Survivorship and growth of corals in Hawai‘i two years post-bleaching: signs of resilience

Le résumé fourni par la source

The persistence of coral reefs is contingent on the capacity of corals to survive heat stress events, which are driving the worldwide increase in the frequency and severity of coral bleaching events. We used large-area imagery to track the post-bleaching fate of 2150 coral colonies of 4 common taxa in Hawai‘i, USA (Montipora capitata, M. patula, Porites lobata, Pocillopora meandrina) at 18 sites in the Main Hawaiian Islands from the peak of a moderate bleaching event in 2019 to 2021. We examined variability in, and predictors of, survivorship across taxa post-bleaching. We also explored how bleaching impacted short-term growth and size structure. Overall, corals exhibited high survivorship post-bleaching; the highest rates of survivorship were detected for P. lobata (92.3%) and the lowest for P. meandrina (78.5%). Survivorship of all taxa was significantly predicted by colony size, with lower survivorship for smaller colonies. Bleaching extent in 2019, the severity of prior heat stress exposure, and depth were negatively correlated with survivorship for some taxa. For colonies that survived to 2021, species-level growth did not significantly differ between colonies that bleached in 2019 versus those that did not bleach. Size structure at the taxon level changed significantly between years, exhibiting a shift towards larger colonies for all taxa except M. patula. Investigating the fate of corals, including sub-lethal effects following bleaching events, is critical for identifying resilient populations, predicting effects of future heatwave events, and guiding management and intervention strategies.

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