Gulf of Mannar Biosphere Reserve (GoMBR), extends between Toothukudi and Ramanathapuram districts. It is located in the southeastern coastline of India, and is a unique marine environment rich in biodiversity. This is the first Marine Biosphere Reserve in South & South -East Asia. GoMBR is situated between Longitudes 78o08’E to 79o30’E and along Latitudes from 8o35’N to 9o25’N, with a total area of 52671.88 hectares, running along the mainland coast for about 170 nautical miles encompassing a chain of 21 islands adjoining coral reefs off the coasts forming the core zone, i.e., the Marine National Park (MNP). The surrounding seascape of the National Park and a 10 km strip of the coastal landscape together make up the total area. GoMBR is influenced by both SW and NE monsoons and hence, physical, chemical, and biological characteristics are unique. The GoMBR is part of the southward extension of the Bay of Bengal, meeting the Indian Ocean, and straddling India and Sri Lanka. The GoMBR came into existence on 18th February 1989, by a joint declaration of the Government of India and the Government of Tamil Nadu. The same has been recognized by the Man and Biosphere (MAB) Programme of UNESCO. Nestled within the GoMBR, is the Gulf of Mannar Marine National Park that surrounds 21 islands and was set up by Forest & Fisheries departments, on 10th September 1986. Fishing is the predominant livelihood here. GoMBR is one of the most biologically diverse regions in India, comprising 117 species of corals, >450 species of fishes, 4 species of sea turtles, 38 species of crabs, 2 species of lobsters, 12 species of sea grasses, 147 species of marine algae, 160 species of birds, 641 species of crustaceans, 108 species of sponges, 731 species of molluscs, 99 species of echinoderms, 4 species of sea horses, 12 species of sea snakes, besides 11 species of mangroves. The Reserve is also home to several globally important and highly threatened species like the Dugong, whale shark, sea horses, Balanoglossus, green sea turtle, Hawksbill turtle, dolphins, sacred chanks etc. The influence of oceanic water mass appears to be conspicuous in the Gulf. The strong currents from the north from November to March flow southward; the direction of the current reverses between April to October flowing from the South towards the North bringing the Indian Ocean waters into the Gulf.

A wetland should be considered internationally important if it contains a representative, rare, or unique example of a natural or near-natural wetland type found within the appropriate biogeographic region.

A wetland should be considered internationally important if it supports vulnerable, endangered, or critically endangered species or threatened ecological communities.

A wetland should be considered internationally important if it supports populations of plant and/or animal species important for maintaining the biological diversity of a particular biogeographic region.

A wetland should be considered internationally important if it supports plant and/or animal species at a critical stage in their life cycles, or provides refuge during adverse conditions.

A wetland should be considered internationally important if it regularly supports 20,000 or more waterbirds.

A wetland should be considered internationally important if it regularly supports 1% of the individuals in a population of one species or subspecies of waterbird.

A wetland should be considered internationally important if it supports a significant proportion of indigenous fish subspecies, species or families, life-history stages, species interactions and/or populations that are representative of wetland benefits and/or values and thereby contributes to global biological diversity.

A wetland should be considered internationally important if it is an important source of food for fishes, spawning ground, nursery and/or migration path on which fish stocks, either within the wetland or elsewhere, depend.

A wetland should be considered internationally important if it regularly supports 1% of the individuals in a population of one species or subspecies of wetland-dependent nonavian animal species.