Temporal Changes and Possible Sources of Dissolved Calcium Levels in Stream, River, and Lake Waters in Western Kentucky

ABSTRACT Zebra Mussels (Dreissena polymorpha) are an exotic and invasive mollusk that spread extensively over various rivers and lakes in the United States. These mussels are known for being notorious in their “biofouling” capabilities, costing the U.S. government billions of dollars in removal operations. Recently, zebra mussel colonies were found in Kentucky Lake possibly due to human activities increasing the salinity of today’s freshwater resources. The increase in salinity from human activities may have adversely affected the ecosystems and water supplies. The Specific aim of this study was to determine the temporal trend of dissolved calcium in Kentucky Lake water, as well as to track the sources of calcium . Surface and bottom water samples were collected during the Kentucky Lake Monitoring Program (KLMP) cruises as well as selected locations in the Ohio River, two tributary streams, and samples from one of the tributary streams. Water Samples were filtered using 0.45 µm filters, acidified and analyzed for dissolved calcium using an Atomic Absorption Spectrometer. The results revealed an increasing trend in calcium concentrations during the past decade. Particularly, calcium levels gradually/steadily increasing in concentration from 16.0 ppm (May 2012) to 40 ppm (April 2018). Elevated levels are more prominent during winter or early spring months when road salts are applied. KLMP long-term monitoring data revealed an increasing trend of chloride levels during the past three decades. In addition, the calcium levels were examined and whether the levels reached zebra mussels’ survival and reproduction threshold. Our results give credence to conclude that human activities including road salt application during winter and subsequent runoff due to heavy rain during early spring months contribute to rise in the calcium levels and emergence of zebra mussels in our waters