The world's coral reefs are facing another mass bleaching event — maybe the biggest ever
CBC
The world's oceans are experiencing another global mass coral bleaching event because of unprecedented heat, scientists at the U.S. National Oceanic and Atmospheric Administration confirmed.
"This is the fourth time, on record, that coral bleaching has occurred simultaneously within all major ocean basins," said Derek Manzello, ecologist and co-ordinator of NOAA's Coral Reef Watch.
Bleaching — a ghostly discolouration, in stark contrast to vibrant colours found in reefs — can occur when corals are heat-stressed, expelling microscopic algae from within. The longer and hotter it gets, the more likely the corals will die, disrupting fragile ecosystems as well as the lives and livelihoods of people who depend on them.
But the full extent of damage is yet to come. Manzello is seeing an increase in affected reefs every week.
"If that trend continues, this will be the most spatially expansive, global bleaching event on record — in as little as a few weeks, potentially," Manzello warned.
Global sea surface temperatures have reached new heights in the last year, driven in part by oceans absorbing the excess atmospheric carbon from greenhouse gas emissions.
NOAA has confirmed mass bleaching in reefs throughout the world, from Panama to the Persian Gulf to the South Pacific. Manzello says just over half of the world's reefs were affected by the current event, but it was near total in the Atlantic — a record-setting 98.5 per cent of the coral zones there experienced bleaching-level heat.
Just last week, the Australian Marine Conservation Society raised the alarm about bleaching in the southern Great Barrier Reef, where the last global bleaching event ended up killing a third of all corals.
Coral Reef Watch's satellite data shows that hotspots are being seen in every ocean, with Atlantic, Pacific and Indian ocean corals experiencing a range of moderate to extreme heat stress. The unprecedented ocean temperatures even forced a revision of this alert system last year — adding Levels 3 to 5, the last of which represents "risk of near complete mortality."
Rohan Arthur, a marine biologist who has extensively studied the reefs in Lakshadweep off India's southwest coast, expected this declaration. But as he put it, darkly, "with all the enthusiasm of an undertaker measuring a corpse."
Arthur, who is with the Nature Conservation Foundation based in Mysuru, India, has been tracking sea surface temperatures in Lakshadweep over the last year and has seen an unprecedented 1 C rise above average. The corals are starting to show it, too.
"A mass bleaching event itself is a morbidly beautiful sight," Arthur wrote to CBC News via email, "with the reef turning every shade of pink and blue and white on its way to a surreal death."
Having spent more than 25 years looking at those reefs, including past bleaching events, Arthur feels the impending devastation in the pit of his stomach. It's a connection echoed an ocean away by Nicola Smith, assistant professor of biology at Concordia University in Montreal.
"It hits me personally when I think about these damages," said Smith, who was born and raised in the Bahamas. When these marine heat waves hit, there's little escape.