Scleractinian coral species survive and recover from decalcification

Increasing global concentrations of atmo-spheric carbon dioxide (CO2) enhance hy-drolysis of CO2 in seawater, ultimately decreasing seawater pH (1). This has already caused the pH of modern surface waters (8.0 to 8.3) to be about 0.1 pH unit less than in pre-industrial times, and geochemical models have estimated further acidification of up to 1.4 pH units over the next 300 years (1). Increased atmospheric CO2 also reduces car-bonate ion concentrations in seawater, which decreases the saturation of aragonite (W-arag), the principal mineral deposit of corals. W-arag, together with temperature and light, sets bound-aries for coral reef biogeography (2). Reef com-munities thrive where W-arag is 3.1 to 4.1, but under CO2 doubling W-arag is projected to dro