Rapid Hydrogen Peroxide release from the coral Stylophora pistillata during feeding and in response to chemical and physical stimuli

Corals make use of different chemical compounds during interactions with prey, predators and aggressors. Hydrogen Peroxide (H 2 O 2 ) is produced and released by a wide range of organisms as part of their defense against grazers or pathogens. In coral reefs, the large fluxes and relatively long half-life of H 2 O 2, make it a potentially important info-chemical or defense molecule. Here we describe a previously unstudied phenomenon of rapid H 2 O 2 release from the reef-building coral Stylophora pistillata during feeding on zooplankton and in response to chemical and physical stimuli. Following stimuli, both symbiotic and bleached corals were found to rapidly release H 2 O 2 to the surrounding water for a short period of time (few minutes). The H 2 O 2 release was restricted to the site of stimulus and an increase in physical stress and chemical stimuli concentration resulted in elevated H 2 O 2 release. Omission of calcium (a key regulator of exocytotic processes) from the experimental medium inhibited H 2 O 2 release. Hence we suggest that H 2 O 2 is actively released in response to stimuli, rather than leaking passively from the coral tissue. We estimate that at the site of stimulus H 2 O 2 can reach concentrations potentially high enough to deter predators or motile, potentially pathogenic, bacteria.