What kind of corals are present in Lakshadweep islands
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Answer:
The Lakshadweep islands lie scattered in the Arabian sea about 225 to 450 km from the Kerala coast. Geographically, the islands lie between 8°N - 12°3'N lat. And 71 °E- 74°E longitude. The islands consist of coral formations built up on the Laccadive-Chagos submarine ridge rising steeply from a depth of about 1500 m to 4000 m off the "west coast of India. The U.T of Lakshadweep along with the Maldives and the Chagos Archipelagoes form an interrupted chain of coral atolls and reefs on a contiguous submarine bank covering a distance of over 2000 km. This ridge is supposed to be a continuation of the Arravali mountains, and the islands are believed to be remnants of the submerged mountain cliffs (P.S.B.R. James et al: 1986).
There are 36 tiny islands, 12 atolls, 3 reefs and 5 submerged banks, covering an area of 32 km2 with lagoons occupying about 4200 km2. Only 11 of the 36 islands are inhabited. They are Andrott, Amini, Agatti, Bangaram, Bitra, Chetlat, Kadmat, Kalpeni, Kiltan, Minicoy and the headquarters at Kavaratti. The Minicoy island is separated from the rest of the islands by a 180 km wide stretch of sea known as the nine degree channel. Kavaratti is the administrative headquarters. Agatti houses the only airport and airstrip. A resort catering to international tourists has been functioning in Bangaram since 1988 and a resort catering to national tourists with a dive school has been set up at Kadmat in 1995. In addition tourist huts have been erected at Kavaratti, Minicoy and Agatti.
The islands are flat and scarcely rise more than two meters. They are vulnerable to storms and sea erosion. They are made up of coral sand and boulders which have been compacted into sandstone. These islands have a warm humid climate (air temperature 17°-38° C, humidity 70%). The surface water temperature varies between 28-31 °C. While the salinity ranges from 34-37 ‰ Ground water is found a couple of meters below the land surface and is replenished by an annual rainfall of about 150 cm during the south west monsoon from June to September.
Structure of the Reef
Coral reefs of the islands are mainly atoll except one platform reef at Androth. Almost all the atolls have an orientation of NE-SW with the low lying island on the east, a broad well developed reef on the west, with a lagoon in between, connected to the open ocean by one or more channels.
The reef flat occupies 136.5 sq km area. Sea grass occupies 10.9 sq km and lagoon occupies 309.4 sq km (Bahuguna, A and Nayak, S, 1994). The depth of the sea increases outside the coral reef and can reach up to 1500-3000. Andrott is the largest island with an area of 4.84 sq km and the only island that does not have a lagoon. Bitra with an area of 0.10 sq km is the smallest in land area but perhaps has the most magnificent lagoon. All the islands lie north to south, excepting Androth which lies east to west. The distance betweeen them varies from 11 km to 378 km.
On the seaward side the reef slopes into the sea. The first plateau is found around a depth of 5-6 mts. The second plateau with sandy patches is found around 25 mts - 30mts (Andreas: 1997). During high tide water exchange takes place between the lagoon and the open sea over the reef. The lagoons have sandy bottoms with scattered coral boulders and pinnacles followed by extensive sea grass beds at the landward side.
Reef diversity and resources
A detailed report on the islands, their coral fauna, reef associated resources and suggestions of conservation and management are set in a detailed report based on an intensive survey of scientists by CMFRI (bull No 43,1989) and Rodrigues (1996). The coral fauna of Lakshadweep is known to harbour a total of 105 species divided among 37 genera (Pillai 1996). Rodrigues (1996) has recorded 29 new records for species in Lakshadweep. The lagoon and reef flat faunal elements are dominated by Accropora spp., Pocillopora spp., Ponies spp. and massive and encrusting favids. Psammocora spp is common in the northern islands. There is a profusion of blue coral Helipora coerulea. Millepora spp. forms the dominant element in the lagoon. One finds a latitudinal difference in coral fauna assemblage in the lakshadweep. Minicoy has some elements such as Lobophyllia and Diploastrea that are common to the Maldives but rarely found in the northern Islands. Similarly the genera Montipora and Echinopora recorded from the northern group of atolls are not recorded in Minicoy (Pillai, 1996).
86 species of macrophytes, 10 species of Anomuran crabs, 81 spp of Brachyran crabs, 155 spp of Gastropods, 24 spp of bivalves, 13 spp of sea stars, 6 spp of brittle stars, 23 spp of sea cumbers, 15 spp of sea urchins and 120 spp offish are found in the lakshadweep (Rodrigues, 1996). The green turtle and the hawksbill turtle are also found in all the islands. They graze on the sea grass beds and are hunted for their fat.