March 21, 2016
By Katie Valentine

Record-breaking (click here) temperatures in Australia have triggered a severe coral bleaching event in the Great Barrier Reef, threatening coral survival in the World Heritage site.

Australia’s government raised the bleaching threat for the Great Barrier Reef to its highest level Sunday, after researchers said earlier this month that bleaching off the coast of northern Australia was the worst they’d seen in 15 years. This comes as Australia has been seeing strong summer and fall heat, with early March high temperatures about 4 degrees Celsius hotter than normal.

Coral bleaching occurs when stressed corals expel the symbiotic algae living in their tissues. The algae gives coral its pigment, so without it, the coral turns white. High ocean temperatures make coral more susceptible to bleaching, and bleached corals are at higher risk of death, especially if water temperatures don’t fall enough for the coral to recover.

“The corals in the remote far north of the Reef experienced extremely hot and still conditions this summer, and were effectively bathed in warm water for months, creating heat stress that they could no longer cope with,” Great Barrier Reef Marine Park Authority Chairman Russell Reichelt said in a statement....