Great Barrier Reef Australia

The Great Barrier Reef
The World's Largest Coral Reef

The Great Barrier Reef stretches along the east coast of Queensland Australia. It is the world's largest coral reef and the only living organism large enough to be visible from space. It is over 2000km (1250 miles) long and between 60 kilometres to 250 kilometres wide. It is made up of a collection of over 2900 individual reefs very close to each other. It was declared a World Heritage area in 1975.

Over 1.6 million tourist visit the the Great Barrier Reef each year and over 6000 ships navigate through it each year. It is ideal for water sports such as sailing, snorkelling, and diving.  There is also an underwater observatory from where you can see the fantastic underwater biodiversity.

Barrier Reef Coral

What is a Coral Reef

A coral reef   is a natural barrier made of the bodies of millions of living and dead coral polyps. These polyps grows just below the surface to a depth of up to 60 m in warm climates where there is clear salt water and sunlight. It is made of two parts: Coral Polyp

Coral polyps: The colourful part of the coral is made up of millions of different sorts of marine polyps. These are soft-bodied invertebrate animals which have no backbone. An individual polyp has a tubular body with tentacles surrounding the mouth at the upper end. They form the living part of the coral. These polyps feed on various small organisms, from microscopic plankton to small fish. The polyp's tentacles grab onto their prey and kill them using stinging cells called nematocysts. The tentacles then contract to bring the prey into the stomach. Once digested, the stomach reopens and the waste products are eliminated. The polyp lives inside a stony limestone case it makes by extracting calcium from the water. Symbiotic algae live on the coral and transform sunlight into sugars through photosynthesis. The coral host help itself to some of the sugars and contributes some colour to the coral.

Hard corals: These are the remains of the cases dead polyps which have accumulated over the eons to form the solid portions and some the frameworks of some of the delicate and intricate structure of the of the reef.

Who Lives in the Great Barrier Reef?

The Great Barrier Reef is home to one of the world's most diverse range of underwater plants and animals.

  • 1500 species of fish
  • 360 different types of coral
  • 5,000 molluscs (like clams and the sea slug)
  • 500 species of seaweed
  • 215 species of birds
  • 17 species of sea snake
  • 6 species of sea turtle (all listed as threatened)
  • 400 species of marine algae
  • 600 species of echinoderm ( starfish, sea urchins)
  • 30 species of cetaceans (whales and dolphins).
  • 22 species of sea birds and 32 species of shorebirds

Threats to the Great Barrier Reef

Crown of Thorns Starfish

Natural Factors

Environmental: Coral is very sensitive changes to temperature, nutrient and water quality. Just a 1 or 2 degree change in the water temperature has been known to stress coral and cause coral bleaching. It is feared that global warming may severely impact the reef.

Crown of Thorns: These starfish destroy coral by eating it. It was once thought of as a great risk to the reef but recent research has shown that it is actually native to this habitat and may actually act as a means of natural population control by eating coral polyps and making room for new coral to form. Once in a bout every 17 years they appear to plague proportions denuding vast tracts of the reef. It is thought that these outbreaks are related to increased rainfall and nutrient flows from flooded rivers.

Algae: The symbiotic algae which usually resides with the coral can sometimes put strain on the host causing it to to eject the algae. Mass expulsions of the algae is known as coral bleaching (because the algae contribute to coral's brown colouration). This ejection seems to increase the polyp's chances of dealing with short-term stress. If the stressful conditions persist, the polyp eventually dies.

diving in the Great Barrier Reef


These reefs take thousands of years to form. People can easily damage them by carelessness such as by:

  • Walking on them
  • Dropping anchors on them
  • Dragging diving gear over them
  • Breaking them and taking them home as souvenirs
  • Knocking and grounding boats on them

Fortunately strict guidelines are presently enforced on all tour operators to ensure the protection of this vital natural asset.


Stranded ship on the reef


The Great Barrier Reef is a protected wilderness areas and since 1975 is now being strictly managed to minimise human induced pollutants. However the reef straddles an area with significant human activity.

Oil Spills and Ships Running Aground: Busy shipping channels traverse the reef and Stranded Ship on Barrier Reefoccasionally mishaps occur. Most recently bulk coal carrier Shen Neng 1 ran aground about 70km east of Great Keppel Island damaging its hulk and leaked a quantity of fuel oil into the water (The light blue area in the photograph on the left is caused by sand stirred up by the grounded vessel and not the actual fuel oil which was quickly contained).

Dumping and River Run-offs: Sediments and nutrients, fertilisers, pesticides, toxic chemicals, sewage, rubbish, detergents, heavy metals and oil run into rivers and out to the Great Barrier Reef lagoon, where they can threaten plants and animals on the reef.





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