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(26-09) Comparison of direct and trophic contamination of with Orconectes limosus by Uranium. Simon, Olivier*,1, Morlon, Helene1, Garnier-Laplace, Jacqueline1, 1 Inst. of Protection and Nuclear Safety (IPSN), Saint-Paul-Lez-Durance, France ABSTRACT- Little ecotoxicological information is currently available regarding the impact of natural uranium on freshwater ecosystems. In natural conditions, organisms are exposed to contamination from two principle sources: direct contamination from the water column and trophic transfer via ingestion of contaminated food. In order to predict the transfer of uranium present in the environment, to the biotic components, the importance of both of these two contamination routes needs to be assessed in order to properly predict bioaccumulation and the potential subsequent toxicity. Initially, we measured the accumulation capacities of the filter-feeding mollusc Corbicula fluminea and the American crayfish Orconectes limosus after direct exposure. The composition of the exposure medium (spring water, pH=7) was carefully chosen to favour the existence of the most bioavailable uranium solution species. The distribution of solution species was calculated using the computer program Jchess with the OECD/NEA Thermochemical database. Additionally, we have studied the capacity for trophic transfer of uranium between a prey species, C. fluminea, and a predator, O. limosus, and the influence of the U distribution in the prey on the efficiency of its transfer to the predator. To order to obtain preys at the same level of U contamination but with different U distributions within the organism, 3 groups of prey were exposed to different levels of direct contamination. They were fed to the crayfish (one soft body per day per individual)l during a period of ten days.The bioaccumulation by O. limosus has been studied at the level of both the entire organism and the individual organs in order to identify and to compare the target tissues and cells of the contamination for both of the exposure routes. Key words: URANIUM, DIRECT, TROPHIC, CRAYFISH |
