Aggregate Extraction Impacts on Unionid Mussel Species Richness and Density

Kentucky Reservoir on the Tennessee River supports a diverse freshwater mussel community including federally-listed endangered species. Resource extraction operations have been conducted on the Tennessee River since at least the 1920s. The condition of abandoned dredge sites as aquatic habitat for benthic organisms, including freshwater mussels, is relatively unknown. Objectives of this study were to determine the condition of abandoned dredge sites as aquatic habitat for freshwater mussels, compare species richness and density between sites in relation to years post dredging, collect information relevant to future permitting consultations, and provide a greater understanding of the effects of resource extraction in a large regulated river. Six hundred 0.25 m-2 quadrat samples were collected and processed from 12 study sites. Both mean density (54.51 mussels · m-2; SD = 58.335) and species richness (15 taxa; SD = 1) were significantly higher at reference sites than at the dredged sites (P < 0.0001). Correlation analysis indicated no significant relationship (r = 0.2059, P > 0.10) between mean mussel density and time (in years) since the last dredge event. The Wilcoxon's rank sum tests indicated significantly lower mussel abundance (P < 0.05) and richness (P <0.05) at the dredge sites relative to the reference sites. Based on data obtained during this study, we will advocate additional protection of specific sites within the lower Tennessee River reach currently permitted for commercial dredging.

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