Australia's Great Barrier Reefs

One of the great wonders of the natural world

The reefs were declared a World Heritage Site in 1981
The Great Barrier Reefs off the coast of Australia are one of the seven great wonders of the natural world. The reefs were declared a World Heritage Site in 1981. The Australian government created a Marine Park in June 1975 that included the reefs. The park includes all of the Barrier Reefs and the World Heritage Area which is even larger. The park was designed by the government to protect the area for people living today and for future generations.

Crown of Thorns starfish, NOAA

Crown of Thorns starfish (seastar)

Barrier reefs along queensland coast

2,900 reefs and 900 islands
The Great Barrier Reefs stretch along the Queensland coast that make up the World Heritage Site. There are more than 2,900 individual reefs and 900 islands in the area included in the Great Barrier Reefs Park. The reefs are only about 7% of the protected areas along the Queensland coast. The entire park area is over 3000 kilometers (1800 miles) long. The coral reefs are located between 15 kilometers (9.3 miles) and 150 kilometers (93 miles) off the Queensland’s coast. Each coral reef is about 65 kilometers (40 miles) wide.

Hard and soft corals

Reefs are coral skeletons
The 2,900 individual coral reefs that make up the Great Barrier Reef are the skeletons of coral. Coral polyps are tiny invertebrate animals about the size of a pencil eraser. There are hard and soft corals that live in the oceans but it is the hard corals that create reefs. They extract calcite (calcium carbonate) from ocean water to create the hard structures that make up their exoskeletons. These hard structures protect them from predators.

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Coral polyps and zooxanthellae

Zooxanthellae are algae
The body of coral polyps are clear or colorless. They get their beautiful colors from algae that live inside their body called zooxanthellae (zoo-an-thel-lee). The colors vary in coral reefs depending on the zooxanthellae that live with the coral polyps in a symbiotic relationship.

How The original corals started a coral reef

Reefs increase in size as corals build new homes
The original corals that created each reef are attached to the rocks on the seafloor. Each succeeding generation builds their homes on top of the previous generation’s exoskeleton made of calcite extracted from seawater. Over the centuries the reefs increase in size. The Great Barrier Reef is so large that it is the only living structure that can be seen from outer space by the astronauts.

Sanctuary and home for plants and animals

600 species of corals in the reefs
The coral reefs provide a sanctuary and home for a large variety of plants and animals. There are over 600 different species of hard and soft corals that make up the reefs. Jellyfish, mollusks sharks, whales and dolphins are just some of the animals that live all or at least part of the time around the coral reefs.

crown of thorns starfish

Destroying coral reefs 
The Crown of Thorns starfish have been destroying many coral reefs as they eat the tiny polyps that make up some of the reefs. Scientists studying the problem have found this is the only place on Earth where Crown of Thorns starfish live. Today, many scientists believe that the starfish are nature’s way of opening up new areas along the coast line for new coral reefs to develop.

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