Dynamics of an Eutrophic Lake (Wilgreen Lake, Madison County, Kentucky): A First Step in Cleansing a Lake System Impaired by Nutrient Loading

Wilgreen Lake (Madison County, Kentucky) is an eutrophic lake formed by damming Taylor Fork, part of the Silver Creek watershed. Two principal tributaries drain urban areas of the city of Richmond, agricultural land typified by cattle grazing, and a highdensity residential area using septic systems. The lake is listed “nutrient impaired” by the Commonwealth and EPA, so it is likely that nutrient input from human activities is affecting water quality. Our study aims first to characterize the physical characteristics and water quality of the lake (2006), and then to determine the specific proportion of nutrient inputs (2007) to the lake with the aim of remediating its water quality. We will use nitrogen isotopes and microbial DNA templates to identify specific nutrient sources. Research started in May 2006 with work occurring throughout the 2006 field season with the intent of establishing a baseline for key lake parameters. We used an YSI probe to measure temperature, conductivity, oxygen concentration, and pH and assayed for total ammonia nitrogen using the sodium hypochlorite, colorimetric method. The lake was already strongly stratified in May with disoxic and anoxic water below about 4 meters. Stratification strengthened in the summer with the disoxic-oxic boundary moving upward to about 3 meters, showing a sharper gradient oxygen gradient. Ammonium concentrations are typically zero in the oxic zone, and increase in concentration with increasing water depth in anoxic waters to about 5 ppm. We anticipate that phosphate and nitrate concentrations will mirror ammonium concentration profiles in character