Economic Importance

Algae have real commercial and ecological value beyond their role as primary producers. Several genera (Chlorella, Laminaria, Sargassum, Ulva, Enteromorpha) are eaten directly as food. Red algae such as Gracilaria, Gelidiella and Gigartina yield agar-agar, used as the solid base for microbiology culture media and in food packing, cosmetics, textiles and paper; Chondrus crispus yields carrageenan, used in toothpaste, paint and as a blood coagulant; and brown algae such as Laminaria and Ascophyllum yield alginate, used in ice cream, paints and flame-proof fabrics. Several brown algae (Laminaria, Sargassum, Ascophyllum, Fucus) are used as animal fodder. Diatoms' silica-rich (siliceous) cell walls, once fossilised, form diatomaceous earth, used in water filters, insulation and as a reinforcing agent in concrete and rubber. Lithophyllum, Chara and Fucus are used as fertiliser, Chlorella yields the antibiotic chlorellin, and Chlorella, Scenedesmus and Chlamydomonas are used in sewage treatment and as pollution indicators. On the harmful side, Cephaleuros virescens causes red rust disease of coffee. …