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Dr Monika Raghuvanshi
Secretary, N.Y.P.I., Doctorate of Philosophy (Green Marketing), Master in Business Administration (Triple Specialization), 2 International Books Published, 220 International and National Conferences and Webinars, 50 National Magazine Articles Published, 13 National Awards, Certified in Information Technology, Certified in Consumer Protection, Certified in French Basics and Certificate in Computer and Oracle
A coral reef is actually a collection of structures of which only a portion is made up of living corals or algae, although other related structures result from this living segment. Accumulations of carbonate sand and mud provide habitat for seaweed beds and mangroves, as well as nearly invisible beds of blue-green algae. These plants and algae trap and stabilize sediments, and their accumulations also accumulate throughout the reef complex. Storms and waves deposit fragmented material on beaches and shorelines, and these can develop into sand or pebble islands or into cliff-top cairns. Coral reef, a ridge or mound formed in shallow areas of the ocean by algae and the calcareous skeletons of certain coelenterates, of which coral polyps are the most important. A coral reef can develop into a permanent coral island. Often called the "tropical forests of the sea", coral reefs are home to a spectacular diversity of organisms.
Seafloor corals: Corals and other reef-building organisms- Coral polyps- resemble sea anemones, to which they are closely related, but unlike most anemones, most corals are colonial. The initial polyps divide into daughter polyps, which in turn divide to form colonies that can reach several meters in diameter, all held together by a rigid, continuous limestone skeleton. They remain attached to the sea floor and become so large and heavy that only storms disturb them. In favorable conditions, generally clear water with good circulation, but not too rough, corals grow abundantly next to, or even on top of, each other. Corals build limestone because their skeleton is composed of calcium carbonate. Reef-building corals, mainly stony corals or Scleractinia, grow best in shallow, sunny waters between shallow water and a depth of 11 meters (36 feet), but can also build reefs in water as deep as 40 meters (about 130 feet) and can be distributed between 40 and 58 meters and 58 meters. These corals prefer normal salinity waters with a maximum annual temperature above 22 ° C (72 ° F) but below 28 ° C (about 82 ° F).
Shore corals: A second group of corals in modern seas grow in patches and clumps that form shores rather than reefs on the outer, deeper, cooler, and darker parts of continental shelves and platforms. These organisms thrive in waters with minimum winter temperatures between 4 and 15 °C (39 and 59 °F) at depths of about 60 to 200 meters (200 to 650 feet).
Deeper sea corals: The third group of modern sea corals is associated with colder or deeper seas. It consists of small, solitary corals belonging to a relatively small number of genera, found on the deep ocean floors and shelves around Antarctica, Patagonia, and the Falkland Islands, in waters with temperatures between 2 and 6 °C (36 and 43 °F). Calcareous algae (rock algae), mollusks, echinoderms, and protozoa also contribute to the reef. Different organisms play different roles in reef-building. Some, especially corals, form the main structure of growing reefs, although, in some parts of the world, such as the central Pacific, where the surf is very strong, calcareous algae may be more important in more rugged areas. Almost all shell and calcareous organisms, as well as those with spines, such as sponges and sea cucumbers, provide fragments that penetrate or fall into the interstices between the corals. Other organisms, especially algae and protozoa, bind and cement everything together with a leafy growth.
Main forms
Coral reefs come in four main forms:
(1) Marginal reefs are areas of flat rock that directly border an island or a land mass without a reef, often volcanic.
(2) Barrier reefs are also close to a non-rocky land mass but are several kilometers offshore, separated from the land by a lagoon or channel often about 50 meters (160 feet) deep. Some barrier reefs are more or less circular, surrounding an island, but larger reefs, such as those along the Red Sea coast and the Great Barrier Reef of Australia, are complex linear structures composed of chains of rock plates, some of which are elongated into ribbon reefs.
(3) Atolls are like circular barrier reefs but without their central land mass.
(4) Finally, there are platform or slab reefs, which have irregular features in the form of a table or pinnacle. Smaller patches are found in atoll lagoons. Larger patches occur as isolated parts of larger developments of one of the other three categories of reefs. Sometimes they are completely separate from other types of reefs.
Coral tourism: Coral reefs provide ecosystem services for tourism, fisheries, and coastal protection. Approximately more than 500 million people benefit from the ecosystem services provided by coral reefs. To improve the management of coastal coral reefs, the World Resources Institute (WRI) has developed and published tools to calculate the value of coral tourism, coastal protection, and fisheries, in partnership with five Caribbean countries.
Coastal protection: Coral reefs protect coastlines by absorbing wave energy, and many small islands would not exist without reefs. Coral reefs can reduce wave energy by 97%, helping to prevent loss of life and property damage. Coasts protected by coral reefs are also more resistant to erosion than those without them. Reefs can soften waves as well as, or better than, artificial structures designed to protect the coast, such as breakwaters. Reef restoration is significantly less expensive than constructing artificial breakwaters in tropical environments. Predictable flood damage would double and the costs of frequent storms would triple without the rock gauge.
Fisheries: About more than six million tons of fish are caught on coral reefs each year. Well-managed reefs have an average annual yield of 15 tons of seafood per square kilometre.
Threats: Since their emergence 485 million years ago, coral reefs have faced numerous threats, including disease, predation, invasive species, bioerosion by grazing fish, algal blooms, and geological hazards. Recent human activities pose new threats. From 2009 to 2018, coral reefs worldwide declined by 14%. Human activities that threaten corals include coral mining, bottom fishing, and dredging of channels and access to islands and bays, which can damage marine ecosystems if not carried out sustainably. Other localized threats include blast fishing, overfishing, overexploitation of corals, and marine pollution, including the use of the banned antifouling biocide tributyltin; although absent in developed countries, these activities continue in countries where environmental protection is weak or where regulations are poorly enforced. Greenhouse gas emissions pose a broader threat through rising temperatures and sea levels, leading to widespread coral bleaching and loss of coral cover. Climate change is causing more frequent and violent storms and is also altering ocean circulation patterns, which can destroy coral reefs. Ocean acidification also affects corals by reducing calcification rates and increasing dissolution rates, although corals can adapt their calcifying fluids to changes in seawater pH and carbonate levels to mitigate the impact. Pollution from volcanic and anthropogenic aerosols can modulate regional sea surface temperatures.
Coral restoration has gained importance in recent decades due to the unprecedented loss of coral reefs around the world. Stressors to corals include pollution, warming ocean temperatures, extreme weather events, and overfishing. As the world's coral reefs deteriorate, fish habitats, biodiversity, coastal development and livelihoods, and natural beauty are threatened.
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