“How this event unfolds will depend very much on local weather conditions over the next few weeks,” Marine Park Authority Director of Reef Recovery Dr. David Wachenfeld said in a statement.
The vibrant colors that draw thousands of tourists to the Great Barrier Reef each year come from algae that live in the coral's tissue. When water temperatures become too high, coral becomes stressed and expels the algae, which leave the coral a bleached white color. While some of the areas are expected to regain their normal color when temperatures drop, other parts of the reef have already experienced significant mortality of bleached coral.
The back-to-back summers of widespread coral bleaching likely mean that the water temperatures did not become low enough to allow the corral to adequately recovered, Neal Cantin from the Australian Institute of Marine Science said in a statement.
“We are seeing a decrease in the stress tolerance of these corals,” Cantin said. “This is the first time the Great Barrier Reef has not had a few years between bleaching events to recover.”