Coral reefs in Andaman & Nicobar Island; an Eye view.
Coral reefs in Andaman & Nicobar Island are some of the most diverse underwater ecosystems of the globe. Coral reefs are structures of calcium carbonate made of millions of tiny coral creatures. They are a large group of invertebrates called cnidaria, in various colours, shapes, and sizes. Each animal is referred to as a polyp.
Coral reefs in Andaman and Nicobar Island.
Coral reefs in Andaman & Nicobar Island are some of the most diverse underwater ecosystems of the globe. Coral reefs are structures of calcium carbonate made of millions of tiny coral creatures. They belong to the Anthozoa group of phylum cnidaria.
The corals and algae have unseparated natural bonding. The green and brown colour of the reefs are the contributions of algae called zooxanthellae. However the colour like red and blue, the brighter ones is due to coloured proteins produced by coral creatures.
Corals are a large group of invertebrates, called cnidaria, named after the phylum they belong, in various colours, shapes, and sizes. Each individual animal is referred to as a polyp.
Andaman and Nicobar Island is an underwater paradise of coral diversity with reported as many as 179 species, 61 genera. It appears like rocks but corals are live fauna. It is an amazing fact that a polyp has tentacles to catch prey, and a simple stomach with a single mouth but has no eyes, ears, nose, tongue, or brain, a nerve network keeps the creature alive. Polyps prey on zooplankton, the floating tiny creatures. The bigger one can catch tiny fish to eat. At night polyps come out of the coral shell to catch the prey. Coral reef harbors approximately 25% of marine species.
Types of coral in Andaman and Nicobar Island:
Corals in Andaman and Nicobar Island can be divided into two types on the basis of coral formation and activities. Hard corals or scleractinian corals are referred to as reef-building corals. They extract calcium from seawater and carbon from algae(microscopic flora cells called zooxanthellae live within polyps) and built the hard structures around them for growth and protection. The concerted growth of varieties of corals gives rise to large colonies called coral reefs.
The common genera responsible for reef formations are Acropora, Montipora, Pocillopora, Millepora, etc.
Soft corals on the other hand include sea fans (Gorgonia ventalina,), sea fingers, sea whips, etc. They do not have shells of calcium carbonates like hard corals but tend to live in colonies.
Types of coral reefs in Andaman and Nicobar Island:
Andaman and Nicobar Island mainly witnessed two types of reefs, covered by an area of approximately 2000km2.
- Fringing reefs
- Barrier reefs.
Fringing reefs are the most common types found on the eastern sides of the island. The reefs grow very close to the shore and come under the intertidal zone. They are separated from the shore by a narrow and shallow path.
Barrier reefs are seen on the western side of the island. Such reefs are very close and run parallel to shore and are separated by a deep water channel. The reefs are also coming under the intertidal zone of the island and the water channel act as a barrier.
Who are the dwellers in the coral reefs in Andaman and Nicobar Island?
Both flora and fauna are found in the coral reefs in Andaman and Nicobar Island. Many live permanently and others come in search of food or breeding purposes. They are part of the vibrant ecosystem and take part in energy transfer in the food chain. Jellyfish and anemones are dwellers of the reefs including varieties of crabs, lobsters, and starfish species.
The periphery seawater of the island shelters around 1200 reported fish species, out of which overwhelming 571 species are coral reef fish. The common fish community found in the reefs of the island are butterfly fish, clown fish, parrot fish, starfish, eels, cardinal fish, coalfish, stone fish, scorpion fish, triggerfish, etc. add more colour to the wonderful ecosystem.
Some important corals in the coral reefs in Andaman and Nicobar Island:
Hard corals of the islands harbor algae called zooxanthellae. They provide the corals’ extensive range of colours. Such corals are called hermatypic coral and are mostly found in the upper part of reef slopes.
The ahermatypic corals do not contain zooxanthellae and are found in deeper parts of the reef slope. The branching corals are colorful and include species of Acropora, which form dense branches. The stag horn coral, Pocillopora (cauliflower coral looks like cauliflower), and table coral (which looks like table form), all belong to the Acropora species.
Bolder shape coral (Porites species) has very small polyps and can grow into large colonies on the reef edge and upper slopes. The Favites abidita or larger star coral ([looks like a star) have irregular shape colony with adjacent larger polyps sharing a common wall, whereas the lesser star coral (Goniastrea retiformis, family Merulinidae) has small polyps. The valley coral, (platygyra species), mushroom coral (Fungi species), and brain coral(Lobophyllia species) are some of the important coral species found in the coral reefs in Andaman and Nicobar Island.
Important locations of coral reefs in Andaman and Nicobar Island:
Andaman and Nicobar Islands comprise 836 islands/islets which enriches the coral ecosystems. The important coral reef locations of the islands are Mahatma Gandhi Marine National Park near Wandoor, 281 km2. (1983), Rani Jhansi Marine National Park, 256km2(1986) North Reef Island Sanctuary, Smith Island, Rass Island, Avis Island, Lamia Bay, Harminder Bay, etc.
Challenges for the survival of coral reefs in Andaman and Nicobar Island:
The island coral ecosystems face many natural and man-made challenges. Such as;
- Hurricanes, severe cyclonic circulations, and strong waves are enemies of the corals.
- White band disease.
- Climate change leads to the rising of sea surface temperature.
- The pollution of the sea by seepage of oil and discharge of garbage.
- Illegal collection of marine resources.
- Illegal fishing.
- Increase of sediments.
The coral reefs in Andaman and Nicobar Island, are nature’s underwater wonders of a vibrant ecosystem. The corals and algae have unseparated natural bonding. The green and brown colour of the reefs are the contributions of algae called zooxanthellae. However the colour like red and blue, the brighter ones is due to coloured proteins produced by coral creatures. The change of climate and some un foresight activities of humans are real threats to the existence of coral reefs.