Seawater Acidity Reduces the Physiological Ability of Corals to Calcify

by Dawn Barlow

This study by Venn et al. (2013) addresses how ocean acidification reduces the calcification rate of corals by reducing internal pH at the calcifying tissue-skeleton interface. They aim to predict how corals will respond and potentially acclimate to ocean acidification by looking at how acidification impacts the physiological mechanisms that drive calcification itself. Coral skeletons are formed from calcium carbonate crystals (aragonite), produced in the fluid-filled subcalcioblastic medium (SCM), which underlies the calcifying tissue. The calcifying tissue elevates pH the SCM relative to the pH of the exterior seawater, favoring the conversion of bicarbonate to carbonate, and enhancing precipitation at the site of calcification. This ability of corals to regulate internal pH is anticipated to be critical in their resilience to ocean acidification, and overall, findings from this study suggest that reef corals may be able to mitigate the effects of seawater acidification by regulating pH in the SCM. Continue reading