Coral bleaching isn't just about the colour of the coral - it can have very dramatic impacts on the reef.

Coral Bleaching at Lizard Island
Coral bleaching off Lizard Island in 2016 Image: Lyle Vail
© Australian Museum

Increasingly, coral colonies around the world are being bleached (turning white) when water temperatures rise. When the water warms above a certain temperature, corals expel the colourful algal cells living inside them and providing them food. The body tissue of the coral then becomes white. This bleaching often then leads to the coral dying and has major consequences for the reef as we know it, and the biodiversity it supports.

So what happens to dead coral? Bleached coral becomes wonderful habitat for worms and sponges which invade this new home by boring into the skeleton. While this provides a temporary benefit to the worms and sponges, it’s not necessarily what the tourist wants to see!

The consequences of these new coral invaders also means that bleached coral becomes like honeycomb and increasingly fragile and more susceptible to being dislodged by storms.

If bleaching occurs regularly, the colourful and biodiverse reef becomes a dead reef which can no longer support all the fish and other animals which depend on live coral.

Dr Pat Hutchings
Senior Principal Research Scientist

More Information:

Hutchings, P., Peyrot-Clausade, M. and Stuken, A. 2014. Internal macrobioerosion on five species of Acropora following the 1998 bleaching event: Implications for the long-term impact of bleaching on the Great Barrier Reef. Pacific Conservation Biology 19: 409-417.