Scientists alarmed at Great Barrier Reef coral-bleaching

Australian scientists managing the Great Barrier Reef have raised their emergency response to the highest level, following the publication of video footage of damage caused by coral-bleaching.

Authorities said that areas of the World Heritage site were experiencing the worst bleaching in 15 years, partially as a result of the current El Nino, which is one of the strongest in two decades.

During coral-bleaching, coral expels living algae, causing it to calcify.