ABSTRACT:

The purpose of my PhD research is to explore variation in bleaching susceptibility within and among coral species, which is the first step in understanding the capacity of species and assemblages to withstand ongoing climate change. Dire predictions about the fate of scleractinian corals typically ignore the potential for acclimation and/ or adaptation, and generally assume that all corals, especially within species, will respond similarly to climate-related increases in ocean temperatures. My experiments have already revealed large differences in the time to bleach among similar sized colonies of two common corals (Acropora nasuta and Pocillopora damicornis) collected from within the same habitat. Further experiments are planned to compare variability in bleaching susceptibility for coral populations at different latitudes and across a range of species, and also assess whether prior exposure to moderate thermal stresses (resulting in sub-lethal bleaching) increases or decreases subsequent bleaching susceptibility. This research is expected to show that individual corals vary greatly in their responses to increasing ocean temperatures. If this phenotypic plasticity in bleaching responses is due to heritable genetic variation within local populations, then this will suggest a capacity for corals to adapt, and thereby withstand moderate increases in ocean temperatures.