PARENT SESSION
33 - Metal Pollution: From Exposure to Ecological Effects (2)
2:10 PM to 5:20 PM, Tuesday, 14 May 2002
Session Chair: Migula, Pawel ¹, Laskowski, Ryszard ², ^{1 2} .
Strauss C

(33-01) Radionuclide bioaccumulation by freshwater organisms can be modified by the presence of Cd or Zn.

Garnier-Laplace, Jacqueline^*,1, Adam, Christelle¹, Fraysse, Benoit¹, Ausseil, Olivier¹, Boudou, Alain², ¹ IPSN, Saint-Paul-lez-Durance, France² UMR CNRS-5805, Arcachon, France

ABSTRACT- Should realism of radioecological assessments be enhanced by taking into account the deleterious influence of stable pollutants on aquatic organisms which can be physiologically stressed, and therefore modify their response to radionuclide bioaccumulation? Direct transfer experiments on a bivalve (Dreissena polymorpha) and a fish (Oncorhynchus mykiss) involved metals (Cd, Zn) and radionuclides (radioactive isotopes of Co, Cs, and Ag). Chronic metallic waterborne exposures (1-4 g/L Cd and/or 170-250 g/L Zn) led to a decrease in radionuclide bioaccumulation with respect to the reference group (^110mAg and ¹³⁷Cs for fish with respectively −60% and −30%; ⁵⁷Co for bivalve with −50%, on average); while no effect was noticed with other radionuclide/organism pairs (Co for fish, Cs and Ag for bivalve). Some explanations are given (1) to link the stable pollutant-induced stress in organisms (especially biomarkers of oxidative stress and protein synthesis) and the modification of the radionuclide bioaccumulation level and kinetics, (2) to provide evidence of the mechanisms involved. Illustration will be mainly given for the bivalve for which the inhibiting effect of Zn on the ⁵⁷Co uptake rate was clearly evidenced and explained with (1) a net decrease in ⁵⁷Co input through biological barriers, (2) a cellular redistribution of ⁵⁷Co with a decrease of the cytosolic fraction and an increase of the storage in the form of mineral granules, (3) a modification of the ⁵⁷Co tissue distribution with a storage in the form of granular deposits in the mantle and the excretory organs. These fundamental biomineralisation processes in bivalves could explain the marked difference of effect between the two biological models.

Key words: bioaccumulation, metal, radionuclide, interaction