These ecosystems are different from freshwater ecosystem mainly because of its salty water. Marine ecosystems are among the Earth's aquatic ecosystems. They include: Oceans, Estuaries and Lagoons, Mangroves and Coral reefs, the Deep Sea and the Sea floor. These are the gigantic reservoirs of water covering approximately 71% of the Earth's surface (an area of some 361 million square kilometers). The salt concentration in an open sea is usually 3.5% (35 parts per thousand (ppt)). Dominant ions are sodium & chloride. Average temperature of Marine ecosystem is 2-3 degree centigrade, devoid of light