In India, major coral reef ecosystems are seen in Gulf of Mannar, Gulf of Kachchh, Andaman & Nicobar, and Lakshadweep Islands,
India has all the three major reef types (atoll, fringing, and barrier) and include diverse and extensive reef areas of the Indian Ocean.Coral are made up of genetically identical organisms called polyps.
These polyps have microscopic algae called zooxanthellae living within their tissues.
Fringing reef, barrier reef and atoll (coral islands are formed on atolls) are the most important relief features.
Fringing reefs are reefs that grow directly from a shore. They are located very close to land, and often form a shallow lagoon between the beach and the main body of the reef.
Barrier reefs are extensive linear reef complexes that parallel a shore, and are separated from it by lagoon.
An atoll is a roughly circular (annular) oceanic reef system surrounding a large (and often deep) central lagoon.
The lagoon has a depth 80-150 metres and may be joined with sea water through a number of channels cutting across the reef.