Abstract

With the availability of data from the Copernicus-Program, jointly developed by the EU and ESA, a new promising tool for monitoring Sargassum from Space has been made available. While the Sentinel-3 satellite sensor OLCI, swath 1270km, 300m pixel, covers the entire globe, the Sentinel-2 with 10m pixel maps the Caribbean islands every 5 days. The Maximum Chlorophyll Index from S-3 data is extremely sensitive to floating algae as proved with S-2, Landsat-8, MODIS and sea-truth campaigns. Even sparse distribution of algae and patches much less than 100m wide can be detected. For coastal sur-veillance, we used the Floating Algae Index from Sentinel-2 to detect Sargassum. Using digitized shorelines, precise map-ping of beaching algae was done regularly using multispectral images. However fixed marine vegetation need to be exclud-ed by experience. A pilot service has been set up all through 2018 based on manual interpretation. This initiative was origi-nally introduced for optional studies to students at the Lycée Polyvalent Nord Grande-Terre and demonstrated to the envi-ronment office (DEAL) in Guadeloupe. DEAL much welcomed our reports, as they had no similarly detailed information available. Data is usually available on Copernicus website 12 hours after satellite acquisition. With a reasonable quality computer and good internet-connection a trained operator can download, analyse and prepare a report within an hour. Data and software are available for free. The development of semi-automatic interpretation and reporting is envisaged to secure higher reliability. However, the timely requirement will not be much reduced. Beaching-forecasts still lack understanding of local currents and wind forcing interactions on floating algae. However just by doing such regular analysis work, valua-ble experiences also in this respect is gained.

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