The Great Barrier Reef, located in the Australian continental shelf, is the largest coral reef group in the world.
Single reefs up to nearly 3,000 in number – scatter from Gladstone, Queensland to the Gulf of Papua in Papua New Guinea – make up this natural wonder.
According to scientists, the Great Barrier Reef started forming around 500,000 years ago, when the sea was approximately 20 meters higher than its present level.
Around 125,000 years ago, when the sea was believed to be more or less the same as its present level, was when the reefs started developing on the Australian continental shelf. Large portion of this shelf was exposed as a continental plain some 20,000 years ago; when the sea was 130 meters lower than its current level and majority of the earth’s body of water was in the form of ice.
aerial view of The Great Barrier Reef
Green Island - Great Barrier Reef - Australia
Around 18,000 years ago, the level of the sea rose again, forming new seas which covered the existing reefs, those which rose from the continental plain – hills made up of limestone. During this time, corals started growing in the new seas.
CORAL REEF BUILDERS
Reefs are made up of skeletons of coralline algae and dead corals that were held together by lime stones from tiny animals known as coral polyps and plants known as coralline algae.
The most suitable condition for the growth of coral reef builders is that which provides constant water temperature [20º C or higher] and the presence of sunlight. Such condition can only be found from mid-tide down to a level of about 40 meters. Aeration or the joining of air and water and the presence of nutrients which serve as food are also very essential to the coral reef builders’ growth.
The presence of color in the reef is caused by pigments in the polyps’ tissues. Polyps’ tissues also serve as habitats of zooxantellae. These are single-celled plants which are partly responsible for the success of coral reef builders.
Among marine environments that give shelter to different kinds of marine animals, particularly fish, the coral reefs are said to cater the most inhabitants.
TERMS TO REMEMBER
Continental islands
These are mountains that were cut off from the mainland as the sea covered the coastal plain.
Coral cays
These are small islands that were formed as the waves, wind and tidal currents piled rubble, shingle or sand deposit on large reef tops.
PLACES TO VISIT:
Whitsunday Island
Although the Whitsunday group is where most resorts in the region can be found, only the resorts located in Green Island, Heron Island and Lady Elliott Island are the ones that can be considered part of the reef itself.
Source: World Book Millennium 2000 [International]
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