Pictured left: An estuary mouth and coastal waters, part of an aquatic ecosystem

An aquatic ecosystem is an ecosystem located in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.

Marine ecosystems cover approximately 71% of the Earth's surface and contain approximately 97% of the planet's water. They generate 32% of the world's net primary production. They are distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, in the water. Approximately 85% of the dissolved materials in seawater are sodium and chlorine. Seawater has an average salinity of 35 parts per thousand (ppt) of water. Actual salinity varies among different marine ecosystems. Classes of organisms found in marine ecosystems include brown algae, dinoflagellates, corals, cephalopods, echinoderms, and sharks. Fish caught in marine ecosystems are the biggest source of commercial foods obtained from wild populations.

Freshwater ecosystems cover 0.80% of the Earth's surface and inhabit 0.009% of its total water. They generate nearly 3% of its net primary production. Freshwater ecosystems contain 41% of the world's known fish species. There are three basic types of freshwater ecosystems:

• Lentic: slow-moving water, including pools, ponds, and lakes.
• Lotic: rapidly-moving water, for example streams and rivers.
• Wetlands: areas where the soil is saturated or inundated for at least part of the time.

Wetlands are dominated by vascular plants that have adapted to saturated soil. Wetlands are the most productive natural ecosystems because of the proximity of water and soil. Due to their productivity, wetlands are often converted into dry land with dykes and drains and used for agricultural purposes. Their closeness to lakes and rivers means that they are often developed for human settlement. (Full article...)

William Skinner Cooper (August 25, 1894 – October 8, 1978) was an American ecologist.

Cooper received his B.S. in 1906 from Alma College in Michigan. In 1909, he entered graduate school at the University of Chicago, where he studied with Henry Chandler Cowles, and completed his Ph.D. in 1911. His first major publication, "The Climax Forest of Isle Royale, Lake Superior, and Its Development" appeared in 1913.

Cooper served briefly in 1914-1915 as a lecturer in plant ecology at Stanford University before beginning his long career in the botany department at the University of Minnesota, where he taught from 1915 to 1951. Among his students at Minnesota was Frank Edwin Egler and Arnold M. Schultz; the latter went on to teach "Ecosystemology" at U.C. Berkeley, and received U.C. Berkeley's "Distinguished Teaching Award" in 1992. Cooper was the president of the Ecological Society of America in 1936 and the president of the Minnesota Academy of Science in 1937. Other professional accolades included receipt of the Botanical Society of America's Merit Award in 1956 and the Eminent Ecologist Award from the Ecological Society of America in 1963. (Full article...)