Updated by: Arabinda Naik
Fringing Reefs
Coral reefs that grow along the continental margins or along the Islands are known as fringing reefs. Fringing reefs are reefs that develop directly from the shore. They are located very near to land. A fringing reef runs as a narrow belt of around 1-2 km wide. The seaward slope is steep, shallow, and narrow while the landward slope is gentle. Therefore, these coral reefs are generally long but narrow in width. Fringing reefs are generally attached to the coastal land but sometimes there is a gap between fringing reefs and the mainland which forms a Lagoon, and such lagoons are known as Boat channels. Coral polyps do not extend outwards of these reefs due to sudden and large increases in-depth as they lack food there. The fringing reefs are the most found reefs across the world in all major types of reefs. In India, the Gulf of Kachchh, the Gulf of Mannar, the coastline of Andaman and Nicobar Islands is covered with these reefs.
Fringing reefs grow directly from the shorelines of land masses, whether they be continents or islands. They form a border along the coast, and in some cases, they may be separated from the shore by a shallow lagoon.
The reef slope, which extends seaward from the reef flat, descends to greater depths.
The Ningaloo Reef, Western Australia: The largest fringing reef in the world, Ningaloo Reef stretches for over 260 kilometers along the western coast of Australia. It is home to a vast array of marine life, including over 500 species of fish, 300 species of coral, and 600 species of molluscs.
The Red Sea, Egypt: The Red Sea is home to some of the most pristine fringing reefs in the world.
The Maldives: The Maldives is home to many fringing reefs.
Andaman and Nicobar Islands The Andaman and Nicobar Islands are home to an extensive network of fringing reefs, stretching over 500 kilometers, and encompassing an area of nearly 1,300 square kilometers. harbouring an estimated 560 species of coral, 600 species of fish, and a myriad of invertebrates.
The Gulf of Mannar, located between India and Sri Lanka, is home to a rich tapestry of fringing reefs,
The western coast of India, from Gujarat to Kerala, is dotted with fringing reefs, providing a vital habitat for a diverse array of marine life. These reefs, though facing challenges due to urbanization and pollution, are still home to a variety of corals, fish, and invertebrates.
Barrier reefs
Though like fringing reefs, barrier reefs are situated at some distance away from the shore. The stretch of water, separating the barrier reef from land, may be half a mile to 10 miles. This stretch is called lagoon. The lagoons are 10-50 fathoms deep and are best suited for navigation. This is the largest of the three, extends as a broken irregular ring around the cost of an island running almost parallel to it. A barrier reef is characterised by distant location of other reef from the cost with a broader and deeper lagoon, which is sometimes joined with the sea water through one or more water channels cutting across the barrier reef. The Great Barrier Reef of the north-eastern Australia is the most famous barrier reef. Barrier reefs are situated parallel to the coastline, but they are separated from the land by a lagoon, which can vary in width. The distance between the reef and the shore can range from a few hundred meters to several kilometers.The lagoon is a distinctive feature of barrier reefs. It is a relatively shallow area of water between the reef and the landmass. The lagoon can have varying depths and may contain seagrass beds, patch reefs, or other features. Barrier reefs, like other types of coral reefs, form as coral colonies build up over time, with the older, dead coral forming the foundation for new growth. The growth of the reef is influenced by factors such as water depth, wave action, and the availability of hard substrates.
The Belize Barrier Reef, Belize: The second-largest barrier reef in the world, the Belize Barrier Reef runs along the country's eastern coastline for approximately 290 kilometers (180 miles). It comprises over 400 individual reefs and numerous cays (small, sandy islands).
The New Caledonia Barrier Reef: Situated off the southeastern coast of New Caledonia, this barrier reef is the third largest in the world, stretching over 600 kilometers (370 miles).
Atolls
These atolls are also known as coral islands or lagoon islands. They are ring-like or horseshoe-shaped reefs which encircle a lagoon. The lagoon may be complete or broken by several channels of which only a few are navigable. Outer side of the reef slopes off into the depth of the ocean. The lagoon has a depth of 80-150 meters and may be joined with sea water through a no of channels cutting across the reef. The atoll of Biking is a coral reef in the Marshall Island which is famous for hydrogen and atomic bomb tests is situated in the Pacific Ocean. Such as a submerged island and volcanic cone provide suitable conditions for coral growth. Atolls are generally formed on mid-oceanic ridges as they provide prerequisites for the formation of Atolls. Atolls are more common in the Pacific Ocean than in any other ocean. The Fiji atoll, the Funafuti atoll in the Ellice Island, atolls of Cook Island are a few examples. The Indian Ocean also contains numerous atoll formations. Such as found in the Maldives and Chagos island groups, Lakshadweep Islands, Seychelles, and in the Cocos Island group.