Different calcification responses of two hermatypic corals to CO2-driven ocean acidification.

Understanding how calcification is influenced by the enhanced dissolution of CO2 in the oceans is the key to evaluating the effects of ocean acidification (OA) on coral reefs. In this study, two branching hermatypic corals widely distributed in the South China Sea, Pocillopora damicornis and Seriatopora caliendrum, were used to study the calcification responses to CO2-driven OA (7.77 ± 0.07 vs. 8.15 ± 0.12). Our results showed that the calcification rate (0.17 ± 0.04%/day to 0.21 ± 0.12%/day) in P. damicornis remained unchanged in the acidified seawaters, but that in S. caliendrum decreased significantly (0.62 ± 0.21%/day to 0.44 ± 0.11%/day). Our results suggested that reef corals with high calcification rates may be more susceptible to the enhanced dissolution of CO2. Differential calcified response to elevated CO2 may be closely attributed to coralline capacity of the upregulation at their site of calcification in acidified seawater.