Susceptibility of coral assemblages to successive bleaching events at Moorea, French Polynesia

In 2002, bleaching was reported throughout many Indo-Pacific coral-reef regions, including French Polynesia. Bleaching occurred again in French Polynesia in 2003, providing an opportunity to compare the effects of successive bleaching events on coral susceptibility. During 2002 and 2003, underwater video surveys were completed in stations at four depths (lagoon: 0-2, 2-4 m; outer reef slope: 6-8, 12-14 m) at two locations on the northern and northwestern coast of Moorea (Society Archipelago) to compare the cover of healthy-appearing, the cover of partially bleached and the cover of fully bleached coral. Bleaching patterns were genus specific and differences in susceptibility among major genera were generally consistent between 2002 and 2003, with Acropora showing the greatest susceptibility. Some genera exhibited substantial spatial variability in bleaching susceptibility between years (e.g. Pocillopora, Montipora); however, this variability was significant only for fully bleached and partially bleached Acropora. Multivariate analyses showed that spatial patterns in the proportion of healthy-appearing coral were similar over time within the assemblages, whereas the cover of partially bleached and the cover of fully bleached coral were more variable among depths and locations. This variability has important implications for assessing changes to coral community structure over time and for estimating coral-reef resistance and resilience to future bleaching disturbance.