Steven J. Hamilton

Metallothionein in Fish: Review of Its Importance in Assessing Stress from Metal Contaminants

Abstract Metallothionein, a low-molecular-weight protein whose apoprotein, thionein, is induced by exposure to cadmium, copper, mercury, and zinc, plays an important role in the transport and storage of heavy metals; it also provides a protective role against the toxic effects of these metals by sequestering and thus reducing the amount of the free metal ions. Interest in the detoxification role of metallothionein in fisheries research and aquatic toxicology has increased because of the increasing contamination of aquatic habitats by heavy metals. Reports of laboratory and field investigations have shown that metallothionein synthesis is induced in fishes during chronic and acute exposures to metals. There is also evidence of the presence in fish of low-molecular-weight inorganic-binding proteins that are different from metallothionein, as well as evidence that cadmium is not sequestered by metallothionein in rainbow trout Salmo gairdneri. The sequestering of metal contaminants by metallothionein and subs...

Interactive Toxicity of Aluminum and Acidity to Early Life Stages of Brook Trout

Abstract The influences of exposure to aluminum and increased acidity on mortality, growth, behavior, and biochemical responses of brook trout Salvelinus fontinalis were evaluated as a function of developmental stage. Eyed eggs and young brook trout were exposed until 30 d after hatching in proportional diluters to pHs of 4.5, 5.5, and 7.2, with and without aluminum (300 μg/L); 37-d-old brook trout that had been held in experimental control water since hatching were exposed to these same conditions for 30 d. Exposure conditions (i.e., aluminum and calcium concentrations and pH) simulated conditions in some headwater lakes and streams in the northeastern United States. Adverse effects on exposed brook trout generally increased as pH decreased from 7.2 to 4.5 and potentiation of effects by aluminum occurred at pHs of 5.5 to 7.2. However, embryos and fish older than 36 d were more tolerant of acidic conditions and aluminum than were larvae less than 15 d old. We conclude that the adverse effects on mortality...

Relative sensitivity of early life stages of arctic grayling, coho salmon, and rainbow trout to nine inorganics

The acute toxicity of nine inorganics associated with placer mining sediments to early life stages of Arctic grayling (Thymallus arcticus), coho salmon (Oncorhynchus kisutch), and rainbow trout (O. mykiss) was determined in soft water (hardness, 41 mg liter-1 CaCO3) at 12 degrees C. The relative toxicities of the inorganics varied by four orders of magnitude; from most toxic to least toxic, the rank order was cadmium, silver, mercury, nickel, gold, arsenite, selenite, selenate, and hexavalent chromium. In general, juvenile life stages of the three species tested were more sensitive to these inorganics than the alevin life stage. Among juveniles, no single species was consistently more sensitive to the inorganics than another; among alevins, Arctic grayling were generally more sensitive than coho salmon and rainbow trout. Based on the results of the present study, estimated no-effect concentrations of arsenic and mercury, but not cadmium, chromium, gold, nickel, selenium, or silver, are close to their concentrations reported in streams with active placer mines in Alaska. Thus, arsenic (as arsenite(III)) and mercury may pose a hazard to Arctic grayling and coho salmon in Alaskan streams with active placer mines.

Acute toxicity of boron, molybdenum, and selenium to fry of chinook salmon and coho salmon

The acute toxicities of boron, molybdenum, and various forms of selenium, individually and in environmentally relevant mixtures, to swim-up and advanced fry of chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) were determined in site-specific fresh and brackish waters. Boron and molybdenum were relatively non-toxic (96-hr LC50s > 100 mg/L) to both life stages of both species. Selenite was significantly more toxic than selenate to both species. Swim-up fry tested in fresh water were significantly more sensitive than advanced fry in brackish water to selenate and selenite. No mortalities occurred in any concentrations tested of seleno-DL-methionine; however, in the highest concentration (21.6 mg Se/L), at least 50% of the fish showed pronounced surfacing behavior. Coho salmon were more sensitive than chinook salmon to both selenate and selenite at either life stage; only the swim-up fry of coho salmon were more sensitive than chinook salmon to boron. In additional tests with swim-up chinook salmon, differences in the characteristics of the dilution water did not significantly modify the relative toxicities of boron, selenate, and selenite. In binary mixture studies, the joint acute toxic action of selenate and selenite, combined in various ratios, was additive to both species. Based on a comparison of the individual acute values for chinook salmon to the expected environmental concentrations, the margin of safety for boron was only 56 in fresh and 46 in brackish water. The margins of safety for selenate and selenite exceeded 275 in both fresh and brackish waters. However, the margin of safety for both selenate and selenite in the mixture test was 145 in fresh water and 220 in brackish water.

Evaluation of Metallothionein Measurement as a Biological Indicator of Stress from Cadmium in Brook Trout

Abstract A modification of an established technique for quantifying metallothionein (MT) in mammals was used to evaluate the toxicological importance of MT as a biological indicator of stress from chronic cadmium toxicity in brook trout Salvelinus fontinalis. In a 30-d study, fish mortality was significantly increased but growth was not altered by exposure to 3.6 μg Cd/L or more. After chronic exposure to cadmium, both mortality and whole-body residues showed a dose-response relation over the exposure range of 3.6 to 60.6 μg Cd/L. Concentrations of MT were increased significantly in all exposures that resulted in significant mortality; however, they showed no dose-response relation to cadmium exposure, nor were they correlated with mortality or whole-body cadmium residues. Consequently, measurement of MT alone was not a useful indicator of cadmium toxicity in brook trout. A better biological indicator was the amount of free cadmium in liver tissue. Free cadmium (the difference between the amount of cadmiu...

Toxicity of sodium selenite to rainbow trout fry

In a study designed to examine the long-term effects of inorganic selenium (IV) on early life stages of rainbow trout (Salmo gairdneri), survival was significantly reduced at selenium concentrations of 47 and 100 μg l−1 after 90 days of exposure. Length and weight were significantly reduced after 90 days of exposure to 100 μg l−1. Whole-body residues of selenium increased with increasing exposure concentrations but appeared to decline between 30 and 90 days of exposure. Analyses of trout backbone indicated little change in bone development with exposure to selenium (IV) with one exception; calcium concentrations were significantly decreased in fish exposed to ⩾ 12 μg l−1 of selenium. Results of our study indicates that a recommended safe level of 10 μg l−1 for inorganic selenium would not significantly affect growth and survival of rainbow trout; however, concentrations of selenium near this level can reduce the levels of calcium in the backbones of trout.

Chronic toxicity of the bromoxynil formulation Buctril® to Daphnia magna exposed continuously and intermittently

Two chronic toxicity tests were conducted in which Daphnia magna were either continuously or intermittently exposed to bromoxynil octanoate (BO; as Buctril®) for 28 d. In the intermittent exposure test, daphnids were exposed to daily pulses of BO with 24-h mean concentrations equal to those in the continuous exposure test, and the peak concentrations were three times the 24-h mean values. After 28 d of continuous exposure to BO, survival of daphnids was reduced at 80 μg/L, whereas mean number of young per adult, intrinsic rate of natural increase, and mean weight of adults were all reduced at ⩾40 μg/L. Intermittent exposures to daily pulses of BO for 28 d caused reduced survival of daphnids at 24-h mean concentrations ⩾40 μg/L and reduced mean number of young per adult, intrinsic rate of natural increase, and mean weight of adults at 24-h mean concentrations ⩾20 μg/L. The estimated geometric mean-maximum acceptable toxicant concentrations of BO based on 24-h mean nominal values were 28 μg/L for continuous exposures and 14 μg/L for intermittent exposures. These results demonstrated that continuous-exposure studies may not be adequate in assessing herbicide toxicity to aquatic biota when concentrations fluctuate temporally.

Concentrations of Boron, Molybdenum, and Selenium in Chinook Salmon

Abstract The concentrations of boron, molybdenum, and selenium in young chinook salmon Oncorhynchus tshawytscha were determined in three partial life cycle chronic toxicity studies. In each study, fish were exposed to a mixture of boron, molybdenum, selenate, and selenite in the proportions found in subsurface agricultural drainage water in the basin of the San Joaquin Valley, California. Tests were conducted in well water and in site-specific fresh and brackish waters. No boron or molybdenum was detected in fish exposed to concentrations as high as 6,046 μg boron/L and 193 μg molybdenum/L for 90 d in well water or fresh water; however, whole-body concentrations of selenium increased with increasing exposure concentrations in well water and fresh water, but not in brackish water. Concentrations of selenium in chinook salmon were strongly correlated with reduced survival and growth of fish in well water and with reduced survival in a 15-d seawater challenge test of fish from fresh water. Concentrations of ...

Selenium in eggs and milt of razorback Sucker (Xyrauchen texanus) in the middle Green River, Utah.

Eggs from three female and milt from five male endangered razorback suckers (Xyrauchen texanus) were collected from the Razorback Bar (about 20 km upstream of Ashley Creek) in the Green River of northeastern Utah. Eggs, but not milt, had concentrations of selenium that were above the range of selenium concentrations in control fish from laboratory studies or reference fish from field studies. The concentrations, however, were below those reported in selenium-exposed fish that had reproductive problems in laboratory studies or field investigations. Tests with three streamside spawned pairs of razorback suckers, which were sampled for eggs and milt in this study, resulted in no hatching of fertilized eggs. Concentrations of selenium in eggs and milt were significantly correlated with selenium concentrations in muscle plugs taken from the same fish, but egg and milt concentrations were not significantly different from muscle plugs. Selenium concentrations in eggs of razorback suckers in the Green River may be sufficiently elevated to cause reproductive problems that are contributing to the decline of this species in the upper Colorado River basin.

Safety assessment of selected inorganic elements to fry of chinook salmon (Oncorhynchus tshawytscha)

The acute toxicities of arsenate, arsenite, cadmium, chromate, copper, mercury, silver, vanadium, and zinc were determined, individually and in two environmentally relevant mixtures, to two life stages of chinook salmon in reconstituted fresh and brackish waters that stimulated potential conditions in the San Joaquin Valley, California. The relative individual toxicities of the elements varied over four orders of magnitude; from most toxic to least toxic, the rank order was cadmium greater than copper greater than mercury greater than zinc greater than vanadium greater than arsenite greater than arsenate greater than chromate (no definitive tests for silver). In general, young fish tested in fresh water were more sensitive to the individual elements and the two mixtures than were advanced fry tested in brackish water. A 13-element mixture simulating concentrations in the San Luis Drain had the same toxicity to fish as the same mixture plus selenate and selenite, thus demonstrating that the presence of selenium at its environmental ratio in the mixture contributed no toxicity in short-term tests. As judged by a comparison of the individual acute values for salmon to the expected environmental concentrations in the San Luis Drain, the margins of uncertainty for cadmium and copper in both waters, zinc in fresh water, and mercury in brackish water were less than 100, whereas for the two environmental mixtures the margins were less than 15 in both test waters. These low margins of uncertainty, especially for the mixtures, indicate a high potential for environmental hazard to chinook salmon in the reconstituted waters tested.