Study on the reproductive output of the non-zooxanthellate colonial coral Astroides calycularis (Scleractinia, Dendrophyllidae) naturally living at CO2 vents in Ischia Island.

The escalating impacts of climate change, particularly ocean acidification, pose unprecedented challenges to marine biodiversity. This study investigates the resilience of Astroides calycularis populations at Magician's Cave in Ischia, Italy, to natural high-CO2 exposure. Through reproductive analyses, significant tolerance of A. calycularis to elevated pCO2 was revealed. Consistent functional sexual reproduction along the annual reproductive cycle was observed, characterized by uniformity in abundance, gonadal index, and polyp diameter. These findings corroborate previous research, indicating novel patterns in colony response to acidification and prioritizing sexual reproduction over asexual reproduction. The study suggests that natural populations of A. calycularis have developed tolerance mechanisms, potentially through local acclimatization to acidification. Furthermore, the findings position A. calycularis as a valuable model for understanding the coping strategies of temperate corals in the face of future ocean acidification scenarios. Overall, the research underscores the importance of considering regional variations and natural adaptation processes in assessing the impacts of climate change on marine biodiversity. Further investigations into the long-term effects of ocean acidification on A. calycularis and other temperate corals will be crucial for informing conservation and management strategies aimed at preserving coral reef ecosystems in a changing climate.