Elevated temperatures reduce the resilience of the Red Sea branching coral stylophora pistillata to copper pollution.

Copper (Cu) is a common marine pollutant of coastal environments and can cause severe impacts on coral organisms. To date, only a few studies assessed the effects of Cu contamination in combination with elevated seawater temperatures on corals. Furthermore, experiments focusing on coral recovery during a depuration phase, and under thermal stress, are lacking. The present study investigated the physiological response of the common and thermally tolerant scleractinian coral Stylophora pistillata from the northern Red Sea to Cu contamination (2.5, 5 or 10 µg L - 1) in combination with thermal stress (5 °C above local ambient temperatures (26 °C)) for 23 days, and assessed the impact of elevated temperatures on its ability to recover from such pollution during a one-week depuration period. Variation in coral photo-physiological biomarkers including antioxidant defense capacity, were dose, time and temperature-dependent, and revealed additive effects of elevated temperatures. Successful recovery was achieved in ambient temperature only and was mediated by antioxidant defenses. Elevation of temperature altered the recovery dynamics during depuration, causing reduced Cu bioaccumulation and photosynthetic yield. The present study provides novel information on the effects of elevated temperature on the resilience (resistance and recovery processes) of a scleractinian coral exposed to a common marine pollutant. Our findings suggest that ocean warming may alter the resilience strategies of corals when exposed to local pollution, an impact that might have long-term consequences on the chances of survival of reefs in increasingly populated and warming coastal environments.