Barrier Reef coral bleaching getting worse

Coral bleaching on the iconic Great Barrier Reef is getting worse, with authorities raising the threat level for the second time in a week after discovering it is more severe than previously thought.

The Great Barrier Reef Marine Park Authority has lifted its response to level three - its highest - which means severe regional bleaching has been detected.

Environment Minister Greg Hunt flew over the reef on Sunday to observe some of the hardest hit areas around Lizard Island, north of Cairns.

The level-three upgrade comes a week after the authority increased the coral bleaching warning from level one to two after surveys carried out by divers over the preceding fortnight detected widespread bleaching.

The surveys found reefs around Lizard Island and further north were the worst impacted.

In the worst affected sites in the remote far north on inshore Cape York reefs, divers found up to half of the coral has died from prolonged higher than average sea surface temperatures.