• Coral reefs are found in circum-tropical shallow tropical waters along the shores of islands and continents. The reef substrate is mainly composed of calcium carbonate from living and dead corals. Many other invertebrates, vertebrates, and plants live in close association to the corals, with tight resource coupling and recycling, allowing coral reefs to have extremely high productivity and biodiversity, such that they are referred to as ‘the Tropical Rainforests of the Oceans’.
• Corals live in very nutrient poor waters and have certain zones of tolerance to water temperature, salinity, UV radiation, opacity, and nutrient quantities.
• Zooxanthellae live symbiotically within the coral polyp tissues and assist the coral in nutrient production through its photosynthetic activities. These activities provide the coral with fixed carbon compounds for energy, enhance calcification, and mediate elemental nutrient flux. The host coral polyp in return provides its zooxanthellae with a protected environment to live within, and a steady supply of carbon dioxide for its photosynthetic processes. The symbiotic relationship allows the slow growing corals to compete with the faster growing multicellular algaes because the tight coupling of resources and the fact that the corals can feed by day through photosynthesis and by night through predation.

The tissues of corals themselves are actually not the beautiful colors of the coral reef, but are instead clear. The corals receive their coloration from the zooxanthellae living within their tissues.

Geographical Conditions Required
• Corals generally flourish in clear tropical oceans usually between 30°N and 30°S of the equator.
• They grow best in the brightly lighted water about 5 to 10 meters deep. The suspended particles interfere with feeding.
• Corals live in saline water (27%).
• Coral reef can from to depth of 90 meters, but growth rate declines rapidly after 5 to 10 meters depths.
• The reef building corals are found within the 21°C isotherm.
• Corals are not near the mouths of rivers.
• Temperature below 18°C causes their death.
• Individual coral organisms are however, found in some cold, high latitudes waters as well (Norway and Cap Verde Island and off New Zealand and Japan)

Uses of coral reefs
• Remove and recycle CO2 a greenhouse gas
• Protect the shore from erosion by storms and floods
• Are home to over 4,000 species of fish, 800 species of coral and thousands of other forms of plant and animal life, all of which will not survive without the reefs
• Account for 12% of the marine fish catch
• Could provide important medicines including anti-cancer drugs and a compound that blocks ultraviolet rays
• Coral skeletons are being used as bone substitutes in reconstructive bone surgery.

Coral reefs are threatened by
• Destructive fishing practices, such as dynamite or cyanide fishing and trawling in deeper waters, cause direct physical damage to corals.
• Widespread over fishing leads to very low levels of herbivorous fish, which check coral killing algae.
• Nutrient-laden sewage released near the shore causes algal blooms which block sunlight, stunting coral growth and interfering with reproduction.
• Shoreline construction disturbs sediments, which smother corals.
• Tourism and tourists cause physical damage to reefs by construction activities, trampling, boat abrasion and the removal of corals “souvenirs”.

Conservation of coral reef
• The coral reefs of India come under the jurisdiction of the department of forests and wildlife and it is their responsibility to monitor, manage and conserve these fragile eco-system.
• The Ministry of Environment and Forests is responsible to develop an action plan to manage the reef resources and issue guidelines for the sustainable utilization of coral reefs.
• Ministry of Environment and forests has taken charge of Marine national Parks which have coral reefs in them.
• The National Committee constituted for conservation and management of wetlands and mangroves advises the Government on policy issues related to conservation and management of coral reefs. State level steering committees have been set up for the formulation and implementation of the Management Action Plans for the identified coral reef areas.
• Management plans for the Gulf of Kutch Marine National Park and Sanctuary has been prepared by the Conservator of Forests in 1994. Recently the Ministry of Environment and Forests has sanctioned preparation of management action plans for the Andaman and Nicobar and Gulf of Mannar coral reefs.
• The coastal regulation zone notification 2011 offers the only legal protection to all coral reefs and In this coral reef areas come under the CRZ1 category. A special category CRZ 4 has been prepared for the Islands of Andaman, Nicobar and Lakshadweep. Norms for regulation of activities within the CRZ state that corals and sand from beaches and coastal water shall not be used for construction and other purposes. Dredging and underwater blasting in and around coral formations shall not be permitted. Notification also states that construction of beach resorts/hotels shall not be permitted in ecologically sensitive areas such as marine parks and coral reefs.
• The Union Ministry of Environment and Forests is currently undertaking a UNDP supported pilot project, “Management of Coral Reef Ecosystem of the A&N Islands” for developing a full project to ensure the conservation and management of A&N Islands’ reefs. An Indian Coral Reef Monitoring Network has also been established for the purpose. Besides, the Wildlife Institute of India is engaged in a project to develop a management plan for the Mahatma Gandhi Marine National Park at Wandoor, which is one of the few marine national parks in India. In 1996, the Department of Environment and Forests of Andaman and Nicobar Islands notified three islands in the Ritchies Archipelago, comprising Outram Island, Henry Lawrence Island and John Lawrence Islands and the coastal waters surrounding them, as the Rani Jhansi Marine National Park.
• Though monitoring of reefs remains poor in India, the WWF-India project has, hopefully, provided the impetus for all concerned to take the right step for the preservation of our coral reefs.