Standardised protocols enable efficient assessment of coral bleaching severity across tropical reefs

Once thriving ecosystems, coral reefs are now undergoing widespread decline as climate change intensifies marine heatwaves. Effective monitoring of these events is critical at global and regional scales. Standardised, repeatable protocols are essential to assess impacts and guide timely management responses. The fourth global coral bleaching event, which began in April 2023, affected roughly 84% of the world's coral reefs, causing extensive stress and mortality. In this study, two bleaching severity assessment protocols were applied to coral reefs of the Maldives (Indian Ocean) to evaluate their effectiveness in quantifying bleaching severity during global events. The simple protocol, which identifies corals by growth form, proved efficient for rapid, large-scale surveys while capturing key patterns in benthic community structure. The complex protocol, which records corals to the genus level, required greater taxonomic expertise and effort but yielded valuable insights into genus-specific resistance and sensitivity. Our findings indicate that scaling the simple protocol to regional levels, complemented by sentinel sites implementing the complex protocol, represents an effective and replicable monitoring strategy for tropical regions. Together, these approaches offer a robust, standardised toolset for the rapid detection, evaluation, and management of coral bleaching events worldwide.