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NOAA Coral Reef Watch Satellite Bleaching Alert System


Current list of available reef sites

The NOAA Coral Reef Watch (CRW) Satellite Bleaching Alert (SBA) system is an automated e-mail system designed to alert subscribers to thermal stress conducive to coral bleaching at select locations around the globe. The system automatically delivers up-to-date information on changes in the Bleaching Alert status of local coral reef environments as detected by CRW's 5-km global satellite monitoring products. The SBA is a convenient data delivery system that allows critical information about coral bleaching thermal stress to reach a user's e-mail account immediately, without the user having to manually check the CRW website for updated information. The first SBA was launched in July 2005 as a companion product for the original 24 operational Virtual Stations. These original Virtual Stations were based on CRW's 50-km heritage thermal stress products and were expanded to 227 stations in 2013. With the release of CRW's 5-km product suite, a new set of Regional Virtual Stations were developed to take advantage of the higher spatial and temporal resolution of the data. In October 2016, the SBA was upgraded to provide 5-km satellite observational data across 212 Regional Virtual Stations. For more information regarding the changes, please see the Regional Virtual Station description page .

Once subscribed, an automated e-mail is sent when the level of coral bleaching thermal stress changes (see table below) at the Regional Virtual Stations to which the user subscribes. A sample html version of the SBA message can be viewed here and the alternate, text version here. The messages are designed to incorporate information found on the Coral Bleaching Virtual Stations page including links to the time series graphs and regional images and a history of previous bleaching alerts issued. The bleaching thermal stress levels are defined in the table below based on the current values on the NOAA CRW Coral Bleaching HotSpot and Degree Heating Weeks (DHW) products

Stress Level
    Potential Bleaching Intensity
No Stress
Bleaching Watch
Bleaching Warning
Bleaching Alert Level 1
Bleaching Alert Level 2
HotSpot <= 0
0 < HotSpot < 1
1 <= HotSpot and 0 < DHW < 4
1 <= HotSpot and 4 <= DHW < 8
1 <= HotSpot and 8 <= DHW
No Bleaching
Possible Bleaching
Bleaching Likely
Mortality Likely

To receive automated e-mail alerts for any of the 212 Regional Virtual Stations, follow the link "Subscribe to Satellite Bleaching Alerts" at the top of this page. Once a subscription is added to the e-mail alert system, a user can view and alter selection(s) or unsubscribe from the e-mail list through the same subscription portal. If at any time you would like to unsubscribe from the automated e-mail alert service, please visit the unsubscription page.

Detailed Description of 5-km Regional Virtual Station Data
CRW Daily 5-km Product Suite

Reports of coral bleaching (including observations of no bleaching) are greatly appreciated. Bleaching observations can be reported to your regional network or to .

Should you have any questions or feedback on the Satellite Bleaching Alert (SBA) system, please e-mail

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