Gulf of Mannar and Palk Bay (Tamil Nadu, Southeast coast of India), 658 km long coastline
Geographic features & other Importance of research Location:
- Marine ecosystem with coral reefs and seagrass beds
- Gulf of Mannar Marine National Park
- Gulf of Mannar Marine Biosphere Reserve
- High dependence of coastal community on fishery resources
- Loss / damage of key coastal habitats and biodiversity due to anthropogenic impacts and elevated sea surface temperature
Brief background on Gulf of Mannar
- The Gulf of Mannar (GoM) is located at the southeastern coast of Tamil Nadu, India extending from Rameswaram in the North to Kanyakumari in the south. The 140 km GoM stretch extending from Rameswaram to Tuticorin includes 21 uninhabited islands, which are surrounded by coral reefs. The islands occur at an average distance of 8-10 km from the mainland. In 1980, the Government of Tamil Nadu notified the public of the intention of setting up the Marine National Park. After re-notification in September 1986 the Gulf of Mannar Marine National Park was declared, including 21 islands and the surrounding shallow coastal waters, covering an area of 560 km2. The islands are located between Lat. 8o 47’ N and 9o 15 N and Long. 78o 12’ E 79o 14’ E and are grouped into four for management purposes namely, Mandapam group (7 Islands – Shingle, Krusadai, Pullivasal, Poomarichan, Manoliputti, Manoli and Hare), Keezhakkarai group (7 Islands – Mulli, Valai, Thalaiyari, Appa, Poovarasanpatti, Valimunai, and Anaipar), Vembar group (3 Islands – Nallathanni, Puluvinichalli and Upputhanni), and Tuticorin group (Kariyachalli, Vilanguchalli, Koswari and Vaan). In addition, in 1989 the GoM was declared as “Marine Biosphere Reserve” covering an area of 10,500 km2 from Rameswaram to Kanyakumari.
- The GoM is influenced by seasonal monsoonal patterns, southwest monsoon and northeast monsoon. The islands lie at an average distance of 8-10 km from the main land. Narrow fringing reefs are mostly located at a distance of 100 to 350 m from the islands and patch reefs rise from depths of 2 m to 9 m and extend up to 1 – 2 km in length with width as much as 50 m. The large areas of reefs along the GoM are generally in poor condition due to a number of destructive activities by several hundreds of people who live along the coast and depend on fishery resources of reef areas for their livelihood. International well known coral taxonomist
- Dr. C.S. G. Pillai dedicated 40 years of his service in this reef area and described 94 species of 37 genera (Pillai, 1986), with the most common being Acropora sp., Montipora sp and Porites sp. Patterson et al., (2004) updated the list of corals of GoM from 94 to 104 species. Patterson et al., (2007) further updated the list of corals to 117 species. There are several conservation initiatives implemented by Government, Research Organizations and Non Governmental Organizations to protect the reefs and seagrass beds for sustainable utilization by the dependent fisher folk. The recent noted initiative is the establishment of Gulf of Mannar Biosphere Reserve Trust (GOMBRT) which has implemented the GEF-UNDP funded project on “Conservation and sustainable use of Gulf of Mannar Biosphere Reserve’s coastal biodiversity”. This programme made tremendous change in creation of awareness among all stakeholders in particular the fisher folk, administrators and policy makers; developed capacity in resource management and alternative livelihood; and research and monitoring to collect baseline information on various key resources like soft corals, seagrasses, fishery resources, pearl oysters, scheduled molluscs etc. The good news for all hard work was the increase of live coral cover from 36.98% in 2005 to 42.85% in 2009.
- The Gulf of Mannar coast and Islands have relatively dense growth of seagrass meadows, mainly between the mainland and the islands (shoreward from island), as well as towards the seaward sides of the islands. In the seaward sides of the islands, seagrass appeared as patches. They are found about 2 to 3 km wide from the Island shores towards the open sea. Seagrass meadows around the islands of Gulf of Mannar form a significant grazing ground for the sea cow, Dugong dugon.
Brief background on Palk Bay
- The Palk Bay is shallow basin with an average depth of 9 meters. Reefs occur at a depth between 0.5m and 5 m in South Pak Bay, starting 100 m from shore up to 5 m depth and abundance between 0.5 and 2.0 m. Four distinct coral areas are identified in South Palk Bay, which includes, Mandapam North, Pamban, Thangachimadam and Olakuda.
- Dr. C.S.G. Pillai who has carried out detailed study on the Palk Bay corals made his observations in 1969 as provided below: The poor representation of corals, on the reef as well as widely spaced nature of the colonies indicate that the reef in consideration is not an actively growing one in Palk Bay. The widely spaced and poor growth of corals at Palk Bay indicates that the existing ecological factors are not very congenial for a luxuriant growth of corals. The shore as well as the lagoon bottom in the Palk Bay being sandy, a large quantity of silt is stirred up during the period of north-east monsoon, the wind at this period mostly crossing the shore in a north-east direction. The stirred up sand and silt get suspended and the lagoon waters look muddy during this period. The effect of silt during north-east monsoon is a marked degree here, which prevents a healthy growth of corals. Further, the living colonies show a large number of buds at the onset of calm period indicating a state of active growth. Dr. Pillai recorded 63 coral species belonging to 22 genera in Palk Bay.
- The Palk Bay area has more extensive seagrass growth compared to Gulf of Mannar because of its topography and sediment texture. The seagrass beds are present from the shore towards the sea up to 9 km distance. The area between Pamban and Athiramapattinam has approximately 254 km2 seagrass cover. The luxuriant seagrass meadows in Palk Bay support the high number of dugong population presently in India.