United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
EPA-600/3-79-092
August 1979
Research and Development
Browns Ferry
Biothermal Research
Series
Effects of
Temperature on
Bluegill and Walleye,
and Periphyton,
Macroinvertebrate,
and Zooplankton
Communities in
Experimental
Ecosystems
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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.
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EPA-600/3-79-092
August 1979
BROWNS FERRY BIOTHERMAL RESEARCH SERIES
II. EFFECTS OF TEMPERATURE ON BLUEGILL AND WALLEYE, AND
PERIPHYTON, MACROINVERTEBRATE, AND ZOOPLANKTON COMMUNITIES
IN EXPERIMENTAL ECOSYSTEMS
by
William B. Wrenn, Brian J. Armitage,
Elizabeth B. Rodgers, Thomas D. Forsythe,
and Kenneth L. Grannemann
Biothermal Research Station
Division of Forestry, Fisheries, and
Wildlife Development
Tennessee Valley Authority
Decatur, Alabama 35602
TV-35013A
Project Officers
Thomas H. Ripley Kenneth E. Biesinger
Division of Forestry, Environmental Research Laboratory
Fisheries, and Wildlife Development Duluth, Minnesota 55804
Forestry Building
Norris, Tennessee 37828
This study was conducted
in cooperation with
Tennessee Valley Authority
Norris, Tennessee 37828
ENVIRONMENTAL RESEARCH LABORATORY - DULUTH
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
DULUTH, MINNESOTA 55804
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DISCLAIMER
This report has been reviewed by the Environmental Research Laboratory-
Duluth, U.S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the views
and policies of the U.S. Environmental Protection Agency- nor does mention
of trade names or commercial products constitute endorsement or recommen-
dation for use.
11
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FOREWORD
The aquatic environment must be protected from the adverse effects of
thermal discharges. Large volume thermal discharges, if not properly managed,
can have deleterious effects on fish populations and their food-chain
organisms and thus ultimately diminish the quality of man's environment;
conversely, excessive control measures can result in inefficiencies in
energy use and economic penalties to the public. A balance must therefore
be maintained between the industrial utilization of water and the maintenance
of a high-quality environment. The Browns Ferry Biothermal Research Program
contributes to the search for this acceptable balance through investigations
on
—the effects of increased temperature on growth, survival and
reproduction of sport and commercially important fish species
and their food organisms, and
—the effects of increased temperature on the ecological relationships
between fish and their food organisms.
This report presents the results of the first full-scale experiment
with heated water at the Biothermal Research Station. Specifically, this
report addresses the effects of elevated thermal regimens on two important
fish species, bluegill (Lepomis macrochirus) and walleye (Stizostedion v.
vitreum) and on population and community responses of macroinvertebrates,
zooplankton and periphyton. In doing so, it presents significant new data
on thermal effects relative to longer acclimation periods and higher
acclimation temperatures than previously reported.
Clyde W. Voigtlander
Office of Natural Resources
Tennessee Valley Authority
111
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ABSTRACT
Effects of long-term, March-September 1977, temperature elevations on
aquatic communities in 12 outdoor experimental channels were evaluated.
Macroinvertebrates, periphyton, and zooplankton colonized the channels
naturally from the water supplied from Wheeler Reservoir, Tennessee River.
The fish community consisted of stocked adult bluegill and juvenile walleye.
Four temperature regimens, with three replicate channels per regimen, were
maintained. The ambient temperature of the water pumped from Wheeler
Reservoir provided the lowest treatment. Elevated regimens of ca. 2°, 4°,
and 6° C above ambient were maintained in the remaining nine channels.
The work upon which this publication is based was performed pursuant to
an Interagency Agreement between the Tennessee Valley Authority and the
Environmental Protection Agency. This report was submitted in partial
fulfillment of Contract No. TV-35013A by the Tennessee Valley Authority
under partial sponsorship of the U.S. Environmental Protection Agency. The
report covers field work from March 1977 to September 1977, and analyses
completed as of August 1978.
IV
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CONTENTS
Foreword iii
Abstract iv
Figures vii
Tables x
1. INTRODUCTION 1
Objectives 1
References 3
2. CONCLUSIONS 4
3. TEMPERATURE AND WATER QUALITY. W. B. Wrenn, B. J. Armitage, and
E. Goode, Jr 6
Temperature . . 6
Water Quality 7
4. PRODUCTION AND BIOMASS OF BLUEGILL AND WALLEYE. W. B. Wrenn and
T. D. Forsythe 20
Materials and Methods 21
Results 22
Discussion 34
References 37
5. BLUEGILL REPRODUCTION. W. B. Wrenn and K. L. Grannemann .... 40
Materials and Methods 40
Results 41
Discussion . ........ 46
References 49
6. ZOOPLANKTON. T. D. Forsythe 51
Materials and Methods 52
Results 54
Discussion 61
References 65
v
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7. MACRO INVERTEBRATES. E. B. Rodgers 66
Materials and Methods 66
Results 67
Discussion 107
References 123
8. PERIPHYTON. B. J. Armitage 127
Materials and Methods 127
Results 128
Discussion 130
References 134
9. APPENDICES 154
VI
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LIST OF FIGURES
Number Page
1. Schematic diagram of the water supply system for the Browns
Ferry experimental channels 9
2. Average minimum daily temperatures in experimental channels,
1977 10
3. Mean number of bluegill nests in the upper sections of
divided channels . ........... 43
4. Hatching success of bluegill eggs in experimental channels . . 44
5. Mean zooplankton densities of each channel over the study
period and the proportions of the five most abundant taxa . . 56
6. Time-series plots of mean densities per treatment for the five
most abundant zooplankton taxa ............... 58
7. Time-series plots of Shannon diversity, community biomass
composition, and total zooplankton density for each
treatment 59
8. Mean zooplankton densities during June - August in the upper
and lower channel sections of divided and undivided
channels ..... ............. 60
9. Trends across treatments for mean zooplankton density and mean
Shannon diversity, June - August, for upper and lower channel
sections of divided and undivided channels ......... 62
10. Mean zooplankton density per treatment over the study period and
the proportions contributed by the five most abundant taxa . 63
12. Monthly mean dry weight of total macroinvertebrates excluding
Mollusca in four temperature treatments (three channels per
treatment): A (ambient temperature of Wheeler Reservoir,
Tennessee River), and +2°, +4°, and +6° C above ambient. . . 73
VII
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Number
13. Monthly mean dry weight of total macroinvertebrates excluding
Mollusca in three habitats (rocks, walls, pools) and four
temperature treatments (three channels per treatment): A
(ambient temperature of Wheeler Reservoir, Tennessee River),
and +2°, +4°, and +6° C above ambient 75
14. Monthly mean density of total macroinvertebrates including
Mollusca in four temperature treatments (three channels
per treatment): A (ambient temperature of Wheeler Reservoir,
Tennessee River), and +2°, +4°, and +6° C above ambient. . . 77
15. Monthly mean density of Physa heterostropha in four temperature
treatments (three channels per treatment): A (ambient
temperature of Wheeler Reservoir, Tennessee River), and +2°,
+4°, and +6° C above ambient . 79
16. Monthly mean density of Physa heterostropha in three habitats
(rocks, walls, pools) and four temperature treatments
(three channels per treatment): A (ambient temperature of
Wheeler Reservoir, Tennessee River), and +2°, +4°, and +6° C
above ambient 80
17. Monthly mean dry weight of Amphipoda in four temperature
treatments (three channels per treatment): A (ambient
temperature of Wheeler Reservoir, Tennessee River), and +2°,
+4°, and +6° C above ambient 82
18. Monthly mean density of Amphipoda in four temperature treatments
(three channels per treatment): A (ambient temperature of
Wheeler Reservoir, Tennessee River), and +2°, +4°, and +6° C
above ambient 85
19. Monthly mean density of Amphipoda in three habitats (rocks,
walls, pools) and four temperature treatments (three channels
per treatment): A (ambient temperature of Wheeler Reservoir,
Tennessee River), and +2°, +4°, and +6° C above ambient. . . 88
20. Monthly mean dry weight of Caenis sp. in four temperature
treatments (three channels per treatment): A (ambient
temperature of Wheeler Reservoir, Tennessee River), and +2°,
+4°, and +6° C above ambient 89
21. Monthly mean density of Caenis sp. in four temperature treatments
(three channels per treatment): A (ambient temperature of
Wheeler Reservoir, Tennessee River), and +2°, +4°, and +6° C
above ambient. 90
viii
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Number Page
22. Monthly mean dry weight and density of Caenis sp. on rock areas
of four temperature treatments (three channels per treatment):
A (ambient temperature of Wheeler Reservoir, Tennessee River),
and +2°, +4°, and +6° C above ambient 94
23. Monthly mean dry weight and density of Caenis sp. on wall areas
of four temperature treatments (three channels per treatment):
A (ambient temperature of Wheeler Reservoir, Tennessee River),
and +2°, +4°, and +6° C above ambient 95
24. Monthly mean dry weight and density of Caenis sp. in pool areas
of four temperature treatments (three channels per treatment):
A (ambient temperature of Wheeler Reservoir, Tennessee River),
and +2°, +4°, and +6° C above ambient 96
25. Monthly mean dry weight of Chironomidae in four temperature
treatments (three channels per treatment): A (ambient
temperature of Wheeler Reservoir, Tennessee River), and
+2°, +4°, and +6° C above ambient 99
26. Monthly mean density of Chironomidae in four temperature
treatments (three channels per treatment): A (ambient
temperature of Wheeler Reservoir, Tennessee River), and
+2°, +4°, and +6° C above ambient 101
27. Monthly mean density of Chironomidae in three habitats
(rocks, walls, pools) and four temperature treatments
(three channels per treatment): A (ambient temperature
of Wheeler Reservoir, Tennessee River), and +2°, +4°, and
+6° C above ambient 102
28. Monthly mean density of Amphipoda and Physa heterostropha on
rock areas in four temperature treatments (three channels
per treatment): A (ambient temperature of Wheeler Reservoir,
Tennessee River), and +2°, +4°, and +6° C above ambient. . . 121
29. Phenograms derived from periphyton presence-absence data . . . 136
IX
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LIST OF TABLES
Number Page
1. Physical Characteristics of the Experimental Channels 2
2. Comparison of Mean Daily Water Temperatures at 1.0 m in Upper
Channel Sections 12
3. Representative Mean Daily Surface and Bottom Water Temperatures
in Upper Channel Sections 13
4. Representative Mean Daily Surface and Bottom Water Temperatures
in Lower Channel Sections 15
5. Summary of Water Quality Conditions in Experimental Channels . 17
6. Mean Production Statistics of Bluegill in the Experimental
Channels 23
7. Production and Biomass of Adult and Young-of-the-Year Bluegill
in Upper Channel Sections 26
8. Examples of Population Sizes and Mean Weights of Young-of-the-
Year Bluegill. . 27
9. Mean Growth, Survival, and Biomass of Age I Bluegill for 185
Days 29
10. Mean Growth, Survival, and Biomass of Walleye for 118 Days . . 31
11. Mean Production Statistics of Walleye in Experimental Channels 32
12. Total Larvae Produced and Standing Stocks of Young-of-the-Year
Bluegill 45
13. Zooplankton Taxa Observed in Channels and Mean Dry Weight Per
Individual 55
14. Comparison of Divided and Undivided Channels. Pool Sediments. 69
15. Comparison of Divided and Undivided Channels. Rock Areas. . . 70
16. Comparison of Divided and Undivided Channels. Walls 71
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Number Page
17. ANOVA of Treatment Effects on Dry Weight (mg m 2) of Total
Macrolnvertebrates (Excluding Mollusca) 72
18. ANOVA of Treatment Effects on Dry Weight (no m~2) of Total
Macroinvertebrates Including Mollusca 76
19. ANOVA of Treatment Effects on Mean Density (no m~2) of Physa
heterostropha 78
20. ANOVA of Treatment Effects on Dry Weight (mg m~2) of Amphipoda 81
21. ANOVA of Treatment Effects on Mean Density (no m""2) of Amphipoda 84
22. ANOVA of Treatment Effects on Mean Density (no m~2 ) of Hyalella
azteca 86
23. ANOVA of Treatment Effects on Mean Density (no m~ ) of
Crangonyx 87
24. ANOVA of Treatment Effects on Dry Weight (mg m~2) of Caenis Sp. 92
25. ANOVA of Treatment Effects on Mean Density (no. m~") of Caenis
Sp " 93
26. ANOVA of Treatment Effects on Dry Weight (mg m~2) of
Chironomidae 98
27. ANOVA of Treatment Effects on Mean Density (no m") of
Chironomidae 100
28. ANOVA of Treatment Effects on Dry Weight (mg m-2) of
Hirudinea 104
29. ANOVA of Treatment Effects on Dry Weight (mg m~2) of
Libellulidae 105
30. Species Diversity (Shannon-Weaver H ) 108
31. Biomass Diversity (Shannon-Weaver H ) 109
32. Results of Student's t-Test on Macroinvertebrate Diversity
Indices 110
33. Stomach Contents of Bluegill Recovered 1 September from
Four Temperature Treatments Ill
34. Periphyton Presence-Absence Data from Monthly Wall Scrapes . . 137
35. Algal Export (kg Fresh Weight) - 1977 145
XI
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Number Page
36. Periphyton Fresh Weight (gm nr2) - Pool 2 146
37. Periphyton Dry Weight (gm m~2) - Pool 2 146
38. Periphyton Chlorophyll a* (mg m~2) - Pool 1 147
39. Periphyton Chlorophyll a* (mg m~2) - Pool 2 147
40. Periphyton Total Protein (mg m~2) - Pool 2 148
41. Periphyton Total Protein/Dry Weight (gm gnT1) - Pool 2 .... 148
42. Periphyton Total Carbohydrate (gm m~2) - Pool 2 149
43. Periphyton Total Carbohydrate/Dry Weight (gm gm-1) - Pool 2. . 149
44. Periphyton Total Protein/Total Carbohydrate - Pool 2 150
45. Periphyton Total Phosphate/Dry Weight (gm gm-1) - Pool 2 ... 150
46. Periphyton Net Oxygen Production (gm m~2 hr"1) - Pool 2. ... 151
47. Periphyton Assimilation Ratio (gm 02 hr"1 girT"1 chla) 151
48. Tetrazolium Violet (ETS) Activity - Pool 2 152
49. Regression Equations for the Dependent Variables Net Oxygen
Production and Tetrazolium Violet (ETS) Activity 153
Xll
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SECTION 1
INTRODUCTION
This report covers the first full-scale experiment with heated water at
the Browns Ferry Biothermal Research Station, funded jointly by the
Environmental Protection Agency (EPA) and the Tennessee Valley Authority
(TVA) in recognition of their common interests and concerns regarding energy
production and environmental protection. The primary feature of the
facility, located on the Tennessee River in northern Alabama, is a series of
12 temperature-controlled outdoor channels designed to assess the thermal
requirements of fish and other aquatic organisms under essentially natural
conditions (e.g. seasonal and diurnal temperature fluctuations, photoperiod,
and predator-prey interactions). The major objective is to provide
information for establishing temperature criteria for protection of important
sport and commercial fish species; moreover, since the channels are colonized
by diverse algal, macroinvertebrate, and zooplankton communities, temperature
criteria also can be evaluated in relation to protection of the ecological
intergrity (Cairns, 1977) of an aquatic ecosystem. Documentation of the
algal and invertebrate organisms which have colonized the channels, and a
description of the facility were provided by Armitage et al. (1978). A
summary of the physical characteristics of the channels is presented in
Table 1.
In general, evaluation of thermal requirements of fish species tested
in the experimental channels follows the protocol described by Brungs and
Jones (1977), i.e. determining mean and maximum numerical criteria based on
the protection of desirable or important species. Primary emphasis is on
determining the long-term or chronic effects of elevated thermal regimens on
growth, survival, and reproduction. Initially, this facility was designed
to test warmwater species; however, species now recognized as coolwater
forms (e.g. sauger and walleye) (Hokanson, 1977; Kendall, 1978) will also be
evaluated. Species tested in the channels are selected by three criteria:
(1) contributing information on important species as identified by EPA and
TVA, (2) inhabiting the Tennessee River, and (3) adaptation to the channel
environment.
OBJECTIVES
This experiment, with bluegill (Lepomis macrochirus) and walleye
(Stizostedion vitreum vitreum) as the target fish species, was conducted
from 3 March to 8 September, 1977, in 12 outdoor experimental channels.
Four temperature regimens (treatments), with three replicate channels per
regimen were established. The ambient temperature of Wheeler Reservoir
(Tennessee River) provided the lowest regimen. The three elevated
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TABLE 1. PHYSICAL CHARACTERISTICS OF EACH OF THE 12 EXPERIMENTAL
CHANNELS AT THE BROWNS FERRY BIOTHERMAL RESEARCH STATION.
Characteristic
Metric Units
Channel length (total)
Channel length (water surface)
Channel width
Channel depth
Water depth over pool areas
Water depth over rock areas
Water surface area
Water volume
Water discharge rate
Water turnover time
Number of pool areas
Pool substrate type
Water velocity in pool areas
Number of rock areas
Rock type
Water velocity over rock areas
114 m
112 m
4.3 m
2.10 m
1.2 m
0.3 m
0.048 hectares
480 m2
530 m3
0.66 m3/min
14 hrs
50-cm layer of
reservoir sediments
0.14 m/min
5-15 cm rocks of
crushed limestone
0.56 m/min
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temperature regimens, superimposed on the seasonal and diurnal temperature
cycle of the reservoir, were +2 C, +4 C, and +6 C.
Specific objectives in evaluating effects of the elevated thermal
regimens were:
1. Determination of production and biomass of adult bluegill and
juvenile walleye.
2. Determination of production and biomass of young-of-the-year
bluegill.
3. Evaluation of bluegill reproduction.
4. Evaluation of both population and community responses of
macroinvertebrates on the basis of species composition,
relative biomass and density, and life cycle turnover
rates.
5. Determination of species composition and relative biomass
and density of zooplankton.
6. Determination of biomass, community structure, and metabolic
activity of the periphyton.
REFERENCES
Armitage, B. J., T. D. Forsythe, E. B. Rodgers, and W. B. Wrenn. 1978.
Colonization by periphyton, zooplankton, and macroinvertebrates.
Browns Ferry Biothermal Res. Ser. I. U.S. Environ. Prot. Agency,
Duluth, Minn., EPA-600/3-78-020. 46 pp.
Brungs, W. A., and B. R. Jones. 1977. Temperature criteria for freshwater
fish: protocol and procedures. U.S. Environ. Prot. Agency, Duluth,
Minn., EPA-600/3-77-061. 130 pp.
Cairns, J., Jr. 1977. Aquatic ecosystem assimilative capacity. Fisheries
3(2): 5-7.
Hokanson, K.E.F. 1977. Temperature requirements of some percids and
adaptations to the seasonal temperature cycle. J. Fish. Res. Board
Can. 34(10): 1524-1550.
Kendall, R. L. (ed.). 1978. A symposium on selected coolwater fishes
of North America. Special Publ. No. 11, Amer. Fish. Soc., Washington,
D.C., 437 p.
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SECTION 2
CONCLUSIONS
1. Twelve outdoor experimental channels, naturally colonized by
diverse periphytic and invertebrate communities and stocked with a forage
(bluegill) and a predator (walleye) fish species, simulated natural aquatic
ecosystems which provided a unique opportunity to evaluate long-term effects
of elevated temperature regimens on aquatic communities and on species, as
well.
2. Elevated temperature regimens (ca. 2°, 4°, and 6° C above the
ambient temperature of Wheeler Reservoir, Tennessee River) which ranged from
ca. 31° to 34° C for more than 70 days had no significant effect on the
production and biomass of bluegill.
3. The only temperature effect on bluegill reproduction was the
earlier inception of spawning in the elevated regimens. Hatching success of
eggs was 95% at 34° C.
4. Young-of-the-year bluegill provided an abundant food source for the
walleye.
5. The biomass of juvenile walleye was highest in the ambient regimen
(which exceeded 28° C for 78 days) but this was not significantly greater
than the biomass of walleye held in an elevated temperature regimen which
reached 32° to 33° C for 75 days.
6. Total mortality of the walleye in the highest temperature regimen
occurred at ca. 34° C.
7. Walleye in this study were more temperature-tolerant than
previously indicated by laboratory studies. The longer acclimation period,
higher acclimation temperatures, and the predator-prey conditions in the
channels apparently influenced this higher tolerance.
8. Elevated temperature regimens ranging from ca. 31° to 34° C for
more than 70 days were not of sufficient magnitude to cause measurable
stress to the zooplankton community structure. The dominant zooplankters
were the copepod Mesocyclops edax, the ostracod Physocypria sp., and the
cladocerans Bosmina longirostris, Chydorus sphaericus, and Simocephalus
vetulus.
9. Although young bluegill predation on zooplankton had a significant
effect on abundance and species composition, temperature had no apparent
4
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effect on the biomass of young bluegill directly affecting zooplankton
turnover rates.
10. A greater monthly and total biomass of floating algal mats (algal
export) was produced in the warmest temperature treatment.
11. Within both the floating mats and the attached algal wall
communities, shifts in dominance and succession were accelerated in the
warmest treatment.
12. The attached algal wall communities provided no clear indications
of thermal effects in terms of biomass.
13. The accelerated algal succession and increased biomass accumlation
in the heated channels apparently increased the herbivore food supply during
the spring and early summer, while apparently decreasing the food supply
during the late summer.
14. Numerically dominant macroinvertebrates evaluated from March
through August were: Physa heterostropha (Gastropoda), Hyalella azteca and
Crangonyx sp. (Amphipoda), Caenis sp. (Ephemeroptera), and Chironomidae
(Diptera).
15. Neither Chironomidae nor Physa heterostropha densities or biomass
were affected by elevated temperatures in any consistent way.
16. Amphipoda responded inversely to increased temperature, both in
terms of peak biomass and duration of population existence.
17. Caenis sp. and Chironomidae showed accelerated life cycles.
18. The relative decimation of the macroinvertebrate community in
warmer channels in late summer was not reflected in the biomass of bluegill
recovered at the end of the experiment.
19. Neither diversity index nor percent abundance data were useful in
defining temperature effects.
20. Future studies should be directed toward (a) determining whether
the macroinvertebrate community decimated by temperature elevation would
recover during a longer study (1.5-2 yr), and (b) determining food sources
of bluegill during periods of macroinvertebrate community decline.
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SECTION 3
TEMPERATURE AND WATER QUALITY
INTRODUCTION
The water supply system for the biothermal channels is designed so that
up to four temperature regimens, with three channels per regimen, can be
established simultaneously. Multiple inlet pipes and valves allow
randomization (by sets of three) in the application of the temperature
regimens (Fig. 1). Water pumped from Wheeler Reservoir, which is the source
for all 12 channels, provides the lowest temperature regimen. Three
elevated temperature regimens, superimposed on the seasonal and diurnal
temperature cycle of the reservoir, can be established by passing the
inflowing ambient water through heat exchangers (with stainless-steel tube
bundles) before entering the channels. The heat source for the exchangers
is the condenser cooling water pumped from the Browns Ferry Nuclear Plant.
Flow rates (0.66 m3/min or 180 gal/min per channel) and the physical
dimensions of the channels are such that elevated increments established at
the inlet are expected to be maintained at "constant" levels (± 1° C) only
in the upper 44 m of the channels. Downstream from this point, the
temperature usually begins to decline so that a zone of thermal gradients
occurs in the lower 68 m of the channels. In order to have the option of
confining fish to the upper "constant" section in a given treatment, the
channels were constructed so that fine mesh (2 mm) screen barriers could be
installed to divide the channels into upper and lower sections of 190 and
290 m2, respectively. The upper channel sections of the elevated temperature
regimens are considered to simulate conditions that would occur if the
temperature increased (either naturally or induced by man) in an entire
water body so that cooler refuge areas would not be available to the fish or
other mobile organisms. Temperature conditions in the lower section of a
divided channel or in an undivided channel, simulate thermal plumes such as
those associated with heated discharges from power plants. In the case of an
undivided channel, the highest temperature in the plume would impact ca. 40%
of the mixed water body (channel), but the fish would not be prevented from
seeking cooler zones along a thermal gradient or vice versa.
TEMPERATURE
In the present study, two of the three channels for each temperature
regimen were divided, and the third was undivided. The nominal elevated
temperature regimens were 2, 4, and 6° C above the ambient reservoir
temperature. Actual temperature regimens maintained are presented in
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Figure 2. These regimens were based on daily mean temperature at 1 m, which
represented the average minimum temperature accessible to the bluegill and
walleye. Diurnal temperature changes in the upper sections seldom exceeded
2° C. For the upper sections temperature was measured at the inlet and
38 m, and in the lower sections at 70 and 102 m. Temperature was measured
(Honeywell RT/1 Transmitter, Resistance thermometer-to-current) at hourly
intervals at these four locations and the data stored by computer. To check
the automatic monitors, temperatures were measured two days each week at
0700 and 1530 hours with a calibrated (ASTM), portable electrical thermometer
(Table 2). Temperatures at 0.3 m were also monitored at this time to
evaluate vertical differences (Table 3 and 4). As expected, vertical
temperature differences were more pronounced in the lower sections. Vertical
differences in the lower sections were also indicative of the range of
horizontal temperatures that could be selected by the fish in these sections
Abrupt declines in the elevated regimens (Fig. 2) were caused by valve
failures or the loss of heat from the nuclear plant (unit outage or load
reduction). Precise flow control was usually maintained to each channel
(180 gal/min); this was accomplished with Jamesbury ball valves and
electronic accuators in combination with Honeywell diffused silicon AP
(flow) transmitters.
WATER QUALITY
Most water quality parameters were estimated using methods outlined in
Standard Methods (1976). Underwater light transmittance (%) was estimated
at 0.3, 0.6, and 0.9 m using a Montedoro-Whitney Submarine Photometer.
Total gas saturation and N2~Ar saturation were estimated with a Weiss
Saturometer. Dissolved oxygen was measured two days per week from each
channel. Measurements were made with a YSI portable meter at 0700 and 1600
hrs at 0.3 and 0.9 m in the upper section (second pool) and lower section
(sixth pool).
Water quality was monitored to insure no abnormal chemical or physical
events, except temperature, affected the results. As can be seen from the
mean values listed in Table 5, very few parameters differed among temperature
treatments.
Minimum values for dissolved oxygen at 0.9 m in the heated channels
(upper sections), although only half those in the ambient channels, seldom
dropped below 4 ppm. This decline is probably indicative of higher
respiration rates in the sediments by microorganisms stimulated by increased
temperature. Greater light penetration in the ambient channels were
indicated by secci disk and light photometer measurements. Complementing
this difference between ambient and heated channels was the lower mean
nonfilterable residue in the ambient channels. Apparently, temperature-
stimulation of planktonic populations in the upper sections of the heated
channels accounted for the decrease in light penetration and the increase in
nonfilterable residue. Support for this effect is drawn from infrequent
carbohydrate analyses of plankton samples which indicated increased total
carbohydrate with increased temperature treatment (e.g. June 9, 1977:
ambient = 178, +2 = 206, +4 = 215, +6 = 231 yg total carbohydrate/liter).
Increases in pH between upper and lower sections was a natural result of
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photosynthetic activity which assimilated carbon dioxide and drove the
bicarbonate equilibrium to the right.
Examination of data (not presented) from atomic absorption analyses of
dissolved metal species indicated no variation between heat treatments.
Also, levels of some metals (e.g. Fe) were at higher concentrations (but not
toxic) than those reported from Wheeler Reservoir (Water Quality Branch,
TVA) . These higher concentrations resulted from the position of the cold
water intake pipe, 7.6 m deep, in the overbank area of Wheeler Reservoir.
Water from this area would be expected to vary from normal samples taken
from mid-channel due to the greater influence of the sediment layers as a
source of metal species. Samples from the intake pool of the Browns Ferry
Nuclear Plant exhibited similarly raised concentration levels over mid-
channel samples.
In conclusion, data derived from biweekly, monthly, and quarterly water
quality monitoring did not indicate levels or concentrations which would
affect the results of the temperature-dependent experiments. Differences of
a few parameters among heat treatments were indicative of temperature
effects.
REFERENCES
American Public Health Association, Inc. 1976. Standard Methods for the
Examination of Water and Wastewater. 14th ed. Washington, B.C.
-------
r
k
j
k
-c
Ch
CONTRI
FISH HOLDING PONDS
NO 3 HEAT EXCHANGER 9 MIXING STATION
NO 2 HEAT EXCHANGER a MIXING STATION
NO I HEAT EXCHANGER ft MIXING STATION
SELF-CLEAN ING
STRAINERS (2mm MESH)
AMBIENT TEMPERATURE
RIVER WATER
HEATED CONDENSER EFFLUENT
FROM NUCLEAR PLANT
Figure 1. Schematic diagram of the water supply system, Browns Ferry
experimental channels.
-------
35
30
r~J ^4. /\\ '-^^^+
10
MAR
APR
MAY
JUN
JUL
AUG
SEP
Figure 2. Average minimum daily temperature in experimental channels,
1977; A = ambient temperature regimen of Wheeler Reservoir (Tennessee
River). Upper section included 40% of the area of each channel.
10
-------
TABLE 2. COMPARISON OF MEAN DAILY WATER TEMPERATURES AT 1.0 m IN UPPER SECTIONS OF THE CHANNELS, 1977,
AS DETERMINED BY AUTOMATIC AND MANUAL MEASUREMENTS (A = AMBIENT, B = +2 C, C = +4 C, D = +6 C).
Day
of
Year
67
70
74
78
83
88
92
97
101
104
108
110
113
116
118
123
125
130
132
139
144
146
151
153
158
160
A
Auto.*
11.2
12.8
14.5
14.4
12.8
15.0
16.5
14.4
17.0
17.7
19.3
19.9
19.5
18.6
19.5
20.7
21.0
21.3
20.9
22.9
23.6
24.1
25.6
25.4
25.7
25.1
Man.t
10.6
12.7
14.2
14.7
-
14.9
-
-
17.0
-
19.0
-
-
18.6
19.0
20.0
21.2
21.5
21.2
23.0
23.9
23.9
25.5
25.9
25.7
24.8
B
Auto.
12.3
14.3
15.1
15.9
14.0
16.8
18.0
15.5
17.8
18.9
20.4
21.0
21.2
20.7
20.6
21.8
22.1
22.9
22.6
24.6
24.8
25.7
26.3
27.1
26.7
26.8
Man.
12.3
14.1
15.7
16.1
-
16.9
-
-
18.5
-
20.8
-
-
20.5
19.8
21.7
21.8
22,9
22.4
24.4
24.7
25.3
25.9
27.9
26.9
26.3
C
Auto .
14.5
16.1
17.9
17.9
16.2
18.8
19.9
17.9
20.5
21.4
22.8
23.4
23.1
22.4
22.3
24.2
24.4
24.9
24.3
26.4
26.6
27.5
28.1
28.8
27.0
28.8
Man.
14.0
16.0
17.0
18.1
-
18.7
-
-
20.4
-
22.7
-
-
22.2
20.9
23.8
24.0
24.4
24.5
26.0
26.4
27.1
27.5
28.8
27.2
28.2
D
Auto.
15.6
18.0
18.5
19.8
18.1
20.5
21.9
20.0
22.6
23.4
24.9
25.4
23.7
23.7
24.2
26.3
26.4
27.1
25.9
27.1
27.6
28.6
29.8
30.4
28.2
30.8
Man.
15.0
17.8
18.8
19.8
-
21.1
-
-
22.6
-
25.1
-
-
23.0
22.4
26.0
25.9
27.1
26.8
26.6
27.2
28.1
29.2
30.6
28.6
29.8
* Mean daily temperature as determined from hourly intervals - automatic monitors.
t Mean daily tempers! e as determined from manual measurements at 0700 and 1530 hours.
(continued)
-------
Table 2 (continued).
Day
of
Year
165
167
172
174
179
181
186
188
193
195
200
202
206
207
209
214
216
221
223
228
230
235
237
242
244
A
Auto.
26.6
25.9
27.2
27.8
28.9
28.9
28.4
30.1
29.2
30.3
29.7
29.4
29.5
-
27.7
27.6
27.9
28.7
28.8
28.5
28.1
28.0
28.5
28.7
28.7
Man.
26.7
26.1
27.5
28.0
29.0
28.7
28.7
29.9
29.3
30.1
29.9
29.6
-
29.4
28.2
28.4
28.3
29.2
29.3
29.7
28.7
28.5
28.8
28.6
29.1
B
Auto.
28.0
28.0
28.5
29.3
29.8
30.2
30.0
30.8
31.6
31.4
31.3
31.3
31.3
-
30.0
29.9
30.0
30.1
30.4
30.4
30.3
30.0
30.0
29.8
30.3
Man.
28.1
28.0
22.4
29.2
29.6
30.0
30.1
30.7
31.7
31.4
31.2
31.3
-
31.3
30.1
30.1
30.0
30.0
30.1
31.0
30.4
30.0
30.2
29.9
30.5
C
Auto.
30.1
30.0
30.4
31.3
32.2
32.1
31.7
32.4
33.1
32.9
32.7
32.9
32.8
-
31.9
31.7
31.9
32.2
32.5
32.6
32.2
32.2
32.4
32.3
32.5
Man.
29.8
29.8
30.1
30.9
32.4
31.7
32.0
32.5
32.9
32.7
32.5
33.0
-
33.1
32.2
31.9
31.9
32.7
32.5
33.1
32.1
32.5
32.7
32.7
32.9
D
Auto.
32.3
32.1
32.5
33.1
33.6
34.0
33.4
34.2
32.9
33.6
33.6
34.1
33.6
-
33.5
34.2
34.1
33.9
34.5
34.4
33.6
33.3
33.2
33.3
34.1
Man.
32.0
31.7
32.5
33.3
33.7
33.8
33.6
34.2
32.1
33.1
32.7
33.0
-
34.7
33.8
33.6
34.0
34.5
34.0
33.1
34.1
33.5
33.5
33.7
34.3
-------
TABLE 3. REPRESENTATIVE MEAN DAILY SURFACE (0.3 m) AND BOTTOM (1.0 m) WATER TEMPERATURES IN THE UPPER
SECTIONS OF THE CHANNELS 1977 (A = AMBIENT, B = +2 C, C = +4 C, D = +6 C).
Day
of
Year
67
70
74
78
88
101
108
116
118
123
125
130
132
139
144
146
151
153
158
160
165
167
172
174
179
181
186
188
193
A
0.3 m
_
-
-
-
-
-
19.9
18.8
19.3
21.1
21.6
21.5
21.5
23.6
24.1
24.0
25.8
26.6
25.7
25.0
26.7
26.2
27.8
28.3
29.1
28.9
29.0
30.2
29.3
1.0 m
10.6
12.7
14.2
14.7
14.9
17.0
19.0
18.6
19.0
20.0
21.2
21.5
21.2
23.0
23.9
23.9
25.5
25.9
25.7
24.8
26.7
26.1
27.5
28.0
29.0
28.7
28.7
29.9
29.3
B
0.3 m
-
-
-
-
-
21.4
21.0
20.1
22.2
22.9
23.2
23.0
25.1
25.1
25.5
26.7
28.2
27.8
27.0
28.5
28.4
29.2
29.8
30.4
30.7
30.7
31.3
31.9
1.0 m
12.3
14.1
15.7
16.1
16.9
18.5
20.8
20.5
19.8
21.7
21.8
22.9
22.4
24.4
24.7
25.3
25.9
27.9
26.9
26.3
28.1
28.0
22.4
29.2
29.6
30.0
30.1
30.7
31.7
C
0.3 m
-
-
-
-
-
22.9
22.3
21.1
24.1
24.8
24.7
24.8
26.9
26.9
27.2
28.2
30.1
28.0
28.4
30.2
30.1
31.1
31.6
32.5
32.0
32.2
32.7
33.0
1.0 m
14.0
16.0
17.0
18.1
18.7
20.4
22.7
22.2
20.9
23.8
24.0
24.4
24.5
26.0
26.4
27.1
27.5
28.8
27.2
28.2
29.8
29.8
30.1
30.9
32.4
31.7
32.0
32.5
32.9
D
0.3 m
-
-
-
-
-
25.1
23.3
22.7
26.0
26.8
27.1
27.0
27.4
27.8
28.2
29.9
32.0
29.6
30.4
32.2
32.2
33.2
33.5
33.7
34.0
33.9
34.5
32.2
1.0 m
15.0
17.8
18.8
19.8
21.1
22.6
25.1
23.0
22.4
26.0
25.9
27.1
26.8
26.6
27.2
28.1
29.2
30.6
28.6
29.8
32.0
31.7
32.5
33.3
33.7
33.8
33.6
34.2
32.1
(continued)
-------
TABLE 3 (continued).
Day
of
Year
195
200
202
207
209
214
216
221
223
228
230
235
237
242
244
A
0.3 m
30.3
29.8
29.6
29.5
28.2
28.5
28.4
29.4
29.6
29.9
28.7
28.6
29.0
28.9
29.4
1.0 m
30.1
29.9
29.6
29.4
28.2
28.4
28.3
29.2
29.3
29.7
28.7
28.5
28.8
28.6
29.1
B
0.3 m
31.9
31.1
31.6
31.7
30.2
30.6
30.2
30.8
30.9
31.6
30.8
30.5
30.7
30.4
30.9
1.0 m
31.4
31.2
31.3
31.3
30.1
30.1
30.0
30.0
30.1
31.0
30.4
30.0
30.2
29.9
30.5
C
0.3 m
32.9
32.4
33.1
33.2
32.2
32.0
31.9
32.9
33.2
33.2
32.1
32.6
32.8
32.7
32.9
1.0 m
32.7
32.5
33.0
33.1
32.2
31.9
31.9
32.7
32.5
33.1
32.1
32.5
32.7
32.7
32.9
D
0.3 m
33.4
32.5
33.0
34.7
33.7
33.7
34.0
34.7
34,8
33.3
34.1
33.6
33.6
33.7
34.3
1.0 m
33.1
32.7
33.0
34.7
33.8
33.6
34.0
34.5
34.0
33.1
34.1
33.5
33.5
33.7
34.3
-------
TABLE 4. REPRESENTATIVE MEAN DAILY SURFACE (0.3 m) AND BOTTOM (1.0 m) WATER TEMPERATURES IN THE LOWER SECTIONS
OF THE EXPERIMENTAL CHANNELS, 1977 (A = AMBIENT, B = +2 C, C = +4 C, D = +6 C).
Day
of
Year
67
70
74
78
88
101
108
116
118
123
125
130
132
139
144
146
151
153
158
160
165
167
172
174
179
181
186
188
190
A
0.3 m
-
-
20.3
18.4
19.6
20.9
22.5
21.0
21.8
24.1
24.5
23.5
26.1
27.3
25.0
25.1
26.5
26.2
28.2
28.6
29.2
29.1
29.2
30.4
29.5
1.0 m
10.0
13.1
13.4
14.1
15.0
15.5
19.3
17.5
18.0
19.9
20.3
20.2
20.2
22.6
23.8
23.4
24.6
25.0
24.5
23.6
26.0
25.6
26.9
27.4
28.1
27.8
28.1
29.4
28.8
0.3 m
!
-
21.8
20.4
20.7
21.9
24.1
22.5
23.2
25.8
25.6
24.6
26.6
29.0
26.0
26.7
28.0
28.2
29.4
29.9
30.4
30.8
30.9
31.4
32.0
B
1.0 m
11.7
13.5
14.0
14.9
16.3
16.6
20.3
19.3
19.1
20.9
21.4
21.2
21.7
24.0
24.0
24.7
25.2
26.3
25.0
25.0
26.9
27.4
27.9
28.5
29.1
29.4
29.4
30.3
30.7
0.3 m
;
-
22.9
21.6
21.8
23.6
25.6
23.8
25.1
26.8
26.9
26.1
27.9
30.5
26.3
26.4
29.4
29.7
31.4
31.7
31.9
31.8
32.2
32,6
32.7
C
1.0 m
11.9
14.9
14.9
16.5
17.3
18.2
21.0
20.0
20.6
22.4
22.3
22.5
23.3
25.0
25.4
25.8
26.7
27.4
25.1
26.1
28.2
28.5
29.4
30.2
30.6
30.6
30,8
31.7
31.6
D
0.3 ra
-
-
24.6
22.6
23.5
25.1
27.2
25.6
27.0
27.3
27.7
26.9
29.5
31.8
27.3
29.4
30.8
31.4
33.2
33.1
33.0
33.1
33.7
34.0
32.0
1.0 m
12.4
15.3
16.0
18.0
17.8
19.2
23.3
21.1
21.6
23.2
23.5
24.2
24.9
25.0
26.2
27.0
27.8
28.3
25.6
27.4
29.7
29.9
30.8
31.5
31.6
31.9
32.3
32.9
30.8
(continued)
-------
TABLE 4 (continued).
Day
of
Year
195
200
202
207
209
214
216
221
223
228
230
235
237
242
244
A
0.3 m
30.8
29.2
29.8
29.5
27.7
28.5
28.2
29.5
29.7
30.2
28.6
28.4
29.2
29.0
29.6
1.0 m
29.7
29.2
29.0
29.0
27.6
27.5
27.7
28.5
28.6
29.1
28.0
27.6
28.2
27.8
28.5
B
0.3 m
32.1
30.5
31.6
31.1
29.2
30.3
29.6
30.9
31.0
31.8
30.4
30.3
30.7
30.4
31.0
1.0 m
30.9
30.7
30.7
31.4
28.8
29.3
29.0
29.0
29.8
30.3
29.6
29.0
29.5
29.1
29.8
C
0.3 m
33.4
31.5
32.7
32.7
30.7
31.6
31.0
32.6
32.7
32.9
31.4
32.2
32.4
32.3
32.5
1.0 m
32.3
31.5
31.9
31.9
30.2
30.7
30.6
31.3
31.5
31.9
30.7
31.2
31.4
31.3
31.6
D
0.3 m
33.4
32.2
32.4
33.9
31.7
33.0
32.2
34.2
34.1
32.2
33.1
33.0
33.0
32.9
33.7
1.0 m
32.3
32.3
31.8
32.4
31.4
32.1
31.5
32.9
32.9
30.9
32.6
32.1
32.2
32.0
32.9
-------
TABLE 5. SUMMARY OF WATER QUALITY CONDITIONS IN BROWNS FERRY EXPERIMENTAL CHANNELS, MARCH TO AUGUST 1977.
Upper Section
Dissolved Oxygen (PPM) @ 0.3 in
Dissolved Oxygen (PPM) @ 0.9 m
PH
Phenolphthalein Alkalanity (PPM)
Total Alkalinity (CaCo3) (PPM)
Total Hardness (CaCo3) (PPM)
Conductivity (Micromhos)
Secchi Disc (cm)
Nonfilterable Residue (PPM)
Underwater Light Photometer
(% Transmit tance) 0.3 m
0.6 m
0.9 m
Nitrate (PPM)
Nitrite (PPM)
Ammonia (PPM)
Min.
5.3
3.9
6.6
0.0
29.5
23.1
50.0
14.0
14.5
7.2
0.6
0.04
0.014
0.007
0.018
Ambient
Mean
7.3
6.7
7.4
0.0
45.3
55.5
120.0
39.0
26.7
33.1
11.9
4.0
0.283
0.014
0.047
Max.
9.7
10.8
7.9
0.0
5.2
64.6
172.0
72.0
49.6
39.0
26.0
10.0
0.651
0.032
0.081
Min.
5.3
1.8
6.6
0.0
31.0
23.1
48.0
13.0
17.7
6.4
0.4
0.02
0.027
0.005
0.019
+2 C
Mean
7.3
7.0
7.5
0.05
46.0
55.5
122.0
38.0
28.9
30.3
9.2
3.0
0.272
0.014
0.051
Max.
9
14
8
0
51
64
174
66
52
48
16
7
0
0
0
.8
.8
.2
.5
.5
.6
.0
.0
.5
.0
.0
.0
.631
.032
.076
Min.
5.0
1.9
6.6
0.0
31.0
23.5
48.0
13.0
18.9
3.4
0.6
0.02
0.017
0.005
0.029
+4 C
Mean
7.2
7.6
7.4
0.0
45.5
55.2
126.0
36.0
33.1
30.0
10.2
3.3
0.276
0.014
0.049
Max.
9.6
16.8
7.8
0.0
51.5
64.1
180.0
57.0
52.1
52.0
20.0
7.0
0.603
0.032
0.066
Min.
3.9
1.8
6.6
0.0
31.0
24.4
46.0
12.0
20.7
10.0
0.5
0.05
0.023
0.005
0.017
+6 C
Mean
7.1
7.0
7.4
0.0
45.7
55.4
125.0
35.0
31.8
27.9
9.6
3.1
0.275
0.014
0.046
Max.
9.7
16.0
7.8
0.0
51.5
64.6
180.0
63.0
53.7
46.0
18.0
6.3
0.059
0.033
0.075
(continued)
-------
TABLE 5 (continued).
CO
Upper Section
Organic Nitrogen (PPM)
Total Phosphate (PPM)
Ortho Phosphate (PPM)
Organic Carbon (PPM)
Biological Oxygen Demand (PPM)
Total Gas Saturation (%)
Saturation - N2+Ar (%)
Lower Section
Dissolved Oxygen (PPM) @ 0.3 m
Dissolved Oxygen (PPM) @ 0.9 m
PH
Phenolphthalein Alkalanity (PPM)
Total Alkalinity (CaCo3) (PPM)
Total Hardness (CaCos) (PPM)
Min.
0.10
0.070
0.029
1.7
0.8
96
98
6.1
3.8
6.7
0.0
33.5
35.1
Ambient
Mean
0.20
0.151
0.062
3.0
1.2
99
103
8.2
8.1
7.8
0.3
47.6
57.6
+2 C
Max.
0.27
0.405
0.097
4.7
1.6
101
107
10.4
16.5
8.7
3.5
53.0
65.0
Min.
0.12
0.080
0.032
1.8
0.3
99
101
5.8
3.9
6.6
0.0
33.5
35.9
Mean
0.
0.
0.
3.
1.
100
103
8.
7.
7.
0.
49.
57.
18
142
062
2
1
5
8
0
6
2
1
Max.
0.20
0.308
0.097
4.9
1.8
103
107
10.6
15.3
8.9
5.0
53.0
65.0
Min.
0.13
0.085
0.029
2.1
1.1
99
101
6.0
3.9
6.7
0.0
33.5
33.8
+4 C
Mean
0.19
0.162
0.066
3.0
1.4
101
105
9.1
9.1
8.0
1.1
49.1
56.8
Max.
0.26
0.428
0.097
4.7
1.9
105
109
13.2
>20.0
8.9
4.5
52.5
65.0
Min.
0.13
0.083
0.034
1.7
0.7
99
99
6.6
0.5
6.7
0.0
34.0
33.8
+6 C
Mean
0.19
0.167
0.066
3.3
1.5
101
104
9.7
9.4
8.0
0.9
49.8
56.8
Max.
0.25
0.428
0.103
6.4
2.1
106
113
13.0
>20.0
9.0
5.0
52.5
64.6
(continued)
-------
TABLE 5 (continued).
Lower Section
Conductivity (Micromhos)
Secchi Disc (cm)
Nonfilterable Residue (PPM)
Underwater Light Photometer
(% Transmittance) 0.3 m
0.6 m
0.9 m
Nitrate (PPM)
Nitrite (PPM)
Ammonia (PPM)
Organic Nitrogen (PPM)
Total Phosphate (PPM)
Ortho Phosphate (PPM)
Organic Carbon (PPM)
Biological Oxygen Demand (PPM)
Total Gas Saturation (%)
Saturation - N2+Ar (%)
Min.
72.0
13.0
3.4
8.2
0.5
0.02
0.020
0.006
0.015
0.12
0.053
0.018
1.8
0.9
96
89
Ambient
Mean
125.0
68.0
12.9
38.8
17.4
7.1
0.264
0.014
0.045
0.18
0.131
0.051
3.2
1.4
100
101
Max
176.
122.
33.
75.
40.
22.
0.
0.
0.
0.
0.
0.
7.
2.
106
105
.
0
0
7
0
0
0
620
032
070
30
310
103
0
1
Min.
72.0
13.0
6.6
6.0
0.4
0.01
0.010
0.005
0.017
0.09
0.550
0.016
1.8
0.4
98
88
+2 C
Mean
126.0
64.5
15.0
36.1
15.3
5.7
0.260
0.014
0.036
0.19
0.128
0.050
3.4
1.4
101
100
Max
176.
122.
37.
52.
28.
14.
0.
0.
0.
0.
0.
0.
8.
2.
107
106
.
0
0
4
0
0
0
618
034
062
33
321
105
0
6
Min.
70.0
13.0
3.5
6.4
0.4
0.01
0.009
0.005
0.005
0.07
0.050
0.018
1.1
0.3
99
85
+4 C
Mean
127.0
66.0
14.0
36.4
16.7
6.8
0.259
0.014
0.036
0.17
0.117
0.050
3.0
1.2
101
98
Max
176.
122.
37.
56.
31.
19.
0.
0.
0.
0.
0.
0.
6.
2.
108
106
.
0
0
4
0
0
0
601
038
061
29
246
110
4
2
Min.
70.0
13.0
3.2
7.4
0.5
0.01
0.023
0.005
0.005
0.12
0.053
0.018
0.8
0.7
99
80
+6 C
Mean
129.0
61.0
14.8
36.8
16.6
5.9
0.263
0.014
0.032
0.18
0.120
0.053
2.8
1.6
102
96
Max.
180.0
96.0
39.0
53.0
29.0
15.0
0.599
0.036
0.072
0.27
0.305
0.113
4.6
3.5
109
105
-------
SECTION 4
PRODUCTION AND BIOMASS OF BLUEGILL AND WALLEYE
INTRODUCTION
Evaluation of temperature requirements of bluegill and walleye is
characterized by contrast. The bluegill is a widely distributed eurythermal
species for which the field and laboratory thermal data base is essentially
complete (Brungs and Jones, 1977). The corresponding data base for walleye,
a coolwater species or temperate mesotherm (Hokanson, 1977), is less
complete. Field observations have pertained primarily to spawning
temperatures, and walleye have received only limited attention in the
laboratory. The most definitive study on growth and survival in relation to
temperature was done in the laboratory by Smith and Koenst (1975).
To some extent, upper tolerance limits for walleye growth and survival
have been inferred on the basis of geographical distribution. Since walleye
are more commonly associated with northern lakes and streams, a general
assumption has been that walleye are excluded from most southern waters
because of higher summer temperatures. However, in review of percid
populations in the southeastern United States, Hackney and Holbrook (1978)
reported that walleye distribution and abundance were relatively independent
of temperature. Also, walleye have been stocked successfully in several
Texas reservoirs (Prentice and Clark, 1978) .
Although records of distribution have application in determining
thermal requirements of a fish species, apparently the most sensitive
function for establishing an upper temperature limit for long-term exposure
is growth (NAS/NAE, 1973; Brungs and Jones, 1977). Since it has been
practically impossible to assess growth in relation to temperature under
field conditions, temperature requirements for growth have usually been
determined in the laboratory (e.g. Brett et al., 1969; McCormick and Kleiner,
1976), although there are exceptions (Bennett and Gibbons, 1974; Bisson and
Davis, 1976). Utilizing large outdoor channels in which temperature
treatments were replicated, the purpose of this phase of the study was to
determine the effect of elevated temperature regimens on the growth of
bluegill and walleye under simulated field conditions during the spring-
summer season. Since the growth success of natural fish populations is
usually measured on the basis of production and biomass, these parameters,
which are a function of both growth and survival, were used to assess the
experimental populations of bluegill and walleye in the channels.
Since walleye are more commonly associated with other prey species
(e.g. yellow perch), walleye-bluegill could be considered an unlikely
20
-------
predator-prey combination; however, it has been reported that walleye will
forage on bluegill and other lepomids (Dendy, 1946; Forney, 1966; Schneider,
1975). Also, in our preliminary studies under ambient temperature conditions
in the channels, juvenile walleye readily utilized young-of-the-year
bluegill (Forsythe and Wrenn, 1978).
MATERIALS AND METHODS
Bluegill and walleye for this study were obtained from the Carbon Hill
National Hatchery (Alabama). Age I bluegill (spawned in late summer 1976)
were from a stock maintained at this hatchery, where the water temperature
normally ranges from 5° C in the winter to 32° C in the summer. The walleye
were obtained initially as sac-fry from Senecaville National Hatchery (Ohio)
and reared for a month at Carbon Hill; origin of the broodstock was
Linesville, Pennsylvania. Bluegill (mean TL 70 mm; mean weight 5 g) were
stocked in the channels on 3 March 1977, and walleye (mean TL 42 mm; mean
weight 0.5 g) were stocked on 13 May 1977. Although the mean weight of the
bluegill was only 5 g, previous experience showed that they would be large
enough (ca. 30 g) to spawn in May. Also, Regier (1963) noted that differ-
ences in the size of bluegill in the fall did not affect the probability
that they would spawn at Age I the following spring. Young-of-the-year
(YOY) bluegill were expected to provide the forage base for the walleye.
Although the bluegill were stocked on 3 March, temperature treatments were
not established until 8 March. Bluegill were stocked 150 (3,125/ha) per
channel or 60 and 90 in the upper and lower sections, respectively. Walleye
numbers stocked in the upper and lower sections of divided channels were 12
(632/ha) and 20 (690/ha), respectively. The undivided channel in each
treatment (regimen) received 32 walleye (667/ha). Stocking densities for
bluegill and walleye were derived, on the basis of maximum walleye growth
and survival, from previous evaluation of stocking rates under ambient
temperature conditions in the channels (Forsythe, 1978). At stocking, the
bluegill in each population were weighed and measured individually, whereas
mean length and weight of walleye were derived from a composite sample. With
one undivided and two divided channels in each of the four temperature
regimens, a total of 20 bluegill-walleye populations were stocked.
To determine growth, each population was sampled monthly by electro-
fishing (pulsed DC; 20 cycles/sec; 150 V AC input; output ca. 2 amperes).
Sample sizes were 10 to 30% of the walleye population and 10% of the
bluegill. Decreases in population numbers were estimated from daily visual
inspection of the channels for dead fish. After 185 days (118 days for the
walleye) the channels were drawn down partially, and the adult bluegill,
walleye, and YOY bluegill were recovered with rotenone. Although precise
limits for the fish growing season are not available for this region, we
assume that the interval of this study covered approximately 90 percent of
the growth season, and therefore, would be representative of the annual
growth or production. Jones et al. (1977) reported that over 90% of the
fish production (seven species, including bluegill and largemouth bass) in a
Texas pond (similar latitude to northern Alabama) occurred from June through
September.
21
-------
Production in this study is defined as the total incremental growth of
fish tissue throughout the duration of the study, including that formed by
individuals which did not survive to the end of the experiment (Ivlev, 1966
as cited by Chapman, 1971). Production (as wet weight) of the adult bluegill
and walleye was estimated numerically according to the Ricker formula (1946),
on the basis of six monthly sampling intervals for bluegill, four for the
walleye, between 8 March and 9 September. For each sampling interval,
production was calculated as:
P = G ¥
where P is production in kg, G is the instantaneous rate of increase in
weight, and B is the mean biomass of the population. Exponentia_l models of
growth and mortality were applied to the calculations of G and B (Chapman,
1971). For the adult bluegill, estimates of mean individual weights and
population numbers were used in the calculation of production for the frist
five intervals, and actual mean weights and numbers of bluegill recovered by
rotenone were used for the last interval. For the walleye, estimates of
mean weight and population numbers were used for the first three intervals
(months), and actual mean weights and numbers were used for the fourth
production interval.
Production (as wet weight) of YOY bluegill in the upper channel sections
of the four temperature regimens was also estimated. These estimates were
calculated by the graphical or Allen method (Chapman, 1971) on the basis of
(1) estimated total numbers of larvae hatched, (2) an intermediate estimate
of larval densities and mean weights, and (3) total numbers and mean weights
of YOY bluegill recovered by rotenone.
The biomass of each population was calculated as the difference between
the biomass of the population stocked and the biomass of the population
recovered at the end of 185 days for the bluegill and 118 days for the
walleye. Biomass of YOY bluegill was the biomass recovered by rotenone at
the end of the study.
BLUEGILL
Total production of adult (Age I) bluegill in the upper channel sections
for the four temperature treatments ranged from 20 g/m2 in the ambient
regimen to 15 g/m2 in the +6 C regimen (Table 6). The highest monthly
production for adults occurred in all treatments during 11 April to 10 May
when production ranged from 6.7 g/m2 in the +2 C regimen to 5.1 g/m2 in the
+4 C regimen. This period preceded the onset of spawning in all treatments
except in the +6 C channels (see Section 5). Combined production of adult
and YOY bluegill in the upper sections ranged from 99 g/m2 (999 kg/ha) in
the +6 C regimen to 75 g/m2 (752 kg/ha) in the +2 C regimen (Table 7).
Population numbers and mean weights of YOY bluegill used to establish the
Allen production curves for the upper sections are presented in Table 8.
Ratios of production (adult plus YOY) to biomass were as follows: ambient -
1.9:1, +2 C - 1.9:1, +4 C - 2.1:1, and +6 C - 2.4:1.
22
-------
TABLE 6. MEAN PRODUCTION STATISTICS OF BLUEGILL IN EXPERIMENTAL CHANNELS. WATER TEMPERATURES IN CHANNELS WERE AMBIENT (WHEELER RESERVOIR, TENNESSEE
RIVER), OR ELEVATED + 2 C, +4 C, +6 C ABOVE AMBIENT IN THE UPPER CHANNEL SECTIONS. WITHIN EACH TEMPERATURE REGIMEN, TWO CHANNELS WERE DIVIDED INTO
UPPER (ISOTHERMAL) AND LOWER (COOLING) SECTIONS, AND ONE CHANNEL WAS UNDIVIDED.
Individual Instantaneous
Time Size Growth
Interval (g) Rate
A +2C +4C +6C A +2C +4C +6C
UPPER SECTION
8 Mar 6575
8 Mar-10 Apr 13 13 21 18 0.72 0.83 1.02 1.04
11 Apr-10 May 26 28 32 29 0.73 0.76 0.42 0.49
11 May- 8 Jun 44 48 48 47 0.54 0.58 0.42 0.50
9 Jun-10 Jul 63 63 57 57 0.34 0.25 0.16 0.17
11 Jul- 8 Aug 69 64 60 54 0.10 0.02 0.05 -0.12
9 Aug- 8 Sept 70 62 58 57 0.02 -0.03 -0.03 0.06
Totalb
Population Biomass Production
Numbers3 (g) (g/m2)
A +2C +4C +6C A +2C +4C +6C A +2C +4C
60 60 60 60
60 60 60 60 540 540 825 705 2.05 2.36 4.43
60 60 59 59 1,155 1,159 1,565 1,365 4.44 4.64 3.46
59 59 59 58 2,046 2,211 2,325 2,208 5.81 6.75 5.14
58 58 59 58 3,112 3,250 3,083 3,005 5.57 4.28 2.60
57 58 59 56 3,802 3,723 3,421 3,144 2.00 0.39 0.90
58 52 57 55 4,002 3,450 3,408 3,046 0.42 -0.54 -0.54
20 18 16
+6C
3.86
3.52
5.81
2.69
-1.98
0.96
15
a Mean of 2 replicates in upper and lower sections rounded to whole fish.
b Production value rounded to nearest gram.
(continued)
-------
TABLE 6 (contioued).
Individual
Time Size
Interval ($>)
A +2C +4C -1-6C
LOWER SECTION
8 Mar 6565
8 Mar-10 Apr 13 17 21 19
11 Apr-10 May 29 27 33 29
11 May- 8 Jun 47 53 52 53
9 Jun-10 Jul 64 59 57 57
11 Jul- 8 Aug 63 61 52 56
9 Aug- 8 Sept 66 62 55 56
Totalb
UNDIVIDED
8 Mar 5665
Instantaneous
Growth Population Biomass Production
Rate Numbers3 (g) (g/m2)
A +2C +4C +6C A +2C +4C +6C A +2C +4C +6C A +2C +4C +6C
90 90 90 90
0.76 1.04 1.18 1.15 90 90 90 90 838 968 1,193 1,058 2.20 3.47 4.85 4.19
0.80 0.50 0.44 0.43 89 89 89 89 1,783 1,932 2,363 2,064 4.92 3.33 3.58 3.06
0.48 0.69 0.49 0.64 89 89 88 88 3,321 3,474 3,734 3,516 5.50 8.27 6.31 7.76
0.24 0.11 0.09 0.07 83 88 87 88 4,491 4,959 4,767 4,823 3.72 1.88 1.48 1.16
0.09 0.03 -0.09 -0.01 79 88 86 88 5,076 5,287 4,704 4,963 1.57 0.64 -1.46 -0.17
0.01 0.01 0.06 0.001 69 81 79 80 4,878 4,992 4,408 4,700 0.17 0.17 0.15 0.02
18 18 15 16
150 150 150 150
a Mean of 2 replicates in upper and lower sections rounded to whole fish.
' Production value rounded to nearest gram.
(continued)
-------
TABLE 6 (continued).
Time
Interval
UNDIVIDED
8 Mar-10
11 Apr-10
11 May- 8
to
9 Jun-10
11 Jul- 8
9 Aug- 8
Total
Individual
Size
(S)
A +2C +4C +6C
Instantaneous
Growth Population Biomass
Rate Numbers3 (g)
Production
(g/m2)
A +2C +4C +6C A +2C +4C +6C A +2C +4C +6C A +2C
+4C
+6C
(continued)
Apr
May
Jun
Jul
Aug
Sept
13 15 20 20
33 43 34 36
55 55 55 53
56 62 62 68
60 61 55 63
60 60 57 60
0.84 0.81 1.06 1.22 150 150 150 150 1,350 1,575 1,950 1,875 2.36 4
0.93 1.05 0.53 0.59 149 149 149 149 3,208 3,972 3,943 4,068 6.22 8
0.53 0.25 0.50 0.40 147 148 149 149 6,430 7,270 6,564 6,596 7.09 3
0.02 0.11 0.11 0.23 145 145 149 149 8,101 8,531 8,717 9,015 0.34 1
0.07 -0.02 -0.12 -0.08 141 144 148 147 8,289 8,886 8,677 9,690 1.21 -0
0 -0.02 0.04 -0.05 118 138 128 132 7,750 8,530 7,710 8,573 0 -0
17 18
.40
.69
.79
.96
.37
.36
4.31
4.35
6.84
2.00
-0.36
-0.32
17
4.77
5.00
5.50
4.32
-1.62
-0.89
17
Mean of 2 replicates in upper and lower sections rounded to whole fish.
° Production value rounded to nearest gram.
-------
TABLE 7. PRODUCTION AND BIOMASS OF ADULT AND YOUNG-OF-THE-YEAR (YOY)
BLUEGILL IN UPPER SECTIONS OF EXPERIMENTAL CHANNELS (MARCH-SEPTEMBER).
WATER TEMPERATURES WERE AMBIENT (WHEELER RESERVOIR, TENNESSEE RIVER)
OR ELEVATED +2 C, +4 C, and +6 C ABOVE AMBIENT.
Temperature Production,1 kg/ha Biomass,1 kg/ha
Regimen
Adult2 YOY Total
Ambient 200 687 887
+2 C 178 574 752
+4 C 177 632 809
+6 C 159 840 999
% YOY Adult YOY Total % YOY
77 195 270 465 58
76 155 224 378 59
78 155 216 371 58
84 144 269 413 65
Mean of two replicates.
ry
Age I bluegill stocked in channels in March.
26
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TABLE 8. EXAMPLES OF POPULATION SIZES (IN THOUSANDS) AND MEAN WEIGHTS (G)
OF YOUNG-OF-THE-YEAR BLUEGILL USED TO PLOT ALLEN PRODUCTION CURVES FOR
UPPER CHANNEL SECTIONS.
Temperature
Regimen
Ambient
+2 C
+4 C
+6 C
Bluegill larvae Intermediate YOY bluegill
hatched3 population"3 recovered
No. Wt. No. Wt. No. Wt.
343 - 20 0.03 9.4 0.55
355 - 20 0.03 11.6 0.36
485 - 20 0.03 13.0 0.31
500 - 20 0.03 8.3 0.61
Calculated on basis of number of nests with eggs and 5,000 larvae per nest;
mean weight plotted as zero.
Peak density of post larvae as determined from net tows.
27
-------
Biomass of adult bluegill in the upper channel sections ranged from 195
kg/ha in the ambient channels to 144 kg/ha in the +6 C regimen, while biomass
in both the intermediate treatments (+2 C and +4 C) was 155 kg/ha (Table 9).
Mean biomass of adults between treatments in the upper sections was
significantly different but there was not significant linear regression
(analysis of variance with regression, P <_ 0.05). However, the total biomass
of adult plus YOY bluegill in the upper sections, which ranged from 465
kg/ha at ambient to 371 kg/ha in the +4 C regimen (Table 7), was not
significantly different between treatments (analysis of variance, P <_ 0.05).
In the lower sections of the two divided channels within each treatment,
mean biomass of adult bluegill, which ranged from 144 kg/ha in the +2 C
regimen to 132 kg/ha in the +4 C regimen, was not significantly different
between temperature regimens (P £ 0.05). However, while the biomass of YOY
bluegill and the total biomass were significantly different, there was no
apparent relation to temperature since biomass was lowest in the +4 C and
+2 C regimens with 256 and 278 kg/ha, respectively. The biomass of both
adult and YOY bluegill in the upper sections was significantly higher than
that in the lower sections of the divided channels (t-test, P 5. 0.05).
Biomass of adult bluegill in the undivided channels (one channel per
treatment) ranged from 156 kg/ha in the +2 C regimen to 131 kg/ha in the
ambient regimen. Total biomass of adults plus YOY ranged from 260 kg/ha in
the +4 C regimen to 364 kg/ha in the +6 C regimen.
Temperature treatments had no apparent effect on survival of adults.
Mean survival of the adult bluegill in the upper sections ranged from 97% in
the ambient regimen to 88% in the +2 C regimen after 185 days (Table 9).
While in the lower sections, survival ranged from 89% in the +6 C regimen to
77% in the ambient channels, and survival in the undivided channels ranged
from 92% in the +2 C regimen to 79% in the ambient channel. The lower
survival rate of bluegill in the lower sections and undivided channel of the
ambient regimen was attributed to an outbreak of gill lice (Ergasilus sp.) .
From the observed mortalities and the numbers of bluegill recovered by
rotenone at termination of the study, the mean percent of recovery of the
original adult stocks for the 20 populations was 92.2% (range 84 to 100%).
Mean individual weight gain of bluegill (sexes combined) surviving for
the duration of the test ranged from 64 g in the ambient regimen (upper
section) to 49 g in the lower sections of the +4 C regimen; the specific
growth rates (%/day) were 1.32 and 1.19, respectively (Table 9). Males were
larger than females; at termination of the study, mean weight of males and
females was 68 g and 51 g, respectively. Also, mean weight of females
(62 g) in the ambient regimen (upper section) was significantly higher than
the mean weight for females in the elevated regimens (t-test, P < 0.05).
Mean weight of males between treatments was not significantly different.
Male to female sex ratios of the bluegill recovered at the end of the
experiment were as follows: 1:1.2 (ambient), 1.3:1 (+2 C), 1:1 (+4 C), and
1.1:1 (+6 C). The initial sex ratio (M:F) for all populations was 1:1.1, as
determined by dissecting a sample (57) of the composite stock upon arrival
from the hatchery.
28
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TABLE 9. MEAN GROWTH, SURVIVAL, AND BIOMASS OF AGE I BLUEGILL IN 12 EXPERIMENTAL CHANNELS FOR 185 DAYS (MARCH-SEPT.). WATER
TEMPERATURES IN CHANNELS WERE AMBIENT (WHEELER RESERVOIR, TENNESSEE RIVER) OR ELEVATED + 2 C, +4 C, OR +6 C ABOVE AMBIENT IN THE
UPPER CHANNEL SECTIONS. WITHIN EACH TEMPERATURE REGIMEN, TWO CHANNELS WERE DIVIDED INTO UPPER (ISOTHERMAL) AND LOWER (COOLING)
SECTIONS, AND ONE CHANNEL WAS UNDIVIDED.
Upper Section
Parameter
Length increase (nun)
Weight increase (g)
Specific growth rate
(•at.) (%/day)
Specific mortality rate
(%/day)
Survival %
Yield (kg/hectare)
(± 1 SD)
A
77
64
1.32
0.02
97
195
(2.8)
+ 2C
70
57
1.36
0.07
88
155
(17.6)
+4C
65
51
1.14
0.02
96
155
(7.1)
+6C
67
52
1.31
0.05
91
144
(14.1)
A
74
61
1.39
0.14
77
141
(17.7)
Lower Section
+2C
70
57
1.36
0.09
84
144
(8.5)
+4C
65
49
1.19
0.07
88
132
(1.4)
+6C
68
51
1.30
0.06
89
140
(2.8)
Undivided
A +2C
68 69
55 54
1.34 1.24
0.12 0.04
79 92
131 156
-
+4C
70
51
1.21
0.08
85
136
-
+6C
72
55
1.34
0.07
88
150
-
-------
WALLEYE
After 118 days, mean biomass of walleye from the upper channel sections
ranged from 36 kg/ha in the ambient regimen to 0 kg/ha in the highest regimen
(+6 C), in which none of the walleye survived to the end of the test (Table
10). Ambient temperature conditions exceeded 28° C for 78 days, and the
maximum was 30° C for about 5 days (Fig. 2, Section 3). Biomass from the
upper sections of the intermediate temperature regimens, +2 C and +4 C,
decreased to 28 and 18 kg/ha, respectively. With the exception of the +6 C
regimen, the mean biomass between treatments in the upper sections were not
significantly different but the decline in biomass was significant (analysis
of variance with regression P <_ 0.05). Also, there were no significant
differences in biomass between treatments for the lower sections. With the
exception of the +6 C treatment, there were no significant differences in
biomass from upper and lower sections within treatments. Biomass from the
undivided channels, similar to that for the lower sections, ranged from 26
kg/ha in the +2 C and +4 C regimens to 20 kg/ha in the +6 C regimen. Maximum
temperatures at which walleye survived and continued to grow (Table 11) were
32-33° C which occurred for about 75 days in the upper sections of the +4 C
regimen; similar thermal conditions also occurred in the lower sections of
the +6 C regimen.
Production estimates followed the same trend as that for biomass in the
upper sections in that production was highest (5.5 g/m2) in the ambient
temperature regimen, intermediate (3.9 g/m2) in the +4 C regimen, and lowest
(2.8 g/m ) in the +6 C regimen (Table 11). In the lower sections and
undivided channels, production was not indicative of biomass in every case,
e.g. production in the undivided channels was highest in the ambient regimen
(5.1 g/m2 or 51 kg/ha), but the biomass (21 kg/ha) was next to the lowest
for the four temperature regimens.
Production at the end of the first month (13 May-8 June) was progress-
ively higher in the elevated temperature regimens (Table 11). In the upper
sections, production in the +6 C regimen was 1.1 g/m2 or more than twice
that from the ambient regimen (0.4 g/m2). However, at the end of the third
month (8 August). production estimates for the ambient regimen (upper
section) (2.3 g/m2) exceeded that in the +6 C regimen by 1.4 g/m2. Any
change in production for the +6 C treatment (upper section) after 8 August
was not accounted for since no walleye were recovered from this treatment at
the end of the test. Walleye production was also greater initially in the
other elevated temperature regimens, but production in the ambient channels
eventually equaled or exceeded this early gain.
Based on the actual numbers of walleye recovered after 118 days,
survival in all treatments was overestimated (Table 11) for the first three
production intervals which would cause production to be overestimated also.
Although we believe that the unaccounted mortalities (or possibly escapement)
occurred when the walleye were very small (40-50 mm, TL), no attempt was
made to distribute these missing fish in estimating production. Unaccounted
fish were essentially the same among treatments.
30
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TABLE 10. MEAN GROWTH, SURVIVAL, AND BIOMASS OF WALLEYE LN 12 EXPERIMENTAL CHANNELS FOR 118 DAYS (HAY-SEPT.). WATER TEMPERATURES
IN CHANNELS WERE AMBIENT (WHEELER RESERVOIR, TENNESSEE RIVER) OR ELEVATED +2 C, +4 C, or +6 C ABOVE AMBIENT IN THE UPPER CHANNEL SECTIONS.
WITHIN EACH TEMPERATURE REGIMEN, TWO CHANNELS TORE DIVIDED INTO UPPER (ISOTHERMAL) AND LOWER (COOLING) SECTIONS, AND ONE CHANNEL WAS UNDIVIDED.
Upper Section
Parameter
Length increase3 (mm)
Weight increase (g)
Specific growth rate
(wt.) (%/day)
Specific mortality rate
(%/day)
Survival (%)
Yield (kg/hectare)
(± 1 SD)
A
175
90
4.40
0.41
63
36
(8.4)
+ 2C
175
88
4.37
0.52
54
29
(11.3)
+4C +6C
141 147b
61
4.07 -c
0.66
46 0
18 0
(6.6)
A
178
88
4.38
0.63
48
25
(2.9)
Lower Section
+2C
167
77
4.27
0.54
53
28
(2.8)
+4C
153
66
4.14
0.63
48
21
(1.6)
+6C
146
65
4.13
0.59
50
22
(0.6)
Undivided
A +2C
168 162
78 70
4.27 4.18
0.76 0.49
41 56
21 26
— •*
+4C
151
68
4.16
0.49
56
26
~
+6C
132
57
4
0
53
20
—
.01
.54
a Initial mean length (TL) - 42 mm; mean wt. - 0.5 g.
Mean length (TL) of 3 dead walleye recovered in mid-August.
c Not computed, no walleye surviving at end of test.
-------
TABLE 11. MEAN PRODUCTION STATISTICS OF WALLEYE IN EXPERIMENTAL CHANNELS. WATER TEMPERATURES IN CHANNELS WERE AMBIENT (WHEELER RESERVOIR, TENNESSEE
RIVER) OR ELEVATED +2 C, +4 C, +6 C ABOVE AMBIENT IN THE UPPER CHANNEL SECTIONS. WITHIN EACH TEMPERATURE REGIMEN, TWO CHANNELS WERE DIVIDED INTO
UPPER (ISOTHERMAL) AND LOWER (COOLING SECTIONS, AND ONE CHANNEL WAS UNDIVIDED.
Individual Instantaneous
Time Size Growth Population Biomass
Interval (g) Rate Numbers3 (g)
A +2C +4C +6C A +2C +4C +6C A -t-2C +4C -t-6C A +2C +4C +6C
UPPER SECTION
13 May 0.5 0.5 0.5 0.5 12 12 12 12
13 May-8 Jun 5 9 10 12 2.66 3.25 3.38 3.66 12 12 12 11 30 46 51 61
9 Jun-10 Jul 24 34 26 24 1.47 1.31 0.92 0.63 12 12 12 11 174 255 210 204
11 Jul-8 Aug 62 58 53 42 0.95 0.52 0.73 0.56 12 12 11 10 479 544 439 337
9 Aug-8 Sept 91 87 62 0 0.38 0.42 0.15 0 7760 708 610 454 0
Total
LOWER SECTION
13 May 0.5 0.5 0.5 0.5 20 20 20 20
13 May-8 Jun 5 98 13 2.66 3.27 3.10 3.71 20 20 20 20 50 77 70 108
9 Jun-10 Jul 28 32 26 35 1.57 1.23 1.14 0.95 20 20 19 19 330 400 323 463
Production
(g/m2)
A +2C +4C +6C
0.42 0.79 0.91 1.17
1.35 1.76 1.02 0.68
2.39 1.49 1.68 0.99
1.42 1.35 0.36 0
5.58 5.38 3.96 2.84
0.46 0.87 0.75 1.38
1.79 2.17 1.27 1.52
a Mean of 2 replicates in upper and lower sections rounded to whole fish.
(continued)
-------
TABLE 11 (continued).
Time
Interval
Individual
Size
(K)
+2C +4C+6C
Instantaneous
Growth
Rate
Population
Numbers3
+2C
+4C
+6C
+2C +4C +6C
Biomass
(g)
+2C +4C +6C
Production
(g/m2)
+2C
+4C
+6C
LOWER SECTION, Continued
11 Jul-8 Aug 61 58 41 59
9 Aug-8 Sept 82 77 60 65
Total
0.81 0.61 0.48 0.54
0.28 0.28 0.38 0.10
20 20 19 19 858 869 633 890
10 11 10 10 951 974 677 857
2.40 1.83 1.05 1.66
0.92 0.94 0.89 0.30
5.57 5.34 3.95 4.87
Oo
Co
UNDIVIDED
13 May
13 May-8 Jun
9 Jun-10 Jul
11 Jul-8 Aug
0.5
7
28
59
9 Aug-8 Sept 78
Total
0.5 0.5 0.5
7 13 14
27 32 36
57 40 58
70 68 57
3.05 3.05 3.76 3.84
1.30 1.27 0.84 0.89
0.75 0.75 0.22 0.48
0.28 0.21 0.53 -0.02
32 32 32 32
32 32 32 32 105 105 178 190
32 32 31 31 560 544 704 782
32 32 31 29 1,392 1,285 1,111 1,380
13 18 18 17 1,406 1,525 1,231 1,292
0.66 0.66 1.40 1.53
1.52 1.43 1.24 1.44
2.16 2.00 0.52 1.37
0.82 0.65 1.36 -0.05
5.16 4.75 4.51 4.29
a Mean of 2 replicates in upper and lower sections rounded to whole fish.
-------
Mean survival of walleye after 118 days ranged from 63% in the upper
sections of the ambient regimen to no survival in the upper sections of the
+6 C regimen (Table 10). The last observed mortality in the +6 C regimen
was 15 August; four additional mortalities occurred in this treatment from
22 July to 15 August. No moribund or distressed walleye were observed prior
to the finding of dead specimens. Average minimum temperatures during this
interval ranged from 33.6° to 34.7° C. Mean survival for the five walleye
populations in the ambient regimen was 50%, essentially the same as that
(52%) in all elevated regimens, except the +6 C treatment. Mean individual
weight gain of walleye surviving for the duration of this test ranged from
91 g in the ambient regimens (upper sections) to 57 g in the undivided
channels at the +6 C regimen, while the respective specific growth rates
(%/day) ranged from 4.40 to 4.01 (Table 10).
DISCUSSION
Maximum elevated temperatures, which ranged from ca. 31° to 34° C for
more than 70 days in the upper channel sections, had no significant effect
on production and biomass of the experimental bluegill populations in this
study. Although production and biomass of the adult stocks were less in the
elevated treatments, there were compensatory increases in production and
biomass by YOY bluegill (Table 7). Production, which ranged from 999 kg/ha
in the +6 C regimen to 752 kg/ha in the +2 C regimen, was greater than the
revised estimate of bluegill production (625 kg/ha) in a thermally unaltered
lake (Gerking, 1962; Mahon, 1977). The high YOY production (840 kg/ha) in
the +6 C channels resulted from the earlier onset of spawning (by a month)
which yielded a greater total number of spawns, 3.3 per female as opposed to
2.5 per female in the ambient channels (see Section 5). Since the eggs may
comprise up to 13% of the total biomass of female bluegill (Toetz, 1967),
the longer spawning season was considered to be a factor in reducing adult
production in the +6 C treatment (159 kg/ha vs. 200 kg/ha in the ambient
channels). Biomass from the elevated temperature regimens (e.g. 413 kg/ha
in the +6 C regimen) was comparable to the relatively high standing stocks
associated with bass-bluegill ponds (Swingle, 1950).
In general, the effect of temperature on bluegill in the present study
was similar to results obtained in the laboratory. Lemke (1977) reported
that maximum bluegill growth over a 30-day interval was highest at 30° C but
that growth was not significantly different at temperatures ranging from 22°
to 34° C. Also, adult and YOY bluegill tolerated temperatures that
approached 35° C in the highest regimen (+6 C), which is within the tolerance
limit reported by Stauffer et al. (1976). The survival rate was 0.91 in the
+6 C regimen which was considered to be comparable to the 0.70 survival of
Age II bluegill (1 May-1 Nov.) in a natural population (Ricker, 1945).
The ambient temperature regimen in the channels, typical of summer
temperatures in mainstream reservoirs of the Tennessee River, had no apparent
adverse effect on the biomass of experimental populations of juvenile
walleye. Carlander (1977) reported that the biomass of walleye in three
lakes under 100 hectares averaged 26.8 kg/ha; mean biomass of walleye in 23
North American lakes was 16 kg/ha. Mean biomass of the five walleye
populations held at ambient temperatures in the channels was 28 kg/ha. Mean
34
-------
individual growth (total length > 200 mm) in the ambient regimen was equal
to the rapid growth reported for walleye in Norris Reservoir and other
southeastern waters (Stroud, 1949; Hackney and Holbrook, 1978). The mean
specific mortality rate (0.60%/day) was within the range of natural
mortality rates determined for juvenile walleye in Oneida Lake (Forney,
1971). In general, the survival and growth of walleye in the ambient regimen
were comparable to the results obtained with walleye in Texas reservoirs
(Prentice, 1977; Prentice and Dean, 1977; Prentice and Clark, 1978). Their
results showed that survival, growth and harvest of stocked walleye could be
expected in almost all Texas reservoirs, where growth of Age I walleye
ranged from 267-454 mm. Mid-summer temperatures in these reservoirs
generally ranged from 27-30° C (J. A. Prentice, personal communication).
The significant relationship to temperature was that self-sustaining walleye
populations could not be maintained if temperatures during the spawning
season exceeded 12° C.
The upper channel sections of the elevated temperature regimens were
considered to simulate conditions that would occur if the temperature
increased in an entire water body such that cooler refuge areas would not be
available to the walleye. After 118 days, mean individual size of walleye
in the +2 C and +4 C regimens was less than that for walleye in the ambient
regimen, and no walleye survived to the end of the test in the +6 C regimen
(Table 10). Obviously, the total mortality in the +6 C regimen was
ecologically significant; however, the significance of the reduced size of
walleye in the +4 C regimen was not clear since the size attained by walleye
in this treatment was not abnormal (mean TL 183 mm and weight 62 g). Under
conditions similar to those in the channels (abundant forage and no competing
fishes). Walker and Applegate (1976) reported that walleye attained a mean
length of 167 mm and weight of 41 g in a 12.5 hectare pothole in South
Dakota (13 June-13 September).
Effects of temperature on walleye growth and survival in the upper
sections contrasted to results obtained by Smith and Koenst (1975) under
laboratory conditions. They reported that the optimum temperature for
growth of juvenile walleye in a 28-day experiment was 22° C and that the
incipient lethal temperature (50% mortality) was 31.6° C; the temperature
for zero net growth was 29° C as extrapolated by Hokanson (1977). Ambient
temperatures in the channels were near or above 29° C for the last 75 days
of the experiment and the average minimum temperature in the +4 C regimen
exceeded 29° C for 95 days. According to the interval production statistics
(Table 11), walleye in both the ambient and +4 C regimen were growing during
these periods. The upper lethal temperature for walleye in the channels
(+6 C regimen, upper section) was about 34° C although this was not
determined on the basis of 50% mortality. Differences in the results
between the laboratory and channel studies probably were due to the lower
acclimation temperature (26° C) and the direct transfer technique in
handling the fish that were employed in the laboratory study (Hokanson,
1977).
Thermal conditions in the undivided channels were considered to
simulate thermal plumes such as those associated with heated discharges from
power plants. In this case, the highest temperature in the plume would
35
-------
occur in 40% of the mixed water body (channel), but the walleye were not
prevented from seeking cooler zones along a thermal gradient or vice versa.
Although the mean size of walleye attained after 118 days in the elevated
regimens was less (8 to 21 g) than that in the ambient channel, the biomass
which reflected both growth and survival was about equal to or higher than
that in the undivided ambient channel (Table 10). Apparently, the thermo-
regulatory behavior of walleye (Ferguson, 1958; Hokanson, 1977) enabled the
population in the undivided channel of the +6 C regimen to avoid the lethal
temperatures (ca. 34° C) for walleye confined to the upper channel sections
in this treatment. Average minimum temperatures in the lower section of the
+6 C regimen ranged from 32° to 33° C during the period (22 July-15 August)
when lethal conditions were apparently reached in the upper section. Based
on the interval production statistics between 10 July and 8 August (Table
11), growth occurred during this interval in both the lower divided sections
and the undivided channel in the +6 C regimen.
Although the juvenile stage is perhaps the most thermally tolerant
stage in the life cycle of percids, with walleye being the least tolerant
(Hokanson, 1977), results from the present channel experiment indicated that
walleye were more thermally tolerant than previously considered. Thermal
tolerance of walleye in this study was more similar to that determined for
young yellow perch (Perca flavescens) (McCormick, 1976) . Although there may
be differences in the thermal tolerance of different genetic strains, there
was no intent to test this hypothesis although a northern stock of walleye
was used in the present study. However, the experimental channels would be
appropriate for evaluating different geographical or genetic stocks of
walleye.
36
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REFERENCES
Bennett, D. H. and J. W. Gibbons. 1974. Growth and condition of juvenile
largemouth bass from a reservoir receiving thermal effluents. In
Thermal Ecology, J. W. Gibbons and R. R. Sharitz (Eds.), AEC Symposium
Ser. (CONF-730505). pp. 246-254.
Bisson, P. A. and G. E. Davis. 1976. Production of juvenile chinook
salmon, Oncorhynchys tshawygtscha, in a heated model stream. Fishery
Bulletin, 74(4): 763-774.
Brett, J. R., J. E. Shelbourn, and C. T. Shoop. 1969. Growth rate and
body composition of fingerling sockeye salmon, Oncorhynchus nerka, in
relation to temperature and ration size. J. Fish. Res. Board Can.
26: 2363-2394.
Brungs, W. A. and B. R. Jones. 1977. Temperature criteria for freshwater
fish: protocol and procedures. U.S. Environ. Prot. Agency, Duluth,
MN. EPA-600/3-77-061. 130 pp.
Carlander, K. D. 1977. Biomass, production, and yields of walleye
(Stizostedion vitreum vitreum) and yellow perch (Perca flavescens) in
North American lakes. J. Fish. Res. Board Can. 34(10): 1602-1612.
Chapman, D. W. 1971. Production. Pages 199-214. In W. E. Ricker, ed.
Methods for assessment of fish production in freshwaters. IBP Handbook
No. 3, 2nd ed., Blackwell, Oxford, and Edinburg.
Forney, J. L. 1966. Factors affecting first-year growth of walleyes in
Oneida Lake, New York. New York Fish and Game Jour. 13(2): 146-167-
Forney, J. L. 1971. Analysis of year class formation in a walleye
population. Federal Aid Project F-17-R, Rep. Job I-a, N.Y. State
Dept. Environ. Conserv.
Forsythe, T. D. 1978. Predator-prey interactions among crustacean
plankton, young bluegill (Lepomis macrochirus), and walleye (Stizostedion
vitreum vitreum) in experimental ecosystems. Ph.D. Thesis, Mich.
State Univ., East Lansing. 98 pp.
Forsythe, T. D. and W. B. Wrenn. 1978. Predator-prey relationships
among walleye and bluegill in experimental ecosystems. In H. Clepper,
ed. An International Symposium on Predator-Prey Systems in Fish
Communities and Their Role in Fisheries Management (in press) .
Gerking, S. D. 1962. Production and food utilization in a population
of bluegill sunfish. Ecol. Monogr. 32: 31-78.
Hackney, P. A. and J. A. Holbrook III. 1978. Sauger, walleye, and
yellow perch in the southeastern United States. Pages 74-81. In
R. L. Kendall, ed. Symposium on Selected Coolwater Fishes of North
America. Special Publ. No. 11, Amer. Fish. Soc., Washington, D.C.
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Hokanson, K.E.F. 1977- Temperature requirements of some percids and
adaptations to the seasonal temperature cycle. J. Fish. Res. Board
Can. 34(10): 1524-1550.
Jones, F. V., W. D. Pearson, and L. C. Fitzpatrick. 1977. Production
of a fish taxocene in a Texas pond. Env. Biol. Fish. 2(3): 241-259.
Lemke, A. E. 1977. Optimum temperature for growth of juvenile bluegills.
Prog. Fish-Cult. 39(2): 55-57.
Mahon, R. 1977. A second look at bluegill production in Wyland Lake,
Indiana. Environmental Biol. of Fishes. 1(1): 85-86.
McCormick, J. H. 1976. Temperature effects on young yellow perch,
Perca flavescens (Mitchell). U.S. Environ. Prot. Agency, Duluth, MN.
EPA-600/3-76-057. 18 pp.
McCormick, J. H. and C. F. Kleiner. 1976. Growth and survival of
young-of-the-year emerald shiners (Notropis atherinoides) at different
temperatures. J. Fish. Res. Board Can. 33(4): 839-842.
Prentice, J. A. 1977. Statewide walleye stocking evaluation. Federal
Aid Project F-31-R-3, Texas Parks and Wildl. Dept. 45 pp.
Prentice, J. A. and W. J. Dean, Jr. 1977. Effect of temperature on
walleye egg hatch rate. Proc. Southeast. Game and Fish Comm., Vol. 31
(in press).
Prentice, J. A. and R. D. Clark, Jr. 1978. Walleye fishery management
program in Texas - a systems approach. Pages 408-416. In R. L. Kendall,
ed. Symposium on Selected Coolwater Fishes of North America. Special
Publ. No. 11, Amer. Fish. Soc., Washington, B.C.
Regier, H. A. 1963. Ecology and management of largemouth bass and
bluegills in farm ponds in New York. N.Y. Fish and Game J. 19(1): 1-
89.
Ricker, W. E. 1945. Natural mortality among Indiana bluegill sunfish.
Ecology, 26(2): 111-121.
Ricker, W. E. 1946. Production and utilization of fish populations.
Ecol. Monogr. 16: 373-391.
Smith, L. L., Jr. and W. M. Koenst. 1975. Temperature effects on eggs
and fry of percoid fishes. U.S. Environ. Prot. Agency, Duluth, MN.
EPA-660/3-75-017. 91 pp.
Stauffer, J. R., Jr., K. L. Dickson, J. Cairns, Jr., and D. S. Cherry.
1976. The potential and realized influences of temperature on the
distribution of fishes in the New River, Glen Lyn, Virginia. Wildlife
Monogr., No. 50. 40 pp.
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Stroud, R. H. 1949. Growth of Norris Reservoir walleye during the
first 12 years of impoundment. J. Wildl. Mange. 13(2): 157-177.
Swingle, H. S. 1950. Relationships and dynamics of balanced and unbalanced
fish populations. Bull. 274, Agric. Exp. Station, Auburn, Alabama.
Toetz, D. W. 1967. The importance of gamete losses in measurements of
freshwater fish production. Ecology 48: 1017-1020.
Walker, R. E. and R. L. Applegate. 1976. Growth, food, and possible
ecological effects of young-of-the-year walleyes in a South Dakota
prairie pothole. Prog. Fish-Cult. 38(4): 217-220.
39
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SECTION 5
BLUEGILL REPRODUCTION
INTRODUCTION
Reproduction of bluegill (Lepomis macrochirus) has been studied
extensively throughout the geographical range of this species, but maximum
temperatures associated with these natural spawning populations were usually
less than 30° C (Carlander, 1977). However, Clugston (1966) observed
natural spawning of bluegill at 32° C in southern Florida. In the
laboratory, artificially spawned bluegill eggs were incubated and hatched at
34° C but with 50% mortality (Banner and Van Arman, 1973). Results from
other studies indicate that the hatching success of artificially fertilized
bluegill eggs is less than that for naturally spawned eggs regardless of
temperature (Nakamura et al., 1971; Toetz, 1966).
In conjunction with the evaluation of temperature effects on other
aquatic communities in 12 outdoor, experimental channels, the objectives of
this phase of the experiment were: (1) to evaluate the effects of elevated
temperatures on bluegill reproduction under natural spawning conditions and
(2) to evaluate the effects of temperature on the resulting standing stocks
of young-of-the-year (YOY) bluegill which served as the food source for the
top predator in the channels, juvenile walleye (Stizostedion vitreum
vitreum). Results from previous studies under ambient temperature
conditions showed that bluegill were prolific spawners in the channels and
that YOY standing stocks of 200 to 300 kg/ha could be expected (Forsythe and
Wrenn, 1978).
MATERIALS AND METHODS
The following parameters were used to evaluate bluegill reproduction:
(1) onset and cessation of spawning, (2) hatching success, (3) mean number
of larvae per nest, (4) relative abundance of postlarvae, and (5) biomass
and numbers of YOY bluegill recovered by rotenone. Evaluation of parameters
1, 2, and 3 were limited to the upper channel sections within each
temperature regimen, where nesting substrates were added.
Although bluegill had previously spawned successfully in the channels
which contained two substrates, clay-silt in pool areas and limestone rock
(5-30 cm diameter) in the shallow zones, we anticipated that the addition of
gravel in specific areas would concentrate spawning in those areas and thus
facilitate observations. Smith (1975) reported spawning in two Lepomis
species in aquaria containing pans filled with gravel. In this study, nine
40
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galvanized pans (9.5 cm deep x 42 cm diameter), coated with epoxy paint and
filled with gravel (0.5-2.5 cm diameter), were placed on the rock areas in
the upper section of each channel. In the divided channels, approximately
30 females and 30 males had access to the nest pans, whereas, in the
undivided channel, ca. 75 females and 75 males had access. Pans were placed
adjacent to outer channel walls at a depth of 0.3 m, and the tops of pans
were flush with the bottom contour. To determine the onset and cessation of
spawning these pans were inspected daily with the aid of an underwater
viewer constructed of a piece of clear plastic glued to a 0.6 m section of
7.5 cm diameter PVC pipe.
Hatching success of eggs was determined for a minimum of 10 nests from
each temperature regimen. After the male bluegill had constructed the nest,
three beaker coverglasses (6.4 cm diameter) were placed near the center of
the nest. After spawning had occurred, the coverglasses and adhering eggs
were transferred to a 1-liter wide-mouth plastic jar. The mouth of the jar
was covered with fine-meshed netting and replaced adjacent to the nest.
After 48 hours the jar was removed from the channel, and the newly hatched
larvae and dead eggs were counted to determine percent hatch.
We found in preliminary trials that it was practically impossible to
count or estimate the eggs per nest; however, it was possible to remove the
nest pan and count the larvae that hatched. The entire pan of gravel was
washed through a series of sieves. The larvae were recovered and placed in
a beaker to which water was added to make a volume of 300 ml. The larvae
were counted in five 10-ml subsamples, and the mean was used to compute the
total number of larvae per nest.
Relative abundance of postlarval bluegill was determined from biweekly
tows with a No. 10 plankton net (153 y mesh), mouth diameter 30 cm. The
frame of the net was mounted on a pole and horizontal tows were taken just
below the surface in pool areas of the channels. The distance towed was
25.6 m in the upper channel sections and 39.3 m in the lower sections.
Assuming 80% filtering efficiency (Cummins et al., 1969), the volume
filtered was 1.45 and 2.22 m3, respectively. All samples were collected
between 2200 and 2400 hr CDT.
Biomass and total number of YOY bluegill in each population were
determined when all fish were removed with 3 mg/liter rotenone (9 September),
RESULTS
Bluegill readily spawned in the gravel-filled pans and seemed to prefer
this substrate rather than the clay-silt or larger limestone rocks. In the
upper sections of the divided channels, the pans appeared to be used
exclusively for nesting sites. In the undivided channels, which also had
pans only on the first two rock areas, the pans were used extensively but
spawning was also observed on rock areas without pans. Spawning usually
occurred between 0900 and 1500 hours. Initially, males constructed nests as
long as one week before eggs were deposited, but later in the season nest
construction preceded spawning by only one or two days. Numerous nests were
constructed in which spawning did not occur; however, individual nest sites
41
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were used repeatedly at irregular intervals throughout the summer in all
four temperature regimens. On nine occasions, two separate nests were
observed within a single pan.
Spawning occurred first in the +6 C regimen on 28 April at 23° C.
Spawning began in the +4 C, +2 C, and ambient regimens on 5 May, 9 May, and
24 May at respective temperatures of 24°, 23°, and 24° C. Spawning
continued throughout the summer and ended during the last week of August in
all temperature regimens (Fig. 3). Cessation of spawning was confirmed by
examining the gonads of bluegill recovered at the end of the experiment on
9 September. Maximum temperatures at which spawning was observed in the
four temperature regimens of ambient, +2, +4, and +6 C were 30.8°, 32.1°,
33.4°, and 34.2° C, respectively.
A grand total of 1,049 nests with eggs were observed. The total in the
upper sections of the two divided channels in each temperature treatment
was: ambient - 137, +2 C - 142, +4 C - 194, and +6 C - 200. Adding the
number of nests from the undivided channels, there was a total of 217, 199,
319, and 314 observed spawns in the respective treatments. Assuming there
were 30 females in each upper section of a divided channel, the mean number
of spawns per female in the respective temperature regimens was: 2.3, 2.4,
3.2, and 3.3. We saw no relationship between temperature and the period of
time between spawns per female. Male to female sex ratios of the adult
bluegill recovered from the upper sections at the end of the experiment were
as follows: 1:1.2 (ambient), 1.3:1 (+2 C), 1:1 (+4 C), and 1.1:1 (+6 C).
Hatching Success
Bluegill eggs hatched at temperatures ranging from 23° to 34° C. Mean
hatching success was 95% (range 76-99) and there appeared to be no
relationship between hatching success and temperature (Fig. 4). The
incubation period ranged from 24 to 40 hours; however, any relationship with
temperature was not quantified since it was often difficult to determine the
exact time of spawning. Mean number of prolarvae per nest, on the basis of
18 nests sacrificied, was 5,939 (range 1,118-14,484). The estimated mean
total number of larvae produced (number of nests X mean number of larvae) in
upper sections of the divided channels ranged from 406,000 in the ambient
regimen to 593,000 in the +6 C regimen (Table 12).
The size of 50 fertilized eggs (1-3 hrs old) was as follows: total
diameter 1.7 ± 0.23 mm, yolk diameter 1.01 ± 0.06 mm, and oil droplet
diameter 0.29 ± 0.03 mm. Total length of 50 newly hatched larvae was 3.45
± 0.11 mm. Based on measurements of 14 specimens, larvae at swim-up had a
total length of 4.89 ± 0.25 mm. Larvae remained in the nest from 2 to 4
days before swim-up. As water temperature increased, larvae absorbed yolk
materials sooner and spent less time in the nest; however, no attempt was
made to quantify this relationship.
Relative Abundance and Biomass
Peak densities of postlarval bluegill as determined from net tows
ranged from 50/m in the +2 C channels to 150/m in the ambient channels.
42
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or
lOr
co
I- 5
CO
UJ
0
'0
0
AMBIENT
\\ \N
+4C
+6C
APR I MAY I JUN I JUL I AUG
Figure 3. Mean number of bluegill nests with eggs (per 5-day interval) in the upper sections of
divided experimental channels for four temperature regimens, ambient (Tennessee River), and +2'
+4°, and +6° C above ambient.
-------
100
x
o
LJ
O
o:
LJ
CL
75
50
(25)
(12)
(2)
f
22-23 24-25 26-27
TEMPERATURE, °C
31-32
33-34
Figure 4. Hatching success of bluegill eggs in experimental channels,
vertical lines denote range. Number of nests observed in ( ).
44
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TABLE 12. TOTAL LARVAE PRODUCED AND STANDING STOCKS OF YOUNG-OF-THE-YEAR
BLUEGILL RECOVERED FROM UPPER CHANNEL SECTIONS.
Temperature
Regimen3
Ambient
+2 C
+4 C
+6 C
Total No.
Nestsb
75
62
74
68
80
114
87
113
No . Larvae
Produced
(X 1000)
445
368
439
403
475
677
516
671
No.
8,499
10,368
10,812
12,552
14,182
11,910
8,293
8,354
Standing Stock
Biomass, kg/ha
246
294
179
268
272
160
272
265
Ambient temperature of Wheeler Reservoir, Tennessee River, or elevated
+2, +4, and +6° C.
Mean number of larvae per nest - 5,939.
45
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The mean peak density was ca. 100/m3 for all temperature regimens. Since
there was approximately 200 m3 of water in an upper section, estimated peak
abundance was 20,000 in these sections. Mean total length of larvae
captured in tow nets was 5.69 ± 0.98 mm (range 5-11 mm).
Although spawning continued throughout most of August in all tempera-
ture regimens, drastic declines in the number of postlarval bluegill
captured in net tows occurred in each treatment. These declines, which
occurred in the same sequence as the onset of spawning, i.e. +6, +4, +2, and
ambient, were attributed to intense predation on eggs and swim-up larvae by
the larger juvenile bluegill. Nest predation became intense in the four
temperature regimens on the following dates: +6 C - 29 June, +4 C - 5 July,
+2 C - 15 July, and ambient - 27 July. Juveniles were observed feeding in
nests, and stomachs of juveniles (15-30 mm TL) captured adjacent to nests
contained as many as several hundred eggs and larvae.
Mean biomass of YOY bluegill recovered from the upper channel sections
ranged from 4.1 kg (216 kg/ha) in the +4 C regimen to 5.2 kg (270 kg/ha) in
the ambient regimen (Table 12). Mean number recovered ranged from 13,046
(686,000/ha) in the +4 C regimen to 8,323 (438,000/ha) in the +6 C
treatment. In the lower sections of the two divided channels in each
treatment, mean biomass ranged from 3.6 kg (123 kg/ha) in the +4 C channels
to 6.4 kg (220 kg/ha) in the ambient channels. In the undivided channels,
biomass ranged from 5.9 kg (124 kg/ha) in the +4 C regimen to 10.3 kg (214
kg/ha) in the +6 C regimen. Statistical analyses of the biomass between
treatments are presented in Section 4.
DISCUSSION
Although considerable variation is seen in the reproductive timing
mechanisms of teleosts, photoperiod and temperature have been the most
frequently studied environmental factors (De Vlaming, 1972) . This author
also noted that a confounding factor in evaluating photoperiod and
temperature is that photoperiodism seems to be temperature-sensitive in the
majority of species studied. Stevenson et al. (1969) reported that
temperature was the key environmental factor controlling bluegill reproduc-
tion in an Ohio pond. For the pumpkinseed, Lepomis gibbosus, Burns (1976)
indicated that spring recrudescense was controlled by temperature but that
fall cessation was not. Our results also indicated that initiation of
spawning for bluegill was controlled by temperature and that the cessation
of spawning, which occurred the last week of August (Fig. 3), was not.
However, Clugston (1973) collected ripe bluegill from a reactor cooling
reservoir throughout the year and concluded that spawning can occur during
almost any month of the year if the water temperature has been above 20° C.
Since our study was concluded on 9 September, we can only speculate that
spawning could have resumed later in September or October; however, from
November through March we cannot maintain temperatures above 20° C at this
facility.
In the present study, mean daily temperatures that .reached 34° C did
not inhibit spawning, and the minimum temperature at which spawning occurred
was 23° C (further results obtained in 1978 indicate that spawning was not
46
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inhibited at 37° C). Periods of decreasing water temperatures inhibited
nesting activity and at times caused males to desert nests in all
temperature regimens. In June, a temperature drop of 3° to 4° C (from 30°
to 26° C) in the +6 C channels, disrupted nesting activity and several nests
suffered mortalities of eggs or larvae. Hunter (1963) also observed a
decline in spawning activity of Lepomis cyanellus when water temperatures
were decreasing.
On the basis of 50% mortality, the upper and lower temperatures for
hatch of normal bluegill fry in the laboratory was 33.8° and 21.9° C,
respectively (Banner and Van Arman, 1973) . Our results showed a 95%
hatching success of normal fry at ca. 34° C. Factors that may have
attributed to this higher hatching success were: (1) acclimation temp-
erature of adults, (2) method of fertilization, and (3) conditions during
incubation. The adult bluegill in the channels were acclimated to the same
temperature (34° C) at which spawning occurred; whereas, in the laboratory
study, the adults were acclimated at 26° C prior to spawning. As opposed to
natural fertilization of eggs in the channels, eggs in the laboratory were
stripped from females receiving harmone injections and artificially
fertilized. Various experiments with the artificial fertilization of
bluegill eggs have yielded a hatching success of 50% under normal temp-
erature conditions (Nakamura et al., 1971; Smitherman and Hester, 1962;
Toetz, 1966). A third factor which may have enhanced hatching success of
natural spawns in the channels was that numerous invertebrates, including
amphipods (Hyalella azteca and Crangonyx sp.) , were present in the nest
pans. Oseid (1977) reported that amphipods (Asellus militaris and Gammarus
pseudoliimaeus) eliminated fungus-related mortalities on embryos of white
sucker (Catostomus cornmersoni) and walleye.
Multiple spawning by female bluegill, which we observed in the present
study, has been observed under laboratory conditions. Nakamura et al.
(1969) reported that female bluegill spawned 4 or 5 times during one
breeding season. The highest mean number of spawns per female in our study
was 3.3 which occurred in the +6 C regimen. However, in one of the
replicates at this treatment females apparently spawned 4 to 5 times. From
60 bluegills stocked initially, 19 females and 31 males were recovered at
the end of the study. Five females died during the course of the study.
The number of nests with eggs observed in this channel was 113.
Although the total number of spawns was highest in the upper sections
of the +4 and +6 C channels, the biomass of YOY recovered was not
significantly different between treatments (Table 12). Since hatching
success was not inhibited by temperature in any of the elevated temperature
regimens, other factors were apparently involved in equalizing the standing
stocks. Walleye predation pressure may have been greater in the higher
treatments; however, in the +6 C regimen (upper sections) all the walleye
had apparently succumbed to the high temperatures by mid-August. We
concluded that the greatest impact on reducing the YOY biomass in channels
with the higher total spawns, was the intense predation by juveniles on the
eggs and larvae. Apparently the number of larvae surviving through the
swim-up stage was inversely proportional to the number of larger juveniles
in each population. Therefore, any advantage that was gained by the earlier
47
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spawning, and thus a greater number of spawns, in the warmer temperature
regimens was negated by this intense predation. This density-dependent or
"compensatory" mortality is common for many species of fish (Ricker, 1954;
Nikolskii, 1962).
Standing stocks of YOY bluegill in the upper sections of the channels
divided by screen barriers (2-mm mesh) was significantly higher than those
in the lower sections (see Section 4). This was considered to be a barrier-
effect rather than temperature. These differences were probably influenced
by two factors, spawning substrate and food supply. Gravel-filled nest
pans, which appeared to be used exclusively when available, were placed only
in the upper sections. Apparently this provided an optimum substrate for
spawning that enhanced larval survival. The second factor was food supply.
Zooplankton densities were also higher in the upper sections of the divided
channels (see Section 6). Larval fish densities have been correlated with
food supply in various studies (Crawford, 1923; Emig, 1966; Hall et al.,
1970).
In summary, we conclude that: (1) initiation of spawning was
controlled by temperature and spawning occurred earlier in the elevated
temperature regimens, (2) temperature had no direct effect on numbers and
biomass of YOY bluegill recovered, (3) there was no relationship between
number of spawns and biomass of YOY bluegill recovered, and (4) YOY bluegill
provided an abundant food source for the walleye.
48
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REFERENCES
Armitage, B. J., T. D. Forsythe, E. B. Rodgers, and W. B. Wrenn. 1978.
Browns Ferry Biothermal Research Series I. Colonization by periphyton,
zooplankton, and macroinvertebrates. U.S. Environ. Prot. Agency,
Duluth, Minn. EPA-600/3-78-020, 46 pp.
Banner, A. and J. A. Van Arman. 1973. Thermal effects on eggs, larvae,
and juveniles of bluegill sunfish. U.S. Environ. Prot. Agency, Duluth,
Minn. EPA-R3-73-041, 111 pp.
Burns, J. R. 1976. The reproductive cycle and its environmental control
in the pumpkinseed, Lepomis gibbosus (Pisces: Centrarchidae). Copeia
1976(3): 449-455.
Clugston, J. P. 1966. Centrarchid spawning in the Florida Everglades.
Quart. J. Florida Acad. Sci., 29: 137-143.
1973. The effects of heated effluents from a nuclear
reactor on species diversity, abundance, reproduction, and movement of
fish. Ph.D. Dissertation, Univ. Georgia. 104 pp.
Cummins, K. W., R. R. Costa, R. E. Rowe, G. A. Moshiri, R. M. Scanlon,
and R. K. Zajdel. 1969. Ecological energetics of a natural population
of the predaceous zooplankton Leptodora kindtii (Focke) (Crustacea:
Cladocera). Oikos 20: 189-223.
Crawford, D. R. 1923. The significance of food supply in larval
development of fishes. Ecology 4(2): 147-153.
De Vlaming, V. L. 1972. Environmental control of teleost reproductive
cycles: A brief review. J. Fish. Biol. 4: 131-140.
Emig, John W. 1966. Bluegill sunfish. In Inland Fisheries Management
(Alex Calhoun, ed.). California Dept. Fish and Game, pp. 375-391.
Forsythe, T. D. and W. B. Wrenn. 1978. Predator-prey relationships amon£
walleye and bluegill in experimental ecosystems. In H. Clepper (ed.),
An International Symposium on Predator-Prey Systems in Fish Communities
and Their Role in Fisheries Management, Atlanta, GA, July 1978 (in
press).
Hall, D. J., W. E. Cooper, and E. E. Werner. 1970. An experimental
approach to the production dynamics and structure of freshwater animal
communities. Limnol. Oceangr., 15(6): 839-929.
Hunter, J. R. 1963. The reproductive behavior of the green sunfish,
Lepomis cyanellus. Zoologica 48(1): 13-24.
49
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Nakamura, N. , S. Kashara, and T. Yada. 1969. Studies on the usefulness
of the bluegill sunfish, Lepomis macrochirus, as an experimental
standard animal, I. On the breeding habits. J. Fac. Fish, and Animal
Husbandry, Hiroshima Univ., 8(1): 1-11.
t s. Kashara, and T. Yada. 1971. Studies on the usefulness
of the bluegill sunfish, Lepomis macrohirus, as an experimental standard
animal, II. On the development stages and growth from the egg through
one year. J. Fac. Fish, and Animal Husbandry, Hiroshima Univ., 10(2):
140-151.
Nikolskii, G. V. 1962. On some adaptations to the regulation of
population density in fish species with different types of stock
structure. pp. 265-280, In The Exploitation of Natural Animal
Populations (Le Cren, E. D. and M. W. Holdgate, eds.), B.E.S. Symp.
No. 2, Oxford: Blackwell.
Oseid, M. 1977. Control of fungus growth on fish eggs by Asellus
militaris and Gammarus pseudolimnaeus. Trans. Amer. Fish. Soc.,
106(2): 192-195.
Ricker, W. E. 1954. Stock and recruitment. J. Fish. Res. Bd. Can.,
11(5): 559-623.
Smith, W. E. 1975. Breeding and culture of two sunfish, Lepomis cyanellus
and L. megalotis, in the laboratory. Prog. Fish-Cult., 37(4): 227-
229.
Smitherman, R. 0. and F. Eugene Hester. 1962. Artificial propagation
of sunfishes, with meristic comparisons of three species of Lepomis
and five of their hybrids. Trans. Amer. Fish. Soc., 91(4): 333-341.
Stevenson, F., W. T. Momot, and F. J. Svoboda, III. 1969. Nesting
success of the bluegill, Lepomis macrochirus (Rafinesques), in a small
Ohio farm pond. Ohio J. Sci., 69(6): 347-355.
Toetz, D. W. 1966. The change from endogenous to exogenous sources of
energy in bluegill sunfish larvae. Invest. Indiana Lakes and Streams,
7(4): 115-146.
50
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SECTION 6
ZOOPLANKTON
INTRODUCTION
The impact of heated water discharges from electrical generating plants
on zooplankton communities in reservoirs is difficult to assess in the
field. Utilizing large-scale microcosms, a series of temperature-controlled
experiments are planned in an attempt to elucidate the ecological
consequences of elevated temperature regimens on zooplankton communities.
These are the findings of the first elevated temperature study, whereby
temperature was incremented above ambient at 2°, 4°, and 6° C for a 185-day
period beginning in March 1977. Crustacean zooplankton were studied from
March through August 1977.
Prior to this study a two year study was conducted to determine the
impact of bluegill predation on zooplankton community structure (Forsythe,
1978). Cladocerans such as Daphnia, S.imocephalus, Ceriodaphnia, and Bosmina
were always abundant in the absence of bluegill predation or when predation
pressure was not intense. With increasing intensity of bluegill predation
pressure, Daphnia quickly disappeared, Ceriodaphnia became very rare,
Simocephalus was significantly reduced in numbers, and Bosmina maintained a
sizable population density. With further increases in bluegill predation,
the ostracod Physocypria and the copepod Mesocyclops became the dominant
taxa. Bluegill predation can become so intense that zooplankton community
biomass is held low, species diversity is low, and bluegill begin feeding on
vegetation. Only in the presence of a piscivore which could control young
bluegill numbers was zooplankton community biomass and species diversity
able to reach proportions similar to natural reservoir conditions.
The purpose of this study was to determine gross effects of elevated
temperature regimens on crustacean zooplankton community structure.
Subsequent studies will take a more mechanistic approach to determine cause/
effect relationships.
Although many controlled experiments have been conducted to study the
effects of elevated temperature on single zooplankton populations, only one
study assessed changes in zooplankton community structure under controlled
temperature conditions. Carlson (1974) treated replicate outdoor microcosms
(small plastic swimming pools) to temperature increments of 5°, 7°, 14°, and
21° C above ambient and observed changes in the community composition of
pond plankton inoculations over a 35-day period. His ambient temperature
averaged 21° C and the four treatments averaged 25°, 27°, 31°, and 42° C.
51
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In general, he noted a marked reduction in community density for the 14° C
treatment above ambient and total mortality in the 21° C treatment above
ambient. The 5° C treatment above ambient had the greatest zooplankton
diversity and density; however, these were only slightly higher than the
ambient's diversity and density. It is unlikely that the results of
Carlson's study could be used to predict the ecological consequences of
similar elevated temperatures in the field because (1) the duration of the
study was relatively short (35 days); (2) the microcosms were small, lending
to "enclosure effects"; and (3) most important, the microcosms lacked
predation pressure by fish that zooplankton communities in nature encounter.
The results of the present study are the most comprehensive produced to
date under controlled experimental conditions because: the channels are
large compared to other microcosms; fish predation pressure was a force
interacting with temperature stress; and the studies ran for 185 days.
MATERIALS AND METHODS
Descriptions of the experimental channels, the heated water treatments,
and the stocking of bluegill and walleye are given in other sections of this
report.
Prior to this study, zooplankton were studied in the channels for three
years under ambient temperature conditions (Armitage et al., 1978 and
Forsythe, 1978). The primary problem associated with studying zooplankton
communities in shallow-water environments is that of obtaining representative
samples. The channels each contained five pools and five shallow rock
areas; therefore, there were two habitat-types and ten microhabitats. Among
these microhabitats the zooplankton exhibited considerable spatial and
temporal variability in their distribution patterns within a channel.
During daylight hours as much as ninety percent of the zooplankton community
biomass was found concentrated within 20 cm of channel walls, pool bottoms,
and rock areas. These areas contained dense growths of filamentous algae
and, in the case of pool bottoms, Chara was often present. After sunset
most of the zooplankton populations migrated from the daytime habitats to
become fairly evenly distributed throughout the pools and remain dispersed
as such until sunrise.
Several types of sampling gear were tested. The most practical and
efficient means of sampling was to tow a plankton net horizontally over the
entire length of a channel. This method was further modified by mounting a
30-cm diameter (mouth opening) plankton net on a wooden pole (Forsythe,
1978)„ An 80-y mesh net sampled most zooplankton taxa but usually became
excessively clogged before the length of one channel could be sampled. A
153-y mesh net sampled most of the microcrustacean species but was
ineffective at sampling planktonic rotifers and copepod nauplii. The 153-y
mesh net was selected for this study because the zooplankton community
biomass was dominated by microcrustaceans and these plankters were the major
food items consumed by young bluegill produced in the channels.
52
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Several twenty-four hour sampling studies were conducted prior to this
study with the objective of developing a sampling scheme which would give
representative and quantitative estimates of microcrustacean community
composition and population densities with a minimal amount of sampling and
enumeration effort. These twenty-four hour studies were conducted quarterly
for one year. Each study consisted of taking four replicate samples in a
channel at two-hour intervals for twenty-four hours. Two subsample counts
were made on each sample. The variance components from an analysis of
variance for total microcrustacean densities showed 84% of the experimental
variance was due to the hour-of-day the samples were taken, 7% was due to
sampling replication error, and 8% was due to subsampling and counting error
(Forsythe, 1978). Therefore, the most representative and quantitative
samples could be collected at night, a time when most zooplankton species
migrated into open water from daytime habitats where they were concentrated
near channel structure and algal vegetation.
For the present study, zooplankton were collected biweekly and at three
hours after sunset. Replicate sampling and subsample counting were
considered unnecessary because the major source of error was the time of
sampling. Initially, the entire length of each channel was sampled, even
though eight of the twelve channels were partitioned with 2-mm mesh screens
(see Sections 3 and 4 of this report). It was assumed the screens would not
partition zooplankton populations within a channel, however, by June the
density and species composition of microcrustaceans were noted to differ in
the upper and lower sections of the four partitioned channels. The sampling
was modified so that the upper and lower sections of each channel were
sampled, giving two samples per channel rather than just one. Undivided
channels were sampled in the same manner as the divided channels.
The plankton net filtering efficiency was determined to be 80% and the
volumes filtered for upper, lower, and whole channel samples were
calculated to be 1.4, 2.2, and 3.6 m3, respectively.
Identification and enumeration of zooplankton was made using an
inverted microscope and a plankton counting chamber designed to hold a 5-ml
subsample. The samples were preserved in formalin and brought to a volume
of 100 ml before subsampling.
Cladocerans and cyclopoids were identified to species except for some
chydorids which were taken only to genus. Calanoids were rare, except for
one species, and were not identified. Ostracods were identified to genus.
Micrometer measurements of dominant taxa were made periodically to obtain
mean body-sizes.
Population densities were calculated by assuming an even distribution
of zooplankton at the time of sampling and no plankton net avoidance by the
zooplankters. Densities (reported as number/m ) were converted to biomass
using literature dry-weight values in relation to mean body-size as
determined in other studies (Hall et al., 1970; Dumont et al., 1975).
Community and population biomass was reported as mg/m (dry-weight).
Shannon-Weaver diversity was calculated for each sample on each sampling
date.
53
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RESULTS
Before the channels were constructed, it was postulated that the
channels would not colonize with an abundance of zooplankton because of the
flow-through design. It was assumed that the species present would
primarily be limnoplanktonic forms pumped from the reservoir. However, the
channels colonized with a diverse assemblage of limnozooplankton, heleo-
zooplankton, and benthic forms soon after they were put in operation in 1974
(see Armitage et al., 1978).
A list of the crustacean zooplankton taxa observed from the March
through August 1977 study shows that the taxa generally considered to be
heleozooplankton and benthic forms far outnumbered the limnozooplankton
forms (Table 13). The dominant species coming into the channels (intake
sampling) from the reservoir were Diaphanosoma sp., Daphnia retrocurva,
Diaptomus sp., Bosmina longirostris, and Mesocyclops edax. Only the latter
two species were abundant in channel samples. The density of crustacean
zooplankton in the channels was always greater than incoming densities by
orders of magnitude.
The five most abundant zooplankton populations collected during the
study period were the same five taxa in all twelve channels (Fig. 5). The
combined densities of the copepod-Afesocyclops edax, the ostracod-Physocypria
sp., and the cladocerans-Bosmina longirostris, Chydorus sphaericus, and
Simocephalus vetulus made up about 75% of the total crustacean zooplankton
densities in each channel when densites on each sampling date (14 dates)
were averaged to give mean abundances over the study period. The combined
densities of Mesocyclops and Physocypria made up 50% of the total zooplankton
density in each temperature treatment.
Fluctuation in population density of the five most abundant taxa
exhibited slight differences in the timing and the magnitude of population
peaks (Fig. 6). Temporal synchrony in the dicyclic population maxima of
Bosmina was observed for all four temperature treatments, suggesting these
plankters come primarily from the reservoir and are influenced little by
elevated temperature once in the channels.
Simocephalus exhibited population maxima two months earlier in all
three elevated temperature treatments compared to the ambient channels (16
March vs. 18 May).
Chydorus population maxima occurred two weeks earlier in all three
elevated temperature treatments compared to ambient channels (19 May vs.
3 June) with the maximum densities similar in magnitude for all four
treatments.
Physocypria exhibited dicyclic population maxima in all four treatments
with the first maxima peak coinciding with that for Chydorus. The second
density maxima occurred on 20 July in all four treatments.
Mesocyclops became abundant on 3 June in all four treatments and
remained abundant for the duration of the study.
54
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TABLE 13. ZOOPLANKTON TAXA OBSERVED IN CHANNELS OVER STUDY PERIOD AND
MEAN DRY WEIGHT (yg) PER INDIVIDUAL.
Major
Group
Cladocera
Copepoda
Ostracoda
Group Taxa
Daphnidae
Ceriodaphnia guadrangula
C. reticulata
Daphnia ambigua
D. catawba
D. laevis
D. parvula
D. pulex
D. retrocurva
Moina affinis
Scapholeberis kingi
Simocephalus serrulatus
S. vetulus
Sididae
Diaphanosoma brachyurum
D. leuchtenbergianum
Latona setifera
Latonopsis occidental is
Sida crystallina
Bosmlnidae
Bosmina longirostris
Macro thricidae
Macrothrix rosea
Ilyocryptus spinifer
Chydoridae
Alona affinis
A. costa
A. karua
A. monocantha
A. quadrangula
A. rectangula
Camptocercus rectirostris
Chydorus globosus
C. sphaericus
Disparalona rostrata
Euryalona occidental is
Eurycercus lamellatus
Kurzia latissima
Leydigia leydigi
L. acanthocercoides
Pleuroxus denticulatus
Cylopoida
Cyclops bicuspidatus thomasi
C. vernalis
Eucyclops agilus
E. prionophorus
E. speratua
Macrocyclops albidus
Mesocyclops edax
Copepodites
Calanoida
Osphranticum labronectum
Diaptomus sp.
Cypridae
Cypridopsis sp.
Physocypria sp.
Stenocypris sp.
Dry
Weight
2.0
2.0
8.0
10.0
18.0
10.0
14.0
12.0
5.0
3.0
12.5
12.5
4.0
4.0
9.0
9.0
9.0
1.4
2.0
3.0
1.8
1.8
1.8
1.8
2.2
1.8
4.0
4.0
1.4
1.8
5.0
15.0
5.0
6.0
6.0
2.0
8.0
8.0
8.0
8.0
8.0
15.0
8.5
3.0
15.0
10.0
6.0
6.0
10.0
55
-------
AMBIENT
LU
o:
2°C
4°C
6°C
DIVIDED CHANNEL
DIVIDED CHANNEL
UNDIVIDED CHANNEL
MESO CYC LOPS ED AX
PHYSOCYPRIA SP.
BOSMINA LONGIROSTRIS
CHYDORUS SPHAERICUS
SIMOCEPHALUS VETULUS
MISCELLANEOUS SPECIES
0 246 8 10
AVERAGE NUMBER CRUSTACEANS PER METER3 x 10
12
Figure 5. Mean zooplankton densities for each channel over the study
period and the proportions of the five most abundant taxa.
56
-------
Although the species diversity was generally highest in the ambient
temperature channels and lowest in the highest temperature treatment (+6 C),
the difference was not statistically significant when comparing the mean
diversities over the study period (X ± SD; T = 2.42 ± 0.29 vs. T6 = 2.24 ±
0.30; t-test, P > .05) (Fig. 3). The patterns of diversity fluctuations
among treatments were remarkably similar over the study period. In each
temperature treatment there was an increase in diversity during May with a
maximum diversity in early June followed by a sharp decline.
The zooplankton counts were converted to biomass and combined into the
three taxonomic groups of Cladocera, Copepoda, and Ostracoda. Cladocera
consisted of about 15 taxa, Copepoda were represented mostly by six
cyclopoids and one calanoid (Osphranticum labronectum). Ostracoda were
mostly Physocypria with some Cypridopsis and very rarely Stenocypris. The
temporal trend in these three groups show Cladocera was the dominant group
during March, April, and May in each treatment but thereafter was the least
abundant group (Fig. 7).
The temporal trends in total zooplankton standing crops show dicyclic
maxima for the communities exposed to each temperature regimen (Fig. 7).
The timing of the first maximum was two weeks sooner in all three elevated
temperature regimens in relation to that in the ambient treatment (18 May
vs. 3 June). The second maximum occurred on 20 July in all four treatments.
The first peak was caused by increases in numbers of cladocerans. After
May., the zooplankton community was overwhelmingly dominated by Mesocyclops
and Physocypria in all four treatments.
The following results pertain to comparisons of upper and lower channel
sections of divided and undivided channels. Figure 8 depicts the total
zooplankton standing crops (averages for the June, July, and August period)
and the average percentages contributed by the two dominant taxa,
Physocypria sp. and Mesocyclops edax. Densities of the two taxa were
compared directly (paired t-test) and percent abundances were compared after
an arcsin transformation was made. Total zooplankton abundance (mean number
m~3) was significantly higher (P < .001) in the upper sections of the eight
divided channels than in the lower sections across all treatments (Fig. 8).
Abundance in the upper section of the four undivided channels were not
significantly (P > .05) different from their respective lower sections.
There were considerable differences in the proportions of Mesocyclops
and Physocypria among the respective upper and lower sections of the
channels (Fig. 8). In all upper sections of the eight divided channels,
Mesocyclops were significantly (P < .001) greater than Physocypria. In all
lower sections of the eight divided channels, Physocypria was significantly
(P < .01) more abundant than Mesocyclops. In the upper and lower sections
of the four undivided channels, abundance of these two taxa were not
significantly different. Although the mesh size (2-mm) of the screens that
divided the channels was large enough to allow both Mesocyclops and
Physocypria to pass through the dividers, apparently the dividers did act to
isolate the two populations.
57
-------
AMBIENT
+ 2°C
4°C
6°C
MESOCYCLOPS
.— ; |
Figure 6. Time-series plots of mean densities per treatment for the five
most abundant zooplankton taxa.
58
-------
ro
E
\
o:
LU
CD
16,000
I2.0OO
3 8,000
CO
LU
Q
4,000
TOTAL ZOOPLANKTON
-•- \MESOCYCLOPS 3 PHYSOCYPRIA
M A : M J J ' A
M I A ! M J J A
M ' A ' M ' J ' J A
"MA ' M u ' j ! A'
__1 r
V
M A M J J A
Figure 7, Time-series plots of Shannon diversity, community biomass composition, and total
zooplankton density for each treatment.
-------
UPPER SECTIONS
LOWER SECTIONS
AMBIENT
+ 2°C
H
•^
LU
UJ
ee
4°C
DIVIDED CHANNEL
DIVIDED CHANNEL
UNDIVIDED CHANNEL
MESOCYCLOPS EDAX
PHYSOCYPRIA SP.
MISCELLANEOUS SPECIES
0 2 4 6 8 10 12 0 2 4 6 8 10 12
AVERAGE NUMBER CRUSTACEANS PER METER3 x I03
Figure 8. Mean zooplankton densities during June - August in the upper and lower channel sections of
divided and undivided channels. Proportions represented by the two most abundant taxa are indicated.
-------
Linear regression analysis was used to test for trends across treatment
levels for zooplankton mean density and Shannon diversity averaged over the
June-July-August period. For the upper and lower sections of the divided
channels there was a statistically significant decreasing linear trend in
zooplankton mean density with increasing temperature elevation (ANOVA with
regression; P < 0.05); however, no such trend existed for the undivided
channel (Fig. 9). Shannon diversity in the upper sections of the divided
channels was greater in all heated channels than in ambient channels but a
linear increasing trend was not found (P < 0.25). In the lower sections of
the divided channels, zooplankton diversity was inversely related to
temperature elevation (P < 0.1). Diversity trends were not evident in the
upper or lower sections of the undivided channels.
DISCUSSION
There were few clearly defined temperature treatment effects on the
zooplankton communities. Elevated temperature regimens produced no effect
on total zooplankton densities or species composition of the five most
abundant taxa (Fig. 10). Carlson (1974) also noted a lack of response by
zooplankton communities to temperature elevations of 7° C above ambient.
He did observe adverse effects from a 14° C temperature rise.
In this experiment, cladocerans were the most abundant zooplankters
early in the study (March, April, May) but they decreased sharply as
Mesocyclops and Physocypria increased. This pattern was similar in all four
treatments and is attributed to increasing bluegill predation pressure due
to continually increasing recruitment over time. In an earlier study at
ambient temperatures (Forsythe, 1978), the same temporal changes in
zooplankton community structure occurred in channels with bluegill, whereas
in channels without fish, cladocerans dominated throughout the study period
(May to October). When bluegill predation pressure is absent or of small
magnitude, cladocerans apparently can out-compete copepods and ostracods.
Cladocerans were the preferred prey of young bluegill (Forsythe, 1978) and
only when cladoceran densities were reduced due to predation were Mesocyclops
and Physocypria able to establish sizable populations. The elevated
temperature regimens in the present study (+2 C, +4 C, and +6 C) did not
cause detectable changes in these predation-competition patterns.
Slight differences in the temporal maxima of some zooplankton
populations were noted, but overall the responses of the five dominant
populations were remarkably similar with respect to synchrony of density
fluctuation as well as magnitudes of population maxima among temperature
regimens. Carlson (1974) noted approximate synchronization in population
maxima, irrespective of temperature treatments up to 7° C above ambient for
Daphnia ambigua, Schpholebris kingi, and Ceriodaphnia quadrangula
populations.
Numerous laboratory and field studies have shown that brood-time
intervals and maturation times for many zooplankton species are inversely
related to environmental temperature. Such findings, however, do not prove
that elevated temperatures will necessarily increase zooplankton production
61
-------
• UPPER SECTIONS
O LOWER SECTIONS
DIVIDED CHANNELS
12,000 -
Q 8,000
a.
8
N
4,000
AMBIENT
2°C
+ 4°C
+ 6°C
12,000
8,000
4,000
UNDIVIDED CHANNELS
O
AMBIENT + 2°C
+ 4°C
-6°C
3.0
tfi
oz
u
a 2.0
z
o
z
1.0
AMBIENT
2«C
3.0 r
2.0
1.0
AMBIENT +2°C
6°C
„ . n rr j TEMPERATURE TREATMENT LEVELS
figure y. Irends across treatments for mean zooplankton density and mean
Shannon diversity, June - August, for upper and lower-channel sections
of divided and undivided channels.
62
-------
MEAN DENSITY 6975 8228 5875 6334
(NO./m3 ± ISO) (957) (2542) (752) (202)
lOOr
tu
o
z
<
Q
Z
^
CD
O
o:
UJ
CL
50
OL
OTHER TAXA
CHYDORUS
SIMOCEPHALUS
BOSMINA
PHYSOCYPRIA
MESOCYLOPS
A +2°C +4°C + 6°C
TREATMENT
Figure 10. Mean zooplankton density per treatment over the study period
and the proportions contributed by the five most abundant taxa.
63
-------
by increasing population turnover rates. On the contary, some species show
decreasing population turnover rates with increasing temperature because of
decreased brood sizes (number of eggs) at higher temperatures (Carlson,
1974).
Although this study did not estimate zooplankton production directly,
it was hypothesized that any production changes caused by the elevated
temperatures, in order to be ecologically significant, would be reflected in
young-of-the-year bluegill biomass at the end of the study. Since the
biomass of YOY bluegill from the upper sections was not significantly
different between treatments (Section 4), any differences in total zooplank-
ton production, if they occurred, were not detected in relation to fish
biomass produced.
Dividing two of three channels in each treatment with screens resulted
in differences in zooplankton abundance, species composition, and species
diversity between the upper and lower channel sections. This result was not
expected because the mesh size of the screens should have allowed zooplank-
ton to interchange between sections. The screens must have restricted
zooplankton movement to some degree since there were differences between
divided and undivided channels for the various parameters studied.
Recommendations for future zooplankton-temperature studies are to use
higher temperature treatments, to partition all twelve channels or none at
all, to try to separate temperature effects on zooplankton from fish
predation impacts.
64
-------
REFERENCES
Armitage, B. J., T. D. Forsythe, E. B. Rodgers, and W. B. Wrenn. 1978.
Browns Ferry Biothermal Research Series I. Colonization by periphyton,
zooplankton, and macroinvertebrates. EPA Ecological Research Series,
EPA-600/3-78-020, Duluth, MM.
Carlson, D. M. 1974. Responses of planktonic cladocerans to heated
waters. In Thermal Ecology, J. W. Gibbons and R. R. Sharitz (Eds.),
Augusta, GA, 1973, DOE Symposium Series (CONF-730505). pp. 186-206.
Dumont, H. J., I. Vande Velde, and S. Dumont. 1975. The dry weight
estimate of biomass in a selection of Cladocera, Copepoda, and Rotifera
from the plankton, periphyton, and benthos of continental waters.
Oecologia. 19(1): 75-97.
Forsythe, T. D. 1978. Predator-prey interactions among crustacean
plankton, young bluegill (Lepomis macrochirus), and walleye
(Stizostedion vitreum vitreum) in experimental ecosystems. Ph.D.
Thesis, Michigan State Univ., East Lansing. 98 pp.
Hall, D. J., W. E. Cooper, and E. E. Werner. 1970. An experimental
approach to the production dynamics and structure of freshwater
communities. Limnol. Oceanogr. 15(6): 839-928.
65
-------
SECTION 7
MACROINVERTEBRATES
INTRODUCTION
The objective of this phase of the study was to evaluate population and
community responses of macroinvertebrates to long-term (185 days) tempera-
ture elevations (ca. 2°, 4°, and 6° C above ambient temperatures of the
Tennessee River). Because of the unique structure of the experimental
system, it was possible to study a naturally colonizing community of
organisms simulating that in the Tennessee River. Unlike typical laboratory
systems, the biothermal channels contained a wide variety of organisms which
were exposed to diurnally and seasonally fluctuating temperature regimens.
Diversity of macroinvertebrates in the biothermal channels is similar
to that in large mainstream reservoirs when both deep water and littoral
zones are considered. Eight phyla, six classes, and approximately 75 species
were identified when colonization was studied in 1974-1975 (Armitage et al,
1978). The most abundant organsims were: Oligochaeta, Corbicula manilensis
(Pelecypoda), Physa heterostropha (Gastropoda), Erpobdella punctata
(Hirudinea), Hyalella azteca and Crangonyx sp. (Amphipoda), Caenis sp.
(Ephemeroptera), and Chironomidae (Diptera). Odonates and Hexagenia
bilineata (Ephemeroptera) were also common as determined from exuviae that
were collected from the channel walls and water surfaces.
Sampling was carried out to determine species composition, relative
densities and biomass, as well as to provide information on life-cycles,
distribution within channels, and inter-specific interactions.
MATERIALS AND METHODS
Macroinvertebrate samples were collected monthly (March-September) in
the three habitats of the biothermal channels; pool sediments, limestone
rock areas, and wall surfaces. Sampling dates are listed in Table A-l. Pool
sediments were sampled with a six-foot length of PVC pipe which was twisted
into the substrate to give a core 23.76 cm2 in area and ca. 12 cm deep. On
each sampling date, 12 cores were taken in the upper sections in all
channels. On 7 July and 8 August cores were also taken in the lower sections
(pool 6).
Rock area samples were collected following 30-day colonization in
galvanized trays (0.09 m2) filled with rock similar to that of the channel
66
-------
rock areas. Three trays were placed in upper channel sections on all dates.
On the last three dates, lower sections were sampled as well. Initial
treatment of rock tray samples involved gently scrubbing each rock to remove
attached organisms. Trays with cleaned rocks were then replaced in channels
on the same day they were removed.
Concrete wall surfaces were sampled with a scraping device with
attached net which removed algae and associated organisms in a 0.25 m area.
Samples were taken in upper sections only in March and April and in both
upper and lower sections on all following dates (see Table A-l).
All types of samples were sieved (#70 mesh), and then subsampled in a
partitioned plexiglas tray; 0.1 of each sample was retained for analysis.
Large organisms (e.g., odonates, large leeches) were not subsampled. All
samples or subsamples were frozen immediately and saved for future analysis.
Results of analysis of variance of subsamples are given in Table A-2.
Macroinvertebrate organisms were picked from thawed samples and sorted
according to taxon. Dominant taxonomic groups from each sample were freeze-
dried and then weighed; less abundant groups were only counted. Relative
size and maturity of organisms were recorded. Total number of monthly
samples were 72 rock trays (24 subsamples), 288 core samples (24 subsamples),
and 72 wall scrapings (36 subsamples).
Differences between divided and undivided channels were tested
statistically (Mann-Whitney U test, Sokal and Rohlf, 1969). Analysis of
variance was performed to detect treatment effects on densities and/or dry
weights of individual taxa and the total macroinvertebrate community. When
upper channel sections were considered, data from the three habitats were
combined according to percent contribution to total area (rock areas, 16%,
wall surfaces, 31%, and pool sediments, 53%). In certain cases densities
and/or dry weights demonstrated different patterns in different habitats.
These variations were analyzed utilizing data from upper and lower sections
of all channels.
Biomass diversity and species diversity indices (Shannon-Weaver H~ )
were calculated for the three major habitats in each treatment on each
sampling date.
When the experiment was terminated the first week of September, 15
adult bluegill from each treatment were dissected and their stomach contents
identified and enumerated.
RESULTS
Dominant organisms in terms of numbers and/or biomass provided the
basis for statistical evaluation of temperature effects. These were the
same taxa which were dominant as the channels were colonized under ambient
temperature conditions (Armitage et al., 1978). They were Gastropoda,
especially Physa heterostropha, Lymnaea sp., and Pyrgulopsis letsoni;
Hirudinea, including Placobdella montifera, Helobdella sp., and Eropbdella
punctata; Amphipoda, including Crangonyx sp., and Hyalella azteca; Caenis
67
-------
sp. (Ephemeroptera); Libellulidae, and Enallagma civile (Odonata), and
Chironomidae.
In the comparison of divided and undivided channels in pool areas,
there were no significant differences seen on any date (Table 14). There
were not enough samples available for analysis on March 30. On August 31,
in rock areas only, Caenis sp. showed a significant difference (P < 0.05)
when it's dry weight was greater in undivided channels (Table 15). On three
dates early in the study there were not enough samples available for the
test used. On wall surfaces, Caenis sp. had significantly greater biomass
in divided channels (P < 0.05) on June 6 and August 2 (Table 16). Total
macroinvertebrates, exclusive of Mollusca, had greater dry weight (P <
0.05) in divided than in undivided channels. Because the spatial
distribution of dominant organisms in the experimental channels was almost
completely uninfluenced by presence of screen barriers used to divide fish
populations, the statistics presented were gathered on data from both
divided and undivided channels. Analyses of biomass and densities in upper
sections are emphasized here because they represented effects of the highest
temperatures in the channels.
Total Macroinvertebrates
Biomass of total macroinvertebrates, excluding Mollusca, was quite
evenly distributed in the channels despite the presence of screen barriers.
Only in the August 2 wall scrapings was there greater biomass (P < 0.05) in
divided than in undivided channels (Table 16).
A list of organisms included in the category "total macroinvertebrates"
appears in Table A-4. See also Armitage et al., 1978, for a list of species
which colonized the channels in 1974-1976.
Peak dry weight of total macroinvertebrates, exclusive of Mollusca,
occurred in all but the +2 C treatment in early May (Table 17, Fig. 12). The
+4 C channels had the greatest biomass at this time (ca. 5 gm m~2) although
it was not significantly different from that in other treatments.
Temperatures in +4 C channels had increased from 19° to 25° C during the
preceding month. The +2 C channels did not attain maximum biomass until
early June (ca. 2 gm m~2) following a temperature increase from 21° to 28°
C the preceding month. At this time, +2 C channel biomass was significantly
greater than that in both ambient and +4 C channels (P £ 0.05). Ambient
channels demonstrated a second biomass peak (ca. 1.6 gm m~2) beginning in
July when the temperature had increased to about 30° C from 26° C the
previous month. Both ambient and +2 C treatments had significantly greater
dry weights (P <_ 0.05) than that of +4 C channels in July. On the final
sampling date in August, dry weight in ambient channels (ca. 1.8 gm nT2)
exceeded that in both +4 C and +6 C channels (P <_ 0.05). Ambient and +6 C
channel temperatures had decreased from 30° to 28° C and 34.5° to 34° C,
respectively, since early July.
Dry weight of total macroinvertebrates, excluding Mollusca, varied
between habitats. Wall surfaces had the least biomass, ranging up to only
68
-------
TABLE 14. COMPARISON OF DIVIDED AND UNDIVIDED CHANNELS.* POOL
SEDIMENTS.
Organism
Mar. 30t May 6 Jun. 10 Jul. 7 Aug. 8
Caenis
(mg nr2)
Chironomidae
(mg nr2)
Amphipoda
(mg m~2)
Libellulidae
(mg m~2)
Hirudinea
(mg m~2)
Total Gastropoda
(no m~2)
N.S.
N.S. N.S.
N.S,
N.S. N.S.
N.S. N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
N.S,
N.S.
Total Macroinvertebrates
minus Mollusca
mg m
no m"
-2
N.S. N.S.
N.S. N.S.
N.S.
N.S.
N.S.
N.S.
* Above weir divided channels compared with whole undivided channels
Mann-Whitney U test.
t Too few samples for statistical analysis.
69
-------
TABLE 15. COMPARISON OF DIVIDED AND UNDIVIDED CHANNELS.* ROCK AREAS.
Organism
Mar 30 Apr 27t May lit May 3It Jun 28 Jul 28 Aug 31
Caenis N.S.
(mg m-2)
Chironomidae N.S.
(mg m~2)
Amphipoda N.S.
(mg m-2) N.S.
Hirudinea N.S.
(mg nT2)
Enallagma N.S.
(mg m-2)
Libellulidae N.S.
(mg m~2)
Total Gastropoda N.S.
(no m~2)
Total Macroinvertebrates
minus Mollusca
N.S. N.S. u
P < 0.05
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S. N.S. N.S.
N.S.
N.S. N.S. N.S.
N.S. N.S. N.S.
mg m
no m~
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
* Upper divided channels compared with whole undivided channels
Mann-Whitney U test
t Too few samples for statistical analysis
u Undivided greater
70
-------
TABLE 16. COMPARISON OF DIVIDED AND UNDIVIDED CHANNELS.* WALLS.
Organism Mar 2 Apr 5 May 1 Jun 6 Jul 1 Aug 2 Sep 2
Caenis N.S. N.S. N.S. d N.S. d N.S.
(mg m-2) P < 0.05 P < 0.05
Chironomidae N.S. N.S. N.S. N.S. N.S. N.S. N.S.
(mg m~2)
Amphipoda N.S. N.S. N.S. N.S. N.S. N.S. N.S.
(mg m~2)
Libellulidae N.S. N.S. N.S. N.S. N.S. N.S. N.S.
(mg nr 2)
Total Gastropoda N.S. N.S. N.S. N.S. N.S. N.S. N.S.
(no. m~2)
Total Macroinvertebrates
minus Mollusca
mg m-2 N.S. N.S. N.S. N.S. N.S. d N.S.
P < 0.05
no. m
r2 N.S. N.S. N.S. N.S. N.S. N.S. N.S.
* Upper divided channels compared with whole undivided channels
Mann-Whitney U test
d Divided greater
71
-------
TABLE 17. ANOVA OF TREATMENT EFFECTS ON DRY WEIGHT (rag m~2) OF TOTAL
MACROINVERTEBRATES (EXCLUDING MOLLUSCA).t
+2 C +4 C
Error Error
+6 C DF S.S. M.S.
Treatment Effects§
Apr*
May
Jun
Jul
Aug
1726
2255
588
1564
1799
381
805
1921
1792
564
1024
5063
920
337
464
865
3133
1363
503
314
2.4431 0.3053
0.1866 0.0233
0.6635 0.0829
0.4569 0.0571
+2 > +4 = A, +6 > A
A = +2 > +4
A > +4 = +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P <_ 0.05.
* Too few samples for analysis.
72
-------
CM
E
103
I02
I I I
Total Macroinvertebrates
(Excluding Mollusca)
M
M
Figure 12. Monthly mean dry weight of total macroinvertebrates
excluding Mollusca in four temperature treatments (three channels
per treatment): A (ambient temperature of Wheeler Reservoir,
Tennessee River), and +2°, +4°, and +6° C above ambient.
73
-------
394 mg nr2 in ambient channels in July. Final samples taken in early
September did not exceed 75 mg m~2 in any treatment (Fig. 13, Table A-3).
Biomass in pool areas generally exceeded that in both rock and wall areas,
especially in ambient and +2 C regimens. The greatest biomass in pool areas
was estimated in +4 C (ca. 4.5 gm nr2) and +6 C (ca. 8.3 gm m~2) channels in
May. However, these values were exceeded in rock areas (ca. 9.8 gm m~ in
+4 C and 16.3 gm nr2 in the +6 C channels). At the end of the study, biomass
in pool areas was greatest; that on wall surfaces was least, and that on
rock areas intermediate.
Densities of all macroinvertebrates including Mollusca peaked in all
but the ambient channels in early June (Table 18, Fig. 14). Both the +2 C
(9740 m~2) and +4 C (11973 m~2) channels had greater macroinvertebrate
densities than did ambient channels (5838 m~2) at this time. The +2 C peak
continued into early July when both it and the ambient value (ca. 10000 m~2)
were significantly greater than densities in +4 and +6 C channels (ca. 3000
m~2). August macroinvertebrate densities in ambient channels (16167 m~ )
were significantly greater than those in the three warmest treatments.
Gastropoda
Physa heterostropha was the numerically dominant gastropod in most
samples, with Pyrgulopsis letsoni occasionally being more numerous. Lymnaea
sp. maintained sparse populations until August and September; Pleurocera sp.
and Helisoma sp. were only infrequently collected (Table A-4) .
P. heterostropha densities were examined for treatment effects in terms
of both combined and separate habitats. Results of analysis of treatment
effects (separate habitats) on P. letsoni, Lymnaea sp., and total Gastropoda
are presented in Tables A-5 through A-8.
P. heterostropha densities ranged between ca. 150 m~2 in +6 C channels
in May and +2 C channels in August, to ca. 2400 m~2 in ambient channels in
May and +2 C channels in June (Table 19, Fig. 15). A treatment effect was
noted only in May, when Physa densities in ambient channels were
significantly greater than those in any other channel.
Effects of temperature elevation on P. heterostropha varied among
habitats. Peak deinsities in rock and wall areas (ca. 3000 m~2) occurred in
April and May in all treatments; populations in the pool areas increased
only upon the decline of wall and rock populations in late May to June
except in the +6 C treatment (Fig. 16). In the +6 C channels P.
heterostropha populations on rock areas increased simultaneously with those
in pools and attained similar peaks (ca. 1200 m~2).
Amphipoda
Two amphipod species, Hyalella azteca and Crangonyx sp., were present;
these were lumped together for consideration of amphipod dry weight. In
only the ambient and +2 C channels did amphipod biomass increase following
the beginning of sampling in April (Table 20, Fig. 17). These channels
attained peaks of 155 mg m~2 in early June (+2 C) and July (ambient).
74
-------
TOTAL MACROINVERTEBRATES MINUS MOLLUSCA
A M J J ASM A M J
10
75
-------
TABLE 18. ANOVA OF TREATMENT EFFECTS ON MEAN DENSITY (no irT2) OF TOTAL
MACROINVERTEBRATES INCLUDING MOLLUSCA.t
Apr
May
Jun
Jul
Aug
A
1897
6103
5838
10142
16167
+2 C
1478
3804
9740
9909
6083
+4 C
1849
5545
11973
3430
4078
+6 C
1249
3045
7553
3167
2250
DF
8
8
8
8
8
Error
S.S.
0
0
0
0
0
.8118
.2836
.0781
.3903
.3996
Error
M.S.
0
0
0
0
0
.1014
.0354
.0097
.0487
.0499
Treatment Effects§
+2 = +4 > A
A = +2 > +4 = +6
A > +2 = +4 = +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P < 0.05.
76
-------
105
E
>v
o
10"
TOTAL MACROINVERTEBRATES
(including Mollusca)
M
M
Figure 14. Monthly mean density of total macroinvertebrates including
Mollusca in four temperature treatments (three channels per treatment):
A (ambient temperature of Wheeler Reservoir, Tennessee River), and +2°,
+4°, and +6° C above ambient.
77
-------
TABLE 19. ANOVA OF TREATMENT EFFECTS ON MEAN DENSITY (no m~2) OF PHYSA
HETEROSTROPHA.t
+2 C +4 C +6 C
DF
Error Error
S.S. M.S. Treatment Effects^
Apr* 689
May 2457
Jun 1957
Jul 1223
Aug 1145
1469
523
2355
385
157
589
806
1977
470
373
478
151
563
961
280
0.5635 0.0704 A > +2
2.8458 0.3557
3.1128 0.3891
2.0851 0.2606
= +4 = +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P £ 0.05.
* Too few samples for analysis.
78
-------
104
N
^ I03
o
c
10'
P heterostropha
A
+2C
M
M
Figure 15. Monthly mean density of Physa heterostropha in four
temperature treatments (three channels per treatment): A (ambient
temperature of Wheeler Reservoir, Tennessee River), and +2°, +4°,
and +6° C above ambient.
79
-------
10'
POOLS
WALLS
ROCKS
10°-
10'
10
10'
10
—i 1 1 r
R heterostropho
AMBIENT
4C
J L
t2C
\
\
+ 6C
10
I03
10 2
10
MAMJJASMAMJJAS
1977
Figure 16. Monthly mean density of Physa heterostropha in three habitats
(rocks, walls, pools) and four temperature treatments (three channels
per treatment): A (ambient temperature of Wheeler Reservoir, Tennessee
River), and +2°, +4°, and +6° C above ambient.
80
-------
TABLE 20. ANOVA OF TREATMENT EFFECTS ON DRY WEIGHT (mg m~2) OF AMPHIPODA.t
Error Error
A +2 C +4 C +6 C DF S.S. M.S. Treatment Effects§
Apr 6 30 138 38 {
May 58 120 140 25 i
Jun 49 153 73 30 {
Jul 160 117 10 2 i
Aug 14 0 0 0 i
J 3.9847 0.498
3 1.5633 0.1954 +2 = +4 > +6
3 0.5413 0.0676 +2 > A = +6
3 1.2187 0.4062 A = +2 > +4 = +6
3 0.6754 0.0844 A > +2 = +4 = +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P < 0.05.
81
-------
102
CM
E
o>
E
10
Amphipoda
+4C
- + 6C
- +2C
M A M J J A
Figure 17. Monthly mean dry weight of Amphipoda in four temperature
treatments (three channels per treatment): A (ambient temperature of
Wheeler Reservoir, Tennessee River), and +2°, +4°, and +6° C above
ambient.
82
-------
Amphipod biomass in the +4 C channels dropped from a maximum of 140 mg m~2
in April and early May to zero in August; the +6 C channel values dropped
from 38 mg m~ in early April to zero in August.
Expected treatment effects became obvious beginning in early July when
both ambient and +2 C channels had significantly greater amphipod biomass
than did the two warmest temperatures (P <_ 0.05) (Table 20). At this time,
temperatures had increased from 27° to 32° C in the +4 C channels from 30°
to 34.5° C in the +6 C channels during the preceding month. By early August
only ambient channels had amphipod populations (ca. 14 mg m~2).
Total amphipod densities ranged to 3176 m~2 in ambient channels in
early June (Table 21, Fig. 18). As was true for biomass, in only the ambient
and +2 C channels did amphipod densities increase after the beginning of the
study. Densities in +4 C channels dropped from 1290 m~2 in April to zero in
August; those in +6 C channels dropped from 208 m~2 to zero.
Expected treatment effects appeared in early May when +6 C channels had
smaller amphipod populations than any other treatment. By August, ambient
channel amphipod densities were greater than those in +2 C channels, which
were in turn greater than those in either +4 or +6 C channels.
The sharpest decreases in +4 and +6 C channel amphipod density and
biomass occurred in June when temperatures were between 27° and 32° C, and
between 30° and 34° C, respectively. Previously, slight decreases in +6 C
populations had occurred at temperatures of 25° to 30° C. The sharpest
decreases in ambient and +2 C amphipod density and biomass followed in July
at temperatures decreasing from 30° to 28° C and from 32° to 30° C,
respectively. Slight decreases in +2 C populations had begun a month
earlier at temperatures of 27° to 31° C.
H. azteca and Crangonyx sp. densities considered spearately illustrate
the relatively earlier decline of Crangonyx populations in all treatments
(Tables 22 and 23). Also, Crangonyx populations in the ambient and +2 C
channels did not increase after May as did those of Hyalella. Treatment
effects on these two species were similar to those on the whole amphipod
populations.
Response of amphipod density to increased temperature varied between
habitats. In the ambient regimen, amphipods reached their peak abundance in
pool areas (3507 m~2 in July). Those in rock and wall areas were between
1000 and 2000 nr2 at the same time (Fig. 19, Table A3). In all the heated
regimens, amphipod densities were greatest in rock areas until late July and
August when they were exceeded by those along walls. In the +6 C channels,
amphipods were never present in pool areas.
Ephemeroptera
Caenis sp. was the dominant ephemeropteran during the study; Hexagenia
bilineata was only occasionally collected. Caenis had two emergence periods
as evidenced by declines in density and biomass (Figs. 20 and 21); these
declines were supported by observations of numerous final nymphal exuviae on
83
-------
TABLE 21. ANOVA OF TREATMENT EFFECTS ON MEAN DENSITY (no m 2) OF
AMPHIPODA.t
Apr
May
Jun
Jul
Aug
A
75
343
1123
3167
331
+2 C
275
762
703
759
21
+4 C
1290
670
439
76
0
Error
+6 C DF S.S.
208 8 2.2484
191 8 0.5575
179 8 0.6621
15 8 1.0651
0 8 0.7620
Error
M.S.
0.
0.
0.
0.
0.
2810
0696
0827
1331
0952
Treatment Effects§
+4 > A
A = +2 = +4 > +6
A = +2 = +4 > +6
A = +2 > +4 > +6
A > +2 > +4 = +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P < 0.05.
84
-------
no/m2
o
N>
O
o<
I I T
1 I I Mill
I I IT
13
I
O
O
Figure 18. Monthly mean density of Amphipoda in four temperature treatments (three channels per
treatment): A (ambient temperature of Wheeler Reservoir, Tennessee River), and +2°, +4°, and
+6° C above ambient.
-------
TABLE 22. ANOVA OF TREATMENT EFFECTS ON MEAN DENSITY (no m~z) OF HYALELLA
AZTECAA
Error Error
A +2 C +4 C +6 C DF S.S. M.S. Treatment Effectst
Apr*
May 232 569 363 111 i
Jun 1071 621 357 131 i
Jul 3112 655 76 15 i
Aug 279 21 0 0 i
3 1.1480 0.1435 +2 > +6
3 0.8849 0.1106 A = +2 > +6
3 1.1670 0.1458 A = +2 > +4 > +6
J 0.8123 0.1015 A > +2 > +4 = +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P _> 0.05.
* Too few samples for analysis.
86
-------
TABLE 23. ANOVA OF TREATMENT EFFECTS ON MEAN DENSITY (no rrT2) OF CRANGONYX
SP.t
Error Error
A +2 C +4 C +6 C DF S.S. M.S. Treatment Effects§
Apr*
May 102 190 306 84 i
Jun 52 79 78 6 i
Jul 55 4 0 0 £
Aug 48 0 0 0 i
I 1.6796 0.2099
3 1.8656 0.2332 A = +2 = +4 > +6
3 0.7326 0.0915 A > +2 > +4 = +6
? 0.4746 0.0593 A > +2 = +4 = +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P <_ 0.05.
* Too few samples for analysis.
87
-------
- 10
M J J A S MAMJjAS
1977
Figure 19. Monthly mean density of Amphipoda in three habitats (rocks,
walls, pools) and four temperature treatments (three channels per
treatment): A (ambient temperature of Wheeler Reservoir, Tennessee River),
and +2°, +4°, and +6° C above ambient.
-------
mg/ m2
o
ro
O
OJ
O
Q
(A
Figure 20. Monthly mean dry weight of Caenis sp. in four temperature treatments (three channels per
treatment): A (ambient temperature of Wheeler Reservoir, Tennessee River), and +2°, +4°, and +6° C
above ambient.
-------
no
O
O
to
O
OJ
O
J>
rn
Figure 21. Monthly mean density of Caenis sp. in four temperature treatments (three channels per
treatment): A (ambient temperature of Wheeler Reservoir, Tennessee River), and +2°, +4°, and
+6° C above ambient.
-------
water surfaces. The first emergence occurred in April in all treatments
when dry weights declined from a maximum of 238 mg m~2 in +4 C channels, to
an early May maximum of 55 mg m~2 in +6 C channels (Table 24). In early May
this +6 C Caenis biomass was significantly greater than that in the +2 C
channels. Caenis densities declined only in the ambient channels in April
(Table 25, Fig. 21). Peak Caenis biomass and density were attained in the
three warmest temperature regimens in early June (225-460 mg m~2 , 950-1170
m~2); these channels had greater dry weight and +6 C channels greater
density than did ambient channels (P <^ 0.05) at that time. Temperatures in
the +2, +4, and +6 C treatments had increased from 20° to 28° C, from 21° to
29° C, and from 22° to 30° C, respectively. After a temperature increase
from 20° to 25.5° C in early June, ambient Caenis did not evidence a mid-
summer peak until early July (425 mg m~2, 1943 m~2). There were no
significant treatment effects detected at this time. In August, at the end
of the study, the biomass of Caenis (61 mg m~2) in the ambient regimen was
signifcantly greater than that in the +6 C regimen (1 mg m~2) with the +2 C
and +4 C channels having intermediate biomass. In August Caenis densities
in ambient channels (632 m~2) were greater than those in both +4 C and +6 C
channels (ca. 175 m~2).
Declines in density, indicating emergence, occurred at different times
in different habitats and temperature treatments (Figs. 22 through 24).
Caenis densities on walls decreased in March through early April and also in
August in ambient channels; in June and August in +2 C channels; in both +4
and +6 C channels in March and April, as well as in June through August.
Rock area density declines differed from those on walls only in the two
coolest treatments; in ambient channels, the spring decrease extended into
early May, while in +2 C channels there was a definite decrease in April.
Pool sediments had declines in April and early May in ambient and +6 C
channels, but no spring declines at the two intermediate temperature
treatments. The late summer drops occurred in July and August in the two
coolest treatments and in June through August in the two warmest
temperatures.
Most changes in density were paralleled by changes in biomass (Figs. 22
through 24)- Sampling intervals which did not show similar trends for these
two parameters revealed either an increased population size at the expense
of biomass or increased biomass with decline in population size. These
trends revealed when and where recruitment occurred, corroborating the
evidence of density alone.
In ambient pool areas, the number of small Caenis nymphs increased in
May and early June, during and following spring density decreases; in +2 C
and +4 C channels, the same relationship was seen earlier, during April and
in early May. In +4 C channels, recruitment occurred in June and July.
Caenis in +6 C channels did not demonstrate trends such as these.
In rock areas, recruitment occurred in ambient channels in May; in +2 C
channels in April and early May, and also in June and July. Neither +4 C
nor +6 C channels provided clear evidence of any early Caenis nymphal
instars.
91
-------
TABLE 24. ANOVA OF TREATMENT EFFECTS ON DRY WEIGHT (mg m"7) OF CAENIS SP.t
Error Error
A +2 C +4 C +6 C DF S.S. M.S. Treatment Effects§
Apr*
May
Jun
Jul
Aug
61
23
18
423
61
49
13
228
87
38
238
23
366
80
13
148
55
465
64
1
8
8
8
8
1.
0.
1.
4.
3308
3339
5067
537
0.
0.
0.
0.
1663 +6 > +2
0417 +2 = +4 = +6 > A
1883
5671 A > +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P 5 0.05.
* Too few samples for analysis.
92
-------
TABLE 25. ANOVA OF TREATMENT EFFECTS ON MEAN DENSITY (no nT2) OF CAENIS SP.t
+2 C +4 C +6 C DF
Error Error
S.S. M.S. Treatment Effects!
Apr*
May
Jun
Jul
Aug
133
41
199
1943
632
98
117
946
643
383
269
370
1207
546
187
317
371
1766
462
150
8
8
8
8
0
0
1
0
.4388
.3617
.0879
.5172
0
0
0
0
.0548 +4 = +6 > A = +2
.0452 +6 > A
.1359
.0646 A > +4 = +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P £ 0.05.
* Too few samples for analysis.
93
-------
10'
CM
E
Cvl
£
10
103
102 -
10
1 1 1 r
CAENIS sp.- ROCK AREAS
~\ T
— no /i
— mg/ i
AMBIENT
4C
-i 1 l i
f 6C
103
10 2
10
103
10'
MAMJJASMAMJJAS
Figure 22. Monthly mean dry weight and density of Caenis sp. on rock areas
of four temperature treatments (three channels per treatment): A (ambient
temperature of Wheeler Reservoir, Tennessee River), and +2°, +4°, and +6° C
above ambient.
10
94
-------
103
10'
"E '0
102
10
no/m'
I 'i r~
CAENIS sp-WALLS
AMBIENT
•2C
6C
M A M J
I 1 I I I _X.
103
10
10'
S M
1977
A M
J A
Figure 23. Monthly mean dry weight and density of Caenis sp. on wall
areas of four temperature treatments (three channels per treatment):
A (ambient temperature of Wheeler Reservoir, Tennessee River), and +2°,
+4°, and +6° C above ambient.
95
-------
103
10*
CM
E
10
102
10
-i r
no./m^
mg/ m2
—I 1 1 1 T
CAENIS sp. -POOL SEDIMENTS
AMBIENT
4 4C
I I I
2C
•i- 6C
103
102
10
103
10*
S M
1977
10
Figure 24. Monthly mean dry weight and density of Caenis sp. in pool
areas of four temperature treatments (three channels per treatment):
A (ambient temperature of Wheeler Reservoir, Tennessee River), and
+2°, +4°, and +6° C above ambient.
96
-------
Wall surfaces recruited young Caenis nymphs in May, June, and July in
ambient channels, and in July in +4 C channels. An increase in biomass at
the expense of population numbers occurred in wall surfaces oftener than in
the other habitats, especially in March and August in ambient'channels; in
August in +4 C channels, and in July and May in +6 C channels.
Chironomidae
At least three subfamilies in the family Chironomidae were represented
in the experimental channels in 1977. No attempt was made to further
classify them.
As for Caenis sp., Chironomidae dry weight peaks occurred in the three
warmest treatments in early June (600 to 950 mg m~2). In the +2 C channels,
the peak extended into July (Table 26, Fig. 25). The ambient peak did not
appear until the final sampling date in August (1087 mg m~2) following a
temperature decrease from 30° to 28.5° C during the preceding month. At the
time of peak biomass in the warmest channels, these channels had greater dry
weight (P £ 0.05) than did ambient channels. In August, biomass in the
ambient channels was greater than that in +2 C and +4 C channels (P £ 0.05)
but not significantly different from that in +6 C channels.
Chironomidae density curves were similar to the dry weight curves with
two exceptions: The +2 C curve did not reach a peak until early July at
6189 nf , and the ambient curve did not decline after early April (Table 27,
Fig. 26). The greatest densities in +4 and +6 C treatments were 5682 and
4265 m~ , respectively, in June. The greatest chironomid density in ambient
channels, which appeared in June, was 11,113 m~2, a significantly greater
density (P <_ 0.05) than in any other channel.
Chironomid densities were generally greatest in pool areas, ranging as
high as 9353 m~2 in +4 C channels in June. The +6 C channel peak in June
(6079 m~2) was not very different from the peak attained in rock areas (5821
m-2) at the same time in the same channels. Densities on wall areas were
the lowest, not exceeding 536 m~2 in any treatment (Fig. 27, Table A-4). In
all treatments on final sampling dates, pool sediments had the highest
densities and walls the lowest, with rock areas having intermediate
densities.
Declines in density, indicating probable emergence, were most clearly
related to temperature treatment in pool areas. Emergence from +4 and +6 C
treatments occurred in June, from +2 C channels in May, and from the ambient
regimen in August following a density peak. Density declines in wall and
rock area curves were evident in all treatments during June.
Hirudinea
Three leech species were dominant during the experimental period;
Erpobdella punctata, Helobdella sp. , and Placobdella montifera. These
species were combined for biomass estimates. Because hirudinids had been
shown to be important fish food organisms (unpublished data), they were
analyzed statistically for effects of treatment; however, because so few
97
-------
TABLE 26. ANOVA OF TREATMENT EFFECTS ON DRY WEIGHT (mg
CHIRONOMIDAE.t
OF
A +2 C +4 C +6 C
DF
Error Error
S.S. M.S. Treatment Effects§
Apr* 531
May 218
Jun 129
Jul 177
Aug 1087
31
108
934
996
174
79
494
621
84
68
2
28
854
180
241
0.4392 0.0549 A = +4 > +6, +2 > +6
0.5878 0.0734 +2 = +4 = +6 > A
1.3056 0.1632 +2 > A = +6 > +4
1.8949 0.2368 A > +2 = +4
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P £ 0.05.
* Too few samples for analysis.
98
-------
Figure 25. Monthly mean dry weight of Chironomidae in four temperature treatments (three channels
per treatment): A (ambient temperature of Wheeler Reservoir, Tennessee River), and +2°, +4°, and
+6° C above ambient.
o
IV
O
OJ
O
o
3.
Q,
O
mg/m2
-------
TABLE 27. ANOVA OF TREATMENT EFFECTS ON MEAN DENSITY (no m~2) OF
CHIRONOMIDAE.t
+2 C +4 C +6 C
DF
Error Error
S.S. M.S. Treatment Effects!
Apr* 1213 160 18 11
May 1571 948 1840 741
Jun 1096 3539 5682 4265
Jul 1750 6189 1068 1264
Aug 11113 1191 318 1347
0.4010 0.0501
1.1067 0.1383
0.8282 0.1035 +2 > = +4 = +6
0.9718 0.1214 A > +2 = +4 = +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P <_ 0.05.
* Too few samples for analysis.
100
-------
no/m2
Figure 26. Monthly mean density of Chironomidae in four temperature treatments (three channels per
treatment): A (ambient temperature of Wheeler Reservoir, Tennessee River), and +2°, +4°, and
+6° C above ambient.
-------
10'
I03
10=
10
10s
10*
10
J L
+ 6C
10s
10"
10
10"
o2
10
MAMJJAS MAMJJAS
Figure 27. Monthly mean density of Chironomidae in three habitats (rocks,
walls, pools) and four temperature treatments (three channels per
treatment): A (ambient temperature of Wheeler Reservoir), and +2°, +4°,
and +6° C above ambient.
102
-------
treatment effects were seen, their population data are not presented
graphically. In early May, greatest biomass occurred in all treatments,
followed by decline in all but the +2 C regimen (Table 28). The +4 C
channels had the largest biomass in May (ca. 41. gm m~2). By the end of the
study, no treatment dry weight exceeded 36 mg m~2 . The only obvious
treatment effect occurred in July, when ambient and +2 C hirudinid dry
weights were greater than those of +4 and +6 C channels.
Other Macroinvertebrates
Other macroinvertebrates occasionally abundant, or adding measurably to
community biomass, were Oligochaeta, Libellulidae, and Trichoptera.
Oligochaete and Trichoptera densities and dry weights appear in Table A-4.
All Anisoptera nymphs sampled were respresentatives of the family
Libellulidae. Their densities were never great; however, because of their
large size, their contribution to total dry weight was measurable. Greatest
libellulid dry weight was estimated in +6 C channels (878 mg m~2) in early
April (Table 29). All other channels had their greatest biomass in early
May, followed by a decline to 12 mg m~ or less in all treatments. A
predictive treatment effect was noted in May, when +6 C libellulid dry
weight was significantly greater than that in ambient and +2 C regimens
(P 5 0.05).
Percent Abundance and Dry Weight Biomass
Percent abundance and percent dry weight, excluding Mollusca, were
determined separately for each habitat, in order to discern community
differences. In general, four organisms were consistently dominant in one
or more habitats; Physa heterostropha, Amphipoda, Caenis sp., and
Chironomidae. In pool areas, oligochaetes were often among the dominant
taxa; in rock areas and on walls, Pyrgulopsis letsoni was occasionally an
important component.
Along walls, P. heterostropha percent abundance ranged from 8% in +4 C
channels in March to 91% in ambient channels in early April (Table A-8).
Except for one measurement in July when they comprised 46% in the +6 C
channels, after May they did not again comprise more than 50% of total
numbers. P. letsoni were never found in ambient channels, but did form 75%
of the community in the +4 C channels in August, following a gradual
increase in dominance. In May, Caenis comprised up to 50% of +6 C channels'
community density, and usually formed a larger part of the warmest channels.
Chironomidae populations ranged from 0 to 39% of total numbers. No trends
were noted, either seasonally nor by treatment. Amphipoda were relatively
abundant (40 to 50%) in +2 and +4 C channels on March 2, and in +2 C
channels on July 1.
The greatest contribution of P. heterostropha to rock-area community
numbers (76%) was noted in + 2 C channels on March 30 (Table A-8). On 27
April and 11 May, ambient channels had Physa populations comprising 54% and
41%, respectively, of total numbers. Toward the end of the study, Physa
were more numerous in warmest channels than in the three cooler treatments.
103
-------
TABLE 28. ANOVA OF TREATMENT EFFECTS ON DRY WEIGHT (mg m~2) OF HIRUDINEA.t
Error Error
A +2 C +4 C +6 C DF S.S. M.S. Treatment Effects!
Apr* 955 284 476 772
May 1628 527 4085 2437 8 11.2487 1.4060
Jun 278 538 31 88 5.7430 0.7178
Jul 270 54 22 15 8 4.3805 0.5475 A = +2 > +4 = +6
Aug 36 3 13 68 4.0975 0.5121
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P £ 0.05.
* Too few samples for analysis.
104
-------
TABLE 29. ANOVA OF TREATMENT EFFECTS ON DRY WIEGHT (mg m~2) OF
LIBELLULIDAE.t
Error Error
A +2 C +4 C +6 C DF S.S. M.S. Treatment Effects!
Apr- 0 0 33 878
May 33 53 326 609 8 5.0134 0.6266 +6 > A = +2
Jun 00 0 68 0.9666 0.1208
Jul 00 0 12 8 1.6147 0.2018
Aug 0 11 12 18 1.2654 0.1581 +2 = +4 > A = +6
t Performed on log-transformed means (three replicates) using least
significant differences (Sokal and Rohlf, 1969).
§ P £ 0.05.
* Too few samples for analysis.
105
-------
P. letsoni achieved percent abundance over 15% only In +4 C channels on
August 31, when it contributed 67% to total numbers. Caenis composed up to
61% of the community, generally being most numerous in all treatments in
June and July. Neither Chironomidae nor Amphipoda percent abundances on
rock areas were affected by treatment.
Community structure in pool sediments was quite different from that in
either rock or wall areas (Table A-8). Chironomids and oligochaetes were
almost always the two most abundant organisms. Chironomids comprised up to
74% numerically in ambient channels in March and only once, on the same date
in +6 C channels, were nonexistent. Oligochaetes tended to be more numerous
in all treatments at the beginning of the sampling period than at the end.
In March, they were 54% of the community in +2 C channels, and 55% in +6 C
channels in both March and May. While P. heterostropha was most numerous in
June and July, it never comprised more than 32% of any treatment. Caenis
was even less numerous, comprising only 15% in +4 C channels in July.
Although Amphipoda numbered 18% and 17% in ambient channels in June and
July, they were usually nonexistent in all treatments.
On wall surfaces, Libellulidae biomass, even when low in numbers, was
often important in the community, attaining 83% in +6 C channels in
September (Table A-4) when in all treatments they were at their highest
percent biomass. Caenis dry biomass ranged from 3% in +2 C channels in
March to 71% in +2 C channels in August. Greatest contribution of Caenis in
ambient channels occurred in April (60%), in +4 C channels in July (61%),
and in +6 C channels in June (51%) . Chironomidae biomass comprised 70% of
the total in +2 C channels in April when no libellulid weight was present.
In ambient channels in March, it accounted for 50% of total weight but in
most cases contributed no more than 20%. Amphipoda occasionally comprised
more than 50% of total weight especially in the two coolest treatments.
In rock areas, both libellulids and Hirudinea were important components
of the community in terms of weight (Table A-9). Libellulids were dominant,
particularly in warmest channels in April and May and were also important
toward the end of the sampling period. Hirudinea biomass was 75% of the
total on May 31 in ambient channels, 50% in +6 C channels in March, and 30%
or less in most other cases. Caenis percent dry weight was greatest in May
when the three warmest treatments had 53, 54, and 62% Caenis by weight. The
highest ambient value was on the first sampling date at 49%. Lowest values
occurred, generally in April and early May in all treatments. Chironomidae
were less important than Caenis in terms of dry weight. Percent contribution
did not range above the 36% value noted in +6 C channels at the end of
August. Amphipoda composed as much as 44% of dry biomass in +2 C channels
in April but on most dates contributed 20% or less in all treatments.
In pool sediments, total dry weight was dominated by Chironomidae,
Hirudinea, and Oligochaeta; Hirudinea were dominant in all treatments (up to
92%) early in the sampling period, Chironomidae from mid-June through
August, and Oligochaeta in July and August. Caenis were relatively more
important toward the end of the sampling period than toward the beginning.
Amphipod weight was significant enough to be measured only in June and July
and only in the two coolest treatments. Libellulidae biomass was noted only
106
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in +6 C channels in March when it contributed 97% to total weight.
Diversity
Species diversity (Shannon-Weaver H1) in the experimental channels
ranged from 0.45 on walls in ambient channels in April to 2.23 in +4 C
channels in rock areas in June (Table 30). Most values ranged between 1.40
and 1.90. No trend was seen relating diversity to temperature treatment.
Annual means indicated greatest diversity in +4 C channels (1.62). Mean
diversity across treatments was greater toward the middle of the sampling
period. Statistically, the only significant difference seen (P <_ 0.01) was
in the pool areas, where +4 C channels had higher diversity than +6 C
channels (Table 32).
Diversity of biomass was also difficult to relate to temperature
treatment or to season (Table 31). Biomass values ranged from 0.15 in March
+6 C pool areas to 1.81 in July ambient pool sediments. Mean biomass
diversity, however, was highest in ambient channels in all habitats.
Statistically, differences in biomass diversity were seen in pool (P j£ 0.01)
and rock areas (P < 0.05) where ambient channel diversities were greater
than +6 C channel diversities (Table 32). Also in rock areas, biomass
diversity was greater in +2 C channels than in either +4 or +6 C channels
(P < 0.05).
Bluegill Stomach Contents
In a sample of bluegill (15 per treatment) ranging from 136 to 146 mm
TL, collected 8 September, Chironomidae were dominant in stomach contents
(Table 33). In the ambient and +2 C channels, chironomid larvae were the
prevalent form; in +4 C channels, both larvae and pupae were present and in
fish from +6 C channels, pupae were prevalent. P- heterostropha were seen
primarily in stomachs from +6 C channel fish; 60% of these had ingested
Physa. Thirty percent of +2 C channel bluegill and 13% of ambient and +4 C
fish had fed on Physa. All other organisms were present in 30% or fewer
stomachs. Hydroptilidae larvae were seen only in fish from the two coolest
channels; Amphipoda were seen only in fish from ambient channels. Caenis
were found in four ambient treatment bluegill and one +6 C bluegill. Most
stomachs from all treatments contained at least some algae along with
macroinvertebrates.
DISCUSSION
Of the groups of organisms observed during this experiment, some were
greatly affected by temperature treatments, some moderately affected, and
some not at all affected.
Total Macroinvertebrates
Although the evaluation of the total macroinvertebrates included more
than 75 species, there were treatment effects in terms of peak abundance.
Elevated temperature regimens, particularly +4 and +6 C, advanced the time
107
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TABLE 30. SPECIES DIVERSITY (SHANNON-WEAVER H1) IN THREE HABITATS
OF FOUR TEMPERATURE TREATMENTS ON ALL SAMPLING DATES.
Walls
March 2
April 5
May 2
June 6
July 1
August 2
September 2
x"
Pool Sediments
March 24
May 6
June 10
July 7
August 8
X
Rock Areas
March 30
April 27
May 31
June 28
July 28
August 31
X
A
1.64
0.45
0.87
1.57
1.43
1.66
1.86
1.35
1.04
1.85
1.59
2.10
1.26
1.57
1.54
1.51
1.70
1.96
1.93
1.84
1.75
+2 C
1.31
0.52
1.38
1.66
1.87
1.81
1.84
1.48
1.48
1.84
1.69
1.38
1.42
1.56
0.94
1.95
1.61
1.88
1.51
1.66
1.59
+4 C
1.74
0.86
1.31
2.10
1.76
1.18
1.02
1.43
1.69
1.63
1.53
1.58
1.81
1.65
1.62
2.03
1.67
2.23
1.86
1.36
1.79
+6 C
1.54
0.94
1.69
1.76
1.77
1.85
1.65
1.60
1.27
1.18
1.06
1.44
1.49
1.29
1.42
2.09
1.08
1.62
1.42
1.56
1.53
X
1.55
0.69
1.31
1.77
1.70
1.62
1.59
1.37
1.62
1.46
1.62
1.49
1.38
1.89
1.51
1.92
1.68
1.60
108
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TABLE 31. BIOMASS DIVERSITY (SHANNON-WEAVER H1) IN THREE HABITATS
OF FOUR TEMPERATURE TREATMENTS ON ALL SAMPLING DATES.*
Walls
March 2
April 5
May 2
June 6
July 1
August 2
September 2
X
Pool Sediments
March 24
May 6
June 10
July 7
August 8
X
Rock Areas
March 30
April 27
May 31
June 28
July 28
August 31
X
A
1.13
0.80
1.48
1.17
1.12
1.64
1.25
1.23
0.93
0.40
1.12
1.81
1.27
1.12
1.22
1.32
1.61
1.54
1.71
1.67
1.51
+2 C
1.04
0.80
1.29
1.05
1.21
1.01
1.13
1.08
0.31
0.47
1.09
1.24
0.92
0.81
1.48
1.51
1.22
1.29
1.42
1.56
1.41
+4 C
1.39
1.07
1.11
1.21
1.17
1.31
0.74
1.14
0.84
0.38
0.59
1.13
0.91
0.77
1.48
1.35
1.21
1.04
1.34
1.38
1.30
+6 C
1.42
1.15
1.17
1.36
1.32
1.29
0.59
1.19
0.15
0.61
1.31
0.47
0.64
1.31
0.71
0.83
1.18
1.00
1.58
1.10
X
1.25
0.96
1.26
1.20
1.21
1.31
0.93
0.56
0.73
0.85
1.37
0.89
1.37
1.22
1.22
1.26
1.37
1.55
Mean dry weights m 2 of dominant populations related to
each other.
109
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TABLE 32. RESULTS OF STUDENT'S t TEST ON MACROINVERTEBRATE DIVERSITY
INDICES.t
A
+2 C
+4 C
+6 C
A
+2 C
+4 C
+6 C
A
+2 C
+4 C
+6 C
Numbers
A +2 C +4 C +6 C
N.S. N.S. N.S.
N.S. N.S.
N.S.
—
Pool
A +2 C +4 C +6 C
N.S. N.S. N.S.
N.S. N.S.
+4
0.01
—
Rock
A +2 C +4 C +6 C
N.S. N.S. N.S.
N.S. N.S.
N.S.
—
Walls
A
A
+2 C
+4 C
+6 C
Sediments
A
A
+2 C
+4 C
+6 C
Areas
A
A
+2 C
+4 C
+6 C
Biomass
+2 C +4 C +6 C
N.S. N.S. N.S.
N.S. N.S.
N.S.
—
+2 C +4 C +6 C
N.S. N.S. A
0.01
N.S. N.S.
N.S.
—
+2 C +4 C +6 C
N.S. N.S. A
0.05
+2 +2
0.05 0.05
N.S.
-
t P < values indicated.
A, +2, +4 - indicates treatment with greater diversity.
N.S. - non significant.
110
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TABLE 33. STOMACH CONTENTS OF BLUEGILL RECOVERED 1 SEPTEMBER FROM FOUR
TEMPERATURE TREATMENTS.
Ambient
1
3
4
5
6
7
8
9
10
11
12
13
14
15
+2 C
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Chironomidae
pupae
^
3
1
1
1
1
2
1
1
2
4
Chironomidae
larvae
4
11
O
1
23
2
5
60
2
1
4
2
10
1
45
1
1
58
1
24
13
11
42
10
3
40
1
60
0)
cd
13
•H
cd co i — i
TJ 0) -H
0 C 4-1
CO P* -H P^
••S -H 13 O rg
c x; 3 M w ,-c
CD PJ M 13 Di CO
n F- - i >^- n* ._j
o
-------
TABLE 33 (continued).
+4 C
1
2
3
4
5
6
7
9
10
11
12
13
14
+6 C
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0)
m ft -H ft
Oft O ^ 'H 'H T3 O H3
>-< 3 s-jrt q,c 3 M tn,c;
•Hft-HiH CD ft M T3 3i W
,C ^ 03 S -H >~, J5 -H
O O Cj^ffJtdDH^
4
2 6
2 6
78
2 1
1
9 13 1
6
24 1
4
1
39 1
17 3
10
8 1
5
10 1
18 4
9 1
15 12
17 2
7 4
5 81
10 1 31
Miscellaneous
3 adult Chironomidae,
1 coroxid
1 Ceratopogonidae
1 Ceratopogonidae
1 adult Chironomidae
2 adult Chironomidae
1 hemipteran
2 Pyrgulopsis
1 Pyrgulopsis
2 Ceratopogonidae,
2 Pyrgulopsis
1 nematode
1 Hydrophilidae
112
-------
of greatest density at least one month. This phenomenon was true also for
total biomass, exclusive of Mollusca. Also, in May, greatest dry weights in
the two warmest treatments (3-5 gm m~2) surpassed those in the two coolest
treatments (ca. 2 gm m~2).
The relative decimation of macroinvertebrate biomass in +4 and +6 C
channels and of macroinvertebrate densities in +2, +4, and +6 C channels
during the last month, as compared with those in cooler channels may be
attributed directly to temperature increase, indirectly to excessive
predation, or a combination of both. The highest growth rate of bluegill in
all treatments generally coincided with the density-biomass peaks of
invertebrates. However, the decline of macroinvertebrate populations in the
heated channels was not reflected in the yield (biomass) of bluegill
recovered 9 September, which was not significantly different between
temperature treatments. Future studies should be continued into the winter
to determine if the macroinvertebrate populations would recover their
initial levels. Dry weight of the macroinvertebrates in ambient channels
was about the same at the end of the experiment as it was at the beginning,
indicating effective efficient turnover while providing a food base for
bluegill.
Gastropoda
Gastropods are almost ubiquitous components of freshwater lotic and
lentic ecosystems. Those occurring in the experimental channels are common
in many areas; Lymnaea spp. are common in almost every area in the United
States, as are Helisoma spp. Pleuroceridae are found mainly east of the
Mississippi River and are common in Alabama, and Physa spp. inhabit all
types of waters, but are most often found in waters of northern states.
Pyrgulopsis spp. have several representatives in the upper Mississippi
Valley, Great Lakes region, Alabama, and Nevada (Pennak, 1953).
Experiments to determine effects of temperature on gastropods have
typically been carried out in small laboratory systems utilizing one species
at a time at constant temperatures. Several of these studies demonstrated
that whereas temperatures near 30° C were optimal for maximum growth, these
temperatures also inhibited reproduction (e.g., Michelson, 1961; and Berrie,
1969). Van der Shalie and Berry (1973) showed in laboratory studies that
lymnaeids grew best at 18° C with viability reduced at 22° C and above, that
planorbids grew best at 25° C with reproduction inhibited at 30° C, and
that physids tolerated the widest temperature range, sometimes living at 30°
C and above. None of the snails in these studies reproduced in the
laboratory at above 30° C. McDonald (1975) showed 30° C to be the incipient
lethal level for Lymnaea stagnalis. This was the highest temperature to
which this species could be exposed while maintaining behavior patterns
observed at lower temperatures. In thermal gradients in the laboratory,
Chernin (1967) found that Lymnaea palustris accumulated in cool regions and
avoided the area above 32° C. Bovjerg (1975) noted that Lymnaea stagnalis
in an experimental gradient ranging from 25° to 35° C avoided the 35° C
area. Dewitt (1954) found oviposition in Physa gyrina to be induced by a
rise in temperature and that the time needed for development prior to
hatching was directly proportional (within limits) to temperature. Imhof
113
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(1973) showed growth regulation in lymnaeids to be related to laboratory
temperature within the range prevailing during the warm season in the snails'
habitat. Above specific threshold values, no correlation existed between
temperature level and intensity of spawning. Imhof also showed that
lengthening daylight stimulated spawning.
Mattice (1975) subjected Lymnaea obrussa Say to both constant and
varying temperatures and found varying temperatures to be more conducive
to growth; snails held at 30° C died at the end of the third week of the
experiment without producing eggs.
Two recent studies on Physa were conducted in natural systems receiving
heated effluents. Sankurathri and Holmes (1976) studied Physa gyrina in two
areas of Lake Wabamun in Alberta, one area with heated effluent, ranging to
32° C, about 8° C above the other unheated area. In the unheated area was
found a preponderance of miniature snails, and a preponderance of large
mature snails occurred in the heated area. There was little seasonal
pattern to the appearance of egg masses, immature and mature snails, in the
heated areas; all sizes were present throughout the year. There was egg
development up to 32° C.
McMahon (1975) refuted evidence of laboratory experiments that pulmonate
snails will not reproduce at temperatures above 30° C (Van der Schalie and
Berry, 1973). He studied the life cycle of Physa virgata in an impoundment
in Texas (Lake Arlington) in which one area received heated effluent while
another did not. He found that in the heated effluent, this species
completed three generations per year and cited this as the first case in
which this phenomenon had been shown in the Physidae. P. virgata spawned at
temperatures up to 39.5° C in this heated area. He observed a more rapid
rate of growth of the second generation in the heated effluent and inferred
that in 17 years of temperature elevation, separate physiological races had
developed in the heated and unheated areas of the impoundment.
Physa heterostropha in the experimental channels were not greatly
affected by the temperature increments to which they were exposed. Eggs
were observed in this study in late August in all treatments. Those in +6 C
channels were laid in temperatures of 33° to 34.5° C, corroborating
Sankurathri and Holmes' (1976) and McMahon's (1975) findings. Whether these
eggs were viable was not determined due to termination of the experiment.
The size distribution in all treatments (although not examined statistically)
was similar to that in the heated areas of Lake Wabamun (Sankurathri and
Holmes, 1976) where all sizes were present most of the time. However, the
predominance of large snails in warmer water and small snails in cooler
water was not seen in the channels.
Physa densities in ambient channels at the end of the study were at
least three times greater than those in any other treatment. Although this
difference was not significant, it indicates that of the four treatments,
ambient was most favorable for growth, assuming the absence of differential
predation by fish or large invertebrates. In an earlier study in which two
channels with fish were compared with two without, there was no significant
difference in gastropod densities between treatments (unpublished data).
114
-------
However, the data from examination of bluegill stomachs at the termination
of the present study implied greatest predation on P. heterostropha in +6 C
channels and least in ambient and +4 C channels. Not clearly demonstrated,
therefore, was that temperature alone effected treatment variance.
In all but the warmest channels, Physa populations along walls and on
rock areas began to decline in April and May, while those in pool areas
increased. There was either a migration at this time and/or a dying-off
with young snails. One common pulmonate life cycle has two generations per
year (McMahon, 1975), a spring generation which hatches from eggs laid by
overwintering snails and which matures and breeds in late summer or fall,
giving rise to a second generation. Most snails die after breeding but
usually some of those breeding in the fall survive through the following
winter and reproduce a second time in the spring. Eggs were observed in all
treatments in late March and early April, in June and July, and in early
September. Masses of large Physa were seen floating at the surface of the
water, feet up, toward the end of March and also in mid-June. Possibly
these were snails which had reproduced and were dying. McCraw (1970) who
studied Lymnaea palustris (Muller) also remarked that most of a generation
may die during the month after a period of active egg-laying. If true,
Physa had at least two generations in the channels, regardless of temperature
treatment. Further studies concentrating on individual species will be
necessary to better define the life cycle. Although final densities varied
between treatments, life cycles apparently did not. Pool area populations
in the warmest channels did not recover as much in June as they did in other
treatments, but the small recovery was synchronized with recoveries in other
treatments, indicating the same life cycle.
The preponderance of Pyrgulopsis letsoni in +4 C channels existed early
in the study and was evidently not initiated by temperature treatment. The
population which colonized these channels was able to persist undecimated
for the duration of the experiment. Because significant populations were
never present in other treatments, it is impossible to say that temperature
was a factor influencing the persistence of this snail in +4 C channels.
Predation by fish was probably not a factor, since bluegill had not shown
significant feeding on Pyrgulopsis (unpublished data and Table 33).
The laboratory studies cited showed lymnaeids to be somewhat less
tolerant of elevated temperature than physids. Lymnaea densities in the
channels decreased to zero toward the end of the sampling period and did so
earlier in heated than in ambient channels, supporting these studies.
Amphipoda
The two genera of amphipods inhabiting the experimental channels,
Hyalella and Crangonyx, are widely distributed and common in shallow clean
waters of all types (Pennak, 1953). These genera differ in food habits,
geographic distribution, and life cycles. Hyalella feeds largely on
epibenthic algae and the bacterial community while Crangonyx is often
carnivorous (Mathias, 1971). Hyalella occurs on both the North and South
American continents while Crangonyx is restricted to the North American
continent. Crangonyx females die after producing only one brood per year;
115
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Hyalella females average 15 broods in 152 days (Pennak, 1953).
Few studies have been designed specifically to elucidate the effects of
elevated water temperatures on amphipods. Observations of temperature
effects have occasionally arisen from population studies in natural systems.
Mathias (1971) studied Hyalella azteca and Crangonyx richmondensis
occidentalis in Marion Lake, British Columbia. He found amphipods of the
Crangonyx group to be more tolerant of cold water than were Hyalella and
that the former group often bred in winter and spring when water temperatures
were as low as 5-15° C. Mathias also demonstrated that Hyalella''s brood
period, or the mean period between deposit of eggs in the female brood pouch
and release of free-swimming young, ranged from 33 to 7 days as temperature
was increased from 10° to 25° C. Strong (1972) reported that H. azteca
reproduced year-round in a hot spring at temperatures between 12° and 40° C.
Temperature effects on Crangonyx and Hyalella life cycles differed.
Crangonyx were usually less numerous and less heat-tolerant than Hyalella.
The trophic status of Crangonyx as carnivores might account for their lesser
abundance, and their cold-tolerance (Mathias, 1971) might imply a lack of
heat-tolerance in this experimental system. The first gravid female
Crangonyx were found in ambient and +2 C channels in March. They were not
found in warmer channels until April and were again seen in ambient channels
in May, possibly indicating two brood periods, which could be verified only
through further study of Crangonyx.
Hyalella populations first had gravid females in early April in +6 C
channels, in late April in +2 C and +4 C channels, and in early May in
ambient channels. These data indicated later breeding in Hyalella than in
Crangonyx and a temperature effect as well. In early June, gravid Hyalella
females were still seen in all treatments; in late June, they were found
only in the two coolest treatments, and by early July only in ambient
channels. Apparently, when temperatures rose above about 30° C, Hyalella
were no longer able to reproduce, unlike H. azteca of hot springs (Strong,
1972).
The decreases in biomass curves of Caenis sp. and Chironomidae indicated
primarily emergence, while decreases in Amphipoda indicated mortality.
These population decimations all occurred at temperatures near 30° C,
implying a direct temperature effect. However, data from separate habitats
indicated a more complex system. Ambient channel amphipods were densest in
pool areas; in +6 C channels there were never amphipods in pool areas. This
may have been attributable to low dissolved oxygen concentrations combined
with elevated temperature in these areas and/or possible greater fish
predation. On rock areas, amphipod densities attained highest levels in +2 C
and +4 C channels, indicating a positive response to temperature up to the
+6 C level in these areas. Possibly, amphipods were also best able to
escape fish predation among rocks. The above results demonstrated the need
for a more detailed study of amphipod populations in each habitat.
Ephemeroptera
The two dominant Ephemeroptera genera found in the experimental
116
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channels, Hexagenia and Caenis, are widely distributed in North America
(Edmunds et al., 1976). The Hexagenia life cycle is typically univoltine,
as is that of Caenis spp. in the northern part of their range (Edmunds et
al,, 1976). However, sporadic Caenis emergence close to but not synchronized
with the primary one might indicate the potential for multivoltine life
cycles in the southern part of their range.
Temperature has been shown to affect mayfly emergence time (Nebeker,
1971), as well as growth and development (Sweeney, 1976). The emergence of
Caenis at different times in different temperature treatments demonstrated
the influence of increased temperature on these organisms. Observation of
final nymphal exuviae on the water surfaces of the channels determined that
in early April, emergence from the +4 and +6 C treatments occurred
approximately ten days before emergence from the ambient and +2 C treatments.
The second generation's emergence began in early June in all treatments but
ambient. This second generation was less synchronized in its emergence in
heated channels than in ambient, extending from early June through August
(Wrenn, et al., 1978). The potential for multivoltinism was evident in
these warmest channels.
Recruitment in all but the warmest channels occurred primarily in pool
areas and on rock areas. The data do not indicate whether this lack of
recruitment in the +6 C channels was caused by non-viable eggs, newly
hatched nymphs unable to survive the increased temperature, or predation.
Except in ambient channels, no recruitment occurred along walls; rather,
more mature populations of fewer, larger nymphs were observed on walls
oftener than in other areas, particularly toward the end of the sampling
period. Since Caenis lay their eggs at the water surface, young nymphs
would likely be found in pools and rocks at the bottom surface of the
channels. Slightly increased population densities along walls could have
been expected as nymphs grew and moved out of the areas in which they had
hatched. Protection from fish predation along walls of the experimental
channels was predicted from earlier studies (unpublished data).
Differences in density and dry weight from treatment during the sampling
period occurred primarily beacuse of life-cycle differences. Because ambient
channel populations matured more slowly than those in heated channels, their
weights were low during the middle of the experiment. With maturity, these
ambient-channel populations rallied, surpassing the others, which declined.
In the two warmest treatments, density and biomass levels in August were
lower than those seen in any previous month. Presumably, these populations
were reduced by the effects of increased temperature and/or fish predation.
Chironomidae
Chironomidae are ubiquitous components of freshwater ecosystems, with
world-wide distribution; their taxonomic diveristy precludes a detailed
species list except in studies devoted to a family or any one of the sub-
families .
Few attempts have been made to determine effects of increased
temperature on Chironomidae populations, probably because of the
117
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aforementioned taxonomic problems. Laboratory studies that have been
conducted involved constant temperatures. Harvey (1971) was concerned
primarily with the effects of temperature on the sorption of radionuclides,
but he observed some population responses. Glyptotendipes paripes larvae
showed an increased rate of emergence and increased numbers of adults with
temperature elevation from 21° to 31° C. Nebeker (1973) found that
development rate in Tanytarsus dissimilis increased at temperatures ranging
from 21° to 28° C; however, an increase in temperature to 32° C brought no
further acceleration. Ryals and Ingram (1973) studied the interaction of
temperature and day-length on several midge species. They observed
development rates and responses to different photoperiods to be markedly
influenced by temperature.
Assuming that declines in density and dry weight were indicative of the
emergence period, chironomid emergence from +4 and +6 C channels occurred in
early June following temperature increases from 23° to 30° C and 22° to 29°
C, respectively, during the preceding month. These temperatures are within
the range proposed by Harvey (1971) at which the emergence rate of G.
paripes increased.
Although numerous chironomid species with overlapping emergence periods
were present in the experimental channels, distinct periods of peak biomass
varied with treatment. Mid-summer maximum biomass in the two warmest
treatments occurred in June, approximately one month earlier than that in +2
C channels, which in turn preceded that in ambient channels by a month.
Chironomid emergence, indicated by density declines, varied with
habitat. Mid-summer emergence from pools in the two warmest treatments
began in June, approximately one month earlier than in +2 C channels, which
in turn preceded emergence in ambient channels by a month. Declines in
density on rocks and along walls did not demonstrate the same relationship
to treatment. These chironomid results differed from Caenis emergence,
which indicated treatment effects during the emergence period in all three
habitats. Chironomids in rock areas did evidence a treatment effect
on densities at the end of May, when population size was positively
correlated with rise in temperature; however this was the only treatment
effect noted outside of pool areas. It is possible that chironomid species
composition was different enough in the three habitats that responses to
heat varied. Tanypodinae were often the prevalent sub-family in pool areas
but not on rocks or walls. Another possibility is that because temperature
in pool sediments was generally lower than that on walls and rocks (up to
approximately 3° C lower, especially at lower ends of channels) emergence in
cooler treatments lagged somewhat behind that in the warmest channels. Only
further studies could elucidate the relative sensitivity to temperature of
the various chironomid species present in the channels.
These treatment effects indicated different food resources for foraging
fish. Because pool areas were of greatest importance to total area and
because greatest chironomid biomass per unit area was in these areas (up to
2 gm m~ ) effects on Chironomidae might have had greater influence on fish
production than those on any other single macroinvertebrate group.
118
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Hirudinea
Leeches are commonly found in ponds, marshes, lakes, and slow streams
especially in the northern half of the United States (Pennak, 1953).
Treatment effects in this group were so infrequent that one might conclude
that those differences detected did not greatly influence fish production.
In terms of dry-weight biomass, these organisms at times contributed a major
portion to the whole, especially in pool areas (ca. 3 gm m~2 in ambient
channels in May). However, hirudinid turnover rates are slow relative to
most other organisms in the channels. Erpobdella spp. have been shown to
have a two-year life cycle with breeding occurring at the end of the second
year (Elliott, 1973; Aston and Brown, 1975). Because Helobdella spp.
typically have only two generations per year, with one generation over-
wintering (Davies and Reynoldson, 1975) , standing-stock biomass utilized by
fish would not be quickly replaced. The tapering off of hirudinid
populations in all channels toward the end of the sampling period was
probably due to the effects of fish predation.
Other Macroinvertebrates
Oligochaetes were treated only perfunctorily because handling them with
the care necessary to keep them intact for weighing would have required an
inordinate amount of time. Because it is possible that they formed an
important part of the bluegill diet, they were accounted for among total
macroinvertebrates. Although treatment effects were not analyzed
statistically at the end of the sampling period, there were at least 10
times as many oligochaetes in ambient channels as in heated channels. This
effect may have been caused by heat directly, by fish predation, by oxygen
depletion, or by a combination of these factors precipitated by heat
elevation.
Libellulids represented a major source of potential fish food in terms
of biomass early in the study. Because those nymphs which formed the main
component of this biomass were large, they were able to find refuge from
large bluegill among rocks; also, they were too large to fall prey to young-
of-the-year bluegill. The relative absence of libellulids on walls and in
pools was probably due to fish predation. Previous studies showed intensive
predation by bluegill on these nymphs (unpublished data). Only temperature
elevations above spring ambient temperatures (ca. 21.5° C) elicited a
treatment response. Ambient temperatures exceeding 25° C induced no further
treatment effect. It is possible that most of the nymphs present in April
and May emerged and gave rise to a second generation of nymphs which were
small enough to be fed on by young of the year .bluegill.
Trichoptera demonstrated a treatment response similar to that of Caenis
and other organisms; at the end of the study, ambient channels contained
significantly larger densities and greater biomass than did any of the
heated water channels.
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Community Interactions
Few shifts in percent abundance were attributable to temperature treat-
ment. Most such shifts were seasonal although the decimation of amphipod
populations in warm channels at the end of the experiment was reflected in
their lower percent abundance. Percents dry weight were likewise less
affected by treatment than by time. Where libellulids or hirudinids
occurred, they usually exerted a profound effect on dry weight composition
relative to their numbers. Diversity indices were no more useful than
percent composition data in defining treatment effects. Temperature
elevation, therefore, did not conspicuously alter community composition.
Although not perceptibly influenced by temperature, a relationship
between Physa and Amphipoda occurred which might, with further study, be
determined as competitive. On rock areas, where densities of both groups
were high, this interaction was especially clear (Fig. 28). Both amphipods
and physids are generally grazers, although Crangonyx sp. is inclined to
carnivorism; therefore, their food source is essentially the same. Toward
the middle of the sampling period, there were evident increases in numbers
of amphipods concurrent with decreases in Physa densities. This relation-
ship deteriorated toward the end of the study, however, giving reason for
further study at a later time.
The examination of bluegill stomach contents at the termination of the
experiment gave an indication of the food supply available in each treatment,
Chironomidae pupae were relatively more abundant than larvae in the +6 C
channels, while the reverse was true in ambient channels; this implied a
higher turnover rate for chironomids in heated channels. The decrease of
physids in +6 C pool areas in August (Table A-2) was reflected in their high
percent occurrence in fish stomachs. Amphipods, which disappeared from
heated channels before August, were not found at all in fish from +6 C
channels; probably because Caenis and Hydroptilidae were relatively more
abundant in cooler channels than in the two warmest channels, they appeared
more frequently in fish from these channels. The almost exclusive feeding
of bluegill upon physids and chironomidae pupae in the +6 C channels
indicated a lack of other food sources caused by earlier predation, or by
increased temperature. Chironomidae were the major food source in all
treatments at the end of the study.
In summary, the primary effects of long-term temperature elevation upon
macroinvertebrates in the biothermal channels were: acceleration of growth
and metamorphosis; greater density and biomass during mid-summer; and lower
density and biomass in late summer and early fall. Rarely were effects
linearly correlated with temperature increase; most frequently, groups of
two or three treatments adjacent in terms of temperature responded at the
same time. For example, Caenis emergence occurred simultaneously from the
two warmest treatments about ten days before emerging from the two coolest
treatments. Chironomidae peak dry weights in the two warmest treatments
were synchronized; those in cooler channels followed in stepwise fashion.
Amphipod peak abundance on rock areas occurred in the three warmest
treatments a month before occurring in ambient channels.
120
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103
10'
(M
E
10
103
10'
10
R heterostropha AND AMPHIPODA-ROCK AREAS
- P. heterostropho
- AMPHIPODA
AMBIENT
+ 4C
2C
10
103
I02
A S
10
Figure 28. Monthly mean density of Amphipoda and Physa heterostropha on
rock areas in four temperature treatments (three channels per treatment)
A (ambient temperature of Wheeler Reservoir, Tennessee River), and +2°,
+4°, and +6° C above ambient.
121
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Finally, temperature affected different habitats unequally, especially
for Chironomidae, which were dominant organisms and important fish food. In
the density and biomass fluctuations of chironomids, effects were seen only
in pool areas, indicating different species composition, or different
physico-chemical characteristics generated by temperature treatment.
These effects indicated different food resources available to foraging
fish in different treatments. Potential food organisms were most plentiful
in all but +2 C channels early in the study, in +2 C channels in mid-summer,
and in ambient channels at the end of the study. Total yield of adult and
young-of-the-year bluegill at the termination of the study did not reflect
final total macroinvertebrate biomass. Neither Physa heterostropha nor
Chironomidae demonstrated responses to treatment directly correlated with
temperature increase. It is possible that these organisms provided the
primary food base for bluegill in August in +6 C channels when other
macroinvertebrate populations had severely declined.
122
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REFERENCES
Armitage, B. J., T. D. Forsythe, E. B. Rodgers, and W. B. Wrenn. 1978.
Browns Ferry Biothermal Research Series I. Colonization by periphyton,
zooplankton, and macroinvertebrates. EPA Ecological Research Series,
EPA-600/3-78-020, Duluth, MN.
Aston, R. J. and D. J. A. Brown. 1975. Local and seasonal variations in
populations of the leech Erpbodella octoculata (L.) in a polluted river
warmed by condenser effluents. Hydrobiologia, Vol. 47(2-3): 347-366.
Berrie, A. D. 1969. Factors affecting growth and reproduction of freshwater
Planorbidae in East Africa. Malacologia 9(1): 35-36.
Bovbjerg, Richard V. 1975. Dispersal and dispersion of pond snails in an
experimental environment varying to three factors, singly and in
combination. Physiological Zool. 48(3): 203-215.
Chernin, Eli. 1967. Behavior of Biomphalaria glabrata and of other snails
in a thermal gradient. The Journal of Parasitology 53(6): 1233-1240.
Davies, Ronald W. and Trefor B. Reynoldson. 1975. Life history of
Helobdella stagnalis (L.) in Alberta. Verh. Internat. Verein. Limnol.
19: 282-2839.
DeWitt, Robert M. 1954. Reproduction, embryonic development, and growth
in the pond snail Physa gyrina SAY. Trans. Amer. Microsc. Soc. 73:
124-137.
Edmunds, George F., Jr., Steven L. Jensen, and Lewis Berner. 1976. The
Mayflies of North and Central America. University of Minnesota Press,
Minneapolis.
Elliott, J. M. 1973. The life cycle and production of the leech Eropbdella
octoculata (L.) (Hirudinea: Erpobdellidae) in a lake district stream.
J. Anim. Ecol. 42: 437-50.
Harvey, R. S. 1971. Temperature effects on the maturation of midges
(Tendipedidae) and their sorption of radionuclides. Health Physics 20:
613-616.
Imhof, Gerhard. 1973. Der einfluss von temperatur and photoperiode
auf den lebenszyklus einiger Siisswasserpulmonaten. Malacologia 14:
393-395.
Mathias, Jack A. 1971. Energy flow and secondary production of the
amphipods Hyalella azteca and Crangonyx richmondensis occidentals in
Marion Lake, British Columbia. J. Fish. Res. Board Canada 28: 711-726.
123
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Mattice, Jack. 1975. Effect of constant and varying temperature on egg
production of Lymnaea obrussa SAY (Mollusca: Gastropoda). Ver.
Internat. Verein. Limnol. 19: 3174-3178.
McCraw, Bruce M. 1970. Aspects of the growth of the snail Lymnaea palustris
(Muller). Malacologia 10: 399-413.
McDonald, S. L. C. 1975. Behavior of the snail Lymnaea stagnalis (L.)
in relation to temperature. Ph.D. Thesis, U. of Mich. 283 p.
McMahon, Robert F. 1975. Effects of artificially elevated water
temperatures on the growth, reproduction and life cycle of a natural
population of Physa virgata Gould. Ecology 56: 1167-1175.
Michelson, Edward H. 1961. The effects of temperature on growth and
reproduction of Australorbis glabratus in the laboratory. American
Journal of Hygiene 73: 66-71.
Nebeker, Alan V. 1971. Effect of high winter water temperature on adult
emergence of aquatic insects. Water Research 5: 777-783.
1973. Temperature requirements and life cycle of the midge
Tang tarsus dissimilis (Diptera: Chironomidae). J. Kans. Ent. Soc. 46:
160-165.
Pennak, Robert W. 1953. Fresh-water Invertebrates of the United States.
The Ronald Press Company, New York.
Ryals, G. L. and Byron R. Ingram. 1973. Laboratory responses of midge
larvae to daylength and temperature (Diptera: Chironomidae). American
Zoologist 13: 1341.
Sankurathri, C. S. and J. C. Holmes. 1976. Effects of thermal effluents on
the population dynamics of Physa gyrina SAY (Mollusca: Gastropoda) at
Lake Wabamun, Alberta. Can. J. Zool. 54: 582-590.
Sokal, Robert R. and F. James Rohlf. 1969. Biometry. W. H. Freeman and
Company, San Francisco.
Strong, Donald R., Jr. 1972. Life history variation among populations of
an amphipod (Hyalella azteca). Ecology 53(6): 1103-1111.
Sweeney, Bernard W. 1976. The response of aquatic insects to thermal
variation. Ph.D. Thesis, University of Pennsylvania.
Van Der Schalie, Henry and Elmer G. Berry. 1973. Effects of temperature on
growth and reproduction of aquatic snails. EPA Ecological Research
Series, EPA-R3-73-021.
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Wrenn, W. B., B. J. Armitage, E. B. Rodgers, and T. D. Forsythe. 1978.
Browns Ferry Biothermal Research Series II. Effects of temperature on
bluegill and walleye, and periphyton, macroinvertebrate, and
zooplankton communities in experimental ecosystems. EPA Ecological
Research Series (in press) .
125
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SECTION 8
PERIPHYTON
INTRODUCTION
Thermal additions to ambient water can affect algal populations and
community structure in various ways. The optimum temperature threshold
for some algal species may be attained resulting in increased phytosynthetic
rates and increased growth (Phinny and Mclntire, 1965). Concomitantly,
increased respiration may also result, negating gains in gross photosynthesis
(Phinney and Mclntire, 1965; Mclntire, 1966). Although generalizations
concerning the thermal maxima of taxonomic groupings of algae and other
microorganisms can be made (Cairns, 1956; Patrick, 1969; Patrick et al.,
1969; Mitchell, 1974), specific thermal limits are species dependent
(Stockner, 1967; Stockner, 1968; Patrick, 1969) and sometimes vary among
physiological strains of the species as well (Boylen and Brock, 1973;
Sorokin, 1971). The thermal tolerance of some algal species may be
exceeded resulting in lower phytosynthetic efficiency, encystment, or
death (Patrick, 1971; Hickman and Klarer, 1975). Indirect effects, such
as increased nutrient recycling or elimination of algal grazers, may
enhance the productivity of some algal species. Often, several of these
effects will occur simultaneously. All, of course, are governed by the
intensity, constancy, and duration of thermal addition as well as site-
specific chemical and physical variations which often overrule attempts
at generalities.
On a community scale the effects of thermal additions have led to
the following: (1) changes in species composition (Boylen and Brock,
1973; Klarer and Hickman, 1975; Hickman and Klarer, 1975); (2) changes
in species dominance (Klarer and Hickman, 1975; Hickman and Klarer,
1975); (3) changes in species diversity (Brown, 1973; Klarer and Hickman,
1975); (4) increases in standing crop and growth rate (Bellis, 1968;
Brown, 1973; Boylen and Brock, 1973; Hickman, 1974; Klarer and Hickman,
1975; Hickman and Klarer, 1975); (5) acceleration in light-independent
succession (Patrick et al., 1969); and/or (6) changes in abundance and
nutritional value of algae grazed by herbivores (Hickman and Klarer,
1975; Patrick, 1978).
The purpose of the research presented in this report was to identify
the effects of elevated temperature regimens on natural periphyton
assemblages found in large outdoor, semi-controlled channels.
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MATERIALS AND METHODS
Sampling for periphyton began in late March. Initially, artificial
substrates were used (cellulose acetate strips suspended in the water
column). However, because of increased losses of these substrates by fish
activity during April and May, wall scrapings were later used as a sample
source. Normally, three 0.25 m2 scrapings were taken from the channel walls
in the first two pool areas. Samples from the first pool areas were analyzed
for fresh weight, freeze-dried weight, and chlorophyll. Samples from the
second pool were analyzed for fresh weight, freeze-dried weight, chlorophyll,
total protein, total carbohydrates, net oxygen production, tetrazolium
violet activity (respiration estimator), and total cellular phosphorus.
Additionally, the fresh weight of floating algal mats (algal export) leaving
each channel was estimated.
For estimating chlorophyll a*, subsamples were macerated in a tissue
grinder with a 90% acetone (MgC03-saturated) solvent, centrifuged, and
decanted. Using a Coleman (Model 111) spectrophotometer, absorbancy values
were estimated at 750, 663, 645, and 630 nm. Correction was made for
phaeophytin. The concentration of the chlorophylls and phaeophytin were
calculated using the formula of EPA (1973).
Total protein was determined by using a modified version of the Lowry
and Biuret methods (Dorsey et al., 1975). Total carbohydrates were estimated
using a modified version of the anthrone method (Jermyn, 1975) . Net oxygen
production was estimated in situ using light bottles and an incubation
period of four hours. Estimates of the activity of the respiratory electron
transport system (ETS) were made using tetrazolium violet (Packard et al.,
1971). Periphyton subsamples were placed in 300-ml BOD dark bottles,
containing channel water and 3 ml of 0.2% w v~ solution of tetrazolium
violet, and incubated in situ for four hours. Total phosphorus concentra-
tuons in periphyton subsamples were estimated following procedures listed in
Standard Methods (see Section 3).
Qualitative microscopic examination of the periphyton from walls,
rocks, and floating mats was made to determine community composition and
dominance. Incubation (2 hr) of random scrapings with tetrazolium violet
(0.2% w v"1) facilitated the subsequent microscopic examination (Packard
et al., 1971). Metabolically active cells accumulated the reduced form of
this dye - a purple formazan percipitate. A taxon comprising 50% or more of
the algal standing crop was referred to as "dominant" while a "subdominant"
taxon comprised less than 30% of the standing crop. If two or three were
abundant, no one of which clearly exceeded 50% of the standing crop, the
term "codominant" was employed. The use of the phrase "change (shift) in
dominance" implies a change at the species level, involving the replacement
of one dominant taxon by another. "Succession", however, is used to refer
to community or assemblage changes, i.e. diatoms -> filatamentous green algae
->- blue-green algae.
127
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RESULTS
A total of 177 taxa of algae were identified, including 53 taxa
identified for the first time from the channels during this experiment
(Table 34). The 53 newly observed taxa included green algae (28), diatoms
(9), and blue-green algae (16). Similarity-matices for five sample dates
were created from presence-absence data (Table 34) employing simple matching
and Jaccard's coefficients. Cluster analysis was performed on the Jaccard
coefficients employing the unweighed pair-group method with arithmetic
averages. Resulting phenograms (Fig. 29) indicate that algal assemblages in
the +2 and +4 C treatments had the closest similarity for all sampling
dates; and that a reversal in the similarities of the algal assemblages in
the ambient and +6 C treatments occurred during the study. The assemblage
in the +6 C treatment was least similar to the other treatment assemblages
during the spring, and the assemblage in the ambient channels was least
similar during the summer. A coefficient of cophenetic correlation was
calculated for each phenogram to indicate distortion (Fig. 29). Acceptable
values were obtained for all sampling dates except those at the end of
spring and during the warmest days of summer.
Changes in dominance within the periphyton communities occurred first
in the +6 C treatment, and followed later, to varying degrees, in other
treatments. Temperature conditions for each treatment and month mentioned
below can be determined from Figure 4. During March and early April,
Tetraspora lamellosa codominated with the winter diatom Melosira varians in
the ambient channels and with Oedogonium kurzii in the +2 C and +4 C
channels. However, no significant population of Tetraspora lamellosa was
found in the +6 C channels, which were dominated by Stigeoclonium
subsecundum, Cladophora glomerata, and Oedogonium kurzii. During April,
Oedogonium kurzii was the dominant alga in the ambient, +2 C, and +4 C
channels, forming dense growths on the walls. However, in the +6 C channels
Cladophora glomerata covered the walls with Oedogonium kurzii subdominant.
During mid- to late May, Oedogonium kurzii dominated the biomass in the
ambient channels; however, little metabolic activity was noted. Cladophora
glomerata was also abundant in these channels with Characium obtusum and to
a lesser extent Cymbella minuta and Gomphonema parvulum epiphytic on the
older filaments. In the +2 C and +4 C channels Cladophora glomerata
encircled by Spirogyra gratiana and colonized by Cymbella minuta and
Gomphonema parvulum, was dominant; however, much of its former metabolic
activity had diminished. Spirogyra gratiana and the epiphytic diatoms were
highly active. In the +6 C channels a similar situation existed with the
addition that a larger number of desmid species were present, while the
blue-green algal Oscillatoria limosa and O. amphiba were subdominant.
Oedogonium kurzii was still present in large amounts in all the heated
channels, however, metabolic tests indicated that it was senescent.
During June, Spirogyra gratiana and the Cymbella-Gomphonema epiphytes
of Cladophora glomerata were the most metabolically active dominants in all
channels. Cladophora glomerata covered extensive areas but had decreased in
metabolic activity. Hydrodictyon reticulatum contributed the greatest
percentage of floating mat biomass in the ambient and +2 C channels, but was
128
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not present in significant quantities in the +4 C and +6 C channels. Of the
two diatoms epiphytic on Cladophora glomerata, Cymbella minuta was consis-
tently more numerous. However, in the +6 C channels this was reversed with
Gomphonema parvulum more numerous. During this sampling period, the largest
number of species (53) was identified from all the channels with the green
algae contributing the most taxa (31)-
During July, Spirogyra gratiana was dominant in all treatments, covering
walls and rock areas, and forming extensive floating mats. Cladophora
glomerata and its epiphytic diatoms were still present but had decreased in
importance. The blue-green alga Oscillatora princeps became an important
part of floating mat and attached communities in the +6 C channels.
During August, floating mats of Spirogyra gratiana, Oscillatoria
princeps, and Cladophora glomerata were prevalent in all the channels. The
number of blue-green algal taxa increased significantly in all channels,
many forming a thick, mud-encased scum on the walls. The number of diatoms
increased during this month, especially on mud-surfaced walls in the ambient
channels.
Monthly treatment means for algal export (floating mats) (Table 2)
indicate a maximum for all treatments during June. The +6 C treatment
consistently produced the largest monthly biomass (wet weight) of algae and
had a five month total 2 to 3 times that of other treatments.
Fresh and dry weight estimates (Tables 36-7) indicate no apparent
temperature effects. High variation within and between pools and between
channels in a treatment were common for these parameters as well as most of
the following. Sample estimates of active chlorophyll, total protein, and
total carbohydrates (Tables 38-43) indicated no apparent temperature effects.
Total protein, per gram dry weight, decreased in all treatments during the
summer. Protein to carbohydrate ratios also decreased toward the end of the
summer (Table 44). Total phosphate, per gram dry weight, was significantly
different in the +4 and +6 C treatments during the last sampling date (Table
45). Treatment means of assimilation ratios (mg 02 hr"1 mg"1 chlorophyll)
are presented in Table 47. Only during July were statistically significant
differences (P > .01) noted. Estimates of ETS (tetrazolium violet) activity
(ml 02 consumed hr"1) are presented in Table 48. Statistically significant
(P > 0.1) treatment differences were found for the ETS/chlorophyll a* ratios
during the last two monthly sampling dates. Step-wise regression procedures
(SAS Institute Inc., Raleigh, NC) were performed upon all the variables
estimated for the last three monthly sampling dates (7 July, 3 August, and
31 August). A significance level of 0.1 was used as a criterion by which a
variable was added to the model. Regression equations for the dependent
variables (net oxygen production and ETS activity) are found in Table 49.
129
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DISCUSSION
Although many parameters were estimated, variation of periphyton
biomass was too high for statistical comparison among treatments for
individual channel sampling locations. However, because a channel's
contributions to algal export were derived from the entire channel, variation
within treatments for this parameter were comparatively low. In addition,
indications of temperature effects from shifts in dominance and community
succession were not affected by patchy distributions.
Sampling Variation
One of the most difficult decisions when initiating an experiment is
determining the number of samples needed to satisfy both statistical
reliability and economic-time practicalities. This problem was made evident
during the past several years by macrobenthic workers attempting to
determine the number of areal samples needed for a single riffle. Estimates
have ranged from a small fraction of the riffle's area to several times the
riffle's area.
The number of samples needed for estimating periphyton parameters is no
less uncertain. Patchy distributions in many natural habitats are the norm,
formed partially by random dispersal of propagules, by macrohabitat
variations, and by competition for substrate attachment sites. Compounding
this macro-sampling problem is a subsampling problem; subsamples of a
periphyton sample will contain varying percentages of actively growing,
senescent, and dead algal cells. A subsample used for estimating net oxygen
production, therefore, may have little correlation with an estimate of total
protein or chlorophyll taken from another subsample. This problem can be
partially circumvented by making multiple estimates from the same subsample
(e.g., determining net oxygen production, then extracting the chlorophyll,
then measuring total protein in the remaining residue). However, this also
has obvious limitations.
While the primary objective of this experiment was to determine the
effect of elevated temperatures on various periphyton parameters; the
results indicate that variation between temperature treatments was usually
less than variation within and between pools and among channels in a
treatment. This was especially true for biomass estimates from wall
scrapings. Estimates of physiological parameters (e.g., mg 02 produced/mg
chl, etc.) were no more illuminating. Obviously, any temperature effects on
wall periphyton were masked by patchy distribution, subsampling deficiencies,
and/or other factors.
One of these "other" factors affecting periphyton density on the
channel walls was shading by algal mats. Floating algal mats, composed of
filamentous green and blue-green algae, were formed by contributions from
the channel walls (Oedogonium, Cladophora, and Hydrodictyon), from the rock
areas (Cladophora and Spirogyra), and from the pool sediment surface
(Spirogyra and Oscillatoria). Additional growth occurred along the edges
130
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of the mats. When located near a wall or over a pool or a rock area, the
mats effectively depressed phytosynthetic activity for attached algae below
them. This decreased growth along one section of the channel and allowed
growth along another section, thus increasing the variation in biomass.
Thermal Effects
During the present study, two effects of increased temperature on the
algal community were noted. First, a greater monthly and total biomass of
algal export was observed in the +4 C and +6 C treatments versus the +2 C
and ambient treatments. Algal export provided the best indication of
thermal enhancement. Because of the extreme patchiness of the attached wall
communities, no definite thermal effects on standing crop for this sub-
stratum could be discerned. Second, within both the floating mats and the
wall communities, succession and shifts in dominance were accelerated in the
+6 C channels.
More algal biomass was exported monthly from the +6 C treatment channel
(Table 2). Converting to dry weight, the total yield ranged from ca. 1600
kg ha-1 in the ambient channels to ca. 4100 kg ha"1 in the +6 C channels.
Examination of nutrient data indicates sufficient total ortho-phosphorus
(0.03-0.10 ppm) and nitrate (0.02-0.66 ppm) concentrations for algal blooms.
Because the experimental channels are a flow-through system, these nutrients
were supplied constantly. Nutrient rich sediment inputs following heavy
rains and anaerobic release from pool sediments provided additional nutrient
sources to sustain blooms. Luxuriant growths of algae are typical of many
canals and channels. Oksiyuk (1969, as cited in Coutant, 1970) stated that
these growths are a general problem of canals occurring wherever growth
supporting nutrients are present in sufficient quantities. Thus, the
differences in magnitude of algal export among treatments were attributed to
temperature related stimulation. However, the magnitude of yield in all
treatments was attributed to temperature and continuous inputs of nutrients
in sufficient concentrations to maintain growth.
The influence of thermal increments was evidenced in species composition
and dominance during the first sampling in March. Tetraspora lamellosa, an
early spring bloomer, and Melosira varians, a winter dominant, were
codominant only in the ambient channels. These species were the standard
early spring dominants during the previous two years. However, in the +2 C
and +4 C channels, Melosira varians declined while Oedogonium kurzii was
codominant with Tetraspora lamellosa. In the +6 C channels Tetraspora
lamellosa failed to establish any significant populations. It might be
postulated that the filamentous green algae which dominated the +6 C channels
at this time out-competed the Tetraspora lamellosa for substratum space or
that extracellular substances inhibited colony formation. Although these
mechanisms might have been contributory, temperature increases appear to be
a direct factor affecting the Tetraspora lamellosa in the +6 C channels.
The presence of significant populations of Cladophora glomerata in the
+6 C channels during March was evidence of accelerated succession.
Cladophora glomerata normally was dominant during May in ambient waters.
131
-------
The temperature during late March in the +6 C channels was 20-22C, similar
to the optimum growth temperature (22-23C) for Cladophora glomerata noted by
Gerloff and Fitzgerald (1976). Cladophora glomerata was persistent, main-
taining a significant, if not active, biomass throughout the spring and
summer months. Even when metabolic activity decreased, as indicated by
tetrazolium violet reduction, Cladophora glomerata filaments provided a
substratum for Characium obtusum, Gomphonema parvulum, and Cymbella minuta
populations which exhibited high metabolic activity during late spring and
early summer.
Oedogonium kurzii was another persistent alga. Although tests in-
dicated little metabolic activity after mid-May, filaments were commonly
found in wall scrapings for the entire study period. This species also
provided a substratum for diatoms, green algae, and later some smaller
filamentous blue-green algae. Previous observations of Oedogonium kurzii in
the channels, indicated population maxima during the winter months and again
in the spring in ambient waters. In this study, Oedogonium kurzii decreased
in metabolic importance earlier in the heated channels.
The summer dominant, Spirogyra gratiana, assumed importance in the
heated channels 2-3 weeks earlier than in the ambient channels. As opposed
to Oedogonium kurzii and Cladophora glomerata, Spirogyra gratiana filaments
did not support an epiphytic flora. A mucilaginous sheath barred such
exploitations. The optimum temperature threshold for phytosynthesis and
growth was reached in the heated channels during May, with Spirogyra gratiana
continuing as the dominant or codominant alga throughout the summer. The
maximum lethal temperature (44C) cited for this alga (DeVries, 1870) was
never attained.
The filamentous blue-green algae also appeared initially in the heated
channels and became subdominant or codominant in those channels prior to
being prevalent in the ambient channels. Oscillatora limosa and O. amphiba
became subdominant during May in the +6 C channels. Oscillatoria princeps
replaced O. limosa and O. amphiba as the dominant blue-green in the +6 C
channels. As the summer progressed, the +4 C, +2 C, and finally the ambient
channels developed large populations of 0. princeps. Similarly, the blue-
green dominated, mud-encased scum on the channel walls developed first in
the +6 C channels and last in the ambient channels. The free floating blue-
green filaments harbored no epiphytic flora; however, the mud-encased scum
did provide a substratum for several diatom species.
Changes in the composition of algal communities may directly affect the
growth, reproduction, or survival of herbivores and ultimately carnivores.
Certain groups of algae have generally higher prey value than others (Bush
et al., 1974; Patrick, 1978), e.g. diatoms > green algae > blue-green algae.
Even within these general groups some genera are more favorable prey than
others in terms of availability and nutritional value (Patrick, 1978), e.g.
Navicula-Nitzschia > Cocconeis-Melosira, and Cladophora > Spirogyra. During
this experiment, the early disappearance of Tetraspora lamellosa in the +6 C
channels, replaced by filamentous green algae and attached diatoms, was not
detrimental to the herbivores either in terms of nutrition or availability.
The dense mucilage which encloses Tetraspora cells presumably inhibited
132
-------
grazing. Later in the spring, the epiphytic diatoms on Cladophora glomerata
and Oedogonium kurzii filaments provided a good prey source for herbivores.
The major nutritional impact of accelerated succession on herbivores
occurred during July and August when Spirogyra gratiana and Oscillatoria
princeps began to dominate the algal communities. These taxa offered low
prey value and, additionally, harbored few epiphytes. This negative impact
was partially offset during August by an increase in numbers and taxa of
diatoms on the sediment layers on walls, pools, and rock areas. In general,
the accelerated succession and increased biomass accumulation in the heated
channels appeared to increase the herbivore food supply during the spring
and early summer, but appeared to decrease the supply temporarily during
late summer.
A general effect of temperature on periphyton communities was to
accelerate the timing of shifts in dominance or succession. All algal
species which developed populations in +2 C, +4 C, and +6 C channels
eventually developed populations in the ambient channels. There were no
thermophilic species noted for this experiment which developed only in the
warmest channels. The maximum temperatures attained (< 36C) were probably
not high enough to accomodate or enhance such taxa. Another general effect
was an increase in biomass in the warmest channels. Although wall biomass
was not a good indicator of this due to sloughing, shading, grazing, etc.,
algal export, fueled by inputs from the walls, pool sediments, and rock
areas, did provide a clear indication of increased biomass accumulation.
Factors other than temperature, such as extracellular metabolites (Keating,
1976) and mega- and micronutrients (Patrick, 1978) can cause shifts in
species composition and increases in standing crop. However, the semi-
controlled nature of the biothermal channels (identical flow rates, substrate
types, nutrient inputs, etc.) precluded many of these factors. Thus it was
concluded that temperature increments above ambient were responsible for the
nonsynchronous population shifts and the increased accumulation and export
of algal biomass.
133
-------
REFERENCES
Bellis, V. J. 1969. Unialgal cultures of Cladophora glomerata (L.)
Kutz. I. Response to temperature. J. Phycol. 4: 19-23.
Boylen, C. W. and T. D. Brock. 1973. Effects of thermal additions from the
Yellowstone geyser basins on benthic algae of the Firehole River.
Ecology, 54: 1282-1291.
Brock, T. D. and J. Hoffman. 1974. Temperature optima of algae living in
the outfall of a power plant on Lake Monona, Wise., Wise. Acad. Sci.
Arts Letts., 62: 195-203.
Brown, S. D. 1973. Site variation in littoral periphyton populations:
correlation and regression with environmental factors. Int. Rev. ges.
Hydrobiol., 58: 437-461.
Bush, R. M., E. B. Welch, and B. W. Mar. 1974. Potential effects of thermal
discharge on aquatic systems. Envir. Sci. Tech., 8: 561-568.
Cairns, J., Jr. 1956. Effects of increased temperature on aquatic
organisms. Indus. Wastes, 1: 150-152.
Coutant, C. C. 1970. Biological aspects of thermal pollution I.
Entrainment and discharge canal effects. pp. 341-381, CRC Crit. Rev.
Envir. Control.
DeVries, H. 1870. Materiaux pour la connaissance de 1'influence de la
temperature sur les plantes. Arch. Neer. Sci. Exactes Natur., 5: 385-
401.
Farrell, J. and A. Rose. 1967. Temperature effects on microorganisms.
Ann. Rev. Microbiol., 21: 101-120.
Gerloff, G. C. and G. P. Fitzgerald. 1976. The nutrition of Great Lakes
Cladophora. EPA-600/3-76-044, Envir. Res. Lab, Duluth, MN.
Hickman, M. 1974. Effects of discharge of thermal effluent from a power
station on Lake Wabamun, Alberta, Canada - The epipelic and epipsammic
algal communities. Hydrobiol., 45: 199-215.
Hickman, M. and D. M. Klarer. 1975. The effects of the discharge of thermal
effluents from a power station on the primary productivity of an
epiphytic community. Br. Phycol. J., 10: 81-91.
Keating, K. I. 1976. Algal metabolite influence on bloom sequence in
eutrophied freshwater ponds. EPA-600/3-76-081, EPA, Corvallis, OR.
Klarer, D. M. and M. Hickman. 1975. The effect of thermal effluent upon
the standing crop of an epiphytic algal community. Int. Revue ges.
Hydrobiol., 60: 17-62.
134
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Mclntire, C. D. 1966. Some factors affecting respiration of periphyton
communities in lotic environments. Ecology, 47: 919-930.
Mitchell, R. 1974. The evolution of thermophily in hot springs. Quart.
Rev. Biol., 49: 229-242.
Packard, T. T., M. L. Healy, and F. A. Richards. 1971. Vertical
distribution of the activity of the respiratory electron transport
system in marine plankton. Limnol. Oceanogr., 16: 60-70.
Patrick, R. 1969. Some effects of temperature on freshwater algae, In:
Biological Aspects of Thermal Pollutions. Symposium Proceedings,
Portland, OR, June 3-5, 1969. pp. 161-198. Vanderbilt Univ. Press,
Nashville.
Patrick, R. 1971. The effects of increasing light and temperature on the
structure of diatom communities. Limnol. Oceanogr., 16: 405-421.
Patrick, R. 1974. Effects of abnormal temperatures on algal communities.
In: Thermal Ecology, J. W. Gibbons and R. R. Sharitz (eds.). pp. 335-
349. U.S. ERDA, Washington, D.C.
Patrick, R. 1978. Effects of trace metals in the aquatic ecosystem.
Amer. Sci., 58: 185-191.
Patrick, R., B. Crum, and J. Coles. 1969. Temperature and manganese as
determining factors in the presence of diatom or blue-green algal
floras in streams. Proc. Nat. Acad. Sci., 64: 472-478.
Phinney., H. K. and C. D. Mclntire. 1965. Effect of temperature on
metabolism periphyton communities developed in laboratory streams.
Limnol. Oceanogr. 10: 341-344.
Sorokin, C.. 1971. Calefaction and phytoplankton. Bioscience, 21: 1153-
1159.
Stockner, J. G. 1967. Observations of thermophilic algal communities in
Mount Rainier and Yellowstone National Park. Limnol. Oceanogr. 12: 13-
17.
Stockner, J. G. 1968. The ecology of a diatom community in a thermal
stream. Br. Phycol. Bull., 3: 501-514.
135
-------
0.5
1.0
MARCH (.93)
A
2
4
6
MAY (.96)
A
2
4
6
JUNE (.67)
A
2
4
6
JULY (.84)
A
2
4
6
AUGUST (.68)
A
2
4
Figure 29. Phenograms derived from periphyton presence-absence data
(Jaccard coefficients - unweighed pair group method with arithmetic
averages; * - coefficient of cophenetic correlation).
136
-------
TABLE 34. PERIPHYTON PRESENCE-ABSENCE DATA FROM MONTHLY WALL SCRAPES.
Class/Species Date: March May June July August
Treatment: A +2 +4 +6 A +2 +4 +6 A +2 +4 +6 A +2 +4 +6 A +2 +4 +6
Chlorophyceae
*Characium obtusum
*Characium sp.
Chlamydomonas sp.
Cladophora glomerata
*Closterium ehrenbergii
var. malinvernianum
*Closterium littorale
Closterium lunula
*Closterium parvulum
Cosmarium botrytis
X
X
X X X X
X X X X X
X
XX XXXX XXXX XXXX
X X
X X
XXXX X
X X
Periphyton species identified for the first time during this experiment.
XXXX
var. tumidum X X
Cosmarium exiguum X
*Cosmarium granatum X XXX
^Cosmarium impressulum
Cosmarium margaritatum X
X X
X XX
X
X
(continued)
-------
TABLE 34 (continued).
Class/Species Date: March May June July August
Treatment: A +2 +4 +6 A +2 +4 +6 A +2 +4 +6 A +2 +4 +6 A +2 +4 +6
Cosmarium ochthodes
var. amoebum X X
*Cosmarium subcrenatum X
*Cosmarium tinctum X
*Cosmarium sp. XX
Hydrodictyon reticulatum X XX X X X X
Oedogonium kurzii XXXX XXXX XXXX XXXX XXX
Pandorina morum X X
*Pediastrum duplex X X
var. clathratum
*Pediastrum duplex X X
var. duplex
*Pediastrum duplex x
var. gracilimum
Pediastrum duplex X
var. reticulatum
*Pediastrum sculpatum X
-A- Periphyton species identified for the first time during this experiment.
(continued)
-------
TABLE 34 (continued)
Class/Species Date: March May
Treatment: A +2 +4 +6 A +2 +4 +6
*Pediastrum simplex
var. duodenarium
*Pediastrum simplex
var. simplex
*Pediastrum tetras
*Pediastrum sp.
*Pleurotaenium maximum
*Pleurotaenium trabecula
Protodertna viride
June
A +2 +4 +6
July
A +2 +4 +6
X X
X
X
August
A +2 +4 +6
*Scenedesmus acuminatus
*Scenedesmus bujuga
var. alterans
*Scenedesmus dimorphus
Scenedesmus quadricauda
*Sphaerocystis schroeteri
Spirogyra gratiana
Spirogyra sp.-l
X
X
X
XX XXX X X
X
X XXXX XXXX XXXX XXXX
X X X X XX
Periphyton species identified for the first time during this experiment.
(continued)
-------
TABLE 34 (continued).
Class/Species Date: March May June
Treatment; A +2 +4 +6 A +2 +4 +6 A +2 +4 +6
July
A +2 +4 +6
August
A +2 +4 +6
-C-
o
*Spirogyra sp.-2
*Stigeoclonium subsecundum XX X
*Tetraedron pentaedricum
Tetraspora lamellosa XXX
"Ulothrix sp.
Bacillariophyceae
Achnanthes exigua X
*Achnanthes sp.
Cocconeis disculus X
Cymbella affinis X
Cymbella minuta
Cymbella postrata X
Cymbella tumida X X
Diatoma hiemale X
*Eunotia sp.
X
X
X
X
XXX
X X
X
xxxx xxxx xxxx
X X
X
X X
X
XXX X
* Periphyton species identified for the first time during this experiment.
(continued)
-------
TABLE 34 (continued).
-e-
Class/Species Date: March May June
Treatment: A +2 +4 +6 A +2 +4 +6 A +2 +4 +6
*Fragilaria capucina XXX X X X X
Fragilaria crotonensis X X X X X X X
Gomphonema angustatum X X X X
Gomphonema parvulum X X XXXX XXXX
*Gyrosigma kutzingii XXX
*Gyrosigma scalproides X XXX
Melosira granulata XXXX XXX
Melosira granulata X X XXXXXX
var . angustissima
Melosira varians XXXX XXXX XXXX
*Navicula capitata XXXX
*Navicula confervacea
Navicula mutica
Navicula radiosa XX X X
*Navicula viridula
var. rostellata
July August
A +2 +4 +6 A +2 +4 +6
XXX XXX
X XX
XXXX X
XXXX XXXX
X XX
X
XXXX XXX
X X
XXX X
X
X
*Periphyton species identified for the first time during this experiment.
(continued)
-------
TABLE 34 (continued).
Class/Species Date: March
Treatment: A +2 +4 +6
Navicula sp .
Nitzschia acicularis X
Nitzschia dissipata X X
Nitzschia palea
Nitzschia tryblionella
Opeophora martyi
Rhoicosphenia curvata
Stauroneis anceps X
*Surirella linearis
Synedra actinastroides
Synedra acus X X
Synedra rumpens
Synedra ulna
May June July August
A +2 +4 +6 A +2 +4 +6 A +2 +4 +6 A +2 +4 +6
X X X X XXX
XXX X
X XX
XX XXX
X XX
X
X
X XXXX XXX
XXX X
XXXX
X
XX XXXX XXXX
Synedra ulna
var. longissima
XXXX XXXX
Periphyton species identified for the first time during this experiment.
(continued)
-------
TABLE 34.(continued).
-C-
LO
Class/Species Date: March
Temperature: A +2 +4 +6
Cyanophyceae
*Aphanocapsa pulchra
*Aphanothece gelatinosa
*Calothrix stellaris
3'cChroococcus sp.
*Lyngbya gardneri
*Lyngbya major
*Lyngbya nigra
*Lyngbya spirulinoides
*Lyngbya versicolor
*Lyngbya sp.
Merismopedia sp.
*0scillatoria amphibia
*0sc illatoria decolorata
*Oscillatoria limosa
XXX
X
XXX
X X
May June
A +2 +4 +6 A +2 +4 +6
XXX
XXX
XXX
July
A +2 +4 +6
XXXX X XXX
XXX X
XXXX X XX
*Periphyton species identified for the first time during this experiment.
XXX
August
A +2 +4 +6
X X
XXX X
XXX
X X
XXX X
X X
XXX X
XXXX
(continued)
-------
TABLE 34 (continued).
Class/Species Date: March May June
Treatment: A +2 +4 +6 A +2 +4 +6 A +2 +4 +6
July
A +2 +4 +6
August
A +2 +4 +6
Oscillatoria nigra
Oscillatoria princeps
^Oscillatoria proboscidea
^Oscillatoria sancta
^Oscillatoria subbrevis XXX
X X
XXX
X
XXX X
XXX X
X
X
.p-
-p-
*Periphyton species identified for the first time during this experiment,
-------
TABLE 35. ALGAL EXPORT (KG FRESH WEIGHT) - 1977.
TEMPERATURE
REGIMEN APRIL
Ambient
+2 C
+4 C
+6 C
x a 4
s b 2
x 1
s 0
I 12
s 14
x 34
s 18
.3
.1
. 2
.6
.4
.5
.1
.8
MAY
66.
32.
14.
7.
60.
63.
85.
41.
JUNE
4
4
2
0
4
5
3
2
111.
14.
81.
41.
109.
28.
306.
59.
3
0
6
4
7
9
1
5
JULY
53.
7.
71.
10.
91.
15.
123.
11.
1
4
6
5
8
8
7
2
TOTAL KG
AUGUST CHANNEL- 1
23.
3.
36.
3.
69.
15.
109.
13.
1 258.2
4
8 205.4
0
5 343.8
7
5 658.5
6
TOTAL KG
HA"1
5379
4279
7163
13719
Treatment mean (n = 3).
Standard deviation (±).
145
-------
TABLE 36. PERIPHYTON FRESH WEIGHT (GM M-/) - POOL 2.
TEMPERATURE
REGIMEN
AMBIENT
+2 C
+4 C
+6 C
•q
Treatment
Standard
TABLE 37.
TEMPERATURE
REGIMEN
AMBIENT
+2 C
+4 C
+6 C
1977:
— a
X
b
s
X
s
X
s
X
s
mean (n = 9) .
deviation ( + ) .
PERIPHTYON DRY
1977:
— a
X
b
s
X
s
X
s
X
s
6-20
51
38
49
27
39
24
23
17
WEIGHT
6-20
7
5
8
4
6
4
6
4
7-06
60
19
112
58
99
37
93
91
(GM M~2)
7-06
11
5
24
7
27
11
18
13
7-21
33
9
57
30
88
36
69
20
- POOL 2.
7-21
9
2
14
5
23
7
16
5
8-03
67
49
90
48
110
32
89
13
8-03
21
15
30
20
31
7
28
8
8-16
58
29
53
6
102
34
45
19
8-16
14
6
15
5
25
8
10
6
8-31
45
7
68
41
92
11
48
21
8-31
12
4
21
11
16
5
9
4
Treatment mean (n = 9)
Standard deviation (±)
146
-------
TABLE 38. PERIPHYTON CHLORPHYLL A* (MG M~z) - POOL 1.
TEMPERATURE
REGIMEN 1977:
AMBIENT x a
b
s
+2 C 'x"
s
+4 C x
s
+6 C x:
s
Treatment mean (n =
Standard deviation
TABLE 39. PERIPHYTON
TEMPERATURE
REGIMEN 1977:
AMBEINT x" a
b
s
+2 C x
s
+4 C x:
s
+6 C x
s
5-12
132
89
108
81
38
11
52
16
9).
5-23
56
37
79
69
104
68
99
36
CHLOROPHYLL
5-12
157
22
83
42
77
60
113
121
5-23
90
32
169
102
114
65
258
155
6-09
117
17
126
96
46
41
54
23
A* (MG
6-09
148
190
45
46
57
36
124
114
6-20
75
66
51
52
62
51
34
21
M~2) -
6-20
48
45
42
34
31
24
21
17
7-06
18
11
70
36
144
146
44
13
POOL
7-06
36
13
92
58
105
44
104
109
7-21
40
18
68
59
81
20
109
17
1.
7-21
30
11
63
44
100
53
88
18
8-03
95
44
69
28
160
82
61
17
8-03
51
42
55
9
115
48
116
29
8-16
100
90
70
40
153
51
50
17
8-16
90
50
60
17
172
121
59
18
8-31
56
52
68
89
158
22
80
48
8-31
50
10
76
41
130
36
78
29
3 Treatment mean (n = 9).
b Standard deviation (±).
147
-------
TABLE 40. PERIPHYTON TOTAL PROTEIN (MG M~2) - POOL 2.
TEMPERATURE
REGIMEN
AMBIENT
+2 C
+4 C
+6 C
Treatment
Standard
TABLE 41.
TEMPERATURE
REGIMEN
AMBIENT
+2 C
+4 C
+6 C
1977: 6-09
x a 631
s b 206
~x 358
s 67
x 479
s 250
x 547
s 293
mean (n = 9) .
deviation (±) .
PERIPHYTON TOTAL PROTEIN
1977: 6-09
— a c
x -
b
s -
X -
s
x -
s -
X
s -
6-20 7-06 8-03 8-31
465 320 748 307
314 70 631 77
534 658 646 487
290 275 63 348
308 806 774 394
349 231 91 115
250 852 886 249
172 703 247 97
/ DRY WEIGHT (GM GM~ l ) - POOL 2.
6-20 7-06 8-03 8-31
.066 .036 .033 .027
.015 .020 .015 .006
.066 .027 .027 .023
.015 .005 .006 .006
.050 .038 .023 .027
.028 .019 .006 .006
.043 .050 .033 .027
.012 .030 .015 .006
Treatment mean (n = 9)
Standard deviation (±)
Data not available.
148
-------
TABLE 42. PERIPHYTON TOTAL CARBOHYDRATE (GM M 2) - POOL 2.
TEMPERATURE
REGIMEN 1977:
AMBIENT x E
b
s
+2 C x
s
+4 C x
s
+6 C x'
s
Treatment mean (n = 9) .
Standard deviation (±) .
TABLE 43. PERIPHYTON TOTAL
TEMPERATURE
REGIMEN 1977:
AMBIENT x a
b
s
+2 C x
s
+4 C x
s
+6 C x
s
7-06
2.15
.33
4.57
2.99
3.51
1.51
2.69
2.69
CARBOHYDRATE
7-06
.16
.02
.18
.11
.13
.01
.14
.06
8-03
3.28
2.55
2.04
.82
4.48
2.30
2.70
.85
/ DRY WEIGHT (GM GM"1)
8-03
.14
.03
.08
.05
.14
.04
.10
.01
8-31
2.57
1.21
2.55
.94
3.73
1.82
2.51
1.29
- POOL 2.
8-31
.22
.09
.13
.03
.23
.09
.27
.08
Treatment mean (n = 9)
Standard deviation (±)
149
-------
TABLE 44. PERIPHYTON TOTAL PROTEIN / TOTAL CARBOHYDRATE - POOL 2.
TEMPERATURE
REGIMEN
AMBIENT
+2 C
+4 C
+6 C
0
Treatment
Standard
TABLE 45.
TEMPERATURE
REGIMEN
AMBIENT
+2 C
+4 C
+6 C
1977:
— a
X
b
s
X
s
X
s
X
s
mean (n = 9) .
deviation (±) .
PERIPHYTON TOTAL
1977:
— a
X
b
s
X
s
X
s
X
s
7-06 !
.15
.01
.19
.11
.25
.09
.37
.13
PHOSPHATE / DRY WEIGHT
7-06
.047
.015
.045
.004
.047
.016
.040
.016
3-03
.27
.11
.35
.14
.20
.10
.35
.16
(GM GM"1)
8-03
.026
.004
.027
.005
.042
.017
.033
.002
8-31
.13
.04
.18
.07
.12
.07
.12
.05
- POOL 2.
8-31
.028
.016
.035
.002
.064
.012
.061
.021
Treatment mean (n = 9).
Standard deviation (±).
150
-------
TABLE 46. PERIPHYTON NET OXYGEN PRODUCTION (GM M~2 HR-1) - POOL 2.
TEMPERATURE
REGIMEN 1977: 4-25 5-12 6-09 7-06 8-03
AMBIENT x a 1.06 .05 .66 .20 .13
+2 C I .35 .09 .24 .27 .15
+4 C x .51 .10 .35 .22 .24
+6 C x .67 .12 .62 .26 .35
•3
Treatment mean (n = 3) .
TABLE 47. PERIPHYTON ASSIMILATION RATIO (GM 0 HR"1 GM~ 1 CHL A).
2
TEMPERATURE
REGIMEN 1977: 4-25 5-12 6-09 7-06 8-03
AMBIENT ^ a 4.2 0.4 4.1 5.6 2.9
+2C x" 8.0 1.0 6.4 2.9 2.7
+4C I 7.6 1.8 5.4 2.2 2.3
+6C :x 11.6 2.4 4.2 2.9 3.0
ANOVAb ns ns ns P>.01 ns
8-31
.12
.18
.32
.20
8-31
2.4
2.5
2.5
2.6
ns
Treatment mean (n = 3)-
Analysis of variance of treatment (temperature) effect; ns -
not significant (P>.05).
151
-------
TABLE 48. TETRAZOLIUM VIOLET (ETS) ACTLVLTY - POOL 2.
TEMPERATURE ML 02 M~2
REGIMEN 6-09 7-06
AMBIENT 1? -° 1.
b
s
+2 C x: - 2.
s - 1.
+4 C x .69 2.
s .33 2.
H- +6 C jc 1.48 2.
Ul
s 1.24 1.
09
69
61
52
98
79
23
79
HR-1
8-03
1.71
1.30
1.92
.31
1.72
.30
3.42
1.23
8-31
1.28
.56
1.67
1.17
1.81
.35
1.11
.50
ANOVAd :
UL 02 HR-1
6-09 7-06
31
22
30
4
15 28
8 18
24 30
10 22
ns
MG-1 CHL A
8-03 8-31
45
26
35
8
17
7
29
4
P>.06
25
6
21
5
14
1
14
1
P>.01
UL 02 HR-1 MG"1
6-09 7-06 8-03
3.2
1.3
3.8
.8
1.5 3.3
.1 2.2
4.0 2.6
1.0 .4
ns
2.7
1.0
3.0
.8
2.2
.2
3.8
.9
ns
PROTEIN
8-31
4.1
.9
4.0
2.1
4.7
.4
4.4
.4
ns
Treatment mean (n = 3).
Standard deviation (±).
Data not available.
Analysis of variance of treatment (temperature effect; ns - not significant (P>.10).
-------
TABLE 49. REGRESSION EQUATIONS FOR THE DEPENDENT VARIABLES NET OXYGEN AND
PRODUCTION AND TETRAZOLIUM VIOLET (ETS) ACTIVITY.
COEFFICIENT OF
DATE EQUATION DETERMINATION (R2)
7-6-77 [02]a = 0.721 * [carbohydrate] + 2.61 .76
[TV] + 1.183 * [protein] - 3.023 .78
8-3-77 [02] = 0.882 * [chlorophyll a] + 1.246 .93
[TV] = 0.41 * [chlorophyll a] +
0.797 * [protein] -
0.484 * [carbohydrate] - 2.528 .88
8-31-77 [02] = 1.107 * [chlorophyll a] -
0.288 * [protein] + 1.506 .89
[TV] = 1.055 * [chlorophyll a] -
4.032 * [temperature] + 4.143 .87
The brackets around each parameter signifies the log concentration.
i o
153
-------
APPENDICES
154
-------
TABLE A-l. SAMPLES TAKEN IN EXOTHERMAL CHANNELS.
Date
1977
3-2
3-24
3-30
4-5
4-27
5-2
5-6
5-11
5-27
6-6
6-10
6-28
7-1
7-7
7-28
8-2
8-8
8-31
9-2
W - Wall Scraping
C - Core
R - Rock Tray
* - Not Subsampled
Type
of
Sample
W*
C*
R
W
R
W
C
R
R
W
C
R
W
C
R
W
C
R
W
Pool or
Rock
Area
1,
2
1
1,
1
1,
2
2
1
1,
2
1,
1,
2,
1,
1,
2,
1,
1,
3
3
3,
3,
6
3,
6
6
3,
6
6
3,
6
6
6
6
6
155
-------
TABLE A-2. ANOVA IN PLEXIGLAS SUBSAMPLER.
Wall Scrapings
Amphipoda
Chironomidae
Caenis
Gastropoda
Hydroptilidae
Total Organisms
Rock Trays
Amphipoda
Chironomidae
Caenis
Gastropoda
Erpobdella
Cores
Amphipoda
Chironomidae
Caenis
Gastropoda
Oligochaeta
Total Organisms
N
10
10
10
10
10
10
8
8
8
8
8
10
10
10
10
10
10
X
3.70
27.40
12.60
27.40
1.10
72.10
2.50
11.75
7.88
3.25
6.25
7.6
3.0
4.4
40.9
12.2
71.00
95% Conf.
Int.
0.79
2.65
1.93
4.34
0.53
8.57
0.50
0.70
0.95
0.48
0.53
1.74
0.96
1.08
4.77
2.72
8.78
S
1.27
4.27
3.11
7.00
0.87
13.83
1.41
1.98
2.69
1.39
1.49
2.80
1.55
1.74
7.69
4.38
14.17
S2
1.61
18.22
9.70
49.04
0.77
191.29
2.00
3.93
7.26
1.93
2.21
7.84
2.4
3.04
59.09
19.16
200.8
C.V
0.34
0.15
0.25
0.25
0.79
0.19
0.56
0.17
0.34
0.42
0.24
0.36
0.52
0.40
0.18
0.35
0.19
156
-------
TABLE A-3. DRY WEIGHTS (MEAN mg m 2) OF DOMINANT TAXA AND TOTAL MACROINVERT-
EBRATE TAXA EXCLUDING MOLLUSCA IN THREE HABITATS (ROCKS, WALLS, POOLS) AND
FOUR TEMPERATURE TREATMENTS.
Total Macroinvert.
excluding Mollusca
i
Total Gastropoda
Physa and /or Lymnaea
Pyrgulopsis
Amphipoda
Caenis
Chironomidae
Hirudinea
Enallagma
Libellulidae
Trichoptera
Rocks
o
m
Vj'
S
r^
CM
C
<
l — 1
^
S
ro
>,
S
00
CM
.
C
3
^
CO
CM
rH
!-)
^
rn
oc
3
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
561
601
2549
3916
532
1332
3698
3958
723
1858
9805
16289
996
1644
1748
3146
1603
1646
861
602
893
511
406
289
640
279
139
146
9040
8055
2512
1906
1632
2617
1974
288
1014
607
593
236
58
510
8658
43
79
85
982
5774
337
1059
3374
4756
949
670
2997
4114
9040
8055
1697 819
1906
1632
2383 234
1153 821
288
1014
607
593
236
58
510
8658
43
28
18
758
5625
331 6
765 294
2364 1010
4756
535
620 50
1222 1775
4114
52
145
761
65
175
587
743
96
128
390
130
23
80
452
171
47
243
380
33
1
46
3
278
228
1045
768
68
78
138
200
53
27
299
983
46
874
961
1968
441
342
462
333
297
224
203
204
120
82
31
35
22
37
12
9
57
249
77
122
66
175
26
314
115
209
420
1072
40
14
45
90
96
45
41
31
101
42
10
54
194
140
302
1996
233
154
707
75
226
182
38
21
756
109
196
49
657
283
164
68
193
24
43
30
11
86
46
13
15
57
124
235
134
118
8
76
63
144
2
39
315
843
239
1898
3347
229
1084
9310
14872
19
159
102
5
193
57
49
24
92
76
40
42
111
22
11
20
27
9
3
(continued)
157
-------
TABLE A-3 (continued)
Total Macroinverts.
excluding Mollusca
Total Gastropoda
Physa and/or Lymnaea
Pyrgulopsis
Amphipoda
Caenis
Chironomidae
03
Cd (Q -H
0) E rH
d Cn 3
•H 03 rH
TJ M rH
3 r— ) ,
cd
a
C
"^
1 — 1
rH
^
CM
W)
<
CM
4-J
ft
0)
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
113
129
445
561
35
10
37
72
211
113
80
196
156
279
163
119
394
101
60
47
200
142
43
38
75
54
21
65
3089
3670
929
2762
6319
3585
2783
2405
3072
944
1668
181
924
257
1665
1318
737
670
1164
1747
1200
1047
4571
1653
2742
574
809
199
3089
3670
876
2762
6319
3486
2006
2405
3072
906
1048
179
924
178
628
1248
701
160
377
1609
1027
705
1327
1522
456
259
217
188
53
99
111
38
620
2
79
1037
70
40
510
790
140
173
342
3244
131
2
315
592
11
24
86
99
80
1
2
23
13
54
47
23
13
72
145
64
21
260
61
8
3
36
4
6
30
4
30
42
21
1
4
12
49
8
4
44
55
54
61
61
55
18
37
11
26
102
13
18
5
14
3
6
57
22
42
5
13
7
7
30
26
7
16
20
53
34
21
2
2
1
1
36
10
3
9
11
9
1
4
1
6
6 38 229
135 242
42
7 70
32
46
6 117
2
1 2
3 13
32 3
12
1
1 26
42
16
20
1
42
28
16
54
27
8
8
4
4
4
3
3
11
3
1
1
(continued)
158
-------
TABLE A-3 (continued)
Total Macroinverts.
excluding Mollusca
Total Gastropoda
Physa and/or Lymnaea
Pyrgulopsis
Amphipoda
Caenis
Chironomidae
01
ca nj
tJ I-l
n) tj -H a)
0) 6 rH 4J
C Ol 3 PL,
•H ra iH O
T3 M iH ft
3 M 01 0
M n3 ,n -H
•H q -H S-l
tti bq nJ H
Pools
,
cd
S
o
r-t
C
3
!->
r~~
.
rH
D
>-!
CO
60
3
<
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
3066
533
1142
408
3366
1086
8383
4570
678
2995
1106
1539
2378
2281
440
404
2956
111
565
378
236
6944
669
481
608
6445
299
9540
300
3992
418
3467
4678
5146
49
1264
144
236
6944
481
608
6445 193
299 212
7997
300
3992 457
418 23
2695 772 2
4678
5416
29
166 1098
144
17
117
32
140
255
239
542
160
93
30
93
33
14
2
1021
38
217
374
105
888
191
1661
851
1246
546
1313
268
216
1669
287
275
322
1742
494
808
375 15041
2993
947
7494
4570
293
983
208
600
86
187
159
-------
TABLE A-4 DENSITIES (MEAN no m ) OF HACROINVERTEBRATE5 IN THREE HABITATS (ROCKS. WALLS. POOLS) AMD FOUR TEMPERATURE TREATMENTS.
? ! ^
o o f] £J > a)
H H ^1 eJI i. K
ROCKS
S A 1165 407 396 10 1
. +2 C 42B7 3270 3263 1 6 1
% +4 C 6454 2324 2166 5 153
^ +6 C 4032 1672 1636 36
5 A 5833 3155 3155 24
. +2 C 7638 1113 1047 72
£. +4 C 8284 1028 849 179 12
" +6 C 4519 514 514
^ A 3061 1303 1279 24 48
-1 +2 C 3733 383 383
J- +4 C 3720 395 383
= +6 C 5146 203 203
_ A 1267 48 36 12
" +2 C 7880 120 120
1' +4 C 9008 538 48 490
£ +6 C 12542 36 24 12
» A 6353 12 6 6
+2 C 7443 54 36 18
g +4 C 5559 628 502 126
-> +6 C 4733 1297 1208 89
« A 5411 193 186 6 6
+2 C 5556 359 233 126
-3 +4 c 3250 1010 502 508
-i +6 C 3617 1040 1040
2 A 3850 199 197
+2 C 1010 138 120 18
3> +4 C 1428 1165 179 957
< +6 C 1193 592 592
0
Q.
M a O. Xl Ml W
E 1 - -1 1 3 1 1
p 5 « " ej c Sn«
^ 0 0 >J 1- a] 0) 03
n. u E-, £1 ol u :cl u
124 77 47 489
502 311 191 375 1
2556 1913 643 1369 1
358 215 143 1707
1052 490 562 108
3382 2199 1183 84
4351 2438 191'3 215
1565 1063 502 813
801 215 586 84
1842 1447 395 347
12 920 693 227 1207
120 96 24 2116
323 48 275 156
2702 2224 478 2367
12 1280 789 491 2713
478 442 36 5821 :
1572 1327 245 2438
2522 2486 36 1830
6 275 275 2235
30 30 2235
543 394 149 2361
18 18 3395 2
6 1387
1859
2 12 36 36 1034
425
29 144
180
c c
a ~o
3 2 J 2-,
§ - 2 2
U <0 0 0 -
6O *J 01
H U S
117 8 8
96 12 11
1 93 17 17
82 94 94
1159 48 48
1757 932 143 It
801 1435 120 131
1064 179 143 3
263 359 359
598 299 299
299 598 562 3
1877 36 36
514 215 215
2247 156 156
3813 263 132 12
6 5655 120 60 £
269 627 137 4S
126 239 54 IE
6 532 257 36 22
532 126 18 1C
801 257 72 IS
424 54 6 4
359 54 18 3
335 18 6 1
933 18 12
293 12 12
42 30 24
281 12 6
-• cd
J 0 0)
J M> r-l
^J C
O w
1
2
2
60
9 275
5 179 3
6 72 1
131 1
108
6 72
323
108
1 108 1
0
0 735 4
5 1363 4
1 687
8 155 1
5 60
8 640
6 149
2 96
6 1160
18
6 18
6 30
•O 0)
ffl
-------
TABLE ft-4 (continued).
A
+2 C
+4 C
+6 C
A
+2 C
+4 C
+6 C
2876
1823
1455
667
7833
5378
7599
3344
9587
14964
17302
8885
53
298
18
35
35
298
35
2104 2104
585 585
3156 3156
4326 4326
3976 3391
468 468
53
193
158
701
1286
116
585
88 2139 158
18 210 70
245 544 88
105 35
158
70
35
333
999
350
368
35
35
123
234 234 2455 701 701 1403
234 234 116 1052 451 117 234 1987
585 3156 468 468 2338
1052 234 234 1871
1754 1754 234 1754 117 117 2572
1169 1169 935 5845 117 117 1520
234 234 1169 9353 117 117 1520 117
1052 6079 1169
234
701
351
351
117
117
A
+2 C
+4 C
+6 C
A
+2
+4
+6
19640
13917
7189
4386
25779
6021
5613
2981
4092 4092
1228 1228
2163 1871
1286 1286
2163 2163
59
1112 234
117
58 58 3507 3507
64 234 234
117 117
59
878
117
2397 3975 526 58
1520 8826 175 175
1111 2689
176 2048 58 58
877 17186
117 1988
117 1520
59 1754
58
58
468 2923
994
701
643
3566
2981
1929
409
935 935
234 468
58
59 58
175
175
351
58
818 643 175 234
59 58 292 292
117 58 468 234 58
58 292 292
-------
TABLE A-4 (continued)
. ^ , s
p 1 1 1 1 1
WALLS
A 618 227 213 13 1
+2 C 636 240 236 4
j +4 C 1073 97 86 11
=: +6 C 1041 466 391 75
,„ A 3123 2897 2873 7 17
+2 C 2540 2307 2277 30
£ +4 C 1891 1622 1466 157
" +6 C 1391 1077 1060 17
A 3709 2940 2916 11 13
" +2 C 2650 1511 1504 7
J +4 C 1909 1437 1293 30 114
* +6 C 1382 269 238 13 18
0 A 2077 948 942 7
+2 C 2326 171 142 29
§ +4 C 2387 831 524 7 300 2
-> +6 C 2430 997 940 4 53
A 3888 1119 1097 11 S 2
+2 C 1587 508 228 280
•5 +4 C 1298 920 313 40 567
+6 C 1131 608 531 4 73
A 1736 391 371 9 11
+2 C 1468 783 356 427
5f +4 C 2110 1807 413 1387 7
< +6 C 962 411 338 71 2
™ A 513 82 64 22 14
j +2 C 726 318 102 216
e- +4 C 1418 1235 182 1053
f- +6 C 458 111 100 11
0 C
00 >• • CTi 'nj .C 0 1-
f
47 31 \6 190 131
302 284 18 16 76
510 495 15 232 136
205 191 *4 314 47
12 6 6 70 117
10 127 127 : 17 60
3 203 200 .3 33 17
127 127 120 7 7
224 195 .29 142 318
7 380 369 11 264 427 4 4
133 131 • 2 162 118
129 120 - 9 700 169
529 511 18 269 7 233
2 1066 1062 »4 324 7 536
477 473 4 407 2 389 2 2
153 153 660 7 418
1956 1956 382 2 20 20
647 647 178 84 2
98 98 149 36
20 20 307 122
391 391 540 318 2
44 44 360 184
164 47
236 7 178
91 91 44 202 1 1
136 180
44 31
136 136
c rc ~o
~-< & a r$ c 5
1
3 2
5 3
27
7 13
13
23 37
1 2 53
13 1 9 2 33
44 22 47
2 13 29
27 40 22 20
140 4 42 2 4 27
127 20 44 11 24 51
67 13 6 60 47 36 2
20 127 22 7 158 2 4 2 56
2 60 4 56 2 24 2 20
11 2 27 4 9 18 24
11 2 4 33 4 20
2 13 14 18 16 2 29 2
4 2 1 33 4 11 42
1 18 4 51 18
7 1 24 2 60 36
38 2 53
3 13 29 47
1 16 69 22
2 1 16 36 20
(continued)
-------
TABLE A-5. ANOVA OF TREATMENT EFFECTS ON P. LETSONI DENSITY
(no m-2) AND DRY WEIGHT (mg nr2) IN THREE HABITATS.
Date
3-2
3-24
3-30
4-5
4-27
5-1
5-11
5-31
6-6
6-10
6-28
7-1
7-7
7-28
8-2
8-8
8-31
9-2
Sample
Loc.t
W
P
R
W
R
W
R
R
W
P
R
W
P
R
W
P
R
W
Para-
P meter
N.S.
0.05
N.S.
N.S.
N.S.
0.01
N.S.
0.05
N.S.
N.S.
N.S.
0.01
N. .S
N.S.
N.S.
0.01
N.S.
N.S.
0.01
N.S.
N.S.
0.05
N.S.
N.S.
N.S.
0.05
0.01
0.05
0.05
0.01
0.01
0.01
0.01
0.05
0.05
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
N
44
44
8
8
36
33
24
24
12
12
36
36
12
12
12
12
12
36
36
12
12
36
36
24
24
24
24
36
36
24
24
24
24
36
36
Treatment Effects
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
> A =
> A =
> A =
> A =
> A =
> A =
> A =
> A =
> A =
> +2
> A =
> A =
> A =
> A =
> +2
> +2
> +2
+2 =
+2 =
+6
+2 =
+2 =
+2 =
+2 =
+ 2 =
+2 =
> A =
+2 =
+2 =
+2 =
+2 =
> A =
= A =
= A =
+6
+6
+6
+6
+6
+6
+6
+6
+6
+6
+6
+6
+6
+6
+6 +2 > A
+6 +2 > A
t W - Walls
P - Pool Sediments
R - Rock Areas
163
-------
TABLE A-6. ANOVA OF TREATMENT EFFECTS ON GASTROPODA* DENSITY
(no m~2) AND DRY WEIGHT (mg m~2) IN THREE HABITATS.
Date
3-2
3-24
3-30
4-5
4-27
5-1
5-6
5-11
5-31
6-6
6-10
6-28
7-1
7-7
7-28
8-2
8-8
8-31
9-2
Sample
Loc.t
W
P
R
W
R
W
P
R
R
W
P
R
W
P
R
W
P
R
W
P
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
0.01
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
N.S.
0.05
0.05
N.S.
N.S.
0.01
0.01
N.S.
. N.S.
N.S.
N.S.
0.05
0.05
N.S.
N.S.
0.05
N.S.
N.S.
0.05
0.05
N.S.
Para-
meter
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
no
mg
N
44
44
8
8
36
33
24
24
12
12
36
36
12
12
12
12
12
12
36
36
12
12
24
24
36
36
24
24
24
24
36
36
24
24
24
24
36
36
Treatment Effects
A = +2 = +4 > +6
A = +4 = +6 > +2
A = +4 = +6 > +2
+4 = +6 > A = +2
+4 > A = +2 = +6
+4 = +6 > A = +2
+4 = +6 > A = +2
A = +4 > +2 = +6
+4 = +6 > A = +2
+2 = +4 = +6 > A
* no - P. heterostropha
mg - P. heterostropha and Lymnaea sp.
t W - Walls
P - Pool Sediments
R - Rock Areas
164
-------
TABLE A-7. ANOVA OF TREATMENT EFFECTS ON TOTAL GASTROPODA
DENSITY (no nT2) IN THREE HABITATS.
Date
3-2
3-24
3-30
4-5
4-27
5-1
5-6
5-11
5-31
6-6
6-10
6-28
7-1
7-7
7-28
8-2
8-8
8-31
9-2
Sample
Loc.t
W
P
R
W
R
W
P
R
R
W
P
R
W
P
R
W
P
R
W
P
N.S.
N.S.
N.S.
0.05
N.S.
0.01
N.S.
N.S.
N.S.
0.05
N.S.
0.05
N.S.
N.S.
0.05
N.S.
0.05
0.01
0.01
N
8
36
24
12
36
12
12
12
36
12
24
36
24
24
36
24
24
36
Treatment Effects
A
A
A
+4
+4
A
+4
+4
= +2
> +2
= +4
= +6
= +6
= +4
= +6
> A
> +6
= +4 >
= +6 >
> +2
> A =
> +2 =
> A =
= +2 =
+6
+2
> A
+2
+6
+2
+6
t W - Walls
P - Pool Sediments
R - Rocks
165
-------
TABLE A-8. PERCENT ABUNDANCE OF MACROINVERTEBRATE TAXA IN THREE HABITATS
(ROCKS, WALLS, POOLS) AND FOUR TEMPERATURE TREATMENTS.
fC
to
Lymnaea
Pyrgulopsis
Caenis
Chironomidae
ra
0)
3i
Crangonyx
Total Amphipoda
Libellulidae
cd
-------
TABLE A-8 (continued).
in
CL.
Lymnaea
Pyrgulopsis
Caenis
Chironomidae
Hyalella
Crangonyx
Total Amphipoda
Trichoptera
Oligochaeta
Hydracarina
Nematoda
Others
Walls
CM
(-4
^
LO
cx
-------
TABLE A-8 (continued).
CN
(-1
cd
S
VO
cd
s
o
1-1
c
^
-
i-H
3
00
M
3
to
Dl
•d
Pyrgulopsis
Caenis
Chironomidae
Hyalella
Libellulidae
cd
Q)
4-1
ft
0
O
•H
H
Erpobdella
Oligochaeta
Corbicula
Ceratopogonidae
Nematoda
Hydracarina
Others
Pools
A
+2 C
+4 C
+6 C
A
+2 C
+4 C
+6 C
A
+2 C
+4 C
+6 C
A
+2 C
+4 C
+6 C
A
+2 C
+4 C
+6 C
1
16
1
5
26
0
7
0
32
28
19
5
20
8
26
29
8
0
4
0
0
0
0
0
0
0
0
0
0
0
3
0
0
0
4
0
0
0
15
3
3
0
16
15
0
2
7
0
2
6
6
11
12
10
15
4
3
1
2
1
74
11
37
0
31
19
41
31
18
39
54
68
20
63
37
46
66
33
27
58
0
0
3
0
2
4
0
0
18
7
1
0
17
1
1
0
0
0
0
0
0
0
0
18
0
0
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
4
0
4
1
0
1
3
0
2
1
5
3
6
5
8
2
6
6
1
0
0
0
0
1
0
1
0
0
0
0
11
54
24
55
17
36
30
55
26
10
8
13
14
7
9
14
13
49
34
13
1
10
10
0
8
23
1
0
0
0
0
0
0
0
0
0
0
2
0
0
1
1
0
0
2
0
0
0
0
0
0
0
4
3
0
1
2
0
1
0
0
0
0
0
0
6
4
3
0
5
0
0
0
0
0
1
0
4
8
9
0
0
0
0
0
0
0
0
0
0
0
0
0
1
4
0
0
4
4
9
4
5
3
2
6
8
4
3
3
4
5
3
8
5
4
3
5
7
3
6
168
-------
TABLE A-9. PERCENT DRY WEIGHT OF DOMINANT MACROINVERTEBRATE TAXA EXCLUDING
MOLLUSCA IN THREE HABITATS (ROCKS, WALLS, POOLS) AND FOUR TEMPERATURE
TREATMENTS.
Caenis
Chironomidae
Amphipoda
Hirudinea
Enallagma
Libellulidae
cd cd
S-l 4-1
0) CU
•p cd
ft &
o a w
,£ o n
o M >
cd
S
i— 1
ro
>-,
cd
a
00
CS1
c
3
!-D
CO
CN
.H
3
>-3
iH
01
Ml
3
<;
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
A
+2
+4
+6
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
C
49
37
40
19
12
5
3
5
1
1
3
6
4
53
54
62
27
20
53
55
33
43
50
71
18
29
22
23
3
6
10
18
2
3
9
9
1
11
12
24
34
2
5
14
10
8
10
10
15
15
7
36
9
24
29
1
32
44
20
2
17
20
1
8
27
9
1
15
23
3
5
34
23
11
50
43
11
19
1
31
9
75
6
11
1
40
17
19
11
21
4
10
10
1
30
33
8
2
9
4
6
3
2
1
3
8
6
12
21
17
51
84
31
58
94
91
2
31
25
1
30
20
35
16
3
1
4
3
3
5
2
3
4
3
1
3
2
2
2
2
5 8
4
4
6
12 17
4 10
2 3
6 2
4 24 8
312
2 1
2 1 12
(continued)
169
-------
TABLE A-9 (continued).
Caenas
Chironomidae
Amphipoda
Enallagma
Libellulidae
Trichoptera
w
M
-------
TABLE A-9 (continued).
Pools
> +4 C
S +6 C
o A
^ +2 C
c +4 C
^ +6 C
A
+2 C
rn' +4 C
3 +6 C
A
«; +2 c
ao +4 C
3 +6 C
to
"H
c;
0)
03
0
10
4
23
15
19
6
18
6
3
4
2
0)
•H
5
o
C
O
S-i
•H
i [~1
0
33
7
19
11
9
10
28
55
76
80
20
55
52
46
56
36
48
85
cd
cd
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-79-092
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE Browns Ferry Biothermal Research Series
II. Effects of Temperature on Bluegill and Walleye,
and Periphyton, Macroinvertebrate, and Zooplankton
Communities in Experimental Ecosystems
5. REPORT DATE
August 1979 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
William B. Wrenn, Brian J. Armitage,
Elizabeth B. Rodgers, Thomas D. Forsythe , and
Crannpmarm
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Tennessee Valley Authority
Biothermal Research Station
P. 0. Box 2000
Decatur, Alabama 35602
10. PROGRAM ELEMENT NO.
1BA608 1NE625
11. CONTRACT/GRANT NO.
TV-35013A
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory—Duluth, MN
Office of Research and Development
U.S. Environmental Protection Agency
Duluth, Minnesota 55804
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA-600/03
15. SUPPLEMENTARY NOTES
Research performed in cooperation with Tennessee Valley Authority, Norris, Tennessee
37828
16. ABSTRACT " ~~~
Effects of long-term, March-September 1977, temperature elevations on aquatic
communities in 12 outdoor experimental channels were evaluated. Macroinvertebrates,
periphyton, and zooplankton colonized the channels naturally from the water supplied
from Wheeler Reservoir, Tennessee River. The fish community consisted of stocked
adult bluegill and juvenile walleye. Four temperature regimens, with three
replicate channels per regimen, were maintained. The ambient temperature of the
water pumped from Wheeler Reservoir provided the lowest treatment. Elevated
regimens of ca. 2°, 4°, and 6° C above ambient were maintained in the remaining
nine channels.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Algae
Aquatic animals
Aquatic biology
Aquatic plants
Fresh water fishes
Zooplankton
Thermal effects
Experimental channels
Walleye
Bluegill
Invertebrates
Periphyton
06/C
Release to public
19. SECURITY CLASS (This Reportl
Unclassified
>0 SECURITY CLASS (This pagej
Unclassified
21. NO. OF PAGES
184
22. PRICE
EPA Form 2220 — 1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
172
*US GOVERNMENT PRINTING OFFICE 1979-657-060/5397
------- |