Increased temperature mitigates the effects of ocean acidification on the calcification of juvenile Pocillopora damicornis, but at a cost

This study tested the interactive effects of increased seawater temperature and CO 2 partial pressure ( p CO 2 ) on the photochemistry, bleaching, and early growth of the reef coral Pocillopora damicornis . New recruits were maintained at ambient or high temperature (29 or 30.8 °C) and p CO 2 (~ 500 and ~ 1100 μatm) in a full-factorial experiment for 3 weeks. Neither a sharp decline in photochemical efficiency (Fv/Fm) nor evident bleaching was observed at high temperature and/or high p CO 2 . Furthermore, elevated temperature greatly promoted lateral growth and calcification, while polyp budding exhibited temperature-dependent responses to p CO 2 . High p CO 2 depressed calcification by 28% at ambient temperature, but did not impact calcification at 30.8 °C. Interestingly, elevated temperature in concert with high p CO 2 significantly retarded the budding process. These results suggest that increased temperature can mitigate the adverse effects of acidification on the calcification of juvenile P. damicornis , but at a substantial cost to asexual budding.