"Numerous species of brown algae (Class Cyclosporeae: Order Fucales: Family Fucaceae) of the genus Sargassum occur throughout the world's tropical and temperate oceans. The pelagic complex in the western North Atlantic is comprised primarily of Sargassum natans and S. jluitans. Both species are hyponeustonic and fully adapted to a pelagic existence (Parr, 1939). Known commonly as gulf-weed, sea holly, or sargassum, they are characterized by a brushy, highly branched thallus (stem) with numerous leaf-like blades and berry-like pneumatocysts (floats). These floating plants may be up to several meters in length but are typically much smaller. See Hoyt (1918), Winge (1923), Parr (1939), Taylor (1960), Prescott (1968), and Humm (1979) for detailed descriptions of the various species"--Introduction, paragraph 1.

National Marine Fisheries Service (NMFS)