A Simple, Fast, and Reliable Method to Predict Sargassum Washing Ashore in the Lesser Antilles

Since 2011, the Lesser Antilles have faced major events of the washing ashore of pelagic Sargassum. Windward, exposed island coasts receive tons of algae that alter the quality of coastal ecosystems and the environment. The events repeated in 2012, 2014, 2015 and 2016. A major concern for local governments is to predict arriving floating algae and assess the risk of washing ashore. Here, we present a method to use a Sargassum Watch System (SaWS), based on satellite imagery and numerically-modelled surface currents, for near-real-time tracking of floating algae in the central Atlantic. The analysis of satellite data and numerical HYCOM surface ocean currents was used to predict washing ashore events days before they occur. These online products are integrated and made available to users in Keyhole Markup Language (KML) format and uploaded in Google Earth. Tracking of Sargassum slicks, combined with distance from coast and HYCOM current vectors’ direction and speed, can provide an effective prediction tool for possible washing-ashore in specific locations. Comparisons of events between the years 2011 and 2015 show some intensification of the presence of Sargassum in the western Atlantic and a significant increase in the risk of Sargassum washing ashore on the beaches of small islands. The demonstration using simple analyses of existing near real-time online products provides a template for governmental agencies and environmental groups to use, effectively, existing resources towards coastal management