v>EPA
Labor
Duluth MN 55804
•pmfint
Entrainment
at a Once-Through
Cooling System
on Western Lake Erie
Volume I
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/3-78-070
July 1978
ENTRAINMENT AT A ONCE-THROUGH COOLING
SYSTEM ON WESTERN LAKE ERIE
Volume I
by
Richard Allen Cole
Institute of Water Research and
Department of Fisheries and Wildlife
Michigan State University
East Lansing, Michigan 48824
Grant No. R801188
Project Officer
Nelson Thomas
Large Lakes Research Station
Environmental Research Laboratory - Duluth
Grosse He, Michigan 48138
ENVIRONMENTAL RESEARCH LABORATORY - DULUTH
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 Agnecy, 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.
ii
-------
FOREWORD
Our nation's freshwaters are vital for all animals and plants, yet our
diverse uses of water—for recreation, food, energy, transportation, and
industry—physically and chemically alter lakes, rivers, and streams. Such
alterations threaten terrestrial organisms, as well as those living in water.
The Environmental Research Laboratory in Duluth, Minnesota, develops methods,
conducts laboratory and field studies, and extrapolates research findings
—to determine how physical and chemical pollution affects aquatic
life
—to assess the effects of ecosystems on pollutants
—to predict effects of pollutants on large lakes through use of
models
—to measure bioaccumulation of pollutants in aquatic organisms
that are consumed by other animals, including man.
This report provides insight into the effects of a once-through cooling
system of a fossil fuel plant located on western Lake Erie. Studies were
conducted to determine the impact on water chemistry, plankton, periphyton,
benthos, and fish larvae.
Donald I. Mount, Ph.D.
Director
Environmental Research Laboratory
iii
-------
ABSTRACT
This study assessed entrairunent rates and effects for important components
of the aquatic community in the once-through cooling system of a steam-electric
power plant (the Monroe Power Plant), which can draw up to 85 m3/second of cool-
ing water from Lake Erie (-80%) and the Raisin River (-20%). Phytoplankton,
periphyton, zooplankton, ichthyoplankton, and community metabolism were sampled
bimonthly from November 1972 through September 1975. Sampling was conducted at
fixed locations in the intake region, discharge canal, thermal plume and the
lake-shore waters. Concentrations of chloride and dissolved and total solids
were used to trace water masses and their associated nutrient and plankton
concentrations.
River and lake water were well-mixed in the discharge canal following
passage through the condenser where the water was heated an average of 6° to
10°C. The thermal plume lost most of its heat to the receiving water rather
than to the atmosphere.
The cooling water could rapidly change in chemical and biological charac-
ter over a few hours because of spatial variation in the source waters. This
spatial variation often produced sampling station differences on a particular
date which reflected natural, patchy distributions more than cooling system
effects. Seasonal and annual means, however, consistently revealed subtle
entrainment effects for most of the parameters examined.
Oxygen concentrations in the discharge canal were supersaturated 110 to
120% in winter. No excessive loss of oxygen occurred under the thermal plume.
At temperatures above 15°C in the discharge canal, photosynthesis was depressed
and community respiration was accelerated. Dissolved organic carbon decreased
from decomposition while particulate organic carbon increased enough to offset
change in total organic carbon. Algal abundance increased slightly as green
and blue-green algae increased more than other taxa during passage, but algal
diversity remained basically unchanged. None of the changes in phytoplankton
were related to time of day or chlorination schedule. Total non-gaseous nitro-
gen, inorganic carbon and phosphorus all declined in the plume, apparently
improving the water quality from the standpoint of eutrophication. Erosion
from the discharge canal, however, contributed excess sediment to the basin.
Although zooplankton densities declined about 40% in the cooling system,
diversity remained unchanged and the impact was masked by mixing in the receiv-
ing waters. Pilot studies indicated that mortality may have been size related.
Leptodora kindtii, along with fish larvae, appeared to be killed by cooling
water passage more than smaller plankton. The large zooplankton also were
favored as food by juvenile and adult fish in the study area.
iv
-------
Larval fish were at least as effectively sampled with a one meter, 571-y
plankton net as with a Kenco Pump or a high-speed net. Although there was no
difference in larval catch in tows of different lengths from one to five minutes,
the.mesh size was important. Larval fish were concentrated near bottom at night
and moved up from bottom during the day. Geographical and temporal variations
in larval fish distribution were great, but certain species seemed most abun-
dant offshore while others were concentrated near shore. Because of differen-
tial vertical and geographical distribution, some fish larvae seemed more
vulnerable to entrainment than others.
Large enough numbers of certain ichthyoplanktonic species and Leptodora
kindtii may be entrained to at least slightly influence population abundances
of adult organisms in western Lake Erie. Refined assessments are required to
ascertain the degree of effect. The regeneration rates of smaller planktonic
organisms in the source waters are likely to negate the local impacts of the
cooling system on their populations.
This report was submitted in fulfillment of Grant No. R801188 by the
Institute of Water Research and the Department of Fisheries and Wildlife at
Michigan State University under the sponsorship of the U.S. Environmental
Protection Agency. This report covers the period November 1, 1972 to July 1,
1976, and work was completed as of November 30, 1976.
-------
CONTENTS
Disclaimer
Foreword
Abstract iv
Figures vii
Tables ix
Acknowledgment xii
1. Introduction 1
2. Conclusions 3
3. Site Description 6
Power plant description 6
The cooling water sources 9
4. Materials and Methods 11
Water movement 11
Chemistry, plankton and periphyton 11
5. Results 25
Hydrodynamics 25
Temperature 39
Oxygen 39
Suspended solids 43
Carbon &
Phosphorus 49
Nitrogen 50
Phytoplankton 50
Periphyton 60
Community metabolism 65
Zooplankton 65
Midges . . 83
Larval fish 83
6. Discussion H3
Mixing 113
Temperature and oxygen 114
Nutrients and primary producers 114
Zooplankton H?
Foods of fish 119
Larval fish sampling 121
References i33
Appendices (Separate volume)
A. Report on fish food habits
B. Tabular data •
C. Figures
vii
-------
FIGURES
Number
1 Hap of the study area showing the locations sampled for water
chemistry, phy toplankton , zooplankton, community metabolism
and perlphyton .......................... 7
2 Map of the study area showing the locations sampled
for larval fish .......................... 8
3 Relative water velocity at different depths in the
study area near stations 2 and 3 .............. ... 27
4 Mean daily resultant water velocity and direction
calculated for each season from 1970 to 1975 ........... 30
5 Long-term and short-term (1970-75) monthly discharge of the
Raisin River compared to maximum and minimum discharge
since 1936 and full pumping rate on the Monroe Power Plant .... 31
6 Conductivity in the intake region of the Raisin River ....... 34
7 Representative categories of chloride profiles in the
cooling system of the Monroe Power Plant ... .......... ^
8 Surface temperatures in the Raisin River and discharge
canal compared to nearby lake temperatures at bottom and
surface during the study period .................. 4°
9 Temporal variation of chemical concentration selected
for study in the lake source used for cooling water at
the Monroe Power Plant . ..................... 44
10 Accumulation of periphyton during four seasons in the
cooling system at the Monroe Power Plant ............. 64
11 Mean densities of zooplankton in the cooling system at
the Monroe Power Plant ...................... 74
12 Mean density of copepods and cladocerans at each depth sampled
for the summers of 1973, 1974 and 1975 .............. 80
13 The mean number of larval fish captured (+SE) for length
of time towed (1, 2, 3, 4, and 5 min.) and each mesh size
tested (363, 571, 760 and lOOOy) ................. 89
•j^ Mean number of larval fish captured in oblique tows
compared to the mean of stratified tows at surface, mid-
depth, and bottom ........................ 90
viii
-------
Number Page
15 Mean number of larval fish captured (+SE) during the
day (D) and night (N) for each depth stratum at station
P17 (S = surface; MD = mid-depth; D = deepwater; and
0 = oblique tow) ............. ........... 98
16 Mean number of larval fish (+SE) captured along a 16-m
transect ............................ 99
17 Seasonal variation in abundant species of larval fish
in the intake region and upper discharge canal (mean
+ 95% conf . int.) .......................
18 Minimum and maximum variation (+95.1 conf. int.) in
the catch of larval fish near the Monroe Power Plant ...... 103
19 Sampling intensity required at various permissable
errors of the mean .......................
ix
-------
TABLES
Number Page
1 Summary of samples collected and processed for chemistry,
primary producers and zooplankton, 1972-1975 12
2 Larval fish sampling schedule 20
3 Calculated volume-flow/second by various techniques in
different parts of the cooling system 26
4 Drogue and current meter estimates of mean water velocity
and resultant direction 28
5 Amounts of river and lake water,velocity and passage
time in the discharge canal 32
6 Mean annual concentration of chloride, dissolved solids,
and total solids 37
7 Mean river water contribution calculated from concentrations
of chemical tracers and U.S.6.S. measures of river discharge
and plant pumping rates 38
8 Mean and maximum temperatures in warm and cool seasons
recorded during the study 41
9 Oxygen percent saturation in the cooling system 42
10 Mean annual concentration of suspended solids, phosphorus,
nitrogen, and carbon in the cooling system of the Monroe
power plant 45
11 Mean annual phytoplankton abundance by major class 51
12 Vertical distribution (percent of total and total
number at each depth) in the cooling system (after-
noon data only) in 1973 at stations over three meters
deep 53
13 Mean annual algal densities, volume, and mean individual
volumes for classes and dominant species in the cooling
system during 1973 55
-------
Number
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Mean annual algal density by class at different times of
. the day in 1973
Mean abundance and size of important phytoplankton species
Diversity and equitability calculated from density and
Mean annual phytoplanktonic generic diversity and
equitability in the cooling system from 1973 to 1975
Mean gross primary productivity in the cooling system
Mean respiration rate in the cooling system for cold
P/R ratios in the cooling system for warm and cold
months of 1973-75
Mean annual density of zooplankton in the cooling
system
Mean annual biomass of zooplankton in the cooling
system • • • •
Mean annual size per individual of zooplankton in the
cooling system
Mean density of zooplankton at different times of the
Mean size per individual for the major taxa at the
daily time periods . .
Comparison of mean density, biomass, and size of
zooplankton among the lake stations and lower dis-
charge station 14 at 0.5 m below the surface in 1973
Zooplankton diversity in the cooling system
Preliminary estimate of zooplankton mortality in the
cooling system at the Monroe power plant
The distribution of chironomid larvae in the cooling
system in 1973 .....
Page
58
59
61
63
66
68
70
72
73
76
77
78
0*1
ol
82
Of.
ot
85
xi
-------
Number Page
30 Mean catch of fish larvae per 100 m3 in oblique 1-m
plankton net tows from may through July in 1974 and
1975 86
31 Comparison of the mean catch in a 571-y, 1-m plankton
net, a modified hardy "high-speed" sampler, and a
Kenco pump 87
32 Daytime and nighttime compariosns of mean catch (5
replicates) per 100 m in oblique, surface, midwater,
deep tows and towing with a bottom sled using a 571-u,
1-m plankton net 91
33 Preliminary estimates of mortality in the cooling system
at the Monroe Power Plant 106
34 Foods in fish larvae of different lengths captured near
the Monroe Power Plant 107
35 Stomach contents of fish larvae captured day and night
in western Lake Erie Ill
36 Estimated number of larvae potentially entrained at
the Monroe Power Plant in 1973, 1974 and 1975 126
37 Estimated relative vulnerability of important larval
fish to entrainment at the Monroe Power Plant from an
area 16 km by 16 km in Lake Erie immediately adjacent
to the power plant 128
xii
-------
ACKNOWLEDGMENTS
I thank the Detroit Edison Company for cooperating; especially Jack Gross
and Evelyn Madsen who helped coordinate field efforts and supplied information
pertaining to the operation of the Monroe Power Plant,
Several graduate-student research assistants contributed to the completion
of this work. James Wojcik and Thomas Wallace completed work on the primary
producers, Mark Simons and Roger Jones worked with zooplankton, and Thomas
Ecker analyzed water chemistry. Fish larvae were investigated by Don Nelson
and John MacMillan, and fish foods were examined by David Kenaga and Norman
VanWagner. Others who aided with data acquisition and analysis include Dennis
Lavis, Charles Warner, and Stephen Kilkus. Diana Weigmann edited the text. Dr.
Frank D'ltri's water chemistry laboratory at the Institute of Water Research
supplied an indispensible service.
I also acknowledge the encouragement of Drs. Thomas Bahr, Director,
Robert Ball, Associate Director of the Institute of Water Research, Niles
Kevern, Chairman of the Department of Fisheries and Wildlife at Michigan State
University, and Nelson Thomas, Project Officer at the Large Lakes Research
Station, U.S. Environmental Protection Agency.
xiii
-------
SECTION 1
INTRODUCTION
Large quantities of planktonic organisms may be drawn into (entrained by)
once-through cooling systems at steam-electric power plants. Several decades
ago, once-through cooling usually turned out to be the least expensive of a
number of possible cooling alternatives. Because the magnitude of the cooling
requirement appeared too small to warrent much environmental concern, cost
comparisons rarely included assessments of detrimental impact on aquatic com-
munities. This attitude rapidly changed with recognition that the magnitude
of the cooling requirement was doubling every decade, an increasing rate that
was much faster and in greater quantities than all other combined industrial
use. Accordingly, numerous studies of power-plant impact were initiated
during the past decade.. Only a few of the earlier studies were designed to
comprehensively examine impact over several annual cycles (Merriman and Thorpe,
1976). When this study was initiated in 1972, no comprehensive long-term
evaluation of cooling-system entrainment had been initiated on the lower Great
Lakes. The massive cooling water requirements projected for the Great Lakes
region by Dennison and Elder (1970) had signaled potential damage from entrain-
ment effects. This study was conceived to evaluate that potential at the
Monroe Power Plant on the west shore of Lake Erie.
The Monroe Power Plant has an exceptionally large once-through cooling
system; it pumps up to 85 m3/sec for cooling purposes. The primary concern
of this research was to assess the amount of plankton transported through the
cooling system. A secondary objective was to estimate the plant's impact on
the structure and function of the entrained planktonic community. The studies
results were to be interpreted with regard to the ultimate concern, the impact
of the entrainment on the source-water community.
Reviews of the large body of literature on power plant effects (Coutant
and Talmage, 1976; Coutant and Pfuderer, 1974) have indicated that entrained
organisms may be damaged by plant operation in a number of ways. At the
Monroe Power Plant, specific sources of potential damage included (1) altera-
tion of water quality caused by mixing of cooling sources, (2) toxic effects
of chlorine, (3) the mechanical damage caused by pump and condenser passage,
and (4) thermal "shock" caused by exposure to rapid and prolonged temperature
changes. Any of these physical and chemical alterations might have killed at
least some organisms or affected their metabolism, growth, and vulnerability
to predation or disease.
Other studies have been conducted to specifically assess entrainment
impact; some in the field and others in the laboratory. Most of the laboratory
studies have inadequately represented power-plant conditions (Shubel, 1974)
-------
and many of the field studies have inadequately ascertained variability in the
amounts of organisms entrained or the impact of entrairunent. To some
researchers (Shubel, 1974) the exceptional variability often encountered in
field studies requires greater emphasis on laboratory studies; but no labora-
tory study can estimate the actual quantities of plankton entrained under vary-
ing natural conditions. A few studies (Marcy, 1976; Massengill, 1976) have
incorporated diurnal, seasonal and annual variation in estimates of entrainment
rates or entrainment effects. Most studies have concentrated on some limited
aspect of entrainment input such as primary productivity, heterotrophic
microorganisms, phytoplankton, zooplankton, or larval fish. Few have integrated
their approach to derive a wholistic view that can be contrasted with comparable
data from the source-water community. Most comprehensive, completed field
studies have been conducted on estuaries or rivers rather than freshwater lakes.
This study used an integrated, community approach which emphasized assess-
ment of both short and long-term variation in order to identify more subtle
field impacts than generally have been recognized in the past. To reach that
end, studies were simultaneously conducted on phytoplankton, periphyton, zoo-
plankton, ichthyoplankton and community metabolism. These entrainment studies
were conducted simultaneously with related studies in the receiving waters
described by Cole (1976). Few data are otherwise available for the large,
shallow, turbid, warm-water lakes and reservoirs that comprise extensive
potential sources of cooling water in the United States. Many of the conclu-
sions presented here may generally apply to those kinds of sites.
-------
SECTION 2
CONCLUSIONS
1. Based on local studies of currents, planktonic organisms from anywhere in
the 2500 hectare western basin could be entrained at the Monroe Power
Plant, but the most probable regional source is the southwest corner of the
basin near the mouth of the Maumee River.
2. Tracers (chloride, dissolved solids and total solids) revealed that chemi-
cally discrete water masses often pass through the cooling system over
periods of less than one day. Associated plankton populations and nutrient
concentrations similarly varied because of spatial variation in the source
waters. On any particular sampling date, statistical differences identified
among sampling stations in the cooling system reflected patchy distributions
more than power plant effects. Seasonal or annual mean concentrations
tended to average out the effect of patchiness on the distributions
observed in the cooling system.
3. Power plant operation consistently caused minor changes in the mean annual
concentration of nutrients and plankton in the receiving waters of Lake
Erie. But, in most cases the effects were unrecognizable' after the plume
water had mixed into the receiving waters.
4. Mean annual gross primary productivity declined about 50% following con-
denser passage while mean annual community respiration nearly doubled.
Gross primary productivity and community respiration recovered as water
passed through the cooling system and mixed with the lake waters. Algal
concentrations increased slightly, particularly among the green and blue-
green algae, as discharge water passed back to the lake.
5. The increased respiration presumably was caused by decomposition of dis-
solved organics drawn into the cooling system. Particulate organic carbon
increased with passage as dissolved organic carbon declined but the total
organic carbon exported to the lake remained unchanged. Oxygen depletion
in the plume was about the same as in the lake. Winter passage caused an
oxygen supersaturation of 100 to 120%.
6. Total non-gaseous nitrogen, inorganic carbon, and phosphorus declined more
than expected by simple dilution as water mixed with receiving waters.
Considering changes in nutrient concentrations in the water column, the
quality of discharge water improved with passage; adding heat may have
accelerated the decay of the excessive organic load in the Raisin River.
On the other hand, erosion in the discharge canal increased the sediment
loading in the discharge water.
-------
7. Mean annual zooplankton densities in the water samples were nearly halved
by condenser passage before water passed beyond the upper discharge canal.
Pilot studies indicate that mortality was size-related but the numerical
decline was not related to the time of day, size or taxonomy of the
organism. For most of the smaller species, 50% mortality would have a
negligible effect on western Lake Erie because of the relatively large
water volume and effective mixing in the basin.
8. Several fish species in the area tend to feed selectively, particularly
favoring the large Leptodora kindtii. This species also seemed particulaly
susceptible to entrainment effects. The Monroe Power Plant may have acted
like a competitor for planktivorous fishes.
9. Open, plankton nets were at least as effective for sampling fish larvae as
a Kenco pump or a high-speed net. Length of tow from 1 to 5 minutes did
not affect catch rate, but the size of mesh used was crucial. The smallest
mesh used, 361-u, caught more larvae than mesh sizes of 571-y, 760-y, or
1000-p. Oblique tows yielded approximately the same mean yield as strati-
fied tows above the bottom.
10. Larval studies indicated that mortality caused by passage was high, but
the larvae of some fish species probably hatched in the discharge canal.
Spatial and temporal variability was very great, making it difficult to
precisely describe geographical distributions in the basin, particularly
for scarce species. Geographical distributions of fish larvae seemed
species dependent and some species appeared more abundant offshore than
onshore.
11. All larvae appeared to be concentrated very near the bottom during the day
and moved up from the bottom at night. Some species stayed close to the
bottom more than others, indicating that currents were less likely to carry
them long distances than species that moved farther from the bottom.
Because of this diurnal cycle, larger numbers of fish larvae are likely to
be entrained at night than during the day.
12. Because larvae are closely associated with the bottom during the day and
the effectiveness of net sampling near the bottom without using a bottom
sled is depth dependent, daytime sampling without a bottom sled is likely
to indicate spuriously higher concentrations near shore compared to off-
shore. Nighttime sampling without a sled is less biased because larvae
are less concentrated near the bottom.
13. Species of larval fish and other organisms associated mostly with the
river and adjacent marshes seem more vulnerable to entrainment effects
than lake populations because most of the river water is used for cooling
purposes* Some of these species are relatively important economically
and ecologically but are so scarce as larvae in the open lake that it is
impossible to effectively judge the impact of the power plant on their
populations. These species include centrarchids, ictalurids, esocids and
some cyprini-ds,
14, Relatively small proportions of lake populations appeared to be vulnerable
to power plant entrainment; usually less than 0.1 to 1.0% of crudely
-------
estimated basin-wide abundances including yellow perch, white bass, smelt
and shiners. Other species may have relatively large proportions of
their populations entrained; particularly clupeids and freshwater drum.
More information on larval fish distributions, recruitment, and natural
mortality is required to refine these preliminary estimates.
-------
SECTION 3
SITE DESCRIPTION
POWER PLANT DESCRIPTION
This study was conducted at the Monroe Power Plant, a fossil-fuel, steam-
electric facility operated by the Detroit Edison Company on the western shore of
Lake Erie near the Raisin River (Fig. 1 & 2). All four of the plant's genera-
ting units were completed by mid-1974 with a net, total capability of 3,150
megawatts. The water demand for once-through cooling depends on power production
and ambient water temperature, but the maximum requirement is about 85 m3 per
second. The water is pumped in varying proportions from the Raisin River and
Lake Erie. During spring runoff the Raisin River may contribute more than 95
percent of the cooling water while it contributes less than five percent during
the low flow of late summer. The biota of the lake and river sources differs,
so the species composition in the water passing through the condenser system
reflects changes in source-water proportions as well as natural, seasonal
fluctuations.
Water enters the cooling system through a 100-m long intake canal that is
located about 650-m upstream from the river mouth. Prior to condenser entry,
the water passes through a traveling screen with 1-cm, diagonal openings. Water
then enters the condenser where water velocities usually exceed 2 m/sec and the
temperature rises to about 10°C above ambient at full pumping and power produc-
tion. But, power generation and pumping rates have varied widely so recorded
temperature elevations have ranged from 0 to 17°C. The highest temperature
elevations were recorded in winter when cooling water pumping rates per unit
of power generation were reduced to supply heated effluent for a recirculation
system that is used to control ice accumulation in the intake.
The cooling system has a 27,917 m2, double-flow Type M, single-pass,
divided-surface condenser with 18,154 tubes. Each tube has an effective length
of 17.6 m and 2,54-cm outside diameter. The heated condenser water is released
into a 350-m long, concrete conduit where water velocities are about 1 m/sec
at full operation. The water then passes into a rock-walled, discharge canal
which averages 175-m wide, 7-m deep in the upper end, 3-m deep in the lower end
and is 2000-m long. At full pumping, the upper discharge canal velocities
average about 6 cm/sec and lower canal velocities average about 12 cm/sec.
However, the velocity is not uniform because high velocity waters, approaching
1 m/sec, enter the discharge canal from the overflow conduit and form an eddy
of slower water on the east side. This adds to the variability of organismic
residence times in the discharge canal. Plum Creek drains into the discharge
canal but contributes less than one percent of the volume-flow through the
lower canal.
-------
MAUME RIVER
Figure 1. Map of the study area showing the locations sampled for water
chemistry, phytoplankton, zooplankton, community metabolism
and periphyton.
-------
Figure 2. Map of the study area showing the locations sampled for larval
fish.
a
-------
At full operation, water passage through the cooling system back to Lake
Erie averages nearly 4,5 hours. Calculated passage times through the three
main parts of the cooling system were seven seconds through the condenser, 20
minutes through the concrete conduit, and four hours through the discharge canal.
The first plant unit started in May, 1971, and the remaining units started
at approximately one year intervals thereafter until completion in May, 1974.
Preliminary operations were erratic, but stabilized as more units contributed
power; 94 percent of all plant shutdowns to date occurred in 1971 and 1972
(The Detroit Edison Company, 1976).
After leaving the discharge canal, the heated effluent formed a plume
which extended up to 6 km from the mouth of the canal. The largest plume
measured by The Detroit Edison Company (1976) encompassed about 860 ha to the
1.7°C (3PF) isotherm. The plume position and size depended on the pumping
rate, power generation rate and the direction and velocity of the wind. Heat
dissipation from the plume occurred within one to two days.
Chlorine was added to the cooling water at the intake to control growths
in the condenser; two times per day during summer and once per day during
winter. During the warm months (April-October), chlorine was added at one
hour intervals for four hours starting at 0700 hours and then again for four
hours at 2030 hours. In winter, chlorine was injected for 0.5 hour periods at
0700, 0900, 1100, and 1300 hours. The highest concentration of chlorine
measured in the upper discharge canal by the Company was 0.29 mg/liter (The
Detroit Edison Company, 1976).
THE COOLING WATER SOURCES
The western basin of Lake Erie is a shallow (d = 7.3 m), highly turbid
area that is partially separated from the rest of Lake Erie by the Bass Islands
and Point Pelee. Beeton (1961) attributed the high turbidity to wind-generated
resuspension of sediments, river discharges, and plankton. Photometric mea-
surements made during this study indicated that only 0.1 percent of the total
mean surface light penetrated to the 5-m depth during spring and summer. Wind-
generated mixing usually maintains vertical homeothermy in the basin but calms
occasionally allow temporary stratification for a few consecutive days (Carr
et al., 1965).
The surface area of the basin is 3,276 km2 (Carr .et al., 1965) and the
shoreline is characterized by natural and artificial islands, peninsulas,
spits, and flooded river mouths. The spatial diversity along the shores pro-
vides numerous types of fish-spawning habitat including marshes, rocky reefs,
and sand and gravel bars. Most of the bottom sediment near shore is composed
of coarse, medium, and fine sand which grades into silt and clay in the deeper
waters off shore (Kelly and Cole, 1976).
The Detroit River annually contributes about 95 percent of the flow to the
western basin of Lake Erie while the Maumee River, the second largest tribu-
tary, contributes 2.5 percent. The Raisin River contributes less than 0.3
percent (Ecker and Cole, 1976). The locations of these rivers are shown in
Figures 1 and 2. Significant numbers of larval fish may enter the study area
-------
from each of these rivers. The combination of tributaries and prevailing south-
westerly winds generally causes the water in the southwestern corner of the
basin to circulate in a clockwise eddy (Hartley et al., 1966), But, pronounced
day to day variations can occur because of changing winds and tributary discharge.
Water from the Detroit River predominates off shore while water from the Maumee
and Raisin Rivers dominate the west shore south of Stony Point. Mean resultant
water velocities in the lake are 1.6 to 2,0 km/day; but during storms, plankton
from either the Detroit or Maumee Rivers could reach the study area within a
day and plankton from the island region of the basin could reach the power plant
in two days. Wind velocities of 51.5 km/hour or more occur an average of 23
days/year.
Until recently, the lower Raisin River was highly polluted with municipal
and industrial wastes, particularly biodegradable organics. Anoxia was once
common during summer, but improvements in waste treatment have partially
mitigated harmful impacts.
10
-------
SECTION 4
MATERIALS AND METHODS
WATER MOVEMENT
Current velocities were estimated with drogues, a Gurley Current Meter, a
film recording current meter (General Oceanics) and calculations based on cool-
ing system morphometry and pumping rates. The Gurley Current Meter was used to
sample 23 to 26 points along a cross sectional profile of the concrete conduit
just upstream from where it entered the discharge canal. Drogues were con-
structed from two masonite panels (0.6 x 1.2 m) set perpendicular to each other
and weighed to equilibrium with the water. These were attached to a 38 cm x
2.5 cm styrofoam float. The drogues were followed for one to several hours
and the distances recorded. The film recording current meter yielded data from
near bottom in the lower discharge canal for 14 days in 1973 and at P10 in the
lake for 20 days in 1975. It also yielded data from 2.5 m at P10 for nine days
in 1975. Drogues were set at the surface and 1-m and 3-m below the surface at
station P10. For current measurements within the cooling system drogues were
set at 1 to 5-m depths in sets of five replicates. Pumping rates were obtained
from records kept by the Detroit Edison Company and calculations based on
chloride concentrations.
CHEMISTRY, PLANKTON AND PERIPHYTON
Chemistry
The water chemistry, phytoplankton, zooplankton and primary productivity
all were sampled at the same stations (Fig. 1) and on the same schedule (Table
1).
The sampling for plankton, primary productivity and water chemistry was
conducted at seven stations in the cooling system. The river and lake source-
waters were sampled at stations 9 and 17. The water at those two locations
could be representatively assessed with relatively few samples in contrast to
the water in the short (100 m) intake canal which was usually incompletely
mixed with highly variable proportions and distributions of lake and river
waters. Therefore, intake station 18 was calculated by proportioning flows
from the river and lake once the proportions of lake and river water had been
calculated from data gathered on chlorides, total solids, dissolved solids,
plant pumping rates and U.S.G.S. measures of river discharge. Virtually all river
water is drawn into the cooling system, and the balance is made up by lake
water. U.S.G.S. flow data came from 10-km upstream, and therefore,
11
-------
TABLE 1. SUMMARY OF SAMPLES COLLECTED AND PROCESSED FOR CHEMISTRY, PRIMARY PRODUCERS AND ZOOPLANKTON,
1972-1975
Date
Temperature
(Hours) and Oxygen
1972-73
Nov.
Nov.
Nov.
Jan.
Jan.
Jan.
Mar.
Apr.
Apr.
June
June
June
Aug.
Aug.
Aug.
Sept
Sept
Oct.
*S -
9 (5-10)
9 (21-2)
10 (12-17)
18 (21-2)
25 (12-17)
26 (5-10)
30 (21-2)
5 (12-17)
6 (5-10)
11 (21-2)
12 (12-17)
13 (5-10)
8 (21-2)
9 (12-17)
10 (5-10)
. 28 (21-2)
. 29 (12-17)
1 (5-10)
S* R//
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
Tt
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
Chloride and Nutrient
Total Solids Chemistry Phytoplankton
S R
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
T S R T
35
35
35 7 5 35
35 7 5 35
35
35
35 7 5 35
35
35
35
35
35 7 5 35
35 7 5 35
35
35
35 7 5 35
35 7 5 35
35 7 5 35
S R
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
7 5
T
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
Gross
Productivity
S R
7 3
5 3
6 3
7 3
7 3
7 3
3 3
7 3
6 3
7 3
7 3
7 3
7 3
7 3
7 3
7 3
7 3
7 3
T
21
15
18
21
21
21
9
21
18
21
21
21
21
21
21
21
21
21
Zooplankton Periphyton
S R T S R T
7 5 35
7 5 35
7 5 35 Ice Problems
7 5 35
7 5 35
7 5 35
7 5 35 May 5 -May 30
7 5 35 7 2 14
7 5 35
7 5 35 July 10-July 31
7 5 35 7 2 14
7 5 35
7 5 35
7 5 35
7 5 35
7 5 35
7 5 35
7 5 35
Number of stations
#R •» Replicates per
tT =
Total samples
station
(continued)
-------
TABLE 1 (continued).
Dace (Hours)
1973-74
Dec. 12 (21-2)
Dec. 13 (12-17)
Dec. 14 (5-10)
Jan. 31 (21-2)
Feb. 1 (12-17)
Feb. 2 (5-10)
April 10 (21-2)
April 11 (12-17)
April 12 (5-10)
June 11 (21-2)
June 12 (12-17)
June 13 (5-10)
Aug. 14 (21-2)
Aug. 15 (12-17)
Aug. 16 (5-10)
Oct. 19 (5-10)
Oct. 20 (21-2)
Oct. 21 (12-17)
Temperature
and Oxygen
s*
7
7
7
7
7
7
7
7
7
4
4
7
7
7
7
7
7
R#
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
Tt
35
35
35
35
35
35
35
35
35
20
20
35
35
35
35
35
35
Chloride and
Total Solids
S R T
7 5 35
7 5 35
7 5 35
7 5 35
7 5 35
7 5 35
7 5 35
7 5 35
7 5 35
7 3 21
7 3 21
7 3 21
7 5 35
7 5 35
7 5 35
7 5 35
7 5 35
7 5 35
Nutrient
Chemistry Phytoplankton
S R
7 5
7 5
7 5
7 5
7 5
7 5
4 5
4 5
7 5
7 5
T
35
35
35
35
35
35
20
20
35
35
S R
7 5
4 5
7 5
5 5
4 5
5 5
7 5
4 5
7 5
7 5
7 5
7 5
7 5
4 5
7 5
7 5
4 5
4 5
T
35
20
35
25
20
25
35
20
35
35
35
35
35
20
35
35
20
20
Gross
Productivity
S R
7 3
7 3
7 3
7 3
7 3
7 3
7 3
7 3
7 3
7 5
7 3
7 3
7 3
7 3
7 3
7 3
T
21
21
21
21
21
21
21
21
21
35
21
21
21
21
21
21
Zooplankton Periphyton
S R T S R T
4 5 20
4 5 20
7 5 35
4 5 20 Feb- 14-Mar. 15
4 5 20 7 2 14
5 5 25
4 5 20
4 5 20
7 5 35
July 10-July 31
4 5 20
4 5 20
4 5 20
4 5 20
4 5 20
*S = Number of stations
#R = Replicates per station
tT = Total samples
(continued)
-------
TABLE 1 (continued).
Temperature
Dace (Hours)
1974-75
Jan. 24 (21-2)
Jan. 25 (5-10)
Jan. 25 (12-17)
March 15 (12-17)
March 16 (21-2)
March .17 (5-10)
May 16 (21-2)
May 17 (12-17)
May 18 (5-10)
July 27 (21-2)
July 28 (12-17)
July 29 (5-10)
Sept. 15 (21-2)
Sept. 16 (12-17)
Sept. 17 (5-10)
and Oxygen
S*
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
R#
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
Tt
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
Chloride and Nutrient
Total Solids Chemistry Phytoplankton
S
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
R
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
T S R T S R T
35 7 5 35
35
35 4 5 20
35 4 5 20
35 7 5 35
35
35 7 5 35
35 4 5 20
35
35 7 5 35
35 4 5 20
35
35 7 5 35
35 4 5 20
35
Gross
Productivity
S
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
R
3
3
3
3
3
3
3
3
3
3
3
J
3
3
3
T
21
21
21
21
21
21
21
21
21
21
21
21
21
21
21
Zooplankton Periphyton
S
4
4
4
4
4
4
4
4
4
4
R T S R T
5 20
5 20
5 20
5 20
5 20
5 20
5 20
5 20
5 20
5 20
*S = Number of stations
#R = Replicates per station
tT = Total samples
-------
underestimated river flow at the power plant, A partial correction of 1,5
m3/sec was made to account for additions from the City of Monroe, Michigan,
The discharge canal was sampled at the upstream end (station 12), the
middle (station 8), and the downstream end (station 14). The thermal plume
was sampled at station 15, a point located along the central axis where the
temperature was about one-half the difference between the lake temperature and
the temperature in the lower discharge canal. For example, when Lake Erie was
10°C and the lower discharge canal was 18°C, station 14 was about 14°C. Sta-
tion 16 was located along the central axis near the plume edge at a tempera-
ture about 1 to 2°C above ambient.
Chemical distributions were sampled every 8 to 10 weeks. Each station was
sampled with a 4.1 or 8.1-liter Van Dorn water bottle. Five replicates were
obtained from each station at randomly located depths except at stations 14 to
16. Because these latter stations were shallow, station 14 (3-m deep) was
sampled near the surface and just above the bottom, while the two plume sta-
tions (1 to 2m deep) were sampled only near the surface.
Water temperature and oxygen concentration were measured in duplicate at
each of the seven stations at 1-m intervals from the surface to the bottom.
Those samples, as well as samples used to assess the concentrations of chloride
and total solids, were taken at three time, periods on each sampling trip. The
time periods were in the morning (0800 to 1200), afternoon (1300 to 1800), and
evening (0900 to 0100). This sampling effort was the same from November, 1972,
to September, 1973» The remaining chemical parameters were measured only for
one of the three sampling times on each sampling trip (Table 1); but not
necessarily the same time period on all trips. These chemical parameters included
suspended solids, dissolved solids , total phosphorus , nitrate-nitrogen, ammonia-
nitrogen, total organic carbon, and dissolved organic carbon (<0.45y). Par-
ticulate phosphorus and organic carbon were calculated by difference between
total and dissolved concentrations. Organic nitrogen was calculated by the
difference between Kjeldahl-nitrogen and ammonia-nitrogen. Previous work
(Cole, 1972) established that nitrite concentrations were negligible in the
study area so total inorganic nitrogen and total non-gaseous nitrogen were calcu-
lated only from nitrate-notrogen, ammonia-nitrogen, and organic-nitrogen.
Temperature and oxygen were measured with a YSI oxygen meter that was
regularly standardized against Winkler titrations. Oxygen measurements were
within 0.5 mg/liter of the Winkler determinations. Percent saturation of
oxygen was calculated from data presented in A.P.H.A, (1971). Chemistry was
measured mostly as outlined in EPA (1971), Water samples for everything but
chloride were preserved in the field with Hg2Cl2> then analyzed as described
by EPA (1971). Chloride samples were not preserved.
The total suspended solids (seston) were defined as the dry weight gain
of a millipore filter (0.45-w) from 100-ml of water passed through the filter.
The filters were dried in a dessicator, weighed and then dried
to constant weight. Two sample blanks were flushed with dis-
tilled water and handled similarly in every respect. Weight changes in the
blanks were assumed to be caused by moisture. The estimates of suspended
solids were corrected for the measured moisture accumulation that could not
15
-------
be removed from the filter by dessication, To determine total solids,
tered samples were evaporated to constant, dry weight. Dissolved solids were
calculated as the difference between total solids and suspended solids.
Phosphorus concentrations were determined by a modification of a technique
described by Wadelin and Mellon (1953). Both total and filtered (0.45-y), 50-ml
aliquots were hydrolized to determine total and "dissolved" phosphorus,
respectively. About 10-ml of double-distilled water were added to the boiling
flasks, then the contents were neutralized with phenothalien, 0.02 ^I^SO* and
0.2 NaOH. Then the samples were transferred to 500-ml, pear-shaped, separatory
funnels. Each flask was rinsed twice with 10 ml of double-distilled
water and each rinse was added to the funnel with 4 ml of concentrated hydro-
chloric acid, 15 ml of 1-buterol and 15 ml of chloroform-buterol mixture. The
funnel was then stoppered and shaken for 5 minutes. After complete separation,
the lower layer was drained away. Exactly 10 ml of chloroform-buterol were
added with 3 ml of a 10 percent, ammonium molybdate solution. The funnel was
then shaken for 4 minutes and, after separation, the absorbance of the lower
layer was determined at 310 my.
Nitrate-nitrogen was determined with the modified Brucine method described
by Jenkins and Medsker (1964). Ammonia-nitrogen and Kjeldahl nitrogen were
determined as described by EPA (1971) but the 50-ml sample was distilled follow-
ing nesslerization.
Carbon concentrations were determined on a Beckman single-channel carbon
analyzer as described by the EPA (1971). Total organic carbon was determined
after adding HC1 to a pH <1. Dissolved organic carbon was analyzed by passing
a sample through a cleaned (flushed with 250-ml of distilled water), 0.45-y
Millipore filter, treating with HC1 until the pftwas_< and then sweep ing with nitrogen.
Phytoplankton
Phytoplankton samples were drawn from the same Van Dorn water collections
used for chloride and total solids (Table 1). During the first year of the
study; to September, 1973, emphasis was placed on the short-term variation
associated with different times of the day (morning, afternoon and evening) and
different locations in the cooling system. All phytoplankton were identified
to the most specific taxa possible only in the afternoon samples. Morning and
evening samples were identified to class.
After September, 1973, in the last two years of the study, the emphasis was
placed on long-term annual comparisons of entrainment rates rather than short-
term variations. Plankton were sampled only at stations 17, 9, 12 and 14 (5
replicates each as in the first year) in the afternoon. All phytoplankton were
identified to genus, except at station 12, where they were still identified to
species whenever possible.
Subsamples of 480 ml were drawn off and preserved with 20 ml of 37% formal-
dehyde solution for all phytoplankton collections. Algae were enumerated with
the membrane-filter (0.45-y) technique described by McNabb (1960) and adapted
by APHA (1971). Algal counts were based on the natural living unit, be it a
cell, colony, or filament. The conversion from a taxon's frequency in 30
16
-------
microscope fields to their sample density was determined using the following
equation:
numbers/ml = d
(quadrant area in ym2) x (ml filtered)
where d is the theoretical density corresponding to a given frequency.
The diatoms collected on the filter could be reliably identified only to
the centric or pennate taxonomic level. Species identifications were made from
permanent mounts prepared according to Weber (1970) from combined concentrates
of replicates from one station. The proportions of species found in these pre-
parations were then used to calculate the abundance of each species collected
on the filter.
The phytoplankton identifications were derived from keys and descriptions
which included Hustedt (1930), Taft (1945), Taft and Taft (1971) and Weber
(1970). The coccoid blue-green algae were classified according to the revisions
byDrouetand Daily (1956). Some questionable forms were referred to Dr. D.C,
Jackson and Dr. F. Begres of Eastern Michigan University at Ypsilanti, Michigan.
The volume of a taxon in a sample was calculated by multiplying the density
by the estimated, mean specimen volume. The mean specimen volume was determined
from modified, geometric formulae applied to sizes of the counted specimens.
The mean volumes were averaged for all stations sampled on one date. If fewer
than 10 specimens were observed on a single collecting date, a mean annual,
specimen volume was used for all dates. The mean specimen volumes of phyto-
plankton classes were calculated as the sum of all class volumes. The biomass
(carbon content) was derived from volume estimates using formulae calculated
by Strathmann (1967).
Diversity indices were computed for algae collected at each station using
Shannon's index as described in Pielou (1969, pg._231-235). Evenness, or
equitability, was computed as E = H/logiQS where H is the diversity index and
s is the number of different taxa present.
Tests of differences among stations were conducted using analysis of vari-
ance after all data were transformed logarithmically. When significant
differences appeared, Tukey's multiple comparison test was applied at
a = 0.05.
Periphyton
The attached communities were sampled during each of the four seasons in
1973 and 1974 at the same stations sampled for chemistry and plankton (Table 1).
Weather sometimes disrupted sampling at stations 15 and 16 in the lake. Rates
of periphytic accumulation were assessed with replicate pairs of styrofoam
blocks (2.5 cm x 5.1 cm x 7,5 cm) which were collected every 5 to 7 days over
a 3 to 4 week period. The slides were suspended about 0.5 m below the surface.
The retrieved substrates were frozen until they were processed. The styrofoam
outer wall, along with the attached growth, was shaved into xylene which dis-
solved the styrofoam. Then the attached growth was filtered from the solution
with 0.45-y millipore filters.
17
-------
Zooplankton
The zooplankton were sampled from the same 5 replicates per station used
for chloride and total solids. As with phytoplankton, the first year's (Novem-*
ber, 1972, to September, 1973) sampling emphasis was placed on short-term
variation associated with different times of the day and different locations in
the cooling system. All zooplankton were identified to the most specific taxa
in all replicates. After September, 1973, in the last two years of the study,
the emphasis was placed on long-term, annual comparisons of entrainment rates
rather than short-term variation. Zooplankton were then sampled with 4 repli-
cates at a station only in the afternoon and evening at stations 7, 9, 12 and
8.
The zooplankton were sampled with an 8,1 liter, Van Dorn water bottle. The
contents were concentrated in the field by pouring them through a #25 Wisconsin
plankton bucket. They were preserved with 5 percent formalin. Samples were
diluted to known concentrations before a 1-ml subsample was counted in a
Sedgwick-Rafter cell. The animals were counted, identified to species when
possible, and measured using a whipple micrometer,
Zooplankton volumes were estimated by using linear measurements of the
length and maximum width to calculate the volume of common geometric figures
which best approximated the shape of the animal. Dry weights were calculated
from the volumes by assuming that the organisms were 90% water and their speci-
fic gravity was 1.0 (Cummins and Wuycheck, 1971). Like phytoplankton, the
zooplanktonic diversity was determined using the diversity index described by
Pielou (1969).
Spatial and temporal differences were tested with analysis of variance
after the data were corrected for heterogeneity of variance. Tukey's test of
multiple comparisons was applied when significant (« < 0.05) differences existed.
Linear regression analyses were also used to assess the relation between depth
and the distribution of the major taxa.
Community Metabolism
Gross primary productivity and community respiration were measured at the
same 7 stations in the cooling system by the change in oxygen technique des-
cribed in APHA (1971). Three, 300-ml light bottles and three, 300-ml dark
bottles were set near the surface (0.5-m deep in 1972-73 and 0.2-m deep in
1973-75) at all stations. Bottles were suspended in the morning, afternoon and
evening on all trips made from 1972 to 1975. Water was collected at the sur-
face with an 8.1-liter Van Dorn bottle from which all station test-bottles were
filled. The bottles were suspended at 0800 to 1230 hours, 1200 to 1800 hours
and 2100 to 0100 hours over the study period. Incubations on a particular date
never were less than 2 hours or more than 4.5 hours.
18
-------
FISH AND MIDGES
Midges
Midges, drifting through the cooling system as larvae or pupae, were col-
lected in the 1973 samples that were intended for pilot studies of larval fish
distributions. They were captured at stations PI to P5 (Fig. 2) using a 1-m
plankton net with 571-y mesh openings. Each station was sampled with 6 tows;
each 5-min long (about 150m3 of water). Two tows each were made at the bottom,
mid-depth and the surface wherever there was enough depth to differentiate.
Sampling was conducted every 1 to 2 weeks during May and June. All samples
were preserved in 5 percent formalin. No attempt was made to identify the
midge larvae and pupae.
Non-larval Fish
Food habits of non-larval fish found in the cooling system were investigated
during the study period. The zooplanktivorous food habits of four fish species
common in the study area were examined in conjunction with studies conducted on
zooplankton entrainment. These data are presented in a report by Kenaga and
Cole (1975) which is included in Appendix (A) .
Larval Fish
Larval fish were first sampled in a pilot study conducted during 1973
(Table 2). Sampling took place at Stations PI through P5, In 1974 and 1975,
studies of larval fish entrainment were expanded and modified so that samples
were taken at stations P2, P3, P6, P7, P10, Pll and P12. The changes were made
to improve estimates of larval fish entrainment into the cooling system. Samp-
ling in the plume at Station PI was not satisfactory because the area to be
sampled was often too shallow. Instead, sampling was conducted at three perma-
nent stations in deeper water which were usually down-current (north) from the
thermal plume. These three stations served to estimate the variability of
larval populations in the lake near shore where there was a high probability
of eventual entrainment into the cooling system.
In May and June, 1975, additional studies were conducted on larval fish
distribution in the lake, larval fish mortality in the cooling system, and the
comparability of different capture techniques for larval fish in the lake. Four
stations, P13 through P16, were sampled along a transect which extended 16-km
toward the center of the western basin. The purpose of this sampling effort
was to tentatively assess how fish larvae were distributed in relation to shore.
At another station, P17, daytime comparisons were made of results from differ-
ent sampling techniques including a Kenco pump, high-speed plankton sampler,
and 1-m plankton nets of several different mesh sizes. Station P17 was also
the site used to compare plankton-net tow lengths and larval depth distributions
during the day and night.
The Kenco pump, high-speed plankton sampler and 1-m plankton net were used
on the same days for comparison. The Kenco pump was submersible with a realized
pumping capacity of 6,9 liters per second. It was submersed at the bow of an
anchored boat to a depth of 0.25 meters and run for one hour. Pump effluent
19
-------
TABLE 2. LARVAL FISH SAMPLING SCHEDULE
Dates PI
Cooling system
distributions
1973*
05/11 X
05/17 X
06/01 X
06/08 X
06/15 X
1974f
05/10
05/29-30
06/11
06/21
07/01
07/15
07/26
1975f
05/12-13
06/02
06/25
07/09
07/31
P2
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
P3 P4
X X
X X
X X
X X
X X
X
X
X
X
X
X
X
X
X
X
X
X
P5 P6
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
P7
X
X
X
X
X
X
X
X
X
X
X
X
STATION
P10 Pll
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
P12 P13 P14 P15 P16 P17
X
X
X
X
X
X
X
X
X
X
X
X
(continued)
-------
TABLE 2 (continued)
Dates
Transect*
1975
05/22
05/23
06/09
06/16
06/19
07/02
07/22
STATION
PI P2 P3 PA P5 P6 P7 P10 Pll P12 P13
X
X
X
X
X
X
X
P14
X
X
X
X
X
X
X
P15
X
X
X
X
X
X
X
P16 P17
X
X
X
X
X
X
X
Gear Comparison
and Day-Night*
05/21 X
05/23 X
05/24 X
06/18 X
06/19 X
06/20 . X
Mesh Sizes**
05/20 X
05/22 X
06/18 X
06/19 X
(continued)
-------
TABLE 2 (continued)
STATION
Dates PI P2 P3 P4 P5 P6 P10 Pll P12 P13 P14 P15 P16 P17
nn
Tow Length
05/20 X
05/21 X
06/18 X
06/20 X
*0n each date in 1973 cooling system distributions were sampled near the bottom, mid-depth
and surface; two samples at each depth for a total of 6 samples per station.
each date in 1974 and 1975 cooling system distributions were sampled at each station
with 5 oblique tows from bottom to surface.
^Transects were sampled with a combination of discrete-depth and oblique tows. On each date,
each station was sampled with 3 oblique tows from bottom to surface and 2 samples each from bottom,
mid-depth and surface for a total of 9 discrete samples.
#Five separate samples were taken with each kind of gear on each date sampled. Day and night
comparisons were made with 5 samples each from bottom, mid-depth and surface for 15 samples during
the day and 15 samples during the night on each date sampled.
Five samples were taken with each mesh size on each date sampled.
'"'Five tows were made for each towing time tested on each date sampled.
-------
was filtered through a, 571-y nylon net with a 1,8-liter bucket. Approximately
25m3 were processed in one hour. Five replicates were collected each sampling
date.
The high-speed plankton sampler, described by Miller (1961), was towed
initially at 0,5m/sec but that was decreased to about 0,2m/sec because larval
fish extrusion was suspected from the high proportion of mutilated larvae in
the samples. The sampler was mounted off the side of the boat and towed at a
depth of 0.25 meters for 25 minutes. Approximately 22m3 were sampled at the
reduced speeds. Five replicate tows were made on each sampling date.
The variation in catch with length of towing time was estimated with a
1-m, 571-y net. A General Oceanics (Model 2030), digital flow meter was sus-
pended in the center of all nets towed and all nets were outfitted with plastic,
1.8 liter buckets. Tows of 1, 2, 3, 4, and 5 minutes were made at the surface
at station P17 (Fig. 2). An average of 35m3/min was sampled in the tows with
no apparent variability related to towing time. Five replicates were made for
each tow-length.
Capture rates of larval fish in 1-m nets of different mesh size were com-
pared using 361-y, 571-y, 760-y, and 1000-y, nylon-mesh sizes. Five replicate
samples were taken with each mesh size on each date. The nets were towed at
O.lm/sec at the surface for 3 minutes, filtering about 90m3 of water.
Samples of surface, mid-depth, deep (about 5-m deep and 1 to 2-m above
bottom) and oblique tows were made at station P17 with a 571-y net. Oblique
tows were drawn at a constant rate to the surface from about the 5-m depth.
Five, 1-min replicates (filtering about 33m3 of water) were made for each
stratum sampled. The station was similarly sampled at night with surface,
mid-depth, deep and oblique tows. In addition, during the day, a 571-y net was
towed on a bottom sled for 3 minutes at a speed of 0.2-m/sec. Approximately
31m of water were sampled (estimate based upon known speed and net area).
Five replicates were collected on each date sampled.
A transect perpendicular to shore was sampled to define differences in
larval fish densities at various distances from shore (Fig. 2). Four stations
along the transect were sampled during the day with a 571-y net. At each of
the transect stations, three replicates were collected from the surface, three
from deep water, and three with oblique tows from deep water to the surface.
About 100m3 of water were sampled during a 3-min tow (1 m/sec). Stations P13,
P14, P15, and P16, all along the transect, were 2, 6, 11, and 16 km from shore,
respectively.
Tows with 571-y mesh, 1-m nets were used during 1973, 1974, and 1975 to
estimate larval fish abundance and distributions in the study area. Prelimin-
ary sampling was conducted at different depths in 1973 but it indicated no con-
sistent, significant differences among surface, mid-depth, and deep samples
(Nelson and Cole, 1975). Therefore, in 1974 and 1975 a 1-m, 571-y nylon net
was towed at an oblique angle through the water column at a constant rate from
about 5-m deep to the surface for 2.5 min. Towing speed was approximately
1 m/sec. A 1.8 liter plankton bucket was attached and a general Oceanics
(Model 2030) digital flow meter was fitted at the center of the net opening.
23
-------
Two separate stations were sampled in the Raisin River channel (Fig. 2) to avoid
the complex mixing in the short intake. The upstream river site (P7) was located
about 1 km upstream from the plant intake. Another station (P6) was located at
the mouth of the river to sample lake water that was drawn up the old river chan-
nel. Abundance at the intake (station FO) was calculated from concentratons at
P6 and P7, which were weighed for river and lake volume-flow contributions to
the cooling system. River-discharge rates were provided by the U.S.G.S. and
plant pumping rates were provided by The Detroit Edison Company. Evaluations
of water movements made during this study indicated that virtually all river
water is drawn into the cooling system and the balance is made up by lake water.
Samples also were taken from the upper (F2) and lower (P3) ends of the discharge
canal, and 3 Lake Erie stations (P10, Pll, and P12). The latter were sampled to
assess the concentration and spatial variation of lake larval abundances.
Mortality was estimated at three stations within the immediate vicinity of
the plant. Larvae were captured with a stationary, 1-m, 571-y nylon net with a
General Oceanics (Model 2030), digital, flow-meter suspended at its center. A
modified (bolting cloth on the inside rather than the outside of the bucket)
582-y, 1.8 liter bucket was attached to the net. The stationary net was set in
a low velocity current of 1.15 to 0.25 m/sec to reduce mortality stemming from
the technique and to ensure comparable sampling conditions at all sites. A
reference station was sampled in the intake canal near station PO to estimate
combined natural and net-caused mortalities. The second station was located
near P2 within 100-m of the out-fall from the concrete conduit into the discharge
canal. Dead or dying larvae were separated from live animals by color and
mobility. Translucent or mobile individuals were counted as alive while opaque,
immobile ones were assumed to be dead. A field observation device, similar to
one described by Marcy (1971), was used to maintain the ambient and elevated
water temperatures around separation dishes while live larvae were counted.
All larvae collected were preserved in 5 percent formalin and later counted
and identified to the most specific taxa possible. Rose-bengal dye was added to
ease sorting. All samples were standardized to number per 100 m3.
All data were tested for normality using the Shapiro-Wilk test (Gill, in
press) and homogeneous variance using Bartlet's test. A log (x + 1) transforma-
tion was applied to all data to correct for non-normality. Then Bartlet's test
was applied to the transformed data. Heterogeneous variance was usually indi-
cated and a modified Scheffe's post-data test (Gill, 1971) was applied when
applicable. Tukeyfs multiple range test was used to identify differences among
means when departures from homogeneity were minor. It was applied to the
technique comparisons, comparison of stations along the transect, and the com-
parisons among stations in 1975. Analysis of variance was applied to compari-
sons of day and night abundances.
24
-------
SECTION 5
RESULTS
HYDRODYNAMICS AND WATER TEMPERATURES
The Lake
Currents in the lake were measured with drogues and a film recording current
meter to assess the relative impact of wind on the direction and velocity of
water movement. All studies in the lake were conducted near stations P10 and
Pll (Fig. 2). The continuous film recording meters were placed, about 5.0 m
below the surface near the bottom and 2.5m below the surface where they were
partially protected from vandalism and storms. Instruments were lost to storms
on two occasions and the film record was usable from a relatively small part of
the time that instruments otherwise remained installed. The wind and water
relationships in Table 3, Bl and B2 were derived from the retrieved record.
A significant (p < .05) regression between wind and water velocity and
direction appeared at 2.5 m below the surface (Fig. Cl) but not at 5 m. The
velocities at 5 m were barely measurable; error probably precluded the identifi-
cation of any relationship which may have existed. At 2.5 -m, far from all of
the variation in water velocity was explained by the wind. Part of the unex-
plained variation could have been effected by the length of the observation times
that were compared. Water measurements were the means of instantaneous measure-
ments made every 30 minutes during 9-hr spans. The data available for wind
measurements were the means of instantaneous measurements of wind taken at the
U.S. Weather Station (Toledo, Ohio) at 3-hr intervals over 9-hr spans. Improved
estimates of the relationships might be determined from continuous records of
wind and currents corrected for lags in the water response to wind change.
The current-meter recordings were compared to drogue estimates of water
velocity and directionwhich were obtained from the Detroit Edison Company and
reported in Cole (1976). These estimates were made at 3 depths (Table B2) . Con-
siderable difference existed in the estimates of water velocity made by drogues
and current meters set at 2.5-m to 3-m depth; the metered velocities exceeded
drogue estimates by nearly 4 times (Table 4). A range of possible velocities,
calculated from the two techniques, is presented in Figure 3.
The current meter may have been a better estimator of horizontal velocity
than drogues, based on limited observations from a current meter placed in the
lower discharge canal at 1-m above the bottom in an area about 3-m deep. That
meter recorded average velocities similar to the velocity which was calculated
from pumping rates and the cross-sectional area in the canal.
25
-------
to
TABLE 3. CALCULATED VOLUME-FLOW/SECOND BY VARIOUS TECHNIQUES IN DIFFERENT PARTS OF THE COOLING SYSTEM
(numbers in parentheses indicate the number of replications)
Date
April 5, 1973
June 11, 1973
June 12, 1973
INTAKE
River Lake Drogue Sum
Drogue Drogue for Intake
23 m3 (4) 38 m3 (4) 61 m3
20 m3 (4) 35 m3 (4) 55 m3
June 13, 1973 -10 m3 (4) 75 m3 (5) 65 m3
August 10, 1973
February 2, 1974
UPPER DISCHARGE LOWER DISCHARGE
Gurley Probable Rate
Meter from Pump Ratings* Drogue
60 m3 63 m3
63 m3 17 m3 (4)
63 m3 46 m3 (1)
63 m3
68 m3 63 m3
60 m3 63 m3
Drogue
33 m3 (5)
23 m3 (2)
From the Detroit Edison Company. Pump records are incomplete and the actual numbers of pumps operating
is unknown.
-------
to
1.0
J2.0
0)
°
4,0
5,0
6.0
Water Velocity as % of Wind Velocity
1.0 2.0 3.0 4.0 5.0
METER
BOTTOM
V
Figure 3. Relative water velocity at different depths in the study area
near stations 2 and 3.
-------
TABLE 4. DROGUE AND CURRENT METER ESTIMATES OF MEAN WATER VELOCITY AND RESULTANT DIRECTION
S3
09
Drogue
Om
M
Drogue"
1m
Drogue*
2m
Current
meter"*"
2.5m
Current
meter"*"
5.0m
Wind
Velocity
n cm/sec
5 678.4
23 507.4
20 556.2
34 301.3
20 330.8
Resultant
Azimuth*
74°
164°
154°
143°
138°
Water
Velocity
cm/sec
7.8
6.7
5.8
12.2
4.1
Resultant
Azimuth*
76°
146°
206°
143°
189°
Velocity as
% of Wind
1.3
1.4
1.1
4.1
1.3
Deviation
from Wind
-27°
+ 8°
+ 5°
- 9°
33°
*Direction of origin.
"'Data from the Detroit Edison Company.
"^General Oceanic Film Recording Current Meters.
-------
Water velocities at the upper 3 meters seemed nearly uniform but velocity
dropped rapidly from 3-m down to the bottom. Current directions for all depths
averaged slightly to the right of the wind movements. Depth related velocity
differences could profoundly effect plankton transport because different biases
in vertical distributions will produce differential rates of horizontal movement
through the basin. Some species could be more vulnerable to entrainment than
others. A seasonal profile of water movements was calculated for Figure 4 from
wind records at Toledo and a water velocity averaging 3 percent of wind velocity
(from the drogue and current meter results). From day to day, water movements
vacillated as unpredictably as the wind, but over a season, net water movements
were northeastward nearly parallel to shore. This was generally true for all
seasons and years included in the analyses. Therefore, the water and plankton
in the study area frequently came from the Maumee Bay region to the south.
Although the resultant water movements at 1 to 2-km from shore were north-
ward through the study area, the resultant movement of water immediately next to
shore appeared to be southward. A sand pit along shore, just to the north of
the discharge canal, has extended about 75 m into the discharge canal since the
canal was constructed. A natural, sandy shoal extended southward from the mouth
of the discharge canal, out into the basin more than 1 km from shore before it
sharply dropped off to a bottom comprised of silty sediments. The thermal dis-
charge emptied to the lake over the shoal and probably continued to maintain it
as the Raisin River once did naturally.
The Raisin River
The river discharge was variable but typical of smaller, mid-western tribu-
taries where the discharge in winter and spring months is 10 or more times the
discharge in late summer or fall (Fig. 5). Mean monthly discharges have been
recorded as high as 130 m /sec and as low as 1 m /sec. River discharge can
change an order of magnitude in hours following storms and rapid thaws. The
average annual river discharge is equivalent to 20 percent of the total cooling
water demand, about 17 m /sec. The rest must be drawn from the lake. The pro-
portion actually contributed by the river depends on the discharge at the time
(Table 5). In winter and spring, the river contributed much more than it did
in late summer. This variability in contribution affected the calculation of
total annual entrainment of organisms in the study area because species composi-
tion in the river and lake differed. Most species of planktonic organisms were
particularly vulnerable to entrainment for only a few weeks in the year; there-
fore, differences in species phenology may produce differences in the vulnera-
bility of species to entrainment,
The Intake Region
Water from the river and lake mixed in the river channel and the intake
before water was pumped through the condensers. Conductivity in the river
channel was surveyed 4 times to document mixing (Fig. 6). River water was
approximately twice as conductive as lake water on each survey although there
were date-to-date differences in the conductivity. These data indicated that
lake water could intrude up-river past the intake for nearly 1-km and river water
could progress beyond the intake toward the lake at least 0.5-km. The distribu-
tions also indicated that little river water reached the lake; most, if not all,
of the river must have been pumped into the cooling system on the dates sampled.
29
-------
CO
o
84^
.0-
-
6.0-
—
4.0-
2.0-
WINTER
70
90
mmm
70
mmm
90
T
70
SPRING
140 100
5^90
mm
mm
60
[60
mmm
mt
mm
SUMMER
70
60
\f\f
mmm
50
mmm*
O/"\
80
mmm
70
• %^
mmm
FALL
60
mmm
50
8Q
80
70
197071 727374757071727374757071 727374 7071 727374
SEASONAL WATER VELOCITY (cm/sec)
AND DIRECTION (°HEADING)
Figure 4. Mean daily resultant water velocity and direction calculated for each
season from 1970 to 1975.
-------
150
125
o 100
-------
TABLE 5. AMOUNTS OF RIVER AND LAKE WATER, VELOCITY AND PKSSAGE TIME IN THE DISCHARGE CANAL
u>
ro
Date
Nov. 9, 1972. (eve)
Nov. 10, 1972 (aft)
Nov. 10, 1972 (morn)
Jan. 18, 1973 (eve)
Jan. 24, 1973 (aft)
Jan. 25, 1973 (morn)
March 30, 1973 (eve)
April 5, 1973 (aft)
April 6, 1973 (morn)
June 11, 1973 (eve)
June 12, 1973 (aft)
June 13, 1973 (morn)
Aug. 8, 1973 (eve)
Aug. 9, 1973 (aft)
Aug. 10, 1973 (morn)
Sept. 2 , 1973 (eve)
Sept. 29, 1973 (aft)
Oct. 1, 1973 (morn)
Dec. 12, 1973 (eve)
Dec. 13, 1973 (aft)
River*
Water
57.4
52.0
49.0
17.4
42.2
44.0
63.0
43.0
38.0
22.0
20.0
23.0
11.0
10.5
12.0
3.7
5.0
7.0
12.2
12.8
Lake
Water
(m-Vsec)
0
0
0
45.6
20.8
19.0
0
20.0
25.0
41.0
43.0
40.0
31.0
31.5
30.0
38.3
37.0
35.0
30.0
29.4
Total
Discharge
(m-Vsec)
42
42
42
63
63
63
63
63
63
63
63
63
42
42
42
42
42
42
42
42
Mean
Velocity
(cm/ sec)
Upper
Discharge
3.9
3.9
3.9
3.9
5.8
5.8
5.8
5.8
5.8
5.8
5.8
5.8
3.9
3.9
3.9
3.9
3.9
3.9
3.9
3.9
Number
of
Pumps
6*
6
6
9
9
9
9
9
9
9
9
9
6
6
9*
6
6
6
6
6
Passage
Time
(hrs)
11.4
11.4
11.4
7.5
7.5
7.5
7.5
7.5
7.5
7.5
7.5
7.5
11.4
11.4
7.5
11.4
11.4
11.4
11.4
11.4
A,
From U.S.G.S. measurements corrected for 1.5 m/sec added by Monroe, Michigan.
"*" Recorded by the Detroit Edison Company.
f Estimated from chloride concentrations.
(continued)
-------
TABLE 5 (continued)
co
Date
Jan. 31, 1974 (eve)
Feb. 1, 1974 (aft)
April 7, 1974 (eve)
April 8, 1974 (aft)
June 11, 1974 (eve)
June 12, 1974 (aft)
Aug. 14, 1974 (eve)
Aug. 15, 1974 (aft)
Oct. 19, 1974 (eve)
Oct. 21, 1974 (aft)
Jan. 24, 1975 (eve)
Jan. 25, 1975 (aft)
March 16, 1975 (eve)
March 15, 1975 (aft)
May 16, 1975 (eve)
May 17, 1975 (aft)
July 27, 1975 (eve)
July 28, 1975 (aft)
Sept. 15, 1975 (eve)
Sept. 16, 1TJ5 CaiO
*
River
Water
(m-Vsec)
123.3
102.3
96.6
94.7
16.6
16.2
6.6
6.1
4.9
4.13
17.3
17.5
26.0
25.8
17.6
16.7
4.8
4.6
12.2
12.. 5
Lake
Water
(m^/sec)
0
0
0
0
60.8
61.3
70.8
64.3
44.4
51.8
32.0
38.8
16.3
30.5
17.6
17.6
79.7
79.9
72.3
12.0
Total
Discharge
(nr/sec)
42
42
42
42
77
77
77
70
49
56
49
56
42
56
35
35
84
84
84
84
Mean
Velocity
(cm/.sec)
Upper
Discharge
3.9
3.9
3.9
3.9
7.1
7.1
7.1
6.4
4.5
5.2
4.5
5.2
3.9
5.2
3.2
3.2
7.8
7.8
7.8
7.8
Number
of
Pumps
6
6
6
6
11
11
11
10
7
8
7
8
6
8
5
5
12
12
12
12
Passage
Time
(hrs)
11.4
11.4
11.4
11.4
6.3
6.3
6.3
7.0
9.9
8.6
9.9
8.6
11.4
8.6
14.0
14.0
5.7
5.7
5.7
5.7
From U.S.G.S. measurements corrected for 1.5 m/sec added by Monroe, Michigan.
-------
NORTH IANK
TOO TOO «iO_/iTi
TOO TOO /iro «io
TOO TOO/ MO (M
190 TOO >^^ft aao «M
IH
4«
OUTMU. MMWUUmM
CHANNEL
INTAKE
•OUTH SANK
RIVtA MOUTH
29 APRIL 1974
PLANT IHTAKI
IOUTH IANK
«IVt» MOUTH
4 FEBRUARY 1975
SUftfACf
III
4H
NORTH IANK
U. MKCIRCULATIOfl
CANAL
•OUTH OAHN
INTAKE ICE LINE
4 APRIL 1975
2BO / 140 140
240 140
140 140 140
240 140 240 240
CHANNU
•OUTH IANK
RIVER MOUTH
3 JULY 1975
Figure 6. Conductivity in the intake region of the Raisin River.
-------
Chloride profiles made at stations 17 and 9 confirmed the complexity of mix-
ing in the river channel (Fig. 7). The water in the river channel often was
vertically homogenous but lake water intruded upstream into the river water about
25 percent of the time. Intrusions occurred at various depths, and were not
related simply to thermal differences in the water masses. Only on 4 percent of
the occasions examined did river water reach the river mouth (station 17). The
chloride distribution reinforced our belief that most (90 to 100%) of the river
water was pumped through the condenser except when the river discharge exceeded
pumping demands.
Discharge Canal and Plume
The discharge canal, as expected, was almost vertically well-mixed, but
horizontal variations between stations 12 and 8 were great enough (greater than
3 mg/liter in 15 percent of the measurements) to indicate that an important water
mass transition could occur within a few hours (Tables 6, B3). The flow time
between stations 12 and 8 usually was less than 5 hours. These rapid transitions
probably influenced the precision of predictions for the mixing of lake and river
water in the intake at station 18 because the flow times between stations 9 and
17 and station 18 were similar to the flow time between stations 12 and 8. Errors
in measurements from the same water sample were usually about 5 percent. On any
particular day, expected differences between the predicted mixture of lake and
river water (from stations 9 and 17) at station 18 would vary from that at station
12 by 1 to 2 mg/liter and, occasionally, by 4 or 5 mg/liter. These variations
were too great to enable reasonable estimates of source-water proportions on any
particular date. But, annual means averaged out the daily variation and provided
a reasonable estimate of average conditions.
Table 7 summarizes the results of two different approaches used to estimate
the average annual proportions of river (9) and lake (17) water in the intake
and discharge flow. For the first approach, chloride and total solids, were
used as tracers to separately estimate proportions of lake and river water. In
the second case, the pumping rate, reported by Detroit Edison, and the river dis-
charge, reported by the U.S.G.S. (corrected for additions from the City of Monroe),
were used to calculate the amount drawn in from the lake, assuming that the river
was totally pumped through the condenser and lake water comprised the balance.
This method could only be applied to dates when pumping rates were actually
measured by the company. Pumping rates were not recorded for about one third of
the sampling dates. The only available estimates were calculated from the chemi-
cal tracers measured in the cooling system and the pumping rates reported for the
closest dates.
The mean annual averages estimated by both techniques (Table 7) indicate
that, most if not all, river water was pumped through the condensers as expected
from profiles of chloride and conductivity in the river channel. In fact, the
river contribution appeared to be slightly underestimated. This could have been
caused by a slight underestimate of river flow since U.S.G.S. measurements came
from 10-km upstream and, although corrections were made for water additions from
the City of Monroe (1.5 m3/sec), no corrections were made for other additions
over the 10-km reach.
Using tracers (Tables B3, B5, B6), differences in the properties of the
source waters were calculated for stations in the intake and the discharge canal.
35
-------
l-S-74
WITHOUT STRATIFICATION
13 15 17 19 21 33 25 27 29 31 33 35 37 39 41
13 15 IT 19 21 23 25 27 29 31 33 35 37 39 41
ON
00
ir
LU
tj
LJ
Q
6-I2-T4
LAKE WATER PREDOMINANT
46%
13 15 17 19 21 23 25 27 29 31 33 35 37 39 41
12-13-73
1 WINTER STRATIFICATION
13 15 17 19 21 23 25 27 29 31 33 35 37 39 41
3-B-75
RIVER VWTEF PREDOMWANT
14%
. 17 12
13 15 17 19 21 23 25 27 29 31 33 35 37 39 41
-f-
-H ^-
13 15 17 19 21 23 25 27 29 31 33 35 37 39 41
CHLORIDE (MG/LITER)
Figure 7. Representative categories of chloride profiles in the cooling
system of the Monroe Power Plant with percentage of time that
each of the conditions accrued.
-------
TABLE 6. MEAN ANNUAL CONCENTRATION OF CHLORIDE, DISSOLVED SOLIDS, AND TOTAL SOLIDS
(mg/liter)
to
Chloride
1973*
1974*
1975@
Grand Mean
Dissolved Solids
1973+
19 74+
1975f
Grand Mean
Total Solids
1973*
1974*
1975@
Grand Mean
17
21
19
21
20
304
243
222
256
293
286
252
277
.4
.9
.3
.9
.4
.4
.1
.6
.1
.3
.5
.3
9
29
31
32
31
385
398
361
381
433
412
457
434
.4
.7
.2
.1
.7
.5
.4
.9
.5
.4
.6
.5
18
25.0
22.7
24.4
24.1
344.2
275.0
268.5
295.9
372.2
311.3
319.1
334.2
12
25
23
26
24
341
316
294
317
386
332
342
354
.0
.3
.1
.8
.4
.2
.2
.3
.9
.4
.9
.1
8
25.6
23.3
26.5
25.1
347.7
302.0
317.5
322.4
389.2
338.9
362.2
363.4
14
26.0
23.2
26.5
25.2
365.2
305.0
301.8
324.0
418.6
341.7
360.8
373.7
15
22.8
20.6
24.8
22.7
296.6
235.0
280.3
270.6
331.0
286.1
307.9
308.3
16
20.6
18.7
23.4
20.9
244.0
208.1
238.1
230.1
282.4
241.9
283.4
269.2
*Mean for each station was calculated from 90 samples.
@Mean for each station was calculated from 75 samples.
for each station was calculated from 30 samples.
for each station was calculated from 25 samples.
-------
TABLE 7. MEAN RIVER WATER CONTRIBUTION CALCULATED FROM CONCENTRATIONS
OF CHEMICAL TRACERS* AND U.S.G.S. MEASURES OF RIVER DISCHARGED
AND PLANT PUMPING RATESt
(percent)
Year
1973
1974
1975
Mean Annual
Chloride
12 8
30.3 36.3
30.1 29.4
39.4 42.1
33.3 35.9
Station and Measure TT c r c-
. U.o.vi.o.
Dissolved and Pumping
Total Solids Solids Ratet
12 8
27.2 37.1
29.3 28.9
39.7 46.8
32.1 37.6
12 8
28.3 38.2
38.5 32.0
53.3 52.4
36.7 40.8
34.7
20.0
26.2
26.9
*0nly those dates when both the river and lake contributed water
were used for the calculations.
^U.S.G.S. measurements of river discharge were taken 11 km upstream
from the intake.
^Pumping rates were obtained from records of the Detroit Edison
Company.
t For this calculation it was assumed that all river water was
drawn into the intake and the balance came from the lake.
38
-------
An intake station (18) was calculated for the mixed concentrations of all com-
pounds and organisms sampled at stations 9 and 17. These estimates were influ-
enced by at least the same variability in water masses reflected by chloride
concentrations. Therefore, differences in the cooling system on any single day
were, by themselves, considered to be relatively meaningless in terms of cooling
system effects. Seasonal or annual differences on the other hand were considered
more reliable indicators of cooling-system impact because they averaged out ran-
dom spatial variation.
In the plume, chloride, total solids and dissolved solids all were diluted
to about the same proportions as temperature, the criterion used to choose the
sampling sites in the plume. Based on these tracers, most of the waste heat is
mixed into the receiving waters rather than the atmosphere.
TEMPERATURE
Ambient water temperatures in the study are a closely followed meteorological
change (Fig. 8). We never observed any sharp changes in water temperature that
could have originated with upwellings of hypolimnetic waters, nor was a thermal
bar ever observed. The temperatures in the lake and Raisin River usually varied
by 1 to 2°C except in mid-winter when all water temperatures approach 0°C
(Table 8). The annual thermal cycle in the river and lake basically were
similar before they mixed in the intake to the plant condenser.
Winter temperatures were elevated as high as 17°C above ambient during con-
denser passage but elevations during other seasons rarely exceeded 10°C. The
temperature elevation at the condenser varied as a function of power generation
and the amount of water pumped. Both varied widely over the study period,
therefore, temperature elevations ranged from 0 to 17°C. The discharge was
usually close to homothermous through its length. Exceptions to this probably
resulted from fluctuating heat-rejection rates. Less than 10 percent of the
waste heat carried by the discharge -canal was lost before the water reached the
lake (Table 8).
The thermal plume spread over a sandy shoal at the mouth of the discharge
canal; the largest plume measured by the Detroit Edison Company during the study
period was about 860 hectares (The Detroit Edison Co., 1976). The location of
the plume varied with the direction and velocity of the wind and the rate of
thermal discharging. Our observations indicated that the outer edge moved from
4-km south of the discharge-canal mouth to about 1-km north of the mouth of the
Raisin River. Profiles measured in the plume at stations 15 and 16 indicated
that the plume was usually mixed well vertically (Table B7). The greatest
vertical variation occurred at times when stratification also occurred under
ambient conditions in the lake at station 17. The combination of consistent
winds and shallow water seemed to maintain homeothermy within the plume.
OXYGEN
In winter, the intake waters of the river and lake typically were saturated
to slightly supersaturated with oxygen at all depths (Tables 9; B7). As the
season warmed, diurnal variation in the percent saturation of oxygen increased
39
-------
36
32
28
24
20
16
12
6
4
1973
U
tu
cr
tr
IU
0-
2
LU
36
32
26
24
20
16
12
8
4
1974
38
36
32
28
24
20
16
12 |-
8
4
1975
M
M
gg DISCHARGE
^ UPPER RIVER
• LAKE SURFACE
— LAKE BOTTOM
N
Figure 8.
Surface temperatures in the Raisin River and discharge
canal compared to nearby lake temperatures at bottom and
surface during the study period.
40
-------
TABLE 8. MEAN AND MAXIMUM TEMPERATURES IN WARM AND COOL SEASONS RECORDED DURING THE STUDY
Mean Ambient
1972-1973
Nov-March
April-Sept
1973-1974
Oct-March
April-Sept
1974-1975
Oct-March
April-Sept
Lake
(17)
6.3
18.3
8.4
20.0
5.3
18.6
River
(9)
7.3
19.1
9.0
20.8
9.7
19.6
Mean Discharge
(12)
13.9
24.3
18.6
27.5
17.9
28.5
(14)
11.4
24.1
15.9
26.4
16.9
27.1
Mean
Elevation
6.6
5.9
9.6
7.5
8.7
9.9
Maximum
Lake
(17)
9.0
27.5
10.0
26.0
12.0
26.7
Maximum
Elevation
10.0
9.0
17.0
10.0
10.0
13.0
Maximum
Discharge
(12)
19.0
31.0
21.0
35.5
21.7
35.0
-------
TABLE 9. OXYGEN PERCENT SATURATION IN THE COOLING SYSTEM
Time
No v- Apr
Surface
1973
1974
1975
Mean
Bottom
1973
19 7 A
1975
Mean
Grand Mean
May-Oct
Surf 3.C6
1Q7^
A.J I J
1974
•L S 1 *T
1975
^fff^/
Mean
Bottom
1973
1974
1975
Mean
Grand Mean
M*
102
82
100
95
100
78
98
92
93
75
80
118
91
56
75
110
80
86
Grand Annual Mean 90
17
A
97
106
98
100
96
95
99
97
99
88
99
122
105
72
86
115
91
97
98
E
91
103
105
100
89
104
99
97
99
85
160
108
118
71
156
91
106
112
105
M
104
74
119
99
100
43
97
80
90
52
54
107
71
14
39
97
50
61
75
9
A
99
104
107
103
94
102
93
96
100
62
68
115
82
28
50
91
56
69
84
E
90
111
139
113
90
102
99
97
105
76
101
93
90
49
16
84
50
70
88
STATION
12
MAE
113
90
130
111
113
90
129
111
111
67
84
129
93
64
80
124
89
91
101
108
120
114
109
98
109
118
108
109
82
85
124
97
78
90
127
98
98
103
111
120
117
116
105
109
117
110
113
84
175
117
125
76
175
113
121
123
118
M
111
81
117
103
109
72
94
92
97
65
82
119
89
59
75
108
81
85
91
8
A
103
107
100
103
102
109
93
98
101
85
86
122
98
72
67
114
84
91
96
E
109
114
110
111
99
104
96
100
105
76
158
110
115
66
33
96
65
90
98
M
110
85
104
100
106
86
94
95
98
64
82
121
89
58
75
67
67
77
88
14
A
100
104
101
102
101
91
96
96
99
82
86
116
95
67
65
113
82
88
94
E
104
106
103
104
99
104
100
101
103
89
147
126
121
83
140
111
111
116
109
M » morning; A = afternoon; E » evening.
-------
in amplitude, probably in response to increased photosynthesis during the day and
increased community respiration at night. The expected pattern of high daytime
and low nighttime concentrations materialized irregularly (Table 9), presumably
because of time lags and changes in water masses passing by the fixed stations.
In summer, oxygen demand near the lake bottom was high enough to reduce oxygen
concentrations to 50 percent saturation. Very low concentrations occurred near
the river bottom in summer, 1973, they appeared to be higher in 1974 and 1975,
perhaps because of improved waste treatment at Monroe, Michigan. In winter, pri-
mary productivity was low, the source waters were near saturation before they
passed through the condenser, and the percent of oxygen saturation commonly
increased 10 to 20 percent with temperature elevation. Condenser passage tended
to mix oxygen concentrations uniformly from surface to bottom and increase the
percent saturation. During warmer months, the overall change was relatively
samll (Table 8), but winter values increased substantially. The highest percent
saturation (175%) occurred in August, 1974, probably as a consequence of high
primary productivity throughout the study area. Relatively little change
occurred in this water mass as it passed through the cooling system.
The percent saturation of oxygen in the discharge canal usually decreased as
the water flowed to the lake. Declines seemed slightly stronger at the bottom
than at the surface. Thermal stratification in the plume did not commonly cause
extreme oxygen reduction beneath the plume. In fact, oxygen concentrations in
the plume were very similar to those observed in the lake-source waters. The
lowest concentration observed near bottom in the plume was 4.0 mg/liter (43 per-
cent saturation) at a time when the lake concentration near the bottom was 3.1
mg/liter (32 percent). Because of warm, calm weather on that date, temporary
stratification occurred throughout the study area. If anything, power plant
operation may have reduced the impact of natural stratification on aquatic com-
munities.
SUSPENDED SOLIDS
Concentrations of suspended solids in the lake and river tended to be highest
in winter and spring (Fig. 9). Neither of the lake or river sources were con-
sistantly more turbid with suspended solids (Table 10; B8). River concentrations
often fluctuated differently from lake concentrations. Boat traffic may have
been responsible for a particularly high river concentration on March 17, 1975
(193 mg/liter), which was six times the average concentration.
The predicted intake concentrations closely matched the observed concentra-
tions in the upper discharge canal. This was expected because there was little
erodable surface between the intake and upper discharge canal. Between the upper
and lower stations in the discharge canal, suspended solids increased a mean of
20 percent over the three years, apparently because of erosion from the canal
walls. Based on the chloride tracer, concentrations of suspended solids in the
plume should have been diluted to 60 percent of the discharge canal concentrations
compared to a realized dilution of 32 percent. This could have been caused by
turbulence over the shoal at the mouth of the discharge canal which resuspended
solids from the bottom until water masses moved out to deeper water and the solids
settled down to ambient concentrations. Concentrations at the plume edge indicate
that suspended solids there were diluted like chloride.
43
-------
I]
JSE1
• torn
6A
9.0.
40.
10.
to.
1.0.
SUSPENDED SOLOS
•66
4 • 0.12.
* 0.10.
• 0.08.
^ . 0.08.
" ' 1 „ 4 . 4 4 «»•
0.02
mRTICULATE PHOSPHORUS
• 0.17 0.12.
• O.K3.
• • ooa
• 0.06
• 1 * » 0.04.
• B * OD2.
DISSOLVED PHOSPHORUS A ~^
• 1975
•
4 • • •
« • 4
4 4
• • 4
JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND
6.
3
4^
3.
2.
'•
36.
32
28
24
20
16
NITRATE
A 0.90.
, * 0.40.
A 0.30.
• 0.20.
'• • 1 4 ° '°-
"*l • * *
AMMONA
I.ZO.
1.00.
0.8O.
, • 0.60.
4 • . 0.40.
• A • A
ORGANIC NITROGEN
• • •
4
• ••
* 4
" • * *
" • •
JFMAMJJASOND JFMAMJJASOND JFMAMJJASOND
INORGANIC CARBON 2.8
2.4
4
. 2.0
4 1.6
^ * • 1.2
• 4 * • 4 * 8
4
*,
^^ .
12
10
8
• 4 6
* . 4
2
, . .•.•.*. , , ^ r , —
DISSOLVED ORGANIC CARBON
.
*
• 4 »
• • • • 4 •»
• * »
iE-tiAti i i A c n w n
JFMAMJJASOND
J F M A M J JASOND
MONTH
Figure 9. Temporal variation of chemical concentration selected for study in the lake
source used for cooling water at the Monroe Power Plant.
-------
Ln
TABLE 10. MEAN ANNUAL CONCENTRATION OF SUSPENDED SOLIDS, PHOSPHORUS, NITROGEN, AND CARBON
IN THE COOLING SYSTEM OF THE MONROE POWER PLANT
(mg/liter)
Suspended Solids 1973]J
197411
1975f
Three-year Mean
Chloride Prediction^
Total Phosphorus 1973
1974
1975
Three-year Mean
Chloride Prediction
Particulate 1973
Phosphorus 1974
1975
Three-year Mean
Chloride Prediction
17
44.8
31.4
22.7
33.0
.14
.10
.10
.11
.08
.06
.06
.07
9
32.7
32.2
67.9
44.3
.19
.19
.22
.20
.08
.09
.10
.09
18
41.2
29.8
45.8
38.7
.17
.12
.15
.15
.08
.07
.09
.08
12
42.2
35.9
32.1
36.7
39.9
.17
.14
.13
.15
.15
.08
.07
.04
.06
.08
8
40.6
43.0
39.1
40.9
40.3
.18
.16
.13
.16
.15
.09
.10
.03
.07
.08
14
46.1
43.7
41.9
43.9
40.4
.17
.13
.14
.15
.15
.09
.09
.05
.08
.08
15
47.6
47.5
26.1
40.4
36.4
.15
.13
.11
.13
.13
.08
.09
.05
.07
.07
16
39.9
33.2
26.9
33.3
33.5
.12
.08
.08
.09
.12
.07
.05
.03
.05
.06
* See Appendix for daily mean values.
The mean of five replicates for each of six dates; a total of 30 samples.
^ The mean of five replicates .for each of five dates; a total of 25 samples.
t The chloride prediction is the expected concentration from mixing alone nsing chloride as an
internal tracer.
(continued)
-------
TABLE 10 (continued)
Dissolved 1973
Phosphorus 1974
1975
Three-year Mean
Chloride Prediction
Total Non-gaseous 1973
Nitrogen 1974
1975
Three-year Mean
Chloride Prediction
Nitrate Nitrogen 1973
1974
1975
Three-year Mean
Chloride Prediction
17
.06
.04
.04
.05
3.21
2.52
1.78
2.50
2.00
1.69
1.07
1.59
9
.11
.10
.12
.11
4.60
3.84
3.65
4.03
3.21
2.34
2.10
2.55
18
.09
,05
.06
.07
4.21
2.93
2.37
3.18
2.93
1.97
1.46
2.13
12
.09
.07
.09
.08
,08
4.45
3.17
2.84
3.49
3.25
2.96
2.07
1.83
2.29
2.21
8
.09
.06
.10
.08
.08
4.39
2.90
2.83
3.37
3.31
3.22
2.05
1.78
2.35
2.25
14
.08
,06
.09
.08
,08
4.40
3.14
2.96
3.50
3.34
2.94
2.02
1.86
2.27
2.27
15
.07
,04
,06
.05
,07
3.55
1.95
2.50
2.67
3.00
2.23
1.02
1.49
1.58
2.04
16
.05
,03
.05
.04
,06
2,31
1.46
2.36
2.04
2.77
1.41
.73
1.40
1.18
1.88
(continued)
-------
TABLE 10 (continued)
Ammonia Nitrogen 1973
1974
1975
Three-year Mean
Chloride Prediction
Organic Nitrogen 1973
1974
1975
Three-year Mean
Chloride Prediction
Total Organic 1973
Carbon 1974
1975
Three-year Mean
Chloride Prediction
17
.20
.09
.14
.14
1.00
.74
.58
.77
7.8
5.9
6.2
6.6
9
.37
.27
.38
.34
.45
1.23
1.16
1.14
8,9
8.3
10.1
9.1
18
.27
.11
,19
.19
.75
.84
.73
.86
8.4
6.4
7.9
7.5
12
.43
.18
,19
.27
.20
1,08
.92
.82
.95
.89
8.6
6.9
7.5
7.7
7.6
8
.38
.17
,19
.25
.20
1.00
.93
.85
,94
.91
8.3
8.1
7.3
7.9
7.6
14
.33
.17
,22
.24
.20
1,03
.95
.89
1,00
.92
8.4
7,4
7.4
7.8
7.7
15
.25
.11
,15
.17
.18
.78
.91
.87
.85
.83
7,2
6.9
6.6
6,9
6.9
16
.16
.06
,10
.11
.17
,72
.74
,86
.78
.76
6,4
5.8
6.4
6.2
6.3
(continued)
-------
TABLE 10 (continued)
oo
Total Inorganic 1973
Carbon 1974
1975
Three-year Mean
Chloride Prediction
Particulate 1973
Organic Carbon 1974
1975
Three-year Mean
Chloride Prediction
Dissolved 1973
Organic Carbon 1974
1975
Three-year Mean
Chloride Prediction
17
23.4
24.7
24.5
24.2
1.6
0.4
1.7
1.2
6.2
5.5
4.5
5.4
9
33.2
37.9
38.3
36.4
1.4
0.9
3.9
2.1
7.5
7.4
6.2
7.0
18
28.3
27.4
28.9
28.2
1.5
0.6
2.8
1.6
6.9
5.8
5.1
5.9
12
28.8
30.6
30.0
29.8
29.3
2.2
1.0
2.0
1.8
1.7
6.4
5.9
5.5
5,9
6,1
8
29.5
29.2
29.5
29.3
29.8
2.3
0.9
2.3
1.8
1.7
6.0
7.2
5.0
6.1
6.2
14
29.2
28.8
29.7
29.2
30.1
2.6
1.1
2.9
2.2
1.8
5.8
6.3
4.5
5.6
6.3
15
25.4
24.5
25.8
25.2
27,0
2.5
1.0
2.0
1.8
1.6
4.7
5,9
4.6
5.1
5.7
16
21.4
21.5
22.1
21.7
25.0
2.3
1.4
2.4
2.0
1.5
4.1
4.4
4.0
4.2
5.2
-------
CARBON
Neither dissolved organic carbon or total inorganic carbon varied with a
seasonally regular pattern (Fig. 9). Particulate carbon varied erratically all
year but was frequently most concentrated during the warm growing season from
April through September.
Only minor differences occurred among the station means in the cooling system.
Both organic and inorganic carbon fractions in the river exceeded respective lake
concentrations (Table 10; B9; BIO; Bll); 66 percent in the aggregate. But
because the greatest carbon concentrations occurred in warm months when river
discharge was least, lake concentrations dominated the annual rate of carbon
transport through the cooling system. Certain changes within the cooling system
consistantly emerged each year, but variation from sampling date to sampling date
confounded statistical determination of differences among stations in the cooling
system.
Total carbon concentrations hardly changed (less than 5% increase) as water
passed from the intake to the upper discharge canal, in close agreement with
slight changes in concentrations of chloride and dissolved solids. Condenser
passage caused no immediate response, and total organic carbon fluctuated slightly
about a stable concentration as water passed down the discharge canal. But the
concentration of particulate organic carbon consistantly increased as dissolved
organic carbon decreased. Total inorganic carbon concentrations behaved like
chloride in the discharge canal.
Once the water entered the lake plume, the concentration of particulate
organic carbon remained higher and the dissolved organic carbon declined more
than anticipated by the dilution predicted from chloride concentrations. The
decline of dissolved carbon slightly exceeded the gain of particulate carbon by
an average of 0.3 mg/liter (5%). Both total carbon and total inorganic carbon
concentrations declined more (10% mean) than anticipated by simple dilution.
The total carbon loss from the cooling system was small and only identifiable
because of the consistency of results from year to year.
PHOSPHORUS
Phosphorus concentrations in the source waters varied erratically; both par-
ticulate and dissolved phosphorus fluctuated irregularly with no indication of
seasonally related changes (Fig. 9). River concentrations averaged nearly twice
the lake concentrations (Table 10; B12; B13; B14), but the total river contribu-
tion during most of the growing season was much less than the lake contribution.
Mean phosphorus concentrations revealed no consistent changes within the
cooling system. Similar concentrations occurred at all stations within the
intake and discharge canal. However, at the high concentrations observed, and
the precision used, changes caused by biological activity could take place with-
out materializing in the data. In the plume, phosphorus concentrations declined
more than predicted from chloride concentrations. Presumably, phosphorus pre-
cipitated from the water column as the thermal discharge mixed with lake water.
Both particulate and dissolved concentrations behave similarly.
49
-------
NITROGEN
Total nitrogen usually was most concentrated in the lake during winter and
spring (Fig. 9). This reflected high winter and spring concentrations of nitrate-
nitrogen and ammonia-nitrogen; both regularly declined to relatively low summer
and fall concentrations. Unlike inorganic nitrogen, the concentration of organic-
nitrogen varied unpredictably, but the ratio of organic and inorganic nitrogen
peaked sharply in late sunmer and early fall when inorganic nitrogen was relatively
dilute and organic nitrogen was particularly concentrated.
Total, nongaseous nitrogen changed insignificantly as water passed through
the condenser and the discharge canal. In the plume, it usually declined more
than predicted by simple dilution (Table 10; B15). Unlike any other substance
examined, ammonia-nitrogen rapidly increased as water passed through the short
section from the intake to the discharge canal (Table 10; B16). Once water
reached the discharge canal, both nitrate-nitrogen and ammonia-nitrogen declined
slightly more than explained by simple dilution while organic nitrogen increased
a complementary amount (average of 0,05 mg/liter) (Table 10; B16; B18) . The ratio
of the average increase in organic nitrogen to the average increase in particulate
organic carbon was 0.1.
Carbon and nitrogen may have been photosynthetically fixed as water passed
down the canal. The average changes in nitrogen concentrations were less than
10 to 20 percent and impossible to define precisely with the existing variability,
but the year to year trends indicated consistantly integrated biogeochemical
changes while water passed through the cooling system. As indicated by these
changes, slightly more organic matter was decomposed than was fixed during passage
through the cooling system. There appeared to be little regeneration of inorganic
nitrogen in the process. In fact, inorganic nitrogen tended to decrease more
than could be incorporated in algae as organic nitrogen,
PHYTOPLANKTON
The phytoplankton assemblage was species rich but most taxa were rare. About
20 species accounted for over 90 percent of the phytoplankton density. The
Bacillariophyceae, Chlorophyceae and Cyanophyceae predominated over lesser densi-
ties of Cryptophyceae, Dinophyceae, Euglenophyceae, Chlorobacteriae and Chryso-
phyceae (Table 11; B19; B20). The yearly mean density of all algae sampled in
the lake at station 17 varied from 6691.4/ml in 1973 to 14,755.6/ml in 1975.
This annual fluctuation was caused mostly by the relatively great variability of
blue-green algae. The other important algal classes were more stable.
Vertical distributions in the cooling system were very consistant (Table 12);
nearly constant from top to bottom. The phytoplankton were well-mixed throughout
the sampled water column.
Yearly mean densities were similar in the lake and river sources in 1973 when
blue-green algae were uncommon in both areas (Table 3). But in 1974 and 1975,
lake densities exceeded river densities because green and blue-green algae were
more common in the lake. The lake algae were more evenly distributed among the
50
-------
TABLE 11. MEAN ANNUAL PHYTOPLANKTON ABUNDANCE
(no./ml)
BY MAJOR CLASS
Class
Bacillariophyceae
197311
197411
1975f
Three-year Mean .
Chloride Prediction*
Cyariophyceae
1973
1974
1975
Three-year Mean
Chloride Prediction
Chlorophyceae
1973
1974
1975
Three-year Mean
Chloride Prediction
Euglenophyceae
1973
1974
1975
Three-year Mean
Chloride Prediction
17
4373
2568
3878
3606
826
1254
9128
3736
1455
2391
1495
1780
25
38
86
50
9
7773
1993
7471
5746
552
36
251
279
932
467
1310
903
104
33
275
138
18
4543
2486
5440
4156
784
1164
8755
3568
1394
2278
1660
1777
76
32
169
92
12
4688
2048
3946
3561
4280
1007
3861
4682
3184
3675
1454
836
1089
1126
1831
80
32
44
52
95
14
5921
4220
5412
5184
4365
863
1574
13965
5467
3748
1460
1975
1423
1619
1867
63
48
149
87
97
* Afternoon data only.
11 Mean of five samples, one station on six dates.
"f Mean of five samples, one station on five dates.
^ Chloride prediction is the expected concentration based on
mean chloride concentrations.
(continued)
-------
TABLE 11 (continued).
Class
Dlnophyceae
1973
1974
1975
Three-year Mean
Chloride Prediction
Cryptophyceae
1973
1974
1975
Three-year Mean
Chloride Prediction
Chrysophyceae
1973
Chlorobacteriae
1973
Total
1973
1974
1975
Three-year Mean
Chloride Prediction
17
0
12
34
15
11
149
133
98
0
0
6691
7375
14755
9607
9
0
0
0
0
2
13
29
14
6
0
7205
2544
4330
7895
18
0
5
31
12
7
140
126
91
2
0
6807
5107
16184
9366
12
0
0
6
2
13
21
3
0
8
92
0
2
0
0
7248
6749
9769
7922
9647
14
0
5
23
9
13
13
70
42
42
92
8
2
19
0
7702
7894
21015
14844
9840
-------
TABLE 12. VERTICAL DISTRIBUTION (PERCENT OF TOTAL AND TOTAL NUMBER AT EACH DEPTH)
IN THE COOLING SYSTEM (AFTERNOON DATA ONLY) IN 1973 AT STATIONS OVER
THREE METERS DEEP
Ln
OJ
STATION
Depth and Class
Bacillariophyceae
0
2
3
4
6
Chlorophyceae
0
2
3
4
6
Cyanophyceae
0
2
3
4
6
Total Abundance (no. /ml)
0
2
3
4
6
17
73.2
70.1
71.7
77.1
72.8
16.5
20.4
19.6
17.0
16.0
9.7
8.4
7.5
5.6
10.4
7123.2
7388.2
6612.5
7704.3
7951.2
9
77.3
78.3
81.3
77.9
79.6
11.2
12.9
12.3
12.7
12.5
8.7
5.7
3.4
5.6
5.6
6859.3
7769.8
9628.9
8335.7
7726.4
12
71.6
72.7
70.3
70.8
73.3
17.0
17.3
14.4
17.0
16.7
6.8
7.3
12.8
9.4
8.5
8628.5
8026.1
8130.3
8178.0
7489.5
8
65.4
66.0
71.0
70.2
73.3
20.7
17.2
16.0
16.3
14.9
9.2
11.0
8.5
10.0
8.5
8729.3
8080.6
8760.1
8307.0
8587.6
-------
three important classes than the diatom-dominated river algae. Year to year
variations in river discharge contributed to the annual variation of entrained
algae. In 1975 the river contributed only one fourth of the cooling water com-
pared to about half in the preceeding years. Because of low summer discharges,
the river contributed relatively little to the dynamics of green and blue-green
algae.
Total algal densities consistantly increased as water passed from the upper
to the lower discharge canal from station 12 to station 14 during each of the
three years (Table 11). Algal abundances in the plume were measured only in
1973 when the mean of all sampling dates and time periods indicated that the
algae maintained greater densities in the mixing plume than expected from dilution;
particularly green and blue-green algae (Table 13),
The mean density of most algal classes consistantly increased as water passed
from the upper to the lower end of the discharge canal. The major exception, the
blue-green algae probably vacillated because they were variable in the source
water. In 1975, an extraordinary bloom of blue-green algae on one date generated
an atypically high mean algal increase in the discharge canal; otherwise, the
increments were only 10 to 20 percent. The variability of blue-green algae also
materialized in the 1973 comparisons of morning, afternoon and evening samples
(Table 14). Although the daily mean algal concentrations remained greater in the
plume than predicted by dilution, this observation was inconsistant for different
times of the day. Mean afternoon densities declined more than predicted, while
mean morning and evening densities remained higher than predicted. This varia-
tion was caused mostly by variation in blue-green algal response and secondarily
by green algal response. These two classes varied up to 35 percent from one time
period to another. In contrast, diatom concentrations were relatively similar
at all three time periods and exhibited consistent changes with passage through
the cooling system. Although the differences in concentration from one time
period to another could be as much as 35 percent, there was no indication that
entrainment was consistently different at specific times of the day.
The changes in mean annual density, volume and individual volume, of the
important species, exhibited no consistant trends from year to year which were
related to the length of power plant operation (Table 15). Although the mean
annual concentration of a few species varied by up to 2 orders of magnitude, their
variation appeared to be independent of time. Most of the common species remained
consistantly abundant during the three-year study; their mean annual concentra-
tions varied only by 2 to 5 times. The mean annual size of the algal units (cells,
filaments, or colonies) varied independently of numerical abundance as did the
mean annual volumes of each species.
The response of dominant species to cooling water passage in 1973 was highly
variable; some species seemed to decrease more than predicted by chloride con-
centrations (Anacystis incerta. Scenedesmus quadricaudus, Cyclotella menegheniana),
another species seemed to increase (Ulothrix subtillissima) but most species
behaved generally without notable trend. The mean size of classes and the most
important species varied without trend. As expected with taxa comprising small
samples, the rare classes changed erratically in mean size and abundance. .The
species composition may have shifted slightly as plankton drifted through the
cooling system, but the impact, if it were real and not a product of patchy
54
-------
TABLE 13. MEAN ANNUAL ALGAL DENSITIES, VOLUME, AND MEAN INDIVIDUAL VOLUMES FOR CLASSES AND DOMINANT
SPECIES IN THE COOLING SYSTEM DURING 1973*
(no./ml; V3/ml; v3/individual)
Ul
Ol
STATIONS
Taxa
Cyanophyceae
Numbers
Volume
Mean Size
Aphanizomenon gracile
Numbers
Volume
Mean Size
Anacystis incerta
Numbers
Volume
Mean Size
Chlorophyceae
17
1895
583596
308
105
182650
1738
94
28617
306
f\ nno
9
1612
416676
258
20
39713
1956
30
7796
263
ono
18
1787
502900
281
70
123047
1748
81
24703
307
01 AA
12
1901
512722
270
80
134727
1688
151
40184
267
?nn
8
2438
638273
262
50
90752
1833
106
29565
278
2233
14
2184
651822
297
53
95232
1790
60
17691
293
2342
15
2261
732119
324
58
125310
2146
5
1443
267
2708
16
2587
802987
310
61
130840
2163
0
0
2213
^ £\)£ Z.I/O £. JLV/~T *. -*..^ v — — — —
1702333 1304603 1576254 1472888 1525274 1601120 2262384 1876212
733 627 729 691 683 684 835 848
4! 50 44 48 38 96 37 19
5804 8300 6395 7131 5316 13321 7378 3642
142 166 147 147 141 139 196 191
Numbers
Volume
Mean Size
Scenedesmus quadricauda
Numbers
Volume
Mean Size
Ulothrix subtillissima
Numbers
Volume
Mean Size
* Class data is averaged for all periods, species data is averaged on afternoons only.
(continued)
241
231984
965
66
65931
1007
187
178928
959
130
125383
962
212
195620
923
128
118282
926
557
560344
1006
579
582092
1006
-------
TABLE 13 (continued)
Taxa
17
18
12
STATIONS
8
14
15
16
Ui
OS
Bacillariophyceae
Numbers
Volume
Mean Size
CoBcinodiscus radlatus
Numbers
Volume
Mean Size
Cyclotella meneghiniana
Numbers
Volume
Mean Size
Euglenophyceae
Numbers
Volume
Mean Size
Cryptophyceae
Numbers
Volume
Mean Size
Chrysophyseae
Numbers
Volume
Mean Size
4567 5171 4620 4855 4790 5204 4419 4234
16781518 12766022 14003792 14898492 13304654 15221607 14639830 15453619
3674 2468 3031 3068 2777 2925 3312 3649
808 146 611 634 544 681 534 691
6344544 1045601 4817834 4923665 4221031 5344670 4292718 5478816
7853 7152 7883 7764 7765 7855 8034 7919
966 2197 1308 1176 1506 1504
1122787 2458304 1439562 1200589 1511954 1562975
1163 1119 1101 1021 1004 1039
78
47786
615
11
9348
858
1
4
10
104
58153
562
7
6244
855
2
2291
1041
98
54003
549
11
9041
861
1
573
1146
86
39849
462
9
7838
852
1
758
842
111
64777
585
23
19560
858
3
2747
858
84
49762
586
16
13472
869
3
3304
1032
894
729339
816
102
68325
670
20
17904
873
0
0
566
457379
808
77
57753
747
9
8055
857
0
0
(continued)
-------
TABLE 13 (continued)
STATIONS
Taxa
Dinophyceae
Numbers
Volume
Mean Size
Chlorobacteriae
Numbers
Volume
Mean Size
17
0
0
—
0
708
1770
9
1
5019
3585
0
0
—
18
1
1832
3664
0
0
—
12
1
552
552
0
0
—
8
1
3612
3612
2
114
63
14
2
3863
2033
6
9395
1468
15 16
0 0
0 2796
3495
0 0
0 0
— —
Ui
-------
TABLE 14. MEAN ANNUAL ALGAL DENSITY BY CLASS AT DIFFERENT TIMES
OF THE DAY IN 1973
(no./ml)
Station
Ij WCL W AX/ It
and Time
17 morn.
aft.
eve.
9 morn.
aft.
eve.
18 morn.
aft.
eve.
12 morn.
aft.
eve.
8 morn.
aft.
eve.
14 morn.
aft.
eve.
15lf morn.
eve.
16 morn.
eve.
CLASS
A*
902
827
1098
772
552
1010
842
785
1044
897
1001
984
1336
1065
1161
1162
864
1122
1131
1210
1318
1393
B*
1350
1456
999
1222
932
1240
1300
1394
1073
1253
1454
1000
1363
1648
931
1366
1460
1193
1466
1479
1237
1041
C*
5126
4373
4130
4667
5611
5251
4968
4543
4295
4938
4688
4940
4981
4832
4559
5026
5275
5311
5068
3799
4694
3983
D*
134
25
73
98
105
108
109
77
112
321
80
58
119
102
112
111
64
80
134
85
87
77
E*
0
0
0
4
0
0
2
0
0
0
3
0
0
3
0
6
0
0
0
0
2
0
F*
11
11
11
5
2
16
10
8
15
6
22
0
11
41
16
11
13
22
33
23
17
8
Total
7523
6692
6311
6768
7202
7625
7221
6807
6489
7415
14663
6982
7810
7691
6779
7682
7676
7728
7832
6496
7355
6502
* A = Cyanophyceae
B » Chlo
rophyceai
a
C = Bacillariophyceae
D = Euglenophyceae
E - Dinophyceae
F = Cryptophyceae
Afternoon samples were incompletely sampled during summer
and were left out of the comparison.
58
-------
TABLE 15. MEAN ABUNDANCE AND SIZE OF IMPORTANT PHYTOPLANKTON SPECIES SAMPLED IN THE UPPER DISCHARGE
CANAL AT STATION 12
Species
Numbers/ml
1973 1974 1975
Volumes (u3/ml)
1973
1974
1975
Mean Volume/ml
1973 1974 1975
Ul
VO
Bacillariophyceae (Diatoms)
Cocconeis placentula
Coscinodiscus radiatus
Cyclotella meneghiniana
Melosira granullta -
Navicula ?r^pToIip"hala
-
Stephanodiscus Laaae
Tabellaria fenestrata
Chlorophyceae (Green algae)
- Actinastrum hantzxchii
Binuclearia Iriensis
Dictyosphaerium pulchellum
Mougeotia elegant -
Scenedesmus quadricauda
Ooevstis parva" -
Ulothrix subtillissima
Cyanophycea (Blue-greens)
Anacystis incerta
Aphanizomenon gracile
Euglenophyceae
Trachelomonas volvocina
30 15
633 332
1175 222
256 4
67
62
241
272
44
21
39
60
18
117
16
20
34
47
41
18
25
0
74
75
97
23
130 142
150 23
79 179
59 0
11
438
288
64
90
68
139
9
25
37
45
53
1
150
20
1
62
503
25
15781
4923665
1200589
704159
22792
36298
655837
3527071
80497
1082
441043
21662
127439
28902
3646
125383
40185
134728
11515
5626
2179994
383329
4922
12009
23187
138680
412548
385346
1718
0
2520
635597
16761
6840
115812
12431
244633
9237
6887550
438699
81721
49162
25341
318039
130142
734764
5422
62147
56707
1744
40904
15455
3416
16407
201701
8569
523
7778
1021
2742
337
577
2711
12948
2519
368
6562
1725
1158
586
680
2952
9846
4328
67
49
11109
360 34
6889 8374
246 172
225 296
962 813
267 52
1688 1361
194
840
15721
1519
1273
545
368
2286
14146
151426
145
1172
1056
1163
273
765
2277
262
401
335
*Afternoon data only.
-------
distribution, did not seem to have more than a transitory influence on the lake
composition.
Although some compositional changes may have occurred among the entrained
phytoplankton, diversity measures indicated that a stable structure was main-
tained throughout the cooling system (Tables 16, 17), Generic diversity and
species diversity were similar for the same data collected in 1973. Both
diversity measures indicated that no important, consistent changes occurred in
the cooling system or the plume during cooling water passage. Generic diversity
was stable over the three years in the lake at station 17 but river diversity
decreased in 1975 and seemed to influence the diversity in the discharge canal
as a consequence of mixing. Passage through the cooling system had no measured
affect on algal diversity.
In summary, the affects of entrainment on phytoplankton were subtle if real
at all. Variability in the spatial distribution of algae precluded consistent
statistical differentiation of abundances in the cooling system. But, overall,
the mean effects integrated over the annual cycle were at most minor effects.
Mean annual algal concentrations probably increased slightly in the cooling
waters discharged to the lake. Although responses were inconsistant, the
increase seemed to be caused by growth of blue-green and green algae.
PERIPHYTON
Periphyton was rare in the study area because appropriate substrate was scarce,
but periphyton accumulation on artificial substrates was used to assess the inte-
grated effects of water quality on productivity at a fixed site within the cool-
ing system. Periphytic growth was throught to be less likely than entrained
phytoplankton to reflect previous impacts from mechanical damage, thermal
"shock", or chemical "shock" caused by transport through the pumps and condenser.
Because periphyton samples are particularly vulnerable to weather, the varia-
tion among replicates was high in some instances so the effects of the cooling
system were not always clear (Fig. 10; C4). Of the four tests conducted, peri-
phyton accumulation rates were clearly affected in the upper discharge canal
only in mid-summer when water temperatures were highest. Spring accumulations
may have been influenced also but replicate variation interfered with the deter-
mination. The least differences occurred among the sampling stations in winter
when the absolute temperatures were lowest.
During summer and spring, greater productivity occurred at the mouth of the
discharge canal than in the upper part of the discharge canal where no differ-
ences were observed in winter or late summer samples. Neither temperature nor
light penetration (suspended solids) seemed to be different enough in the upper
and lower discharge canal to explain the difference in periphyton accumulation
rates. If chlorine were responsible for differences, its impact was inconsis-
tent for the different sampling dates. The thermal regimes were similar for
spring and late summer but the affects appeared to be different.
60
-------
TABLE 16. DIVERSITY AND EQUITABILITY CALCULATED FROM DENSITY AND
BIOMASS DATA COLLECTED FROM THE COOLING SYSTEM
STATION
Diversity
Date-Period 17 9 18 12 8 14 15 16
Morning
11/09/72 Numbers 1.18* 1.21 1.21 1.06 1.03 1.09 1.25 1.17
Biomass 0.83 1.14 1.14 1.11 1.08 1.17 0.92 0.91
Evening
11/09/72 Numbers 1.11 0.96 0.96 1.07 0.97 1.06 1.12 1.14
Biomass 0.88 0.96 0.96 1.07 1.00 1.13 0.73 0.81
Afternoon
11/10/72 Numbers 1.23 1.13 1.13 1.03 1.08 1.25 1.16 1.15
Biomass 0.93 1.02 1.02 1.07 1.13 0.96 0.89 0.73
Afternoon
01/24/73 Numbers 1.49 1.46 1.55 1.49 1.39 1.34 1.43 1.33
Biomass 1.31 1.40 1.47 1.41 1.37 1.34 1.26 1.09
Afternoon
04/05/73 Numbers 1.34 1.26 1.39 1.34 1.28 1.42 1.32 1.41
Biomass 1.07 1.22 1.35 1.34 1.28 1.41 1.30 1.33
Afternoon
06/12/73 Numbers 1.35 1.37 1.43 1.40 1.42 1.44 1.28 1.14
Biomass 1.17 1.26 1.26 1.19 1.23 1.25 1.08 0.96
Afternoon
08/09/73 Numbers 1.52 1.33 1.55 1.48 1.52 1.38 —
Biomass 1.14 1.08 1.19 1.01 1.12 0.95 --
Afternoon
09/29/73 Numbers 1.38 — 1.38 1.35 1.36 1.32
Biomass 0.94 — 0.99 1.13 1.20 1.06
*The mean of five samples.
(continued)
61
-------
TABLE 16 (continued)
STATION
Equitability
Date-Period 17 9 18 12 8 14 15 16
Morning
11/09/72 Numbers 0.70* 0.76 0.76 0.67 0.65 0.68 0.74 0.70
Biomass 0.49 0.73 0.73 0.70 0.68 0.73 0.55 0.54
Evening
11/09/72 Numbers 0.72 0.70 0.70 0.65 0.66 0.75 0.70 0.68
Biomass 0.54 0.65 0.65 0.68 0.66 0.69 0.43 0.49
Afternoon
11/10/72 Numbers 0.72 0.70 0.70 0.65 0.66 0.75 0.70 0.68
Biomass 0.54 0.63 0.63 0.67 0.69 0.57 0.53 0.43
Afternoon
01/24/73 Numbers 0.88 0.87 0.85 0.88 0.87 0.81 0.84 0.81
Biomass 0.78 0.84 0.80 0.84 0.85 0.81 0.74 0.66
Afternoon
04/05/73 Numbers 0.80 1.34 0.77 0.81 0.76 0.82 0.79 0.84
Biomass 0.64 0.75 0.75 0.81 0.76 0.82 0.78 0.79
Afternoon
06/12/73 Numbers 0.78 0.78 0.76 0.82 0.83 0.82 0.77 0.67
Biomass 0.68 0.73 0.67 0.70 0.72 0.71 0.65 0.57
Afternoon
08/09/73 Numbers 0.82 0.73 0.77 0.79 0.81 0.76
Biomass 0.61 0.60 0.59 0.54 0.59 0.52
Afternoon
09/29/73 Numbers 0.75 — 0.72 0.77 0.75 0.75
Biomass 0.51 — 0.52 0.65 0.66 0.60
The mean of five samples.
62
-------
TABLE 17. MEAN ANNUAL PHYTOPLANKTONIC GENERIC DIVERSITY AND
EQUITABILITY IN THE COOLING SYSTEM FROM 1973 to 1975*
STATION
17 9 18 12 14
Diversity
Numbers
197311 1.12 1.00 1.10 1.07 1.08
1974^ 1.07 .79 1.05 .96 1.11
1975f 1.13 .71 .88 .95 .87
Biomass
1973 0.93 0.98 1.02 0.98 0.97
Equitability
Numbers
1973
1974
1975
Biomass
1973
0.76
0.72
0.60
0.63
0.71
0.49
0.52
0.69
0.72
0.62
0.57
0.67
0.74
0.69
0.70
0.69
0.74
0.75
0.60
0.67
*Afternoon data only.
^Mean of five replicates, one station on six dates in 1973 and 74.
'Mean of five replicates, one station on five dates in 1975.
63
-------
ON
^ 14.0
•a
X.
CM
E
u
E
o>
5^
o 10.0
o
"5
3
0
U
•g 5.0
£
"5
oc
E
1
*x
0
•
9
17
|U
2
1-
1
o!2
•
17
JL
2
Z
2
1'
9
2-JJ
II
_i_
8
|
2
^H
15 16
2
J ~
2
- STATION
> REPLICATES
^
14
2 12
1
9
1
1
2
fl
It
t
15
1
2
8
f
4
[
1
1
a
1
U
2
,2
*
-
5-4 to 5-24 8-29 to 9-28
1973
2-14 to 3-8
7-15 to 7-31
• 14.0
• 10.0
- 5.0
1974
Figure 10. Accumulation of periphyton during four seasons in the cooling system at the Monroe
Power Plant.
-------
COMMUNITY METABOLISM
Mean annual gross primary productivity in the upper discharge canal usually
was less than expected from the simple mixing of river and lake waters. Water in
the upper discharge canal usually was less productive than lake water and similar
to the river water. Mean afternoon productivities were similar to morning pro-
ductivities. Evening productivity averaged close to 0 as expected for the dark
hours. At least three possibilities could have been totally or partly responsible
for the inhibition of productivity in the upper discharge canal; some inhibitor(s)
associated with the river water, temperature elevation or the mechanical effects
from condenser passage. No chlorination occurred in the afternoon so depressions
at that time had to be caused by some other alternation(s).
Primary productivity was much more intense during the warm months (Table 18;
B21) than during the cool months so the average inhibition mostly reflected summer
conditions. There was little obvious relationship between the absolute tempera-
ture and the intensity of the measured response on any particular date, but, at
higher ambient temperatures, the productivity in the discharge canal appeared to
be inhibited more by the passage.
Productivity appeared to recover as water passed from the discharge canal
back into the lake (Table 18). By the time discharged water reached mid-plume at
station 15, mean productivity usually exceeded that at the lake source (station
17). This elevated productivity (mean of 50%) persisted to the plume edge where
temperatures were only slightly elevated above ambient.
Mean annual respiration in the upper discharge canal usually was slightly
greater than respiration in the source waters (Table 19; B22). The increases
associated with condenser passage occurred at all times of the day regardless of
the chlorination schedule. Either temperature elevation or mechanical effect may
have been responsible. After community respiration accelerated, it tended to
return to source-water respiration rates as the cooling water mixed back into the
lake, but remained elevated above the level in the source waters even at the plume
edge where temperatures were nearly ambient.
The mean annual ratios of gross primary productivity and community respiration
in the upper discharge canal usually were less than that projected for the mix of
source waters (Table 20). The ratios remained relatively low throughout the dis-
charge flow then returned to levels similar to ratios observed in the lake source
water. No consistent changes in the metabolic "balance" of the plume waters
occurred because of the cooling water passage.
ZOOPLANKTON
Zooplankton abundance varied from nearly negligible quantities of copepods,
cladocerans and rotifers in winter to greatest concentrations in late summer and
early fall (Table 21; 22; B23; Fig. 11). Biomass varied over the year more than
density because small rotifers were relatively numerous in winter. The three most
abundant species during the study were Bosmina sp., Cyclops vernalis and Daphnia
retrocurva. These species were most abundant from June through September; and
nearly all zooplankton entrainment occurred between April and November.
65
-------
TABLE 18. MEAN GROSS PRIMARY PRODUCTIVITY IN THE COOLING SYSTEM FOR COLD AND WARM MONTHS OF 1973-75
(mg 02/liter/hour)
STATIONS
Period
Year-Season
Morning
1973-cool*
-warm1'
1974-cool
-warm
1975-cool
-warm
Grand cool mean
Grand warm mean
3 year grand mean
Afternoon
1973-cool
-warm
1974-cool
-warm
1975-cool
-warm
Grand cool mean
Grand warm mean
3 year grand mean
17
o.ost
0.76
0.04
0.52
0.08
0.54
0.05
0.61
0.33
-0.04
0.26
0.04
0.43
Data
0.70
0.00
0.46
0.23
9
0.06
0.39
0.06
0.22
-0.02
0.56
0.03
0.39
0.21
0.01
0.13
-0.01
0.33
18
0.06
0.66
0.04
0.49
0.04
0.62
0.05
0.59
0.32
0.00
0.22
0.00
0.42
not gathered —
0.34 0.62
0.00
0.27
0.13
0.00
0.42
0.21
12
0.03
0.34
0.04
0.33
0.08
0.58
0.05
0.47
0.24
0.01
0.21
0.04
0.41
assumed
0.33
0.02
0.32
0.18
8
0.00
0.36
0.01
0.48
0.07
0.54
0.03
0.46
0.24
0.03
0.12
-0.02
0.40
to be zero
0.41
0.00
0.31
0.16
14
0.03
0.42
0.03
0.50
0.02
0.74
0.03
0.55
0.29
0.05
0.16
0.00
0.43
based
0.41
0.02
0.33
0.18
15
0.05
0.62
0.05
0.61
-0.05
0.64
0.02
0.62
0.32
0.07
0.31
0.00
0.58
on 1973
0.95
0.02
0.61
0.22
16
0.01
0.79
0.00
0.73
0.12
0.64
0.04
0.72
0.44
0.00
0.30
0.01
0.43
and 1974
0.88
0.00
0.54
0.27
Cool season extended from November through April with temperatures generally less than 10°C.
season extended from May through October with temperatures generally above 15°C.
mean of three replicates.
(continued)
-------
TABLE 18 (continued)
STATIONS
Period
Year-Season
Evening
1973-cool*
-warmer
1974-cool
-warm
1975-cool
-warm
Grand cool mean
Grand warm mean
3 year grand mean
OVERALL GRAND MEAN
17
0.02f
0.02
-0.05
-0.01
-0.04
0.04
-0.02
0.02
0.00
0.22
9
-0.02
0.02
0.01
0.02
-0.04
-0.04
-0.02
0.00
-0.01
0.13
18
-0.01
0.04
0.02
-0.01
-0.04
0.03
-0.01
0.02
0.00
0.21
12
0.00
-0.03
-0.01
-0.02
-0.03
-0.05
-0.01
-0.03
-0.02
0.14
8
0.00
0.00
0.03
-0.08
-0.02
-0.10
0.00
-0.06
-0.03
0.15
14
0.00
0.01
0.01
-0.01
-0.04
0.07
-0.01
0.02
0.00
0.18
15
0.01
-0.06
-0.01
0.00
0.00
0.04
0.00
-0.01
0.00
0.30
16
0.00
-0.01
-0,03
-0.01
-0.01
0.03
-0.01
0.00
0.00
0.30
*Cool season extended from November through April with temperatures generally less than 10°C.
^Warm season extended from May through October with temperatures generally above 15°C.
"^The mean of three reolicates.
-------
TABLE 19. MEAN RESPIRATION RATE IN THE COOLING SYSTEM FOR COLD AND WARM MONTHS OF 1973-75
(mg 02/liter/hour)
CTi
00
Period
Year-Season
Morning
1973-cool*
-warm^
19 7 4- cool
-warm
19 75- cool
-warm
Grand cool mean
Grand warm mean
3 year grand mean
Afternoon
1973-cool
-warm
1974-cool
-warm
1975-cool
-warm
Grand cool mean
Grand warm mean
3 year grand mean
STATIONS
17
0.00'
0.08
0.04
0.10
0.00
0.10
0.01
0.09
0.05
0.10
0.09
0.02
0.03
data
0.09
0.06
0.07
0.06
9
^ 0.05
0.07
0.03
0.05
0.06
0.06
0.05
0.06
0.05
0.05
0.16
-0.01
0.04
missing
-0.02
0.02
0.06
0.04
18
0.04
0.08
0.00
0.09
0.03
0.06
0.02
0.08
0.05
0.01
0.11
-0.02
0.04
0.08
0.00
0.08
0.04
12
0.01
0.05
0.05
0.08
0.10
0.14
0.05
0.09
0.07
0.07
0.12
0.05
0.13
0.10
0.06
0.12
0.09
8
0.02
0.08
0.03
0.08
0.12
0.13
0.06
0.10
0.08
0.11
0.05
0.03
0.14
0.13
0.07
0.11
0.09
14
0.05
0.08
0.03
0.09
0.06
0.10
0.05
0.09
0.06
0.12
0.08
0.02
0.13
0.11
0.07
0.11
0.09
15
0.02
0.09
0.02
0.09
0.02
0.03
0.02
0.07
0.05
-0.02
0.11
-0.02
0.03
0.12
-0.02
0.09
0.04
16
-0.01
0.10
0.00
0.09
0.00
0.05
0.00
0.09
0.05
0.00
0.08
0.00
0.12
0.17
0.00
0.12
0.06
Cool season extended from November through April with temperatures generally less than 10°C.
Warm season extended from May through October with temperatures generally above 15°C.
The mean of three replicates.
(continued)
-------
TABLE 19 (continued)
10
STATIONS
Period
Year- Season
Evening
1973-cool*
-warm
1974-cool
-warm
1975-cool
-warm
Grand cool mean
Grand warm mean
3 year grand mean
OVERALL GRAND MEAN
17
-0.021"
0.03
-0.01
0.06
-0.06
0.02
-0.03
0.04
0.01
0.04
9
-0.05
0.09
-0.04
0.04
0.00
0.05
-0.03
0.06
0.02
0.04
18
-0.05
0.05
-0.03
0.06
-0.04
0.01
-0.04
0.04
0.00
0.04
12
0.03
0.09
0.05
0.07
0.08
0.09
0.05
0.08
0.07
0.08
8
0.03
0.07
0.05
0.11
0.06
-0.05
0.05
0.04
0.04
0.07
14
0.06
0.04
0.09
0.05
0.05
0.09
0.07
0.06
0.06
0.07
15
0.02
0.04
-0.02
0.09
0.01
0.08
0.00
0.07
0.04
0.05
16
0.00
-0.04
-0.04
0.04
0.04
0.09
0.00
0.03
0.01
0.06
Cool season extended from November through April with temperatures generally less than 10°C.
season extended from May through October with temperatures generally above 15 °C.
The mean of three replicates.
-------
TABLE 20. P/R RATIOS IN THE COOLING SYSTEM FOR WARM AND COLD MONTHS OF 1973-75
STATIONS
Period
Year- Season
Morning
1973-cool*
-warm^
1974-cool
-warm
1975-cool
-warm
Grand cool mean
Grand warm mean
3 year grand mean
17
.t
9.50T
1.00
5.20
00
5.40
5.00
6.78
6.66
9
1.20
5.57
2.00
4.40
-0.33
9.33
0.60
6.50
4.20
18
1.50
8.25
00
5.44
1.33
10.33
2.50
7.38
6.40
12
3.00
6.80
0.80
4.12
0.80
4.14
1.00
4.67
3.43
8
0.00
4.50
0.33
6.00
0.58
4.15
0.50
4.60
3.00
14
0.60
5.25
1.00
5.56
0.33
7.40
0.60
6.11
4.83
15
2.50
6.89
2.50
6.78
-2.50
21.33
1.00
8.86
6.40
16
-1.00
7.90
0.00
8.11
oo
8.00
00
8.00
8.80
*Cool season extended from November through April with temperatures generally less than 10°C.
11 Warm season extended from May through October with temperatures generally above 15°C.
"*"When respiration equals zero; and productivity is positive, the calculated ratio is 20.
These ratios were left out of grand mean calculations.
fThe mean of three replicates.
(continued)
-------
TABLE 20 (continued)
STATIONS
Period
Year-Season
Afternoon
1973-cool*
-warm
1974-cool
-warm
1975-cool
-warm
Grand cool mean
Grand warm mean
3 year grand mean
OVERALL GRAND MEAN
17
-0.40t
2.89f
2.00
14.33
7.78
0.00
3.83
5.50
9
0.20
0.81
1.00
8.25
-17.00
0.00
4.50
4.00
3.25
18
oo
2.00
0.00
10.50
7.75
0.00
6.25
3.50
5.25
12
0.14
1.75
0.80
3.15
3.30
0.50
2.67
1.85
1.75
8
0.27
2.40
-0.67
2.86
3.15
0.00
2.82
1.78
2.14
14
0.42
2.00
0.00
3.31
9.09
0.29
3.00
2.00
2.57
15
-3.50
2.82
0.00
19.33
7.92
-2.00
6.78
5.50
6.00
16
0.00
3.75
00
3.58
5.18
0.00
4.50
4.50
5.00
*
Cool season extended from November through April with temperatures generally less than 10°C,
11 Warm season extended from May through October with temperatures generally above 15°C.
^When respiration equals zero; and productivity is positive, the calculated ratio is 20.
These ratios were left out of grand mean calculations.
*The mean of three replicates.
-------
TABLE 21. MEAN ANNUAL DENSITY OF ZOOPLANKTON IN THE COOLING SYSTEM
(numbers/liter)
vj
N9
STATIONS
Taxa
1972-73
Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult C. vernalis
Nauplli
Total Copepoda
Total
1973-74
Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
1975
Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
17
76.3 (56.1)*
28.8 (16.5)
13.6 (6.2)
10.9 (5.4)
61.6 (48.1)
57.7 (36.7)
26.4 (20.7)
88.0 (68.8)
193.1 (141.4)
162.1 (181.2)
31.7 (30.2)
9.0 (15.8)
18.7 (12.7)
6.1 (8.5)
4.2 (5.8)
54.9 (50.2)
61.0 (58.7)
254.8 (270.1)
145.2 (183.0)
17.6 (11.0)
6.6 (2.0)
2.4 (4.0)
2.8 (1.9)
1.5 (1.1)
15.6 (19.4)
18.4 (21.3)
181.2 (2.5.3)
9
43.0 (43.3)
22.3 (22.3)
3.2 (1.2)
5.0 (8.5)
31.2 (5.0)
27.0 (4.8)
18.3 (14.0)
49.5 (19.0)
114.8 (84.6)
107.7 (85.0)
11.9 (13.3)
.5 (0.0)
7.4 (5.8)
3.6 (.8)
2.7 (.8)
22.3 (20.2)
25.9 (20.2)
145.5 (118.5)
47.3 (35.5)
5.3 (2.0)
2.4 (0.0)
.8 (1.0)
1.1 (.2)
1.0 (.1)
11.5 (2.5)
12.6 (2.5)
65.2 (40.0)
18
65.7 (51.6)
27.0 (13.2)
10.3 (5.1)
9.1 (7.2)
54.5 (31.8)
52.3 (27.4)
24.3 (16.7)
78.8 (48.5)
171.5 (113.3)
155.1 (173.3)
28.4 (27.3)
7.2 (6.7)
16.2 (11.7)
5.2 (5.8)
3.6 (5.6)
48.4 (46.6)
53.6 (52.4)
237.1 (253.0)
109.0 (129.2)
16.5 (10.0)
6.1 (1.9)
2.0 (3.7)
2.1 (1.4)
.9 (1.0)
14.1 (16.3)
16.2 (17.7)
141.7 (156.9)
12
45.0 (51.1)
11.5 (11.5)
3.6 (2.5)
6.2 (5.4)
44.0 (47.5)
43.5 (39.2)
16.1 (13.5)
60.1 (60.7)
116.6 (123.3)
103.7 (104.6)
17.6 (11.0)
3.0 (0.0)
12.1 (9.4)
4.9 (5.0)
3.5 (5.0)
39.2 (26.0)
44.1 (31.0)
165.4 (146.6)
70.9 (77.1)
8. 6. (4.1)
1.4 (3.0)
2.8 (.12)
2.8 (4.1)
1.8 (4.0)
15.8 (8.4)
18.6 (12.5)
98.1 (93.7)
8
60.4 (54.4)
14.5 (5.2)
5.6 (3.3)
7.2 (4.4)
52.6 (30.8)
40.9 (28.7)
25.6 (22.1)
78.2 (52.9)
153.1 (112.5)
113.1 (78.2)
17.2 (5.8)
1.8 (1.7)
12.6 (2.7)
6.2 (5.0)
3.8 (3.3)
42.3 (39.8)
48.5 (44.8)
178.8 (128.8)
69.6 (71.2)
15.3 (2.6)
2.9 (1.0)
1.6 (1.0)
3.3 (3.5)
2.3 (3.5)
17.6 (16.6)
20.9 (20.1)
105.8 (93.3)
* Number in parentheses is the mean number at the surface
-------
TABLE 22. MEAN ANNUAL BIOMASS OF ZOOPLANKTON IN THE COOLING SYSTEM
(yg/llter)
Taxa
1972-73
Rot if era
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
1973-74
Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult JC. vernalis
Nauplii
Total Copepoda
Total
1975
Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult £. vernalis
Nauplii
Total Copepoda
Total
17
8.6 (7.1)*
175.7 (79.3)
134.8 (74.6)
17.1 (28.9)
219.7 (148.0)
153.8 (109.9)
4.4 (3.6)
224.1 (151.6)
408.4 (238.0)
14.3 (12.8)
94.8 (182.8)
83.4 (175.5)
12.3 (6.9)
26.5 (45.0)
15.4 (18.7)
6.2 (4.5)
36.2 (51.6)
145.3 (247.2)
12.9 (13.5)
69.8 (13.7)
41.3 (9.3)
2.3 (2.9)
11.7 (10.6)
6.7 (2.8)
3.2 (3.4)
16.7 (15.3)
99.4 (42.5)
9
7.0 (7.7)
49.8 (14.0)
44.9 (6.9)
4.2 (7.0)
133.0 (47.7)
107.1 (47.4)
3.9 (2.7)
136.9 (50.4)
193.7 (72.1)
16.4 (11.3)
15.0 (4.1)
8.5 (0.0)
4.1 (1.0)
9.4 (1.6)
7.2 (1.6)
2.4 (2.0)
12.7 (4.2)
44.1 (19.6)
5.9 (3.8)
41.2 (1.0)
19.9 (0.0)
.1 (.92)
3.5 (.62)
3.5 (.3)
2.7 (.27)
7.4 (4.5)
54.5 (49.5)
STATIONS
18
7.1 (5.3)
138.7 (61.5)
119.1 (56.1)
10.2 (4.7)
209.5 (107.4)
170.2 (89.4)
2.6 (1.9)
212.1 (109.3)
357.9 (176.1)
15.0 (12.6)
77.3 (145.8)
67.8 (138.8)
10.7 (6.1)
22.9 (36.8)
13.8 (14.0)
5.5 (4.1)
28.4 (40.9)
120.7 (199.3)
10.2 (9.5)
63.4 (12.9)
38.8 (8.8)
2.3 (1.8)
9.4 (8.9)
6.3 (2.2)
2.5 (2.4)
11.9 (11.3)
85.5 (33.7)
12
5.4 (6.6)
136.1 (56.0)
38.7 (41.5)
5.0 (3.6)
171.9 (170,8)
148.1 (138.2)
1.7 (1.4)
173.6 (172.2)
315.1 (234.8)
11.8 (12.9)
24.7 (4.7)
19.0 (0.0)
5.2 (4.1)
14.5 (12.2)
11.3 (12.2)
4.9 (5.9)
22.2 (19.4)
58.7 (37.0)
7.6 (5.3)
58.0 (57.0)
53.1 (54.7)
3.1 (.05)
11.0 (19.9)
5.5 (14.8)
3.5 (.94)
16.8 (24.4)
82.4 (86.7)
8
9.2 (9.2)
98.2 (24.6)
54.9 (19.0)
4.3 (4.6)
134.1 (103.2)
111.0 (93.3)
2.3 (1.9)
136.4 (105.1)
243.8 (138.9)
19.4 (8.7)
19.6 (10.6)
11.1 (5.6)
7.9 (3.6)
22.0 (18.1)
11.8 (11.1)
3.9 (3.6)
28.6 (23.4)
67.6 (42.7)
12.4 (7.3)
46.4 (8.2)
39.7 (7.8)
1.5 (.4)
10.5 (11.2)
8.2 (8.6)
3.1 (3.6)
15.1 (15.6)
73.9 (31.1)
* Number in parentheses is the mean biomass at the surface.
-------
*00( !»•*»• S9-4S'C
o:
UJ
iC:J!!"rr-Tr*-T*T^Tr-r
* f« <2 « M
Rotifera
cc
LU
rv*
-1-
/ i
i.iijl.ti
I L._,_,-, ..<-._*_^—
i» ^ » ^ i« T 12 f • »4 T e ^^ it
Qophnto reifocurvo
-»*"^ii>.
yioo
5
6*
"If** i * if U '•>'' t4 '—B * It
-* -r-*-rr»-ir-*-T ^-Tr->-Tr-*-Tr-
t*«09*2)O^
r>. .rinmnj«i • ..n • Ji
IT • » ' il ' 1! ' I ' 14 ' B ' K
(T ~ * ' « ' It ' • ' W
Cladocera
Bosmino sp
STATIONS
IT • !• IZ •
Cope pod o
> t >—ii > n (—r>—rri—art—ir—
C 300
TKacsr'-1*-^
wt. m.i»«f)i-»!-j'o-c
9 it )2 • M o 't
Cyclops vernalis
Figure 11. Mean densities of zooplankton in the cooling system at the Monroe
Power Plant.
-------
Abundances varied less dramatically over the short-term periods when the
cooling system was sampled in the morning, afternoon, and evening of 1972-73
(Fig. 11). Even so, the abundances found at different times of the day commonly
varied up to 100 percent or more of the mean. However, there was no consistent
relationship between the abundance and the time of the day sampled. Mean annual
densities for different times of the day revealed no consistant differences
related to the time of the day (Table 23), Density differences between day and
night were inconsistant and less than 50 percent among the major taxa. The
densities of major taxa seemed to vary independently from one time of day to the
next. There may have been a slight tendency for larger organisms to be captured
more frequently at night. The mean individual size calculated in 1972-73 was
slightly greater in the evening samples, particularly for C.. vernalis and I).
retrocurva (Table 24).
The short-term density comparisons revealed no consistent effects from regu-
lar chlorine application in the morning and evening. If chlorine had been impor-
tant, the morning and evening zooplankton concentrations in the upper discharge
canal at station 12 should have been consistently lower than afternoon concentra-
tions in 1972-73 (Tables 21; 22). Because chlorinated water reached station 8
from 4 to 6 hours later, afternoon densities at station 8 should have been
depressed below morning and evening densities if chlorine were an important fac-
tor. To the contrary, densities at station 12 and 8 were similar for all times.
Consistent trends appeared in the comparisons of annual station means
(Tables 21, 22), but significant (« = 0.05) differences rarely occurred at the
individual sampling times because the sampling intensity was not enough to accom-
modate the spatial variability that existed. Lake concentrations at intake
station 17 averaged about twice as great as river concentrations at station 9
and these consistent differences were significant (« = 0.05) on several dates for
most of the taxa (Table B24). Among stations in the intake and discharge canals,
the significant (« = 0.05) differences may have been caused by naturally patchy
distributions in the study area rather than by entrainment effects. However,
discharge concentrations were significantly (tt = 0.05) lower 3 out of 9 times
when zooplankton were common in 1973; they were never significantly higher.
Although patchy distributions increased in variability, there appeared to be
consistent depressions in abundances as a consequence of passage through the
cooling system. Among the most abundant species caught in 1973, significant
differences (« = 0.05) were about equally represented by higher and lower concen-
trations in the discharge canal compared to the intake. The incidence of sta-
tistical difference seemed not to be related to absolute water temperature or the
elevation at the condenser.
The mean annual density of zooplankton consistently decreased one third to
two thirds in passage from the intake to the upper discharge canal in all three
years (Table 21). The biomass decreased less consistently because the mean size
of animals encountered seemed to vary. In passage from the upper to the lower
discharge canal, the mean annual densities of most taxa remained about the same
or increased slightly while mean annual biomass changed little or decreased
slightly. Therefore, mean annual sizes of" zooplankters seemed to remain constant
or decreased slightly as water passed through the discharge canal (Table 25).
These size changes during the passage were most pronounced in the cladocera which
decreased in mean size about 40 to 60 percent. The small rotifers consistently
seemed to increase in size while copepods varied inconsistently.
75
-------
TABLE 23. MEAN ANNUAL SIZE PER INDIVIDUAL OF ZOOPLANKTON IN THE COOLING SYSTEM
(yg)
STATIONS
Taxa
1972-73
Rotifera
Cladocera
Daphnia sp.
Bosmlna sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
1973-74
Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
1975
Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
17
0.1
6.1
9.9
1.6
3.6
2.7
0.2
2.5
2.1
0.1
3.0
9.3
0.7
4.3
3.7
0.1
0.6
0.6
0.9
4.0
6.2
1.0
4.2
4.5
0.2
0.9
0.5
(0.1)*
(4.8)
(12.0)
(5.3)
(3.1)
(3.0)
(0.2)
(2.2)
(1.7)
(0.1)
(6.0)
(11.1)
(0.5)
(5.3)
(3.2)
(0.1)
(0.9)
(0.9)
(0.1)
(1.2)
(4.6)
(0.7)
(5.6)
(2.5)
(0.2)
(0.7)
(0.2)
0.2
2.2
14.0
0.8
4.3
4.0
0.2
2.8
1.7
0.2
1.3
17.0
0.5
2.0
2.7
0.1
0.4
0.3
0.1
7.8
8.3
0.1
3.2
3.5
0.2
0.6
0.8
9
(0.
(0.
(5.
(0.
(9.
(9.
(0.
(2.
(0.
(0.
(0.
(0.
(0.
(2.
(2.
(0.
(0.
(0.
(0.
(0.
(0.
(0.
(3.
(3.
(0.
(1.
(1.
18
2)
6)
7)
8)
5)
9)
2)
6)
8)
1)
3)
0)
2)
0)
0)
1)
2)
2)
1)
5)
0)
9)
1)
0)
1)
8)
2)
0.1
5.1
11.6
1.1
3.8
3.2
0.1
2.7
2.1
0.1
2.7
9.4
0.7
4.4
3.8
0.1
0.5
0.5
0.1
3.8
6.4
1.1
4.5
7.0
0.2
0.7
0.6
(0.1)
(4.7)
(11.0)
(.65)
(3.4)
(3.3)
(0.1)
(2.2) .
(1.5)
(0.1)
(5.3)
(20.7)
(0,5)
(6.3)
(2.5)
(0.1)
(0.8)
(0.8)
(0.1)
(1.3)
(4.6)
(0.5)
(6.4)
(2.2)
(0.1)
(0.6)
(2.1)
12
0.1
11.8
10.7
0.8
3.9
3.4
0.1
2.9
2.7
0.1
1.4
6.3
0.4
3.0
3.2
0.1
0.5
0.4
0.1
6.7
37.9
1.1
3.9
3.0
0.2
0.9
0.8
(0.1)
(4.9)
(16.6)
(0.7)
(3.6)
(3.5)
(0.1)
(2.8)
(1.9)
(0.2)
(0.4)
(0.0
(0.4)
(2.4)
(2.4)
(0.2)
(0.6)
(0.3)
(0.1)
(13.9
(18.2)
(0.4)
(4.8)
(3.7)
(0.1)
(1.9)
(0.9)
0.2
6.8
9.8
0.6
2.5
2.7
0.1
1.7
1.6
0.2
1.1
6.2
0.6
3.5
3.1
0.1
0.6
0.4
0.2
3.0
13.7
0.9
3.2
3.6
0.2
0.7
0.7
8
(0.2)
(4.7)
(5.7)
(1.0)
(3.3)
(3.2)
(0.1)
(2.0)
(1.2)
(0.1)
(1.8)
(3.3)
(1.3)
(3.6)
(3.4)
(0.6)
(0.5)
(0.3)
(0.1)
(4.1)
(7.8)
(0.4)
(3.2)
(2.4)
(.94)
(0.8)
(0.3)
* Number in parentheses is the mean individual size at the surface
-------
TABLE 24. MEAN DENSITY OF ZOOPLANKTON AT DIFFERENT TIMES OF THE DAY
(numbers/liter)
STATIONS
Taxa
1972-73
Rotifera
Cladocera
Daphnia sp.
Bosmlna sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
1973-74
Rotifera
Cladocera
Daphnia sp.
Bosmlna sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
1975
Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
17
Afternoon
100.2
43.7
18.2
13.3
73.3
62.6
26.7
100.0
243.9
191.6
36.9
14.7
11.3
4.2
3.4
73.8
78.0
306.5
141.0
22.6
8.6 -
3.2
2.0
.4
19.3
21.3
184.9
Evening
80.7
25.5
7.7
8.1
56.7
52.8
110.6
167.3
273.5
132.6
26.5
3.3
20.1
8.0
5.1
36.0
44.0
203.1
149.4
12.6
4.6
1.6
3.6
2.6
11.9
15.5
177.5
9
Afternoon
46.2
10.0
3.6
6.0
42.3
30.2
25.0
67.3
123.5
111.3
11.3
.3
8.0
3.2
2.3
24.1
27.3
149.9
38.6
3.2
1.2
.34
.15
.05
11.6
11.75
53.55
Evening
39.9
7.9
3.3
3.7
28.1
22.0
11.6
39.7
87.5
104.0
12.5
.6
8.1
3.9
3.2
20.6
24.5
141.0
55.9
7.4
3.6
1.3
2.0
2,0
11.5
13.5
76.8
12
Afternoon
53.0
8.4
14.7
3.6
57.1
51.8
21.7
78.8
140.2
119.2
14.8
3.3
10.5
.5
.4
40.9
41.4
175.4
69.1
10.0
1.2
2.8
1.5
.4
17.2
18.7
97.8
Evening
58.4
14.7
12.2
7.1
40.3
35.8
9.5
49.8
122.9
88.2
20.3
2.6
13.6
9.3
6.7
37.6
46.9
155.4
72.7
7.2
1.6
2.8
4.2
3.2
14.4
18.6
98.5
8
Afternoon
78.0
12.2
3.7
6.9
43.6
42.7
31.4
75.0
165.2
94.2
10.0
3.0
6.3
7.0
4.4
48.2
55.2
159.4
56.7
19.2
2.0
.8
1.8
1.2
19.5
21.3
97.2
Evening
42.8
17.7
7.5
8.4
49.7
42.9
20.7
70.4
130.9
132.1
24.3
1.3
18.9
5.3
3.3
36.3
41.6
210.0
82.4
11.4
3.8
2.4
4.7
3.4
15.7
20.4
114.2
-------
TABLE 25. MEAN SIZE PER INDIVIDUAL FOR THE MAJOR TAXA AT THE DAILY TIME PERIODS
Taxa
1973: Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
1974: Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult .C. vernalis
Nauplii
Total Copepoda
Total
1975: Rotifera
Cladocera
Daphnia sp.
Bosmina sp.
Adult Copepoda
Adult C. vernalis
Nauplii
Total Copepoda
Total
Morning
0.1
6.5
12.5
1.3
2.2
2.8
0.1
1.7
2.7
— -
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
^^
Afternoon
0.1
5.0
11.1
1.0
2.2
3.0
0.1
1.7
2.3
0.1
2.5
7.2
0.6
2.6
2.4
0.1
0.3*
0.3*
0.1
3.7
7.6
1.0
4.1
3.6
0.2
0.5*
0.6*
Evening
0.1
4.6
10.9
1.1
3.2
5.0
0.1
2.7
2.5
0.1
1.5
10.4
0.6
4.0
3.6
0.1
0.8
0.4*
0.1
5.8
15.5
0.8
3.5
3.6
0.2
0.9
0.7
Low value a result of large numbers of nauplii and rotifers.
78
-------
Based on day and night comparisons, there was no significant diurnal, verti-
cal migration in any of the major taxa but cladocerans and copepods exhibited
depth-biased distributions (Fig, 12), On several dates, both of these taxa were
more abundant near the bottom than near the surface at three of the four stations
(17, 9, 12 and 8) where depths were randomly sampled over 5-m from top to bottom,
Other stations were too shallow to sample similarly. The time of day did not
seem to influence the vertical orientation, but it did not occur equally on all
dates sampled. No depth biased distribution was ever observed in the upper dis-
charge canal (station 12). On the dates when vertically biased distributions
occurred, condenser passage caused uniform vertical distribution. Whatever dis-
rupted this effect ceased after the water mass approached the middle of the dis-
charge canal at station 8.
Based on the mixing measured by chloride concentrations, the concentration of
zooplankton in the thermal plume was expected to be a mixture of populations in
the lake receiving water and populations that had passed through the cooling
system at least once. Sampling in 1972-73 verified this proposition. By the
time that water from the cooling system and the lake mixed back to ambient chlor-
ide concentrations and temperatures at station 16, zooplankton concentrations
also mixed back to concentrations like those found in the lake reference areas
(Table 26).
As at station 16, sampling at station 15 was conducted only at the surface
(0.5 m) because the thermal plume tended to float and the water depth averaged
only 1 to 1.5 m. Station 15 was located about midway between the mouth of the
discharge canal and the plume edge at a point where temperature and chloride
concentration averaged close to midway between the conditions in the discharge
canal and the lake. Based on mixing ratios defined by chloride concentration
and temperature, zooplankton concentrations in the plume at station 15 were
expected to average midway between those at stations 14 and 16. This they tended
to do but sampling variability obscured differention of concentrations estimated
at station 15 from population estimates for other locations in the study area.
Mortality
Pilot studies of mortality conducted to assess the potential at times of the
year when zooplankton were abundant and temperatures in the cooling system would
approach 30°C or more (June and July). In 1974, sampling was directed at the
smaller zooplankters and in 1976 it concentrated on the relatively large
Leptodora kindtii. The mean percent that were dead in the intake and discharge
canal is summarized in Table 27. From 8 to 19 percent of the organisms were
dead in the intake reference collections. For the rotifers and nauplii, the
smallest plankters, an average of 7 to 8 percent were dead in the discharge
canal. The percent dead averaged 12 percent for the intermediate-sized copepods.
For the class with the largest organisms, the percentage averaged 26% dead.
The largest zooplankter, Leptodora kindtii, averaged 60 percent dead in 'the
cooling system. Only the Cladocera, and particularly the largest cladocerans,
appeared to be appreciably affected by the condenser passage.
This data is insufficient by itself to demonstrate the impact of power plant
operation on zooplanktonic survival. It does point out the need for further
79
-------
ICOZOOaOO
«620036o 1)0 200 300 100200300
JUNE. 1975
Qa
Zi
3.
5.
6,
1
o j a
*
o { a
o\a
a01
2.
3.
4.
5.
6.
D ,ft
a > p
•>?''
i \ o
I/I
°tr a"
2.
3.
4
&
&
a>0
r''
°k%
X
I ^
°^
1
1.
2.
3,
4,
5.
p&
a \p
\
\
* * ^t a
a f''i
i / a
if ,»^ ,
|60200360
CO 200300
^60^260300 oo
AUGUST B75
DO 330 300
(60260360
00260360
|,.V
4.
5.
160260360
WO 200300 00200300 100 200300
SEPTEMBER B»
OO 200300
(00200300 100260360 60260360
JUNE. 1973
(00200300
DO 300 900
SMionlT
DO 300 900
Stations
AUGUST. S73'
DO 300 900
.Station 12
DO 300 900
Station 8
mg/lHer
Figure 12. Mean density of copepods (open) and cladocerans (closed)
at each depth sampled for the summers of 1973, 1974, 1975.
80
-------
TABLE 26. COMPARISON OF MEAN DENSITY, BIOMASS, AND SIZE OF ZOOPLANKTON AMONG THE LAKE
STATIONS AND LOWER DISCHARGE STATION 14 AT 0.5 m BELOW THE SURFACE* IN 1973
00
Station
Taxa
.3*
4#
5#
14
15
16
17
Density
Rotifera
Cladocera
Total Copepoda
Total
107.0
30.2
106.7
243.9
109.0
27.6
70.6
207.2
90.0
18.8
101.8
210.6
83.0
16.4
114.3
213.7
70.3
24.0
111.2
205.6
78.8
41.0
112.6
232.4
81.5
25.2
144.7
251.4
Biomass
Rotifera
Cladocera
Total Copepoda
Total
9.8
162.8
115.5
288.1
10.9
110.6
141.4
262.9
12.8
59.7
92.7
165.2
8.2
59.5
172.0
239.7
8.7
52.3
265.9
326.9
8.5
79.1
218.7
306.3
8.9
86.1
209.0
304.0
Mean Size/Individual
Rotifera
Cladocera
Total Copepoda
Total
0.09
5.4
1.1
1.2
0.10
4.0
2.0
1.3
0.14
3.2
0.9
0.8
0.10
3.6
2.1
1.1
0.12
2.2
2.4
1.6
0.11
1.9
1.9
1.3
0.11
3.4
1.4
1.2
*0nly samples collected from April to November, 1973, are included because no winter
samples were taken at stations 3, 4, and 5.
#Data from Cole (1976).
-------
TABLE 27. PRELIMINARY ESTIMATE OF ZOOPLANKTON MORTALITY IN THE COOLING SYSTEM
AT THE MONROE POWER PLANT
(percent dead)
Intake (18) 10
Upper Discharge (12) 60
Middle Discharge (8)
Lower Discharge (14)
Copepoda* Nauplii*
8
16
7
25
15
9
6
13
Cladocerans^ Rotifers^
19
17
50
10
9
6
3
17
*Mean of three replicates sampled on July 6 through 9, 1976.
'Mean of three replicates sampled on June 27, 1974.
82
-------
investigations on what may be size^selection or other taxa-specific, selective
mortality in the cooling system.
Diversity
Zooplanktonic diversity did not consistently change with passage through the
cooling system. Organisms were abundant enough to contrast diversity only during
warm months (Table 28). Differences in diversity over a three-day period at
specific stations were often as great as differences observed among stations on
any particular date. There were no consistent trends in diversity related to the
time of sampling. Short-term variations appeared to be caused primarily by spatial
variability among samples at each station and may have been effected secondarily
by patchy distributions associated with different water masses. Entrainment
seemed to have little effect on diversity.
MIDGES
Chironomid entrainment was estimated in 1973 at the time we tentatively inves-
tigated larval fish distributions in the cooling system. Midges were transported
through the cooling system as larvae and pupae (Table 29), Most midges were
captured in the deepest tows, at 4 m. Because the tow depth was 2 m or more over
the bottom at most sites, the actual number of midges entrained was probably under-
estimated by the averages generated from the data. Estimates of numbers varied
widely over the sampling period, but river abundances appeared to exceed lake
abundances. At rates estimated for the sampling period, an average of 700,000
midges per day could pass through the plant at full operation.
LARVAL FISH
Species Composition
The most abundant of 15 taxa captured from 1973-1975 included gizzard shad,
Dorosoma cepedianum, and the alewife, Alosa pseudoharengus (together 43.6 percent;
hereafter referred to as "clupeids"); yellow perch, Perca flavescens (25.3 per-
cent); carp, Cyprinus carpio. goldfish, Carassius auratus. and their hybrids
(together 10.6 percent);.white bass, Morone chrvsops (7.3 percent); emerald and
spottail shiners, Notropis atherinoides and JS. Hudsonius (together 3.2 percent);
and freshwater drum, Aplodinotus grunniens (2.0 percent). The combinations of
species listed above could not be routinely separated to species as larvae. These
species accounted for 92 percent of the total catch. Prolarvae (yolk-sac larvae)
represented 19.1 percent of the total catch and postlarvae represented 80.9 per-
cent. Less abundant species are listed in Tables 30 and B26.
Comparison of Surface Sampling Techniques
The 1-m plankton net was the most effective surface sampling technique tested
in the comparison of the Kenco pump, the high-speed plankton sampler, and the
571-y, 1-m, plankton net. Significantly (= = 0.05) more fish larvae of all
species were captured by the 1-m net on most of the dates sampled (Table B27) ;
white bass were captured only in the 1-m net (Table 31) .
83
-------
TABLE 28. ZOOPLANKTON DIVERSITY IN THE COOLING SYSTEM
Station
1973:
1974:
1975:
Date
06/11
06/12
08/08
08/09
09/28
09/29
06/11
06/12
08/14
08/15
10/19
10/21
05/16
05/17
07/27
07/28
09/15
09/16
17
0.53
0.70
0.42
0.48
0.84
0.81
0.98
0.70
0.63
0.51
0.66
0.74
0.59
0.55
0.72
0.81
1.01
0.91
9
0.59
0.51
0.49
0.69
0.76
0.83
1.08
1.08
0.94
0.90
0.64
0.60
0.80
0.78
0.99
0.92
0.59
0.89
18
0.53
0.59
0.45
0.64
0.92
0.83
1.00
0.78
0.67
0.54
0.66
0.73
0.67
0.67
0.73
0.82
0.95
0.91
12
0.57
0.73
0.50
0.40
0.87
0.93
0.81
0.94
0.92
0.72
0.67
0.65
0.62
0.76
0.87
1.06
0.94
1.10
8
0.59
0.78
0.43
0.45
0.95
0.96
1.00
0.94
0.82
0.81
0.67
0.67
0.84
0.68
0.80
1.00
1.00
0.86
84
-------
TABLE 29. THE DISTRIBUTION OF CHIRONOMID LARVAE IN THE COOLING
SYSTEM IN 1973
(no./lOO m3)
Date and Depth*
pi
P2
Station
P3
P4
Pll
1 May 1973
15
1
8
0.0 m
2.5 m
4.0 m
Mean
May 1973
0.0 m
2.5 m
4.0 m
Mean
June 1973
0.0 m
2.5 m
4.0 m
Mean
June 1973
0.0 m
1.0*
—
3.0
2.0
0.5
0.0
3.0
1.2
3.5
15.5
28.0
15.7
0.8
4.0
—
17.0
10.5
1.0
1.5
10.0
4.2
1.5
0.0
24.0
8.5
3.3
1.5
—
14.0
7.8
1.5
3.0
13.0
5.8
1.0
12.0
8.0
7.0
0.5
3.5
—
—
3.5
1.2
—
—
1.2
0.2
—
—
0.2
1.8
0
—
— —
0
0.5
0.0
0.5
0.3
6.5
1.0
1.0
2.8
1.0
15 June 1973
0.0 m
2.5 m
4.0 m
Mean
0.5
0.0
13.0
4.5
3.0
47.0
500.0
183.3
6.0
2.0
19.0
9.0
0.3
—
—
0.3
0.0
3.0
2.0
1.7
*Maximum depth is 1.5 meters
#Mean of 2 replicates
85
-------
TABLE 30. MEAN CATCH OF FISH LARVAE PER 100 m3 IN OBLIQUE 1-m PLANKTON NET TOWS FROM MAY THROUGH
JULY IN 1974* AND 1975 #
00
ON
P6
Clupeids
Yellow perch
Carp-goldfish
White bass
Shiners
Freshwater drum
Smelt
Sunfish
Black bass
Channel catfish
Crappie
Trout perch
Log perch
Walleye
White sucker
Total
74
13.7
15.0
1.4
2.4
0.5
2.4
0.1
0.7
0
0.1
0
0.1
0.1
0.2
0.1
36.8
75
7.8
9.7
0
0.6
0.2
0
0.4
0
0
1*0
0
0.1
0
0
0
18.8
P7
74
3.6
1.6
12.7
0.1
0.4
2.1
0.1
1.9
0.9
0.1
0.3
0
0
0
0
21.4
75
2.3
0.4
3.8
1.1
3.6
0
0.5
1.0
0.5
0.3
0.5
0
0
0
0.4
15.4
P2
74
17.0
11.7
10.7
14.5
2.5
3.0
0
1.1
0.1
4.0
0
0.1
0
0.1
0
64.8
75
11.0
7.1
4.1
1.3
2.6
0
0.5
0.2
0
0.3
0.1
0
0.3
0
0
27.5
P3
74
15.4
6.2
3.5
3.5
0.5
1.1
0
0.6
0
0.5
0
0
0
0
0
31.3
P P,
rio 11
75
6.7
0.6
0.9
0.4
0.1
0.1
0
0.2
0
0
0
0
0
0
0
9.0
74
9.5
7.6
0.2
1.0
. 0.7
1.7
0.2
0.1
0
0
0
0
0
0
0
21.0
75
8.5
5.6
0
0.4
0.4
0.1
0.2
0
0
0
0
0
0
0
0
15.2
74
36.8
1.5
0.2
1.5
0.8
1.2
0.4
0.1
0
0
0
0
0
0
0
42.5
75
9.0
2.5
0
0.8
0.8
0
0.1
0
0
0
0
0
0
0
0
13.2
P12
74
20.4
1.0
0.8
2.6
1.6
0.8
0.1
0.2
0.3
0
0.1
0
0
0
0
27.9
75
3.8
13.2
0
0.5
0.2
0
0.5
0
0.1
0
0
0
0
0
0
18.3
*Sampled on 6 dates; 5 replicates/iate
Sampled on 5 dates; 5 replicates/iate
-------
00
TABLE 31. COMPARISON OF THE MEAN CATCH AT THE SURFACE IN A 571-y, 1-m PLANKTON NET, A MODIFIED
HARDY "HIGH-SPEED" SAMPLER, AND A KENCO PUMP*
(number/100 m3)
Clupeids
1-m net
High-speed
Pump
Yellow perch
1-m net
High-speed
Pump
White bass
1-m net
High-speed
Pump
Smelt
1-m net
High-speed
Pump
Shiners
1-m net
High-speed
Pump
Total
1-m net
High-speed
Pump
05/21/75
0*
0
0
4.3
0
0
0
0
0
1.4
0
0
0
0
0
5.7
0
0
05/23/75
2.8
0
0
3.7
0
0
0
0
0
0.8
0
0
0
0
0
7.3
0
0
05/24/75
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
06/18/75
62.1
343.7
21.3
0.7
5.3
0
0.7
0
0
8.7
0.9
0
9.3
0.9
0
63.5
350.8
21.3
06/19/75
8.3
0.9
0
0
0
0
0
0
0
0
0
0
0
0
0
8.3
0.9
0
06/20/75
0
0
0.7
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.7
Total
73.2
344.6
22,0
8.7
5.3
0
0.7
0
0
10.9
0.9
0
9.3
0.9
0
84.8
351.7
22.0
*5 replicates
-------
The Kenco pump was the least effective sampling technique tested. Sig-
nificantly (« - 0.05) fewer larvae of all taxa were captured (Table B27).
Fish larvae were captured only on June 18 and 19 when clupeids were common.
About 40 percent of the captured larvae were damaged; 10 percent were damaged
so badly they could not be identified or included in the statistical analysis.
The high-speed plankton sampler seemed most effective when fish larvae
were dense at the surface (Table 31). This occurred only on June 18, when
more (p "< 0.05) yellow perch and clupeid larvae were captured with the high-
speed sampler than with the other surface techniques (Table B26) . On all
other dates the 1-m plankton net performed best.
Mean Size and the Length of Time Towed
The 353-u, 1-m net usually caught more fish larvae than 1-m nets with
larger mesh sizes (Figure 13). The 1000-p nets caught fewer (p <_ 0.05) larvae
than the 363-u or 571-y nets. The 760-y net caught fewer (p £ 0.05) larvae
than the smaller mesh sizes on one of two dates that it was compared.
The relative capture effectiveness of the two smaller mesh sizes appeared
to depend on the species and size (age) of the larvae (Table 23). Prolarval
fish were caught most effectively with the 363-y net. On May 21, more (« =
0.05) smelt prolarvae. were caught with the 363-y net compared to the others
(Table B27). On May 20, more (p _< 0.05) yellow perch postlarvae were caught
with the 571-y net; On June 21, more (p _<_ 0.05) postlarval clupeids were
captured using the 363-y net.
No consistently significant (« - 0.05) large differences appeared between
1, 2, 3, 4, and 5-min tows (Fig. 13; Table B28). The 1, 2, and 3-min tows
averaged slightly more fish larvae per unit effort but the 5-min tow caught
more fish larvae per unit effort than the others on one of the sampling dates.
Vertical Distributions
Daytime Tows—
Oblique tows from deep water to surface usually were as effective as the
mean of stratified tows made at the surface and deep position at the transect
stations P13, P14, P15, and P16. Minor difficulties in species suseptibility
may have existed. Clupeids and smelt tended to be captured more effectively
with stratified tows although the capture rate was not statistically differ-
ent (« • 0.05) from the oblique tows. Yellow perch and white bass tended to
be caught more efficiently with oblique tows (Fig. 14). No consistent dif-
ferences in the catch effectiveness of stratified and oblique tows appeared
anywhere along the transect, regardless of distance from shore or differences
in depth to the bottom.
At station P17, the daytime capture efficiency at different depths was
inconsistent in time and by species but in no instance did the mean of oblique
and stratified tows differ (Table 32). Fish larvae appeared to be concentra-
ted near the bottom during the day (according to bottom-sled yield ) but
populations above the bottom exhibited no consistent vertical distributional
88
-------
00
VO
45-
40-
» 35-
2
§ 30-
S 25-
00
5
r> 20-
z
< 1 5-
UJ
10-
Bi§aS IlliB
1 2 3' 4' '5' V '2' '3' 4 "5" 1 '
5-20 5-22
DATE AND TOW LENGTf
H
•1
I
1
H
1
<
•
E
jj
•
s
&
i
5
N
-
1
1 40-
135-
to
Jg
8 30-
1 1 i o: 25-
= i B E y
' E i §
B il E H - z
H : S • ^
5 : • rf IK
a ! B uj
: 5
i ^
1 ID-
S'
l"4' '5'l 'l"2"3"4"5'l p
8 6-19
NIMUM)
;
:
;
1
1 r
• ™ •
• H • * H
if - - 5
\ \ M
• • ™ *
• :
•*
1;
1
p g
M B D
3-tf Vl'gT '5' T I '3' '3' Y 1 '3"5' Y I
670 670 676 676
310 310 310 310
0 0
5-20 5-21 6-18 6-20
DATE AND MESH SIZE (u)
Figure 13. The mean number of larval fish captured (+SE) for length of time towed
(1, 2, 3, 4, and 5 min.) and each mesh size tested (363, 571. 760 and
lOOOu).
-------
5-22-75 5-23-75 6-9-75 6-16-75 6-19-75 7-2-75
80-i
70.
60.
50.
40.
30-
20-
10-
44 H
42-
38.
34-
32-
28.
24.
20
16.
12.
8-
4-
18 -|
16 .
14 .
12 -
10.
8 -
6-
4 .
2 .
20 J
18 -
16 .
14 -
12 -
K> -
8.
6.
4 .
2 .
12 J
10 -
8 .
6 .
4 .
2 .
£ III.,
15 T*
5-22-T
f 1
5 5-23-7!
Lnl
Ml m-lm-, ^ISi •-• »- i 1
11
• Oblique tows
O Mean of the surface and deep tows
1 'nlr^T
> 6-9-75
ttllM FtofitL
> ' 13 14 B 16 ' 13 M B 16 ' 13 14 15 16
6-16-75 6-19-75 7-2-75
1 i 1 — - — — 1 1
75 14 B 16 ' 13 14 6 16 ' 13 14 15 l(
5^2-75 5-23-75 6-9-75
HJI
BI4BI6 8 14 B 16 B 14 6 1
5-22-75 5-23-75 6-9-75
.Sumo.
_-nlil
5 ' 13 14 B 16 ' 13 14 15 16 ' 13 14 B 16
6-6-75 6-19-75 7-2-75
ll — — _^IB-, — •_ — i •- rf~l ri -_
S ' 13 14 15 16 ' 13 14 B 16 ' 13 14 6 16
6-16-75 6-19-75 7-2-75
IJlfc^M-ll ^lllllllll
13 14 B 16 13 14 6 16 13 14 6 16 « 13 14 6 16 ' 13 14 B 16 ' 13 14 15 16
5-22-75 5-23-75 6-9-75 6-16-75 6-19-75 7-2-75
S1
101
6-16-75 6-19-75 7-2-75
DATE AND STATION NUMBER
Figure 14. Mean number of larval fish captured in oblique tows
compared to the mean of stratified tows at the surface
and bottom.
90
-------
TABLE 32. DAYTIME AND NIGHTTIME COMPARISONS OF MEAN CATCH C5 replicates) per 100 m3
IN OBLIQUE, SURFACE, MIDWATER, DEEP TOWS AND TOWING WITH A BOTTOM SLED USING A
571-u,l-m PLANKTON NET
Species
Clupeids
5/21/75
Day
Night
5/23/75
Day
Night
5/24/75
Day
Night
6/18/75
Day
Night
6/19/75
Day
Night
6/20/75
Day
Night
Mean
Day
Night
Surface
0
2,2
2.8
0
0
0
62.1
81.0
8.3
45.0
0
3.2
12.4
21.9
Midwater
0
3.4
0.5
0.6
0
1.7
21.9
89 . 3
1.3
88.9
1.1
6.8
4.4
31.8
Deep
0
5.2
0
0.5
0
0
3.3
94.9
0
64.1
0.5
0.5
0.6
27.5
Mean*
0
3.6
1.1
0.4
0
0.6
29.1
88.4
3.3
66.0
0.5
3.5
5.7
27.1
Oblique
0.9
4.3
1.2
1.8
0.3
0.7
12.7
89.4
7.4
103.5
1.2
2.6
3.4
33.7
Water
Bottom Column
Sled Mean#
I-*. 0
18.0
5.5
1.8
0
2.8
698.6 815.0
442.0
81.1 93.9
330.0
124.2 126.3
17.5
301.3 173.4
135.4
(continued)
-------
TABLE 32 (continued).
fo
Species
White Bass
5/21/75
Day
Night
5/23/75
Day
Night
5/24/75
Day
Night
6/18/75
Day
Night
6/19/75
Day
Night
6/20/75
Day
Night
Mean
Day
Night
Surface
0
0
0
0
0
0
0.7
6.6
0
0
0
0.8
0.1
1.2
Hidwater
0
0.6
0.6
0
0
0
1.6
7.3
0.5
5.0
0
10.8
0.5
4.0
Deep
0
0
1.1
0
0.7
0
2.8
5.8
0
1.0
0
9.2
0.8
2.7
Mean*
0
0.2
0.6
0
0.2
0
1.7
6.6
0.2
2.0
0
6.9
0.5
2.6
Oblique
0
0
0.5
0
0
0
2.3
4.9
0
1.2
0
9.6
0.5
2.6
Water
Bottom Column
Sled Mearrf
0
1.0
3.0
0
1.0
0
36.7 43.5
32.8
27.0 27.8
10.0
25.1 25.1
34.7
29.6 16.7
13.1
(continued)
-------
TABLE 32 (continued).
vo
u>
Species
Yellow Perch
5/21/75
Day
Night
5/23/75
Day
Night
5/24/75
Day
Night
6/18/75
Day
Night
6/19/75
Day
Night
6/20/75
Day
Night
Mean
Day
Night
Surface
4.3
29.0
3.7
0
0
1.3
0.7
1.1
0
0
0
0
1.5
5.2
Midwater
2.2
57.7
0.5
3.6
0.7
13.0
0
7.6
0
3.0
0
0
1.1
14.2
Deep
1.6
32.7
0.5
35.1
0.7
31.3
3.0
7.3
1.0
10.4
0
4.3
2.3
20.2
Mean*
2.7
39.8
1.6
12.9
0.5
15.2
1.2
5.3
0.3
4.5
0
1.4
1.2
13.2
Oblique
0.9
33.5
2.0
17.9
2.0
23.1
0.3
9.7
0
2.2
0
0.9
1.2
14.6
Water
Bottom Column
Sled Mean #
13.5
199.0
8.0
64.5
9 c
£. 9 D
76.0
0.0 4.8
26.7
11.0 12.2
22.3
3.9 3.9
7.2
6.2 7.5
65.9
(continued)
-------
TABLE 32 (continued).
VO
Species
Smelt
5/21/75
Day
Night
5/23/75
Day
Night
5/24/75
Day
Night
6/18/75
Day
Night
6/19/75
Day
Night
6/20/75
Day
Night
Mean
Day
Night
Surface
1.4
18.5
0.7
8.3
0
17.5
8.7
6.3
0
0
0
0.8
1.8
8.6
Midwater
2.7
11.8
0.6
35.1
0
61.0
5.7
11.3
0.5
2.5
0
3.4
1.6
20.8
Deep
1.1
13.4
1.1
46.6
1.2
29.1
8.1
15.1
0.5
0.9
0
13.3
2.0
19.7
Mean*
1.7
14.6
0.8
30.0
0.4
35.9
7.5
10.9
0.3
1.1
0
5.8
1.8
16.4
Oblique
3.5
10.2
1.5
42.5
0.2
44.2
7.2
10.0
0.7
0.2
0
0.9
2.2
18.0
Water
Bottom Column
Sled Mean#
8.7
72.8
4.0
150.0
2.0
179.3
632.0 662.0
54.5
27.7 28.0
5.7
2.6 2.6
29.2
222.9 117.9
81.9
(continued)
-------
TABLE 32 (continued)
vO
Ul
Species
Shiners
5/21/75
Day
Night
5/23/75
Day
Night
5/24/75
Day
Night
6/18/75
Day
Night
6/19/75
Day
Night
6/20/75
Day
Night
Mean
Day
Night
Surface
0
0.6
0
1.4
0
0.7
9.3
6.9
0
2.4
0
0.9
1.6
2.2
Midwater
0
0
0
0
0
1.2
2.1
7.6
0
0.5
0.6
2.0
0.5
1.9
Deep
0
0
0
0
0
0
3.2
7.3
0
0.5
0
0.5
0.5
1,4
Mean*
0
0.2
0
0.5
0
0.6
4.9
7.3
0
1.1
0.2
1.1
0.9
1.8
Oblique
o
0
o
0.7
o
0.5
7.3
6.5
0
0.2
0
1.8
1.2
1.6
Water
Bottom Column
Sled Mean//
— n
u
1.0
— n
u
2.3
— 0
\J
3.2
33.5 53.1
36.3
3.2 3.2
5.7
2.6 2 8
*• • V 4m, • \J
5.7
6.6 9.8
9.0
(continued)
-------
TABLE 32 (continued)
vo
CM
Species
Carp
5/21/75
Day
Night
5/23/75
Day
Night
5/24/75
Day
Night
6/18/75
Day
Night
6/19/75
Day
Night
6/20/75
Day
Night
Mean
Day
Night
Surface
0
0
0
0
0
0
0
4.0
0
8.1
0
70.2
0
13.7
Midwater
0
0
0
0
0
0
0
5.3
0
24.0
0
130.7
0
26.7
Deep
0
0
0
0
0
0
0
2.9
0
53.2
0
61.4
0
19.6
Mean*
0
0
0
0
0
0
0
4.1
0
28.4
0
87.4
0
20.0
Oblique
0
0
0
0
0
0
0
3.1
0
29.9
0
80.6
0
18.9
Water
Bottom Column
Sled Mean//
0
0
0
0
0
0
12.9 12.9
20.3
9.0 9.0
142.2
0.6 0.6
437.2
7.5 7.5
99.9
*Mean of surface, midwater and deep tows.
//Weighted mean of all strata, including bottom sled yield, for a 5 m depth.
-------
patterns. For example, (p _< 0.05) yellow perch prolarvae were captured using
surface and mid-water tows (Table B29) on May 21 and 23 than in deep or oblique
tows; but on May 24 no yellow perch prolarvae were captured at the surface
even through they were captured in all other tows. Similarly, the catches of
clupeid and shiner larvae at the three discrete depths usually did not signifi-
cantly (tt = 0.05) differ from one another. On exceptional dates, more (p <_
0.05) clupeids were captured at the surface (June 19) and fewer (p <_ 0.05)
shiners were captured in mid-water (June 18). Much of the inconsistent vari-
ation that occurs in vertical distribution above the bottom appears to be
caused by day to day vertical changes in the clumped distribution of larvae.
When the 571-y, 1-m plankton net was towed on a bottom sled, it yielded
more (p <__ 0.05) fish larvae of the important species than the sum of all net-
ting at the other three strata sampled above the bottom (Table 32). Capture
rates with the bottom sled were greatest on June 18 when clupeids and smelt
dominated the catch. On this date, over 100 times more larvae were captured
with the bottom sled than with all of the other tows tested. Daytime catches
of all taxa were greatest with the bottom sled. It appears that more larvae
concentrated near the bottom during the day, but any larvae caught above that
bottom concentration exhibited no consistent stratification.
Nighttime tows—
Nighttime capture rates in the water column above the bottom averaged at
least two to three times the daytime capture rates (excluding the bottom sled)
for all of the major taxa (Fig. 15). The ratios ranged from 1.5:1 to 49:1.
The nighttime capture rates of yellow perch, white bass, and freshwater drum
were significantly (a = 0.05) greater than daytime capture rates on all dates
sampled. On most dates, nighttime capture rates of clupeids, smelt, and
shiners also were significantly (<= = 0.05) less than daytime rates. The mean
ratios over all sampling dates of nighttime to daytime captures were: fresh-
water drum, 14.3; yellow perch, 5.5; smelt, 5.0; clupeids, 4.1; white bass,
3.4; and shiners, 2.4. Although the nighttime ratios of most larval taxa
captured at each depth were not always consistent for the whole sampling
period, deep catches tended to exceed surface catches. Compared to other
species, relatively more yellow perch and smelt were caught near the bottom
at night, while relatively more shiners and clupeids were caught closer to
the surface.
Distribution in Relation to Distance From Shore
Daytime larval distribution along a 16-km transect perpendicular to shore
revealed species specific gradients on dates when larvae were relatively abun-
dant. Clupeids were relatively abundant at near-shore stations (Fig. 16)
where on June 9 and July 2 these stations yielded significantly (« = 0.05)
more larvae (Table B30) . Yellow perch prolarvae were significantly (oc = 0.05)
more abundant at offshore stations, as were smelt and, to a lesser extent,
white bass and shiners. On May 22 and 23 yellow perch larvae were caught
along a distinct gradient from shore with greatest abundance at station 16.
White bass were captured mostly offshore at station P16. Freshwater drum
were captured primarily on June 16 when most (p <_ 0.05) were captured near
shore at station P13.
97
-------
!•»
IM
M
•o
T»
•e
M
•O
1O
K
»
cumin
r.««« •. , ... . . a
n T "
II i "
1
II
i
10
1 >
. 1. 1 I...J..
•MTX MM
III, 1
1 I1 I
h
» »]
^ w
^~ M
^s. **
cc
z "
I -
UJ
5
VKCVW •
f
1
l>«*
•••••3
Iie
I
, '
1 'i i
>
i! !i-t a •B-i
_ , ...
' ,
i i .
..J'1 ! . llHi'1 ,
rev
10*
M0
ito
•O
«c
»•« »«••!««• *«WV
1
! «.'
M 5 ! ,ils
LM!Lu. "L. '.....-.. 1. ^..i.. . i.-. . .-..i.-.^'jtl '-.... ..l.-v ;-'•
TIME
Figure 15. Mean number of larval fish captured (+SE) during the day (D)
and night (N) for each depth stratum at station P 17 (S = surface;
MD « mid-depth; D = deepwater; and 0 = oblique tow).
98
-------
vO
70"
60"
50-
40'
30-
20
i
5
O 10-
o
^
NUMBER
z
2 45-
40-
35"
30"
25-
20-
15-
10-
5-
CLUPEIOS gj
8Q 18-
U |6.
1 I4~
J 12-
1 10
8-
1 6-
BLJ B
2-
B B B
RRiR i i P * i P 8 n P zz
Pl3 Pl4 PIS Pis' PIS PI4 PIS Pis' PI3PHPIS Pl«' PI3 PI4PIS PIS ' PI3P14PISPIS PIS PI4 PIS PI6
5-22 5-23 6-9 6-16 6-19 7-2 *
18-
14
SMELT 12
n -°
1 B ::
2"
B f] 20-,
i 18
1 6
LJ 14
12-
10-
6-
8 ':
I i BPR|HBsB -|BR ,
PI3 PI4 PIS PIS ' PI3 PI4 PIS PIS ' PI3 PI4 PI9 PIS1 PI3 PI4 PIS PIS' PIS PI4 PIS PIS ' PI3 PI4 PIS PIS
5-22 5-23 6-9 6-16 6-19 7-2
YELLOW PERCH
B
B
B
B
•a _ B Q
PIJ PI4 PIS PIS1 PIS PI4 PIS PI61 PIJPI4PI3 Pi's' PI3PI4PI5 PI6 ' PIS PI4PI3PI« ' PI3 Pl^'pis 'PI'S
5-22 5-23 6-9 6-16 6-19 7-2
WHITE BASS
8
H8B 8«*B B*B
Plj PI4 PIS PIS PIS PI4 PIS PIS' PI3PI4PI5 Pis' Pl3 PI4PIS PIS ' PI3PI4 PIS PIS ' PI3 PI4 PIS PIS
5-22 5-23 6-9 6-16 6-19 7-2
SHINERS
B
Bn
n
a8 B B B
T r ..... 1 .^ i^. T , T , t — f^ ... 1 ^^. . . ^Ti ^^ 1 . . ^^. r**. rH 1 . i
T i n n i* i'it i * i ^T i ii<— i*lt Tit ttt flfillllllTIfllfll 11(1
PI3PI4PIS PIS PIS PI4 PIS PIS1 PI3P14PI3 PIS PIS PI4 PIS PIS PI3PI4PI9PIS PIS PI4 PIS PIS
5-22 5-23 6-9 6-16 6-19 7-2
DATE AND STATION
Figure 16. Mean number of larval fish captured (+SE) during the day (D) and night (N) for each depth
stratum at station P17 (S = surface; MD = mid-depth; D = deepwater; and 0 = oblique tow).
-------
Distributions in the Cooling System
Temporal—
Figure 17 shows the temporal variation in the capture of important larval
taxa from the upper discharge canal and the intake region. Seasonal patterns
repeatedly emerged in each year despite erratic, short-term variation in larval
abundance. Yellow perch and smelt were the first of the common species to
appear; their peak abundances were followed by carp-goldfish and white bass,
and then, clupeids, shiners, and freshwater drum. The species that spawned
earliest persisted as catchable larvae for the shortest time, while the pro-
geny of later spawners were more likely to be caught over a longer time.
Larvae of carp, white bass, and clupeids consistently appeared in the discharge
canal before they appeared in the intake region; evidently some hatching occurred
in the discharge canal. The larvae of channel catfish were almost exclusively
captured in the discharge canal and the intake region.
Spatial—
Some species may hatch in the upper discharge canal according to total
densities of larvae caught at different stations (Table 30; B26). Carp-goldfish,
white bass and clupeids were captured consistently in the upper discharge canal
in greater numbers than in the intake region. This was not apparent with the
perch, shiners or drum larvae. Larvae of most species were consistently less
abundant in the lower end of the discharge canal than in the upper end of the
discharge canal. All but one of the abundant taxa were common in the lake.
The exception, carp-goldfish larvae, were much more abundant in the river, as
were several of the rarer taxa in the Ictaluridae and Centrarchidae (Table 30).
Variability of Results—
Even though consistent annual patterns emerged from the temporal and
spatial patterns of larvae around the cooling system, great spatial variation
only allowed statistical discrimination (a = 0,05) of major differences. This
variability appeared to be caused by "patchy" distributions and strong fluctu-
ations in recruitment during the spawning season.
Figure 18 shows the influence of patchy variation for important species on
the dates that spatial variation was minimum and maximum in the cooling system.
Abundances tended to fluctuate at any one particular station, presumably in
response to patches of larval fish moving through the lake ecosystem and the
cooling system. Concentrations at the three lake stations, all within 4-km of
each other, could be indistinguishable on one day and exceed an order of magni-
tude difference on another day.
The degree of variation determines the sampling intensity required to dif-
ferentiate concentrations at different area stations for various permissable
errors of the mean. Figure 19 illustrates how the variation was influenced by
patchy distributions and temporal change. The variation was greatest when the
mean catch was low and least when the mean catch was high. The minimal varia-
tion encountered for replicates at one station defined the situation requiring
a minimum sampling intensity. The additional spatial variation introduced by
100
-------
100-
-
50'
Z „
INTAKE
CLUPEIDS
. J
Li.
O D44D 4Q4 D4 D4A
O MAY JUN
tc
LJ
CO
s
z 100-
z
UJ
5
50
UPPER DISCHARGE
CLUPEIDS
n D
!
UAV JtIM
0 1973 I0°
4 1974
A 1975
50
1
B 0
INTAKE 50
YELLOW PERCH
i
44444 4 '
JUL AUG
100-
•
50"
1
W n
P
25-
B • D D n.
INTAKE
WHITE 8ASS
.L,
MAY JUN JUL AUG MAY JUN JUL AUG
UPPER DISCHARGE
YELLOW PERCH .,
I
1'
1
100-
\
i B Ql 1
UPPER DISCHARGE
WHITE BASS
n
. &t *_IL m BB
: rf TS 4 '0440 40404 D4A4 44 4O 4 u.o u .u«u. u«a> .a .a .
, AUG MAY JUN JUL AUG MAY JUN JUL AUG
Figure 17. Seasonal variation in abundant species of larval fish in the intake region and upper discharge
canal (mean ± 95% conf. int.)
(continued)
-------
SO'
25 •
M
o o
g
tr
L_| Ul
o S
to §
i30l
Ul
s
23'
0-
INTAKE 50
SHINER
23
...A. «o
INTAKE 2.0
CARP-GOLDFISH
1 18
1.6
1.4
1.2
I.O
0.8
_ 0.6
l_Bl a BI ill' IB .
INTAKE
CHANNEL CATFISH
"••""" »•••• v M • u • DBOOAAQAQAOA AA AAAA • OAAOAADAQAQA
UPPER DISCHARGE mo
SHINER
SO
= DJ ,.H J D
UPPER DISCHARGE 50
CARP - GOLDFISH
1
•
B
1 SB ;
,* H* *QT t • a m a 0
UPPER DISCHARGE
CHANNEL CATFISH
a mi,.
i
JUL AUG
MAY JUN JUL AUG
MAY JUN JUL AUG
MAY
JUN
JUL
AUG
Figure 17 (continued).
-------
•o-
99
SO
49
40
59
50
15 <
ZO
19
10
ft
Z 9
0
O
V
cc
1
!•"
<
Ul 1 10
2
IOO
•0
to
TO
•0
90
40-
SO
20
10.
CLUPCI09 YELLOW PERCH
9/Zt/T4 f/t/T5
MINIMUM VARIATION ||()1 MINIMUM VARIATION T§
110
IOO
(0
10
TO
• 0
90
4O
SO •
to
1 1 °1
90
29
. I . _ . 1 B
PIO Pll PIZ ft PT PO PZ PS PK> Pll PIZ P« PT PO PZ P3
CLUKIDS
(/II/74
_ MAXIMUM VARIATION ,,„
Ii-2Z*l99.l
B
1
1
1
n
fa
a a
B M
H
1
I 1
i § i
H H
B 3
1 10
IOO
to
90
TO
40
190 •
40
SO
ZO
B
i I '0
i in
' , , i 1 , , ,
YE
S/
M
,.
B
i
B
1
.LOW PERCH
Z/T5
IMUM VARIATION
940
490
4ZO
S«O
IOO
2TO
Z40
210
11(0
ISO
IZO
*0
•0'
JO
WHITE tASS
T/15/74
MINIMUM VARIATION (0
99
SO
49
40
39
50
Z9
ZO
19
10
i 1 - i T i i i
CARP AND OOLOflSM
9/12 / 75
MINIMUM VARIATION
I.I
PIO Pll PIZ P< PT PO PZ PI •>l° p" "• " '7 PO PZ P3
WHITE BASS
•/II/74
MAXIMUM VARIATION "°
too
190'
•
,
.
B • • 1
CARP AND GOLDFISH
4/11/74
MAXIMUM VARIATION
§
- i
a B
,,,•.•"
PIO Pll PIZ P« PT PO PZ P3
PIO Pll PI2 P« PT PO P2 P3
PIO Pll PIZ PC PT PO PZ P3
PIO Pll PIZ P6 PT PO PZ PS
STATIONS
Figure 18. Minimum arid maximum variation (+ 95.1 conf. int.) in the catch of larval fish
near the Monroe Power Plant.
-------
CO
\
llj
lO.OOOr
SflOO •
I.OOO
soo
200
10.000
o
—: 3,000
CL
Ld
(T
1,000
soo
200
too
10,000
5,000
I POO
500
200
100
50
20
10
IO.OOO
3,000
YELLOW PERCH
1000
500
200
100
30
20
10
.1 .2 .3 .4.3
10
.1 .2 J .4 .3
SHINERS
.3 .4 .5
PERMISSABLE ERROR
Figure 19. Sampling intensity required at various permissable errors
of the mean.
104
-------
sampling at two other nearby (2 to 4-km apart) stations on the same date
required 6 to 10 times more intensive sampling to maintain the same permis-
sable error. Based on the results from the three lake stations, the inten-
sity of sampling on a particular date must be increased at least 100 times
(depending on species and date) to reduce the permissable error from 50 per-
cent to 10 percent of the mean with a 95 percent confidence interval. When
variation at the three lake stations is included, the sampling intensity
required increased from 10 to 1000 percent depending on the species and the
year sampled.
There was considerable difference in the seasonal variability defined for
two consecutive years; 1974 was less variable than 1975 for all important
species. The long-term sampling intensity required over a sequence of annual
studies to meet a specified error cannot be determined confidently with data
from one year alone. To a great extent, the variability encountered was pro-
portional to the mean larval concentration. The rare species encountered in
the study would require an extraordinary sampling intensity to precisely esti-
mate their population sizes.
Estimated Mortality
Substantial proportions of entrained larval fish may have died in the
cooling system following condenser passage (Table 33). The percent killed at
the intake station by capture technique and natural events varied with species.
A relatively large proportion of white bass and carp larvae were dead in the
intake canal while a relatively large proportion of yellow perch were alive.
Following condenser passage, the proportion of dead larvae of all taxa cap-
tured increased from 20 to 80 percent. Considering the high probability that
some larvae hatch in the discharge canal, these estimates of larval mortality
caused by passage through the cooling system may be conservative. For example,
yellow perch were among the least likely of the fish to hatch in the discharge
canal and their death rate was among the highest. Consistently high variation
(Table B31) interfered with the precise estimation of mortality. But these
estimates, in combination with the consistently lower numbers observed in the
lower discharge canal compared to the upper discharge canal, indicate that a
large proportion of the larvae died as a consequence of condenser passage.
Foods
Comparisons of larvae of the same size obtained from light and dark times
of the same day revealed no differences in mean size of foods, but in some
species there seemed to be differences in the number of food items (Table 34).
White bass and freshwater drum caught at night had a greater number of organ-
isms in their stomachs than their daytime counterparts (Table 35). The
stomach contents of yellow perch were similar for both time periods. Regard-
less of the time, Cyclops were the most numerous food organisms. Cladocerans
may have been slightly more common in the larvae collected at night. Because
light and dark times of only one date were compared, conclusions about the
diurnal regularity of these differences are unwarranted. However, it seems
like the species composition of foods remains similar even though the total
numbers consumed may change.
105
-------
TABLE 33- PRELIMINARY ESTIMATES OF MORTALITY IN THE COOLING SYSTEM AT
THE MONROE POWER PLANT
(ratio of dead to total catch of alive and dead)
Species
Total
Number
Intake Caught
Total
Upper Number
Discharge Caught
Total
Lower Number
Discharge Caught
Carp 0.09 20
Yellow perch 0.20 40
Clupeid 0.15 66
White bass 0.04 25
All larvae 0.16 176
0.27
0.72
0.79
0.25
0.73
8
5
11
3
29
low
abundance
low
abundance
0.80
0.80
0.59
2
2
5
10
106
-------
TABLE 34. FOODS IN FISH LARVAE OF DIFFERENT LENGTHS CAPTURED NEAR THE MONROE POWER PLANT
-vl
- - S?flt:7, - - Whit6 Bass - _ Perch _ Gizzard Shad
8- 11- 14- 17- 8- 11- 15- 9- 11- 8- 11- 14- 17- -
_ 11 14 17 32 Tot. 5-8 11 14 21 Tot. 5-7 7-9 11 15 Tot. 5-8 11 14 17 20 Tot.
Percent empty
stomachs 60 50 66 12 60 16 0 0 56 4 0 0 63 13 6 16 20
No. fish with
food 4 4 1 7 16 7 15 8 6 36 6 25 7 8 46 6 13 18 10 4 51
Food Taxa
Cyclops
number 4 12 9 19 44 20 69 45 46 180 1 4 28 41 74 2 15 64 38 62 181
percent 67 71 100 54 68 71 97 98 92 90 43 88 93 31 14 47 59 81 82 69
Trophocvclops
number j_ j_
percent 1 >05
Calanoids
number 2 1 12 15 33
percent g ^
Other Copepods
number 2 2
percent 12 3
(continued)
-------
TABLE 34 (continued).
Smelt White Bass
8- 11- 14- 17- 8- 11- 15-
11 14 17 32 Tot. 5-8 11 14 21 Tot.
Ceriodaphnia
number 115 3 8
percent 3 2 18 6 4
Diaphanosoma
number 113 3
percent 3 2 11 2
Chydorus
number
M percent
0
00
Boomina
number 2 2
percent 12 3
Daphnia
number 1 45
percent 1 83
Other Cladocera
number 2
percent 6
Synchaeta
number
percent
Perch Gizzard Shad
9- 11- 8- 11- 14-
5-7 7-9 11 15 Tot. 5-8 11 14 17
33 3
71 6
1 1
1 2
111
1 0.3 1
1 1
1 2
1 1
3 0.3
1 1 111
1 0.3 3 1 2
17-
20
8
11
2
3
2
3
1
1
2
3
Tot.
11
4
1
0.3
4
0.7
2
0.7
1
0.3
2
0.7
(contined)
-------
TABLE 34 (continued).
Smelt
8- 11- 14- 17-
11 14 17 32 Tot.
Trichocera
number
percent
Brachionus
number
percent
Keratella
number
percent
H *
fg! Actinastrum
number
percent
Other Rotifers
number
percent
Rotifer eggs
number
percent
Copepod eggs
number
percent
White Bass
8- 11- 15-
5-8 11 14 21 Tot. 5-7
12
44
2
7
2
7
2
7
4
15
4
15
Perch
9-
7-9 11
42
32
31
23
1
1
4
3
45
34
2
2
15 Tot.
54
23
33
14
3
1
6
2
49
21
6
2
5-8
1
7
2
14
1
7
1
7
6
43
Gizzard Shad
8-
11
3
9
1
3
1
3
7
22
11-
14
4
4
5
5
3
3
10
9
14- 17-
17 20 Tot.
1 2
1 0.7
9
3
7
3
2 7
4 3
1 24
2 9
(continued)
-------
TABLE 34 (continued).
Nauplii
number
percent
Protozoans
number
percent
Smelt White Bass Perch
8- 11- 14- 17- 8- 11- 15- 9- 11- 8-
11 14 17 32 Tot. 5-8 11 14 21 Tot. 5-7 7-9 11 15 Tot. 5-8 11
2 212
2 0.7 7 6
2
6
Gizzard Shad
11- 14- 17-
14 17 20
18 1
17 2
Tot.
3
1
21
8
Total
-------
TABLE 35. STOMACH CONTENTS OF FISH LARVAE CAPTURED DAY AND NIGHT IN WESTERN LAKE ERIE
No. Food Items/Ten Fih
~~ ~
Food Size mm
Fish
Mean Mean No. items
Cyclops Daphnia Leptodora Bosmina Diaphanosoma Ceriodaphnia Calanoids Length Width per fish
Drum
Day
Night
White Bass
Day
Night
Perch
Day
Night
53
98
68
197
114
97
2
4
5
6
12
13
5
1
2
4
17
2
2
2
3 1
1.70
1.64
1 4 1.41
5 1.48
3 1.45
1 — 1.54
0.59
0.54
0,47
0.50
0.51
0.55
0.53
1.02
0.79
2.10
1.29
1.13
-------
The major apparent difference in the food habits of larvae compared to
the older fish, described by Kenaga and Cole (1965; Appendix A), was size
related. In older fish, chironomids were among the major food items and
rotifers were scarce. In larvae, rotifers were common while chironomids
were absent. Leptodora kindtii was an important food for older fish and
some of the large postlarvae captured, but it was not found in the guts of
small larvae.
112
-------
SECTION 6
DISCUSSION
MIXING
The evaluation of mass transport of entrained plankton and nutrients at the
Monroe Power Plant depended on estimates of mixing in the intake and the dis-
charge plume. This was required to separate the effects of dilution from power
plant operation. Two, fundamentally different sampling designs were available
to choose from; the first was to follow and sample the same water mass as it
passed through the cooling system and mixed with other water masses and the
second was to sample specific points, almost simultaneously, using internal
tracers as described in Spain and Andrews (1970) and Hem (1970).
The second approach was chosen because of tactical advantages. To follow
and sample water mass moving through the cooling system over 24 to 48 hr
required extraordinary effort. Following water masses requires frequent crew
changes, tracking techniques are imperfect, sampling runs are excessively vul-
nerable to interruption by weather or mechanical failures, and diurnal cycles
or meterological events may confound the results.
The major disadvantage of simultaneous sampling is the variability intro-
duced by spatial variation in water masses, so-called patchy distributions.
The tracer studies conducted in this research showed that patchy distributions
could easily confound interpretation of differences observed among sampling
stations on any specific date. The method required that the interpretation of
results rest primarily on the consistency of annual mean differences which
averaged .out variability caused by patchy distributions. We assumed that
spatial variation occurs randomly over the annual cycle. After being inte-
grated as seasonal or annual means the data revealed consistent plant impacts
that might otherwise be unidentified. From the standpoint of ecosystem dynamics,
this approach is probably a more realistic assessment of overall impact than
short-term sampling which could represent unique conditions that occur only for
a brief time.
Based on this technique, the lake and river source waters differed mostly
in quantity rather than quality of their chemical and biological constituents.
The material composition was basically similar, but the river was richer in con-
centrations of carbon, nitrogen, and phosphorus and poorer in plankton. Oxygen
concentrations and plankton diversity in the lake often exceeded that in the
river. Virtually all of the river water was used for cooling while only a small
fraction of the volume-flow through western Lake Erie (almost 1.5 percent) was
circulated through the cooling system. Therefore, the planktonic community in
the river was more vulnerable to entrainment than the lake community.
113
-------
According to tracer studies of lake and river water masses, water sampled
in the river channel was a product of lake and river mixing and; the estimated
concentrations of dissolved and suspended matter reflected that mixing. River
water diluted plankton concentrations in the lake water and the lake source
diluted nutrient concentrations in the river water. Over the longrun, the
degree of dilution depended mostly on river water. During high spring discharge,
river water usually predominated in the intake while, in late summer, lake water
predomina ted.
TEMPERATURE AND OXYGEN
The rapid and prolonged temperature change caused by once-through cooling
may have been one of the causal mechanisms associated with some of the observed
changes in community structure and function. The mean annual temperature ele-
vation varied only from about 6 to 9°C, but day to day variations ranged from
0 to 17°C. This wide variation undoubtedly could have effected a wide variation
in community response. But the mean elevation, maximum elevation, and even the
stability of elevation observed at Monroe were not atypical for steam-electric
plants (Contant, 1971). Maximum summer temperatures may be of particular con-
cern because many warm water, species appear to reach their upper thermal
tolerance limits between 30 to 35°C (Strangenberg and Pawlacyzk, 1960; Massen-
gill, 1976; Marcy, 1971). Those temperatures could occur at the Monroe Power
Plant about 25 percent of the year in June to September, when it operates with
a 10°C elevation of the cooling water.
Following condenser passage during summer, the oxygen concentration tended
to increase because concentrations were usually depressed in the source waters.
At that time of year, the partial pressure of oxygen was influenced by intense
primary productivity as well as community respiration and change in temperature.
During the cooler months when community metabolism was relatively low, cooling
water generally became supersaturated because of temperature change alone.
Other researchers have warned that gas supersaturation, especially from nitrogen,
could cause damage to the fish but Cole (1976) reported that no such effects were
observed at the Monroe Power Plant. Nitrogen gas concentrations were not mea-
sured but, based on winter observations made at other sites (Adair and Haines,
1974), the percent saturation of oxygen probably reflected the percent satura-
tion of nitrogen near the condenser. At Monroe, that would most commonly be
110 to 120 percent of saturation.
NUTRIENTS AND PRIMARY PRODUCERS
Changes in material concentrations that resembled changes in the tracers
were assumed to be caused by mixing alone. Deviations from tracer projections
indicated material losses or gains which could not be explained by mixing alone.
The annual mean concentrations of nutrients and primary producers consistantly
deviated from the anticipated mixed concentrations and revealed relatively minor
but real changes in water quality which could not be consistently identified
with statistical confidence because of high background, spatial variation.
114
-------
Ammonia may have been rapidly released from protein decomposition
before water reached the upper discharge canal; but that was the only recogni-
zable nutrient change in water at the upper end of the discharge canal. Mean
annual gross primary productivity at the upper end of the discharge canal
remained unchanged or was depressed. Since cool weather productivities were,
in most cases, too low to identify differences, the observed depressions were
generated mostly at temperatures above 15 to 20°C. Morgan and Stress (1969),
Hamilton ^t al. (1970), and Warinner and Brehmer (1966) all found similar depres
sions at warmer temperatures.
" The annual mean community respiration about doubled by the time water
reached the upper discharge canal. With a mean annual temperature rise of 8°C.
It appeared as if the general relationship between respiration and temperature
approximated the QIQ rule.
Even though the P/R ratios dropped sharply in the upper discharge canal,
they remained high enough to produce more organic material than was consumed in
the cooling system. Particulate organic carbon increased, presumably from
photosynthetically fixed organics in the discharge water, as discharge water
passed back to the lake. Gains of particulate carbon were accompanied by con-
sistant increases in algal abundance, a decline in the inorganic nitrogen and
a complimentary increase in organic nitrogen. Phosphorus concentrations could
have been drawn upon for photosynthesis, but the amount required was so slight
that the technique could not identify the changes caused by phytoplankton up-
take if it existed. Dissolved inorganic carbon declined, possibly from photo-
synthetic demand, C02 losses to the atmosphere or from the precipitation of
carbonates.
By the time the cooling water reached the lower discharge canal, from 6 to
12 hours later the mean P/R ratio and the mean ratio of particulate to dissolved
organic carbon had increased slightly. The P/R ratio still remained nearly
half that in the intake waters, indicating that the water in the lower discharge
canal continued to be less autotrophic than the source waters. Respiration
remained almost the same while gross primary productivity increased, but not
enough to completely make up for the depression started in the upper discharge
canal.
In the plume, particulate organic carbon, and organic nitrogen increased
slightly above the expected concentrations while dissolved organic-nitrogen,
inorganic nitrogen, inorganic carbon and total phosphorus all declined by 15 to
25 percent. Carbonates and phosphates seemed to precipitate as the plume mixed
with the receiving waters. Inorganic nitrogen and carbon may have settled with
particulate organics or escaped from the water as ammonia, nitrogen gas and
carbon dioxide. The latter explanation seemed to be the the most reasonable
of the two. Suspended solids declined only about as suspected by dilution at
the plume edge and there was no indication that much particulate matter settled
to the bottom over the shallow shoal.
In spite of a prolonged 6 to 12 hour exposure to elevated temperature, the
primary productivity began to increase before the cooling water reached the
lake. Even after the cooling water had mixed with lake water, the primary pro-
ductivity continued at an intensity higher than expected from mixing. These
115
-------
results differed from those of Morgan and Stress (1969) who concluded that
photosynthetic depression persisted until the water had cooled to ambient
temperatures.
Although the changes were slight, the consistently measured increases in
algal abundance and particulate organic carbon indicated that photosynthetic
biomass increased as water passed through the cooling system and net production
continued to remain higher than predicted by the mixing of the thermal plume
with ambient waters. Nutritional changes in the mixing waters of higher algal
biomass may have caused slightly higher productivities at the plume edge than
in nearly ambient waters. Light limitations, as effected by changing concen-
trations of suspended solids, appeared to be unimportant. No consistant rela-
tionship appeared between distributions of productivity and concentrations of
suspended solids in the cooling system.
Community respiration like gross productivity, was higher than predicted
by mixing in the plume and the P/R ratios returned to values like those at the
intake. Although there was a small gain in algal standing crop and, possibly,
slight temporary changes that favored green and blue-green algae, there was
little net change in the organic carbon transported to the lake because dis-
solved carbon had declined before the cooling water mixed with the lake water.
The water leaving the plume probably had a potential oxygen demand similar to
water entering the intake. In fact, water quality may have improve slightly
because phosphorus, and nitrogen concentrations also declined before the cool-
ing water mixed into the lake water. The same patterns of community metabolism
consistently materialized in the discharge water regardless of chlorine appli-
cation schedules. These observations, along with the fact that chlorination
occurred no more than 33 percent of the time, indicated chlorine affected
planktonic community metabolism very little.
Periphyton rates of accumulation were extremely variable, but trends indi-
cated that the upper discharge canal rates were less than at other sites
including the lower discharge canal where temperatures were similar. Chlorine
may have inhibited periphytic growth in the upper discharge canal even though
it did not seem to be primarily responsible for phytoplanktonic responses. It
is also possible that periphytic organisms were not entirely unaffected by
mechanical stress or thermal shock. The colonizing capacity of organisms
adrift in the cooling water might have been temporarily incapacitated by con-
denser passage. Whatever the effect on periphyton, it did not seem to persist
far down the discharge canal or in the thermal plume.
Although subtle but real changes in community metabolism appeared to be
caused by entrainment, community structure changed little. The diversity of
phytoplankton in the cooling system appeared to be regulated almost entirely
by the mix of river and lake source waters. Although slight population shifts
appeared in certain species, they had no recognizable impact on diversity
estimates. Given the rapid regeneration rates of phytoplankton and the size
of Lake Erie, the entrainment effect on the phytoplankton of western Lake
Erie was a transitory disturbance superimposed on an aquatic community that is
prone to erratic, relatively massive, meterological disturbances (Chandler,
1944). Based on basin-wide estimates of phytoplankton distributions (Hartley
and Potos, 1971) and flow through the western basin, even complete destruction
116
-------
of all phytoplankton entrained at Monroe would amount to less than 1 to 2 per-
cent of the total in the western basin. But more important in western Lake
Erie is the threat of increased oxygen demand generated by eutrophication. If
anything, the thermal discharge accelerates the recovery of nutrient enriched
waters entering the basin via the Raisin River without locally aggravating
oxygen depletion rates. Even though this is a desirable reduction of nutrient
loading to the basin it is a relatively minor deduction, at most 1 percent of
the total estimated (IJC, 1969) from all tributaries.
One negative impact observed was the apparent effect of erosion from the
cooling system. If this erosion rate were maintained over the next 35 years,
there could be a net export of sediments equivalent to 1-m deep by 1 km2 of
lake bottom off the discharge canal. Of course, much of this material would
be dispersed by lake currents over a large part of the western basin. If it
were evenly dispersed over the entire basin, it would accumulate about 0.01
mm/year. " This amount is equivalent to about 2 percent of the estimated sedi-
ment load (IJC, 1969) entering Lake Erie via the Maumee River.
ZOOPLANKTON
The mean annual distributions of all the major taxonomic groups of zoo-
plankton indicated consistent entrainment impacts. A mean annual average of
about 40 percent of all zooplankton disappeared from the water column somewhere
between the intake and the sampling location in upper discharge canal. The
effect at the Monroe Plant was consistent for all of the major taxa present
regardless of size or behavioral differences. Beck and Miller (1974) and Car-
penter (1974) reported even higher losses caused by mechanical damage. Although
declines may be expected for zooplankton abundance downstream from a power
plant, other field studies usually identify little recognizable impact in the
receiving water (Davies and Jensen, 1974).
The specific cause of the impact at the Monroe Power Plant is perlexing.
It is unlikely that the depression is an artifact caused by incorrect estimates
of the mixing rates of river and lake water. It could have been caused by
sampling error if the contribution of river water had been overestimated. But
such a sampling artifact should be reflected in the abundance ratios of specific
taxa. For example, rotifers were relatively more abundant than copepods in the
river water compared to lake water. If the estimated river contribution were
too high, then rotifer densities should have decreased less than copepod den-
sities. Just the opposite appeared in the data. According to trace data, the
river-water contribution, if anything, was underestimated.
Whatever depressed zooplankton density did so before the water reached the
upstream station in the discharge canal. After that, densities remained fairly
constant in the discharge canal. Before reaching the discharge canal, the plank-
ton passed through the pumps, then the condensers at about 2, m/sec and finally
into the concrete overflow canal which carried them at about 0.75 m/sec to the
upper discharge canal within 20 minutes of the condenser passage. Potential
fish predators have never been sampled in the overflow canal, but water veloci-
ties seemed too high and the canal too short to foster high fish abundances
like those in the discharge canal (Cole, 1976).
117
-------
Chlorine was not applied in the afternoon, but the differences in popula-
tion density changes between that time and the chlorination times was not enough
to implicate chlorine as a primary factor. Even if chlorine were killing
animals, it would not completely destroy the bodies of individual zooplankters.
Dead, dying, or "shocked" animals could have settled to the bottom from
the sampled water column, although this was unlikely in the rapidly flowing
water of the overflow canal. Zooplankton may have settled from the upper dis-
charge canal soon after water emptied into it from the overflow canal. Veloci-
ties in the discharge canal averaged less than 0.15 m/sec and may have been
much less than that near the bottom. Some of the animals may have moved toward
the bottom as soon as they passed into the upper discharge canal. McLaren
(1963) and Gehrs (1974) found that at least certain species swam toward bottom
when they were exposed to higher temperatures. Many of the zooplankters may
have moved or settled to depths below those that were sampled, causing an
apparent loss only.
Other slight changes in the abundance and size distribution of zooplankton
may have occurred after the plankton drifted downstream from the upper discharge
canal. Although the density increased only slightly, if at all, as the plankton
passed down the discharge canal, the mean size of zooplankton, particularly
cladocerans, appeared to decrease. These size changes in cladocerans may have
occurred because larger animals, more than smaller ones, were eaten, settled
out, or emigrated from the water column, or there was some combination of size
related recruitment and mortality. Among copepods, the mean size of adults and
nauplii changed without constant trend during passage. On the other hand, the
mean size of rotifers seemed to increase as if in response to some competi tive
release.
Regeneration probably contributed little to the decreased mean size that
was witnessed during passage through the discharge canal, but the densities
seemed to increase slightly as the water passed through the cooling system. A
very small change could have been caused by recruitment. Under optimal con-
ditions, with a life expectancy of 2 weeks and a mean fecundity/individual of
about 10 young (Ceiling and Cambell, 1972; Eckstein, 1964; and Munro, 1974) the
density of copepods and claderans could have increased only 2 to 3 percent in 6
to 12 hours. Vertical profiles of zooplankton abundance indicated that many of
the cladocerans and copepods recovered their ability to orient to depth related
gradients by moving toward bottom within a few hours of the time that they
passed through the condenser.
At least some of these larger organisms could have moved far enough away
from the surface to entirely avoid capture. The mean size of cladocerans, in
particular, seemed to decrease as the plankton passed down the canal, perhaps
because larger animals settled or moved out of the water column or because they
were eaten. Kenaga and Cole (1975) indicated that certain fish species caught
in the vicinity of the power plant tended to be size-selective feeders. Kelly
and Cole (1976) also found parallel size changes in benthic organisms inhabit-
ing the discharge canal. Cole (1976) reported that fish densities in the dis-
charge canal usually exceeded those in the nearby lake, so the depressed sizes
may have reflected the effect of intense predation.
118
-------
If a size-related selection process was operating in the cooling system,
it had no recognizable impact on the diversity. Diversity indices have been
promoted as one integrative means for identifying community-wide influences of
man-caused perturbations (Wilhm and Dorris, 1968). But, none of the diversity
estimates made during this study indicate that passage through the cooling
system had any consistent impact on community structure.
The chloride tracer indicated that little cooling water was recycled by
power-plant operation even though the wind frequently forced the plume waters
northward toward the intake. Neither samples of zooplankton or chloride, taken
ovet two to three-day periods, revealed any trends in changing concentration
that would suggest a cumulative effect from recycling. The dilution of discharge
waters by the receiving waters effectively diminished any recognizable entrain-
ment impact at the plume edges.
The abundance of zooplankton in the cooling system followed patterns simi-
lar to adjacent parts of western Lake Erie (Cole, 1976) during the same
years of study. None of the entrainment effects persisted beyond the plume
into western Lake Erie.
Based on the rates used during this study, the power plant pumped about
0.005 km3/day. In the study reported by Cole (1976), zooplankton were sampled
along the central axis of a rectangular coastal area that was about 15-km x
4-km and averaged 5-m deep. The volume of that area comprised the equivalent
of 0.3 km3 of cooling water. Assuming no mixing with other lake water, it
would take about 2 months to move all of that water through the cooling system.
Even if all zooplankters were killed in passage, the residual populations
within that relatively small part (less than 2%) of the western basin would be
capable of turning over 2 to 4 times during the summer months based on a 2 to
4 week life expectancy of most zooplankton. The western basin is well mixed
and the calculated replacement rate for water in the whole basin is also about
2 months. There could be little entrainment impact of consequence on total
zooplankton abundance in such a large dynamic system even though entrainment
may have temporarily disoriented animals, increased their vulnerability to
predation and, perhaps, even destroyed up to 50 percent of all entrained
animals. However, one species of zooplankton, Leptodora kindtii. may have been
exceptionally affected because of its relatively large size and relatively slow
regeneration rates.
FOODS OF FISH
Entrainment could indirectly disrupt trophic relationships between impor-
tant fish populations and their prey. Much of the economic and ecological value
of some invertebrates and small fish manifest in their importance as fish food.
One major conclusion has emerged from our work on fish foods; the size of the
consumed food is related to fish size. The smallest fish larvae used rotifers,
copepod nauplii and other small, planktonic organisms. Larger larvae depended
more on larger copepods and cladocera. Juvenile fish, over 30-mm long, ate few
rotifers and appeared to select the largest food items available to them; the
large cladoceran, L_. kindtii, and two genera of midge larvae, Procladius and
Chironomus.
119
-------
A continuously abundant and diverse assemblage of small zooplanktonic
foods appeared to be available to small fishes from April to October, but
larger food species appeared less diverse. Among potential zooplankton foods,
less than 0.2 mm long, there were 23 species of small rotifers and the nauplii
of 10 copepod species. In a slightly larger group of food species, ranging
from 0.5 to 3 mm long, there were 10 species of juvenile and adult copepods
and 5 species of cladocerans. Only one zooplanktonic invertebrate commonly
exceeded 1 cm, L_. kind til.
Other large food organisms were found among the twenty-six taxa of benthic
macroinvertebrates encountered in the study area (Kelly and Cole, 1976). Half
of these species were tubificids, a group which was not found in the stomachs
of any fish examined (Kenaga and Cole, 1975; Appendix A). These organisms
seemed not to be available as a food source. The remaining benthic species
were mostly arthropods and mollusks, of which three genera of midges com-
prised 98 percent (Kelly and Cole, 1976). The stomachs of some of the
largest fish also had fish remains (Kenega and Cole, 1976).
Among the carnivorous fish over 30-mm long, 60 to 95 percent of the
food volume was comprised of L_. kindtii, Chironomus and Procladius; all over
1-cm long. Large cladocerans and copepods made up most of the remaining
stomach contents. The larger species were relatively rare in the study area
but they were selcted as food much more often than the common but smaller
species. Both LeBrasseur (1969) and Brooks (1968) found that organisms below
a given size were ignored when larger alternative organisms were present.
Lake Erie has suffered from increased siltation, oxygen demand, contamina-
tion with toxic materials and parallel changes in the species composition of
the benthic macroinvertebrates (Regier and Hartman, 1973), Many of the larger
species of arthropods have radically declined in abundance while tubifids have
increased (Carr and Hiltunen, 1965), leaving a monotonous benthic community
dominated by midges and tubificids. Since tubificids seem not to be consumed
by fish, the forage base has become restricted to fewer species than in the
past. Juvenile and adult fish may now rely more continuously on zooplankters
for food, especially L. kindtii. The change in the food resource may have
intensified competitive interactions among the different sizes of fish enough
to cause some decline in the growth of older age groups.
To some unidentified extent, condenser passage may, at least locally,
depress the diversity of food sizes by selectively killing larger organisms
(McNaught, 1972). Our preliminary studies of plankton mortality, like those
reported by Massingill (1976) for the Connecticut River, indicate that L_. kindii
is relatively vulnerable to condenser passage compared to smaller zooplankters.
Massengill (1976) also indicated that entrained midges suffered high mortali-
ties. The relatively large larval fish also seem prone to high mortality from
mechanical damage (Marcy, 1971, 1973 and 1976).
Because Leptodora kindii were relatively rare in the samples, any power
plant impacts on their abundance could have been missed. Conclusions reached
for zooplankton populations in general probably do not apply specifically to
120
-------
Ji- kindii. Destruction of this important forage species could have a local
impact on the growth of some fish species. It is an exceptionally important
organism that deserves more attention than it has received.
LARVAL FISH SAMPLING
Techniques
The entrainment of larval fish may best be mitigated by appropriately loca-
ting intakes during plant construction. Useful information for appropriate
plant siting, or the evaluation of an operating plant's effect, requires a
precise, representative, cost-effective assessment of larval fish distributions.
The comparability of sampling results from biologically and physically diverse
environments, must be a paramount concern for an objective inventory. Both fish
distributions and sampling techniques may be independently influenced by the
physical aspect of the environment; mostly by variations in depth current
velocity, turbulence, bottom configuration, and water clarity. The primary
objective of our technique comparisons was to establish the relative effective-
ness of some commonly applied techniques in the open water of western Lake Erie.
We concentrated on use of open, 1-m, plankton nets because of their many prac-
tical advantages. The results of these technique comparisons may be applicable
to any comparable, turbid, shallow lake or reservoir populated with similar
fish species.
The 1-m, plankton net has operational advantages on small vessels that
favor its use over small pumps or high-speed nets. Water can be processed more
rapidly and it is relatively easy to manipulate the plankton net for depth-
discrete or depth integrated sampling. The high-speed sampler is particularly
impractical in relatively shallow, shorezone areas. In this study, pumping
took 20 times as long as tow-netting to process the same amount of water proces-
sed by to the 1-m net. Both pumping and high-speed netting damaged more larvae.
But, most importantly, the 1-m net consistantly was at least as effective as
the Kenco Pump and the high-speed plankton sampler. Using another pump type
for zooplankton, Icanberry and Richardson (1972) similarly found no difference
between the pump and a 150-y net.
With the 1-m net, the mesh-size time of day, and depth of tow all profoundly
influenced the capture rate of larvae. These studies indicated that the most
effective, daytime sampling would be a combination of bottom-sled and oblique
tows. During the day, oblique tows alone cannot account for the sharply stra-
tified, high concentration of larvae at the bottom because the net cannot be
reliably drawn close to the bottom except in very shallow water. Without a
bottom-sled, daytime tow-netting is more likely to catch larvae in shallow
water than in deeper water. Above the dense larval layer near bottom, the verti-
cal distribution of larvae revealed no consistent, depth-related patterns. Yet,
enough differences occur among the discrete depths sampled to warrant pooling
the variation by sampling with oblique tows.
The nighttime sampling effort yielded more larvae then the daytime effort.
This is a commonly described phenomenon in a variety of environments (Miller
et al., 1963; Clutter and Anraku, 1968; Noble, 1970; Faber, 1967; and Marcy,
121
-------
1973). From 2 to 50 times more larvae were captured at night than day in
oblique tows. The estimated nighttime catch per square meter of surface,
without the bottom sled, averaged roughly similar to the daytime estimate
with the bottom sled. This similarity in estimated day and night densities
per unit of surface suggests that larvae were not concentrated near the bottom
at night like they were during the day. The cumbersome sled may be an unneces-
sary addition to oblique sampling after dark. The nighttime variation among
the station replicates was less than the daytime variation. As long as naviga-
tion is not too time consuming, night sampling probably will yield more infor-
mation than day sampling.
Oblique, night sampling was more efficient than stratified night sampling.
Although species like perch and smelt tended to concentrate in the lower strata,
the differences in nighttime vertical distributions above the bottom were not
nearly as great as vertical differences in current velocities. Depth related
variations in water velocity were much more likely to influence the determina-
tion of the nighttime changes in larval fish distributions than the relatively
minor vertical variations in larval densities. Studies of wind-generated
movements in various environments indicated that velocities can change an
order of magnitude within a few meters of the surface (Hutchinson, 1957) and
this appeared to be substantiated by our studies (Hartley et al., 1966) in the
vicinity of the Monroe Power Plant.
Hypothetically, both mesh size and tow length may influence the catch rate
of plankton nets. Wichstead (1963) and Tranter (1963) found that different
mesh sizes affected the yield of zooplankton because of the animals size dis-
tribution, the net filtration efficiency and the rate of net clogging with
suspended matter. In this study, all nets larger than 363 y captured far fewer
prolarvae than the 363 y nets. Whereas the 1000 y mesh was unsuitable for all
sampling, the 571 y and 760 y nets appeared to catch postlarvae about as
effectively as the 363 y nets. Where there are strong spatial and temporal
variations in the suspended solids, the optimum net size will vary accordingly.
Either a "compromise" mesh size needs to be selected or the mesh size will have
to be adjusted to suit the specific conditions. In the study area, the compro-
mise mesh size for all larval sizes appeared to be between 361 y and 571 y.
For postlarvae alone, the compromise mesh size may be 760 y.
The length of a tow that can be made without affecting the capture rate
may depend on the mesh size because the amount of clogging from suspended matter
depends on the time towed (Vanucci, 1968). The results of towing 571-y nets
from 1 to 5 minutes indicated no differences in capture rates for any towing
times under thevconditions that were sampled in Lake Erie. The patchiness in
larval fish distributions may influence the choices of a tow length if the
filtering efficiency is not greatly affected by the towing time. Noble (1970)
noted that short tow times may enable an increased number of samples and
decreases the variability which may be introduced by longer tows. This is
most likely to be true when the larvae are grouped in relatively large patches
or are not at all clumped in their distributions. On the other hand, Wiebe
(1971) thought he gained precision by lengthening tows whenever larvae formed
small patches because there was a greater probability of sampling a similar
number of patches.
122
-------
In our studies, the length of tow between 1 and 5 minutes did not affect
the catch rate or variability of catch even though the variability among repli-
cates reached a 300 percent coefficient of variation. The Lake Erie distribu-
tions appear to be less variable than those described by Wiebe (1971). Consid-
ering the information return per unit effort for estimates of abundant larvae
on western Lake Erie, shorter 1- to 2-min tows should yield more than longer
tows because a greater number of samples can be gained within the total time
available for study. If rare species are to become the target, the tow length may have
to be elongated to avoid too many empty tows or individual tows may be pooled for analyses.
In situations where densities are unknown, the latter approach allows more flexibility.
An efficient approach to defining horizontal distributional variations
near shore would be to sample at night with 1 to 2-min oblique tows. Even
though night navigation can be difficult and night sampling is more time-
consuming than day sampling, greater information appears to be gained from
night sampling. The size of the water body, distance from shore and availa-
bility of lighted landmarks and buoys will help to determine the relative
effectiveness of night sampling.
Distributions
The kinds of distributions exhibited by different fish species not only
helps to clarify their relative vulnerability to intake entrainment but also
aids in choosing a suitable sampling design to determine their abundance. The
combination of environmental heterogeneity and behavioral attributes of the
larvae often causes non-random, "patchy" (Gushing, 1961), "clumped" (Wiebe,
1971), "aggregated" (Barnes and Marshall, 1951), or "overdispersed" (Cassie,
1959) distributions which are usually described or approximated by the negative
binomial (Taylor, 1953) or Poisson-log-normal distribution. These distribu-
tional variants have been hypothesized to originate from water discontinuities
and heterogeneity arising from weather phenomena and tributary hydrodynamics
or interspecific and intraspecific behavioral patterns (Cassie, 1962; Saville,
1965; Barnes and Marshall, 1951; and Wiebe, 1971), In western Lake Erie, both
wind and tributaries could influence the patchiness of larval fish distributions.
The relatively great sample variation among replicates at a station many indi-
cate that the larvae are concentrated in "swarms" of relatively small volume
(less than a few meters in diameter) like those described in Barnes and Marshall
(1951). However, the average concentration within groups of swarms at differ-
ent stations could vary by an order of magnitude within a few kilometers, just
as Silliman (1946) found in the distributions of pilchard, Sardinops caerula,
eggs. The distributions of most larval species frequently seemed to occur at
patches over 100-m long (length of a 3-min tow) . It was not possible to tell
whether gradual density gradations or large, discontinuous patches occurred in
the study area. Therefore, the upper size limits of any patches present were
unknown.
The configuration of these patchy distributions may be at least partly
dependent on the fluctuations of tributary mixing with lake water, wind-
generated vascillations, and larval locomotion. Both Bishai (1960) and Saville
(1965) thought that current was the most important determinant of larval fish
distribution in oceanic environments. In western Lake Erie, currents are
123
-------
controlled mostly by the wind and the Detroit River, Prevailing southerly
winds tend to maintain a clockwise gyre off the mouth of the Maumee River in
the southwestern corner of the lake (LJC, 1976) j therefore, the prevailing
currents move a combination of Maumee and Detroit River water northward along
the shore past the power plant intake. Several kilometers off shore, the
water is derived almost entirely from the Detroit River (Hartley et al., 1966).
The results from the sampling transect, which extended deeply into Detroit
River waters, suggest that, on the dates sampled, dense concentrations of yellow
perch, white bass and smelt larvae entered the western basin with water from
the Detroit River. The shiners followed no clear density gradient associated
with the distance from shore, but the clupeids and freshwater drum were most
abundant near shore on those dates. They may have hatched near the power
plant or drifted northward from the Maumee Bay region. On the otherhand, with
the few dates sampled the apparent distributions of these larvae may have
arisen from a fortuitous combination of relatively abnormal conditions. Larval
groups, including catfishes, sunfishes, and carp-goldfish, were common in the
river but not in the lake. These species require marshy or protected shoreline
environments for successful spawning and most river larvae probably came from
marsh overflow or protected river edges. No simple generality appears to apply
to the distributions of all larval fish species in the vicinity of the Monroe
Power Plant.
Neither are the larvae all distributed alike in the water column, although
both pro- and post-larvae of abundant species seem able to move vertically,
apparently in response to changing light intensity. Nighttime concentrations
of pro- and post-larvae in the water colume were much greater than daytime
concentrations above the bottom, but they were similar (although variable)
when daytime bottom tows were included in the comparison. Larvae may have
differentially avoided the net during these tow times, but vertical movement
seems to be a more plausible explanation. Although slower prolarvae are more
likely to be vulnerable to capture during the day than the faster postlarvae,
there was little evidence of difference. Also, the high-speed plankton
sampler should have been consistently more effective than a tow net if net
avoidance had been very important. This diurnal vertical migration between
the slowly moving bottom waters and the relatively rapidly moving surface waters
strongly affects the probability that discretely-located larvae will be carried
to an intake.
Some subtle differences occurred in the vertical distribution of the abun-
dant species. Most members of all species remained close to the bottom during
the day and mostly in the lower half of the water column at night. Freshwater
drum larvae seemed to move toward the bottom almost immediately after hatching
from their floating eggs, and remained particularly close to the bottom during
the day. Yellow perch, smelt, and white bass also tended to avoid surface
waters, at least more so than the clupeids, which were the least likely of all
the species sampled to avoid the relatively rapid currents near the surface.
Therefore, a larger proportion of the clupeids could have been carried greater
horizontal distances away from their points of origin than other species.
Relatively small proportions of the demersal larvae were likely to be carried
long distances away from their hatching sites.
124
-------
Entrainment Susceptability
Counting entrained animals alone (Table 36) cannot reveal what impact a
once-through cooling system has on populations in the source waters. Data also
should be gathered in the source waters as well as the cooling system. These
results, similar to Marcy's (1971; 1973), point out that entrainment probably
kills larvae at high rates. But, the sampling intensity required to identify
an entrainment effect on lake populations depends on what proportion of the
population can be sacrificed to plant operation without endangering the
resource value of the lake.
It is possible, from the data presented here, to tentatively estimate the
vulnerability of the abundant larval fishes to entrainment. It must be
recognized, however, that these estimates are based on temporally and spatially
limited sampling efforts which may be representative only of conditions that
existed at the time of sampling. These generalizations have little statistical
validity because they assume a temporal and spatial uniformity which is unlikely
to occur in the study area. They provide pilot assessments of the potential
larval proportions entrained by the power plant and potential differences in
the relative vulnerability of larval populations to entrainment. For Table
37, relative entrainment vulnerabilities were estimated by using information
gathered from the 16-km transect, the proportion of daytime and nighttime
larvae in the water column, and the estimated rate of water movements at dif-
ferent depths in the water column. It was assumed that the proportions of
larvae captured at each of the transect stations was representative of a lake
area between lines 8-km to the north and south of the transect (See Fig. 2) .
Data from stations P10, Pll, and P12 were used to estimate the abundances in
the shore zone (arbitrarily defined as within 4-km of shore) and abundances in
the three offshore zones centered on the transect were proportioned in relation
to known concentrations in the shore zone and the percent captured at stations
along the transect. All data from lake stations P10, Pll, and P12 and the
cooling system were sampled at two to three week intervals; it was assumed that
few, if any, larval cohorts were sampled more than once. An estimate of the
total abundance of larvae present in the water column during the day was then
calculated for an area 16 by 16 km (approximately 10 percent of the shoreline
and the area of the western basin). At average wind speeds, all of this area
could be within a one-week drift time to the plant intake.
Based on estimates in Table 37, there may be one to two orders of magni-
tude difference in the vulnerability of different larval species to entrain-
ment. Of course these estimates are crude because of the nature of the sampling
effort, but they give some indication of the magnitude of entrainment impact.
These estimates would improve by further research, but they indicate that the
proportions entrained could be fairly large for certain species, especially
freshwater drum and clupeids. Assuming the study area is roughly representa-
tive of the whole basin, less than 1 percent of most fish populations were
entrained at the plant. However, from 5 to 15 percent of the drum and clupeid
larvae may be entrained. Based on theoretical considerations of commercial
catch and fecundities, Nelson and Cole (1975) estimated similar percentages
for yellow perch. At the present time, the intake at the Monroe Power Plant
exceeds the intake of all other cooling waters taken from the western basin in
125
-------
TABLE 36. ESTIMATED NUMBER OF LARVAE POTENTIALLY ENTRAINED AT THE MONROE POWER PLANT IN 1973*,
1974 and 1975
(millions/year ± mean 95% conf. int.*)
Species 1973 1974 1975
Clupeids 0 £ 0.8 £ 1.6 102.1 £ 168.9 £ 255.0 29.0 £ 62.9 £ 102.3
Carp Of 3.3 <. 6.9 94.4 £ 132.6 £ 180.3 14.8 £ 25.7 £ 36.6
White bass 1.1 £2.6 £ 4.1 28.l£ 95.2 £ 200.0 0.3 £ 7.8 £ 15.3
Yellow Perch 0 £ 2.2 ± 5.1 59.6 £ 83.1 £ 111.5 13.7 £ 29.3 £ 44.9
Channel catfish - .1 6.8£ 28.6 £ 64.9 0 £ l-7£ 4.3
Freshwater drum 0 7.8 £ 20.3 £ 38.3 - 0.1
Shiners 0.8 £ 1.6 £ 2.4 1.1 £ 15.7 £ 39.6 1.4 £ 10.3 £ 19.2
Sunfish -0.3 1.1 £ 8.6 £ 19.9 0 £ 1.4 £ 3.4
Bass 0 -0.7 -0.9
Smelt -0.2 -0.7 0.2 £ 3.2 £ 6.2
Crappie -0.6 -0.3 0
Walleye -0.1 -0.2 0
(continued)
-------
TABLE 36 (continued).
Species
Suckers
Trout perch
Log perch
Total Larvae
1973
-0.2
-0.1
-0.1
1.9 £12. 2£ 20.1
1974
-0.2
-0.2
-0.1
398.4 <_ 556.0 <_ 841.3
1975
0
-0.2
-1.0
59.4 £1445 <_ 232.2
*1973 sampling was completed in mid-June, therefore many species are incompletely repre-
sented and numbers are lower than they should be.
//Calculated by multiplying the number of larvae/m /sampling date (and associated
confidence intervals) at the upper discharge by the volume flow through the cooling system
on that date to determine a daily estimate of entrainment. The daily estimate was assumed
to represent that sampling date plus half the number of days to a subsequent sampling date.
Each daily estimate was multiplied by the number of days that it represented and the sum of
these gave the annual estimate of entrainment.
-------
N>
00
TABLE 37. ESTIMATED RELATIVE VULNERABILITY OF IMPORTANT LARVAL FISH TO ENTRAINMENT AT
THE MONROE POWER PLANT FROM AN AREA 16 km by 16 km IN LAKE ERIE IMMEDIATELY ADJACENT
TO THE POWER PLANT
(numbers in millions)
Species Vel.* Dist. #
Drum 1.0 2.0
Clupeids 1.0 7.9
Shiners 0.9 11.0
White 0.7 13.7
bass
Smelt 0.9 13.4
Yellow 0.9 13.9
Perch
Days
to
Shoret Yr.
2 74
75
8 73
74
75
12 74
75
15 74
75
15 73
74
75
16 73
74
75
Estimated
2 km
27
0
60
498
113
69
9
114
9
133
1
3
19
75
113
.50
.64
.16
.34
.81
,44
.05
.24
.06
.12
.47
.93
.52
.84
.92
Numbers
6 km
0.56
0.01
51.04
422.83
218.56
52.08
6.79
371.28
29.46
665.60
73.60
19.68
683.20
265.44
398.92
in Relation to Shore* Entrainment
11 km
0
0
32.81
271.82
62.08
86.80
11.32
314.16
24.93
272.89
301.76
80.68
224.48
872.16
1310.08
16 km
0
0
38
312
72
138
18
205
163
3128
345
92
653
2540
3816
.28
.12
.42
.88
.11
.63
.20
.32
.92
.49
.92
.64
.32
Est 1§ Est 2'
22.47
49.5
37.45
688.39
141.87
85.89
10.72
119.97
7.08
85.27
20.37
3.24
14.90
58.58
54.90
21.68
20.56
3.30
122.67
55.67
17.99
9.56
104.04
6.88
1.18
0
2.77
9.25
83.89
36.60
Entrainment
Percent
Est ]
80%
76%
21%
46%
41%
25%
24%
4%
3%
1%
3%
2%
2%
2%
1%
L* Est 2*
77%
31%
2%
8%
16%
5%
21%
4%
3%
0.1%
0
1%
1%
2%
0.1%
*This is the average velocity (km/day) that a species population moves. It is calculated
from the proportion of fish captured during the day and night from each of the three depths sampled
(continued)
-------
over all dates that larvae were captured. Daytime was assumed to be 14 hrs and nighttime was assumed
to be 10 hrs. Each stratum represented a proportion of the total population present. The proportion
captured was multiplied by the estimated water velocity for that stratum and the results summed over
all strata. Mean surface and midwater current velocities were assumed to represent 2% of the mean
resultant wind velocity while the deep current represented 10% of the surface current (Hutchinson,
1957):
n
I
m
l = 1
X
I D. P.+ N. PVT
. _ ., 1 D l N
n
i
i = 1
x _ _
1 D t N
1 J_
D
= V
H
Where D» = mean number/m3 captured during the day for each depth stratum; where N; = mean number/m3
captured during the night for each depth strata; where P^ = proportion of daylight hrs; P« = pro-
portion of the nighttime hours; n = number of strata; x = number of dates with fish in samples; V
is the mean horizontal water velocity; Vu = mean horizontal velocity of population.
n
#The mean capture distance from shore was calculated by apportioning the total number of larvae
for each species captured along the transect into the propotion of the total each transect station
represented. The proportion captured at each station was then multiplied by the distance from shore
and the results were summed:
n
E
i = 1
t. D.
= D
Where T = total number/m3 caught at all k stations along the transect; where t. = number/m3 caught
at each station along transect over all sampling dates; where D. = distance of each transect station
from shore; where D = mean capture distance from shore.
(continued)
-------
fThe average number of days to move larvae to the Intake at the power plant was calculated
by dividing the mean capture distance from shore by the weighted horizontal velocity:
D
=- - Days
VH
fThe estimated numbers present at different distances from shore was calculated by assuming
the mean catch at the three lake stations (or one In 1973) within 2 km of shore represented the
total capture within the first 2 km plus half the distance to the second transect station during
the time larvae were estimated to be present. The volume within an area 16 x 4 km was calculated
with a mean depth of 5 m, and the number of larvae within that volume was determined. Using the
prior proportion of larvae captured along the transect in 1975, the total present within a 16 x
16 km area was determined and the number within each transect sector was determined:
Aj - T • Vj
A2 - J • Vj- ta/T
A3 - T • V3« t3/T
Ai, - 7 • Vu* ti»/T
Where F » mean catch/m3 at station P10, Pll, and P12 (or station P5 in 1973) over all dates of
capture. Where V » volume of area surrounding P10, Pll, and P12 (16 x 4 km) to a depth of 5 m.
Where Aj » area in first transect sector (Figure 1); where Aa * area in second sector; where AS =
area in third transect sector; where T = total number/m3 caught at all 4 stations along the transect;
where t% = number/m3 caught at station P14; where t$ = number/m3 caught at station P15; where t<* =
number/m3 caught at station P16.
(continued)
-------
^Theoretical maximum lake entrainment was estimated by assuming maximum pumping'of cooling water
(85m3/sec). By weighting the amount of water derived from the lake compared to the amount from
the river for each month the larvae were present, a mean daily lake water requirement was computed.
The weighted mean lake water requirements per day was extrapolated to the length of time a particular
larval species would be present to yield the total lake water requirements. This water was assumed
to be obtained primarily from the immediate 4 km area while any additional requirements would be
met by the succeeding areas. The percent of the water derived from each transect sector was
calculated and that percent also represented the percentage number of larvae entrained. This percent
was multiplied times the number present in the transect sector to yield numbers entrained. G =
larvae in first transect sector plus any additional larvae from adjacent sector, if required; V =
volume within first sector of transect and additional volume from adjacent sector, if required; L =
length of time (captured days + 14) larvae estimated to be present; R{ = riverine larvae entrained
over period that larvae were present:
G V
n
i— i —
(jj l ~
H
theoretical maximum condenser passage assumed an 85 m3/sec pumping rate. The mean number/m3
of larvae captured in the upper discharge canal was multiplied by the total number of days the larvae
were estimated to be present. This number was then multiplied by the total amount of water pumped
during a comparable time period yielding the total number of larvae present.
C = as above
U = mean number of larvae/m captured in upper discharge canal
L = length of time larvae estimated to be present (days of capture = 14 days)
M = estimated number of larvae to pass through condenser
M = L [(U)(C)]
V Percent total entrainment was calculated by comparing the theoretical maximum entrainment
to the total number of larvae estimated to be present within a 16 x 16 km
0 Percent total condenser passage was calculated by dividing the estimated lake population
by the maximum number estimated to pass through the condenser.
-------
Lake Erie, by about 2 to 1. However, future expansion on the Great Lakes may
require 10 times the present cooling needs over the next few decades. There-
fore, the potential mortality percentages of drum and clupeids border on those
that may have a measurable impact on adult populations, especially in the dis-
tant future.
Jensen (1971) has indicated that a reduction of as little as 5 percent in
recruitment may eventually affect the adult population of at least one species
of fish. Beland (1974) has questioned Jensen's conclusions and there have been
no empirical studies published that verify these kinds of projections. Deter-
mining a 5 percent impact on recruitment with statistical confidence for any
particular year of study would demand a much more intensive sampling effort
than that executed during this study because of the high variability in larval
fish distributions.
The variability is derived from vertical and horizontal variation, and
temporal variation caused by changing rates of larval recruitment. Although
variability at a particular sampling site in the lake may be only moderately
high, the variability among different stations only a few kilometers apart
often is high and inconsistent from one day to the next. This "patchiness"
greatly affects any assessments of change in population abundance within the
cooling system as well as estimates of the proportions of lake populations
that are entrained. We do not know enough about the lengths of time that
larvae are susceptible to net capture and the probability of overestimating
or underestimating the actual number of larvae recruited into the lake popula-
tion. At the intensity of sampling applied during these studies, the annual
entrainment of abundant populations may be reasonably estimated, at a 95 per-
cent confidence interval, within 100 to 1000 percent of the mean. Variability
in the lake is as great as variability in the cooling system. Consequently,
the intensity of sampling in the lake must be comparable to that in the cooling
system to produce similar confidences.
Taking into consideration the exploratory nature of these pilot studies,
there is a need to refine estimates. Future estimates of larval fish distri-
bution and potential entrainment could be improved in several ways. Almost
all of the fish are most vulnerable to entrainment at night because they are
in the faster moving waters near the surface. Therefore, horizontal distribu-
tions would be better estimated at night anywhere night navigation is feasible.
If night sampling proves infeasible, a combination of sled-netting and oblique
tows should be used during the day. If this combination is not used, the
densities of larvae are likely to be underestimated in deeper water. The
actual growth rate of larval fish and their capacity to avoid net capture as
they grow should be better evaluated. Also, the relative vulnerability of
larval fish to natural mortality should be identified as it is related to distri-
bution. Are near-shore populations more likely to die from natural causes
than off-shore populations? Are larvae that hatch in the tributaries more
likely to survive to reproductive age classes than those that hatch in the lake?
Answers to these questions should provide suitable information for the appro-
priate siting and operating of cooling systems and other coastal zone manage-
ment.
132
-------
REFERENCES
Adair, W., and J. H. Raines. 1974. Saturation values of dissolved gasses
associated with the occurrence of gas-bubble disease in fish in a heated
effluent. In Thermal Ecology, J. W. Gibbons and R. R. Sharitz, eds.
U. S. Atomic Energy Commission, pp. 59-78.
American Public Health Association. 1971. Standard methods for the examina-
tion of water and wastewater. 13th ed. 769 pp.
Barnes, H., and S. M. Marshall. 1951. On the variability of replicate plank-
ton samples and some applications of "contagious" series to the statisti-
cal distribution of catches over restricted periods. J. Mar. Biol.
Assoc. U. K. 30:233-263.
Beck, A. D., and D. C. Miller. 1974. Analysis of inner plant passage of
estuarine biota. Paper presented at the Amer. Soc. Civil Eng. Power
Div. Spec. Conf., Boulder, Colo., Aug. 12-14.
Beeton, A. M. 1961. Environmental changes in Lake Erie. Trans. Amer. Fish.
Soc. 90:153-159.
Beland, P. 1974. On predicting the yield from brook trout populations. Trans.
Amer. Fish. Soc. 103(2):353-355.
Bishai, H. M. 1960. The effect of water currents on the survival and distri-
bution of fish larvae. J. Cons. Int. Explor. Mer. 25(2):134-146.
Brooks, J. L. 1968. The effect of prey size selections by lake planktivores.
Syst. Zool. 17:273-291.
Carpenter, E. S., B. B. Peck, and S. J. Anderson. 1974. Survival of copepods
passing through a nuclear power station on north eastern Long Island
Sound, U. S. A. Marine Biol. 24:49-55.
Carr, J. F., V. C. Applegate, and M. Keller. 1965. A recent occurrence of
thermal stratification and low dissolved oxygen in western Lake Erie.
Ohio J. Sci. 65(6):319-327.
Carr, J. F. , and J. K. Kiltunen. 1965. Changes in the bottom fauna of western
Lake'Erie from 1930 to 1961. Limnol. and Oceanogr. 10:551-569.
Cassie, R. M. 1959. An experimental study of factors inducing aggregation in
marine plankton. New Zealand J. Sci. 2:339-365.
133
-------
Cassie, R. M. 1962, Frequency distribution models in the ecology of plankton
and other organisms. J. of An, Ecol. 31:65-91.
Chandler, D. C. 1944. Limnological studies of western Lake Erie. IV.
Relation of limnological and climatic factors to the phytoplankton of
1941. Trans. Am. Micro. Soc. 63(3):203-236.
Clutter, R. I., and M. Anraku. 1968. Avoidance of samplers, Monogr. Oceanogr.
Methodol. 2:57-76.
Cole, R. A. 1972. An ecological evaluation of a thermal discharge, Part I:
Physical and chemical limnology along the western shore of Lake Erie.
Technical Report No. 13, Institute of Water Research, Michigan State
university, East Lansing, Michigan. 121 pp.
Cole, R. A. 1976. The impact of thermal discharge from the Monroe Power Plant
on the aquatic community in western Lake Erie. Technical Report No. 32.6,
Institute of Water Research, Michigan State University, East Lansing,
Michigan. 571 pp.
Coutant, C. C. 1971. Effects on organisms of entrainment in cooling water:
steps toward predictability. Nuc. Saf. 12:600-607.
Coutant, C. C., and S. S. Talmage. 1976. Thermal effects. J. Water Poll.
Control Fed. 48:1476-1544.
Coutant, C. C., and H. A. Pfuderer. 1974. Thermal effects. J. Water Poll.
Control Fed. 46:1476-1540.
Cummins, K. W., and J. C. Wuycheck. 1971. Caloric equivalents for investiga-
tions in ecological energetics. Pub. No. 18, Int. Assoc. of Theor. and
Appl. Limnol. 158 pp.
Gushing, D. H. 1961. Patchiness. • Raupp. Proces. Verb. Cons. Internat. Explor.
Mer. 153:152-164.
Davies, R. M., and L. D. Jensen. 1975. Zooplankton entrainment at three mid-
Atlantic power plants. J. Water Poll. Control Fed. 47(8):2130-2192.
Denis on, P. J., and F. C. Elder. 1970. Thermal inputs to the Great Lakes 1968-
2000. Internat. Assoc. Great Lakes Res. Proc. 13th Conf. Great Lakes Res.
pp. 811-828.
Detroit Edison Company, The. 1976. Monroe Power Plant Thermal Discharge
Demonstration. The Detroit Edison Company, 2000 Second Avenue, Detroit,
Michigan.
Douet, F., and W. A. Daily. 1956. Rivision of the coccoid myxophyceae.
Butler University Botanical Study. 12:1-218.
134
-------
Ecker, T. J., and R. A. Cole. 1976. Chloride and nitrogen concentrations
along the west shore of Lake Erie. Technical Report No. 32.8, Institute
of Water Research, Michigan State Univeristy, East Lansing, Michigan.
132 pp.
Eckstein, H. 1964. Untersuchungen uber den ein fluss des Rheinwassers auf
die limnologie des Schlussee 4. Arch. Hydrobiol. Suppl. 28:119-182.
In Ceiling and Campbell, 1972.
Environmental Protection Agency. 1971. Methods for chemical analysis of
water and wastes. Water Quality Office, Analytical Quality Control
Laboratory, Cincinnati, Ohio. 312 pp.
Faber, D. J. 1967. Limnetic larval fish in northern Wisconsin lakes. J.
Fish Res. Bd. Can. 24(5):927-937.
Gehrs, C. W. 1974. Vertical movement of zooplankton in response to heated
water. In Thermal Ecology. Proceedings of a symposium held in Augusta,
Georgia, May 3-5, 1973. pp. 285-290.
Ceiling, W. T., and R. S. Campbell. 1972. The effect of temperature on the
development rate of the major life stages of Diaptpmus pallidus (Herrick)
Limnol. and Oceanog. 17(2):304-307.
Gill, J. L. 1971. Analysis of data with heterogeneous variance: A review.
J. Dairy Sci. 54(3):369-373.
Gill, J. L. In press. Design and analysis of experiments in the animal and
medical sciences. Iowa State University Press.
Hamilton, D. H., Jr., D. A. Flemner, C. W. Keefe, and J. A. Mihursky. 1970.
Power Plants: Effects of chlorination on estuarine primary production.
Science. 169:197-198.
Hartley, R. P., C. E. Herdendorf, and M. Keller. 1966. Synoptic water
sampling survey in the western basin in Lake Erie. Univ. Michigan
Great Lakes Res. Div. Proc. 9th Conf. on Great Lakes Res., Pub. 15.
pp. 301-322.
Hartley, R. P., and C. P. Potos. 1971. Algal-temperature-nutrient relation-
ships and distribution in Lake Erie. U. S. Environmental Protection
Agency, Water Quality Office, Washington, D. C. 87 pp.
Hem, J. D. 1970. Study and interpretation of the chemical characteristics
of natural water, 2nd edition. Geological survey water supply paper
1473. U. S. Geological Survey, U. S. Government Printing Office,
Washington, D. C. 363 pp.
Hustedt, F. 1930. Bacillariophyta (Diatomeae). In A. Pasche, ed. Die
Susswasserflora raitteleuropas, Heft 10; Gustau Fisher, Jena. VIII
+466 pp.
135
-------
Hutchinson, G. E. 1957. A treatise on limnology. Vol. 1. Geography,
physics, and chemistry. John Wiley and Sons, Inc., New York, N.Y.
pp. 265-295.
Icanberry, J. W., and R. W. Richardson. 1973. Quantitative sampling of
live zooplankton with a filter-pump system. Limnol. and Oceanogr.
18(2):333-335.
International Joint Commission. 1969. Pollution of Lake Erie, Lake Ontario
and the international section of the St. Lawrence River. II - Lake
Erie. Internat. Lake Erie Water Pollution Bd. and Internat. Lake
Ontario-St. Lawrence River Water Pollution Bd. I. J. C., Washington,
D. C. 316 pp.
Jenkins, D., and L. L. Medsker. 1964. A brucine method for the determina-
tion of nitrate in ocean, estuarine, and fresh waters. Anal. Chem.
36:610-612.
Jensen, A. L. 1971. The effect of increased mortality on the young in a
population of brook trout, a theoretical analysis. Trans. Amer. Fish.
Soc. 100(3):456-459.
Kelley, J. E., and R. A. Cole. 1976. The distribution and abundance of
benthic macroinvertebrates along the western shore of Lake Erie.
Technical Report No. 32.7, Institute of Water Research, Michigan State
University, East Lansing, Michigan. 77 pp.
Kenaga, D. E., and R. A. Cole. 1975. Food selection and feeding relation^
ships of yellow perch Perca flavescens (Mitchell), white bass Morone
chrysops (Rafinesque), freshwater drum Aplodinotus grunniens, goldfish
Carassius auratus (Linneaus) in western Lake Erie. Technical Report
No. 32.5, Institute of Water Research, Michigan State University, East
Lansing, Michigan. 50 pp.
Lavis, D. S., and R. A. Cole. 1976. Distribution of fish populations near
a thermal discharge into western Lake Erie. Technical Report No. 32.9,
Institute of Water Research, Michigan State Univeristy, East Lansing,
Michigan. 61 pp.
LeBrasseur, R. J. 1969. Growth of juvenile chum salmon, Oncorhynchus kita
under different feeding regimes. J. Fish. Res. Bd. Can. 26(6):1631-
1645.
MacLaren, Ian A. 1963. Effects of temperature on growth of zooplankton, and
adaptive value of vertical migration. J. Fish. Res. Bd. Can. 20(3):
685-727.
Marcy, B. C., Jr. 1971. Survival of young fish in the discharge canal of a
nuclear power plant. J. Fish. Res. Bd. Can. 28:1057-1060.
Marcy, B. C., Jr. 1973. Vulnerability and survival of young Connecticut
River fish entrained at a nuclear power plant. J. Fish. Res. Bd. Can.
30(8):1195-1203.
136
-------
Marcy, B. C., Jr. 1976. Planktonic fish eggs and larvae of the lower Connec-
ticut River and the effect of the Connecticut Yankee Plant including
entrainment. In The Connecticut River Ecological Study; The impact of a
thermal power plant. D. Merriman and L. M. Thorpe, eds. Monograph No.
1. American Fisheries Society, Washington, D. C. pp. 115-140.
Massengill, R. R. 1976. Entrainment of zooplankton at the Connecticut Yankee
Plant. In The Connecticut River Ecological Study; The impact of a
nuclear power plant. D. Merriman and L. M. Thorpe, eds. Monograph No.
1. American Fisheries Society, Washington, D. C. pp. 55-59.
McNaught, D. C. 1972. The potential effects of condenser passage on the
entrained zooplankton at Zion Station. In Review of Recent Technical
Information Concerning the Adverse Effects of Once-through Cooling on
Lake Michigan. Prepared for the Lake Michigan Enforcement Conference,
Sept. 19-21, 1972, Chicago, 111. Thomas A. Edsall and Thomas G. Yocom.
Merriman, D., and L. M. Thorpe, eds. 1976. The Connecticut River Ecology
Study; The impact of a nuclear power plant. Monograph No. 1. American
Fisheries Society, Washington, D. C. 252 pp.
Miller, D. 1961. A modification of the small Hardy plankton sampler for
simultaneous high speed plankton hauls. Bull. Mar. Ecol. 5:165-172.
Miller, D. J., J. B. Colton, Jr., and R. R. Marak. 1963. A study of vertical
distribution of larval haddock. J. Cons. Int. Perm. Explor. Mer. 28:
37-49.
Morgan, R. P., and R. G. Stress. 1969. Destruction of phytoplankton in the
cooling water supply of a steam electric station. Chesapeake Sci.
10:165-176.
Munro, I. G. 1974. The effect of temperature on the development of egg,
naupliar, and copepodite stages of two species of copepods, Cyclops
vicinus (Uljanin) and Eudiaptomus gracilis (Sars), Oceolog. (Brit.).
16:355-367.
Nelson, D., and R. A. Cole. 1975. The distribution and abundance of larval
fishes along the western shore of Lake Erie at Monroe, Michigan. Tech-
nical Report No. 32.4, Institute of Water Research, Michigan State
University, East Lansing, Michigan. 66 pp.
Noble, R. L. 1970. An evaluation of the Miller high-speed sampler for
sampling yellow perch and walleye fry. J. Fish. Res. Bd. Can. 27(6):
1033-1044.
Pielou, E. C. 1969. An Introduction to Mathematical Ecology. Wiley, New
York. 286 pp.
Regier, H. A., and W. L. Hartman. 1973. Lake Erie fish community 150 years
of cultural stress. Science. 180:1248-1255.
137
-------
Saville, A. 1965. Factors controlling dispersal of the pelagic stages of
fish and their influence on survival. Spec. Publ. Int. N. W. Comm.
Atlant. Fish. 6:335-348.
Shubel, J. R. 1974. Some comments on the thermal effects of power plants
on fish eggs and larvae. In Fisheries and Energy Production, S. B.
Soda, ed. D. C. Heath and Company, Toronto, pp. 31-55.
Silliman, B. P. 1946. A study of variability in plankton tow-net catches of
Pacific pilchard (Sardinops caerula) eggs. J. Mar. Res. 6(1):74-83.
Spain, J. D., and S. C. Andrews. 1970. Water mass identification in a small
lake using conserved chemical constituents. Univ. Michigan Great Lakes
Res. Div. Proc. 13th Conf. on Great Lakes Res. pp. 733-743.
Strothmann, R. R. 1967. Estimating the organic carbon content of phytoplank-
ton from cell volume or plasma volume. Limnol. Oceanogr. 12(3):411-418.
Stragenberg, M., and M. Pawlaczyk. 1960. The influence of warm-water influx
from a power-station upon the formation of biocenotic communities in a
river. Zesz. Nauk. Politech. Wrochaw. Inz. Sanit. 1:67-106.
Taft, C. E. 1945. The demids of the west end of Lake Erie. Ohio Journal
of Sci. 45:180-205.
Taft, C. E., and C. W. Taft. 1971. The algae of western Lake Erie. Bull.
Ohio Biol. Survey. 4:1-189.
Taylor, C. C. 1953. Nature of variability in trawl catches. U. S. Fish and
Wildl. Serv., Fish. Bull. 54(83):145-166.
Tranter, D. J. 1963. Comparison of zooplankton biomass determinations by
Indian Ocean standard net, Juday net, and Clarke-Bumpus sampler. Nature.
198(4886):1179-1180.
Vanucci, M. 1968. Loss of organisms through the meshes. Monogr. Oceanogr.
Methodol. 2:77-86.
Wadelin, D., and M. G. Mellon. 1953. Extraction of hetecopoly acids applica-
tion to determination of phosphorus. Analytical Chemistry. 25:1668-1673.
Warinner, J. E., and M. L. Brehmer. 1966. The effects of thermal effluents
on marine organisms. Air Water Pollut. 10:277-289.
Weber, C. I. 1970. Methods of collection and analysis of plankton and peri-
phyton samples in the water pollution surveillance system. F.W.P.C.A.,
Cincinnati, Ohio. Reprint. 27 pp.
Wichstead, J. H. 1963. Estimates of total zooplankton in the Zanzibar area
of the Indian Ocean with a comparison of the results with two different
nets. Proc. Zool. Soc. Lond. 141(3):577-608.
138
-------
Wiebe, P. H. 1971. A computer model study of zooplankton patchiness and its
effects on sampling error. Limnol. and Oceanogr. 16:29-38.
Wilhm, J. L., and T. C. Dorris. 1968. Biological parameters for water quality
criteria. Bio-Science. 18:477.
139
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-78-070
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Entrainment at a Once-Through Cooling System
on Western Lake Erie, Volume I
5. REPORT DATE
July 1978 issuing date
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
Richard A. Cole
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Institute of Water Research
Dept. of Fisheries and Wildlife
Michigan State University
East Lansing, Michigan 48824
10. PROGRAM ELEMENT NO.
1BA769
11. CONTRACT/GRANT NO.
801188
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Environmental Research Laboratory - Duluth
Office of Research and Development
U.S. Environmental Protection Agency
Duluth, Minnesota 55804
9/1/72 - 12/31/75
14. SPONSORING AGENCY CODE
EPA/600/03
15. SUPPLEMENTARY NOTES
Project Officer: Nelson Thomas, Larg. Lks. Research Station, ERL-Dul, Grosse He,
MI 48138. Volume II available through NTIS only.
16. ABSTRACT
This study assessed entrainment rates and effects for important components of the
aquatic community in the once-through cooling system of a steam-electric power plant
(the Monroe Power Plant), which can draw up to 85 or/second of cooling water from
Lake Erie (-80%) and the Raisin River (-20%). Phytoplankton, periphyton, zooplankton,
ichthyoplankton, and community metabolism were sampled bimonthly from November 1972
through September 1975. Sampling was conducted at fixed locations in the intake
region, discharge canal, thermal plume and the lake-source waters. Concentrations
of chloride, dissolved and total solids were used to trace water masses and their
associated nutrient and plankton concentrations. At temperatures above 15 C in the
discharge canal, photosynthesis was depressed and community respiration was accelera-
ted. Algal abundance increased slightly as green and blue-green algae increased
more than other taxa during passage, but algal diversity remained basically unchanged.
Although zooplankton densities declined about 40% in the cooling system, diversity
remained unchanged and the impact was masked by mixing in the receiving waters. Larva
fish were concentrated near bottom at night and moved up from bottom during the day.
Geographical and temporal variation in larval fish distribution were great, but
certain species seemed most abundant offshore while others were concentrated near shor
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Electric Power Generation
Algae
Fisheries
Zooplankton
Western Lake Erie
Power Plant Entrainment
06 F
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
None
21. NO OF PAGES
154
20. SECURITY CLASS (Thispage)
None
22. PRICE
EPA Form 2220-1 (9-73)
T »n ft U.S. GOVERNMENT MUKDNG OFFICE: 1978-757-140/1415 Region No. 5HI
140
------- |