Seawater carbonate chemistry and sperm motility and fertilisation success in blood clam, Tegillarca granosa

Although it has been shown that ocean acidification generally has a negative impact on fertilisation success of broadcast spawning marine organisms, whether induced fertilisation success reduction is a consequence of elevated pCO2 or decreased pH remains unclear. Therefore, the impacts of HCl- and CO2-induced acidified seawater on sperm motility and gametes fertilisation capability of a broadcast spawning bivalve species, Tegillarca granosa were investigated in the present study. The results showed that the fertilisation capability of both gametes was significantly reduced in either HCl- or CO2-acidified seawater. In addition, significant impacts on sperm motility were observed in the group exposed to CO2-acidified seawater, suggesting that this parameter is sensitive to pCO2 instead of solely pH value. The differences between the two seawater acidification manipulating methods may be due to the intrinsic difference in diffusion capability of CO2 and protons.