98% of Great Barrier Reef has suffered coral bleaching: study

Sydney, Australia, Nov 5 (EFE).- Ninety-eight percent of the corals of Australia’s Great Barrier Reef have suffered bleaching due to global warming, a scientific study released on Friday said.

The Great Barrier Reef is the largest coral reef system in the world and covers around 344,400 square kilometers.

Lead author Professor Terry Hughes from James Cook University said the frequency, intensity and scale of climate extremes is changing rapidly due to global warming – and this includes the record-breaking marine heatwaves that cause corals to bleach and die.

The study indicates that since 1998, the world’s hottest year on record, the Great Barrier Reef has suffered several coral bleaching events and only 2 percent has escaped these.

“Five bouts of mass bleaching since 1998 have turned the Great Barrier Reef into a checkerboard of reefs with very different recent histories, ranging from 2 percent of reefs that have escaped bleaching altogether, to 80 percent that have now bleached severely at least once since 2016,” Hughes said in a statement.

The main cause of this phenomenon is an increase in sea temperature, which causes the corals to expel zooxanthallae, microscopic algae living in their tissues that produce oxygen and provide them with food resulting from photosynthesis. This causes the coral to turn white, and although they do not necessarily die, they are under more stress and more susceptible to disease and death.

Scientists noted that in 2020 severe bleaching was observed for the first time in all three Great Barrier regions: north, center and especially in the south, which had in 2016 and 2017 been spared.

In contrast, the northern area was spared in 1998 and 2002, although it was hit the hardest in the 2016 event.

“To our surprise, we found the threshold for bleaching was much higher on reefs that had experienced an earlier episode of heat stress,” co-author Dr Mark Eakin, formerly of the US National Oceanic and Atmospheric Administration, said.

The study, published during the COP26 climate summit, advocates a “drastic cut in greenhouse gas emissions by all countries” to protect the Great Barrier Reef, the health of which has been officially rated “very poor.”

The reef, which is home to 400 types of coral, 1,500 species of fish and 4,000 varieties of mollusks, began to deteriorate in the 1990s due to the double impact of marine warming and an increase in its acidity due to the greater presence of carbon dioxide in the atmosphere. EFE


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