Assessing Contaminant Sensitivity of Endangered and Threatened Species: Effluent Toxicity Tests
United States Environmental Protection Agency Office of Research and Development
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Toxicity tests using standard effluent test procedures were conducted (EPA 1994) with Ceriodaphnia dubia and fathead minnows and four endangered fish species: bonytail chub (Gila elegans), Colorado squawfish (ptychocheilus lucias), razorback sucker (Xryauchen texanus) and Gila topminnow (Poeciliopsis occidentalis). We conducted 7-d survival and growth studies with embryo-larval fathead minnows and analogous exposures using the listed species. Survival and reproduction were also determined with C. dubia. Tests were conducted with: 1) carbaryl; 2) ammonia; and 3) a mixture of carbaryl, copper, 4-nonylphenol, pentachlorophenol, and permethrin. The fathead minnow 7-d growth and survival test appears to be a reliable estimator of effects to the listed species used in this study. Additionally, the C. dubia survival and reproduction test was generally more sensitive than any of the fish tested. When the listed species and fathead minnow were different, the listed species was often less sensitive than the fathead minnow. However, other studies have shown listed species to be similar to or slightly more sensitive than fathead minnows when tested using effluent procedures. This study was conducted with fish species that have not been typically tested so factors such as handling procedures, optimum feeding rates, optimum test temperature, expected test to test variation and expected survival or growth have not been previously documented, and therefore results of this study should be interpreted cautiously. Our laboratory has evaluated only 10 aquatic vertebrate species (mostly fish) and there are over 90 fishes listed by the FWS. The database for fishes should be expanded to include additional species from different areas of the United States. Amphibian population declines have been recognized worldwide and the FWS has over 10 listed species, therefore, greater emphasis should be placed on testing additional amphibian species. Additional testing is also needed to evaluate sublethal effects of contaminants on listed species. Finally, other listed species including freshwater mussels and other invertebrates should also be examined.