| Summary: | International audience The study of early life stages such as larval development, settlement, survivorship, and recruit growth iscritical to better understand the resilience and persistence of coral populations. While the deleterious effectsof ocean acidification on calcification and growth on adult corals are well known, the impacts on early lifestages are still poorly documented. Here, we investigate whether past-exposure of parental colonies tonaturally acidified environments at CO2 vents can increase the offspring's tolerance to low pH. Larvae of theMediterranean azooxanthellate coral Astroides calycularis were obtained from parent colonies collected fromlow and ambient pH sites in Ischia, Italy. Larvae were exposed in the laboratory to three pH treatments:ambient (pHT ~8.05), low (pHT ~7.7, pH projected for the end of the century under RCP 8.5) and extreme low(pHT ~7.5, pH as extreme condition, only for the larvae from the CO2 vent site). Several traits of the early lifestages were monitored for 5 months: larval size, settlement success, survival and growth of the recruits. Keydifferences were observed between the site of origin of the larvae. For instance, larvae from the CO2 ventsite were shorter and exhibited a higher rate of mortality than the larvae from the ambient pH site regardlessof the pH treatment they were exposed to. Also, larvae from the CO2 vent site had a lower settlementsuccess at low and extreme low pH. Our results suggest that future acidification conditions will have animpact on survival and settlement of early life stages. These findings provide new insights into coralrecruitment and the ability to respond to present and future ocean acidification conditions
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