Repeated bleaching events may result in high tolerance and notable gametogenesis in stony corals: Oculina patagonica as a model

Abstract

Coral bleaching events (BEs) are occurring in coral reefs worldwide and are expected to become annual, triggered by seasonal changes in water temperature. The stony coral Oculina patag- onica experiences repeated seasonal BEs along the Israeli Mediterranean coast. It thus constitutes a good model for assessing the potential effects of expected repeated BEs on coral physiology. Previous studies have shown that the overlap between bleaching and reproduction seasons in O. patagonica impedes gametogenesis. In the present study, we assessed the effect of bleaching on gametogenesis of populations commonly undergoing repeated seasonal BEs, and compared it with the effect of first and second summer BEs on gametogenesis of a population that has not experienced a summer BE in recent years. Interestingly, we found no differences between bleached and non-bleached colonies in most of the reproductive parameters tested in populations undergoing repeated seasonal BEs. We did find, however, that a population that experienced a summer BE for the first time presented signifi- cantly lower reproductive parameters in bleached colonies when compared to non-bleached colonies. Furthermore, in the following year, such bleached colonies showed an improvement in reproductive performance when compared to the previous year. The remarkable differences in gametogenesis between colonies experiencing first summer BE and those experiencing repeated seasonal BEs may be the result of improved utilization of alternative energy sources. This study pro- vides the first evidence for notable gametogenesis in corals undergoing repeated bleaching, and sug- gests that adjustment processes may increase tolerance levels and may play a role in the ability of corals to overcome the expected repeated BEs.