Coral bleaching is the loss of colour from corals under stressful environmental conditions. While several sources of stress can cause corals to bleach, unusually high water temperature and light intensity has been the major cause of coral bleaching events worldwide in recent decades. In 1998 and 2002, major bleaching events in waters of the Great Barrier Reef raised concerns about the health of the reef. With predictions that temperatures will continue to increase as a result of global climate change, there is growing concern about the future of tropical coral reefs.

Global climate change

In the past, global climate has changed due to a variety of causes. Increasing amounts of greenhouse gases in the atmosphere ............

Temperature tolerance limits of corals

Maximum summer sea temperatures that are only 2-3°C above normal values can kill corals............

The biology of coral bleaching

Corals belong to a group of animals called Cnidarians which include anemones, jellyfish, bluebottles and hydroids. Most corals are classified as a soft coral or a hard coral.................

Can corals adapt to warmer temperatures?

For corals to survive the increase in seawataer temperature predicted for this century, they would need to adjust...............

1998 coral bleaching event

The summer of 1997-1998 was the hottest recorded on the Great Barrier Reef since records began in the late 19th Century...................

Can coral reefs recover from bleaching?

Coral reefs can recover from bleaching events in the short-term. When a reef is only slightly stressed...

2002 coral bleaching event

In 2002, the Great Barrier Reef suffered another coral bleaching event. It was not associated with extreme ENSO conditions, but the effects were worse than 1998..............

El Nino Southern Oscillation

The El Nino Southern Oscillation or ENSO has a major influence on world climates. ENSO refers to the see-saw of climatic conditions near the Equator....

What can be done?

The impacts of climate change on ecosystems such as the Great Barrier Reef are complex, and to some extent, uncertain......

Acknowledgements

This brochure was written by Terry Done (Australian Institute of Marine Science, CRC Reef), Vicki Harriott (formerly of CRC Reef), Ray Berkelmans (AIMS, CRC Reef), and Louise Goggin (CRC Reef).

Thanks to Ove Hoegh-Guldberg (The University of Queensland), Paul Marshall (Great Barrier Reef Marine Park Authority), and Janice Lough (AIMS).

Other information: reports of the Intergovernmental Panel on Climate Change 2001; 'Climate Change: an Australian Guide to the science and potential impacts' edited by B Pittock.