Feeding activity by the blenny Exallias brevis causes multifocal bleaching in corals: Reply to Carlson (2012)

Abstract

We previously reported the sudden emergence of a disease-like syndrome in which numerous circular white spots were observed in Millepora dichotoma colonies in the Gulf of Aqaba (Zvuloni et al. 2011; Mar Ecol Prog Ser 441:25−32) and termed this phenomenon Multifocal Bleaching (MFB). Carlson (2012; Mar Ecol Prog Ser 463:297−299), based on his observations from Hawaiian coral reefs, suggests that the MFB is caused through foraging by the blenny Exallias brevis. Carlson's suggestion led us to perform new field and laboratory studies to confirm or discount this possibility. We were unable to document biting of the hydrocorals by E. brevis in the field, but our aquarium experiment demonstrated that the white spots are indeed a direct result of the blenny's biting. In addition, we found a strong linkage between the presence of E. brevis and the presence of MFB in M. dichotoma colonies. We accept Carlson's suggestion, which leads to the following questions: (1) Is the sudden emergence of MFB in the Red Sea caused by a sudden surge in the population of E. brevis? (2) Has a change in environmental conditions prompted E. brevis to suddenly begin feeding on M. dichotoma? (3) What will be the long-term impact of E. brevis on populations of M. dichotoma, an important component of shallow reefs in the Red Sea?