EFFECTS OF WATER QUALITY ON APPALACHIAN ELKTOE MUSSELS IN THE LITTLE TENNESSEE RIVER

Alasmidonta raveneliana, the Appalachian Elktoe, is a freshwater mussel currently listed as critically endangered. An effort to restore their populations began in the mid-1990s, when only two populations were known to exist. After hurricanes Ivan and Francis in 2004 both populations were reduced to critical numbers and have steadily declined; by 2006 populations in the Little Tennessee River decreased by 80%. A hypothesized reason for this decline is a reduction in sediment and/or water quality associated with a combination of sedimentation from land use changes, agricultural runoff, mining, and industrial discharges.

Alterations in sediment and water quality, and their potential impact on biota, have been tested by examination of dissolved and particulate trace metal concentrations and water quality parameters indicating the suitability of habitat available for sufficient aquatic health.

Over the 2010 water year, hydro labs were deployed at three monitoring sites along the Little Tennessee River to evaluate the aquatic habitat. Collection and analysis of water samples for total, particulate, and dissolved concentrations of selected trace metals through ion chromatography and ICP-MS analysis was accomplished and variations in total suspended and dissolved sediment loads were determined along with flood events from sediment sampling and water grab samples collected across the hydrograph.

Mussel shell material collected between 1990-2010 was analyzed to determine threats and bioaccumulation during the time of population decline. Findings show levels of trace metals in the sediment well above probable effect thresholds, backed by diluted uptake in the shells, but with limited copper or ammonia currently found through pore-water investigations at bio-available levels. Sediment analysis coupled with cores taken from an impoundment along the water-course show trends suggesting an increasing source of sulfitic rich minerals. The deposition of newly eroded sediment exposed across the basin by recent development is believed to be contributing to the exposure of this aquatic environment to fresh sulfitic oxides compared with the highly eroded sulfides normally present in a naturally eroding environment.