The Great Barrier Reef is a group of coral reefs, shoals, and islets in the Pacific Ocean off the northeastern coast of Australia. It is the longest and largest reef complex in the world. The Great Barrier Reef is more than 1,250 miles (2,000 km) long and runs roughly northwest to southeast.
It is 10 to 100 miles (16 to 160 km) out to sea, and its width is between 37 and 155 miles (60 to 250 km). The Great Barrier Reef is about 135,000 square miles (350,000 square km) in size, and it has been called the largest structure ever built by living things. This is not quite true. The Great Barrier Reef was added to the World Heritage List by UNESCO in 1981.
Interesting Facts about the Great Barrier Reef
The reef is actually made up of about 2,100 separate reefs and about 800 reefs along the edges (formed around islands or bordering coastlines). At low tide, many are dry or just barely wet. Some have coral-sand islands or cays, and others are near high islands or the coast of the main land.
Even though the reefs are different, they all came from the same place: the skeletons and waste from the skeletons of a large number of living marine organisms. The coral polyps and hydrocorals that live in reefs leave behind calcareous remains that make up the “bricks” of the reef.
Coralline algae and bryozoans make up a lot of the “cement” that holds these remains together. The spaces between the rocks in this structure have been filled with a huge amount of broken bones left behind by the waves and organisms that eat bones.
Great Barrier Reef History
In 1770, the British explorer Capt. James Cook ran his ship aground on the reef. This was the first time Europeans saw it. Cook was the first person to try to figure out how to get through the reefs. This work continued in the 19th century.
The Great Barrier Reef Expedition of 1928–1929 taught scientists a lot about how coral reefs work and how they live. On Heron Island, scientists are doing research in a modern lab, and studies have also been done in other places.
The reef has grown on a shallow shelf off the coast of Australia, where the water is warm enough for corals to grow (corals can’t live where the average temperature is below 70 °F or 21 °C). Borings show that reefs were already growing on the continental shelf in the Miocene Epoch (23.0 million to 5.3 million years ago). Since the beginning of the Miocene, the continental shelf has been sinking, with some stops and starts.
The Great Barrier Reef’s water environment is made up of the top layer of water in the southwestern Pacific Ocean. The water temperature at the surface of the reef doesn’t change much from season to season. It stays between 21 and 100 °F (70 and 38 °C). The water is usually as clear as glass most of the time. At depths of 100 feet or 30 meters, it is easy to see the parts of a submarine.
At least 450 different kinds of hard coral live there, along with anemones, sponges, worms, gastropods, lobsters, crayfish, prawns, and crabs. The reef is home to more than 1,500 kinds of fish and other vertebrates. Wrasses, damselfish, triggerfish, and angelfish are some of the most common fish.
Larger fish like rays and sharks are also common (e.g., tiger sharks and whale sharks, the largest living fish). The reef is also home to six of the seven types of sea turtles, more than a dozen types of sea snakes, and almost two dozen types of birds.
The crown-of-thorns starfish (Acanthaster planci) is the animal that does the most damage to reefs. It eats a lot of living coral, which makes many central reefs less colorful and interesting. Lithothamnion and Porolithon, two types of red algae, grow together to make the Great Barrier Reef’s distinctive purple-red algal rim.
Halimeda, a green algae, grows almost everywhere else. Above the surface, there aren’t many plants on the cays. There are only about 30 to 40 species. In the northern cays, there are different kinds of mangroves.
In addition to being interesting to scientists, the reef is becoming more and more important as a place for tourists to visit. As people worry more about protecting its natural heritage, they have tightened rules on activities like drilling for oil that could be dangerous.
At the end of the 20th century and the beginning of the 21st, there was a lot of debate about how much tourist boats should be used and how long commercial fishing should last.But other things also put the health of the reef at risk. It is prone to coral bleaching, which is when the coral’s relationship with algae called zooxanthellae breaks down and the coral’s skeleton turns white.
Are coral reefs dying
Since 1998, climate change has caused at least six large-scale coral bleaching events, which have killed a lot of coral. Some marine scientists say that between 1985 and 2012, the reef’s coral coverage dropped by almost half. This was caused by coral bleaching, invasive species like the crown-of-thorns starfish (Acanthaster planci), and tropical cyclones.
Great Barrier reef map
In 2016 and 2017, bleaching caused coral coverage in the northern part of the reef to drop by up to a third. In 2020, the southern parts of the reef were affected by another big bleaching event. The Great Barrier Reef Marine Park, which was made in 1975 and covers most of the area, is mostly in charge of keeping an eye on the reef. Smaller state and national parks are also there.