Sargassum is a genus of large brown seaweed. Smaller fishes, such as filefishes and triggerfishes, reside in and among brown Sargassum. [ Related: A stinky, 5,000-mile-long wad of seaweed is about to gunk up Florida’s beaches. ] The annual bloom now stretches over 5,500 miles of ocean between Africa and the Caribbean and weighs an estimated 31 million tons. The CariCOOS Sargassum map shows that the bulk of the bloom is currently east of Puerto Rico, but it has already been spotted along Florida’s Atlantic coast.