Most of Australia’s Great Barrier Reef is affected by coral bleaching | EUROtoday

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Australia’s Great Barrier Reef is experiencing one in all its worst bleaching occasions since monitoring started almost 4 a long time in the past, authorities say, with a lot of the famed reef displaying indicators of harm as warming ocean temperatures blight reefs worldwide.

Bleaching happens when heat-stressed coral flip white after expelling symbiotic algae that present meals and colour. It’s a results of irregular ocean temperatures prior to now 12 months that scientists fear might signify a serious change to Earth techniques.

In the Great Barrier Reef marine park, 73 p.c of the reefs surveyed have prevalent bleaching — which implies that greater than 10 p.c of the coral cowl is bleached, the Great Barrier Reef Marine Park Authority, which manages the realm, mentioned Wednesday. Very excessive and excessive bleaching was noticed throughout almost 40 p.c of the reef system.

“Climate change is the greatest threat to the Great Barrier Reef, and coral reefs globally,” mentioned Roger Beeden, the authority’s chief scientist. “The Great Barrier Reef is an incredible ecosystem, and while it has shown its resilience time and time again, this summer has been particularly challenging.”

The dire replace on Earth’s largest reef system comes simply days after scientists with the U.S.-based National Oceanic and Atmospheric Administration and the International Coral Reef Initiative mentioned anomalous ocean temperatures are afflicting reefs worldwide.

According to NOAA scientists, the world is experiencing its fourth world bleaching occasion, and the second within the final decade. At least 53 nations and native areas have skilled mass bleaching throughout the Atlantic, Pacific and Indian oceans, they mentioned.

Ocean temperatures started constructing within the Great Barrier Reef space in late December and continued to rise all through the Southern Hemisphere summer time, inflicting “the highest levels of thermal stress on record,” the marine park authority mentioned.

The most intense and extended warmth stress occurred at inshore reefs within the southern a part of the marine park, with sea floor temperatures peaking at 2.5 levels Celsius above common.

This is the Great Barrier Reef’s fifth main bleaching occasion in 9 years. Scientists say it might be the most important check but of the 1,400-mile-long world marvel’s capability to get well. For the primary time, excessive bleaching — the place greater than 90 p.c of coral cowl on a reef is bleached — was noticed in all three areas of the marine park.

“Southernmost parts of the reef, which had been largely spared previously, have been hit particularly hard this time, with bleaching affecting many more species, extending to greater depths, and affecting some of the oldest and most resilient corals,” mentioned Simon Bradshaw, a analysis director with the nonprofit Climate Council. “This is a disaster at our doorstep.”

The large reef system — which is so massive it may simply be noticed from house — has bounced again from disturbances prior to now, together with underwater warmth waves in 2016 and 2017 that triggered coral bleaching occasions so extreme that scientists apprehensive the reef would by no means look the identical once more.

Scientists say the restoration from these occasions was pushed by fast-growing Acropora corals, that are extra susceptible to thermal stress and coral bleaching.

“The Great Barrier Reef has seen increases in coral cover to high levels in recent years, indicating it is still a resilient system. But this resilience has its limits,” mentioned David Wachenfeld, analysis program director on the Australian Institute of Marine Science, a authorities company.

Wachenfeld mentioned the extent of warmth stress, and the outcomes of the aerial surveys, point out that the most recent bleaching occasion is “one of the most extensive” the reef has skilled because the company started monitoring the reef almost 40 years in the past.

Research divers had noticed coral fatalities in each area of the reef, he mentioned.