Tropical reefs are under rapid decline owing to a combination of impacts, such as pollution, overfishing and climate change. Coral loss has been overlooked in the southwestern Atlantic turbid-zone reefs, prompting a climate change refugia hypothesis that was largely based on the region's relatively low bleaching levels and stable total coral cover. Here, using a novel functional classification, we examine coral reef cover dynamics in Abrolhos, the southwestern Atlantic’s largest reef complex. Monitoring was carried out over 18 years (2006–2023) and across three heatwaves. Results show insidious shifts in coral assemblages, including the collapse of branching corals and the replacement of previously dominant massive endemic forms by fast-growing, small and typically brooding species. Unexpectedly, coral decline occurred regardless of protection levels and herbivorous fish biomass. Macroalgae declined alongside corals, albeit with higher spatial heterogeneity. These trends signal a loss of structural complexity and ecological functions, highlighting the need for robust sampling design for long-term monitoring, improved environmental licensing to reduce pollution and sedimentation near coral reefs, and effective climate policy to address greenhouse gas emissions.
Carlos-Júnior et al. (Thu,) studied this question.