The Coral Reef Ecosystem and Biodiversity in India

The corals exhibit extensive biodiversity in structure and forms. Coral islands as well as coral reefs are secretory products of the skeleton forming Cnidarians. The term 'Corallum' is the total coral bush and the 'Corallite' is the calcareous cup within which the coral polyps, the living elements remain embedded. These polyps secrete mucous to entrap plankton and other food materials, which are engulfed. The mesentrial filaments in the coelenterons digest the food particles and the absorption takes place through simple diffusion. The photosynthetic products of algae are directly supplied to the hosts and the algae inturn receive nutrients and carbon dioxide from the coral polyps. All reef building corals contain symbiotic zooxanthellae in the calcioblastic endoderm. Most probably the zooxanthellae support the growth and secretory activity of the coral polyps.

DISTRIBUTION OF CORAL REEFS IN INDIA :

Coral reefs are distributed in the world in some restricted places only. These are not found everywhere in the World, even these are not found anywhere and everywhere in the India. The coral reefs of the Indian Ocean have been built up during the tertiary and quaternary periods. The coral reef ecosystems are restricted in the main seven regions in India, such as :

1. Coral reef ecosystem in Kerala coast.

2. Coral reef ecosystem in Goa coast.

3. Coral reef ecosystem in Gulf of Kachchh.

4. Coral reef ecosystem in Lakshadweep Islands.

5. Coral reef ecosystem in Gulf of Manner.

6. Coral reef ecosystem in Palk Bay.

7. Coral reef ecosystem in Andaman and Nicobar Islands.

Among the coral reefs of India, fringing reefs are found in the Gulf of Manner and Palk bay, Platform reefs are found along the Gulf of Kuchchh, Atoll reefs are found in the Lakshadweep archipelago, Patchy reefs are found near Ratnagiri and Malwan coasts, Fringing and barrier reefs both are found in Andaman and Nicobar islands.

In the Indian subcontinent, coral reefs are distributed along the west and east coasts at certain places. A total number of 155 hermatypic coral species belonging to 50 genera and 44 ahermatypic species belonging to 21 genera have been recorded by the research workers from the Indian coral reef areas. Satellite imagery gives the ideas of scattered patches of corals in the intertidal regions and occasionally at subtidal depths down to a few meters along the west coast of India.

There are no significant coral reef formations on east coast of India, because :

1. Due to the highest freshwater flow through a large number of rivers mixing with the Bay of Bengal.

2. The sea around the east coast of India is very shallow.

3. The eastern coastal plains are much wider and drier than the western coastal plains.

4. Due to more human activities formation of coral reef and biodiversity is severely affected.

CONDITIONS NECESSARY FOR THE CORAL REEF FORMATION :

Coral animals are well adaptive in warm, shallow, well illuminated and well oxygenated aquatic bodies. These conditions are found in tropical and subtropical seas. Thus the reef building corals remain quite restricted in their distribution.

Coral reefs extend over an area of 68 million square miles in tropical and subtropical seas. They are best developed where the mean annual temperature of the water lies within the range of 23°C to 25°C, they do not develop to any significant extent in the regions where temperature fall below 18°C. Ample amount of oxygen supply is very important. Another important factor for coral reef formation is the intensity of surface illumination of radiant energy.

TYPES OF CORAL REEFS MAINLY FOUND IN INDIA :

Mainly four type of coral reefs are found in India :

1. FRINGING REEF S: This type of reef lies much closer to the shore of mainland; this may be either an island or a stretch of continental coast line. But in either case the intervening water constitute only a narrow channel i.e. Lagoon. These types of reefs have an edge, the reef front, where the most effective coral growth occurs.

2. BARRIER REEFS : There are also reefs similar to fringing reefs but are separated from the mainland by a narrow strip of sea perhaps upto 1000 ft. deep, which is not much less than greater depth obtained by the lagoons. The greater barrier reef in Australia is the best known example outside the India.

3. ATOLLS: These are mainly oceanic and without association with land. They consist of low reef rising no more than 30 ft. above the sea level and enclosing a central area of water called lagoon.

4. PLATFORM REEFS : These are flat reefs without lagoon. They rest on the shallower part of the continental shelves, they may appear between the coast and the barrier reefs or they may be associated with atolls.

BIODIVERSITY OF CORAL REEFS IN INDIA:

a) The composition of coral reef is really interesting rather unique, and it includes near about 185 species of benthic algae, 15 species of sea grass, 15 species of sea weeds, 110 species of poriferas, 6 species of crustaceans, 105 species of echinoderms, 599 species of bony fishes, and additionally, different species of crabs, bivalves, gastropods, cephalopods, in Indian coral reef ecosystems.

b) Coral reefs are hard limestone structures built up by the cementing process and depositional activities of the class Anthozoa, scyphozoan, and Hydrozoa, and also the calcifying algae.

c) In some areas of coral reef in India, rich algal diversity was seen such as Sargassum, Ulva, Cladophora etc.

d) In some reef areas there are well biodiversity of 70 species of Sponges, 27 species of prawns, 200 species of molluscs, 3 species of marine mammals were also seen.

e) Both Stony and soft corals are present in the sub-tidal regions of the reefs. The genera of stony corals found in the Indian reefs are Favia, Favites, Goniopora, Montipora, Sinularia etc. The genera of soft corals found are Nephthya, Dendronephthya etc.

f) In the different Indian coral reefs contain about 23 species of ammonifying bacteria, 15 species of nitrifying bacteria, 3 species of nitrogen fixing bacteria, 23 species of phosphate producing bacteria etc.

g) About 50 species of Diatoms out of 55 species of Phytoplankton were found in the Gulf of Manner and other different reefs of India.

h) In Lakshadweep islands about 20 groups of Polychaete worms, and different types of Nematodes were found.

So, it is clear from the above discussion that a coral reef is very much rich in biodiversity in India.