t l y lower

308 TABLE 4 C:N r a t i o in d i f f e r n t p a r t s of & t h a l l u s

14-15 June

and community. 20-21 July

14.8 16.4 23.2 24.4

23.4 24.3 23.8 25.8

8.8

12.1

Phytoplankton

6.2 7.8

Microbenthos

7.6

7.3 6.5 a

Fucus -

Epi phyton

a

ends

upper mi ddl e 1ower total on ends

-

not measured

i n t h e epiphytic, planktonic and benthic communities than i n t h e d i f f e r e n t p a r t s of t h e Fucus t h a l l u s (Table 4 ) . T h u s t h e microalgal communities presumably provided n u t r i t i o n a l l y b e t t e r food than t h e i r host. The lower C:N r a t i o s of t h e ends and upper p a r t of t h e @ t h a l l u s on 14-15 June were probably r e l a t e d t o a period of a c t i v e growth and reproduction. 18.4 DISCUSSION Although comparison of the d i f f e r e n t methods showed t h a t both t h e 02and C02 method produced similar r e s u l t s f o r comnunity photosynthesis and r e s p i r a t i o n ( c f . Guterstam 1977, Guterstam e t a l . 19781, some points i n the measuring techniques need more d e t a i l e d consideration, I n the f i r s t experiment. t h e water i n s i d e the chamber became s t r a t i f i e d within a short time a f t e r enclosing the system unless r e l a t i v e l y slow, continuous s t i r r i n g was used i n addition t o t h a t provided by t h e s t i r r e r connected t o the oxygen probe. However, strong s t i r r i n g might influence t h e gas-liquid equilibrium i n t h e water and t h u s a f f e c t t h e gas exchange r a t e s . Other problems may a l s o a r i s e when measuring t h e O2 and C02 exchange of t h e community i n a closed system. During daylight, O2 s a t u r a t i o n generally exceeds 100 % i n t h e B a l t i c l i t t o r a l during high primary production and may cause oxygen bubbles t o be deposited on t h e walls of t h e chamber. To eliminate t h i s problem we i n i t i a t e d the measurements l a t e i n the evening and measured t h e dark r e s p i r a t i o n f i r s t (Fig. 38). However, when the O2 concentration in the water i s low, t h e r e s p i r a t i o n r a t e may decrease ( c f . Guterstam 1977). Only a s l i g h t change in O2 consumtion was recorded during the dark period on 20-21 July (Fig. 381, which may a l s o have been p a r t l y due t o a decrease i n water temperature from 12.5 t o 11.5 "C. Nevertheless, especially a t higher temperatures, the incubation

309 time should be kept short enough t o ensure valid r e s p i r a t i o n r e s u l t s ( c f . Dawson e t a l . 1981). High concentrations of DIC in t h e B a l t i c water body have s e t l i m i t s f o r t h e use of DIC change as a measure of photosynthesis and r e s p i r a t i o n . The methods we used allowed us t o determine D I C concentration accurately enough (S.D./mean * 100 f 0.5 % ) t o produce r e s u l t s comparable with O2 change. Furthermore, t h e C02 method allowed us t o compare t h e r e s u l t s with those of t h e 14C method d i r e c t l y , without a P.Q. c o e f f i c i e n t . The DIC change was r e l a t i v e l y low compared t o t h e corresponding O2 change and t h u s affected t h e gas diffusion r a t e l e s s . On the other hand, t h e change i n pH by one u n i t (from 6.9 t o 7.9) during the measurement caused f l u c t u a t i o n s in COP and HC03 concentrations and r a t i o s , which may have affected carbon metabolism ( c . Dromgoole 1978). 14C incorporation yielded conradictory r e s u l t s . I n t h e f i r s t measurement t h e r e s u l t s were comparable t o t h e O2 net production, whereas in t h e second one they were about one t h i r d lower. I n t h e experiments, we did not measure t h e 14C excretion by Fucus, which might be of relevance t o t h e observed difference. However, as muchas 30 % of t h e f r e s h l y photosynthesized 14C should have been excreted i n t h e l i g h t , which i s an order of magnitude g r e a t e r than t h a t presented by Guterstam e t a l . (1978). As such, i t might be expected t h a t t h e freshly photosynthesized carbon exudates would most l i k e l y have been assimilated by t h e epiphytes on @, b u t t h i s was not measured i n t h e present study. If some a n t i b i o t i c exudates had been released by the macroalga, these products most probably did not include high l e v e l s of 14C ( c f . Anthoni e t a l . 1980). Photor e s p i r a t i o n could not explain the low 14C y i e l d e i t h e r , since a high photor e s p i r a t i o n r a t e would have lowered the P.Q. values. 14C dark f i x a t i o n , which increased t h e 14C incorporation, was not taken i n t o account i n t h e comparisons. The incorporated 14C could be used as a t r a c e r f o r a c t i v e photosynthesis and herbivory, and more generally f o r the energy f l u x within t h e community, since carbon has been shown t o be a relevent parameter of energy flow (e.g. Salonen e t a l . 1976). The contribution of microalgae t o t h e t o t a l 14C incorporation was surprisingly low (Table 2 ) . I n a freshwater helophyte stand (Equisetum f l u v i a t i l e L . ) i n t h e l i t t o r a l of Lake Paajarvi (Kairesalo 19831, t h e contribution of microalgae was very high u n t i l t h e emergence of t h e macrophytes and t h e decrease of l i g h t a v a i l a b i l i t y . Epiphytic cover i s normally more harmful f o r submerged plants than f o r helophytes, which have t h e i r photosynthesizing p a r t s above t h e water surface. Fucus vesiculosus may be able t o control the microbial growth (e.g. Hornsey and Hide 1974, Wium-Andersen e t a l . 19821, as well as i n h i b i t e feeding by herbivores (e.g. Levin 1976, Geiselman and McConnell 19811, by producing a n t i b i o t i c o r r e p e l l e n t substances. However, i t i s s t i l l questionable as t o whether some a n t i b i o t i c substances a r e excreted by macrophytes t o a meaningful extent t o diminishing epiphytic growth.

31 0 The Fucus b e l t i s t h e most diverse biotope i n t h e B a l t i c , o f f e r i n g protection, nourishment and spawning places f o r many d i f f e r e n t animal groups (Haage 1975). Idotea species, f o r instance, use Fucus vesiculosus both as a substratum and f o r nourishment. The adults prefer t o browse t h e old p a r t s of t h e t h a l l u s (Salemaa 1979, Kangas e t a l . 19821, ingesting on the average 10-30 mg f r e s h weight of alga per day a t summer temperatures (Korheina 1981 1. The microbial and d e t r i t a l material epiphytic on Fucus vesiculosus, however, provides n u t r i t i o n r i c h e r in protein than does t h e fucoid t h a l l u s (Table 4 ) . This suggests t h a t t h e r i c h epiphytic f l o r a of diatoms and filamentous algae might be p r e f e r e n t i a l l y consumed by t h e herbivorous and omnivorous species ( c f . Haage 1975). Hutchinson (1975) has suggested t h a t t h e epiphytic cover may even play a p r o t e c t i v e function f o r t h e underlying macroalga against herbivores. However, i t s t i l l remains uncertain which circumstances promote t h e grazing pressure within some FucUs stands t o such an extent t h a t only t h e midribs of the Fucus t h a l l i remain ( c f . Kangas e t a l . 1982). I n our f i r s t experiment on 14-15 June ca. 1 % of t h e freshly Photosynthesized carbon was assimilated by t h e herbivores during t h e 5 hr incubation period (animal d e n s i t i e s were based on average values i n 1981 presented by Kangas e t a l . 1982: Table 3). The 1 % value corresponds t o an ingestion r a t e of about 0.7 mg C h r - ’ , which i s equivalent t o 37 mg f r e s h weight of epiphytic material or 20 mg f r e s h weight of FucUs t h a l l u s per hour. I f t h e grazing a c t i v i t y was focused only on t h e epiphytic algae, a 10.7 % f r a c t i o n of the epiphytic algal production was ingested by t h e herbivores during t h e 5 h r experiment (faeces and r e s p i r a t i o n l o s s e s o m i t t e d ) . This r e s u l t , although t e n t a t i v e , suggests t h a t the accumulation and reduction of epiphytic algal biomass on Fucus vesiculosus may be p r i n c i p a l l y controlled by t h e density and composition of herbivores. I n conclusion, t h e methods u t i l i z e d . i n t h i s study would seem t o be applicable in a more d e t a i l e d study of processes within Fucus communities a t d i f f e r e n t succesional stages and under various environmental conditions. Such i n s i t u methods together with more d e t a i l e d laboratory work on adjusted 02, C02 and pH conditions ( c f . Titus e t a l . 1979, Weber e t a l . 1981, Denny e t a l . 1983) i n conjunction with perturbation experiments ( c f . Bender e t a l . 1984) will provide a more accurate description of the Fucus community on which f u t u r e predictions can be based. Acknowledgements - W e a r e g r e a t l y indepted t o the s t a f f of Tvarminne Zoological Station f o r providing us with excellent working f a c i l i t i e s . Pentti Kangas, Si obhan Lysaght, Roger Jones, Kyle Hoagl and and an anonymous reviewer read the manuscript and made relevant comments on i t , which i s g r e a t l y appreciated. Financial support f o r t h i s work was provided by t h e Walter and Andre6 de Nottbeck Foundation.

31 1 18.5 REFERENCES Anthoni, U., Chistophersen, C . , Madsen, J.O., Wium-Andersen, S. and Jacobsen, N . , 1980. Biologically a c t i v e su p h u r compounds from t h e green alga Chars c l o b u l a r i s . Phytochemistry, 9: 1228-1229. Bender, E . A . , Case, T.J. and Gi pin, M.E., 1984. Perturbation experiments in community ecology: theory and practices. Ecology, 65: 1-13. Dawson, F.H., Westlake, D.F. and Williams, G.I., 1981. An automatic system t o study t h e responses of r e s p i r a t i o n and photosynthfsi s by submerged macrophytes t o environmental variables. Hydrobiologia, 77: 217-285. Denny, P . , Orr, P . T . and Erskine, J.C., 1983. Potentiometric measurements of carbon dioxide f l u x o f submerged aquatic macrophytes in pH-statted natural waters. Freshwater Biol., 13: 507-519. Dromgoole, F . I . , 1978. The e f f e c t s of pH and inorganic carbon on photosynthesis and dark r e s p i r a t i o n of Carpophyllum (Fucales, Phaeophyceae). Aquat. Bot., 4: 11-22. Fogg, G . E . , 1969. Oxygen versus 14C methodology. I n : R.A. Vollenweider ( E d i t o r ) , A manual on Methods f o r Measuring Primary Production in Aquatic Environments. IBP Handbook No 1 2 . Blackwell S c i e n t i f i c Publications, Oxford, pp. 76-78. Geiselman, J.A. and McConnell, O.J., 1981. Polyphenols in brown algae Fucus vesiculosus and Ascophylluin nodosum: chemical defenses against t h e Z X i i e herbivorous s n a i l , L i t t o r i n a l i t t o r e a . J . Chem. Ecol., 7: 1115-1133. Guterstam, B . , 1977. An in s i t u study of the primary production and metabolism of a B a l t i c Fucus vesiculosus L . community. In: B.F. Keegan, P.O. Ceidigh and P.J.S. Boaden ( t d i t o r s ) , Biology of Benthic Organisms. 11th Europ. Symp. Mar. Biol., Galway, Oct. 1976. Pergamon Press, Oxford, pp. 311-319. Guterstam, B . , Wallentinus, I . and I t u r r i a g a , R . , 1978. I n s i t u primary production of Fucus vesiculosus and Cladophora glomerata. Kieler Meeresforschungen, Sonderheft 4: 25/ -266. Haage, P., 1975. Quantitative investigations of t h e B a l t i c Fucus b e l t macrofauna. 2. Q u a n t i t a t i v e seasonal f l u c t u a t i o n s . Contr. Asko Lab. ,%. of Stockholm, No. 9. Hornsey, I.S. and Hide, D., 1974. The production of antimicrobial combounds by B r i t i s h marine algae. I . Antibiotic-producing marine algae. Br. phycol. J . , 9: 353-361. Hutchinson, G . E . , 1975. A Treatise in Limnology. 111. Limnological Botany. John Wiley and Sons Inc., New York. 660 p. Jansson, A.-M., Kautsky, N . , von Oertzen, 3.-A., Schramm, W . , S j o s t e d t , B . , von Wachenfeldt, T. and Wallentinus, I . , 1982. Structural and functional r e l a t i o n s h i p s i n a southern B a l t i c ecosystem. Contr. Asko Lab., Univ. of Stockholm, No. 18, pp. 54-63. Kairesalo, T . , 1983. Photosynthesis and r e s p i r a t i o n within an Equisetum f l u v i a t i l e L. stand i n Lake Paajarvi, southern Finland. Arch. Hydrobiol., 8-. Kangas, P . , Autio, H . , Hallfors, G . , Luther, H . , Niemi, A. and Salemaa, H . , 1982. A general model o f t h e decline of Fucus vesiculosus a t Tvarminne, south coast of Finland i n 1977-81. Acta Bot. Fennica, 118: 1-27. Korheina, A.K., 1981. Environments and co-existence of Idotea species in t h e southern B a l t i c . Ph.D. Dissertation, Univ. o f Lund. Levin, D.A., 1976. The chemical defenses of p l a n t s t o pathogens and herbivores. Ann. Rev. Ecol. Syst., 7: 121-159. . Luther, H., Hallfors, G . , Lappalainen, A. and Kangas, P . , 1975. L i t t o r a l benthos o f the northern B a l t i c Sea. I . Introduction. I n t . Revue ges Hydrobiol., 60: 289-296. McMahon, R.F., Hunter, R.D. and Russell-Hunter, W.D., 1974. Variations in Aufwuchs a t six freshwater h a b i t a t s i n terms of carbon biomass and o f carbon: nitrogen r a t i o . Hydrobiologia, 45: 391-404. Niemi, A., 1973. Ecology of phytoplankton i n t h e Tvarminne area, SW coast of Finland. I . Dynamics of hydrography,nutrients, chlorophyll 5 and phytoplankton. Acta. Bot. Fennica, 100: 1-68. Salemaa, H . , 1979. ecology of Idotea spp. (Isopoda) i n the northern Baltic.

31 2 Ophelia, 18: 133-150. Salonen, K., 1981. Rapid and precise determination of t o t a l inorganic and gaseous organic carbon in water. Water Res., 15: 403-406. Titus, J.E., Adams, M.S., Gustafson, T.D., Stone, W . H . and Westlake, D.F., 1979. Evaluation of d i f f e r e n t i a l i n f r a r e d gas analysis f o r measuring gas exchange by submerged aquatic p l a n t s . Photosynthetica, 13: 294-301. Wallentinus, I . , 1979. Environmental influences on benthic macrovegetation in the Trosa-Ask0 area, northern B a l t i c proper. 11. The ecology of macroalgae and submerged phanerograms. Contr. Ask0 Lab., Univ. of Stockholm, No. 25. Weber, J.A., Tenhunen, J.D., Westrin, S . S . , Yocum, C.S. and Gates, D.M., 1981. An analytical model of photosynthetic response of aquatic p l a n t s t o inorganic carbon and pH. Ecology, 62: 697-705. Wium-Andersen, S . , Anthoni, U . , Christophersen, C . and Houen, G . , 1982. Allelopathic e f f e c t s on phytoplankton by substances i s o l a t e d from aquatic macrophytes (Charales). Oikos, 39: 187-190.

313

Index Achnanthes 4,8, 11, 14-18,25,26,56,8389,95, 101,104-107, 110-112, 163,215, 216,238-240,242,243,255-259,261-263, 266,274,278,282,285,290 Actinoptychus 238,239 adhesion 69,76, 145, 153 adhesion disc 68,70-76 adhesive 69,75, 145 adsorption-desorption reactions 129,132 Alaria 185, 190,214 ammonium 115-117, 120,123, 161, 163, 165,166,170 Amphiprora 4,8, 11, 14-18,56, 82-87,95, 98,238,239 Amphora 4, 8, 11, 14-18,26,41-52,56,59, 60,62,82-87,95,98, 101, 104-107, 109, 110, 112, 146-149, 151-153, 156,215,238, 239,266,282, anemones 183, 184 animals 14, 16, 17 Ankistrodesmus 27 antibiotic exudates 309 anticorrosive 94 anticorrosives, fouling of 231-244 antifouling paints 1-18,55-64,79-112, 137, 145, 175, 183,190,213,221 Antithamnion 185 Aphanocapsa 27 arsenic 136 arthropod 65.75

ascidians 8, 88,90 Ascophyllum 221 Asterionella 25, 26 attachment processes 65-77 Audouinella 185 Aulacosira 26,41, 145,249,261,263,264, 266,274,276,278,280,287-290,291

bacteria 41,56,79, 145,249,261,263,264, 266,274,276,278,280,287-290.292 Balanus 88,89,96,307 Bangia 185 barnacles 1,2,4, 8, 14-17,218 Biddulphia 104,111,238,239 bioadhesion 146 biocide resistance 18 biofilms 247-249,290,292 biotope 310 biphasic granules 68,70,7 1,75 Blidingia 11 blue-green algae 119, 120,216,221,222,237 Bonnernaisonia 185 boundary layer 60,74 bridging complexes 76 bridging polymer 67,71,75 bryozoans 88,89,96 Bugula 4

314

C:N ratios 307,308 Ca2+ 43.46, 50, 51 calcareous scale 232 Callithamnion 4 Caloneis 26 Calothrix 120 Campylodiscus 237-240, 243,244 cathodic protection 213,221,222,231,235239,241 Caulobacterium 280 CCCP 43,50 cell attachment 65-77 cell pemieability 60, 61 Ceramium 4,8, 185 Chaetoceros 238,239,289 Cliaetornorpha 14, 185, 186 Cliaraciurn 74, 75 chemosensing of glucose 42,45 Chironomidae 307 Ciilamydomonas 61,75 Clilorella 176 chlorinated rubber paint system 213 Chorda 74 Cludophora 4, 11,83-88, 175-178, 185 Closterium 27 coal-tar epoxy paints 213, 221, 231-233 Cocconeis 26, 104-107, 112, 215,237,238240,242,243,285 Colacium 65-77 colonization 193-209 community metabolism 301-310 community photosynthesis 308 community structure 254,263,274 complexation-dissociationreactions 129, 133 copper 145 copper antifouling paints 1-18, 101-112 copper bioavailability 129-138 copper sulphate 175-178 copper tolerance 176, 178 copper toxicity 129-138 coppedtributyltinanti-fouling paints 79-99

copper/zinc anti-fouling paints 79-99 corals 183, 184 corrosion 187,211-226 corrosion fatigue 219,224 Coscinodiscus 14 Cosmarium 27 cuprous oxide 2,55,79, 80, 82,9597-99 cyanobacteria 4, 8, 11 cycloheximide 43,48,50 Cyclotella 26 Cylindrotheca 237-240,243,244 Cymatopleura 26,256 Cymbella 2 5 2 6

D-600 43,50 dark respiration 304-305 dark fixation 309 DCMU 43,46 Delessaria 185 Denticula 26 depth-influenceon fouling 79-99 Derbesia 8 Desmarestia 185,214 I-DGA 56-62 2-DGA 57-62 diatom adhesion 41-52 diatom community composition 243 diatom slimes 2,4, 11, 15, 16,SS-64, 101, 112, 145, 149, 1.54 Diatoma 26, 34, 197, 198 differential aeration cells 217, 223 Diploneis 26, 105,238,239 dissolved inorganic carbon 302, 303,305, 309 dissolved inorganic nitrogen 115-117, 121-123 1-dodecylguanidineacetate 56 2-dodecylguanidineacetate 56 dodine 56 drag 2 drag-reducing molecules 146

315

Ectocarpus 1,4,6, 11, 14, 15, 17,56,76, 8289,94-96, 149, 153, 175, 178, 185, 186, 190, 194 effects on adhesion of, D-600 43 effects on adhesion of, Ca2+ 43 effects on adhesion of, CCCP 43 effects on adhesion of, CH 43 effects on adhesion of, DCMU 43 EGTA 47,50 Electra 307 encroachment 22,24, 25, 33,35 energy transfer inhibitor 62 Enteromorpha 1,4, 8, 11, 14, 15, 17, 62, 74, 75, 82-89,94,95, 153, 154, 185, 186, 188, 189,214,215,217,219,221 epibiont 65 epibiosis 65 epilithic 24, 31, 34,45 epilithic community 22 epiphyton 301,306-308 Epithemia 285 Equisetum 309 Erythrotrichiu 185 eulittoral 116, 118-120, 122-124 eulittoral periphyton 121 Eunotia 258,262,268,282,290 eutrophication 159, 170, 172

fluoropolymers 146 fouling of anticorrosives 231-244 fouling of navigation buoys 179-190 fouling of offshore structures 179-190 fouling - effects on corrosion 211-226 Fragilaria 22,25,26,28,31,34, 197, 198, 202,257,262,284 FUCUS 301-3 10

Glenodinium 27 glycoprotein 51,75, 145 Golgi apparatus 51 Gomphoneis 26, 115,118,120, 121,123, 162,163 Gomphonema 27, 198,202,255-259,261263, 266,268, 272,278,280,288-290 Grarnmatophora 104-106 grazing 248-249,255,278,282,285-287 ground water 161, 163, 167-171 growth rates 193-209 guanidinododecaneacetate 61 2-guanidinododecane phosphate 61 helophytes 309 herbivores 301, 307,309, 310 heteromorphy 282, 284 Hormidium 178 hydrodynamic loading 187,213,214,210 hydrogen embrittlement 218,224 Hydroides 4, 14, 15 hydroids 89, 183, 184 Hypoglossum 185

Idotea 307,310 immigration 193,209 immobilization of copper 16 impingement 22,23,28, 31, 33, 34 in-service ships 18 iron 137

Jaera 307 Jassa 4, 8, 11

kelp 186, 190,219

Gammarllr 307 Gelidium 185 Giffordiu 4, 88,96, 185

Laminaria 88, 89, 185, 186, 190, 214

316

LC-50 values 16,57 leaching rate 15, 16,98 Licmophora 83-89,96,238,239 life forms 274,282,284,289-292 Lamentaria 185 low energy surface 146-156 Lymnaea 307 Lyngbya 27 macroalgae 2, 17 Macrocystis 123 macrofouling 16 manganese 134,137 Melosira 14,83-89, 110,238-240,242,243, Meridion 256,257,261,266,268,280,282, 284 Merismopedia 27 microalgae 22 microalgal fouling of FUCW 301-310 microbenthos 306,308 microcommunities 249,272,274,286,288, 29 1 microtubules 5 1 model 194,198,201,206-209 modelling 193-209 moisture cured silicone elastomers 146-156 Mougeotia 27 muciferous bodies 7 5 7 6 mucilage 75,254,263,264,266,268,274, 278,280,282,284,287,289 mucccysts 68,70,7 1,75,76 mussel 88,96, 183, 184,214 Mytilus 186

Navicula 8, 14, 15, 17, 18,27,46,56,83-89, 96,101,104-107,109,110,112,197,198,

202,215,237-240,242-244,255259,261263,268,272,282,285 Neomysis 307 nitrate 115-117, 120-123,

nitrogen 115-117,120-123, 162,163, 165168,170,171 nitrogen fixation 117, 119-121 Nitzschia 11, 17, 18,27,46, 83-87, 89,90, 105,215,238-240,243,255-259,261-263, 266,280,285,287,288 non-biocidal antifouling systems 146-156 nonstick surfaces 146-156 Nostoc 120 nutrient loading 159,163,165, 166,168,170, 171

Obelia 4 Oedogonium 178,264,276 offshore fouling communities 179-190 oligotrophic 115, 159 Oocystis 27 organotin 79,95, 135, 137 organotin antifoulingpaints 101-112 organotin varnish 1-18 Oscillatoria 28,220 oxidation-reduction reactions 129,135

P.Q. 305,309 Palmaria 185 Paralia 101,237-240,242,243 Pediastrum 28 pellicular pores 68-7 1 Percursaria 8 periphyton 22,24,34-36, 115-120, 122, 123, 135,159-161,163-167, 171,172,248,250, 255-259,261,263,264,266,268,271,272, 274,276,278,280,284286,288,289,292 pH concentration cells 217 Phacotus 28 Phacus 28 phenyl- methyl silicone fluid 146-156 Phom'dium 28 phosphorus 162,163,165,166,168,170, 171

317

photoactivation reactions 129,136 photorespiration 309 photosynthetic quotient 305,309 phytoplankton 306-308 Pilayella 185 Pinnularia 263 pitting corrosion 217,223,225 platinum cured silicone elastomers 146-156 Pleurosigma 238,239,242,243 Plumaria 185 pollution 16, 135 polymer 68,70-72,75,76 polyox 146 polysaccharides 7576, 145 polysaccharide-protein complexes 75,76 Polysiphonia 4,8, 11,88, 154, 185, 186, 188,190,214 Porphyra 185,221 Porphyridium 221 precipitation-dissolutionreactions 129-131 primaryfilm 231 primary producers 307 primary production 304,305 productivity 159,161,162,165,166,171 protein 76 Pseudocharacium 75 Pseudomnas 220

R.Q. 305 radial flow chamber 153 raft tests 1-18,79-99,101-112,146-156 recolonization 22-24,33,35,36 reproduction rates 193,194.204,207 reservoir 22-24,3436 respiratory quotient 305 Reynolds number 74 Rhizosolenia 238,239 Rhodomela 185 Rhodotorula 134 Rhoicosphenia 27,259

Saccharomyces 60 sacrificial anodes 231-233 Scenedesmus 28, 176 Scytosiphon 14,186 seasonal fouling variation 79-99 secretion channels 68 sediments 250,254,259,261,264,266,268, 272,274,276,278,280,287-290 sediment nap 25,26-34,36 selective community development 241-244 Selenastrum 132, 133 selenate 136 selenite 136 SEM 250,252,257,259,263,264,271, 272,274,276,278,287-290 serpulids 88,89,96 ships 'in-service' 94 silane-based coatings 153 silicone elastomers 146-156 silicone RTV polymers 146-156 slime 56,101,145 slime-forming organisms 55 soil erosion 250,290,292 SPC anti-fouling paints 1-18,55-62,79-99 specific growth rate 175-178 Spirobis 14, 15,89 Spirogyra 28 sponges 88,90,96 Spongomorpha 185 Spongonema 185 S?+ 46 stalks 67-69,71-76 Staurastrum 28 Sruuroneis 4, 11, 14, 15, 17, 18,56,82-87, 95.96,101,263 Stephanodkcus 26 Stigeoclonium 28,178 streams 193.194,196,197,202,204,250, 255,257,258,261,262,264,268,271, 272,280,282,285,287,288,290,291 Sublittoral 119-121.123

318 substratum preference 243,244 sulphate reducing bacteria 187,215,218,220, 22 1,223,225, sulphur oxidising bacteria 187,220 Surirella 27,257,258,262,264,268,276, 282 Synedra 27,34, 101, 104-107, 111, 112, 163, 197,198,255,257,258,261,263,268, 274,276,282,284,288 synergism 55-64

Trypsanoma 75 tubeworms 183,184 Tubularia 4, 8, 88, 89,94 tunicamycin 43.47,48,51 turbulence 31,32,35,36

Tabellaria 88, 89 Thalassiosira 137 Theodoxm 307 Thiobacilli 220 tin bioavailability 29- 38 tin toxicity 129-138 Tofypothrir 120 Trachelomonas 28 tributyltin 1,2,55,62,80,82,94-97,99 tributyltin oxide 55-60 tributyltin varnish 1-18 triorganotin 1,55,56,62,79, 145 triphenyltin chloride 62 Tropidoneis 46

Vaucheria 185 vinyl-matrix paint 97 Vorticella 4. 14

Ulothrix 4,8, 11, 14,28,62, 82-88,94,95, 154, 186 Ulva 4, 11,75,88, 89, 154, 185, 186, 188, 214,221

watermovement 118, 119, 123, 124 wave action 23,31,35

zinc bioavailability 129-138 zinc oxide 79,80,82,94-99 zinc toxicity 129-13 zinc/tributyltin anti-fouling paints 79-99 zygnema 122