Ocean acidification alters the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and gene expression of a bivalve species, Sinonovacula constricta

Although the impacts of ocean acidification on fertilization, embryonic development, calcification, immune response, and behaviour have been well studied in a variety of marine organisms, the physiological and molecular mechanism manifesting acidification stress on behavioural response remains poorly understood. Therefore, the impacts of future ocean acidification scenarios (pH at 7.8, 7.6, and 7.4) on the burrowing behaviour, Ca2+/Mg2+-ATPase activity, metabolism, and expression of energy-producing-related genes of the razor clam Sinonovacula constricta were investigated in the present study. The results showed that elevated CO₂ partial pressure (pCO₂) (pH at 7.6 and 7.4) led to a significant reduction in the digging depth of the razor clam. In addition, exposure to pCO₂-acidified seawater depressed the metabolism and activity of Ca2+/Mg2+-ATPase, which may partially contribute to the reduced digging depth detected. Furthermore, the expression of energy-producing-related genes was generally induced by exposure to acidified seawater and could be accounted for by an increased energy demand under acidification stress. The results obtained suggest ocean acidification may exert a behavioural impact through altering physiological condition in the razor clam.