Increasing atmospheric CO2 can decrease the seawater pH and carbonate ions, which may adversely affect the larval survival of calcareous animals. In this study, we simulated future atmospheric CO2 concentrations (800, 1500, 2000 and 3000 $μ$atm) and examined the effects of ocean acidification on the embryonic and larval stage of an infaunal clam Paphia undulate. Significant decrease of hatching of P. undulate was observed when the pCO2 reached 3000 $μ$atm, and larval deformation rate increased significantly when pCO2 reached 2000 $μ$atm, indicating a strong tolerance to ocean acidification compared with the embryonic development of other bivalves. The larvae cultured in 1500 $μ$atm pCO2 exhibited the fastest growth, highest survival and shortened planktonic period, which unordinary phenomenon reflected the beneficial effect of ocean acidification on P. undulate larval development. The better development of P. undulate larvae under a higher CO2 condition maybe an adaptation in response to the acidified sediment in which they live.
