Studies on ecology, chemical constituents and culture of marine macroalgae of Minicoy Island, Lakshadweep

摘要

The Union Territory of Lakshadweep is situated in theudArabian Sea about 200 to 400 km off the Kerala coast. Thisudarchipelago consists of 36 islands and five s.ubmerged banksudwith a total area of 32 sq. km .The islands lie between 08° 00 -ud12° 30' N latitude and 71 ° 00 - 74° 00 E longitude. Theseudislands consist of coral formation built on submerged ridgeudraising steeply from a depth of about 1500 to 4000 m in theudArabian Sea. The Lakshadweep, Maldives and Chagosudarchipelagos foon an uninterrupted chain of coral atolls andudreefs on a submarine bank covering a distance of over 2000 km.udMost of these islands have sandy beaches with gentle slope onudthe lagoon side and on the seaward side there is a steep slopeudwith boulders, coral rocks, living corals and debris. Coralsudcannot grow very deep in the oceans and what is seen at presentuddepicts millennia of interaction between the submarine bank,udtectonic activity and the level of the oceans, particularly duringudthe Pleistocene period (Jones, 1986).udCoral reef ecosystems are the most diverse andudcolourful of any communities with the most complexudinterrelationship between species. Corals grow where the meanudsea temperature is at least 20 °C throughout the year, preferablyudmore than 23 °C. They also need clean sea water and are wlableudto grow where rivers dilute the sea or bring in mud. Coral reefudcommunities may be very old and their foonation is a result ofudpersistent accumulation of calcareous deposits over longudperiods, extending from hundred to thousands of years (Qasim,ud1998). Coral reefs are of three types: (I) Barrier reefs alongudcontinents (2) Fringing reefs around islands (3) Atolls, brokenudfringes of reef and islands around a central lagoon. The IndoPaciudfic region is particularly rich in corals. The AustralianudGreat Barrier Reef is an intermittent series of reefs stretchingudover 1900 km along the coast of Queensland. Other coastaludreefs lie off East Africa and in the Red Sea. The Pacific and theudIndian Oceans have thousands of atolls. In the West Atlantic,udcoastal reefs extend 200 km. southwards from Yucatan andudmany Caribbean islands are fringed with coral reefs. The coralsudare coelenterate polyp animals which extent their tentacles atudnight to feed on zooplankton washed over the reefs. Theirudtissues house symbiotic green algae (zooxanthillae).udZooxanthillae and other algae living in or on their calcareousudskeleton conduct photosynthesis in the sunlight. Many reefs areudin trade wind belts, the windward side being exposed to waveudaction, the leeward side being sheltered. Reef systems are oftenudbioenergeticaly more or less self maintaining, completeudecosystem in themselves, beautifully adapted to use, hoard orudrecycle any inputs from the surroundings.