Oh Zooxanthellae, wherefore art thou?

The Great Barrier Reef is the world’s largest coral reef system, composed of roughly 3,000 individual

reefs and 900 islands, that stretch for over 1,600 miles. The reef is located in the Coral Sea

off the coast of Queensland in north-east Australia.

Warmer sea surface temperatures as a result of global warming are blamed for an increase in a phenomenon called coral bleaching, which is a whitening of coral caused when the coral expels a single-celled, symbiotic alga called zooxanthellae. This alga usually lives within the tissues of the corals and, among other things, gives them its spectacular range of colors.

Zooxanthellae are expelled when the coral is under stress from environmental factors such as abnormally high water temperatures or pollution. Since the zooxanthellae help coral in nutrient production, their loss can affect coral growth and make coral more vulnerable to disease. Major bleaching events took place on the Great Barrier Reef in 1998 and 2002, causing a significant die-off of corals in some locations.