Mussel Survivorship, Growth Rate and Shell Decay Rate in the New River Basin of Tennessee: an Experimental Approach Using Corbicula fluminea

The New River Basin (NRB) of Tennessee is home to a number of rare endemic aquatic communities. One such community of particular importance to the area, experiencing a precipitous population decline due to the fouling and pollution of their freshwater systems, is that of freshwater mussels (Bogan 2006). This study in the NRB involves measuring the mortality rates of live Asian clams (Corbicula fluminea) assemblages and the shell decay rates of their death assemblages. This study also examines the decay rates of the native Villosa iris to gather information on molluscan health and the ability of their shells to be incorporated into the freshwater record, or to be used by other organisms for ecological engineering. A common property of aquatic systems influenced by anthropogenic activity is increased conductivity (a proxy correlated to the ability of water to pass an electric current because of increased metal and dissolved solids concentrations) which studies show may impair clam health and enhance shell decay rates. Our study of five impacted streams within the NRB and a control stream of similar geology tests this correlation. Silos containing live Corbicula fluminea were placed in several localities in streams of the NRB that receive mining drainage as mine drainage is commonly associated with elevated conductivity. To measure the effects of this anthropogenic activity on shell decay rates, mesh bags containing shells of Corbicula fluminea and Villosa iris were placed in several localities in creeks of the NRB that receive varying degrees of mine drainage. The weight of these shells were periodically measured, over the course of 120 days, to determine the rate of decay. I found that growth and mortality rates of the life assemblages are correlated with the conductivity and water temperature levels that the living clams are exposed to, and that shell decay rates did not correlate with conductivity but were influenced by calcium levels and water velocity.

This study was conducted to assist the conservation of unique freshwater mussel species of the New River Basin in the Cumberland Mountains of Tennessee.