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Effects of hypolimnetic aeration on functional components of the lake ecosystem Ashley, Kenneth Ian 1981

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EFFECTS OF HYPOLIMNETIC AERATION ON FUNCTIONAL COMPONENTS OF THE  LAKE ECOSYSTEM  by KENNETH B.Sc,  The U n i v e r s i t y  IAN ASHLEY Of B r i t i s h Columbia, 1976  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS  FOR THE DEGREE OF  MASTER OF SCIENCE  in  THE FACULTY OF GRADUATE STUDIES (Department  of Zoology and I n s t i t u t e of Animal Resource Ecology)  We accept t h i s t h e s i s as conforming to the r e q u i r e d  standard  THE UNIVERSITY OF BRITISH COLUMBIA March 20, 1981  ©Kenneth  Ian Ashley, 1981  In p r e s e n t i n g  this thesis i n partial  f u l f i l m e n t o f the  requirements f o r an advanced degree a t the U n i v e r s i t y 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 o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head o f my department o r by h i s o r her r e p r e s e n t a t i v e s .  Iti s  understood t h a t c o p y i n g o r 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 n o t be allowed without my  permission.  Department o f The U n i v e r s i t y o f B r i t i s h 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5  nir_ £  10  /"7Q \  Columbia  written  11  ABSTRACT  E f f e c t s Of Hypolimnetic A e r a t i o n On F u n c t i o n a l Components Of  The  Lake Ecosystem  by Kenneth Ian Ashley  The  whole-lake  experimental  approach was  used to examine  the e f f e c t of h y p o l i m n e t i c a e r a t i o n on s e v e r a l key components of the lake ecosystem. These i n c l u d e d c i r c u l a t i o n and processes, major n u t r i e n t , phytoplankton max.=9.0  and  m)  experimental  ion and-pH i n t e r a c t i o n s  zooplankton  naturally and  control  from  April  had no e f f e c t on season  but  thermal  circulated  lake  halves  1978  by  in  increased  along  the  Hypolimnetic was  added  a  stratification  ten  nitrification  aerobic  accumulated  CO^  P  into  half  and  Hypolimnetic a e r a t i o n during  turbidity  fold  rise  to  the  ice-free  regeneration,  and  not  oxygen  I n t e r n a l phosphorous  l e v e l s were a l s o Aeration  and decreased  magnesium, bicarbonate and orthophosphate  did  oxygen l e v e l s were  sufficient  increased.  from the hypolimnion  but  i n oxygen consumption.  occur.  l o a d i n g and h y p o l i m n e t i c orthophosphate however  as  e n t i r e experimental h a l f under i c e  ammonia l e v e l s were reduced for  divided  experimental  transparency. Hypolimnetic with  well  a p l a s t i c c u r t a i n , and a  cover. A e r a t i o n i n c r e a s e d h y p o l i m n e t i c affect epilimnetic  was  to March 1979.  the  as  p o p u l a t i o n s . A small (3.9 ha, Z  eutrophic  hypolimnetic a e r a t o r i n s t a l l e d operated  decomposition  content  reduced vented  i t s calcium, via  calcium  carbonate composition by  coprecipitation.  Phytoplankton abundance and s p e c i e s  (averaged over the water column) were  hypolimnetic  aeration.  not  affected  The zooplankton community e x h i b i t e d  s i m i l a r v e r t i c a l d i s t r i b u t i o n on both halves of the lake however g r e a t e r numbers  were  found  on  the  s e v e r a l months a e r a t i o n . Management a e r a t i o n are a l s o d i s c u s s e d .  experimental  half  after  i m p l i c a t i o n s of h y p o l i m n e t i c  iv  TABLE OF CONTENTS  Abstract  i i  List  of T a b l e s  vii  List  of F i g u r e s  viii  Acknowledgements  x  Introduction  1  H i s t o r y of Lake A e r a t i o n  7  Destratification  7  Hypolimnetic A e r a t i o n  9  Study Area  ,  11  Lake H i s t o r y  11  Climate and Watershed  12  Lake D e s c r i p t i o n  12  Materials  and Morphometry  and Methods  Aeration  System  16 16  Curtain  18  Operation  19  Sampling  19  Physical  20  Chemical  20  Phytoplankton  21  Zooplankton  22  Aerator  22  Statistics  23  Results C i r c u l a t i o n Processes  24 24  V  Temperature  25  Transparency  28  Decomposition  30  Processes  30  Oxygen Total  33  Organic Carbon  35  Major N u t r i e n t s Nitrogen  35  Phosphorus-  40  N:P R a t i o s  45  Major  47  Ions Alkalinity  47  Calcium and Magnesium  48  Manganese  50  Total  52  pH I n t e r a c t i o n s Phytoplankton  53  Biomass  53  Composition Zooplankton Discussion  •  55 59 66  Circulation  67  Decomposition  70  Major N u t r i e n t s  77  Nitrogen  77  Phosphorus  81  N:P R a t i o s  84  Major  Ions  pH Phytoplankton  86 90  92  vi  Zooplankton  94  Management I m p l i c a t i o n s and Suggestions  99  Summary and C o n c l u s i o n s  101  Literature Cited  104  Appendix  116  vii  LIST OF TABLES  Table 1. Morphometric Features Of Black Lake Table 2. Environmental  Laboratory Water Chemistry  Table 3. L i s t Of Personal Communications  15 Methods  .116 118  Table 4. L i s t Of F Values For Water Q u a l i t y Parameters ....119 Table 5. L i s t Of F Values For Zooplankton  ..  120  vi i i  LIST OF  Figure  1.  Black  Lake  FIGURES  showing depth contours,  s i t e , c u r t a i n p o s i t i o n , aerator  location  compressor  and  sampling  sites Figure  13 2.  A  hypolimnetic  schematic  diagram  of  the  Black  aerator  17  F i g u r e 3. Temperature i s o p l e t h s f o r experimental control Figure  4.  Secchi  5.  control  26  and  1%  Figure  Oxygen  7.  isopleths  experimental  29 (west) and 31  i n experimental  (west)  and  8.  9.  32 experimental  c o n t r o l (east) s i d e s  Ammonia  nitrogen  isopleths  34 for  experimental  c o n t r o l (east) s i d e s  Nitrate  nitrogen  isopleths  36 for  experimental  c o n t r o l (east) s i d e s  10.  experimental Figure  for  T o t a l organic carbon i s o p l e t h s for  (west) and Figure  for  (east) s i d e s  (west) and Figure  depths  (east) s i d e s  (west) and Figure  transmission  (west)' and c o n t r o l (east) s i d e s  F i g u r e 6. T o t a l oxygen content control  (west) and  (east) s i d e s  experimental Figure  Lake  11.  experimental  Total  organic  nitrogen  38 isopleths  for  (west) and c o n t r o l (east) s i d e s Orthophosphate (west) and  phosphorus  isopleths  c o n t r o l (east) s i d e s  40 for 41  F i g u r e 12. content Figure  Hypolimnetic  i n experimental  dissolved  (west) and c o n t r o l  13. T o t a l phosphorus content  and c o n t r o l  organic  phosphorus  (east) s i d e s  i n experimental  F i g u r e 15.  45  16.  Total  46  alkalinity  isopleths  experimental  Dissolved  calcium  48  i s o p l e t h s f o r experimental  (east) s i d e s  49  F i g u r e 17. D i s s o l v e d manganese i s o p l e t h s (west) and c o n t r o l 18.  for  (east) s i d e s  (west) and c o n t r o l  Figure  (west) and  (east) s i d e s  (west) and c o n t r o l Figure  for  experimental  (east) s i d e s  Hypolimnetic  (west) and c o n t r o l  pH  51  levels  in  the experimental  (east) s i d e s  53  F i g u r e 19. C h l o r o p h y l l a i s o p l e t h s f o r experimental and c o n t r o l  and c o n t r o l 21.  quadrata control Figure  22.  composition  i n experimental  (west) 57  T o t a l zooplankton, (numbers/m ) i n 2  Daphnia pulex and K e r a t e l l a  the  experimental  (west)  and  (east) s i d e s Cyclops  60  b i c u s p i d a t u s n a u p l i i , copepodites and  (numbers/m )  control  (east) s i d e s  23.  54  (east) s i d e s  adults  Figure  (west)  (east) s i d e s  F i g u r e 20. Phytoplankton  Figure  (west)  (east) s i d e s  F i g u r e 14. Whole lake N:P r a t i o s i n experimental control  43  2  Diaptomus  adults  (numbers/m )  control  (east) s i d e s  2  in  the  experimental  (west)  and 63  leptopus in  the  nauplii,  copepodites and  experimental  (west)  and 65  X  ACKNOWLEDGEMENTS  A  project  without  of  t h i s magnitude c o u l d not have been p o s s i b l e  the a s s i s t a n c e  grateful mechanical successful  to  F.A.  of s e v e r a l i n d i v i d u a l s . I  Ashley  intuition  and  and  construction  G.T.  "Ozone"  construction and  am  S u t h e r l a n d whose  skills  installation  equipment. C.J. B u l l , D. McKay, D. Smith and  especially  ensured of  K.  the  experimental  Tsumura  (Fish  and W i l d l i f e Branch) were h e l p f u l on a continuous b a s i s . I would like  to  thank  Dr. W.E.  Neill  and  Dr. Adrienne Peacock f o r  i n t r o d u c i n g me to experimental l i m n o l o g y . Edgar Guindon and G.J. Steer p r o v i d e d  valuable  computer  programing.  Dr. T.G.  Northcote  Special and  suggestions throughout improving  assistance  Dr.  with  their  knowledge  of  thanks are due t o Dr. K.J. H a l l , A.F. Tautz  who  offered  timely  my t h e s i s program and g r e a t l y a s s i s t e d i n  the manuscript.  Finally,  I would l i k e t o express my  g r a t i t u d e t o the students (past and present) and f a c u l t y of the I n s t i t u t e of Animal  Resource  Ecology f o r p r o v i d i n g a s t i m u l a t i n g  and thoroughly e n t e r t a i n i n g r e s e a r c h This  environment.  study was supported by the F i s h e r i e s Research  of the B r i t i s h Columbia  F i s h and W i l d l i f e  Environment) and an NRC grant  Branch  Section  (Ministry  of  (67-3454) to Dr. T.G. Northcote.  1  INTRODUCTION  Excessive  fertilization  of n a t u r a l waters  is  one  most s e r i o u s water q u a l i t y problems i n the world today al.,  1974;  excessive  NAS,  1969).  Cultural  eutrophication  of  (Dunst et  i s caused by  a d d i t i o n of n u t r i e n t s such as phosphorus and  nitrogen  to l a k e s , streams, r i v e r s , e s t u a r i e s and c o a s t a l waters 1975).  In  plant  lakes,  growth,  oxygen  these  additions  undesireable  depletions,  fish  (Wetzel,  r e s u l t in increased  changes  in  the  species  aquatic  composition,  k i l l s and decreased water q u a l i t y f o r  domestic, r e c r e a t i o n a l and i n d u s t r i a l use (Lee, 1970a). Following 1960's,  the l i m i t i n g - n u t r i e n t controversey  attention  in  the  1970's focused  recovered  from excessive  d i v e r s i o n eg. Lake Washington Lake  Sammamish  d i d not  1972).  unchanged Lakes  maintain  of  their  Certain  (Edmondson, 1972), however  respond  type  present  nutrient  lakes.  similarly  i n which the e u t r o p h i c  were  state  nearby  (Rock, 1974). Lake  following nutrient diversion this  late  nutrient loading a f t e r nutrient  Trummen i n Sweden i s another lake remained  the  on reducing  inputs and r e h a b i l i t a t i n g c u l t u r a l l y eutrophied lakes  of  sufficiently  status  (Bjork et a l . , eutrophic  to  v i a internal nutrient recycling  long a f t e r e x t e r n a l n u t r i e n t sources were removed. As a r e s u l t , existence  as  the  field  limnologists  of and  methods f o r r e s t o r i n g eutrophic  lake  restoration  came  into  engineers attempted to develop  l a k e s . Lake  restoration  refers  to "... the .manipulation of a lake ecosystem to e f f e c t an i n - l a k e improvement al.,  1974).  in  degraded,  Artificial  or u n d e s i r a b l e aeration  is  conditions"  one  technique  (Dunst et used  in  2  restoring  eutrophic  aeration  reoxygenates  technically  lakes  (Lorenzen  and  depleted  F a s t , 1977).  hypolimnetic  Artificial  waters  and  c r e a t e s o l i g o t r o p h i c oxygen c o n d i t i o n s in e u t r o p h i c  lakes. However, artificial initially impact  as  is  often  aeration  as  the a  a p p l i e d with l i t t l e  (eg.  restoration  Patriarche, i s not a  case  lake  new  restoration  understanding  1961).  science  with  of  technique its  Shapiro  (1978)  It  still  yet.  is  technology, was  ecological  s t a t e d "Lake in  need  of  r e s e a r c h . . . . If only 5% of the moneys a l l o c a t e d f o r doing were to be d i v e r t e d to understanding, Fast the  (1975)  the r e t u r n s would be s u b s t a n t i a l . "  e l o q u e n t l y suggested "...lake medicine i s s t i l l  fifthteenth  century.  Lake  doctors  bags  dredges,  the medical  e q u i v a l e n t of the b l o o d l e t t i n g stage." C l e a r l y ,  of  lake  and  their  toxicants,  field  coagulants  with  restoration  other d e v i c e s are s t i l l  requires  in of in the  increased  ecological  examine  functional  awareness. The  purpose of t h i s experiment was  components viewpoint  of  the  using  Specifically  its  lake the  ecosystem  . whole  objectives  from  lake were  to  to  a  process  perturbation  approach.  investigate  particular  components of the lake ecosystem which I f e l t , literature  review,  were  response to hypolimnetic  poorly  oriented  understood  after  extensive  i n terms of  their  a e r a t i o n . These component areas were as  follows: 1. C i r c u l a t i o n Processes. lakes  circulates  slowly  in  The  hypolimnion  relation  to  of  stratified  the e p i l i m n i o n ,  and  3  v e r t i c a l exchange c o e f f i c i e n t s between the two low  ( H e s s l e i n and Quay, 1973). Hypolimnetic  transfer  of  c o u l d have s e r i o u s delivered  to  substances  consequences  the  are  very  aeration accelerates  c i r c u l a t i o n c u r r e n t s w i t h i n the hypolimnion vertical  zones  and may  i n c r e a s e the  a c r o s s the t h e r m o c l i n e . T h i s if  epilimnion  essential  during  the  nutrients critical  were  summer  s t r a t i f i c a t i o n period. In  addition,  sediment-water  the  effects  the  exchange  r e a c t i o n s and may  rate  controlling  sediment-water  questions  must  exchange  reduces  complete aeration  reactions  (Fillos, suggests in  mediated  controlling  1970b).  These  Processes.  below  1976)  Decomposition  of  organic thermal  the  may  thermocline and  lead  treatment.  and experimental  oxygen  evidence  consumption  However (Smith et  which  short-term  increase  consumption  as  accumulated  organic  e v e n t u a l l y l e a d i n g to a long-term side  effects  in  hypolimnetic  debris  is  fold  further  oxygen l e v e l s . I b e l i e v e h y p o l i m n e t i c a e r a t i o n a  to  hypolimnetic  h y p o l i m n e t i c a e r a t i o n s t i m u l a t e s a 3-4  hypolimnetic  addition,  be  technique.  in  In  (Lee,  i s o f t e n recommended as a remedial  increase  result  chemically  i c e cover preclude oxygen renewal during most  anaerobiosis  1975)  decreases  in  (Fast, 1973). In e u t r o p h i c lakes t h i s  theoretical al.,  step  h y p o l i m n e t i c oxygen c o n c e n t r a t i o n s as  s t r a t i f i c a t i o n - and of the year  on  be answered before h y p o l i m n e t i c a e r a t i o n can  Decomposition  material  currents  be the o v e r r i d i n g f a c t o r  recommended as a lake r e s t o r a t i o n 2.  circulation  exchange mechanisms are l a c k i n g . P h y s i c a l mixing  is often  all  of  should oxygen  oxidized,  d e c l i n e i n oxygen consumption. of  hypolimnetic  aeration  4  (eg. hypolimnetic  warming  and  benthic  recolonization)  may  i n f l u e n c e hypolimnetic oxygen consumption. 3.  Major  limnological  Nutrients. research  One  involves  of the most i n t r i g u i n g areas of nutrient  regeneration  a e r o b i c and anaerobic c o n d i t i o n s . Mortimer's P  release  i n d i c a t e s P r e l e a s e i s minimal  tension  (Schindler  most  1971;  et  a l . , 1980).  the hypolimnion,  hypolimnetic  support  (1941-42) theory of  i s w e l l documented i n the l i t e r a t u r e , however recent  evidence  oxygenating  under  aeration  regardless  Hypolimnetic  of  a e r a t i o n , by  should reduce  P  release.  experiments  have  been  t h i s c o n t e n t i o n due to poor experimental  oxygen  However  unable to  design  (Fast,  G a r r e l et a l . , 1977; and Smith et a l . , 1975). Nitrogen  release  during a e r o b i c / a n a e r o b i c c o n d i t i o n s a l s o  i n f l u e n c e s a lake's n u t r i e n t budget. Nitrogen may denitrification  (Chen  et a l . , 1973), gained through  (Home, 1979) or transformed 1969).  The  influence  be  biochemically  lost  N fixation  (Brezonik  et  provide  insight  al.,  of hypolimnetic a e r a t i o n on the n i t r o g e n  c y c l e and subsequent N/P r a t i o s i s l a r g e l y unknown. The l a k e " experimental  via  "split-  approach should e l i m i n a t e design problems and into  nutrient  behaviour  during hypolimnetic  aeration. 4. Major Ions. Major ion behaviour sensitive to i o n  (Ca ,Mg ,HCO^") +2  +2  is a  i n d i c a t o r of lake metabolism, e s p e c i a l l y with respect  exchange  Preliminary  processes  evidence  at  the  suggests C a  + 2  sediment-water  interface.  p r e c i p i t a t i o n occurs during  h y p o l i m n e t i c a e r a t i o n ( F a s t , 1971). I b e l i e v e t h i s c o u l d phosphorus c o n c e n t r a t i o n s v i a carbonate Sediment  release  of metals  reduce  coprec.ipitation.  under reducing c o n d i t i o n s i s a  5  well known phenomenon (Wetzel, toxic  to  aquatic  aeration  should  quality  for  in  P  precipitation  aeration  ( F a s t , 1975;  5.  pH  lake  of of Mn  metals,  which  and  reduced  thus  should  occur  pH  is  an  ecosystem.  However,  pH  response  received  little  1975)  lake metabolism by  and  magnesium).  precipitating  to  of  ions  (1971) observed  pH  (Smith  (bicarbonate,  hypolimnetic  within  hypolimnetic  a  small  this  should  i n c r e a s i n g ammonia t o x i c i t y  major  aspect  variable  a e r a t i o n of  hydrogen s u l f i d e t o x i c i t y  This  hypolimnetic  reactions  a t t e n t i o n . Fast  l e v e l s f o l l o w i n g hypolimnetic  1972), d e c r e a s i n g  involved  important  Michigan l a k e . If a e r a t i o n c o n s i s t a n t l y i n c r e a s e s affect  water  Mortimer, 1971).  biological  pH  are  addition,  be  during  and  increased  In  Fe compounds may  chemical  has  improving  organisms.  numerous  aeration  metals  King, 1977). Hypolimnetic  aquatic  Interactions..  influencing the  variety  reduction  and  (LaBounty and  o x i d i z e reduced  a  o x i d a t i o n and  life  1975)  (Trussel,  and  Oseid,  calcium  aeration  and  requires  further investigation. 6.  Phytoplankton.  The  e f f e c t of hypolimnetic  aeration  the phytoplankton community i s l a r g e l y unknown. Bernhardt documented p h y s i c a l aeration  currents,  redistribution however  e p i l i m n e t i c algae. Fast's  (1971)  leaks  tower  in  the  aeration  of  few  hypolimnetic  studies  results stimulated  by  focused  on  questionable  as  dense a l g a l blooms.  Generating hypotheses about a l g a l response i s d i f f i c u l t the  number  of  impinging  understood. These include 1980),  nutrient release  variables, iron  (1967)  algae  have  are  due  many of which are  availability  (Fast, 1975), pH  on  (Murphy  shifts  to  poorly  et  al.-,  (Shapiro,  1978)  6  and t u r b i d i t y changes (Fast, 1971). I would immediate  not  expect  effect  hypolimnetic  in  species  occur a f t e r  composition  attention  isolation  levels.  Hypolimnetic  Long-term should  numbers i n c r e a s e .  from the i n i t i a l aeration,  the p h y s i c a l , chemical and  potential  to a l t e r  affect  oxygen  due  o b j e c t i v e of r a i s i n g  by  virtue  of  biological  to i t s oxygen  its ability  environment,  to has  zooplankton d i s t r i b u t i o n , abundance and (1978) demonstrated  zooplankton by changing  food source. K i t c h e l l and K i t c h e l l how  hypolimnion.  zooplankton community has a l s o r e c e i v e d  s p e c i e s composition. Shapiro could  the  i n h y p o l i m n e t i c a e r a t i o n experiments  relative  the  an  s e v e r a l c i r c u l a t i o n p e r i o d s as phosphorus l e v e l s are  7. Zooplankton. The  modify  exert  ( i e . fewer blue-greens)  g r a d u a l l y reduced and zooplankton  little  to  on the phytoplankton community as c i r c u l a t i o n  c u r r e n t s are g e n e r a l l y c o n f i n e d to changes  aeration  stratification  can  that pH  the p a l a t a b i l i t y  (1980) e l e g a n t l y modify  shifts of t h e i r  demonstrated  zooplankton  community  s t r u c t u r e . I would expect h y p o l i m n e t i c a e r a t i o n to s i g n i f i c a n t l y increase  zooplankton  v e r t i c a l d i s t r i b u t i o n and p o p u l a t i o n s i z e  by i n c r e a s i n g oxygen l e v e l s , v e n t i n g t o x i c gases o x i d i z i n g reduced metals The research  whole-lake project.  provides • a while  and  manipulating  large  within  + 2  Experimental  for errors  economic/logistic lakes. the  realm  was  Several of  and  selected for t h i s of  experimental of  NH^)  hypolimnion.  manipulation  setting  extrapolation  experiments  available  + 2  experimental approach  realistic  avoiding  ( F e , M n ) i n the  (H^S,  small  lakes  investigation  laboratory/enclosure  problems  associated  strategies  whole-lake  are  with  currently  experiments.  Among  7  these,  the  project allows  " s p l i t - l a k e " design,  (Schindler,  1974)  similar  was  to S c h i n d l e r ' s Lake  226  chosen f o r t h i s experiment as i t  simultaneous experimental  and  c o n t r o l treatments w i t h i n a  s i n g l e lake b a s i n .  HISTORY  Artificial air  or  OF  LAKE AERATION  a e r a t i o n of lakes r e f e r s to the process  oxygen  is  injected  to  increase  whereby  dissolved  oxygen  c o n d i t i o n s and c i r c u l a t e the water. There are a v a r i e t y of aeration  techniques,  d e s t r a t i f i c a t i o n and  commonly  divided  hypolimnetic  into  two  lake  groups:  aeration.  Destratification Destratification aerating  thermally  i s the  most  stratified  widely  used  l a k e s . T h i s technique  d i s s o l v e d oxygen in bottom waters by reducing and  homogenizing  the  D e s t r a t i f i c a t i o n was  entire  first  procedure  thermal  for  increases gradients  water mass (Dunst et a l . , 1974).  used in 1919  (Scott and  F o l e y , 1919),  8  and  i s u s u a l l y accomplished by mixing c o l d  water  with  oxygen and entire  warmer  e p i l i m n e t i c water. The  heat before  lake  can  s i n k i n g to a new  usually  air  (Fast and  bottom water absorbs  equilibrium  depth.  The and  St. Amant, 1971).  most common d e s t r a t i , f i c a t i o n method i n v o l v e s compressed  i n j e c t i o n through p e r f o r a t e d pipes  located  near  bottom (Fast, 1968). T h i s i s the most e f f i c i e n t technique  as  rising  bubbles l i f t  where t u r b u l e n t mixing i s induced. include  the  Aero-Hydraulic  Cannon.  pumping  has  of  s u r f a c e , and reservoir  lake  by  operates  via  been  employed  method  periodic  in  several  destratified  hypolimnetic  water  Summerfelt et a l . (1976) d e s t r a t i f i e d  by  this  et a l . , 1972).  also  pumping  surface  T h i s i s a low-head, high-  d e s t r a t i f i c a t i o n p r o j e c t s . Hooper et a l . (1952) Michigan  lake  destratification  Variations  e j e c t i o n of l a r g e a i r bubbles (Toetz Mechanical  the  bottom waters to the  volume p o s i t i v e displacement pump which  small  hypolimnetic  be c i r c u l a t e d from a s i n g l e s i t e  e v e n t u a l l y becomes isothermal The  anoxic  a  to  a the  eutrophic  pumping e p i l i m n e t i c water to the bottom v i a a x i a l  flow pumps. R i d l e y et a l . (1966) employed angled  jets  of  water  to d e s t r a t i f y a l a r g e above ground r e s e r v o i r . The  principle  disadvantage of d e s t r a t i f i c a t i o n  i n c r e a s e d heat budgets. Thermal g r a d i e n t s are  reduced  e n t i r e water mass u s u a l l y approachs normal s u r f a c e This  is  a  serious  problem  warm  habitats  and  and  the  temperatures.  summer months as i t  eliminates cold  water  increases  sediment  oxygen  In a d d i t i o n , c i r c u l a t i o n c u r r e n t s may  transport  demand.  nutrients production.  to  the  fish  during  is greatly  photic  zone  and  stimulate  phytoplankton  9  Hypolimnetic Hypolimnetic  aeration  i s the  a e r a t i o n d e v i c e s . T h i s technique hypolimnetic  water  while  Aeration second  enables  generation  one  maintaining  to  thermal  aerate  Hypolimnetic late  1940's  hypolimnion  a e r a t i o n was f i r s t and  Lake  Perret,  used i n S w i t z e r l a n d 1949).  Bret by mechanically  water to a shore based splash basin where allowed  to  return  maintain  i n warm c l i m a t e s .  (Mercier of  anoxic  stratification.  T h i s procedure minimizes heat budget i n c r e a s e s and can c o l d water f i s h e r i e s  of lake  by  gravity  flow  They pumping  i t was  through  a  i n the  aerated  the  hypolimnetic aerated pipe  and  to the  hypolimnion. The occurred  next s i g n i f i c a n t development i n hypolimnetic i n 1967 (Bernhardt,  water was a i r l i f t e d  1967). In t h i s system  This  i n t o most modern h y p o l i m n e t i c  Hypolimnetic  aeration  systems  principle  lift  devices  are  mixture does not upwell lift  designs  those  returned has  been  a e r a t i o n systems.  using  i n j e c t i o n a r e c a t e g o r i z e d as p a r t i a l and f u l l Partial  hypolimnetic  to the surface and oxygenated water  to the hypolimnion v i a r e t u r n tubes. incorporated  aeration  systems  compressed a i r air l i f t  designs.  where the a i r / w a t e r  to the lake s u r f a c e , whereas i n f u l l a i r  i t reaches the s u r f a c e .  S e v e r a l advanced methods of hypolimnetic  a e r a t i o n have been  r e c e n t l y developed. These i n c l u d e down-flow a i r i n j e c t i o n which uses a mechanical water pump t o f o r c e an a i r / w a t e r i n t o the hypolimnion  (Speece,  1970).  The  advantage  (DAI), mixture  of  this  system i s i n c r e a s e d oxygen t r a n s f e r e f f i c i e n c y , however n i t r o g e n gas may a l s o reach  supersaturation  levels.  10  Side  stream  pure oxygen Oxygenated high  pumping  water  i s then returned discharge  r a i s i n g d i s s o l v e d oxygen effective  Speece,  depths i n the  to  lines.  l e v e l s , however  lift  1971)  the  This  at reducing hydrogen  than p a r t i a l or f u l l (DOBI;  (SSPS) operate by  hypolimnion  system it  is  hypolimnion.  expensive  s u l f i d e and ammonia  d e s i g n s . Deep oxygen  involves  pure oxygen  Theoretically,  bubble  and  levels  injection  i n j e c t i o n at great most  bubbles  will  destratify  l a k e . T h i s system has not been t e s t e d f u l l - s c a l e i n a l a k e .  Downflow  bubble  essentially  contact  a DAI  aeration  high  oxygen  (Lorenzen and F a s t ,  (DBCA;  Speece,  1971)  device using pure oxygen. The a e r a t i o n  used i n t h i s experiment was a f u l l its  through  i s e f f i c i e n t at  d i s s o l v e before reaching the t h e r m o c l i n e and w i l l not the  injecting  i n t o water m e c h a n i c a l l y pumped from the hypolimnion.  pressure  less  systems  transfer 1977).  air lift  capability  and  system  design . chosen energy  is  for  efficiency  11  STUDY AREA  Lake H i s t o r y Black Lake l i e s at an e l e v a t i o n of 750 m near the between  Keremeos  Interior  Creek  Plateau  (Northcote  and  and  the Marron V a l l e y  limnological  region  i n the  British  Southern Columbia  L a r k i n , 1956). Black Lake o r i g i n a t e d as part of  nearby Yellow Lake, whose b a s i n was major  of  division  cut i n t o v o l c a n i c rock by  meltwater outflow which d r a i n e d the Kaledon  tongue of the  main Okanagan i c e lobe (Nasmith,  1962). F o l l o w i n g  approximately  Black Lake became i s o l a t e d  8900  years B.P.,  a  deglaciation,  Yellow Lake by gradual e r o s i o n and a l l u v i a l d e p o s i t s from  from  Yellow  Lake Creek. The area was investigating  stream channel connected  highway was  provincial  the two  engineers  indicated  lakes ( J . E . F a r r e l ,  p e r s . comm.). However, i n 1947  the  present  with s e v e r a l meters of roadbed m a t e r i a l . The  connected  by a s i n g l e 0.76  as  the  partially  fill  Ministry  Yellow lakes  m x 22 m c u l v e r t which d r a i n s  Black Lake at h i g h water l e v e l s . The doubt  by  c o n s t r u c t e d and the channel between Black and  filled  are now  1907  southwest of Yellow Lake. T h e i r report  Water R i g h t s Branch,  Lake  in  p o t e n t i a l storage r e s e r v o i r s i t e s f o r the town of  Keremeos, 19 km a vestigial  surveyed  f u t u r e of Black Lake i s  in  of T r a n s p o r t a t i o n and Highways plan to  i t during f u t u r e highway  Makeiv, Dept. of Highways, p e r s . comm.).  improvement  work  (J.H  12  CIimate and The  Southern  Interior  mild, continental climate Keremeos,  average  Watershed  Plateau  with  annual  low  of B r i t i s h Columbia  has a  annual  precipitation.  is  cm/yr  rainfall  25  In  with a June  maximum and a M a r c h - A p r i l minimum. Mean annual s n o w f a l l of 60 cm occurs c h i e f l y August  i n December and January.  average  22  C and may  Temperatures  in  reach 41 C, while temperatures i n  January average -3.3  C, o c c a s i o n a l l y dropping to -30 C  of B r i t i s h Columbia,  1976).  The  Black Lake watershed  (1524 m max.) Water  with poor water  Rights  one  very  retention  capacity  small creek  e s t i m a t e d ' at  (Yellow  (D.E.  Lake's  surface  surface runoff a c t u a l l y  268,000  p e r s . comm.).  Lake m,  Creek). however  3  Reksten,  Water  Yellow Lake Creek  up  Tertiary  (Learning, uplands (Lyons,  1973),  volcanic forming  characteristic  75%  Investigations  mainly  rolling  ha)  (3.95  runoff  is  flowed from A p r i l  rock,  (1532  area  annual  to  3  Botham,  reaches the lake v i a  Mean  peaking i n mid-May at 3-5 m /niin. Drainage porous  (J.  Branch, p e r s . comm.). Although i t s s i z e  little  evaporation  (Climate  i s south f a c i n g , low i n e l e v a t i o n  appears l a r g e i n r e l a t i o n to Black ha),  July-  basin basalt  ponderosa  of B r i t i s h Columbia's  lost  via  Branch,  to June  1978,  lithology and  is  is  andesite  pine-sagebrush dry i n t e r i o r  zone  1952).  Lake D e s c r i p t i o n and Morphometry ' Black Lake (Figure 1) i s lake  with  marked  thermal  a  naturally  stratification  eutrophic in  dimictic  summer, inverse  14  stratification dissolved  in  winter  oxygen  and  (Halsey  historically  and  low  MacDonald,  levels  1971).  of  Aquatic  v e g e t a t i o n i s c o n f i n e d to the shallow west and southeast ends of the  lake,  consisting  Potamogeton  sp.  mainly  of  Ceratophyllum  ( J . Pinder-Moss,  U.B.C.  sp.  Herbarium  and  Curator,  p e r s . comm.). The north, east and south s h o r e l i n e s are barren of t e r r e s t r i a l v e g e t a t i o n and composed mainly of broken natural c l i f f  rock  from  e r o s i o n and highway c o n s t r u c t i o n . A small grove of  mixed d e c i d u o u s - c o n i f e r o u s t r e e s i s l o c a t e d at the western end. Algal  blooms  readings averaged were  loosely  u s u a l l y reduced  transparency and Secchi d i s k  (over the i c e - f r e e season)  3.7  m.  Sediments  compacted i n shallow water and deep water samples  were h i g h l y organic and g e l a t i n o u s with a strong H^S odour. F i s h were not present trout  (  fontinalis 1978  i n Black Lake i n i t i a l l y ,  Salmo  qairdneri  )  and  brook  through  cm  curtain trout east  trout  the drainage  culvert  to  and  2.5  Yellow  ( Salvelinus  were caught (control)  Important The  Lake.  Following  cm d i a g o n a l mesh) was set on each s i d e of the  f o r 48 hours during each sampling  1.  rainbow  net (5.8 m x 12.8 m; 5 cm,  on the west  side.  trip. A  total  of  96  (experimental) s i d e and 18 on the  Ambystoma  tigrinum  melanostictum  present on both s i d e s of the c u r t a i n throughout  Table  some  ) entered the lake d u r i n g high water i n the s p r i n g of  t h e i r d i s c o v e r y i n Black Lake, a g i l l 3.8  however  was  the experiment.  morphometric f e a t u r e s of Black Lake are l i s t e d i n contour  a p p l i e d t o an a e r i a l  map was based  on echo-sounder t r a n s e c t s  photograph of the lake o u t l i n e .  15  TABLE 1 Morphometric Features Of Black Lake 1. L o c a t i o n - L a t . 49 20' 30" Long. 119 44' 5" 2. E l e v a t i o n - 7 5 0 m 3. Area-3.95 ha 4. Volume-178,543  m  3  5. Max. Depth-9.0 m 6. Mean depth-4.52 m 7. S h o r e l i n e development-1.32 8. S h o r e l i n e length-927 m 9. Max. Length and o r i e n t a t i o n - 3 6 3 m, NW-SE 10. Max. Width and o r i e n t a t i o n - 1 3 4 m, 11. Max.  N-S  l e v e l change ( s p r i n g - f a l l ) - 0 . 7 3 m  12. Drainage area-1532 ha 13. Ice off-March 31,1978 14. Ice on-November 14, 1978 15. Max. i c e t h i c k n e s s -0.38 m Experimental Whole Lake Vol. S t r a t a Vol.(m ) Area 20204 19047 37464 0-1 0 39456 17912 1-2 15965 1 35506 32850 27652 14094 13261 2 30279 2-3 11407 3-4 12445 23206 3 25114 9512 19662 10400 4 21350 4-5 16041 • 8650 7791 5-6 5. 18020 6-7 11967 6962 14141 5988 6 3602 7 5065 9920 7-8 6975 1398 8-9 2726 2316 8 4399 651 9 1348 87971 Total 178543 z Area (m ) 2  3  Control Vol. Area 18417 19252 17594 16885 16185 14391 12669 11799 10150 10950 9370 8250 7179 5979 4855 3373 2083 1328 697 90572  16  MATERIALS AND METHODS  Aeration The based  hypolimnetic  on  systems  System  a e r a t i o n system used  described  in  of  an  insulated  study  open  box  ". The  f i l l e d pontoons (0.3 m x 0.3 m x 2.4 m) were  0.76  of  the box and provided  aerator  (2.4 m x 1.2 m x 0.9 m)  c o n s t r u c t e d of 19 mm plywood and 5 cm .x 10 cm framing.  sides  attached  Styrofoam to  both  360 kg of p o s i t i v e buoyancy. Two  m c i r c u l a r holes were c u t i n the f l o o r through which 0.76 m  x 7.3 m g a l v a n i z e d  s t e e l pipes were f i t t e d . An a i r d i f f u s o r  installed  inside  0.3  m  d i f f u s o r c o n s i s t e d of four connected  to  a  the  bottom  0.38  m  of  iron  degree elbow t o prevent The  unit  was  the intake p i p e . The pipes  (3.81 cm  ID)  common c e n t e r , and d r i l l e d with ten 1.5 mm a i r  r e l e a s e holes per arm. The o u t l e t pipe  was  fitted  r e c i r c u l a t i o n of aerated  was b u i l t  with  a  45  water.  i n Vancouver, disassembled  to Black Lake, then reassembled ice  was  by Bernhardt and Wilhelms (1975),  Hess (1975), and Smith et a l . (1975) (Figure 2) consisted  this  and trucked  i n a h o r i z o n t a l p o s i t i o n on the  s u r f a c e . Chain saws were used t o remove i c e from around the  aerator,  which  operating  was  then  the  aerator  into  i t s normal  vertical  p o s i t i o n . The e n t i r e u n i t weighed 453 kg and was f r e e  floating. After ice-off above  lowered  9  m  the a e r a t o r  contour  and  was  securely  towed  into  position  anchored i n p l a c e . The  f l o a t e d 0.6 m above water at r e s t , the lake bottom  being  1.4 m below the lower end of the o u t l e t tube. A concrete  pad. (3 m x 3 m. x 0.3 m) was poured a t the l a k e ' s  west end, 18 m from the s h o r e l i n e and a plywood shed e r e c t e d  to  17  WASTE  AIR  COMPRESSED AIR  WATER WATER FIGURE  2.  INLET A SCHEMATIC DIAGRAM OF BLACK LAKE HYPOLIMNETIC  THE AERATOR.  OUTLET  18  house  the  compressor  contractor three  installed  phase  (Hydrovane  filter,  fuse panels and  operation. SR  purchased  and p r o v i d e working space. An  4000  and  A  new  rated  installed  transformers  7.5  1.13  kw  electrical  for  230  volt  r o t a r y vane compressor  m /min.  @  3  7.0  in the shed. An automatic  r e g u l a t o r and v a l v e s were connected  to  kg/cm )  was  2  drain o i l / a i r  the  compressor  thus a l l o w i n g p r e c i s e volume and p r e s s u r e r e g u l a t i o n of  oil-free  air. A  weighted a i r l i n e  way, v a l v e s was  laid  (106 m x 1.9  out  on  the  cm  ice  I.D.)  f i t t e d with one-  surface  connecting  the  compressor and a e r a t o r and allowed to sink i n t o p o s i t i o n at i c e off.  Curtain The  lake was  d i v i d e d i n t o approximately  by a p l a s t i c c u r t a i n author  and  (Figure 1 and  manufactured  in  Table  Vancouver  L t d . ) . The main s e c t i o n (103 m x 10.4 polyolefin  (Dupont  Fabrene  Type  m)  two  1)  equal s e c t i o n s  designed  was  composed  (W.R.  Eadie, DuPont L t d . , p e r s . comm.).  collar  (103  m  0.3  of u l t r a - v i o l e t  polyolefin  (Dupont Fabrene Type TM)  the  section.  main  This  prevent  surface  punctures.  surface marked the c u r t a i n distance  (103  m)  was  was  particular  minimize shadow formation, r e s i s t A  woven  attached to the design  was  ultra-violet rope  double  stretched  rope  top  of  intended  to  degradation  and  a c r o s s the i c e  cut open by c h a i n saws. The kg of l e a d  A  r e s i s t a n t black woven  i n s t a l l a t i o n p o s i t i o n and  unfolded along the s l o t , 113  of  P) which t r a n s m i t s 80-85% of  light  m)  the  ( F a l s e Creek I n d u s t r i e s  visible  x  by  the  entire  curtain  attached  to  was its  19  lower  edge and a styrofoam  black  gillnet  floatline  strung through the  s u r f a c e c o l l a r . The c u r t a i n was then pushed i n t o p l a c e and  sunk i n t o p o s i t i o n . Rocks were p i l e d on the near-shore ensure a snug f i t and SCUBA o b s e r v a t i o n confirmed was  well  a r e a , to  the lower edge  s e a l e d i n t o the sediment. The f l o a t i o n c o l l a r  10 cm above  the  water  surface  and  minimized  floated  surface  water  exchange.  Operat ion The  west  designated  end  of  the  lake contained  as the experimental  the a e r a t o r and was  s i d e while the east end served as  the simultaneous c o n t r o l s i d e . The compressor period  started  continuously entire  April  11, 1978, 11 days a f t e r  u n t i l March 6, 1979, a  system  was  and  installed  period  experimental  i c e - o f f , and ran  of  329  days.  The  i n ten 3-4 day t r i p s to P e n t i c t o n  s t a r t i n g J u l y 20, 1977 and f i n i s h i n g March 31, 1978.  Sampling All  samples were c o l l e c t e d  l o c a t e d near the center of apart  20  meters  on e i t h e r s i d e of the c u r t a i n (Figure 1 ) . Maximum  station  depth ranged from 8.27 period. angles the  from permanent sampling s t a t i o n s  The  west  m  the  to  lake  9.0  (experimental)  m  approximately  during  the  experimental  s t a t i o n was s i t u a t e d at r i g h t  to the a e r a t o r o u t l e t tube t o a v o i d sampling d i r e c t l y plume  of  aerated  water.  Replicate  p r o f i l e s taken p r i o r to the experiment  in  oxygen-temperature  i n d i c a t e d the two c e n t r a l  s t a t i o n s were r e p r e s e n t a t i v e s i t e s . A f t e r i c e formation  circular  20  holes were cut above each sample s i t e rubber quick  pails  and  100  litre  weighted  i n s e r t e d i n t o each opening. T h i s procedure allowed  entry  to  the  lake  during  sub-zero  temperatures  and  minimized water d i s t u r b a n c e when sampling. Samples 1978  were  taken  and at three week  March  1979.  Black  every two weeks from A p r i l  intervals  Lake  was  from  November  sampled  twenty  experiment, each f i e l d  t r i p a v e r a g i n g three days  addition  data  to  regular  maintenance,  collection,  to October  1978  through  times d u r i n g the i n d u r a t i o n . In  routine  compressor  a e r a t o r adjustments and l o g c l e a r i n g s were c a r r i e d  out on each t r i p .  Samples were u s u a l l y  collected  between  1000  and 1400 h r s .  Physical Physical Temperature ARC).  data  were  at  1  m  depth  s e r i e s were taken with a t h e r m i s t o r  Transparency  disc  collected  using  a  transmission  was  glass was  measured  bottom  obtained  Model  54  with a standard 20 cm Secchi  viewing with  (YSI  intervals.  box.  Percent  light  a Beckman EV3 Enviroeye l i g h t  meter.  Chemical D i s s o l v e d oxygen was measured at one meter an  oxygen  meter  (YSI 54 ARC).  Two  (Azide m o d i f i c a t i o n ) were used to each sampling All  intervals  r e p l i c a t e Winkler calibrate  the  with-  titrations  meter  during  period.  other  chemical parameters  were c o l l e c t e d at two meter  i n t e r v a l s with a e l e c t r i c b i l g e pump (Jabsco @ 26  litres/min.).  21  Samples  were poured  i n t o p o l y e t h y l e n e b o t t l e s , s t o r e d at 0 C i n  l i g h t - p r o o f c o n t a i n e r s and t r a n s p o r t e d to the l a b o r a t o r y 24 hours. The Environmental L a b o r a t o r y (Water Resources Ministry  of  the  Environment,  analyses according Service,  1976).  the appendix  to  their  within Service,  3650 Wesbrook UBC) performed a l l methods  manual  (Water  Resource  A b r i e f d e s c r i p t i o n of each method i s given i n  (Table 2 ) .  Chlorophyll a C h l o r o p h y l l a samples were taken at 2 meter stored  intervals  i n l i g h t - p r o o f c o o l e r s p r i o r to f i l t e r i n g . Two  and  replicate  sample volumes were vacuum f i l t e r e d at 2/3 atmosphere, preserved with magnesium carbonate s o l u t i o n , bottles  containing  a  silica  stored  at  desiccant  and  -73  C  in  dark  d e l i v e r e d t o the  Environmental Lab w i t h i n 48 hours. C h l o r o p h y l l a and phaeophyton a  concentrations  extraction  were  i n 90% acetone  determined  colorimetrically  ( S t r i c k l a n d and Parsons,  after  1968).  Phytoplankton Phytoplankton l i t r e Van Dorn preserved  were c o l l e c t e d a t 2 meter i n t e r v a l s with a 3  water  bottle,  with Lugol's s o l u t i o n  ml subsamples were p i p e t t e d  combined  into  sample  ( L i n d , 1979). For a n a l y s i s ,  and 100  i n t o graduated c y l i n d e r s and allowed  to s e t t l e o v e r n i g h t . The supernatant l i q u i d and  one  the remaining 25 mis r i n s e d  was  then  decanted  i n t o sedimentation chambers and  allowed to r e s e t t l e f o r 24 hours. Plankton were counted at 400 x using an i n v e r t e d microscope view,  and  results  were  with a  expressed  300 as  u  diameter  numbers  of  field  of  cells/ml.  22  Plankton genera were p a r t i t i o n e d remaining  genera  i n t o four major phyla with  lumped i n t o one group. Due  to the q u a l i t a t i v e  nature of the phytoplankton data only g e n e r a l trends were and  no  quantitative  analysis  i d e n t i f i c a t i o n and counting was  was  the  undertaken.  noted  Plankton  performed by Mr. A l Redenback at  U.B.C.  Zooplankton Zooplankton were c o l l e c t e d at one meter i n t e r v a l s with a 27 litre  S c h i n d l e r - P a t a l a s t r a p ( S c h i n d l e r , 1969)  mesh.  During  meter was  the  first  five  using 84 u  Nytex  sampling t r i p s one t r a p set per  used, a f t e r which two  r e p l i c a t e sets  (54 l i t r e s  total)  were combined f o r each depth i n t e r v a l . Samples were r i n s e d plastic  vials  solution  and  preserved  with  4%  formaldehyde/sucrose  (Haney and H a l l , 1973). Plankton were subsampled  1 ml Stempel counted  pipette  under  a  Subsample s i z e was  into  10  dissecting  ml  Sedgwick-Rafter  microscope  (Wild  a d j u s t e d to o b t a i n at l e a s t  cells  M5) 100  with a  at  the  entire  sample  expressed as numbers/m designed  for  2  was  and  counted.  tabulated  the experiment  on  Sample a  counts  counts  computer  and 25 x.  any given s p e c i e s up to a maximum of 10 mis per subsample, which  into  for after were  program  (G.J. S t e e r , S.F.U. Grad..Student,  p e r s . comm.).  Aerator Water flow r a t e s were measured with a flowmeter the  (General  Oceanics  No.  recently  calibrated  2035) s i t u a t e d 2 meters  s u r f a c e i n the downflow tube. A i r flow was  calculated  below from  23  nomograms  and  diameters flow  tables  for  various  air  p r e s s u r e s and  ( A t l a s Copco, 1978). Oxygen was  tube  at  oxygen meter  measured i n  a depth of f i v e meters with a Winkler  (YSI 54  orifice  the  down  calibrated  ARC).  Statistics The  statistical  experimental written  data  by N.E.  is  a  Gilbert  creates  two-way  sampling  dates  experimental  test  of  the program  produces  differences  between  a  By  i t s duplicate two-way  experimental  and  significant  differences the  differences.  between sides  differences,  and  by  Lake  table control  If  however,  program  variable  subtracting  control  sides were s i m i l a r the net r e s u l t should be near no  the  as the row  variable.  single  Black  Conceptually,  depths  column  (west) data from  analyse  a n a l y s i s of v a r i a n c e program  U.B.C.  using  the  to  two-way  tables as  used  and the  (east) data  based  on  the  s i d e s . If both zero  and  show  there  are  real  the program analyses the magnitude  of  using the a p p r o p r i a t e F t e s t one  can  e i t h e r accept the n u l l h y p o t h e s i s or r e j e c t i t and a t t r i b u t e the observed were  r e s u l t s to the  performed  experimental  manipulation.  in  the  appendix  and  zooplankton  recommended by N.E.  Larkin  i n f u r t h e r d e t a i l by G i l b e r t  i s outlined  list is  (Table 4 and Table 5). T h i s p a r t i c u l a r  method of a n a l y s i s was and  tests  at the 1% l e v e l of s i g n i f i c a n c e . A complete  of F v a l u e s f o r water chemistry parameters given  All  G i l b e r t and Dr. (1972).  P.A.  24  RESULTS  C i r c u l a t i o n Processes The  compressor  was  s t a r t e d on A p r i l 11, 1978  a f t e r p r e - a e r a t i o n data were c o l l e c t e d  from both  immediately  sides  of  l a k e . A i r bubbles r i s i n g up the inflow tube acted as an pump  and  generated a l a r g e volume-low v e l o c i t y water  a i r - w a t e r plume rose 10 separator  box  towards the  while  cm  above  degassing,  downflow  tube.  strong  odour  of  H^S  water  then  Aerated  downflow tube and d i s c h a r g e d back A  the  water  separator  box.  No  then  the  remainder  of  remained c l e a r d u r i n g  aerator  immediately  the  experiment.  initial  startup  was examined  to determine an e f f i c i e n t  under  released away  daily  m /day.  circulation was  1.2  Water and  15365  from  i n the a e r a t o r  regular  operation  s e v e r a l water flow regimes  3  m /min  which  3  Theoretical  time (hypolimnion volume=18779 m ) 3  at  setting  generated  a  hypolimnetic this  setting  days, and 5.7 days were r e q u i r e d to c i r c u l a t e the e n t i r e  experimental s i d e The 11, 1978 in  of  from  persisted  o p e r a t i o n a l s e t t i n g . The f i n a l 10.67  rate  the  not o c c u r r i n g .  chosen f o r the experiment was flow  the box  odour was evident d u r i n g the next  i n d i c a t i n g sediment d i s r u p t i o n was The  the  entered  sampling p e r i o d , however a c h a r a c t e r i s t i c musty odour for  in  i n t o the hypolimnion.  was  H^S  flow. The  across  upwelling water and c o u l d be d e t e c t e d s e v e r a l meters the  air-lift  surface  flowed  the  early  (87971 m )  compressor  3  was  under  i c e cover.  intended to run c o n t i n u o u s l y from A p r i l  to March 6, 1979 however e l e c t r i c a l problems September.  As  a r e s u l t , the compressor  developed  operated f o r  25  only three days  i n the p e r i o d from September 5, 1978 to  23,  1978.  1978  and the e n t i r e system f u n c t i o n e d  winter  October  The separator box f r o z e i n t o the i c e during November  season.  normally  throughout  the  A small r i n g of i c e formed around the i n s i d e of  the separator box but t h i s was kept to a minimum by the moving a i r - w a t e r  rapidly  current.  Temperature Black 1978  Lake experienced balmy weather  spring  disappeared  i c e melt. within  Consequently  three  c o n d i t i o n s d u r i n g the  the  entire  ice  days and the lake q u i c k l y  without f u l l y c i r c u l a t i n g . A e r a t i o n s t a r t e d 11 days off  when  temperatures  (bottom). In s p i t e aerated  side  i t s lowermost Thermal  of  ranged this  stratified  from  small  8.5  Maximum  C  after i c e -  temperature  gradient,  normally while the a e r a t o r  the  circulated  four meters. s t r a t i f i c a t i o n was maintained throughout the summer  s u r f a c e temperature  and maximum bottom 11.0  stratified  C ( s u r f a c e ) to 4.0 C  in both experimental and c o n t r o l p o r t i o n s of 3).  cover  (control)  on  lake  (Figure  (22 C) was reached on August 1  temperatures of occurred  the  12.6  August  C  (experimental) and  29  and  September  10  respectively. The most aeration of  an  between entire  pronounced  temperature  effect  was c i r c u l a t i o n of the bottom isothermal five year  and and  characteristics  hypolimnion.  The  of h y p o l i m n e t i c  four meters and c r e a t i o n temperature  differential  nine meters was 0.5 C or l e s s throughout the the  new' hypolimnion  assumed  temperature  of the f i v e to s i x meter stratum. T h i s  resulted  26  Fig. 3  Temperature i s o p l e t h s f o r e x p e r i m e n t a l (east) s i d e s . '  (west) and c o n t r o l  27  from mixing and d i l u t i o n of smaller c o l d with l a r g e r c o o l s t r a t a Heat  content  volumes  on  the  aerated  side  increased  calories/day.  Both  October  experienced  and  circulation until small  sides  destratified vigorous  of  (5 m x 10 m) area near tube  i n mid autumnal  the shore d i r e c t l y  remained  ice-free  in l i n e  throughout  the winter. Aerated water d i s c h a r g i n g from the outflow  tube c o n t a i n e d s u f f i c i e n t momentum  to  flow  d e f l e c t up the steep s h o r e l i n e , p e n e t r a t e and melt small  driven  across  the  lake,  inverse s t r a t i f i c a t i o n  s e v e r a l c e n t i m e t e r s of i c e cover. The a e r a t o r c r e a t e d a  open water area near  nearby as i t remained f i r m l y  itself frozen  however one c o u l d s a f e l y work in  the  i c e . Hypolimnetic  a e r a t i o n under i c e cover c i r c u l a t e d the e n t i r e experimental (except  for microstratification  a e r a t o r . The throughout  control  side  maintained  inverse  by the  stratification  winter.  Control  side  heat  content  decreased  1323 x 1.0' c a l o r i e s  from August 1 to i t s lowest p o i n t on March 6, 10' c a l o r i e s / d a y . The a e r a t e d s i d e l o s t 1  side  at 0-1 m) as the weak i n v e r s e  s t r a t i f i c a t i o n c o u l d not r e s i s t mixing c u r r e n t s generated  August  10'  i c e formation i n mid November.  with the a e r a t o r ' s outflow most  x  simultaneously wind  x  absorbing  c a l o r i e s over the same p e r i o d and averaging 8.6  5  A  956 x 10'  r a t e of 8.5  c a l o r i e s / d a y . C o n t r o l s i d e heat gain was s i m i l a r ,  968 x l O  8-9m)  (5-6m, 6-7m).  c a l o r i e s from A p r i l 11 to August 1, at an average 10'  (7-8m,  to  i t s . coldest  point  averaging  6.1  1315 x 10' c a l o r i e s  on February  x  from  13, c o o l i n g more  r a p i d l y at 6.7 x 10' c a l o r i e s / d a y . Temperature r e s u l t s were s i g n i f i c a n t  (2 way ANOVA, p < .01)  28  as the experimental hypolimnion summer,  and  cooler  through  was  warmer  fall  during  spring  and  and winter than the c o n t r o l  hypolimnion.  Transparency Secchi d i s k transparency was both s i d e s throughout mid  July,  greater m  mid  August  were  and  the  onset  (aerated) and  7.0  through  of  on  f o r three p e r i o d s i n  when  c o n t r o l values were  April  bloom. Secchi summer  m (aerated) and  and  depths  reaching  gradually,  maximum  increased  values of 5.4  conjunction  near  with  3 m through  fall  August as c h l o r o p h y l l values were at a  the f a l l  phytoplankton  surface  light  s i m i l a r to S e c c h i depths ( F i g u r e 4 ) . Low sides  were  recorded  during  the  i n c r e a s i n g to maximum readings of 5.2 (control)  in  late  bloom and  c i r c u l a t i o n and winter  Values of 1% i n c i d e n t  July  to  remained  i c e cover. followed  a  values of 2.5  spring m  August  bloom,  (aerated)  pattern m on  and  6.4  began  bloom developed  i n l a t e August as the f a l l fall  cover. Minimum 1% depths of 2.0 late  January-early  thickness.  February  m  e a r l y August. C o n t r o l values were August.  continued downward through  both  gradually  c l e a r l y g r e a t e r (>1 m) during l a t e J u l y and declining  m  remained  seasonal minimum. Secchi depths began d e c r e a s i n g i n l a t e in  1.0  25, c o i n c i d i n g with the  m ( c o n t r o l ) on.July 18. Transparency  July  on  except  January  obtained  v e r n a l phytoplankton  high  the experiment  (< 1 m d i f f e r e n c e )  ( F i g u r e 4 ) . Minimum readings of 1.6  (control)  with  similar  circulation  into  1%  depths  winter  and ice  m were recorded on both s i d e s i n  when i c e cover reached  i t s maximum  BLACK L A K E DATA  +  SECCHI  X  DEPTH EAST  BLRCK L A K E DATA  Fig.  4  1978-79  SECCH1 DEPTH WEST  1978-79  1/  TRANSMISSION DEPTH WEST  +  1/  TRANSMISSION DEPTH EAST  X  S e c c h i and 1% t r a n s m i s s i o n depths f o r e x p e r i m e n t a l (west) and c o n t r o l (east) s i d e s .  30  Decomposition  Processes  Oxygen The a e r a t o r i n c r e a s e d d i s s o l v e d oxygen by an average mg/1  on each c y c l e through  the system. Water flow  at  15365 m /day, t h e r e f o r e a t o t a l of 10.76  to  the  hypolimnion  (5-9  m).  As  a  h y p o l i m n e t i c oxygen c o n c e n t r a t i o n s i n c r e a s e d from 0.2 mg/1  after  13  0.1-0.3 mg/1 below  days  added  result, to 2.0-2.5  a e r a t i o n while c o n t r o l values remained at  (Figure 5).  Hypolimnetic  oxygen  levels  remained  s a t u r a t i o n a l l summer however near bottom values (9m)  the a e r a t e d p o r t i o n were c o n s i s t e n t l y higher in the c o n t r o l p o r t i o n similar  on  both  0.7  constant  kg O^/day was  3  experimental  was  of  (0.2  sides  mg/1  and  av.).  averaged  (2.7 mg/1  Surface 8.5  mg/1  av.)  in than  values  were  from May  until  August. Oxygen s t r a t i f i c a t i o n was  d i s r u p t e d by f a l l  by October  24 s u r f a c e and bottom values d i f f e r e d  0.8  F a l l c i r c u l a t i o n was  mg/1.  observed  over  the  Consequently,  whole  oxygen  content  w i t h i n three weeks (October completely of 7.2 7.1  lake  less  than  vigorous and breaking waves were surface  for  the  first  on both s i d e s doubled  levels  (0 m) mg/1  Black  (Figure 6)  on November 14 and entered winter with oxygen to 7.6  24-November 14).  time.  froze  (0 m) mg/1  (experimental) and  5.5  (9  m)  to  (control).  A e r a t i o n continued throughout side  remained above 4.9 recorded  by  and  Lake  (9 m)  experimental  circulation  value  under mg/1  was  winter c i r c u l a t i n g the  i c e cover. Experimental  a l l winter and by 6.0  mg/1.  In  March  contrast,  oxygen 6  entire levels  the  lowest  control  oxygen  31  Fig. 5  Oxygen i s o p l e t h s f o r e x p e r i m e n t a l sides.  (west) and c o n t r o l  (east)  32  BLRCK  Fig. 6  LAKE DflTfl  1978-79  TOTAL OXYGEN WEST  +  TOTAL OXYGEN EAST  X  T o t a l oxygen c o n t e n t i n e x p e r i m e n t a l (east) s i d e s .  (west) and c o n t r o l  33  c o n c e n t r a t i o n s d e c l i n e d markedly d u r i n g winter and mg/1  was  present  to March  i n the lowermost s t r a t a  1.0  (8-9 m)  from January  23  oxygen  consumption  as  6.  Hypolimnetic  aeration  experimental  side  considerably  higher  values  l e s s than  stimulated  hypolimnetic  oxygen  (0.39-0.78  depletion  mg/l/day)  than  rates  were  control  side  (0.03-0.09 mg/l/day). Summer and winter oxygen d e p l e t i o n  r a t e s were v a r i a b l e however winter experimental;  0.04-0.06  than summer v a l u e s mg/l/day  (2 way  As  (0.39-0.61  mg/l/day  mg/l/day c o n t r o l ) were g e n e r a l l y lower  (0.46-0.78 mg/l/day  control).  significant  values  would  experimental;  be expected,  ANOVA, p < .01)  0.03-0.09  oxygen r e s u l t s were  as the experimental  side  was  (experimental) and  7-16  c o n s i s t e n t l y higher i n d i s s o l v e d oxygen.  T o t a l Organic TOC mg/1  levels  ranged  Carbon  from 8-14  mg/1  ( c o n t r o l ) i n e a r l y A p r i l . C o n c e n t r a t i o n s remained  l a t e A p r i l and May maximum  (Figure  as the s p r i n g phytoplankton 7). TOC  when phytoplankton values  (0  however  m)  hypolimnetic  experimental  side  av. c o n t r o l ) sedimentation TOC autumnal overturn.  as  in  bloom reached i t s  then d e c l i n e d during the summer months  biomass was  averaged  high  at i t s seasonal minimum.  8.7  mg/1  values (9.3  (9  on both s i d e s d u r i n g summer, m)  mg/1  circulation  Surface  were  higher  on  av. experimental;6.7 currents  reduced  the mg/1  detrital  rates.  increased bloom TOC  again  developed declined  t.o and  12-18  mg/1  remained  slightly  i n September as the high'  after  ice  through formation  fall as  34  3LRCK-LRKE-WEST-ORGAN IC-CRRBQN-MG/L  "APRIL  MAY 1  9  7  JUNE  JULY  AUG  AUG  SEPT  OCT  SAMPLING DATE  8  DEC  FEB  "  APRIL 1979  ! BLRCK-LRKE-ER5T-GRGRNIC-CRRBON-MG/L °~  \  APRIL  V  MAY 1  9  7  8  Fig. 7  1V0  MO  JUNE  JULY  I  600  AUG  ^  y  AUG SAMPLING DATE  T o t a l o r g a n i c carbon i s o p l e t h s and c o n t r o l (east) s i d e s .  \  \  SEPT  Vl<KJ  OCT  DEC '  f o r experimental  FEB  APRIL 1979  (west)  35  p a r t i c u l a t e • matter allochthonous TOC  levels  settled  inputs on  significantly  the  from  the  were reduced. aerated  water  column  Despite higher  side,  TOC  and  hypolimnetic  values  were  not  (p > .01) i n f l u e n c e d by h y p o l i m n e t i c a e r a t i o n .  Major N u t r i e n t s  (Note:Nitrogen  and phosphorus data are expressed  amount of N and P they  i n terms of the  contain.)  Nitrogen The  immediate e f f e c t of experimental  reduction  i n hypolimnetic ammonia  the experimental after  s i d e decreased  a e r a t i o n was a marked  l e v e l s . Hypolimnetic  from 3900  ug/1  to  l e v e l s on  25-54  ug/1  j u s t 13 days a e r a t i o n whereas bottom c o n c e n t r a t i o n s on the  c o n t r o l s i d e remained at 2100-3090 ug/1 (Figure 8 ) . Hypolimnetic (9  m)  ammonia  experimental than  control  l e v e l s g r a d u a l l y i n c r e a s e d d u r i n g summer however  values  (300 ug/1 av.) remained  values  lower  (1741 ug/1 a v . ) . Surface c o n c e n t r a t i o n s of  NH -N were s i m i l a r on both s i d e s ug/1 (aerated) and 36 ug/1 Ammonia  considerably  during  summer,  averaging  33  (control).  stratification  was  eventually  d i s r u p t e d by  fall  c i r c u l a t i o n and l e v e l s d e c l i n e d and converged during three weeks of  vigorous mixing. Ammonia l e v e l s on  distributed  sides  beneath i c e cover and changed l i t t l e  Ammonia r e s u l t s were s i g n i f i c a n t aeration  both  reduced  experimental  d u r i n g s p r i n g and summer months.  (2  way  ANOVA,  were  evenly  during  winter.  p  <  .01)  s i d e h y p o l i m n e t i c ammonia  as  levels  36  B L R C K - L R K E - W E 5 T - N ITRQGEN : RMMONIR-;JG/L  '  APRIL  MAY  JUNE  JULY  AUG .  1978  AUG  SEPT  OCT  DEC  FEB  DEC  FEB  SAMPLING DATE  B L R C K - L R K E - E R 5 T - N I T R G G E N : RfiMQN I R - j J G / L  APRIL  MAY 1978  Fig. 8  JUNE  JULY  AUG  AUG SAMPLING DATE  SEPT  OCT "  Ammonia n i t r o g e n i s o p l e t h s f o r e x p e r i m e n t a l c o n t r o l (east) s i d e s -,  '  APRIL 1979  (west) and  37  B a c t e r i a l n i t r i f i c a t i o n was aeration. Nitrate f i r s t (> 0.02 then 0.12  mg/1)  appeared  a l s o i n f l u e n c e d by hypolimnetic in  measureable  on June 13. Experimental  side hypolimnetic  rose d u r i n g summer, i n c r e a s i n g from 0.05 mg/1  (August  levels,  29)  ( F i g u r e 9). However,  nitrification  d i d not occur  concentrations  mg/1  due  (June 13)  to  low  i n the c o n t r o l  low  nitrate  24  were undetectable u n t i l October  Surface n i t r a t e was 0.02  mg/1  to  c o n s i s t a n t l y low a l l  0.04  mg/1  summer,  (experimental) and  to  oxygen  hypolimnion.  As a r e s u l t , c o n t r o l s i d e bottom l e v e l s remained samples  nitrate  and  9  (Figure 9).  ranging  0.02  m  from  to 0.08  mg/1  (control). Nitrate increased of  increased considerably during f a l l  oxygen  levels stimulated n i t r i f i c a t i o n  the l a k e . A w e l l  observed.  Initially  defined NH^-N  nitrification decreased  i n t e r m e d i a t e product. N i t r i t e after  4  weeks  circulation  fall  stabilized  circulation,  at  then  on both s i d e s  sequence  and NO^-N  was  then  appeared  as an  0.014-0.016  began  mg/1  declining  e v e n t u a l l y decreased  below d e t e c t i o n l e v e l s  January. N i t r a t e was  homogeneously d i s t r i b u t e d at 0.33-0.34  on both s i d e s at i c e formation and progressed. mg/1  (0.005 mg/1)  increased  Maximum values of 0.50  mg/1  slowly  and  in late  as  mg/1  winter  (experimental) and  0.48  ( c o n t r o l ) were recorded on March 6 a f t e r n e a r l y four months  o f . i c e cover. N i t r a t e l e v e l s were s i g n i f i c a n t l y <  as  .01)  data was blank  higher i n the a e r a t e d hypolimnion  (2 way  ANOVA,  p  d u r i n g summer. N i t r i t e  not s t a t i s t i c a l l y analyzed as 70 % of the samples  were  (< 0.005 mg/1). Total  organic  r e l a t e d to seasonal  nitrogen trends  (TON) in  results  phytoplankton  were v a r i a b l e abundance.  and Pre-  38  B L . R C K - L R K E - W E 5 T - N I TROGEN : N I T R R T E - M G / L .020  "APRIL  MAY 1  9  7  t  JUNE  .  JULY  AUG  AUG  , ,,  SEPT  OCT  SAMPLING DATE  8  DEC  FEB  '  APRIL 1979  BLRCK-LRKE-ER5T-NITROGEN:NITRRTE-MG/L  APRIL  MAY "  7  8  Fig. 9  . JUNE ,  JULY  AUG  AUG SAMPLING DATE  SEPT  OCT  DEC  FEB  APRIL  '  1979  N i t r a t e nitrogen i s o p l e t h s f o r experimental c o n t r o l (east) s i d e s .  (west) and  39  aeration  v a l u e s of TON ranged  (2 m experimental) control).  After  and 0.53 two  from  mg/1  weeks  0.96 mg/1 (8  m)  (0 m) t o 1.22 mg/1  to  1.18  mg/1  a e r a t i o n experimental  values d e c l i n e d to 0.98 mg/1, then  averaged  (6 m  bottom (8 m)  0.75  mg/1  during  summer ( F i g u r e 10). C o n t r o l bottom values i n c r e a s e d to 0.90 mg/1 on  April  24  and  averaged  only  0.63  mg/1 through  q u i e s c e n t c o n d i t i o n s allowed sedimentation of 10).  Surface  values  averaging 0.57 mg/1 values  averaged  of  TON  mg/1.  detritus  This  while  stages of the experiment.  s i d e s at f a l l  circulation,  values  significantly  were  between  sides  hypolimnion  as  then (2  difference  side  may r e s u l t  from  s i d e during  TON i n c r e a s e d s l i g h t l y on both decreased way  experimental  and lower  side,  experimental  stream water d i l u t i n g TON v a l u e s on the experimental initial  (Figure  were higher on the c o n t r o l  (May 9-August 29)  0.50  summer as  during  ANOVA,  values  winter.  TON  p < .01) d i f f e r e n t  were  higher  in  the  i n the e p i l i m n i o n during summer months.  Phosphorus Hypolimnetic ions  in  the  hypolimnetic  aeration  experimental PO^-P  p r e c i p i t a t e d orthophosphate hypolimnion.  v a l u e s reached  Prior  to  (PO^-P)  aeration,  1100 ug/1 (experimental) and  995 ug/1 ( c o n t r o l ) . A f t e r two weeks a e r a t i o n experimental  8  and  9 m PO4-P d e c l i n e d to 321-322 ug/1, while c o n t r o l 8 and 9 m PO^P remained a t 735-955 ug/1 ( F i g u r e 11). Hypolimnetic during  (9 m) v a l u e s on the experimental  405  ug/1  (May  9) t o 480 ug/1 (August  sedimentation  of  side  averaged  summer, however PO^-P i n c r e a s e d from 344 ug/1 15) due to  epilimnetic  P  aerobic  compounds.  P  release  Control  and  side 9 m  40  BLACK-LAKE-WEST-NITROGEN:ORGAN IC-MG/L  JUNE  JULY  AUG  AUG  SEPT  OCT  DEC  FEB  SAMPLING DATE  1979  BLRCK-LHKE-EA5T-NITROGEN:ORGANIC-MG/L  JUNE  JULY  AUG  AUG SAMPLING DATE  F i g . 10  SEPT  OCT  DEC '  T o t a l organic nitrogen i s o p l e t h s f o r experimental and c o n t r o l (east) s i d e s .  FEB  APRIL 1979  (west)  41  BLRCK-LRKE-WE5T-0RTH0PH05PH0RU5-AIG/L  APRIL  MAY "78  JUNE  JULY  AUG  AUG  SEPT  SAMPLING DATE  OCT  DEC  FEB  APRIL  '  1979  '  1979  BLRCK-LRKE-ERST-0RTH0PH05PH0RU5-/JG/L  1978  F i g . 11  SAMPLING DATE  Orthophosphate phosphorus i s o p l e t h s f o r e x p e r i m e n t a l (west) and c o n t r o l (east) s i d e s .  42  v a l u e s were much-higher ug/1  (May  9)  to  (682 ug/1  809  ug/1  av.)  and  (August  increased  from  625  29) as anoxic c o n d i t i o n s  s t i m u l a t e d anaerobic P r e l e a s e . Unusually high e p i l i m n e t i c PO^-P Lake.  Both  sides  averaged  a e r o b i c hypolimnion other.  This  large  phosphorus  and  phytoplankton biological  on one  284  low  r e s u l t s ) suggests and  PO^-P  and  became  most  PO^-P  the  level  of  levels  is  in  excess  eliminated  i s o c h e m i c a l at 360 350 ug/1  ug/1  during  way  throughout  p  <  .01)  began i n c r e a s i n g again  in  the  aeration  mg/1  and  experimental  increased  d i s s o l v e d organic phosphate (DOP)  in  late  anaerobic lower  hypolimnion  in  the  the  concentration  aerated  sedimentation (theoretical  rates  by  actively  hypolimnetic  more  time  which  is  for  circulating  circulation decomposition  reflected  in  phosphate  the  detrital  hypolimnion  days).  of sedimenting  higher  consumption r a t e s on the experimental Particulate  time=1.2  of  hypolimnion  (Figure 12). T h i s o c c u r r e d as a e r a t i o n c u r r e n t s reduced  material  24.  most of the year.  Experimental  allowed  by  on both s i d e s during w i n t e r .  oxygen l e v e l s d e c l i n e d below 0.5  ANOVA,  of  fall  on October  r e l e a s e o c c u r r e d . Orthophosphate l e v e l s were s i g n i f i c a n t l y (2  (see  would not be markedly a f f e c t e d  However, c o n t r o l s i d e 9 m PO^-P as  on  activity.  l e v e l s remained near  January  background  chlorophyll  Orthophosphate s t r a t i f i c a t i o n was circulation  Black  during summer d e s p i t e an  constant  unusually  seasonal changes i n a l g a l  ug/1  in  s i d e and an anoxic hypolimnion  relatively  requirements  l e v e l s occurred  hypolimnetic  This  detrital oxygen  side.  r e s u l t s were a l s o i n f l u e n c e d by  the  43  BLACK  L A K E DATA  HYPOLIMNETIC  OOP WEST  +  HYPOLIMNETIC  DOP EAST  X  SAMPLING  F i g . 12  1978-79  DATE  H y p o l i m n e t i c d i s s o l v e d o r g a n i c phosphorus c o n t e n t i n e x p e r i m e n t a l (west) and c o n t r o l (east) s i d e s .  44  experimental trends  in  treatment. phytoplankton  Epilimnetic  values  followed  abundance and were g e n e r a l l y higher i n  the c o n t r o l s i d e i n s p r i n g and i n the experimental The  reason  for this  side in f a l l .  i s not c l e a r , however stream d i l u t i o n may be  i n v o l v e d . Hypolimnetic values r e f l e c t e d d e t r i t a l Midsummer  values  were  higher  phosphate were s i g n i f i c a n t l y  in  increased  the  sedimentation.  g e n e r a l l y higher on the a e r a t e d s i d e as  c i r c u l a t i o n c u r r e n t s delayed sedimentation particulate  seasonal  experimental  r a t e s . Both  DOP  and  (2 way ANOVA, p < .01)  hypolimnion.  Although  aeration  a e r o b i c P r e g e n e r a t i o n , t o t a l P remained lower on the  experimental  s i d e (Figure 13).  N:P- R a t i o s Total Nttotal P ratios Black  Lake  were  (weight:weight)  remarkably  constant  experiment. Whole l a k e , e p i l i m n e t i c  on  both  throughout  sides the  of  entire  (0-5 m) and h y p o l i m n e t i c (5-  9 m) r a t i o s were examined on both experimental and c o n t r o l s i d e s and a l l r a t i o s were between 1.6-3.8 (Figure  14). E a r l y  spring  N:P r a t i o s were the h i g h e s t , r e a c h i n g 3.8 (experimental) and 3.6 (control) values ratios  in  April  1978. R a t i o s then d e c l i n e d to t h e i r  (1.6 experimental;1.7 started  rising  lowest  c o n t r o l ) during summer months.  again  in  early  fall  and  N:P  gradually  i n c r e a s e d to 3.1 (experimental) and 3.0 ( c o n t r o l ) i n March 1979.  45  BLACK LAKE DATA 1978-79 TOTAL P WEST' + TOTAL P EAST X  APRIL  MAY  JUNE  JULY  AUG  FEB  SEPT  1979  1978  SAMPLING  F i g . 13  DRTE  T o t a l phosphorus c o n t e n t i n e x p e r i m e n t a l c o n t r o l (east) s i d e s .  (west) and  MARCH  46  BLACK LAKE DATA 1978-79 N:P RATIO WEST + N:P RATIO EAST X  3.06 O  CE  Q_  2.72 4  2 ..38 + 2.04  APRIL  MAY  JUNE  JULY  AUG  AUG  SEPT  OCT  NOV  DEC  JAN  FEB 1979  1978  SAMPLING  F i g . 14  DATE  Whole lake N:P r a t i o s i n e x p e r i m e n t a l c o n t r o l (east) s i d e s .  (west) and  MARCH  47  Major  Total  Hypolimnetic  aeration  Ions  Alkalinity  profoundly  influenced  exchange r e a c t i o n s at the sediment-water hypolimnetic  alkalinity  to 213 mg/1 a f t e r values  were  (9 199  hypolimnion  ion  i n t e r f a c e . For example,  (as CaCO^) decreased from 233-261 mg/1  j u s t 13  days  aeration.  Control  hypolimnion  near 256 mg/1 d u r i n g the same p e r i o d . Experimental  hypolimnion averaging  major  m)  levels  mg/1  as  remained  compared  much  to  lower  241  a l l summer,  mg/1 i n the c o n t r o l  (Figure 15).  E p i l i m n e t i c a l k a l i n i t y was not a f f e c t e d by the experimental treatment as both s i d e s averaged circulation  197 mg/1 through  eliminated a l k a l i n i t y  summer.  Fall  s t r a t i f i c a t i o n and both  sides  maintained s i m i l a r l e v e l s throughout  winter.  Calcium and Magnesium Hypolimnetic c a l c i u m l e v e l s a l s o decreased d u r i n g a e r a t i o n , thus  supporting  introduction.  precipitation  Experimental  from 49 mg/1 to values  the  43  increased  mg/1 from  theory  outlined  the  h y p o l i m n e t i c (9 m) c a l c i u m d e c l i n e d following  49  mg/1  to  aeration 51 mg/1  e f f e c t p e r s i s t e d a l l summer (43 mg/1 av.  calcium  was same  not  whereas  (Figure 16). T h i s mg/1  circulation.  affected  period.  control  experimental;58  av. c o n t r o l ) , e v e n t u a l l y d i s a p p e a r i n g at f a l l Epilimnetic  in  averaged  42 mg/1 during the  similar  on both s i d e s . Magnesium ions responded  and  Winter  both  sides  values  were  i n an analogous  F i g . 15  T o t a l a l k a l i n i t y i s o p l e t h s f o r experimental and c o n t r o l (east) s i d e s .  (west)  BLHCK-LflKE-WEST-CflLCIUM-MG/L  APRIL  MAY  JUNE  JULY  AUG  1978  AUG  SEPT  OCT  DEC  FEB  S A M P L I N G DATE  APRIL 1  9  7  9  BLRCK-LAKE-ERST-CRLCIUM-MG/L  APRIL  MAY 1978  F i g . 16  JUNE  JULY  AUG  AUG  SEPT  OCT  DEC  FEB  S A M P L I N G DATE  Dissolved calcium i s o p l e t h s f o r experimental and c o n t r o l (east) s i d e s .  APRIL 1  9  7  9  (west)  50  fashion av.  ie.  lower hypolimnetic  experimental;18  levels  (11.6 mg/1  s i d e s through  mg/1  l e v e l s during  av. c o n t r o l ) ,  av.) and  equivalent  summer  similar  (13  mg/1  epilimnetic  concentrations  on  both  winter.  Manganese Hypolimnetic manganese l e v e l s i n Black Lake were 20-60 f o l d higher  than  epilimnetic  levels.  Low oxygen c o n d i t i o n s  hypolimnion reduced the o x i d i z e d b a r r i e r at interface As  was  the  sediment-water  and l a r g e q u a n t i t i e s of reduced ( M n ) were +2  expected,  the  effect  of  i n the  hypolimnetic  released.  aeration  on  manganese d i s t r i b u t i o n was s t r i k i n g . Experimental s i d e d i s s o l v e d manganese  (<  mg/1) w i t h i n  0.45  u) was reduced below d e t e c t i o n  l i m i t s (0.02  2 weeks (Figure 17). P a r t i c u l a t e manganese  (>  0.45  u) then b r i e f l y appeared, sedimented and remained absent f o r the remainder  of  the  summer.  hypolimnion remained high  Dissolved  manganese i n the c o n t r o l  (0.88-1.04 mg/1)  during  this  (Figure 17) however p a r t i c u l a t e manganese was a l s o This  effect  persisted  a l l summer  values  mg/1  av.) than c o n t r o l values  were  similar  on  (1.15  (9 m)  of magnitude lower  mg/1  av.).  Surface  both s i d e s throughout summer and were  u s u a l l y below 0.02 mg/1. Autumnal c o o l i n g and disrupted  detected.  as hypolimnetic  l e v e l s on the experimental side were an order (0.20  period  fall  circulation  d i s s o l v e d manganese s t r a t i f i c a t i o n and the o x i d a t i o n -  sedimentation sequence was repeated. Manganese was homogeneously d i s t r i b u t e d at 0.04-0.05 mg/1 this  level  both  sides.  during  by October  winter as aerobic  A l l major  ions  24,  and  remained  c o n d i t i o n s were present  examined  (alkalinity,  at on  calcium,  51  BLflCK-LRKE-WEST-DI550LVED-MRNGRNE5E-MG/L  "APRIL  MAY "78  JUNE  JULY  AUG  AUG  SEPT  OCT  DEC  SAMPLING DATE  FEB -  APRIL "79  BLRCK-LRKE-EflST-DISSOLVED-MRNGflNESE-MG/L  '.'78  SAMPLING DATE  '  F i g . 17 . D i s s o l v e d manganese i s o p l e t h s f o r e x p e r i m e n t a l c o n t r o l (east) s i d e s .  "79  (west) and  52  magnesium  and manganese) were s i g n i f i c a n t l y  p < .01) i n the experimental  hypolimnion.  were u s u a l l y below d e t e c t i o n l e v e l s  lower Iron  (2 way ANOVA, concentrations  (0.1 mg/1).  pH I n t e r a c t i o n s  The  hypolimnion  experimental (7.7-7.8)  Black  Lake  a e r a t i o n . As a r e s u l t ,  in  Hypolimnetic  of  relation  to  anoxic  prior  i t s pH l e v e l s were  normal  surface  aeration s i g n i f i c a n t l y  .01) pH l e v e l s on the experimental  was  values  depressed (8.0-8.1).  i n c r e a s e d (2 way ANOVA, p <  s i d e . E p i l i m n e t i c values were  not a f f e c t e d however h y p o l i m n e t i c l e v e l s were g e n e r a l l y pH  units  to  0.1-0.4  higher than corresponding c o n t r o l s i d e v a l u e s (Figure  18). F a l l c i r c u l a t i o n minimized  pH d i f f e r e n c e s between s i d e s and  homogeneous l e v e l s p e r s i s t e d throughout  the w i n t e r .  Phytoplankton  Biomass ( c h l o r o p h y l l The  s p r i n g phytoplankton  sampling  started  in  early  a)  bloom  was  well  April  1978.  c h l o r o p h y l l v a l u e s were among the h i g h e s t experiment. C o n t r o l c h l o r o p h y l l a  43  a  way  when  result,  April  recorded  during  the  reached a maximum of 54 ug/1 and  ug/1 maximum was recorded on the experimental  the s p r i n g bloom, c h l o r o p h y l l on levels  As  under  both  sides  side. After  declined  to low  (Figure 19). Average s u r f a c e values d u r i n g summer months  (May-August) (control).  were  4.2  ug/1  (experimental)  and  4.5  ug/1  Bottom v a l u e s (9 m) were a l s o low averaging 5.5 ug/1  53  BLACK LAKE DATA 1978-79 HYPOLIMNETIC (9 M) P H WEST + HYPOLIMNETIC (9 M) P H EAST X  F i g . 18  H y p o l i m n e t i c pH l e v e l s i n the e x p e r i m e n t a l c o n t r o l (east) s i d e s .  (west) and  F i g . 19  C h l o r o p h y l l a i s o p l e t h s f o r experimental c o n t r o l (east) s i d e s . .  (west)  and  55  (experimental) and 4.5 The  fall  s t a r t e d two fall  ug/1  (control).  phytoplankton  bloom  occurred  weeks e a r l i e r on the experimental  September  onset of f a l l  c i r c u l a t i o n and  confined  to  the  surface  10  ug/1  (0-2 the  m) winter  i c e formation.  and  was  layers. bloom  Chlorophyll  bloom  and  lower during the f a l l  d e t e c t e d d u r i n g the s p r i n g bloom and l e v e l s f o r the remainder  remained  The  seasonal  (2 way  ANOVA, p  d i f f e r e n t as c o n t r o l s i d e v a l u e s were higher  spring  ug/1  generally  and  f o r the d u r a t i o n of the experiment.  c o n c e n t r a t i o n s of c h l o r o p h y l l were s i g n i f i c a n t l y < .01)  with the  experimental; 85  December-January  concentrations declined after below  max.  experimental  (4-8 ug/1)  remained low u n t i l  A l a r g e under-ice bloom (55 ug/1 c o n t r o l ) occurred in  levels  and  s i d e . As a r e s u l t ,  c h l o r o p h y l l c o n c e n t r a t i o n s were higher on the  s i d e . C h l o r p h y l l then d e c l i n e d to low  max.  in  during  the  bloom. Phaeophytin  remained  below  was  detection  of the year.  Composition  Cyanophyta Blue-green  algae i n Black Lake were represented by s e v e r a l  taxa: c o l o n i a l Merismopedium sp., Aphanizomenon sp. and a (2-4  u  dia.)  unidentified  n u m e r i c a l l y . Merismopedium throughout  the  entire  only d u r i n g the f a l l appeared  i n August  Blue-greens  coccoid  sp. and  which  present  year whereas Aphanizomenon sp.  appeared  addition,  coccoid  dominated  were  bloom. In  the  form  small  Anabaena  sp.  briefly  samples.  appeared  i n l a r g e numbers i n l a t e s p r i n g (4000-  56  6000 c e l l s / m l ) before d e c l i n i n g to low l e v e l s June  and  July  (Figure 20). T h e i r abundance i n c r e a s e d again i n  e a r l y autumn and reached.a cells/ml  then  experiment. on both  fall  peak  on  (experimental) and 5135 c e l l s / m l  numbers  (1760 c e l l s / m l ) i n  declined The  steadily  October  at  (control).  f o r the  seasonal occurrence  10  Blue-green  remainder  of blue-greens  6775  of  the  was s i m i l a r  sides.  Cryptophyta Chroomonas Cryptophyta  sp.  and  identified  Cryptomonas  the  two  i n Black Lake samples. Cryptophyta  were  most abundant during s p r i n g and f a l l through  sp. were  months and  less  prevalent  summer and w i n t e r . The seasonal abundance of Cryptophyta  was s i m i l a r on both s i d e s (Figure 20). The 24  spring  bloom peaked on May 9 (experimental) and A p r i l  ( c o n t r o l ) , then d i m i n i s h e d over  declined  to  increased  due  enhancement  undetectable to  summer  levels.  reappearance  as  Cryptomonas  A f t e r August 15 both s i d e s  of  Cryptomonas  of e x i s t i n g Chroomonas sp. The f a l l  sp.  cells/ml.  winter  Total  numbers  of  Cryptophyta  and  bloom peaked on  November 14 (experimental) and December 5 ( c o n t r o l ) at 340  sp.  376  and  then dwindled as  progressed.  Chlorophyta Two genera  of Chlorophyta, Chlamydomonas sp. and S c h r o d e r i a  sp., were i d e n t i f i e d . was  initially  i n Black  present  Lake  samples.  Chlamydomonas  sp  i n samples but d e c l i n e d t o low l e v e l s  BLACK LAKE PHYTOPLANKTON CYHNOPHYTA WEST-CELLS/ML + CYHNOPHYTA EAST-CELLS/ML X  BLACK LAKE PHYTOPLANKTON CIILOROPHYTH UFiHT- CF.LLS/Ml. CHLOROPHYTA EHST-CELLS/ML  + X  58  a f t e r a few weeks appeared  and  abundance months. levels  aeration  became  of  the  (Figure  The  seasonal  fluctuated  the  summer  side  throughout  Chlorophyta  Both s i d e s i n c r e a s e d to 360  as Chlamydomonas sp. reappeared  the  sp. then  dipped to undetectable  i n l a t e August while c o n t r o l s i d e numbers remained at  cells/ml.  bloom  Schroderia  dominant Chlorophycean.  Chlorophyta  Experimental  20).  persisted remaining  seasonal  cells/ml  i n the water  in early  column.  October  The  fall  u n t i l December 5, then g r a d u a l l y dwindled winter  trends  with  bloom on the c o n t r o l  months.  Both  sides  exhibited  90  over  similar  the e x c e p t i o n of a l a t e December-January  side.  Baciliariophyceae Bacillariophyta orders  Centrales  developed spring  in  Black  Lake  and Pennales.  were  represented  was  20). Experimental  not observed  May  9,  on the experimental  s i d e diatoms e v e n t u a l l y appeared  however  both  s i d e s converged  on June  at 54 c e l l s / m l on October  winter pulse of diatoms peaked on January November  14  abundant  for  experimental fall  ( c o n t r o l ) at 409 and the side  duration diatoms  of were  161 the  23  a  s i d e (Figure  The abundance of diatoms f l u c t u a t e d d u r i n g the f a l l however  the  A small s p r i n g pulse of diatoms  on the c o n t r o l s i d e and peaked on  pulse  by  13. bloom,  10.  (experimental)  The and  c e l l s / m l . Diatoms remained experiment.  In  more numerous through  general, summer,  and winter months whereas c o n t r o l s i d e diatoms dominated i n  spring.  59  Zooplankton The quite  l i m n e t i c macrozooplankton  simple,  consisting  of  community i n Black  a  Lake  was  c a l a n o i d copepod, a c y c l o p o i d  copepod, one Daphnia s p e c i e s and a s i n g l e s p e c i e s of r o t i f e r . Zooplankton  data  was  analysed  f o r both  vertical  and  seasonal d i f f e r e n c e s i n d i s t r i b u t i o n and abundance. The v e r t i c a l distribution  of  zooplankton was not s i g n i f i c a n t l y d i f f e r e n t (2  way  ANOVA, p > .01) between c o n t r o l and experimental  sides for  any  s p e c i e s , t h e r e f o r e zooplankton abundance was converted to an  a r e a l b a s i s and expressed as no./m . 2  Total Total  zooplankton  Cyclops b i c u s p i d a t u s statistically  and  different  T h i s was p r i m a r i l y due control  (  Zooplankton Daphnia pulex  Diaptomus• (2  to  leptopus  )  numbers  were  way ANOVA, p < .01) between s i d e s .  2-4  fold  greater  numbers  on the  s i d e d u r i n g the s p r i n g bloom ( F i g u r e 21). T o t a l numbers  were s i m i l a r d u r i n g summer, however were  , K e r a t e l l a quadrata ,  experimental  side  numbers  g e n e r a l l y higher d u r i n g f a l l and winter months. I w i l l now  examine the which  zooplankton  species  were  community  individually  responsible  for  the  to  determine  aforementioned  differences.  Daphnia pulex The  seasonal  significantly  abundance  of  Daphnia  pulex  was  not  (2 way ANOVA, p > .01) i n f l u e n c e d by h y p o l i m n e t i c  a e r a t i o n as n e a r l y i d e n t i c a l  seasonal trends  occurred  on  both  60  BLACK LAKE ZOOPLANKTON TOTAL ZOOOLflMKTOH VEST + T0FHL ZOOPLANKTON EAST X  17000000  LJJ  UJ O LO  8710.000  SLACK LAKE ZOOPLANKTON • DAPHNIA WEST-NO./SO.M. + DAPHNIA EAST-NO./SO.M. X  CK  251000  LjJ LiJ 125000  APRIL  MAY  JUNE  JULY.  AUG  AUG  SEPT  OCT  NOV  1978  DEC  JAN  FEB  MARCH  1979 .  BLACK LAKE ZOOPLANKTON KERATELLfl WEST-NO./SO.M. + KERHTELLA EAST-NO./SO.M. X  UJ  7iaooo ;  !  F i g . 21  T o t a l zooplankton, Daphnia pulex and Keratella quadvata (numbers/m ) i n the e x p e r i m e n t a l (west) and c o n t r o l (east) s i d e s . 2  61  sides  of  the  lake  numbers (< 6 0 0 m )  at the s t a r t  2  appeared 80,500/m  in  expanded early  appreciable  control)  2  and  fall  21).  (Figure  on  of  9.  May  numbers  weeks of f a l l had  throughout  313,800/m  increased  circulation, declined  considerably  seasonal  abundance  initially  higher  detected  several  (2 way  13  June  more  As f a l l fold  and  by  mid  and  the f i r s t  November  continued  two  Daphnia  decreasing  throughout  fall  numerous  experiment.  Keratella  quadrata  on the  was  experimental  and winter months. K e r a t e l l a  abundance  was  but remained scarce  then  increased  above  ( F i g u r e 2 1 ) . C o n t r o l s i d e r o t i f e r s were  abundant  than  their  the summer and e a r l y  experimental fall  side  months.  c i r c u l a t i o n commenced K e r a t e l l a abundance i n c r e a s e d  over  2  during  ANOVA, p < . 0 1 )  Rotifer  c o u n t e r p a r t s throughout  898,300/m  the summer and  (experimental)  2  i n l a t e A p r i l - e a r l y May  weeks.  on  2  generally  more  rapidly  quadrata of  side, p a r t i c u l a r l y during f a l l  2-3  then  the winter months. •  statistically  10,000/m  briefly  however  Keratella  for  throughout  first  experimental;  2  population 2  and  (control).  2  The  (113,800/m  The  remained above 6 0 , 0 0 0 / m  experiment  i n low  months. Maximum abundance o c c u r r e d d u r i n g mid June to  Daphnia  numbers  the  numbers  mid August with peak numbers of 262,200/m  Daphnia were present  The  late  September v a l u e s and c o n t i n u e d  and w i n t e r . Experimental and  remained  higher  increasing  s i d e r o t i f e r s were  now  for  the  the  rest  f a l l - w i n t e r p o p u l a t i o n peaked on January'  (experimental) and  745,700/m  2  ( c o n t r o l ) , then  of 23  at  started  62  declining. 81,400/m  J  C o n t r o l side r o t i f e r s decreased more r a p i d l y as only were present on March 6 as compared to  the experimental  560,300/m  on  2  side.  Cyclops b i c u s p i d a t u s The  population  of  Cyclops  b i c u s p i d a t u s i n h a b i t i n g Black  Lake d u r i n g the experimental p e r i o d was  multivoltine,  a l a r g e s p r i n g p u l s e and a s m a l l e r f a l l  peak i n  majority stage  of Cyclops overwintered  copepodites.  (nauplii,  Each  copepodites  abundance.  adults)  was  stage  investigated  similar  in  d i s t r i b u t i o n on both s i d e s , however each stage was (2 way  ANOVA, p < .01) d i f f e r e n t  In side  g e n e r a l , each stage was  The  i n the form of p l a n k t o n i c l a t e  developmental  and  exhibiting  vertical  significantly  i n terms of seasonal abundance. more  d u r i n g the s p r i n g months and  abundant  on  the  control  s i m i l a r on both s i d e s through  summer ( F i g u r e 22). T h i s l a r g e s p r i n g p o p u l a t i o n was r e s p o n s i b l e for  the 2-4  f o l d d i f f e r e n c e observed  in spring t o t a l  numbers ( F i g u r e 21). The experimental populated  in  fall  and  side  was  zooplankton  slighlty  more  both s i d e s were v a r i a b l e d u r i n g winter  months. The development of Cyclops b i c u s p i d a t u s from n a u p l i i copepodites  to  adults  was  through both s p r i n g and  fall  well  defined  to  and e a s i l y f o l l o w e d  generations.  Diaptomus leptopus Diaptomus leptopus was present contrast  in to  Black  Lake  Cyclops  the only l i m n e t i c  during  the  bicuspidatus,  calanoid  experimental Diaptomus  copepod  period.  leptopus  In was  63  5 L " K LAKE Z^PLRNKFON CYCLOPS NflfJPLIJ W - . 5 r - N 0 . / 5 0 . M . CYCLOPS NAUPLII i.ASr-NO./SQ.M.  o ^~A)  4,2 3 0.000  APRIL  MAY  JUNE  AUG  AUG  SEPT  OCT  FEB  1978  BLACK LAKE ZOOPLANKTON CYCLOPS COPEPODITES 1-5 WEST-NO.NO./SO.METER CTCLOPS COPEPODITES 1-5 ERST-NO.NO./SQ.METER  APRIL  MAY  MARCH  1  1979  JUNE  JULY.  AUG  AUG  + X  FES  SEPT  1978  MARCH  1979  SLACK LAKE ZOOPLANKTON CYCLOPS ADULTS WEST-NO./SO.M. + CYCLOPS P.DULTS EAST-NO . /SO . M. X  APRIL  MAY  JUNE  JULY  AUG  AUG  JAN  SEPT  F i g . 22  FEB  MARCH  1979  1978  Cyclops bicuspidatus n a u p l i i , c o p e p o d i t e s and a d u l t s (numbers/m ) i n the e x p e r i m e n t a l (west) and c o n t r o l (east) s i d e s . 2  64  univoltine  and produced  and copepodites water  column  overwintered  a b r i e f midsummer generation of n a u p l i i  (Figure 23). Adult Diaptbmus were present from  in  June  the  1978  to  March,  1979.  form of r e s t i n g eggs produced  i n the  Diaptomus during  fall  circulation. Copepodite  stages of Diaptomus leptopus were not i n f l u e n c e d  by h y p o l i m n e t i c a e r a t i o n , significant  (2  way  however  ANOVA,  p  <  nauplii .01)  and  early  summer  Experimental to  and  similar  more  f o r the r e s t of the  s i d e a d u l t s were more abundant during  f a l l months and v a r i a b l e at other  showed  d i f f e r e n c e s i n seasonal  abundance. In g e n e r a l , c o n t r o l s i d e n a u p l i i were in  adults  times.  abundant  experiment. late  summer  65  BLACK LAKE ZOOPLfmfOX DIAPTOMUS -NAUPLII WESfN 3 . / 3 0 METER 4DIAPTOMUS NAUPLII EASTNO./30.METER X  3^800  /.—l—xz APHIL  MAY  AUG  19/8  AUG  SEPT  OCT  NOV  DEC  L* MARCH  1979.  BLACK LAKE ZOOPLANKTON DIAPTOMUS ADULT WEST-NO./SO.M. DIAPTOMUS ADULT EAST-NO./SO.M.  APRIL  FEB  MAY  JUNE  F i g . 23  JULY  AUG  AUG  SEPT  OCT  NOV  + X  DEC  JAN  FEB  MARCH  Diaptomus leptopus n a u p l i i , c o p e p o d i t e s and a d u l t s (nurabers/m ) i n the e x p e r i m e n t a l (west) and c o n t r o l (east) s i d e s . 2  66  DISCUSSION  The both  a  hypolimnetic a e r a t i o n of Black Lake was a success technical  theoretical  viewpoint  standpoint  of  of  simultaneously  f u n c t i o n a l components of the lake considerable  experimental  and  anoxic  during  the  first  during summer, f a l l  Black  circulation  Lake  in  fall  indicated  despite  the  influence  which  of  meromixis  the  hypolimnion  and winter of 1977-78, and that in f a l l  experienced 1978  temporary  1977 and s p r i n g 1978.  several  weeks  minimized  d i f f e r e n c e s between s i d e s - f o r the remainder Therefore,  However,  h a l f of the experiment. P r e -  (K.I. Ashley, unpub.)  Black Lake d i d not f u l l y c i r c u l a t e However,  several  experiment.  Black Lake was i n a s t a t e of  a e r a t i o n data was  vigorous  physical-chemical  of  hypolimnetic  the  experiment.  aeration  was most  n o t i c e a b l e during s p r i n g and summer of 1978, e s p e c i a l l y lower  i n the  (8+9 m) p o r t i o n s of the hypolimnion. Secondly,  the  creek  which flowed  Lake Creek) was dry i n 1977 and no for  a  planning and forethought, c e r t a i n events beyond my  Firstly, to  and  examining  ecosystem.  c o n t r o l i n f l u e n c e d the outcome of t h i s  prior  design  from  historical  records  flow p e r i o d s . U n f o r t u n a t e l y the creek  (Yellow existed  flowed  from  A p r i l t o June i n 1978. Creek water entered the experimental  side  of  previous  i n t o Black Lake  the l a k e , mixed with lake water and flowed around the c u r t a i n  i n t o the c o n t r o l s i d e . The lake l e v e l rose 0.75 water  reached  experimental the  the  outflow  culvert  which  m  before  drained  from  s i d e i n t o Yellow Lake (Figure 1 ) . T h i s f l u s h i n g  experimental  side  during  spring  1978  was  lake the of  probably  67  responsible  for  lower  zooplankton  numbers  and  epilimnetic  organic water chemistry measurements (eg. c h l o r o p h y l l a, organic N) on the experimental side d u r i n g s p r i n g 1978.  Circulation C i r c u l a t i o n c u r r e n t s generated by the a e r a t o r had no e f f e c t on  the  formation  and  maintenance  throughout  s p r i n g , summer and e a r l y  increased  at  similar  rates  of fall  thermal  stratification  months.  Heat  content  on both s i d e s , i n d i c a t i n g  minimal  d i s t u r b a n c e from the a e r a t o r . Maximum s u r f a c e temperature o c c u r r e d on the same date bottom  temperature  on  (August 1) on both s i d e s the experimental s i d e  1.6 C warmer than the c o n t r o l s i d e mixing  within  inflow  and  the  outflow  stratification  hypolimnion tubes.  and  heat  epilimnion  with  from  t r a n s f e r a c r o s s the normal  to i s o l a t e an a c t i v e l y  (theoretical circulation danger  (12.6 C) was only  indicates  hypolimnion  no  maximum  (11.0 C ) . T h i s r e s u l t e d  This  is sufficient  and  (22 C)  time=1.2  circulating  days)  of d e s t r a t i f i c a t i o n  density  from  the  or thermocline  erosion. Both s i d e s d e s t r a t i f i e d (October  10).  The  aerator  at  approximately  continued  the  operating  same  time  during  fall  c i r c u l a t i o n and d i d not delay i c e formation as both s i d e s over  in  mid  November.  Total  heat l o s s to the atmosphere was  s i m i l a r on both s i d e s however the  experimental  r a t e was higher due to c i r c u l a t i o n  of f r e e z i n g water  beneath  the  temperatures  froze  i c e s u r f a c e and exposure  side  depletion immediately  of lake water to sub-zero  i n the s e p a r a t i o n box.  The a e r a t o r c i r c u l a t e d  the e n t i r e  lake  under  ice  cover.  68  This  is a  common  feature  inverse s t r a t i f i c a t i o n (Wirth  et  of winter  i s too weak  a l . , 1975).  hypolimnetic  to  resist  mixing  currents  Winter a e r a t i o n d i d not weaken the i c e  s u r f a c e and minimized the open water hazard with  a e r a t i o n as  usually  associated  such a c t i v i t i e s . Secchi d i s k and 1% t r a n s m i s s i o n depths were s i m i l a r on both  sides  of the lake when Secchi and 1% depths were l e s s than 5 m.  T h i s i n d i c a t e s hypolimnetic vertical  circulation  d i d not  increase  t r a n s f e r of substances a c r o s s the thermocline.  hypolimnetic  aeration  transparency through  when  experiments  nutrient  the a e r a t o r  rich  walls  have  A  to  Secchi=7.0  m,  aerator  (>1 m) d i f f e r e n c e occurred when Secchi and 1%  approximately  1%=5.2 m) whereas  Lake  occurred.  t r a n s m i s s i o n depths exceeded 5 meters. Experimental restricted  leaked  i n t o the e p i l i m n i o n and s t i m u l a t e d  and no leakage  noticeable  surface  water  dense a l g a l blooms (Fast et a l . , 1973). The Black was w a t e r t i g h t  Previous  decreased  hypolimnetic  the  control  max.  depths  were  5 meters (max. Secchi=5.4 m, max. depths  were  m)  (Figure  1%=6.4  not  restricted  4). I  (max.  believe  this  d i f f e r e n c e was due t o i n c r e a s e d t u r b i d i t y  i n the  hypolimnion  a c t i v e c i r c u l a t i o n by  (5-9 m) which was e x p e r i e n c i n g  the a e r a t i o n system ( c i r c u l a t i o n Hypolimnetic experimental  the year decreased  time=1.2 days). increased  turbidity  s i d e because c i r c u l a t i o n c u r r e n t s reduced  sedimentation hypolimnion  aeration  experimental  r a t e s . Temperature data temperatures  indicating the  a  differed well  transparency  mixed of  support  in  the  detrital  t h i s c o n c l u s i o n as  by 0.5 C or l e s s throughout hypolimnion. an  Fast  oligotrophic  (1971) lake  as  69  circulation al.  c u r r e n t s kept d e t r i t u s i n suspension, and R i d l e y  (1966) observed decreased sedimentation of s i l t  d e b r i s i n an E n g l i s h r e s e r v o i r  due  to  artificial  et  and organic circulation  currents. Increased h y p o l i m n e t i c t u r b i d i t y hypolimnetic  aeration.  This  transparency as c i r c u l a t i o n hypolimnion  during  circumstances  the  should  degrade  epilimnetic  thermal function  stratification. of  Under  these  the hypolimnion changes from a circulating  decomposition  not u n l i k e a "dark e p i l i m n i o n . " D e t r i t a l m a t e r i a l  the hypolimnion  sedimenting consumption  material.  circulated nutrient  ensures more complete One  would  r a t e s and higher l e v e l s  dissolved  organic  hypolimnion. levels  entering  i s kept i n suspension much longer than usual and  i n c r e a s e d oxygen l e v e l s  (eg.  not  c u r r e n t s are u s u a l l y c o n f i n e d to the  p a s s i v e s e t t l i n g zone to an a c t i v e l y zone  may be a common f e a t u r e of  P  and  Analysis  expect of  increased  decomposition  organic of  decomposition  N)  oxygen  to  of  oxygen  products  appear  consumption  in a and  (see decomposition and n u t r i e n t s ) i n Black Lake  c o n f i r m t h i s h y p o t h e s i s . Continued suspension of d e t r i t u s should reduce organic l o a d i n g to the e v e n t u a l l y decrease sediment  sediments  (Hargrave,  1975)  and  oxygen demand. T h i s i s an important  step i n the r e s t o r a t i o n of c u l t u r a l l y e u t r o p h i c l a k e s .  70  Decomposition  Experimental  aeration s i g n i f i c a n t l y  increased hypolimnetic  oxygen c o n c e n t r a t i o n s and maintained a e r o b i c c o n d i t i o n s sediment-water  interface  throughout  h y p o l i m n e t i c oxygen l e v e l s (1.6-3.7 mg/1) the  the  fluctuated  year.  within  a  at  However,  narrow  a l l summer d e s p i t e a d d i t i o n of 10.76  the  range  kg O^/day by  a e r a t o r . I b e l i e v e h y p o l i m n e t i c a e r a t i o n m o d i f i e d Black Lake  decomposition processes i n two ways. Firstly,  circulation  currents  generated  by  the a e r a t o r  s t i m u l a t e d sediment oxygen demand. The water column component of whole-lake  oxygen  consumption  is  generally  less  than  the  sediment component due to the accumulation of sedimented organic material  and  b a c t e r i a at the sediment-water i n t e r f a c e  1975; Mathias and B a r i c a , therefore  results  oxygen demands anaerobic  of  layers  from  1980).  Sediment  biological  reduced (Fillos,  oxygen  respiration  substances  concentrations  exceed 2-3 mg/1.  in  However,  consumption and  emanating  chemical  from  deeper  1976). Sediment oxygen uptake r a t e s  e x h i b i t asymptotic responses and appear l a r g e l y oxygen  (Wetzel,  overlying when  independent  waters when oxygen  oxygen  declines  to  of  levels  threshold  l e v e l s of 2-3 mg/1,  oxygen uptake decreases as eddy d i f f u s i o n i s  unable  oxygen g r a d i e n t s at the sediment s u r f a c e and  the  to overcome  r a t e of oxygen  Mathias  and  supply  Barica,  becomes 1980).  limiting  Artificial  (Hargrave, mixing  1969;  eliminates  c o n c e n t r a t i o n g r a d i e n t s and markedly i n c r e a s e s oxygen uptake low  dissolved  oxygen  levels  aeration continually replenished  (Hargrave, the  1969).  at  Hypolimnetic  sediment-water  interface  71  with  oxygen and prevented anaerobic c o n d i t i o n s from d e v e l o p i n g ,  thereby  i n c r e a s i n g sediment oxygen consumption.  Secondly, material oxygen  continued  increased  the  consumption.  suspension  of  sedimenting  organic  water column component of hypolimnetic  Once  sedimenting  material  leaves  the  e p i l i m n i o n of a shallow lake such as Black Lake (Z max.=9 m), i t travels  a  reaching  relatively the  hypolimnetic  lake  short d i s t a n c e i n the hypolimnion  bottom.  decomposition  As  a  occurs  Hypolimnetic a e r a t i o n i n c r e a s e s the hypolimnion settling  by  actively  r a t e s . Sedimenting  greater  of  sediment  the  column  majority  of  and  reducing  and  the  as a decomposition  column  zone i n r e l a t i o n  i s analogous  in l a r g e r l a k e s which r e s u l t s  water  to  increased  i n g r e a t e r water 1973).  During experimental a e r a t i o n , h y p o l i m n e t i c r e s p i r a t i o n restricted  decomposition, dependent  by  low  oxygen  control  side  values  higher  temperature-  oxygen.  The  a d d i t i o n a l oxygen  aerator demand  (5-9  m)  s i d e consumption  '(0.39-0.78  mg/l/day)  (0.03-0.09 mg/l/day). As the a e r a t o r  s u p p l i e d more oxygen, the sediments and  about  maximum  as experimental  magnitude  was  sediment-oriented  r a t e . A mass balance a n a l y s i s of h y p o l i m n e t i c  r a t e s were an order of  more  and  and consumed oxygen at i t s  oxygen confirms t h i s assumption  than  levels  the  then experiences more  column m i n e r a l i z a t i o n of organic m a t e r i a l (Hargrave,  not  of  surface.  depth"  detritus  o r g a n i c matter  importance  mixing  at  "effective  to the sediment s u r f a c e . T h i s process depth  the  circulating  complete o x i d a t i o n i n the water assumes  result,  before  was  water  column  p h y s i c a l l y unable  consequently  the  consumed  to exceed  system  the  oscillated  a s t e a d y - s t a t e c o n d i t i o n (1.6-3.7) f o r the summer p e r i o d .  72  L i t e r a t u r e t h r e s h o l d oxygen l e v e l s Mathias  and  B a r i c a , 1980)  range in the aerated and  lake was levels  levels  increased  suggests  usually  ranged  (Hargrave,  1969),  r e l a t e d to  decreased  Winter  oxygen  rates. Graneli for  the  1976;  observed  oxygen  supply  and  6-7  mg/1.  variations  in  sediment  benthic  depletion  and  and  water  and  and  uptake  column  was  consumption.  lower than summer  values  of  2.0-3.0  (TOC)  organic  carbon during  not  s u p r i s i n g as the m a j o r i t y  between  that d e s p i t e higher  r e s u l t s were  m i c r o b i a l degredation  hypolimnetic of TOC  (Wetzel and  winter  compounds  Otsuki,  would  to  f r a c t i o n a t e TOC  changes  little  i s d i s s o l v e d organic  impact of hypolimnetic  collect  significantly  the  carbon  resistant  1974). In order a e r a t i o n on TOC  into i t s dissolved  samples at s h o r t e r in  change  aeration. This result i s  a c c u r a t e l y assess the  p a r t i c u l a t e components and  not  (1971) a l s o reported  which i s p r i m a r i l y r e f r a c t o r y organic  possible  values  demand remained c l o s e l y balanced.  in  deliniate  oxygen  temperature  indicates  carbon  necessary  strongly  in winter oxygen  sediment Q10  oxygen  d i f f e r e n t between s i d e s . Fast  be  oxygen  C. T h i s approximates observed d i f f e r e n c e s  side  supply  winter  Temperature  r a t e s were g e n e r a l l y  (1978) reported  T o t a l organic  (DOC)  experimental s i d e  hence the observed r i s e  winter,  oxygen l e v e l s ,  c i r c u l a t i o n as the e n t i r e  between  i n t e r v a l 5-10  experimental  summer  at f a l l  v i g o r o u s l y mixed, and  seasonal  to  (Fillos,  s u p r i s i n g l y c l o s e to the  hypolimnion which  influences  to  mg/1)  demand were c l o s e l y matched. Oxygen  in  are  (2-3  more l a b i l e  to it and  intervals dissolved  organic f r a c t i o n s . The  a e r a t i o n system  was  incapable  of  meeting  increased  73  oxygen  demands  in  the  experimental  hypolimnion as d i s s o l v e d  oxygen i n c r e a s e d  by a mere 0.7 mg/1 on each  system.  increases  Oxygen  (Smith et a l . , 1975) to reason  saturation  values  shallow depth of Black Lake. Previous  force  the  efficient  at  oxygen  hydrostatic decreasing to  poor  inflow  tube  in  on  hypolimnetic  progressively depths.  for this  efficiency  less  Declining  drop,, however  oxygen content of r i s i n g a i r bubbles a l s o transfer  The  mode of bubble-water  shallow  head i s mainly r e s p o n s i b l e  1971).  pressure as the d r i v i n g  becomes  transfer  (Fast,  studies  f o r oxygen t r a n s f e r . The c o - c u r r e n t in  the  The main f a c t o r was the  have r e l i e d on high h y d r o s t a t i c  transport  through  per c y c l e u s u a l l y range from 2.3 mg/1  f o r such low values i s twofold.  aeration  cycle  i n shallow water  contributes  (Speece et a l . ,  1974) . Smith et a l . (1975) from  reported  dissolved  0 to 2.3 mg/1 i n the lower 6 m of t h e i r M i r r o r  m) a e r a t i o n  tube,  Reservoir  the  further  most oxygen t r a n s f e r occurred  surface.  (Zm=44  m)  increased' Lake (Zm=13  increase  Bernhardt  (1967) a l s o  i n the lower  aerator,  i n the  20  by  Hess  (1976)  during  hypolimnetic  mechanical  from r i s i n g a i r aeration  T h e r e f o r e hypolimnetic handicapped  by  low  bubbles  i n an  was  effort  aeration  low  and  pressure  e f f i c i e n c i e s . The Black Lake a e r a t o r  further  transfer  switched  to  to improve oxygen t r a n f e r .  i n shallow lakes  hydrostatic  of  a e r a t i o n of  (Zm=6 m) Spruce Knob Lake. Hess (1976) r e a l i z e d  efficiency  m  with no increase  the remainder of the ascent. T h i s phenomenon was  substantiated shallow  to  no  discovered  during  rise  observed  6  Wahnbach  m  and  remaining  the  oxygen  floated  (<  10  m)  is  and oxygen t r a n s f e r 7.3  m  below  the  74  surface,  and next  to Spruce Knob Lake i s the shallowest lake t o  have undergone hypolimnetic a e r a t i o n . I n c o r r e c t bubble s i z e cycle.  The  influence  also  of  reduced  bubble  size  oxygen on  i n c r e a s e per  oxygen t r a n s f e r i s  r e l a t e d t o the mechanics of oxygen d i f f u s i o n a t the bubble-water i n t e r f a c e and e f f i c i e n c y of a i r - l i f t process  occurs  Initially,  i n three  stages  oxygen molecules  transported  to  the  from  liquid  pumps. The oxygen  ( E c k e n f e l d e r and Ford, the gas  surface,  oriented second  with  are  1968). rapidly  in saturation  i n t e r f a c e or f i l m  t h i c k and i s composed of  water  i s at  molecules  t h e i r negative ends f a c i n g the gas phase. In the  phase,  molecular  phase  resulting  c o n d i t i o n s a t the i n t e r f a c e . T h i s l i q u i d l e a s t three molecules  transfer  oxygen  diffusion.  molecules In  pass  through  this  film  the t h i r d stage, oxygen i s mixed  by into  the water body by d i f f u s i o n and c o n v e c t i o n c u r r e n t s . At very low mixing  l e v e l s the rate of oxygen  molecular  diffusion  through  absorption  the undisturbed  turbulence l e v e l s i n c r e a s e , the s u r f a c e f i l m renewal to  i s controlled liquid  i s disrupted  and  ( E c k e n f e l d e r , 1969).  T h e r e f o r e , t o maximize t r a n s f e r e f f i c i e n c y bubble be h i g h i n r e l a t i o n  (Suschka,  1971).  velocities  pump  bubbles  Small bubbles  (<  to water v e l o c i t y  Unfortunately,  decrease  reduce a i r - l i f t between  film.- As  of the f i l m becomes r e s p o n s i b l e f o r t r a n s f e r r i n g oxygen  the l i q u i d  should  by  and  large  bubbles  a i r - b u b b l e c o n t a c t time efficiency liquid  0.5mm),  by  ie.  velocity  large  bubbles  and  higher  i n the a e r a t o r and  increasing  slip  velocity  i n the i n f l o w tube (Andeen, 1974).  in addition  to  having  lower  rise  v e l o c i t i e s , • provide a higher s u r f a c e area t o volume r a t i o which  75  enhances oxygen exchange small  (Andersen  Hurd,  1971).  at very  j u s t to overcome surface  severely  reduce a e r a t o r  Consequently, mm  t e n s i o n and  efficiency  bubble  form  bubbles  contributed bubbles may  suggest  to r i s e  difficult  can  efficiencies Aside  be  aeration  (Speece et  Firstly,  kills)  would not few  these  years may before  coalesce  to measure,  however during  regulate  in t h i s f i e l d  ascent i t  bubble  size.  size  and  firm  aerators.  results  of  increased  hypolimnetic  uptake  suggest  several  conclusions.  rates  reflect  s e v e r a l years  m a t e r i a l , and  not  significantly  cause  drastic  immediate  changes  declines  reduce sediment oxygen  operation, required  noticeable  i t would i n c r e a s e  to o x i d i z e  in in  declines  in  oxygen  evidence from the Yellow  (Halsey  MacDonald,  1971)  organic  consumption  Lake  supports  demand  i t . Therefore  accumulated  Circumstantial and  I  transfer  ( G r a n e l i , 1978). Consequently, hypolimnetic  be  since  i s necessary before  bubble  benefits  oxygen  would  months  al.,  o x i d a t i o n of reduced substances, e l i m i n a t i o n  accumulation of organic  consumption  and  accurately  obvious  sediment  productivity  efficiency  reached regarding  oxygen l e v e l s (eg. fish  to  to  in diameter. T h i s l a r g e s i z e  transfer  i n hypolimnetic from  mm  in "clouds"  f u r t h e r research  conclusions  of  at 5-20  to poor oxygen  tend  be very  eye  may  s i z e in the diameter range of 2.0  1974). Bubble s i z e at Black Lake, although d i f f i c u l t by  energy  (Smith et a l . , 1975).  i s recommended for hypolimnetic  estimated  lead to  small bubble diameters the  required  was  However  bubbles r e q u i r e small d i f f u s o r o r i f i c e s which can  c l o g g i n g problems, and  2.5  and  aeration  this  lake  benthic aeration after  a  several material appear. project  hypothesis  as  76  increased  oxygen l e v e l s are f i n a l l y  intermittent  aeration  appearing  (C.J. B u l l ,  Fish  after  and W i l d l i f e  pers. comm.). The Black Lake experiment operated days,  therefore  significant declines  11  years Branch,  f o r only  329  i n sediment oxygen demand  were u n l i k e l y . Secondly, when oxygen c o n c e n t r a t i o n s levels  physical  artificial  aeration  stimulating al.  mixing will  sediment  and  and  hasten  the  hypolimnetic  aeration.  d e c l i n e s i n oxygen l e v e l s o f t e n aeration  projects  below  threshold  input  associated  onset  of  with  anoxia  by  water column oxygen demand. Smith et  (1975) a l s o observed a 3-4x i n c r e a s e  during  al.,  oxygen  are  (Patriarche,  This  in  oxygen  explains  associated 1961;  consumption  the c a t a s t r o p h i c  with  late-starting  Seaberg, 1966; Wirth et  1975). Finally,  hypolimnetic  benthic aeration  recolonization may  increase  Benthic  macroinvertebrates increase  oxygen  transport  following sediment  aeration requires  over  demand. which  (Lee, 1970) and c i r c u l a t e  s u b s t a n t i a l q u a n t i t i e s of water ( B r i n k h u r s t , of hypolimnetic  oxygen  the surface area  and r e a c t i o n s occur  successful  1972). T h i s  further investigation.  aspect  77  Major N u t r i e n t s  Nitrogen  The  nitrogen  mediated  by  modifying  cycle  microbial  the  nutrient  example,  of  of  environment, profoundly  this  biologically  levels  decreased  during aeration f a c i l i t a t e d  a  ammonium  equilibria  the gaseous form (NH^) which i s more e a s i l y  volatilized  oxygen  ion  (NH^*)-ammonia  pH  t h i s r e a c t i o n by  ( S t r a t t o n , 1969).  levels  enabled  nitrifying  to NO_^-N and NOj-N thereby  et  Secondly,  reducing  available  phytoplankton.  nitrate  would  be  NH^-N  was  rapidly  In a d d i t i o n , the presence  increased  bacteria  a l . , 1969). N i t r a t e was not i n i t i a l l y  the water column however s i n c e the s p r i n g bloom  (Graetz et a l . , 1973). Ammonia  experimental  temperatures  and  hypolimnion increased  during  biological  levels  under  way  utilized  by  of d i s s o l v e d oxygen  gradually summer production  to  detected in  lake bottom o x i d i z e d the sediment s u r f a c e and reduced  release  was  (NH^)  o x i d i z e NH^-N (Brezonik  ammonia  the s e p a r a t i o n box. E l e v a t e d h y p o l i m n e t i c  encountered  hypolimnetic  the  mediated  i n t e r a c t i n g p r o c e s s e s . An unknown amount of  d u r i n g vigorous bubbling  the  by  d i r e c t l y to the atmosphere when h y p o l i m n e t i c water  d i s p l a c i n g the  any  aeration,  j u s t two weeks a e r a t i o n . T h i s d e c l i n e  c i r c u l a t e d through  towards  hypolimnetic  several  escaped  levels  chemical  components  dramatically after  NH^-N  and  Hypolimnetic  cycle.  For  result  reactions.  physical  influenced several  i s a complex dynamic system p r i m a r i l y  NH^-N  increased as  at  in  higher  accelerated  78  bacterial  ammonification  of  Hypolimnetic pH l e v e l s a l s o ammonia  venting  sedimented  decreased  organic  slightly  which  v i a the a e r a t o r . F a l l c i r c u l a t i o n  The  bacterial  nitrification  hypolimnetic oxidized  process  and NO^-N  a  was  by  b a c t e r i a . The o v e r a l l n i t r i f i c a t i o n NH^  + 20—rN0 "  +  the  3  also  influenced  Nitrosomas  and N i t r o b a c t e r  reaction: + H^O + 2H  +  oxygen  f o r the o x i d a t i o n of each mole of NH^  Surface  n i t r a t e on  levels  (<  +  0.02  mg/1)  intense photosynthetic the  experimental  for  nitrification  new  the f i r s t  below  detectable  weeks of a e r a t i o n by nitrate  sufficient  and a dramatic d e c l i n e i n NH^-N. T h i s on A p r i l  11 was  of  (Wetzel, 1975).  uptake. However, hypolimnetic  liberated  appeared on June 13 and  the remaining  represent  reduced  moles  directly  on  oxygen  suggests t o the  and l i t t l e converted t o NO^-N or NO^-N. Hypolimnetic  NO^-N e v e n t u a l l y during  during  was  side d i d not appear d e s p i t e  most NH^-N present atmosphere  sides  by  i s progressively  proceeds normally above 0.3 mg/1 0^, and r e q u i r e s two  both  sediment  nitrification.  a e r a t i o n . In t h i s r e a c t i o n NH-j-N  t o NO "N  reduced  reduced NH -N  l e v e l s on both s i d e s as d i s s o l v e d oxygen o x i d i z e d surface and s t i m u l a t e d  material.  summer  the time r e q u i r e d  substrate  given  months.  gradually This  accumulated  initial  for n i t r i f y i n g bacteria to  c o o l temperatures and a previous  anoxic c o n d i t i o n s . C o n t r o l  delay may  s i d e hypolimnetic  remained low a l l summer as i n s u f f i c i e n t  nitrate  oxygen was  colonize  h i s t o r y of (8 m + 9 m)  present  for  n i t r i f y i n g b a c t e r i a to e x i s t . Fall oxygen  to  circulation  introduced  both  and  sides  a  substantial  clearly  defined  quantities  of  nitrification  79  sequence was observed. N  appeared.  by  NO3-N  After  which  Experimental accumulating  I n i t i a l l y , NH^-N l e v e l s d e c l i n e d and NO^-  s e v e r a l weeks c i r c u l a t i o n NO^-N was r e p l a c e d  then  accumulated  evidence  suggests  NO -N  the  will  ?  winter.  not continue  under a e r o b i c c o n d i t i o n s but a c t u a l l y decrease  time as NO^-N d i f f u s e s i n t o lake beneath  throughout  the s u r f i c i a l  sediments  (which  over  are anoxic  l a y e r ) and l o s t v i a d e n i t r i f i c a t i o n  (Chen  et a l . , 1972). Experimental however  control  nitrate  remained  constant  NO^-N)  nitrogen  Pseudomonas  and  Achromobacter  d e n i t r i f i c a t i o n and t h i s r e a c t i o n the  anaerobic )  are  is particularly  (NO^-N  underwent bacteria  capable  of  prevalent i n  anoxic hypolimnia of e u t r o p h i c lakes where l a r g e q u a n t i t i e s  of o x i d i z a b l e organic m a t e r i a l have The  response  hypolimnetic  of  aeration  total was  accumulated.  organic  confounded  s p r i n g months. Surface (0 m) v a l u e s were  nitrogen by stream  on  (TON)  to  inflow during  the experimental  side  n o t i c e a b l y lower on May 9, c o i n c i d i n g with the peak i n f l o w  of Yellow Lake  Creek  runoff  epilimnetic  period  ( K . I . Ashley, TON  unpub. d a t a ) .  values  seasonal f l u c t u a t i o n s i n phytoplankton was  ions  trapped i n the anoxic c o n t r o l hypolimnion  b a c t e r i a l d e n i t r i f i c a t i o n . Many f a c u l t a t i v e (eg.  winter  (9 m) n i t r a t e began d e c r e a s i n g i n January when  oxygen d e c l i n e d below 0.5 mg/1. O x i d i z e d and  in late  s t i m u l a t e d decomposition  the  on both s i d e s f o l l o w e d  biomass. Hypolimnetic TON  g e n e r a l l y higher on the experimental  hypolimnion  After  side  as  and reduced  the a e r o b i c  s e t t l i n g rates  of sedimenting organic m a t e r i a l . In  summary,  hypolimnetic  aeration  influenced  several  80  r e a c t i o n s w i t h i n the n i t r o g e n c y c l e . Sedimenting o r g a n i c s experimental nitrite  hypolimnion were r a p i d l y ammonified and  and  uptake and nitrogen  nitrate,  which  then  became  d e n i t r i f i c a t i o n . T h i s i s an cycle  as  NH^-N  tends  be  o x i d i z e d to  a v a i l a b l e for a l g a l  important  to  i n the  lost  link  in  from s o l u t i o n by  s o r p t i o n onto p a r t i c u l a t e m a t e r i a l or v o l a t i l i z a t i o n at high values  (Brezonik,  1973). Conversion i n t o NO^-N  the  pH  r e s u l t s in a more,  s t a b l e form. The  implications  i o n i z e d ammonia (NH^) and  becomes  Downing,  1957).  so at low  ammonia  process  hypolimnion  NH 3 -N  with pH  ensured  (1976)  subsequent  rich  of t o x i c  the  reduced  habitat  conditions  aquatic  community.  un-ionized  ammonia  levels  ammonia  increased  NO-^-N  enhance  oxidation  of  a  did  exposure l e v e l s f o r f i s h  novel  organic  (NHjj )  not  exceed  (EIFAC, 1970).  in  the  bottom  experimental  sediments.  Ripl  technique f o r " i n s i t u " o x i d a t i o n of  sediments  via  nitrate  injection  and  denitrification: 2N0 - + 3CH 3  0  ?  Anderson (1976) a l s o d i s c o v e r e d enhanced  (Merkens and  increasing dissolved  improve  benefit  organisms  greatly  while  of  reported  nutrient  will  and  un-ionized  presence  hypolimnion may  aeration  Un-  ( T r u s s e l , 1972), the o v e r a l l d e c l i n e i n t o t a l  recommended c h r o n i c The  oxygen l e v e l s  concentrations  Although the c o n c e n t r a t i o n increases  r e s u l t s are wide-ranging.  i s h i g h l y t o x i c to most aquatic  Hypolimnetic  oxygen l e v e l s . T h i s the  these  increasingly  hypolimnetic  within  of  organic  denitrification.  matter Therefore  + 3CCy+  3H^O.  water column a d d i t i o n of  degradation  nitrate  i n lake sediments through  hypolimnetic  aeration,  by  adding  81  oxygen  and  stimulating  sediment s u r f a c e Nitrogen  in Black  could  alternating  This  to  be  removed of  procedure  significant nitrogen systems may  N  result  a has  oxidize  the  lakes  by  removal  eutrophic  aeration  and  nitrification-denitrification been  (Brezonik,  proposed f o r N removal in  1973)  and  could  result  in  from l a k e s . Chen et a l . (1979) examined  transformations and  from  hypolimnetic  effect  sewage treatment p l a n t s  should  Lake.  periods  restratification sequence.  nitrification,  in  concluded  simulated  lake  sediment-water  nitrification-denitrification  i n s i g n i f i c a n t N l o s s e s from the  reactions  system.  Phosphorus Phosphorus r e a c t i o n s at the sediment-water i n t e r f a c e are i n t e g r a l component of the phosphorus c y c l e . T h e i r d i r e c t i o n net  r e s u l t are d i r e c t l y  interface  phosphorus c y c l e i n Black The  P  and  increased oxygen at  significantly  (< 0.1  observed  mg/1,  PO^-P. The  p r e c i p i t a t e with association  K.I. Ashley,  decline. PO^-P  with  influenced  a e r a t i o n was  exact  the  a  large ~  mechanism by which  PO^-  because i r o n l e v e l s appeared  unpub. data)  to  account  for  O x i d i z e d manganese compounds do not (Hutchinson,  Fe  complexes  1957) it  precipitation contributes s i g n i f i c a n t l y lake sediments (Syers  the  Lake.  l e v e l s were reduced i s u n c e r t a i n  too low the  aeration  immediate e f f e c t of experimental  d e c l i n e in hypolimnetic  and  r e g u l a t e d by the presence or absence of  d i s s o l v e d oxygen. Hypolimnetic sediment-water  an  et  al.,  1973).  and is  unlikely  to PO^-P I  despite  co-  their  that  Mn  accumulation in  believe  most  PO^-P  82  coprecipitated the  initial  Phosphorus  with  calcium  stages of has  carbonate compounds formed d u r i n g  aeration  may  i n the  Experimental summer  despite  i n t e r f a c e . The  the pH  rise  have been s u f f i c i e n t  a d d i t i o n , phosphorus may circulating  major  ions  discussion).  been shown to p r e c i p i t a t e with c a l c i u m  (Otsuki and Wetzel, 1972). and hypolimnion  (see  in  the  carbonate  experimental  to cause t h i s r e a c t i o n . In  have adsorbed onto p a r t i c u l a t e d e t r i t u s  hypolimnion. hypolimnetic aerobic  PCXrP  increased  conditions  work of Mortimer  at  (1941-42)  slowly  the is  during  sediment-water often  cited  as  evidence  that orthophosphate r e l e a s e from lake sediments i s at a  minimum  under a e r o b i c c o n d i t i o n s . The  sediment s u r f a c e forms an e f f i c i e n t iron  o x i d i z e d microzone at  barrier  for  as w e l l as PO4-P which i s adsorbed onto and  ferric  oxides,  1975).  This  hydroxides, superficial  apatites oxidized  movement out of the sediments P O L I - P from the water column However, occurs  Lee  under  probably  aerobic  lie  by Burns and  (1970b)  by  precipitated microzone. ferric  This  constant  r a t e of PO^-P  (Wetzel, phosphorus  simultaneously  scavenging  Actual  regeneration  extremes as 25%  of Lake E r i e and  hydroxides readily  hydroxy-phosphate  with  prevents  discovered  decomposition  would  complexed  i n d i c a t e s a p p r e c i a b l e POu/-P r e l e a s e  Ross (1972). They  ferric  and  carbonates  layer  somewhere between the two  organic  manganese  (Mortimer, 1971).  conditions.  from the a e r o b i c hypolimnion produced  while  and  the  is  in  contained  P  and  exemplified regeneration  suggest most  PGv^P  close proximity in  the  l e a d to formation  complexes  rates  explain  to  oxidized  of i n s o l u b l e the  r e l e a s e under a e r o b i c c o n d i t i o n s .  low  but  83  Hypolimnetic reducing oxygen  aeration  sedimentation levels.  result,  particulate  T h i s allowed  sediment also  temperatures  controlling  and  aerobic  organic  PO.J-P  in  dissolved  despite  aerobic  factor  release  loading during  release.  sediment  Although  water  Control profiles anoxic  levels  POL<--P  conditions  divalent  oxygen c o n c e n t r a t i o n  mg/1  (Burns  1975).  These  and  and  the theory  were  PO^-P  at which anoxic 0.5  mg/1.  differences  on  pH the  in e x t r a PCv-P  PO^-P  may  be  release  under  hydroxy-phosphate  and  ferrous  PO 4-P r e g e n e r a t i o n range  (Bernhardt  explained  by  (1970b) d i s c o v e r e d  sediment  clinograde  iron,  i n t o the hypolimnion.  to 4 mg/1  stratification  c i r c u l a t i o n , however i r o n  PO^-P  a  and  The  occurred from  0.6  Wilhelms,  the  various  POu~P r e l e a s e  c h a r a c t e r i s t i c s and  varied  depending on sample l o c a t i o n .  Orthophosphate  insufficient  of  L i t e r a t u r e values  Ross, 1972)  h i g h l y dependent  considerably  result  reduced  released  sediment • types i n v o l v e d as Lee was  is  above  e x h i b i t e d marked i n v e r s e  sediments  manganese and  between 0.2  Higher  exchange r e a c t i o n s ,  (Morimer, 1941-42). F e r r i c  the  was  and  Bates, 1979).  in accordance with  complexes in  P  pH  not  should  As  summer would  p o i n t of minimum P f i x a t i o n and and  i n the  conditions.  a e r a t i o n were  (Nur  increasing  organic  s h i f t s encountered during hypolimnetic  release  by  f r e e of f e r r i c hydroxides.  PO^-P,  increased  stimulate  P  more complete decomposition  relatively  hypolimnetic P  aerobic  r a t e s of organic m a t e r i a l and  water column which was a  increased  and  was  calcium  to cause complete PO^-P  e l i m i n a t e d during carbonate  levels  fall were  p r e c i p i t a t i o n . Consequently  l e v e l s on both s i d e s converged and  remained near 350  ug/1  84  all  winter. In summary, the c l a s s i c model  and  precipitation  operated  l e v e l s were low and considerable  P  levels  increased  Black  Lake.  unusually  and  aerobic  release  Unfortunately  high.  As  aerobic  conditions.  P  release  decomposition. Organic d e t r i t u s was recycled  iron-phosphorus  a  throughout  the  quickly  hypolimnion  on  initial  Hypolimnetic stimulating  decomposed a  rather than resuspended at s p r i n g and f a l l  by  Fe  result,  PO^-P remained i n the water column d e s p i t e  p r e c i p i t a t i o n reactions aeration  in  of  and  P  continuous b a s i s ,  c i r c u l a t i o n as on the  c o n t r o l s i d e . Although a e r a t i o n  increased  total  s i d e remained lower than on the  P  on  control  the  side.  internal  experimental  This  phosphorus  indicates loading  aerobic  hypolimnetic  P  release,  aeration  reduced  which i s the primary goal of most  lake r e s t o r a t i o n p r o j e c t s . It should  i s c l e a r however, that the not  be  accepted  per  classic  se f o r every l a k e . Aerobic  r e l e a s e does occur and some lakes do not the in  ferric-phosphate  limnological  operate  than  redox-  or no e f f e c t on N:P r a t i o s  Black Lake. T h i s was a d i s a p p o i n t i n g  coprecipitation  would  increase  the  nuisance blooms of blue-green algae P  to  Ratios  Hypolimnetic a e r a t i o n had l i t t l e  high  according  minerals.  N:P  in  PO -P  model (Lee et a l . , 1977), e s p e c i a l l y those  which PO -P i s bound to humic substances rather  sensitive  model  l e v e l s were p a r t i a l l y  r e s u l t as I p r e d i c t e d P  N:P  ratio  and  inhibit  ( S c h i n d l e r , 1977). Unusually  responsible  f o r t h i s r e s u l t which  85  minimized the e f f e c t concentrations ratios  by  sediments • N).  P, hypolimnetic  precipitating and c o n v e r t i n g  This  periods  of  of P p r e c i p i t a t i o n .  process  and should  blue-green  forms.  would  P,  lakes  a e r a t i o n should  preventing  nitrogen  In  P  with  lower  i n c r e a s e N:P  release  from  the  i n t o a more s t a b l e form (NOj-  require  eventually s h i f t  several  annual  a l g a l composition  circulation away from  86  Major  The temporal and s p a t i a l regulated hydrogen  by  Ions  distribution  of  major  ion a c t i v i t y . Experimental a e r a t i o n  series  major  of  increased dissolved  ions. accumulated  from the hypolimnion. Although escaping gas was content,  Firstly, water  its  removal  was  venting  not analysed f o r  engineering  removal  i s common p r a t i c e  (Sawyer  and  McCarty,  HS  and NH .  Z  Rainwater  Finally,  5  and  Thatcher  the  1978).  effective  calculation  (1969)  h y p o l i m n e t i c CO^ decreased from 10.2 two weeks of a e r a t i o n while c o n t r o l  in  indicates  of  experimental  to 4.2 mg/1 (9 m) CO^  method  in  the  first  i n c r e a s e d from  7.8  mg/1.  Hypolimnetic  pH  levels  response to CO_z. removal +2  in  h y p o l i m n e t i c gases as evidenced by the r a p i d removal of  accumulated  to 12.5  dioxide  i n f e r r e d from s e v e r a l sources.  a e r a t i o n of water f o r CO^ treatment  carbon  Secondly, v i g o r o u s bubbling w i t h i n the a e r a t o r was  Mg  initiating  r e a c t i o n s i n v o l v i n g both dynamic and c o n s e r v a t i v e  Experimental a e r a t i o n removed  CO^  is  a v a r i e t y of f a c t o r s i n c l u d i n g oxygen t e n s i o n and  oxygen l e v e l s and vented h y p o l i m n e t i c gases, thereby a  ions  and  HCO^"  increased  pH  units  (see pH d i s c u s s i o n ) . As a r e s u l t ,  p r e c i p i t a t e d as carbonates. CaC0  in n a t u r a l waters can be r e p r e s e n t e d by and Wetzel,  0.1-0.4  two  3  Ca  in + 2  ,  precipitation  reactions  (Otsuki  1974): 1. C a  + 2  + 2HCCV 2. Ca  Reaction  1,  + 2  —>  + C0 " 5  CaC0 2  5  + CO^ CaC0  i n c o n j u n c t i o n with CCK  + H 0  3  removal,  i n c r e a s e s pH  87  values while  r e a c t i o n 2 decreases  pH.  Since  bottom  pH  i n c r e a s e d d u r i n g a e r a t i o n , r e a c t i o n 1 i s the equation CaCOj  values  explaining  precipitation. Magnesium  ions  terms of chemical natural nature,  are more c o n s e r v a t i v e than c a l c i u m  reactivity  and  lakes systems (Wetzel,  biological  hypolimnetic compounds  are  more  only  Fast  hypolimnetic suggest  this  considerably  at  et  soluble high  than  pH  levels  response  to  s i n c e magnesium  calcium  (>10)  in  conservative  in  a e r a t i o n . T h i s i s an unusual r e s u l t  precipitate However,  requirements  1975). Despite  magnesium l e v e l s decreased  ions i n  compounds (Wetzel,  and  1975).  a l . (1973) observed a s i m i l a r d e c l i n e during  a e r a t i o n of a small  magnesium  hardwater  precipitated  in  lake.  Therefore  conjunction  with  I  CaCO^,  p o s s i b l y as CaMg(CO^) . 2  These c o n c l u s i o n s are supported Solubility  product  CaMg(C0j)2  by  calculations  p r e c i p i t a t i o n could  several  indicate  occur  under  observations.  both  CaCO  these  conditions.  Secondly, d i s s o l v e d c a l c i u m , magnesium and bicarbonate the 13  experimental days  hypolimnion  aeration  stratification.  of  April  reactions  hypolimnion  maintained  levels  preventing  by  1979  throughout  of  sediment  at  8  m  just  thermal  samples (n=2,  revealed  calcium  31.3 mg/gr (dry wt.) on the c o n t r o l s i d e and  43.0 mg/gr (dry wt.) on the precipitation  lower  analysis 15,  levels in  declined significantly after  remained  Finally,  upper 10 cm) taken concentrations  and  and  aerated  side.  After  a e r o b i c c o n d i t i o n s i n the  lower b i c a r b o n a t e , anaerobic  d i s s o l u t i o n of p r e c i p i t a t e d CaCO,.  release  the  experimental  c a l c i u m and of  initial  magnesium  bicarbonates  and  88  In summary, major i o n r e a c t i o n s aeration  a r e analogous  intense a l g a l a c t i v i t y calcium the  levels  author  increased  i n t r i g u i n g . Wetzel  calcium  of  any  results,  should  levels  population  (1971) study  which a r e  CaCO ^ p r e c i p i t a t i o n  and  organic  carbon  typical  l e a d t o a p a t i t e formation."  is a  and  stated  concentrations  Otsuki  and Wetzel  c o p r e c i p i t a t i o n of phosphate ions with CaCOj as and  indicated  this  c o n t r o l mechanism for primary aeration  coprecipitation. orthophosphate  of  by  CO^ and  aeration  implications  (1975) suggested  increased,  hypolimnetic  caused  decreased  hypolimnetic  the  f o r inorganic  (1972) reported pH  hypolimnetic  reactions  pH,  " E l e v a t i o n of the pH of water c o n t a i n i n g of  by  and CaCO^ p r e c i p i t a t i o n . Other than Fast  similar  sink  epilimnetic  ie.  i s unaware  reporting  major  to  initiated  could  levels  Therefore,  phosphate  aeration  i n Black  f u n c t i o n as a  producers.  reduce  Experimental  may  reduced  Lake  levels  hypolimnetic  and i t appears  phosphate c o p r e c i p i t a t i o n was r e s p o n s i b l e  by  for t h i s  calcium-  r e s u l t (see  phosphate d i s c u s s i o n ) . The  effect  of  hypolimnetic  d i s t r i b u t i o n was s t r i k i n g . S o l u b l e experimental mg/1) w i t h i n by  side  reduced  two weeks as M n  the presence  -particulate  was  of  manganese  +Z  remained  absent  conditions  i n the aerated  on  manganese  (< 0.45 u) manganese  on the  t o undetectable l e v e l s (< 0.02  was o x i d i z e d t o p a r t i c u l a t e  hypolimnetic (MnO^)  aeration  then  oxygen.  Experimental  gradually  f o r the d u r a t i o n hypolimnion  of  sedimented  the summer.  oxidized  the  MnO^ side and  Aerobic sediment  s u r f a c e and prevented l a r g e accumulations of M n . +2  In  contrast,  the c o n t r o l hypolimnion remained anoxic and  89  high  concentrations  summer.  When  conversions reduced  of  oxygen  reduced  concentrations  were  declined,  present a l l a  sequence of  occurred and manganese changed from i t s o x i d i z e d  (Mn )  divalent  +2  state.  sediment-water i n t e r f a c e released  manganese  from  hypolimnion.  then  the sediments  The  oxidized  disappeared and  to  b a r r i e r a t the  and  manganese  accumulated  was  i n the anoxic  Manganous manganese ( M n ) i s t o x i c t o a q u a t i c +2  and c r e a t e s s e r i o u s problems i n p u b l i c water s u p p l i e s  life  (LaBounty  and King, 1977) . At reduced  fall Mn  circulation  the e n t i r e procedure was repeated as  was o x i d i z e d t o MnC^, which then p r e c i p i t a t e d out of  +2  s o l u t i o n . D i v a l e n t manganese l e v e l s remained low on the c o n t r o l side  during  circulation  winter as s u f f i c i e n t t o prevent  Brezonik to  oxygen was i n t r o d u c e d a t f a l l  reoccurrence  of most reducing c o n d i t i o n s .  et a l . (1969) reported o x i d a t i o n of  p a r t i c u l a t e manganese oxides and i t s subsequent  during  soluble  manganese  aeration  experiments  concentrations  have  following  also  aeration  +2  precipitation  d e s t r a t i f i c a t i o n of Cox Hollow Lake, Wisconsin.  hypolimnetic  Mn  Previous  reported (eg.  lower  Bernhardt,  1974). O x i d a t i o n of reduced sediment-water from  interface  redox-sensitive ions  compounds  (Hutchinson,  (Mortimer,  undergoing  at the  precipitate 1957),  with  oxidized  1971).  Although  oxidized  manganese  iron  complexes  (eg. FePO<{) and c o u l d be an important  reducing hypolimnetic lakes  not  compounds  should minimize n u t r i e n t r e g e n e r a t i o n  sediments  phosphate  orthophosphate  do  i r o n and manganese  phosphorus  hypolimnetic  concentrations  in  with  factor in iron-rich  a e r a t i o n . D i v a l e n t manganese has  90  caused  major  hypolimnetic  fish  kills  aeration  in  of  hatcheries  the  source  (Ingols,  1975)  lake would prevent  and this  problem.  pH  As mentioned i n the hypolimnetic  and  major  ions  discussion,  pH l e v e l s i n c r e a s e d 0.1 t o 0.4 u n i t s i n response to  experimental COj7  results  aeration.  The a e r a t i o n process  from the hypolimnion,  and s i n c e CO^  vented accumulated  i s an  acidic  gas, i t s  removal i n c r e a s e d pH a c c o r d i n g t o : C0 (Sawyer  and  + H,0^-~ H CO.,  7  McCarty,  number of important The  this  +  T h i s s h i f t was r e s p o n s i b l e f o r a  increased  bicarbonate  and  hypolimnetic  phosphate  pH  on  calcium,  l e v e l s has already been  (see major ions and major n u t r i e n t s ) . Needless to say,  reaction  significantly  decreased  s e v e r a l ions i n the experimental the  " + H  reactions.  i n f l u e n c e of  magnesium, discussed  1978).  HCO  influence  of  hypolimnion.  pH on ammonia  ammonium ion (NH^ )-ammonia +  the  of  Also discussed  was  s p e c i a t i o n which d i s p l a c e d the  (NH ) e q u i l i b r i a 5  form (NH^) which was more e a s i l y  concentration  vented  by  towards the gaseous the  aerator  (see  major n u t r i e n t s ) . The  effect  of  higher  hypolimnetic  pH l e v e l s on hydrogen  91  s u l f i d e t o x i c i t y was detected  on  the  l e s s obvious. Hydrogen  experimental  t r i p , however on the remaining  side trips  sulfide  odour  d u r i n g the f i r s t i t s odour was  was  sampling  r e p l a c e d by a  musty scent. In c o n t r a s t , c o n t r o l 8 + 9 m samples contained odour  throughout  spring,  summer  and  early f a l l .  Although  c o n c e n t r a t i o n s were always below d e t e c t a b l e l e v e l s extreme t o x i c i t y warrants f u r t h e r d i s c u s s i o n . (1975)  reported  acute  toxicity  levels  long-term  impairment of growth and  Hydrogen  sulfide  u n d i s s o c i a t e d H^S, (S" ) H^S  and HS"  whereas present  ions  i s nontoxic  and  (HS")  e l i m i n a t i o n of H^S  processes.  Firstly,  pH  s h i f t e d the hydrogen assisted nontoxic  in  reducing  and odourless  ionized" H S was bubbling about the  the  separator to  SO^"  emits a  strong  odour  and HS"  accounts  are over  a r e s u l t of at l e a s t  three  1978).  i n c r e a s e d during a e r a t i o n . T h i s  l e v e l . Secondly,  aerator  within  d i s s o l v e d oxygen indroduced 2H S + 50^ i  ions  towards  HS"  which  the c o n c e n t r a t i o n of u n - i o n i z e d H^S  box.  2  forms:  range of lakes only  relationship  purged d i r e c t l y  within  mg/1.  for  (WHO,  odour was  sulfide  discovered  sulfide  o d o u r l e s s . At pH 7, H^S  levels  H S for  in three  and  i n equal amounts, however at pH 8 HS"  The  and  water  1957). In the normal pH  90% of the t o t a l hydrogen s u l f i d e  oxidized  lake  are p r e s e n t . H S i s t o x i c and  HS"  Oseid  r e p r o d u c t i o n at 0.009  in  hydrosulfide  (Hutchinson,  z  occurs  and  of 0.025 mg/1 )  H S  (1 mg/1), i t s  Smith  j u v i n i l e brook t r o u t ( S a l v e l i n u s f o n t i n a l i s  H^S  i n t o the atmosphere by as evidenced  Finally, the  an unknown amount of  some  un-ionized  by the a e r a t o r : 2  H  un-  vigorous  by i t s strong odour  hypolimnion  2SO "  to a  +^H^O  by  H^S  was  r e a c t i n g with  92  U n f o r t u n a t e l y no data e x i s t Black  Lake.  Nonetheless,  to c o n f i r m these  these  c o n c e n t r a t i o n of u n - i o n i z e d H^S  reactions  and  would  restoration  of  eutrophic  lakes  to  H^S  the  any  important  since  at  reduced  apply  e x p e r i e n c i n g an anoxic hypolimnion. T h i s i s an the  processes  lake  s t e p in  removal  is  ne.cessary p r i o r to r e c o l o n i z a t i o n of a e r o b i c organisms. Although phytoplankton and  zooplankton  feeding  s p e c i e s composition rates  (Shapiro,  (Kring and O'Brien, 1976a) are  i n f l u e n c e d by pH s h i f t s , a e r a t i o n induced s h i f t s were too small to cause any  1978)  in  Black  Lake  effects.  Phytoplankton  The phytoplankton community i n Black Lake was by  seasonal  blooms  of  Chlorphyta,  superimposed a g a i n s t a r e l a t i v e l y  Cryptophyta  characterized and  diatoms  l a r g e background p o p u l a t i o n of  blue-green a l g a e . S l i g h t d i f f e r e n c e s d i d e x i s t  between  control  and experimental s i d e s , however these were g e n e r a l l y s h o r t - l i v e d and the o v e r a l l p a t t e r n of seasonal abundance was  similar  except  for the December-January p e r i o d . During  this  period,  diatom  abundance was  up to ten  higher on the experimental s i d e and Chlorophyta numbers were to  four ' f o l d  d i f f e r e n c e was  greater related  on to  the c o n t r o l p o r t i o n . I b e l i e v e aeration  currents  circulating  fold up this the  93  experimental  s i d e under i c e cover. Diatoms would be favoured i n  t h i s environment as they conditions  such  as  often  spring  occur  and  fall  would be favoured on the c o n t r o l s i d e would  allow  immediately  them  to  naturally  stratify  in  beneath the i c e cover  circulation. as  the  and  midwinter  however  o l i g o t r o p h i c values despite (Schindler, mg/1,  to  quiescent shallow  high  midsummer  large  reserves  zone  during  spring, resembled  orthophosphate  occur. T h e i r absence and  fixing  0.02  blue-green  low numbers of other s p e c i e s  i n Black Lake  were  restricted  some form of m i c r o n u t r i e n t . Murphy et a l . (1976) and Goldman  s t i m u l a t i n g phytoplankton  algae.  Molybdenum  levels  c o n s i s t a n t l y below 0.1  of  Epilimnetic  were not determined  mg/1  experimental stream  during  summer  affected depth  by  however i r o n  months.  This  was may  algae.  I b e l i e v e t h i s was  a  on  the  result  of  and d i l u t i o n by Yellow Lake Creek which peaked  3-5  m /min.  stream  3  Algal  flushing  intervals. Chlorophyll a  phytoplankton  i n blue-green  c h l o r o p h y l l a values were lower  s i d e i n e a r l y May.  flushing  mid-May at  (0-4 m)  micronutrients  growth and N f i x a t i o n  e x p l a i n the absence of l a r g e blooms of N f i x i n g  in  photic  of  (1966) have both demonstrated the importance in  conditions  levels  l a r g e blooms of N  suggests midsummer phytoplankton by  Chlorophyta  1974). N i t r a t e l e v e l s were g e n e r a l l y l e s s than  t h e r e f o r e I expected  algae  turbulent  (Wetzel, 1975).  Black Lake c h l o r o p h y l l a values were fall  in  composition  as  i t was  data  also  data  averaged  indicated  which had accumulated  probably due  less  over s e v e r a l  bloom s t a r t e d two weeks e a r l i e r and was  the a e r a t e d s i d e . T h i s r e s u l t was  was  the  fall  l a r g e r on  to m i c r o n u t r i e n t s  i n the experimental hypolimnion  throughout  94  the  summer.  throughout  At  fall  the  turnover  water  column  these and  nutrients  stimulated  were  mixed  an e a r l i e r  fall  bloom. Murphy et a l . (1980) d i s c o v e r e d higher i r o n v a l u e s on the aerated  side  of  Black  Lake  which  lends  support  to  this  hypothesis. Long-term  effects  phytoplankton several  community  annual  of  hypolimnetic  should  circulation  algal  more  as  the  Lake  the after  to p r e d i c t  micronutrients  which  growth were not i d e n t i f i e d . I suspect one of the  few ways to s i g n i f i c a n t l y a l t e r the phytoplankton Black  on  apparent  periods. It i s d i f f i c u l t  e x a c t l y which changes w i l l occur limited  become  aeration  would  be  via  total  community  destratification  in  or i r o n and  n i t r o g e n a d d i t i o n s (eg. B a r i c a et a l . , 1980).  Zooplankton  The zooplankton community expected  to the experimental treatment. The reasons  twofold. F i r s t l y , was  aerobic  effect  i n Black Lake d i d not respond  of  the 5 to 7 m s t r a t a  throughout hypolimnetic  distribution  as  the  aeration  two  sides  on  hypolimnion  T h i s reduced the  zooplankton  vertical  c o n t r o l hypolimnion was a l r e a d y p a r t i a l l y  a e r o b i c . T h e r e f o r e , as f a r as the the  f o r t h i s are  i n the c o n t r o l  the e n t i r e experiment.  as  zooplankton  were  of Black Lake were r e l a t i v e l y s i m i l a r  concerned, hence the  95  similarity  i n v e r t i c a l distribution«  Secondly, Cyclops  stream  numbers  flushing  on  the  experimental  inflow peaked i n e a r l y May difference  between  which  Cyclops  experimental s i d e s . T h i s chlorophyll  i n s p r i n g 1978  reduced  s i d e . Yellow Lake Creek  c o i n c i d e d -with numbers  theory  is  juvinile  on  the  the  supported  maximum  control  by  and  organic  N,  a, d i s s o l v e d o r g a n i c P and p a r t i c u l a t e P data which  were a l s o unexpectedly  lower on the experimental  side  at  this  time. T h e r e f o r e , zooplankton data must be i n t e r p r e t e d with these confounding The  f a c t o r s i n mind.  seasonal abundance of Daphnia pulex was  by h y p o l i m n e t i c a e r a t i o n . T h i s i s an low  oxygen  levels  respiration die-offs  are  interesting  long-term exposure  et to  (1976b)  observed  depressed  filtering  a l . , 1980). One low  low  (8-12  oxygen oxygen  levels  collected  stimulated  noticeably  red  during  • stained,  s y n t h e s i z e d i n response Daphnia  to  similarity  remain  in  Kring  (1-3  spring  and mass  O'Brien initially  however  prolonged  production  high f i l t e r i n g  and  possibly  and  mg/1)  haemoglobin  summer  to low oxygen l e v e l s . T h i s  and  r a t e s . Many  months  representing  were  haemoglobin would  allow  the c o n t r o l hypolimnion and e x p l a i n  the  i n v e r t i c a l and seasonal d i s t r i b u t i o n .  The p o p u l a t i o n of K e r a t e l l a quadrata exhibited  since  possible explanation i s  pulex,  enabled Daphnia to resume i t s i n i t i a l Daphnia  result  and even cause  levels.  r a t e s i n Daphnia  hrs)  influenced  to reduce Daphnia f i l t e r i n g  r a t e s (Heisey and P o r t e r , 1977)  (Nicholls  exposure  known  not  a  late  autumn-winter  c o l d stenothermal type  of  i n h a b i t i n g Black  maximum, thus conforming  seasonal  distribution  Lake to a  (Hutchinson,  96  1967).  The  seasonal abundance was  s p r i n g , summer and e a r l y numbers  were  reflect  in  the  rotifer  understood  control  or  hypolimnion  metabolic  population  and  quite  feed  and  (8+9  side.  Low  did  not  m)  may  to  low  oxygen  on  in  rotifers  are  poorly  (Wetzel,  sedimenting  generated  by  1975).  seston,  the  and  aerator  s i d e food supply by d e c r e a s i n g s e t t l i n g  Planktonic I believe  enhanced  the  r a t e s of seston  d u r i n g the c r i t i c a l winter p e r i o d when autochthonous was  winter  t h i s response  adaptations  changes  variable  mainly  c i r c u l a t i o n currents aerated  fall  ( R u t t n e r - K o l i s k o , 1975).  Seasonal  rotifers  late  v e r t i c a l d i s t r i b u t i o n , and  behavioural  conditions  however  c o n s i d e r a b l y higher on the experimental  oxygen l e v e l s influence  fall  s i m i l a r on both s i d e s through  production  low and a l l o c h t h o n o u s inputs n e g l i g i b l e . In a d d i t i o n , l o n g -  term exposure to higher oxygen l e v e l s may r o t i f e r growth or r e p r o d u c t i v e b i o l o g y experimental The s i m i l a r on  both  distribution sides  of  despite  depletion  in  unexpected  as Cyclops sp.  anaerobic  metabolism  vertically  thus  r o t i f e r numbers during f a l l  vertical  improve some aspect of explaining  and winter months.  Cyclops  bicuspidatus  hypolimnetic  (8+9  the c o n t r o l p o r t i o n . T h i s r e s u l t was  during  are  capable  (Chaston,  part  of  of  day  to  m) not  briefly  1969). Cyclops may  the  higher  escape  was  oxygen entirely  undergoing  have migrated low  oxygen  conditions. Cyclops  nauplii  and copepodites were more abundant on  c o n t r o l s i d e d u r i n g s p r i n g and on the experimental fall. stream  side  the  during  I b e l i e v e s p r i n g d i f f e r e n c e s i n abundance were a r e s u l t of f l u s h i n g on the experimental  s i d e . T h i s reduced  juvinile  97  Cyclops numbers however other s p e c i e s were not a f f e c t e d they  were not present at t h i s time  t h e i r a d u l t form and able  to  (eg.  resist  Daphnia ). F a l l d i f f e r e n c e s were due on fall  the  experimental  Diaptomus ) or were i n  flushing  currents  (eg.  to an i n c r e a s e d food supply  side r e s u l t i n g  from an e a r l i e r and  larger  bloom. In  addition,  reduces  Cyclops  and diapause Higher  long-term  of  exposure  of copepodite  stages  Unfortunately circulation  s i d e oxygen  levels  both  sides  i n October  levels  and Reynolds,  may  the  have  1977).  reduced  the  water  experienced  vigorous  of  Diaptomus  i n f l u e n c e d by the experimental in  adults  l a t e summer-fall.  in  early  summer  leptopus  and  Copepodite  development  aerobic/anaerobic  conditions.  conditions,  more  stages, abundant  seasonal d i f f e r e n c e s between s i d e s were r e l a t e d  egg  with Diaptomus  experimental  side.  believe  resting  was  treatment. C o n t r o l  while not s i g n i f i c a n t l y d i f f e r e n t , were s l i g h t l y on the a e r a t e d  wind-driven  experiment.  distribution  numerous  during  s i d e to s i d e d i f f e r e n c e s  n a u p l i i were more abundant more  column  higher c o n t r o l s i d e numbers.  which minimized  of the  seasonal  significantly  in  despite i n i t i a l l y  for the remainder  I  oxygen  Cyclops m o r t a l i t i e s and d i a p a u s i n g c o p e p o d i t e s . As a  summer-fall  The  low  (Heberger  r e s u l t , more Cyclops were present late  to  b i c u s p i d a t u s abundance through a d u l t m o r t a l i t y  experimental  number  to  because  stagnalis  and  survival  under  Brewer (1964) worked e x t e n s i v e l y  resting  were a necessary  adult  eggs  and  concluded  anoxic  stimulus f o r s u c c e s s f u l hatching of  r e s t i n g eggs. Diaptomus leptopus i n Black Lake  overwintered  as  98  resting  eggs  d e p o s i t e d during f a l l  c i r c u l a t i o n of the p r e v i o u s  year. Hypolimnetic  a e r a t i o n of the experimental  delayed  of r e s t i n g eggs by reducing t h e i r exposure to  hatching  low oxygen  conditions.  This  would  explain  c o n t r o l numbers. However, once experimental higher  oxygen  levels  may  remaining  increased  altered  basis  the  could  occur  r e v e r t e d to i t s  r e s t i n g eggs hatched s u r v i v a l as  (Cooley,  1971).  surveyed  zooplankton  after  former  possibility several  state  (Chaston,  1969;  of  community  of  any  tolerate  years.  1971;  anoxia  limnetic  anoxia or the t o x i c products  s e v e r a l years I would expect  fewer  changes  below  the  literature Reynolds,  zooplankton  (H^S, M n ) which +2  f o r extended  a e r a t e d s i d e to s i g n i f i c a n t l y expand t h e i r experience  not  I f the c o n t r o l s i d e  Heberger and  indicates  accumulate i n an anoxic hypolimnia Therefore, after  was  long-term  complete  Cooley,  Heisey and P o r t e r , 1977)  cannot  low Fall  both s i d e s and minimized  t h e r m o c l i n e , these changes would be a c c e l e r a t e d . Most  1977;  higher  by one year of h y p o l i m n e t i c a e r a t i o n . However,  t h i s does not e l i m i n a t e the which  on  have  s i d e to s i d e d i f f e r e n c e s .  On an o v e r a l l greatly  oxygen  may  initially  have enhanced t h e i r  oxygen l e v e l s are t o x i c to Diaptomus sp. circulation  side  p e r i o d s of  zooplankton  vertical  time. on  range  anoxia r e l a t e d m o r t a l i t i e s than t h e i r  the and  control  side counterparts. The follows  introduction successful  by p r o v i d i n g refuge  of  planktivorous  fish  (which  a e r a t i o n ) would i n t e n s i f y these  experimental  zooplankton  with  a  usually  differences  predation-free  (Shapiro, 1978). Increased l i g h t t r a n s m i s s i o n may  t h i s advantage i n c e r t a i n  lakes  (eg.  Kitchell  and  offset  Kitchell,  99  1980)  however  increased  this  would  hypolimnetic  importance  not  occur  turbidity.  in  Black  This  of oxygen s t r a t i f i c a t i o n  Lake  due  demonstrates  to the  in s t r u c t u r i n g the l i m n e t i c  macrozooplankton community.  Management I m p l i c a t i o n s and  Practical research.  applications  This  i m p l i c a t i o n s and  often  Suggest ions  evolve  p r o j e c t was  no exception  suggestions  arose  from  and  during  theoretical  s e v e r a l management  the  course  of  the  experiment. Hypolimnetic months as water  aeration  i t maintains the  is  i c e s u r f a c e and  hazard u s u a l l y a s s o c i a t e d with  becoming i n c r e a s i n g l y important sites  e s p e c i a l l y useful during  and  preserve  hypolimnetic  the  as  aeration  i c e s u r f a c e and  minimizes  winter  the  open  such a c t i v i t i e s . Lakes are winter  allows  outdoor the  recreation  lake manager to  r e t a i n m u l t i p l e use  options  for  the  lake. Many l a k e s are surrounded their  water  addition  to  hypolimnetic c a t i o n s . The  by  houses  which  directly  from the l a k e . Hypolimnetic  removing  objectionable  hardness  by  odours  precipitating  d e c l i n e i n hardness s h i f t e d Black  often  obtain  aeration, in  (H S), divalent  .decreases metallic  Lake bottom water  100  from very hard  (181-300 mg/1)  to  hard  (121-180  mg/1)  (Lind,  1979). T h i s s h i f t would b e n e f i t water consumers by reducing soap consumption and pipe s c a l i n g problems. Lake r e s t o r a t i o n p r o j e c t s are  often  partially  funded  by  surrounding  b e n e f i t s of t h i s type would encourage t h e i r Aeration  stimulates  concentrations  are  aeration projects projects critical  should  oxygen  becomes . an begin  warming  oxygen l e v e l s . minimize  before  hypolimnetic  necessary  a  and  oxygen  sediment  1971)  aerators  aeration  l e v e l s d e c l i n e to oxygen  Hypolimnetic  (eg. F a s t ,  may  should  demand  a e r a t o r s which actually  be  of q u e s t i o n a b l e value  reduce  designed  warming, and d e s t r a t i f i c a t i o n of  lakes d u r i n g summer months may  Finally,  when  factor  oxygen  addition,  Hypolimnetic  and H a r l i n , 1970;  consumption  important  well  c o n c e n t r a t i o n s . In  sediment  support.  below t h r e s h o l d l e v e l s . T h e r e f o r e timing of  i n c r e a s e s markedly with temperature. cause  home owners, and  to  shallow  (eg. Leach  N i c h o l l s et a l . , 1980). long  term  commitment  to lake r e s t o r a t i o n i s  and a great deal of r e s e a r c h remains to be done. Lakes  d i d not become e x c e s s i v e l y e u t r o p h i c o v e r n i g h t , and a e r a t i o n should not be expected  to cure them  hypolimnetic  instantly.  101  SUMMARY  AND CONCLUSIONS  1. Hypolimnetic a e r a t i o n had no e f f e c t on the formation and maintenance of thermal season  stratification  as normal d e n s i t y s t r a t i f i c a t i o n  from the a c t i v e l y c i r c u l a t i n g 2.  throughout  and  experimental  hypolimnetic  i s o l a t e d the e p i l i m n i o n  was too  weak  aeration  to  resist  circulated  mixing  the  entire  s i d e under i c e c o v e r .  3 . Winter minimized  ice-free  hypolimnion.  Inverse s t r a t i f i c a t i o n  currents  the  a e r a t i o n d i d not  the  open  water  weaken  the  i c e surface  and  hazard u s u a l l y a s s o c i a t e d with  such  activities. 4. transfer  Hypolimnetic c i r c u l a t i o n d i d not increase of  substances  the  vertical  a c r o s s the thermocline and e p i l i m n e t i c  transparency was u n a f f e c t e d . 5.  Hypolimnetic a e r a t i o n thoroughly mixed the  hypolimnion  and i n c r e a s e d t u r b i d i t y  sedimentation 6.  l e v e l s by reducing d e t r i t a l  rates.  Hypolimnetic  hypolimnion  experimental  from  a  aeration passive  c i r c u l a t i n g decomposition 7. Continued  changed  the  collecting  function  zone  to  of the  an a c t i v e l y  zone.  suspension  of d e t r i t u s should  l o a d i n g to the sediments and e v e n t u a l l y decrease  reduce  organic  sediment oxygen  demand. 8.  Hypolimnetic  hypolimnetic  oxygen  aeration  concentrations  significantly and  maintained  c o n d i t i o n s at the sediment-water i n t e r f a c e throughout 9.  Experimental  aeration . increased  increased aerobic the year.  hypolimnetic  oxygen  102  consumption by s t i m u l a t i n g sediment oxygen demand and  enhancing  the water column component of h y p o l i m n e t i c oxygen consumption. 10.  Hypolimnetic  oxygen s a t u r a t i o n was  high oxygen demand, shallow depths and  not achieved due  i n c o r r e c t bubble s i z e  to in  the a e r a t o r . 11.  Artificial  the onset of anoxia  aeration  at low oxygen l e v e l s w i l l  by s t i m u l a t i n g  sediment  and  hasten  water  column  oxygen demand. 12. A e r a t i o n reduced a  variety  of  h y p o l i m n e t i c ammonia c o n c e n t r a t i o n s by  mechanisms  and  increased  nitrate  levels  by  s u p p l y i n g s u f f i c i e n t oxygen for b a c t e r i a l n i t r i f i c a t i o n . 13. Lower h y p o l i m n e t i c ammonia aquatic sediment  community  while  oxidation  increased  and  allow  nitrification/denitrification 14. Hypolimnetic c a l c i u m carbonate  levels  would  benefit  n i t r a t e l e v e l s may nitrogen  enhance  removal  through  sequences.  a e r a t i o n reduced  orthophosphate l e v e l s v i a  coprecipitat ion.  15. A e r a t i o n i n c r e a s e d a e r o b i c P r e l e a s e by enhancing column  decomposition  of  organic  material  i n t e r n a l phosphorous l o a d i n g by m a i n t a i n i n g at  the sediment-water  from the hypolimnion  17. hypolimnion  was  a e r a t i o n vented and  reduced  l e v e l s through  Reduced  but  reduced  aerobic  water total  conditions  interface.  16. Experimental  and bicarbonate  the  manganese  o x i d i z e d and  accumulated carbon  dioxide  h y p o l i m n e t i c c a l c i u m , magnesium  c a l c i u m carbonate (Mn ) +2  precipitated  in  precipitation.  the in  experimental  accordance  with  Mortimer's o b s e r v a t i o n s . 18.  Experimental  a e r a t i o n i n c r e a s e d h y p o l i m n e t i c pH  levels  103  by CO^  removal,  shifted  which  initiated  ammonia • s p e c i a t i o n  general  ion  precipitation,  towards the gaseous form  (NH^) and  reduced H S t o x i c i t y . 19. Hypolimnetic phytoplankton high  aeration  m i c r o n u t r i e n t s and  20.  levels,  confinement  d u r i n g thermal Stream  21. treatment  minimal  effect  flushing  response  Daphnia  an of  apparent aeration  shortage  currents  of  to the  on  the  on  experimental  the  control  side  side  and  a  confounded  to h y p o l i m n e t i c a e r a t i o n .  pulex  was not i n f l u e n c e d by the experimental  due to long-term a d a p t a t i o n to low oxygen  levels.  22. The winter p o p u l a t i o n of K e r a t e l l a quadrata was on  on  stratification.  p a r t i a l l y a e r o b i c hypolimnion zooplankton  a  abundance and s p e c i e s composition due to u n u s u a l l y  orthophosphate  hypolimnion  exerted  larger  the experimental s i d e as a e r a t i o n c u r r e n t s enhanced i t s food  supply. 23. generally  Cyclops  bicuspidatus  more abundant a f t e r  and  Diaptomus  include  Management retention  implications of  were  s e v e r a l months a e r a t i o n as higher  oxygen l e v e l s i n c r e a s e d a d u l t and j u v e n i l e 24.  leptopus  multiple  of use  survival.  hypolimnetic options  i n c r e a s e d p o t a b i l i t y of h y p o l i m n e t i c water,  aeration  during  winter,  timing  suggestions  for a e r a t i o n , p r o j e c t s and m o d i f i c a t i o n s to minimize  hypolimnetic  warming.  104  LITERATURE CITED Andeen,  G.B.  1974.  Bubble pumps. Compressed A i r Magazine. 79:16-19.  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V e r e i n . Limnol. 19:1960-1970.  116  APPENDIX  TABLE 2 Environmental Laboratory Water Chemistry Methods General Ions - u n f i l t e r e d , unpreserved, 3.785 l i t r e  4.5,  1. A l k a l i n i t y : T o t a l - p o t e n t i o m e t r i c  bottle.  titration,  pH  endpoint  2. Calcium-atomic a b s o r p t i o n . D i r e c t a s p i r a t i o n , 211 nm. 3. Magnesium-atomic a b s o r p t i o n . D i r e c t a s p i r a t i o n , 420  4. nm.  Nitrogen:Ammonia-automated c o l o r i m e t r i c ;  5. Nitrogen:Nitrate-cadmium r e d u c t i o n 520  8. N i t r o g e n : K j e l d a h l - a c i d 9.  orthotolidine,  plus d i a z o t i z a t i o n .  6. N i t r o g e n : N i t r i t e - a u t o m a t e d c o l o r i m e t r i c ; nm. 7. N i t r o g e n : O r g a n i c - c a l c u l a t i o n ,  285 nm.  diazotization,  TKN-NH3=ON.  digestion  plus  Nesslerization.  pH:pH meter.  10. Phosphorus:Orthophosphate-filtration (0.45 u M i l l i p o r e ) , automated c o l o r i m e t r i c ; a s c o r b i c a c i d r e d u c t i o n , 885 nm. 11. digestion  Phosphorus:Total phosphate-automated plus a s c o r b i c a c i d r e d u c t i o n , 885 nm.  colorimetric,  12. Phosphorus:Total d i s s o l v e d p h o s p h a t e - f i l t r a t i o n (0.45 u M i l l i p o r e ) , automated c o l o r i m e t r i c , d i g e s t i o n p l u s a s c o r b i c a c i d r e d u c t i o n , 885 nm. 13. Phosphorous:Dissolved TDP-OP=DOP. 14. TDP=PP.  Phosphorous:Particulate Dissolved  organic  phosphate-calculation,  phosphate-calculation,  TP-  Metals  -field pressure f i l t r a t i o n (0.45 u M i l l i p o r e ) preserved with 2 ml cone. HNO , i n a c i d washed 500 ml b o t t l e s .  117  248  15. nm.  Iron:Dissolved-atomic  16. aspiration,  absorption,  Manganese:Dissolved-atomic 279 nm. Unfiltered  -preserved 17. 279  with 2ml cone. HNO  Iron:Total-acid  direct  aspiration,  absorbtion,  direct  Metals  , a c i d washed 500 ml  digestion,  bottles.  atomic a b s o r p t i o n , 248  18. Manganese:Total-atomic a b s o r p t i o n , nm.  direct  nm.  aspiration,  Carbon - u n f i l t e r e d , unpreserved, 19. CarbonrTotal  250  ml  bottles.  organic-infrared  analyzer.  Sulfide - u n f i l t e r e d , preserved  with 1 ml 2N z i n c a c e t a t e , 500  20. S u l f i d e : T o t a l - i o d o m e t r i c  titration.  ml  bottle.  118  TABLE 3 List  of Personal Communications  1. J.A. Botham. T e c h n i c i a n . Water R i g h t s Branch (Kelowna), M i n i s t r y of Environment, Province of B r i t i s h Columbia. 2. W.R. Eadie. Technical Service Supervisor, P o l y o l e f i n s D i v i s i o n , DuPont of Canada L t d . , O n t a r i o .  Woven  3. J.E. F a r r e l l , P.Eng. Regional Engineer, Water R i g h t s Branch (Kelowna), M i n i s t r y of Environment, Province of British Columbia. 4. J.H. Makiev. Design and Survey Branch, P r o j e c t Engineer, (Penticton), Ministry of T r a n s p o r t a t i o n and Highways, P r o v i n c e of B r i t i s h Columbia. 5. J . Pinder-Moss. Herbarium C u r a t o r , Department of Botany, U n i v e r s i t y of B r i t i s h Columbia. 6. D. E. Reksten, P.Eng. Senior Hydraulic Engineer, Hydrology D i v i s i o n , Environmental and E n g i n e e r i n g S e r v i c e , Water Investigations Branch, M i n i s t r y of Environment, Province of B r i t i s h Columbia. 7. G.J. S t e e r . Graduate Student. Simon Burnaby, B r i t i s h Columbia.  Fraser  University,  8. C.J. B u l l . Regional F i s h e r i e s Biologist, Fish and W i l d l i f e Branch ( P e n t i c t o n ) , M i n i s t r y of Environment, P r o v i n c e of B r i t i s h Columbia.  119  TABLE 4  L i s t Of F Values For Water Q u a l i t y  row 5 d.f./90 d . f . 1%=3.23, columns  Parameter  Row  Alkalinity  13 .72  3 .37  Calc ium  11 .03  2 .26  Carbon:TOC  1 .19  1 .07  Chlorophyll a  0 .25  2 .59  Magnesium  12 .15  3 .38  Manganese:Di s s .  27 .79  1 .58  3 .11  1 .44  Nitrogen:NH3  30 .54  1 .72  Nitrogen:N03  18 .44  2 .11  Nitrogen:TON  0 .89  2 .37  Oxygen  11 .60  2 .56  Phosphorus:Ortho.  25 .16  1 .51  Phosphorus:DOP  6 .15  0 .80  Phosphorus:PP  1 .85  2 .40  pH  7 .87  3 .34  Temperature  5 .08  3 .74  Manganese:Part.  Column  Parameters  18 d.f./90 d . f . 1%=2.15  120  TABLE 5  L i s t Of F Values For Zooplankton  row 9 d.f./162 d . f . 1%=2.52, columns 18 d.f./162 d . f . 1%=2.05  Parameter  Row  Column  Cyclops:Naupli i  0.96  2.20  Cyclops:Cl-C5  1.81  Cyclops:Adults  0.72  4.01  Daphnia  1.35  1.29  Diaptomus:Naupli i  1.02  3.20  Diaptomus:CI-C5  1.40  1.6  Diaptomus:Adults  0.69  3.02  Keratella  0.81  2.79  T o t a l zooplankton  2.10  11.8  10.5  

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