Aquatic Ecosystems

         In an aquatic ecosystem, that environment is water, and all the system's plants and animals live either in or on that water.
        Aquatic ecosystems are generally divided into two types --the marine ecosystem and the freshwater ecosystem. The largest water ecosystem is the marine ecosystem, covering over 70 percent of the earth's surface. Oceans, estuaries, coral reefs and coastal ecosystems are the various kinds of marine ecosystems. Marine ecosystems, the largest of all ecosystems. 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. 

Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides; in this figure it is termed the littoral zone. Other near-shore (neritic) zones can include salt marshes, coral reefs, lagoons and mangrove swamps etc. In the deep water, hydrothermal vents may occur where  chemosynthetic  sulfur bacteria  form the base of the food web.

Classes of organisms found in marine ecosystems include brown alge, corals, echinoderm, and sharks etc. Fishes caught in marine ecosystems are the biggest source of commercial foods obtained from wild populations.