Gulf of Mannar

Topic: India and her Neighbours · NCERT: Class 11, Ch 1 "India - Location"; Class 11, Ch 5 "Natural Vegetation"

Meaning

The Gulf of Mannar is a shallow inlet of the sea that lies south of Adam's Bridge, between the southeast coast of Tamil Nadu and the northwest coast of Sri Lanka. It is rich in coral reefs, seagrass and dugongs.

It matters for three reasons:

• It was India's first marine biosphere reserve (1989) and became a Ramsar site in 2022.
• It is one of the two water bodies that separate India from Sri Lanka. The other is the Palk Strait.
• It is at the centre of debates over the Sethusamudram shipping channel and the India–Sri Lanka maritime boundary.

Explanation

Position: a gulf, not a strait or a bay

• A gulf is a large part of the sea that cuts into the land, with land partly closing it in.
• Order of the waters from north to south:

• Bay of Bengal → Palk Strait → Palk Bay → Adam's Bridge → Gulf of Mannar.

• Adam's Bridge (Rama Setu) is a chain of limestone shoals (shallow sandbanks and rocks just under the sea surface), about 48 km long.

• It runs from Pamban (Rameswaram) Island in India to Mannar Island off the northwest coast of Sri Lanka [7].

• It works like a wall under the water. Palk Bay lies to its north and the Gulf of Mannar lies to its south.

• Many of the shoals are so shallow that ships cannot pass through. Ships coming from the Gulf of Mannar side therefore have to sail all the way round Sri Lanka.

How the living system works: coral, seagrass and dugong

• Shallow, warm, clear water lets sunlight reach the sea floor.
• Coral reefs grow well in these conditions.

• Seagrass (flowering plants that grow under the sea) covers large parts of the floor.

• Reef types around the islands:

• Fringing reefs: reefs that grow along the shore.
• Patch reefs: small, separate reefs.

• Together they are called an "underwater tropical rainforest" [4].

• Food chain link (cause → process → result):

• Cause: the seagrass beds give a steady supply of food.
• Process: the dugong (Dugong dugon, the "sea cow") is an endangered mammal that eats only plants, and it grazes on this seagrass [4].

• Result: the Gulf of Mannar is the last important refuge for the dugong off the Indian coast [4]. A refuge is a safe place where an animal can still survive.

• About 3,600 species of plants and animals live here [4].

The Biosphere Reserve: parts and timeline

• A biosphere reserve is a large protected area.
• Its core is kept strictly for nature.

• The people living around it use the land and sea in a sustainable way, which means they take resources without using them up.

• Timeline:

• 1986: Tamil Nadu declared the area a Marine National Park [4].
• 1989: the Government of India declared it India's first marine biosphere reserve. It is also the first marine biosphere reserve in South and South-East Asia [4].
• It is part of UNESCO's Man and the Biosphere (MAB) network [3].

• 2022: it was listed as a Ramsar site (a wetland of international importance) [5].

• Core zone: the 21 islands

• The Marine National Park is a chain of 21 islands with their coral reefs.
• The islands lie off the Ramanathapuram and Thoothukudi (Tuticorin) districts of Tamil Nadu [4].
• They form three groups of seven islands each: Mandapam, Keelakarai and Tuticorin [4].

Boundary and shipping pressures

• Maritime boundary:
• The 1974 agreement fixed the boundary in the historic waters of the Palk Strait [2]. It did not cover the Gulf of Mannar.
• The agreement of 23 March 1976 fixed the boundary in the Gulf of Mannar and the Bay of Bengal [2].
• A Supplementary Agreement of 22 November 1976 extended the Gulf of Mannar boundary [2].

• NCERT notes that the 1976 agreement limited Indian fishing in Sri Lankan waters.

• Sethusamudram Ship Channel Project:

• Aim: dredge (dig out) a channel through Palk Bay, Palk Strait and Adam's Bridge, so ships would not need to go round Sri Lanka. The Government of India approved it in 2005 [7].
• Halt: on 14 September 2007, the Supreme Court suspended dredging at Adam's Bridge [6]. All dredging in Palk Bay and Palk Strait stopped in July 2009 [6].
• Progress: only 9.52 million cubic metres had been dredged. This is 19.81% of the planned 48.05 million cubic metres [6].
• Objections: the religious importance of Rama Setu, possible loss of thorium deposits, and fear of higher tsunami risk [7].
• New plan: in March 2018, the government said it would look for a different route that does not harm Adam's Bridge [6].

Where it occurs

• India side: off the southeast coast of Tamil Nadu, along the Ramanathapuram and Thoothukudi (Tuticorin) districts [4].
• Sri Lanka side: off the northwest coast of Sri Lanka, south of Mannar Island.
• Northern limit: Adam's Bridge, from Pamban (Rameswaram) Island to Mannar Island [7].
• Island groups inside the reserve: Mandapam, Keelakarai and Tuticorin, with 7 islands each, 21 in all [4].
• Status: Marine National Park (Tamil Nadu, 1986) [4]; Biosphere Reserve (Government of India, 1989) [4]; UNESCO MAB network [3]; Ramsar site (2022) [5].

Don't confuse with

• Palk Bay: lies north of Adam's Bridge, between the Palk Strait and the bridge. The Gulf of Mannar lies south of it.
• Palk Strait: a narrow strait that joins the Bay of Bengal to Palk Bay. Katchatheevu lies here, not in the Gulf of Mannar.
• 1974 vs 1976 agreements: 1974 covered the Palk Strait and gave Katchatheevu to Sri Lanka [2]. 1976 covered the Gulf of Mannar and the Bay of Bengal [2].
• Gulf of Mannar Marine National Park vs Biosphere Reserve: the National Park (1986, declared by Tamil Nadu) is the core of 21 islands. The Biosphere Reserve (1989, declared by the Government of India) is the larger protected area around it [4].

Prelims Hooks

• North to south: Bay of Bengal → Palk Strait → Palk Bay → Adam's Bridge → Gulf of Mannar.
• The Gulf of Mannar was India's first marine biosphere reserve (1989) and the first in South and South-East Asia [4]. It became a Marine National Park in 1986 [4] and a Ramsar site in 2022 [5].
• 21 islands in 3 groups of 7: Mandapam, Keelakarai, Tuticorin, off the Ramanathapuram and Thoothukudi districts [4].
• Flagship animal: the dugong (sea cow), a plant-eating mammal that feeds on seagrass. The Gulf of Mannar is its last important refuge off India [4].
• Trap: Katchatheevu is in the Palk Strait, not the Gulf of Mannar. The Gulf of Mannar boundary came from the 1976 agreements [2].
• Adam's Bridge is about 48 km of limestone shoals from Pamban Island to Mannar Island. It separates Palk Bay from the Gulf of Mannar [7].

Mains Points

• Development versus environment (GS-III):
• The Sethusamudram channel would shorten shipping routes round Sri Lanka.
• But dredging threatens the coral reefs, seagrass and dugong habitat of the Gulf of Mannar Biosphere Reserve. It also touches the religious meaning of Rama Setu.

• Dredging has stopped since 2009 at 19.81% completion, and the government is looking at a different route [6].

• Protecting a fragile marine ecosystem (GS-III):

• Its layered protection (National Park core → Biosphere Reserve → UNESCO MAB → Ramsar site) shows how India manages marine areas.
• Coastal people depend on the same sea, so sustainable use around the core is key.

• Threats such as coral bleaching (coral turning white and dying when the sea gets too warm) and loss of seagrass put the dugong's last refuge at risk.

• Livelihood versus sovereignty (GS-I/II):

• The narrow, shallow sea between Tamil Nadu and Sri Lanka makes it easy for boats to cross the boundary line.
• The 1976 agreement limited Indian fishing in Sri Lankan waters, and Tamil Nadu trawlers (boats that drag large nets) are often arrested.
• Possible answers: deep-sea fishing boats, ending bottom trawling (dragging nets along the sea floor), and joint working groups.

Related concepts

• Sri Lanka
• Palk Strait
• Adam's Bridge
• Katchatheevu
• Maldives

Read more

• Sri Lanka and the Maldives: the island neighbours