Great Barrier Reef bleaching event

An assessment of the Great Barrier Reef by Australian authorities found that 22 percent of the coral reef was dead from bleaching. The worst mass bleaching event on record, the results were announced on Oct. 14.

Coral bleaching occurs when symbiotic algae, which provides most of the nutrients for the coral, is killed or expelled; exposed to the elements and without its source of food, the coral eventually dies and turns white. There are many causes of bleaching, including rising water temperatures and exposure to pollution.

The worst-bleached area of the reef was between Cape York and Lizard Island off the far-northern tip of Queensland, which accounted for 85 percent of all the bleached coral. No bleaching was discovered south of the city of Mackay, on Queensland’s central coast.