SURVEY OF CORAL REEF BIODIVERSITY IN KRUSADAI ISLAND IN THE GULF OF MANNAR ISLANDS

The Gulf of Mannar (GoM) is located in Tamil Nadu, on the mainland southeast coast of India, mostly between Rameswaram on the north and Tuticorin on the south. The reefs are formed around the 21 islands situated between lat. 8’ 47 - 9’ 15’ N and long. 78’ 12 ‘ - 79’ 14’ E. The GoM with its islands provides a very interesting heterogeneous group of fauna and flora with about 3,600 species (Ramadhas et al., 1999). GoM is well recognized due to its exclusive ecological systems and richest marine biodiversity regions, mainly contributed by coral reefs, sea grass beds and mangroves. The GoM was declared as Marine National Park in 1986 for the intention of protecting marine life and its environment (Kumaraguru, 2006). The area is under the Man and Biosphere programme of UNESCO and elected as Gulf of Mannar Biosphere Reserve (GoMBR) in the year 2001. For organizational reasons and to provide better supervisory examination, the 21 islands are grouped in to four viz. Mandapam (7 islands), Keezhakkarai (7 islands), Vembar (3 islands) and Tuticorin (4 islands) based on the geographical distributions. The islands are coming under three wildlife forest ranges which include Mandapam, Keezhakkarai and Tuticorin. The islands positioned 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, patch reefs rise from depths of 2.5 m to 8 m, extended 1- 4 km in length and are up to 50 m wide (Patterson et al., 2007). The reef flats are widespread in almost all the reef areas (Pillai, 1977). The coast is closely populated. Over 100,000 numbered traditional fisher folk mainly depend on the reef, seagrass and Mangrove associated fishery resources for livelihood. The anthropogenic pressures on this coastal area and the reefs is comprehensive, that includes coral mining (Mahadevan and Nayar, 1972); critical fishing practices (Patterson et al., 2007); Sewage disposal (Ramachandran et al., 1989); toxic discharges from several chemical industries and thermal plant stations (Easterson, 1998) including mangroves (Ramanathan, 2017,2019, Gurudeepan et al.,2010, Arunprabu et al., 2017).; and bio-invasion of exotic seaweed, like Kappaphycus alvarezii (Chandrasekaran et al., 2008; Patterson and Bhatt, 2012). The climate change effects on the Reefs and related fishery (Patterson et al., 2008; Patterson and Samuel, 2004). The conservation and management of coral reefs become difficult in Gulf of Mannar. The focus on systematic and scientifically supported data collection is important to monitor, not only to obtain real data on the coral status, but also to protect the reefs from various local threats and environmental stresses in order to protect the coral reefs. Krusadai Island is positioned in the Gulf of Mannar near Rameswaram and Dhanuskodi in the Ramanathapuram district of Tamil Nadu (latitude 9° 14'N, longitude 79° 13'E). The island is 6 kilometers away from Mandapam on the mainland and 4 kilometers away from Pamban Island. It measures approximately 2050 meters in length and 700 meters in width, a total area of 67 hectares. The coral reefs are found surrounding the island, as well as the shallow lagoon-like area between the reef and the beach, which provides excellent opportunities for collecting flora and fauna. The most distinguished feature of the island is its easy access to a various range of flora and animals, including living coral reefs in their native habitat. Krusadai Island has been known as the "Biologist’s Paradise.Since around 1898. This is because of its feature of attracting a steady stream of students, Scholars, Professors, Researchers, Environmentalists, Taxonomists from India and overseas (Jeyabaskaran and Lyla, 1996). The popular Galaxea reef is located on the southeastern side of Krusadai Island. Tow net collections are immense in the Kundugal canal, which runs along the northern shore of Krusadai island. A strong current runs from the Gulf of Mannar to Palk Bay. The Dolphins can be seen swimming and diving in large numbers. The western portion of the northern shore is quite muddy, hence nicknamed as 'Bushy Point. The survey on coral reef biodiversity was taken from Krusadai island.