2023: The first mass coral bleaching event in the Veracruz Reef System National Park, southwestern Gulf of Mexico

The 2023 Fourth Global Bleaching Event impacted coral reef ecosystems worldwide. At the Veracruz Reef System National Park (VRSNP), the mean monthly sea surface temperature in August reached 30.3 ºC, and the Degree Heating Weeks values were 15 ºC-weeks. Mass coral bleaching was seen soon after in early September. The aim of this study was to quantify the bleaching prevalence of the hermatypic coral community at the onset of the first mass coral bleaching event in the VRSNP. Bleaching prevalence was determined through the visual analysis of videotransects of the reef bottom at the Anegada de Adentro, Blanquilla, and Isla Verde reefs, at different depths. The bleaching prevalence of the coral community ranged from 31.3% at 12 m in the Anegada de Adentro reef to 73.7% at 12 m in Isla Verde reef, with an overall prevalence of 55.3% for the VRSNP. Bleaching affected 24 coral species. Those with the higher prevalences, like Siderastrea siderea (73.2%), Acropora cervicornis (66.5%), Orbicella faveolata (62.7%), and Montastraea cavernosa (62.5%), are also the dominant species in the VRSNP. Considering the available SST data gathered by the Coral Reef Watch program for the Veracruz virtual station, VRSNP’s corals bleached when the sea surface temperature reached 30.3 ºC, that is 0.5 ºC above the calculated bleaching threshold temperature (29.8 ºC).