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.

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2021) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2023-03-08.