Coral bleaching is often associated with the naturally occurring El Niño climate phenomenon (representative)
London:
The US National Oceanic and Atmospheric Administration (NOAA) says the world is on the brink of a fourth mass coral bleaching event that could kill large swaths of tropical reefs, including parts of Australia’s Great Barrier Reef.
Marine biologists are on high alert as climate change and the El Niño weather pattern lead to months of record-breaking ocean temperatures.
“It looks like the entire Southern Hemisphere may experience bleaching this year,” said ecologist Derek Manzello, coordinator of the National Oceanic and Atmospheric Administration’s (NOAA) Coral Reef Watch, the global coral Albino Risk Monitoring Agency.
“We are literally on the cusp of the most severe bleaching event in Earth’s history,” he said.
These details have not been previously reported.
Coral bleaching occurs when corals excrete the colorful algae in their tissues due to heat stress. Without these beneficial algae, corals become pale and susceptible to starvation and disease.
Coral bleaching can be devastating to marine ecosystems and to the fishing and tourism economies that rely on healthy, colorful reefs to attract scuba divers and snorkelers.
ominous sign
The last major global coral bleaching event occurred from 2014 to 2017, during which time the Great Barrier Reef lost nearly a third of its coral. Preliminary results indicate that approximately 15% of the world’s coral reefs experienced mass coral mortality during this event.
As observations continue to emerge, this year could be even worse.
After last year’s northern hemisphere summer, the Caribbean experienced the worst coral bleaching on record.
Now in late summer, “basically everywhere in the Southern Hemisphere is bleaching,” Manzello said. “The entire Great Barrier Reef is bleaching. We’ve just received reports of bleaching in American Samoa.”
Previous global bleaching events occurred in 2010 and 1998.
Coral bleaching is often associated with the naturally occurring El Niño climate phenomenon, which causes seawater to warm.
But the world has also just experienced its first 12-month period in which average temperatures were more than 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels.
Over the longer term, a temperature rise of 1.5 degrees Celsius is considered the tipping point for mass coral death, with scientists estimating that 90% of the world’s corals could disappear.
Field trips
For an event to be considered global, widespread bleaching must occur in three ocean basins—the Atlantic, Pacific, and Indian oceans.
Scientists evaluate sea surface temperature data and satellite images to determine whether coral reef pixels have exceeded critical thresholds for bleaching.
To be worthy of a global mass bleaching event, a certain proportion of coral reef pixels would need to reveal the level of heat stress in each ocean basin. Based on this definition alone, “technically we’re already there in 2024,” Manzello said.
However, he said NOAA is still waiting for final confirmation from Indian Ocean scientists or photos of Indian Ocean reefs to raise the flag for a fourth mass bleaching event.
Australia’s Great Barrier Reef has experienced six localized bleaching events since 1998, and scientists are conducting flyovers of the reef to determine the extent of the bleaching.
Australian Institute of Marine Science spokesperson Joanne Manning said aerial surveys so far have shown widespread coral bleaching in the Keppel area and the Capricorn Bunker complex.
“Aerial surveys are continuing as coral bleaching has been reported in all areas of the marine park, with varying degrees of severity,” she said, adding that they aimed to complete fly-by surveys in the coming weeks and expand to water Lower coral survey.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
