Our friends at Allen Coral Atlas have contributed a fascinating guest blog this week announcing that scientists using the Allen Coral Atlas have the ability to see predictions of marine heating areas, and simultaneously assess the location, extent and severity of coral bleaching events. An amazing step forward in our ability to monitor threats to our precious coral reef ecosystems.

After years of research and development on our methodology, the Allen Coral Atlas team is thrilled to release a new product feature on our website: monitoring of coral reef brightening. To start, we are offering this capability for only the Hawaiian Archipelago, to depict the bleaching that occurred in August through November of 2019.

“So, how was this developed?”

Scientists from our team at Arizona State University’s Center for Global Discovery and Conservation Science (GDCS) established and operate an extensive field-based network of sites for coral reef composition and spectral color, known technically as spectroscopy, along the coast of Hawaiʻi Island. The spectral data were collected by divers deployed aboard GDCS vessels across a wide range of coral reef conditions, from shallow to deep reef, and from intact, healthy to degraded, unhealthy reef. This provided the range of conditions used in developing baselines of coral condition and spectral color.
Bleached coral in Hawaii. Credit: The Ocean Agency / Coral Reef Image Bank
In the 2019 marine heatwave that engulfed the Hawaiian Islands, the GDCS was prepared with the baseline sites and utilized these sites to monitor coral bleaching and spectral color.  This information was subsequently used to calibrate a new satellite-based index of coral reef color change, referred to as “whitening”.  Algorithms developed by the GDCS team automatically compare satellite images to hunt for differences between them over timescales of days to weeks to months and even years. To detect coral bleaching, the algorithms find regions where pixels appear unusually light compared to baseline images. The system then generates dynamic heatmaps of where coral brightening might be occurring based on differences between pixel brightness. “This is years in the making and personally satisfying that Hawaii is the proof-of-concept site. Our team was able to work coral by coral, reef by reef, day in and day out to make this happen,” said Greg Asner, Director of Global Discovery and conversation Science at Arizona State University and an Allen Coral Atlas partner. “This functionality is foundational to understanding rates of reef change as well as providing geospatial information on reef resilience and candidate sites for reef restoration.” Marine heatwaves are tracked using NOAA’s Coral Reef Watch sea surface temperature data to identify areas that are undergoing episodic ocean warming events. When a marine heatwave occurs, it triggers the Atlas monitoring system to begin this pixel brightening assessment. In the coming months, we will be bringing this process into real-time on a weekly basis, based on Coral Reef Watch’s more severe Bleaching Alert levels. When fully up and running, the monitoring system will globally reveal the location, extent, and severity of potential coral reef bleaching. This information is foundational to understanding rates of reef change as well as providing geospatial information on reef resilience and candidate sites for reef restoration.
Brightening hotspots, indicated by the blue markings on the map, for the week of October 21, 2019 on Kauai Island. These hotspots indicate likely coral bleaching in that time period.

If you are excited about this new capability, we’d love to hear from you! Let us know at engagement@allencoralatlas.org how you plan to use the tool in your work. You can find more information about our methods for creating it on the Monitoring tab of our Methods page.

You can also read more about the brightening monitoring system in the Q&A Feature with Greg Asner of Arizona State University.