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Great Barrier Reef

2007 Schools Wikipedia Selection. Related subjects: Geography of Oceania
(Australasia)

   Satellite image of part of the Great Barrier Reef adjacent to the
   Queensland coastal areas of Proserpine and Mackay.
   Enlarge
   Satellite image of part of the Great Barrier Reef adjacent to the
   Queensland coastal areas of Proserpine and Mackay.

   The Great Barrier Reef is the world's largest coral reef system,
   composed of roughly 3,000 individual reefs and 900 islands, that
   stretch for 2,600 kilometres (1,616 mi) covering an area of
   approximately 344,400 km^2. The reef is located in the Coral Sea, off
   the coast of Queensland in northeast Australia. A large part of the
   reef is protected by the Great Barrier Reef Marine Park.

   The Great Barrier Reef can be seen from outer space and is sometimes
   referred to as the single largest organism in the world. In reality, it
   is made up of many millions of tiny organisms, known as coral polyps.
   The Great Barrier Reef was also selected as a World Heritage Site in
   1981. CNN has labelled it one of the seven natural wonders of the
   world. The Queensland National Trust has named it a state icon of
   Queensland.

Geology and Geography

   An aerial photograph of a section of the Great Barrier Reef
   Enlarge
   An aerial photograph of a section of the Great Barrier Reef

   Reefs fluctuate (grow and recede) as the sea level changes. The
   Cooperative Research Centre Reef Research Centre has found coral
   'skeleton' deposits that date back half a million years.

   According to the Great Barrier Reef Marine Park Authority, the current,
   living reef structure is believed to have begun growing on an older
   platform about 18,000 years ago. The Australian Institute of Marine
   Science places this event at 20,000 years ago - both of these estimates
   place the event at the time of the Last Glacial Maximum. At around that
   time, the sea level was 120 metres lower than it is today. The land
   that formed the substrate of the Great Barrier Reef was a coastal plain
   with some larger hills (some of which were themselves remnants of older
   reefs).

   From 20,000 years ago until 6,000 years ago, the sea level rose
   steadily. As the sea level rose, the corals could grow higher on the
   hills of the coastal plain. By around 13,000 years ago the sea level
   was 60 metres less than the present day, and corals began to grow
   around the hills of the coastal plain - by then, continental islands.
   As the sea level rose further still, most of the contiental islands
   were submerged. The corals could then overgrow the hills, to form the
   present cays and reefs. Sea level on the Great Barrier Reef has not
   risen significantly in the last 6,000 years. The research outcomes
   funded by the CRC Reef Research Centre estimates the age of the
   present, living reef structure at 6,000 to 8,000 years old.

   In the northern part of the Great Barrier Reef, ribbon reefs and
   deltaic reefs have formed - these reef structures are not found in the
   rest of the Great Barrier Reef system. The oldest dated coral on the
   reef now is a species of Porites known as boulder coral, which is only
   about 1,000 years old (it grows about 1 centimetre per year).

   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.

Species of the Great Barrier Reef

   Giant Clam on the Great Barrier Reef
   Enlarge
   Giant Clam on the Great Barrier Reef

   The Great Barrier Reef supports a diversity of life, including many
   vulnerable or endangered species. 30 species of whales, dolphins, or
   porpoises have been recorded in the Great Barrier Reef, including the
   Dwarf Minke Whale, Indo-Pacific Humpback Dolphin and the Humpback
   Whale. Also, large populations of dugongs live there. 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 Olive Ridley. 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. 5000 species of mollusc have been recorded
   on the Great Barrier Reef including the Giant Clam and various
   nudibranches and cone snails. 17 species of sea snake live on the Great
   Barrier Reef. More than 1500 species of fish live on the reef,
   including the Clownfish, Red Bass, Red-Throat Emperor, and several
   species of Snapper and Coral Trout. 400 species of corals, both hard
   corals and soft corals are found on the reef. There are 15 species of
   seagrass near the reef that attract the dugongs and sea turtles. 500
   species of marine algae or seaweed live on the reef. The irukandji
   jellyfish also lives on the reef.

Environmental threats

Water quality

   Storage Silos on the Gladstone waterfront - An industrial area in the
   water catchment area.
   Enlarge
   Storage Silos on the Gladstone waterfront - An industrial area in the
   water catchment area.

   The coastline of north eastern Australia has no major rivers, (except
   during tropical flood events caused by tropical cyclones). It also has
   several major urban centres including Cairns, Townsville, Mackay,
   Rockhampton and the industrial city of Gladstone.

   Cairns and Townsville are the largest of these coastal cities with
   populations of approximately 150,000 each. Unlike most reef
   environments worldwide, the Great Barrier Reef is the only one where
   the water catchment area is home to industrialised urban areas and
   where extensive areas of coastal lands and rangelands have been used
   for agricultural and pastoral purposes.

   Due to the range of human uses made of the water catchment area
   adjacent to the Great Barrier Reef some 400 of the 3000 reefs are
   within a risk zone where water quality has declined owing to sediment
   and chemical runoff from farming, and to loss of coastal wetlands which
   are a natural filter. Principal agricultural activity is sugar cane
   farming in the wet tropics and cattle grazing in the dry tropics
   regions. Both are considered significant factors affecting water
   quality.

   It is thought that the mechanism behind poor water quality affecting
   the reefs is due to increased light and oxygen competition from algae,
   but it has also been suggested that poor water quality encourages the
   spread of infectious diseases among corals. The long-term monitoring
   program has found an increase in incidences of coral disease in the
   period 1999-2002, although they dispute the claim that on the Great
   Barrier Reef, coral diseases are caused by anthropogenic pollution.

   Copper, a common industrial pollutant found in the waters of the Great
   Barrier Reef, has been shown to interfere with the development of coral
   polyps.

Climate change

   Bioerosion (coral damage) such as this may be caused by coral
   bleaching.
   Enlarge
   Bioerosion (coral damage) such as this may be caused by coral
   bleaching.

   Some people believe that the most significant threat to the status of
   the Great Barrier Reef and of the planet's other tropical reef
   ecosystems is climate change - comprising of global warming and the El
   Niño effect. Many of the corals of the Great Barrier Reef are currently
   living at the upper edge of their temperature tolerance, as
   demonstrated in the coral bleaching events of the summers of 1998, 2002
   and most recently 2006.

   As demonstrated in 1998, 2002 and 2006, corals expel their
   photosynthesising zooxanthellae and turn colourless, revealing their
   white calcium carbonate skeletons, under the stress of waters that
   remain too warm for too long. If the water does not cool within about a
   month, the coral will die. Australia experienced its warmest year on
   record in 2005. Abnormally high sea temperatures during the summer of
   2005-2006 have caused massive coral bleaching in the Keppel Island
   group.

   Global warming may have triggered the collapse of reef ecosystems
   throughout the tropics. Increased global temperatures are thought by
   some to bring more violent tropical storms, but reef systems are
   naturally resilient and recover from storm battering. While some
   believe that an upward trend in temperature will cause much more coral
   bleaching, others suggest that while reefs may die in certain areas,
   other areas will become habitable for corals, and form coral reefs.

   However, the trend towards ocean acidification suggests that as the
   sea's pH decreases, corals will become less able to secrete calcium
   carbonate.

   Reef scientist Terry Done has predicted a 1 degree rise in global
   temperature would result in 82 percent of the reef bleached, 2 degrees
   resulting in 97 percent and 3 degrees resulting in 'total devastation'.

Crown-of-thorns starfish

   Crown-of-thorns starfish
   Enlarge
   Crown-of-thorns starfish

   The crown-of-thorns starfish is a coral reef predator that preys on
   coral polyps by climbing onto them, extruding the stomach over them,
   and releasing digestive enzymes to then absorb the liquified tissue. An
   individual adult of this species can wipe out up to 6 square metres of
   living reef in a single year.

   Although large outbreaks of these starfish are believed to occur in
   natural cycles, human activity in and around the Great Barrier Reef can
   worsen the effects. Reduction of water quality associated with
   agriculture can cause the crown-of-thorns starfish larvae to thrive.
   Overfishing of its natural predators, such as the Giant Triton, is also
   considered to contribute to an increase in the number of
   crown-of-thorns starfish. The CRC Reef Research Centre defines an
   outbreak of crown-of-thorns starfish to be when there are more than 30
   adult starfish in an area of one hectare.

Overfishing

   The unsustainable overfishing of keystone species, such as the Giant
   Triton, can cause disruption to food chains 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. 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.

Shipping

   Shipping accidents are also a real concern, as several commercial
   shipping routes pass through the Great Barrier Reef. From 1985-2001,
   there were 11 collisions and 20 groundings on the inner Great Barrier
   Reef shipping route. The leading cause of shipping accidents in the
   Great Barrier Reef is human error.

   Although the route through the Reef is not easy, reef pilots consider
   it safer than outside the Reef in the event of mechanical failure since
   a ship can sit safely while being repaired. On the outside, wind and
   swell will push a ship towards the reef and the water is deep right up
   to the Reef so anchoring is impossible. Captain Cook in the Endeavour
   nearly came to grief that way, being utterly becalmed and pushed
   towards the reef by the swell. Right up to within 80 metres of the
   Reef, the water was so deep that no ground (to anchor against) could be
   felt with 220 metres of line.

   Waste and foreign species discharged in ballast water from ships (when
   purging procedures are not followed) are a biological hazard to the
   reef. Tributyltin (TBT) compounds found in some antifouling paint on
   ship hulls leaches into seawater and is toxic to marine organisms and
   humans; efforts are underway to restrict its use.

Oil

   It is suspected that the Great Barrier Reef is the cap to an oil trap.
   In the 1960s and early 1970s, there was some speculation about drilling
   for oil and gas there. In 1970, two Royal Commissions were ordered
   "into exploratory and production drilling for petroleum in the area of
   the Great Barrier Reef". Oil drilling is not permitted on the Great
   Barrier Reef, yet oil spills are still considered "one of the biggest
   threats to the reef", with a total of 282 oil spills between 1987-2002.

Human use of the Great Barrier Reef

   Starfish on coral - typically, tourists photograph the natural beauty
   of the reef.
   Enlarge
   Starfish on coral - typically, tourists photograph the natural beauty
   of the reef.

   The Great Barrier Reef has long been known to and utilised by
   Indigenous Australian people, whose occupation of the continent is
   thought to extend back 40,000 to 60,000 years or more. For these 70 or
   so clan groups, the reef is also an important part of their Dreamtime.

   The Reef first became known to Europeans when the HM Bark Endeavour,
   captained by explorer James Cook, ran aground there on June 11, 1770
   and sustained 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.

Management

   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. 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 marine ecosystems. While protection across the
   Marine Park was improved, the highly protected zones increased from
   4.5% to over 33.3%. At the time, it was the largest marine protected
   area in the world, although as of 2006, the Northwestern Hawaiian
   Islands National Monument is the largest.

   In 2006, a review was undertaken of the Great Barrier Reef Marine Park
   Act 1975. Some recomendations of the review are that there should be no
   further zoning plan changes until 2013, and that every five years, a
   peer-reviewed Outlook Report should be published, examining the health
   of the Great Barrier Reef, the management of the Reef, and
   environmental pressures.
   A scuba diver looking at a giant clam on the Great Barrier Reef
   Enlarge
   A scuba diver looking at a giant clam on the Great Barrier Reef

Tourism

   Due to its vast biodiversity, warm clear waters and its accessibility
   from the floating guest facilities called ' live aboards', the reef is
   a very popular destination for tourists, especially scuba divers. Many
   cities along the Queensland coast offer boat trips to the reef on a
   daily basis. Several continental islands have been turned into resorts.

   As the largest commercial activity in the region, it has been estimated
   in 2003 that tourism in the Great Barrier Reef generates over AU$4
   billion annually. (A 2005 estimate puts the figure at AU$5.1 billion.)
   There are approximately two million visitors to the Great Barrier Reef
   each year. Although most of these visits are managed in partnership
   with the marine tourism industry, there are some very popular areas
   near shore (such as Green Island) that have suffered damage due to
   overfishing and land based run off.
   A glass-bottomed boat on the Great Barrier Reef
   Enlarge
   A glass-bottomed boat on the Great Barrier Reef

   A variety of boat tours and cruises are offered, from single day trips,
   to longer voyages. Boat sizes range from dinghies to superyachts.
   Glass-bottomed boats and underwater observatories are also popular, as
   are helicopter flights. But by far, the most popular tourist activities
   on the Great Barrier Reef are snorkelling and diving. Pontoons are
   often used for snorkelling and diving. When a pontoon is used, the area
   is often enclosed by nets. The outer part of the Great Barrier Reef is
   favoured for such activities, due to water quality.

   Management of tourism in the Great Barrier Reef is geared towards
   making tourism ecologically sustainable. A daily fee is levied that
   goes towards research of the Great Barrier Reef. This fee ends up being
   20% of the GBRMPA's income.Plans of management are also in place for
   the popular tourist destinations of Cairns and the Whitsunday Islands,
   which comprise 85% of tourism in the region. Policies on cruise ships,
   bareboat charters, and anchorages limit the traffic on the Great
   Barrier Reef. The 2003 Pixar film, Finding Nemo, featured the Great
   Barrier Reef as a setting.

Fishing

   The fishing industry in the Great Barrier Reef, controlled by the
   Queensland Government, is worth AU$1 billion annually. It employs
   approximately 2000 people, and fishing in the Great Barrier Reef is
   pursued commercially, for recreation, and as a traditional means for
   feeding one's family. Wonky holes in the reef provide particularly
   productive fishing areas.

Gallery

   Clownfish on the Great Barrier Reef

   Satellite image of the northernmost part of the Great Barrier Reef

   Snapping Turtle on the Great Barrier Reef
   Retrieved from " http://en.wikipedia.org/wiki/Great_Barrier_Reef"
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   with only minor checks and changes (see www.wikipedia.org for details
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