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ASSESSING CONTAMINANT SENSITIVITY OF ENDANGERED AND THREATENED AQUATIC SPECIES WITH ACUTE TOXICITY TESTS
Citation:
Mayer Jr., F L., F. J. Dwyer, D. R. Buckler, C. M. Bridges, D. K. Hardesty, C. E. Henke, J. L. Kunz, L. C. Sappington, D. W. Whites, T. Augspurger, D R. Mount, K. Hattala, AND G. Neuderfer. ASSESSING CONTAMINANT SENSITIVITY OF ENDANGERED AND THREATENED AQUATIC SPECIES WITH ACUTE TOXICITY TESTS. ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY. Springer, New York, NY, 48:143-154, (2005).
Impact/Purpose:
We present a summary of the 96-hour acute toxicity results and compare the sensitivities of listed and related species with common test species tested using similar procedures.
Description:
Assessment of contaminant impacts to endangered and threatened (listed) species requires understanding of a species' sensitivity to particular chemicals. The most direct approach would be to determine the sensitivity of a listed species to a particular contaminant or perturbation. An indirect approach for aquatic species would be application of toxicity data obtained from standard test procedures and surrogate organisms typically used in laboratory toxicity tests. Standard surrogate test species (fathead minnow, Pimephales promelas; sheepshead minnow, Cyprinodon variegatus; rainbow trout, Oncorhynchus mykiss) and 17 listed or closely related species were tested with 5 chemicals (carbaryl, copper, 4-nonylphenol, pentachlorphenol, permethrin) representing a broad range of toxic modes of action. No single species was the most sensitive to all chemicals. For the three standard surrogate test species evaluated, the rainbow trout was more sensitive than either the fathead minnow or sheepshead minnow, and was equal to or more sensitive than listed species 81% of the time. To estimate an LC50 for a listed species, a factor of 0.63 can be applied to the geometric mean LC50 of rainbow trout toxicity data, and more conservative factors can be determined using variance estimates (0.46 based on 1 standard deviation (SD) of the mean and 0.33 based on 2 SD of the mean).
Regardless of the factor used, the estimates are less of an adjustment than division by a safety factor of 10. Additionally, for the listed species tested, a low-or no-acute effect concentration can be estimated by multiplying their respective LC50 by a factor of about 0.56 which supports
the USEPA approach of multiplying the final acute value by 0.5 (division by two). When captive or locally-abundant populations of listed fish are available, consideration should be given to direct testing. When direct testing cannot be performed, approaches for developing protective measures using surrogate species toxicity data are available.