This paper presents the results of a study examining the impact of CO2 variations in water on uranium bioaccumulation in the bivalve Corbicula fluminea. The objectives were to evaluate the effect of CO2 on bivalve behavior (valve activity and ventilation rate) that are related to bioaccumulation and on the bioavailability of uranium carbonate complexes to the bivalve. It was demonstrated that at a total inorganic carbon concentration of CCO 2 5 276 mmol/L, the daily valve opening duration and ventilation rate are significantly (p , 0.05) lower than those obtained at 27.6 mmol/L (228 and 247%, respectively). For both CCO 2 values, exposure to uranium at 0.25 mmol/L had no impact on valve activity; however, ventilation decreased significantly compared to the reference condition, down to the same lower level for the two CCO 2 conditions. Consequently, the quantity of uranium passing through the bivalve was identical for both CCO 2 conditions. Thus, bivalve ventilatory and valve activity could not explain increased bioaccumulation in the gills and mantle measured under the low-CCO 2 condition. Consequently, we suggest that the quantity of carbonate bound to the U fraction must be less bioavailable than other U species such as the free-ion , which 21 UO2 is in accordance with the biotic ligand model.
(1) Laboratoire de Radioécologie Expérimentale, Institut de Radioprotection et de Surete Nucléaire, Cadarache, Bat. 186, BP3, 13115 Saint Paul-Lez-Durance, Cedex, France
(2) UMR 5805, Laboratoire d’Ecophysiologie et Ecotoxicologie des Systèmes Aquatiques, Universite Bordeaux 1 et CNRS, Place du Dr. Peyneau 33120, Arcachon, France