Comparison of direct and trophic contamination of Orconectes limosus by Uranium.

Simon O., Morlon H and Garnier-Laplace J. 12th annual meeting of SETAC Europe , Vienne (Autriche), 12-16 mai 2002.

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 potential involved 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 (OECD/NEA Thermochemical Data Base Project). Following on from this step, 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 predator. To order to obtain preys at the same level of U contamination but with different U distribution within the organism, 3 groups of prey were exposed by 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.