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The Great Barrier Reef in Australia is the world's largest Coral Reef system,12 composed of roughly 3000 individual reefs and 900 islands stretching for 2600 kilometres (1,616 mi) over an area of approximately .34 The reef is located in the Coral Sea , off the coast of Queensland in northeast Australia . The Great Barrier Reef can be seen from Outer Space and is the world's biggest single structure made by living organisms.5 This reef structure is composed of and built by billions of tiny organisms, known as Coral Polyp s.6 The Great Barrier Reef supports a wide diversity of life and was selected as a World Heritage Site in 1981. CNN has labelled it one of the Seven Natural Wonders Of The World .7 The Queensland National Trust has named it a state icon of Queensland.8 A large part of the reef is protected by the Great Barrier Reef Marine Park , which helps to limit the impact of human use, such as overfishing and tourism. Other environmental pressures to the reef and its ecosystem include water quality from runoff, climate change accompanied by mass coral bleaching, and cyclic outbreaks of the Crown-of-thorns Starfish . GEOLOGY AND GEOGRAPHY and Mackay .]] The Reef Research Centre, a Cooperative Research Centre , has found coral 'skeleton' Deposits that date back half a million years.9 The Great Barrier Reef Marine Park Authority says that corals have been growing in the region for as long as 25 million years, but have not always formed coral reef structures. The GBRMPA considers the earliest evidence to suggest complete reef structures to have been 600,000 years ago.10 Dating inconsistencies stem from how reefs fluctuate (grow and recede) as the Sea Level changes. They can increase in diameter from 1 to 2 centimetres per year, and grow vertically anywhere from 1 to 15 centimetres (0.4–12 In ) per year; however, they are limited to growing above a depth of due to their need for sunlight, and cannot grow above sea level.11 According to the of the Great Barrier Reef was a Coastal Plain with some larger hills (some of which were themselves remnants of older reefs).12 , a coral cay in the southern Great Barrier Reef.]] From 20000 years ago until 6000 years ago, the Sea Level Rose steadily. As it rose, the corals could then grow higher on the hills of the coastal plain. By around 13000 years ago the sea level was lower than the present day, and corals began to grow around the hills of the coastal plain, which were, by then, Continental Islands . As the sea level rose further still, most of the continental islands were submerged. The corals could then overgrow the hills, to form the present Cay s and reefs. Sea level on the Great Barrier Reef has not risen significantly in the last 6,000 years.The CRC Reef Research Centre estimates the age of the present, living reef structure at 6000 to 8000 years old. The remains of an ancient barrier reef similar to the Great Barrier Reef can be found in The Kimberley , a northern region of Western Australia .13 The Great Barrier Reef World Heritage Area has been divided into 70 Bioregion s,14 of which 30 are reef bioregions,15 and 40 are non-reef bioregions.1617 In the northern part of the Great Barrier Reef, Ribbon Reef s and Deltaic Reef s have formed; these structures are not found in the rest of the Great Barrier Reef system. ECOLOGY on the Great Barrier Reef]] The Great Barrier Reef supports a diversity of life, including many Vulnerable , Endangered Species and some which may be Endemic to the Great Barrier Reef.1819 Some 30 species of whales, dolphins, and porpoises have been recorded in the Great Barrier Reef, including the Dwarf Minke Whale , Indo-Pacific Humpback Dolphin and the Humpback Whale . Large populations of Dugong s live there.2021 Six species of Sea Turtle come to the reef to breed – Green Sea Turtle , Leatherback Sea Turtle , Hawksbill Turtle , Loggerhead Sea Turtle , Flatback Turtle and the Olive Ridley . 15 species of seagrass attract the dugongs and turtles. The most common Genera of seagrasses are ''Halophila'' and ''Halodule''.22 The Green Sea Turtles on the Great Barrier Reef have two Genetically Distinct Populations - one in the northern Great Barrier Reef, and the other in the southern Great Barrier Reef.23 Salt Water Crocodile s live in mangrove and saltmarshes on the coast near the Great Barrier Reef.24 Over 200 species of birds (including 40 species of waterbirds) live on the Great Barrier Reef, including the White-bellied Sea Eagle and Roseate Tern . Most nesting sites are on islands in the northern and southern regions of the Great Barrier Reef, with 1.4-1.7 million birds using the sites to breed.2526 Around 125 species of shark, stingray, skates or chimera live on the Great Barrier Reef.27The Irukandji Jellyfish also lives on the reef. Close to 5000 species of Mollusc have been recorded on the Great Barrier Reef including the Giant Clam and various Nudibranch es and Cone Snail s. Seventeen species of Sea Snake live on the Great Barrier Reef. They take three or four years to reach sexual maturity and are long lived but with low fertility. They are usually Benthic , but different species live on the soft sediment as compared to the reefs themselves. They live in warm waters up to deep. They are more common in the southern Great Barrier Reef than the northern Great Barrier Reef. None of the seasnakes found in the Great Barrier Reef World Heritage Area are endemic to the Great Barrier Reef, nor are any of them endangered.28 More than 1500 species of fish live on the reef, including the and Coral Trout . Four hundred species of corals, both Hard Coral s and Soft Coral s are found on the reef. The majority of these spawn gametes, breeding in Mass Spawning events that are controlled by the rising sea temperatures of spring and summer, the lunar cycle, and the diurnal cycle. Reefs in the inner Great Barrier Reef spawn within the week after the full moon in October, but the outer reefs spawn in November and December.29 The common soft corals on the Great Barrier Reef belong to thirty-six genera.30 500 species of Marine Algae or Seaweed live on the reef. ENVIRONMENTAL THREATS See Also: Environmental threats to the Great Barrier Reef .31 ]] The most significant threat to the Great Barrier Reef is Intergovernmental Panel On Climate Change states that the Great Barrier Reef is at grave risk and will be "functionally extinct" by 2030. Climate change has implications for other forms of life on the Great Barrier Reef as well - some fish's preferred temperature range lead them to seek new areas to live, thus causing chick mortality in seabirds that prey on the fish. Climate change will also affect the population and available habitat of sea turtles.33 Another key threat faced by the Great Barrier Reef is pollution and declining water quality. The rivers of north eastern Australia provide significant pollution of the Reef during tropical flood events with over 90% of this pollution being sourced from farms.34 Farm run-off is polluted as a result of overgrazing and excessive Fertiliser and pesticide use. Due to the range of human uses made of the water catchment area adjacent to the Great Barrier Reef, Water Quality has declined owing to the sediment and chemical Runoff from farming, and to loss of coastal Wetland s which are a natural filter.353637 It is thought that the mechanism behind poor water quality affecting the reefs is due to increased light and oxygen Competition from Algae .38 The by poor water quality and overfishing of the starfish's predators.40 (PDF) The unsustainable Overfishing of Keystone Species , such as the Giant Triton , can cause disruption to Food Chain s vital to life on the reef. Fishing also impacts the reef through increased pollution from boats, By-catch of unwanted species (such as dolphins and turtles) and reef Habitat Destruction from Trawling , Anchors and nets.41 As of the middle of 2004, approximately one-third of the Great Barrier Reef Marine Park is protected from species removal of any kind, including fishing, without written permission.42 Other threats to the Great Barrier Reef include shipping accidents, oil spills, and tropical cyclones. HUMAN USE The Great Barrier Reef has long been known to and utilised by the Aboriginal Australian and Torres Strait Islander peoples. Aboriginal Australians have been living in the area from at least 40,000 years ago,43 and Torres Strait Islanders since about 10,000 years ago.44 For these 70 or so clan groups, the reef is also an important part of their culture and spirituality.45 The reef first became known to there on June 11 , 1770 , sustaining considerable damage. It was finally saved after lightening the ship as much as possible and re-floating it during an incoming tide. One of the most famous wrecks was that of the HMS ''Pandora'' , which sank on August 29 , 1791 , killing 35. The Queensland Museum has been leading archaeological digs to the ''Pandora'' since 1983.46 Management See Also: Great Barrier Reef Marine Park After the Royal Commissions' findings, in 1975 the Government Of Australia created the Great Barrier Reef Marine Park and defined what activities were prohibited on the Great Barrier Reef.47 The park is managed, in partnership with the Government Of Queensland , through the Great Barrier Reef Marine Park Authority to ensure that it is widely understood and used in a sustainable manner. A combination of zoning, management plans, permits, education and incentives (such as Eco-tourism certification) are used in the effort to conserve the Great Barrier Reef. In July 2004, a new zoning plan was brought into effect for the entire Marine Park, and has been widely acclaimed as a new global benchmark for the conservation of , 15 June 2006 |
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