Effects of ocean acidification on Cd, Co, and Cs bioconcentration by the European oyster (Ostrea edulis): Biokinetics and tissue-to-subcellular partitioning.

The uptake and depuration kinetics of dissolved Cd, Co and Cs were determined experimentally in the European flat oyster Ostrea edulis (Linnaeus, 1758) under different pH conditions (i.e., 8.1, 7.8 and 7.5) for 59 days. Uptake and depuration rates were variable within these elements; no effects were observed under different pH conditions for the uptake biokinetics of Cd and Co and depuration of Cd and Cs in oyster. The uptake and depuration rate constants of Cs differed during the exposure phase between treatments, while the steady state concentration factors (CF) were similar. The resulting Cs activity that was purged during short- and long-term depuration phases differed, while the remaining activities after thirty-nine days depuration phase (RA) were similar. Co-57 depuration was affected by pCO conditions: RA were found to be significantly higher in oysters reared in normocapnia (pCO = 350 μatm) compared to high pCO conditions. Co-57 tissue distribution did not differ among the variable pCO conditions, while Cd and Cs accumulated in soft tissue of oysters were found to be higher under the highest pCO. Additionally, Cd, Co and Cs were stored differently in various compartments of the oyster cells, i.e. cellular debris, metal-rich granules (MRG) and metallothionein-like proteins (MTLP), respectively. The subcellular sequestration of the elements at the end of the depuration phase did not differ among pH treatments. These results suggest that bioconcentration and tissue/subcellular distribution are element-specific in the oyster, and the effects of higher pCO driven acidification and/or coastal acidification variably influence these processes.