Extirpation of Acropora cervicornis genotypes from a coral nursery during the 2023 marine heatwave undermines conservation efforts

Global climate change has decimated historical baseline coral cover in the Caribbean, including wild Acropora cervicornis , now listed as Critically Endangered by the IUCN Red List of Species. Although still at risk to the same environmental conditions that decimated wild populations, propagating A. cervicornis genotypes with increased disease resistance and thermal tolerance could help prevent extinction. Here we document the impacts of the 2023 marine heatwave on the health and survival of nursery reared A. cervicornis corals in Little Cayman that experienced 19.4 Degree Heating Weeks (DHW). In total, 91.6% of the 415 colonies suffered complete mortality with seven out of ten genotypes being eradicated, suggesting a genetic basis for thermotolerance. This accentuates the importance of genetic diversity for survival of A. cervicornis . However, the eradication of over 90% of coral colonies also highlights the futility of putting corals back into the same environment, emphasizing the need for innovative conservation strategies that incorporate novel tools capable of enhancing resilience and ensuring restoration remains viable under future climate conditions.