Influence of metal (Cd and Zn) waterborne exposure on radionuclide (134 Cs, 110m Ag and 57 Co) bioaccumulation by rainbow trout (oncorhynchus mykiss) : a field and laboratory study
Résumé
Field and laboratory experiments were carried out to assess the influence of Cd and Zn on the contamination levels of Ag-110m, Co-57, and Cs-134 in rainbow trout. During a four-week prior exposure phase, two fish groups were held in tanks in the Lot River (France) at a reference (<0.05 mu g Cd/L and 68 mu g Zn/L) and at a polluted site (1.5 mu g Cd/L and 152 mu g Zn/L). During a subsequent phase, organisms were brought back to thee laboratory, where the radionuclide accumulation and depuration were studied for 14 and 7 d, respectively. During this second phase, the water used in the experiments was brought back from the two sites on the Lot River in order to work under the same chemical conditions. The potential effect of chronic exposure to stable metals on several biomarkers has been explored: Plasma analysis indicated the disruption of certain variables linked to the energetic metabolism and to the maintenance of the ionic balance. In contrast, no significant disruption of the measured enzyme activities was observed. With regard to the bioaccumulation of radionuclides, concentrations in fish exposed to metals are much lower than those in fish from the control group. Various hypotheses are proposed to link fish metabolic profiles due to metal exposure to the radiocontamination of organisms.