The Great Barrier Reef's health has entered "uncharted territory" after researchers found there had been mass coral bleaching for two summers in a row for the first time. The Great Barrier Reef Marine Park Authority and its partners took to the skies for six hours on Thursday to conduct aerial surveys of water between Cairns and Townsville.

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Groundhog Day At the Great Barrier Reef, Where Mass Bleaching is Again Hitting World’s Largest Coral Reef Systemhttps://t.co/AKhAJ3BiXL pic.twitter.com/Cl2gzcWFnW

— Assaad Razzouk (@AssaadRazzouk) March 15, 2017

Australian coral reef experts made that conclusion after flying over the Great Barrier Reef. According to a press release issued by the Great Barrier Reef Marine Park Authority (GBRMPA), corals can survive bleaching events, but rising sea surface temperatures have caused some to worry about the long term outlook for these biodiverse regions.

The Great Barrier Reef is the world's largest reef and "largest living structure", a 2300km expanse of colourful coral hosting thousands of species of fish, molluscs, jellyfish and other sea creatures. These coral rely on microscopic algae embedded in their tissue to produce food via photosynthesis.

But if the water gets too warm or polluted, those algae can be expelled from the Great Barrier Reefs. The starving coral then turns bone white and becomes more susceptible to disease. If the coral dies, it will turn a nasty greenish-brown as other opportunistic algae grow on its surface.

Last year's warm water brought coral bleaching events worldwide, which were made worse by the El Niño climate pattern, according to a story published last year in The Guardian. This year's reports are fairly unsurprising - we've basically been experiencing the same continuous global coral reef bleaching event since 2014, Mark Eakin, Coordinator of NOAA's Coral Reef Watch program explained to Gizmodo.

Great Barrier Reef Marine Park rangers started receiving reports back in January that the coral wasn't looking too good this year. By February, corals were starting to show signs of stress from elevated water temperatures. Yesterday's survey of the central third of the Reef's length revealed severe bleaching; this area largely escaped last year's event, according to the GBRMPA.