What's the Great Barrier Reef?

Remy Melina, Life's Little Mysteries Staff Writer

Date: 05 April 2010 Time: 03:20 PM ET

Satellite image shows islands of the Great Barrier Reef.
CREDIT: NASA/Landsat 7

Australia's Great Barrier Reef is the largest living organism on the planet, stretching some 1,430 miles (2,300 kilometers). Home to 400 coral species, the Great Barrier Reef is a mosaic of approximately 2,900 offshore and inshore reefs. For comparison, the 135,000-square-mile reef ecosystem is about the size of Germany.

A coral reef consists of coral polyps, which are animals in the jellyfish family, along with algae called zooxanthellae. In return for a cozy, safe place to live, the algae provide the building blocks polps need to survive and make limestone to build the reef structures. The vast structures that result do more than awe snorkelers.

The Great Barrier Reef supports a vast array of life forms, including:

5,000 mollusk species (think giant clams)
1,500 fish species
215 species of birds
30 species of whales, dolphins and porpoises
14 species of sea snakes
6 breeding sea turtle species

The reefs are vital to the survival of several endangered species, so much so that in 2004, the Great Barrier Reef Marine Park Authority (GBRMPA) increased the amount of highly protected zones by almost 30 percent.

A tourism hotspot, approximately 2 million people visit the Great Barrier Reef every year, according to the Australian government. There is widespread concern that such intense tourism might be harming the fragile reefs.

Pollution is another concern, as another oil spill occurred on April 4, when the Chinese coal-carrying ship Shen Neng1 ran aground on the reef, leaking a 1.86-mile-long (3 km) ribbon of oil and destroying precious coral and marine life.

Declining water quality is a major factor in the pollution of the Great Barrier Reef. During tropical floods, runoff containing fertilizer and pesticides is dispensed into the reef's waters and harms its delicately balanced ecosystem. The runoff problem is made worse by the loss of coastal wetlands along the Queensland coast, which act as a natural filter for toxins. The area of wetlands in the Great Barrier Reef catchment has decreased by over 50 percent, according to the Great Barrier Reef Coastal Wetlands Protection Program.