Coral trophic strategy and growth mode affect tissue recovery response to ocean warming and acidification at a shallow CO2 vent

Human activities primarily drive significant changes in ocean waters, causing warming and acidification. Climate change has a profound impact on marine communities leading to diverse physiological responses in various organisms, including corals. Here we examined the combined effects of increasing seawater acidification and warming on the tissue regeneration rate of three Mediterranean scleractinian coral species with distinct trophic strategies and growth modes. Specifically, the solitary zooxanthellate Balanophyllia europaea, the solitary non- zooxanthellate Leptopsammia pruvoti and the colonial non- zooxanthellate Astroides calycularis were transplanted along a natural pH gradient generated by continuous and localized CO2 emissions from a volcanic vent off Panarea Island (Mediterranean Sea, Italy). While we did observe a generalized decrease in tissue regeneration rate with increasing seawater temperature and acidification in all species, the zooxanthellate coral showed the highest declines, possibly as a result of re- allocation of available resources to processes such as reproduction and calcification at the expense of tissue maintenance. These findings contribute to growing evidence indicating that the projected combination of warming and acidifying conditions in the forthcoming decades could prove harmful to crucial aspects of shallow-water benthic ecosystems. This, in turn, may impede the ability of Mediterranean stony corals to recover from physical damage.