by The southern Great Barrier Reef is suffering from extensive coral bleaching due to heat stress, reef managers said Wednesday, raising fears that a seventh mass bleaching event could be occurring across the vast, ecologically important site.
Aerial surveys by the Great Barrier Reef Marine Park Authority and the Australian Institute of Marine Science last weekend found bleaching was “extensive and fairly uniform across all reefs surveyed.”
The teams flew over 27 inshore reefs in the Keppel and Gladstone Islands region and 21 offshore reefs in Goat Bunkers off the south Queensland coast last weekend.
Dr Mark Read, the authority’s director of reef health, said most corals surveyed showed “some level of bleaching with white and fluorescent colonies observed in shallow reef areas.”
Covering nearly 133,000 square miles (345,000 square kilometers), the Great Barrier Reef is the largest coral reef in the world, home to more than 1,500 species of fish and 411 species of hard coral. It contributes billions of dollars to Australia’s economy every year and is heavily promoted to foreign tourists as one of the country’s – and the world’s – greatest natural wonders.
But ocean temperatures are rising enough to cause devastating reef bleaching, as the world continues to burn planet-warming fossil fuels. Ocean temperatures are getting even warmer under the current El Niño – a natural climate pattern that brings warmer-than-average sea surface temperatures – which is one of the strongest on record.
Bleaching occurs when a stressed coral sheds algae from its tissues, leaving it a food source. If the water temperature remains higher than normal for too long, corals can starve and die, turning white as their carbonate skeleton is exposed.
Great Barrier Reef managers plan to expand aerial and underwater surveys across the entire reef in the coming weeks. Although the southern side of the reef is most affected, the reef authority has received reports of bleaching from all other regions of the marine park.
“Aerial surveys are a great tool for estimating the spatial extent of bleaching, but we need to go underwater to understand more about the severity of the bleaching and how deep the bleaching spreads,” said Dr. Neal Cantin, senior research scientist with Dr. Australian Institute of Marine Science.
A CNN team that visited the Great Barrier Reef two weeks ago noticed bleaching at the southernmost coral cay, Lady Elliot Island and on four different reefs outside Cairns, in the center of the reef.
And a separate report by a team at James Cook University reported areas of moderate to severe coral bleaching around the Keppel Islands, where water temperatures were well above the summer average.
“I’ve been working on these reefs for almost 20 years and I’ve never felt the water this warm,” said Dr Maya Srinivasan, a scientist at the university’s center for research on tropical water and aquatic ecosystems. in a statement last week. .
“When we were in the water, we could immediately see parts of the reef that were completely white from intense bleaching. Some corals were already dying.”
Fear of the seventh mass bleaching
Scientists say corals can recover if sea temperatures stabilize.
“Fish abundance and coral cover are declining in this region following impacts like this in the past. But we’ve seen the recovery of coral and fish communities on many reef areas – there just needs to be enough time between impacts for this recovery to happen,” said Srinivasan.
Warmer ocean temperatures caused major mass bleaching at the Great Barrier Reef in 2016, 2017 and 2020. Previous bleachings occurred in 1998 and 2002.
Another bleaching event in 2022 – the first during a La Niña event, El Niño’s counterpart, which usually has a cooling effect – raised serious concerns about the reef’s prospects.
There are concerns that 2024 will see the seventh major bleaching event.
“Although we have to wait for official confirmation from the Marine Park Authority, it certainly looks like the seventh mass bleaching event is occurring on the Great Barrier Reef, with reports of severe bleaching along its length,” David Ritter , CEO of Greenpeace Australia Pacific. , CNN said.
“We know that the climate crisis is driving marine heat waves and leading to these bleaching events, but the frequency and scale at which they are happening now is alarming – every summer we are holding our breath. “
Coral populations around Florida and the Caribbean “declined” last year due to a record sea heat wave and observers in Australia fear a similar fate could befall the country’s reefs.
“What we’re seeing in Florida and the Caribbean in general is a lesson in what’s going to happen in the next 12 months as this thing moves forward,” Ove Hoegh-Guldberg, climatologist and chief scientist at the Great Barrier Reef Foundation , CNN said recently.
Last year, the warmest year since global records began in 1850, according to the US National Oceanic and Atmospheric Administration’s (NOAA) annual climate report, sea temperatures rose to 100 degrees Fahrenheit (37 degrees Celsius) in some regions and the complete bleaching. reefs.
With water temperatures climbing to unprecedented heights, NOAA earlier this month added three new levels to its alert system to account for increasingly severe coral bleaching and higher mortality rates.
Alert Level 5, the new highest level classified as “almost complete mortality,” means that more than 80% of corals in the highlighted area are at risk of death due to high, long-term water temperatures.
Last year, UNESCO’s World Heritage Committee decided not to include the Great Barrier Reef on its list of “at risk” sites, despite scientific evidence suggesting it is at risk of a major bleaching event.
Greenpeace’s Ritter said after the decision, “the Australian government has pledged to do everything possible to protect the Great Barrier Reef. This must include addressing climate change as an existential threat to the reef, and ensuring that our emissions reduction plans are aligned with a 1.5 degree pathway.“
He added that “Australia demands that the health of the Great Barrier Reef be taken seriously as we continue to expand and subsidize the coal and gas industry to the tune of billions every year.”
According to the Australian Institute’s Coal Mine Tracker, the Labor government has approved four new mines or expansions since coming to power in May 2022.
CNN’s Rebecca Wright and Hilary Whiteman reported.
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