Species-specific control of external superoxide levels by the coral holobiont during a natural bleaching event

The reactive oxygen species (ROS) superoxide (O2?-) is both beneficial and detrimental to life. In corals, superoxide has been implicated in bleaching, or the loss of their symbiotic algae, as well as defense against pathogens. However, superoxide dynamics within corals remain unclear due to a lack of direct in situ observations. By conducting the first field measurements of superoxide produced by corals during a bleaching event, we show substantial species-specific variation in external superoxide levels, which reflect the balance of production and degradation processes within Porites lobata, Porites compressa, Pocillopora damicornis, Fungia scutaria, and Montipora capitata coral species. Furthermore, the composition of coral-associated bacterial communities for each species and health state was analyzed to understand the role that prokaryotes may play in extracellualr superoxide production. Overall, these results suggest interspecies differences in the production and physiological function of superoxide in the coral holobiont