A mechanistic approach to evaluate the influence of Cd and Zn on ⁵⁷Co, ^110mAg and ¹³⁴Cs accumulation and depuration by a freshwater mussel (Dreissena polymorpha)

¹ Institute of Protection and Nuclear Safety, DPRE/SERLAB, Laboratory of Experimental Radioecology, CEN Cadarache, bâtiment 186, 13108 Saint-Paul-lez-Durance cedex, France
² National Center of Scientific Research, 13108 Saint-Paul-lez-Durance cedex, France
³ Laboratory of Ecophysiology and Ecotoxicology of Aquatic Systems, UMR 5805 du CNRS, University of Bordeaux 1, Arcachon, France

Abstract

The effects of Cd and Zn on ^110mAg, ⁵⁷Co and ¹³⁴Cs uptake and depuration in the freshwater mussel Dreissena polymorpha were investigated under laboratory controlled conditions. Differences at the whole body level were identified between groups exposed to radionuclides alone or to radionuclides and metals under different conditions (Cd or Zn alone or a mixture of Cd and Zn). The accumulation of ⁵⁷Co was reduced in the presence of Zn, at the whole organism level and in the soft body. On the opposite, ¹³⁴Cs increased in the presence of Cd or Zn. Finally, ^110mAg uptake decreased in the presence of both metals in the whole organism but increased in the soft tissues. Two hypotheses related to the major mechanisms governing the influence of metals on radionuclides were tested. First, the uptake was hypothesised to be directly related to the filtration rate, which has been shown to decrease with increasing zinc concentrations. On the other hand, whole organism zinc regulation mechanisms may include the radioactive pollutant as well. None of these two hypotheses could be validated. Consequently, further explanations were provided to link metal exposure to the radionuclide uptake by the bivalves.