Wednesday, March 13, 2024

World on brink of fourth mass coral reef bleaching event, NOAA says

A Healthy brain coral rests under Port of Miami regardless of extreme heat in Miami, Flordia, U.S., July 14, 2023. REUTERS/Maria Alejandra Cardona/File Photo
From Reuters by Gloria Dickie
  • Southern Hemisphere reefs set to bleach in coming months
  • Follows heat records fuelled by climate change and El Nino
  • Scientists conduct fly-overs at Australia's Great Barrier Reef
  • Previous mass bleaching events in 1998, 2010 and 2014-2017
The world is on the verge of a fourth mass coral bleaching event which could see wide swathes of tropical reefs die, including parts of Australia's Great Barrier Reef, the U.S. National Oceanic and Atmospheric Administration (NOAA) said.
Marine biologists are on high alert following months of record-breaking ocean heat fuelled by climate change and the El Nino climate pattern.
Images showing the bleaching and death of coral off Heron Island from 2021 through to February. Photograph: CoralWatch
"It's looking like the entirety of the Southern Hemisphere is probably going to bleach this year," said ecologist Derek Manzello, the coordinator of NOAA's Coral Reef Watch which serves as the global monitoring authority on coral bleaching risk.
"We are literally sitting on the cusp of the worst bleaching event in the history of the planet," he said.

These details have not previously been reported.
Triggered by heat stress, coral bleaching occurs when corals expel the colourful algae living in their tissues.
Without these helpful algae, the corals become pale and are vulnerable to starvation and disease.
Coral bleaching can be devastating for the ocean ecosystem, as well as fisheries and tourism-based economies that depend on healthy, colourful reefs to attract scuba divers and snorkellers.
A recent photo of the bleaching damage on the Great Barrier Reef
courtesy of Climate Council

Ominous signs

The last global mass coral bleaching event ran from 2014 to 2017, during which time the Great Barrier Reef lost nearly a third of its corals.
Preliminary results suggest that about 15% of the world's reefs saw large coral die-offs in this event.
This year is shaping up to be even worse as observations trickle in.
Following the Northern Hemisphere summer last year, the Caribbean registered its worst coral bleaching on record.

Now at the end of its summer, "the Southern Hemisphere is basically bleaching all over the place," Manzello said. 
"The entirety of the Great Barrier Reef is bleaching. We just had reports that American Samoa is bleaching."
Previous global bleaching events occurred in 2010 and 1998.
Coral bleaching is often tied to the naturally occurring El Nino climate phenomenon which leads to warmer ocean waters.
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