Indian Ocean Coral Bleaching

The 2024 WIO Coral Bleaching Summary

Sequential maps illustrating sea surface temperature (SST) anomalies (top row) and Degree Heating Weeks (DHW) (bottom row) in the Western Indian Ocean region.

The 2024 coral bleaching season in the Western Indian Ocean (WIO) region was severe, driven by El Niño and positive Indian Ocean Dipole (IOD) phases that developed in late 2023, and record temperatures globally that started in May 2023. Together, these climatic conditions led to elevated sea surface temperatures, resulting in widespread coral bleaching and mortality across the region.

73% of the submitted field observations indicated moderate to severe bleaching. 43.3% of these cases were categorized as Medium bleaching severity, while 30.9% were classified as
High severity. In terms of coral mortality, most observations were within the Low (34.3%) and Medium (29.1%) categories. However, there were notable instances of high mortality, with
9.9% of observed reefs reporting severe impacts, though with potential for high-mortality observations to be confirmed after this report is produced.

The report embedded right confirms substantial thermal stress affected coral reefs throughout the WIO in early 2024, as part of the fourth global coral bleaching event announced on 15 April 2024. It includes detailed analyses of the regional data, highlighting the ongoing threat to coral health, and it also offers recommendations for future actions to mitigate the impacts of coral bleaching.

For materials and guidance on responding to coral bleaching and mortality, watch the following video or download the following guide. Bleaching alerts from 2009 to date are available further down the page. 

Indian Ocean Bleaching observations Dashboard 2016-2024 click to open the dashboard 

Report Coral Bleaching

Submit basic observations on coral bleaching through this embedded window, in the google-form below. All data will be submitted to the global bleaching form supported by the NOAA Coral Reef Watch programme, and made accessible on a WIO regional database under development.

HISTORICAL BLEACHING – 2009 TO PRESENT

All past bleaching alerts, from 2009 to the current year, are in the window below. Click on the relevant year, or scroll left/right within each year for additional alerts. Alerts are published between January and May each year, with fewer alerts when bleaching risk is low.