Intraspecific variability in the response to ocean warming and acidification in the scleractinian coral Acropora pulchra

Studies of coral colonies show that ocean acidification and temperature can affect calcification; however, less is known about the consequences for their populations. Understanding intraspecific variation in the response of corals to these conditions will be important for evaluating population-level consequences of environmental change. We examined intraspecific variability in the effects of elevated temperature and carbon dioxide levels on net calcification (G(n)) in the coral Acropora pulchra in Moorea, French Polynesia. A common garden experiment showed that G(n) in four colonies was affected negatively by high partial pressure of CO2 (pCO(2)) (similar to 1000 mu atm cf. similar to 400 mu atm ambient conditions), whereas elevated temperature (30 degrees C cf. 27 degrees C) had a negative effect on one colony. Together, these results reveal intraspecific variation in the response of G(n) to temperature but not to pCO(2). The fastest growing colonies under ambient temperature and ambient pCO(2) showed the greatest decline in G(n) at high temperature and elevated pCO(2). For reef corals, effects of temperature and pCO(2) on calcification that depend on the intrinsic growth rate have potentially important consequences, because they imply that coral colonies contributing the most to population- level calcification will be disproportionately affected by changing environmental conditions.