Accumulation of mercury and methylmercury by mushrooms and earthworms from forest soils

Accumulation of total and methyl-Hg by mushrooms and earthworms was studied in thirty-four natural forest soils strongly varying in soil physico-chemical characteristics. Tissue Hg concentrations of both receptors did hardly correlate with Hg concentrations in soil. Both total and methyl-Hg concentrations in tissues were species-specific and dependent on the ecological groups of receptor. Methyl-Hg was low accounting for less than 5 and 8% of total Hg in tissues of mushrooms and earthworms, respectively, but with four times higher concentrations in earthworms than mushrooms. Total Hg concentrations in mushrooms averaged 0.96 mg Hg kg−1 dw whereas litter decomposing mushrooms showed highest total Hg and methyl-Hg concentrations. Earthworms contained similar Hg concentrations (1.04 mg Hg kg−1 dw) whereas endogeic earthworms accumulated highest amounts of Hg and methyl-Hg. ► Hg and MeHg concentrations in mushrooms and earthworms at unpolluted forest soils. ► Mushrooms and earthworms contained similar Hg concentrations. ► MeHg was present in traces but four times higher in earthworms than in mushrooms. ► Ecophysiological group influenced Hg and MeHg concentration in both receptors. Accumulation of Hg and methyl-Hg by mushrooms and earthworms is species- and ecophysiological group dependent.