Organic micropollutants enhance radionuclide (134Cs and 57Co) uptake by rainbow trout (Oncorhynchus mykiss).

C Adam, O Ausseil, J Garnier-Laplace, JP Baudin, JM Porcher Congrès IUR-SETAC, Anvers (Belgique), 4-8 février 2002.

In the context of the multipollution of aquatic ecosystems, a laboratory experiment was performed to address the question of whether the presence of organic micropollutants can influence the bioaccumulation of 57Co and 134Cs by the rainbow trout. This work is based on the hypothesis that beyond a certain concentration and exposure duration, exposure to various pollutants induces physiological disruptions that subsequently generate alterations in the uptake characteristics of radionuclides by the organism. The selected organic micropollutants belong to the categories of PCBs (PCB-77, Aroclor 1254), PAHs (fluoranthene, benzo(a)pyrene), herbicide (atrazine) and endocrine disruptors (17-b-estradiol). Six groups of fish were contaminated i.p. via a single injection of a solution of the compound of interest in corn-oil. The doses administrated were high enough to induce an effect but below the toxic levels. The trouts of the control group were only injected with corn-oil. During this first phase, several biomarkers were measured to evaluate the exposure to and the effect of these micropollutants (EROD activity, fluorescent aromatic compounds, vitellogenine, plasmatic parameters…). After 7 days, the fish were exposed to waterborne 134Cs and 57Co for 2 weeks to study the radionuclide uptake kinetics. Finally, the trouts were transferred to a non-contaminated medium to monitor the radionuclide depuration. The results showed that the exposure to organic pollutants lead to an increase in radionuclide bioaccumulation. In the case of 57Co, this increase ranged from 30 % for PCB-77 to 60% for 17-b-estradiol. As regards 137Cs, the increase observed was of 15 % for benzo(a)pyrene and of 45 % for PCB-77. In any case, this increase was due to a rise in the uptake rate and a reduction of the depuration rate. These findings are discussed in terms of relevancy for bringing together radioecology with traditional ecological risk assessments.