Great Barrier Reef

III

Marine Life

Coral reefs provide the ideal conditions for marine life. They are found in shallow tropical waters that stay warm year-round. Their exposure to sunlight provides energy to the algae and plants that feed animals living in the reef. The reef itself provides creatures with a large, intricate surface area on which they can find food and shelter. For these reasons, more animal species are found on coral reefs than in any other marine ecosystem (localized group of interdependent organisms and the environment they inhabit). Although the coral reefs in Indonesia and the Philippines contain the greatest numbers of species, the Great Barrier Reef also has tremendous numbers of plants and animals.

The Great Barrier Reef possesses an abundance of coral types. Their variety creates a magnificent display of different shapes and colors. About 350 species of stony corals have been scientifically identified in the Great Barrier Reef. Also plentiful are other corals that have less rigid skeletons made of protein, such as sea whips and sea fans, and soft corals, which do not have skeletons.

About 1,500 species of fish are found in and around the Great Barrier Reef. Common in all areas are the gobies, the smallest fish of the reef; some of the reef’s dwarf gobies are fully grown at 2.5 cm (1.0 in). Several types of shark are regular reef inhabitants, including silvertip, blacktip, and whitetip sharks. Visiting sharks include hammerheads and the whale shark, the reef’s largest fish at up to 12 m (39 ft) in length. Along with sharks, groupers are among the most important predators of the reef. Many groupers are quite small, but the giant, or Queensland, grouper is known to reach a length of 2.7 m (8.8 ft) and a weight of more than 400 kg (880 lb). The butterfly fish is one of the most colorful reef dwellers, with 45 different types known to live in the Great Barrier Reef, including some that eat coral.

Other plant and animal life in the reef includes 500 kinds of algae, 4,000 types of mollusks, and 20 species of sea snakes. The Great Barrier Reef Marine Park is an important refuge for a number of threatened species, including 30 species of whales and dolphins, 6 species of sea turtles, the dugong (sea cow), and giant clams.

---

---

One of the most spectacular events on the Great Barrier Reef occurs once a year when the coral colonies spawn. For a few nights after the full moon in November or December, all corals of the same species release their eggs and sperm at the same time, with remarkable precision. By spawning all at once, the corals increase the number of their offspring and the chances that at least some will survive.

IV

Economic Uses

Tourism on the reef is a huge industry that significantly contributes to the economy of Queensland. The Great Barrier Reef attracts about 1.6 million tourists each year. The central and northern towns of Cairns, Port Douglas, and Townsville as well as the Whitsunday Islands are the largest centers for reef tourism. Some islands farther offshore offer more secluded resorts. Hundreds of tourism operators are licensed to offer services such as diving and boating excursions in the Great Barrier Reef Marine Park.

Fishing is permitted to varying degrees in the marine park. Both commercial and recreational fishing take place in the park, including line fishing directly on the reefs. In the lagoon there is a large prawn-trawling industry, as well as fishing for barramundi (a popular sport fish) and mud crabs.

Some Aboriginal and Torres Strait Islander people, the indigenous inhabitants of Australia, maintain a legal right to practice traditional methods of fishing and hunting on the Great Barrier Reef. They are allowed to hunt some endangered species, including dugong and turtles. However, the extremely low levels of such hunting are unlikely to pose a threat to these species.

V

Environmental Issues

Nearly 60 percent of the world’s coral reefs are classified as threatened. The reefs of Australia are ranked as some of the least threatened, with only 30 percent classified as at risk, and only 1 percent at high risk. However, the Great Barrier Reef is a delicately balanced ecosystem that is susceptible to damage.

Activities on land often impact the sea. The clearance of forests and intensification of agriculture have increased the amount of nutrient-rich sediments flowing out to the reef waters. These sediments inhibit the growth of coral by making the waters murky and reducing the amount of sunlight the coral receive. The outflow of sediments has led to the degradation of a number of the reefs closest to the coast.

Since 1962 scientists have observed periodic population explosions of the crown-of-thorns starfish on the Great Barrier Reef. This giant starfish is a predator of corals, feeding on the polyps. Plagues of these starfish can destroy all of the corals on individual reefs. Reefs can recover, but it takes years or even decades. Scientists suspect that human activities contribute to the population explosions of the starfish. For example, fishing reduces the number of starfish predators. In addition, freshwater runoff from land into coastal waters often contains fertilizers and other nutrients that enable starfish larvae to survive in greater numbers.

Coral bleaching may be one of the greatest threats to the Great Barrier Reef. Coral bleaching is a stress response that often occurs when the surrounding waters become too warm for the corals. In the stressful situation, the corals expel their brownish zooxanthellae and lose their color. Without the zooxanthellae, the coral cannot obtain sufficient nourishment. If conditions remain difficult, the corals may die. Major coral bleaching incidents on the Great Barrier Reef in 1998 and 2002 led to widespread death of corals in some areas.

Marine scientists are concerned that global warming is raising ocean temperatures, thereby increasing the frequency of coral bleaching episodes. It is not known how quickly corals can adapt to rising temperatures. Large reef areas, such as the Great Barrier Reef, may be able to recover more quickly from mass bleaching episodes than smaller reefs. The close connection between reefs would allow live corals to repopulate dead reefs by traveling on tides from adjacent areas.

VI

Conservation Efforts

The Great Barrier Reef is one of the world’s most important areas of marine wilderness. In recognition of this significance, the Great Barrier Reef Marine Park was created in 1975. It is the largest marine park in the world. Its borders extend from the low-water mark on the mainland coast to past the edge of the continental shelf, and from the tip of Cape York Peninsula to just north of Fraser Island, near Bundaberg.

A federal agency, the Great Barrier Reef Marine Park Authority, is responsible for overall planning and management of the park. The marine park authority has zoned the park in order to designate which activities, such as fishing and tourism, are allowed in different zones. Many activities require licenses. Some areas have been set aside for strict protection. For example, a small proportion of the park is closed to any activities, such as fishing, that would remove anything from the reefs. Given the size of the park, monitoring the zones and enforcing regulations presents a challenge.

The state government of Queensland is responsible for enforcing federal and state laws that can help protect the Great Barrier Reef, such as the Environmental Protection Act and the Marine Parks Act. The state government and the marine park authority often work together to address reef-conservation issues. They collaborate on education and research efforts, particularly in relation to land-use planning and site management. For example, they have coordinated their efforts to involve landowners and others in reducing runoff from rivers and other watersheds that carry pollutants and sediments from land into the marine park.

	More from Encarta
	•  Important Notice: MSN Encarta to be discontinued. Learn more. •  Presidential Myths Quiz •  Coffee break: Recharge your brain