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The relative importance of food availability and predation to the juvenile survival of Diacyclops thomasi Bowerman, Joy E. 1983

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c .  THE RELATIVE IMPORTANCE OF FOOD A V A I L A B I L I T Y AND TO THE JUVENILE SURVIVAL DIACYCLOPS  PREDATION  OF  THOMASI  by JOY  E.BOWERMAN  BSc(Hon) C a r l e t o n  University  1980  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department o f Z o o l o g y ) We  a c c e p t t h i s t h e s i s as conforming required standard  t o the  THE UNIVERSITY OF BRITISH COLUMBIA September 1983  0  J o y E.Bowerman,  1983  »  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of  requirements f o r an advanced degree a t the  the  University  o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make it  f r e e l y a v a i l a b l e f o r reference  and  study.  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may department o r by h i s or her  be granted by  the head o f  representatives.  my  It is  understood t h a t copying or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain  s h a l l not be allowed without my  permission.  Department of  uoc y  The U n i v e r s i t y of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3  DE-6  (3/81)  written  ABSTRACT  In  situ  Lake,  enclosure  British  availability D. t h o m a s i  Columbia  and .  nauplii. lake 20%  densities of n a u p l i i most  with  D.  In  results  the  interspecific  was  Eunice  Lake,  limitation  interspecific thomasi  the s u r v i v a l  o f D.  thomasi  that  D.  on n a u p l i i  p e r day and t h i s  was  at  at a rate of  seemed  nauplii  kenai  to  account  i n enclosures  limited  results  D. t h o m a s i  t r o u t and a m i l d i n D.  kenai  two  community,  t o year  i n w h i c h D. t h o m a s i  previously  to  oligotrophic  j u d g e d t o be t h e m a j o r m o r t a l i t y  and c o m p e t i t i o n  i n f l u e n c e d by y e a r  decline  food  of  by D.  of p r e y i n g  r e s p e c t i v e l y , and  experimental  the  food  survival  that  s t u d i e s showed  Lake  predation  dominant,  cutthroat  of  predation  were e x t r a p o l a t e d  Placid  i n the season  effect  Placid  .  lakes, cannibalism  agent.  in  effect  assemblage,  t h e m o r t a l i t y o f D. t h o m a s i  When t h e s e  later  were c a p a b l e  the  revealed  grazing  feeding  conducted  naupliar  and i n t r a s p e c i f i c  per predator  of  kenai  montane  the  a l l substantially affect  Subsequent  for  on  from t h e  were  determine  These e x p e r i m e n t s  by D. k e n a i  adults could  to  predation  due t o c o m p e t i t i o n predation  experiments  acted  the  effect  only  magnitude  variation  of  earlier of  and  their  i n weather.  In  has r e c e n t l y become a community suggested  i n the l a k e .  winter  the  that The  seemed t o be  and c o n c u r r e n t  increase  D. k e n a i  had  i n t r o d u c t i o n of responsible i n D. t h o m a s i  for .  iii  TABLE OF CONTENTS  ABSTRACT  i i  L I S T OF TABLES  v  L I S T OF FIGURES  vi  ACKNOWLEDGEMENTS  v i i  GENERAL INTRODUCTION  1  CHAPTER  8  1  Materials  and methods  8  Study area  8  Placid  9  Lake Community  E x p e r i m e n t a l Methods  14  Experimental design  19  Analysis  20  Results  23  Precision Set  o f sample d a t a  up o f e n c l o s u r e s  Results  of s u r v i v o r s h i p c a l c u l a t i o n s  Discussion  26 28 49  CHAPTER 2 Materials  23  55 and methods  55  E x p e r i m e n t a l methods  55  Experimental  56  design  Results  62  Discussion  67  GENERAL DISCUSSION  71  i v  REFERENCES  76  APPENDIX A. S e t up o f E n c l o s u r e s  84  Zooplankton  84  Diacyclops  thomasi  84  Diaptomus kenai  85  Grazing  assemblage  86  Diaptomus o r e g o n e n s i s  86  Daphnia  87  rosea  Holopedium  gibberum  88  Nauplii  88  Phytoplankton  89  Fertilizer  89  Grazing  91  APPENDIX  B.  assemblage Evaluation  o-f  Methods  for  Calculation  of  Survivorship  97  Duration  of n a u p l i a r s t a g e s  97  Analysis  of n a u p l i a r s u r v i v a l  APPENDIX  C.  Temperature  experimental  and  period(May-June,  Precipitation  during  1982)  APPENDIX D. R e s u l t s o f s u r v i v o r s h i p c a l c u l a t i o n s  the 116 119  V  L I S T OF  Table  I  Some  TABLES  physical,  characteristics  of P l a c i d  chemical and  Eunice  and Lakes  biological in  the  UBC  Research Forest Table  II  12  Stocking  densities  of  zooplankton  in  the  enclosures  16  Table  III Precision  Table  IV P r e c i s i o n  of z o o p l a n k t o n of p h y t o p l a n k t o n  T a b l e V D y n a m i c s of z o o p l a n k t o n T a b l e VI  The  effect  Diacyclops Table  VII  data  of  24  data  25  in enclosures  s u r f a c e s on  D.  kenai  27 predation  on  nauplii  66  Predation  rates  of  carnivorous  copepods  on  nauplii Table VIII Table  69 Effect  IX E f f e c t  of  of  fertilizer  fertilizer  on  chlorophyll  on p h y t o p l a n k t o n  content size  ....  92  classes 93  Table  X  Effect  chlorophyll Table size  XI  of  fertilizer  and  grazers  on  total  content  Effect  of  95  fertilizer  and  g r a z e r s on  phytoplankton  classes  T a b l e XII  Results  96 for  estimation  immature D i a c y c l o p s t h o m a s i  of  stage  duration  of 100  L I S T OF FIGURES  Figure Lake  V Spring from  zooplankton  2 Location  Figure  3 Experimental 4  survival Figure  6  design  kenai  survival  Figure  Effect  on n a u p l i a r  of  Summary  thomasi alone  on n a u p l i a r 33  the successive survival  of  (Integration)  successive  survival the  a d d i t i o n of m o r t a l i t y  of the  the  (Curve  effect  end  effect of  35  addition  of  of  the  of  mortality  fitting)  t o t h e end o f t h e n a u p l i a r  to  fertilization,  fitting)  of the  9 Summary  survival  fertilization,  thomasi alone  assemblage,  and D i a c y c l o p s  (Curve  7 Effect  8  assemblage,  31  of the g r a z i n g  a g e n t s on n a u p l i a r Figure  21  and D i a c y c l o p s  a g e n t s on n a u p l i a r Figure  10  (Integration)  Diaptomus  Figure  area  of the g r a z i n g  kenai  5 Effect  survival  4  of study  Effect  Diaptomus  i n Eunice  1975-1982  Figure  Figure  community c o m p o s i t i o n  37  a s i n g l e f a c t o r on stages  (Integration)  a. s i n g l e  naupliar  factor  stages  on  (Curve 42  fitting) Figure  10 Summary  survival  of the  effect  t o the beginning  of  a  single  of the t h i r d  factor  copepodite  on  stage 44  (Integration) Figure  11 Summary o f t h e  effect  of  a  single  factor  on  vii  survival  to  the  beginning  of  the  third  copepodite  stage  (Curve-fitting) Figure  12 D e s i g n  Figure  13  Figure  response  of  60 Diaptomus  kenai  to 63  representation  of G e h r s and  Robertsons  survivorship calculation  15 G r a p h i c a l  curve  cages  densities  14 G r a p h i c a l  method of Figure  experimental  Functional  naupliar Figure  of  46  fitting  representation  104  of  f i t  obtained  from  procedure  16 G r a p h i c a l  111  representation  of  error  in survivorship  curves Figure  113 17  Temperature  experimental  period  and  (May-June,  precipitation  during  1982)  Figure  18  Survivorship c a l c u l a t e d using  Figure  19 S u r v i v o r s h i p c a l c u l a t e d u s i n g  the 117  integration  120  curve  125  fitting  vi i i  ACKNOWLEDGEMENTS I  have been a i d e d  many p e o p l e ,  many  i n the course  of  whom  are  at  which  has  provided  Resource  Ecology,  discussion  and l e a r n i n g .  I idea The  am i n d e b t e d for  this  identify  Walters  those  Ludwig, drizzle  to  care  Peter  about  data  that  Don  always  that  Hird, Neill  Dad  nauplii  seemed  v e r y many) h e l p f u l  for  original  to h i s data.  helped  me  either  Krause,  sorting  discovered  and B i l l  Don  zooplankton. the  j o y of  t o f e e d t o Diaptomus  need  to  s h i v e r e d i n the  g r a p h e d and p r o d u c e d  to  Myers  forum  the  Edith  yesterday.  o r e n c o u r a g e d me - w h i c h e v e r was Judy  Animal  are too small f o r  a d v i c e on methods o f a n a l y s i s  Ludwig,  some c a s e s  for  my  has u n c o m p l a i n i n g l y  provided helpful discouraged  animals  Bill  Rob P u r d y and  of  open  Peacock  i n t h e sun f o r many h o u r s  fishing  I  an  generous a c c e s s  Wendy  and  Institute  providing  Adrienne  about.  r e s e a r c h by a g r e a t  K r a u s e and Don R o b i n s o n h a s s a v e d  little  Morrison  or b o i l e d  Robinson  work.  funny  Peter Morrison, rowing  of  the  for  r e s e a r c h and g i v i n g  hours  anyone e l s e  Don  to Carl  i n v a l u a b l e a d v i c e of E d i t h  many, many  of t h i s  kenai.  numerical Don Ludwig  and  unfailingly  neccessary.  Neill  p r o v i d e d many ( i n  comments on e a r l i e r  drafts  thank  who  of t h i s  manuscript. I  wish  especially  to  questions  until  they  skillfully  guided  me t h r o u g h  To world  must  have  Bill come  out  his  answered  e a r s and has  the r e s e a r c h and the r e d t a p e .  the thousands of zooplankton,  of beauty  Neill  who i n t r o d u c e d me t o a new  and wonder and who gave  their  lives  for  this  ix  research,  I am p r o f o u n d l y  Lastly, of  Ma B e l l This  $SIGNOFF  I w i s h t o thank T r e v o r  has s u s t a i n e d me more t h a n r e s e a r c h was s u p p o r t e d  Canada t h r o u g h Council.  grateful.  the N a t u r a l  Dee, whose g e n e r o u s anything  by t h e p e o p l e  Sciences  and  support  else. and government o f  Engineering  Research  1  GENERAL  Systems e c o l o g y , is  concerned  them w i t h i n  however,  large  with  Holling  (1973)  a  began  to  systems.  no  for  large  perturbation  of  in  the  explained system.  years the  A small  might domain  perturbation  why  years  and  had  was  then  above  and  behaviour  he  o f some  persisted  in  one  suddenly appeared to  structure,  sometimes even when  He  attributed  this  o f a "domain o f a t t r a c t i o n " i n w h i c h However once t h e b o u n d a r y reached, This  until  this  system c o u l d  quickly  way  of  systems  perturbation  perturbation,  to  the  was needed  applied  only  a  viewing  over  a  t o change number  of  t o the boundary of small  would be needed t o p u s h t h e s y s t e m  configuration.  for  quantitative  ecosystems  often  occurred.  no l a r g e  attraction  the  a rigorous  push a s y s t e m c l o s e r and c l o s e r of  theory  of  qualitative  change t o a n o t h e r c o n f i g u r a t i o n . also  difficulties  systems  studying  ecosystems  existed.  attraction  role  of ecosystems,  and  because  than  general  t o the presence  system u s u a l l y  domain  rather  that  many  events  that  i n b e h a v i o u r and community  phenomenon the  the  He o b s e r v e d  configuration change  suggested  be more u s e f u l  examine  other  a much l a r g e r  nature  behaviour,  in  developed.  qualitative  approach might  systems  events play  stochastic  quantifying  h a s n o t been w e l l  problems,  most  Because of t h e c o m p l i c a t e d of  disciplines,  w h i c h a c t on s y s t e m s t o keep  Unlike  stochastic  influence  associated ecology  systems-oriented  with the c o n s t r a i n t s  ecosystems.  the  other  c e r t a i n boundaries.  disciplines in  like  INTRODUCTION  additional  into a different  2  Several behaviour of  g r a s s and  Lakes the  budworm  et a l .  communities, blooms and  work has  Research  in d e t a i l  herbivorous  has  suddenly  became  unpubl.  present  (Figure  trout  fertilization  the  1).  lake  during  No  large the  was  fertilized  of G w e n d o l i n e Lake  b i o m a s s of C l a d o c e r a However,  in that  this  zooplankton  of B r i t i s h  Columbia  in  community  1975  through  d o m i n a t e d by  the m o s t l y 1981,  the  community  both  Holopedium  p e r t u r b a t i o n was period  although  and  1979  1981").  in  greatly  until  applied  (Hume 1978)  resulted  year,  copepod  configuration  (Hay  the  herbivorous  cladoceran  transition  in  algal  however,  the c a r n i v o r o u s c y c l o p o i d  were i n t r o d u c e d i n 1974  Lake  plankton  changes.  was  in this  that  of t h e s e  In t h e y e a r s  herbivorous  Great  sudden  in  sh'ift  community  seems t o have c o n t i n u e d  to t h i s  Gwendoline  dramatic  In  In  composition,  the causes  r o s e a and  the  of s u r p a s s i n g  to cause  changes  kenai.  d o m i n a t e d by and  found  data).  Diaptomus  thomasi  g i b b e r u m and  Lakes.  a  between  have r e v e a l e d  result  i n the U n i v e r s i t y  shown  of  outbreaks  of  variable.  community  determine  of  many  1973)  examine  c l a d o c e r a n Daphnia  copepods  of  are the  been  sort  s e m i - a r i d g r a z i n g savannas  critical  Lake z o o p l a n k t o n  calanoid  cutthroat  and  to  E u n i c e Lake  the Eunice  directly  some  been done  (Walters  Diacyclops  of  this  1978), t r a n s i t i o n s  in Holling  in zooplankton  Forest  structure  1969  exhibit Analysis  the c o l l a p s e  e u t r o p h i c a t i o n has  Recently,  the  et a l .  in configuration  value  shifts  communities  and  (Beeton  threshold  1980,  to  in d e t a i l .  (Ludwig  1981)  fisheries  little  appear  woody v e g e t a t i o n i n A f r i c a n  sudden c h a n g e s  the  which  have been examined  spruce  (Walker  systems  upstream The  increased  i n G w e n d o l i n e and  Eunice  i n c r e a s e i n biomass o c c u r r e d o n l y d u r i n g  3  the  year  of  fertilization  former  community  to gain  i n s i g h t i n t o the  montane shifts  structure  lacustrine  dominant.  importance  i n the  shift  the in  community  suggests  dynamics  period  of  stages.  of  i n community  this  and  Peacock  stages,  This  of  in freshwater  Gehrs  Robertson.1975, Confer  and and  marine systems Brooks  1970  of  this  of  many s p e c i e s  and  pattern  that  and  d o m i n a t e d by There influence be  (Heinle  suggests  the  a  number of  s u r v i v a l of  exceptionally  copepod Calmoecia food  act  lucasi, intake  the  Green  and  and of  food  the  causes  of  found  that  seemed t o  occur  early  Cooley  naupliar  Copepoda has  1977,  Peacock  1981)  al.  1969,  1978a).  The of  the  Mullin  uniformity  the  mortality  naupliar  influencing structure  stages  population  of  these e a r l y  communities  stages. could  N a u p l i i appear  limitation.  (1975) f o u n d  been 1974,  f a c t o r s which h y p o t h e t i c a l l y  to  a  Cooley  n a u p l i i in general.  vulnerable  the  1981)  major p o r t i o n  during  to being  Lake.  i n the  factors  such  greater  examination  R i g l e r and  community  order  number  reveal  in  1978b, L a n d r y  significant  therefore  the  Parsons et  the  rare  for Diacyclops  and  in  in  Peacock  1971,  1966,  that  c o p e p o d s may  the  that  of c o p e p o d s o c c u r s d u r i n g  are  assimilated  (Burgis  i n Landry  the  regulation  change  mortality  found both and  from b e i n g  particularly  pattern  In  oligotrophic  examined  in Eunice  mortality  an  its  mechanisms m e d i a t i n g was  1980,  regained  data).  on  o r g a n i s m may  structure  highest  naupliar  situation  radical  (Neill  acting  the  This  Peacock  the  and  Lake  unpubl.  thomasi changed  community  the  (Walters  constraints  this  Diacyclops  population  Gwendoline  community  in structure,  detail.  and  In  that  r e s p i r a t o r y output  was  the  the  to  calanoid  balance  negative  of  only  4  Figure  1 S p r i n g z o o p l a n k t o n community c o m p o s i t i o n i n E u n i c e Lake from 1975-1982. Zooplankton biomasses are a v e r a g e d from t h o s e f o u n d from mid-May t o e a r l y J u l y . The t o t a l z o o p l a n k t o n b i o m a s s i s d i v i d e d i n t o t h e c a t e g o r i e s shown b e l o w . Samples were c o l l e c t e d w i t h a 200 jim n e t . (Walters (unpubl. data)  all  nauplii  and  small calanoid tyrrelli) Diaptomus  calanoid  copepods  copepodites  (Diaptomus l e p t o p u s ,  D.  kenai  s m a l l C l a d o c e r a (Bosmina l o n g i r o s t r i s , D i a p h a n o s o m a b r a c h y u r u m , Polyphemus p e d i c u l u s ) Daphnia  Holopedi  rosea  . gibberum  Diacyclops  thomasi  5  6  for  the  naupliar  observation metabolic for  that  to the and  (Epp  stronger  a thin  and  feeding of  Lewis  line  copepodite  stages  a  This  Little  r e s p o n s e s of  nauplii  Brooks  Paffenhoffer  1970,  possible  that  resources  and  algae  nauplii  are  1971, are  grazers.  It  their.food  requirements with  deficiency  of  an  nutrients  the  from  structuring  larger  particular  for  smaller 1980).  effect  on  the on  1974,  work  graze  more  (Mullin  for  do  and  and  it  the  not  and  diet  smaller  However  is food  copepod  overlap  there  is  due  to other  or  competition  to play  in a  factors  on  for  be  a  nauplii  s t r u c t u r e have  1978b).  Landry  1977,  Lane  However  survival  role  1978,  several  found  1979, has  studies  extrapolated that  (McQueen  Intraspecific  agents  predation  and  in  predators  major m o r t a l i t y  invertebrate  r a t e s on  Cooley  a strong  invertebrate  t o be  cladocerans.  community  to  food  Kerfoot  and  found  of  regime  suggested  naupliar  been  grazers  suggested  substantially affect  also  nauplii  survival  the  to  competitors  are  actual  although  1977).  than  nauplii  the  larger cladoceran  size  can  1977,  nauplii  successful  found  c o m m u n i t i e s and  w h i c h have examined p r e d a t i o n their  and  algae.  (Dodson  predation  by  nutrient  have been  Much o f  size  l a r g e r stages  Poulet  larger  is frequently  animals  the  poor  appropriate  zooplankton  in  involved  i n nature  possible that  inappropriate  Predation  Zaret  also  between  i s known a b o u t  than  out-competed  is  the  calanoid  some m a r i n e c o p e p o d s have been small  with  1979,1980) s u g g e s t s t h a t  stages.  on  combined  correlation  between s t a r v a t i o n and  efficiently  s u c h as  result,  r a t e s e x i s t s f o r c y c l o p o i d and  adults  treading  stages.  predation  1969,  predation  Confer has  major m o r t a l i t y f a c t o r f o r copepod  7  nauplii  in several circumstances  It to  therefore  competition  seems t h a t  or  either  inter-  or  large  influence  other  on  play  in  oligotrophic  enclosure  lack for  of this: other  2.  nauplii  zooplankton low.  described  nauplii grazers  T h e s e two  utilized  use  the  an  fertilizer  to  increase that  There  1.  intraspecific  2.  interspecific  the  enclosures  enclosures. Diacyclops Chapter  2.  Chapter  the  the  system  the  same  the  nauplii were  two  predation  and  by by  of  D. in  thomasi a  being  explanations  out-competed;  'cells  and  as  the (2)  examined  grazing  affected of  in  more  by  and  These  thomasi  Diaptomus  of  predation:  thomasi  kenai.  was  adding  (2) a d d i n g a d u l t D i a p t o m u s k e n a i  was  other  a l t e r n a t i v e set  sources  by  a  were  (1) a d d i n g D i a c y c l o p s  nauplii  these  b e c a u s e of  heavily  Diaptomus  of  phytoplankton  Diacyclops  predation  set  In  (1) a d d i n g  An  a  these  s i z e s w h i c h were u s e d  supply.  possible  predation  Interspecific thomasi  were  exert  of  of  enclosure  food  predation,  role  possible  and  either  The  were d y i n g  sizes the  due  1.  same s i z e s  1978a).  to  examined  nauplii  experimental  h y p o t h e s e s were t e s t e d by to  survival  h y p o t h e s e s were t e s t e d by  to  predation.  nauplii.  was in  abundance of  assemblage  h y p o t h e s e s was  potential  T h e r e were two  in  d i d not but  that  food.  of  lake  Landry  f a c t o r s , and  naupliar  montane  I hypothesized  1.  as  survival  1969,  availability,  have t h e  i n i n f l u e n c i n g the  available  food  non-competitive  the  experiments  experiments,  both  intraspecific,  factors an  (McQueen  two  adults to  the  kenai  on  detail  in  8  CHAPTER 1 Naupliar in  the  life  survival history  Food  l i m i t a t i o n and  act  as major  The  relative  competitive inter-  and  i s s u s p e c t e d t o be t h e of  predation  mortality  thomasi appear  of  food  non-competitive  i n t r a s p e c i f i c was  (Neill  and  t o have  agents d u r i n g  importance and  D.  major  bottleneck  Peacock  the  potential  t h i s developmental limitation,  factors,  examined  in  and a  1980).  due  to  period.  both  to  predation,  both  set  of  enclosure  i n the  University  experiments.  Materials  Study  in  of Vancouver the  (Efford are  study  was  B r i t i s h Columbia  east  conducted  Research Forest 1967,  mostly  small  Eunice  zooplankters limiting conditions  Lake,  be  (Fig.  Consequently  Neill  more  likely  i n E u n i c e Lake  prior  more to  importance  the n a u p l i a r  to  survival  1979. of o f D.  Placid play  Lakes  but  they  thomasi  abundant Lake,  a major  closely  km  elsewhere  1978),  Diacyclops  in  2).  in detail  a l t h o u g h i t i s much l e s s  thus  on  1975,  lakes.  population,  examine t h e r e l a t i v e  predation  have been d e s c r i b e d  Lake.  would  the  Range M o u n t a i n s  oligotrophic  in  Lake  l o c a t e d a p p r o x i m a t e l y 40  N o r t h c o t e and C l a r o t t o  in Placid  nearby  in Placid  Research F o r e s t  i n the Coast  abundant  to  methods  area This  of  and  is than  other role  in  approximating  Enclosure experiments food  availability  thomasi  were  and  conducted  9  in P l a c i d Lake i n May and June 1982.  Due to i t s small s i z e  and  l a r g e watershed i n comparison to i t s volume (Table I ) , t h i s lake undergoes  relatively  and water l e v e l . zooplankton the  Nevertheless  a  similar  community with comparable dynamics to other  takes i n  Research F o r e s t  Eunice Lakes  Placid  populations  The p o p u l a t i o n  however  Lake  (Walters, unpubl.  support  clarki clarki). native,  sudden and d r a s t i c changes of temperature  the  shows  data).  of  Both P l a c i d and  cutthroat  trout  (Salmo  i n P l a c i d Lake i s presumed to be  population  from nearby Loon Lake i n 1974 and  i n Eunice Lake was  introduced  1975.  P l a c i d Lake Community In order to a f f e c t the other  zooplankton  temporally major  naupliar  survival  Diacyclops  i s univoltine  burst of production o c c u r r i n g i n e a r l y  the water column from a winter diapause  adults  produce  and  molts  nauplii  in  to  during  p r o d u c t i o n o c c u r r i n g at the mainly  end  spring.  reproductive May of  and  June  May.  The  present  cladoceran  quadrangula  These  with a peak i n nauplii  occur  Examination species  of  copepod, two s p e c i e s of c a l a n o i d copepods and s e v e r a l which occur  in significant  the same time as D i a c y c l o p s n a u p l i i .  The  the  I t enters  adults.  the upper 2 meters of the water column.  s p e c i e s of c l a d o c e r a n s  Cladocera  with  i n l a t e A p r i l as stage 4  of the seasonal p a t t e r n s i n P l a c i d Lake r e v e a l s one cyclopoid  D. thomasi,  i n P l a c i d Lake would have to o v e r l a p at l e a s t  with the n a u p l i i .  and 5 copepodites  of  are  species  Holopedium Bosmina  densities  at  The most common s p e c i e s of gibberum and Daphnia rosea. longirostris,  Ceriodaphnia  and Polyphemus p e d i c u l u s are a l s o present  but occur  10  Figure  2 Location  of  study  area.  (from  Neill,  1978)  1 2  Table  I Some p h y s i c a l , c h e m i c a l and b i o l o g i c a l c h a r a c t e r i s t i c s of P l a c i d and E u n i c e L a k e s i n t h e UBC Research Forest, ( m o d i f i e d from N e i l l , 1978)  Character i s t i e s Elevation, m D r a i n a g e a r e a , ha S u r f a c e a r e a , ha Maximum d e p t h , m Mean d e p t h , m C o l o u r , Pt u n i t s Transparency ( S e c c h i d e p t h , m) Total dissolved solids, mg/1 Maximal e p i l i m n e t i c depth, m Crustacean-zooplankton species; Diaptomus kenai Diaptomus t y r r e l l i Diaptomus o r e g o n e n s i s Diaptomus l e p t o p u s Daphnia rosea Holopedium gibberum Diaphanosoma b r a c h y u r u m Bosmina l o n g i r o s t r i s Ceriodaphnia quadrangula Polyphemus p e d i c u l u s D i a c y c l o p s thomasi T r o p o c y c l o p s p_. p r a s i n u s A i n d i c a t e s abundant R indicates rare - i n d i c a t e s absent  -Plac i d  .  Eunice  510 44 1.6 7 4.3 20-25  480 191 18.2 42 15.8 1 5  4-4.5  6-10  1 7-23 4 A  -  A  -  A A A R R A A R  1 6 7 -1981 A A  -  -  1981R R  -  A A A A  R A A A A  A R A  A A R  -  -  13  in  low numbers  naupliar  and  are  survival.  unlikely  Holopedium peaks  of May, o f t e n c o n t r i b u t i n g lake  at  this  time.  spring  but begins  peaks  in  the  the  lake  D. o r e g o n e n s i s adult of  Daphnia  summer.  summer. later  to  kenai  spring  i n high d e n s i t i e s  and p r o b a b l y (1.8  high d e n s i t i e s  -  of  t h e D. k e n a i  present  period  and  the  beginning  i n the s p r i n g  mm  starting  in July.  adult  the  D. k e n a i water  Diaptomus  length)  d u r i n g t h e summer. in  retreats  column  which  completely  in early  D. t h o m a s i  June and  adults  are  t h e upper w a t e r column d u r i n g t h e  of n a u p l i a r p r o d u c t i o n .  T h e s e s p e c i e s c a n be g r o u p e d t o g e t h e r possible  effect  are herbivorous nauplii  (1.25 - 1.5 mm  p o p u l a t i o n remains deeper a l t h o u g h i t  of  occur  Kenai.  The  lower  depths  from  D.  i n t h e upper water c o l u m n .  to  also  and  early  t o the s u r f a c e a t n i g h t .  disappears completely  May  lake only during very  migrates the  i n the  i n d e n s i t y during the  peaking  3.0  in Placid  when s m a l l numbers o c c u r  majority  i n the  of  and  s m a l l copepod  produces n a u p l i i  D. t h o m a s i  in  oregonensis  t h e end o f J u n e , d r o p p i n g  i s a l a r g e copepod  occurs  biomass  i n b i o m a s s a t t h e end  a comparatively  D. o r e g o n e n s i s than  i n d e n s i t y t o w a r d t h e end  The two s p e c i e s o f c a l a n o i d c o p e p o d s i n  l e n g t h ) which o c c u r s  October  influence  i s g e n e r a l l y i n low numbers  Diaptomus  is  significantly  the m a j o r i t y of the  increasing  are  to  on except  f o r food.  carnivorous predator.  naupliar mortality.  to  The C l a d o c e r a  their present  f o r Polyphemus and c o u l d compete w i t h t h e  Some c a l a n o i d c o p e p o d s have been  and Lane  (1978) s u g g e s t e d  The s m a l l s i z e  t o make t h i s  according  possibility  t h a t D. o r e g o n e n s i s  o f D. o r e g o n e n s i s unlikely  found  in Placid  so i t c a n a l s o  Lake  to  be  was a seems  be r e g a r d e d  as  1 4  a  competitor.  hereinafter  The above a n i m a l s collectively  assemblage".  D. k e n a i  referred  has a l s o  h e r b i v o r o u s but i t s l a r g e predation.  Krause  predatory a b i l i t y .  on  i t s own  consuming  until  situ June  involved  divided then  used  bags  allowing depth  nutrient larvae  "grazing  the  has found  strictly  possibility  of  some e v i d e n c e f o r  i s known t o be  cannibalistic  t o be c a p a b l e o f  (McQueen,  1969).  test  were c o n d u c t e d the  naupliar  4  hypotheses  survival.  to those of  The  styrofoam  45 cm  from  these  initially a 54 um  filled  net  to  with remove  grazable seston to pass. of s e v e r a l for  The  (1981).  plywood  was  frame  was  meters the  300  1  predation  pressure  and P e a c o c k  on  in  1  volume.  a l l crustaceans  The water u s e d  of  over  l a k e water w h i c h had been  in the lake to allow  duration  of the  T h i s arrangement  the  was t a k e n  while from  f o r an a d e q u a t e  experiment.  o f t h e phantom midge, C h a o b o r u s , have been  1979, N e i l l  potentially  bags s l i g h t l y  frames.  25  experimental  and  square.  e n c l o s u r e s w h i c h were a p p r o x i m a t e l y  supply  May  d e s c r i b e d by N e i l l  polyethylene plastic  suspended  were  from  t h e b o t t o m w i t h cement b l o c k s a t each  4 mil clear  considerable (Lynch  for  production  consisting  to  pumped t h r o u g h  a  to  were s i m i l a r  collar  were  provided The  1982  limiting  anchored  deep  the  has been c a l c u l a t e d  i n frames a p p r o x i m a t e l y  corners. m  data)  enclosure experiments 16,  floating  as  Methods  in  enclosures A  and  t o g e t h e r and a r e  been c o n s i d e r e d t o be  D. t h o m a s i  nauplii  to  allows  31% o f i t s own y e a r l y  Experimental In  size  (unpubl.  its  were g r o u p e d  found  invertebrate  1980), 2 m i l , c l e a r  Since to exert  communities polyethylene  15  plastic  t e n t s were c o n s t r u c t e d o v e r  to prevent allow  Chaoborus  maximal  from  light  laying  the e x p e r i m e n t a l e n c l o s u r e s  eggs  penetration.  the  The  f o r sampling.  plastic  screening to allow for a i r c i r c u l a t i o n .  crustacean  enclosures  were  zooplankton,  determined  Clarke-Bumpus  sampler  the  apparatus  sampling  vertical  hauls  Clarke-Bumpus calibrated  S i n c e D. and  haul  migrates  The the  o v e r a 24  day  addition  animals  adults  were  all  obtain  Diacyclops  the d e s i r e d  of  range  of  t h e p r o p o r t i o n of D. of  lake  the  that  nauplii  was  proportion The  found  i t was  d u r i n g t h e day  of  starting  in Table I I .  i n t h e w a t e r column d u r i n g t h e  found  the  oregonensis in  sample. be  nauplii,  day  stocked at a  to average  out  period.  were 153  individually  c o n s i d e r e d t o be  densities  collect  number  s t u d y were c o l l e c t e d  e n c l o s u r e s were s e t up.  using a  by  on  same d e p t h  The  covered  S i n c e t h e mesh s i z e to  the  be  a  upwards a t n i g h t ,  i n the  Nauplii  larger  and  lake  o b t a i n e d by Min s i e v e . pipetted  those animals and  D.  densities  of  filtering D.  out. which  from  the  lake  They were s o r t e d  to the e n c l o s u r e s u s i n g a combination  pipetting.  was  h  used  the  the  yet  with  large  Clarke-Bumpus  than  were  sampling  representative  vertically  animals  with  i n t h e e n c l o s u r e s may  higher density  the d e n s i t y  too over  that  the  of a n i m a l s  by  taken.  was  in  stocked  was  made  by a s s u m i n g  tents  days e a r l i e r .  kenai o c c u r s deeper  slightly  on  were  oregonensis  densities  3  sample was  the v e r t i c a l D.  ends o f t h e  enclosures  tents could easily  removed  The  The  in  sieving  The  and  out a l l of  thomasi  and  D.  the  the  kenai  g r a z i n g assemblage  remained  after  nauplii  k e n a i c o p e p o d i t e s were removed. in  for  experimental  To  enclosures,  1 6  Table  II S t o c k i n g  densities  of  zooplankton  Lake Density (l- ) 1  Diacyclops  thomasi  Diaptomus kenai Diaptomus o r e g o n e n s i s Holopedium gibberum Nauplii  1.0 .06  i n the  enclosures.  Enclosure Density (l- )  Number i n Enclosure  1.0  300  1  .22  66  3.6  3.5  1050  .6  .6  180  3.6  3.5  1050  1 7  D. k e n a i  and D. t h o m a s i  densities  of n a u p l i i  adding  the  zooplankton To some  individually.  required  amount  of  a  calibrated  concentrated  f o o d abundance  for nauplii,  "soup". limiting  t h e e n c l o s u r e s were f e r t i l i z e d w i t h  N:P a t o m i c  ratio  to  u s i n g NH„C1  the  experiment, subsequently  and  enclosures  once  while  after  the  u  twice  the  2  during  bags  the  were  experiments  phosphorus  edible and,  n i t r o g e n was c h o s e n  algae without  in particular,  nitrogen-fixing All for  blue green  zooplankton, was  collected  from  starting sampled  several  battery-operated  sucrose-5% samples  the a l g a l  algae  bilge  were  microscope.  later  (Neill  were c o u n t e d  pump.  Cyclopoid  under  and  12 d a y s .  the  amount  and t h e u s e o f  composition e x c e s s i v e l y  the  zooplankton from  15  enclosure  1973)  A l l nauplii a  50X.  1  using in a  and a l l  and immature  binocular  and c o p e p o d i t e s under  The  intervals  were p r e s e r v e d  (Haney and H a l l  on  day  animals  i n each  Animals  50X  (1974) and s t a g e d  four  set-up.  i_n t o t o •  nauplii  of  p e r s . comm.).  and a r e a s  solution  were c o u n t e d  Torke  removing  counted  filled  f a v o u r i n g t h e growth o f l a r g e  t h e day a f t e r  depths  the  of  t o t r y t o i n c r e a s e t h e growth  unduly  by  formaldehyde  copepodites  following  without  course  doubled  A l a r g e N:P r a t i o  o f t h e e n c l o s u r e s were sampled a t  community  a  shifting  was  had been r u n n i n g  of  t h e water."  Fertilizer  being  amount o f f e r t i l i z e r a d d e d a p p r o x i m a t e l y in  6 jxg/1 P i n a 30:1  (NH ) HPOi,.  The  ammoniacal  The d e s i r e d  and t h e g r a z i n g a s s e m b l a g e were o b t a i n e d by  enhance p o t e n t i a l l y  of  added  were c o u n t e d  were  dissecting identified  Larger  animals  under 25X.  Chlorophyll  and  phytoplankton  were a l s o  sampled a t 4 day  18  intervals. set-up  However  prior  to  After  the f i r s t  with  zooplankton  sampled  sampling  Chlorophyll  approximately  1 m into  enumeration  of  fixed  with  phytoplankton  cells.  was done  samples were s t o r e d  in  synchrony  and p h y t o p l a n k t o n  A  were  from  each  3 cm i n d i a m e t e r  250  fibre  After  of  to the enclosures.  Lugol's solution  on i c e .  day  An 80 ml a l i q u o t  a Whatman GF/C g l a s s  put i n t h e dark  the  700 ml o f water  the e n c l o s u r e .  was  through  these  animals  on  a p i e c e o f hose a p p r o x i m a t e l y  sample  immediately  of  period,  sampling.  well-mixed  filtered  sample was t a k e n  addition  sampling  using  extending  lab,  the  by w i t h d r a w i n g  enclosure and  the f i r s t  ml  at approximately  the  for later  aliquot  filter,  transport  of  was  f o l d e d and back t o t h e  -20 °C f o r 4  to  6 months. Chlorophyll following using was  a measurements were made on t h e f r o z e n  a method m o d i f i e d from  a Turner Design not  added  to  the  inactive  chlorophyll,  before  and  Calculation was  Model  after  Strickland  and  10 f l u o r o m e t e r .  samples.  was made several  by  Parsons  Magnesium  (1965)  carbonate  Correction  f o r phaeophytin  measuring  the  sample  HOC1  was  drops  o f t h e amounts o f l i v e  samples -  of  1%  chlorophyll  and  ,  both added.  phaeophytin  done u s i n g t h e e q u a t i o n s : live  chlorophyll  phaeophytin  =  r(BA-AA)/(r-1)  = r(BA - l i v e  chlorophyll)  Where BA= f l u o r e s c e n c e b e f o r e  acid  AA  acid  r  = fluorescence after = conversion  Phytoplankton  factor  cell  counts  were made by s e t t l i n g  50 ml o f  1 9  preserved  samples  counting  chamber  Phytoplankton into >18  f o r 48 h o u r s , and  cells  the s i z e  transferring  settling  for  were t h e n c o u n t e d <2 nm,  classes  was  criterion  counted  has been  sample v a r i a n c e  Experimental Four naupliar  from  were  D.  (4)  kenai  by  mentioned  above.  hours. divided  13-18 ixm,  Mm,  or  sample. in  30 This  reducing  comm.).  significantly  food  limitation  (2) f o o d l i m i t a t i o n predation  the g r a z i n g  (2)  adding  thomasi  to  due t o non-  by  by D.  affect due  D.  kenai  thomasi .  These  assemblage  fertilizer  t o an e n c l o s u r e  to and  treatments.  Figure  Nauplii  these  not  The  combination 3  provides  were added t o e v e r y experimental  of t h e t r e a t m e n t was  e n c l o s u r e s were s e t up w i t h  possible  additional  treatments,  D.  experimental  every  it  a  to an (4)  t o an e n c l o s u r e .  included  Since  pers.  to  (1)  (1) a d d i n g  adult  experimental  replicates  9-13  efficient  predation  enclosure,  different  two  and  f o r each  Krause  were:  interspecific  (3) a d d i n g  Eighteen  The  nm,  class  (3) i n t r a s p e c i f i c  were t e s t e d  treatments.  E.  other grazers,  experimental  adding  size  hypothesized  These  factors,  and  enclosure,  400X  24  The minimum o f 200 c e l l s  t o be t h e most  Robinson,  survival.  hypotheses an  (D.  under  to  design  competition  adults  found  factors  competitive  f o r each  residue  additional  2-5 /xm, 5-9  /xm, c o l o n i e s and f i l a m e n t s .  fields  an  the  of  feasible  3 replicates  sixteen of  a  the  were  treatments four  summary  of  experimental  factors these  enclosure.  e n c l o s u r e s were s e t up t o be  fertilizer to  sixteen  and  replicate used  as  nauplii  a l l an  only.  experimental estimate  of  20  between  enclosure  increase  v a r i a n c e between bags  treatments the  would  treatment  priori  variability.  phytoplankton  within  few  the  On  the  final  taken  from  samples  were  (Neill,  and  fertilizer  pers.  nauplii  greatest day  of  o n l y was  potential  from  t o o b t a i n an  5  this  effect,  zooplankton  3 chlorophyll  enclosures. of  a  experimental  three  estimate  to  these  considered  for  sampling,  taken  i s known  comm.) and  e a c h e n c l o s u r e and  were  used  Since  organisms to s t a b i l i z e  fertilizer  have  were  replicates  have  with  to--  samples  variability.  sample  and  These variance  enclosures.  Analysis Analysis  of v a r i a n c e was  t h e most commonly u s e d  was  using a pocket  technique  and  computer  program  either  case,  conducted.  of  UBC  If  test  (Grieg  for  and  the  test was  not  Curve  fitting  N2SNO f o u n d  CURVE  (Moore  s i m u l a t i o n s and  is explicitly analyses.  not  of  In  were  In  most  cases,  the  once t h e d a t a  were  performed  1981).  1977).  homogeneous, t h e d a t a  were a l l p e r f o r m e d was  the  was  significant  II m i c r o c o m p u t e r .  packaged program  Bjerring  or  variance  re-applied.  Simulation analyses  i n UBC  and  calculator  homogeneity  t h e v a r i a n c e was  homogeneity  transformed.  GENLIN  Bartlett's  log-transformed lack  done e i t h e r  statistical  Unless  on  an  u s i n g the the  s t a t e d , I w r o t e and  use  Apple  package of  a  performed a l l  ure  3 Experimental design. F o u r f a c t o r s were u s e d i n t h e e x p e r i m e n t t o examine t h e i r e f f e c t on D i a c y c l o p s t h o m a s i naupliar survival: (1) fertilization ( 2 ) p r e s e n c e of the g r a z i n g a s s e m b l a g e ( 3 ) p r e s e n c e of D i a p t o m u s k e n a i ( 4 ) p r e s e n c e of D i a c y c l o p s t h o m a s i . E v e r y p o s s i b l e c o m b i n a t i o n of t h e s e 4 f a c t o r s was i n c l u d e d i n t h e e x p e r i m e n t a l d e s i g n , In t h i s r e p r e s e n t a t i o n , e v e r y box r e p r e s e n t s an e n c l o s u r e and the symbols i n i t i n d i c a t e the t r e a t m e n t s i t c o n t a i n s . F o r example, t h e box i n t h e u p p e r l e f t hand c o r n e r r e p r e s e n t s t h e e n c l o s u r e w h i c h c o n t a i n s f e r t i l i z e r and grazers-.  G K D  Grazers Diaptomus Diacyclops fertilizer  kenai thomasi  FERTILIZER A b s ent  P r e s ent  GRA; JERS  GRA; ZERS  F  Absent  G  Present  Absent  Present  F F DG D  Absent  F G  Absent  K F K F G  K  Present  D I A C Y 'CLOPS D I A C Y 'CLOPS  Pres>ent  AbS(  Present  K F K F D G D  K K DG D  DG D G  K  23  Results  Precision  of  sample  Coefficients replicate end  of  of  the  between  40  This  The Table  counted were of for  this from  The data  are  increased  is  shown  for  expected  at  the  is  of  zooplankton  treatment  of v a r i a t i o n  three  coefficient  a l l  to which the t e s t e d  o n l y one The  cell  was  not  consistently  i f the v a r i a n c e i n c r e a s e d w i t h  can  coefficients  judge  f o r both  However,  found  reported  by Wiebe and  the  Holland  variable  s i n c e a l l samples were from  the zooplankton  those  in  which  replicates estimates  than  those  chlorophyll.  i s p r o b a b l y due  taken.  seen  measurements showed t h a t  or t o t a l  than  be  were p r o b a b l y more  were c o n s i d e r a b l y more v a r i a b l e  phaeophytin  variation  to  data  of t h e e n c l o s u r e s  chlorophyll  larger  counts  difficult  samples  error.  is  the  a l l enclosures  consistent  of the p h y t o p l a n k t o n  chlorophyll  either  %  from  abundance.  taken.  live  be  Phytoplankton  although  50  from  fairly  the c o e f f i c e n t  would  precision  IV.  and  were c a l c u l a t e d  taken  A  I f samples  added a r e e x c l u d e d ,  decreasing  samples  experiment.  III).  lower.  variation  zooplankton  variation (Table  data  by  and  Marmorek  phytoplankton (1983).  t o t h e s m a l l volume  variation  is  (1968) i n t h e i r  similar study  of  The  of  the  to  that  sampling  24  Table  III Precision  of z o o p l a n k t o n  Organism Daphnia  data No. of Enclosures  rosea  Mean of  Coefficient Variation  18 8 *  48.5 42.6  18 8 **  72.1 44.6  Diaptomus o r e g o n e n s i s  18 8 *  54.0 46.9  H o l o p e d i u m gibberurn  18 8 *  50.9 40.8  Calanoid  nauplii copepodites  18 18  52.3 42.7  Cylopoid  n a u p l i i and copepodites  84  Diacyclops  thomasi  ***  48.0  - c a l c u l a t e d from o n l y e n c l o s u r e s c o n t a i n i n g t h e g r a z i n g assemblage. - c a l c u l a t e d from o n l y e n c l o s u r e s c o n t a i n i n g D. thomasi. - c a l c u l a t e d over a l l s t a g e s .  25  Table  IV P r e c i s i o n  of phytoplankton  data  No. of Mean C o e f f i c i e n t Enclosures of V a r i a t i o n Chlorophyll live  measurements 5  89.1  phaeophytin  5  51.4  total  5  26.0  Cell  chlorophyll  chlorophyll  counts <  2 Mm  1  84.0  2 -  5 Mm  1  11.4  5 -  9 Mm  1  7 6.9  9 - 13 Mm  1  52.8  13 - 18 Mm  1  68.5  18 - 30 Mm  1  78.7  Mean o f s i z e c l a s s e s  62.1  26  Set  up o f e n c l o s u r e s Count  data  of  e n c l o s u r e s were experimental  to  and  phytoplankton  confirm  Details  i n A p p e n d i x A.  observed  differences  examined  enclosures.  may be f o u n d were  zooplankton  proper  In g e n e r a l ,  f o r a l l treatments  treatments  appeared  treatment  after  w i t h s e t up and were much l o w e r  lake  the  difference adult the  These  were a t l a k e d e n s i t y a r e summarized  Fertilizer chlorophyll  increase  in  increases classes  a  total  phaeophytin only  after,  since  live  and t h i r d  examined  to  the  resulted the  This  experiment  for  since densities in The d i f f e r e n c e s period.  sampling  was l a r g e l y  chlorophyll periods.  increases in  period.  if  showed  significant  Examination  fertilization  food  Phytoplankton the  grazing  impact  showed t h a t  the g r a z i n g assemblage d e c r e a s e d sampling  This  in  f o r the  were  assemblage  total  of s i z e  resulted  data  availability.  period  This  made up o f i n c r e a s e s  i n p l a n k t o n o f t h e 5-18 Min range  the  the  period.  in significant  first  showed t h a t  determine  i n the t h i r d  than  experimental  significant  starting  A l l  i n T a b l e V.  sample p e r i o d s .  on  experiment.  a t the b e g i n n i n g of the experiment.  d u r i n g 2 sampling  increases  analysis  these  in density  of  the  and  breaking diapause.  chlorophyll  of phytoplankton  significant second  treatments  of  differences  up  experimental  f o r C l a d o c e r a a t t h e end o f t h e  results  total  the  the  extensive mortality  and t h e g r a z i n g a s s e m b l a g e  l a k e r o s e due t o a n i m a l s  Nauplii  in  of  increased during the course  D. t h o m a s i  decreased  set  to suffer  associated  beginning  up  of the s t a t i s t i c a l  continued f o r the d u r a t i o n of the  zooplankton  at  set  from  also had  a  analysis  chlorophyll a  and c o n t i n u i n g t o t h e end  Table  V Dynamics of z o o p l a n k t o n  in enclosures  Density in Enclosures ( 1 ) ( P e r c e n t a g e o f Lake D e n s i t y ) B e g i nn i ng Middle End _ 1  O r g a n i sm  D i acyc1 ops thomas i  E f f e c t of Treatment  E f f e c t of Time  0.75 (75)  0.45 (50)  0.45 (35) 0.07  D i aptomus kena i Diaptomus oregonens i s  0. 72 (20)  0.67 (50)  0.84 (400)  Daphn i a rosea  0.13 (67)  0.20 (10)  1 .80 (115)  H o i o p e d i urn Qi bberum  0.47 (75)  7 . 40 (115)  4.29 ( 130)  Naupli i  *** ns p  3 . 58 ( 100)  - i n d i c a t e s s i g n i f i c a n c e at the level .001. - indicates non-significance. - i n d i c a t e s t h a t no s t a t i s t i c a l t e s t was d o n e b u t v i s u a l assured the presence in enclosures.  inspection  28  of  the  experiment.  An  i n t e r a c t i o n between  grazing  assemblage  occurred  periods.  Examination  of  classes  on  the  third  the  during  period  assemblage d e c r e a s e d p h y t o p l a n k t o n interaction  an  the  5-9  nm  range.  Results  of  survivorship calculations methods  between  for  the  examined  in  population  abundance c u r v e  frequently method  used  to  investigated  conditions the  detail  actual  squares.  i n the  within both  involved  indicated naupliar other  that  fairly  Figure naupliar  of  20.  results  the  a  factors  The  or  general  most  The  other  show an effects  of  b o t h methods  had  and  consistent  calculated  some  survival  Figure level  effect  whereas  extent, in  e f f e c t of of  from  general  had  shown  using  results  very  lesser  of  sums  the  i n A p p e n d i x D,  a  are  model  to  The  tested  fitting  These r e s u l t s a l s o  survival.  on  increased  greater  from c u r v e  therefore  presented  results  Fertilizer  to  was  the  curve  robust  compared.  curve are  these  all  Results  seemed  Survivorship  survival.  survival.  both  were  been  simulated  that  in  under  has  minimizing  but  range  occurred  simulation  the  revealed  and  factors,  fitting  abundance c u r v e by  under the  Examination  a  grazing  jum  survivorship.  constructing and  5-13  size  survivorship  which  investigations  themselves. techniques  method  the  sampling  the  Integration  copepod  enclosures  These  integration 19.  examine  population  some d i f f i c u l t i e s  i s the  that  grazers  of  B).  two  i n the  and  calculation  and  phytoplankton  revealed  fertilizer  (Appendix  last  of  biomass  and  Two  the  abundance  sampling  fertilizer  on  all  decreased  Appendix  D,  a l l factors  on  these  factors  on  29  overall  survival  the r e s u l t s  from  When t h e examined, sampling in  to the t h i r d  1.  Integrating  s u r v i v o r s h i p and reproducing  Curve  D.  thomasi  D.  are  becomes more  thomasi  the  examined  below:  the p o p u l a t i o n curve  effect  underestimates  noticeable  are present.  differences  This  in  when  technique  developmental  rate.  i n the e n c l o s u r e s .  inadequacies  results  in  in  every  no  This model  large  statistical  t r e n d s were o b s e r v e d .  on  error  adult  technique used  for  in  daily  in approximately  the  survival  containing  curve.  the  of a p p r o x i m a t e l y  a  same  the  same  error.  variability  similarity  variation  resulted  enclosures  the sampling  relative  the  10%  point  seemed t o show an  Because of the  in  a  This variation  between'  m a g n i t u d e as  s u r v i v o r s h i p when  curve.  error  variation  calculations,  to  the  Sampling  treatment  underestimates  are present  Differences  general  this  survivorship  These e f f e c t s ,  summarized  under  adult  vulnerable  survival  the  are  fitting  generating  and  B,  of  between e n c l o s u r e s .  2.  25%  t h e same as  o f t h e methods o f a n a l y s i s and  a l s o vulnerable to s l i g h t  rates  3.  calculation  t e c h n i q u e must be c o n s i d e r e d . i n Appendix  is  of the  shortcomings  detail  is  s t a g e was  integration.  results  the  copepodite  of  the  i n the results  calculated of the  survivorship  a n a l y s e s were p e r f o r m e d . The  curves  most c o n f i d e n c e was  Instead, placed in  30  trends  which  (a)  appeared  i n the r e s u l t s  from  survivorship calculation,  (b) were c o n s i s t e n t  (i.e.  or d e c r e a s e d  always  increased  e n c l o s u r e ) and ( c ) d i f f e r e d the  from  sample and w i t h i n t r e a t m e n t The  accuracy  be compared. test it  was  since  not  t h e model The  to  effects and  from  in  5).  and  effect.  to estimate  by  t o an  more  than  t h e two methods c o u l d n o t simulations to  under t h e  curve,  f o r the c u r v e - f i t t i n g the e f f e c t  both  methods  method  of i n a d e q u a c i e s of  than  In b o t h  and  the other  g r a z e r s seemed t o of a n a l y s i s .  showed  that  on n a u p l i a r s u r v i v a l cases,  A d u l t D. t h o m a s i  D. k e n a i  methods  effect  used.  4  .effect.  from  do t h i s  t e s t e d had a n e g a t i v e e f f e c t  negative  their  when added  treatments  of t h e method o f i n t e g r a t i o n  no way  results  (Figures  survival  i t was p o s s i b l e t o p e r f o r m  possible  t h e r e was  in  methods o f  variation.  of the r e s u l t s  Although  the accuracy  other  both  grazers  fertilizer  showed  a  a l l by  showed a  A d u l t D. t h o m a s i  be  in  their  An example o f t h i s  negative  , D.  effect  additivity  slight  negative  stronger  two f a c t o r s . additive  themselves.  stronger  showed s t i l l  factors  kenai  in  both  c a n be  seen  F i g u r e s 6 and 7 . An e s t i m a t i o n o f t h e o v e r a l l  influencing between of  survivorship  treatments  these  summaries  i t c a n be seen  until  the beginning  this  factor  sightly  negative  factors  in  c a n be made by c o m p a r i n g s u r v i v o r s h i p  which o n l y d i f f e r  comparisons  is  s t r e n g t h of these  are  shown  that  by one  i n F i g u r e s 8-11.  fertilizer  of t h e c o p e p o d i t e  positive using curve  using  factor.  Summaries From  has a v e r y mixed  effect  The n e t e f f e c t  of  t h e method o f i n t e g r a t i o n  and  fitting.  phase.  these  If  the  net  effect  of  31  Figure  4 E f f e c t of the g r a z i n g assemblage, f e r t i l i z a t i o n , D i a p t o m u s k e n a i and D i a c y c l o p s t h o m a s i a l o n e on n a u p l i a r survival (Integration). The d i s t a n c e on t h e x - a x i s between d e v e l o p m e n t a l s t a g e s i s p r o p o r t i o n a l t o the d u r a t i o n of the s t a g e s . — — N a u p l i i alone D i a c y c l o p s thomasi Diaptomus kenai G r a z i n g assemblage — Fertilizer  32  DEVELOPMENTAL  STAGE  33  Figure  5 E f f e c t of the g r a z i n g assemblage, f e r t i l i z a t i o n , D i a p t o m u s k e n a i and D i a c y c l o p s t h o m a s i a l o n e on n a u p l i a r s u r v i v a l (Curve f i t t i n g ) . The d i s t a n c e on t h e x - a x i s between d e v e l o p m e n t a l stages i s p r o p o r t i o n a l t o the d u r a t i o n of the s t a g e s . — — N a u p l i i alone D i a c y c l o p s thomasi Diaptomus kenai G r a z i n g assemblage Fertilizer  34  1  0-  — I —  —i—  C 1  N4  DEVELOPMENTAL  STAGE  C3  35  Figure  6 E f f e c t of the s u c c e s s i v e a d d i t i o n of m o r t a l i t y agents on n a u p l i a r s u r v i v a l ( I n t e g r a t i o n ) . The d i s t a n c e on t h e x - a x i s between d e v e l o p m e n t a l s t a g e s i s p r o p o r t i o n a l to the d u r a t i o n of the stages. I^^M N a u p l i i alone D i a c y c l o p s thomasi * D i a c y c l o p s t h o m a s i and g r a z e r s > D i a c y c l o p s t h o m a s i , g r a z e r s and D i a p t o m u s k e n a i  DEVELOPMENTAL  STAGE  37  F i g u r e 7 E f f e c t of the s u c c e s s i v e a d d i t i o n of m o r t a l i t y agents on n a u p l i a r s u r v i v a l ( C u r v e f i t t i n g ) . The d i s t a n c e on the x - a x i s between d e v e l o p m e n t a l s t a g e s i s p r o p o r t i o n a l t o t h e d u r a t i o n of the s t a g e s . N a u p l i i alone D i a c y c l o p s thomasi D i a c y c l o p s t h o m a s i and g r a z e r s D i a c y c l o p s t h o m a s i , g r a z e r s and Diaptomus k e n a i  DEVELOPMENTAL  STAGE  39  fertilizer  is  copepodite  stage,  more  a l l stages  of  pattern The  negative  also  curve  both  showed  although  to  the  additions  effect  Diacyclops analysis. over  the  third becomes  stages.  The  inconsistent  strong  strong  which  positive  effect  negative  largely  with  i n the c u r v e - f i t t e d  expect  a  in  the a d u l t s to eat.  However  D. t h o m a s i  D.  i n both  kenai  methods stages  methods  showed a s l i g h t  positive  whereas  of  the  on a l l  integrated  developmental  cannibalism  in  the  t h i s method.  results  The  i s somewhat  are c a n n i b a l i s t i c ,  slight suspect.  one would only  effect  of a d u l t D.  thomasi  else on  g r a z e r s c o u l d be e x p l a i n e d i f t h e a d u l t s  for juveniles  (1969)  on n a u p l i i  i n the  s i n c e t h e r e would be n o t h i n g  A positive  containing  McQueen  effect.  more  s u r v i v o r s h i p i n the e n c l o s u r e with  a d u l t s and n a u p l i i  competition  showed  be due t o t h e u n d e r e s t i m a t i o n of  i t i s known t h a t D. t h o m a s i  reduced  large  two  effect  effect  i s known t o o c c u r  decrease  effects  stages,  Because  treatments  results of  developmental  consistent  net e f f e c t  results  negative  r e s u l t s may  survival  a  the  results.  showed  a  the  showed  seemed t o i n c r e a s e i n t h e c o p e p o d i t e  a l l developmental  showed  D. t h o m a s i  gave  negative  t o be t h a t of  analysis  integrated  The c u r v e - f i t t e d  results  integrated  results  consistent  the c u r v e - f i t t e d  effect  of  d i d n o t change o v e r  fitted while  appeared  i n magnitude and d i r e c t i o n a  this  effect  B o t h methods  and e f f e c t s  effect  variation  for  up  fertilizer  most c o n s i s t e n t n e g a t i v e  stages.  of  the e f f e c t  g r a z i n g assemblage.  same  of  over  positive. The  the  examined  was  found not  by  preying  on  competitors.  t h a t t h e p r e d a t i o n r a t e of a d u l t affected  by  the  presence  of  -  40  Figure  8 Summary of t h e e f f e c t o f a s i n g l e f a c t o r on s u r v i v a l t o t h e end of t h e n a u p l i a r s t a g e s ( I n t e g r a t i o n ) . This t a b l e shows a summary of c o m p a r i s o n s between t r e a t m e n t s w h i c h o n l y d i f f e r by one factor. indicates a positive var i a n c e .  effect  less  i n d i c a t e s .a p o s i t i v e sample v a r i a n c e .  effect  greater  indicates variance.  a negative  effect  less  indicates a negative sample v a r i a n c e .  effect  greater  indicates  no  than  the  than  than  the  than  sample the sample the  effect  An example of t h e i n t e r p r e t a t i o n of t h i s t a b l e i s as follows: The upper l e f t hand box shows t h a t fertilizer c a u s e s a n e g a t i v e e f f e c t l e s s t h a n t h e sample v a r i a n c e when a d d e d t o an e n c l o s u r e c o n t a i n i n g n a u p l i i o n l y . A summary of t h e net e f f e c t of e a c h f a c t o r i s p r o v i d e d a t t h e b o t t o m of e a c h c o l u m n . S o l i d arrow are c o n s i d e r e d t o be w o r t h t w i c e as much as h o l l o w a r r o w s . ? D G  Fertilizer Diaptomus kenai D i a c y c l o p s thomasi Grazers  NB Arrows which r e s u l t from comparisons i n v o l v i n g t r e a t m e n t KG ( e g . column 4, row 2) must be treated w i t h c a u t i o n as u n u s u a l l y low numbers o f n a u p l i i r e d u c e d t h e p r e c i s i o n of the c a l c u l a t e d s u r v i v o r s h i p i n t h i s treatment.  ADDED  F  TREATMENT  K  G  D  o  nauplii only F K D G  o  FK FD FG KD KG DG FK D FK G FDG KDG  6  , °  5  °  8  o  4  o  42  Figure  9 Summary t o t h e end This table treatments  ^^.^ , •  o f t h e e f f e c t o f a s i n g l e f a c t o r on s u r v i v a l of the n a u p l i a r s t a g e s (Curve f i t t i n g ) . shows a summary o f c o m p a r i s o n s between w h i c h o n l y d i f f e r by one f a c t o r .  indicates a positive var i a n c e .  effect  less  than  indicates a positive sample v a r i a n c e .  effect  greater  indicates a negative e f f e c t variance.  less  indicates a negative e f f e c t sample v a r i a n c e .  greater  indicates  t h e sample  than the  than  t h e sample  than the  no e f f e c t  An example o f t h e i n t e r p r e t a t i o n o f t h i s t a b l e i s a s follows: The u p p e r l e f t hand box shows t h a t f e r t i l i z e r c a u s e s a n e g a t i v e e f f e c t l e s s t h a n t h e sample v a r i a n c e when a d d e d t o an e n c l o s u r e c o n t a i n i n g n a u p l i i o n l y . A summary o f t h e n e t e f f e c t o f e a c h f a c t o r i s p r o v i d e d a t the bottom of each column. S o l i d arrow a r e c o n s i d e r e d t o . b e w o r t h t w i c e a s much a s h o l l o w a r r o w s . F K D G  Fertilizer Diaptomus kenai D i a c y c l o p s thomasi Grazers  ADDED  F  TREATMENT  K  G  D  nauplii only  O  F  -  K  —  D G  •  —  O  FK  z LD z>  r< UJ  rr LU UJ CO  < m  —  FD FG KD KG DG  —  —  FK D -  FKG FDG KDG  3  o  7  <3>  4  ^>  1 1  o  44  Figure  10 Summary of t h e e f f e c t of a s i n g l e f a c t o r on s u r v i v a l t o the b e g i n n i n g of the t h i r d c o p e p o d i t e s t a g e (Integration). T h i s t a b l e shows a summary of c o m p a r i s o n s between t r e a t m e n t s w h i c h o n l y d i f f e r by one factor. indicates a positive variance.  effect  less.than  indicates a positive sample v a r i a n c e .  effect  greater  indicates a negative e f f e c t variance.  less  indicates a negative sample v a r i a n c e .  greater  indicates  no  effect  the than  than  the  than  sample the sample the  effect  An example of t h e i n t e r p r e t a t i o n of t h i s t a b l e i s as follows: The u p p e r l e f t hand box shows t h a t fertilizer c a u s e s a n e g a t i v e e f f e c t l e s s t h a n the sample v a r i a n c e when added t o an e n c l o s u r e c o n t a i n i n g nauplii'only. A summary of t h e net e f f e c t of e a c h f a c t o r i s p r o v i d e d a t t h e b o t t o m of e a c h c o l u m n . S o l i d arrow a r e c o n s i d e r e d t o be w o r t h t w i c e as much as h o l l o w a r r o w s . F K D G  Fertilizer Diaptomus kenai D i a c y c l o p s thomasi Grazers  NB Arrows which r e s u l t from comparisons i n v o l v i n g t r e a t m e n t KG ( e g . c o l u m n 4, row 2) must be treated w i t h c a u t i o n as u n u s u a l l y low numbers of n a u p l i i r e d u c e d t h e p r e c i s i o n of t h e c a l c u l a t e d s u r v i v o r s h i p i n t h i s treatment.  ADDED  TREATMENT  K  F  G  D  nauplii only F  —  K D G FK  —  UJ  FD < LU  or.  FG  UJ  KD LU CO < CO  i  KG DG FK D  —  FKG FDG KDG 7  o  5  °  11  °  4  ^  46  Figure  11 Summary o f t h e e f f e c t o f a s i n g l e f a c t o r on s u r v i v a l to t h e beginning of the t h i r d copepodite stage (Curvefitting). T h i s t a b l e shows a summary o f c o m p a r i s o n s between t r e a t m e n t s w h i c h o n l y d i f f e r by one f a c t o r . indicates variance.  a positive  effect  less  indicates a positive sample v a r i a n c e .  effect  greater  indicates variance.  a negative  effect  less  ^mp- i n d i c a t e s a n e g a t i v e sample v a r i a n c e .  effect  greater  r—,  indicates  than  t h e sample  than the  t h a n t h e sample than the  no e f f e c t  An example o f t h e i n t e r p r e t a t i o n o f t h i s t a b l e i s a s follows: The u p p e r l e f t hand box shows t h a t f e r t i l i z e r c a u s e s - a n e g a t i v e e f f e c t l e s s t h a n t h e sample v a r i a n c e when a d d e d t o an e n c l o s u r e c o n t a i n i n g n a u p l i i o n l y . A summary o f t h e n e t e f f e c t o f e a c h f a c t o r i s p r o v i d e d a t t h e bottom o f e a c h c o l u m n . S o l i d arrow a r e c o n s i d e r e d to. be w o r t h t w i c e a s much a s h o l l o w a r r o w s . F K D G  Fertilizer Diaptomus kenai D i a c y c l o p s thomasi Grazers  ADDED  F  K  TREATMENT  G  D  o  nauplii only F K  —  D G  —  —  <>  FK FD FG KD KG DG FK D FKG FDG KDG  4  ^>  1 0 <z>  3  o  14  o  48  alternate  prey.  a l s o does not D. t h o m a s i  of  D. t h o m a s i  .  observations  were  (Appendix  B),  down  influencing  the  results  one  results  the j u v e n i l e i t falls  the  adult  kenai or in  containing  When  negative  relatively  the adult  supported  the model.  constant  by  initial  mortality  consistent  ( i . e . examining  when the  c o n t a i n i n g a d u l t D i a c y c l o p s a s shown results  mortality importance  survival  and  a s a g r o u p seemed t o  was  minimized.  of  o f D. t h o m a s i  somewhere  integration  D.  error  further  minimize  held  negative  obscure  from  is  remained  factor  an  competition when  containing  enclosures  However D i a c y c l o p s  as  that  in  to  survival  indicate  calibrating  adjusted  19c).  difficulties  probable  while  in  treatments  conclusion  from a l l e n c l o s u r e s  Figure  increase  observations  This  conditions  shift  to  b e n e f i t due t o r e d u c e d  recruitment  made  examined w i t h  the  added  These  modelling  in  indirect  explain  were  fertilizer.  results  An  cannibalism .  However  These in i ti s  between t h e e x t r e m e s shown i n  curve-fitting.  49  Discussion In grazing  the  experimental  a s s e m b l a g e and  effect  on  adult  D.  that  this  D.  cannibalistic  and  thomasi  on  to prey  D.  kenai  is  on  small  food  were  assemblage,  which  observation  suggests  of  found. D.  kenai  20%  of  the  It therefore on  The  naupliar  survivorship  and  nauplii seems  d i d not  per  likely  s u r v i v a l was of  appear  due  that  appeared  show c o n s i s t e n t  enclosures t o have any  This  occurring.  a  litre  the  main  predation per  on  food  seemed  in general  density  effect.  to p r e d a t i o n  assemblage  to  day  was  effect  of  nauplii. limitation  to  decrease  increase i t .  e f f e c t s within  containing effect.  on  grazing  and  to  Krause  the  per  results relating  grazing  In  predator  feeding  its  of  2)  adult  i t s effect  have been  (Chapter  of  1982,  since  similar  and  cannibalism.  Chapman  may  affect  c a p a b l e of  that  an  (McQueen  effect to  and  than  predation  fertilizer  method of a n a l y s i s .  the  to competition  confirmed  d i d not  1978,  a  i s however  nauplii  due  feeder  overall  containing  carnivorous  on  that  lower  although  substantially be  the  consistent  factors  i t seems u n l i k e l y t h a t  that  The  fertilizer  fertilizer  filter  much  interpretation  i s more d i f f i c u l t .  However  a  later  that  more  There  to  was  (Buckingham  had  p r e d i c t i o n was  known  entirely so  also  probable  However due  other  uncertain.  survival  particles  " data).  biomass  rate  is  known t o be  s u r v i v o r s h i p was  This  than  preferentially  naupliar  appeared  a l a r g e r and  may  is  it  it  survivorship in enclosures  species  thomasi  Therefore  D.  and  had  survival  in estimating  survival.  unpubl.  kenai  t h o m a s i make i t s s t a t u s  indication  1969).  D.  juvenile  difficulties  enclosures,  nauplii This  result  either alone, could  50  be  explained  i f nauplii  w h i c h were not  stimulated  Comparison  of  unfertilized  enclosures  there that was  was the  not  small  no  the  The  this  competition  copepods. the  algal  despite  organisms  feeding  are  the  food  show any  of  which  eating  explanation  for  reduced  survival  nauplii (as the  were a l s o p r e s e n t .  indicated survival  of  due  appeared  t o be  enclosures. food  algal  by  to the  phytoplankton  increase only  have  of  for  not  sampling program.  presumed  to  size  of  with  D.  about  one  would a l s o Changes been  It i s  grazers was  present more  increased  size  data),  actually  nauplii.  imply  a  in  the  undetectable  is  also  thomasi,  quarter  therefore  classes  grazers  were not  number of  these  possible  c o n d i t i o n s would  noted. but  on  that  phytoplankton  i n the in  occurred  are  and  effect  Another  adult  the  competition  w h i c h was  explanation  shown  resources  in f e r t i l i z e d  case  Naupliar  supply, classes  an  net  When f e r t i l i z e r or  increased  a consistent  presence  Enclosures  If food  examination  nauplii  any  detectable  data).  grazers  indicating  phytoplankton  smaller  i n the  that  larger cladocerans  have  the  nauplii.  containing  decrease  in  nauplii.  oregonensis  enclosures  showed  the  unpubl.  in  consuming  and  showed  small  from  Krause  D.  the  probable  1978,  contained  fertilized  c l a s s e s which n a u p l i i  studies  from o t h e r  fertilizer.  alone  The  (Buckingham  competition  of  grazers  d i d not  capable  part  assemblage  size  of  between  nauplii  phytoplankton  d i f f e r e n c e between them,  survival.  These g r a z e r s  smaller  eat,  containing  for  s i z e s of  application  phytoplankton  grazing  in naupliar  smallest  the  larger  reduction is  by  r e s p o n s e on  to  production.  the  significant  l a c k of due  ate  This  of  the  reduction smaller with  difficult  my to  51  draw  any  however on  specific  i t appears that  naupliar In  summary,  predation  large  other  n a u p l i i had  intraspecific substantial  the  has  in naupliar by  naupliar  suggested  by  up  of  to be  that  has  in  tyrrelli  seemed t o  Diaptomus  Eunice  leptopus.  naupliar  not  also  possible from  been  to  and  Cooley  calanoid  by  D.  may found  affect Neill  have on  the  on  major  McQueen  .  that  inflict  of  (1969)  production  Landry  in  (1978b)  population pac i f i c u s ,  respectively. s u g g e s t e d as  there  affect survival.  primarily  a  f o r most  Calanus  however  that  eat,  (1977) f o u n d  account  thomasi  15%  a  sources  play  naupliar  been p r e v i o u s l y  mortality,  to  comment  to  minutus.  A c a r t i a tonsa, not  importance,  fertilizer.  suggested  the  and  survival.  non-competitive  t r i s p i n o s a could  18%  from  which n a u p l i i p r o b a b l y  Diaptomus of  its  seemed  zooplankton could  of  Lake  on  either  c o p e p o d s or  assessing  Confer  competition  working  in  enclosures  competition  calanoid  a p p l i c a t i o n of  eaten  54%,  naupliar  indication  and  food  Labidocera  Competition of  the  30%  P a r a c a l a n u s p a r v u s and  cause  competition  experimental and  thomasi  is  previously  mortality  that  mortalities  D.  mortality.  M a r i o n Lake c o u l d suggested  by  omnivorous  that  kenai  phytoplankton,  stimulated  predation  s o u r c e of  does have s u b s t a n t i a l e f f e c t  effects  existed  It  smaller  D.  largest  a s h o r t a g e of  Predation role  the  effect.  the  were not  the  i n the  grazers  predation  of  that  from  cladoceran  difficulties  importance  competition  i t appeared  from  Although  about  survival.  interspecific  since  conclusion  competition the  (in press),  has  a  major  been  some  Olenick from  naupliar  a l s o working  (1982)  Diaptomus stages  of  i n the  UBC  52  R e s e a r c h F o r e s t , has f o u n d can  limit  with  cladocerans  organisms  populations may  i n these  that competition  of r o t i f e r s  indeed  the  difficulties  enclosures  and  the  (i.e.  must  early  May,  near  D. t h o m a s i  .  the experimental  passed  into  naupliar not  probably become D.  kenai  factor  these  survival.  period,  by  carnivorous.  in  D. t h o m a s i  importance  to  both  depend t o some  extent  During  years  cooler remain  by t h e t i m e have  D.  Lake  season  interspecific year  to  nauplii  thomasi)  nauplii  the large had l i t t l e  in  the  lake,  was  start  to  proceeds,  importance  as  a  biomass  importance  i n c r e a s e , presuming  proportionally. and  more  The  competition  climatic  develop  i n t h e upper w a t e r column  on  they a r e  Both g r a z i n g  predation year  increases  since they  would  had  effect  and  in  of  copepodites  either  does n o t i n c r e a s e  when  the  period  i n c r e a s e and t h e r e f o r e t h e  on  up  changed g r e a t l y of  young  change  naupliar survival  productivity of  majority  competition  the  adult  of c o m p e t i t o r s  naupliar survival.  competition  Placid  Placid  reproductive  i n number and t h e r e f o r e  of  D. k e n a i  the  As  t h e number o f n a u p l i i  algal  the  would  not as v u l n e r a b l e t o  to  setting  the  low  S u r v i v o r s h i p of the  affected  decrease  on s m a l l e r  c o n d i t i o n s which occur i n  the  stage  changes  and  that  of  densities  the copepodite  greatly  effect  in of  and  accurately  the beginning Although  and  competition  The c o n d i t i o n i n t h e e n c l o s u r e s  D. k e n a i  fairly  during  occurred  dynamics  be c o n s i d e r e d .  reflect  rosea  that  from t h e e n c l o s u r e s  experienced  seasonal  low g r a z e r s , h i g h  probably  Daphnia  lakes.  both  community  suggesting  have a s i g n i f i c a n t  In e x t r a p o l a t i n g t h e r e s u l t s Lake  from  variation. slowly  f o r a longer  and  p e r i o d of  53  time,  D.  kenai  would  agent.  During  early  i n the year  when  and  the  However  and  Cannibalism  in  been  found  (Lynch heavily  t o be  which  rises  the  small  eats  and  on  nauplii  are  also  extremely  therefore  relatively  encounter  rates.  probably  decreasing  the  addition,  since  is likely at  i s the  to the  highest.  t o have an  mortality  effect  1980,  at  which  i n c l u d e d i n the are  and  controlling  column  for a  C.  known  community  1975).  night.  do  Placid  slow  swimmers  time  each  (Gerritson  not  this still  have  affected  abundance fish  i n importance  of  prey  of C h a o b o r u s  predators heavily  a  spatially  1979)  and  are  to  low  experiment  indirectly  competitors.  Polyphemus  unlikely  species  Nauplii  on C h a o b o r u s ,  fish.  would be  and  only  day.  the  naupliar survival  i n lakes with  L a k e and  in  prey  have  i n v u l n e r a b l e t o ambush p r e d a t o r s due inclusion  have  Chaoborus Lake,  Although  be  structure  Smaller  i t would p r o b a b l y  s h o r t p e r i o d of  to  americanus  N e i l l . 1 9 8 1 ) but  are  enclosure  s i n c e i t would o n l y o v e r l a p  The  in Placid  of  species resident in  nauplii  the  littoral  of  smaller organisms,  with  reduced  rise  reproductive period  Polyphemus  (Fedorenko  i s the water  effect  would  to  important  to n a u p l i i  were n o t  Peacock  nauplii  flavicans,  probably  the  Chaoborus t r i v i t t a t u s  capable  Neill  on  in  L a k e but  Larger  1979,  of  sources  B o t h C h a o b o r u s and  predators.  end  mortality  likely  competition  p r e d a t i o n would c o n t i n u e  potential  Placid  experiments.  a t the  a  reproductive period.  There are other present  as  w o u l d be most  of o l d e r c o p e p o d i t e s  intraspecific the  importance  increase rapidly,  particularly  ratio  throughout  more  warm s p r i n g s when c l a d o c e r a n s a r e  be more i m p o r t a n t . beginning  assume  by In  i t i s often is  to greatly  mainly affect  54  naupliar  the  limnetic  D.  From t h e p a t t e r n of  seasonal  dynamics  Lake,  survival  it  would  mortality  agent  community,  of  appear over  it  would  the  cannibalism although could  have an  other season.  1978a). Placid for  agent  have has  in  by  exist  adults. in  enclosure much  these  was  by  of D.  kenai  additional  early  from e i t h e r  ecosystems  lower  McQueen  in  larger  grazers  although  75-80%.  calculated  could s i g n i f i c a n t l y may  reported mortality rates.  a  account  the  Landry  accounted  that  25-30% of  results  survival  the  nauplii from  rates  from o t h e r affect  of  be  c a n n i b a l i z e d by  The  or  major  1969,  t h a t m o r t a l i t y of  that competition  factors  could  (1969) f o u n d  (1981) f o u n d  in  t h a t the p o p u l a t i o n  than  by  season  later  (McQueen  Lake  mostly  the  effect  t h o m a s i c o u l d be  approximately  indicated D.  kenai  Placid  is limited  substantial  at a l e v e l  experiments,  lower,  predation these  Lake  D.  i s some s u g g e s t i o n  However P e a c o c k  Placid  thomasi  i n the  Placid  important  been p r e v i o u s l y i m p l i c a t e d as  cannibalism alone.  the y e a r l y p r o d u c t i o n  a  aquatic  However t h e r e Lake may  by  in  i s t h e most  Therefore,  Competition  'could  Cannibalism  mortality  predation  effect.  nauplii  season.  . observed  that cannibalism  seem t h a t D.  -  thomasi  my  were  grazers  survival  f o r the d i s c r e p a n c y  and and in  55  CHAPTER 2 Results that  D.  kenai  D. t h o m a s i was  from e n c l o s u r e e x p e r i m e n t s could  nauplii.  predation.  be t o t a l l y was  substantially  Because  D.  both  collected also  were  from P l a c i d  ability  simulate spring  into  were  1.983.  the U n i v e r s i t y  of  the  used  for  In May,  A l l animals  D.  kenai  o f D. t h o m a s i  the  light  were  conditions 3.5  pipetted  after  equilibrate  for  experiments  a l l t h e a n i m a l s and  conducted  in  a  individually  pipetted  were were was water  controlled  unless otherwise  1 l a k e water 4  1  into  filtering 24  for  Lake.  identical  immediately  were  British  s e t t o 8 °C w i t h a 16:8 h l i g h t : d a r k  t h e day o f c o l l e c t i o n ,  a 54 jum s i e v e  k e n a i on n a u p l i i  Nauplii  a n d water  experiments  chamber  from  Lake.  from E u n i c e L a k e .  environment  of D.  In October,  Gwendoline  feeding  D. k e n a i  been assumed t o  i t s predatory  1982 and May,  obtained  from E u n i c e Lake  were c o l l e c t e d  On  influence  and methods  predation  i n October,  from  taken  All  the  Research F o r e s t .  collected  to  on  experiments  Columbia  this  methods  Experiments  the  indicated  this hypothesis.  Materials  conducted  of  1)  t h e s u r v i v a l of  k e n a i has p r e v i o u s l y  to substantiate  Experimental  influence  The p r o p o s e d mechanism f o r  herbivorous, confirmation  required  (Chapter  purple the  was  specified.  filtered  plastic  cycle  through  containers.  experimental  containers  was  completed  and  allowed  to  the  following  day  nauplii  were  h.  On  into  small  formalin-free  j a r s of  filtered  56  lake water.  Cyclopoid  specified.  The c o n t e n t s  experimental  containers  water then D.  within left  a total  24 ±  kenai  .  and t h e n  samples  15 m i n u t e s .  At t h e  end  from e a c h  added  to  immediately  were  later  dissecting  out the gut i n a drop of  microscope.  determine  contents  gut  was  Since  and t h e jar  was  remaining containing formalin.  50 X on a b i n o c u l a r remaining  o f some D.  kenai  water  number  of  were e x a m i n e d by  under  a  dissecting  under a c o v e r s l i p and t h e  t h e e x p e r i m e n t s were d e s i g n e d  possible  preliminary  d e n s i t i e s of a n i m a l s  series  decrease d i d occur containers  containers  A duration  of experiments when  but t h a t  probably  D.  kenai  the d u r a t i o n  have a s i g n i f i c a n t is  to provide  information  i n t e r a c t i o n s i n lake c o n d i t i o n s , a l l experiments  found a t l a k e c o n d i t i o n s .  effect  container  design  were c o n d u c t e d w i t h  not  the  squashed  a l l the  concentrated  under  were  examined.  Experimental  about  The  using  lake  15 m i n u t e s u s i n g a  a siphon  counted  The  within  time  appropriate  fixed  nauplii.  gut  to  this  experimental  the  microscope  filtered  The c o n t a i n e r s  of  jars  dissecting  contents  r i n s e d with  t h r o u g h a 54 ixm s i e v e u s i n g  animals c o l l e c t e d ,  These  of a b o u t  The water  otherwise  of a l l t h e j a r s were t h e n a d d e d t o t h e  were removed i n t o s m a l l  filtered  kenai  were a l w a y s used u n l e s s  and t h e j a r s  2 hours  406 Min s i e v e .  D.  nauplii  effect  naturally  of 24 h was c h o s e n  were  added  since a  significant  to  experimental  of t h e e x p e r i m e n t  (24-96 h) d i d  on t h e number  has been  were  i n d i c a t e d that a  due t o k e e p i n g D.  since there  which  eaten.  kenai  some e v i d e n c e  This  l a c k of  in relatively that  the  small  feeding  57  response  may  change  with  holding  Research Forest  lakes  (Buckingham,  24  since  this  h  was u s e d  though  one  started  between  A  complete  set  determine  of  experiments  the f u n c t i o n a l  5,  and  1250 p e r 100 1) were  field  experiments to  experiments. (25/100  1)  enclosure  t o go  Experiments  was  conducted  chosen. to  A  highest  was-  the Each  A  f o r background I found that  concerned  surface.  that  repeatedly  a surface,  found  chosen  was  approximate  of  375/  in 1  might  would whether  cages  made  be  per  density  1  container  used  i n the  4  only  times. to serve  trap  p r e y on  their  has  of  ( J o h n s t o n 1981,  been  observed i n calm  a s much a s p o s s i b l e  prey  nauplii  inflated.  (Fig.  12).  nauplii,  prey a g a i n s t a  o c c u r r e d , an e x p e r i m e n t  o f NITEX n e t t i n g  to eliminate  1250/100  and c o u n t i n g e r r o r .  on t h e m o r t a l i t y  trapping  1  the enclosure  I f D. k e n a i t r a p p e d t h e i r  artificially  100  a t the time  of  15 n a u p l i i  1982) and D. k e n a i  effect  densities  t r e a t m e n t was r e p l i c a t e d  mortality  they  Prey  density  D. k e n a i d i d , i n f a c t ,  comm.).  their  enclosures  designed  .  come up and h i t t h e s u r f a c e o f t h e l a k e  pers.  determine  1982 t o  N e o m y s i s have been o b s e r v e d t o do t h i s  J o h n s t o n and L a s e n b y  (Neill,  i n October,  density  c o n t a i n e r s were s e t up c o n t a i n i n g  was  always  density  density  The p r e d a t o r d e n s i t y  experiments.  After  were  (125, 250, 375, 625,  the naupliar  were s e t up.  the  which  as c o n t r o l s  using  allowed the containers  r e s p o n s e o f D. k e n a i  approximately  corresponds  I  than  10, 15, 25 and 50 n a u p l i i / c o n t a i n e r  corresponds  Four  shorter  cycle.  No t i m e  from t h e  1600 and 1800.  of  the  f o r animals  1978).  duration  light  time  In was  to  water  against  in  small  order  to  devised  The c a g e s  the area a v a i l a b l e  were to  58  the  D. k e n a i  nauplii. was  for  entrapment  by  allowing  T h e s e c a g e s were c o n s t r u c t e d  large  enough  to  enough t h a t D. k e n a i  be e a s i l y  an e s c a p e a r e a f o r  o u t o f 47 1 nm mesh  permeable  to nauplii  were u n a b l e t o p a s s t h r o u g h .  was t e s t e d b e f o r e h a n d and I f o u n d  that  while  p a s s t h o u g h , b o t h D. t h o m a s i  and D. o r e g o n e n s i s  therefore  the  Although volume  I  assumed  that  t h e c a g e s were c o n s t r u c t e d available  occurred  to  (1-1.5 1 ) .  similar-sized were added  the  cages  were  t o the cages  the  same i n c a g e s o f b o t h  surface  D. k e n a i  constructed  to test  were  divided  container  this hypothesis,  in  volume,  o f 54 Mm mesh.  Nauplii  trapped  sides.  at the  beginning  Twenty had  t h e impact  experimental  had  mesh  small  cages  was  mesh  cages  mesh c a g e s w i t h  remaining  5 had s m a l l mesh c a g e s w i t h 1 container  Twenty-five  the  were  water  contained  nauplii  enclosure  mesh  top  set  In  cages  of  up.  the Five  submerged, submerged,  surface  a water  water '  submerged and one  completely a  a  of p r e d a t i o n .  completely  had-large  used as a c o n t r o l .  below  containers  containers  4 treatments,  case  b o t h l a r g e and s m a l l  o f t h e w a t e r was j u s t  large  against  In t h i s  i n t o two g r o u p s : one c o m p l e t e l y  where t h e s u r f a c e  these  i n volume  l a r g e and s m a l l mesh, a s s u m i n g an even  would n o t o v e r e s t i m a t e  order  of  decrease  the  of n a u p l i i .  experiments  containers  also.  t h e a v e r a g e number a v a i l a b l e t o D. k e n a i  and not a g a i n s t  containers  not  decrease  , some r e d u c t i o n  was a l s o p o s s i b l e t h a t D. k e n a i  cage.  could  could  minimally  this  net s i z e  a d u l t s c o u l d and  nauplii  i n d e n s i t i e s such t h a t  the experiment,  distribution  to  To c o n t r o l f o r  of  It  smaller  but s m a l l  This  D. k e n a i  which  surface.  no D. k e n a i  and  5 5 the  In e a c h and was  were added t o c o n t a i n e r s  59  with  s m a l l mesh c a g e s and 3 5 n a u p l i i  with  large  available added  to nauplii  comparison  calanoid  and  experimental 8  with  up  containers  of c a g e s .  i n volume  A l l animals  cyclopoid  nauplii.  treatment.  c o n t a i n e r s were s e t up: 8 w i t h c a l a n o i d n a u p l i i  and  D.  kenai  Twenty-five  comparison  was  a similar  also  being  manner  cyclopoid  nauplii  used.  One  the o t h e r  g r o u p was h e l d a t 16 °C.  were  nauplii  on t h e p r e d a t i o n r a t e o f D. in  this  kenai 16  nauplii.  In  were  experiment  A  temperature  to  f o r the d i f f e r e n c e  of t h e c a g e s r e g a r d l e s s o f  o f each. t y p e .  container.  set  t h e two t y p e s  added  was done between t h e f e e d i n g r a t e o f D.  cyclopoid  containers  was  cages to c o r r e c t  t o the i n s i d e A  on  mesh  were  done kenai  not  added  to  3  were added t o e a c h on .  the This  effect  of  experiment  t o t h e p r e v i o u s one w i t h g r o u p was h e l d a t 8 °C  only while  60  Figure  12 D e s i g n  of e x p e r i m e n t a l  cages.  V eIc ro  I  .  18  cm  _ l  62  Results The  determination  of  the f u n c t i o n a l  showed a h i g h l y s i g n i f i c a n t .01)  with  analysis for  o f Y=  regression  (0.198 ±  72.8% of t h e t o t a l i s shown  controls  variation.  in Figure  associated  13.  with  o f D.  kenai  (F=93.678,  p  0 . 0 6 2 ( S E ) ) X - 0.514.  of v a r i a n c e showed t h a t t h e l i n e a r  equation in  an e q u a t i o n  linear  response  The  regression  calculated  There appeared  naupliar  < An  accounted  regression  t o be no l o s s e s  mortality  or  counting  error. The  linear  suggested the prey D.  i t was  number.  kenai  the  that  response  were  guts  of p r e y  in fact  although  the  to prey  p r e d a t i o n that caused  To c o n f i r m t h i s , examined  disappearance  majority  a decline in  the gut c o n t e n t s  and a n i m a l  of  ca.  r e m a i n s were f o u n d of  the  gut  density  25  i n 8% o f  contents  were  phytoplankton. When t h e r e s u l t s effect  of the experiments  t o examine t h e  of s u r f a c e s on p r e d a t i o n r a t e were e x a m i n e d , t h e r e was a  loss  i n c o n t r o l s a s s o c i a t e d with  and  handling error.  any  designed  additional  variance  was  experimental results  In o r d e r  naupliar  mortality,  to d i s t i n g u i s h  counting  whether t h e r e  l o s s e s a s s o c i a t e d w i t h p r e d a t i o n , an a n a l y s i s performed  on  treatments.  appropriate If  of each e x p e r i m e n t a l  these  sets  proved,  significant,  analysis  performed  eaten).  These  shown  i n Table  significant in  VI.  difference  data  An  ( number  analysis  of  variance  i n p r e d a t i o n between D.  s m a l l mesh c a g e s and t h o s e  the  c o n t a i n e r were s u b t r a c t e d from t h e further  are  of  of c o n t r o l s and  mean o f t h e a p p r o p r i a t e c o n t r o l s and any on t h e r e s u l t a n t  were  contained  in  large  results  showed  kenai  was  no  contained  mesh  cages.  63  Figure  13 F u n c t i o n a l densities.  r e s p o n s e of  Diaptomus kenai  to  naupliar  Number Eaten ( / 4 I )  65  This  result  trap nauplii situ  gives  uncaged  was p r o b a b l y  of p r e d a t i o n  D. k e n a i  significant container  a  treatments controls)  to  compared  those  and  rates  showed  either  no  A  obtained  comparison i n the f a l l  with  of r e s u l t s a l s o showed  A  those  of  reduction  in  r a t e s o f D. k e n a i on  cyclopoid  . and  t e m p e r a t u r e s were made i n above  (controls  subtracted significant  from  and  mean o f  difference  on c a l a n o i d v s . c y c l o p o i d n a u p l i i  P < .75) o r between d i f f e r e n t  .50).  rates  described  treatments  the i n  of e n c l o s u r e .  the  the feeding  predation  in  d e n s i t i e s a l s o showed no  that  and between d i f f e r e n t  These r e s u l t s  predation .29,  suggesting  between  manner  observed  n o t an a r t i f a c t  volume d i d n o t a f f e c t  similar  use s u r f a c e s t o  r a t e s o f c a g e d D. k e n a i  difference,  nauplii  effect  conducted at s i m i l a r  Comparisons calanoid  t h a t D. k e n a i  and t h u s t h e p r e d a t i o n  experiments  comparison  no i n d i c a t i o n  temperatures  obtained  (F = 1.23,  in (F = P  <  i n the s p r i n g t o those  no d i f f e r e n c e (F =  1.29,  P  <  .50). A  comparison  f e m a l e s and t h o s e comparison expressed Since  nauplii  showed  also  f o r males.  between  made  To i n c r e a s e  different  as p r o p o r t i o n  between p r e d a t i o n  prey  of n a u p l i i  sample s i z e  d e n s i t i e s , these eaten  per predator  t h e f u n c t i o n a l r e s p o n s e was d e t e r m i n e d  procedure  mean  was  did  consumed  for  not  introduce  bias.  The  rates for and  results are per  t o be l i n e a r mean  allow  day. , this  p r o p o r t i o n of  by f e m a l e s was 0.225 ± 0.105(SE, n=16) and  males  was  0.254 ± 0.137(SE, n=32).  no d i f f e r e n c e i n f e e d i n g  (F=.224, P > . 7 5 ) .  This  the  comparison  r a t e s between m a l e s and  females  T a b l e VI T h e e f f e c t o f s u r f a c e s o n D. k e n a i p r e d a t i o n on D i a c y c l o p s n a u p l i i . 471 mesh r e p r e s e n t s t h e l e a s t s u r f a c e a v a i l a b l e f o r e n t r a p m e n t . Numbers number o f n a u p l i i e a t e n i n 24 h.  47 1 f,m +water s u r f a c e  471  j,m  54 ^m +water s u r f a c e  54 »m  no  cage  15.5  6.5  9  9  2.7  8.5  6.5  5  2  7.7  10.5  4.5  5  9  8.7  5.5  6.5  4  5  2.7 10.7  Mean  8.0  6.0  6.0  6.3  6.5  A cage wi represent t  67  Discussion D. k e n a i  has  herbivorous (Olenick capable  in  been  the  1982),  coastal  and  of e a t i n g  previously  regarded  montane  Krause  lakes  ( i n prep.)  a wide range  of s i z e  has found  A r e c e n t study  of t h e m o u t h p a r t s o f D. k e n a i  the U n i v e r s i t y  of B r i t i s h  Columbia  D. k e n a i  has  mouthparts  typical  Diaptomus  species.  be u s u a l l y  a filter-feeder  particles  due  She  also  very  D.  the  suggested  that  algal  the  robust"  shoshone  larger has  to  large  lacks  algal  been  Gerritson  and  armature  (1980)  not l i s t  Krause  of  the  that  that  relatively  short period  suggestions. found  mortality  done a t e x t r e m e l y studies  (Table  However, s i n c e  very  small  and l a b i a l  setae.  of  capturing since i t  found  in  rates  of time.  low d e n s i t i e s  may  be  omnivorous.  D. k e n a i may be a p r e d a t o r  of  and  of experiments  D. k e n a i  seemed  calanoid  T h i s study  to  he  by E . produce  nauplii  over a  has c o n f i r m e d  o f D. k e n a i p r e d a t i o n  w i t h a s l o p e o f 0.20.  These experiments  these was were  when compared w i t h o t h e r f e e d i n g  V I I ) w h i c h may a c c o u n t this  i s l i k e l y to  Nevertheless, there  A series  T h e . f u n c t i o n a l response  t o be l i n e a r  other  for his classification  showed t h a t  large  for  maxilipeds  D. k e n a i  i t a s an o m n i v o r e .  extremely  that  t h e y may be c a p a b l e o f c a p t u r i n g some  has suggested  (unpubl. data)  showed  found  D. k e n a i  and s o f t - b o d i e d a n i m a l s .  indication  1982) from  stronger bodied animals  a l t h o u g h he p r o v i d e s no e v i d e n c e does  Forest  of the l a b r a l  they a r e  of phytoplankton.  D. k e n a i may be i n c a p a b l e  cells  cells  that  Vancouver  (Chapman  those  totally  that  and c a p a b l e o f i n g e s t i n g  density  but conceded  some  Research  Chapman s u g g e s t e d  around  classes  of  as  f o r the l i n e a r  s t u d y was s e t up w i t h  densities  response. that  were  68  found  in  probably linear  t h e l a k e and i n t h e e n c l o s u r e s ,  occurs  response  copepodites  and  Other  studies  r e s p o n s e when d e n s i t i e s were low.  linear  edax  naturally.  this  for  and t h e m a j o r i t y  done by J a m i e s o n Frost  D. t h o m a s i  (1974)  have  feeding  of feeding  that  at  studies  low  of response  also  Peacock  (1980b) showed a l i n e a r  found  type  found  a  (1981) f o u n d a on  T.  prasinus  on  Mesocyclops  response.  densities,  Ambler  the  feeding  response of the marine c a l a n o i d copepod T o r t a n u s d i s c a u d a t u s d i d not  differ The  significantly predation  from a s t r a i g h t  rate  found  0.20 a t l a k e d e n s i t i e s e x p r e s s e d eaten  per  feeding  higher  on  nauplii  with  however  this  influenced surprising water" declined  as the  proportion  This  recorded the  the  two  study, the  values.  there  was  predation  lower  s i n c e Buckingham  species  and  Calanoid  on  their  increased  VII).  feeding  feeding  studies  with  rates  rate  ,  temperature  This  result i s a  "cold  r a t e s on  seston  a l s o seemed t o be  taken  L o n s d a l e e t a l . ( 1979) f o u n d t h a t A c a r t i a  showed a much l o w e r p r e d a t i o n  for  and D. k e n a i  D. k e n a i  filtering  marine  recorded  that  nauplii.  predators  the  done  lacustris  It  above 8 °C.  and c y c l o p o i d n a u p l i i  same r a t e .  of  Most  (1978) c o n s i d e r e d  found t h a t  as temperature  end  indication  rates  nauplii  i s well within the  have been  no  of  for cyclopoid  predation  these  approximately  (See T a b l e  predators.  on n a u p l i i  was  rate  studies.  c a l a n o i d copepods, E p i s c h u r a  c o n s i s t e n t with In  rates  calanoid  calanoid predators  freshwater  the  for  study  day.  but c o n s i s t e n t w i t h  recorded  in this  f o r other  than p r e d a t i o n  zooplankton  are  per  rates recorded  is  rates  predator  line.  on  i t s own  nauplii  at  tonsa while  T a b l e V I I A c o m p a r i s o n o f p r e d a t i o n r a t e s o f c y c l o p o i d and c a l a n o i d c o p e p o d s on copepod n a u p l i i . A l l p r e d a t i o n r a t e s a r e e x p r e s s e d as p r o p o r t i o n of n a u p l i i eaten per p r e d a t o r per d a y . Where t h e r e s p o n s e was l i n e a r , t h e r a n g e o f v a l u e s o v e r w h i c h t h e r a t e was s t u d i e d i s shown. If the response was n o n - l i n e a r , t h e r a t e a n d d e n s i t y shown a r e t h o s e o f maximum s1 o p e .  Prey Dens i t y (1-')  Prey (NaupIii)  Predator  P r e d a t i on Rate  Reference  Acartia  c l aus i i  A. c 1 a u s i-i  500  . 38  Landry,  Acart i a  tonsa  A.  280 280  .06 .03  Lonsdale  280 280  .09 . 17  280 280  16 12  180  .05  McQueen  1-1.5  . 20  this  tonsa  (N1-3) (N4-6)  • i thona colcarva  (N1-3) (N4-6)  Scottolana canadensis  (N1-3) (N4-6)  Diacyclops thomas i  D.  D i aptomus kena i  D i acyclops thomas i  Epi s c h u r a 1acustri s  D i aptomus s i c i1 i s  Mesocyc1 ops edax  calanoid  Tortanus di scaudatus  Ca1 a n u s p a c i f i c u s N3 N5  *  - rates  thomasi  nauplii  measured a t one d e n s i t y  only  1978a e t a l . 1979 *  1969  study  60  . 28-.55  Confer  6-50  .06-.09  Jamieson  20 50  . 55 . 78  Ambler  and B l a d e s  1975 *  1980  and F r o s t  1974  70  Jamieson  (1980b)  found  cyclopoid  nauplii.  different  temperatures  study  may  be  treatments This  The  due  because  variability  that  M. edax  similarity  and  to  my  of  the  i s common  preferred of  predation  d i f f e r e n t prey inability large  to  types  i n many s t u d i e s  to  rates  found  at  in this  distinguish  variability  between  i n the r e s u l t s .  of c r u s t a c e a n  1978, L a n d r y  may r e f l e c t  p h y s i o l o g i c a l d i f f e r e n c e s among i n d i v i d u a l a n i m a l s .  majority  that  the  1969,  Confer  1981). capture  predation  rate  dry  weight  larger  are  it  of  1974,  view  t o look  daily  of c a l a n o i d  the c y c l o p o i d  the prey p o p u l a t i o n  ration.  copepods  in in  copepods.  little  has a s m a l l e r  i s that  chance of being  the higher  From t h i s  this  Table  more  standpoint  way, VII  the large are  copepods l i s t e d  easily  there are  However when t h e d y n a m i c s  From t h e p r e y ' s  d i f f e r e n c e why t h e p r e d a t o r  sole consideration  Peacock  requiring  examined, these  i n t e r e s t i n g but i r r e l e v a n t .  found  (McQueen  1980,  of  and  r a t e s as the p r o p o r t i o n of  viewed  a r e being  animals  Wong  result  1981)  have  of the predator,  at predation When  predation  on s m a l l e r  s i n c e most o f t h e c a l a n o i d  than  makes v e r y The  and F r o s t  p r e y may be a  consumed.  rates  copepod  i s higher  point  of small  on  t o make up t h e i r  explainable  of  the  may be u s e f u l  predation  rate  1971, Ambler  From  individuals it  of s t u d i e s  1980b, P e a c o c k  feeding  (Buckingham  The  1978, J a m i e s o n  calanoid  acts  considerations standpoint, i t as  i t  does.  a s an i n d i v i d u a l becomes l a r g e r , eaten.  71  GENERAL DISCUSSION Food  limitation  potentially Diacyclops Lake  important thomasi.  using  strong  due and  .  cannibalism  dynamics  the of  into  the  With  and  these  these  a scenario' for the s h i f t  Lake  trout  were  Andrew, p e r s .  introduced,  in  univoltine. years,  juvenile  to P l a c i d  Lake,  suggested  that  t h e whole  by  is  season  D. k e n a i  and  a substantial  reproductive now  community  period,  possible  to  structure  in  particularly  Several  "carrying  years  i s probably  (Hume  after  due  on D. k e n a i 1978).  vulnerable  I n 1978, a f t e r  D. t h o m a s i  their  D. k e n a i  began t o a p p e a r  to  had  a r e now  trout  D. k e n a i  declined  where  t h e t r o u t were  they  predation  i n regular  i n 1974  capacity"  rare  predation  , particularly  The to  Lake  t o the p o i n t  began t o d e c r e a s e u n t i l  This decline  and s p r i n g  i n t o Eunice  increased  t o be a t  t r o u t a r e known t o p r e y  be  over  i t  introduced  comm.).  D. k e n a i  the l a k e .  would  by  (Fig 1).  (J.  winter  Placid  predation  of  results  the  results,  in  food  survivorship  of  s u r v i v a l of  that  assemblage e x e r t e d  end  be  by a d u l t D. t h o m a s i had  predation  grazing  to  revealed  consideration,  interspecific  c a n now be c o n s i d e r e d  the  naupliar  interspecific  1975 (Hume 1978) and have s i n c e  since  considered  experiments  predation  on  they  in  enclosure  Extrapolation  from  Cutthroat and  effects  both  respectively.  Eunice  the  competition,  a t the beginning  construct  affecting  was t h e major m o r t a l i t y a g e n t  competition effect  in  intraspecific  seasonal  although  were  In s i t u  to  negative  D. t h o m a s i taking  predation  n a t u r a l d e n s i t i e s of zooplankton  limitation D. k e n a i  and  during  population since for  zooplankton  it  is  several samples  72  in  consistent  winter.  Before  occurred  in  remained These are  low  their  decline,  capable  of  that  combined  kenai  E u n i c e Lake to the zooplankton  was  fertilized  of  Daphnia  continued  lake  late  the  i n the  previous  and  naupliar  D.  of  increase that  of D.  in  thomasi rare  the  summer.  Lake  in  D.  thomasi D.  kenai the  until  almost  increased  reduced  Lake  warm and  number  disappeared  in  biomass  while  1980-1981 was  assemblage  greatly  kenai  upstream Gwendoline  increase kenai  time.  survival,  extremely  in Eunice  winter  of  knowledge t h a t D.  was  The  increased  explanation  with  releasing  months  period  it  thomasi  was  they  where  grazing  s p r i n g and  possible  sediment. been  the  i n P l a c i d L a k e and  population  1979,  early had  the  i n number  D.  Eunice  limited  In  and Lake  influencing  i n E u n i c e Lake d u r i n g  community.  warm w i n t e r  well,  the  r e s u l t e d i n an  The  in  fall  it  entirely  in  density  i n number compared  to  years.  One The  this  increase  lake  with  samples.  froze.  dominated  had  point  to d e c l i n e .  never  from t h e  rosea  to  continued  and  kenai  late  f o r a much l o n g e r  substantially D.  D.  the  d e n s i t i e s than  water column  observations,  regular  numbers d u r i n g  much h i g h e r  i n the  suggest in  but  by  previously  nutrients  released  increased.  D.  lengthen  its  (Peacock  1981).  open water a l l o w e d  into  level  f o r these events  of  the  water  nutrients  wind  column i n the  to  sediment  fertilization  w h i c h had  in  an  lake  into  thomasi  the  water  i s known t o  reproductive Increased  naupliar  and  follows. the from  had  occurred  therefore  production  to  the  fifteen  i t s clutch size  i n response  lake  probably  column were p r o b a b l y  increase  period  mix  nutrients  the  upstream  i s as  the also and  fertilization combined  with  73  increased D.  survival  kenai  and  due  reduced  to reduced  interspecific  competition  probably  responsible  Cyclopoid  c o p e p o d p r e d a t o r s have been  attack  smaller  prey  1975,1978, J a m i e s o n their  spring  copepodites  not  in  been  to  1979,  by  warm  Findley,  examining  congeneric found  abundance  of  D.  variation  in  the  explanation  for  cannot the  The  the s m a l l e r  be c o n f i r m e d ,  and  they  began  neonate the  idea  cladoceran  from  in  cool  spring  the  lake,  . with  what would have  D.  kenai D.  thomasi .  been  although i t  level  in  if  the  appears  k e n a i has and  also Litt  o c c u r r e n c e of Diaptomus year  to  year  nauplii  of  concluded  but  adults.  that  were t e m p o r a l l y s e p a r a t e d .  Eunice  Some p o s s i b l e  phenomenon b u t , a f t e r  since  Fernando  Cladocera  dominant  Pederson  abundance  of both organisms,  and  present configuration  that  by  large  cycles  preferentially  a t a much lower  franciscanus  this  on  winter  i t appeared  Washington.  ,  the  .  persist.  limitation  the  kenai  should  to  thomasi  have been enough D i a c y c l o p s  thomasi  cool.  were  Brandl  probably hastened D.  grazers  i n e d i b l e Holopedium gibberum  p r e d a t i o n from D.  population  D.  levels  found  impact  in  from  i n c r e a s e i n D.  time  may  effect  shift  of a  s t a b l e and  limited  Lake  this  other  1969,  the  there  the  increase  had  Prior  for  By  would have e q u i l i b r a t e d  relatively  was  by  nutrient  gradual  probably  and  Although  combination  increased  spring  1980b).  r o s e a t o the r e l a t i v e l y  The  a  large  t o have a s i g n i f i c a n t  supported  Daphnia  the  (McQueen  increase,  cladocerans. is  for  from  predation  they  been  evidence found i n  (1976),  in  relatively  not  the  little  offered  examining did  in  franc iscanus  variation  They  lake  the  no life  compete  However, e x a m i n a t i o n  of  74  their  life  reach D.  cycles reveals  peak  densities  franciscanus  variation from D.  kenai  The probably  almost  entirely  occur  of  to  are:  the  food  that  to  of  time  explanation  thomasi  by  as  for  the  predation  animals  adult.  (2)  adults  by  that  Polis  to  The  in Eunice  cannibalism  feed  on  seem t o h o l d  food  resources  Lake.  carnivorous  that  for this  McQueen while  to  inaccessible  resources  (Polis  by  resources  immature a n i m a l s and  adult population  in Eunice  incidence  availability  required conditions on  is  have  carrying capacity  transform  feed  may  large  food  Lake  (1981) s u g g e s t e d  previously unavailable  t o the  and  the  low  population  immature a n i m a l s  limiting  thus  and  (3)  1981).  These  (1969)  found  nauplii  are  known  herbivorous. Eunice  Lake t h u s a p p e a r s t o have s h i f t e d  attraction"  configuration predation  by  mediated  by  vertebrate delayed the  D. by  the  a d u l t s were c o m p l e t e l y  t o be  of  the  incorporate  conditions  of  limited  increase  adults;  is  copepodites  is limitation  (1975) s u g g e s t e d  immature  (1)  indirectly  and  period  One  i t s carrying capacity  Fox  can  unavailable  adults  same  nauplii  r a t e s of c a n n i b a l i s m .  cannibalism making use  the  present.  population  increased  increase  kenai  .  of c a n n i b a l i s m . may  are  abundance of  current  actually  during  nauplii  i n the  t h a t D.  D. D.  to  another.  thomasi kenai  a decrease predation  competition  fertility  of  D.  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SET UP OF ENCLOSURES  Zooplankton The that  count  proper  data  set-up  achieved.  of  those  t o which  in  average  question  effect  were  done between  h a d been added  i t had n o t . of the  (eg.  experimental  been  populations  (i.e.  grazing  the middle  added  and  )  t h e l a k e were between  the  the stocking density.  i n t h e upper  fertilizer  the  The  behaviour  2 m of the l a k e w i t h  of those  t h e same c o n d i t i o n s a s t h o s e o f  absent  and D. t h o m a s i  assemblage p r e s e n t ) .  , D. k e n a i  T h i s comparison  and end o f t h e e x p e r i m e n t a l  period.  and  was made a t  A l l comparisons s a m p l e s were  s m a l l t o a l l o w an a c c u r a t e measurement o f l e n g t h f o r b i o m a s s  calculations.  Diacyclops  D. t h o m a s i those  These c o m p a r i s o n s a r e summarized  i n T a b l e V.  thomasi  Analyses  .001  been  D. t h o m a s i  were made u s i n g n u m e r i c a l , d e n s i t i e s s i n c e e n c l o s u r e too  had  enclosures to  period  o f e n c l o s u r e was e x a m i n e d by c o m p a r i n g  lake  the  those  Comparisons with  t h e e n c l o s u r e which c o n t a i n e d  the  conditions  d e n s i t y of a l l e n c l o s u r e s t o which t h e treatment  had  zooplankton in  experimental  treatment  made a t t h e b e g i n n i n g initial  the  Comparisons  which a p a r t i c u l a r and  o f t h e e n c l o s u r e s were examined t o c o n f i r m  of  adults  without  variance  of  between  the  treatments  showed an e x t r e m e l y  i n a l l b u t one c a s e ,  difference  in  numbers  of  c o n t a i n i n g D. t h o m a s i a n d  significant difference  P < .005 i n t h e f i f t h  sampling  (P  <<  period)  85  that  was m a i n t a i n e d  2-way the  analysis  2 factors,  effect  of  either  time  This  to  or  cycle lake  held  significant  data,  (P  with handling  overwintering  D. k e n a i the 3  statistical captured  D. k e n a i  difference  compared  i n enclosures  i n c r e a s e d t o 50% a s  appeared  sampling  with a  to  be  mortality  period  and  i n the  thereafter  t h e i n c r e a s e i n t h e l a k e was a s s o c i a t e d and e n t r y  increasing  into  t h e water column o f  difference  between  the  i s expected.  capture  analyses  occurred  If perfect  capture  c o u l d be e x p e c t e d efficiency  time  d u r i n g the experiment  been a d d e d .  swimmers.  and  never  Visual  done  on  i n very  t o be c a u g h t  every  captured  low  than  this  numbers  of  densities  in  i s assumed,  i n each  However, D. k e n a i from  the  efficiency  i s much l e s s  strong  added  were  s i n c e they  are  been  When  time.  kenai  enclosures.  fact,  period.  s i n c e t h e numbers o f D. t h o m a s i  the  l a k e and t h e e n c l o s u r e s  and  when d e a l i n g w i t h a n i m a l s  There  of diapause  animals,  e f f e c t s of  treatment  o f a d u l t D. t h o m a s i  the f i r s t  Since  extremely  between  the experimental  rose.  after  an  .001) b u t i n s i g n i f i c a n t  a t s e t - u p and t h i s  the breaking  No  <<  interaction  than  i n the lake  Diaptomus  showed  the d e n s i t i e s  constant.  with  results  i s t o be e x p e c t e d  bags d e c r e a s e d  When a  the  longer  associated  period.  and t i m e a s  the  were 25% lower numbers  the experimental  o f v a r i a n c e was done u s i n g t r e a t m e n t  treatment  result  life  throughout  sample.  since  only In  D. k e n a i  was c a p t u r e d  a t some  e n c l o s u r e t o which  i t had  from  i n s p e c t i o n a t each  those  t o which  sampling  i t had not  period  assured  86  that  D.  kenai  were  present.  the  last  .22  / l w h i c h were o r i g i n a l l y  Grazing  sampling  still  p e r i o d gave an  almost  the  entirely  the  species  were  quadrangula  i t s size,  to  the e n c l o s u r e s  was  oregonensis . (P  showed  <<  .001  treatments  without  treatment  both  The due  t o be  and  .  These  l o n g i r o s t r i s,  pediculus  were  found  in enclosures Polyphemus  wide-spread,  p i c k e d up  with  occurred  albeit  to i t s small s i z e .  low  Because  in a pipette  l o o s e eggs a r e more l i k e l y  Analyses  between  analysis  grazers.  Diaptomus  gibberum Bosmina  seemed t o o c c u r  i s probably  and  species:  to pass  and  through  sieve.  differences  those  / l compared  oregonensis  thomasi  .005)  detail. Polyphemus  i t i s more l i k e l y  undetected  D.  three  g r a z e r s whereas C e r i o d a p h n i a  the n a u p l i u s  D.  .07  l a k e and  Holopedium  in and  Bosmina  of Bosmina  Diaptomus  of  r o s e a and  more i n e n c l o s u r e s w i t h density  up  examined  infrequently. without  made  Daphnia  Ceriodaphnia  remain  of  added.  g r a z i n g b i o m a s s of b o t h  oregonensis,  of  estimate  during  assemblage  • The  and  R e p l i c a t e sampling  for  a of  except  similar  pattern  variance  showed  f o r sampling  (P <<  .001)  and  the  effects  interaction  term  of  significant  assemblage  the experiment.  of v a r i a n c e showed s i g n i f i c a n t  that  p e r i o d 5 where P <  c o n t a i n i n g the g r a z i n g  t h e d u r a t i o n of  to  of (P <  and  A two-way both .01)  time, but  the  87  F  of the t r e a t m e n t  term  was  15 X a s l a r g e  = 168.16, F t i m e  = 10.24) i n d i c a t i n g  was much l a r g e r  than  that  D. o r e g o n e n s i s  were  80%  of t i m e . lower  variable  in  density.  In  densities  were a p p r o x i m a t e l y  t h e end o f t h e e x p e r i m e n t ,  higher  the  of time  treatment  (Ftrt effect  When compared t o l a k e d a t a ,  in density  the b e g i n n i n g of the e x p e r i m e n t a l  at  that  as t h a t  period  i n the e n c l o s u r e s at and  were  much  more  the middle  of the sampling  period,  50% o f t h o s e  i n the lake.  However  densities  s i n c e most D. o r e g o n e n s i s  i n the  enclosures  i n t h e l a k e had moved  t h e w a t e r column and n u m e r i c a l d e n s i t i e s  i n the  lake  were  lower i n had  also  decreased.  Daphnia  rosea  Daphnia  also  showed  between t r e a t m e n t s the  entire  differences < .01  was  A two-way a n a l y s i s  effect  of treatment,  although the i n t e r a c t i o n  < .001), to  be  spring steady Those the  two terms  Ftxt  = 3.42  expected  increase  in  i n the lake a l s o lake  peaked  (P < .001  the  number  Ftime  The s i g n i f i c a n c e  enclosures  The D a p h n i a  i n the  during  the  showed an i n c r e a s e  during  in 3 cases,  of v a r i a n c e a g a i n  (P < .001),  the middle  for  of the P  showed  t i m e and t h e i n t e r a c t i o n  = 111.94  (P < . 0 1 ) ) .  growth phase.  grazers  was an o r d e r o f m a g n i t u d e s m a l l e r  (Ftrt  since  without  differences  although the s i g n i f i c a n c e  i n g e n e r a l n o t so g r e a t  in 3 cases).  other  significant  w i t h g r a z e r s and t h o s e  experimental period  significant  the  consistent  term than  = 30.33 (P  of  time  is  were s e t up d u r i n g t h e enclosures  showed  experimental although  period.  numbers  of the e x p e r i m e n t a l  a  in  period  88  rather in  than  the  but  end.  enclosures  difference eggs  at the  in  The  after  Holopedium  at  the  end  were  were  case). effects <  .001,  The  again  (P < A  .001  lower of  this  overwintering  experimental  period  period.  although  of  the  the  and  of the  treatment  than  those  variance  was  showed a peak of abundance a t period.  The  Holopedium  D e n s i t i e s i n the  the e n c l o s u r e s a f t e r were a c t u a l l y  set-up 30%  higher  .05  the  in  1  significant  the  i n the  of  lake also higher  P  largest.  the middle  became a l m o s t than  by  term, a l l w i t h again  l a k e were 25%  but  P <  and  These  shown  showed  interaction effect  with  experiment.  P <.025 i n 1 c a s e ,  analysis time  manner t o D a p h n i a  between t r e a t m e n t s  significant  in 4 cases,  two-way  pattern.  peak and  of t h e  similar  differences  less  of t r e a t m e n t ,  experimental  in  from  experimental  in a f a i r l y  -consistent  Holopedium  this  the  33%  magnitude  recruitment  g r a z e r s d u r i n g the c o u r s e  once  copepods  of  the  was  gibberurn  Holopedium behaved  without  with  and  l a k e d u r i n g the m i d d l e  became e q u a l  There  set-up  i n c r e a s e d t o 90% the  d e n s i t y of D a p h n i a  showed  than  equal  the  at  lake d e n s i t y at the  those the end.  Naupli i The sampling  densities period  differences between t h o s e  to  between  of  nauplii  check  setup  treatments.  treatments  were  without  examined  densities No  a d u l t D.  at  and  differences thomasi  and  the  first  check  for  were  found  those  with  89  (ones where n a u p l i i In  contrast  the  to  average  were  theoretically  the o t h e r z o o p l a n k t o n  density  significantly density)  c o u l d have  of  nauplii  different  (z = -.43,  cyclopoid  p =  (D.  from .33).  enclosures  stocking  density  Approximately  thomasi)  and  recruited).  added t o t h e e n c l o s u r e s ,  in  the  been  the  50%  rest  was  not  (i.e.  of the were  lake  nauplii calanoid  (D. o r e g o n e n s i s ) .  Phytoplankton  Fertilizer The  effect  e n c l o s u r e s was a.  This  by c o u n t s  supplemented  periods,  period  food  and  g r a z e r s was  after  the  had  a has  The  bags  had  previously  and  been  been u s e d  (Marmorek  1983)  c o n s i d e r e d to  second  of  the  virtually  the  t o the  and  that  taken  fertilizer.  (Daley  a.  before  the Live  available  phaeophytin a  1973,  a  can Daley  however, t h e d e n s i t y most o f t h e  be  identical  chlorophyll  as a measure o f since  two  first  s a m p l e s were  filled  experiment  i t seems l i k e l y  was  total  or d i g e s t e d c h l o r o p h y l l In t h i s  the  t o be  since  to respond  for  results  a and  expected  a chance  1973). low  time  growth.  what was  of degraded  Brown  this  a, p h a e o p h y t i n  f o r zooplankton  consist  classes  showed a l l t r e a t m e n t s  exactly  phytoplankton  size  since  naupliar  chlorophyll  chlorophyll  i n the  abundance was  of p h y t o p l a n k t o n  immediately  phytoplankton  e s t i m a t e of p h y t o p l a n k t o n  sampling  is  the  chlorophyll  for  This  on  t h e amount o f  critical  live  fertilizer  e s t i m a t e d by m e a s u r i n g  experimental  in  of  of  phaeophytin  90  measured was d e g r a d e d true  for  those  rather  cases  enclosures.  Some  in enclosures  These  results  phytoplankton maintain  this  in  of  high  the  chlorophyll  classes  and  in  period,  difference  was  in  2-5 Mm, no  inedible  P  if  unfertilized  in  .005)  food,  measure  biomass  second same  not the  be  total  of  found  food  between  (r = .76).  of the  between  This  phytoplankton  of v a r i a n c e  sampling  period.  analysis  showed  showed a  fertilized  In a  m e n t i o n e d above  an  and  the t h i r d significant  did  inedible  enclosures  were  there  chlorophyll.  Total  measure'  of the i n c r e a s e  enclosures  was  not  due  seem  algae not  (P < .05  ), a l t h o u g h  effective  majority  This large  the  phaeophytin i n  was a l s o  Analyses <  rate with  as  better  algal  the  few d a y s and t h e n  available a  present.  caused  Since  d i f f e r e n c e i n the l i v e  in fertilized  differences  were  t h e a b u n d a n c e s o f t h e same s i z e c l a s s e s  would  algae.  be  the  i n t h e 2-5 /xm, 5-9 nm, 9-13 um and 13-18  the  significant  availability  was  correlation  P < .001 i n o t h e r s  chlorophyll  biomass  and  (  Mm  sampling  the f i r s t  to  i n phaeophytin  fertilization  senescent.  VIII).  enclosures the  added  nauplii  by t h e e x a m i n a t i o n  (Table  unfertilized  in  being  total  difference  classes  were  i s especially  increases  only  that  The g r e a t e s t  i s supported  significant  which  probably  chlorophyll  sizes  largest  This  b i o m a s s b u t grow a t a slow  cells  would  availability.  conclusion  grazers  t o grow r a p i d l y d u r i n g  c a s e was n o t d i g e s t e d  total  no  the  suggest  a fairly  majority  where  of  occurred  than d i g e s t e d .  to to  of  in  phytoplankton  an  increase  be t h e c a s e .  between  significant  food  fertilized  in The and  i n t h e samples  91  examined  (F < 1 ) .  and  unfertilized  an  result  held  Visual  until  the  second  .025) s a m p l i n g significant  significant  (F  <  from a  to  differences  fertilized  indicate  there  differences  chlorophyll  treatments  from  in  live  .001) and s i x t h  However,  .025)  and t o t a l  unfertilized  seemed  = 136.4, P <<  periods.  (P  phaeophytin  enclosure  of d a t a  that  t h e end of t h e e x p e r i m e n t a l p e r i o d .  of v a r i a n c e showed in  inspection  were  chlorophyll (F = 6.4,  the  in  the . second  Analyses  consistent  between  present  this  and  amount  of  fertilized  sampling  P <  and  period  on  (Table I X ) . In  summary,  chlorophyll Live  and p h a e o p h y t i n  chlorophyll  second  and  the s i z e  Grazing The  was  sixth  significantly in  fertilizer  from  sampling  2-18  periods.  only  Phytoplankton and t h i r d  total  period  on.  during  the  biomass  was  sampling  periods  fim. .  assemblage phytoplankton  hypothesis  with n a u p l i i difference  data can a l s o  was  that  f o r food, in  impact  be e x a m i n e d t o d e t e r m i n e i f  on t h e f o o d a v a i l a b l e .  i t i s important  available  food  in  t o show t h a t  chlorophyll  (Table X),  way  of  treatments  analyses  c o n t a i n i n g the f a c t o r  sampling  period,  compete  t h e r e was  a  e n c l o s u r e s w i t h g r a z e r s and  When t h e t o t a l  two  Since  t h e g r a z i n g a s s e m b l a g e might  those without.  second  sampling  increased  i n c r e a s e d i n the second  range  increased  the second  significantly  g r a z e r s had a s i g n i f i c a n t the  significantly  c o n t e n t was  variance,  of i n t e r e s t ,  fertilizer  which showed  increased  examined  pools a l l that the  i n the total  c4  cr Table VIII as „g/l.  Effect  of  fertilizer  Live  S a m p l i ng ir i od  Chlorophyll No F e r t ii 1 i z e r F e r t i 1 i z e r  on  chlorophyll  content.  Phaeophytin No Fert i1i zer Fert i1i zer  Chlorophyll  content  Total  is  Chlorophyll No Fert i1i zer F e r t i l'i z e r  1.  0. .836  0. .844  0 .511  0. .493  1 . 336  1 .337 .  2  3 .. 367  0. 969  1 .413  0. .484  4 .675  1 .453 .  3  1 .004 .  0. 538  2 .046  0. .433  2 .962  0. .972  4  0. .910  0. .411  1 . 574  0. , 323  2 . 323  0. .734  5  0. .928  0. . 185  2 . 328  0. .618  3 .035  0. .803  6  2 .. 168  O. . 356  2 .678  0, ,606  4 .097  0, .948  expressed  93  Table  IX Effect A l l biomasses  of f e r t i l i z e r on p h y t o p l a n k t o n s i z e a r e e x p r e s s e d as Mg/1. Sampling 2  Period  Sampling  3  classes.  Period  Size classes  Fertilizer  No Fertilizer  Fertilizer  < 2 y m  7.6  9.3  6.0  7.5  4.7  15.2  4.4  16.1  2 - 5  Mm  No Fertilizer  5  -  9 Mm  40.6  79.0  27.4  83.3  9  -  13 Mm  43.3  106.8  22.9  107.1  13  -  1 8 Mm  23.3  60.9  12.4  78.0  >  18  12.8  24.1  10.0  13.1  94  chlorophyll  (F = 148.8, P «  continued (P < .001 grazers third  t o be s t r o n g u n t i l except  sampling  significantly sampling  t o t h e end  sampling  period,  that  (F = 8.0,  P  decreased  <  .005).  size  classes  10.9, P < .005)  and  5-9 the  g r a z e r s had a s i g n i f i c a n t 50.5, P <  .001) .  P <  P  <  fertilizer  .025) and t h i s  between  period  .005),  chlorophyll  experiment.  sampling  period size  fertilizer  however  d u r i n g the effect  also  the  fifth  During  and g r a z e r s  presence Mm  (F = 17.4, P<  classes  .001) and of  grazers  effect  between  on t h e s i z e  .005).  5-9  13-18  showed jum (F =  ixm  (F  =  significantly  (F = 61.1, P < .001),  interaction  effect  (Table XI)  increased size classes  (F = 22.4, P < The  of  P <.025) and t h e i n t e r a c t i o n  significantly um  where  the t o t a l  of p h y t o p l a n k t o n  65.7, P < .001) 9-13 11.0,  the  d u r i n g the l a s t  fertilizer  4  the i n t e r a c t i o n  became s i g n i f i c a n t  Examination  period  (F = 7.6,  of  The e f f e c t  t h e end o f t h e e x p e r i m e n t a l  decreased  period  continued  increased  .001).  Mm  (F =  fertilizer  and  classes  9-13  5-9  nm  (F =  95  Table  X Effect of- f e r t i l i z e r a n d g r a z e r s on t o t a l content. C h l o r o p h y l l i s shown a s Mg/1.  Sampling Period  No Fertilizer or ' Grazers  chlorophyll  Fertilizer  Grazers  Fertilizer and Grazers  1  1.374  1.394  1.299  1.278  2  1.535  5.197  1.370  4.153  3  1.245  3.402  0.698  2.521  4  1.021  3.129  0.447  1.517  5  0.931  4.138  0.674  1.931  6  0.842  5.870  1.054  2.3231  96  T a b l e XI E f f e c t classes.  Size  of f e r t i l i z e r and g r a z e r s on p h y t o p l a n k t o n A l l b i o m a s s e s a r e e x p r e s s e d as Mg/1.  Classes  No Fertilizer or Grazers  Fertilizer  Grazers  size  Fertil and Graze:  <  2 Mm  5.8  6.3  6.3  8.8  2 -  5 Mm  5.8  17.8  3.0  14.5  5 -  9 Mm  39.0  114.5  15.8  52.0  - 13 Mm  37.0  1 45.3  8.8  69.0  - 18  Mm  20.5  75.3  4.3  80.8  18  Mm  5.0  15.0  15.0  11.3  9 13  >  97  APPENDIX B.  EVALUATION OF METHODS FOR CALCULATION OF SURVIVORSHIP  Since  the  enclosure  analysis  of  t o determine  their  Duration Estimates  of  the  critical  to  the  duration  of  stages  composition The  effect  (Auvrey  rapidly in  of v a r i o u s  1976,  increases  the  literature  increases  are  Increasing  developmental also  Jacobs  and  whether  1979,  rate. this  (Landry  (Munro  or  whether  the developmental  and  Dussart  1980a) a n d  1966, S p i n d l e r  1971).  to increase the  Increasing rate.  these  Some a t t e n t i o n  (Auvrey  appeared  often  i s proportional  1973, J a m i e s o n  1971).  1979,  i s some d e b a t e  1974).  (Auvrey and D u s s a r t  (Spindler  1974, L a n d r y  temperature  increase 1975)  rates  Sarvala  There  has  reports  developmental  1971, Munro  to the q u a l i t y of d i e t  seemed t o i n c r e a s e  o f age  development  Increasing  i n t e n s i t y and d u r a t i o n  rate  The  estimates  Most o f t h e s e  Bowhuis  1980).  history  of l i g h t  light  static  on  Spindler  1970, W h i t e h o r s e and L e w i s  to the e f f e c t  estimates.  f a c t o r s on n a u p l i a r  disproportionate  a l s o been g i v e n Smyly  between  stages a r e  and i t s d y n a m i c s .  1966,  about  were  reliability.  naupliar  survival  the developmental  the l i f e  1966,  of  the  of temperature  1980a, V i j v e r b e r g  throughout  has  tothe  stages  i n the l i t e r a t u r e .  Dussart  George  of  i s the l i n k  the e f f e c t  and  Jamieson  duration  calculation  reported  investigated  b e h a v i o u r and  of n a u p l i a r  i n a population  well  1975,  was c r i t i c a l  e x p e r i m e n t s , methods o f s u r v i v o r s h i p c a l c u l a t i o n  investigated  been  survivorship  food q u a l i t y Some  species  98  seemed  more s e n s i t i v e  m i x t u r e s of quantity  food a l s o  has  also  copepods.  than  seemed t o p r o d u c e  been  found  Weglenska  concentrations significantly  of  better  to increase  (1971)  natural  increased  graciloides.  o t h e r s ( A u v r e y and D u s s a r t  that  from  the developmental  Klekowski  and  results.  a  Shushkina  of  c o n c e n t r a t i o n s of a  single  although  there  increase, Mesocyclops  relatively the  range  insensitive  of  estimating  these  factors  developmental  temperature  i s important  previously  significantly the  to d i f f e r e n c e s  working  with  found  that  source  albidus  i n food c o n c e n t r a t i o n over  results  rates  of  i n my  little  ones.  However,  development  rates,  of e n c l o s u r e s w i t h  significance  enclosures.  o n l y when c o m p a r i n g  reported  influences  are  The  thomasi  in  the  method o u t l i n e d reproduce  over a d i s c r e t e  of  developmental  each  abundance. the  The  difference  instars involved without  time stage  were  Cooley  i f quantity this  between  examining  initially (1974).  interval, vs  method o f R i g l e r  involved.  adult  and  time and  initial  juvenile  stage  copepods  Diacyclops to f i n d  graphs  could  of  of  food  influence  stages  Because  copepods  of t h e abundance  involves  the d u r a t i o n of from  of  made u s i n g t h e  show d i s t i n c t  Cooley  the peaks t o h a l f The  effect  fertilizer.  enclosures  by R i g l e r  in  estimated durations  E s t i m a t e s of the d u r a t i o n s of the d e v e l o p m e n t a l D.  was  tested.  Most  with  a slight  lake  Eudiaptomus  different  was  of  increasing  (1966),  food  rate  eutrophic  rate  and Food  developmental  found  seston  1966)  this those  when t h e s e p e a k s  peaks i n setting  of t h e  two  calculation enclosures i n abundance  99  occurred. of  B e c a u s e of  food  without  quantity  on  fertilizer within  significant  difference  mean was  One  of  examined  each  used  of  was  unknowns i s a l w a y s one  low.  shown  initial  Table  XII.  These,  survivorship. rates  D.  Tropocyclops  the  and  estimate  including  for  underestimated.  In o r d e r  the d u r a t i o n s , a  combination  (1981)  obtained  and  simulation only  those  modelling  nauplii  so  the  enclosures.  XII.  The  calculated each  durations. calculated  t o the  These  d u r a t i o n s i s due and The  the  from  in  of  other  the  values  estimates  Peacock same  stages  from  n1-3  enclosures  the  to the  between due  fitted  short  fitted  badly  value  by  for  Peacock using  containing  shown  found in  relative  in  Table  d u r a t i o n s and  persistence  sampling  for  showed  was  to those  values are a l s o  to  (1981) f o r  lake  obtained  up are  when u s e d  t h e e n c l o s u r e s were f i t t e d  results  values are probably  number  t h i s method  failed  made by  d u r a t i o n of  infrequent  difference  The  d u r a t i o n w h i c h ended  of c o u r s e ,  between  no  equations.  t o o b t a i n a more r e a s o n a b l e  fitted  of  i s that  the  t h e number of  obtained  those  from  after  method  since  t h a t the p e a k s c o r r e s p o n d e d  difference  stage  estimated  prasinus  the  means  (Table X I I ) .  Cooley's  Comparisons with  developmental thomasi  and  a l w a y s one  estimates  The  and  calculations.  g r e a t e r than  done, t h e r e was  The  in  calculate  that  between them  t h e v a r i a b l e s must a l w a y s be  was  effects  g r o u p s were p o o l e d  the problems w i t h R i g l e r  of  the  enclosures with  separately.  for further  of  When t h i s  rate,  these  found  one  very  uncertainty surrounding  developmental  were  enclosures  overall  the  the  time  of  to  the  v a l u e s and p r e v i o u s l y  to d i f f e r e n c e  in  temperature.  o 0  Table  a)  XII R e s u l t s f o r e s t i m a t i o n of stage  Appearance  o f Peak  Developmental  i n Abundance  Stage  d u r a t i o n o f immature D.  thomasi  i n enclosures  Curves Fert i 1 i zed (day i n e x p e r i ment)  Unfert i1i zed (day i n exper iment) (± S.E.)  n a u p l i us  1-3  1.0 +  2.0  nauplius  4-6  5.0 ±  5.8  copepodite  1  13.3 ±  2.3  copepodite  2  17.2 ±  2.3  copepodite  3-4  18.7 ±  2.3  (±  S.E.)  0.8  ±  1.8  6.8  ±  1.8  11.2 ±  1.8  12.8 ±  3.4  18.0 ±  2.0  Pooled (day i n e x p e r i ment) (± S.E.) 0.9 6 12 14.5 18.3  )b C a l c u l a t e d D u r a t i o n s Developmental  Stage  F i tted  **  Diacyclops thomas i *  Tropocyclops p r a s i nus *  naup1i us  1-3  1  5  7  3  n a u p 1 i us  4-6  9  7  1 1  7  copepodite  1  3  2  7  5  copepodite  2  2  2  7  5  7  6  c o p e p o d i t e 3-4  * **  Calculated  - from Peacock (1981). - calculated using Rigler  5  and C o o l e y  (1974).  101  As  the temperature  d u r i n g the experiment  was f o r a l a r g e p o r t i o n o f t h e t i m e higher (13  (Appendix  C) t h a n  those  later  g i v e any i n d i c a t i o n  effect  Methods t o a n a l y s e divided  into  continuous  which  Copepoda).  that  estimates  which  the s u r v i v a l  for  the  for  other.  does n o t change r a p i d l y  the organism  being  1981).  done w i t h  investigated the with  other  of i n t e g r a t i n g  under  outlined  in  (1966).  Southwood  and  G e h r s and R o b e r t s o n  the  zooplankton  to estimate  for  (usually  is  general  in  or  at  least  one  1981).  Many o f t h e m o d e l s the l i f e 1968,  history  Taylor  and  hand, most work w h i c h h a s been generations  the curve  has  used  the  o f abundance v s t i m e a s  Both R i g l e r  (1975) have  literature  those  with  1968, A r g e n t e s i e t a l .  (Edmondson  discrete  technique  2.  be  r e c r u i t m e n t methods o f  age s t r u c t u r e , (Edmondson  to  cohorts  m o r t a l i t y r a t e s throughout  On  copepods  and  category  1979, T a y l o r and S l a t k i n  a l s o assume c o n s t a n t  Slatkin  one  seem  for populations  discrete  Continuous  o f t e n assume a s t a b l e  Seitz  those  in  significant  survival  Cladocera)  reproduce  Peacock  .  of z o o p l a n k t o n  1.  (usually  by  f o o d q u a n t i t y had a  of n a u p l i a r  The method u s e d  unsuitable  1974,  previous  categories:  recruitment  populations  analysis  two  much  I t i s worthy o f note  on t h e n a u p l i a r d u r a t i o n o f D. t h o m a s i  Analysis  and  a t w h i c h P e a c o c k ' s work was done  n e i t h e r my e n c l o s u r e s n o r  (1981)  frequently  i n the experiment  - 18 ° C ) , t h e r e s u l t s a r e r e a s o n a b l e .  that  of  varied  and C o o l e y  introduced this  (1974)  technique i n  and s e v e r a l o t h e r s have s i n c e u s e d i t  s u r v i v o r s h i p (Confer  and  Cooley  1977,  Neill  and  1 02  Peacock the  1980,  Peacock  enclosure  place  and  1981).  since  continuous  method  G e h r s and of  Robertson  calculated  using  and  equation and  is  constant  the  for  was  mortality was  and  the  duration  i s given  not  in  taking  contained  rate  Cooley  t h i s method, t h e for  cases  ),  the  examined.  method f o r  the  of  methods o f t e n  Rigler  instar  trapezoidal  t h i s method  is listed  by  In  i n each  corrected  for  analysis  outlined  (1975).  animals occurring  curve  (i.e.  majority  recruitment  recruitment  g e n e r a t i o n method of  This  i n the  experiments, continuous  untenable assumptions discrete  Since  (1974)  total  and  number  whole g e n e r a t i o n integrating  of  i n G e h r s and  each  under  instar.  Robertson  is a The  (1975)  below. k = L x=j  N i  ((1  +1 i,x  )/2)(W i,x+1  /D x,x+1  ) i  Where l=number  of  i=instar  individuals  designation  x=collection j=first k=  designation  collection prior  c o l l e c t i o n following  W  alive  =  to  the  last  a p p e a r a n c e of  a p p e a r a n c e of  instar  instar  i n t e r v a l i n d a y s between c o l l e c t i o n x  i  i  and  x,x+1 collection D  x+1  = duration  of  instar  i  i N  = number of  individuals  of  instar  that  i s the  i produced  in  the  i interval of  instar  x=  j to  x=  i produced  k,  in a p a r t i c u l a r  number of  individuals  generation  1 03  A  geometric  illustration  in  F i g 14.  There  are  of  this  method of  integration  i s shown  some i n h e r e n t p r o b l e m s w i t h t h i s  approach  which are a s s o c i a t e d with numerical shown  in  curve  Fig  is  However  with if  the  comparison  when  gentle  the  evaluating  number of  i n phase w i t h t h e  particularly  important  damp  The or  effect  accentuate  if  sampling is  interval  damped; when t h e  accentuated.  If  c h a n c e s of  sampling  error  the  of  varying interval  and  found  increased  long or  i f the  becomes  instars times.  do  not  of e a c h  instars  instar  can  on  the  is  instar  d u r a t i o n s a r e of u n e q u a l  exactly  on  i n the  relative  are  is  relative If  the  is  either  interval;.  large,  a  have  This effect  sampling  then  much  behaviour  to the d u r a t i o n , the  t h e peak  in  p o p u l a t i o n through  sampling  interval  in  persists.  i s small r e l a t i v e  the error  error  is  l e n g t h , the  diminished.  The  becomes g r e a t e r due  to  m a g n i t u d e s of  the  sampling  the d u r a t i o n .  When t h e e q u a t i o n was I  a  i f the  survivorship estimate  differences  of  persistence  the  short  c o n s e q u e n c e s of t h i s  phenomenon d e p e n d i n g  m a g n i t u d e of t h e d u r a t i o n and  The  instar  estimation  of t h e d u r a t i o n of t h e this  well.  instar  of t h e  sampling  the  case  relatively  time  survivorship be p r o f o u n d  the  interval  the  is  the  The  peaks e x a c t l y  short.  time  interval  & d).  can  of  sampling,  the  instars  sampling  persistence  during  (See F i g 14b,c  and  length  the  In  method e s t i m a t e s t h e a r e a  sampling  with  i s missed  poorer  this  relatively  comparison  peak  14a,  integration.  used  with  i t t o be q u i t e a c c u r a t e . w i t h d e c r e a s i n g sample  simulated f i e l d The  width  accuracy (W  of t h e ),  x,x+1  conditions, equation  however  the  1 04  Figure  14 G r a p h i c a l r e p r e s e n t a t i o n of G e h r s and R o b e r t s o n s method of s u r v i v o r s h i p c a l c u l a t i o n . The t o t a l number i n e a c h s t a g e ( o n l y one shown h e r e ) i s c a l c u l a t e d by n u m e r i c a l l y i n t e g r a t i n g under t h e c u r v e u s i n g c o n t i g u o u s trapezoids. E a c h t r a p e z o i d has an a r e a of (W )(1 x, x+1 x + 1 )/2. In t h i s example, t h e d u r a t i o n of the s t a g e s x+1 i s assumed t o be one and t h u s d r o p out of t h e calculation. The s a m p l i n g i n t e r v a l i s r e p r e s e n t e d by W . Lx r e p r e s e n t s the abundance a s a m p l i n g p e r i o d x,x+1 x. a) I n t e g r a t i o n under a g e n t l e c u r v e w i t h a r e l a t i v e l y short sampling p e r i o d . b) I n t e g r a t i o n under a g e n t l e c u r v e where the peak i s m i s s e d . c) - I n t e g r a t i o n w i t h a long sampling i n t e r v a l . d) I n t e g r a t i o n w i t h a l o n g s a m p l i n g i n t e r v a l where the peak i s m i s s e d .  £0  o  1 06  error  was o n l y  duration  (and  exception several  slightly  to  this  successive  increased. as  1% even when W was t w i c e than  accuracy  In  sampling  a t weekly  the  stage  result  cannibalism group with water  has  of n a u p l i i on  in  nauplii  have d e v e l o p e d  integration of than the  adults  that  for  development  will  be  will  the  nauplii  t o t h e next  subject  be i m p o s s i b l e  to  i f the  cannot  persist  be  that  a  curve,  which  in  turn  to separate  environmental,  this  effect  from  if  accurate  adults,  time means  where t h e a d u l t s a r e p r e s e n t  different  that  the c a l c u l a t i o n  is  longer  there  the o r i g i n a l  presence of  much  the  distinguished  be l e s s  cohort  of as a  in  where  T h i s means  factors will  a  effect  out, nauplii  in situations  stage.  of  experiment  of the c o h o r t  20 d a y s ,  examining the  n o t p r o d u c e any eggs u n t i l  means  the  However i f  the  neccessarily  time t h a n  development  this  If  and  for  Anytime  f o r m o r t a l i t y associated with  Unfortunately  situ  consequences  m o r t a l i t y of other  complete  required  do  accuracy  f o r more t h a n  i s p e r f o r m e d under t h e e n t i r e  background  the  dropped d r a m a t i c a l l y  needs t o be s e p a r a t e d  Additional  the  water  enclosures.  for a shorter  unless  case,  gave an e r r o r ' o f < 1%.  severe  nauplii  recruitment.  the l e n g t h of  p e r s i s t e d decreased.  the  The  8 d a y s t h e e r r o r was 190%.  no a d u l t s p r e s e n t  column  others).  12 d a y s , t h e e r r o r was 8%  p e r s i s t e d only  This  in  intervals  p e r s i s t e d only  same s t a g e  survival  persisted  this  of the equation  t h e l e n g t h of time each stage stage  a l l the  was when t h e W c o i n c i d e d w i t h durations.  The  fastest  is  longer  as l o n g as the s h o r t e s t  if  examined. span  is  that the will  in  c o n d i t i o n s and i t the  effect  of  1 07  adults. the  Enclosure  whole  first  area  stage  e x p e r i m e n t s a l s o have t h e added p r o b l e m  under  the  because adding  curve  cannot  nauplii  the  peak a t t h e  beginning  can  be  adjusted  h a l v i n g the developmental  instar  and  a s s u m i n g an  even age  the  integrated for  enclosures  sets  by  of  to  be  the  essentially  experiment.  distribution  that  This  r a t e of within  problem  the  first  the  first  found  that  once  the  instar. In  simulations  survival  rates  duration  of  lack  the  variation The rates  of  was  nauplii  survivorship it  for  noticeable  the  with  when  of  analogy. to  the  in  rates  the  the  of i t s  that  reduced  on  the  calculated  under t h e  a  40%  t o an  simulations, i.e. This technique  stages.  numbers  of  This nauplii  for this,  ignoring  the  later  overestimated underestimated  the d i f f e r e n c e i n effect are  is  more  produced.  i t is helpful  to  In think  Imagine a f r e e w a y w h i c h goes from t h e c e n t r e suburbs.  8%  survival  same r e g i o n of  s h o r t d u r a t i o n s and  reason  distribution  rate.  adults.  with  was  l o n g d u r a t i o n s b e c a u s e of  the  spite  fairly  showed  data  integrating other  was  In  from a l o g - n o r m a l  production  large  to understand  town  drawn  developmental  order an  technique  survival  for stages  stages  l e n g t h of  by  corrected.  survival  i n the  production  was  the  variation  used  underestimated  A Monte C a r l o s i m u l a t i o n t o d e t e r m i n e  of  of egg  I  to  examined by  as was  conditions,  robust  in data  i n the d a i l y effect  instar  however, t h e  calculation  coefficient  curve  first  of v a r i a t i o n  the  enclosure  consistently  i n the d a t a .  effect on  were  of a c c u r a c y  errors  of  Suppose e v e r y o n e works i n t h e c e n t e r  of of  108  town and hour, is  lives  the  i n the  getting  Now  s u p p o s e one  o f f at each e x i t  flying  over  several  different  speed  the  freeway  of  the  i s taken  is  up,  freeway a t  "mortality" was  taken  the  traffic  .will  number  will  decides  be.  taking  an  traffic this  will  be  the  suburbs of  this  by  photograph  i s moving a t t h e  method w i l l  one  the  traffic  t o have l e f t  underestimated  (i.e.  but  those  photograph  the a c c i d e n t s i g n i f i c a n t l y with  the  subsequent  I f the a e r i a l  increase  good  of  o c c u r r e d and  at  same  give a  if  overestimated)  would  rush  number  do  aerial  However,  overestimated.  effects  i n the  to  of c a r s e s t i m a t e d  be  evening  freeway  a c c i d e n t has  of a l a r g e a r e a , and these  one  t h e way,  where an  the  on  and  I f the  the p r e v i o u s e x i t  stayed  the  "mortality".  photographs backed  on  the  wants t o e s t i m a t e  and  points.  at a l l p o i n t s along  estimate  which  that during  number of c a r s g e t t i n g  negligible.  cars  s u b u r b s so  the  slowed  volume  of  traffic. Because  of  the  investigated  another  dynamics  immature  least  of  squares  method  parameters. time  D. of  curves  approximation  determining  convergence  was  curve  of  to  estimate  fitted  has  curve.  calculations. the  the  survival thomasi  vs  (Moore  T h i s method u s e s and  technique.  I  using a  r o u t i n e N2SNO  estimation.  some p r o b l e m s a s s o c i a t e d w i t h  modelling  immature D.  u s i n g the  the d e r i v a t i v e  in these  method,  i n t h e e n c l o s u r e s and  fitting  the  this  involved  of abundance of  c o n v e r g e n c e of used  with  which  thomasi  f o r n o n - l i n e a r parameter  numerical  has  approach  were f i t t o s i m u l a t e d c u r v e s  1981)  for  The  difficulties  three  a  methods  Variability  T h i s method Least  also  squares  109  is  known t o be  other the  susceptible  models,  structure  initial fitted  the a c c u r a c y  conditions mortality  the  with  nauplii  so t h a t  of t h i s  One  the  deficiency initial  to occur  mortality.  results.  obtained  is  technique  shown by  and  the  technique  negative mortality unknown that  deficiency  survival  also  tested  by  had  t o be to  Negative  i n the  in  real  I  not  The  significantly  precision  of  the  It is negative  affect  of  the  that  of  the f i t  The  data due  caused  to  curve  curves.to model-generated  the  some  important  comparable,  affect  the  conditions  i t i s more be  than  survival.  probably  Since  this  (rather  found  s i n c e adjustment  the m o d e l .  for  i n i t i a l conditions  copepodite  data,  model.  estimated.  When t h e  the  Although  minimize  data,  set-up  i m p o s s i b l e and  representation  15.  those  the  accurate f o r model-generated the  fitting  (i.e.  t h e s e c h a n g e s d i d not  underestimated  should  factors..  were  conditions.  r a t e s w i t h i n the e x p e r i m e n t  underestimation mortality  up  model-generated  in  t h e model  a d j u s t a b l e areas  adjusted  graphical  was  the  s t a g e were known, t h e age  in Figure  fact,  set  on  to  minimized.  is clearly  with  dependent  adjusting  was  easily  v a l u e s were not a d j u s t e d f u r t h e r so  and  As  sensitive  indicates a deficiency  cases,  fitting  in  alone)  were  A  be  be  conditions  unknown and  most  relative  were t e s t e d  was  will  simplest  the  each  which  In  also  generation)  i s in  in  estimates  results  1981).  c o n d i t i o n s of  obvious  stage) d i s t r i b u t i o n these  can  (Moore  initial  phenomenon  most  number  the  negative mortality  (spontaneous  presence of  The  examining  enclosures  of  of t h e model and  conditions. by  to o u t l i e r s  this  r a n k i n g of  fitting data which  was had  1 10  been drawn  from a l o g - n o r m a l  variation  of  40%.  This procedure  was  reduced  t o 8%  of  a  variation  40%  distribution) There  on  variation in  also  enclosures containing  end  larger  a  fluctuated  and  difference from  increase  my  the experiment  of  the  enclosures  to develop  experiment  -  those  The  change  incorporated  in  the  assumptions  which  needed  would  effect  of t h i s  survival  not  increase  of  the  trapezoidal  method of  severe  more  as  be more e a s i l y  analogy.  (Table  for  improved  naupliar  understood  this  "mortality".  hatched  later  durations over  that  time  the  were  was  not  additional  the e x t r a  and  parameters The  probable  stages. effect  and  use  the  overestimation As  will  by a g a i n r e f e r r i n g  This  and  those at the-beginning  to the system.  same f r e e w a y  (1981)  i s u n d e r e s t i m a t i o n of  naupliar  a r e added  the  progressively  the a c c u r a c y .  stages  integration,  nauplii  which  felt  i n temperature  water  Unfortunately this  rate  I  the  Peacock  in developmental since  with  developmental  i n the  nauplii than  technique  of  XII).  faster  16.  warmer t o w a r d s  duration  is reflected  effect  log-normal  Since  the  later  C o n s i d e r the  e s t i m a t i o n of  .  would have been made and  o f t h e younger  survival  this  considerably the  a  of  variation The  in Fig  which  model  have  rate.  i s shown with  a l s o caused  this  (assuming  between v a l u e s r e c o r d e d by  calculated.  for  data  was  coefficent  showed t h a t  Diacyclops  This  i n temperature  in  with a  survival  problem  adult  became s h o r t e r .  values  can  the  of t h e e x p e r i m e n t a l p e r i o d ,  stages  the  in daily  survivorship curves  was  temperature  distribution  with the  become This  to the  of  more effect  freeway  t h e same t e c h n i q u e  t i m e however, t h e  freeway  111  Figure  15 G r a p h i c a l r e p r e s e n t a t i o n f i t t i n g procedure. estimated actual  abundance  abundance  of f i t o b t a i n e d  from  curve  1 13  Figure  16 G r a p h i c a l r e p r e s e n t a t i o n o f e r r o r i n s u r v i v o r s h i p curves. E a c h c u r v e was g e n e r a t e d from a model d r a w i n g d a t a from a l o g n o r m a l random d i s t r i b u t i o n w i t h a c o e f f i c i e n t o f v a r i a t i o n o f 40% ( v a r i a n c e o f . 4 ) . The f i g u r e shows t h e a p p r o x i m a t e amount o f v a r i a t i o n expected i n c a l c u l a t e d s u r v i v o r s h i p curves with the v a r i a t i o n found i n the d a t a .  11-4  DEVELOPMENTAL  STAGE  1 1 5  has  been  for  a  updated  certain  information the p o s t e d speed, one  the  than  limit  has  actually  very  little  will  imagine  that  show  to  do  with  Using  known the  this  that  actual  technique  through  However,  the when  p o i n t where t h e r e a r e  fewer  up.  lanes  additional  It i s well  faster.  later  feeder  the  of c a r s g o i n g  some of t h e  lanes w i l l  has  lanes.  number  a  l a n e s and  limit.  a r e moving at  d i d because  were i n t h e e x p r e s s  speed  the  examined  l a n e s , one  also  i n the e x p r e s s  underestimate  are  of e x p r e s s One  the p o s t e d  l a n e s because they  data  express  speed  distance.  particularly  will  express  of  to a system  cars  cars l e f t missed  the  no  freeway  while  they  1 16  APPENDIX C.  TEMPERATURE  EXPERIMENTAL  AND  PRECIPITATION  PERIOD(MAY-JUNE,  DURING THE  1982)  11 7  Figure  17 T e m p e r a t u r e a n d p r e c i p i t a t i o n d u r i n g t h e e x p e r i m e n t a l p e r i o d (May-June, 1982). Water t e m p e r a t u r e o f P l a c i d L a k e i s m a r k e d when i t was S water temperature a t the s u r f a c e . B water t e m p e r a t u r e 1 m below s u r f a c e . .— d a i l y maximum t e m p e r a t u r e d a i l y minimum t e m p e r a t u r e total daily precipitation  taken.  TEMPERATURE (C) PRECIPITATION (mm)  APPENDIX D.  RESULTS OF SURVIVORSHIP CALCULATIONS  1 20  Figure  18 S u r v i v o r s h i p c a l c u l a t e d u s i n g i n t e g r a t i o n . T h i s method c a l c u l a t e s s u r v i v o r s h i p by i n t e g r a t i n g t h e a r e a u n d e r t h e abundance c u r v e o f e a c h i n s t a r . The d i s t a n c e on t h e x - a x i s between d e v e l o p m e n t a l stages i s p r o p o r t i o n a l t o the d u r a t i o n of t h e s t a g e s . The s u r v i v o r s h i p curves are p r e s e n t e d i n four graphs: (a) e n c l o s u r e s c o n t a i n i n g f e r t i l i z e r (b) e n c l o s u r e s c o n t a i n i n g D i a p t o m u s k e n a i (c) e n c l o s u r e s c o n t a i n i n g D i a c y c l o p s thomasi (d) e n c l o s u r e s c o n t a i n i n g t h e g r a z i n g a s s e m b l a g e . The s u r v i v o r s h i p of n a u p l i i from t h e e n c l o s u r e c o n t a i n i n g n a u p l i i a l o n e i s shown i n e a c h g r o u p . The t r e a t m e n t i s marked a t t h e end of e a c h c u r v e . — n a u p l i i alone F Fertilizer K Diaptomus kenai D D i a c y c l o p s thomasi G G r a z i n g assemblage  122  DEVELOPMENTAL STAGE  123  DEVELOPMENTAL STAGE  124  DEVELOPMENTAL STAGE  1 25  Figure  19 S u r v i v o r s h i p c a l c u l a t e d u s i n g c u r v e f i t t i n g . This method c a l c u l a t e s s u r v i v o r s h i p by m i n i m i z i n g t h e sum of s q u a r e s between t h e a c t u a l p o p u l a t i o n c u r v e s and simulated curves. The d i s t a n c e on t h e x - a x i s between developmental s t a g e s i s p r o p o r t i o n a l t o t h e d u r a t i o n of the s t a g e s . The s u r v i v o r s h i p c u r v e s a r e p r e s e n t e d i n four graphs: (a) e n c l o s u r e s c o n t a i n i n g f e r t i l i z e r (b) e n c l o s u r e s c o n t a i n i n g D i a p t o m u s k e n a i (c) e n c l o s u r e s c o n t a i n i n g D i a c y c l o p s thomasi (d) e n c l o s u r e s c o n t a i n i n g t h e g r a z i n g a s s e m b l a g e . The s u r v i v o r s h i p of n a u p l i i from t h e e n c l o s u r e c o n t a i n i n g n a u p l i i a l o n e i s shown i n e a c h g r o u p . The t r e a t m e n t i s marked a t t h e end o f e a c h c u r v e . n a u p l i i alone F Fertilizer K Diaptomus kenai D D i a c y c l o p s thomasi G G r a z i n g assemblage  126  DEVELOPMENTAL  STAGE  127  DEVELOPMENTAL S T A G E  c)  129  10  C1  N4  DEVELOPMENTAL STAGE  C3  

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