Home https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Science https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Dying coral reefs turn vibrant neon colors into an obvious effort to survive

Dying coral reefs turn vibrant neon colors into an obvious effort to survive

For years, coral reefs all over the world have been ravaged by mass whitening events as the oceans continue to warm due to climate change. Corals have little chance of giving up these events – but a new study suggests they have an unusual method of survival: acquiring a vibrant neon color.

When whitening events occur, prolonged heat spikes cause ghostly white corals, often leading to their death. But “color bleaching” has the opposite effect: dying corals acquire more pigment and glow in shades of bright pink, purple and orange.

Scientists first noticed the mysterious neon coral a decade ago, but could not understand why it happened. This study, published Thursday in the journal Current Biology, suggests that corals change color as a last resort. survives,,

Richard Wevers / Ocean Agency / XL Catlin Seaview Survey
Colorful whitening corals Acropora in New Caledonia.

Richard Weaver / The Ocean Agency / XL Catlin

Coral animals coexist symbiotically with miniature algae, providing them with shelter, nutrients and carbon dioxide in exchange for their photosynthetic powers. Even slight increases at annual ocean temperatures, it can wreak havoc on this relationship by expelling algae from coral tissues and exposing its white skeleton. Once coral is exposed, it often decays and dies, changing the ecosystem for the diverse array of life that relies on it.

Researchers at the University of Southampton’s Coral Reef Laboratory studied 15 color whitening events around the world between 2010 and 2019 – including one in the Great Barrier Reef, the world’s largest coral reef system – and recreated these ocean temperatures in laboratory. They found that color whitening events occur when corals produce “what is an effective sunscreen” on their surface to protect themselves from harmful rays and create a luminous display that researchers say encourages algae to return.

The Ocean Agency described the process as a “chilling, beautiful and heartbreaking” final cry for help as corals try to attract the attention of algae.

“Our research shows that color whitening involves a self-regulating mechanism, the so-called optical feedback cycle, which includes both partners of the symbiosis,” lead researcher Prof. Jörg Wiedenmann of the University of Southampton said in a statement. “The resulting sunscreen layer will subsequently promote the return of symbionts. As the recovering algae population begins to absorb light for their photosynthesis again, the light levels inside the corals will drop and coral cells will reduce the production of color pigments to their normal level.”

Color bleaching corals Acropora in the Philippines.

Ryan Gorung, University of Washington

Coral reefs support more species per unit area than any other marine environment, including about 4,000 species of fish, 800 species of hard corals and potentially millions of other undiscovered species, according to the National Oceanic and Atmospheric Administration. Interruptions in coral reefs have far-reaching consequences for ocean ecosystems.

It’s not just the warming of the oceans that is causing color bleaching. According to the researchers, changes in nutrient levels in coral reefs due to leakage of fertilizers from farms also lead to bleaching events – a problem that can be solved locally.

Experts consider only corals that have encountered slight or brief disturbances, not extreme mass whitening events, you can try to save using this process. These corals can still undergo some of their normal functions in a short period of time, as they hope the algae will return – while drastic changes in ocean temperature almost always lead to the death of corals.

Reports of color whitening during the latest mass whitening event in the Great Barrier Reef in March and April gave scientists hope that the system’s patches have a chance to recover.

“Bleaching is not always a death sentence for corals. A coral can still be alive,” said Dr. Cecilia D’Angelo, a professor of molecular biological coral at the University of Southampton. “If the stressful event is mild enough, corals can re-establish symbiosis with their algae partner.”

Internal changes that allow color whitening to occur.

Jörg Wiedenmann, Elena Bolati and Cecilia D’Angelo / University of Southampton, Palawan color whitening image by Ryan Goerung / University of Washington

Whitening events were few and far between, but now they happen almost every year. In 2017 alone, almost half of the corals on the Great Barrier Reef died – and experts say we have time to save them.

“Unfortunately, recent episodes of global bleaching caused by unusually hot water have led to high coral mortality, leaving the world’s coral reefs struggling to survive,” D’Angelo said.

Scientists have stressed that while color bleaching is a good sign, only a significant reduction in global greenhouse gases – in addition to improving local water quality – could save coral reefs after this century.

“Now that we know that nutrient levels can also affect color bleaching, we can more easily identify cases where heat stress can be exacerbated by poor water quality,” the researchers said. “This can be managed locally, while ocean heat waves caused by climate change will need global leadership. Together, these actions can secure the future of coral reefs.”

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