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Quantification of the effects of rate of temperature change on aquatic biota
Water Research Pergamon Press 1972. Vol. 6, pp. 1283-1290. Printed in Great Britain
QUANTIFICATION OF THE EFFECTS OF RATE OF TEMPERATURE CHANGE ON AQUATIC BIOTA J. N. SPEAKMAN United States Army Corps of Engineers, Buffalo District, Buffalo, New York, U.S.A. and P. A. KRENKEL Department of Environmental and Water Resources Engineering, Vanderbilt University, Nashville, Tennessee, U.S.A.
(Received 1 May 1972) INTRODUCTION THE ACCELERATINGincrease in the demand for low-cost, convenient industrial and residential power has resulted in the construction of steam-electric generating plants of increasing capacity, a greater proportion of which are nuclear plants. Because of the nuclear plant's lower efficiency and larger capacity as compared to the fossilfueled units, nuclear units can be expected to contribute more concentrated heat loads to the environment. Furthermore, the increasing use of steam-electric units to fulfil peaking power requirements may result in frequent, large fluctuations in the temperature of the streams receiving heated condenser water. Since the 1968 publication of the report of the National Technical Advisory Committee (Water Quality Criteria, 1968), all fifty states and five other jurisdictions have proposed maximum temperature and maximum temperature rise criteria for interstate waters. A major source of contention, however, has centered around the allowable rate of temperature change that will not adversely affect aquatic life. BRETT(1960) stated that rapidly onsetting low temperatures can constitute one of the greatest threats to the survival of fish and ALABASTER(1963) concluded that rapidly achieved temperature maxima below steam-electric power plants, while not reaching ultimate lethal levels, may kill fish. Conversely, the significance of rate of temperature change as a factor in the survival of fish has been questioned (DoUDOROFF, 1959), primarily because of a lack of supporting evidence. The National Technical Advisory Committee for Fish, Other Aquatic Life and Wildlife, in summarizing the research needs in establishing the temperature requirements for aquatic life, included rate of temperature change as an important consideration (ALLEN, 1969), and the Water Quality Office of the Environmental Protection Agency included the evaluation of the rate of temperature change that is acceptable for various fish species as one of its immediate objectives (MOUNT, 1969). MATERIALS AND METHODS The bluegill sunfish (Lepomis macrochirus) was selected as the test specimen because of its wide geographical distribution, thus its importance in the fisheries of a large area, and because of the wide range of temperatures which can be tolerated by the species. The bluegill specimens were from 2-year classes (1967 and 1968) from the same hatchery brood stock, and varied in size from less than two inches to about four inches. Prior to acclimatization the fish were stored in a 1000-gal steel tank which had been 1283
1284
J.N. SPEAKMANand P. A. KRENKEL
lined with a continuous layer of polyethylene to prevent heavy metal toxicity. The dissolved oxygen was maintained above 5 mg 1-1 by diffused-air aeration, and the water was continuously renewed with dechlorinated tap water to prevent the accumulation of excretory products to a toxic level. Acclimatization was accomplished in five 50-gal glass aquaria equipped with temperatme control apparatus capable of maintaining the temperature within 0.5°C of the desired level, above or below ambient. The temperature controllers included a constant-capacity cooling coil with a remote compressor, coupled with a thermostatically controlled heater of greater capacity. Diffused air injection at two points in each acclimatization aquarium insured a dissolved oxygen concentration above 5 mg 1-1, and continuous renewal with dechlorinated tap water prevented the accumulation of excretory products. The temperature in an acclimatization aquarium was adjusted from the level in the stock tank to the desired acclimatization temperature at a rate of I°C day-1. To insure complete acclimatization, those specimens which were acclimatized to temperatures higher than that in the stock tank were not tested until at least 1 week of exposure to the acclimatization temperature had elapsed. Since low temperature acclimatization is accomplished much slower than high temperature acclimatization, the period of exposure to a constant low acclimatization temperature was at least 1 week for each 5°C decrease below that in the stock tank. Acclimatization temperatures from 5 to 30°C, at 5°C intervals, were selected for testing, and final temperatures were selected at the same intervals. Tests were conducted to determine the lethal rates of temperature change between every combination of selected acclimatization and final temperatures. The rate of temperature change at which just 50 per cent of the specimens survived, for a given combination of acclimatization and final temperatures, was defined as the median rate limit, symbolized KL,,. The acclimatization and final temperatures were indicated in the symbol as subscripts preceding and following the symbol, respectively. For example, ~oKL,,,ao symbolizes the median rate limit for a temperature change from 10 to 30°C. The test chamber consisted of a "shell and tank" arrangement. The 10-gallon stainless steel test tank isolated the test medium from the heat transfer medium circulating through the shell, thus eliminating possible toxicity to the test specimens by heavy metals emanating from the temperature control apparatus. The heat transfer medium circulated through a heat pump cooler and circulation pump, to a heat exchanger, then returned to the shell through a series of orifices, thus mixing the medium in the shell surrounding the test tank. While the heat pump cooler operated at a constant capacity, the heat exchanger, consisting of an immersion heater positioned inside a 3-in. pipe discharging into the shell, was controlled by a proportional-integral-derivative controller. The controller was also equipped with a versatile cam-type programmer which allowed the programming of any rate of temperature. The controller was capable of reproducing a temperature change in the test tank which deviated from the programmed temperature change less than 1.5°C at any time. Prior to each test, the test tank was filled from the dechlorinated water supply, and the temperature in the test tank was brought to the appropriate acclimatization level. Ten specimens were then collected from the acclimatization aquarium and transferred to the test tank. After transferring the test specimens, the temperature
Quantification of the Effects of Rate of Temperature Change on Aquatic Biota
1285
in the test tank was held at the acclimatization level for one day in order to minimize the stress induced by handling. Following the programmed temperature change, the temperature in the test tank was held at the final level for 1 additional day, after which the survivors were transferred to an acclimatization aquarium in which the temperature was at the final level. A uniform, 1-week observation period followed each test in which the temperature increased, insuring the observation of all mortalities resulting directly from the rate of change tests. Since lethal rates of decreasing temperature were much lower than the lethal increasing rates, a "rule-of-thumb", that observation should continue beyond the one-week period until no specimen demonstrated symptoms of distress, was adopted for tests in which the temperature decreased. RESULTS The combinations of acclimatization and final temperatures of importance in the study of lethal rates of temperature change to fish are those which exceed the zone of tolerance of the species, determined by the shock test, but within the range of adaptability as determined by the chronic test. The ultimate upper lethal limit, found to be approximately 36°C, and the ultimate lower lethal limit of 0°C (BRETT, 1960) define the range of adaptability of the bluegill. The zone of tolerance of the bluegill was determined by combining the results of HART (1952) and a number of shock tests conducted in the Vanderbilt University laboratory, the resulting tolerance tlapezium being shown in FIG. 1. The arrows in FIG. 1 indicate the relation of the lethal limit to the results of the shock tests. For example, all ten specimens survived the shock test in which the acclimatization temperature was 5°C and the test temperature was 20°C; therefore, the upper lethal limit for that acclimatization temperature exceeded 20°C, which is indicated by the arrow directed upward at those coordinates. 4o~-
I
r
Data
from Hart
0
I
j
r
,
J
~
f / 1
" °/
q "
I
I
o
E 2O
1
r
I
I0 Acclimatization
I
P
20 femp,
50
[ 4O
°C
FIG. 1. Temperature tolerance trapezium for bluegills.
1286
J . N . SPEAKMAN a n d P. A. KRENKEL
FIGURE 1 demonstrates the six combinations of the selected acclimatization and final temperatures for which the rate of temperature change is a significant factor in the survival of the bluegill sunfish. The results of a series of four or five tests were utilized in order to estimate each median rate limit. The median rate limit was estimated by the regression of the "probit" transformation of survival percentage on the logarithm of the rate of temperature change. The median rate limits and their confidence limits, resulting from those regressions, are summarized in TABLE 1. TABLE 2 demonstrates the rate constants allowing 99 per cent survival and their confidence limits tor the various combinations of acclimatization and final temperatures. TABLE 1. MEDIAN RATE LIMITS AND THEIR CONFIDENCE LIMITS
AcclimaFinal tization temperature temperature (°C) (°C) 5 5 10 25 30 30
25 30 30 5 5 10
Symbol
Median rate limit (°C h - 1)
~KL,n2S sKL,~ao loKLmao 2sKLm5 zoKLms 3oKL,,lo
6.5 1.9 3.9 --0.19 --0.072 --0.32
95 per cent confidence limit (°C h - 1) Upper
Lower
8.6 2.2 4.6 --0.20 --0.076 --0.38
5.4 1.5 3.4 --0.18 --0.067 --0.27
TABLE 2. RATES OF TEMPERATURE CHANGE ALLO~vVING99 PER CENT SURVIVAL AND THEIR CONFIDENCE LIMITS
Acclimatization temperature
(°c) 5 5 10 25 30 30
Final temperature
(oc) 25 39 30 5 5 10
95 per cent confidence limit (°C h - ' ) 99 per cent survival rate
(oc h- ~) 2.5 0.78 1.8 --0.15 --0.053 --0.16
Upper
Lower
3.7 1. I 2.4 --0.16 --0.059 --0.21
0.53 0.06 0.49 --0.11 --0.040 --0.056
The phenomenon of temperature acclimatization makes the estimation of application factors for rates of temperature change unique. Acclimatization allows poikilotherms which survive a given temperature fluctuation to adjust to the altered conditions to such an extent that, after sufficient exposure to the new conditions, fluctuations from them constitute stress. Therefore, an estimate of the rate of temperature change producing no mortalities could be compared with the median rate limit for the same initial and final conditions, directly producing a reasonable application factor. Although the regression of survival percentage on rate of temperature change could not be extrapolated to 100 per cent survival, total survival was estimated by the lower 95 per cent confidence limits of the rates of change allowing 99 per cent survival. The
Quantification of the Effects of Rate of Temperature Change on Aquatic Biota
1287
application factors for the significant combinations of acclimatization and final temperatures for the bluegill sunfish appear in TABLE 3. TABLE 3. APPLICATION FACTORS FOR SIGNIFICANT RATES OF TEMPERATURE CHANGE ON THE BLUEGILL SUNFISH
Acclimatization temperature (°C)
Final temperature (°C)
Median rate limit (°C h- 1)
Lower confidence limit for 99 per cent survival (°C h- ~)
5 5 10 25 30 30
25 30 30 5 5 10
6.5 1.9 3.9 --0.19 --0.072 --0.32
0.53 0.06 0.49 --0.I1 --0.040 --0.056
Application factor 0.08 0.03 0.13 0.60 0.54 0.16
CONCLUSIONS Rate of temperature change was shown to be an important factor in the survival of bluegills subjected to temperature increases from 5 to 30°C, from 10 to 30°C, and from 5 to 25°C; and decreases from 30 to 5°C, from 30 to 10°C, and from 25 to 5°C. Lethal rates of temperature increase were at least 20 times the corresponding lethal rates of temperature decrease, thus corroborating the conclusion of BRETT (1960), that rapidly onsetting low temperatures may constitute one of the greatest threats to the survival of fish. The median rate limits included in TABLE 3 quantitatively describe, for the bluegill, the relationships between acclimatization temperature, total temperature change, and rate of temperature change. For increasing temperatures: 1. At a constant acclimatization temperature, reduced lethal rates of change are associated with increased magnitudes of temperature rise. 2. At a constant total temperature increase, reduced lethal rates of change are associated with the final temperatures which more closely approach the ultimate upper lethal limit. 3. At a constant final temperature, reduced lethal rates of change are associated with increased magnitudes of temperature rise. For dccreasing tcmperatures: 1. At a constant acclimatization temperature, reduced lethal rates of change are associated with increased magnitudes of temperature decrease. 2. At a constant total temperature decrease, reduced lethal rates of change are associated with final temperatures more closely approaching the ultimate lower lethal limit. 3. At a constant final temperature, reduced lethal rates of change are associated with increased magnitudes of temperature decrease. The results of this investigation were combined with those of the shock and chronic tests to produce the three-dimensional representation of the temperature tolerance of
1288
J.N. SPEAKMANand P. A. KRENKEL
the bluegill sunfish in FIG. 2, in which the axes represent the acclimatization temperature, the lethal temperature, and the period of accomplishment of the temperature change. The solid is bounded at time equal to zero by the tolerance trapezium and at infinite time by the range of adaptation of the species. Definition of the surfaces connecting those extremes was accomplished through a multiple regression analysis. The regression data points included the extremes of the
i
o @
3o
d E 2o
_~
I
f
~o
t-'l I0
20
Acclimafizafion
50
femp,
40 "C
F[o. 2. Three-dimensionalrepresentation of temperature tolerance for bluegills. upper and lower lethal limits from the tolerance trapezium and from the transforms of the KL,,'s. The transformation to period of accomplishment from the KL,, was accomplished by dividing the total temperature change by the KL,n value. Those regression planes, outlined by heavy lines in FIG. 2, are defined by equations (1) and (2).
where 0,z 0,~ 0Q T~
= = = = Ta =
0u~ = 20.9 + 0.62(04) ÷ 0.46(T~)
(1)
0~4 = --6.93 -k 0.58(04) -- 0.016(Ta)
(2)
upper lethal temperature; lower lethal temperature; acclimatization temperature; total time for accomplishment of temperature increase; and total time for accomplishment of temperature decrease.
The regression equations are applicable only between the ultimate lethal limits (0 and 36°C) of the species. Although the multiple correlation coefficients for the upper and lower planes were 0.999 and 0.993, respectively, they must not be interpreted as proof of linear relationships inasmuch as five data points for each regression are insufficient for conclusive interpretation.
Quantification of the Effects of Rate of Temperature Change on Aquatic Biota
1289
Furthermore, the relationship between lethal temperature and the period of accomplishment probably reflects the capability of the species to acclimatize, a relationship which has been demonstrated to be first-order DOUDOROFF, (1942). In this case, the regression equation represents one linear relationship, which combined with the horizontal plane representing the ultimate lethal limit, produces a good approximation of a relationship of a higher degree. Regardless of the limitations mentioned above, the linear regression planes represent good first appioximations of the relationships among acclimatization temperatures, periods of accomplishment, and lethal temperatures. Situations in which fish may encounter lethal rates of temperature change include: 1. The essentially instantaneous discharge of heated effluents from an industrial " b a t c h " operation into a stream. 2. The involuntary passage of migrating fish through a stationary plume of heated effluent. 3. The operation of steam power plants as peaking power facilities, resulting in widely varying temperatures of the rejected condenser water. 4. The release of cold hypolimnetic water through a peaking power hydro-electric plant after an extended period of non-operation. The magnitudes of the temperature fluctuations associated with rates of change which are lethal to the bluegill (greater than 15°C) approach the m a x i m u m temperature increases through modern steam power plants (Hoo~:, 1961) and exceed the reported decreases below peaking power hydro-electric generating facilities (KRENKEL and PARKER, 1969). However, the growth of the power industry in the immediate future will result in more intensified waste heat discharges, resulting in greater temperature fluctuations in receiving waters. Therefore, the rate of temperature change constitutes a potential threat to the survival of bluegills in the vicinity of power plant discharges. Acknowledgements--The authors gratefully acknowledge the support given by the Sport Fishery
Institute through the efforts of RICnARD STROUD,Vanderbilt University, and the Environmental Protection Agency. REFERENCES ALABASTERJ. S. (1963) Effects of heated effluents on fish. Int. J. Air Wat. Pollut. 7 (3), 541-563. ALLEN,J. FRANCES(1969) Research needs for thermal pollution control. Biological Aspects of Thermal Pollution (Edited by KRENKELP. A. and PARKERF. L.), pp. 382-392. Vanderbilt Univ. Press, Nashville, Tenn. BRETT J. R. (1960) Thermal requirements of fish--three decades of study, 1940-1970. Biological Problems in Water Pollution, Technical Report No. W60-3. pp. 110-117. DOUDOROFFP. (1942) The resistance and acclimation of marine fishes to temperature changes: I. Experiments with girella nigricans (Ayres). Biol. Bull. 83 (2), 219-244. DOUDOROFFP. (1959) Water quality requirements of fishes and effects of toxic substances. The Physiology of Fishes (Edited by MARGARETE. BROWN), pp. 403--443 Academic Press, New York, N.Y. HART J. S. (1952) Geographic variations of some physiological and morphological characters in certain freshwater fish. University of Toronto Biological Series No. 60, Publication of the Ontario Fisheries Research Laboratory, No. 72. pp. 1-79. HOAKR. D. (1961) The thermal pollution problem. J. War. Pollut. Control Fed. 33 (12), 1267-1276. KRENKELP. A. and PARKERF. L. 0969) Engineering aspects, sources, and magnitude of thermal pollution. Biological Aspects of Thermal Pollution (Edited by I~RENKELP. A. and PARKERF. L.), pp. 10-52. Vanderbilt Univ. Press, Nashville, Tenn.
1290
J . N . SPEAKMANand P. A. KRENKEL
MOUNT D. I. (1969) Research on temperature effects on fishes. Proceedings of the Eighth Annual Environmental and Water Resources Engineering Conference, Nashville, Tenn. pp. 129-135. U.S. DEPARTMENT OF THE INTERIOR (1968) Water-Quality Criteria: A Report to the Secretary of the Interior by the National Technical Advisory Committee, Federal Water Pollution Control Administration, Washington, D.C. : U.S. Government Printing Office.
QUANTIFICATION OF THE EFFECTS OF RATE OF TEMPERATURE CHANGE ON AQUATIC BIOTA J. N. SPEAKMAN United States Army Corps of Engineers, Buffalo District, Buffalo, New York, U.S.A. and P. A. KRENKEL Department of Environmental and Water Resources Engineering, Vanderbilt University, Nashville, Tennessee, U.S.A.
(Received 1 May 1972) INTRODUCTION THE ACCELERATINGincrease in the demand for low-cost, convenient industrial and residential power has resulted in the construction of steam-electric generating plants of increasing capacity, a greater proportion of which are nuclear plants. Because of the nuclear plant's lower efficiency and larger capacity as compared to the fossilfueled units, nuclear units can be expected to contribute more concentrated heat loads to the environment. Furthermore, the increasing use of steam-electric units to fulfil peaking power requirements may result in frequent, large fluctuations in the temperature of the streams receiving heated condenser water. Since the 1968 publication of the report of the National Technical Advisory Committee (Water Quality Criteria, 1968), all fifty states and five other jurisdictions have proposed maximum temperature and maximum temperature rise criteria for interstate waters. A major source of contention, however, has centered around the allowable rate of temperature change that will not adversely affect aquatic life. BRETT(1960) stated that rapidly onsetting low temperatures can constitute one of the greatest threats to the survival of fish and ALABASTER(1963) concluded that rapidly achieved temperature maxima below steam-electric power plants, while not reaching ultimate lethal levels, may kill fish. Conversely, the significance of rate of temperature change as a factor in the survival of fish has been questioned (DoUDOROFF, 1959), primarily because of a lack of supporting evidence. The National Technical Advisory Committee for Fish, Other Aquatic Life and Wildlife, in summarizing the research needs in establishing the temperature requirements for aquatic life, included rate of temperature change as an important consideration (ALLEN, 1969), and the Water Quality Office of the Environmental Protection Agency included the evaluation of the rate of temperature change that is acceptable for various fish species as one of its immediate objectives (MOUNT, 1969). MATERIALS AND METHODS The bluegill sunfish (Lepomis macrochirus) was selected as the test specimen because of its wide geographical distribution, thus its importance in the fisheries of a large area, and because of the wide range of temperatures which can be tolerated by the species. The bluegill specimens were from 2-year classes (1967 and 1968) from the same hatchery brood stock, and varied in size from less than two inches to about four inches. Prior to acclimatization the fish were stored in a 1000-gal steel tank which had been 1283
1284
J.N. SPEAKMANand P. A. KRENKEL
lined with a continuous layer of polyethylene to prevent heavy metal toxicity. The dissolved oxygen was maintained above 5 mg 1-1 by diffused-air aeration, and the water was continuously renewed with dechlorinated tap water to prevent the accumulation of excretory products to a toxic level. Acclimatization was accomplished in five 50-gal glass aquaria equipped with temperatme control apparatus capable of maintaining the temperature within 0.5°C of the desired level, above or below ambient. The temperature controllers included a constant-capacity cooling coil with a remote compressor, coupled with a thermostatically controlled heater of greater capacity. Diffused air injection at two points in each acclimatization aquarium insured a dissolved oxygen concentration above 5 mg 1-1, and continuous renewal with dechlorinated tap water prevented the accumulation of excretory products. The temperature in an acclimatization aquarium was adjusted from the level in the stock tank to the desired acclimatization temperature at a rate of I°C day-1. To insure complete acclimatization, those specimens which were acclimatized to temperatures higher than that in the stock tank were not tested until at least 1 week of exposure to the acclimatization temperature had elapsed. Since low temperature acclimatization is accomplished much slower than high temperature acclimatization, the period of exposure to a constant low acclimatization temperature was at least 1 week for each 5°C decrease below that in the stock tank. Acclimatization temperatures from 5 to 30°C, at 5°C intervals, were selected for testing, and final temperatures were selected at the same intervals. Tests were conducted to determine the lethal rates of temperature change between every combination of selected acclimatization and final temperatures. The rate of temperature change at which just 50 per cent of the specimens survived, for a given combination of acclimatization and final temperatures, was defined as the median rate limit, symbolized KL,,. The acclimatization and final temperatures were indicated in the symbol as subscripts preceding and following the symbol, respectively. For example, ~oKL,,,ao symbolizes the median rate limit for a temperature change from 10 to 30°C. The test chamber consisted of a "shell and tank" arrangement. The 10-gallon stainless steel test tank isolated the test medium from the heat transfer medium circulating through the shell, thus eliminating possible toxicity to the test specimens by heavy metals emanating from the temperature control apparatus. The heat transfer medium circulated through a heat pump cooler and circulation pump, to a heat exchanger, then returned to the shell through a series of orifices, thus mixing the medium in the shell surrounding the test tank. While the heat pump cooler operated at a constant capacity, the heat exchanger, consisting of an immersion heater positioned inside a 3-in. pipe discharging into the shell, was controlled by a proportional-integral-derivative controller. The controller was also equipped with a versatile cam-type programmer which allowed the programming of any rate of temperature. The controller was capable of reproducing a temperature change in the test tank which deviated from the programmed temperature change less than 1.5°C at any time. Prior to each test, the test tank was filled from the dechlorinated water supply, and the temperature in the test tank was brought to the appropriate acclimatization level. Ten specimens were then collected from the acclimatization aquarium and transferred to the test tank. After transferring the test specimens, the temperature
Quantification of the Effects of Rate of Temperature Change on Aquatic Biota
1285
in the test tank was held at the acclimatization level for one day in order to minimize the stress induced by handling. Following the programmed temperature change, the temperature in the test tank was held at the final level for 1 additional day, after which the survivors were transferred to an acclimatization aquarium in which the temperature was at the final level. A uniform, 1-week observation period followed each test in which the temperature increased, insuring the observation of all mortalities resulting directly from the rate of change tests. Since lethal rates of decreasing temperature were much lower than the lethal increasing rates, a "rule-of-thumb", that observation should continue beyond the one-week period until no specimen demonstrated symptoms of distress, was adopted for tests in which the temperature decreased. RESULTS The combinations of acclimatization and final temperatures of importance in the study of lethal rates of temperature change to fish are those which exceed the zone of tolerance of the species, determined by the shock test, but within the range of adaptability as determined by the chronic test. The ultimate upper lethal limit, found to be approximately 36°C, and the ultimate lower lethal limit of 0°C (BRETT, 1960) define the range of adaptability of the bluegill. The zone of tolerance of the bluegill was determined by combining the results of HART (1952) and a number of shock tests conducted in the Vanderbilt University laboratory, the resulting tolerance tlapezium being shown in FIG. 1. The arrows in FIG. 1 indicate the relation of the lethal limit to the results of the shock tests. For example, all ten specimens survived the shock test in which the acclimatization temperature was 5°C and the test temperature was 20°C; therefore, the upper lethal limit for that acclimatization temperature exceeded 20°C, which is indicated by the arrow directed upward at those coordinates. 4o~-
I
r
Data
from Hart
0
I
j
r
,
J
~
f / 1
" °/
q "
I
I
o
E 2O
1
r
I
I0 Acclimatization
I
P
20 femp,
50
[ 4O
°C
FIG. 1. Temperature tolerance trapezium for bluegills.
1286
J . N . SPEAKMAN a n d P. A. KRENKEL
FIGURE 1 demonstrates the six combinations of the selected acclimatization and final temperatures for which the rate of temperature change is a significant factor in the survival of the bluegill sunfish. The results of a series of four or five tests were utilized in order to estimate each median rate limit. The median rate limit was estimated by the regression of the "probit" transformation of survival percentage on the logarithm of the rate of temperature change. The median rate limits and their confidence limits, resulting from those regressions, are summarized in TABLE 1. TABLE 2 demonstrates the rate constants allowing 99 per cent survival and their confidence limits tor the various combinations of acclimatization and final temperatures. TABLE 1. MEDIAN RATE LIMITS AND THEIR CONFIDENCE LIMITS
AcclimaFinal tization temperature temperature (°C) (°C) 5 5 10 25 30 30
25 30 30 5 5 10
Symbol
Median rate limit (°C h - 1)
~KL,n2S sKL,~ao loKLmao 2sKLm5 zoKLms 3oKL,,lo
6.5 1.9 3.9 --0.19 --0.072 --0.32
95 per cent confidence limit (°C h - 1) Upper
Lower
8.6 2.2 4.6 --0.20 --0.076 --0.38
5.4 1.5 3.4 --0.18 --0.067 --0.27
TABLE 2. RATES OF TEMPERATURE CHANGE ALLO~vVING99 PER CENT SURVIVAL AND THEIR CONFIDENCE LIMITS
Acclimatization temperature
(°c) 5 5 10 25 30 30
Final temperature
(oc) 25 39 30 5 5 10
95 per cent confidence limit (°C h - ' ) 99 per cent survival rate
(oc h- ~) 2.5 0.78 1.8 --0.15 --0.053 --0.16
Upper
Lower
3.7 1. I 2.4 --0.16 --0.059 --0.21
0.53 0.06 0.49 --0.11 --0.040 --0.056
The phenomenon of temperature acclimatization makes the estimation of application factors for rates of temperature change unique. Acclimatization allows poikilotherms which survive a given temperature fluctuation to adjust to the altered conditions to such an extent that, after sufficient exposure to the new conditions, fluctuations from them constitute stress. Therefore, an estimate of the rate of temperature change producing no mortalities could be compared with the median rate limit for the same initial and final conditions, directly producing a reasonable application factor. Although the regression of survival percentage on rate of temperature change could not be extrapolated to 100 per cent survival, total survival was estimated by the lower 95 per cent confidence limits of the rates of change allowing 99 per cent survival. The
Quantification of the Effects of Rate of Temperature Change on Aquatic Biota
1287
application factors for the significant combinations of acclimatization and final temperatures for the bluegill sunfish appear in TABLE 3. TABLE 3. APPLICATION FACTORS FOR SIGNIFICANT RATES OF TEMPERATURE CHANGE ON THE BLUEGILL SUNFISH
Acclimatization temperature (°C)
Final temperature (°C)
Median rate limit (°C h- 1)
Lower confidence limit for 99 per cent survival (°C h- ~)
5 5 10 25 30 30
25 30 30 5 5 10
6.5 1.9 3.9 --0.19 --0.072 --0.32
0.53 0.06 0.49 --0.I1 --0.040 --0.056
Application factor 0.08 0.03 0.13 0.60 0.54 0.16
CONCLUSIONS Rate of temperature change was shown to be an important factor in the survival of bluegills subjected to temperature increases from 5 to 30°C, from 10 to 30°C, and from 5 to 25°C; and decreases from 30 to 5°C, from 30 to 10°C, and from 25 to 5°C. Lethal rates of temperature increase were at least 20 times the corresponding lethal rates of temperature decrease, thus corroborating the conclusion of BRETT (1960), that rapidly onsetting low temperatures may constitute one of the greatest threats to the survival of fish. The median rate limits included in TABLE 3 quantitatively describe, for the bluegill, the relationships between acclimatization temperature, total temperature change, and rate of temperature change. For increasing temperatures: 1. At a constant acclimatization temperature, reduced lethal rates of change are associated with increased magnitudes of temperature rise. 2. At a constant total temperature increase, reduced lethal rates of change are associated with the final temperatures which more closely approach the ultimate upper lethal limit. 3. At a constant final temperature, reduced lethal rates of change are associated with increased magnitudes of temperature rise. For dccreasing tcmperatures: 1. At a constant acclimatization temperature, reduced lethal rates of change are associated with increased magnitudes of temperature decrease. 2. At a constant total temperature decrease, reduced lethal rates of change are associated with final temperatures more closely approaching the ultimate lower lethal limit. 3. At a constant final temperature, reduced lethal rates of change are associated with increased magnitudes of temperature decrease. The results of this investigation were combined with those of the shock and chronic tests to produce the three-dimensional representation of the temperature tolerance of
1288
J.N. SPEAKMANand P. A. KRENKEL
the bluegill sunfish in FIG. 2, in which the axes represent the acclimatization temperature, the lethal temperature, and the period of accomplishment of the temperature change. The solid is bounded at time equal to zero by the tolerance trapezium and at infinite time by the range of adaptation of the species. Definition of the surfaces connecting those extremes was accomplished through a multiple regression analysis. The regression data points included the extremes of the
i
o @
3o
d E 2o
_~
I
f
~o
t-'l I0
20
Acclimafizafion
50
femp,
40 "C
F[o. 2. Three-dimensionalrepresentation of temperature tolerance for bluegills. upper and lower lethal limits from the tolerance trapezium and from the transforms of the KL,,'s. The transformation to period of accomplishment from the KL,, was accomplished by dividing the total temperature change by the KL,n value. Those regression planes, outlined by heavy lines in FIG. 2, are defined by equations (1) and (2).
where 0,z 0,~ 0Q T~
= = = = Ta =
0u~ = 20.9 + 0.62(04) ÷ 0.46(T~)
(1)
0~4 = --6.93 -k 0.58(04) -- 0.016(Ta)
(2)
upper lethal temperature; lower lethal temperature; acclimatization temperature; total time for accomplishment of temperature increase; and total time for accomplishment of temperature decrease.
The regression equations are applicable only between the ultimate lethal limits (0 and 36°C) of the species. Although the multiple correlation coefficients for the upper and lower planes were 0.999 and 0.993, respectively, they must not be interpreted as proof of linear relationships inasmuch as five data points for each regression are insufficient for conclusive interpretation.
Quantification of the Effects of Rate of Temperature Change on Aquatic Biota
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Furthermore, the relationship between lethal temperature and the period of accomplishment probably reflects the capability of the species to acclimatize, a relationship which has been demonstrated to be first-order DOUDOROFF, (1942). In this case, the regression equation represents one linear relationship, which combined with the horizontal plane representing the ultimate lethal limit, produces a good approximation of a relationship of a higher degree. Regardless of the limitations mentioned above, the linear regression planes represent good first appioximations of the relationships among acclimatization temperatures, periods of accomplishment, and lethal temperatures. Situations in which fish may encounter lethal rates of temperature change include: 1. The essentially instantaneous discharge of heated effluents from an industrial " b a t c h " operation into a stream. 2. The involuntary passage of migrating fish through a stationary plume of heated effluent. 3. The operation of steam power plants as peaking power facilities, resulting in widely varying temperatures of the rejected condenser water. 4. The release of cold hypolimnetic water through a peaking power hydro-electric plant after an extended period of non-operation. The magnitudes of the temperature fluctuations associated with rates of change which are lethal to the bluegill (greater than 15°C) approach the m a x i m u m temperature increases through modern steam power plants (Hoo~:, 1961) and exceed the reported decreases below peaking power hydro-electric generating facilities (KRENKEL and PARKER, 1969). However, the growth of the power industry in the immediate future will result in more intensified waste heat discharges, resulting in greater temperature fluctuations in receiving waters. Therefore, the rate of temperature change constitutes a potential threat to the survival of bluegills in the vicinity of power plant discharges. Acknowledgements--The authors gratefully acknowledge the support given by the Sport Fishery
Institute through the efforts of RICnARD STROUD,Vanderbilt University, and the Environmental Protection Agency. REFERENCES ALABASTERJ. S. (1963) Effects of heated effluents on fish. Int. J. Air Wat. Pollut. 7 (3), 541-563. ALLEN,J. FRANCES(1969) Research needs for thermal pollution control. Biological Aspects of Thermal Pollution (Edited by KRENKELP. A. and PARKERF. L.), pp. 382-392. Vanderbilt Univ. Press, Nashville, Tenn. BRETT J. R. (1960) Thermal requirements of fish--three decades of study, 1940-1970. Biological Problems in Water Pollution, Technical Report No. W60-3. pp. 110-117. DOUDOROFFP. (1942) The resistance and acclimation of marine fishes to temperature changes: I. Experiments with girella nigricans (Ayres). Biol. Bull. 83 (2), 219-244. DOUDOROFFP. (1959) Water quality requirements of fishes and effects of toxic substances. The Physiology of Fishes (Edited by MARGARETE. BROWN), pp. 403--443 Academic Press, New York, N.Y. HART J. S. (1952) Geographic variations of some physiological and morphological characters in certain freshwater fish. University of Toronto Biological Series No. 60, Publication of the Ontario Fisheries Research Laboratory, No. 72. pp. 1-79. HOAKR. D. (1961) The thermal pollution problem. J. War. Pollut. Control Fed. 33 (12), 1267-1276. KRENKELP. A. and PARKERF. L. 0969) Engineering aspects, sources, and magnitude of thermal pollution. Biological Aspects of Thermal Pollution (Edited by I~RENKELP. A. and PARKERF. L.), pp. 10-52. Vanderbilt Univ. Press, Nashville, Tenn.
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J . N . SPEAKMANand P. A. KRENKEL
MOUNT D. I. (1969) Research on temperature effects on fishes. Proceedings of the Eighth Annual Environmental and Water Resources Engineering Conference, Nashville, Tenn. pp. 129-135. U.S. DEPARTMENT OF THE INTERIOR (1968) Water-Quality Criteria: A Report to the Secretary of the Interior by the National Technical Advisory Committee, Federal Water Pollution Control Administration, Washington, D.C. : U.S. Government Printing Office.