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Great Barrier Reef has record levels of coral, says survey

Most of the Great Barrier Reef has the highest amount of coral cover ever recorded since monitoring began 36 years ago, a new survey has found.

The survey, which was conducted by the Australian Institute of Marine Science (AIMS), found that the northern and central areas of the reef – two thirds in total – have record amounts of coral never before seen after several years of bleaching.

The northern region was found to have increased its coral cover from 27% last year to 36% this year – a 9% increase. Meanwhile, the central area increased from 26% to 33% – a 7% increase.

The southern third of the reef appears to have lost some coral cover, going from 38% last year to 34% this year – a 4% decrease.

However, AIMS attributes this primarily to a surge in crown-of-thorns starfish, which eat healthy coral.

“A third of the gain in coral cover we recorded in the south in 2020/21 was lost last year due to ongoing crown-of-thorns starfish outbreaks,” said AIMS CEO Dr. Paul Hardisty.

The development comes after several years of “coral bleaching,” where the reef would turn white following stresses placed upon it by its environment.

The stress can come in the form of temperature, light or a change in available nutrients. When stressed the coral expels algae which usually gives it its colour, causing the reef to become white, or “bleached.” While the coral is not dead in this state, it is more at risk of starvation or disease.

This phenomenon has been documented for decades, and occurred in the Great Barrier Reef in 1980, 1982, 1992, 1994, 1998, 2002, 2006, 2016 and 2017.

Significantly, between 1985 and 2012, the Great Barrier Reef was found to have declined by half. However, a 2012 study found that 90% of this decline was attributable to either tropical cyclones or crown-of-thorns starfish feeding on the coral. Only 10% was the result of bleaching.

For years news reports have been quick to warn of climate change’s impact on reefs, with RTÉ reporting last month that “many of [Australia’s] most prized ecosystems, such as the Great Barrier Reef which has been hit by mass coral bleaching, are threatened by climate change.”

 

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