Corals get up to 90% of their energy supply from the zooxanthellae that live within them. Stressful conditions (including high water temperature) cause the corals to expel their zooxanthellae. Bleached corals begin to starve once they bleach.
The Great Barrier Reef has been affected by mass bleaching events. Widespread bleaching occurred in 1998 and again in 2002. In both of these years, bleaching was recorded on 50-60 per cent of reefs.
More recently in the summer of 2006, reefs in the southern part of the Great Barrier Reef were affected by bleaching. Unusually high sea temperatures around inshore reefs caused 40% of corals to die at these reefs.
We can all make a difference to the health of the reef by minimising our contributions to climate change by reducing our greenhouse gas emissions.
This story has been provided by Great Barrier Reef Marine Park Authority. Learn more...