Largest coral die-off ever in Great Barrier Reef

Australia's iconic Great Barrier Reef has lost more corals this year than ever recorded due to a mass bleaching event that wiped out over two-thirds of the coral species in some areas, scientists said today.
The worst affected area, a 700 kilometres swath of reefs in the northern region of the Great Barrier Reef has lost an average of 67 per cent of its shallow-water corals in the past eight to nine months.
Further south, over the vast central and southern regions of the Great Barrier Reef, the scientists found a much lower death toll.
"Most of the losses in 2016 have occurred in the northern, most-pristine part of the Great Barrier Reef," said Terry Hughes, Director of the Australian Research Council (ARC) Centre of Excellence for Coral Reef Studies based at James Cook University.

"This region escaped with minor damage in two earlier bleaching events in 1998 and 2002, but this time around it has been badly affected," said Hughes, who undertook extensive aerial surveys at the height of the bleaching.
"The good news is the southern two-thirds of the Reef has escaped with minor damage. On average, six per cent of bleached corals died in the central region in 2016, and only one per cent in the south," said Andrew Baird, also from the ARC Centre.

"The corals have now regained their vibrant colour, and these reefs are in good condition," said Baird, who led teams of divers to re-survey the reefs in October and November.

"This is welcome news for our tourism industry," according to Craig Stephen, who manages one of the Great Barrier Reef's largest live-aboard tourist operations.
"The patchiness of the bleaching means that we can still provide our customers with a world-class coral reef experience by taking them to reefs that are still in top condition," said Stephen.
Another silver lining was unveiled in the northern offshore corner of the Great Barrier Reef Marine Park, where the loss of coral was lower than the other northern reefs.
"We found a large corridor of reefs that escaped the most severe damage along the eastern edge of the continental shelf in the far north of the Great Barrier Reef," said Hughes.

"We suspect these reefs are partially protected from heat stress by upwelling of cooler water from the Coral Sea," he said.
Scientists expect that the northern region will take at least 10-15 years to regain the lost corals, but they are concerned that a fourth bleaching event could happen sooner and interrupt the slow recovery.