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Bioavailability of sediment-associated mercury to Hexagenia mayflies in a contaminated floodplain river

Naimo, T. J., Wiener, J. G., Cope, W. G., and Bloom, N. S., 2000, Bioavailability of sediment-associated mercury to Hexagenia mayflies in a contaminated floodplain river: Canadian Journal of Fisheries and Aquatic Sciences, v. 57, no. 5, p. 1092-1102.

Abstract

We examined the bioavailability of mercury in sediments from the contaminated Sudbury River (Massachusetts, U.S.A.). Mayfly nymphs (Hexagenia) were exposed in four 21-day bioaccumulation tests to contaminated and reference sediments (treatments) from reservoirs, flowing reaches, palustrine wetlands, and a riverine lake. Mean total mercury (Sigma Hg) ranged from 880 to 22 059 ng.g dry weight(-1) in contaminated sediments and from 90 to 272 ng.g(-1) in reference sediments. Mean final concentrations of methyl mercury (MeHg) in test water were greatest (8-47 ng Hg.L-1) in treatments with contaminated wetland sediments, which had mean Sigma Hg ranging from 1200 to 2562 ng.g(-1). In mayflies, final mean concentrations of MeHg were highest in treatments with contaminated wetland sediments (122-183 ng Hg.g(-1)), intermediate in treatments with contaminated sediments from reservoirs, flowing reaches, and a riverine lake (75-127 ng Hg.g(-1)), and lowest in treatments with reference sediments (32-41 ng Hg.g(-1)). We conclude that the potential entry of MeHg into the benthic food chain was greater in contaminated palustrine wetlands than in the contaminated reservoirs, which had the most contaminated sediments

Keywords: Atomic fluorescence detection, methyl mercury, water column, experimental reservoir, rigida ephemeroptera, gas-chromatography, nymphs Hexagenia, aquatic insects, methylmercury, temperature