The impacts of As accumulation under different pH levels: Comparing Ruditapes decussatus and Ruditapes philippinarum biochemical performance.

Marine bivalves have been used to assess environmental As contamination and the effects of seawater acidification when both factors are acting alone, but limited information is available regarding the impacts of both factors acting in combination. The aim of this study was to compare physiological (glycogen) and biochemical (lipid peroxidation, superoxide dismutase, catalase, glutathione-S-transferase and alkaline phosphatase) responses in both native (Ruditapes decussatus) and introduced (R. philippinarum) clams, when exposed to the combined effects of pH (7.8, control; 7.3) and As concentrations (0 and 4mg/L). The combined effect of As and pH on the health risks associated with clam consumption was also analyzed. Results revealed that both species were able to accumulate As under both pH levels, although higher As concentrations where observed under low pH. Thus, predicted pH decrease will potentiate health risks associated with the consumption of such species, since less amount of clams exposed to As is needed for an adult to exceed the provisional tolerable weekly intake (PTWI). Low pH, As exposure and the combination of both factors did not negatively affect the native species, since clams were able to maintain their physiological and biochemical performance among all conditions. On the other hand, R. philippinarum was negatively affected by As exposure at control pH (7.8), inducing biotransformation and antioxidant defense mechanisms against As toxicity. R. philippinarum exposed and non-exposed to As presented similar responses under low pH although at this condition the introduced species accumulated twice the amount of As than R. decussatus.