The bleached corals maps obtained using the PIFs and DII approaches had an overall accuracy of 88.9 and 57.1%, respectively. The former performed better than the latter in terms of classification. The change analysis was conducted using two methods: one radiometric normalization with pseudo invariant features (PIFs) and the other with multi-temporal depth invariant indices (DII). With rapid signal attenuation due to the water absorption effect, the applicable water depth for bleaching detection was recommended to be less than 10 m. However, the detection capability of Sentinel-2 is still limited by the water depth. Band 2 of Sentinel-2 is superior to its other bands for the overall consideration of signal attenuation and spatial resolution. The spectral and image simulations based on the semianalytical (SA) model and the sensor spectral response function, respectively, confirmed that coral bleaching cannot be detected only using one image, and the change analysis was proposed for detection because there will be a featured change signal for bleached corals. In this study, Sentinel-2 imagery was investigated for bleaching detection through simulations and a case study over the Lizard Island, Australia. It has a 5-day revisit time, spatial resolution of 10 m, free data, etc. Sentinel-2 mission has been shown to have promising applications in coral reef remote sensing because of its superior properties. 3School for the Environment, University of Massachusetts Boston, Boston, MA, United States.2College of Information Science and Engineering, Ocean University of China, Qingdao, China.1National Marine Environmental Monitoring Center, Dalian, China.Jingping Xu 1, Jianhua Zhao 1*, Fei Wang 1,2, Yanlong Chen 1 and Zhongping Lee 3
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