Modification de la bioaccumulation du sélénium chez Mytilus edulis en présence du mercure organique et inorganique

Studies of the simultaneous bioaccumulation of selenium and mercury in the blue mussel, Mytilis edulis, in the presence of TiO2 as carrier have shown that there is an interaction between the two elements. We measured the bioaccumulation rates of dissolved selenite (Na2SeO3) and adsorbed organic selenium (C8H7O2Se)2 and determined the impact of the presence of mercury (HgCl2 and [(CH3Hg)3O]OH) in the environment. Mussels measuring 3.6 ± 0.2 cm were distributed in nine contamination tanks with continuously circulating seawater and were exposed to organic or inorganic selenium at a concentration of 50 μg Se∙L−1 for periods of 15–50 d. Some of the tanks were simultaneously exposed to high concentrations of organic and inorganic mercury (3.0 and 30 μg Hg∙L−1, respectively). When mercury was not present, the mussels accumulated the inorganic selenium at a slow rate (0.12 ng Se∙g−1∙d−1), but did not accumulate the organic selenium. When inorganic mercury was added to the water at 30 μg Hg∙L−1, the accumulation rate of inorganic selenium doubled (0.24 ng Se∙g−1d−1), while it tripled (0.40 ng Se∙g−1d−1) when methyl mercury was added at 3.0 μg Hg∙L−1. Even the adsorbed organic selenium seemed to become bioavailable in the presence of methyl mercury, and was accumulated at a rate of 0.15 ng Se∙g−1d−1. However, the phenomenon is not reciprocal, that is, the presence of selenium, no matter what its concentration or chemical nature, had no effect on the accumulation rate of mercury. No toxic effects were observed where selenium was administered alone, but the toxic effects of mercury were observed in all mussels exposed to it. Selenium showed none of the adverse effects previously observed in other animal species.