Water flow facilitates recovery from bleaching in the coral Stylophora pistillata

Exposing partially bleached samples of Stylophora pistillata coral colonies to controlled water-flow treatments revealed differential recovery rates that varied in accordance with flow rate. Recovery of the number of zoo-xanthellae per unit area and chlorophyll a concentrations increased rapidly in moderate-flow treatments (of 20 cm s(-1)), after an initial 3 wk of stasis. Colonies in low-flow treatments (! 3 cm s-1) remained pale for the entire 7 wk experimental period and showed only slight increases in zoo-xanthellae per unit area. In an earlier study, we showed that when corals were subjected to high temperature and high irradiance, coral bleaching occurred in low-flow but not in moderate-flow treatments; the present study shows that recovery from bleaching is facilitated by flow treatment. In combination, prevention of and rapid recovery from bleaching by enhanced water flow suggest that the mechanisms that lead to dysfunction of the algae-coral symbiosis are driven by mass-transfer-limited processes.