Monitoring pelagic Sargassum inundation potential for coastal communities

Abstract

Pelagic Sargassum is a buoyant macroalgae that forms rafts at the ocean surface and serves as abiologically rich habitat for hundreds of diverse marine species. Since 2011, massive blooms ofSargassum have occurred in the tropical Atlantic and swept through the western tropicalAtlantic, Caribbean Sea, and Gulf of Mexico. These recurring annual events have causedsignificant disruptions to coastal communities throughout the region, negatively impactinghuman health, tourism, fishing, navigation, and nearshore ecosystems. We present here theSargassum Inundation Report (SIR), a product that uses satellite-based methodology to estimateand predict the future coastal inundation of pelagic Sargassum. Results from one year of SIRsshow strong spatiotemporal differences in the potential of coastal inundation across the Intra-American Seas, and provide a comprehensive method for assessing its geographic distributionand temporal variation. Comparisons of SIRs to opportunistically collected photographs indicatea qualitative concordance between satellite and in situ observations. This work highlights thevalue of satellite observations, basin-wide and seasonal monitoring, and emphasises the needfor sub-regional and weekly forecasting. SIRs show considerable promise as a tool that caneventually incorporate improved spatiotemporal resolution Sargassum imagery, oceancirculation, wind, and wave conditions to forecast the movement of Sargassum into coastal areas.