Sargassum is a genus of brown macroalgae (seaweed) in the order Fucales of the class Phaeophyceae. This brown macroalgae is spread predominantly in tropical and subtropical areas. It comes from the Sargasso Sea, which was named because it hosts large amounts of Sargassum. Sargassum can extend for kilometers across the ocean surface, forming golden brown drifting mats that move with the currents and wind; in recent years, Sargassum has been known for arriving in large quantities throughout the Caribbean region. More recently, scientists have found using satellite data that a new hotspot has been forming from western Africa and extends into the Caribbean Sea, called the Great Atlantic Sargassum Belt (GASB).