Phaeophyceae

Phaeophyceae is the class of brown algae, a large group of photosynthetic, multicellular organisms within the SAR supergroup. They are the dominant seaweeds of cold, temperate, and polar waters in the Northern Hemisphere, commonly growing along rocky shorelines, with members of the order Fucales especially common intertidally. Some brown algae, such as the kelp genus Macrocystis of the order Laminariales, can grow to sixty meters and form underwater kelp forests rich in biodiversity, while Sargassum forms distinctive floating mats in the tropical Sargasso Sea; several brown algae, including kelps, are also used by humans as food.