HOMOGENIZING SUBSTRATE DURING IN SITU ASIAN CLAM STUDIES STRENGTHENS SPECIFICITY OF ASSOCIATION BETWEEN ECOTOXICOLOGICAL INFLUENCES AND BIOLOGICAL RESPONSES.

M.S. Hull, D.S. Cherry, R.J. Currie, and T.C. Merricks. Department of Biology, Virginia Tech, Blacksburg, Virginia, United States 24061

We investigated ecotoxicological influences from a coal-fired power plant discharge and active coal mining effluent on the survival and growth of field-caged Asian clams (Corbicula fluminea) located in the Clinch River and Dump’s Creek tributary, Carbo, Virginia. Our objective was to determine if substrate variability among 14 Clinch River and Dump’s Creek sites significantly weakened the specificity of association between causes of ecotoxicological impairment and observed biological responses. Two in situ procedures were simultaneously conducted to test for no significant differences (α = 0.05) between 90-d survival and growth when substrate was either homogenized for all sites or left unmodified from a site’s naturally occurring substrate. Corbicula survival and growth for both procedures were significantly reduced at the first site directly below the power plant discharge, relative to all other sites. Values for mean percent survival were not significantly different between both procedures in either system but mean growth was significantly greater for the substrate-homogenizing method at Clinch River (p<0.0001) and Dump’s Creek (p=0.0188) sites. Consequently, relative site rankings differed between the two procedures, suggesting that although both methods may successfully detect more severe Corbicula impairment, failure to homogenize substrate among study sites may confound detection of less severe influences.