Impacts of mine drainage and other nonpoint source pollutants on aquatic biota in the upper Powell River system, Virginia

The Clinch-Powell River system of Virginia and Tennessee, USA, is among the most biologically diverse ecosystems in the world, and has been identified as a conservation priority of national importance. Other researchers have attributed declines in Powell River freshwater mussel populations to coal mining-related activities. The objectives of this paper are to synthesize the results of several studies aimed at assessing acid mine drainage (AMD) impacts in the Powell River watershed, and to describe the relative roles of AMD, nutrient loading, and urban runoff in structuring the benthic macroinvertebrate communities of the Powell River. Impacts ranged from acute toxicity due to the combination of acid and metals, acute aluminum toxicity in circumneutral pH waters, and physical impacts from solid ferrihydrite, to decreased clam growth due to urban runoff. These findings support the concern that AMD negatively impacts aquatic biota in the Powell River watershed in a variety of ways, and emphasize the importance of taking measures to properly reclaim areas that are producing mine drainage. However, past-mining related pollutants are not the only source of aquatic-community impact in these watersheds, as nutrient loading and urban runoff both were associated with substantial changes in community structure and clam growth.