Great Barrier Reef
-
What is the Great Barrier Reef?
The Great Barrier Reef is the world's longest and largest reef complex, located off the northeastern coast of Australia in the Pacific Ocean. It stretches over 1,250 miles (2,000 km) and is composed of approximately 2,100 individual reefs and 800 fringing reefs. Formed over millions of years from the skeletons of marine organisms like coral polyps and coralline algae, it supports a vast array of life, including over 1,500 species of fish and numerous species of coral, sea turtles, and birds. The reef is a significant tourist attraction and is largely protected within the Great Barrier Reef Marine Park, a UNESCO World Heritage site. However, it faces threats from coral bleaching, invasive species, and cyclones.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Where is the Great Barrier Reef located?
The Great Barrier Reef is located off the northeastern coast of Australia, in the Pacific Ocean and the Coral Sea. This extensive reef system stretches for over 1,250 miles (2,000 km). It is situated approximately 10 to 100 miles (16 to 160 km) offshore. The reef is a complex of approximately 2,100 individual reefs and 800 fringing reefs.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What types of animals and plants can be found in the Great Barrier Reef?
The Great Barrier Reef is home to an incredible diversity of life. It hosts at least 450 species of hard coral, along with anemones, sponges, worms, gastropods, lobsters, crayfish, prawns, and crabs. The waters teem with over 1,500 species of fish, including wrasses, damselfish, triggerfish, angelfish, rays, and sharks. Six of the seven species of sea turtles, numerous sea snakes, and nearly two dozen bird species also inhabit the reef.
Plant life on the reef's cays is limited, with some mangrove varieties present in the northern areas. Encrusting red algae form a characteristic purplish-red rim, while green algae are also common.
6 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How was the Great Barrier Reef formed?
The Great Barrier Reef, located off the coast of Queensland, Australia, is the world's largest reef complex. It is formed from the accumulated skeletons and skeletal waste of marine organisms, primarily coral polyps and hydrocorals. These calcareous remains are cemented together by coralline algae and bryozoans. Over millions of years, this process has created the extensive reef structure.
The reef grows on a shallow continental shelf in warm waters, typically where temperatures do not fall below 21°C (70°F). Changes in sea level over the last two million years have also influenced its shape, with erosion and solution weathering occurring during glacial periods and new reef growth over older landscapes as sea levels rose. The accumulation of carbonate sand and mud, along with trapped sediment from plants and algae, further contributes to the reef's complex structure.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why is the Great Barrier Reef important to both nature and people?
The Great Barrier Reef is a vital natural wonder, serving as the world's largest reef complex and a significant tourist attraction. It supports an incredible diversity of life, including over 1,500 species of fish and numerous other marine organisms. For people, it offers economic benefits through tourism and provides opportunities for observing coral life.
However, the reef faces serious threats. These include coral bleaching caused by rising sea temperatures and climate change, as well as damage from predatory species like the crown-of-thorns starfish. Human activities such as overfishing, pollution, and sedimentation also pose risks to its delicate ecosystem. Protecting this natural heritage is crucial for both biodiversity and human interests.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
What threats are facing the Great Barrier Reef and what can be done to protect it?
The Great Barrier Reef faces threats from coral bleaching, invasive species like the crown-of-thorns starfish, and human activities such as overfishing and pollution. Climate change, leading to rising sea temperatures and ocean acidification, is a major driver of coral bleaching.
To protect the reef, efforts include managing marine park areas, controlling petroleum drilling, and regulating commercial fishing. Addressing climate change is crucial, as it exacerbates bleaching events. Reducing pollution and sedimentation from land-based erosion also helps maintain water quality.
5 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
News •
Great Barrier Reef, complex of coral reefs, shoals, and islets in the Pacific Ocean off the northeastern coast of Australia that is the longest and largest reef complex in the world. The Great Barrier Reef extends in roughly a northwest-southeast direction for more than 1,250 miles (2,000 km), at an offshore distance ranging from 10 to 100 miles (16 to 160 km), and its width ranges from 37 to 155 miles (60 to 250 km). The Great Barrier Reef has an area of some 135,000 square miles (350,000 square km), and it has been characterized, somewhat inaccurately, as the largest structure ever built by living creatures.
Geography
The reef actually consists of some 2,100 individual reefs and some 800 fringing reefs (formed around islands or bordering coastlines). Many are dry or barely awash at low tide; some have islands of coral sand, or cays; and others fringe high islands or the mainland coast. In spite of this variety, the reefs share a common origin: each has been formed, over millions of years, from the skeletons and skeletal waste of a mass of living marine organisms. The “bricks” in the reef framework are formed by the calcareous remains of the tiny creatures known as coral polyps and hydrocorals, while the “cement” that binds these remains together is formed in large part by coralline algae and bryozoans. The interstices of this framework have been filled in by vast quantities of skeletal waste produced by the pounding of the waves and the depredations of boring organisms.
European exploration of the reef began in 1770, when the British explorer Capt. James Cook ran his ship aground on it. The work of charting channels and passages through the maze of reefs, begun by Cook, continued during the 19th century. The Great Barrier Reef Expedition of 1928–29 contributed important knowledge about coral physiology and the ecology of coral reefs. A modern laboratory on Heron Island continues scientific investigations, and several studies have been undertaken in other areas.
The reef has risen on the shallow shelf fringing the Australian continent, in warm waters that have enabled the corals to flourish (they cannot exist where average temperatures fall below 70 °F [21 °C]). Borings have established that reefs were growing on the continental shelf as early as the Miocene Epoch (23.0 million to 5.3 million years ago). Subsidence of the continental shelf has proceeded, with some reversals, since the early Miocene.
The water environment of the Great Barrier Reef is formed by the surface water layer of the southwestern Pacific Ocean. The reef waters show little seasonal variation: surface-water temperature is high, ranging from 70 to 100 °F (21 to 38 °C). The waters are generally crystal-clear, with submarine features clearly visible at depths of 100 feet (30 metres).
