MORE than 90% of the Great Barrier Reef is affected by bleaching, research has found.
Aerial and underwater surveying by James Cook University found 93% of the reef was affected by either little, moderate or severe bleaching.
The bleaching has been blamed on increased water temperatures as a result of climate change.
National Coral Bleaching Taskforce convener Professor Terry Hughes said parts of the southern end of the Great Barrier Reef were the least affected and should recover quickly.
But he said the northern reef had been hit hard.
"We've never seen anything like this scale of bleaching before. In the northern Great Barrier Reef, it's like 10 cyclones have come ashore all at once," he said.
Great Barrier Reef Marine Park Authority chairman Dr Russell Reichelt said the bleached coral was not dead but still at risk.
"It's part of a global event triggered by climate change and one of the strongest El Ninos ever recorded - in combination they've driven up sea temperatures to be much warmer," he said.
"Bleached coral is not dead, however it's severely stressed and can result in die-off