A Comprehensive Evaluation of Benthic Invertebrate Communities in the Emory River, Watts Bar Reservoir, TN

The release of fly ash at the Tennessee Valley Authority (TVA) Kingston Fossil Plant (KIF) on 22 December 2008 discharged approximately 4.1 million cubic meters of coal ash into the adjacent aquatic and terrestrial systems. Previous benthic invertebrate investigations conducted by TVA and collaborative researchers concluded that benthic invertebrates in the Emory River were at moderate risk from ash-related constituents, primarily arsenic, in ash-contaminated sediment that remained in the Emory River following extensive dredging efforts. These conclusions were based on the observation of statistically significant reductions in growth and biomass in laboratory toxicity tests with Emory River sediment. Benthic invertebrate community survey results from 2010, however, did not support this conclusion. These previous surveys evaluated benthic invertebrate community data and sediment data across a large spatial scale, providing an “area-wide” interpretation of the relationships between the benthic invertebrate community results to the ash release. In the present research, co-located sediment and benthic invertebrate community samples were collected from nine locations in the Emory River. Community metric results were compared among samples, locations, and previous years and to co-located sediment chemistry and physical sediment properties. Temporal trends were also evaluated over a 5-year period of time at two locations to gauge if an initial impact and/or recovery could be determined. Despite this refined investigation, no trends or significant differences were identified between ash-impacted locations compared to the reference location, and no evidence of an initial impact or subsequent recovery trends were established. Furthermore, no significant relationships could be established between benthic invertebrate community metrics and sediment chemistry results. This information is important for the informed monitoring, remediation, and damage assessment of the benthic invertebrate community at the Kingston Ash Recovery site. This research also increases our knowledge of benthic invertebrate tolerance to metal mixtures in sediment of natural systems.