Coral Atolls of Lakshadweep, Arabian Sea, Indian Ocean

Abstract

The Lakshadweep are least studied coral atoll group situated in the northern part of the Laccadive-Chagos ridge at a distance of 200-300km from the West Coast of India... The islands in the eastern side have lagoons which vary in size and are the habitat for a variety of plants and aquatic animals. They are also sites for harbor, aquaculture, recreation and tourism. The smaller lagoons are virtually filled with sediments The larger lagoons are comparatively deep with depth of about 10 to 16m. At low tide the reef is exposed and during high tide it is submerged. Eastern seaside part of the island has steep storm beach with deposits of shingles and boulders .and the lagoon side beach is sandy. The source of the sediments on the atolls is the coral reefs and the other biological communities. A substantial amount of the sediments in the reef front is lost in the deep sea because of morphology, waves and currents. The inner reef flat has thicker sediment cover, parts of which are transported to the lagoon. The reef areas are the living places of various communities of corals belonging to different families of Acroporidae, Poritidae, Pocilloporidae, Favidae, Fungiidae, Mussidae etc. Besides a large number of speices of Gastropods, Bivalves, Echinoids, Foraminifers, Ostracods and Bryozoans are also present. Halimeda is the most important constituent of the lagoon sands and play most important role in building up the reef. Survey in the lagoons and shallow offshore areas indicated the occurrence of 288 million tonnes of calcareous sands in the lagoons to a depth of about 1 meter below the lagoon floor. .The sands have a low amount of silica, alumina and Fe2O3. They are suitable for a number of industries like cement, chemical, glass and paper. However, the geomorphic situation on the coral islands are delicate and precautions have to be taken while mining those sands The present calcareous sands occur in a loose form on the lagoon floor and will be easier to mine. We can expect a quick return from these deposits without disturbing the delicate balance .If limited quantity of sands are removed, there will not be appreciable change in the rate of production or derivation. Slight changes will be automatically adjusted the most important sediment-forming site is the reef area and it should not be disturbed as far as possible. The lagoon is the most important accumulation site and the lagoon will have the tendency to fill up automatically if the sands are taken out. However, a close environmental monitoring should be done. Once the system of exploitation is established in such an environment it can be widely used in other areas also. All programmes should be oriented according to the guidelines suggested by the Reef Monitoring Network and Management Plans.