*ADA0 9 0832*ADA090832

SI ULATION ODELING OF ZOOPLANKTON ANDBE THOS I RESERVOIRS: DOCU E TATIO A DDEVELOP ENT OF ODEL CONSTRUCTS

FISH AND WILDLIFE SERVICE, FAYETTEVILLE,AR. NATIO AL RESERVOIR RESEARCH PROGRA

MAR 1980

U.S. Department of CommerceNational T chnical Informat ion Servic

unc reas araec - .. _. - - _.U:eullITY C r.,.ASSi' ICA Tl OIoI 0" TillS ~AGE~~.....-..4} . - . - .

t. .. -

.-Ru e triSi ..;j~-REPORT DOCUMENT....TION P....GE 8EFORE COMPLETING FORM. ftE:POftT NU...lEft

VAtlAoDc\(\~3~ ) IIE CIPII:N T'S C AT ALOG NUMBER

Technical Repor t E: - 80- 4 AD/A-090 832~,!.!:.II.r-... - m_) -- . •• TY9E 0' IIIEPORT .. PI:RIOO CO VI:III£D

SIMULATION MODELING OF ZOOPLANKTON AND~ENTHOS Final r eport .IN P SERVOlRS: DOCUMENTATION AND DEVELOPMENT-- ~Eft'O_UIG OftG. II£ POIIT MUM.I:IIOF MODEL CONSTRUCTS

.-JI'l:rTJIO It( .o) - - - COI\ITIIACT O ft GRANT MUM.ER{_),G. R. Leidy __ I nteragency AgreementG. R. Ploshy WES- 77-3t. ~lIft'Ol'UlINOOllOANIZATlOtl MAlIiII: AND ADolllni

_•.. --10. PROGRAM EL E ME NT, PIIIOJ EC T , TA SK,

USCI Fish a nd Wi l dl i fe ServiceAREA" WORK UN IT NI,IM.I:R5

Nat i onal Reservo i r Res earch Program ,EWQOS Task lB. I

Fayet t evi H e. Arkansas 12701 ,11. COIolTI'OLUNG O"ICI: NAMI: AND ADOIIIESS II. IIIEPO III T D IIlTE:

Office . Chi ef of Engineer s. u. s. Anoy March 1980

Washington, o. c. 20314 u . NUMB l R to' PIIlGE 5

308rn::- MONI ORING AGI:NCY NAMI:" AOOft05(1I cIItt_t _ c_...n.... O'fI ...) ". SEC UR IT Y CLASS. (., 1Il,• ....-.>

u. s. Army Engi neer Waterways Experiment Sta t i on Unclas s if i edEnvironmental LaboratoryP. O. aox 631, Vicks burg, Mis s i ssippi 39180 • • . fc!;~~tl:ICATIOI\I/OO_GIIAOINO

I&. OIiTItIBU'nOl\l STATIIMe:NT (., IN. _-'J

Approved forpublic re l ea se; distribution unlimited .

17. D1ITItI_UTIO", ITATRtilENT (_1_ "'_ __ '".,....~. ,,11I,_,_~)

I" su-L1£llt:HTAIIY NOTD . . . .• PIOOUCID nNATIONAL TECHNICALINFORMATION SERVICE

us OI,AIIMlfll OF CDIUUICI. S1'llIcnuO. U . 22161

". IlI:Y WOftOS (e-t____ ..... ,,_.~.. t_.,,., lop W___)

Benthos SimulationEnvironmental effects Stochastic modelsMathematical models ZooplanktonReservoirs

:ao.. ....TIIIACTr=t,__.... . , __,,, ... .,....__)

A 1 ~ era tu re review and a na l ys i s of published data on zooplankton andbenthos bioe nergetics f orm the basis used in this repor t for the dev elopmentof stochastic mode l cons t r uc t s for the s i mul a t ion of zoop l ankton and benthosdynamics in reservoirs . Parameters reviewed and mode l ed were selected fromthe mass ba l ance equation:

b [G(~)- R - NPH - PH]db- . (I )dt

(Continued'

'-

.J- UnclassifiedU:Cl~TY ~_"IC:ATION0' ntll ~AGe: ('WholDal• ...~_04)

,

· Qne 1assjfj edSECURITY CLASSIFICATION OF THIS PAGEe-- D•• ...,....q

20. ABSTRACT (Cont inued) .

where b a biomass (mg carbon). t Q time (days). G = consumption or gr azi ng fate(mg carbonomg carbon-I oday-l), A = ass imilation (mg carbonomg carbon-I oday- ).R = respiration (mg car bon omg carbon-Ioday-l) . NPM = nonpredatory mortality(mg carbonomg ca r bon- Ioday- l . and PM = pr eda tory mortality (mg carbonomgcarbon-I. day-I) •

Mathematical constructs . where appropriate or justified by t he avai l abl el i tera t ur e , were developed t o describe t he e f fects of environment a l components(for example, f ood, t empera ture . and oxygen concen t r a t i on) on r a t e t erms inEquati on 1. Freq uency distributions of rate coef f ici en t s we r e f ormed for asmany t axonomic or functional categor i es of aquatic invertebra t es as pos s i bl e.By using carbon units and providing frequency histograms of car bon- ni t r ogenand carbon-phosphorus ra t i os . the mode l can t race the cyc l i ng of ni t r ogen andphosphorus through zooplank ton and benthos compartmen t s . An eva l ua tion ispresented of streng ths and weaknesses in t he literature on zooplankton andbent hos consumption. assimi l a t i on . respiration. and nonp r edatory mortal i t y.

The findin gs in t his r eport are no t to be construedas an of ficial Depa rtment of t he Army posi t ion unl esss o designated by other a ut horized documents

UnclassifiedSECURITY CLASSI F"'CATIO N O F' THIS PAGE(W/>.n Dat. Enl.,.d)

PREFACE

This report was prepared by the U. S . Department of the Interior,

U. S . Fish and Wildlife Service, National Reservoir Research Program

(NRRP), Fayetteville, Arkansas, for the U. S . Army Engineer Waterways

Experiment Station (WES) under Interagency Agreement WES-77-3 dated

3 February 1977 . The study forms part of the Environmental and Water

Quality Operational Studies (EWQOS), Task IB .l , Improved Description of

Reservoir Ecological and Water Quality Processes . The EWQOS Program is

sponsored by the Office, Chief of Engineers , and is assigned to the WES

under the purview of the Environmental Laboratory (EL) .

The research, documentation, and development of model constructs

for reservoir zooplankton and benthos were conducted by Messrs. George

R. Leidy and Gene R. Ploskey for the NRRP ; Mr . Robert H. Jenkins is the

Director of NRRP .

The study was under the direct WES supervision of Dr . Kent

Thornton and Hr . Joseph Norton and the general supervision of Mr. Donald

L. Robey, Chief, Water Quality Modeling Group; Dr. Rex L. Eley, Chief,

Ecosystem Research and Simulation Division; Dr. Jerry Mahloch, Program

Manager, EWQOSj and Dr. John Harrison, Chief, EL.

The Directors of WES during this study were COL John L. Cannon,

CE, and COL Nelson P. Conover, CEo The Technical Director was Mr. F . R.

Brown .

1

CONTENTS

Modeling ConceptsObjec~ives

Scope • • . . • •

PREFACE

PART I: INTRODUCTION

•

Page

1

9

91011

PART II : ELEMENTAL CARBON , NITROGEN. AND PHOSPHORUS COMPOSITI ONOF ZOOPLANKTON AND BENTHOS 14

PART V: RESPIRATION OF ZOOPLANKTON AND BENTHOS

ASSIMILATION EFFICIENCY , EGESTION, AND EXCRETIONOF ZOOPLANKTON AND BENTHOS

In troduction . . • •.•.Methodology . . . . . . . . • .Factors Affecting Assimilation Efficien cySummary of Constructs . . . • . . . .Conclusions . . . • . . . . . • . . .

105

10510811 3120121

127

14161818192225

26

2728516676859090939397979999

10010010110210210 2103

•

•

•

In~roduc t ion

Ni trogenCarbonCarbon:Nit rogen RatiosPhosphorusSummary of Constructs •Conclusions . • • .

PART III : CONSUMPTION BY ZOOPLANKTON AND BENTHOS

Section A: Zooplankton Grazing . . •..•.Consumption by Filter-Feeding ZooplanktonFood Selectivity by Zooplankton • . . . .Effect of. Temperature on ConsumptionDiel Variations in Filtering and Feeding RatesConsumption by Predatory Zooplankton .... .Seas onal Changes in Grazing • . . . . . . . • .Synergistic Effects of Environmental Variables

Section B: Benthic Grazing • . .Effect of Food ConcentrationEffect of Temperature . •Effect of Diel Variations

Section C: Model ConstructsSummary of Cons t r uc t s • .Definitions . . . • . . .Step I ~ Food ConcentrationsStep 2 - Food SelectivityStep 3 - Temperature . .St e p 4 - Diel VariationsStep 5. . . . . . . . . .

Se ction D: Conclusions . . ..»

PART I V:

2

I ntroduc t ion . . . . . . . . . . . . . .Methodo l ogy . . . . . . . . . . . . . . .Va:riat ion Due to Expe r imental ConditionsVariat i on Due t o Conve rs ion of Uni tsModel Cons t ructs . . . . . . . . . . ..Effects of Body Weight . . . . . . .Effects of Dissolve d Oxyge n Concentra t i onEffects of Temperat ureSummary of Constr uc ts . . .Coacl us i ons . . . . . . . .

PART IV: NONPREDATORY MORTALITY OF ZOOPLANKTON AND BENTHOS

Introduct ion . . . . .Previous Mode l s . . . . . . .Experimental Es timate sFactors Af fec t i ng Nonpredat ory MortalitySummary of Construc t sConclusions . . . . .

PART VII : RECOMMENDATION S

General . . . . . . .Chemica l Compos itionCons umpt i on by Zooplankton and Ben thosAss imi l ation Effi c i ency (A/G) . Egestion (F). and

Excretion (E) . . . . . . .Respiration . . . . . . . . .Nonpre datory Mortali ty (NPM)

REFERENCES . . . . . . . . . . . .

1271271301 3313514014 9154158160

161

1611611621651 74176

177

1771771 78

179180181

183

APPENDIX A: ELEMENTAL CARBON, NITROGEN. AND PHOSPHORUSCOMP OSITION OF ZOOPLANKTON AND BENTHOS . . Al

APPENDIX B: FILTERING RATES REPORTED FOR FRESHWATER ZOOPLANKTERSZOOPLANKTERS . . . . . . . . . . . . . . . . . . . Bl

APPENDIX C: ZOOPLANKTON AND BENTHOS ASS IMILATI ON EFFICI ENC IES CI

C2C3

Dl

Appendix .C

RESPI RAT ION OF ZOOPLk~TON AND BENTHOS

De finit ions of Abbreviations and Symbols Used i nAppendix C . . . . . . . . . . . . . . . .

Def i ni t ions of Experimental Methods List e d i n

APPENDIX D:

E3

E9

Par t I : Res pi rat ion Rates of Aq uatic I nvert ebrat e sfor Var ious Taxomonic and Func tional Groups D4

Part I I : Respi ration Rates of Aquatic Invertebratesas a Funct ion of Body Weight and Temperaturefo r Var i ous Taxonomic and Functiona l Groups . D2 2

APPEND IX E: NONPREDATORY MORTALITY OF ZOOPLANKTON AND BENTHOS El

Par t I : Nonpre datory Mortal i ty Rat e s of Zooplankt onand Benthos . . . . . . . . . . . .

Par t II : Uppe r and Lowe r Lethal Temperat ures ofZooplankton and Benthos . . . . . .

3

LIST OF FI GURES

Page

Fr equency di st ributi on o f mac r obenthos C: N r a t i o s 20

Fr eque ncy d i s tr ibution o f zoop l a nk t on C: N r a tio s 2 0

Fr equenc y d i st ributio n o f c l a d o c e c a n C: N r a t i o s 21

Frequenc y distribution o f c o pe p od C: N r a t i o s 2 1

Fr equency di s tri b ut i on o f mac r obentho s C:P ra ti o s 23

Fr e quenc y dist ri but.i on o f z ooplankto n C: P rat. i o s 23

Freque ncy distribut i on o f cop e p od C: P r a tio s 24

Fr equency di s t ribu t i on o f c l a doce r a n C: P r.a t.L o s 2 4

No .

1

2

3

4

5

6

7

B

9

10

Rela tion among f ood conce nt r a t i on , f i lter i ng r a t e , andgraz i ng r ate, ba sed upon ea r ly s t u d ies of filt e r- fe edi ngmarine zoop lankton

Gra zing rate o f Daphnia ma gn a a t var i ous conc e n tra t i ons ofthree alga l s pe c i e s ba sed on the da t a o f Ryt he r ( 1954 )

32

34

11 Gra zing ra t es o f Da phnia magn a at var i o u s c o ncen t ra t i o n s o ff ou r f o o d s ources b a s e d on t he data o f Mc Ma ho n a nd Rig ler( 19 65 ) 35

12 Re l at i on a mon g f ood c o nce n t ra t ion . fi l t eri ng r ate . a ndg ra z i ng r a t e f i r s t propos ed by Ri gler ( 1961a) . . . . 36

13 Comp a r ison o f t he Ivlev and Mi chae l i s-Hente n fun cti ons withthe same ha lf- s atura t ion value , k . 40

s14 The relation o f the c ons t a n t , k, t o the i n cipie nt linll t i n g

foo d c o nce n t r a t i o n . 81 - . . 47.m15 The rela tio n o f the c o ns t a n t, k, t o t h e maximum g r az i ng

ra t e, G 47max16 Th e relati on o f t h e max imum g razing rate, G • t o t he

i ncip i en t limit ing food con c e n t r a t i o n , B max 48I.m

17 Graz i ng r a t e a s a fun c tion o f t emp e rature f o r Daphniap u lex 72

18

19

20

Gr a z i ng r ate a s a f unction o f tempera ture f or Daphniar osea

The r e l a t ion o f t e mpera t u r e t o t h e r e lat i v e i ncrea s e ing r a z i n g ra tes f o r an imals f ul l y a c climate d to t e s ttempera l u r e s

The r e l a t i on o f tempe ra ture t o t he re la tive i nc rea se i ngrazing ra t e f or animals i n c ompletely a cclimated tot est tempe ratures . . .

4

72

74

75

No .

21

22

23

24

25

26

27

28

29

30

3 1

LIST OF FI GURES

The d i e l pa ttern of f iltering r a t e c ha nge at 18°C in al i ght : da r k 16 : 8 phot ocyc l e

The die l patt e rn o f fi l ter ing rate c ha nge of Da phn i apu lex in Three La ke s , Mich igan . . . .

The di e l g ra zi ng functi on o f fi l t e r- f e ed ing zooplanktonexhib iti ng a un i modal pe a k i n grazing during the night

The di e l grazi ng func tion of f i lter- f eeding zooplanktone xh i b i t i ng a biomodal p eak i n grazing dur ing the ni ght

The da ily ra tion o f Hacrocy c l ops a lb idus fema l e s as afu nc tion o f fo od conce nt r a t ion

Fre quency h i s t ogr am of zooplankt on a ssimilation va l ues (A)as a percentage o f c ons umpt i on ( G)

Fr equency h istogram o f bentho s a s simi l ati on va lues (A)as a perce n t age o f cons umpt i on (G) .

Freq uenc y h i stog r am of be nth i c ca r nivore a s simi lationva l ues (A) as a percentage o f cons ump t ion (G) . .

Freque ncy hi stogram o f benth i c herb i vore-detritivorea s simi lation values (A) as a pe r centage o fcons ump t i on ( G) . .

Fr equenc y h i s t ogr am o f Rotato ria a s simi l ation va lues (A)a s a percentage o f cons umpt i on (G)

Freque ncy h i s t og r a m of Copepo da a s simi lation va l ues ( A)as a percen t age of consumpt i on (G)

79

80

84

84

86

10 7

10 7

114

114

122

122

32 Fre quenc y h i sto gr am o f Cladoce r aa s a perc entage o f cons umpt ion

assimi l a tion value s (A)(G) 123

33 Frequenc y h i s t og ram o f Entomos tra ca ass i mi l a t i on va l ues(A) as a perce ntage o f cons umption ( G) 123

34 Freque ncy h i s t og r am of zoop lankto n eges t ion (F)exc r e t i on (E) va l ues as a percentage ofcons umpt i on ( G) . . .

and

124

35

36

37

Frequenc y histogram o f b e n t hos ege stion (F) ande xc ret ion (E) values as a perc entage of cons ump tion (G) . .

Freque ncy hi s t ogram o f assimila tion v a l ues (A) a s apercentage o f cons ump t ion (G) when zooplankton wer e f e dblue-green algae and/ or de tritus

Frequency h i s t ogram o f a s simi la tion values ( A) as apercentage of con s ump t ion (6) when zoop lankton we r e fedg r e e n algae . . .. . . . . . .

5

124

125

125

No.

38

39

40

41

42

43

44

45

46

47

48

49

5 0

LIST OF FIGURES

Freque ncy h is togram of resp i ra tion ( R). a s a pe r centageof consumption (G). fo r aqua tic inve rte bra t e s ... .

Frequency his togram o f r e spiration rates f or Cladocera

Frequency hist.ogram o f respiration rates for Cope po da

Freq ue ncy his togram of r e s pirat i on r ate s for Rota toria

Frequency h i stog r am of r e spi ra t i o n rates for benthi cCrus t acea . . . . . . . .

Frequency histogram of respiration rates f or aquat i cInsecta . . . . . . . . .

Fr equen cy his togram of r e s pira t i on ra t es f o r Ol igochaeta

Fre qu ency h i s t o g r a m o f respi rat ion rate s for Mo l l us ca .Re s p i r ati on ( R) a s a fun c t i on o f o rga nism weight (W) f o r

aqua ti c invertebrat.es at 200 e . . . . . . . .Frequency hi stogram o f r e s p ira t i o n rates f or aquati c

invertebra tes o f wei gh t c l a ss I . .

F r e quency h i s t o g r a m o f r e spirat i o n r a t e s f o r a q ua tici nve r tebrates of weigh t c lass II

F requency h~s togram o f r espiration r ate s f o r aqua ti cinvertebrates o f weight c l as s III . . . .

Frequency his togra. of the e xpone nt b - 1 f rom t he e q u a t ion:b- l - 1 - I

R = a w ,whe r e R = respi r a tion ( mg C- mg C oda y ) x 10 0a n d w = weight ( mg C) .

139

140

141

141

142

142

143

14 3

144

146

14 7

147

148

5 1 Fre quency h i sto gram o fb- 1

R =aw • where R =x 100 and w = we i gh t

t h e coefficient a from t he equa tion:- 1 - I

respiration ( mg C orng C oday )(m. C) • . . • . • . . • . . . 150

52 Values of t he coe ffi c ien t a as a f unction of t empera ture (1)for a qua ti c i nver teb r ates 150

funct i on o f53

54

Re s p irat i o n co r rection fa c tor (F ) as adissolved oxygen concen t ra t ion~ . •

neaa ra tes o f r e s p i r at i o n ( R) as a f u n c t i o n(T) Eo r- a q uatic i nvertebrates . . . . . .

o f t emp e r a t u r e

154

15 7

5 5

56

57

The c o nve rsion f u nc t i on , Ft o

20 ' f o r a d j u s t i ng r e sp i r atio n

rates (R) a t a mbien t t empera ture s t o r a tes at 20°C

The c o nv e r sio n f u n c tion, Ff r o m

20' for a dj us ting respi ration

rates (R) at 20 QC t o rates at ambient tempera ture

Fre quenc y h i sto g r am of nonpre da tory mo r t al i t y r a t e s (NPn )fo r z o op l ankt on .

6

159

159

163

No.

58

59

60

LI ST OF FIGURES

Frequency histogram of nonpr edator y mor t al i t y rates (NPM)fo r benthos . . .

Uppe r le tha l t emperatures (ULT) and l ower lethalt empe r a t ure s (L LT) for the c l am Co r b icula man i l ens i sa cclimated t o d i f feren t temperature s . . . . . .

Frequen cy h i s t og r am of up pe r l e t hal t empe r a tu r e s ( ULT)for aquatic organ i sms .

163

16 7

169

6 1 Nonp r eda to r y morta l ity ( NPN) as a function o f tempera ture (Tlfo r aquati c o r ga nisms . 169

62

6 3

Nonp r eda to r y mortal ity (NPH) a s a function o f di s solvedoxygen concen tra t i on ( 02) f o r zooplankton and l i t t o r a lbentho s . . . . . . . . . . .

Ncnp reda tory mortality ( NPM) a s a fu nc tion o f di s s o lvedoxygen concen t r a t ion ( 0 2 ) for pro fundal benthos . • .

LI ST OF TABLES

172

173

o f C, N, and P i n Proteins , Lipids ,I

2

Percent Composi t i ona nd Carbohydra t e s

Fa cto r s Repo r t ed t o Inf luence the Fe edingZoop lan kton a nd a List o f Re f e rence s

o f F i l t er-Fe ed ing

17

30

3

4

5

6

7

8

Gr a z i ng Rate Parameters of t he Ivlev Equati on Ca lcu l a t edfrom Expe rimental St udies t ha t Demons trated theExi stence of a Maxi mum Grazing Rate . .

Range o f Gr azing Rate s Ca lcu l a t e d f rom Exp e rime ntalSt udies i n wh i ch a Maximum Gr az i ng Rate Could Not beDemonstrated

Literature Values for the Daily Ration o f Filter-Feed ingZoop l a nktons

Re lati onship Among G , B . and Z as De f i ned byEqua tion 8 and Ba s~axon {he Data i n Table 3

Summa ry o f Lite r ature Da ta on the Effe cts o f Temperatur e onthe Grazing Rates of F i l t e r - Fe ed ing Zoop l a nkton .

Acclimation Te mpe rature , Upper a nd Lower Letha lTemperatures, a nd t he Tempera ture Range fo r a Cons tan tMax imum Gra z ing Rate f or Zoop l a nkt e r s Exp osed t o RapidTempera t ure St ress . . . .

7

42

43

44

50

70

77

No .

9

10

LIST OF TABLES

Values for Re lative Change in Light Intens ity, a s Citedby Haney and Hall (1975). t hat Represent ThresholdLight I ntensity f o r Positive Photo taxis • . • . . . .

Published Values for t he Daily Ration of the Planktoni cOmnivores and Predators . . . . . . . . . . . . .

8 3

81

Daily Ra t i on of Benthi c Organisms . . .

F il ter ing Rates of Mollus c s Repo rte d in the Li t era tu r e

Re sp i ra t i on a s a Percent age of Cons umption f o r Aquat i cInve r t eb r a t e s . . . . . . . . . . . . . . . . . . . .

-1 - 1Re s p irat i on Rate s (R) (mg carbo n ' mg ca r bo n -da y ), as a

Func t i on of 02 Conc entration (mg/! ) , for Severa lAquati c I nvertebrates . . . . . . . . . . . . .

Comparison o f Cri tica l Concen t rations (mg/!) of Di ssolvedOxygen for I nsec ts Expos e d t o These Conditions for 96 hra nd 30 Day s . . . . . . . . . . . . . . . . . . . . . .

11

12

13

14

15

16

Seasona l Cha nges i n theCommunit ies . . . . .

Grazing Rate of Zooplankton91

94

98

131

153

111

8

SIMULATION MODELING OF ZOOPLANKTON AND BENTHOS IN RESERVOIRS :

DOCUMENTATION AND DEVELOPMENT OF MODEL CONSTRUCTS

PART I : INTRODUCTION

Modeling Concepts

1 . Modeling, a s an approa ch to understanding biotic commun it i e s ,

has a chieved conside r able attention in r e cent years . With the i nce p t i on

of the International Biological Program i n 1966, modeling ha s attracted

a growing number of researchers who have a pp lied model ing t e chnique s t o

almo s t al l area s of biolog i cal investigation . To da y. modeling is con­

s i de r e d the s olution f or many problems, e specially in de c i sion making for

r esour c e mana gement.

2. Populations a n d c ommu n ities of organisms c a n be c ons i d e red as

c omp l ica t ed. dynami c s ystems of regul arly interacting and i n t e r dependen t

comp onents f orming a u n i fi e d whole . Environmental factors influence

these systems through i np uts and the s y s t e ms, in turn , influenc e the

e nv i r onme n t through outpu t s . Sy stems analysts have attempted t o provide

a quantita t ive descri p t i o n of the relat ionships within these s ys tems and

thei r f unctions . However, becaus e most b iological c ommu n i t ies are in­

t r ac table t o de t a i led ana l ysi s e ven by d i rect observ a t ion, the mo s t

commo n, effi c ient, and, in ce r t a i n i ns t a nces . t h e o n ly method o f invest i ­

gating t hese s ystems is t hro ugh modeling (Menshutkin 19 71 ) .

3. In developing a mathematica l model of a p op u l a t ion , c ommu n i t y ,

o r ecosyste m, the fir st and most difficult s tep i s to de f i n e the obj e c ­

t ive s o f the analys i s . A model c o ns t r uc ted without c lea r ly stated ob ­

j ec t i ves would in all li ke l i hood r esult in the descr iption o f extraneous

components a n d functiona l relationships, the e f f ec t of whi ch would be t o

was te time, mone y. and e ffort in the co l l ec t i on o f data and development

of c oncepts . Furthermore. critical c omp on e n ts tha t are ne c e ssary for

t he mod el may b e omi t ted , s erious ly affecting model performance and

lead ing to erroneous c o nc l us ion s.

9

4 . The second s tep i n mo de l de ve lopment i s t o de termine which

comp onents a re necessa r y to meet the objec tives. Thi r d, the f unctiona l

r elat i onships among e cosys t e m componen ts mu s t be determi ned a nd q u anti ­

f i ed. Of ten the d evel opme nt o f the se r elat i onships i s diff i cult b e caus e

it require s a thorough knowledge o f the popula tion dynami c s o f t he

org a n isms modeled (e.g ., popula tion size, growth r ate, a nd mor t ality

r ate s ) . S tep fou r i n vo l ves the cons t r uction o f the mathema t i c a l model

i tse l f, a step many biologists a re poo rly prepared to deal with .

F i nally , t h e mode l is applied a nd t h e r e sults compa red t o field da ta .

Ref i neme n ts a re mad e until t he mode l a ch i e v e s t he de s i r ed object i ves .

Objectives

5 . Fol lowi ng c o n s u l t a t i o n with pe rso nne l at the Environmenta l La b ­

o r a t o ry (EL) of t h e U. S . Army En g i n e e r Wa t e rwa y s Experiment St a t ion

(WES), severa l objec tives we r e developed:

a . To r ev i ew a nd e va l ua te t h e l iterature o n z oop lank t on andbenthos c ommuni t y dynami c s and t o s e lec t info rmations u i tab le for developing and d o cumenting v a ri o us modelcon s tru c ts .

b . To s ummari z e , i n frequenc y dis t r i b u t ions. t he l i t eraturevalue s f or vario us mode l pa r ame ters . Th ese f requencydistributions will lat e r b e conver ted t o probab i li t yd is t r i b utions and incorpora ted into the model f or as tochastic capability .

c . To pro p o s e. where a p p ropriate , s u itable model cons t r u c t sthat d e s cribe the dynami c s of z ooplan k ton and benthosc ommun ities .

6 . We d id n o t propose a defin itiv e compart men t a l sch e me f or model ­

i ng z o op l a nkto n a nd benthos . Ba s e d o n objec t i ve ~ a bov e , we have

provided fre quenc y dist r i bu tions of mode l paramete r s fo r po tentia l com­

par tmen ts . Compartment selectio n is r ele g a t e d t o the mode l e r . Th e y

s h o u l d n o t c r e a t e mod e l compa rtmen ts fo r which frequency di s tribution s

of paramete r v a lues are unava i lab l e . Th e do c umentat i on prOVi d ed i n t h i s

r eport s ho u l d a llow the model e r t o c r i tica l l y e va l ua te t he exis t i n g data

base and understand i ts limitations. S toc kma ye r ( 19 78) suc c i nct ly s um­

mar i z ed t he data eva lua tion d i l emma :

10

Unc r i ti c a l acc e p tance o f bad s c i ent i f i c i nfo rma t ion c a n l eadt o s o c ial p e nalt i e s .. . . A parti cularly perni c i ous a spec t o fth i s p r ob l em inv o l ves num e r i cal da ta , wh i ch a r e e ssen ti a l i na l l branche s o f s c i e nce a nd technolo gy a nd are o f t e n ne eded t oa r r ive at v a l i d operational d e cisions . Un fo r t u n a t e l y . thesc i e n t i f ic l i te ratu r e c o n t a i n s many e r ro neo u s values . f e ws c ien t i s ts o r e nginee rs s e e m t o hav e g ive n much tho ught t o themagni tude o f the p r o bl e m, and s ome probab ly rega r d e v e r y nu ­mer i c a l e n t r y in a handb ook a s r e v e a l e d truth . Yet anyone whoha s had t o seek a par ti cu lar numb e r i n t he literature a ndsea r c hed o u t a dozen o r more reports. o n l y t o e nd u p wi t h aset o f wide ly d ispara t e va lues, comes to realize t h a t a s ub ­s t a n tia l intellectual e f f o r t and a c o n s i de r a b le b a ckground inthe f i eld a r e ne e d e d to a rr ive at r e lia b l e f igure s.

7 . Re cent re v i e w papers that comp a r e and con t r ast e xi s t i ng

aqu a t i c Ec o sys tem model s i n c l ude those o f Swa rt zman ( 19 77 ), Swa rtz ma n

a nd Bentle y ( 1978) , and Scavi a and Roberts on ( 19 79 ).

Mode l fl"amework

8 . I n c onduct ing t h e l i t e r a t u r e r e v i e w a nd analys e s, i t wa s ne c ­

e s sa ry t o o r g a n i z e o u r work s o that i t cou l d b e i n t eg r a ted with the

ex i s ting ecologi cal model being deve l o p e d at the WES . The model was

o r i g i n a l l y cons t r uc t e d by Wa t er Resou r ce Eng ine ers. I n c . • o f Walnu t

Cr e e k . Ca l i f o r n i a . Var i o us v e r s i ons of the model have be e n a pp l i e d t o

f ie l d si t ua t ions ( see Ch e n a n d Or lob ( 19 75) f o r a de s cript i on o f t h e

model and a summary o f appl i cat i o n s ) . Ou r analys es we re f ormulated t o

inc lude va r ious s t r uc t u r a l c o n s i de r a t i on s o f t he mo del . Th e first

s t r u c t.u ra I c o ns i de r a t ion was t hat the mo d e l use differential equa tions

t o de s cribe t r ans f e r rates. a nd, s eco n d , tha t the model have comp a r t -

ments. Th i rd . it is a mas s bal anc e model t ha t tra cks ca r bon , nit r ogen,

a nd p hospho r us t o a c c o u n t f or materia l f l ow in the s y s tem. Fo u r t h . the

r e c ommend ed min im um t ime frame f o r model s imu l a tion i s I da y .

Su bjec t a r e as cov e redby the literature r e view

9 . A va st li tera ture e x i s t s dealing wi th the p op u l a t i o n dynami c s

o f z ooplankto n a nd b e n t h o s . Many s ubjects are o f di rect relevance t o

11

simula ti on modeli ng . The o vera l l o b j ec t i v e o f mod e l i n g z ooplankto n an d

be n t hos pop u l ations is h ope fu l l y t o dup l i c a t e . bioma s s c ha n ges in these

populations as t hey r e spond t o c h a n ge s in their e nvi r onme n t . These

c ha n ge s a re r e fle cted in a s e ries o f input s to the popu l at i on a nd o u t ­

puts t o the environment . We ass ume that zoop l a n kto n and bentho s popu­

l a t i o n ( i.e . , model c omp a r t me n ts ) r e s p ond as if the y we re i nd iv i dua l

organ isms faced wi t h a c ha n g i n g e nvironme n t . To keep trac k o f thi s

r e s p on s e we u ti li ze d the f o llowin g mass-balance . differential eq ua t ion

f o r a l l model compart men ts :

R - RPM - PM] ( 1 )

where b = biomass ( mg c a r b o n ) .- 1 - 1

c a r bo n omg c a r bo n · d a y ) , A

t = ti me ( d ays) , G = con s ump t i o n (mg

assimi la tio n (mg c a r bon omg c a r b on - 1 oda y - I) ,

A/G = assimilation effi ciency (%),- ) - 1

carbon -d a y ), NPM = nonpreda tory

a nd

R = resp iration (mg ca rbon o m~

-1 -1morta lity (mg c a r bo n -mg ca r bon -d a y ) ,

-1 -1PM =predatory mortality (mg c a r b on -mg c a r b o n - d a y ) .

10 . Eq ua t ion 1 a lso de fined t h e s ub ject are a s that had t o be

r eviewed in orde r t o d e fi n e the e qu a tion . Each o f the r ema ining

sec t ions of th i s repo rt d esc ribes o u r ef fo rts t o r e vi e w and eva lua te

ea c h o f t he s ubjec ts o n the r ight- ha n d side of t h e equation, with t he

excep tion o f predatory mortali ty . P redatory mortality i s defined a s the

g r a z i n g fun c tion of a cons umer c o mp a r t me n t , i .e ., one c ompa r t me nt' s

cons ump tion is another comp a r t men t's predatory mortal ity .

Ex t en t of the lite r atu r e r ev i ew

11 . Ou r r eview of the s u bjec t are a s relevant to the simu lat ion

mode ling o f zoop l a n kt o n a n d bentho s wa s com p rehensive a n d wo r ldwide i n

s cope but selec tive for relevan t pub lications for s ome subjects . Pro­

ce s s e s most c r i t i c a l to defining z ooplankton and ben t h os population

dyn a mics (e.g _ . g raZing) were given the grea t es t atte nt i o n.

12. Many pape r s t h a t a ppea r e d h ighly r elevant were u n a vai l a b l e i ll

Engli sh transl a tion a nd were not r e v i e we d . Ho st papers in th i s c a t e go r y

were from Eastern Eu r ope . pa rti cularly the USSR (Union o f Sovie t

12

So cia l i s t Rep ubl i c s ) . When t r a n s lations were una v a i l able . En glish

a bs t ra cts s uch as tho s e found in v a rious ab stracting p e riodi cals or

comme nts by o the r aut hors wer e us ed . Pape r s i n Ger ma n a nd F r e nch were

tra ns la ted by t he aut hors when unav a ilab l e in translation e lse wh e r e .

13

PART I I: ELEHENTAL CARBON. NI TROGEN. AND PHOSPHORUSCOMPOSITION OF ZOOPLANKTON AND BENTHOS

I ntrod uc t i o n

13 . The s t udy of e l e me n ta l c hemica l compos i t ion ha s bec ome in­

crea s i n g ly i mpo r t a n t t o o u r understanding o f b i oene rge t i c s , p r o duct i o n ,

a nd b i ochemi ca l c yc l i n g o f e l e me n t s in aqua t i c s ys t e ms (Omori 19 69 ) .

For mode l ing purposes . i t i s ne cessa ry to know the e l emen t a l carbo n (C),

n itrogen (N) , and phospho r us ( P) c o mposi t ion o f the various spe c i e s t h a t

compOSe z o oplankton a n d be n t h o s . Th i s knowl edge i s u s e d t o tra c e t he

c yc l i n g of nu t rients th r ough the e c o s ystem b y appl i cation of t he mas s

bala n c e e q ua t ion previo usly d e s c r ibed ( Eq ua t ion 1).

14 . I n mos t mo d e l s o f a qua t i c e c osystems . ra t ios of c a rbo n t o

nitrogen and o f c a r bo n to p ho spho r us a re ve ry us efu l . Est ima t e s o f zoo­

plankton a nd benthos c a r bo n l o s s e s ( e . g . , eges t ion, e xc re t ion , res p i r a­

t i on. a nd n onp r e da to r y a n d p r edatory mo rtal ity ) c a n readi l y be used t o

e s t i mate l osses o f nitro ge n a n d p ho sphorus . Ni tro gen a n d p hospho r us

compo u nds released from a q ua tic a nimal s se r ve a s impo r tant nu t rients for

phytoplan k t on . periphyton. a nd ma cro phytes . I n s ho r t . t he us e o f C: N

a nd C: P rat ios al l ows the modele r t o trac e the trans fer of c he mica l

s u bs tan ces t hro ugh va rio us trophic l evels (Chen a n d Or lob 19 75 ) . Sca vi a

e t a l . ( 1976 ) s toi chiomet rical l y de t ermined the i ncorpora tion and e xcre­

t i on of P by us ing a C: P rat i o . Twelve model s r ev i ewed by Swar tzma n

a nd Bentle y ( 1978) had phosphorus and n it r o gen f low para lle l t o ca r bon

i n z oop lank ton and det r itus . Ba ca e t al . ( 19 74 ) us ed a r a nge o f r a tio s

(i.e . , C: N ; 5 .9- 20 . 0 ; and C:P = 33 .3-200. 0) t o der i ve the q ua nti ties o f

N and P e x c re t ed. o r t he q uanti ties l o st a f ter no n p r e dato r y mor tali ty .

Stee l e ( 1974) us e d a C: N r a t i o o f 5 .4 t o e s tima t e N a s simila t e d a nd

exc reted b y z oopl a nkton . Carbo n, n i tro gen , a n d pho sphorus a l s o we r e

r el e a sed i n accord a nce with the i r c o nce n t r a t ion i n zoop l a n k ton i n t he

models o f Umnov ( 1972) and Menshut kin and Umnov (1970) .

15. Rat i o s o f C:N a nd C: P a r e Dot cons tan t b u t v a ry signi fica nt l y

among taxonomi c group s of a n i ma l s . a s we l l a s within s i ng l e s pecies ,

14

depending o n s e x , age , and nutriti onal s t a t e . Nutritional state is i n ­

fluenc ed by seas o n of the year and geog raphi cal d istribution . Methods

of determining e l e men t a l C, N, a nd P undo ubte d l y produc e some variation

a mo n g rat i o s, but we do not believe that th i s e f fe c t is signi f i c a n t

e noug h , cons i d e ri n g t h e variability due t o o t he r fac to r s , t o warrant

d e t a il ed d isc u ss i on . Th e handling o f ma r i n e zoop l a n kt o n samp les imme ­

d i a te l y a f t er c o l l ection ( e . g ., rinsing a n d pre s e rvat i on) may g rea t l y

a l t e r C: N a nd C: P rat ios . S i n c e ma ny o f the value s we co l l ec t e d were

f o r mar i ne zoop l a n k ton ( Ap p e ndix A) , th i s problem r equi r es f u r t h e r

comme n t .

16 . Th e d e terminat ion o f s i n g l e C:N a nd C: P r a t i o s probab ly is

i nacc u r a te f or b r o a d ca t e gor i es o f a n i ma l s s u ch a s zooplankton and

be ntho s . The r elat i ve abunda nce o f the various groups compos i n g t he

t ota l b i oma s s differs geog r a phical ly and s e ason a l l y . Vari a tio n s in

p e rcen t C, N, a nd P ( i.e . , percen t o f dry we i ght ) e x is t a mo n g t axa a n d

a re compo un de d when percentage s are e s tima ted for t o t a l zoop l a n k ton - - a n

e ve r c hangi n g a s semb lage o f taxa (Beers 1966 ) .

17. We have c o l lec t e d pe r cent C, N, a n d P d a t a f r om both t he

f r e shwa t e r a nd marine literature . With t h e e x c eptio n of o ne o r two

gro up s o f animals, percen t C, N, a nd P in mar ine and fr e shwater orga­

n i sms d o not d i ffer s ign i f i c a n t l y . Thi s fa ct probably is a fun ction o f

the vari a bi li ty o f percent C, N, and P i n marine and fre shwater a n i mals

(Ap pen d i x A) . Percent P of ma r i n e cop e pods wa s c o ns i s t e n t l y 50 t o

75 perc e n t o f t he v a l ues for o t h e r c r u s t a c e a ( Bee r s 19 66 ) . Co r ne r ( 1973 )

noted that P in ma r i n e zoop lankton varied f r om 0 . 14 percent i n f orms

s u c h a s hydromed usae a n d c t e nop ho res t o a r a n ge of 0 .55 to 1 .16 percent

i n cop e pod s . Bee rs ( 1966) a l so f o und t hat percent C was s i mi l a r in mos t

ma r i ne z oo p l a n k to n , excep t hyd r ome d u s a e whi ch typ i cally ha ve l ow per­

ce n t C con t e n ts. With t he n o t a b l e e xception o f the fre s hwater j e l l yf i s h

(C r aspedacus t a sowe r by i) , which i s e x t reme ly s pora d ic in occu r r e n c e ,

fre sh wa t e rs generally lac k animal s c omp a r a b l e t o ma r i ne me du s a e a nd

c t e n op h o r e s . Cons e qu e n t l y , we d id no t co n si de r p e r cent C, N, a nd P data

f or the s e f orms of ma r ine zoop lank t o n .

18 . I f s a mp l es a r e c o l l e c t e d from s al t wa t e r , the y s h o u l d be washe d

15

to remove adhering inorganic s a l t s that may contain C. N, o r P. Platt

et al . (1969) found t hat significant wei ghts o f i no rganic salts we re re ­

mov ed by a 2-mi n r i n s e i n dis ti l led wa te r . Contrary to the observation

of Omori ( 1978), r i n s e s in disti lled water for periods o f 2 t o 60 min

did not result i n the osmot i c rupture o f c e l ls and subsequent l oss o f

organic mat ter from s pe cimen s . Omori ( 1978) estimated 6 and 7 percent

red uc tions in t he C a nd N conten ts , r espe ctively, o f zoop l a nkters r i nsed

in distil led water . Howe ve r , t hese l o s s e s we r e c a l c u l a t e d a s C a n d N

l ost per individual a nd no t in a f orm compa r a b l e f or an imal s o f a

different size ( e .g ., percent C a nd N). Th e losses o f C a nd N as a

pe r c ent of dry we i ght ( reca l c u la ted f rom Omo r i ( 1978» were n o t

significan t .

19 . Preservation o f samp l e s in f o r mal in . al cohol. o r o t he r l e a c h­

i ng che mica ls may alter percent C, N, and P o r the r a tio s o f C:N and C:P .

Omori (1970) f ound t hat Calanus c ris t a t us pres erved f or 1 mo n t h i n

fo r malin los t 59 and 48 pe r cent of the i r origi nal c a r bon a nd nitrogen,

r e s pec t ively . I n addition , the ra t e s of l o s s of C a nd N we r e di fferent

and r e su l t e d in a de creased C:N ratio . Apparen tly the r a t e o f l os s

depends upon t he original quantity o f matter pre s ent. The eup h a us i d

Nematocel i s d ifficilis l ost 17 pe r c e n t C and 19 percent N afte r 15 ~eek s

i n a bu f f ered Hexami ne so l utio n ( Hop k i ns 19 68 ) . Hopkins be lieved t hat

mos t of the l e a che d ma t eri al was pro tein . Simi la r fi nd ings were pre ­

s e n t e d f or Sagitta nagae and Ca l a n us sini cus (Omor i 19 78 ) .

Nitrogen

20 . Variations o f ' pe rce n t N primarily r e su lt from d i f fe rence s in

gros s body compone nts ( i .e . , prote in, lip id, and c a r boh yd r a te ) . Pe r c en t

N va r i e s a mon g t a xa and within a single taxon , due t o d i f f e re n c e s i n

age , sex. o r nut ri t i onal s ta te. Host bo dy n i t r o gen i s inc luded i n the

a mino a cids o f pro te in (Table I ) .

2 1 . Perc ent N usually is greater in y o u ng than i n o l d Dr eissena

polymorpha, Mo llus ca (Stanc z ykowska and Lawa c z 1976 ); r emora s t y l i f e r a

a nd Ce ntropage s typicus, Copepoda ( Ra z o u!s 19 77); Pareuc hae ta no vegic a ,

16

Tab l e 1

Percent Compos i t ion of C , N, and P in Proteins z

Lipids , and Carbohydrates

Ca r bon* Nitrogen* Pho s phorus ..... k

Prote i n 50-55 13-17 ca O. 10Lipid 79 c a 0 c a 0 .17Ca r bo hyd r ate 37 . 2 c a 0 c a 0

* Ca r bon and nitrogen d a t a of Scho t t elius a nd S chottelius (1973) .** Phosphorus da ta of He a d a nd Li v i ng s t on (unpublished ) a s ci t e d by

Corne r (973 ) .

Copep od a ( Nemata et al . 19 76 ) ; a nd Dap h nia hyal i na, Cladocera (Baudoin

an d Rave r3 1972). Greater pe r cent N con~ent i n young individua l s prob­

ab ly s t ems fr om the f ac t t hat young organisms typically have more pro­

t e in re la tive t o d ry weight tha n o lde r i nd ivi duals. Hi gh p rotein c on ­

t ent resu l t s f rom rap id growt h a ssoc i a ted with p r o t e i n a nabolism and

i nsignifica n t l i p i d a ccumula tion in young a n i ma ls (e .g ., Dap hnia magna,

Ce rioda ph n i a r eticula ta , and Moina macrocopa (C ladocera) a nd Br a chion us

c a l yci flo r us (Rotaj o ria ) ( Bogatova et a l. 19 7 1». Un der t he s a me t rop h i c

con d i t ions, adult fema l e " oceani c Cope poda" ( Lt.o h 19 73) a n d Ca l an u s

c ris t a tus (Omori 19 70 ) o f t e n h a d l e s s percent N t han adult ma l e s . Th i s

may h a v e bee n due t o t he g re a t e r l i p i d c on t e n t in f e ma les . The fa ct

that perc e nt C was g r eater in f e ma l e s see ms t o s uppor t t h i s hyp ot hesis .

Po s t s p a wn ing f e ma les o f Pa reuchaeta n oveg i ca ha d le ss pec ent N than

p r e s p awned females (Nemoto e t a l . 19 76 ). This find i ng sugges ts t hat

c a t a bolism o f b ody p ro t e i n , due to the gre a t energy d eman d f o r

r eproduc tion , r e s u lted i n a decreas ed N co n t e n t per unit d r y weight.

Seve r a l c u t hors ha ve als o ob s erved d iff erences i n t he percent N o f

single s p ec i es a s a r e su l t of s e aso n o f the y e a r a n d ge ographica l

d is t r i b ut i on (Omor i 19 70, Itoh 19 7 3 , Bouc he r et a l. 19 76) . Omori ( 19 70)

f ound that seasona l and geo g r a p h i c al ch a n ges i n t rop h ic con d i t ions we r e

p r i n c i p a l l y r es p o nsi b le fo r p e r c e n t N c h a n ge s i n Ca l a n us c r is t a t us

( Cop e p oda) . Dur i n g t im e s o f (or in a reas o f) poor f ood ava i lab i l i ty ,

copep od s exhib i ted an i n i t i a l fat l o s s t hat r e s ulte d in a n inc r e a s e of

17

~ercent N. Later , s t a rv i ng co pepo ds be gan t o metabol i ze pro tein whi ch

dec reased pe r c ent N.

Carbon

22 . Perce nt ca r bon a lso varies among taxa a nd within a single

taxon due t o age (Omo r i 197 0, Baudoi n a nd Ravera 1972 , I t oh 19 73,

Razoul s 1977 , Omori 19 78 ), s e a s on (Beers 1966, Plat t et a l . 1969, Omori

1970, St anczykows ka and Lawacz 19 76 ), geographi cal di stri but i on (Bou ch e r

e t a l. 197 6), a nd rep r oductive co nd i tion (Nemoto e t al . 19 76 ) . Percen t

ca r bon d id not vary with age in Dre i s s ena polymorpha (S t a nczykowska and

Lawacz 1976 ) o r with s e ason io Daphnia hyalioa (Baudoin and Rav era 1972) .

Omo r i ( 1970) showed that change s i n trophi c condi tions that a f f ect nu­

tritiona l state actually underl i e t he dependence of percent C on geo ­

g raphi cal d i s tribu t i on and season of the yea r .

23 . In ecological models , ei t he r carbon transfer or ene rgy flow

is used t o l i nk trophic l evels . Since carbon and e ne rgy units a re highly

cor r e l a t e d (Sa lonen e t al . 1976), t he choice apparently is arbi t ra ry .

The use of ca r bon un its do es have t he added adva n t a ge o f provi di ng an

i ndex to t he f l ux of matter t hrough troph i c l evels . For t h i s r e as on , we

pre f er ca r bon t r a nsfer data and have emp loye d t he fol lowing fa ctors:

z oop l a nkton = 10. 98 ca l/mg C (Salonen e t a l . 1976 ) a nd phytopl ankton

= 11 .4 cal / mg C ( Pla t t and I rwin 1913) t o co nver t f rom ene rgy to carbon

units .

Ca r bo n: Ni t r ogen Ratios

24 . The dis t r i bu t i on o f ca r bo n and nitrogen amo ng the major body

components, i .e. , prote in , l ipid , a nd ca rbohyd ra t e s (Table I ), and the

r e lative ab unda nce of thes e major compone nt s determi ne the per cen tages

of C a nd N presen t i n an o r ganism. Altho ugh percent C and N a re i n­

f l uence d by the same environmenta l e l eme nt s , t hey do not a l ways f l uc t ua t e

in the same manner . I n general, C:N r at i os shou l d vary direc t ly with

ca r bohyd r a t e a nd lipid content a nd i nverse l y wi th protein c ont e nt .

18

Omori ( 1970) found a nega t ive co r r ela tion between changes i n pe rcen t C

a nd pe rcen t N i n Ca!anus cristatus . Elements affect i ng the C and N

composit i on i n t he copepods were trophic co ndi t i ons a nd sex. Since

lip ids co nt a i n pr imar i l y ca r bon a nd e s s en t i a l l y no nitroge n (Tab le I ) ,

the seaso na l l os s o r gain of l i p ids, as i n f l ue nce d by t rophi c condi t i ons ,

would r es u l t in a concomitant decrea se o r i ncrease , respec t i vely, o f t he

C: N rat i o . If femal e s o f a spec i es conta i n a greater proportion o f fat

than male s, they als o would e xhib i t h igher C:N r a tios than mal e s .

25 . Usi ng the data on percent C and N (Appendix A), we prepared

frequency d i stri butions o f C: N ratios f o r va rious ca tegor i es ( t a xonomic

or other) o f a quat i c i nvertebrates . A freq ue ncy distribut ion of C:N

ra tios f or be nthi c macro inve rteb rate s (Figure 1) appea r ed to have two

po tential peaks (i .e . , a t 3 .5 t o 4 .0 and 5 .0 t o 5 .5) , s o we a t tempted t o

sepa r a t e the distribution on the basis o f feedin g t yp e. Un for tuna t e l y .

insuff i cient data exis t on carn i vo r e C:N rati os . When more e xpe r imen t a l

data on these r a t i os a re available, t hi s potential r e f i nemen t cou l d be

us ed in mode l formulation . The basic form of the frequency distr ibu­

tions of C: N ratios f or zooplank t on, Cl a doce r a . and Copepoda (Figures 2 .

3. and 4. r e s pect i vely ) i s essen tia l ly t he same. Apparently most C:N

r at i os of zo op l a nk ton and ben t hos a re with i n the range of 3 . 5 t o 5 . 5 .

Phosphorus

26 . The t ot a l P in zoopla nk t on is no rmally l ow, often a ccounti ng

fo r les s t ha n 1 percent of d r y weight (Co rne r 1973). The d i stribution

of phos phorus among bo dy p r o t e in , l i pid , and ca rbohyd r a te i s s hown in

Tab le 1 . Phosphorus i s impor tan t in t he s tructure of nuc l e i c aci ds.

whi ch co n t a i n approximately 21 pe r ce n t o f t he t otal P . Of t otal p.

53 percen t i s inorgani c (unpub l i shed data o f Head and Kilving t on a s

c i t e d i n Corne r 19 73 ) .

27 . Pho sphorus uptake and r e l ea s e by zooplank ton is ve ry i mportant

t o t he cyc l i ng of P i n aquatic ecosys tems . Conove r ( 1966a) reco gnized

two pools i n Calan us fi nmar chi cus, 6 percen t a s l abil e co mpounds whi ch

have a ha l f - l i f e of a few hou r s . The remaining 94 percent ha s a

19

22

2B

18

16

>-ty

v:z 12w:::J~ 1:±wa::u..

6

y

zFJ :2 3 Lf s: 5 7 8 9 IF! II l:t

CN RATIOFi gure 1 . Frequency distr ibu t ion of macrobe n t hos C: N ratios

221 !::.at +~

18 ! i16

14I

>- Tv

tz: 12w:=1IZ 12~~ 8 -+

6 +4 t:2

B :2 s 6 7 8 9 H! II 12

C:N RATID

Figure 2 . Fr equency di stri bu t i on of zooplanton C: ratios

20

l:Z! I183

::t'-------------.-+----+----l----~-f

12 t10 +•...

:!~*:2l

.J.a J ~~~4__4__4--__-4-_4_ _._.

a

Fi gure 3 . Fr equency distribution of cladoceran C:N ra t ios

!'S -

Iii + n-t-

:i I

~as £):tet:~

~

:2

a :2 6 7 8 9 IH II 12

C:N RATIO

Figure 4. Frequency di s tribut i on of copep od C:N r atios

21

hal f - l i f e of r ough l y 13 da ys . Altho ugh severa l studies have b een c o n ­

d uc t e d on P e xcretio n (Pomeroy e t al. 1963 , Johannes 19 64 , Satomi and

Pome roy 1965, Butler et a l . 19 70 ) , we s t i l l do not kn ow pre cisely how ,

or in what fo r m, P compo un ds are released ( Co r ne r 19 7 3 ) .

28 . Age, sex , and season o f the year may inf luence the P con t en t

o f aquati c invertebrates . Percent P i nc r e a s e d during the development of

Daphnia hyalina e ggs but , thereafter, de c reased with a g e ( Ba udoin and

Ravera 1972) . Butler et a l . (1970 ) f ound diff ere n ce s i n the pe r cent P

between male a nd female CalaDus finmacchi c us a nd als o between adult and

s ta ge V copepodids . Cala nus finmar cbicus contained about 50 percent

more P during a spring d ia t om i n crease t ha n at o t her t ime s o f the year .

Th i s la rge i n crease ma y ha ve be en the res u lt of uptake be y ond t ha t re ­

q uire d by the body. The pe r c en t composi t ion o f P i n mari ne c ope po d s ,

e u phausids, mysids , polychaetes , and c hae togna t hs c ha nges s i g n i f i c a n t l y

du r i ng the year (Bee rs 19 66 ) . Changes in t he pe r c e n t c omposition i n a ny

of the s e groups probabl y depends on differences in s pec ies o r age g r oups

taken in co l lect ions o r an adjus~men~ of ~he P c omposi ti o n o f individua l

o r ga n i s ms .

29 . Figures 5 and 6 are frequency distributi ons o f C: P ratio s f or

benthos and zoop l a n k ton . r e s pe c t i ve l y . In Figures 7 and 8, the zoo­

p lankton d i stribut i on i s split i n to two taxonomic c a tego r ies , i .e . ,

Cladocera and Copepoda . Copepods tend t o have greater percentages of C

t ha n othe r zooplankt o n (Appendi x A) , a nd th i s fac t ma y a c count fo r

h i gher C:P rat ios i n Copepoda .

Summary of Constructs

30 . By using frequency h i s t o g r ams of C:N a nd C:P , mode lers can

c a l c u l a t e a range of probable nitrogen and phospho rus transfer rates for

compa r tme n t process es. The procedure invo lves t he f ollowing : ( a) co n­

vert hi stograms (Figures 1-8) t o probability di str ibuti ons, ( b) s e l ec t a

s e r i e s o f C: N o r C: P rati os from the appropriate probabil ity di stribu­

tions, and ( c) divide weight- spe cif i c rates (mg C-mg C- I _day- I) of con ­

sumption ( Pa r t I II ) , assimilation (Part IV), egestion + e xcre t ion

22

±4-

n!

~ ~ ~ ~ ~ ~ ~ ~ ~ 5 ~ ~ ~ ~ ~ ~

C=P RATtO

2E

IE +-l.

tti

,.y

~ 12::z:w IZ::larwa: B.La.

E ·y.

2 ·

S IS:

Figure 5. Frequency dis t r i but i on of macrobenthos C:P ratios

~ I++ +..

I ±I..,.

t++

J.

!l.1 -I-I- ,...--

I 11 II

IE

Iii

12

Ii!

B

sLi

2

3 I ~ 2B 2S 3D 3S LiB LiS sa ~ sa ~ 7B 7S ~ ~ sa 9SC=P RRT ID

2B ....1----------------4------------------~IE!

Figure 6 . Frequency distribution of zoopl ankton C:P r a t i os

23

18

16

Pi

>- 12v:z:

Iii~::::ae Ba:Lo..

Ei

Li

:2

B IS 2B 25:

Figure 7 .

38 3S 'is 'is SB ss EB ES 78 7S sa as: sa ss 1HZ

C:P RAT IDFrequency distribution of cop e po d C:P ratios

IS

16

l 'i

12

18

8

E

4

2

2l IS 2H 2S 38 3S liB LiS SB ss 6B 6S 7B 7S: sa as 9B 9S

C:p RRTlD

Figur e 8. Freq ue n c y distrib u tio n o f cladoceran C: P ratio s

24

tT

(Part IV) , re spiration (Par t V) , and nonpredatory mortal ity (Par t VI ) by

the s e lec ted C:N and C: P rat ios .

rate s of Nand P trans f er (mg N or

The r e sults are t he weight-spec i f i c- 1 - 1

mg po mg C -day ) in the ab ove pro-

cesses . Ga i n s a nd l o s s e s o f Nand P from a c omp a r t me n t may be determined

by mult iplying the weight-spec i f i c ra tes o f Nand P transfer. fo r each

of the transfer proces s e s mentioned above , by t h e bioma s s ( mg C) o f the

mo del compartment .

3 1 . Frequency hi stograms o f macrobentho s C: N and C: P ratios

(Fi gu re s 1 a nd 5 , re spe ctively ) s hou l d be used t o e stimate Nand P move ­

me nts through the b entho s c omp a r t ment. When n o be t t e r dat a on the

p rese n t c omp osi t i o n o f Cladocera a nd Cop e poda biomass i n zoop lan kton

a r e available . we recommen d t ha t u s ers a s sign 60 p e r c e n t t o c a ldo c erans

and 40 perc ent t o c op e p o d s a n d us e Fi gure s 8 and 7 . r e spe c tively, t o

de t e r mi ne thei r a p p rop ria te C: N or C:P r a tios . The net fl ux o f P through

Cla do cera. fo r example. may b e es t i ma t e d as 0 .60 b [G(A/ G) - R - NPH ­

PM] + ( C : P ) , where b ::: t otal zoopla n k t on bioma s s, ( C : P ) = c a r b on ­

p hosph o r.u s ra tio o f c Ladoce r a (Figu re 8 ) . and t he items in bra c kets are

as d es c Libed i n Eq uation 1 . A similar c a lcu l a tion may b e performed f or

c opep ods a nd s ummed t o the resu l t s f or c ladoce r a t o y i el d t he f l u x o f P

t hrough t he z ooplankton comp a rtmen t .

Concl us i ons

32. Rat i o s o f C: N and C: P a r e u s e d to trace t he mov ement o f nu­

trients t h rough maj o r e n e rgy pathway s o f z o op l ankton a nd b enthos. E le­

men ta l c a r b on , nitrogen, and p hos p ho r us are not c on s t a n t bu t vary with

g r o s s body compos i t ion (rel a t i v e p r oportions o f lip id, c a r bohydra t e , a nd

p r o te i n) . Gros s body composi ti on varies among s peci es and wi thin a

s i n g le species d ue to d if f e r e n c e s in n utrition (which v a ries seasona l l y)

a nd in sex o r age . Although C: N ra t ios o f zooplank t on and bentho s a re

usual l y within the range from 3.5 t o 5. 5 , most C:P rat i o s v ary g reatly

in bo t h g rou p s ( 20 to 4 0 in bentho s and 30 t o 70 i n z ooplankt on) .

2S