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Great Barrier Reef on sixth life in 30,000 years

31 May 2018

The first two large scale deaths occurred about 30,000 and 22,000 years ago, as the sea level drastically dropped, bottoming out at 118 m (387 ft) lower than it now is.

A landmark worldwide study of the Great Barrier Reef has shown that in the past 30,000 years the world's largest reef system has suffered five death events, largely driven by changes in sea level and associated environmental change.

"Our study shows the reef has been able to bounce back from past death events during the last glaciation and deglaciation", he said.

For scientists, this has particularly concerning ramifications as the rate of sediment input is continuing to increase due to human activities.

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It said the Reef adapted to sudden changes in the environment in the past by moving across the sea floor as the oceans rose and fell.

According to a previous study published in Nature, roughly 29% of the 3,863 individual reefs that make up Australia's Great Barrier Reef were affected by the abnormal warming.

An aerial view of the Great Barrier Reef off the coast of the Whitsunday Islands, along the central coast of Queensland, Australia. The team found that the reef has moved around over the last 30,000 years in response to changing sea levels, at a pace of up to 1.5 meters per year.

The study was conducted over 10 years by an global team of scientists, who drilled fossil reef cores from 16 sites along the northeastern Australian coast, and analyzed the dating, geomorphic, sedimentological and biological data from them.

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Changing sea levels and drops in water quality have caused the reef to fight for its life five times through thousands and thousands of years, but it turns out, the reef is incredibly tough and adept at recovery.

Two more death events occurred at the deglaciation period 17,000 and 13,000 years ago, this time brought about by the sea levels rising rapidly. The last death event reportedly took place near about ten thousand years ago.

The ecosystem is very sensitive when the sea level changes and temperatures shift abruptly.

However the report's authors stress the current pressures being put on the reef, including increasing sediment runoff, rising water temperatures and influxes of pest species, are happening at a much faster rate than in the past. The most recent, which occurred around 10,000 years ago, was associated with a decline in water quality and increase in sediment. Jody M. Webster, Juan Carlos Braga, Marc Humblet, Donald C. Potts, Yasufumi Iryu, Yusuke Yokoyama, Kazuhiko Fujita, Raphael Bourillot, Tezer M. Esat, Stewart Fallon, William G. Thompson, Alexander L. Thomas, Hironobu Kan, Helen V. McGregor, Gustavo Hinestrosa, Stephen P. Obrochta & Bryan C. Lougheed.

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Great Barrier Reef on sixth life in 30,000 years