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Enormous underwater sinkhole discovered in the Great Barrier Reef

Credit: Johnny Gaskell

Marine biologist Johnny Gaskell has discovered a gigantic underwater sinkhole — or blue hole — in the Great Barrier Reef. After noticing the lagoon using Google maps and visiting the area first-hand, he encountered a thriving ecosystem.

Blue holes are large marine sinkholes that have formed during past ice ages when sea levels were far lower —this means they were subject to the same erosion from rain and chemical weathering as any other area. After being submerged, the erosion ceased and the deep blue caverns were left.

Yesterday in the Great Barrier Reef!!! After spotting this deep blue hole on google maps we decided to head far offshore, out further than our normal Reef trips to see what dwelled within. What we found inside was hard to believe considering 5 months ago a Cat 4 cyclone went straight over the top of it. At around 15m – 20m deep there was huge Birdsnest Corals (Seriatopora) and super elongated Staghorn Corals (Acropora) both of which were among the biggest and most delicate colonies I've ever seen. Totally unaffected by the cyclone. The position of this deep hole within the lagoon walls has obviously protected these corals for decades. We may very well be the first to ever dive Gaskell's Blue Hole as it was so far offshore and hidden deep within one of the Great Barrier Reef's biggest lagoons…

A post shared by Marine Bio | UW Photographer (@johnny_gaskell) on

This part of the Great Barrier Reef was devastated by a Category 4 cyclone, said Gaskell, but the blue hole appeared to be “totally unaffected” by the storm. Gaskell notes that the deep walls of the blue hole appear to have protected the coral.

“After spotting this deep blue hole on Google maps we decided to head far offshore, out further than our normal Reef trips to see what dwelled within,” he wrote. “At the depth of around 15-20 m (50-65 ft) there was huge Birdsnest Corals (Seriatopora) and super elongated Staghorn Corals (Acropora) both of which were among the biggest and most delicate colonies I’ve ever seen.”

Section of the Great Barrier Reef as seen from space. NASA/GSFC/LARC/JPL, MISR TEAM
Section of the Great Barrier Reef as seen from space. NASA/GSFC/LARC/JPL, MISR TEAM

While it is not clear exactly where the newly discovered hole is, the storm he refers to may be Cyclone Debbie, which hit Queensland in March. This cyclone moved over the section of the Great Barrier Reef that sits between Townsville and Mackay, Queensland.

“We may very well be the first to ever dive Gaskell’s Blue Hole as it was so far offshore and hidden deep within one of the Great Barrier Reef’s biggest lagoons,” he said.

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