Jeffrey A. Black

Fish and amphibian embryos--a model system for evaluating teratogenicity.

Developmental stages of fish and amphibians were used to evaluate reproductive impairments produced by environmental contaminants. Using static-renewal and flow-through procedures, exposure was initiated at, or soon after, fertilization and maintained through 4 days posthatching. Trace concentrations of many environmental toxicants produced high frequencies of mortality and teratogenesis. When developmental stages of the trout were exposed to inorganic mercury, 10% control-adjusted mortality was observed at 1 microgram/L and frequencies of terata in hatched populations ranged from 8% to 43% for exposure concentrations of 2 to 25 micrograms/L. In similar tests with the narrow-mouthed toad, 45% mortality occurred when mercury was administered at 1 microgram/L; frequencies of teratogenesis ranged from 8% to 17% at exposure concentrations of 1 to 5 micrograms/L; and complete mortality occurred at 7 micrograms/L. Boron-induced teratogenesis in trout ranged from 5% at 1 microgram/L to 51% at higher exposure levels. When catfish embryos were exposed to atrazine at 0.06, 4.8, and 46.7 mg/L, terata appeared in surviving populations at frequencies of 4%, 69%, and 100%, respectively. Fish and amphibian developmental stages constitute simple and effective models for 1) investigating mechanisms of teratogenesis, 2) evaluating the impact of environmental toxicants on aquatic biota, and 3) identifying environmental teratogens which may be of concern to human health.

Ecology of a saline stream: community responses to spatial gradients of environmental conditions

Spatial changes in structural and functional characteristics of fish and macroinvertebrate communities in eastern Kentucky were investigated in a drainage system chronically exposed to high levels of chloride salts from nearby oilfield operations. Salinity levels at biological monitoring stations ranged from 0.12–31.3‰. Lotic regions with salinities greater than 10‰ were dominated by larvae of the dipterans Ephydra and Culicoides. In regions with salinities less than 10‰ species richness increased more or less linearly with decreasing levels of chloride salts. Ephemeropterans appeared to be one of the major invertebrate groups least tolerant of elevated NaCl levels and were absent in regions with salinities greater than 2‰ Availability of food resources, such as periphyton and particulate organic matter, did not appear to be grossly altered in disturbed regions, and it is suggested that the observed distribution of macroinvertebrate fauna was largely in response to taxonomic differences in salt tolerance. Fish seemed to be more tolerant of highly saline conditions, and several species were observed in regions experiencing salinities as high as 15‰. Accordingly, assemblages of fish taxa along the salinity gradient may have been influenced by trophic factors, such as spatial limitations in availability of invertebrate prey.

An integrated assessment of the biological effects of boron to the rainbow trout

Abstract Acute and chronic toxicity tests have been performed in a number of independent laboratories to assess the effects of boron on aquatic life. Among the lowest effect concentrations were those determined in investigations on embryo-larval stages of the rainbow trout (Oncorhyncus mykiss) in reconstituted water. To gain a more precise definition of effect levels with rainbow trout, additional studies were performed with this species in both laboratory and natural dilution waters. Consistent lowest observed effect concentrations (LOECs) ranged from 0.1 to > 18 mg/L boron. The flat concentration-response curve observed for boron (i.e., small changes in effects relative to large increases in boron concentrations) sometimes affected precision in the determination of no-effect or threshold concentrations. Other factors that may have contributed to the wide range of LOEC values related to the effects of different types of dilution water on boron toxicity and the differential sensitivity of the trout strains evaluated. The impact of these variables on defining effect levels is discussed in detail in this paper. Based on the results of the rainbow trout tests, together with data from field surveys, a concentration of between 0.75 and 1.0 mg/L is determined to be a reasonable, environmentally acceptable limit for boron in aquatic systems. This conclusion is consistent with limits proposed by other investigators.

Effects of cadmium-enriched sediment on fish and amphibian embryo-larval stages

Aquatic toxicity tests were conducted to evaluate the effects of cadmium-enriched sediment on embryo-larval stages of the goldfish (Carassius auratus), leopard frog (Rana pipiens), and largemouth bass (Micropterus salmoides). Natural stream sediment was collected and enriched with cadmium to nominal concentrations of 1.0, 10.0, 100, and 1000 mg/kg. Enriched sediments were placed in Pyrex dishes and covered with 350 ml of reconstituted water. Fertilized eggs were placed in the dishes and maintained through 4 days posthatching, giving a total exposure time of 6 to 7 days. For all tests the cadmium concentrations ranged from 1.1 to 76.5 micrograms/liter in water above sediments containing 1 to 1000 mg Cd/kg, respectively. Although low frequencies of mortality were observed in all tests, goldfish, leopard frog, and bass exposed to sediments enriched to 1000 mg Cd/kg accumulated 4.61, 12.55, and 60.0 micrograms Cd/g, respectively. No significant correlations (P less than 0.05) were found between mortality of the goldfish and leopard frog and the cadmium concentrations in either water or sediment. However, all three species showed strong correlations (r greater than or equal to 0.98) between cadmium concentrations in water and tissue, sediment and tissue, and water and sediment. Tissue cadmium concentrations were related to the length of time test organisms were in direct contact with cadmium-enriched sediment.

Effects of acid-mine drainage on the chemical and biological character of an alkaline headwater stream

Distribution of metals in water and sediments, as well as spatial alteration in the benthic macroinvertebrate and fish assemblages, was assessed in an alkaline headwater stream in eastern Kentucky receiving runoff from an abandoned surface mine. Concentrations of aluminum, copper, iron, manganese, and zinc generally increased 2 to 3 orders of magnitude in the receiving water immediately below where the mine runoff entered the creek. Metals in the water column were transported downstream largely in association with suspended particulates and declined in concentration progressively in a linear fashion commensurate to distance below the mine drainage outfall. In contrast, metal enrichment of sediments occurred spatially in a non-incremental pattern and varied among locations in conjunction with sitespecific changes in concentration levels of sediment organic matter. Benthic macroinvertebrate and fish fauna were eliminated for a distance of 0.3 km below the outfall, presumably owing to the presence of high levels of dissolved metals and low pH. Recovery of stream benthos occurred 1.0–2.0 km further downstream and was characterized by numerical dominance of collector-gatherer trophic groups consisting primarily of midge larvae (Chironomidae: Orthocladiini). Fish fauna in downstream reaches consisted exclusively of creek chubs(Semotilus atromaculatus) and stoneroller minnows(Campostoma anomalum). Metal levels in water and sediments remained elevated in regions of biological recovery and, as a consequence, downstream communities were comprised predominantly of metal tolerant taxa.

Toxicity of metal mixtures to chick embryos

The toxic effects of mercury/selenium and certain other metal mixtures on the chick embryo are examined to determine whether antagonistic, additive or synergistic interactions occur. White Plymouth Rock chicken eggs were treated by yolk injection with cadmium chloride, mercuric chloride, zinc chloride and sodium selenate. Test aliquots were injected prior to incubation using the needle track procedure. Using a sample size of 200, percent survival was determined as hatchability of experimental eggs/controls. Metal mixtures used included mercury/cadmium, mercury/selenium, mercury/zinc, cadmium/selenium, and cadmium/zinc. Except for mercury/selenium, all other metal mixtures gave actual values that were within 5% of those for additive toxic effects. Actual hatchability frequencies for test concentrations of mercury/selenium indicated a moderate degree of synergism. Results indicate that the strong mercury/selenium synergism which affects embryonic development in the carp does not apply for the chick embryo; that most two-way combinations of cadmium, mercury, selenium and zinc exert purely additive effects on chick hatchability; and that these metal mixtures give no discernible antagonistic interactions which affect survival of chick embryos. (MFB)

Mercury content of human hair: a survey of dental personnel.

Hair samples from dental and nondental personnel in central Kentucky were collected and analyzed for inorganic mercury. Hair mercury levels in both groups averaged somewhat less than 1.0 micrograms/g, and the maximum concentration observed was 3.0 micrograms/g. There was no significant difference in hair mercury content between the two groups. However, a highly significant negative correlation (r = 0.7110; p less than 0.0001) was found between hair mercury concentration and age of the donor. A possible explanation of this relationship is presented. The analytical procedures employed provided accuracy and precision in recovering mercury from enriched hair samples.