How Corals Can Overcome Ocean Acidification & Global Warming
McCulloch, M., Falter, J., Trotter, J. and Montagna, P. Coral resilience to ocean acidification and global warming through pH up-regulation. Nature Climate Change 2: 623-627.
Using a model of pH regulation combined with abiotic calcification, McCulloch et al. (2012) additionally show that "the enhanced kinetics of calcification owing to higher temperatures has the potential to counter the effects of ocean acidification," adding that "the extra energy required to up-regulate pH is minor, only <1% of that generated by photosynthesis," which highlights the importance of maintaining the zooxanthellae-coral symbiosis for sustaining calcification. And they further note, in this regard, that their model predicts "a ~15% increase in calcification rates from the Last Glacial Maximum to the late Holocene," which increase they describe as being "consistent with the expansion of tropical habitats that occurred during this time despite PCO2 increasing."
Projecting into the future with their experimentally-verified model, the four researchers assess the response of coral reefs to both global warming, with mean tropical sea surface temperatures ~ 2°C higher, and with PCO2 increasing from present-day levels to ~1,000 ppm by the year 2100." And for this scenario, they report that their model predicts "either unchanged or only minimal effects on calcification rates." Thus, from a strictly chemical and kinetic perspective, their model indicates that "ocean acidification combined with rising ocean temperatures should have only minimal effects on coral calcification," which they describe as "a direct outcome" of corals' ability to up-regulate pH at the site of calcification.
Al-Horani, F.A., Al-Moghrabi, S.M. and de Beer, D. 2003. The mechanism of calcification and its relation to photosynthesis and respiration in the scleractinian coral Galaxea fascicularis. Marine Biology 142: 419-426.
Ries, J.B. 2011. A physicochemical framework for interpreting the biological calcification response to CO2-induced ocean acidification. Geochimica et Cosmochimica Acta 75: 4053-4064.
Venn, A., Tambutte, E., Holcomb, M., Allemand, D. and Tambutte, S. 2011. Live tissue imaging shows reef corals elevate pH under their calcifying tissue relative to seawater. PLoS ONE 6: e20013.