A SURVEY OF MERCURY BIOACCUMULATION IN BATS AT MAMMOTH CAVE NATIONAL PARK

Existing levels of bioaccumulatied mercury in bats (bat hair) in Mammoth Cave National Park (MCNP) were measured using direct combustion mercury analysis. The direct combustion analysis was done with a Mercury Analyzer AMA 254 using ASTM Method D 6722-01 which is a test method for total mercury in coal and coal combustion residues. The ASTM D 6722-01 methodology appears to be as accurate as current accepted methods for Hg analysis of hair at the ppm level and has the advantages of minimal sample handling and requires no acid digestion. Mercury levels as a function of bat species, collection location, age, and gender were determined. Quality analysis and control was performed with human hair reference material. Hair from archived bats will also be analyzed and compared to current sample results. Duplicate samples will be analyzed with both direct combustion and cold vapor atomic emission in order to compare both methods. Fish (liver and muscle) tissue may also be analyzed for mercury. Results to date show a wide range of mercury accumulation in bats (1-10 ppm) with clear evidence of species, gender and age sensitivity. The Hg levels in adult male bats are typically greater than that of adult females and juveniles of the same species. The Hg levels in juvenile males are more than the Hg levels in juvenile females of the same species.The potential for Hg sample heterogeneity in an individual appears to be minimal. Variations between individuals are much wider as bats are long-lived species. The current data shows a potential threat of Hg levels in the drinking water and Hg bioaccumulation in a number of surface and subsurface organisms of MCNP. Background levels of mercury, typically, 5-10 ppt in the water and 40-70 ppb in the sediment, have been observed. A number of surface and subsurface organisms are endangered or declining in MCNP due to bioaccumulation of mercury. Observed levels of mercury in fish and clam samples are comparable to values observed in other studies (0-0.50 ppm).