Abstract
Reef-building corals possess endosymbiotic algae that provide essential energy for the host animals through photosynthesis. Therefore, the inhibition of photosynthetic activity is lethal for corals, a potential cause of "coral bleaching" phenomena that threat many coral reef ecosystems globally. Many studies have suggested that photoinhibition is involved in coral bleaching. However, the molecular mechanism remains unclear. Here we show a protective role of water flow on high-light induced photoinhibition in the coral Acropora digitifera. We conducted series of experiments for assessing the effects of water flow on photoinhibition with PAM chlorophyll a fluorometer. For hours to weeks, suppression of photoinhibition was observed in flow-treated corals. Severity of photoinhibition was reduced with increasing water flow velocity; coral bleaching occurred in the flow-limited corals. We conclude that water flow is capable of suppressing high-light induced photoinhibition in the reef building corals.
