Influence Of Interstitial Sediments On An Endangered Freshwater Mussel Population

Erosion and transport of sediment and associated pollutants to rivers and other aquatic systems is among the most commonly-reported yet poorly-understood water quality stressors. Freshwater mussels are benthic invertebrates that spend much of their lives buried within sand and gravel substrates but appear to be sensitive to changes in concentrations of fine sediments associated with anthropogenic activities. I examined the role of sedimentation associated with a highway expansion project on an Appalachian elktoe (Alasmidonta raveneliana) mussel population in the South Toe River in western North Carolina. I compiled abundance data, used freeze cores to extract and quantify interstitial substrate and conducted field and lab experiments using juvenile mussels in order to better understand the degree to which sediment composition affects mussel population size as well as juvenile growth and survival. The data I gathered suggest road construction may be contributing to Appalachian elktoe declines in the South Toe River but the mechanism does not appear to be direct impacts of fine sediments. Instead, the impacts of fine sediments are likely sub-lethal and may involve alteration of streambed microhabitats or exclusion of mussels from the hydraulic refugia that facilitate persistence in this high-gradient mountain stream.