MERCURY SPECIATION AND BIOACCUMULATION IN LOTIC PRIMARY PRODUCERS ANDPRIMARY CONSUMERS

Mercury speciation and bioaccumulation were strongly affected by troph ic position and distance from contamination source in this study of lo wer trophic levels in two eastern Tennessee streams. Methylmercury and inorganic mercury (Hg(II)) were analyzed in samples of periphyton, gr azing fish (stonerollers, Campostoma anomalum), and omnivorous fish (s triped shiners, Luxilus chysocephalus) taken from three sites in an in dustrially contaminated stream and one site in a reference stream. Ino rganic mercury predominated in periphyton and fish samples from all si tes, always exceeding 50% of total mercury. However, the proportion of methylmercury increased significantly with both trophic level and dis tance downstream. Bioconcentration factors for methylmercury increased 0.5-1.5 log units per trophic level at all sites, implying significan t biomagnification of this species. Bioconcentration factors for Hg(II ) declined with increasing trophic level at three of the four sites an d were 1-2 log units lower than those for methylmercury, providing lit tle evidence of Hg(II) biomagnification. Primary producers and primary consumers are critical intermediaries in the movement and biomagnific ation of mercury from water to upper trophic levels.