Too hot to handle? The impact of the 2023 marine heatwave on Florida Keys coral

March 13, 2025

Dr. Karen Neely

Too hot to handle? The impact of the 2023 marine heatwave on Florida Keys coral

The summer of 2023 brought unprecedented thermal stress to reefs in the Florida Keys, and media reports predicted widespread coral mortality. Researchers tracked the fate of over 4,200 brain and boulder corals through this event and found that, in fact, the vast majority of these massive reef-building species survived. However, at one inshore reef site, they observed substantial mortality early in the summer, likely due to corals exceeding their thermal tolerance. These localized losses revealed that boulder corals were much more resilient than brain corals, suggesting they are the most thermally tolerant species on the reef. 

Although not part of the fate-tracking program, regular monitoring on these reefs indicated that branching corals, including restoration efforts, suffered catastrophic losses, and at several inshore reefs, the octocorals that make up a large component of the benthic fauna became locally extinct. While losses of some species at certain sites were significant, the findings suggest that this particular heat wave was not as catastrophic to wild corals as initially expected.

Learn more about Dr. Neely's efforts during the 2023 bleaching event in an interview featured in an NSU press release - link below!