Revealing ENSO-Linked Oceanic and Atmospheric Controls Driving Coral Bleaching: Lessons from Sri Lanka’s Fringing Reef Systems

Sri Lanka, a tropical island in the Indian Ocean, hosts a rich and highly biodiverse fringing coral reef system that has been increasingly degraded over the past few decades due to escalating anthropogenic pressures and recurrent ENSO-induced heatwaves. The physical mechanisms driving ENSO-related coral bleaching remain insufficiently understood, posing challenges to both local and global coral conservation efforts. This study aimed to address this knowledge gap by examining the influence of key physical drivers underlying coral bleaching across five reef sites in Sri Lanka during 1998, 2016, and 2024. The findings reveal that ENSO-linked sea surface temperature anomalies in the Indian Ocean, compounded by climate warming and radiative flux anomalies, intensified coral bleaching around Sri Lanka during these events. Though not fully explored, the positive feedback of delayed monsoon winds on shallow coral bleaching was evident in this study, mainly through triggering the latent heat flux anomaly. April was identified as the critical month for coral bleaching in Sri Lanka, as ENSO impacts peaked during April and extended into May. Furthermore, the study idealizes the occasional disparities of integrating global temperature data for predicting local-scale coral bleaching. These findings underscore the need for continuous in situ oceanic and atmospheric monitoring, long-term coral reef observation, and the integration of coral physiological responses into bleaching threshold assessments. Such approaches are essential not only for the Sri Lankan context but also globally, to enhance predictive capacity to safeguard these invaluable marine ecosystems from further degradation.