What is the Great Barrier Reef?
The Great Barrier Reef is a coral reef which stretches along the east coast of Queensland Australia. It is made up of a collection of over 2,900 individual reefs located very close to each other. It is also dotted with over 900 idyllic white-beached islands.
The Great Barrier Reef is the largest coral reef in the world. It is so large, in fact, that it is the only living organism big enough to be visible from space. It was declared a World Heritage area in 1975.
Over 2.1 million tourist visit the Great Barrier Reef each year this generates approximately $5-6 billion dollars in revenue. It is ideal for snorkelling, scuba diving, sailing, whale and dolphin watching and lots more. There is also an underwater observatory from where you can see the fantastic underwater biodiversity.
Over 6,500 ships navigate through it each year.
Where is Great Barrier Reef Located?
The Great Barrier Reef (marked in Grey on the map) is located off the north-eastern coast of Queensland, Australia. (This coast is also referred to as the Gold Coast). It extends from the tip of Cape York Peninsula in the north to Bundaberg in the south. This is a length of nearly 2,300 km (1,450 miles). The breath of the coral reef varies from between 60 to 250 kilometres wide (37 — 155 miles).
Length of the Great Barrier Reef
The Great Barrier Reef is 2,300 km (1,450 miles) long. This is about the same distance along the west coast of North America starting at Vancouver and ending in San Diego.
What is a Coral Reef?
A coral reef is a natural barrier made of the bodies of millions of living and dead coral polyps.
Corals are constructed by animals related to jellyfish and anemones. An individual coral is known as a polyp. Coral 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:
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.
These are the remains of the cases of dead polyps which have accumulated over the centuries to form the solid framework on which living coral thrive. They give shape to the delicate and intricate structures of the coral reef.
How Old is the Great Barrier Reef?
The age of the Great Barrier Reef is about 6,000 to 8,000 years.
The original coral reefs started forming in the Pacific Ocean, in the Coral Sea, sometime between 58 and 48 million years ago. There were many reefs formed and then destroyed and reformed over the ensuing millions of years. When Australia drifted to its present position, the sea levels were altered around the area accelerating the formation of more coral reefs. The present coral reef is believed the have had two major phases of development. The first was about 600,000 years ago. This reef died due to changes in sea level and climate. The second phase started about 20,000 years ago when new coral started to grow on top of the remains of the older reef. As the sea levels rose, at end of the last glaciation period, the rising sea water started to cover low lying hills along the east coast of Australia. The coral reefs slowly started growing on this newly submerged land. Around 13,000 years ago the sea level stabilized. The current Great Barrier Reef configuration is about 6,000 to 8,000 years old.
Great Barrier Reef Animals
- • 1500 species of fish
- • 360 types of coral
- • 5,000 molluscs (like clams and the sea slug)
- • 215 species of birds
- • 17 species of sea snake
- • 6 species of sea turtle (all listed as threatened)
- • 600 species of echinoderm ( starfish, sea urchins)
- • 30 species of cetaceans (whales and dolphins).
- • 22 species of sea birds and 32 species of shorebirds.
Great Barrier Reef Plants
The Great Barrier Reef is home to a wide variety of underwater grasses and seeweed.
There are 15 species of sea grasses on the Great Barrier Reef.
See grasses grow in shallow water where sun light reaches them as they require sunlight for photosynthesis. They are true plants (unlike seaweed and algae) with roots, flowers and seeds. Since they are true flowering plants (angiosperms), male flowers release pollen into the water where they are moved by waves and ocean current and encounter female flowers to pollinate. These flowers then develop seeds which when release can float many miles before settling onto the sea floor and germinating into new plants. Phenomenally, one square meter of sea grass can generate up to 10 litres of oxygen a day. Vast meadows of them cover such huge areas that they are visible from outer space. They are home to a diverse community of organisms. . Sea grass meadows. They are an important food source for turtles, dugongs, fish, octopuses, squids, cuttlefish, snails, oysters, sponges, shrimps, sea fleas, worms, urchins, anemones, micro-algae, crabs, polychaetes, clams, diatoms, dinoflagellates, copepods and many other creatures.
Seeweeds are marine algae. There are over 400 species of marine algae. Red and brown algae are found closer to the shore while red and green algae are more prevalent in offshore areas. Seaweeds require sunlight for photosynthesis and a firm attachment point of which to fix themselves.
Natural Threats to the Great Barrier Reef
The Great Barrier Reef is a very sensitive ecosystem. Many natural factors affect its heath.
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.
The symbiotic algae which usually resides with the coral can sometimes put strain on the host causing it 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.
Human Threats to 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.
Environmental Threats to the Great Barrier Reef
The Great Barrier Reef is a protected wilderness areas and since 1975. It is strictly managed to minimise human induced pollutants. However the reef straddles an area with significant human activity which invariably results in human environmental damage.
Oil Spills and Ships Running Aground
Busy shipping channels traverse the reef and occasionally 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 on Great Barrier Reef
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.
How to Get to Great Barrier Reef
Great Barrier Reef Attractions
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