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Coral reefs experience biologically-driven p CO 2 oscillations that are predicted to become more extreme in magnitude and duration under ocean acidification (OA) regimes. Understanding the plasticity of responses in common reef-building corals to oscillations in p CO 2 will allow for better predictions of their function in future seawater conditions. This study explored the effects of variation in seawater p CO 2 on coral calcification using experiments conducted over one month between 9 April 2018 and 18 May 2018. Branches (~4-cm long) of Acropora retusa were sampled from colonies at 10-m depth on the fore reef of Mo'orea, French Polynesia (17° 28′ 53.9004" S, 149° 49′ 50.5992" W). We tested the hypothesis that depressed calcification caused by elevated p CO 2 (~1000 μatm) is relaxed (i.e., calcification increases) upon return to ambient p CO 2 (~400 μatm). Corals first were incubated in ambient or elevated p CO 2 for 19 days, with the result that calcification integrated over this period was reduced by 31% under elevated p CO 2. The same corals were then incubated at ambient p CO 2 for 11 days, during which calcification was independent of the experimental p CO 2 exposure history. Our results suggest that a quick relaxation of p CO 2 -depressed calcification in A. retusa following cessation of high p CO 2 indicates that corals are capable of a reversible plastic response of calcification when confronted by p CO 2 oscillations. • Coral reefs experience biologically-driven p CO 2 oscillations • Calcification of A. retusa with two p CO 2 exposure histories differed. • When subsequently placed in common p CO 2 environment, calcification was similar. • Some corals are capable of a reversible plastic response of calcification. [ABSTRACT FROM AUTHOR]