CHANGES IN KENTUCKY’S LICKING RIVER EFFECT ON ISOTOPES OF FRESHWATER MUSSEL SHELLS

Within the Kentucky Licking River and its tributaries, freshwater mussels of varied species and ages are found. As filter feeders, freshwater mussels use nutrients from the water to grow as they age, forming growth bands on the exterior of the shell. Additionally, with lifespans of up to 50 years, they have the potential to be significant records of environmental variation. These characteristics make them ideal recorders of both food web dynamics and environmental conditions. Changes in these variables can be recorded through the investigation of d¹³C and d¹⁵N of the outer organic layer and d¹³C and d¹⁸O of the inorganic shell carbonate respectively.

The primary goal of this study is to determine any correlations between species or locations of the mussels and environmentally indicating isotopic ratios. Eight species of mussels were therefore collected from 11 location sites of the Licking River and its tributaries. Preliminary results show strong correlations between the organic C and N values of a single species found at multiple locations. The range of values are greater than what would be expected by analytical error and shows consistent trends reflecting differences in bedrock composition. Within a specific location, each species typically has distinct isotopic values, reflecting unique ecological niches. Finally, the isotopic analysis of the inorganic fraction show changes across the shell growth axis, potentially reflecting changing environmental conditions.

Future investigations will expand on these comparisons and determine if variations can be attributed to any specific factors. These factors to consider will include pollutants in the water, lack of nutrient rich food sources, harsh weather, and change in quality of life due to the low water dams that have been installed in the Licking River.