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An underwater habitat that is distinguished by the presence of reef-building corals is known as a coral reef. Colonies of coral polyps are what give rise to reefs, which are then kept together by calcium carbonate. The vast majority of coral reefs are constructed from stony corals, which have polyps that cluster together in groups.
The animal phylum Cnidaria is home to a class called Anthozoa, which also houses sea anemones and jellyfish. Coral is a member of this class. Corals, in contrast to sea anemones, produce a rigid exoskeleton made of carbonate that both supports and protects the coral. The majority of reefs flourish in water that is warm, shallow, transparent, bright, and agitated. The first coral reefs emerged 485 million years ago, at the beginning of the Early Ordovician period. They succeeded the microbial and sponge reefs that had existed during the Cambrian period.
Shallow coral reefs, which are sometimes referred to as the rainforests of the sea, contain some of the most diverse ecosystems on Earth. However, they are home to at least 25 percent of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates, and other cnidarians, although taking up less than 0.1 percent of the total surface of the world’s oceans (or roughly half the area of France). Coral reefs are most successful in areas of the ocean that contain relatively little nutrients. They are most frequently discovered at shallow depths in tropical waters, however there are examples of coral reefs in deep water and cold water on a smaller scale in other regions of the world.
Formation
The majority of coral reefs didn’t start growing until after the Last Glacial Period, when melting ice caused the sea level to increase and flood continental shelves, which led to the formation of coral reefs. The majority of the world’s coral reefs are younger than 10,000 years. At the same time as populations were growing upwards, the reefs were growing upwards to keep up with the rising sea level. Reefs that rose too slowly risked becoming submerged and losing their ability to receive adequate light. Coral reefs are most commonly located in the open ocean, far from the edges of continental shelves, and in the waters surrounding oceanic islands and atolls. The vast majority of these islands got their start in volcanic activity. Some of them were caused by plate movements that resulted in the lifting of the ocean floor deep below.
Charles Darwin came up with the idea for his theory of the formation of atoll reefs while he was sailing on the Beagle. In his book titled “The Structure and Distribution of Coral Reefs,” Darwin explains his theory. He proposed that the formation of atolls was due to the lifting and sinking of the Earth’s crust beneath the oceans. Darwin outlined the process of atoll development as having three distinct stages. As the island and the ocean floor continue to sink, a fringing reef will begin to form around the perimeter of the island. As the subsidence continues, the bordering reef eventually transforms into a barrier reef, and then finally into an atoll reef.
Threats
Since their first appearance 485 million years ago, coral reefs have had to contend with a wide variety of dangers, including disease, predation, invading species, bioerosion caused by grazing fish, algae blooms, and geologic risks. New dangers have emerged as a result of recent human actions. Coral reefs around the world had a drop of 14% between 2009 and 2018.
Coral mining, bottom trawling, and the digging of canals and accesses into islands and bays are all examples of human activities that threaten coral reefs. If these activities are not carried out in a sustainable manner, they have the potential to damage marine ecosystems. Other localised threats include blast fishing, overfishing, coral overmining, and marine pollution, including the use of the banned antifouling biocide tributyltin. Although not practised in developed countries, these activities are still carried out in places where there are either few environmental protections or poor regulatory enforcement. Sunscreens contain chemicals that could reawaken dormant viral infections in zooxanthellae, which would have an effect on reproduction. On the other hand, it has been demonstrated that concentrating tourism activities via offshore platforms can restrict the spread of coral disease caused by tourists.
Even though corals are able to adjust their calcifying fluids to accommodate changes in seawater pH and carbonate levels, they are not directly threatened by ocean acidification as a result of greenhouse gas emissions. This threat manifests itself in the form of higher sea temperatures and higher sea levels. Volcanic and artificial aerosol pollution can influence regional sea surface temperatures.
Protection
Marine protected areas, often known as MPAs, are zones that have been declared as such because they offer various forms of protection to coastal and/or estuarine regions. They are designed to encourage responsible management of fisheries and the protection of habitats. MPAs have the potential to incorporate both social and biological goals, such as the restoration of reefs, the preservation of biodiversity, and the enhancement of aesthetics.
There is ongoing discussion on whether or not MPAs are effective. For instance, a research that looked at the effectiveness of a few marine protected areas (MPAs) in Indonesia, the Philippines, and Papua New Guinea discovered that the MPAs and unprotected locations were not significantly different from one another. In addition, in certain instances they might cause local conflict because there is insufficient participation from the community, divergent opinions towards the government and fisheries, the efficiency of the region, and the availability of funds. Local communities can benefit monetarily from marine protected areas (MPAs) in certain instances, such as the Phoenix Islands Protected Area. The amount of money given to them is about equivalent to the amount of money they would have made if there were no controls. Overall, it would appear that the MPAs are capable of providing protection to the local coral reefs; however, there is a need for clear management and sufficient funding.
Restoration
Because reefs have been dying off at an unprecedented rate all around the world for the past few decades, coral reef restoration has gained popularity as a solution to this problem. Some of the things that can put stress on corals are things like pollution, rising ocean temperatures, harsh weather, and exploitation. Fish nurseries, biodiversity, coastal development and livelihood, and natural beauty are all at jeopardy as a result of the degradation of coral reefs around the world. Coral restoration was an area of study that didn’t exist prior to the 1970s and 1980s, but thanks to the initiative of scientists, it exists now.
Culture of corals
Coral aquaculture, also known as coral farming or coral gardening, is showing promise as a potentially effective tool for restoring coral reefs. Other names for coral aquaculture include “coral farming” and “coral gardening.”The procedure known as “gardening” allows corals to skip over the early stages of their growth, when they are at the greatest risk of dying. After being raised in nurseries, coral seeds are eventually placed on reefs. Coral farmers are individuals whose interests range from reef conservation to increased income. They are responsible for farming coral. Coral nurseries have become the most prevalent and, arguably, the most effective method for the restoration of coral reefs. This is largely attributable to the simplicity of the process involved and the substantial evidence that the technique has a significant effect on the growth of coral reefs.
ConclusionÂ
Corals build reefs, which are aquatic habitats. Calcium carbonate binds coral colonies to form reefs. Stony corals with clustered polyps make up most coral reefs.Coral belongs to the Cnidaria Anthozoa class, which also includes sea anemones and jellyfish. Unlike sea anemones, corals secrete strong carbonate exoskeletons. Warm, shallow, clear, bright, and turbulent water is ideal for reefs. Coral reefs replaced Cambrian microbial and sponge reefs 485 million years ago.
