Post-ENSO 2024 mass bleaching and early signs of resilience in Pachyseris speciosa dominated reefs of Raja Ampat, Indonesia.

Marine heatwaves associated with El Niño-Southern Oscillation (ENSO) events are a primary driver of mass coral bleaching, threatening reef ecosystems globally. This study documents a severe mass bleaching event in December 2024 on the reefs of Yenbuba, Raja Ampat, Southwest Papua, Indonesia, following the 2024 ENSO, and assesses subsequent changes within one year. Using standardized Underwater Visual Census methods, we found that > 70% of colonies of the dominant coral Pachyseris speciosa exhibited severe bleaching during the thermal stress peak. Follow-up surveys in November 2025 revealed substantial recovery, with < 20% of P. speciosa colonies showing bleaching signs and widespread repigmentation observed on the reef slope at ~ 20-30 m depth. This rapid recovery, documented through paired quantitative surveys and photographic evidence, highlights that the most pronounced rapid recovery among the taxa assessed occurred in this dominant coral species following acute thermal stress. However, causal mechanisms remain uncertain, and recovery was not universal across all taxa. Our findings emphasize the importance of identifying and protecting potential resilience hotspots like Raja Ampat through targeted conservation strategies in the face of climate change, while acknowledging the need for longer-term monitoring and mechanistic studies.