Abstract
In recent years, coral reef ecosystems have been affected by global climate change and human factors, resulting in frequent coral bleaching events. A severe coral bleaching event occurred in the northwest of Hainan Island, South China Sea, in 2020. In this study, we used the CoralTemp sea surface temperature (SST) and Sentinel-2B imagery to detect the coral bleaching event. From 31 May to 3 October, the average SST of the study area was 31.01 °C, which is higher than the local bleaching warning threshold value of 30.33 °C. In the difference images of 26 July and 4 September, a wide range of coral bleaching was found. According to the temporal variation in single band reflectance, the development process of bleaching is consistent with the changes in coral bleaching thermal alerts. The results show that the thermal stress level is an effective parameter for early warning of large-scale coral bleaching. High-resolution difference images can be used to detect the extent of coral bleaching. The combination of the two methods can provide better support for coral protection and research.
Highlights
Academic Editors: José C.B. da Silva, Caixia Wang and Jorge M
Bands, calculates the regression coefficient using the tion of water bodies in near infrared (NIR) bands, calculates the regression coefficient usreflectance of the near infrared band andband the band to be corrected in the sample area, and ing the reflectance of the near infrared and the band to be corrected in the sample deglints on this band image
The maximum monthly mean (MMM) sea surface temperature (SST) calculated from the long-term historical SST in the study area is
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. CRW developed the CoralTemp SST dataset and products for coral bleaching thermal stress detection, such as hotspot and degree heating week (DHW), etc. They are widely used in global coral reef monitoring and management. Coral bleaching detection methods based on satellite imagery generally include change detection and benthic classification. Hedley et al described the coral bleaching events of the Great Barrier Reef in 2016–2017 using spectral reflectance changes in Sentinel-2A imagery at different times [14]. Two methods on the remote-sensing detection of coral bleaching by thermal stress warning and difference image detection were analyzed and compared
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