Over one-third of the central and northern regions of Australia’s Great Barrier Reef have died in the worst mass bleaching event on record.
Bleaching occurs when coral reefs experience water that run warmer than their summer maximum for over a month. The overly warm water cause corals to lose their colorful symbiotic algae that provide nutrients. If the water becomes stable soon after, corals can heal themselves; but if the condition persists, corals calcify and die out.
The massive bleaching event is being linked to El Nino and the global warming caused by human activity, particularly by the fossil fuel industry.
Almost 93 percent of reefs have been hit by coral bleaching, out of which 57 percent corals have seen moderate to mild bleaching.
The Great Barrier Reef aerial survey that began last month covered 911 individual reefs and found out that only 68 of those reefs escaped bleaching entirely.
“It is fair to say we were all caught by surprise,” said Professor Terry Hughes, director of the ARC Centre of Excellence for Coral Reef Studies at James Cook University. “It's a huge wake up call because we all thought that coral bleaching was something that happened in the Pacific or the Caribbean which are closer to the epicentre of El Nino events.”
In the 1998 and 2002 mass bleaching event in Australia, 40 percent of the coral reefs escaped bleaching and only 18% were severely bleached. This time, the bleaching is five times stronger, stated Professor Hughes.
Scientists warn the recovery of the coral cover might take a decade or even longer; however it would take even longer for the oldest and largest corals to come back to life.