For the second consecutive year, Australia's Great Barrier Reef is experiencing mass coral bleaching.

Experts conducted the first flyover of 2017 this week and noticed severe bleaching in the areas of Ingham to the northern extent of the survey near Cairns, the Great Barrier Reef Marine Park Authority said in a news release.

The experts also discovered coral bleaching in the central part of the reef, which wasn't affected last year.

David Wachenfeld, Marine Park Authority director of reef recovery, said the full impact of the bleaching will depend on the upcoming weather.

"Importantly, not all bleached coral will die. As we saw last year, bleaching and mortality can be highly variable across the 344,000 square kilometre Marine Park — an area bigger than Italy," Wachenfeld stated.

Coral is composed of thousands of small creatures called polyps that can only thrive in a very narrow range of temperatures.

'Decrease in stress tolerance'

He added that the coral bleaching highlights the importance of taking action on climate change and the implementation of the Paris Agreement to reduce greenhouse gas emissions.

The back-to-back bleaching is also an indication that the coral is losing its ability to recover from extreme heat, Neal Cantin from the Australian Institute of Marine Science said in the release.

"We are seeing a decrease in the stress tolerance of these corals," Cantin said. "This is the first time the Great Barrier Reef has not had a few years between bleaching events to recover.

"Many coral species appear to be more susceptible to bleaching after more than 12 months of sustained above-average ocean temperatures."

Another survey of the 1,150 reefs within the Great Barrier Reef will take place next week.