ALGAE-TEMPERATURE -
           NUTRIENT
       RELATIONSHIPS
  AND   DISTRIBUTION
      IN   LAKE    ERIE
                  1968
          ENVIRONMENTAL PROTECTION AGENCY
             WATER QUALITY OFFICE
                 REGION 3C
              LAKE ERIE BASIN

               FEBRUARY 1971

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  FOR RELEASE:  P.M.'s
   April  2,  1971
For further information contact:
Potos   216-522-4876 or 216-333-7000
                      REPORT CALLS FOR STOP TO PHOSPHORUS IN LAKE ERIE

         The U. S. Environmental  Protection today released the first year-round study

  of the effects of phosphorus and nitrogen pollution in Lake Erie.

         In  releasing the  report, Francis T. Mayo, Region V Water Quality Director for
  EPA said,  "This report,  based on data gathered during 1968, substantiates earlier
  findings by  a technical  committee that a stepped-up program of phosphorus removal
  can control  oxygen-robbing algae in the Lake."

         The title of the  report  is "Algae-Temperature Nutrient Relationship and
  Distribution in Lake Erie, 1968."

         That  technical committee in 1967 found that a 92 per cent reduction in
  phosphorus discharged by cities and industries would be necessary to control algae
  in the Lake.  The Federal-State Lake Erie Enforcement conference in 1968 agreed to
  require 80 per cent phosphorus  reduction from municipal and industrial sources
  throughout the Lake Erie basin.

         The report, written by Robert Hartley and Chris Potos of EPA's Lake Erie
  Basin Office, states that "An 80 per cent reduction of municipal and industrial
  soluble phosphorus will  limit the duration but not the maximum populations" of
  tiny diatom  plants.  The report goes on to add that an 80 per cent reduction will
  reduce the population but not the duration of green algae and blue-green algae.
  Blue-green algae indicate advanced pollution.

         The results of this year-round study are expected to be confirmed later this
  spring when  a joint Canadian-American study of pollution in the Lake's western
  basin is released.  Preliminary results from that study, code named "Project Hypo,"
  indicate that Lake Erie  is becoming self-polluting in the summertime when oxygen
  in the western basin disappears and anaerobic decomposition of algae begins.

         The report also concluded that:

         -   Concentrations of phosphorus generally decrease from the shore lakeward
  and from west to east in the Lake.

         - Soluble phosphorus more than doubles in all nearshore areas and in the
  western basin midlake in the winter, but not much is used by the temperature
  regulated  algae.

         -   Any reduction  of nutrients would be somewhat effective in getting rid of
  green algae.  (Copies of the report available from Lake Erie Basin Office, 21929
  Lorain Road, Cleveland 44126.)
                                          #   #  #

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                ENVIRONMENTAL PROTECTION AGENCY
                         UNITED STATES
                                       IN-TE-RKDR
          FEDERAL WATER POLLUTION CONTROL ADMINISTRATION

                        GREAT LAKES REGION

                     LAKE ERIE PROGRAM OFFICE

                        21 929 LORAIN ROAD

                      CLEVELAND. OHIO 44126
                                   April 1, 1971
                      NOTICE OF PUBLICATION
I am pleased to send you a report, prepared by Robert P. Hartley
and Chris Potos of this office, describing the algae-temperature-
nutrient relationships and distribution in Lake Erie.

The report is rather significant in that it shows, for the first
time, that an adequate algal response prediction system can be made
for Lake Erie with perhaps considerably less effort than apparently
first thought possible.  The report also describes, in more precise
terms than ever before, the importance of phosphorus as an algal
nutrient, and the direct benefits in pollution abatement to be de-
rived by a phosphorus control program.

Additional copies of the report are available on request at the
Environmental Protection Agency, Lake Erie Office, 21929 Lorain
Road, Fairview Park, Ohio  MH26.
                                   GeorgeGL. Harlow
                                   Director

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ALG-AL-TEMFERATURE-NUTRIEM' RELATIONSHIPS

      AND DISTRIBUTION IN LAKE ERIE
                  By
           Rotert P. Hartley
                  and
            Chris P. Potos
                    -rotection Agency.
 ENVIRONMENTAL PROTECTION  ASENCY
      WATER  QUAUTY OFFICE
              REGION X
         LAKE  ERIE  BASIN

           FEBRUARY  1971

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EKVIRC.r^r.TTAL PP.CTECTION AGENCY

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                            TABLE OF CONTENTS


                                                                     Page
SUMMARY AND CONCLUSIONS                                                 I

INTRODUCTI ON                                                            8

PHOSPHORUS DISTRIBUTION  IN LAKE ERIE                                   II

     Western Basin

          Soluble Phosphorus                                           12
          Particulate Phosphorus                                       19

     Central Basin

          Soluble Phosphorus                                          26
          Particulate Phosphorus                                      28

NITROGEN DISTRIBUTION IN LAKE ERIE                                    30

     Western and Central Basins

          Organic Nitrogen                                            31
          Ammonia Nitrogen                                            36
          Nitrate Nitrogen                                            40
          Organic-Inorganic Nitrogen Ratios                           45

WATER TEMPERATURE                                                     46

AIR TEMPERATURE                                                       50

SUNSHINE AND SOLAR RADIATION                                          50

WIND                                                                  52

PHYTOPLANKTON                                                         52

DISSOLVED OXYGEN                                                      58

CHEMICAL OXYGEN DEMAND                                                61

CORRELATION OF FACTORS AFFECTING ALGAL PRODUCTIVITY                   61

     Centric Diatoms

          Water Temperature                                           62
          Soluble Phosphorus and Temperature                          63
          Inorganic Nitrogen                                          64

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                           TABLE OF CONTENTS
     Pennate Diatoms                                               Page

          Water Temperature                                         70
          Soluble Phosphorus and Temperature                        70
          Inorganic Nitrogen and Temperature                        72

     Green Coccold Algae

          Water Temperature                                         73
          Soluble Phosphorus and Temperature                        75
          Inorganic Nitrogen and Temperature                        76

     Blue-green Coccoid Algae

          Water Temperature                                         78
          Soluble Phosphorus and Temperature                        80
          Inorganic Nitrogen and Temperature                        80

     Blue-green Filamentous Algae

          Water Temperature                                         82
          Soluble Phosphorus and Temperature                        82
          Inorganic Nitrogen and Temperature                        84

FUTURE INVESTIGATIONS                                               86

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                            LIST OF TABLES



Table No.                        Title                                Page

   I        Summary of Water Intake Physical  Data                      10

   2        Average Seasonal  Concentration of Soluble Phosphorus       15
           in Various Sectors  of the Western Basin of Lake Erie

   3        Average Seasonal  Concentrations of Part IcuI ate             22
           Phosphorus in Various Sectors of  the Western Basin
           of Lake Erie

   4        Average Seasonal  Concentrations of Soluble Phosphorus       27
           in Various Sectors  of the Central  Basin of Lake Erie

   5        Average Seasonal  Concentrations of Particulate             29
           Phosphorus in Various Sectors of  the Central  Basin
           of Lake Erie

   6        Average Seasonal  Concentrations of Organic Nitrogen  in      34
           Various Sectors  of  the Central  Basin of Lake Erie

   7        Average Seasonal  Concentrations of Organic Nitrogen  In      37
           Various Sectors  of  the Central  Basin of Lake Erie

   8        Average Seasonal  Concentrations of Nitrate Nitrogen  in      43
           Various Sectors  of  the Western  Basin of Lake Erie

   9        Average Seasonal  Concentrations of Nitrate Nitrogen  in      43
           Various Sectors  of  the Central  Basin of Lake Erie

  10        Concentrations of  Inorganic Nitrogen and  Phosphorus         68
           Required to  Produce Various Populations of Centric
           Diatoms during Warming Months

  II        Concentrations of  Inorganic Nitrogen and  Phosphorus         73
           Required to  Produce Various Populations of Pennate
           Diatoms during Warming Months

  12        Concentrations of Inorganic Nitrogen and  Phosphorus         75
           Required to  Produce Various Populations of Green
           Coccoid Algae during  Warming Months

  13        Concentrations of Inorganic Nitrogen  and  Soluble            82
           Phosphorus Required to Produce  Various  Populations
           of Blue-green Coccoid  Algae

  14        Concentrations of Inorganic Nitrogen  and  Soluble            86
           Phosphorus Required for Various Populations  of  Blue-
           green Filamentous Algae

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                            LIST OF FIGURES



Figure No.                       Title                               Page

    I        Lake Erie Surveillance Stations                           9

    2        Nearshore Soluble Phosphorus Distribution in Lake Erie   13

    3        Nearshore Seasonal  Distribution of Soluble Phosphorus    14

    4        Midlake Seasonal  Distribution of Soluble Phosphorus      17

    5        Nearshore Particulate Phosphorus Distribution in  Lake    20
            Erie

    6        Nearshore Seasonal  Distribution of Particulate           2!
            Phosphorus

    7        Midlake Seasonal  Distribution of Particulate             23
            Phosphorus

    8        Nearshore Organic Nitrogen  Distribution                   32

    9        Midlake and  Nearshore Seasonal  Distribution of Organic   33
            N i trogen

   10        Nearshore Ammonia Nitrogen  Distribution  in Lake Erie      38

   II        Nearshore and  Midlake Seasonal  Distribution of           39
            Ammonia Nitrogen

   12        Nearshore Nitrate Nitrogen  Distribution  in Lake Erie      41

   13        Nearshore Seasonal  Distribution of Nitrate Nitrogen      42

   14        Midlake Seasonal  Distribution of Nitrate Nitrogen        44

   15        Comparison of  Organic and Inorganic Nitrogen in          47
            Central  Basin  Nearshore for One-year Cycle

   16        Comparison of  Organic and Inorganic Nitrogen in          47
            Western  Basin  Nearshore for One-year Cycle

   17        Nearshore Temperature Distribution in  Lake Erie          48

   18        Water Temperature at  Put-in-Bay                          49

   19        Monthly  Averages  of Various Physical Factors             5|
            Affecting Lake Erie

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                            LIST  OF FIGURES



Figure No.                      Title                                Page

   20       Nearshore Centric Diatom Distribution  in  Lake  Erie         53

   21       Nearshore Pennate Diatom Distribution  in  Lake  Erie         54

   22       Nearshore Coccoid Green Algae  Distribution  in  Lake  Erie    55

   23       Nearshore Coccoid Blue-green Algae  Distribution  in  Lake    56
            Erie

   24       Nearshore Filamentous Blue-green  Algae  Distribution in     57
            Lake Erie

   25       Nearshore Dissolved Oxygen  Distribution  in  Lake  Erie       59

   26       Nearshore COD Distribution  in  Lake  Erie                    60

   27       Centric Diatoms  vs. Temperature  in  Lake Erie Central       65
            Basin Nearshore

   28       Centric Diatoms  vs. Temperature  in  Lake Erie Western       65
            Basin Nearshore

   29       Centric Diatoms  as Related  to  Water Temperature,           67
            Soluble Phosphorus and Inorganic  Nitrogen  in Lake Erie
            Nearshore Waters

   30       Estimated Requirements of Solar Radiation at Lake Erie     69
            Water Temperature for Centric  Diatoms

   31       Pennate Diatoms  as Related  to  Water Temperature,           71
            Soluble Phosphorus and Inorganic  Nitrogen  in Lake Erie
            Nearshore Waters

   32       Green Coccoid Algae vs.  Water  Temperature  in Nearshore     74
            Waters of Central  Basin

   33       Green Coccoid Algae vs.  Water  Temperature  in Nearshore     74
            Waters of Western Basin

   34       Green Coccoid Algae as Related to Water Temperature,       77
            Soluble Phosphorus, and Inorganic Nitrogen  in  Lake  Erie
            Nearshore Waters

   35       Blue-green Coccoid Algae vs. Water  Temperature In          79
            Nearshore Waters of Central Basin

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                            LIST OF FIGURES
Figure No.                       Title                               Page

   36       Blue-green Coccoid Algae vs.  Water Temperature in        79
            Nearshore Waters of Western Basin

   37       Blue-green Coccoid Algae as Related to Water             81
            Temperature,  Soluble Phosphorus and Inorganic
            Nitrogen in Lake Erie Nearshore Waters

   38       Blue-green Filamentous Algae vs.  Water Temperature       83
            in Nearshore  Waters of Central  Basin

   39       Blue-green Filamentous Algae vs.  Water Temperature       83
            in Nearshore  Waters of Western  Basin

   40       Blue-green Filamentous Algae as Related to Water         85
            Temperature,  Soluble Phosphorus and Inorganic
            Nitrogen in Lake Erie Nearshore Waters

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                          SUMMARY AND CONCLUSIONS



     Data gathered In the Lake Erie surveillance program by the Federal

Water Quality Administration Lake Erie Basin Office provide the basis

for discussion of the distribution of algal types and some of the physi-

cal and chemical factors which control algal populations in the western

and central basins of the lake.  Sufficient data are not available to

Include the eastern basin.

     For three seasons of the year, spring, summer, and fall, soluble

phosphorus is remarkably uniform at any one place in Lake Erie, although

there are occasional  substantial variations.  Concentrations generally

decrease from shore lakeward and from west to east in the lake.  It can

be stated for generalization that for those three seasons mldlake western

basin soluble phosphorus as P averages about 30 pg/l  compared to 50 pg/l

near shore.  The central basin nearshore averages 30 yg/l, about the

same as the western basin mid lake, while In the central basin mid lake

soluble phosphorus drops to about 15 ug/l.

     In winter, a season when adequate data have not previously been

available, soluble phosphorus more than doubles in all nearshore areas

and in the western basin mid lake.  Limited non-nearshore data show very

little winter rise in soluble phosphorus at the outlet end of the western

basin and In the western portion of central basin mid lake.  This indicates

considerable winter tributary* input, nearshore sediment resuspension,

limited dispersion, and low utilization by algae In winter.

     Partlculate phosphorus exhibits an erratic distribution throughout

the year and at any one time In the nearshore area, although It generally


* In this text the word tributary refers to totalInputs, municipal,
  Industrial,  and agricultural.

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 Is  less than soluble phosphorus.  The erratic nearshore distribution,



 not so evident In mldlake waters, most likely Is controlled by variability



 In productivity and by variability In runoff and wind-Induced sediment re-



 suspension.  Particulate phosphorus shows no definable seasonal pattern



 except for a slight rise In winter.



     Organic nitrogen, which should reflect fluctuations In biological



 productivity is remarkably uniform on the average throughout the lake



 during all seasons at 300-400 ug/l.  An exception is a slightly higher con-



 centration in nearshore waters of the western basin in spring.  Organic



 nitrogen does not correlate with algal numbers although it may with total



 biomass, a parameter not being determined in the present program.



     Ammonia nitrogen shows no clear seasonal pattern and concentrations



 in midlake are not far from those in the nearshore area, generally at



 200 pg/l or less.  Since nearshore short-term nutrient dispersion Ts



 minimal, it is indicated that the sediments are an important source of



midlake ammonia,  although It is not Implied that sediment Inputs neces-



 sarily cause the  approach to uniformity.



     Nitrate nitrogen, however, does show a clear seasonally changing



 annual pattern in both nearshore and midlake waters.  Nearshore area



 nitrate nitrogen  Is generally  more than twice that of midlake.  During



 winter and spring there is a significant decrease from west to east



 throughout the lake.



     Nitrate nitrogen climbs to levels greater than 1,500 ug/l in winter



 in the nearshore  waters of the western basin, most likely due to higher



 tributary inputs, the introduction of interstitial ammonia during sed-



 iment resuspension with subsequent conversion to nitrate, and  low

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nutrient utilization by limited algal  populations.   The winter rise is




progressively less eastward until  at Conneaut, Ohio, It is insignificant.



     A conspicuous drop In nitrate nitrogen occurs  in spring,  correla-



tive with high algal populations.   However, In the  east half of the



central basin, nitrate nitrogen Increases in spring.  Summer and fall



are characterized by low concentrations of nitrate  nitrogen (200 yg/l  or



less) after strong algal uptake in both nearshore and mid lake waters.



     Organic nitrogen exceeds inorganic between July and November In




Lake Erie.  The excess of organic nitrogen indicates that inorganic



nitrogen is being biologically converted faster than It is being supplied.



The sustenance of such a condition would eventually result In the com-



plete depletion of ambient Inorganic nitrogen and thus create the poten-



tial for nitrogen limitation of certain algal genera.  Blue-green algae,



certain species being nitrogen fixers, are dominant during this period.



     Nearshore data correlations with respect to nutrients and algae



have been made at various temperatures.  During the year of concern



(1968-69) an Investigation of physical factors revealed that water tem-



perature, air temperature, solar radiation, and percent of possible sun-



shine were above average in early spring, below average in late spring



and early summer, and at or above average for the remainder of the year.



Precipitation was below average the first half of the year and above



average the last half.  The winds throughout were lighter than normal  ana



lake levels were above normal.  All nutrient-algal  relationships most



likely are affected by the variations in the physical factors described



above, however, except for water temperature these  effects are not de-



fined In this report.

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     Various types of algae show preference for particular temperature



ranges, and within those ranges there are optimum growth  temperatures.



There are no important Lake Erie algal  types which prefer freezing tem-



peratures.  Diatoms prefer temperatures between 2°C (36°F) and IO°C



(50°F), green algae between IO°C and 20°C (68°F) and blue-green algae



prefer temperatures in excess of 20°C.   The following observations are



based on ambient water nutrient concentrations and phytoplankton popu-



lations at the time of sample collection.  The measurement of algal



metabolic rates was never attempted, consequently any and all correlations



are indirect, and can only be considered indications.  In general and in



opposition to what one might normally expect, it is indicated that for



any algal species nutrient requirements increase as temperatures depart



from the optimum. In addition Increases in temperature do not necessarily



result in increases in populations of algae.  In fact, except for the



occasional and sometimes massive blue-green bloom, which   Is not fully



documented by the present biweekly sampling program but based on many



Individual observations, lower populations are characteristic of the



warmest season of the year.  However, total algal biomass during both



spring and summer may be equivalent as suggested by the comparable organic



nitrogen concentrations during both seasons.



     Diatoms, the first algae to appear In great numbers  In  late winter



or early spring, appear to require relatively low concentrations of nitro-



gen and phosphorus at their optimum temperature although these nutrients



generally are at or near their highest concentrations.  As temperatures



increase the nitrogen and phosphorus requirement appears  to  Increase while



the actual nutrient concentration  is diminishing.  Thus  it appears that

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 control  of the nutrient supply Is most critical  at optimum temperatures.



      To reduce the population  of  green algae at  their preferred temper-



 ature range it appears  that any reduction  of nutrients would be somewhat



 effective.   If the objective were to keep  populations below  200 organ-



 isms/ml,  about 25  percent reduction  of inorganic nitrogen or 80 percent



 reduction  of  soluble phosphorus,  at the time of green algal  dominance,



 would be  required.   Unlike diatoms,  it appears that the duration  of  green



 algae dominance would not change  but that  the amplitude (maximum popu-



 lation) of  the pulse would be  decreased.



      At   temperatures above 20°C  (68°F) blue-green populations  most  likely



 would-not be reduced by  the control  of inorganic nitrogen,  since blooms



 occur at  present after  this nutrient has all  but disappeared  from the



 lake  in summer.    It appears however that  maximum  populations,  but not



 the   period of dominance,  can  be  limited by  soluble phosphorus  control.



 If concentrations  of soluble phosphorus as P can be maintained  below  40



 ug/l  it appears that blue-green populations  can  be controlled to less



 than  500  organisms/ml.   This would be  essentially a 25  percent  reduction



 in soluble  phosphorus.   However the  control  of blue-green algae  Is com-



 plicated  by the  fact that  these organisms,   possibly  more than any other



 algae, apparently  are  largely stimulated by  nutrients  regenerated from



 bottom sediments.  Since the regeneration process  is  not presently con-



 trollable, compensation  for  this nutrient source  must be accomplished



 by further tributary input  reduction.  The necessary additional   reduction



 is not known,  but a total of 80 to 90 percent does  not seem unreasonable to



effectively reduce blue-green populations.



     Based on   limited environmental relationships, of the two nutrients

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which are or may be controllable, phosphorus appears to be the one of-



fering the most feasibility and practicality.   Furthermore blue-green



algae cannot be controlled by nitrogen tributary Input  limitation.



Diatoms also cannot be controlled effectively with less than extreme



nitrogen limitation.  The probable effective nitrogen control of green



algae may extend blue-green dominance for even longer periods due to



minimized ecological competition and since as mentioned above, blue-



greens cannot be controlled by waterborne nitrogen limitation.  The blue-



green algal ability to fix atmospheric nitrogen precludes dependence on



waterborne nitrogen.  Finally, if as indicated by this study a 90 per-



cent input phosphorus reduction can be made to limit diatoms, apparently



there is little doubt that with that same control, all  algae can be  lim-



ited greatly in their abundance.  An 80 percent reduction of soluble



phosphorus will limit the duration but not the maximum population of the



diatom pulse.  This reduction will also reduce the magnitude but not the



duration of the green pulse, and may reduce the magnitude of the blue-



green pulse but unfortunately not the duration.



     The limited correlation analysis made for this report  is only a



beginning but  it has shown that an adequate algal response  prediction



system can be made  for Lake Erie with perhaps considerably  less effort



than apparently first thought possible.  The model most  likely will  not



have optimum practicality since the effected correlations do not consider



exact algal nutrient use as measured by metabolic uptake, nor do they



consider nutrient storage  in cell bodies, a most  likely cause for any de-



 layed ambient  alga I-nutrient response.  As previously mentioned correla-



tions were made using ambient water nutrient concentrations and prevalent

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algal populations.  However a comparison of organic and inorganic nutri-



ent forms does not reveal significant luxuriant consumption allowing for



some degree of confidence in the nutrient concentration versus biological



populations approach.  Thus, it is indicated that a working model formu-



lated with the technique described in this report can be made somewhat



less than optimumly effective with but slight "over-engineering" to com-



pensate for any undefined biological  vagaries.
                                     7

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                  DISTRIBUTION OF CHEMICAL,  PHYSICAL,  AND




                      BIOLOGICAL FACTORS IN  LAKE ERIE








                               INTRODUCTION




     The following report describes the time and space distribution of




measured chemical, physical, and biological  factors for a one-year




cycle in the western and central basins of Lake Erie.   The nearshore




descriptions are based upon data gathered in a biweekly sampling program




at 17 Ohio domestic water supply intakes from March 1968 through March



1969.  It should be emphasized that the Cleveland area sampling locations




are relatively a great distance from shore,  up to 20,000 ft., and for




this reason the water quality in this area is of higher quality espec-




ially when compared to other Ohio nearshore  areas where samples were re-




trieved as little as I3l00 ft. from shore.  The midlake descriptions are




based upon data gathered at 20 midlake stations sampled four times be-




tween May  1967 and January  1968.  Sampling  locations,  depths and distance




from shore are shown on Fig.  I and Table  I.   Although  the sampling times




for nearshore and midlake were one year apart, for the purposes of this




report the data are assumed to be comparable.



     The data are certainly not so abundant nor so precise that the con-




clusions are  indisputable.  Conclusions drawn from data gathered over a




one-year period are subject to argument on  several grounds,  not the  least




of which are  sampling frequency, measurement technique,  living systems




idiosyncrasies and even the unique whims of nature during any one  year.




Even further  danger exists  in comparing midlake data  for one year  with




nearshore  data for the following year, not  only for the above reasons

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FIGURE  I

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but because the overall quality of lake waters may change noticeably



from one year to the next.  For the purposes of this report however it



will be assumed that no significant changes occurred between 1967 and



1968.



     In addition to describing a one-year distribution of various fac-



tors an attempt has been made herein to describe the interrelationships



of these factors.  Although much has been written on the general  bio-



chemical relationships in a lake system, the applicability of these



relationships to the general pollution control effort in Lake Erie has



nearly always been questionable.  The correlation of any two analytical



measurements, such as algal population and phosphorus content,  more



often than not leads to erroneous or conflicting conclusions, thus week-



ening the defensibiIity or justification for pollution control  expendi-



tures.  This report attempts to point out the fallibility of some two



parameter correlations.  Also it demonstrates with a few examples of



multiple-parameter correlations that it is possible to predict an ade-



quate biological response to a given set of physical and chemical factors.



     It is difficult to clearly describe the details of parameter dis-



tributions in the  lake and their changes with time.  For this reason



some rather novel graphic approaches have been devised to simplify ex-



planations.  Most of the illustrations attempt to show three related



factors simultaneously.  Scales have been arbitrarily chosen, with graph-



ics showing distance, not necessarily to scale.






                   PHOSPHORUS DISTRIBUTION IN LAKE ERIE



     The most important nutrient by reason of rapidly increasing ac-



cumulation in Lake Erief is phosphorus.  An abundance of phosphorus is
                                     11

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generally considered as the cause for the remarkably high biological



productivity in Lake Erie.  The acceptance of this as fact does not lead



to the unequivocal conclusion that cessation of phosphorus inputs will



produce a predictable result.  Not only are the mechanics of phosphorus



utilization by biological systems still unclear, but the temporal and



spatial distribution have been largely undetermined.  Without a basic



knowledge of phosphorus distribution in Lake Erie the mechanics of its



quantitative utilization offer little hope of being fully understood,



much less predictable.



     Phosphorus is described herein as soluble phosphorus and particu-



late phosphorus.  Particulate phosphorus is simply the difference be-



tween the soluble phosphorus and total phosphorus forms.  It is that



portion of total phosphorus retained on fluted Whatman filter paper No.



12 while soluble phosphorus is that portion which peisses.  Particulate



phosphorus is assumed to be either chemically or biologically bound to



inorganic or organic particulate matter.






WESTERN BASIN



                          Soluble Phosphorus



     The time - space distribution of soluble phosphorus as P  In near-



shore waters for one year is shown in Fig. 2.  The distance axis from



Toledo to Conneaut  is not to scale.



     Examination of soluble phosphorus data from Toledo and Port Clinton



water  intakes has revealed a remarkable consisfency at near 50 ug/l for



much of the year  (Fig. 3 and Table 2).  Winter however departs dramati-



cally from the previous three seasons, apparently affected by higher



tributary inputs3 the introduction of interstitial soluble phosphorus
                                  12

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FIGURE 2

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                              TABLE 2

          AVERAGE SEASONAL CONCENTRATIONS OF SOLUBLE PHOSPHORUS (As P)
       IN VARIOUS SECTORS OF THE WESTERN BASIN OF LAKE ERIE (yg/l)
Season
Maumee
  Bay
Southern
Nearshore
Mid-basin
Northeast
 sector
(outlet)
Winter

Spring

Summer

Fall
  110

   25

   95

   90
   150

    50

    50

    50
   55

   25

   40

   30
   20

   20

   20

   20
                                     15

-------
during wind-induced sediment resuspension and low utilization by limited



algal populations.   Concentrations above 150 pg/l are probably common in



January and February.  The abrupt rise in concentration at the beginning



of the winter season is followed by an equally abrupt decline at the end



of the winter season.



     Soluble phosphorus data gathered on each of four quarterly cruises



during the year preceding that of the intake data are characterized by



a rather wide variability between stations and between cruises except in



the northeast quarter of the basin (Fig. 4 and Table 2).   In this area a



soluble phosphorus concentration of about 20 ug/l appears to prevail



throughout the year.   In contrast the Maumee Bay area seems to average



near  100 yg/l in summer, fall and winter, but drops to 25 pg/l in spring



In spring soluble phosphorus may be lower and fairly evenly distributed



throughout the basin.  Summer and fall are characterized by a predict-



able  decline across the basin from southwest to northeast.   In winter



the cross-basin decline also occurs but shows more erratic and higher



values in the central  portion of the basin.  This characteristic is also



apparent to a less extent in summer.



      The somewhat erratic behavior of midlake soluble phosphorus concen-



trations in the western basin is undoubtedly influenced by the mid-channel



flow  of the Detroit River.  That flow, containing relatively  low amounts



of phosphorus, can be  expected to meander over a period of time under the



influence of wind and  water density differences.  Of course the mid-channel



flow  is bounded on either side by water of higher phosphorus content.



      From the above description emerge some characteristics of seasonal



patterns of phosphorus distribution  in the western basin, along with some
                                   16

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                                           17

-------
inferences as to the causes for the observed variability.



     In winter,  soluble phosphorus concentrations along shore rise rapid-



ly.   The rise is not impeded at this time of year by significant biolog-



ical uptake of phosphorus because of low temperature.  Low temperatures



also slow the processes of chemical reaction.  These conditions allow an



accretion in phosphorus load, due mainly to increased tributary inputs



and to the early winter introduction of interstitial soluble phosphorus



during wind-induced sediment resuspension.  The soluble phosphorus ac-



cretion is enhanced in late winter under the disruption reducing con-



ditions of ice cover and the rather stable temperature-density barriers



to mixing.  The phosphorus accretion diminishes toward the center of the



basin and does not reach to the northeast part of the basin.  The central



and northeastern portions of the basin are occupied  largely by low phos-



phorus water from the high-volume main flow of the Detroit River.  This



mass^of water also helps to confine the high phosphorus water to the



western and southern parts of the basin.



     In early spring, concurrent with the breakup and disappearance of



ice cover3 the high soluble phosphorus content is rapidly reduced and



approaches uniformity throughout the basin.  The reduction is accom-



panied by a tremendous increase in diatom population.   In general the



areas which had the greatest soluble phosphorus accretion develop the



highest diatom populations.  The populations decrease northeastward



across the basin, so that where soluble phosphorus had not increased



significantly neither had diatoms  increased greatly.



     The preceding description suggests at  least a general relationship



between diatom populations and soluble phosphorus in western basin water.
                                 18

-------
However a detailed examination reveals that the expected immediate in-



verse correlation is in fact delayed.  The rapid spring reduction of



soluble phosphorus occurs,  not simultaneously with a great rise in plank-



ton, but prior to it.  The highest plankton populations occur just after



the soluble phosphorus content has been reduced to the average level  of



spring and summer.  This suggests that one or both of two things have



occurred:  (I) luxury consumption of phosphorus by diatoms in their



early bloom stages or (2) the sedimentation of soluble phosphorus at the



time of  ice breakup.  Examination of particulate phosphorus should reveal



which of these is more likely.



                            Particulate Phosphorus



     The particulate phosphorus as P time-space distribution in nearshore



waters of the western and central basins of Lake Erie is shown in Fig. 5.



Western Basin particulate phosphorus is more erratic and variable over



the short-term than soluble phosphorus although the annual particulate



phosphorus range and average concentration are less.



      In spring nearshore particulate phosphorus (Fig. 6 and Table 3)



averages about 30 yg/l, and is considerably less than soluble phosphorus.



The concentration drops steadily across the lake to about 10 yg/l in the



northeast quarter of the basin (Fig. 7).  Particulate phosphorus rises



in summer in the nearshore area to greater than 50 ug/l.  Toward midlake



it falls-off rapidly to values of 10 to 15 pg/l and these values are



characteristic of most of the basin.  The fall distribution of particulate



phosphorus is similar to that of summer with only a slight decline in



nearshore waters.  In winter however midlake values rise to more than 30



pg/l while nearshore concentrations remain essentially unchanged at an



average of 50 yg/l.   As with soluble phosphorus, particulate phosphorus





                                       19

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20
FIGURE  5

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                              TABLE 3

         AVERAGE SEASONAL CONCENTRATIONS OF PARTICIPATE PHOSPHORUS (As P)
        IN VARIOUS SECTORS OF THE WESTERN BASIN OF LAXE ERIE (pg/l)
Season         Maumee        Southern         Mid-basin        Northeast
                 Bay         Nearshore                          sector
                                                               (outlet)
Winter            45            50               30               20

Spring            55            30               25               10

Summer            40            55               \5               20

Fa I I               70            50               15               20
                                 22

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23
FIGURE   7

-------
in the northeast quarter of the basin does not change substantially



throughout the year.



     Integrating the distribution of soluble and particulate phosphorus



leads to several possible conclusions.  During the winter soluble phos-



phorus increases dramatically while particulate phosphorus does not.



This indicates that particulate phosphorus from tributary inputs and



sediment resuspension settles quickly while soluble phosphorus from the



same two sources remains in solution and rapidly accretes.  Lack of



plankton uptake and limited chemical activity involving phosphorus most



likely allows the accretion.



     At the end of winter more than half of the dissolved phosphorus and



at least one-third of the particulate phosphorus disappear from the



waters of the western basin.  Flushing from the basin can be discounted



because of the seasonal uniformity of the basin phosphorus discharge and



because inputs of phosphorus via runoff have probably increased.   It is



indicated that  in great part phosphorus is precipitated to the western



basin bottom sediments through a biological intermediary.  However since



the  loss appears to occur slightly before the height of the spring diatom



pulse, the possibility exists, that simultaneous with the luxurious con-



sumption of nutrients by algae, phosphorus removal from water to the sed-



iments may be additionally  accomplished by physical adsorption on  clay



and  silt particles  in suspension.  The  lake turbidity at this time of year



is especially high  due to a combination of much runoff and wave stirring



of bottom sediments.  Apparently physical adsorption and biological util-



ization account for an efficient, natural, phosphorus removal process.



In fact the removal mechanism  is so efficient that in spring the total

-------
phosphorus content of western basin waters reaches Its lowest level.




     Again it should be emphasized that phosphorus is not lost from the



basin in unusual quantities as indicated by its stability of concentra-



tion at the main outflow in the northeast corner of the basin.  Rather



it is stored in the sediments through the mechanisms described above.



     A moderate accretion in waterborne total phosphorus, both soluble



and particulate, occurs in summer, while a slight reduction occurs in



the fall.  The summer increase is correlative with a reduction in plankton



populations, while the fall decrease most likely is the result of an in-



crease in plankton.  It would appear that a fair balance is maintained



in summer and fall, and also late spring, between inputs to the basin



and precipitation to the lake bottom.



     Although not completely documented in the intake data, but based



on many individual observations, in late summer blue-green algae pop-



ulations increase dramatically throughout the basin and even in places



such as the northern island area, far removed from tributary Inputs.



This suggests recycling of nutrients, including phosphorus, from the



bottom sediments.  The suggestion is supported by a temporary increase



in midlake phosphorus without a concomitant increase near shore.  How-



ever, the increase is short-lived and.phosphorus returns to moderate



levels, remaining there throughout the fall  and until the beginning of



the winter phosphorus accretion in December.





CENTRAL BASIN




     The central basin phosphorus distribution, both soluble and par-



ticulate, Is more easily described because concentrations are generally



less, short-term and long-term variations are more subdued, and area I

-------
differences are diminished.   The tendency toward  uniformity can  be  as-



cribed to the damping effects of a larger less easily disturbed  basin



and the smaller input to the basin.   The general  annual  distribution of



soluble phosphorus in the central basin is shown  in Fig.  2.



                             Soluble Phosphorus



     Central basin nearshore average soluble phosphorus  is remarkably



stable for seven months of the year, including the spring and summer



seasons and part of the fall (Fig. 3 and Table 4).  The  average  concen-



tration during this period is about 30 yg/l - only 60 percent of the



nearshore concentration in the western basin.  During this period near-



shore soluble phosphorus is similar from one end  of the  basin to the



other.



      In midlake central basin, from spring through fall, soluble phos-



phorus averages 10 to  15 yg/l or  less than one-half that of nearshore



(Fig. 3 and Table 4).  There is  little change areally except in spring



when concentrations are lowest in the western part of the basin.



      In October, centra! basin nearshore soluble phosphorus begins to



rise and by January  I  is averaging 40 yg/l.  A relatively rapid rise



then occurs, reaching more than  100 yg/l at the beginning of March.  This



peak  is followed by a  rapid decline to 30 yg/l again at the advent of



spring.  The winter increase in soluble phosphorus is less than half the



concurrent increase in western basin nearshore waters.  The high winter



period  in the central  basin nearshore  is also characterized by a general



west to east decrease which is not apparent throughout the remainder of



the year.



     Winter phosphorus data from  midlake central   basin is  scarce but it
                                 26

-------
                               TABLE 4

          AVERAGE SEASONAL CONCENTRATIONS OF SOLUBLE PHOSPHORUS (As  P)
       IN VARIOUS SECTORS OF THE CENTRAL BASIN OF LAKE ERIE (yg/l)
Season          Southwest        Southeast        Western       Eastern
                Nearshore        Nearshore        Mfdlake       Mid lake
Winter             80               55              25

Spring             30               25              10             15

Summer             35               25              15             10

Fall               30               30              20             15
                                      27

-------
appears that an increase in soluble phosphorus occurs, although relatively



insignificant (Fig. 4 and Table 4).  The average concentration in midlake



may never exceed 25 vg/l3 that value being approached only in winter.



                              Particulate Phosphorus



     In central basin nearshore, as in the western basin, particulate phos-



phorus is much more erratic in its time and space distribution (Figs.  5 and



6).  The average concentration, except in midsummer, is comparable in both



western and central basin nearshore areas.



     In the central basin nearshore, particulate phosphorus averages about



20 yg/l in spring and summer, considerably less than in the fall  and winter



when an average of about 40 yg/l prevails (Fig. 6 and Tesble 5).  Fall  and



winter levels however are much more variable.  They range from 30 to 80 yg/l



in fall and from 20 to 65 ug/l in winter.  In winter there is a west to east



decrease in particulate phosphorus, not apparent during the other seasons.



     In central basin midlake particulate phosphorus apparently averages



less than  10 pg/l the year-round with perhaps slightly higher values in



spring than during the other seasons (Fig. 7 and Table 5).  Compared to



nearshore, the midlake has a remarkably narrow range in particulate phos-



phorus content.  Central basin midlake also differs radically  in this



respect from the widely variable western basin midlake.



     The areal and time distribution of soluble and particulate phosphorus



in the central basin roughly parallels the distribution in the western



basin but with considerably lower values.  This indicates that the same



factors of biological uptake, wind-induced sediment resuspension, and  inputs



are operating  in a manner similar to that In the western basin, but on a



reduced scale.  One  important difference  is the lack of variation in
                                    28

-------
                               TABLE 5

       AVERAGE SEASONAL CONCENTRATIONS OF PARTICIPATE PHOSPHORUS (As P)
      IN VARIOUS SECTORS OF THE CENTRAL BASIN OF LAKE ERIE (yg/l)
Season         Southwest        Southeast        Western       Eastern
               Nearshore        Nearshore        Mfdlake       Mldlake
Winter            50               35              10

Spring            15               20              10             5

Summer            20               20               5            <5

Fall               50               50               5             5
                                      29

-------
phosphorus in summer, In the central  basin,  indicating perhaps a general



damping effect on all phosphorus input factors.



     The winter soluble phosphorus accretion In  both the central basin



nearshore and mldlake is depleted very rapidly near the beginning of spring,



As in the western basin more than half is lost to the bottom sediments.



The western part of the central basin seems  to "over-react" in spring



(Fig. 4) when compared to ,,ie other portions of  the basin, and concentra-



tions reach their annual low.  As in the western basin the loss of soluble



phosphorus in the western portion of the central basin, accompanied also



by a loss of more than half the particulate  phosphorus, indicates rapid



biological utilization or adsorption on eroded or resuspended clays, or



both, followed by rapid precipitation to the sediments.






                        NITROGEN DISTRIBUTION IN LAKE ERIE



     Nitrogen in Lake Erie has been measured in three forms, organic



nitrogen, ammonia, and nitrate.  Nitrite is  normally present  in  insig-



nificant quantities, and therefore has not been measured as such, but is



included as part of the total nitrate analysis.



     Organic nitrogen is that portion of the total nitrogen .combined  in



organic compounds.  Organic nitrogen should  be more or  less proportional



to the total biological mass.  Data from Lake Erie  indicate that time and



spatial variations are not as great as one might expect.



     Although organic nitrogen should reflect biological productivity in



Lake Erie, it is the inorganic nitrogen forms which are essential to



promote that productivity.  The  inorganic forms, particularly nitrate



nitrogen, follow a more predictable pattern of concentration  throughout



the year  and are more easily relatable to plankton abundance  than is
                                    30

-------
organic nitrogen.  However the classical  materials balance,  relating one



form to the other, is not read!ly apparent.



     Nitrogen is vital  to algal  productivity,  its deficiency in a marine



environment often being a limiting factor to algal biomass.   Although



both ammonia and nitrate are utilized as  nutrients the content of nitrate



normally shows greater depletion characteristics.  It is not clear however



that nitrate is the preferred nutrient since during high algal use periods,



ammonia is continually being replenished  from the sediments  while nitrate



is not.  In addition, the conversion of ammonia to nitrate most likely is



hampered by the  lower oxidation-reduction potentials prevalent during the



summer high nutrient use periods.






WESTERN AND CENTRAL BASINS



                               Organic Nitrogen



     The time-space distribution of organic nitrogen for one year in the



nearshore waters of the western and central  basins of Lake Erie is shown



in Fig. 8.



     In the western basin nearshore area, organic nitrogen in winter, sprlm



and summer averages approximately 700 yg/l but drops to about 400 yg/l in



the fall (Fig. 9 and Table 6).  In western basin midlake organic nitrogen



in spring and summer averages about one-half those of the nearshore area



or about 350 yg/l.  Fall and winter concentrations in western basin midlake



average about 300 yg/l.  In the fall organic nitrogen approaches uniformity



throughout the basin at relatively low concentrations.  Occasional rather



precipitous rises in organic nitrogen in  the nearshore throughout the year



are probably due mainly to stirring and resuspension of bottom sediments



during periods of higher wind velocity and precipitation.

-------

FIGURE 8

-------
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              FIGURE  9

-------
                     TABLE 6

    AVERAGE  SEASONAL  CONCENTRATIONS  OF ORGANIC NITROGEN
IN VARIOUS SECTORS  OF THE WESTERN  BASIN OF  LAKE ERIE  (ug/l)
Season
Winter
Spring
Summer
Fall
Maumee
Bay
500
550
500
500
Southern
Nearshore
750
700
650
400
Mid-basin
300
350
400
250
Northeast
sector
(outlet)
250
400
250
250

-------
     Limited available data indicate that the concentration of  organic



nitrogen in the northeast part of the basin,  in  the Pelee Passage outlet,



is relatively low and uniform at near 250 to  400 yg/l  (Fig. 9 and Table



6).  This suggests since inorganic nitrogen is also lower in these areas,



that nitrogen is accumulating significantly in western basin sediments.



     When examined as averages of all stations during  each sampling per-



iod, central basin nearshore organic nitrogen has a rather stable annual



pattern, averaging 500 Vg/l in spring, and decreasing  steadily  throughout



the summer to less than 200 yg/l in November  (Fig. 9 and Table  6).  It



then begins to rise and continues to rise gradually until the beginning



of spring.



     The pattern of organic nitrogen in nearshore waters is more complex



when examined as variations between sampling  sites during a season and



from one season to the next.  For example in  spring nearshore organic



nitrogen west ot Lorain averages about 700 ug/l  or approximately the same



as western basin nearshore.  At Lorain and eastward however, organic



nitrogen averages less than 500 yg/l and at Conneaut about 400  yg/l.  In



summer nearshore organic nitrogen drops even  more quickly from  600 yg/l at



Sandusky, again near the level in western basin nearshore, to about 350



yg/l at Vermilion.  This concentration prevails relatively well throughout



the Cleveland area in summer but rises dramatically east of Cleveland to



700 yg/l at Madison.  It then decreases again eastward.



     In fall organic nitrogen Is more consistent throughout central basin



nearshore at between 300 and 400 yg/l.  The extremes are in the Cleveland



area with a high averaging 600 yg/l at the westernmost Crown intake and a



low of 200 yg/l  at the Baldwin intake.
                                      35

-------
     In central  basin midlake organic nitrogen appears  to average about



300 vig/l throughout the year (Fig.  9 and  Table 7).   This  is  not greatly



less than nearshore except in spring.  At this time the lowest concentra-



tions are found  in the western half of the basin at less  than 200 yg/l.



However they rise to the east to more than 400 yg/l and may  reach 700



yg/l near the east end of the basin.  The west to east  pattern in spring



in midlake is the reverse of that in nearshore.  Organic  nitrogen in mid-



lake, as in the  nearshore, is on an average lowest in fall and the most



consistent areally, averaging 250 to 300  yg/l  (Table 7).



                                Ammonia Nitrogen



     The distribution of ammonia nitrogen, with distance  and time, in



nearshore waters of the western and central basins for  one year is shown



in Fig. 10.



     Spring ammonia nitrogen in western basin  nearshore averages about



200 ug/l and does not show great variability during the season (Fig. II).



In early summer it begins to decline and continues to do so, except for



a brief rise in October, until the middle of November when it reaches its



lowest  level of less than 100 yg/l.  However ammonia nitrogen then rises



dramatically to more than 400 yg/l   in early December, remaining at this



level through January, then declining to spring  levels.



     In western basin midlake ammonia nitrogen  is highest in summer, aver-



aging more than 200 yg/l  (Fig.  II).   It drops to about 100 yg/l in fall,



and rises to about  150 yg/l in winter.   It then drops again  to about 100



yg/l in spring.



     Central basin nearshore ammonia nitrogen  Is fairly consistent through-



out the year, varying around the average of about  150 yg/l.    It reaches a
                                   36

-------
                                 TABLE 7

           AVERAGE SEASONAL CONCENTRATIONS OF ORGANIC NITROGEN IN
          VARIOUS SECTORS OF THE CENTRAL BASIN OF LAKE ERIE (yg/l)
Season          Southwest         Southeast         Western         Eastern
                Nearshore         Nearshore         Mid lake         Mid lake
Winter             400               300              300

Spring             600               450              250             300

Summer             450               500              300             350

Fall               350               350              250             250
                                     37

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-------
temporary high In early July of  more than 300 yg/l  but then  decreases  to



its annual  low of less than 100  yg/l at the end  of  the summer.



     In central  basin mid lake ammonia nitrogen is again remarkably con-



sistent throughout the year averaging between 100 and 150 yg/l  (Fig.  II),



not much less than in nearshore.  Its lowest level  of less than 100 yg/l



apparently occurs in winter.



     Summarizing, it appears that ammonia nitrogen  does not  show a very



wide variation either areally or temporally throughout the year.



                            Nitrate Nitrogen



     The time-space distribution of nitrate nitrogen i'n nearshore waters



of Lake Erie for one year is shown in Fig. 12.



     The annual  pattern for western basin nearshore nitrate  nitrogen



parallels neither that for ammonia nor organic nitrogen (Fig. 13 and



Table 8).  It averages about 1200 yg/l In early spring but drops dramat-



ically at the end of April to about 400 yg/l.  Nitrate nitrogen rises



again to about 800 yg/l in early July, then drops sharply to less than



100 yg/l.  It virtually disappears  In early fall and begins  to rise again



in November.  The rise In  late fall and early winter is remarkable, ex-



ceeding 2500 yg/l by the middle of January.   In early February nitrate



nitrogen begins a similar remarkable decline to spring levels.



     In western basin midlake, spring nitrate nitrogen averages about



300 yg/l but shows a marked west to east decline, from more than 500 to



about 200 yg/l (Fig.  14 and Table 8).  The  lowest midlake level of about



50 yg/l occurs In summer and then rises to about 150 yg/l in fall.  As  in



nearshore a  remarkable nitrate nitrogen rise occurs  In winter to an average



of about 600 yg/l, but again with a marked west to east decline, the

-------
FIGURE  12

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                        TABLE 8

    AVERAGE  SEASONAL CONCENTRATIONS  OF  NITRATE  NITROGEN
IN  VARIOUS SECTORS  OF THE  WESTERN  BASIN OF  LAKE ERIE  (ug/l)
Season
Winter
Spring
Summer
Fall

1C
Season
Winter
Spring
Summer
Fall
Maumee
Bay
1,500
800
<50
100

AVERAGE SEASONAL
J VARIOUS SECTORS OF
Southwest
Nearshore
600
600
100
100
Southern
Nearshore
1,700
800
250
200
TABLE 9
CONCENTRATIONS OF N
THE CENTRAL BASIN
Southeast
Nearshore
250
400
150
175
Mid-basin
600
300
75
175
*
Northeast
sector
(outlet)
350
200
<50
175

ITRATE NITROGEN
OF LAKE ERIE (yg/l)
Western
Midlake
250
200
<50
<50
Eastern
Midlake
-
<50
<50
<50

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concentration at the northeast corner of the basin being about 300 yg/l.



     Central basin nearshore nitrate nitrogen follows a reasonably smooth



annual curve, highest  in  late winter, (600 yg/l or more) and  lowest In  late



summer (0-50 yg/l).  A short, relatively sharp nitrate nitrogen decline



occurs at the end of April followed by a slight rise, perhaps correspond-



ing to the similar but generally more obvious trend  in western basin near-



shore.



     At all times nitrate nitrogen shows significantly different areal



patterns in central basin nearshore (Fig. 13 and Table 9).  For example



in winter, nitrate nitrogen declines from more than 800 yg/l at Sandusky



to less than 200 yg/l at Conneaut.  In spring it is relatively constant



from Sandusky to Cleveland where it declines.  Then it rises to its highest



level (600 yg/l) eastward at Mentor, and declines again eastward.  In sum-



mer and fall nitrate nitrogen is relatively stable throughout the entire



distance at less than 200 yg/l.



     A similar west to east nitrate nitrogen distribution but at lower



levels, exists in central basin midlake (Fig. 14 and Table 9).  In winter



nitrate nitrogen decreases from about 350 yg/l at the west end of the basin



to about 50 yg/l at the center of the basin.  In spring nitrate nitrogen



reaches its highest level (400 yg/l) at'the center of the basin, declining



eastward to less than 50 yg/l.  In summer and fall  midlake nitrate nitrogen



is uniformly low throughout - less than 50 yg/l.



                         Organic-Inorganic Nitrogen Ratios



     To determine whether nitrogen is a limiting factor In the biological



productivity of any lake, in addition to actual  concentrations, It is nec-



essary to consider the proportion of inorganic to organic nitrogen existing

-------
at any one time.  As long as Inorganic nitrogen exceeds organic nitrogen




(assuming organic nitrogen is directly related to biomass) this nutrient




cannot limit biological growth.  However when organic nitrogen exceeds




inorganic, it is possible for nitrogen to be a limiting factor, simply




because more inorganic nitrogen is necessary for comparably continuing




growth rates than is available.  Obviously such a condition cannot per-




sist for any significant length of time.




     The average concentration of inorganic and organic nitrogen for all




samples in central basin nearshore for each sampling period is plotted




on Fig. 15.  Fig. 16 shows similar data for the western basin.  In the




western basin organic nitrogen exceeds inorganic from the middle of July




through the middle of November.   In the central basin organic nitrogen




clearly exceeds  inorganic from the middle of July through October.  Dur-




ing these times  nitrogen is potentially limiting to further algal growth




except possibly  for the blue-green nitrogen-fixers.




     Averaging all nearshore data for the entire year, the organic and




inorganic portions of the total nitrogen balance fairly well - 52% organic




vs. 4Q% inorganic.






                               WATER TEMPERATURE




     Figure  17 shows the temperature distribution  in nearshore waters for




spring  1968  through winter  1968-69.  This pattern  is probably  similar,




except for possible minor variations, for any year.




     Figure  18 shows the average  water  temperature curve  for the Ohio State




Fish Hatchery at Put-in-Bay  for March  1968 through March  1969, superimposed




on the average annual  curve  (average for 45 years) at  the  hatchery.  Al-




though the  1968-69 curve  is  not far from the average,  it  does  show departures

-------
  0>
    I5OO •
    1000
     500
                                           Dashed  line - inorganic  N
                                           Solid line - organic  N
                                           Shaded - organic >  inorganic
                          7/1
                                8/1
                                 9/1
              ro/i
                                                     11/1
                                                           e/i
      1/1/69   2/1
4/1/158    5/1    6/1
  FIG. 15   COMPARISON  OF  ORGANIC AND INORGANIC NITROGEN  IN
           CENTRAL  BASIN  NEARSHORE  FOR  ONE-YEAR  CYCLE
                                                                       3/1
    3500
    3OOO >
    25OO •
C-  2000 •
 o>
    1500 /
    1000
     5OO •
                        Dashed  line -  inorganic  N
                        Solid line - organic N
                        Shaded  - organic  =-  inorganic
                                                                     /\
     4/1/68   5/1
                   6/1
                    r/i
8/1
                                      9/1
                                             10/1
                     ll/l
12/1   1/1/69   Z/\
                                                                             s/i
       FIG. 16  COMPARISON OF ORGANIC  AND  MORGANS  NITROGEN  IN
                WESTERN  BASIN  NEARSHORE  FOR  ONE-YEAR  CYCLE

-------
  .--    CN    <•>

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-------
 M'A 'M'J  'J'A'S'O'N'D '  J  ' J
FIG. 18 WATER  TEMPERATURE  AT PUT-IN-BAY
       Dashed  line  50-year average
       Solid line  1968-1969
                  4-9

-------
which may have been significant in  lake biological  processes.   Spring



water temperatures were above average while in the  first half  of  summer,



water temperatures were below average.  From about  August I  until  mid-



December, water temperatures were above average from I  to 3°F  (0.5 to  2°C),



The curve of average water temperatures for all intake  sampling stations



closely parallels, but is slightly lower than that  for  Put-in-Bay.  In



general, nearshore water temperatures rise more slowly  in the  central



basin than in the western basin.  Lower values reflect  deeper  water and



greater distance from shore.  (See Table I).






                               AIR TEMPERATURE



     Figure 19 A indicates that the average air temperature curve at



Cleveland for the year described also closely follows the long-term



average but with slightly cooler temperatures  in the spring and warmer



in the early summer of 1968.






                         SUNSHINE AND SOLAR RADIATION



     Figure 19 B, depicting average monthly percent of  possible sunshine



for the year of study, superimposed upon the  long-term  average, indicates



that in this respect the year departed rather  far from  the average.  This



may have had a significant  influence upon productivity  during the year.



Early spring had a greater than normal amount of sunshine.  Late spring



and early summer were rather far below the average as were late fall and



early winter.



     Solar radiation, Figure  19 C, was above average in early spring and



below average  in  late spring and early summer.  A particularly non-



characteristic feature of the radiation curve  occurred   in May when the



radiation was  less than  in April, coinciding with a significant drop  in





                                   50

-------
 s
 I  .5
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 S  10

 •>

 S  '
  -10
        A   M
                JJASONDJ   F
                                   1968   1969
       A.  MONTHLY  AVERAGE AIR TEMPERATURE
     MAM
                                                                D.  MONTHLY  AVERAGE WIND  VELOCITY
                                                             E.   MONTHLY  AVERAGE  PRECIPITATION
      B. MONTHLY AVERAGE % POSSIBLE SUNSHINE
  600
  SCO
2
  300
w    V
i
  zoo
  lOo'r
                       ^
                                      —s
    MAM
                       A   S   0   N   0   J   F
                                    I96B   1969
      C.   MONTHLY  AVERAGE SOLAR  RADIATION
                        0   N   0  J
                             1968  196*

F.   MONTHLY  AVERAGE  LAKE  LEVELS

        (U.S. Lake Survey Data)
     FIG. 19  MONTHLY  AVERAGES  OF VARIOUS  PHYSICAL  FACTORS  AFFECTING  LAKE  ERIE.

             All  data  from  U. S. Weather Bureau  a|t Cleveland  unless  otherwise  noted.

             Dashed  lines - longterm averajge.   Solid lines  - 1968-69.

                                             51

-------
percent of possible sunshine.  A concurrent rise in inorganic nitrogen



(Fig. 15 b) may be related.  Radiation on the average should, and does,



follow a smooth curve coinciding with seasonal expectations.






                                  WIND



     Average monthly wind velocities at Cleveland for the study period



are plotted as an annual curve in Figure 19 D along with the long-term



averages.  The year was slightly calmer than normal, December being the



only month when the long-term average was exceeded.  September was very



calm which may have been reflected in perhaps higher than normal blue-



green phytoplankton populations.






                              PHYTOPLANKTON



     Figures 20, 21, 22, 23, and 24 show nearshore population distribu-



tion of the dominant phytoplankton in Lake Erie western and central basins.



Diatoms  (Figs. 20 and 21) are by far the dominant forms3 numerically speak-



ing j reaching their largest populations in late winter and early spring.



This maximum pulse occurs when water temperatures are 5°C or less and



rising and just after nitrate has reached  its maximum.  Diatoms  reach a



minimum  in summer and generally increase through fall.



     Although not reaching the extreme populations of other types, green



algae uniquely exist at significant populations throughout the year (Fig.



22).  Green algae dominate the phytoplankton in late spring and  early



summer when the lake temperature is rising and between 10°C and  15°C3 and



when nitrate  levels are intermediate and declining.



     The  blue-greens, Figs.  23 and 24 are  virtually absent much  of the



year bu+  may  show a growth explosion  in  late summer and early fall.  They

-------
53
                           FIGURE  20

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FIGURE  22

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generally are dominant for a longer time In the western basin than in the



central basin.  Blue-green algae reach their greatest populations when



nitrate is nearly absent, when water temperature is above 20°C3 and after



the lake has begun to cool.



     Flagellates are not dominant in nearshore waters at any time of the



year.



     All phytoplankton forms appear to decrease quite significantly in



population from west to east in the lake.  By far the largest population



is found in the western basin at all times of the year.



     The attached green filamentous alga Cladophora was not considered



in this report.  Cladophora grows profusely in Lake E>ie, a suitable sub-



strate for "hold-fast1' attachment being the only limiting factor.  Cursory



agency study  indicates that the eastern basin, because of appropriate



substrate produces the largest Cladophora biomass.






                                DISSOLVED OXYGEN



     Figure 25 shows the time and spatial distribution of dissolved oxygen



at the intake sampling stations.  Early spring is characterized by con-



sistently higher percentages of oxygen saturation while summer is char-



acterized by  the lowest.   Fall and winter show  intermediate percentages



of oxygen saturation.  Dissolved oxygen  is apparently related to phyto-



plankton populations, particularly diatoms, see Figs. 20 and 21.  Acute



low oxygen saturation in summer  in the Cleveland area primarily results



from  incursions of hypolimnion water  into the  intake sampling areas.   In



areas  not affected by the  hypolimnion  less acute low oxygen saturation  is



most  likely the result of  chemical deoxygenation from nearshore resuspended



sediments.

-------
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59
FIGURE  25

-------
60
FIGURE  26

-------
                             CHEMICAL OXYGEN DEMAND




     Figure 26 shows the distribution of chemical oxygen demand in the




nearshore waters of the western and central basins.  A clear, relation-




ship between this distribution and that of dissolved oxygen does not exist.




If there is a relationship, it is a direct one.  Lou dissolved oxygen




concentrations in summer are associated with lower COD while higher DO




concentrations in fall and winter are associated with relatively high COD.






               CORRELATION OF FACTORS AFFECTING ALGAL PRODUCTIVITY




     The relationships described herein deal only with the factors de-




scribed in the previous discussion.  It is fully realized that algae re-




quire many kinds of nutrients in addition to nitrogen and phosphorus.  It




is assumed however that trace elements and vitamins necessary for sustain-




ing primary productivity are always in adequate supply and that they do




not become limiting at any time.  Two other elements, silicon and carbon,




necessary in relatively large quantity, have not been measured in this




study.  Silicon is required by diatoms in shell formation but is not a




significant nutrient for other algae.




     Many typical  general  relationships are apparent in Lake Erie.  For




example, various kinds of  algae show preference for different temperature



ranges.  Populations decrease from west to east in Lake Erie correlative



with a general  decrease in nutrient content in that direction.  Popula-



tions are higher in nearshore and other shallow waters correlative with




higher nutrient content.  Shifts in dominance with time are characteristic




of all parts of the lake.   The time shifts may not be relatable to water




temperature alone.  Most likely variations in solar radiation (energy)




due to earth position are  significant.   Finally populations of planktonic
                                       61

-------
algae are generally Inversely correctable with water depth.




     The following discussion examines the five main groups of algae




prevalent in Lake Erie, centric diatoms, pennate diatoms, green coccold




algae, blue-green coccold algae, and blue-green filamentous algae, and




their relationship to various physical, chemical, and biological  factors.




A glaring omission involves the enumeration of zooplankton.  As phyto-




plankton grazers, zooplankton can have a prpnounced effect on phyto-




plankton and consequently on the relationships to be presently described.






CENTRIC DIATOMS




                              Water Temperature




     Centric diatoms show a definite correlation with water temperature




in both the central basin nearshore (Fig. 26) and the western basin near-




shore (Fig. 27).  Populations increase very rapidly at the time of ice




breakup following a winter period of relative dormancy.  Maximum popula-




tions in both basins occur before the temperature reaches 3°C (3?°F).




Above this temperature the central basin population (>6,000 organisms/ml)




declines rapidly to less than 1,000 organisms/ml at a temperature of about



7°C  (45°F).  In the western basin the high populations (>IO,000 organisms/




ml)  persist longer, leveling off at less than 2,000 organisms/ml) when a




temperature of about  I0°C (50°F)  is reached.  Populations  in the western




basin remain fairly stable until a temperature of 20°C (68°F) is reached,




then drop rapidly to  less than 500 organisms/nl.   In the central basin




stability persists through  I2.5°C (54°F) when populations drop to 200 or




fewer organisms/ml.




     Centric diatoms decrease to or near their minimum populations when




the  lake  is warmest, thus showing an  inverse correlation with temperature
                                  62

-------
while the lake is warming.  After cooling begins, one might expect another



inverse correlation; however the cooling season rise in centric diatoms is



non-existent in the central basin and greatly subdued in the western basin.



Maximum western basin populations occur again at between IO°C (50°F) and



3°C (37°F) in fall but they are less than 10 percent of the populations in



spring.  This suggests that some factor other than temperature has a greater



population controlling influence in fall, as will be discussed presently.



                       Soluble Phosphorus and Temperature



     The plot of centric diatoms and soluble phosphorus reveals a varia-



bility difficult to explain.  At times higher populations are associated



with lower phosphorus concentrations following the classical tendencies



toward depletion shown by silica and nitrate.  At other times the reverse



is true, suggesting the biological  mechanisms of nutrient storage and de-



layed phytoplankton response.



     A plot of centric diatoms, soluble phosphorus, and temperature (Fig.



29) reveals quite a different picture.  Although the detailed interpreta-



tion remains difficult, a definite  general trend is shown during the warm-



ing season indicating that, as the  water warms, progressively more phos-



phorus is required to maintain similar populations.  For example, to



maintain a population of centric diatoms greater than 1,000 organisms per



mi I II liter at temperatures less than 5°C (4I°F), less than 10 pg/l solu-



ble phosphorus is required, while at 20 t (68°F) the requirement increases



to greater than 50 ug/l.  In these  types of  correlation, ambient water



nutrient concentration is inferred  to mean a concentration associated with



a specific algal  population.  It is not meant to mean algal metabolic



requirement.
                                      63

-------
     It appears that above 20°C (68°F) both temperature and soluble phos-



phorus are severely limiting to diatom growth in Lake Erie.   This does



not mean that other factors are not also limiting, but does mean that re-



duction of other prevailing non-limiting factors at this time is not



necessary for diatom control.



     After the lake begins to cool the relationship between diatoms, sol-



uble phosphorus, and temperature becomes obscure, indicating that some



other factor becomes more important to diatom production.



     Although a relationship between soluble phosphorus and diatoms is



apparent during the warming season, in the early part of this period the



relationship in detail is not altogether clear.  Below a temperature of



IO°C  (50°F) it appears that a concentration of about 30 yg/l soluble



phosphorus is sufficient for continued diatom growth.   If this  is fact,



it may be difficult to establish, for at this time soluble phosphorus  is



rapidly decreasing.  The possibility exists that during this period,



diatom populations are regulating soluble phosphorus rather than the



reverse.



                       Inorganic Nitrogen and Temperature



      Inorganic nitrogen appears to show a direct correlation with centric



diatoms when nitrogen averages for each sampling period are plotted against



average plankton numbers.  Higher diatom populations are associated with



higher nitrogen values and vice versa.  However the correlation  becomes



nebulous when  inorganic nitrogen and centric diatoms are considered not as



nearshore wide averages but  as  individual station statistics.   For example,



while maximum  populations tend to  increase eastward, the  inorganic nitrogen




associated with these maximums progressively decreases  eastward.

-------
    10,000
    5,000
UJ
o
                                       Solid  line -  warming  season
                                       Dashed  line -  cooling  season
       0             5             10             15             20
                                  TEMPERATURE  °C
       FIG. 27   CENTRIC  DIATOMS  VS.  TEMPERATURE IN  LAKE  ERIE
                CENTRAL  BASIN  NEARSHORE
   20,000
    I5POO
W  10,000
_l
ID
O




   5,000
                                         Solid line -  warming  season
                                         Dashed  line  -  cooling  season
                                                                           25
                                  10             15
                                  TEMPERATURE °C
                                                             20
                                                                           25
       FIG.  28  CENTRIC DIATOMS  VS.  TEMPERATURE  IN   LAKE   ERIE
                WESTERN  BASIN  NEARSHORE

-------
     A plot of centric diatoms, inorganic nitrogen and temperature gives



more insight as to cause and effect between the various considered fac-



tors (Fig. 29).  It appears that between 0°C (S2°F) and 5°C (4l°F)



centric diatoms are virtually independent of the amount of inorganic



nitrogen which exists at the time.   Above 5°C (41°F) the amount of inor-



ganic nitrogen apparently does not greatly affect centric diatom popula-



tions as  long as the nitrogen concentrations are below about 800 Mg/l  and



within the range normally found in nearshore waters.  Sporadic signifi-



cant population increases occur above 800 pg/l  with progressively larger



ambient nutrient concentrations being required  to maintain a certain pop-



ulation at progressively increasing water temperatures.  Above 20°C (68°F)



more than 1000 yg/l is needed to produce a significant diatom population



(>IOOO org/ml).




     After the lake begins to cool  centric diatoms are no longer impor-



tant, showing  little relation to either nitrogen or temperature, until



a water temperature of about  IO°C (50°F) is reached, then Gentries show



a slight  increase, but still  independent of existing nitrogen concentra-



tions.



     Integrating results for temperature, soluble phosphorus, and inor-



ganic nitrogen during the warming season, apparent nutrient requirements



for specified centric diatom populations can be inferred, as shown fn



Table 10.
                                  66

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                                 TABLE 10

  CONCENTRATIONS OF INORGANIC NITROGEN AND PHOSPHORUS  REQUIRED TO PRODUCE
       VARIOUS POPULATIONS OF CENTRIC DIATOMS DURING WARMING MONTHS
Temp.
1
0-5
5-10
10-15
15-20
20-25
1000 org/ml
70
Soluble P
(yg/l)
500 org/ml

-------
                        10           (5
                     WATER  TEMPERATURE - °C
                                                20
FIG. 30 ESTIMATED  REQUIREMENTS OF  SOLAR RADIATION  AT LAKE
      ERE WATER  TEMPERATURES FOR  CENTRIC  DIATOMS.
                              69

-------
any silica deficiency at this time of the year may be controlling diatoms



in general.






PENNATE DIATOMS



                              Water Temperature



     Pennate diatoms show essentially the same kind of response to tem-



perature as do the centric 'diatoms with the exception that populations



are usually considerably less.  The large spr-ing pulse lasts approximately



the same  length of time in both the western and central basins, beginning



during the period of ice breakup and essentially disappearing by the time



the water temperature reaches  I5°C (59°F).



     During the cooling season populations of pennate diatoms rise slight-



ly but do not reach significant numbers, again suggesting, as with Gentries,



that they may be subdued by a  lack of sufficient sunlight or silica at



preferred temperatures.



                       Spjtible Phosphorus and Temperature



     As with centric diatoms, the pennates also show a variable relation-



ship and most likely for the same reasons, with soluble phosphorus alone.



When plotted against soluble phosphorus and temperature some apparently



significant correlations emerge (Fig. 31).  During the warming season at



temperatures below 5°C (41°F) and as evidenced by maximum populations,



the pennates appear to prefer soluble phosphorus concentrations of 30 to



40 vg/lj decreasing in numbers when concentrations are above and below



those levels.  This correlation prevails somewhat through  IO°C  (50°F)



when higher concentrations of  phosphorus appear to begin to stimulate the



pennates.



     From  IO°C (50°F) through  20°C  (68°F) the correlation  becomes clearer
                                      70

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and is direct.  However significant populations, more than 500 cells/ml,



require relatively large quantities of soluble phosphorus, in excess of



70 ug/l.  Above 20° (68°F) pennate diatoms, because of restricting tem-



peratures, cannot be of great significance regardless of phosphorus con-



centrations.



     Duping the cooling season there -is no clear relationship between



phosphorus and pennate diatoms, indicating that another factor is limiting.



                       Inorganic Nitrogen and Temperature



     Inorganic nitrogen appears to show a direct correlation with pennate



diatoms when nitrogen averages for each sampling period are plotted against



average plankton numbers.  Again higher diatom populations are associated



with higher nitrogen values.  As with centric diatoms the correlation is



not altogether consistent, with occasional erratic values indicating some



delayed ambient aIgal-nutrient response.



     A plot of pennates,  inorganic nitrogen, and temperature however re-



veals the following:   Below a temperature of IO°C  (50°F) pennate diatoms



appear to require a concentration of more than 600 ug/l inorganic nitrogen



to produce blooms of more than 500 cells/ml.  Above  IO°C (50°F) the re-



quirement increases to a  large degree,  indicating that temperature  is rel-



atively more controlling.  Above 20°C  (68°F) as with phosphorus, nitrogen



is no  longer  important to pennate diatoms  in Lake Erie, the population



apparently entirely controlled by some other factor, most  likely temperature.



     During the cooling season, a correlation  is not apparent between  in-



organic nitrogen and pennates until a  temperature of  less than  IO°C  (50°F)



is reached.  They then seem to prefer  an  inorganic nitrogen concentration



of 800-1,000 ug/l.  Populations are still  relatively small, however,
                                      72

-------
indicating a response to insufficient sunlight or silica.

     The results of nutrient-temperature-pennate diatom correlations

provide some insight as to probable pertinent plankton requirements as

shown in Table II.

                                TABLE I I

      CONCENTRATIONS OF INORGANIC NITROGEN AND PHOSPHORUS REQUIRED
        TO PRODUCE VARIOUS POPULATIONS OF PENNATE DIATOMS DURING
                             WARMING MONTHS
Temp.
(°C)
0-5
5-10
10-15
15-20
20-25
Inorgani
1 ,000 org/ml 500
1,000
800
1,000
1
-
c N (yg/l)
org/ml 100
800
700
900
,500
1
org/ml
200
200
300
900
,000
Soluble
1 ,000 org/ml 500
30
30
80
-
-
P (pg/l)
org/ml 100
10
30
70
80
-
org/m 1
5
10
10
40
-
GREEN COCCOID ALGAE

                          Water Temperature

     The western basin nearshore green coccoid algae temperature plot (Fig.

33 shows a conspicuous rise during the course of lake warming, with maximum

populations of more than 3,000 cells/ml at about 22°C (72°F).  A precipitous

decline in population occurs above this temperature.  During the lake cooling

period, populations rise again slightly/to about 600 cells/ml at IO°C (50°F)

and then decline again in winter.

     In the central basin green oooooid algae are generally about one-half

those in the western basin.  The relation to temperature alone is quite

different (Fig. 32).  They rise from insignificance at the time of ice

breakup to a maximum (600 cells/ml) at a temperature of about I2°C (54°F)

then decline rapidly, so that the population minimum occurs at the same
                                     73

-------
   1000
   500
o
                                    Solid line  -  warming  season
                                    Dashed  line  - cooling  season
                                 10             15
                                 TEMPERATURE  °C
                                                                          25
      FIG. 32  GREEN COCCOID  ALGAE VS. WATER  TEMPERATURE IN NEARSHORE
             WATERS  OF  CENTRAL BASIN.
  2000
   1500 -
eo  1000
LU
o
   500
Solid  line -  warming  season
Dashed  line  - ' cooling  season
                                 10             15
                                 TEMPERATURE  °C
                                                            20
                                                                          25
      FIG.33  GREEN  COCCOID  ALGAE VS.  WATER TEMPERATURE  IN  NEARSHORE
             WATERS  OF  WESTERN  BASIN.

-------
time and same temperature as the population maximum in the western basin.




A secondary maximum in qreen coccoid algae then occurs in central  basin




nearshore just after the lake begins to cool at about 20°C (68°F).  This




is followed by a gradual decline to winter populations of less than 100




eel Is/ml.




     Based on the description above it is indicated that temperature is




most influential to green coccoid populations in winter and in the early




part of the warming of the lake in spring.  It is also indicated that if




other factors are adequate, as in the western basin the temperature in-




fluence will be extended to the period just prior to lake cooling.




                     Soluble Phosphorus and Temperature




     The plot of green coccoid algae and soluble phosphorus shows  no dis-




cernible trend.  Adding temperature to the relationship still  produces no




clearly defined characteristics.  However a few important conclusions can




be drawn.  Green coccoid algae increase as the water warms in  spring




through a temperature of about 12°C (54°F)3 while not showing  any  really




significant preference for higher phosphorus concentrations.   Above I2°C




however, green coccoid algae appear to become more phosphorus  dependent.




Below I2°C phosphorus concentrations of less than 30 yg/l appear adequate



to sustain populations greater than 400 organisms/ml, whereas  above I2°C,




that requirement rises to 50 yg/l or more.




     The dependence upon phosphorus continues through maximum  water tem-



perature, (25°C (77°F) and into the cooling period.  In the cooling period




and below 20°C (68°F) the correlation disappears and does not  reappear,




although the green coccoid algae do seem to prefer 50-60 pg/l  of soluble




phosphorus for the remainder of the year.
                                     75

-------
                       Inorganic Nitrogen and Temperature

     A plot of inorganic nitrogen temperature (Fig.  34)s  and green cooooid

algae shows that below 10°C (50°F) the green cocooids appear to be more

related to temperature than to nitrogen.   Above IO°C the  influence of in-

organic nitrogen becomes more apparent, the greater the nitrogen concen-

tration, the higher the populations.   As the temperature  increases above

IO°C (50°F) larger amounts of inorganic nitrogen are required to produce

similar populations.  For example at  I2°C (54°F) 200 ug/l inorganic nitro-

gen will produce 300 green coccoid algal  cells/ml,  but at 22°C (72°F) 600

pg/l is needed for the same population.

     Afier the lake begins to cool, there appears to be no clear relation

of green coccoid algae to inorganic nitrogen, the populations being rela-

tively  low regardless of concentration.  If there is any  preference at

all, it seems to be for lower amounts of inorganic nitrogen.

     The relationship between inorganic nitrogen, soluble phosphorus, and

temperature with green coccoid algae  is listed in Table  12.

                                TABLE  12

     CONCENTRATIONS OF INORGANIC NITROGEN AND PHOSPHORUS  REQUIRED TO
    PRODUCE VARIOUS POPULATIONS OF GREEN COCCOID ALGAE DURING WARMING
                                 MONTHS
Temp.
0-5
5-10
10-15
15-20
20-25
Inorgan?
1,000 org/ml 500
_
-
>900
> 1,000
1,100
c N (rig/I)
org/ml 100
_
300
600
850
900
org/ml
400
100
200
400
600
Soluble
1 ,000 org/ml !500
—
-
50
60
50
P (ug/i
org/ml
«
20
10
50
50
1 )
100 org/ml
10

-------
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BLUE-GREEN COCCOID ALGAE



                                Water Temperature



     Lake Erie water temperature and blue-green coccoid algae are clearly



related (Figs. 35 and 36).  It is well-known that blue-greens proliferate



above a temperature of 20°C (68°F) and this study is further confirmation



of that fact.  In Lake Erie however, maximum populations do not occur



when the water temperature is rising.  Rather the maximum nearly always



occurs just after the lake reaches peak temperature and begins to cool in



August and September.  Apparently when the lake temperature begins to drop,



some undetermined phenomenon occurs which In turn stimulates or allows in-



creased blue-green growth.



     It is possible that during the cooling period the actual water tem-



perature, or even the rate of water temperature decline, may trigger the



extensive blue-green coccoid algal growths.  It is also possible that the



algal grazers, the zooplankton which were not considered in this study,



were primarily affected by the temperature downswing killing the grazers



and  indirectly allowing the blue-green accretion.  Most likely, however,



blue-green blooms are stimulated and sustained by nutrients diffused or



resuspended from the bottom sediments, especially where; those blooms occur



at a great distance from tributary inputs, such as the northern island



area or midla'ke.  It would appear that sediment nutrient recycling to



overlying waters is  enhanced by surface cooling, resulting in top-to-bottom



connective mixing.  Under conditions of cooling the lake waters are readily



mixed even without additional wind-induced agitation.  Winds however can



induce upwelling, such as commonly occurs in the northwestern part of the



central basin, making the situation even more  ideal for nutrient recycling
                                      78

-------
c/>
_l
   I50O
   IOOO
    500
Solid  line - warming season
Dashed line  -  cooling  season
                                 10             15
                                 TEMPERATURE °C
                                                            20
      FK3.35  BLUE-GREEN  COCCOID ALGAE VS. WATER  TEMPERATURE  IN
             NEARSHORE WATERS  OF  CENTRAL  BASIN.
   5000 •
   4500
   4000
   35OO
   3000 •
V)
LL)
O  2500
   2000
   I50O •
   IOOO
    500 •
                        Solid  line -  warming  season
                        Dashed  line - cooling  season
                                !   l
                                i   !i
                                1    '
                                i    i
      0             5            10             15            20
                                 TEMPERATURE °C
      FIG. 36  BLUE-GREEN COCCOID  ALGAE VS. WATER  TEMPERATURE  IN

              NEARSHORE WATERS  OF  WESTERN  BASIN.
                                                                          25
                                                                         25
                                      79

-------
and blue-green blooms.




                       Soluble Phosphorus and Temperature




     A plot of blue-green coccoid algae and soluble phosphorus also




shows no discernible trend.  A relation does develop however when blue-




green coccoids are correlated with phosphorus and temperature together




(Fig. 37).  Below a temperature of 25°C (7?°F)3  when the lake is warming,




blue-green coccoid algae respond neither to temperature nor to phosphorus,




But, as noted previously, when the lake begins to cool, they appear, often




in great numbers and as shown in Fig. 37 are responsive to soluble phos-




phorus.  The highest populations appear when soluble phosphorus is 50 yg/l




or more.




     When the temperature falls, during the cooling season, to below 20°C




(68°F), blue-green coccoid algae decline.  By the time the lake has reached




I5°C (59°F) these algae are no longer significant.  Although blue-green




coccoid algae can be found In very small numbers at almost any time of the




year, they are restricted in importance to  late summer and very early fall.




                       [norganic Nitrogen and Temperature




     Fig. 37 shows the correlation of  inorganic nitrogen to blue-green




coccoids.   If a correlation exists it  is inverse, higher populations ex-




isting at  low concentrations of  inorganic nitrogen.



     Since some blue-green algae can fix atmospheric nitrogen, it  is assumed




that this nutrient cannot  limit all blue-green productivity in Lake Erie.




However the possibility  remains that if  inorganic nitrogen were plentiful




at this time of the year, green algae might continue to dominate with blue-




greens subordinate.  It is indicated that limited populations of green




algae due to nitrogen starvation minimise ecological competition thus
                                     80

-------
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allowing the dominance of nitrogen fixing blue-green algae.

                                TABLE 13

        CONCENTRATIONS OF INORGANIC NITROGEN AND SOLUBLE PHOSPHORUS
       REQUIRED TO PRODUCE VARIOUS POPULATIONS OF BLUE-GREEN COCCOID
                                  ALGAE
Temp.         Inorganic N (yg/1)                    Soluble P (ug/l)
(°C   1,000 org/ml  500 org/ml  100 org/ml    1,000 org/ml  500 org/ml  100 org/ml
0-5
5-10
10-15
15-20
20-25
25-20
- -
-
>200
-
-
>200
-
-
50
-
50
40
-
40
10
BLUE-GREEN FILAMENTOUS ALGAE

                               Water Temperature

     Blue-green filamentous algae show the same general correlation with

temperature as do the blue-green coccoids.  That is that maximum populations

occur after the lake begins to cool (Figs. 38 and 39).  It is assumed that

this response is for the same reasons as described for blue-green coccoids.

However in the western basin the blue-green filamentous pulse dies out more

slowly than in the central basin persisting at significant populations

(>1,000 cells/ml) to a temperature of 10°C (50°F) in autumn.  This probably

is a result of a generally higher nutrient supply in the western basin, per-

haps in turn a result of easier mixing in the basirts shallow waters.

                         Soluble Phosphorus and Temperature

     Fig. 40 shows blue-green filamentous algae plotted against soluble

phosphorus and temperature.  From the time of their dominance, at the period

of warmest water, 25°C t, down to a temperature of  IO°C (50°F) or  less, the
                                       82

-------
3OOO
2OOO
IOOO

Solid line - warming season
Dashed line - cooling season
A
•
/ \
y \

                               IO           15
                               TEMPERATURE  °C
                                                        20
                                                                     25
     FI6.38  BLUE-GREEN FILAMENTOUS ALGAE VS. WATER  TEMPERATURE  IN
            NEARSHORE WATERS  OF  CENTRAL  BASIN.
  6000
  5000
  4000
  30OO -
UJ
o
  2000
   1000 -
                           Solid  line - warming season
                           Dashed line -  cooling season
\
                                        . — -"A
                                              \i
                                                M
                              10            15
                               TEMPERATURE °C
                                                                     25
     FIG. 3 9  BLUE-GREEN FILAMENTOUS ALGAE VS. WATER  TEMPERATURE  IN
            NEARSHORE  WATERS  OF  WESTERN  BASIN.
                                  83

-------
blue-qree,n filamentous algae show a rather clear and direct relation to



soluble phosphorus.   At concentrations of 30 yg/l  or less the filamentous



types are not significant but above this level  populations increase greatly.



     In fall after the temperature decreases below 10°C (50°F) and until



it reaches above 20°C (68°F)S the following year,  blue-green filamentous



algae are not an important component of the algal population regardless of



the phosphorus concentration.



                       Inorganic Nitrogen and Temperature



     Fig. 40 also shows the relation of blue-green filamentous algae pop-



ulations to temperature and inorganic nitrogen.  As with the blue-green



coccoids if a relationship exists, it is inverse, higher populations oc-



curring with  lower nitrogen concentrations.  Again the ability to fix



atmospheric nitrogen allows the blue-green filaments to proliferate during



periods of water inorganic nitrogen depletion.



     As with soluble phosphorus3 inorganic nitrogen shows no relation to



blue-green filamentous algae during winter and spring3 populations being



insignificant the entire period regardless of nutrient concentration.



     Table  14 gives requirements for various blue-green filamentous pop-



ulations.

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                                 TABLE 14

        CONCENTRATIONS OF INORGANIC NITROGEN AND SOLUBLE PHOSPHORUS
      REQUIRED FOR VARIOUS POPULATIONS OF BLUE-GREEN FILAMENTOUS  ALGAE
Temp.         Inorganic N (yg/l)                     Soluble P
(°C)  1,000 org/mf 500 org/ml  100 org/ml    1,000 org/ml  500 org/ml  100 org/ml
0-5
5-10
10-15
15-20
20-25
25-20
20-15
15-10
10-5
-
_
-
-
<500
-
<200
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200
200
200
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200
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50
_ -
45 40
- -
55
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_
40
20
20
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40
                          FUTURE INVESTIGATIONS

      This study represents the beginning of the preparation of an algal

response analysis system for Lake Erie.  By present-day analytical stan-

dards it is rather crude.  However it has demonstrated that such a system

most likely can be designed and at minimum expense.  It appears that it can

be designed without an elaborate, sophisticated program of sampling and

analysis.

      At this point an effective algal response predict?on system does not

appear to demand that we determine the part played by trace elements, nor

does it demand that high frequency sampling and analyses be accomplished

during pulses of any particular algal species.  Such determinations might

refine the system, but presently appears unnecessary as long as the gross

features of the system have not been fully defined.

      This study  lacks information with respect to the factors governing

algal metabolism.  This  information deficiency  includes the algal capacity
                                       86

-------
for nutrient storage and subsequent stimulation from dormancy by extraneous



phenomena.



     Furthermore some additional parameters presently appear necessary



namely carbon, silica, and zooplankton.  It appears that the role of carbon



is important and at times may be limiting to algae.  It is possible that



spring diatom repression could  limit Lake Erie carbon content especially



in midlake, to the point where green algae and subsequently blue-green algae



would become insignificant.



     Silica is necessary for diatom skeletal formation.  It may be diatom



limiting during certain parts of the year.  Although silica limitation for



winter and early spring diatom repression is a long way from consideration,



a knowledge of the silica cycle could be most useful in understanding other



pertinent chemical and biological cycles.



     The role of zooplankton must be considered.  As algal grazers they



can affect algal populations to the point where phytoplankton-nutrient re-



lationships can be easily misunderstood and subsequently misrepresented.



     Perhaps the most difficult segment of a response analysis system, is



the determination of bottom sediment nutrient contribution.  Quantification



of recycled nutrients should lead to greater confidence in the prediction



of the results of input control in both immediate and long-term effects on



all algal species.



     Future study will involve the refinement of the biological, chemical,



and physical factors so rudimentally presented in this report.  In addition



new relationships including carbon, silica, and zooplankton will be studied.



At the same time the second year of data will be added to the one year de-



scribed herein.  It is expected also that computer programs will be designed



to facilitate the project.





                                     87

-------