Algae

Algae, large and diverse group of nonvascular (rootless and stemless) aquatic plants that contain chlorophyll and carry on photosynthesis, including some of the simplest organisms known. They range in size from microscopic single-celled organisms to strands of seaweed several yards long. Most species of green algae, which are found mainly in freshwater, are microscopic. Brown algae include the familiar seaweeds found on rocky shores. Red algae, found mostly in warmer seas, include several species of economic importance. Algae are important as the basis of food chains. Many of the larger algae are used in foodstuffs, in medicine, and as manure.

See also: Eutrophication; Seaweed.