Marine heatwaves (MHWs) are intensifying and increasingly linked to coral bleaching, yet region-scale risk estimates remain limited for the South China Sea (SCS). Compiling four bleaching-record datasets, we found that marine heatwaves (MHWs) amplify coral bleaching across the SCS over 1982-2025, but with strong regional heterogeneity. Southern Vietnam exhibits the strongest signal with bleaching 5 times more likely and daily incidence 7 times higher during MHWs, and 27-37% of bleaching statistically associated with MHW exposure. Palawan/North Borneo and the Eastern Philippines show similar likelihood increases (1.7 times), but incidence and associated share are higher in the Eastern Philippines (3.5 times; 11–21%) than in Palawan/North Borneo (1.6 times; 6–11%). By contrast, Southern China shows no positive MHW-associated bleaching burden. Furthermore, bleaching outside MHWs clusters within 30 days after MHW. These results identify where and when MHWs most concentrate bleaching risk, supporting region-specific early warning and monitoring.
 

coral reefs,Marine heatwaves