Heat-driven functional extinction of Caribbean <i>Acropora</i> corals from Florida's Coral Reef.

Abstract

In 2023, a record-setting marine heat wave triggered the ninth mass coral bleaching event on Florida's Coral Reef (FCR). We examined spatial patterns of heat exposure along the ~560-kilometer length of FCR and the mortality of two ecologically important, critically endangered reef-building corals. Sea surface temperatures were ≥31°C for an average of 40.7 days, leading to heat exposures 2.2- to fourfold higher than all prior years on record. In the Florida Keys and Dry Tortugas, 97.8 to 100% of the <i>Acropora palmata</i> and <i>Acropora cervicornis</i> colonies died. Mortality was lower offshore southeast Florida (37.9%), reflecting cooler temperatures in this region. Since the late 1970s, multiple stressors had already reduced the ecological relevance of <i>Acropora</i> in Florida, but the 2023 heat wave marks their functional extinction from FCR.