Bleach Watch

Bleach Watch is an opportunity for everyone to help the Great Barrier Reef Marine Park Authority understand the effects of coral bleaching, and to help the reef survive the effects of climate change.

Why report coral bleaching?

Bleached anemone and anemone fish.

The GBRMPA is keen to enlist the assistance of all reef users in recording and monitoring coral bleaching on the Great Barrier Reef. Bleaching of corals is a natural event that occurs to some extent on the Great Barrier Reef each summer. However, in years when water temperatures increase above normal levels, severe and widespread bleaching can occur (known as a "mass bleaching event"). In conjunction with the Australian Institute of Marine Science and the U.S. National Oceanic and Atmospheric Administration, GBRMPA is closely monitoring bleaching events to improve our understanding of this important phenomenon. However, the immense size of the Great Barrier Reef means that all reef visitors can play a role in watching out for signs of stress.

How can you get involved?

To find out more click on the magnifying glass below.

How to recognise bleached corals

Close up of completely bleached coral branches.

The normal colour of corals can range from brown and green to yellow, blue and even pink. Bleached corals appear extremely pale or bone white because they have lost all or most of their symbiotic algae, which gives them most of their colour. Although totally bleached corals appear similar to corals that have been eaten by crown-of-thorns starfish, they are still alive. On close inspection of bleached corals, it is frequently possible to see the nearly transparent tissue and tentacles, which cover the skeleton. While it is sometimes difficult to distinguish the effects of crown-of-thorns starfish (COTS) from low levels of coral bleaching, mass coral bleaching events are easily recognised. Large areas of reef will be dominated by bright white corals during a bleaching event, whereas the effects of  COTS are more patchy.