Coral Reef Present Condition

A coral reef is an aquatic habitat dominated by corals that construct reefs. 

The Cnidaria animal kingdom is home to a wide variety of marine organisms, including sea anemones, jellyfish, and coral, which are all members of the Anthozoa class.Corals secrete hard carbonate exoskeletons that support and protect them, unlike sea anemones. The majority of reefs require water that is warm, shallow, clear, bright, and disturbed in order to grow. The microbial and sponge reefs of the Cambrian period were replaced by coral reefs at the beginning of the Early Ordovician period, which occurred 485 million years ago.

Some of the most diversified ecosystems on the globe can be found on shallow coral reefs, sometimes known as marine rainforests.They cover less than 0.1 percent of the world’s oceans, roughly half the size of France, but they are home to at least 25% of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates, and other cnidarians . Coral reefs thrive in ocean conditions with little nutrients.

Coral reefs have decreased by 50% since 1950, owing to their sensitivity to sea conditions. Excess nutrients (nitrogen and phosphorus), rising ocean temperatures and acidification, overfishing (e.g., blast fishing, cyanide fishing, scuba spearfishing), sunscreen use, and detrimental land-use practises, such as runoff and seeps, are also threats (e.g., from injection wells and cesspools).

Formation

The majority of coral reefs were produced after the Last Glacial Period, when sea level rose and flooded continental shelves due to melting ice. The majority of coral reefs are under 10,000 years old. Reefs rose upwards as populations grew, keeping pace with rising sea levels. Reefs that climbed too slowly could drown if there wasn’t enough light. [18] Coral reefs can be found in the deep ocean, far from continental shelves, and near oceanic islands and atolls. The majority of these islands were formed by volcanic activity. Others are the result of tectonic events that raised the deep ocean floor.

Charles Darwin laid out his theory of atoll reef development in The Structure and Distribution of Coral Reefs , a notion he conceived during the Beagle voyage. He proposed that the atolls were generated by uplift and subsidence of the Earth’s crust beneath the waters.  Atoll formation is divided into three stages, according to Darwin. As the island and the ocean floor erode, a fringing reef emerges around an extinct volcanic island. The bordering reef eventually becomes a barrier reef and then an atoll reef as the sinking proceeds.

The State of Coral Reefs Today

Coral reefs cover less than 1% of the Earth’s surface but feed and shelter a large number of marine creatures, including over 4,000 fish species. Reefs provide food, coastal protection, and livelihood for at least 500 million people. NOAA estimates that the commercial value of coral reef fisheries in the United States is more than $100 million per year. Reefs provide billions of dollars in revenue each year from fishing and tourists around the world.

Tropical coral reef coverage has dropped by 30 to 50 percent worldwide since the 1980s, according to a report from the National Academies of Sciences, Engineering, and Medicine’s Committee on Interventions to Increase the Resilience of Coral Reefs. Pollution, habitat degradation, overfishing, and, increasingly, a changing climate that raises temperatures, sea level, and acidity in the waters threaten about 75% of the world’s reefs.

Corals struggle to build and maintain their calcium carbonate skeletons as ocean waters absorb carbon dioxide and become increasingly acidic, making reefs more vulnerable to storms and predators. Slow-growing reefs may be deprived of critical sunlight as water levels rise. Disease outbreaks and bleaching occurrences become more common as temperatures rise.

When corals lose their photosynthetic algae, they are said to be bleached. Coral reefs are made up of thousands of individual organisms known as polyps that obtain 80% of their nutrition from algae residing in their tissues. All coral species have specific temperature ranges, and disturbed corals expel the vibrantly coloured algae at temperatures exceeding that range. The skeleton of the coral then appears white, or bleached. If water temperatures return to normal, algae may regrow from a tiny number of cells that were not evacuated. Otherwise, the coral will die of starvation.

Coral bleaching episodes that occur simultaneously in the Atlantic, Pacific, and Indian Oceans are known as global coral bleaching events. Between 1997 and 1998, the first documented global bleaching event occurred, with at least 15% of reefs worldwide dying. A second incident occurred in 2010, and a third occurred between June 2014 and May 2017. According to the National Oceanic and Atmospheric Administration’s Coral Reef Watch, that one devastated more than 70% of the world’s reefs, making it the longest, most extensive, and most devastating event on record. It damaged reefs that had never bleached before, notably the Great Barrier Reef’s northernmost section.

Zones

Coral reef ecosystems are divided into zones that house various habitats. The fore reef, reef crest, and rear reef are the three major zones that are usually recognised (frequently referred to as the reef lagoon).

Physically and ecologically, the three zones are linked. Seawater, sediments, nutrients, and marine life can all be exchanged thanks to reef life and oceanic processes.

The majority of coral reefs are found in waters less than 50 metres deep. Others, such as the Maldives, are found in the deep ocean encircling islands or as atolls. When islands sink into the ocean, reefs grow around them, while atolls form when an island sinks below the water’s surface.

The reef surface is the reef’s shallowest portion. It is affected by tides and surges. Waves shoal when they pass over shallow places, as seen in the diagram below. This indicates that the water is frequently disturbed. These are the ideal conditions for corals to thrive. The photosynthesis of the symbiotic zooxanthellae is sufficient, and agitated water provides plankton to feed the coral.

The shallow seafloor surrounding a reef is known as the off-reef floor. On continental shelves, this zone is found near reefs. Reefs near tropical islands and atolls have no such floor and drop suddenly to tremendous depths. The seagrass meadows, which are key foraging grounds for reef fish, are commonly found on the sandy floor.

Protection

Marine protected areas (MPAs) are defined zones that provide ocean and/or estuary areas with varying types of protection. They’re meant to encourage prudent fisheries management and habitat preservation. MPAs can also be used to achieve social and ecological goals such as reef restoration, beauty, biodiversity, and economic benefits.

MPAs’ effectiveness is still up for dispute. A study evaluating the effectiveness of a small number of MPAs in Indonesia, the Philippines, and Papua New Guinea, for example, found no significant differences between MPAs and unprotected locations. Furthermore, because to a lack of community participation, conflicting perspectives of the government and fisheries, the efficacy of the area, and funding, they can sometimes cause local conflict. MPAs can give revenue to people in some cases, such as the Phoenix Islands Protected Area. The amount of money granted is comparable to what they would have earned without the controls. Overall, it appears that MPAs can conserve local coral reefs, but clear management and enough funding are essential.

According to the Caribbean Coral Reefs – Status Report 1970–2012, coral decline could be slowed or even reversed. Overfishing, particularly of coral reef-critical species like parrotfish, must be prevented as a result. The amount of direct human impact on coral reefs should be reduced, as well as the inflow of sewage. Restricting coastal settlement, development, and tourism could be used to achieve this. The findings demonstrate that reefs in the Caribbean with big, robust populations of parrotfish are healthier. These exist in countries where parrotfish and other species, such as sea urchins, are protected. Fish trapping and spearfishing are frequently prohibited. These measures work together to help create “resilient reefs.”

Conclusion 

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.