Great Barrier Reef suffers heat damage

This year has been the reef's hottest on record

By Phil Mercer BBC correspondent in Sydney

Researchers in Australia have claimed that sea temperatures around the Great Barrier Reef are now so high that major damage has been caused to the world's biggest marine park.

The principal danger to the reef, according to scientists, is the bleaching of coral caused by unusually warm water.

The Australian Institute of Marine Science says that 2002 has been the hottest year on record for the reef, which stretches 2,000 kilometres (1,243 miles) along Australia's east coast.

It has drawn up a heat map that has plotted the change in sea temperatures around the reef over the past 10 years.

The results are causing researchers concern.

Complex causes

They have discovered that significant bleaching of the reef has occurred, causing the coral to lose its energy-giving algae, turn white and, in some cases, die.

The map has allowed scientists to see where the problem areas are.

Bleached coral

Warm weather is considered to be a factor, but the reasons are complex. The exact cause of bleaching is not known.

Solar radiation, extreme low tides, and reduced salinities are also believed to be additional triggers.

What is known is that excessive whitening of the coral can cause the reef to crumble.

Protecting the reef

The Australian Institute of Marine Science was established by the federal government 30 years ago to help protect aquatic environments around the country's vast coastline.

The institute also reports on the impact of humans on the Great Barrier Reef and those of natural disturbances, such as outbreaks of Crown of Thorn starfish and cyclones.

Coral is classified as an animal and is related to sea anemones and jelly-fish.

Reefs are made up of layers of coral skeletons cemented together by algae to form an extremely hard limestone structure.

The Great Barrier Reef is a complex of almost 3,000 separate reefs and is one of Australia's principal tourist destinations.

Last year the Australian Senate passed new laws in an effort to protect the area from negligent mariners and oil-spills following a series of shipping disasters.