Spatiotemporal patterns and cumulative wildfire impact on Coral reefs in the Indo-Pacific Convergence Zone

The Indo-Pacific Convergence Zone, a hotspot for coral reefs, is located within regions prone to wildfires, yet the impact of wildfire aerosols on reef-adjacent seawaters remains unclear. Using satellite and in situ observations from 2003 to 2023, this study identifies a dual-core wildfire pattern across the Indochina Peninsula and the Malay Archipelago. Monsoon winds drive the long-range transport of wildfire aerosols, dispersing them into adjacent marine areas. A cumulative wildfire impact (CWI) index is introduced as an integrated exposure metric linking wildfire activity with aerosol transport. CWI reveals marked spatial heterogeneity, with the highest impacts in the mid-northern South China Sea and lowest values in Wallacea and New Guinea-Solomon, and seasonal peaks associated with alternating northern and southern fire activity. During wildfire seasons, rainwater inorganic nitrogen correlates positively with fire intensity, and chlorophyll-a peaks occasionally follow black carbon aerosol maxima, suggesting wildfire nutrients may enhance phytoplankton growth. The findings reveal spatiotemporal variability in wildfire exposure across coral reef regions within this biodiversity hotspot and suggest potential risk to corals adapted to oligotrophic waters.