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The Great Barrier Reef

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The Great Barrier Reef.

Located in the Coral Sea off the north-east coast of Australia, the Great Barrier Reef is one of the greatest natural wonders of the world and in 1981 was listed as a World Heritage site. It measures 348,700 square kilometres in area and is about 2,300 kilometres long, running from just north of Bundaberg to the tip of the Cape York Peninsula. The Great Barrier Reef contains over 3,000 reefs, which vary in size from 1 hectare to over 10,000. It also includes 760 fringing reefs1, 300 coral cays2 and 618 continental islands3. As the world's largest coral reef ecosystem, the Great Barrier Reef is home to a large population of dugong, 1,500 species of fish, 400 species of coral, 4,000 species of mollusc, 500 species of seaweed, 215 species of bird, 16 species of sea snake and six species of sea turtle.

Past and Present

Historically, the Great Barrier Reef has caused problems for many a ship, dating back to 1770 when Captain James Cook bumped into it in the Endeavour. This event lead to Cooktown being founded. The most famous wreck to have occurred due to the existence of the Great Barrier Reef is that of HMS Pandora in 1791, which is still being examined today. Of course, the reef has been known to the aboriginal people for many millennia: they possibly encountered the reef as long ago as 60,000 BC, at about the time when the reef first started to form. The aboriginals used the reef to sustain themselves as well as others that lived off it; today they help the Great Barrier Reef Marine Park Authority maintain this natural beauty. The GBRMPA was established in 1975. It is the largest marine park in the world and is funded by Australian and Queensland Governments. The latter also oversees the Park Authority and ensures that the Reef is used appropriately, protected and understood by visitors.

Marine Life


At first sight, coral may be believed to be just a rock on the seabed, but in actual fact it is something more fascinating. It is actually created by living animals called polyps that produce a chalky, limestone skeleton as they expand. Coral can be seen to expand when the polyps multiply and divide in a technique known as budding.

Polyps take their nourishment from planktonic4 prey, including simple single-celled algae5 called zooxanthellae6(pronounced zoo-zan-thelly). Coral that lives off zooxanthellae expands faster than that which doesn't. Coral comes in various colours, shapes and sizes. Some agglomerations create features such as bommies7 and drop-off cliffs8. Coral displays many vibrant colours as a result of live coral and its algae that can reach an age of hundreds of years. To see these wonderful colours it is best to view the coral at night using a halogen lamp shone from above. Every year, around the full moon in November, the sea spreading up the reef from Lady Elliot Island in the south gradually turns pink. This is due to 135 species of hard coral releasing their eggs and sperm for fertilisation. It takes about two weeks for coral to reproduce before the water appears clean again.


One of the most encouraging tourist attractions to the Great Barrier Reef is that it is home to about 1,500 million fish and every year this number multiplies - as well as the amount of species that can be found. In just one hectare alone there can be in the region of 200 species of fish with different sizes, shapes and colours that can be categorised and identified. Angelfish, bannerfish, moorish idol, batfish, blennies, gobies, lizardfish, needlefish, halfbeaks, porcupinefish, pufferfish, snappers, soldierfish, squirrelfish, triggerfish, damselfish, Maori wrasse, butterfly fish, cardinal fish, groupers, rockcods and basslets, parrotfish, surgeonfish, triggerfish and anemone fish or clown fish can all be found swimming around the coral. However, as amazing as these fish are, they don't eat food outside the coral reef so it's best if visitors don't feed them.

Sea Turtles

The reef is home to six of the seven known species of sea turtle, which are: green, leatherback, hawksbill, loggerhead, flatback and Olive Ridley. When the eggs belonging to sea turtles are laid, the creatures possess no gender. In fact it is the job of the sand to determine the sex of the sea turtles. The females who become sexually active at 30 - 50 years old can lay 100 eggs at any one time. Ocean currents aid the hatchlings into the waters and they can travel hundreds of miles before becoming fully grown. When they too become old enough to have babies they return to where they were hatched and lay their eggs there. The leatherback is the biggest sea turtle, weighing in at 916kg.


Closely related to elephants rather than any marine animal, the dugong (Dugong dugon) is the smallest member of the order Sirenia (which also includes the manatees and Steller's sea cow). It weighs in at 400 kg and measures 3m in length. Its name originated from the Malay word 'duyung', meaning 'lady of the sea' or 'mermaid'. Dugong can live up to 70 years and feed off sea grass9. They give birth once every 2½ - 5 years after they've had their first calf, between the ages of 6 - 17 years old. Groups of 10,000 or more are present on the Great Barrier Reef of Australia, at Shark Bay, and in Torres Strait, which is south of New Guinea.


The Great Barrier Reef is home to around 4,000 species of mollusc, including the giant clam - the world's largest bivalve mollusc - which reaches the great age of 70 years and measures 1m in length. Most giant clams are hermaphrodites. The feathery gills of a mollusc allow them to absorb the oxygen from the water.


The reef is also home to many sea birds such as reef herons, osprey, pelicans, frigate birds, sea eagles and shearwaters. Among these are also white-breasted sea eagles which inhabit the coast and islands, and feed off fish that swim close to the surface of the water. The roseate tern can also be found here as well as in Japan, while other birds fill the air and live off the reef and its environment.

Sea Snakes

Although most sea snakes can be found living in the waters of Singapore and Borneo, there are also a lot that live off the Great Barrier Reef. In fact, there are in the region of 17 - 21 species of sea snake and Australia is home to at least 14 of them. Ideally, sea snakes are suited to tropical waters, but they can also be found in subtropical seas.


Cetaceans comprise porpoises, dolphins and whales.


Dolphins belong to the Delphinidae and, in some cases, Platanistoidea and Odontoceti families. They evolved about 10 million years ago and there are now in existence about 40 types of dolphin, within 17 genera. They differ in size from the 1.2m and 40kg (Maui's dolphin), to the 9.5m and 10 tons (the orca). Many of the dolphin species are known to weigh about 50 - 200 kg and can be found all over the world. One particular species native to the Great Barrier Reef habitat is the rare irrawaddy inshore dolphin. The irrawaddy dolphin has a rounded head with no beak, and a flexible neck. They can vary in colour from dark and light blue-grey to pale blue. It is grouped as an oceanic dolphin and is carnivorous, living off a diet of fish and squid. Irrawaddy dolphins also carry features which are similar to both the porpoise and the beluga whale, and therefore sometimes prove difficult to define. They have a special relationship with the fishermen at the Great Barrier Reef, helping to guide the fish into their nets.


Porpoises belong to the same Phocoenidae family as whales and dolphins. Although often perceived as similar to dolphins, porpoises differ from them due to the shape of their heads and teeth. There are six varieties of porpoise in the world that swim the oceans close to the shore.


Whales usually appear around the Great Barrier Reef during winter, when they migrate from the waters of the Antarctic to those of the Pacific in order to mate and give birth. Many tour operators run excursions during these months to see the whales, which range from the humpback to the minke, and even dolphins can be seen in these waters too.


Visitors to the Great Barrier Reef have even been known to spot sharks (superorder Selachimorpha). The most common are the white-tip and black-tip reef sharks. Most sharks found at the reef pose no threat to visitors, due to the fact that they eat only fish. However, they may attack if given sufficient provocation.


The box jellyfish inhabits North Queensland coastal waters during the summer months (October to March). People wishing to swim at this time of year should do so in protective clothing or enclosures. The box jellyfish is not commonly found out on the reef, but they do surround the mainland. Although incredibly rare, it is the irukandji and blue bottle jellyfish that are usually linked to the reef's habitat. It is believed that to treat the stings of the box and irukandji jellyfish, vinegar (or alcohol) can be used. However, others believe that vinegar would not work on the irukandji as it is fatal. Blue bottle stings can not be treated by vinegar either, as it heightens the degree of the sting. For blue bottle stings, it is best to use cold water and ice.


Global Warming

It is believed that global warming appears to have the greatest impact on reefs, triggering the collapse of reef ecosystems throughout the tropics. It also appears to create tropical storms, which batter the reef - but due to its ribbons, the inner reef withstands these attacks. Coral bleaching also appears to be happening, due to the water's temperature rising as a result of global warming and the El Nino effect. Coral bleaching is when the coral turns white due it expelling its zooxanthellae while under environmental strain. If the water temperatures continue at this high level, the whole Great Barrier Reef faces extinction.

Crown of Thorns Starfish

Not all the creatures living off the Great Barrier Reef do so in harmony with it. For instance, the crown of thorns starfish, first noted for its existence in the 1960s, creates havoc with the beauty and diversity of the reef by crawling on top of the coral and absorbing its nutrients, leaving the coral helpless and dying. However, the GBRMPA has been closely watching this species, keeping an eye on its spread and is hoping to develop control mechanisms when it is better understood.

Human Activity

Each year, over 2 million visitors view the reef and marvel in its beauty and diversity. However, it is thought that people have a negative effect on the Great Barrier Reef. For if people touch the coral reef, drop an anchor on it or spill fuel on it, then it dies. As a result, people are warned not to anchor on the reef but to do so in its lagoons instead.

Coastwatch and the GBRMPA have set up maps regarding fishing, diving and other activities for people to see.

It is not just the human activity next to the reef that causes negative impacts. Sited on the mainland is agricultural and industrial activity that could affect the reef if poisonous chemicals and the like came into contact with the water.

Furthermore, although the people inside the park are regulated in number, there are also some popular regions nearby - such as Green Island - that don't have such stringent controls.

Land clearance along river banks is causing increased sediment loading of the rivers running into the coral sea, which is also thought to be having an impact upon the reef's ecosystem.

Fisheries in the Great Barrier Reef Marine Park are also vital to the reef, because they help sustain livelihoods, lifestyles and economies of Queensland coastal communities.


With the help of various organisations in Australia, many people are getting involved with helping to secure a brighter future for the Great Barrier Reef. This includes people from the nearby Universities such as James Cook University (JCU), which runs projects on the reef, such as examining its sedimentary dynamics.

If you'd like to help preserve one of the greatest wonders of the world, why not take a trip out to Australia and see the Great Barrier Reef for yourself?

1These are corals that form adjacent to the shoreline.2Small banks or islands covered with sand and coral fragments.3Found on the continental shelf, formed by the same geological processes of folding, etc, as continents. They are distinct from oceanic islands which are the tops of underwater volcanoes.4Plankton is created from both small plants (phytoplankton) and animals (zooplankton), which are carried by the water.5Tiny plants that carry chlorophyll and are carried by the water.6A type of algae that lives within coral tissue and other animals and provides coral food through photosynthesis.7A 'turret' of different corals projecting from the sand seabed, the top of which are usually only exposed at spring low tides.8The vertical drop at the edge of a plateau of mixed corals, down the side of which holes abound in which fish and other predators lurk.9Sea grass differs from seaweed and algae as it has true roots and flowering plants.

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