Images released by Greenpeace show another year of above average water temperatures is "cooking the reef alive", according to biologist Brett Monroe Garner.



“I've been photographing this area of the reef for several years now and what we’re seeing is unprecedented," Monroe Garner said. “In these photos, nearly 100% of the corals are bleaching, and who knows how many will recover. Algae is already beginning to overgrow many of the corals."



In 2016, scientists confirmed a coral die-off as a result of a sustained period of bleaching was the worst on record, with more than two-thirds of corals killed in some areas.

Coral bleaching occurs when abnormally high sea temperatures cause corals to expel tiny photosynthetic algae called zooxanthellae, turning the coral white, often killing it.

The Greenpeace findings are backed by Terry Hughes from James Cook University's Centre of Excellence for Coral Reef Studies, who called the second bleaching event the "worst kept secret in the world".