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COMPARATIVE TOXICITY TESTING OF SELECTED BENTHIC AND EPIBENTHIC ORGANISMS FOR THE DEVELOPMENT OF SEDIMENT QUALITY TEST PROTOCOLS
Citation:
Fulton, M. H., G. I. Scott, P. B. Key, G. T. Chandler, R. F. Van Dolah, AND P. P. Maier. COMPARATIVE TOXICITY TESTING OF SELECTED BENTHIC AND EPIBENTHIC ORGANISMS FOR THE DEVELOPMENT OF SEDIMENT QUALITY TEST PROTOCOLS. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-99/085, 1999.
Description:
Sediment contamination has resulted in the need to develop an appropriate suite of toxicity tests to assess ecotoxicological impacts on estuarine ecosystems. Existing Environmental Protection Agency (EPA) protocols recommend a number of test organisms, including amphipods, polychaetes, molluscs, crustaceans and fish for use in sediment toxicity tests. While this suite of test animals represents a diverse group of fauna, many of the species recommended by the EPA are not indigenous to all geographic regions of the United States, particularly the Gulf of Mexico and South Atlantic. As a result, environmental risk assessment based on these organisms may not adequately protect ecosystem health in the Gulf of Mexico. Ideally, appropriate test organisms to evaluate sediment toxicity should include species indigenous to the Gulf of Mexico that are representative of a variety of faunal classes and feeding types. Additionally, the toxicity test endpoints should include both lethal (mortality) and sublethal (reproduction, growth, physiological impairment) effects and they should be sensitive to either porewater and/or whole sediment exposures for all major classes of chemical contaminants (trace metals, polycyclic aromatic hydrocarbons [PAHs], pesticides). Finally, test species should be easy to collect and maintain in the laboratory. This study examined the relative sensitivity of a variety of test organisms, broadly distributed throughout the southeastern United States and the Gulf of Mexico to several classes of chemical contaminants in both whole sediment and aqueous/porewater exposures. Additionally, several rapid screening assays were compared with these more traditional toxicity evaluations. The three model contaminants selected for study were cadmium (an inorganic toxicant), DDT (a persistent organochlorine pesticide) and fluoranthene (a polycyclic aromatic hydrocarbon [PAH]). These compounds represent contaminants frequently measured in sediments throughout the Gulf of Mexico. Overall, the juvenile clam was the most sensitive species tested in this study from an acute toxicity standpoint. The grass shrimp and the two amphipod species were generally similar in sensitivity to each of the three compounds. The copepod assay, although relatively insensitive in terms of adult mortality, was capable of detecting sublethal effects at contaminant concentrations below those which caused mortality in the other more sensitive species. Both the juvenile clam assay and the copepod partial life cycle test have the potential to serve as sensitive indicators of potential sediment-associated toxicity which might not be detected using standard acute toxicity bioassays. The differing species sensitivities observed with the different classes of chemical contaminants in this study suggest that a multiple species approach may be more appropriate for a holistic ecological risk assessment of sediment contamination. The "Crustacean Triad" (copepods, amphipods and grass shrimp) provide a battery of tests which predict toxicity to epibenthic and benthic crustaceans with known sensitivity to a variety of chemical contaminants and represent the base of the food chain for most recreationally and commercially important finfish species that utilize estuarine nursery grounds. The addition of the juvenile clam assay provides a herbivorous filter feeder with the ability to bioconcentrate pollutants and which is extremely sensitive in the size range tested (>212<350 |m). Field studies in South Carolina have indicated that sites with high sediment contaminant levels have degraded benthos, with significant effects observed in crustaceans and molluscs. These findings support our laboratory results and suggest that an integrated battery of assays may be most appropriate for estimating field effects.