Seawater carbonate chemistry and calcification of 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 (Gn) in the coral Acropora pulchra in Moorea, French Polynesia. A common garden experiment showed that Gn in four colonies was affected negatively by high partial pressure of CO2 (pCO2) (1000 μatm cf. 400 μatm ambient conditions), whereas elevated temperature (30 °C cf. 27 °C) had a negative effect on one colony. Together, these results reveal intraspecific variation in the response of Gn to temperature but not to pCO2. The fastest growing colonies under ambient temperature and ambient pCO2 showed the greatest decline in Gn at high temperature and elevated pCO2. For reef corals, effects of temperature and pCO2 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.