Response of two temperate scleractinian corals to projected ocean warming and marine heatwaves.

The Mediterranean Sea is a hotspot of global change, particularly exposed to ocean warming and the increasing occurrence of marine heatwaves (MHWs). However, experiments based on long-term temperature data from the field are scarce. Here, we investigate the response of the zooxanthellate coral and the azooxanthellate coral to future warming and MHWs based on 8 years of data. Corals were maintained in the laboratory for five months under four temperature conditions: Warming (3.2°C above the mean from 2012 to 2020), Heatwave (temperatures of 2018 with two heatwaves), Ambient ( mean) and Cool (deeper water temperatures). Under the Warming treatment, some colonies severely bleached and colonies presented necrosis. symbiosis was impaired by temperature with a decrease in the density of endosymbiotic algae and an increase in per cent whiteness in all the treatments except for the coolest. Recovery for both species was observed through different mechanisms such as regrowth of polyps of and recovery of pigmentation for . These results suggest that and may be resilient to heat stress and can recover from physiological stresses caused by heatwaves in the laboratory.