Working with Nature to Identify Coral Reefs with Increased Environmental Tolerance

Understanding what drives tolerance among coral species is key to deriving focused and effective management plans for the future. Corals have survived for millions of years and have witnessed great changes in the earth?s climate. This study compares coral species across growth environments looking at architectural differences within the skeletal structure and discusses how this may impact upon their tolerance to stress events. Results identify that variation occurs in the density of coral skeleton, density of aragonite and porosity of the skeleton. Symbiont population densities were found to be variable among coral species, but no significant differences were found across light environments. This study suggests that the micro-density of aragonite, laid down to form the coral skeleton, can vary from the previously assumed density of pure aragonite (2.94g cm-3). Massive corals were found to have greater variability within these values and to be significantly lower that aragonite deposited in the skeletons of branching corals. These differences in skeletal architecture may hold the key in discovering the fundamental variables driving coral tolerance differences. Coral skeleton density may alter the relationship at the skeletal-tissue interface, therefore influence bleaching severity. The ability to identify susceptibility of corals to stress via proxies such as skeletal architecture will enable direction of management to areas most at need and those most likely to become refugia in the future.