Comparison of Asian clam field bioassays and benthic community surveys in quantifying effects of a coal-fired power plant effluent on Clinch River biota

Survival and growth of Asian clams may be more sensitive endpoints than benthic macroinvertebrate community richness parameters at distinguishing biotic impairment attributable to complex effluents from coal-burning utilities. We conducted (1) field bioassays with the Asian clam (Corbicula fluminea) during 2000-02 and (2) rapid bioassessments of benthic macroinvertebrate communities during 2000-01 at sites upstream/downstream of American Electric Power's (AEP) Clinch River Plant (CRP) in Russell County, Virginia (U.S.A). Survival and growth of transplanted C. fluminea were significantly impaired within the CRP effluent plume (averages of 35% and 0.21 mm, respectively) relative to all other study sites within the Clinch River (averages of 89% and 1.58 mm). Conversely, richness metrics for Ephemeroptera, Ephemeroptera-Plecoptera-Trichoptera (EPT), and total taxa were not reduced downstream of the CRP. However, relative abundance metrics for Ephemeroptera and EPT were minimally reduced at the CRP-influenced site during 2000-01. More importantly, our results suggest that richness metrics for benthic macroinvertebrate communities may be inadequate for assessing the effects of complex industrial effluents on C. fluminea. These findings have implications for bioassessment techniques employed to monitor streams inhabited by imperiled freshwater mussels because (1) C. fluminea and Unionoidea are ecologically similar and (2) recent findings suggest certain genera of Unionidae may be more sensitive than C. fluminea.