Adding Injury to Insult

Coral reefs worldwide are under terrible pressure from rising sea-surface temperatures, pollution, and overexploitation. Another emerging threat to their health is ocean acidification--the declining pH of surface seawater layers caused by the absorption of increasing amounts of atmospheric CO2. Many studies have demonstrated recent declines in the coverage and numbers of live coral reefs, as well as reduced coral diversity, but few have examined how rates of coral calcification have been affected. De'ath et al. (p. 116; see the news story by Pennisi) examined growth patterns of 328 massive Porites corals from the Great Barrier Reef of Australia and found that their rates of calcification have declined by nearly 15% since 1990, to values lower than any seen for the past 400 years. The main causes of this continuing decline appear to be increasing water temperatures and ocean acidification.