The World’s Coral Reefs Are Bleaching. What Does That Mean?

This July 26, 2023 image provided by phade® by WinCup, Inc., shows a "Coral Fort," made of biodegradable drinking straws that researchers are using to prevent laboratory-grown coral from becoming really expensive fish food, off the coast of Fort Lauderdale, Fla. (Chris Gug/phade® by WinCup, Inc. via AP)
This July 26, 2023 image provided by phade® by WinCup, Inc., shows a "Coral Fort," made of biodegradable drinking straws that researchers are using to prevent laboratory-grown coral from becoming really expensive fish food, off the coast of Fort Lauderdale, Fla. (Chris Gug/phade® by WinCup, Inc. via AP)
TT

The World’s Coral Reefs Are Bleaching. What Does That Mean?

This July 26, 2023 image provided by phade® by WinCup, Inc., shows a "Coral Fort," made of biodegradable drinking straws that researchers are using to prevent laboratory-grown coral from becoming really expensive fish food, off the coast of Fort Lauderdale, Fla. (Chris Gug/phade® by WinCup, Inc. via AP)
This July 26, 2023 image provided by phade® by WinCup, Inc., shows a "Coral Fort," made of biodegradable drinking straws that researchers are using to prevent laboratory-grown coral from becoming really expensive fish food, off the coast of Fort Lauderdale, Fla. (Chris Gug/phade® by WinCup, Inc. via AP)

Huge stretches of coral reef around the world are turning a ghostly white this year amid record warm ocean temperatures.

On Monday, the US National Oceanic and Atmospheric Administration confirmed the world's fourth mass global bleaching event is underway - with serious consequences for marine life and for the people and economies that rely on reefs.

Here's how warming affects coral reefs and what the future might hold for these fragile underwater ecosystems.

WHAT ARE CORALS?

Corals are invertebrates that live in colonies. Their calcium carbonate secretions form hard and protective scaffolding that serves as a home to many colorful species of single-celled algae.

The two organisms have evolved over millennia to work together, with corals providing shelter to algae, while the algae remove coral waste compounds and deliver energy and oxygen back to their hosts.

WHY DO CORALS MATTER?

Coral reefs cover less than one percent of the ocean floor, but have out-sized benefits for marine ecosystems and economies.

A quarter of marine life will depend on reefs for shelter, finding food or spawning at some point in their lives and coastal fisheries would struggle without corals.

Every year, reefs provide about $2.7 trillion in goods and services, from tourism to coastal protection, according to a 2020 estimate by the Global Coral Reef Monitoring Network. About $36 billion is generated by snorkeling and scuba diving tourists alone.

Coral reefs also help coastal communities by forming a protective barrier against storm surges and large waves. This helps to avoid property damage for more than 5 million people worldwide, a 2022 study in the journal Marine Policy found.

WHAT IS CORAL BLEACHING?

When water temperatures rise, jewel-toned corals get stressed. They cope by expelling their algae — causing them to turn bone white.

Most corals live in shallow waters, where climate-driven warming is most pronounced.

Whether a coral becomes heat-stressed depends on how long the high temperatures last, and how much warmer they are than usual.

Scientists have found that corals generally begin to bleach when surrounding waters are at least 1 degree Celsius warmer than the maximum average temperature - or the peak of what corals are used to - and persist for four or more weeks.

WHAT IS GOING ON WITH OCEAN TEMPERATURES THIS YEAR?

This year has seen an explosive and sustained bout of ocean heat as the planet deals with the effects of both climate change and an El Nino climate pattern, which yields warmer seas.

In March, global average sea surface temperature (SST) reached a record monthly high of 21.07C (69.93F), according to the EU Copernicus Climate Change Service.

"There's been a pretty large step change in the global average SST this year," said Neal Cantin, a coral biologist with the Australian Institute of Marine Sciences. "We're certainly in a new regime. Corals clearly aren't keeping up".

As the El Nino weakens, scientists say some of that ocean heat should diminish. But overall ocean warming will continue as climate change intensifies.

DO ALL BLEACHED CORALS DIE?

Corals can survive a bleaching event if the surrounding waters cool and algae return.

Scientists at the Palau International Coral Reef Center estimate that it takes at least nine to 12 years for coral reefs to fully recover from mass bleaching events, according to research published in 2019.

Disruptions such as cyclones or pollution can slow the recovery.

"Bleaching is like a fever in humans," said ecologist David Obura, director of Coastal Oceans Research and Development in the Indian Ocean East Africa. "We get a fever to resist a disease, and if the disease is not too much, we recover. But if it is too much, we die as a result."

Scientists caution that corals this year have faced harsher and more prolonged high temperatures than ever before.

"What is happening is new for us, and to science," said Lorenzo Alvarez-Filip, a coral reef ecologist at the National Autonomous University of Mexico. "We cannot yet predict how severely stressed corals will do even when they survive the stress event, or how coral recovery will operate."

WHAT HAPPENS TO DEAD CORALS?

Dead reefs can still offer shelter to fish or provide a storm barrier over several years for coastal communities.

But eventually, these underwater graveyards of calcium carbonate skeletons will erode and break apart.

"It might take 10, even 20 years to see these consequences," Alvarez-Filip said.

WHAT CAN BE DONE TO HELP SAVE REEFS?

The best chance for coral survival is for the world to cut greenhouse gas emissions to limit climate change.

Many scientists think that at just 1.2C of warming above preindustrial level, the world has already passed a key threshold for coral reef survival. They expect between 70% and 90% of the world's coral reefs will be lost.

Scientists and conservationists are scrambling to intervene.

Local communities have cleanup programs to remove litter from the reefs to reduce further stresses. And scientists are breeding corals in labs with the hopes of restoring degraded reefs.

However, none of this is likely to work to protect today's corals from warming waters. Scientists are therefore trying to plan for the future by bringing coral larvae into cryopreservation banks, and breeding corals with more resilient traits.

Obura said that while it's important that scientists investigate such interventions, breeding genetically engineered corals is not the answer to climate change. "We have to be very careful about stating that it's the solution and that it's saving corals reefs now," he said.

"Until we reduce carbon emissions, they won't save coral reefs."



China Says its Astronauts Complete Record-breaking Spacewalk

File Photo: Astronaut Liu Yang waves as she is out of a return capsule of the Shenzhou-14 spacecraft, following a six-month mission on China's space station, at the Dongfeng landing site in Inner Mongolia Autonomous Region, China December 4, 2022. China Daily via REUTERS
File Photo: Astronaut Liu Yang waves as she is out of a return capsule of the Shenzhou-14 spacecraft, following a six-month mission on China's space station, at the Dongfeng landing site in Inner Mongolia Autonomous Region, China December 4, 2022. China Daily via REUTERS
TT

China Says its Astronauts Complete Record-breaking Spacewalk

File Photo: Astronaut Liu Yang waves as she is out of a return capsule of the Shenzhou-14 spacecraft, following a six-month mission on China's space station, at the Dongfeng landing site in Inner Mongolia Autonomous Region, China December 4, 2022. China Daily via REUTERS
File Photo: Astronaut Liu Yang waves as she is out of a return capsule of the Shenzhou-14 spacecraft, following a six-month mission on China's space station, at the Dongfeng landing site in Inner Mongolia Autonomous Region, China December 4, 2022. China Daily via REUTERS

Two Chinese astronauts this week completed a world-record spacewalk of more than nine hours, according to a statement from China's Manned Space Agency, marking another milestone for Beijing's rapidly expanding space program.

The spacewalk, carried out by Cai Xuzhe and Song Lingdong outside the Tiangong space station in low-Earth orbit on Tuesday, was at least four minutes longer than the last record set by NASA astronauts James Voss and Susan Helms in 2001, according to Reuters.

The two astronauts of China's Shenzhou-19 mission donned their Feitian spacesuits to carry out an array of tasks on the station's exterior, including the installation of space-debris protection devices, China's space agency said.

"They successfully completed all the planned tasks and felt very excited about it," Wu Hao, a staffer from the China Astronaut Research and Training Center, told China Central Television, a state broadcaster.

The former Soviet Union in 1965 became the first nation to carry out a spacewalk. Since then, Russia and the United States have conducted hundreds of such missions, primarily outside the International Space Station for tasks ranging from solar panel installations to materials research.

The first spacewalk by a Chinese astronaut occurred in 2008.

China's spacewalking milestone this week comes amid a flurry of other recent cosmic achievements that have boosted Beijing's competitive footing with the United States.

China landed its first rover on Mars in 2021 and earlier this year became the first country to retrieve rock samples from the moon's treacherous far side in its Chang'e-6 mission.

Beijing is targeting 2030 to land its first astronauts on the moon to become the second country after the US to put humans there. Beijing has courted roughly a dozen countries for its International Lunar Research Station program, an effort to build a moon base on the moon's south pole.

That program rivals NASA's Artemis program, which aims to return US astronauts to the moon for the first time since the final Apollo mission of 1972.