Res«af>;r> and Dev elopmsnt
EPA
Lake Erie
Nutrient Control
Effectiveness
Regarding
Assessment in
Eastern Basin
-.P 600/3
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-------
RESEARCH REPORTING SERIES
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This report has been ass-gn-vj \,'l"<-_ F COt OG.C AL Rt V;APC/i ser es Tn>s sr nes
describes research 01 th,e t-'fc.is of poiiutior" en r,. ^ar'S plant nnd ar.mal spe-
cies, and materials Problems are assessed for the^ :ong- and short-terrn 'nflu-
ences investigations nclude formation transport and pathway studies to deter-
mine the fate of pollutants and t>-e.r et'eots This worn prov ries ihe teuhmcal basis
for setting standards 'o mimm'/e undes.rable changes in >,'ing organisms in the
aquatic terrestrial and atmospheric environments
This document is available to the puolic through the National Technical Informa-
tion Service, Springfield Virginia 22161
-------
EPA-600/3-80-067
July 1980
LAKE ERIE NUTRIENT CONTROL:
EFFECTIVENESS REGARDING ASSESSMENT
IN EASTERN BASIN
by
Great Lakes Laboratory
State University College
Buffalo, New York 14222
Grant No. R802706
Project Officer
Michael D. Mull in
Large Lakes Research Station
Environmental Research Laboratory
Grosse lie, Michigan 48138
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
DULUTH, MINNESOTA 55804
-------
DISCLAIMER
This report has been reviewed by the Environmental
Research Laboratory - Duluth, U.S. Environmental Protection
Agency, and approved for publication. Approval does not signify
that the contents necessarily reflect the views and policies of
the U.S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or
recommendation for use.
11
-------
FOREWORD
The eutrophic status of Lake Erie has been a subject of
considerable debate by citizens and public officials. The Large
Lakes Research Station, Environmental Research Laboratory-Duluth,
has been supporting programs to more fully assess and monitor the
changes in the state of eutrophication of Lake Erie as pollution
control measures are implemented.
This report represents the results of a study on the Eastern
Basin of Lake Erie to measure, where possible, the response of
the lake to pollution abatement measures.
Michael D. Mullin, Ph.D.
Project Officer
Large Lakes Research Station
Environmental Research Laboratory-Duluth
Grosse lie, Michigan
iii
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ABSTRACT
A three year synoptic monitoring program was conducted on
26 stations in the Eastern Basin of Lake Erie from 1973 to 1975.
The data generated include major nutrients, temperature structure,
and oxygen depletion as well as phytoplankton, zooplankton and
benthic macroinvertebrate dynamics.
The Eastern Basin surface waters were differentiated into
five discrete areas with each water mass characterized by a
different physio-chemical variable. These areas appeared to be
highly influenced by localized inputs into the Basin from specific
tributaries such as the Grand River and Twenty Mile Creek as well
as such population centers as Erie, Port Colborne and Dunkirk.
The nitrogen data in 1974 showed an increase over both 1973 and
1975 levels. There were corresponding increases during 1974 in
both phytoolankton and zooplankton biomasses. Anoxic conditions
were not observed in the hypolimnetic waters of the Eastern Basin
over the study duration and the oxygen demand was calculated to
be approximately 0.011 gOa/m3/day.
The pelagic biotic variables were in close agreement with
findings of earlier investigations. Phytoplankton biomass ranged
between 0.3 and 3.7 g/m3. Chlorophyll-a showed maximum values of
7 mg/m3 and primary productivity ranged from 16 to 20 mg C/m3/day.
The crustacean zooplankton were similar in both numbers and
species encountered to previous work. Furthermore, the ratio of
calanoids to cyclopoids plus cladocerans was 0.11, very low on
the trophic scale.
The benthic macroinvertebrates displayed an increase in
numbers over the past seven years and also showed some species
shifts. A mean number of organisms of 8278/m2 were observed
over the three years (1973-1975). Several organisms, especially
the oligochaetes, associated with more eutrophic values of the
Western and Central Basin have become established in large
numbers within the Eastern Basin.
The results of this synoptic survey appear to indicate
that in general terms the Eastern Basin has remained relatively
stable over the past five years with the exception of a decrease
in phytoplankton biomass (1975), an increase in nitrogen (1974)
and a doubling in numbers of benthic macroinvertebrates. From a
trophic standpoint, the Eastern Basin of Lake Erie can be
classified generally as mesotrophic.
iv
-------
This report was submitted in partial fulfillment of Grant
Number R-802706 to the Research Foundation, State University of
New York, Albany, New York by the U.S. Environmental Protection
Agency. Work was completed as of 31 July 1976.
v
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CONTENTS
Foreword
Abstract iv
Figures viii
Tables xi
Acknowledgements xiii
1. Introduction 1
2. Conclusions 3
3. Recommendations 4
4. Methods
Data collection 7
Data analysis 9
5. Results
Characterizing the Environment 14
Phytoplankton 45
Zooplankton 56
Eastern Basin Benthic Communities 63
6. Discussion 70
References oo
vn
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FIGURES
NUMBER PAGE
1 Bathymetric map of Lake Erie Eastern Basin 5
2 Lake Erie Eastern Basin mean epilimnion
total phosphorus 1973-1975 15
3 Lake Erie Eastern Basin mean epilimnion
dissolved phosphorus 1973-1975 16
k Lake Erie Eastern Basin mean epilimnion
nitrate-nitrite 1973-1975 19
5 Lake Erie Eastern Basin mean epilimnion
ammonia 1973-1975 20
6 Lake Erie Eastern Basin mean epilimnion
total nitrogen 1973-1975 21
7 Lake Erie Eastern Basin mean epilimnion
particulate organic carbon 1973-1975 23
8 Lake Erie Eastern Basin mean epilimnion
pH (standard units) 1973-1975 2k
9 Results of discriminant analysis for epilimnion
physio-chemical variables measured in the
Eastern Basin 1973-1975 27
10 Summary of results from discriminant analysis
on Eastern Basin epilimnion physio-chemical
variables for total three year study period 29
11 Lake Erie Eastern Basin mean bottom
dissolved phosphorus 1973-1975 31
12 Lake Erie Eastern Basin mean bottom
total phosphorus 1973-1975 32
13 Lake Erie Eastern Basin mean bottom
nitrate-nitrite 1973-1975 33
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NUMBER PAGE
1 k Summary of results from discriminant analysis
on Eastern Basin bottom physio-chemical
variables for total three year study period ...... 3^
15 Variations in thermal dynamics of Lake Erie
Eastern Basin as represented by temperature-
depth profiles on a transect of the
longitudinal (east-west) axis of the Basin ....... 36
16 Variations in thermal dynamics of Lake Erie
Eastern Basin as represented by temperature-
depth profiles on a transect of the cross-lake
(south-north) axis of the Basin .................. 37
17 Hypolimnetic boundary and thickness (m)
Cruise III (25-29 July) 1975 ..................... 38
18 Lake Erie Eastern Basin mean horizontal
distribution of total phytoplankton biomass
1973-1975 ........................................ 47
19 Seasonal fluctuations of phytoplankton biomass,
its group composition, chlorophyl 1 -a_ and
primary productivity in Lake Erie Eastern Basin
1973-1975
20 The Lake Erie Eastern Basin phytoplankton group
composition for the discrete areas identified
from the physio-chemical discriminant analyses ... 57
21 Lake Erie Eastern Basin mean horizontal
distribution of crustacean zooplankton biomass
1973-1975 ........................................ 58
22 Seasonal fluctuations of crustacean zooplankton
biomass and its group composition in Lake Erie
Eastern Basin 1973-1975 .......................... 61
23 The Lake Erie Eastern Basin zooplankton group
composition for the discrete areas identified
from the physio-chemical discriminant analyses ... 62
2k Community ordination of the benthic macroinverte-
brate groups in Lake Erie Eastern Basin
1973-1975 ........................................ 65
25 Summary of results from discriminant analysis on
the ordinates (x, y, z) produced from the
ordination analyses of benthic macroinvertebrates
in Lake Erie Eastern Basin 1973-1975 ............. 67
ix
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NUMBER PAGE
26 Distribution of (a) surficial sediments,
(b) mean sediment grain size in phi units
and (c) organic carbon in percent dry weight
of sediment (from Thomas et al, 1976) 77
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TABLES
NUMBER PAGE
1 Comparable Lake Erie Eastern Basin cruise
dates 1973-1975 .................................. 8
2 Factors considered in discriminant analyses of
chemical and physical parameters of Lake Erie .... 11
3 Biological factors considered in regression
analyses ......................................... 12
4 Means and standard deviations for the seasonal
and annual concentrations of total phosphorus,
dissolved phosphorus, total nitrogen, nitrate-
nitrite, ammonia, PIC, and POC in the Eastern
Basin of Lake Erie 1973-1975 ..................... 18
5 Results of a discriminant analysis for water
quality of each Eastern Basin sampling station
compared to itself over the period 1973-1975 ..... 26
6 Summary of 1973 hypolimnetic surveys of the
Eastern Basin of Lake Erie ....................... 40
7 Summary of 1974 hypolimnetic surveys of the
Eastern Basin of Lake Erie ....................... 41
8 Summary of 1975 hypolimnetic surveys of the
Eastern Basin of Lake Erie ................... .... 42
9 Hypolimnetic oxygen demand in the Eastern Basin
of Lake Erie 1973-1975 ........................... 43
10 Correlations between significantly related
variables in the Eastern Basin of Lake Erie
1973-1975
11 Mean values of phytoplankton biomass and its %
composition for all sampling cruises in Lake
Erie Eastern Basin 1973-1975 ..................... 46
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NUMBER PAGE
12 Inshore-offshore comparison of chlorophyl1-a_
(corrected) mean concentrations (mg/m3) in
the Eastern Basin of Lake Erie, July -
December 1973 53
13 Inshore-offshore comparison of chlorophyl1-a_
(corrected) mean concentrations (mg/m3) in
the Eastern Basin of Lake Erie, May -
December 1974 54
14 Inshore-offshore comparison of chlorophyl1-a
(corrected) mean concentrations (mg/m3) Tn
the Eastern Basin of Lake Erie, April -
December 1975 55
15 Mean values (#/m3) of crustacean zooplankton
and its % composition for all sampling cruises
in Lake Erie Eastern Basin 1973-1975 59
16 Total mean benthic biomass (#/m2), % group composition
and total number of species encountered for
each Lake Erie Eastern Basin station 1973-1975 ... 64
17 Classification of each Lake Erie Eastern Basin
station according to a benthic community type .... 68
18 Classification and Central Basin comparison of
oxygen demand 74
Xil
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ACKNOWLEDGEMENTS
Special thanks are conveyed to EPA personnel at the
Great Lakes Research station including Michael Mullin, Nelson
Thomas and William Richardson. Their special cooperation and
suggestions were of considerable aid over the course of this
research project. Acknowledgements are also due to Elaine
Prantner for her patience in typing the report manuscript and
producing the graphics.
XII 1
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SECTION 1
INTRODUCTION
The need for more information concerning the lacustrine
condition of Lake Erie was indicated by the USFWPCA (1968a, 1968b)
and the International Lake Erie Water Pollution Board (1969).
Additionally, the International Joint Commission (1975) pointed
out the need for more information to describe the ecological
status of Lake Erie.
Although many investigations of limnological processes in
Lake Erie have been carried out (Herdendorf et al., 1974), compre-
hensive surveys over several successive years have been infrequent.
Furthermore, while Lake Erie in general has been the object of
numerous studies, the Eastern Basin of the lake has been neglected
to a large extent. In response to concerns about the deteriorat-
ing water quality of Lake Erie, the staffs of the Grosse lie Lab
of the U.S. Environmental Protection Agency and the Great Lakes
Laboratory (GLL), State University College, Buffalo, New York,
planned detailed studies of the Eastern Basin of Lake Erie from
1973 through 1975 which were implemented by the GLL. These studies
were funded by the Environmental Protection Agency (EPA) Grant
#R-802706. The Eastern Basin surveys were coordinated with similar
efforts in the Central and Western Basins of Lake Erie by The Ohio
State University and EPA's Grosse lie Laboratory.
With great variation in physical and chemical parameters
within its boundaries, the Eastern Basin is distinct from other
Lake Erie regions. It contains the greatest depths and because of
land forms and the influence of the Niagara River, the Eastern
Basin has a complex system of currents and seiches that influence
both water condition and biota in a variety of ways. Results from
other research (Burns and Ross, 1972; Burns, personal communication)
imply that many of the processes resulting in ecologically criti-
cal conditions observed during the 1960's in the Central and
Western Basins also were beginning to occur in the Eastern Basin.
Concurrently, municipal and industrial discharges have been
decreased as part of a lakewide abatement program by the United
States and Canada. Therefore, the desirability to obtain infor-
mation that can quantify the above has increased to the point that
the study described in the following pages was initiated.
The objectives of the U.S. Environmental Protection Agency
sponsored multi-year project, whose results for 1973 through 1975
-------
for Lake Erie's Eastern Basin, are described here, were as follows:
a. Establish aquatic baseline information and ascertain
the trophic status of the Eastern Basin through the
collection and analysis of samples for all important
chemical, physical, and biological parameters.
b. Quantitatively identify areas of the Eastern Basin
that may be experiencing more problems with water
quality than other areas.
c. Evaluate the nature and extent of problems associated
with over-enrichment and determine the impact of
abatement programs within the watershed of the Eastern
Basin.
d. Examine the effectiveness of measuring a limited
number of biotic and abiotic parameters to evaluate
the processes of eutrophication in a large lake.
In order to gather information to address the above, major
emphases during this three-year study of the Eastern Basin
included determinations of the level of nutrients in the water,
the concentrations of oxygen and its depletion in the hypolimnion,
and dynamics of the flora and fauna. The Great Lakes Laboratory
has attempted to relate biological responses in Lake Erie's
Eastern Basin to some of the physical and chemical processes which
occur in this aquatic environment, and compare this information
to other studies on the lake (i.e. "Lake Erie in the Early
Seventies", J. Fish. Res. Bd. Can., 33(3), 1976).
With this in mind, we will first characterize the Eastern
Basin of Lake Erie (based on three years of data collection)
according to physical and chemical variables. Secondly, we will
describe the biological communities of the Basin in respect to
the physio-chemical characterization. As part of this description,
we will elucidate important biological mechanisms in relation to
the total Basin dynamics and identify the relationships involved.
Finally, we will discuss the information obtained over the three
years in respect to the objectives of this project.
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SECTION 2
CONCLUSIONS
The data gathered during the 1973-1975 survey of the mid-
lake region of the Lake Erie Eastern Basin (LEEB) by the Great
Lakes Laboratory provided a comprehensive limnological baseline
which can be used to evaluate the rapidity and direction of
future trends in environmental quality. From physical, chemical
and biological observations, it was concluded that the Eastern
Basin generally can be characterized as mesotrophic. Over the
past three to five years there have not been any major changes in
water quality with two possible exceptions. A decline in total
phytoplankton and particularly the Cyanophyta was noted in 1975
and an increase in nitrogen, especially ammonia, during 1974 was
also observed. Contrasting the 1973-1975 quantifications of
benthos with those of a 1968 survey, an increase in the forms
more commonly associated with eutrophic conditions was noted.
While there were few positive correlations between algal
productivity and nutrients (which did not include soluble
reactive phosphorus), there were indications that at times
nitrogen was limiting. There was a positive relationship between
total zooplankton and ammonia.
Higher concentrations of nutrients were observed in areas
believed to be influenced by the discharges from specific tribu-
taries, such as the Grand River and Twenty-Mile Creek. Discharges
believed to emanate from metropolitan regions, such as Erie, Port
Colborne and Greater Buffalo, also had generally negative impacts
on the mid-lake water quality of the Eastern Basin. Additionally,
nutrients were carried into the Eastern Basin from the Central
Basin by entrainment processes.
This study supports the conclusion by previous investi-
gators that the Eastern Basin is the most chemically and
physically complex major area of Lake Erie. This report should
contribute to a better understanding of the nature and extent of
many of the limnological processes within the Eastern Basin.
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SECTION 3
RECOMMENDATIONS
While the design and implementation of the 1973-1975 Lake
Erie Eastern Basin (LEEB) project were adequate to provide the
data necessary to satisfy the objectives of the study, future
efforts should be modified in an attempt to answer the questions
raised during the initial three years of monitoring as well as to
more effectively evaluate the impacts of Canadian and United
States pollution abatement programs. Some efforts also did not
yield sufficient results to justify their continuation.
It is imperative that the communication among the agencies
monitoring the Lake Erie Eastern Basin and its tributaries be
continued. An attempt should be made to prepare and exchange
data from the previous field effort before the next sampling
season is initiated.
A major deficiency in the present LEEB surveillance program
is the lack of a comprehensive monitoring effort in the United
States nearshore waters. While the Lake Erie Wastewater Manage-
ment Study of the Corps of Engineers Buffalo District is examining
the major U.S. tributaries to the Basin and the Great Lakes
Laboratory (GLL) is sampling the mid-lake region of the LEEB, no
agency is monitoring the nearshore areas. The latter are the
regions most visible to the shorebound human population and the
areas most intensely utilized by humans in terms of water supply,
waste dilution and dispersion as well as recreation. The near-
shore and mid-lake monitoring both cannot be accomplished with
financial and other limitations of the GLL's LEEB survey program.
With respect to modifications of the LEEB mid-lake effort,
the number of sampling sites should be reduced from 26 to 18 by
dropping Stations 2, 5, 7, 10, 12, 17, 22 and 62 (Figure 1). The
conditions at the latter eight sites show no difference from
other stations in their immediate area and/or do not provide
information to evaluate pollution abatement efforts. Thus the
remaining stations can be sampled more intensely with adequate
replication. The number of Basin-wide cruises, however, should
be increased from five to eight in an attempt to reduce the time
between cruises to 30 days. Under the present schedule it
appeared that biological "peaks" may have been missed several
times between 1973 and 1975.
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With respect to biological parameters, the sampling for
phytoplankton and chlorophyll-a should be modified. The surface
sample should be replaced by an integrated collection between
one and five meters below the surface. This should reduce the
problems caused by algal migration within the euphotic zone. An
additional sample at a constant depth (7 m) should be collected
within the euphotic zone. An attempt should be made to incubate
the *^C primary productivity bottles in situ at the collection
sites rather than aboard the research vessel. This would
require that such productivity measurements be limited to stations
from which the bottles could readily be retrieved after four hours
by a smaller craft. This approach would add extra flexibility to
our monthly sampling schedule.
The 1973-1975 benthos collections, which were gathered at
each station during 1-3 cruises per year, have provided some
valuable baseline data. With such a sporadic sampling interval,
however, some bottom organisms that are only present seasonally
could be missed and community succession would be impossible to
follow. Therefore, the number of benthos collection stations
should be reduced to ten (Stations 3, 6, 11, 14, 15, 16, 19, 21,
64 and 80), but these should be sampled in triplicate four times
per year (one in spring, two in summer, one in fall). To fully
compliment the benthic data, particle size and total organic
carbon should also be measured on these sediments.
An effort should be made to obtain a pH and conductivity
profile at each sampling site in addition to the dissolved oxygen-
temperature profiles. The former could provide more information
on the nature and distribution of chemoclines which are present
in the Basin.
With respect to chemical parameters, particulate inorganic
carbon should be dropped because of the uniformity of the values
obtained. Soluble reactive phosphorus as well as silica and total
inorganic carbon should be quantified because of the importance of
those chemicals to primary productivity.
In view of the preservation difficulties concerning some
forms of nitrogen and phosphorus, consideration should be given
to installing an autoanalyzer on the research vessel to facilitate
more rapid quantification of such parameters.
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SECTION
METHODS
DATA COLLECTION
In 1973, 25 sampling stations were established in the
Eastern Basin of Lake Erie in an attempt to comprehensively
characterize this region. In 1974 an additional station (Station
80) was added to the sampling schedule to include the area of
Long Point Bay. The location of the 26 Eastern Basin stations
is shown on the bathymetric map in Figure 1. One of the reasons
for selecting these sampling sites, besides giving synoptic
coverage of the Eastern Basin, was to maintain an equal division
between inshore (<25 m) and offshore (>25 m) sampling sites.
During the three year project period a total of 26
synoptic cruises were conducted; eight in 1973, thirteen in 1974
and five in 1975. These cruises were systematically divided to
cover the three seasons of spring, summer, and fall. An attempt
was made in the scheduling to conduct comparable cruises each of
the three years. This was not always possible, however, because
of weather and/or mechanical difficulties. Over the three years,
there were 15 cruises that could be compared (Table 1). These
will receive the major focus of this report.
Sample collection techniques and methods of sample analysis
are thoroughly described in each of the annual reports (Great
Lakes Laboratory, 1974; 1975; 1976) for the project. With the
increase in efficiency and expertise of our laboratory and changes
in EPA-improved procedures and techniques, several methods of
sample collection and analysis were changed over the course of
the study. These will be described briefly.
Modifications in the field sampling procedure did not
involve changes in instrumentation. Procedures such as primary
productivity incubation (light box incubations - 2 hr) and
dissolved oxygen determination, however, were modified to make
our field operation more efficient.
In the laboratory, the nitrogen compounds (N03, NH3, and
Org-N) were determined by manual methods of Kjeldahl digestion
for NH3 and Org-N and the Brucine Method for N03 in 1973 and 1974.
In 1975, GLL changed to the use of the Technicon AutoAnalyzer and
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Table 1. COMPARABLE LAKE ERIE
EASTERN BASIN CRUISE DATES 1973-1975
1973
1974
1975
SPRING
21 May - 1 June
9-12 April
SUMMER
July
18-22 June
2-5 June
31 July - 6 Aug 26-30 July
25-29 July
FALL
-4 October
6-9 September
15-18 September
8-11 October
23-27 October
7-21 December
19 Nov - 5 Dec
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determined N03 using the cadmium reduction method (Technicon
Industrial Method #158-71W). Ammonia was determined on the Auto-
Analyzer by reaction with alkaline phenolhyperchlorite (Technicon
Industrial Method #154-71W) and Org-N with the same reaction after
Kjeldahl digestion. Dissolved and total phosphorus were deter-
mined by the manual Ascorbic Acid Method with persulfate digestion
in 1973 and 1974. In 1975 total and dissolved phosphorus were
measured on the AutoAnalyzer. The Ascorbic Acid Method was used
on both filtered and unfiltered samples after potassium sulfate
digestion (modification of Technicon Industrial Method #155-71W).
Particulate inorganic and organic carbon (PIC and POC, respective-
ly) were measured on the Coleman Carbon-Hydrogen Analyzer in 1973.
Filtered and unfiltered, acidified and unacidified samples
collected in 1974 and 1975 were analyzed on the Beckman Model 915
Carbon Analyzer. POC and PIC values were determined by difference.
Methodological equivalency experiments were conducted for
the phosphorus, nitrogen and carbon analyses to verify the compar-
ison of data generated using "wet" vs. automated methods. These
experiments showed that all phosphorus analyses and carbon analy-
ses using the different methods were not statistically different
at the 0.05 level with N=25 at concentrations of 15 yg P/l, 4.0
mg C/l for PIC and 0.8 mg C/l for POC. With both the phosphorus
and carbon, however, the automated analyses markedly increased
sensitivity with slightly better precision and accuracy.
With respect to the nitrogen series, N03-N analyses also
showed no statistical difference at the 0.05 level with N=25 at
a concentration of 0.12 mg N/l. Again increased sensitivity with
better precision and accuracy was found. The results of Org-N
comparisons between the two methods were statistically different
at the 0.10 level with N=25 at a concentration of 0.35 mg N/l.
Automated analysis did, however, increase sensitivity, accuracy
and precision. It was believed that this slight decrease in
comparability in the Org-N results over the three years was
negligible. Comparison of NH3-N data from the "wet" vs.
automated analyses were statistically different at the 0.12 level
with N=25 at a concentration of 0.05 mg N/l. Again sensitivity,
accuracy and precision were markedly improved. Data comparisons
were made for 1973 through 1975 and are believed to be valid but
must be viewed in light of the lower comparabilities found.
Like the field operation, the methodology employed in the
quantification of phytoplankton, zooplankton and benthos did not
experience any real changes in procedure. However, with
experience as well as advances in the taxonomy and keys, organisms
were identified to more precise levels of classification.
DATA ANALYSIS
Selected chemical and physical data collected from all
Eastern Basin stations over the three years were used in a
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discriminant analysis routine to statistically distinguish between
different areas within the Eastern Basin and characterize these
environments. The discriminating variables used in the analysis
and their units are listed in Table 2. The objective of our use
of discriminant analysis was to combine these variables in some
fashion so that the sampling stations would fall into groups
(areas of the Basin) which were as statistically distinct from
one another as possible.
Stepwise calculations were made in order to determine which
variables were significant in contributing discriminant power to
the areas of the Basin ultimately proved to be different. All
computations were made to a significance level of P ^0.05. The
analyses were done on the State University of New York (SUNY)
IBM 360 Computer using the Statistical Package for Social Scien-
tists (SPSS) Discriminant Package (Nie et al., 1970).
The results of these analyses provided several tools for
the interpretation of the data. Among these were the statistical
tests for measuring the success with which the variables actually
discriminated when combined into discriminant functions. Further-
more, since the discriminant functions obtained could be thought
of as the axes of a geometric space, they were used to study the
spatial relationships among the groups of stations. Most impor-
tantly, however, the discriminant functions and their weighting
coefficients served to identify the variables which contributed
the most to differentiation among the respective groupings of
stations.
Selected physical, chemical and biological data from all
stations for the three years were used in correlation and step-
wise multiple regression analyses to determine the kind and
degree of relationship existing between variables. This
hierarchial method provided the framework for the identification
of relevant associations. The biological variables considered
and their units are listed in Table 3.
Stepwise calculations were made with independent variables
entering the regression in order of decreasing importance.
Computations were done on the SUNY IBM 360 Computer using the
SPSS Regression Package (Nie et al., 1970). All computations were
made to a significance of P <0.01. An attempt was made to
elucidate mechanisms and define relationships between variables;
thus a linear method was used so that results could be justified
on the knowledge of biological mechanisms or comparability with
general biological principles.
Analyses were performed on the data obtained from benthic
collections over the three years using ordination of species
based on principal components analysis (Orloci, 1966). This
technique provided a means of summarizing the raw data of species
lists from the 26 stations and objectively arranging the different
10
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Table 2. FACTORS CONSIDERED IN DISCRIMINANT ANALYSIS
OF CHEMICAL AND PHYSICAL PARAMETERS OF LAKE ERIE
Variable
Abbreviation
Units
PH
PH
standard units
Conductivity
COND
ymoles/cm
Dissolved Oxygen
DO
mg/1
Temperature
TEMP
Chlorophyl1
CHL
mg/m3
Secchi Disc
SD
m
Nitrate (N03~)
NO
yg N/l
Ammonia
NH
yg N/l
Total Nitrogen
TN
yg N/l
Total Phosphorus
TP
yg P/l
Dissolved Phosphorus
DP
yg P/I
11
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Table 3. BIOLOGICAL FACTORS
CONSIDERED IN REGRESSION ANALYSES
Variable
Abbreviation
Units
Total Phytoplankton Biomass
PHYTO
mg/mc
Chlorophyta Biomass
GREEN
mg/m
Pyrrhophyta Biomass
DINO
mg/m
Flagellate Biomass
FLAG
mg/m
Chrysophyta Biomass
DI ATOM
mg/m
Cyanophyta Biomass
BLUG
mg/m
Cladocera Numbers
CLAD
Calanoida Numbers
CALA
#/ms
Cyclopoida Numbers
CYCLO
#/m3
12
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communities (grouping of similar stations) as points in a
graphical display. The assumption of this technique was that the
position of the points or cluster of points along the graphical
axes may reflect community relationships. Assigning meaning to
the axes of the ordination graph, or identifying major community
groups is subjective (Lambert and Dale, 1964) although some state
that the misinterpretation of the data is small (Cattell, 1965).
To remove the subjective nature from this technique, discriminant
analysis calculations were made on results of the community
ordination (3 coordinates) to determine separation of the points
in space. This resulted in groupings of stations classified
according to certain benthic community types in the Eastern Basin.
The community ordination was done using a modified version of a
FORTRAN program developed by D. Young of the Ohio State Univer-
sity (personal communication) and performed on the SUNY IBM 360
Computer.
13
-------
SECTION 5
RESULTS
CHARACTERIZING THE ENVIRONMENT
Lake Erie's Eastern Basin exhibits the characteristics of a
tnonomictic (K. Stewart, personal communication) mesotrophic lake
in the temperate zone. During the 1973, 1974 and 1975 sampling
seasons the thermocline formed near the surface and progressively
moved deeper during the summer and early fall to maximum depths
of greater than 30 m in some instances. Although the GLL never
sampled during winter periods, there was an ice cover over the
Eastern Basin each of the three sampling years. Stewart found a
lack of inverse stratification in 1972 throughout the entire lake.
Very little light penetrated deeper than approximately 14 m
(2.5 times the maximum Secchi disc measurements - Larson, 1972)
during the year. Profiles of pH and specific conductance were
clinograde during summer stratification and vertically uniform
during spring and fall mixing (Great Lakes Lab, 1974; 1975; 1976).
Dissolved and total phosphorus exhibited inverse clinograde
profiles during stratification and relative uniformity after
turnover; nitrate and ammonia also followed this trend, as a rule.
The organic nitrogen profiles, however, were clinograde during
stratification and uniform during mixing. Dissolved oxygen con-
centrations were negatively heterograde during stratification and
uniform during mixing (Great Lakes Lab, 1974; 1975; 1976).
Data were first analyzed to characterize the epilimnetic
waters of the Basin occupied on each cruise (Figure 1) over the
three years. Comparisons of samples taken from a meter below the
surface (S-l m) with mid-epilimnetic samples showed no signifi-
cant difference (P ^0.05). Therefore, 1 m sample data were used
to represent the epilimnetic waters of the Basin.
The diagrams in Figures 2-3 give the distribution of some
of the phosphorus forms in the Eastern Basin. Mean total
phosphorus for each station over the year (Figure 2) shows a
progressive decrease, in the nearshore waters from 1973 to 1.975 at
the western end of the Basin and conversely an increase in the
offshore waters, especially from 1974 to 1975. The eastern end
of the Basin shows a progressive decrease in total phosphorus
similar to the nearshore waters further west. Dissolved
14
-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
ug P/l
15 - 20
21 - 2^4
28
>30
- 30
Figure 2. Lake Erie Eastern
total phosphorus
Basin mean
1973-1975.
e p i 1 i m n i o n
15
-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
yg P/I
3 - 5
8 - 9
10-11
Figure
Lake Erie Eastern Basin mean epilimnion
dissolved phosphorus 1973-1975.
16
-------
phosphorus (Figure 3), the more important of the two phosphorus
forms with respect to utilization by phytoplankton, shows a
definite increase over the three years, Basin-wide. In 1974 there
was a decrease of approximately 4 yg P/l in the western part of
the Basin. This was short lived showing an increase in 1975,
near 1973 levels. The eastern end of the Basin displayed a
definite increase over the entire three years with most waters
showing 5-7 yg P/l in 1973, 7-9 yg P/l in 1974 and 9-11 yg P/l in
1975.
As shown in Table 4, there is no significant change in
total Basin means over the three years for total phosphorus,
while the dissolved phosphorus increases from a mean of 4.3 yg
P/l in 1973 to a Basin mean of 7.4 yg P/l in 1975. The seasonal
concentrations for total phosphorus show the general trend of a
spring peak (1975) with a decrease to mid-summer when a slight
peak appears again leading to a fall minimum. Dissolved
phosphorus, on the other hand, displays minimal values during the
early spring (1975) and summer and higher values during the late
spring and fall seasons.
According to the diagrams of Figures 4-6, the major
nitrogenous compounds of the Eastern Basin epilimnetic waters
reach maximum concentrations in 1974. Nitrate concentrations
(Figure 4) generally range less than 150 yg N/l over most of the
Basin in 1973. In 1975 these concentrations are very similar
except for the southern shore of the Basin which displays nitrate
concentrations in the range of 250 yg N/l off the shores of
Dunkirk and Barcelona. On the contrary, 1974 concentrations are
much higher over the entire Basin. As a rule the ammonia
(Figure 5) and total nitrogen (Figure 6) concentrations follow
the same general pattern of distribution as the nitrate values,
with relatively low values in 1973 and 1975 compared with 1974.
The ammonia and total nitrogen show even lower concentrations in
1975 than in 1973 but the most western end of the Basin shows
some influences from the Central Basin during 1975 because there
are high increases in concentrations of total nitrogen not
reflected in either nitrate or ammonia. These higher values of
total nitrogen reflect increases in organic nitrogen for 1975 in
this area, possibly caused by inflows of rich organic waters from
the Central Basin and upwelling along the northern shore with
subsequent resuspension of bottom materials.
Table 4 further reflects the drastic change in 1974
compared to 1973 or 1975 for the different nitrogen compounds.
The total Basin means for the year for total nitrogen, nitrate
and ammonia are very different in 1974 from either of the other
two years. Nitrate, the most quantitatively available form of
nitrogen for biotic processes, shows the general trend of high
values in the spring and then decreases throughout the remainder
of the year to minimum values in the fall. An unusual trend is
seen with the ratios of total nitrogen with ammonia and nitrate
17
-------
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-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
yg N/I
50 - 100
101 - 150
151 - 200
201 - 250
>250
Figure 4. Lake Erie Eastern Basin mean epilimnion
nitrate-nitrite 1973-1975.
19
-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
ug/i
< 50
[ I 51 - 100
101 - 150
151 - 200
201 - 300
U^n >3oo
Figure 5. Lake Erie Eastern Basin mean epilimnion
ammonia 1973-1975.
20
-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
yg N/l
<350
351 - 400
- 450
451 - 500
501 - 600
Figure 6. Lake Erie Eastern Basin mean epilimnion
total nitrogen 1973-1975,
21
-------
concentrations over the three years. Nitrate and ammonia repre-
sent less than 5070 of total nitrogen during most cruises in 1973
and 1975, implying that organic nitrogen was a large component of
total nitrogen during these years. In 1974, however, ammonia and
nitrate concentrations represent much more of the total nitrogen
concentrations, indicating relatively less organic nitrogen during
this sampling year in relation to the other nitrogen forms.
The particulate organic carbon (POC) observed in the
surface waters of the Eastern Basin over the study duration was
relatively similar from year to year except for an increase seen
during the fall of 1974 (Table 4) which directly affected, the
total mean for that year. Annual trends (Figure 7) illustrated
that the shallower stations of the Basin displayed higher mean
values of POC and the deeper stations were characterized by lower
POC values. In 1975 the trend was higher concentrations observed
on the mid-lake stations and decreases in POC moving toward each
shore of the Basin. Furthermore, the 1975 cruises indicated that
entrainment from the Central Basin may have occurred along the
two shores entering the Eastern Basin. This was especially
apparent during the summer cruises (Great Lakes Lab, 1976) where
the western stations of the Basin showed definite increases. The
vertical profiles for POC (Great Lakes Lab, 1975; 1976) indicated
that there were numerous periods of mixing of the water column
(uniform POC) in 1974 with definite chemocline present during
1975.
The Basin trends for pH (Figure 8) were not very different
over the three years except in isolated areas of the Basin,
Because of this lack of difference between locations, pH was a
definite factor contributing to heterogeneity when a very small
alteration occurred during the sampling cruises. The general
three year trend was a decrease in pH from 8.6 in 1973 to 8.4 in
1975 over much of the Basin. pH at the eastern end of the Basin
was generally higher except for the water mass off Port Colborne
which showed a significantly lower pH in 1975 compared to the
other two years and the other areas of the lake. This may imply
a specific event occurred that didn't take place in 1973 or 1974.
The particulate inorganic carbon (PIC) showed annual
means that were similar between 1973 and 1974 (Table 4) with a
slight decrease in 1975. When higher values were observed during
the study period, they were generally associated with north-
western stations on the Canadian side of the Basin. In 1975 the
seasonal PIC values appeared to correspond to the pH trends of
low spring values and higher summer and fall values (Great Lakes
Lab, 1976). This is an expected trend with the carbonate forma-
tion resulting from high pH.
An important aspect of the data analysis was to observe
the constancy of water quality for each individual station from
year to year. Therefore, individual station water quality was
22
-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
mg C/l
<0.5
0.5
- 1.0
1.1 - 1.5
1.6 - 2.0
>2.0
Figure 7. Lake Erie Eastern Basin mean epilimnion
participate organic carbon 1973-1975.
23
-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
CD
I I
<8.3
8.4
8.5
8.6
8.7
Figure 8. Lake Erie Eastern Basin mean epilimnion
pH (standard units) 1973-1975.
24
-------
compared over the three years for each of the stations using
discriminant analysis to detect changes in that particular area
of the lake and furthermore identify these changes. The results
of the analysis (Table 5) indicated that eight of the 26 stations
were significantly different from themselves every year of the
three. An additional eight stations were significantly different
from themselves when 1974 water quality was compared with either
1973 or 1975. The water quality of these eight stations was not
different, however, when 1973 and 1975 were compared. As illus-
trated by the diagrams in Figures 2-8 and the data in Table 5,
the major parameters contributing to this variation between the
three years were the nitrogen compounds of ammonia and nitrate
and to a lesser extent total and dissolved phosphorus, dissolved
oxygen and the physical parameters of Secchi disc and temperature
Therefore, considering all the facts that have been presented so
far, it would appear that variation in the Eastern Basin of Lake
Erie over the three years of 1973, 1974 and 1975 is primarily
accounted for by variation in nitrogen.
Discriminant analysis was used on the physio-chemical
variables measured at each station over the three years to
differentiate specific water masses of the Eastern Basin based on
variability of the factors measured. The maps in Figure 9 depict
how the stations grouped together as distinct water masses for
each of the three years. Since the discriminant analysis tech-
nique identified the significant variables that caused the
separation of stations, it was possible to characterize the
different water masses for each year observed in Figure 9.
In 1973 there were four discrete masses of water. The
first represented by the eastern and southern shore stations
(1, 2, 3, 4, 8, 62, 64) showed lower Secchi disc readings than
any of the other areas. The northern shore stations (11, 12, 13,
14) displayed higher values of total nitrogen than the other
groups. The mid-lake stations (5, 6, 7, 9, 10, 16) exhibited
very high Secchi disc readings and higher dissolved oxygen
measurements. The westernmost group of stations showed lower pH
values than the other water masses.
The Basin was characterized by six discrete water masses
in 1974. The eastern stations (1, 2, 3, 4, 5, 62) were
described by high dissolved phosphorus values. The north shore
stations (11, 12, 13, 80) were characterized by lower values of
ammonia than other areas. The mid-lake stations (6, 9, 10, 14)
showed relatively low measurements of total nitrogen and higher
values of pH. The southern shore stations (7, 8, 15, 16, 22, 63,
64) displayed higher total nitrogen and lower ammonia values than
the other groups of stations. The western group of stations (17,
18, 19, 20) also characterized by lower total nitrogen values and
very low total phosphorus measurements defined the fifth area.
The last water mass, Station 21, exhibited very low dissolved
phosphorus and high pH compared to other areas of the Basin.
25
-------
Table 5
FOR WATER QUALITY
TO
Also included are
to variati
, RESULTS OF A DISCRIMINANT ANALYSIS
OF EACH EASTERN BASIN SAMPLING STATION COMPARED
ITSELF OVER THE PERIOD 1973-1975
the factors that contributed most (by percent)
on in each station over the three years
Station
Number
1973
1974
1975
(%) Factors
contributing to variation
1
2
3
4
5
6
1
8
9
10
11
12
13
U
15
16
17
18
19
20
21
22
62
63
6k
80
1971+
1974
1974
1975
1975
1974
1975
1971*
1 974
1973
J1975
Il975
[1975
19 75
1 975
1975,
1975
1 974
1974
1 974
1974
1974
1974
1974
1 974
1974
1974
(75%) DP + TP
(79%) COND + NH
(67%) TN
(87%) NH
(36%) SD + NH
(35%) NH
(30%) DO
(33%) NH
(98%) NH
(99%) TP
(89%) NH
(98%) DO
(88%) NH
(83%) TEMP + SD
(86%) NH + NO
(84%) NO
(96%) CHL + NO
(68%) TN + NH
(75%) TEMP + PH
(68%) DP
(59%) NH
(85%) DO
(99%) TN
(85%) TEMP + DO
(84%) SD
(25%) TN
(21%) SD
(33%) SD
(13%) SD
(04%) NO + SD
(05%) SD
(10%) NO
(01%) TN
(02%) DP
(01%) PH
(11%) DO
(02%) NH
(12%) PH
(17%) SD + DO
(14%) TN
(16%) SD
(04%) DO
(32%) NO
(25%) TEMP
(32%) NO
(41%) COND + DP
(15%) DP
(01%) SD
(15%) COND
(16%) DO
(100%) COND + NH + DO
H
No difference
Different from both years
Different only from indicated year
See Table 2 for list of
abbreviations
26
-------
Figure 9. Results of discriminant analysis for api1i mni on
physio-chemical variables measured in the Eastern Basin 1973-1975
Station groupings represent areas of similar water quality.
27
-------
In 1975 the sampling cruises identified four discrete
groupings of stations for the Eastern Basin. The first repre-
sented by Station 1 was characterized by extremely low mean pH
values of 7.9 which were much lower than found at any other
collection sites. The second grouping of stations (2, 3, 4, 5,
62) displayed lower conductivity measurements and slightly higher
nitrate values than the other discrete areas. The mid-lake and
northern shore stations (6, 7, 9, 10, 11, 12, 13, 14, 15, 16, 17,
18, 19, 20, 21, 63, 80) represented the third water mass which
was characterized by extremely low nitrate values throughout the
entire area. The last grouping of stations (8, 22, 64) was
characterized by extremely high nitrate measurements compared to
the previous water mass.
After analyzing each of the three years separately via
discriminant analysis, it was apparent that there were some
patterns that consistently reappeared each year. Therefore, the
epilimnetic data for all 26 stations for the three years combined
were analyzed with the discriminant procedure to obtain a picture
of the Basin for the full duration of the study. The discrete
water masses illustrated in Figure 10 are the result of this
analysis. For the three years combined, the variables were able
to discriminate five areas of the Basin that were different from
one another. The first water mass was represented by the
stations at the eastern end of the Basin and along the southern
shore (1, 2, 3, 4, 5, 7, 8, 62). This area of the lake was
discrete due to the combined effects of generally higher pH and
higher measurements of total phosphorus. As indicated previously,
Station 1 did show low mean pH values for 1975. These values
suggested the results of an isolated event and the ultimate
discriminating power of pH was not enough to separate this
station from the other stations of this particular group. The
second area of the Basin included several of the mid-lake
stations and the north shore stations (6, 9, 10, 11, 12, 13, 14,
80). This group was characterized by lower nitrate values than
the other water masses in the Basin. Station 11 had character-
istics that were similar to both the water masses just described.
Therefore, this station was located in the second group primarily
because of geographical location. The third discrete water mass
included the remaining mid-lake stations (15, 16, 63) and most of
the western stations of the Basin (17, 18, 19, 20). This water
mass was characterized by lower values of both total phosphorus
and nitrate compared to the other station groupings. Station 21
tended to isolate from the other stations similar to what was
observed from the 1974 data. This area of the Basin was discrete
from all others because of the high measurements for total
phosphorus observed. This station definitely showed effects of
Central Basin water entering the Eastern Basin. The last area of
the Basin which also showed effects of the Central Basin as well
as effects believed to be from effluents of Erie, Pa. was the
grouping of Stations 22 and 64. This mass of water was charac-
terized by lower Secchi disc readings and higher values of
28
-------
29
-------
nitrate than the other water masses of the Eastern Basin
described above.
Due to the presence of a thermocline, which was charac-
teristic of the deeper stations for much of the warmer seasons,
several of the parameters measured showed trends in the hypo-
limnetic waters independent of the epilimnion. These waters were
represented by the mid-hypolimnetic sample taken at each station
of every cruise. During unstratified conditions, the mid-
hypolimnetic sample was taken equally spaced between a bottom
sample and a sample 5 m below the surface.
Hypolimnetic dissolved phosphorus (Figure 11) showed a
gradual decrease over the three year period except for a slight
increase in the eastern end of the Basin in 1974. For every year
other than 1974 the deeper-water stations displayed consistently
higher measurements of dissolved phosphorus.
The trend of total phosphorus (Figure 12) for the hypo-
limnetic waters was similar in some respects to the dissolved
phosphorus concentrations. In general there was a consistent
decline in total phosphorus over the entire Basin with the high
values concentrating in the deeper waters, similar to dissolved
phosphorus. Data from 1975 showed that the deep mid-lake stations
appeared to be concentrating both the dissolved and total
phosphorus (Figures 11 and 12) of the Basin.
The nitrate measurements (Figure 13) of the hypolimnetic
waters again appeared to follow the nitrogen pattern for the
epilimnetic waters. There was a definite increase observed in
nitrate in 1974 compared to either 1973 or 1975. Furthermore,
the higher concentrations of nitrate were found in the deeper
areas of the Basin similar to phosphorus.
Discriminant analysis was done on all the offshore stations
(>25 m) to differentiate discrete masses of hypolimnetic waters.
There was little difference between the results of the three
years analyzed separately. Therefore, the analysis was performed
on the 13 offshore stations for all three years combined. The
results of this analysis (Figure 14) showed that the hypolimnetic
waters could be discriminated into four discrete water masses.
Furthermore, it appeared as though this separation of stations
had some relation to water depth. The first group of stations
(6, 7, 10, 16, 17, 18, 19) appeared to separate from the other
water masses primarily due to higher water temperatures caused by
shallower depths. The second group (9, 14, 15, 63) was a discrete
water mass and was characterized by the combined effects of lower
water temperature and higher values of total phosphorus. The
remaining two areas, Stations 20 and 21, respectively, represented
different water from the other two areas based primarily on higher
water temperatures intruding from the Central Basin and differen-
ces in total and dissolved phosphorus. These areas (Stations 20
30
-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
yg P/'l
3 - 5
6 - 7
UJ 8-9
10 - 12
'igure 11 Lake Erie Eastern Basin mean bottom
dissolved phosphorus 1973-1975.
31
-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
yg P/l
15-20
21 -
25 -
28 -
31 -
2k
27
30
Figure 12. Lake Erie Eastern Basin mean bottom
total phosphorus 1973-1975.
32
-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
yg N/l
50 - 100
| | 101 - 150
151 - 200
201 - 250
A 251 - 300
>300
Figure 13. Lake Erie Eastern Basin mean bottom
nitrate-nitrite 1973-1975.
33
-------
34
-------
and 21) were also discrete from one another due to Station 20
being characterized by lower values of total and dissolved
phosphorus and alternatively Station 21 displaying the opposite
trend of high dissolved and total phosphorus.
The Eastern Basin of Lake Erie showed a very unstable
thermal structure over the period of this three year study. The
classical scheme of thermocline formation was apparent in the
lake, usually in early June (Figure 15a and 16a). This thermo-
cline and its associated metalimnion showed a downward movement
as summer progressed, again in a classical fashion (Figure 15b
and 16b). The metalimnion, however, was not always complete over
the entire Basin during many of the summer cruises of the three
years (Figures 15c, 15d, 16c and 16d). With the break-up of this
metalimnion, usually resulting from heavy surface storms and
internal water movements, major upwelling occurred in the deeper
parts of the Basin as seen in Figures 15c and 16d. This
upwelling phenomena caused a great deal of mixing between cold
hypolimnetic water and the warmer epilimentic waters, resulting
in both a cooling of the epilimnion and a warming of the hypo-
limnion. Over the three year duration, the stratification
usually eroded to a unithermal condition by mid-October. After
the ice cover was gone (i.e. April) the unithermal condition was
again observed during cruises in this period.
The data collected on dissolved oxygen suggested that
levels fluctuated in the Eastern Basin on a seasonal basis.
During early spring, surface waters were saturated with oxygen.
Bottom waters during this period were also near saturation. As
the summer season progressed and stratification became more
pronounced, the hypolimnetic waters began to show a depletion of
oxygen. For example, during the last cruise of 1975 that
exhibited conditons of stratification, the hypolimnetic waters
were at levels of 50 to 65% saturation and the volume of the
hypolimnion had steadily decreased.
From temperature data collected during 1973, 1974 and
1975 field years, the hypolimnion boundaries were plotted and
then measured with a planimeter. Plots of hypolimnetic thickness
were used to calculate the hypolimnetic volume (Figure 17 -
Cruise 3 of 1975). Also, incorporating oxygen data using the
Winkler Standardized oxygen probe (American Public- Health
Association, 1971), hypolimnetic oxygen depletion was calculated.
During the period of thermal stratification in all three
years of the study the hypolimnion did exhibit oxygen depletion.
In order to determine the rate and level of this oxygen depletion,
a Mesolimnion Erosion Model (Burns and Ross, 1972) was constructed,
This model assumed:
1) Volumetric changes of the hypolimnion
caused by the loss or gain of water,
35
-------
Hld3Q
36
-------
STATION
13 16 63
(d)
17 August 1973
NORTH
60
METALIMNION BOUNDARY
Figure 16. Variations in thermal dynamics of Lake Erie
Eastern Basin as represented by temperature-depth
profiles on a transect of the cross-lake (south-north)
axis of the Basin (Stations 16, 63, 15, 14 and 13).
37
-------
38
-------
including dissolved oxygen to or
from the overlying tnetalimnion.
2) Exchange of water between the
metalimnion and hypolimnion,
including dissolved oxygen,
without volumetric changes in
either layer.
The results of this model construction for each of the three
years is presented in Tables 6, 7 and 8, respectively. The
summary of the Eastern Basin oxygen demand for the three years
of this study (Table 9) showed that the oxygen demand for 1973
was 0.012 g02/m3/day (4 July - 15 September). In 1974 the
oxygen demand for approximately the same time period (8 July -
9 October) was 0.011. In 1975 the oxygen demand for the Eastern
Basin was calculated to be 0.040 g02/tn3/day for the dates of
2 June - 18 September. This is in agreement with the oxygen
demand for 1974 (0.040) calculated between the dates of 4 June -
9 October. Since the oxygen demand was equal between 1973 and
1974 for similar time periods and the oxygen demand was also
equal between 1974 and 1975 for similar time periods, it was
assumed that there was essentially no change in oxygen levels of
demand over the three years.
In general the demand per unit area was very small for the
hypolimnion and it would appear that the hypolimnetic oxygen
demand has stabilized. Furthermore, the constant erosion of the
metalimnion during peak stratification periods (Figure 15c and
16d) was an added source of reoxygenation for the hypolimnion
waters, reducing chances of oxygen depletion.
Although functional or cause and effect relationships
cannot be determined from correlation analayses, the results do
indicate associated variables and how one parameter varies in
relationship to another parameter (Sokal and Rohlf, 1969).
There were a significant number of correlations, as expected from
a correlation matrix constructed of 11 variables with more than
300 observations. Table 10 illustrates the relationships between
variables that were highly significant (P^O.OOl). As expected,
the nitrogen compounds were all correlated with one another as
were total and dissolved phosphorus. Dissolved oxygen was
negatively correlated with temperature, Secchi disc, conductivity
and pH. The temperature-dissolved oxygen correlation would be
expected since increases in temperature classically reflect
decreases in oxygen. Secchi disc was strongly correlated with
temperature implying that the less turbid waters permit deeper
penetration of light and increased heating. Consequently, Secchi
disc was negatively correlated with dissolved oxygen because of
the temperature increases with increased water clarity. Conduc-
tivity was negatively correlated with dissolved oxygen because of
the positive relationship between conductivity and normal
39
-------
Table 6. SUMMARY OF 1973 HYPOLIMNETIC SURVEYS
OF THE EASTERN BASIN OF LAKE ERIE
Cruise
1
! 1
III
IV
V
VI
VII
VI 1 1
IX
X
Cruise
1
1 1
II 1
IV
V
VI
VII
VI 1 1
IX
X
Date
11-2? June
4-10 July
10-16 July
31 July - 6 Aug
15-20 August
11-15 September
1-5 October
8-11 October
22-26 October
8-12 December
Mean
02 Cone.
(mg/1)
8.03
7.50
6.09
6.25
6.10
5.62
Area Volume Total Heat
(km2) (km3) (kcal x 1012)
INCOMPLETE DATA
3048.3 69.27 819.5
2865.8 55.65 631.1
2541.0 53.69 642.1
2581.0 48.99 553.1
INSUFFICIENT TEMPERATURE DATA
2322.9 33.82 304.4
1615-4 21.11 145.2
LAKE NON-STRATIFIED
LAKE NON-STRATIFIED
Mean Mean 02 Grad.
Temp. Across Mesolimn.
(°C) (gOz/m*)
INCOMPLETE DATA
11.83 0.219
11.34 0.331
11.96 0.698
11.29 0.522
INSUFFICIENT TEMPERATURE DATA
9.00 0.779
6.88 0.861
LAKE NON-STRATIFIED
LAKE NON-STRATIFIED
Total 02
(kg02 x 106)
556.2
417.4
327.0
306.2
206.3
118.6
Mean Temp. Grad.
Across Mesolimn.
(°C/m)
1 .94
1.81
1.96
2.24
2.07
2.22
40
-------
Table 7. SUMMARY OF 1974 HYPOLIMNETIC SURVEYS
OF THE EASTERN BASIN OF LAKE ERIE
Cruise
1
II
1 II
IV
V
VI
VI 1
VI 1 1
IX
X
XI
XI 1
XI 1 1
XIV
XV
XVI
Cruise
i
1 1
n I
IV
V
VI
VII
VI II
IX
X
XI
XI 1
XIII
XIV
XV
XVI
Date
21 May - 2 June
4-7 June
18-22 June
8-11 July
26-30 July
6-9 August
12-16 August
6-9 September
16-21 September
1-9 October
23-27 October
5-11 November
19 Nov - 5 Dec
Mean
02 Cone.
(mg/1)
11.28
10.49
9-13
7.53
7.44
6.35
6.66
7.02
6.82
5.88
Area Volume Total Heat
(km2) (km3) (kcal x 1012)
MECHANICAL FAILURE
MECHANICAL FAILURE
MECHANICAL FAILURE
INSUFFICIENT TEMPERATURE DATA
3956.1 107.80 960.5
2411.9 43-55 421.6
2772.4 49.48 617.5
3666.8 59.67 818.1
2572.1 47.92 642.1
2923.7 50.35 687.3
2816.9 40.10 394.6
1882.4 25.88 249.5
1108.1 13.52 131.4
INSUFFICIENT TEMPERATURE DATA
485.1 4.37 42.5
LAKE NON-STRATIFIED
Mean Mean 02 Grad.
Temp. Across Mesolimn.
(°c) (go2/m*)
MECHANICAL FAILURE
MECHANICAL FAILURE
MECHANICAL FAILURE
INSUFFICIENT TEMPERATURE DATA
8.91 0.180
9.68 0.090
12.48 0.440
13-71 0.610
13.40 0.410
13.65 0.460
9.84 0.350
9-64 0.350
9-72 0.800
INSUFFICIENT TEMPERATURE DATA
8.85 2.880
LAKE NON-STRATIFIED
Total 02
(kg02 x 106)
1216.0
456.8
451.8
449.3
356.5
319.7
267.1
181.7
9?-. 2
29.8
Mean Temp. Grad.
Across Mesolimn.
(°C/m)
0.80
0.77
1.26
1.54
2.14
1.73
1.68
1.67
1.30
2.40
41
-------
Table 8. SUMMARY OF 1975 HYPOLIMNETIC SURVEYS
OF THE EASTERN BASIN OF LAKE ERIE
Area Volume Total Heat Total 02
Cruise Date (km2) (km3) (kcal x 1012) (kg02 x 106)
1
II
1 1 1
IV
V
Cruise
9-12 April
2-5 June
25-29 July
15-18 September
7-9 December
Mean
02 Cone.
(mg/1)
LAKE
3764.
2932.
2443.
LAKE
Mean
Temp.
NON-STRATIFIED
7 75.2 458.7 925.0
6 39.4 295.5 350.7
1 34.0 316.2 275.4
NON-STRATIFIED
Mean 02 Grad. Mean Temp. Grad.
Across Mesolimn. Across Mesolimn.
(g02/m't) (°C/m)
I LAKE NON-STRATIFIED
II 12.3 6.1 0.19 1-43
III 8.9 7.5 0.37 2.45
IV 8.1 9.3 0.26 2.70
V LAKE NON-STRATIFIED
42
-------
Table 9. HYPOLIMNETIC OXYGEN DEMAND
IN THE EASTERN BASIN OF LAKE ERIE 1973-1975
Demand/Unit Demand/Unit Demand/Unit
# Area Volume Area
Year Date Days (g02/m2/day) (g02/m3/day) (mmole02/m2/day)
1973 A July - 15 Sept 99 0.23 0.012 7-188
A June - 9 Oct* 127 0.95 0.040 29.688
8 July - 9 Oct** 93 0.18 0.011 5.625
1975 2 June - 18 Sept 108 0.76 0.040 23.750
" The greater demand over this time period for both per unit area
and per unit volume is believed to be a function of the much
higher volume, area, total heat content and total oxygen in the
hypolimnion during early spring cruises.
See summary tables 7 and 8.
Demand during this time period used for comparison with 1973
results.
43
-------
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biological activity. Increased biological activity (i.e. plank-
ton blooms and decomposition) will result in net reduction of
dissolved oxygen. One further connection in this relationship
was that conductivity was positively correlated with the three
nitrogen forms.
PHYTOPLANKTON
The detailed listings of phytoplankton species observed
in the Eastern Basin of Lake Erie from 1973 to 1975 are contained
in the Annual Reports (Great Lakes Laboratory, 1974; 1975; 1976).
There were 46, 44 and 62 species observed each year for
1973, 1974 and 1975, respectively. Nearly 50% of the species
identified each year belonged to the Chlorophyta. Over the
duration of the study, however, the Chlorophyta was not the dominant
contributor to the group composition of biomass (Table 11). The major
contributions to total biomass were the Chrysophyta in 1973 and
1975 and the Cryptophyta in 1974. The Chlorophyta, however, were
consistently one of the major groups contributing to total biomass.
The algal biomass and its group composition for the three
years of the study for the Eastern Basin are summarized in Table
11 as cruise averages. Considering the total mean biomass, it
is quite evident that there is a definite decrease from 1973 to
1975. The Cyanophyta, which were consistently one of the larger
contributors to total biomass in 1973 and 1974, displayed a sharp
decline in 1975. The Chlorophyta and Chrysophyta each displayed
relatively similar levels for the respective groups in 1973 and
1975 but exhibited decreases of up to 50% for their group
composition to total biomass in 1974. On the other hand, the
Cryptophyta group contribution in 1974 doubled compared to this
group's contribution in both 1973 and 1975.
The horizontal distribution of phytoplankton biomass in
the epilimnetic waters of the Eastern Basin during 1973, 1974
and 1975 are shown in Figure 18. The major areas of activity in
1973 appeared to be in the midbasin region of the lake, the
southwestern end of the Basin (influences from the Central Basin)
and the waters represented by the southeastern stations. The
mean distribution of phytoplankton for 1974 again showed high
activity at the eastern end of the Basin and a pulse in the
western end, The midbasin activity shifted slightly and was
now concentrating more on the northern side of the Basin. In
general the mean biomass ranges were relatively consistent between
1973 and 1974. The picture in 1975, however, was very different.
Again there was a pulse of activity at the western end of the
Basin indicative of Central Basin influences. This pulse,
however, was approximately half of the concentration of phyto-
plankton observed in 1973. The midlake and eastern stations
showed a sharp decline in mean biomass in 1975. There was a
pulse noted in Long Point Bay which was not much different from
45
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LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
3 mrt / 3
10'mg/m
I 0.5 - 1.0
Figure 18. Lake Erie Eastern Basin mean horizontal
distribution of total phytoplankton biomass 1973-1975
47
-------
the previous two years. Another area of higher biomass concen-
tration in 1975 was off the shores of Barcelona,
The seasonal biomass fluctuation for the three years
(Figure 19) generally indicated that a small pulse of activity
was reached in the spring and a maximum peak attained in the
fall (September and October) with minimum biomass observed during
the summer. It must be noted that in both 1973 and 1975 there
was a very large increase in biomass in December. This increase
may have been a false indicator though, since a much smaller
number of stations was sampled during these cruises. The
seasonal variation of chlorophyll-a, primary production and
biomass by group composition for tKe epilimnion are also shown
in Figure 19. Chlorophyll-a tended to follow the seasonal
patterns for total biomass But primary productivity showed some
discrepancies.
One biomass maximum was observed in 1973 in mid-September
when the phytoplankton concentration reached 1.62 g/m3. This
peak was composed primarily of Chrysophyta, Cyanophyta and
Cryptophyta. The chlorophyll-a showed a lag period before
reaching its peak (6.5 mg/m3) in early October. The Cryptophyta
dominated during this period. As the diatoms (Chrysophyta)
became the dominant group, late in the fall, the chlorophyll-a
showed a definite decline.
Two biomass maxima were observed in 1974, probably due to
earlier cruises scheduled during this field year. A smaller
maximum (1.55 g/m3) was displayed in the spring (late May - early
June) with the Cryptophyta composing the majority of the biomass.
The Cryptophyta continued to dominate through the summer until
early September. Chlorophyll-a also showed a peak (7.1 mg/m3)
during the spring maxima and tKen declined through the summer.
Primary productivity, however, did not show its first peak of
1974 until late July (15.2 mg C/m3/hr), well after the peak
spring biomass. During this peak in productivity, the Crypto-
phyta were still the dominant group but the Chlorophyta had also
increased.
The fall maximum for phytoplankton biomass (3.72 g/m3) was
observed in mid-September and the major groups contributing to
this were Cyanophyta and Pyrrhophyta. The peaks of both chloro-
phyll-a (7.1 mg/m3) and primary productivity (16.2 mg C/m3/hr)
were similar, but both lagged behind the peak biomass estimates.
Again, similar to the early peak in chlorophyll and productivity,
as well as the peak in 1973, for both time periods the Crypto-
phyta were the dominant group and as the Chrysophyta increased,
both productivity and chlorophyll declined.
Two peaks of phytoplankton biomass were observed in 1975
but these were much smaller in magnitude than the peaks observed
in 1973 or 1974. The first peak occurred in the early spring
48
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(0.75 g/m3) and was represented almost totally by Chrysophyta.
Similar with the two previous years, because the diatoms were the
dominant group, the chlorophyll and primary productivity did not
show any peaks during this time period. Primary productivity did
show a slight peak (10.0 mg C/m3/hr) in early June which again
corresponded to the dominance of the Cryptophyta,
The second small peak in phytoplankton biomass (0.69 g/m3)
was noted in mid-September (ignoring the December peak for
reasons stated previously). Primary productivity (19.8 mg C/m3/hr)
and chlorophyll (5.9 mg/m3) also peaked during this time period.
The major group contributing to this biomass was the greens
(Chlorophyta).
The apparent trend in primary productivity over the three
years was for a slight increase in the Basin mean from 10.3
mg C/m3/hr in 1973 to 11.7 mg C/m3/hr in 1975. This increase
paralleled an increase in the Chlorophyta group over the three
years (Figure 19). The Cryptophyta also increased slightly when
comparing 1973 to 1975 which again parallels with the increase
in productivity. The 1974 total dominance by the Cryptophyta
(Table 11 and Figure 19) may have been an artifact of our
sampling schedule. One of the major peaks of Cryptophyta
occurred in late October of 1974, There were no comparable
cruises in 1973 or 1975 to detect this peak.
The phytoplankton data were analyzed by stepwise multiple
regression analyses to statistically identify relationships
between the individual phytoplankton groups and total biomass,
primary productivity, and chlorophyll. From the results of these
analyses, much of the variation in total phytoplankton biomass
was able to be significantly explained by a few of the major
groups comprising the total biomass each year. Of the total
variation in biomass for 1973 which ranged from 0.66 g/m3 to
1.62 g/m3, 5270 could be explained by fluctuations in the Pyrrho-
phyta (dinoflagellates) and 26% by fluctuation in the Cyanophyta
(bluegreens). The bluegreens became much more dominant during
the late summer of 1974 and they accounted for 48% of the varia-
tion in biomass, which ranged from 0.44 to 3.72 g/m3 during this
year. The dinoflagellates accounted for 21% of the variation.
Thus, in 1973 and 1974 the dinoflagellate and bluegreen groups
accounted for 78% and 70% respectively in total biomass variation.
The roles of each group were reversed, however, between the two
years.
The Chrysophyta became very important in 1975 compared to
the other two years because they accounted for 4270 of the varia-
tion in total biomass this year. The bluegreens explained 16%
of the biomass variation and the greens accounted for 1470. Thus,
the dinoflagellates and bluegreens had significantly decreased
in terms of their contribution to total biomass and the diatoms
(Chrysophyta) had become more powerful in controlling the total
50
-------
biomass variation over the year. Furthermore, the greens were
more important in 1975 than either of the other two years.
Munawar and Burns (1976) found that relationships between
variables changed significantly with the time of the year.
Therefore, looking at relationships of variables contained in
data sets covering an entire sampling year sometimes may over-
shadow the true picture. The data were therefore split into
the three seasonal sets of spring, summer and fall (Table 1),
and analyzed for each year of the study.
In the spring of 1974 flagellates explained 95% of the
variation in total phytoplankton biomass. The spring season was
sampled much earlier in 1975 and indicated that the diatoms
explained 88% of the variation in total biomass in April of this
year.
The summer seasons for the three years also showed numerous
variations. The Pyrrhophyta explained 87% of the total biomass
variation in 1973 as compared to 67% and 22% being explained by
Cyanophyta and Pyrrhophyta, respectively in 1974. In 1975 the
Chlorophyta were the dominant summer group explaining 56% of the
variation in total biomass. The flagellates explained approxi-
mately 29% of this variation.
The fall sampling cruises revealed that diatoms consistent-
ly dominated in all three years and explained 43%, 79% and 49%
of the variation in total phytoplankton biomass for 1973, 1974
and 1975 respectively. In 1973 the Cyanophyta and Pyrrhophyta
explained an additional 38% in the total biomass variation while
in 1975 the Cyanophyta and Chlorophyta accounted for 48% of the
biomass variation.
Therefore, the information from all three years show that
the Chrysophyta are the most important group early in the spring
(1975) followed by dominance of the Cryptophyta and flagellates
(1974) later in the spring and into early summer. The summer
season biomass appears to be controlled by the Pyrrhophyta and
Cyanophyta with the Chlorophyta becoming more abundant in 1975.
The fall season again shows the dominance of the Chrysophyta in
controlling total biomass variation.
In the analyses of the dependent variables of primary
productivity and chlorophyll, there were not many significant
relationships seen with the phytoplankton groups. The Chloro-
phyta did explain 33% of the variation in primary productivity
over the three years. This would be expected since the Chloro-
phyta are very photosynthetically active (Munawar and Burns,
1976). Primary productivity as an independent variable explained
15% of the variation in chlorophyll over the three years.
51
-------
The chlorophyll values for each year varied to a great:
extent between stations of any cruise. Because there were con-
siderable depth ranges between the stations, the chloropnyll
values were placed into two groups, inshore stations (<25 in)
and offshore stations (>25 m). As a result of these groupings
(Tables 12, 13 and 14) there was a difference observed between
the shallow and deeper areas. The shallow stations consistently
showed higher mean chlorophyll values than the deeper stations.
There was no significant difference, however, between the two
means for any year due to the high standard deviations,
Phytoplankton data from the three years were compared to
the physio-chemical variables to determine any significant
relationships. Over the total three years the general trend in
the Basin was a negative correlation between the phytoplankton
groups and both pH and specific conductance. During this same
period, the phytoplankton were positively correlated witn
dissolved oxygen. There were no significant correlations between
the groups and any of the nutrients for the comparison of the
total three year data set. When the data sets were broken up
into yearly and seasonal comparisons, however, several strong
correlations between nutrients and the phytoplankton were
apparent.
The Chrysophyta showed a strong positive relationship witn.
nitrates both in 1973 and 1975. In 1975 this relationship was
observed in the spring and fall when the diatoms were most
numerous. The diatoms also displayed a positive correlation witn.
total nitrogen in the spring of 1975 and generally showed a
negative relationship with temperature over all tnree years. In
general, in their seasons of abundance, the diatoms were positive-iy
correlated with dissolved oxygen.
The flagellates showed a strong positive correlation wluh
total nitrogen in both the summer of 1973 and the summer of 1974,
They also were positively correlated with dissolved oxygen for
several of their peak seasons over the three years.
The Chlorophyta showed a high positive correlation with
temperature during the summer season of all three years. In
1974 they were positively correlated with nitrate and in 1975
showed a negative relation to this nutrient. The greens were
also negatively related to dissolved oxygen during tneir peaK
growth seasons in 1974 and 1975.
The Pyrrhophyta were not significantly correlated with
any nutrients but did show a negative correlation with dissolved
oxygen in 1974. The Cyanophyta showed a positive relationship
with total phosphorus and temperature in 1975 and were negatively
correlated with dissolved oxygen both in 1973 and 1975.
Chlorophyll, which is often used as a measure of biomass,
52
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Table 12. INSHORE-OFFSHORE COMPARISON OF
CHLOROPHYLL-a^ (CORRECTED) MEAN CONCENTRATIONS
(mg/m3) IN THE EASTERN BASIN OF LAKE ERIE
JULY - DECEMBER 1973
Cruise Date Mean SD <25m SD >25m SD
if 4-10 2.75 1.49 3.35 1.62 2.04 0.95
July
11! 10-16 4.80 2.30 5.60 2.33 3-66 1.83
July
31 July - 4.74 1.63 5-29 1.94 4.14 0.99
6 August
15-20 4.30 1.17 4.45 1.41 4.10 0.83
August
VI 11-15 3.76 1.73 4.15 2.08 3-35 1-30
September
VII 1-4 6.59 1.92 7.23 2.40 5.89 0.86
October
VIII 8-11 6.40 1.35 6.38 1.39 6.48 1.37
October
22-26 6.44 2.70 7.08 1.22 5-75 3.65
October
8-12 3.48 1.08
December
Year 1973 4.90 2.23 5-37 2.20 4.38 2.16
53
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Table 13. INSHORE-OFFSHORE COMPARISON OF
CHLOROPHYLL-a_ (CORRECTED) MEAN CONCENTRATIONS
(mg/m3) IN THE EASTERN BASIN OF LAKE ERIE
MAY - DECEMBER 1974
Cruise Date Mean SD <25m SD >25m SD
21 May - 7.11 5.48 7.30 5-9** 6.88 5.13
1 June
VI 18-22 4.97 2.58 4.60 3.30 5.35 1.39
June
VIII 26-30 3.33 1.78 3.90 2.08 2.60 0.97
July
XI 6-9 4.25 1.32 4.65 1.47 3.78 0.97
September
XIV 23-27 7-14 1.49 7.21 1.21 7.03 1.92
October
XVI 19 November - 3.91 1.23 4.35 1.35 3.39 0.85
5 December
Year 1974 5.11 3.12 5-36 3-28 4.80 2.90
54
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Table 14. INSHORE-OFFSHORE COMPARISON OF
CHLOROPHYLL-a^ (CORRECTED) MEAN CONCENTRATIONS
(mg/m3) IN THE EASTERN BASIN OF LAKE ERIE
APRIL - DECEMBER 1975
Cruise Date Mean SD <25m SD >25m SD
9-12 3.2k 1.76 3.78 2.11 2.71 1.18
Apr! 1
11 2-5 2.46 0.82 2.59 0.95 2.29 0.63
June
111 25-29 2.98 1.05 3.51 1.05 2.36 0.64
July
lv 15-18 5.88 2.09 6.48 2.71 5.19 0.51
September
7-9 3.63 0.83 3.77 1.02 3.51 0.66
December*
Year 1975 3.66 1.90 4.06 2.22 3.21 1.35
* PARTIAL CRUISE (15 stations)
55
-------
was the only phytoplankton parameter that displayed any signifi-
cant correlation with dissolved phosphorus. In 1973 and 1974 a
strong positive relationship existed between these two variables.
In 1973 chlorophyll was negatively correlated with total nitrogen
and in 1975 it was negatively correlated with nitrate and
positively to ammonia.
The mean phytoplankton group composition on a basinwide
scale for the five groupings of stations (Figure 10) derived
from discriminant analysis of the physio-chemical variables is
shown in Figure 20. In general the southern shore stations and
western end of the Basin showed a higher percentage of diatoms
over the three years, whereas the midlake and northern shore
stations possessed the highest percentage of bluegreens. Station
21 didn't really show a dominance of any one group of phytoplank-
ton. Figure 20 indicated that the dinoflagellates were very
high in number at the eastern end of the Basin and along the
Canadian shore.
ZOOPLANKTON
The detailed listings of species of crustacean zooplankton
encountered in the Eastern Basin of Lake Erie from 1973 to 1975
are found in the Annual Reports (Great Lakes Laboratory, 1974;
1975; 1976). For purposes of this report, zooplankton cells is
equated with zooplankton numbers.
The horizontal distribution of crustacean zooplankton in
the waters of the Eastern Basin during 1973, 1974 and 1975 are
shown in Figure 21. The same trend exhibited by the phytoplankton
was also displayed by the zooplankton mean number over the Basin
for the three years of the study. There was a much higher level
of total numbers seen in 1974 compared to the other two years.
The general range in the Basin in 1974 was from 7-12 x 10" #s/m3
compared to 3-9 x 10* #s/m3 in 1973 and 3-7 x 10* #s/m3 in 1975.
In 1973 the higher concentrations of zooplankton appeared
to be in the area, of Long Point Bay and in the waters off the
south shore near Dunkirk. In 1974 the eastern end of the Basin
showed extremely high numbers of cells as did the area of Dunkirk
again. The distribution of organisms in 1975 was similar in
pattern to 1974 except that the higher concentrations off Dunkirk
had shifted slightly west toward Barcelona. There was also a
slight influence from the Central Basin and the Harbor of Erie
noted at Stations 22 and 64.
The yearly trends in zooplankton numbers for the three
years and the associated group composition are illustrated in
Table 15. Again, as depicted by the horizontal distributions,
there was a large increase in mean total number (8.43 x 101*) for
1974 compared to either of the other two years. There appeared
to be a slight decline in the three adult groups of zooplankton
56
-------
57
-------
LAKE ERIE
NUTRIENT CONTROL
PROGRAM
EASTERN BASIN
3 - 5
I I
8 - 9
10 - 12
Figure 21. Lake Erie Eastern Basin mean horizontal
distribution of crustacean zooplankton biomass 1973-1975
58
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(Cladocera, Calanoida and Cyclopoida) over the three years and an
increase in the copepod nauplii. This trend may have been an
artifact of the sample analysis, however, since the expertise in
taxonomy of the nauplii had improved from 1973 to 1975 . Therefore
when one considers only the adult group composition, there was
essentially no change between the three years.
The seasonal patterns of mean total number and group
composition (Figure 22) showed that the peak of zooplankton
numbers usually occurred in late June and early July of all
three years. During this season the cyclopoids and cladocerans
were represented almost equally in number. The calanoids, on
the other hand, only represented 1 to 13% of the total cell
number. Over the three year seasonal trends, the calanoids
never were dominant and usually reached their peak in the irdddle
of the summer season (late July - early September).
The copepod nauplii generally displayed an early peak in
the spring (1974 and 1975) and then showed a progressive decline
through the remainder of the year. This group never represented
less than 20% of the total zooplankton and reached maximums of
over 607o of the total number during the spring peaks.
There was a strong negative correlation exhibited between
the cladocerans and cyclopoids when each was compared to phyto-
plankton biomass. There were not many significant correlations
between the zooplankton groups and the phytoplankton groups. The
calanoids, however, did show a positive correlation with diatoms
and bluegreens. Although not significant, there was generally
a negative relationship between any one of the zooplankton groups
and total phytoplankton biomass.
There were also several relationships between the zoo-
plankton groups and some of the physio-chemical variables. Thp
calanoids were negatively correlated with pH and specific
conductance and positively related to dissolved oxygen. The
cladocerans were also negatively correlated with conductivity.
Furthermore, they were positively correlated with the nutrients
of ammonia and total phosphorus. The cyclopoids were positively
correlated with temperature.
The mean group composition of zooplankton on a basinwide
scale for the physio-chemical station groupings (Figure 10) is
shown in Figure 23. The southern shore stations definitely
showed dominance of Cladocera over the three years studied. The
midlake and most western stations displayed dominance of Cyclo-
poida and the smallest proportion of Calanoida. The northern
shore stations were dominated by Cyclopoida but had a higher
number of cladocerans, as did Station 21.
60
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62
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EASTERN BASIN BENTHIC COMMUNITIES
The species listings for the benthic macroinvertebrates
encountered in the Eastrn Basin of Lake Erie from 1973 to 1975
are detailed in the Annual Reports (Great Lakes Laboratory, 1974;
1975; 1976). The total number of species encountered each year
were 53, 68, and 65 in 1973, 1974, and 1975 respectively. The
oligochaetes and amphipods comprised 81% of the total numbers
of organisms in 1973. In 1974, the oligochaetes, amphipods and
fingernail clams (Sphaeriidae) accounted for 89% of the total
numbers. These same three groups comprised 82% of the total
organismal numbers in 1975.
The break-down of percent group composition for the major
groups observed in the Eastern Basin for each station over the
duration of this study is illustrated in Table 16. Additionally
the mean number of species observed and the mean total number of
organisms (#/m2) for each station is also shown. The total
number of organisms ranged from a low of 1393.9/m2 at Station 11
to a high of 29,138.0/m at Station 19. Considering the general
patterns within the Basin, the Canadian Stations (11, 12, 13,
and 80) displayed fewer total numbers of organisms than most
other areas but showed higher mean numbers of species encountered.
The southern midlake stations and western stations (6, 7, 10,
16, 19, 20, 21) consistently produced a high mean count of total
organisms and except for Stations 10 and 19, displayed a relative-
ly high number of species present, The eastern Stations (1, 2,
3, 4, 5, 62) showed a much lower number of total organisms than
the midlake and western stations but displayed extremely high
mean numbers of species encountered (14-18).
The group compositions for the individual stations (Table
16) showed some interesting trends. The Oligochaeta were the
major group at most stations except the northern shore stations.
The Amphipoda, as a group, were much more numerous at the mid-
lake and northern stations while the Sphaeriidae were high both
on the Canadian side of the Basin and at the eastern end. The
Nematoda and Chironomidae showed a similar pattern of higher
numbers on the northern and eastern stations. The Isopoda were
most numerous on Stations 6, 11, 12, 13, 17, and 21.
Ordination of the benthic data collected for each year of
this project showed very little variation between years in the
benthic environment of the Eastern Basin. Therefore, ordination
of the raw benthic counts for each station on each cruise over
the three year duration was performed to produce a composite
picture of the different community types in the Eastern Basin of
Lake Erie. Plots of the stations along three ordination axes
(X, Y, and Z) are given in Figure 24. These plots showed that
most variation among the stations was along the X and Y axes.
There was much less scatter along the Z-axis and this additional
information contributed little to the final groupings of stations.
63
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Discriminant analysis of the community ordination coordinates
(x, y, and z) produced the grouping of stations seen in Figure
25. These groupings were very similar to the ordination results
(Figure 24) providing an additional check on our separation of
stations. This information plus the community ordination results
(Figure 24) and the actual listings describing the major species
for each station during the study period were critically examined
to derive community types within the Eastern Basin. To
characterize the Basin by different community types, which may
offer additional information concerning water quality, many of
the discrete areas of the Basin were described in terms of "rarer"
species (Table 17) in addition to the dominant worms and crusta-
ceans. This description, which follows, is illustrated via
Figure 24 and Table 17.
The most eastern area of the Basin represented by Stations
2 and 62 displayed a benthic community comprised of oligochaetes,
both mature and immature, and bivalves. P^A^Ld-ium was the
numerically dominant bivalve in this area along with the presence
of the oligochaetes Pe.£o4co£ex ^eAox and Potamothti-Lx. v
-------
67
-------
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discrete. The major community components were the isopod A
and the oligochaet P. ve.jdov&kyi. In species' lists this station
showed some resemblance to the northern shore stations (especially
11) and the area represented by Stations 1, 3, 4, and 5. Station
6 discriminated itself from Station 11, however, by the lack of
Chironomidae and similarity from Stations 4 and 5 by higher
numbers of isopods and lack of the gastropod ValLvata,
The area of Long Point Bay (Station 80) was also comparably
different from other areas of the Basin (figure 24). This
habitat was almost totally dominated by the bivalve-amphipod
grouping with Bphamfi-ivim, Pontopo/ie.i>itui£ and
Pe.£o.ico£e.x as very numerous. Additionally, this area had a high
number of ostracods and Tub-t^ex tublfinx,
The western end of the Basin (7, 16, 17, 20, and 21)
indicated the dominance again of the amphipods and bivalves,
P, a^-in and P^-6-ccf-cam, with fewer oligochaetes observed.
Spkadsi^um also was quite numerous. The isopod A-4e££tu was
represented at all the stations and several of the stations
showed the occurrence of the oligochaet Pa£o4co£ex in relatively
high numbers.
The area of the Basin off Erie, Pa. (Stations 22 and 64)
was dominated by the oligochaetes LLmnodtitLu.t>, Aaiod^-Llu.^ and
Potamothn.4.x.. The chironomids were also present in relatively
high numbers in this area. The isopod vUe££u4 occurred at
Station 64 and the bivalves SpftaeA-ium and P-i-i-id-turn at Stations
22 and 64 respectively.
Similar to Station 8, Station 19 was completely separated
from all other areas of the lake in the ordination plot (Figure
24). This station was characterized almost completely by
Tufa-t^ex tubx^ex and a large majority of immature oligochaetes
many of which were L. This area probably showed the
highest concentration of oligochaetes in the entire Basin.
69
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SECTION 6
DISCUSSION
The basinwide epilimnetic distributions of the major
chemical nutrients described in this report illustrate that in
general the Eastern Basin phosphorus concentrations did not vary
significantly. Total and dissolved phosphorus displayed seasonal
fluctuations but remained relatively constant between the three
years. Total phosphorus ranged annually from a mean of 22.3 to
30.6 ygP/1. Dissolved phosphorus showed a slight increase from
annual means of 4.3 ygP/1 in 1973 to 7.4 ygP/1 in 1975. Concen-
trations of these forms of phosphorus were comparable to values
observed in 1970 (Burns, 1976). The 1970 study illustrated ranges
for total phosphorus in the Eastern Basin of between 18 and 32
ygP/1 depending upon season of the year. The 1970 study didn't
measure dissolved phosphorus but did report particulate phosphorus
(total P - dissolved P), These values ranged from approximately
9 to 18 ygP/1 for the Eastern Basin epilimnion over a yearly
cycle. The range in particulate phosphorus for the three year
study described here was approximately 15 to 26 ygP/1, a slight
increase over 1970. Due to the large standard deviations
associated with the means of the three year study, no real diff-
erences in phosphorus concentrations can be demonstrated between
the 1970 results and those from the GLL 1973-1975 survey.
Changes in concentrations for several epilimnetic nitrogen
forms contrasted sharply with those for phosphorus. All nitrogen
compounds displayed an increase in 1974 as contrasted with 1973
and 1975. This change was most notable for ammonia which varied
from a Basin mean of 73 ygN/1 in 1973 to 203 ygN/1 in 1974. In
1975 this nutrient decreased again to a mean of 38 ygN/1, very
close to the mean value of 28 ygN/1 observed in 1970 (Burns, 1976)
The discriminant analysis of physio-chemical variables over
the three years for each station (Table 5) further illustrated
the variation for ammonia concentrations. The variations in
nitrogen were primarily the result of annual fluctuations in
ammonia concentrations possibly caused by localized inputs into
the Basin. Most of the stations that showed variability due to
ammonia (e.g. 4, 8, 11, 13) were located in the vicinity of a
major tributary. Furthermore, Stations 18 and 21 also showed
variability in ammonia that was the result of entrainment from
the Central Basin (Great Lakes Laboratory, 1976).
70
-------
In the past, ammonia was usually relatively constant over
a yearly cycle in this system and the nitrate-nitrite concentra-
tions showed the greater variations (Burns, 1976). In the present
study relatively low levels of ammonia were seen throughout the
year (except 1974) and high levels of nitrate-nitrite in the
spring were followed by decreased levels in the summer and fall
(Table 4). Furthermore, the phytoplankton annual biomass
reflected the above. The higher ammonia levels seen in 1974 may
have produced increased biomass levels of phytoplankton.
The preceding observations can be explained by the
following. Ammonia is the_preferred form of nitrogen for phyto-
plankton uptake (Healy, 1973). Thus the ammonia increases in
1974, due to localized inputs, increased the phytoplankton biomass.
Furthermore, it appeared that the greater biomasses of phytoplank-
ton being produced in later summer and early fall (Figure 19)
required more ammonia than was available with the result that
nitrate was utilized and decreased in the epilimnion as observed
(Table 4). The large decrease in ammonia concentrations in 1975
may have also been related to the change in bluegreen algae con-
centrations. The 1973 and 1974 ammonia values were relatively
high compared to those reported by Burns (1976). As stated above
the higher values during 1974 were compounded by localized inputs
of ammonia. For both these years, however, bluegreen ^Igae
comprised a mean of approximately 12% of the total phytoplankton
biomass. The ammonia could remain in adequate supply because of
nitrogen fixation by the blue-green algae (Howard et al., 1970)
and their subsequent decomposition resulting in ammonia regeneration
The bluegreens were largely absent in 1975 when the strong local
inputs of ammonia were not observed (Figure 5). Thus ammonia
levels were much lower and in close agreement with 1970 values
(Burns, 1976).
The observed dynamics of nitrogen and phosphorus in this
system over the three year duration raised an additional question.
What nutrient is limiting in the Eastern Basin? In most cases a
nutrient becomes limiting under a specific set of circumstances
including the presence of certain phytoplankton species and the
appropriate ratio of mineral nutrients in the system. Consequently,
when the equilibrium is upset by excessive inflows of a particular
essential nutrient, the ratios of the more important factors
(phosphorus, nitrogen, etc.) can be disrupted. As a result species
may change, and eventually a new steady state is obtained where
one limiting factor is replaced by another. Titman (1976) found
this to be the case with two diatom species and the ratio between
silica and phosphate.
For years phosphorus has been characterized as the limiting
factor in Lake Erie (Vollenweider, 1968; International Lake Erie
Water Pollution Board, 1969; Dobson et al., 1974). Excessive
stimulation of phytoplankton productivity and the trend towards
more eutrophic conditions within Lake Erie are believed to have
71
-------
been the result of increases in phosphorus loadings. The possi-
bility now exists, however, where phosphorus may no longer be the
limiting factor in the Eastern Basin. With 5070 average increases
(Verduin, 1969) in phosphorus loadings, the ratio of phosphorus
to nitrogen may have shifted enough to create a new steady
state in which nitrogen has replaced phosphorus as the limiting
factor. This supposition is reinforced by findings from this
three year study. The nitrogen concentrations, especially
ammonia, showed a large increase in 1974 with very little change
in phosphorus concentrations (Figures 2, 3, and 5). The phyto-
plankton biomass also showed a large peak during this year
(Figure 19) compared to 1973 and 1975. Thus it would appear that
the increase in nitrogen had some effect upon the system.
It must be understood that the above is based solely on
the facts at hand. There is the possibility that because of the
cruise schedules much of the data concerning phytoplankton peaks
and nutrient increases observed in 1974 were simply missed in 1973
and especially in 1975. Furthermore, it must be emphasized that
while there were no apparent changes in phosphorus concentrations
represented by total and dissolved phosphorus, the phosphorus
component directly utilized by phytoplankton (orthophosphorus)
was not measured. Simply because phosphorus change was not
observed, one can not be sure that in fact a change in ortho-
phosphorus did not take place and was not highly contributive.
Another factor that also may have influenced the observed
increases in nitrogen in 1974 was the instability of the thermo-
cline. As mentioned previously, the breakdown of the thermocline
during the periods of peak stratification in the Eastern Basin was
a common occurrence as a result of summer storms and internal
seiches. Furthermore, many of the nutrients including carbon and
nitrogen, displayed uniform values throughout much of the water
column in 1974 (Great Lakes Laboratory, 1975), indicating the
lack of a chemocline and the instability of stratification during
the sampling cruises. These observations were made in contrast
to 1975 data where definite chemoclines were seen on the sampling
cruises (Great Lakes Laboratory, 1976). Thus, the instability of
stratification in 1974 may have further contributed to the higher
observed values of nutrients such as nitrogen due to the constant
recycling of the epilimnetic-hypolimnetic waters.
The apparent instability of stratification over periods of
this study compounded by the large volume of hypolimnetic waters
also had a direct effect on the oxygen depletion of the Eastern
Basin. The calculations presented (Tables 6-9) indicated that
the oxygen demand of the Eastern Basin was low and also stable.
The combined effects of periodic thermocline breakdown, resulting
in oxygen rich epilimnion waters mixing with hypolimnion waters,
and the large volume of the hypolimnion resulted in a very small
oxygen demand over time in these waters.
72
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Table 18 presents results of oxygen demands for lakes in
several different trophic ranges according to calculations by
Hutchinson and Mortimer (Hutchinson, 1957). Oxygen demands are
also shown for the Central Basin of Lake Erie for both 1970 and
1973. When this information is compared with the results of the
Eastern Basin investigation from 1973 to 1975 (Table 9) some
apparent differences are noted. The Eastern Basin, unlike the
Central Basin (Table 18), never experienced anoxic conditions
over the three year study. Secondly, the Eastern Basin calcula-
tions were computed over a much longer time period than the
Central Basin results. The larger hypolimnion volumes and greater
total oxygen content in the Eastern Basin over a longer time
period would continue to increase from the non-limiting quantities
of oxygen available. Therefore, only the shorter time period
computations of the Eastern Basin oxygen demand are comparable to
the Central Basin results and the classification of Hutchinson
(Table 18). Besides not experiencing anoxia, the Eastern Basin
has a much lower demand than the Central Basin and definitely
fits the mesotrophic classification requirements of Hutchinson.
The algal biomass and its seasonal composition are
summarized for the Eastern Basin from 1973-1975 in Table 11 and
Figure 19. From these data it is apparent that the phytoflagellates
contributed the least to the biomass composition on a yearly
basis and only approached the numbers observed in 1970
by Munawar and Munawar (1976) in the summer of 1975. Additionally,
in contrast to the 1970 results, diatoms were the major biomass
component for the GLL's 1973-1975 observation.
The phytoplankton biomass for the three years ranged
between 0.3 g/m3 and 3.7 g/m3. Previously, maximum peaks of
4.0 g/m3 for phytoplankton biomass (Munawar and Munawar, 1976) in
the Eastern Basin were reported. Therefore, the change in biomass
range has been minimal and was possibly more of an artifact of
sampling dates. According to Vollenweider (1968) a mesotrophic
lake can be characterized by phytoplankton biomass concentration
ranges of 3-5 g/m3. Thus the Eastern Basin could be compared to
a mesotrophic environment based both on the phytoplankton data
and the calculated oxygen demands.
The apparent discrepancy between the 1970 results (Munawar
and Munawar, 1976) and the results reported here for the phyto-
flagellates may be related to sampling. The GLL data were repre-
sentative of the upper epilimnetic waters. It has been suggested
that phytoflagellates are more mobile and could migrate into the
hypolimnion. If this were the case, upper epilimnetic samples
could have missed a large proportion of this group during many
sampling periods.
The peak in primary productivity for the three years
reported here for the Eastern Basin ranged from 16 to 20 mg C/m3/
day. These results are in close agreement with the data reported
73
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Table 18. CLASSIFICATION AND CENTRAL BASIN COMPARISON
OF OXYGEN DEMAND
General lacustrine classification
according to oxygen demand
Hutchinson Mortimer
mi 11imoles/m2/day
01igotrophic <5.3 <7-7
Mesotrophic 5.3 - 10.3 7-7 - 17.2
Eutrophic >10.3 >17.2
Previous oxygen demands calculated for the
Central Basin of Lake Erie*
1970 (Burns and Ross, 1972)
12.23 for 26 days
1973 (The Ohio State Univ.)
11.90 for kk days
* For both time periods the hypolimnion
encountered anoxic conditions
74
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in 1970 (Munawar and Munawar, 1976). Chlorophyll-a concentrations
were also similar between the two studies with maximum values
reaching approximately 7 mg/m3.
Very few relationships (significant correlations) were
observed between the phytoplankton and the physio-chemical variables
over the three year study. There are several possibilities that
could explain in part the lack of correlation between such
variables as biomass and nutrients. The most probable explanation
is the fact that many of the scheduled sampling cruises over the
three year duration missed the peak dynamics of many of the groups
comprising the total phytoplankton biomass. Thus, the kinetics
of growth and uptake of nutrients could not truly be explained
and the expected relationships were not revealed. Furthermore,
in a synoptic survey of the type described here, the higher con-
centrations of soluble nutrients and biomass found near river
inputs contrasted with lower midlake levels. This tended to
disrupt the expected biotic-abiotic relationships. Additionally,
settling and turbulence processes could move the phytoplankton
away from the water mass in which they actually grew (Munawar and
Burns, 1976). The lack of correlation was probably a combination
of several of the above explanations.
The results of this three year investigation illustrate
that such parameters as chlorophyll and primary productivity are
influenced by a number of different phytoplankton groups as well
as growth controlling factors in a variety of ways. For example,
the primary productivity and chlorophyll-a values were directly
related to Chlorophyta during certain seasons of the year and at
the same time inversely related to Chrysophyta. During different
time periods other variables were related to primary productivity
and chlorophyll-a. Consequently, to understand the true relation-
ships that exist, a more intensive sampling schedule needs to be
developed.
The Basinwide distribution of crustacean zooplankton
indicated considerable horizontal and seasonal variation through-
out the year. Due to the rapidly changing temporal abundances at
any location, it was difficult to describe in any way but the
most general terms how zooplankton were related to other variables
in the Basin.
Patalas (1972) and Watson (1976) indicated that zooplankton
populations peaked in late June which also were noted in this
1973-1975 study. Examination of the group compositions (Figure
22) indicated that the cladocerans had two peaks of activity,
during early summer and again in the fall, while the cyclopoids
dominated during the remainder of the year. The cyclopoids also
dominated at the midlake stations and in the less eutrophic
northern shore stations, while the cladocerans were more numerous
at sites of river inputs and entrainment from the Central Basin
(Figure 23). The general annual pattern for zooplankton over the
75
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three year study can be illustrated by a eutrophication index
which is the ratio of calanoids to cyclopoids plus cladocerans
(Patalas, 1972). Table 15 shows this index for each year and
indicates a slight decrease represented by a movement towards
less eutrophic conditions.
There were no strong relationships between the zooplankton
groups and either primary productivity or chlorophyll-a. The
cladocerans and cyclopoids did show an inverse relationship with
total phytoplankton biomass, but more importantly the cladocerans
shewed a strong positive correlation with the nutrients of ammonia
and total phosphorus. This is in close agreement with findings
by Watson (1976) when he suggested that the cladocerans were
responding to available food sources in the form of organic
detritus rather than phytoplankton abundance. This would also
partially explain the increase in total zooplankton for 1974 with
the corresponding increases in ammonia and to a lesser degree
phosphorus. It has been suggested that in the more eutrophic
waters the detritus-zooplankton food chain is favored over the
classical herbivore chain of more oligotrophic lakes (Gliwicz,
1969).
The preceding is further supported by the comparison of
horizontal zooplankton distributions for each year (Figure 21)
with ammonia and total phosphorus distributions (Figures 2 and 5).
The higher concentrations of phosphorus and ammonia especially
in the area of tributary inflows were accompanied by high zoo-
plankton concentrations. These organically rich inputs probably
provided impetus for heterotrophic bacterial growth (Watson, 1976)
as well as a direct food source for the local masses of crustacean
zooplankton. Additionally, because of the suggested detritivore
habits for the cladocerans, the closer relationship seen between
zooplankton and nutrient increases rather than between the phyto-
plankton biomass and these same nutrient changes can be explained.
Very little information exists concerning the benthic
communities of the Eastern Basin of Lake Erie. Therefore, the
results obtained from the three year investigation reported here
serves as a very important contribution to the baseline informa-
tion for this component of the Eastern Basin system.
The Eastern Basin did not experience anoxia in any of the
three years of the study. Consequently, oxygen conditions probably
did not play a role in the benthic community distribution. The
primary factors effecting spatial distribution within the Basin
were probably sediment type and organic carbon content of the
superficial sediments. Data obtained from Thomas et al. (1976)
on these variables is presented in Figure 26.
The midlake stations which were characterized by a much
higher carbon content and superficial sediments composed primarily
of mud and silt (median grain size 6-9 ) supported community
76
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MUD
| | SAND + MUD
SAND
SEMI-CONSOLIDATED
CLAY TILL +
GRAVEL DEPOSITS
BEDROCK
(a) Distribution of surfic'al
sed iments.
1 - 3
4 - 6
7 - 8
(b) Distribution of mean grain size
(in phi units) in the surficial
sed iments.
Distri
(in %
<1 .0
1.0 - 2.0
2.1 - k.Q
bution of organic carbon
dry weight) of sediment.
gure 26. Distribution of (a) surficial
sediments, (b) mean sediment grain size in phi units and
(c) organic carbon in percent dry weight of sediment.
(From Thomas et al., 197C)
77
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types dominated by oligochaetes and amphipods. Stylod't^tu.* and
L-imnodfL-iiuA were the major oligochaetes; Pontopofie.i.a was the
dominant amphipod present. The eastern portion of the Basin,
which showed the lowest carbon accumulation probably due to the
higher amount of sand content of the sediment, displayed the
dominance of a bivalve-oligochaete community type. The northern
shore stations, because of the hard clay base and sandy sediments,
supported communities comprised primarily of bivalves and
amphipods. Again the carbon content of the sediment was low which
further discouraged the presence of burrowing forms such as the
worms. This type of environment was also characteristic of
Stations 17, 20 and 21 which again showed the dominance of
bivalves and amphipods.
Prior to this study, the most important oligochaetes
within the Eastern Basin were Styiodfi'ilu.A sp. and Tubx^ex tu.b
-------
by Cook and Johnson, 1974) and the present study. There has been
both an apparent increase in numbers of organisms as well as some
species shifts to those more readily associated with highly
productive environments. The one problem that arises in the
comparison mentioned above is the lack of knowledge concerning
the methods of collection and analysis of the 1968 data, the
sampling time, and the number of sample sites within the Basin
that produced the results quoted. This information may have a
direct bearing on the comparisons made.
The changes in the benthic community with the lack of
change within the water column tend to suggest that the midlake
area of the Basin has displayed a relatively stable
condition concerning nutrients and general productiveness over the
past five years. The bottom waters and benthic habitat have
received the majority of allochthonous inputs to the Basin over
the years, causing the changes observed in the immediate vicinity
of the superficial sediments. Additionally these sediments
serve as a storage pool for excesses of many of the nutrients
associated with eutrophication. Consequently, changes within the
open waters of the Basin resulting from a decrease in nutrient
loadings would be small and very difficult to measure because of
the constant recycling of the nutrients from the sediment pools.
On account of this large scale recycling, it would probably take
many years of reduced loadings to realize a change in nutrient
levels in the midlake region of the Eastern Basin.
The major goal of the GLL's three year study was to address
the four objectives stated at the beginning of this document. The
design of the project and the treatment of the resulting data has
been carried out in light of these objectives.
The results obtained from the three year investigation
definitely contribute a large amount of up-to-date baseline
information to the general knowledge of Eastern Basin dynamics.
Furthermore, this information agrees, in most instances, with
data obtained from other studies within the past five years. The
information obtained on all variables points to the premise that
the Eastern Basin of Lake Erie can presently be characterized as
a mesotrophic body of water that is in a relatively stable
condition concerning nutrient dynamics and biological processes.
The second objective of the project, to identify problem
areas within the Basin, resulted in the conclusion that most of
the problem areas were associated with tributary inflows and
entrainment from the Central Basin. Because the inflow effects
were localized and short-lived, the majority of the midlake
stations showed no real change. An alternative means of examining
these local inputs would have been to investigate the littoral
areas and shallow nearshore waters, an area much neglected in
Lake Erie. The specific problem areas that were identified were
the following: the waters offshore from the Grand River as well
79
-------
as areas west of this inflow (down-current stations); southern
shore stations between Erie, Pa. and Dunkirk including the mouth
of the Twenty Mile Creek all influenced by longshore currents
moving in an easterly direction; and the eastern stations of the
Basin due to the industrial influences of the area (Buffalo and
Port Colborne). Another area of concern, the westerly midlake
stations, primarily were influenced by entrainment processes from
the Central Basin.
The benthic sampling program indicated that two areas were
relatively discrete in the Basin. These areas were the bottom off
of Dunkirk and the eastern benthic environment. Both locations,
which were also identified in the preceding paragraph, were
characterized by fewer numbers of organisms than the Basin mean
and furthermore consisted of much higher percentages of oligo-
chaetes than most other parts of the Basin.
The third objective is the one goal which probably cannot
be completely met over the duration of the study described here.
As mentioned previously, because of the extensive storage
capacity of the Basin sediments and the high degree of recycling
within the water column, a number of years of study are needed
to accurately measure any changes that may occur from reduction
of nutrient loadings to the Basin. Short term effects of local
inputs are identifiable as shown from the nitrogen data collected
in 1974. A study of such short duration, however, cannot measure
changes in water quality from reduced loadings. Consequently,
now that a baseline of data has been established for the Eastern
Basin, the third objective can become the major focal point of
all future work concerning the monitoring and surveillance
program. Furthermore, a little more emphasis can also be placed
on the nearshore waters and littoral areas of the Basin.
This project was also designed to determine the effective-
ness of measuring a limited number of biotic and abiotic parameters
in a synoptic fashion to evaluate eutrophication processes in a
large lake. The results obtained over the three year study period
indicated that in general the variables measured were appropriate
to meet this objective with the exception of not measuring ortho-
phosphorus, dissolved silica, and the two benthic variables of
particle size and sediment organic carbon. In all future work,
therefore, it is suggested that these variables be included.
The fact, however, remains that the variables that were
measured, in many instances, did not provide the information
intended because of the sampling schedules. For example, in 1975
most of the biological peaks were missed due to a lack of sampling
during the peak periods. The problem, therefore, does not lie
with the variables measured as much as it does with when these
variables were measured.
Another point to emphasize concerning the fourth objective
80
-------
was the apparent duplication of information at a large number of
the sampling stations. As illustrated in the results, there were
discrete areas of the Basin which were characterized by unique
physio-chemical processes. In most instances these areas were
represented by a large number of sampling stations. At this
point the appropriate approach may be to delete some of these
duplicative stations as a trade off for: 1) increasing the
cruise schedule; 2) performing a more rigorous sampling routine
at a smaller number of stations (e.g. sample a decreased number
of synoptic stations while increasing the rigor of sampling on
one station from each of the discrete water masses described);
3) begin placing more emphasis upon the nearshore waters and
littoral zone of the Basin.
81
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REFERENCES
Burns, N. M. 1976. Temperature, oxygen and nutrient
distribution patterns in Lake Erie, 1970. J. Fish.
Res. Bd. Can. 33(3):485-511.
Burns, N. M. and C. Ross. 1972. Project Hypo. U.S.E.P.A.
Technical Report TS-05-71-208-24, Fairview Park, Ohio
and Canada Center for Inland Waters Paper No, 6,
Burlington, Ontario. 182 p.
Cattell, R. B. 1965. Factor analysis: An introduction to
essentials. I. The purpose and underlying models.
Biometrics. 21:190-215.
Cook, D. G. and M. G. Johnson. 1974. Benthic macroinverte-
brates of the St. Lawrence Great Lakes. J. Fish. Res.
Bd. Can. 31:763-782.
Dobson, H. N., M. Gilbertson and P. G. Sly. 1974. A summary
and comparison of nutrients and related water quality in
Lakes Erie, Ontario, Huron and Superior. J. Fish. Res.
Bd. Can. 31:731-738.
Gliwicz, Z. M. 1969. Studies on the feeding of pelagic
zooplankton in lakes of varying trophy. Ekol. Pol.
Ser. A. 17:663-708.
Great Lakes Laboratory. 1974. Lake Erie Nutrient Control
Program: An Assessment of its Effectiveness in
Controlling Eutrophication - Eastern Basin. 1973
Annual Report to the Environmental Protection Agency.
185 p.
Great Lakes Laboratory. 1975. Lake Erie Nutrient Control
Program: An Assessment of its Effectiveness in
Controlling Eutrophication - Eastern Basin. 1974
Annual Report to the Environmental Protection Agency.
376 p.
Great Lakes Laboratory. 1976. Lake Erie Nutrient Control
Program: An Assessment of its Effectiveness in
Controlling Eutrophication - Eastern Basin. 1975
Annual Report to the Environmental Protection Agency.
(in press).
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Healey, F. P. 1973, Inorganic nutrient uptake and deficiency
in algae. C.R.C. Grit. Rev. Microbiology. pp. 69-113.
Herdendorf, C. C., S. M. Hartley and L. J. Charlesworth. 1974.
Lake Erie bibliography in environmental sciences. Bull.
Ohio Biol. Soc. 4:1-113.
Howard, D. L., L. I. Frew, P. M. Pfister and P, R. Dugan.
1970. Nitrogen fixation in Lake Erie. Science.
169:61-72.
Hutchinson, G. E. 1957. A Treatise on Limnology. Vol. I:
Geography, Physics and Chemistry. John Wiley and
Sons, New York. 1015 p.
International Joint Commission. 1975. Great Lakes Water
Quality 1974. Appendix C: Annual Report of the Remedial
Programs Subcommittee. Great Lakes Water Quality
Board, IJC. 194 p.
International Lake Erie Water Pollution Board. 1969. Report
to the International Joint Commission on the pollution
of Lake Erie, Lake Ontario and the International Section
of the St. Lawrence River. Vol. 2: Lake Erie. 316 p.
Lambert, J. M. and M. B. Dale. 1964. The use of statistics
in phytosociology. In: Advances in Ecological Research,
J. B. Cragg (ed.). Academic Press. pp. 55-59.
Larson, D. W. 1972. Temperature, transparency and
phytoplankton productivity in Crater Lake, Oregon.
Limnol. Oceanogr. 17(3):410-417.
Munawar, M. and N. M. Burns. 1976. Relationships of
phytoplankton biomass with soluble nutrients, primary
production, and chlorophyll-a in Lake Erie, 1970.
J. Fish. Res. Bd. Can. 33 (3) : 601-611.
Munawar, M. and I. F. Munawar. 1976. A lakewide study of
phytoplankton biomass and its species composition in
Lake Erie, April-December 1970. J. Fish. Res. Bd.
Can. 33(3):581-600.
Nie, N. H., C. H. Hull, J. G. Jenkins, K. Steinbrenner and
D. H. Bent. 1970. SPSS - Statistical Package for
the Social Sciences. McGraw Hill, New York. 675 p.
Orloci, L, 1966. Geometric models in ecology. I. The
theory and application of some ordination methods.
J. Ecology. 54:193-215.
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Patalas, K. 1972. Crustacean plankton and eutrophication of
the St. Lawrence Great Lakes. J. Fish. Res, Bd. Can.
29:1451-1462.
Sokal, R. R. and F. J. Rohlf, 1969. Biometry. W. H.
Freeman and Co. San Francisco. 776 p.
Thomas, R. L., J. M. Jaquet, A. L. W. Kemp and C. F. M. Lewis.
1976. Superficial sediments of Lake Erie. J. Fish
Res. Bd. Can. 33(3):385-403.
Titman, D. 1976. Ecological competition between algae:
Experimental confirmation of resource-based competition
theory. Science. 192:463-465.
United States Federal Water Pollution Control Agency. 1968a.
Lake Erie Environmental Summary 1963-1964. 160 p.
United States Federal Water Pollution Control Agency. 1968b.
Lake Erie Report: A Plan for Water Pollution Control.
86 p.
Verduin, J. 1969. Man's influence on Lake Erie. Ohio
J. Sci. 69:65-70.
Vollenweider, R. A. 1968. Scientific fundamentals of the
eutrophication of lakes and flowing waters, with
particular references to nitrogen and phosphorus as
factors of eutrophication. Organ. Econ. Corp. Dev.
Rep., Paris.
Watson, N. H. F. 1976. Seasonal distribution and
abundance of crustacean zooplankton in Lake Erie, 1970.
J. Fish. Res. Bd. Can. 33(3):612-621.
84
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-80-067
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Lake Erie Nutrient Control: Effectiveness
Regarding Assessment in Eastern Basin
5. REPORT DATE
JULY 1980 ISSUING DATE.
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Great Lakes
8. PERFORMING ORGANIZATION REPORT NO.
Laboratory
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Great Lakes Laboratory
State University College at Buffalo
1300 Elmwood Avenue
Buffalo, New York 14222
10. PROGRAM ELEMENT NO.
1BA608
11. CONTRACT/GRANT NO.
EPA Grant #R-802706
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory-Duluth
Office of Research and Development
U.S. Environmental Protection Agency
Duluth, Minnesota 55804
13. TYPE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
EPA/600/03
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A three-year synoptic monitoring program was conducted on 26 stations
from 1973-75. Data generated included major nutrients, temperature
structure and oxygen depletion as well as phytoplankton, zooplankton,
and benthic macroinvertebrate dynamics. The Basin was separated into
five discrete areas based on physico-chemical variables. While anoxia
was not observed, there was a hypolimnetic oxygen demand of 0.011 g
02/m3/day. The Eastern Basin has remained relatively stable over the
past five years with the exception of a decrease in phytaplankton
biomass, increase in nitrogen, and a doubling of benthic macroinverte-
brates. From a trophic standpoint, the Basin can be classified as
mesotrophic. Reductions in algal growth may be in response to pollu-
tion abatement, particularly phosphorus.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Eutrophication
Phosphorus
Anoxia
Oxygen Demand
Phytoplankton
Lake Erie
08/H
18. DISTRIBUTION STATEMENT
Release to the Public
19. SECURITY CLASS (ThisReport}
Unclassified
21. NO. OF PAGES
100
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
85
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