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.
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.