SARGASSUM

also called Gulfweed, Rockweed, or Sea Holly, genus of brown algae (150 species) adapted for a free-floating tropical environment even though many species grow attached to rocks along the coast. The Sargasso Sea, a free-floating mass of seaweed, predominately S. natans, occurs in the Atlantic Ocean. Sargassum is also known as sea holly because of its highly branched thallus with hollow, berrylike floats (pneumatocysts) and many leaflike sawtooth-edged blades. It is used as fertilizer in New Zealand and as a component of soups and soy sauce in Japan. Most species reproduce sexually; an exception is S. natans, which reproduces only by fragmentation.