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1J - Bioaccumulation (WEP/70) Trophic transfer of uranium in rainbow trout (Onchorynchus mykiss). Accumulation, tissue distribution and biological effects. BUET, Astrid1, SIMON, Olivier1, PRADINES, Catherine1, GARNIER-LAPLACE, Jacqueline1, 1 Institute of Radioprotection and Nuclear safety, Saint-Paul-Lez-Durance, 13, France ABSTRACT- Fish are often among the highest trophic level species in aquatic food chain. As a consequence, they are exposed to heavy metals by several distinct routes: direct contamination from the water column and/or sediment and trophic transfer by ingestion of various contaminated food. Uranium (U) is a widely spread metal in freshwater ecosystems and according to its human uses, environmental situations mostly lead to chronic low concentration exposure. We suggested to confirm the existence of U trophic transfer in rainbow trout (Onchorynchus mykiss) and to evaluate the variability of the assimilation efficiency and tissular U distribution in relation to the type of preys. Then we assessed the possible induced biological effects. Two preys models, the amphipod Gammarus sp. and the zebrafish (Brachydanio rerio) were exposed to a relatively low U concentration in water (100 mg/L) for 20 days. The water composition (soft synthetic water, pH 6) was carefully controlled to reliably predict U aqueous speciation by geochemical modeling (JCHESS software and OECD/NEA Thermochemical Data Base Project review). Then, rainbow trouts were fed with contaminated gammarids or zebrafish at a fixed feeding rate. The influence of prey tissular and cellular U distribution on the transfer to the predator was studied. Finally, a better knowledge of the mechanisms involved in the trophic transfer enabled us to investigate the toxicity of U under chronic exposure conditions. Oxidative stress parameters (glutathione and MDA burdens, SOD, GPx and Catalase enzymatic activities) were measured in exposed and control groups (no U exposure). Relations between biological fish disturbances and U trophic exposure modalities were assessed. Results should allow us to develop and identify some potential uranium toxicity biomarkers. Key words: trophic transfer, uranium, tissue distribution, fish |
