Coral reef

Biodiversity of a coral reef
Marine habitats
Coastal habitats
Ocean surface
Open ocean
Sea floor

A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate.[1] Most coral reefs are built from stony corals, whose polyps cluster in groups.

Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons that support and protect the coral. Most reefs grow best in warm, shallow, clear, sunny and agitated water. Coral reefs first appeared 485 million years ago, at the dawn of the Early Ordovician, displacing the microbial and sponge reefs of the Cambrian.[2]

Sometimes called rainforests of the sea,[3] shallow coral reefs form some of Earth's most diverse ecosystems. They occupy less than 0.1% of the world's ocean area, about half the area of France, yet they provide a home for at least 25% of all marine species,[4][5][6][7] including fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates and other cnidarians.[8] Coral reefs flourish in ocean waters that provide few nutrients. They are most commonly found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas.

Shallow tropical coral reefs have declined by 50% since 1950, partly because they are sensitive to water conditions.[9] They are under threat from excess nutrients (nitrogen and phosphorus), rising ocean heat content and acidification, overfishing (e.g., from blast fishing, cyanide fishing, spearfishing on scuba), sunscreen use,[10] and harmful land-use practices, including runoff and seeps (e.g., from injection wells and cesspools).[11][12][13]

Coral reefs deliver ecosystem services for tourism, fisheries and shoreline protection. The annual global economic value of coral reefs has been estimated at anywhere from US$30–375 billion (1997 and 2003 estimates)[14][15] to US$2.7 trillion (a 2020 estimate)[16] to US$9.9 trillion (a 2014 estimate).[17]

Though the shallow water tropical coral reefs are best known, there are also deeper water reef-forming corals, which live in colder water and in temperate seas.

  1. ^ "How Reefs Are Made". Coral Reef Alliance. 2021. Archived from the original on 30 October 2021. Retrieved 19 April 2022.
  2. ^ Lee, Jeong-Hyun; Chen, Jitao; Chough, Sung Kwun (1 June 2015). "The middle–late Cambrian reef transition and related geological events: A review and new view". Earth-Science Reviews. 145: 66–84. Bibcode:2015ESRv..145...66L. doi:10.1016/j.earscirev.2015.03.002. ISSN 0012-8252.
  3. ^ Coral reefs Archived 10 February 2010 at the Wayback Machine NOAA National Ocean Service. Accessed: 10 January 2020.
  4. ^ Spalding MD, Grenfell AM (1997). "New estimates of global and regional coral reef areas". Coral Reefs. 16 (4): 225–230. Bibcode:1997CorRe..16..225S. doi:10.1007/s003380050078. S2CID 46114284.
  5. ^ Cite error: The named reference Spalding was invoked but never defined (see the help page).
  6. ^ Mulhall, M. (Spring 2009). "Saving rainforests of the sea: An analysis of international efforts to conserve coral reefs". Duke Environmental Law and Policy Forum. 19: 321–351. Archived from the original on 6 January 2010.
  7. ^ "Where are Corals Found?". NOAA Coral Reef Conservation Program. NOAA. 13 May 2011. Archived from the original on 4 March 2016. Retrieved 24 March 2015.
  8. ^ Hoover, John (November 2007). Hawaiʻi's Sea Creatures. Mutual. ISBN 978-1-56647-220-3.
  9. ^ Greenfield, Patrick (17 September 2021). "Global coral cover has fallen by half since 1950s, analysis finds". The Guardian. Retrieved 18 September 2021.
  10. ^ Danovaro, Roberto; Bongiorni, Lucia; Corinaldesi, Cinzia; Giovannelli, Donato; Damiani, Elisabetta; Astolfi, Paola; Greci, Lucedio; Pusceddu, Antonio (April 2008). "Sunscreens Cause Coral Bleaching by Promoting Viral Infections". Environmental Health Perspectives. 116 (4): 441–447. doi:10.1289/ehp.10966. PMC 2291018. PMID 18414624.
  11. ^ "Corals reveal impact of land use". ARC Centre of Excellence for Coral Reef Studies. Retrieved 21 September 2013.
  12. ^ Minato, Charissa (1 July 2002). "Urban runoff and coastal water quality being researched for effects on coral reefs" (PDF). Archived from the original (PDF) on 10 June 2010.
  13. ^ "Coastal Watershed Factsheets – Coral Reefs and Your Coastal Watershed". Environmental Protection Agency Office of Water. July 1998. Archived from the original on 30 August 2010.
  14. ^ Cite error: The named reference Cesar was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Costanza was invoked but never defined (see the help page).
  16. ^ "The Sixth Status of Corals of the World: 2020 Report". GCRMN. Retrieved 5 October 2021.
  17. ^ Costanza, Robert; de Groot, Rudolph; Sutton, Paul (2014). "Changes in the global value of ecosystem services". Global Environmental Change. 26 (1): 152–158. Bibcode:2014GEC....26..152C. doi:10.1016/j.gloenvcha.2014.04.002. S2CID 15215236.