Factors controlling mercury and methylmercury concentrations in largemouth bass (Micropterus salmoides) and other fish from Maryland reservoirs

Abstract

The concentration of mercury (Hg) and methylmercury (MeHg) was determined for largemouth bass (Micropterus salmoides), bluegill (Lepomis macrochirus) and black crappie (Pomoxis nigromaculatus) from Maryland reservoirs. Overall, there was a large difference in normalized bass MeHg concentration (for fish of approximately 370 mm) between the reservoirs, ranging from <100 ng g(-1) to almost 800 ng g(-1). Furthermore, the relationship between fish weight and MeHg concentration varied substantially between lakes, and showed no geographical relationship. The concentration of Hg, MeHg and ancillary parameters were determined in the water and correlations were sought between the normalized concentration of MeHg in bass and both physical and chemical parameters of the reservoirs, as well as the concentration of MeHg in the prey of the largemouth bass. Bass MeHg concentration correlated with dissolved MeHg and dissolved organic carbon, but not with other chemical parameters. There was no relationship to physical characteristics that varied over orders of magnitude for these reservoirs. Dissolved MeHg did not correlate with any chemical or physical attributes. Overall, this study suggests that water column MeHg is a good predictor of fish concentration but that the water column MeHg cannot be predicted based on usually measured chemical and physical characteristics of fresh water bodies.