Modeling pH Regulation During Coral Calcification: Implications for Predicting Coral Calcification Responses to Ocean Acidification and for Interpreting Geochemical Proxies

Abstract:

Coral, like many other carbonate-secreting organisms, exerts strong control over its calcification process, resulting in an internal calcifying environment that departs from the ambient seawater. Most notably, pH of the coral calcifying fluid has been shown to be significantly elevated relative to seawater. Such pH regulation not only determines coral calcification responses to environmental changes (e.g. ocean acidification and rising temperature), but also affects the elemental and isotopic compositions of coral skeleton and complicates the interpretation of various geochemical proxies. Based on existing models of coral calcification and geochemical constraints on its pH regulation, I simulated the chemistry, especially pH, of the coral calcifying fluid, and evaluated the calcification responses to changing seawater chemistry among different coral species. Predictions from these simulations compare favorably with results from laboratory manipulation experiments, and suggest different coral species can exhibit different responses to ocean acidification depending on their respective capabilities to regulate the calcifying environment. The implication of these model results for interpreting geochemical proxies will also be discussed at the meeting.