The adjacent seas of Taiwan, the Philippines, the Malacca Strait, and the waters off Aceh are located within important tropical to subtropical Indo-Pacific oceanic corridors and coral reef/shelf ecosystems. These regions are jointly regulated by monsoonal circulation, regional ocean dynamics, and large-scale climate modes, making them highly sensitive to extreme marine temperature events such as marine heatwaves (MHWs) and marine cold-spells (MCSs). This study integrates multi-source satellite observations and reanalysis datasets to investigate the spatiotemporal characteristics of extreme marine temperature events, coral thermal stress, and related marine environmental changes in these regions, while further considering the influences of major climate modes. The results show that the Philippines, the Malacca Strait, and the waters off Aceh have all exhibited clear warming trends since 2010, accompanied by increases in the frequency, duration, and intensity of MHWs, indicating a marked intensification of extreme warm events in tropical marine environments. In the waters off Aceh, significant MHW events occurred in 2010, 2016, 2019, 2020, and 2024, with degree heating weeks (DHW) values exceeding 8 °C-weeks in 2010, 2016, and 2024, indicating a high risk of coral bleaching. The development of these thermal extremes was closely associated with the accumulation of positive net surface heat flux from January to May, the monsoon-driven reorganization of ocean circulation, and heat retention along sea-surface frontal zones. The Malacca Strait shows a significant SST warming trend, with the deeper northern sector more likely than the shallower southern sector to accumulate extreme heat and develop higher DHW values. At the same time, ocean color and carbonate system parameters exhibit pronounced seasonal cycles and spatial contrasts, indicating that physical warming, biological productivity, and ocean acidification pressure together form a compound ecological risk. Among the 12 coral habitats surrounding the Philippines, Lingayen Gulf, Davao Oriental, and Polillo Island were identified as the most vulnerable areas. Since 2015, thermal stress has no longer depended solely on specific climate mode backgrounds but increasingly reflects the effects of globally accumulated heat stress driven by ongoing warming. In contrast, the adjacent seas of Taiwan have experienced not only a rapid increase in MHWs but also frequent, rapidly developing MCS events in recent years over shallow continental-shelf regions such as the Taiwan Strait and the Penghu Channel, revealing a complex pattern in which warm and cold extremes coexist. Physical mechanism analysis indicates that during winter cold-spell events, northeasterly monsoon winds over the Taiwan Strait strengthen significantly, while the total current in the strait becomes steadily southward and continues to accelerate. In addition, a significant decrease in sea surface salinity is observed from the southern East China Sea to the Taiwan Bank, suggesting the transport of cold and low-salinity water masses. This study emphasizes the importance of a regional, multi-parameter, integrated oceanographic framework for understanding MHWs, MCSs, and their associated ecological vulnerability.  These findings provide a scientific basis for climate risk assessment, conservation management, and early warning of extreme events in coral reefs and shelf seas across the Indo-Pacific region.

Marine heatwaves,Coral thermal stress,Ocean–atmosphere interaction,Ecological vulnerability