Effects of ocean acidification on Cd-109, Co-57, and Cs-134 bioconcentration by the European oyster (Ostrea edulis): Biokinetics and tissue-to-subcellular partitioning

Abstract

The uptake and depuration kinetics of dissolved Cd-109, Co-57 and Cs-134 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-109 and Co-57 and depuration of Cd-109 and Cs-134 in oyster. The uptake and depuration rate constants of Cs-134 differed during the exposure phase between treatments, while the steady state concentration factors (CFss) 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(39d)) were similar. Co-57 depuration was affected by pCO(2) conditions: RA(39d) were found to be significantly higher in oysters reared in normocapnia (pCO(2) = 350 mu atm) compared to high pCO(2) conditions. Co-57 tissue distribution did not differ among the variable pCO2 conditions, while Cd-109 and Cs-134 accumulated in soft tissue of oysters were found to be higher under the highest pCO(2). 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(2) driven acidification and/or coastal acidification variably influence these processes.