In-situ response to injury shows the short-term impacts of elevated temperatures on two Mediterranean corals, Cladocora caespitosa (Linnaeus, 1767) and Balanophyllia europaea (Risso, 1827)

Among the main drivers of critical changes in marine environments is global warming, largely caused by anthropogenic activities. Growing evidence suggests that climate change is rapidly and detrimentally impacting ecosystems worldwide, challenging the survival of marine organisms, including corals. We carried out in-situ experiments to assess the effect of seasonal temperature changes on short-term injury responses of immune-related enzymes (phenoloxidase, glutathione peroxidase and lysozyme) and host-associated bacterial communities in two Mediterranean endemic species: the colonial coral Cladocora caespitosa and the solitary coral Balanophyllia europaea. Our results show that both corals demonstrated strong enzymatic responses in immune parameters to injury under winter conditions. However, during the summer period, there was an alteration (significant in at least one parameter) of enzymatic activities, outlining a general pattern of enhanced effects of elevated temperatures on constitutive activities but a suppressive impact on injury responses. While winter corals showed relative stable bacterial communities, under summer conditions, several taxa of coral-associated microbiota generally associated with coral diseases shifted in abundance and composition. These changes suggest that environmental cues of increasing temperatures could affect coral health and survival, potentially hindering their ability to respond following physical disturbances under summer seawater conditions.