Coral bleaching event is biggest on record

STILL GROWING: The ongoing bleaching event, the fourth since 1998, surpassed the previous record of 65.7 percent in half the time, and is still increasing, an NOAA expert said

AFP, WASHINGTON

A global episode of heat-related coral bleaching has grown to the largest on record, US authorities said on Friday, sparking worry for the health of key marine ecosystems.

From the beginning of last year through Thursday last week, “roughly 77 percent of the world’s reef area has experienced bleaching-level heat stress,” National Oceanic and Atmospheric Administration (NOAA) coral reef watch coordinator Derek Manzello said.

When ocean water is too warm — such as during heat waves that have hit areas from Florida to Australia in the past year — coral expel their algae and turn white, an effect called “bleaching,” which leaves them exposed to disease and at risk of dying off.

Fish swim past bleached coral on a reef off Koh Mak, Thailand, on May 8.

Photo: Reuters

The algae provide coral with food and nutrients, as well as their captivating colors.

The ongoing bleaching event — the fourth since 1998 — had surpassed the previous record of 65.7 percent in half the time, and “is still increasing in size,” Manzello said.

The consequences of coral bleaching are far-reaching, affecting not only the health of oceans but also the livelihoods of people, food security and local economies.

Severe or prolonged heat stress leads to corals dying off, but there is hope for recovery if temperatures drop and other stressors such as overfishing and pollution are reduced.

The last record had been set during the third global bleaching event, which lasted from 2014 to 2017, and followed previous events in 1998 and 2010, Manzello said.

The NOAA’s heat-stress monitoring is based on satellite measurements from 1985 to the present day. It declared the latest mass bleaching event in April.

WWF International Oceans Practice head Pepe Clarke said at the time that the “scale and severity of the mass coral bleaching is clear evidence of the harm climate change is having right now.”

Manzello on Friday said the NOAA had confirmed reports of mass coral bleaching from 74 countries or territories since February last year.

“This includes locations in the northern and southern hemisphere of the Atlantic, Pacific, and Indian Oceans,” he said in an e-mail.

Australian authorities in March announced that the Great Barrier Reef was experiencing its fifth mass bleaching event in eight years.

“Corals can recover if the marine heat stress is not too severe, or too prolonged,” Manzello and colleague Jacqueline De La Cour said in April.

However, there are “lasting physiological impacts for the survivors” and recovery “becomes increasingly challenging as bleaching events become more frequent and more severe,” the pair added.


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