The Gulf of Mannar Marine National Park is a protected chain of 21 coral islands and the shallow sea around them off the coast of Tamil Nadu, forming the core of India’s first marine biosphere reserve and one of the richest coastal ecosystems in South Asia. Stretching along the coast from Rameswaram towards Thoothukudi, it protects coral reefs, seagrass meadows, mangroves and beaches that shelter thousands of marine species, including the dugong, one of the most endangered marine mammals in India.
This explainer covers the park from an ecological and conservation viewpoint: where it lies, how its islands and reefs formed, which species it protects, why seagrass and corals matter, how people depend on the sea, and what threatens it. It was last reviewed on 2 November 2026.
| Attribute | Detail |
|---|---|
| Location | Gulf of Mannar, off the Ramanathapuram and Thoothukudi districts of Tamil Nadu |
| Marine national park | Declared in the 1980s under the Wildlife (Protection) Act, 1972 |
| Biosphere reserve | Notified in 1989, India’s first marine biosphere reserve |
| Islands | 21 uninhabited coral islands in four groups, within a few kilometres of the mainland |
| Stretch of coast | Roughly 140 km from Rameswaram to Thoothukudi |
| Main habitats | Coral reefs, seagrass beds, mangroves, seaweed beds, mudflats and sandy shores |
| Flagship species | Dugong, green sea turtle, hawksbill turtle, seahorses, sea cucumbers, pearl oyster, sacred chank |
| Management | Tamil Nadu Forest Department and the Gulf of Mannar Biosphere Reserve Trust |
| Main threats | Destructive fishing, coral bleaching, pollution, invasive seaweed, overfishing and island erosion |
Key Takeaways
- The Gulf of Mannar Marine National Park protects 21 uninhabited coral islands and their surrounding reefs off Tamil Nadu.
- It lies within the Gulf of Mannar Biosphere Reserve, notified in 1989 and recognised as India’s first marine biosphere reserve.
- Coral reefs and seagrass meadows are its two key habitats, and they support fish nurseries, turtles and the dugong.
- The region is known for historic pearl fisheries and the sacred chank, so its marine life has shaped coastal culture for centuries.
- Thousands of fisher families depend on the surrounding waters, which makes balancing livelihoods and protection a central challenge.
- Main threats are bottom trawling, coral bleaching, pollution, invasive seaweed and the loss of low-lying islands to erosion and rising seas.
Where Is the Gulf of Mannar and What Is Its Geography?
The Gulf of Mannar is a shallow arm of the Indian Ocean between the southeastern tip of India and the western coast of Sri Lanka, bounded on the northeast by Rameswaram island and Adam’s Bridge, a chain of shoals. The Indian part of the marine national park lies along the Tamil Nadu coast, in the districts of Ramanathapuram and Thoothukudi.
The park consists of 21 small islands strung out in a roughly northeast to southwest line, usually within a few kilometres of the mainland. They are grouped into four clusters named after nearby places: Mandapam, Keezhakarai, Vembar and Thoothukudi. Most are low, sandy or rocky islets, often fringed with mangroves, and none has a permanent settlement.
The Gulf is relatively shallow and warm, with fairly stable temperatures through the year, and it receives freshwater and sediments from several small rivers flowing from the Indian mainland. Together these conditions favour the growth of reefs and seagrass. The sea also lies between the Bay of Bengal and the Arabian Sea, so its currents mix species from both waters, adding to its richness.
How Did the Islands and Reefs of the Gulf of Mannar Form?
The islands of the Gulf of Mannar are mostly coral islands, built over long periods by the growth of corals and the accumulation of reef rock, sand and shell on shallow platforms close to the coast. Many sit on ancient limestone and sandstone ridges that run parallel to the shore.
Fringing and patch reefs grow on these platforms, using the shallow, sunlit water. Over thousands of years, wave action broke dead coral into sand and rubble, which piled up above the water line to form low islands. Sea level changes since the last ice age also shaped this coast, repeatedly exposing and drowning shallow platforms.
Because these islands are so low, they are vulnerable. Some have been shrinking or have disappeared. Two islands, known locally as Poovarasanpatti and Vilanguchalli, are reported to have submerged below the sea in recent decades, and others have lost land, a result linked to coral mining in the past, erosion and rising sea level. Restoring reefs is therefore partly about protecting islands themselves.
What Marine Habitats Does the Park Protect?
The park protects a connected set of habitats: coral reefs, seagrass beds, seaweed beds, mangroves, mudflats and sandy beaches. These habitats are tightly linked, and animals move between them at different stages of life.
Coral reefs form the framework. Over a hundred species of hard corals have been recorded in the Gulf of Mannar, including branching Acropora and massive Porites and other reef-builders. Reefs provide shelter for fish, shellfish and crustaceans and break the force of waves along the coast. Seagrass meadows grow in the shallow sandy and muddy bottoms between reefs and the shore, and they contain about a dozen species of seagrass. Mangroves grow on sheltered islands and the lagoons, trapping sediment and offering a nursery for juvenile fish and prawns.
Seaweed beds form another important habitat. Natural seaweeds grow on rocky reef flats and are harvested by coastal communities, but they also support grazing animals and small fish. The sea floor between the islands includes sand, mud and rubble areas that support clams, worms, sea cucumbers and other bottom dwellers.
| Habitat | What it does | Typical species |
|---|---|---|
| Coral reefs | Builds the islands, shelters fish and breaks waves | Acropora and Porites corals, butterflyfish, groupers, lobsters |
| Seagrass beds | Feeds grazers, traps sediment and nurses young fish | Dugong, green turtle, seahorses, pipefish |
| Mangroves | Stabilises shores and shelters juveniles | Mangrove trees, crabs, young fish and prawns |
| Seaweed beds | Provides food and cover on rocky reef flats | Red and green algae, small fish, grazers |
| Sandy and muddy bottoms | Supports burrowers and bottom feeders | Sea cucumbers, chank, clams, sea stars |
Which Species Live in the Gulf of Mannar Marine National Park?
The park and its surrounding waters hold several thousand species of plants and animals, including more than a hundred coral species, hundreds of fish species, turtles, dolphins, whales, the dugong and a wide range of invertebrates. It is among the most biologically diverse marine areas in India.
Reef fish include butterflyfish, damselfish, parrotfish and groupers, and larger visitors such as sharks, rays and tuna also pass through. Marine mammals include bottlenose and spinner dolphins, finless porpoises and, more rarely, whales. Five species of sea turtle are reported in Indian waters, and the green turtle, hawksbill, olive ridley and others use the Gulf for feeding or nesting.
Invertebrates are especially notable. Sea cucumbers, sea fans, sponges, sea anemones, starfish, mollusks and crustaceans fill the reefs and seabed. Seahorses, which are protected under Indian law, live among seagrass and coral. Seabirds and shorebirds feed along the beaches and mudflats, and migratory birds use the islands as stopovers. Because the area is so rich, scientists regularly record new species or range extensions.
Why Is the Dugong Important to the Gulf of Mannar?
The dugong is important because it is a rare marine mammal, classified as Vulnerable globally and critically low in number in India, and the Gulf of Mannar and neighbouring Palk Bay are among its last remaining habitats in the country. Often called the sea cow, it grazes almost entirely on seagrass.
The dugong is a large, slow-moving relative of the manatee. An adult grazes on seagrass meadows, uprooting plants and leaving visible feeding trails on the sea floor. Dugongs breed slowly, with long gestation and widely spaced calves, so even a small number of deaths can harm the population. They are legally protected in India, listed in the highest schedule of the Wildlife (Protection) Act, 1972.
The main threats to the dugong are accidental entanglement in fishing nets, loss of seagrass meadows, boat strikes and pollution. In 2022, Tamil Nadu notified a Dugong Conservation Reserve in the Palk Bay, the first of its kind in India, to protect seagrass beds and reduce conflicts with fishing. Because dugongs depend on seagrass, protecting this habitat is the key to their survival.
Why Do Seagrass Meadows and Coral Reefs Matter?
Seagrass meadows and coral reefs matter because they support fisheries, protect the coast from waves, store carbon and sustain biodiversity that people rely on. Their loss would affect both wildlife and the incomes of coastal communities.
Seagrass meadows act as nurseries for juvenile fish and invertebrates, and they feed turtles and dugongs directly. Their roots bind seabed sediment and their leaves slow water movement, which clears the water and lessens erosion. Like mangroves, they are valued as blue carbon ecosystems because they capture carbon and store it in the sediment.
Coral reefs shelter a huge share of marine life in a tiny area of sea floor. They also form natural breakwaters that absorb wave energy before it reaches the shore. When reefs die, the shoreline becomes more exposed, fish populations decline and tourism or fishing income may follow. This link between healthy reefs and the safety and livelihoods of coastal people is why restoration of corals and seagrass has become a conservation priority in the Gulf.
How Do People Depend on the Gulf of Mannar?
People depend on the Gulf of Mannar for fishing, seaweed collection, and historically for pearls and chank shells, and tens of thousands of fisher families live along its coast. The sea is a main source of income, food and cultural identity for coastal communities.
The region has been known for pearl fishing for more than two thousand years, based on the pearl oyster, and records from ancient and medieval times mention trade from its coast. The sacred chank, a large marine snail whose shell is used in rituals and bangle making, is another traditional resource. Today, small-scale fishing for fish, crabs and lobsters is the mainstay, and seaweed gathering is an important source of income for many women in coastal villages.
This dependence creates a difficult balance. Fishing grounds overlap with reefs and seagrass, and protective rules may restrict access. Conservation programmes have therefore tried to provide alternative livelihoods, such as seaweed farming, artificial reef fishing grounds, crab and fish culture, and community-based management, so that people have a stake in protecting the sea.
What Threatens the Gulf of Mannar Marine National Park?
The main threats are destructive fishing methods such as bottom trawling, overfishing, coral bleaching caused by warming seas, pollution from land and ports, invasive seaweed, and the loss of low islands to erosion. These pressures reinforce each other.
Bottom trawling and the use of fine-mesh nets damage seagrass and reefs, and they catch large numbers of juvenile fish and non-target species. Overharvesting of sea cucumbers led to a steep decline in their numbers and eventually a ban on their collection in 2001. Collection of coral for lime and construction in earlier decades damaged reefs and left islands more exposed to waves.
Warming seas have caused repeated coral bleaching events in the Gulf, in which stressed corals expel their algae and can die if heat persists. Pollution from sewage, industry and port activity along the Thoothukudi coast adds to the stress. An alien red seaweed introduced for farming has spread over some reefs, smothering corals. Rising sea level, finally, threatens the low islands themselves.
How Is the Marine Park Protected and Restored?
The park is protected under the Wildlife (Protection) Act, 1972 and managed by the Tamil Nadu Forest Department and the Gulf of Mannar Biosphere Reserve Trust, which coordinates conservation, research and community programmes. Many species, including dugongs, turtles, seahorses and sea cucumbers, are legally protected.
Conservation measures include patrols to curb illegal fishing and coral mining, monitoring of reefs and seagrass, and restoration projects. Scientists have tested coral transplantation and the installation of artificial reef structures to restore damaged areas and create habitat. Community groups have also been formed to manage resources and to promote alternatives to destructive fishing.
Biosphere reserve status also allows a zoned approach, with strictly protected islands and reefs at the core and managed use in the surrounding waters. Success will depend on reducing the overall fishing pressure, controlling pollution and keeping local people involved.
Bottom Line
The Gulf of Mannar Marine National Park is the heart of India’s first marine biosphere reserve, a chain of 21 coral islands whose reefs, seagrass meadows and mangroves sustain the dugong, turtles and thousands of other species. Its future depends on controlling destructive fishing, pollution and warming seas, while giving coastal communities a share in a healthy sea.
Frequently Asked Questions
Where is the Gulf of Mannar Marine National Park?
It lies off the coast of Tamil Nadu in the Ramanathapuram and Thoothukudi districts, in the Gulf of Mannar between India and Sri Lanka. It consists of 21 islands in four groups, stretching along roughly 140 kilometres of coast from Rameswaram to Thoothukudi.
How many islands are there in the Gulf of Mannar Marine National Park?
There are 21 islands in the park, grouped into four clusters named Mandapam, Keezhakarai, Vembar and Thoothukudi. They are uninhabited coral islands lying a few kilometres from the mainland. Some low islands have shrunk or disappeared because of erosion and rising sea level.
Why is the Gulf of Mannar called India’s first marine biosphere reserve?
The Gulf of Mannar Biosphere Reserve was notified in 1989, and it was the first marine biosphere reserve in India. It protects the park, surrounding sea and coastal areas, with strictly protected core zones and managed buffer areas. It also became part of the UNESCO biosphere reserve network.
What animals live in the Gulf of Mannar?
The Gulf of Mannar supports more than a hundred coral species, hundreds of fish species, dugongs, sea turtles, dolphins, seahorses, sea cucumbers, pearl oysters and sacred chank snails. Seabirds and migratory birds visit the islands. It is one of the most biologically rich marine areas in India.
Are dugongs found in the Gulf of Mannar?
Yes, a small population of dugongs survives in the Gulf of Mannar and Palk Bay, where they feed on seagrass. They are among the rarest marine mammals in India and are fully protected by law. Tamil Nadu declared a Dugong Conservation Reserve in Palk Bay in 2022.
What are the biggest threats to the Gulf of Mannar?
The biggest threats are bottom trawling and other destructive fishing, overfishing, coral bleaching from warming seas, pollution, invasive seaweed and the erosion of low islands. Past coral mining also damaged reefs. Protecting seagrass and reefs while supporting fishing families is the main conservation challenge.
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