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1J - Bioaccumulation (WEP/71) Coupling metal aqueous speciation and ecophysiological approaches to assess uranium accumulation in the Asiatic clam. SIMON, olivier1, TRAN, Damien1, Garnier-Laplace, Jacqueline1, Massabuau, Jean-charles2, 1 IRSN/DPRE/SERLABLRE, Cadarache, France2 LEESA/UMR CNRS 5805, Arcachon, France ABSTRACT- Despite to the wide repartition of uranium in freshwaters, the use of biological models such as bivalves as bioindicators to detect and quantify the bioavailability of this metal to biota has been poorly investigated. Indeed, several mechanisms are controlling the bivalve′s response to uranium exposure and a muldisciplinary approach is needed to explain the metal-organism interactions. Using the Asiatic clam (Corbicula fluminea) and theoretically knowing the chemical speciation of uranium by application of geochemical modelling, a first set of experiments was carried out in a well-defined composition water (soft spring water) to evidence the water uranium concentration, the pH effect and the exposure duration on the bivalve accumulation in terms of assimilation efficiency, tissular and subcellular distribution. Results showed a significant effect of pH on bioaccumulation rate (x 14 ; from pH 8.1 to 7) and a marked difference of U distribution in organs as a function of exposure levels and duration. In a complementary set of experiments, when the bivalves were exposed to uranium (0.25 Key words: speciation, Uranium, behavior, bivalve |
mol.L-1) at a fixed pH, no effect was evidenced on the valve activity but a significant effect on the ventilation flow rate was quantified. This latter decreased by 50% in comparison of control groups (no-added uranium). Some explanations are given concerning the effects of such environmental factors on the relative contribution of (1) the aqueous chemical speciation of uranium, (2) the valve closure response and the ventilatory rate of Corbicula fluminea, on the accumulation patterns in the bivalves, underlying the need for this multidisciplinary knowledge to properly analyse biomonitoring data.