ENVIRONMENTAL FACTORS AFFECTING METHYLMERCURY ACCUMULATION IN FISH OF THE GREAT LAKES REGION

Methylmercury (MeHg) can have toxicologically significant effects on humans and wildlife at concentrations commonly found in the environment. While multiple environmental factors (e.g., mercury loadings, sulfate) are known to influence the accumulation of MeHg in wildlife, the relative significance of individual factors on levels in fish are poorly understood. This study describes spatial distributions of MeHg in four common fish species (largemouth bass Micropterus salmoides, yellow perch Perca flavescens, walleye Sander vitreus, and northern pike Esox lucius) in the Great Lakes region and investigates multiple biogeochemical factors potentially affecting these distributions. Specific environmental factors that were examined included 1) wet atmospheric deposition of mercury, sulfate, nitrate, and acid, 2) watershed:lake area, 3) watershed geology, and 4) physicochemical properties of surface water including, for example, pH, sulfate, and dissolved organic carbon. Linear regression analysis was used to estimate standard-length MeHg concentrations for each fish species in each of several hundred water bodies. Standard-length MeHg levels were compared by multiple-linear regression to a suite of water-body specific environmental characteristics. While atmospheric deposition of mercury appears to be a primary control on MeHg accumulation in fish, preliminary results suggest that secondary atmospheric and water-chemistry factors also have a significant role in the Great Lakes region.