Massive coral deaths in Australia's Great Barrier Reef followed by mass bleaching have been reported because of the excessive warming of surface waters in oceans.

In fact, the year 2016 had the severest bleaching in recorded history of the 2,300-kilometer (1,400-mile) long reef, which is the world's precious heritage.

According to the Australian Research Council Centre of Excellence for Coral Reef Studies, the most affected has been a 700-kilometer (400-mile) patch in the northern part of the Reef.

"Most of the losses in 2016 have occurred in the northern, most-pristine part of the Great Barrier Reef. 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 Professor Terry Hughes, Director of the Australian Research Council Centre of Excellence for Coral Reef Studies.

The James Cook University-based center undertook extensive surveys at the peak of the bleaching to assess the coral death impact.

Expressing concern about the high coral death rates in the north, Hughes said the task of keeping the reef off the UN's "in danger" list will now be a hard job.

The ARC dive surveys in October and November noted that the area to the north of Port Douglas had lost an average 67 percent of shallow-water corals since February.

Researcher Andrew Baird also said the 2016 coral die-off was "substantially worse" than the coral deaths in 1998. The study said the rise in sea water temperatures across the Great Barrier Reef was the sharpest in February, March and April. Hughes noted that much of the initial mortality was due to heat stress that led to corals getting "cooked."

How Coral Bleaching Occurs

The coral starvation happens from the expulsion or loss of the colorful algae zooxanthella which converts sunlight into food for the corals.

The whitening of the coral happens when it is deprived of the main source of energy.

Australia's Minister for Environment Josh Frydenberg noted that the coral cover has been increasing at the rate of 19 percent before the "significant bleaching event" of 2016 triggered by the El Nino effect which reversed the gains.

Now the governments of Australia and Queensland will brief UNESCO World Heritage Center on the progress made in improving the reef including measures on mitigating coral bleaching.

Coal Mining Responsible

Meanwhile, Graeme Kelleher, former chief of the Great Barrier Reef Marine Park Authority, hit out at the political leadership and cautioned Australians against accepting the "political lie" that the reef will be maintained well while running coal mines side by side.

Kelleher said 50 percent of the coral cover on the Great Barrier Reef has already been lost in the last 30 years because of the burning of fossil fuels.

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