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THE LAKSHADWEEP ECOSYSTEM
It is interesting to discuss very briefly some of the components of the island ecosystem and their function found by us or other observers.
1 Upwelling of deep sea water delivers considerable quantities of nutrients to support abundant life near the surface particularly in Minicoy. The food chain of the tuna and the terns starts here.
A zone of sinking which could cause loss of nutrients has also been found in the open ocean east of Minicoy (Nair et al. Op. Cit)
2. Run-off from land enriches the coastal waters.
3. Excreta of oceanic birds like terns is an important source of nutrients in the euphotic zone of the sea (surface layer where there is sunlight penetration), where primary production through photosynthetic activity takes place.
4. Phytoplankton or microscopic plants, sea weeds and sea grasses use the incident sunlight and plentiful supplies of nutrients to produce organic matter.
5. Zooplanktons feed on phytoplankton, and with phytoplankton form the next link in the food of consumers like small fishes and many invertebrates abundant in Lakshadweep waters. Euphausids, a group of zooplankton, especially rich in the seas around Lakshadweep (Nair, et. al. 1986), are the staple food of the small fishes such as sprats which are in turn, consumed by the larger fish like the Tuna.
6. Small fishes like the bait fishes Spratelloids spp are the food of the tertiary consumers like terns and dolphins. Some animal species operate in more than one trophic level, to that extent, terns can be considered to be tertiary.
7. a) The terns which are the most numerous among the visible tertiary consumers have many important roles in the ecosystem. By using different habitats and dividing their time between the sea and land they are the best permeants of the ecosystem. Terns feed on the small fishes on the surface as well as some forms of deep sea fishes, and thereby help to retain the nutrients brought up by the currents for a long time near the surface of the ocean. Thus they act as land-sea bridges of energy.
b) Bird excreta deposited over thousands of years are believed to have contributed to the building of the islands (Jones 1986). It is speculated that by spending long periods of time on the newly formed sand banks they (the terns and waders) fertilize and help to stabilize islands, reversing the process of erosion to some extent. The newly exposed sandbanks of Lakshadweep which are a favorite resting - spot of terns were found to be immensely fertile, and coconut trees grew well without external application of fertilizer. (Varghese pers. com.)
c) Eggs, juvenile and adult terns are eaten by human consumers. Eggs and young are aken by crabs.
8. The highly productive and diverse coral formation of the island also help in land building, in providing the ideal habitat for complex communities of the sea and make the island aesthetically attractive. The corals lead a symbiotic life along with the algae.
9. The importance of crabs in recycling of nutrients by scavenging on the discarded and decomposing bodies of animals must be emphasized. The crabs represent a very vital link in the food chain. They form part of the prey Part of the prey of eels.
Part of the food web of the Lakshadweep including both Land and Sea organisms
(The actual food web will be infinitely complicated).
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