John G. Eaton

Global Warming and Potential Changes in Fish Habitat in U.S. Streams

To project potential habitat changes of 57 fish species under global warming, their suitable thermal habitat at 764 stream gaging stations in the contiguous United States was studied. Global warming was specified by air temperature increases projected by the Canadian Centre of Climate Modelling General Circulation Model for a doubling of atmospheric CO2. The aquatic thermal regime at each gaging station was related to air temperature using a nonlinear stream temperature/air temperature relationship.Suitable fish thermal habitat was assumed to be constrained by both maximum temperature and minimum temperature tolerances. For cold water fishes with a 0 °C lower temperature constraint, the number of stations with suitable thermal habitat under a 2×CO2 climate scenario is projected to decrease by 36%, and for cool water fishes by 15%. These changes are associated with a northward shift of the range. For warm water fishes with a 2 °C lower temperature constraint, the potential number of stations with suitable thermal habitat is projected to increase by 31%.

Chronic Cadmium Toxicity to the Bluegill (Lepomis macrochirus Rafinesque)

Abstract Nine out of 18 adult bluegills exposed for 11 months during a chronic bioassay including reproduction were killed at 80 μg/liter of cadmium in water of 200 mg/liter (as CaCO3 hardness. Progeny exposed for 30 days were killed at 90 μg/liter. Adult fish spawned at 239 μg/liter and at 2,140 μg/liter, but most larvae were severely crippled 6 days after hatching at these concentrations. No effects on survival, development, or reproduction were attributable to cadmium at 31 μg/liter. The highest tissue residues were found in liver, intestine and caecum, and kidney. Cadmium concentrations increased with exposure concentration in gill, liver, and intestine and caecum, but not in kidney. At least until more information is available on cadmium toxicity in different water types, chronically toxic and “just safe” continuous exposure concentrations probably can be estimated better by relatively short-term exposures of embryos and larvae than by the use of application factors.

Simulated Fish Habitat Changes in North American Lakes in Response to Projected Climate Warming

Abstract Fish habitat is strongly constrained by water temperature and the available dissolved oxygen (DO). Fish habitat in small lakes of the contiguous United States was therefore determined from simulated daily water temperature and dissolved oxygen profiles. Twenty-seven types of lakes were simulated under past (1962–1979) climate conditions and a projected doubling of atmospheric carbon dioxide (2×CO2 climate scenario) at 209 locations in the contiguous United States. The 2×CO2 climate scenario was derived from the output of the Canadian Climate Centres General Circulation Model for a doubling of atmospheric CO2. A verified, process-oriented, dynamic, one-dimensional (vertical) lake water quality model (MINLAKE96) was used for the temperature and DO simulations, which were run in a continuous mode over a 19-year simulation period. Water temperature and DO criteria for the survival and good growth of three fish guilds (cold-, cool-, and warmwater fish) were provided by the U.S. Environmental Protecti...

CHRONIC TOXICITY OF A COPPER, CADMIUM AND ZINC MIXtURE TO THE FATHEAD MINNOW ( PIMEPHALES PROMELAS RAFINESQUE)

Abstract Fathead minnows were exposed to a series or concentrations of a copper, cadmium and zinc mixture during a 12.5 month chronic test in water of 200 mg 1−1 total hardness. The metal concentrations in the mixture were selected on the basis of results obtained during previous chronic exposures to each of the metals individually in the same water. Strict summation of the chronic toxicities of the metals was not indicated when they were tested in combination. Toxic effects of the mixture attributable to copper appeared to be increased, but that attributable to cadmium was reduced. The effects thought to be due to zinc were similar in degree to those observed in the single chronic exposure. Summation of effects resulting from a mixture containing about the same proportions of copper, cadmium and zinc occurred at a much higher, acutely lethal concentration. A lethal threshold was attained in the mixture when each metal was present at a concentration of 0.4 or less of its individual lethal threshold.

Chronic malathion toxicity to the bluegill (Lepomis Macrochirus Rafinesque)

Abstract Bluegills were exposed to seven malathion concentrations in a diluter-regulated, flowing-water test system. Concentrations of 66 and 28 μg 1 −1 were lethal to all fish within 16 and 54 days, respectively, and some were killed at 15 μg 1 −1 . The fish spawned under the test conditions and the toxicants effect was observed on all life cycle stages. Reproduction and early fry survival were unaffected by the 7.4 μg 1 −1 concentration that crippled adult fish after several months exposure. Experimentally determined safe (3.6 μg 1 −1 ) and unsafe (7.4 μg 1 −1 ) concentrations, between which must lie the “maximum acceptable toxicant concentration” (i.e. just barely safe concentration), were divided by a short-term toxicity value to obtain a pair of factors. This pair for bluegills (0.043 and 0.090) is compared to one (0.019 and 0.053) previously calculated for fathead minnows exposed to malathion. The similarity of the two pairs indicates that an “application factor,” consisting of the maximum acceptable toxicant concentration divided by the short-term test value, for one species exposed to a toxicant might be useful in estimating long-term safe concentrations of this substance to other species from short-term test results only. This view is strengthened by the fact that the long-term toxicity of malathion to bluegills is more than 50 times that to the fathead minnow.

Residues of PCB's and DDT in the western Lake Superior ecosystem.

Fish from western Lake Superior (1972–73) contained DDT and PCB residues at concentrations greater than 0.1 ppm. The most predominant PCBs were those containing 3 to 6 chlorine atoms per molecule, and GLC data indicated that the mixtures were most like the commercial product Aroclor® 1254. Other chlorinated contaminants identified by GC/MS analyses and occurring at concentrations less than 0.1 ppm were hexachlorobenzene (C6Cl6), chlordane, nonaclor, and dieldrin. Lindane, which has been previously reported in Lake Superior, was below the detection limit of approximately 0.01 ppm.The relationship between the size of lake trout and the concentration of total DDT in the fish was compared to measurements reported in previous studies. The comparison suggests that DDT residues have declined since 1968. The concentration of PCBs was estimated to be 0.8 ng/L in Lake Superior water and 0.1 ppm in large zooplankton. The apparent bioconcentration factor for PCBs in Lake Superior fish ranged from 105 to 106. The concentration of total DDT and PCBs in the larger Lake Superior fish exceeded the 5 ppm tolerance level established by the U.S. Food and Drug Administration for these chemicals in fish to be used for human consumption.

Extreme Value Analysis of a Fish/Temperature Field Database

Abstract Extremes of water temperatures limit the presence of various fishes in streams and lakes. Upper extreme water temperatures and their uncertainties are determined by several statistical methods from a large field database. There are over 140 000 weekly mean fish/stream temperature matched pairs in the database. Three different techniques are employed to estimate upper extremes of habitat temperatures for 12 fish species. To quantify the uncertainty of the estimated extremes the bootstrap method, the method of moments and the residual method are applied. The data above the maximum growth temperature are matched well by a type III extremal or a three-parameter lognormal distribution. Standard error of the estimated extreme habitat temperatures depends on species and varies from 0.1°C to 0.6°C at the 95% cumulative probability of occurrence.

Chronic effects of inorganic and organic mercury onDaphnia magna: Toxicity, accumulation, and loss

The chronic toxicity of mercury (Hg) toDaphnia magna was studied under flow-through and renewed static conditions. Concentrations of mercuric chloride (HgCl2), methyl mercuric chloride (MMC) and phenyl mercuric acetate (PMA) in flow-through tests significantly affecting survival were 1.92, between 0.26 and 0.98, and 2.25μg Hg/L, respectively. Concentrations of HgCl2, MMC, and PMA significantly impairing young production (P⩽0.05) were 0.72, 0.04, and 1.90μg Hg/L, respectively. Body accumulation of mercury was greatly influenced by the chemical form of mercury in the water. About nine times more mercury, added as MMC, was tolerated in daphnids at water concentrations permitting survival than was tolerated when added as HgCl2. At about the same mercury concentration in water (∼0.26μg Hg/L) daphnids accumulated ∼20 times more mercury when it was added as MMC than when it was added as HgCl2. Mercury was rapidly accumulated in daphnids; however, 35 and 57% of the mercury added as MMC and HgCl2, respectively, was lost when animals were placed in control water for four days following exposure. Different forms of mercury behaved quite differently in renewed-static and flow-through systems. The results also indicate the shortcomings of renewed-static tests with volatile and readily degradable compounds.

Validation of a fish habitat model for lakes

Water temperatures and dissolved oxygen concentrations in 27 classes of lakes have been hindcast by simulation models and related to presence of coldwater, coolwater, and warmwater fishes in 3002 Minnesota lakes. A one-dimensional, dynamic water quality model driven by 25 years of daily weather data was used to model water temperature and dissolved oxygen profiles of these lakes. Fish presence data were available for these lakes from the Minnesota Lake Fisheries Data Base. Water temperature and dissolved oxygen criteria derived from a very large United States Environmental Protection Agency fish-temperature database and dissolved oxygen observations were used to define and link simulated water temperatures and dissolved oxygen conditions to suitability of habitats for coldwater, coolwater, and warmwater fish assemblages. Good agreement was found between fish presence and numerical simulations of fish habitat defined by water temperatures and dissolved oxygen concentrations. Generally water temperature and DO are good indicators of suitable fish habitat.

A Field and Laboratory Investigation of Acid Effects on Largemouth Bass, Rock Bass, Black Crappie, and Yellow Perch

Abstract One-half of Little Rock Lake, a small seepage lake in north-central Wisconsin, was gradually acidified by additions of sulfuric acid between August 1983 and November 1990. The ambient pH (6.1) of the lake was reduced at successive 2-year intervals to pH 5.6, 5.1, and 4.7. Responses of largemouth bass Micropterus salmoides, rock bass Ambloplites rupestris, black crappie Pomoxis nigromaculatus, and yellow perch Perca flavescens populations to the pH reductions were recorded and compared to the responses of these species during in situ bioassays and laboratory toxicity tests on embryos and larvae. Laboratory results obtained for largemouth bass and rock bass underestimated, black crappie results overestimated, and yellow perch results were similar to effects observed in field studies. In situ bioassays predicted field responses better than did laboratory toxicity tests. Laboratory results showed that monomeric A1 concentrations of approximately 50 μg/L, which were comparable to A1 concentrations in ...