RECONSTRUCTING THE IMPACTS OF ACID MINE DRAINAGE ON NUTRIENT CYCLING IN A LAKE USING DIATOM AND GEOCHEMICAL ANALYSES

John A. Scott Lake is a wildlife and fishing area open to the public in Southwestern Indiana near the city of Terre Haute. Scott Lake and an adjacent lake, the Green Valley Mine Pond, are located in the Green Valley area, which was an active coal mining site from 1948-1963. Various reclamation efforts were made by the Indiana Department of Natural Resources after the closing of the mining operation. In 2011, the USGS Division of Reclamation conducted an investigation into the hydrogeology of the area. They reported that despite reclamation attempts, there was strong evidence that acid mine drainage was still seeping into the lake from the mining site. John A. Scott Lake is a reservoir that impounds a local stream that is fed from a drainage area around the mining site. A 37 cm core was taken from John A. Scott Lake in the Green Valley coal mine site near Terre Haute, IN in spring 2014. The core was sampled at a 0.5 cm resolution to analyze diatom assemblages, phosphorus concentrations, and metal concentrations in the sediment. Recent geochemical analyses of the lake sediments from this core suggest that since the lake was created, it has experienced leaching of nutrients and metals from the surrounding groundwater and bedrock as a response to dynamic shifts in the pH. Here we present evidence of the biological effects of the acid mine drainage on the lake ecosystem from the same lake sediment cores. Diatoms are particularly sensitive to changes in the lake environment and they leave behind fossil remains in lake sediments that can be analyzed to recreate the environmental history of the lake. We analyzed the fossil diatom assemblage and compared the results with the phosphorus burial and geochemical evidence from the sediment record to allow us to see a more complete picture of past, present, and help us to predict the future trajectory of the lake in terms of environmental change. Since this site is an area that is regularly used for fishing and other recreational activities, we are also exploring whether this area is a safe place for recreational use.