Mitigation of coral bleaching by antioxidants

Coral bleaching, loss of symbiotic dinoflagellate algae from the coral holobiont, is a complex phenomenon that can result in coral death and reef degradation. Reactive oxygen species (ROS) have been suggested as a possible mechanism underlying this event. To determine if antioxidants can be used to reduce ROS production and coral bleaching, we tested the effects of thermal stress in Aiptasia pallida a model system for coral bleaching studies, and the scleractinian coral, Porites astreoides. We analyzed host ROS levels, symbiont dark-adapted quantum yield of photosystem II, and symbiont loss in the presence or absence of antioxidants. We found that a single dose of the antioxidant catechin, significantly reduced ROS levels in the hosts, mitigated the degradation of the symbionts quantum yield and reduced the loss of symbionts from thermally stressed P. astreoides but not from A. pallida. Taken together, these results support a key role of ROS and that antioxidants can prevent symbiont degradation and loss during thermally-induced bleaching in P. astreoides.