Elevated Calcium Levels in Kentucky Lake: A Possible Emerging Problem with an Invasive Species

Zebra mussels (Dreissena polymorpha) are an exotic and invasive mollusk that have spread extensively through various rivers and lakes in the United States. These mussels are notorious for their “biofouling” capabilities costing billions of dollars in their removal from industrial, public, and power plant water supply lines. While having been present in the Tennessee River drainage with occasional small reproducing populations since the early 1990s, zebra mussels were never abundant or widespread. In 2017, high densities were found on structures and solid substrates throughout the lower portion of Kentucky Lake. Calcium is one of the essential elements that contributes to the growth and reproduction of zebra mussels. Calcium concentrations of 20-22 mg/L are considered the threshold for survival and reproduction of zebra mussels. The specific aim of this study was to determine if dissolved calcium levels in the lower reach of Kentucky Lake had increased and reached that threshold. Surface and bottom water samples were collected during Kentucky Lake Monitoring Program (KLMP) cruises as well from selected locations in the Ohio River and two tributary streams. Samples were filtered using 0.45 µm filters, acidified and analyzed for calcium using an Atomic Absorption Spectrometer. Calcium levels and long-term monitoring data on chloride levels in Kentucky Lake were examined for temporal trends. The results showed an increasing trend in calcium concentrations during the past decade. The higher levels of calcium are likely from increased use of road deicing brine, of which CaCl2 is a major component, over the past several years. Increasing levels of these calcium ions may play a role in the elevated occurrences of zebra mussels in Kentucky Lake