Sperm motility of the scleractinian coral Acropora digitifera under preindustrial, current, and predicted ocean acidification regimes

Ocean acidification caused by the uptake of anthropogenic CO2 in the oceans negatively affects the early life stages of corals by reducing their calcification rate. Acidification also inhibits the sperm motility of corals, potentially affecting fertilization success. We investigated the effects of different pCO2 (partial pressure of CO2) conditions on the sperm motility of Acropora digitifera. Using a pCO2-control system, we maintained pCO2 at concentrations from preindustrial and present-day levels up to the level predicted by the year 2100 (300, 400, and 1000 ppm, respectively). Our results indicated that ocean acidification has the potential to suppress the sperm flagellar motility of A. digitifera. Furthermore, sperm motility will likely decline by ~30%, which may impact fertility, if the sensitivity of sperm motility to decreasing pH cannot adapt over a span of ~90 yr.