Pelagic Sargassum Influx

Pelagic Sargassum influx is the mass arrival of free-floating Sargassum seaweed on Caribbean, Gulf of Mexico, and West African coasts, originating from the Great Atlantic Sargassum Belt that has recurred since 2011. Two holopelagic species, Sargassum natans and S. fluitans, never attach to the seabed and reproduce by fragmentation at the surface. Driven by nutrient inputs and altered ocean circulation, the belt has reached tens of millions of tonnes of biomass. Onshore, decaying mats deplete oxygen, release hydrogen sulfide, smother seagrass and turtle nesting beaches, and disrupt fisheries and tourism. At sea the rafts provide open-ocean habitat distinct from the Sargasso Sea population.