Coral-spawn slicks: Reflectance spectra and detection using optical satellite data

[摘要] This study provides the first report of reflectance spectra of coral-spawn slicks and their detection using optical satellite data. The reflectance spectra show that coral-spawn slicks can be discriminated from other sea-surface features such as wave foam and floating Sargassum. Analysis of Planet Dove and Sentinel-2B imagery allowed successful detection of coral-spawn slicks at Ishigaki Island, Okinawa, Japan (24 degrees 31'40 '' N, 124 degrees 17'31 '' E), by using reflectance values in the green and red wavelength regions. This detection was attributable to both their high spatial resolution (3.7 m and 10 m, respectively) and high temporal resolution (1 day and 5 days, respectively), given that coral spawning occurs within a short period (up to several days), typically once a year, and that the coral-spawn slicks have narrow widths of similar to 10 m. The number of the detected coral-spawn slicks was small, possibly because of coral decline around Ishigaki Island caused by the 2016 worldwide mass coral bleaching event. High-frequency satellite observations, including those from satellite constellations, should provide a powerful tool for understanding coral-reef processes and features whose detection requires high spatial and temporal resolution.

[发布日期] 2020-12-15

[关键词] Coral mass spawning;Coral bundle;Coral-spawn slick;Satellite constellation;Planet Dove;Sentinel-2