Use of Bivalve Metrics to Quantify Influences of Coal-related Activities in the Clinch River Watershed, Virginia

Previously, we reported that survivorship and growth of field-caged Asian clams (Corbicula fluminea Müller]) were significantly reduced downstream of the wastewater effluent discharge of the Clinch River Plant (CRP), a coal-fired electric power-generating facility in Russell County, VA (USA). These findings warranted the present study, which investigated whether reduced survivorship and growth of transplanted C. fluminea were predictive of adverse effects on resident bivalves – most notably the Clinch River’s (CR’s) federally protected freshwater mussel fauna (Unionoidea). Thus, surveys of unionoid assemblages and C. fluminea population densities and age distributions were conducted to assess ecotoxicological effects on bivalve assemblages naturally occurring in the CR. Results of these surveys suggested that field bioassays with transplanted C. fluminea were predictive of in-stream C. fluminea densities and the presence/absence of indigenous unionoid assemblages. Relative to C. fluminea, additional field bioassays with a juvenile unionoid species (Villosa iris) native to the CR were less predictive of adverse effects on resident bivalves. Concurrence of transplant studies and in-stream surveys was evident at most study sites, particularly within 0.6 km downstream of the CRP effluent where resident bivalves were virtually non-existent relative to other stream sites having similar habitat conditions. Our findings indicate that in situ field bioassays with transplanted C. fluminea are valuable tools for predicting in stream occurrence and distribution of resident freshwater bivalves, and that field studies integrating multiple bivalve metrics may be useful for prioritizing source-reduction efforts in similar watersheds. Discrepancies observed for transplanted C. fluminea and V. iris have important implications to selection of bivalve species used in field bioassays and warrant further study.