How corals defend themselves against the warm -up of seas

How corals defend themselves against the warm -up of seas

By Rohini Subrahmanyam Edited by Sarah Lewin Frasier

In the depths of the Eastern Tropical Pacific Ocean there is a dazzling landscape of wavy coral reef colored by photosynthetic algae, of which the corals obtain their energy. But at the beginning of the 1980s, an aquatic heat wave caused by the El Niño climate phenomenon led to a record money laundering event, turning more than 90 percent of these corals of a pale and lifeless white. The algae, which had prospered within their hosts of coral for millions of years, could no longer endure to live within them.

The strong events of El Niño warmed the same Pacific waters at the end of the 1990s and again in 2015-2016, but the scientists noticed that these heat waves did not affect the reefs as bad as the first. Diving after the last event, the marine biologist of the University of Miami, Ana Palacio, saw that some of the corals seemed to resist or recover from bleaching. Maybe, Palacio thought, they have found a way to adapt.

Many adult corals are tied to the reefs they build. Swimming colder waters is not an option, which makes them particularly vulnerable to changing climate. But corals are also resistant, and scientists are discovering how they adapt. Some corals change to their algae tenants for heat -resistant species. Others can use rows of small hairs on their bodies to “envive” the excess harmful oxygen released by stressed algae. And certain baby corals modify their own metabolisms to resist heating waters. Scientists hope to use these natural adaptations in the race to preserve these crucial ecosystems anchors.

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When Palacio and his team examined the coral reefs after the 2015-2016 heat wave, they discovered that the private corals called Polypora—The main species of Arrecife construction coral in the Eastern Tropical Pacific, seemed to have expelled the algae that generally reside within them and taken in other species that were more heat tolerant.

“They begin to change their [algae] community as water becomes warmer and warmer, and are increasing Durusdinium glynnii“, Explains Palacio. The name of this species comes from the Latin word Duruswhich means “rough” or “hard.” Most symbiotic algae produce toxic oxygen levels under heat stress, which forces corals to evict them. But Durusdinio It maintains its tolerable levels.

However, corals do not always trust their algae guests to avoid excessive oxygen, researchers have found; Sometimes they can take the matter in their own “hands.” Cilia ranks (tenería and fluid projections) can act as the personal ventilation system of corals of the excess oxygen to the stains that lack it.

In 2022, marine biologists César O. Pacherres and Soeren Ahmerkamp, ​​then at the University of Bremen in Germany, showed that these cilia that are fast create microscopic swirls in the water, turning oxygen and avoid accumulating harmfully anywhere. All corals have this ventilation system, but how much they use it can vary between the species. Scientists now plan to prove if some vulnerable corals, such as those in the great reef barrier, pay their cilia faster in response to higher temperatures.

And the corals are not always trapped in their place; Its larvae float freely through the ocean before establishing, which offers crucial opportunities for a species to change to more hospital waters or spread its heat tolerant genes. That is why Ariana Huffmyer, a marine biologist at the University of Washington, is particularly interested in how baby corals adapt to higher temperatures. She and researchers from the Hawaii Marine Institute of Biology recently showed that the coral larvae, if they are exposed to warm water for just three days in the laboratory, alter your own metabolism to deal with heat stress and avoid bleaching.

The corals generally provide a small amount of nitrogen to their resident algae, they already change carbon, which they use as a source of energy. “Keep [the algae’s] Own survival and give the necessary nutrients to the guest, there is a really complex, delicate and very complex nutritional relationship between the two, ”says Huffmyer. Under stress, corals produce too much nitrogen. This excess causes algae to enter hyperdrive and divide much more, saving carbon and keeping it from their hosts. Huffmyer discovered that baby corals exposed to short heat stress periods learn to maintain excess nitrogen for themselves and do not share with algae, maintaining stable symbiosis.

Pacherres warns that such adaptations can protect an organism only to some extent. “They have the tools to resist certain things, but beyond that limit there is not enough that they can do. For example, if it’s hot, [humans] You can sweat to relieve heat. But if it’s too hot, we die, ”he says. “At one time, sweat is not enough.”

But whatever the heat stroke tool that corals have can help scientists develop protection strategies. Baby corals that can resist stress are especially important for conservation efforts because they can travel between reefs and potentially share heat tolerant genes In new places. “The larvae of those reefs are already previously trained for the increase in temperatures, so we need to protect them because they are somehow the source of the future,” says Madhavi Colton, a conservation scientist who investigated science -based tactics in the non -profit organization Coral Reef Alliance.

Natural coral adaptations can also help direct interventions such as corals hardeal in stress in nurseries before re -planting them in oceanic reef. “It must cultivate corals that are more likely to survive than the corals that died before,” says Palacio. If researchers can persuade corals to adopt heat -resistant algae or if they activate genes that can deal with heat stress, increase the possibilities of corals to survive future ocean heat waves.

“When you immerse yourself and see a beautiful healthy reef with these colorful corals … I still feel this euphoria of being in all this underwater alien world,” says Huffmyer. “It’s hard to return after a laundering event and see him dead. But that gives you the motivation to want to use whatever your skill set, whatever your passion, to try to help. “