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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 (Σ 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 Σ 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