Validation of Reef-Scale Thermal Stress Satellite Products for Coral Bleaching Monitoring

Abstract

Satellite monitoring of thermal stress on coral reefs has become an essential component of reef management practice around the world. A recent development by the U.S. National Oceanic and Atmospheric Administration's Coral Reef Watch (NOAA CRW) program provides daily global monitoring at 5 km resolution-at or near the scale of most coral reefs. In this paper, we introduce two new monitoring products in the CRW Decision Support System for coral reef management: Regional Virtual Stations, a regional synthesis of thermal stress conditions, and Seven-day Sea Surface Temperature (SST) Trend, describing recent changes in temperature at each location. We describe how these products provided information in support of management activities prior to, during and after the 2014 thermal stress event in the Commonwealth of the Northern Mariana Islands (CNMI). Using in situ survey data from this event, we undertake the first quantitative comparison between 5 km satellite monitoring products and coral bleaching observations. Analysis of coral community characteristics, historical temperature conditions and thermal stress revealed a strong influence of coral biodiversity in the patterns of observed bleaching. This resulted in a model based on thermal stress and generic richness that explained 97% of the variance in observed bleaching. These findings illustrate the importance of using local benthic characteristics to interpret the level of impact from thermal stress exposure. In an era of continuing climate change, accurate monitoring of thermal stress and prediction of coral bleaching are essential for stakeholders to direct resources to the most effective management actions to conserve coral reefs.

Remote Sensing of Coral Bleaching Using Temperature and Light: Progress towards an Operational Algorithm

“…Figure 6b indicates that the DHW product recorded 7.8 in 2004, which was sufficient to have caused ecologically significant bleaching (above DHW of 4) and was bordering on being classed as a severe bleaching event (above DHW of 8) [20,25]. This is out of step with the AIMS bleaching records, which indicate that the corals paled with no bleaching.…”

“…These products have been demonstrated to perform well when used to describe the onset of coral bleaching [25,26]. However, they occasionally predict bleaching for coral reefs where the phenomenon was not observed and vice versa.…”

Remote Sensing of Coral Reefs for Monitoring and Management: A Review

“…The 5 km SST is derived using full-resolution data from multiple POES and Geostationary Orbiting Environmental Satellites (GOES) instruments: an order of magnitude more input data than the heritage DSS. Qualitative analysis for the 5 km DSS has indicated strong performance in the Pacific [185] and Caribbean [M. Eakin, private communication] during 2013-2015. The first quantitative analysis for the 5 km DSS [185] confirmed the use of these products to monitor coral bleaching in the Northern Mariana Islands during 2014.…”

“…Qualitative analysis for the 5 km DSS has indicated strong performance in the Pacific [185] and Caribbean [M. Eakin, private communication] during 2013-2015. The first quantitative analysis for the 5 km DSS [185] confirmed the use of these products to monitor coral bleaching in the Northern Mariana Islands during 2014. The 5 km DSS is, at present, being used to guide reef stakeholders to undertake targeted coral surveys; the resulting dataset of observations will be used for further quantitative comparison with these monitoring products.…”

Predicting Heat Stress to Inform Reef Management: NOAA Coral Reef Watch's 4-Month Coral Bleaching Outlook

“…The third, longest, and most widespread global coral bleaching event on record started in the Commonwealth of the Northern Mariana Islands (CNMI) and Guam in June 2014 (Heron et al, 2016b;Eakin et al, 2017). It continuously affected coral reefs around the world until May 2017, when it appeared the global extent of the event had ended (Eakin et al, 2017).…”