Tanvet C. auteur aut IRD Camp E. F. auteur aut IRD Sutton J. auteur aut IRD Houlbrèque Fanny auteur aut IRD Thouzeau G. auteur aut IRD Rodolfo-Metalpa Riccardo auteur aut IRD text journalArticle eng text/pdf reformatted digital access Ocean acidification (OA) is a severe threat to coral reefs mainly by reducing their calcification rate. Identifying the resilience factors of corals to decreasing seawater pH is of paramount importance to predict the survivability of coral reefs in the future. This study compared corals adapted to variable pH(T) (i.e., 7.23-8.06) from the semi-enclosed lagoon of Bourake, New Caledonia, to corals adapted to more stable seawater pH(T) (i.e., 7.90-8.18). In a 100-day aquarium experiment, we examined the physiological response and genetic diversity of Symbiodiniaceae from three coral species (Acropora tenuis, Montipora digitata, and Porites sp.) from both sites under three stable pH(NBS) conditions (8.11, 7.76, 7.54) and one fluctuating pH(NBS) regime (between 7.56 and 8.07). Bourake corals consistently exhibited higher growth rates than corals from the stable pH environment. Interestingly, A. tenuis from Bourake showed the highest growth rate under the 7.76 pH(NBS) condition, whereas for M. digitata, and Porites sp. from Bourake, growth was highest under the fluctuating regime and the 8.11 pH(NBS) conditions, respectively. While OA generally decreased coral calcification by ca. 16%, Bourake corals showed higher growth rates than corals from the stable pH environment (21% increase for A. tenuis to 93% for M. digitata, with all pH conditions pooled). This superior performance coincided with divergent symbiont communities that were more homogenous for Bourake corals. Corals adapted to variable pH conditions appear to have a better capacity to calcify under reduced pH compared to corals native to more stable pH condition. This response was not gained by corals from the more stable environment exposed to variable pH during the 100-day experiment, suggesting that long-term exposure to pH fluctuations and/or differences in symbiont communities benefit calcification under OA. specialized adaptation Bourake calcification coral natural analogue New Caledonia ocean acidification physiology Symbiodiniaceae NOUVELLE CALEDONIE 036 034 13 5 e10099 [21 ] 2023 2045-7758 https://www.documentation.ird.fr/hor/fdi:010088099 10.1002/ece3.10099 2045-7758 [F B010088099] https://www.documentation.ird.fr/hor/fdi:010088099 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2023-07/010088099.pdf IRD - Base Horizon / Pleins textes 2023-07-06 2025-02-24 fdi:010088099 fre