EFFECTS OF WATERBORNE MERCURY ON TERRESTRIAL WILDLIFE AT CLEAR LAKE: EVALUATION AND TESTING OF A PREDICTIVE MODEL

Abstract

Birds and mammals exposed to waterborne mercury (Hg) and methylmercury (MeHg) were collected and/or sampled at Clear Lake, California, USA, to field test the predictive wildlife criteria model developed for the Great Lakes Water Quality Initiative (GLWQI). Tissue samples collected from sampled animals were analyzed for Hg and organochlorine residues, and for selected physiologic parameters known to be affected by Hg. All mammalian organ tissues analyzed contained less than 12 ppm total Hg, wet weight. All avian tissue samples analyzed contained less than 3 ppm total Hg, wet weight. No evidence of Hg-associated health effects was found. Tissue Hg residues were compared with water, sediment, and animal food samples to characterize bioaccumulation of mercury in the Clear Lake food web. Total Hg bioaccumulation factors for the Clear Lake site closest to the Hg source were: TL-2: 11,100; TL-3: 31,200; TL-4, 190,000. Our results support the final wildlife criterion (1,300 pg/L) and suggest that the GLWQI model, with site-specific modifications, is predictive for other Hg-bearing aquatic systems.