Seawater carbonate chemistry and physiological energetics of juvenile clams Ruditapes decussatus

Effects of coastal ocean acidification, other than calcification, were tested on juvenile clams (Ruditapes decussatus) during a controlled CO2 perturbation experiment. The carbonate chemistry of natural (control) seawater was manipulated by injecting CO2 to attain two reduced pH levels: -0.4 and -0.7 pH units as compared with the control seawater. After 87 days of exposure, we found that the acidification conditions tested in this experiment significantly reduced the clearance, ingestion and respiration rates, and increased the ammonia excretion rate of R. decussatus seeds. Reduced ingestion combined with increased excretion is generally associated with a reduced energy input, which will likely contribute to a slower growth of the clams in a future high CO2 coastal ocean. These results emphasize the need for management policies to mitigate the adverse effects of global change on aquaculture, which is an economically relevant activity in most coastal areas worldwide.