The English–Wabigoon River System: II. Suppression of Mercury and Selenium Bioaccumulation by Suspended and Bottom Sediments

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Abstract
Bioaccumulation of 203Hg and 75Se by several members of the food chain, including fish, was followed in large in situ enclosures in the presence and absence of organic-poor sediment. When the sediment was absent, 203Hg was bioaccumulated 8- to 16-fold faster than when it was suspended in the water or present on the bottom of the enclosures. Hg-contaminated and uncontaminated sediments were equally effective at reducing the rate of radiolabeled Hg bioaccumulation, apparently by binding the Hg to fine particulates making it less available for methylation and/or bioaccumulation. Based on these results, a Hg ameliorating procedure involving semicontinuous resuspension of organic-poor sediments with downstream deposition onto surface sediments was suggested. The presence of sediments, in the water or on the bottom of enclosures, also reduced radiolabeled Se bioaccumulation. The degree of inhibition (2- to 10-fold) may have been related to the concentration of organic material in the predominantly inorganic sediments. Implications of this research with respect of Hg-Se interactions in aquatic ecosystems were discussed.

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