海角大神

On a moonless summer night in Hawaii, krill, fish, and crabs swirl through a beam of light as two researchers peer into the water above a vibrant reef.

Minutes later, like clockwork, they see eggs and sperm from spawning coral drifting past their boat. They scoop up the fishy-smelling blobs and put them in test tubes.

In this Darwinian experiment, the scientists are trying to speed up coral鈥檚 evolutionary clock to breed 鈥渟uper corals鈥� that can better withstand the impacts of global warming.

For the past five years, the researchers have been conducting experiments to prove their theories would work. Now, they鈥檙e getting ready to plant laboratory-raised corals in the ocean to see how they survive in nature.

鈥淎ssisted evolution started out as this kind of crazy idea that you could actually help something change and allow that to survive better because it is changing,鈥� said Kira Hughes, a University of Hawaii researcher and the project鈥檚 manager.

Speeding up nature聽

Researchers tested three methods of making corals more resilient:

• Selective breeding that carries on desirable traits from parents.
• Acclimation that conditions corals to tolerate heat by exposing them to increasing temperatures.
• And modifying the algae that give corals essential nutrients.

Ms. Hughes said the methods all have proven successful in the lab.

And while some other scientists worried this is meddling with nature, Ms. Hughes said the rapidly warming planet leaves no other options.

鈥淲e have to intervene in order to make a change for coral reefs to survive into the future,鈥� she said.

When ocean temperatures rise, coral releases its symbiotic algae that supply nutrients and impart its vibrant colors. The coral turns white 鈥� a process called bleaching 鈥� and can quickly become sick and die.

For more than a decade, scientists have been observing corals that have survived bleaching, even when others have died on the same reef.

So, researchers are focusing on those hardy survivors, hoping to enhance their heat tolerance. And they found selective breeding held the most promise for Hawaii鈥檚 reefs.

鈥淐orals are threatened worldwide by a lot of stressors, but increasing temperatures are probably the most severe,鈥� said Crawford Drury, chief scientist at Hawaii鈥檚 Coral Resilience Lab. 鈥淎nd so that鈥檚 what our focus is on, working with parents that are really thermally tolerant.鈥�

A novel idea聽

In 2015, Ruth Gates, who launched the resilience lab, and Madeleine van Oppen of the Australian Institute of Marine Science published a paper on assisted evolution during one of the world鈥檚 worst bleaching events.

The scientists proposed bringing corals into a lab to help them evolve into more heat-tolerant animals. And the idea attracted Microsoft co-founder Paul Allen, who funded the first phase of research and whose foundation still supports the program.

鈥淲e鈥檝e given [coral] experiences that we think are going to raise their ability to survive,鈥� Ms. Gates told The Associated Press in a 2015 interview.

Ms. Gates, who died in 2018, also said she wanted people to know how 鈥渋ntimately reef health is intertwined with human health.鈥�

Coral reefs, often called the rainforests of the sea, provide food for humans and marine animals, shoreline protection for coastal communities, jobs for tourist economies, and even medicine to treat illnesses.

A recent report from the National Oceanic and Atmospheric Administration (NOAA) and other research organizations concluded bleaching events are the biggest threat to the world鈥檚 coral reefs. Scientists found that between 2009 and 2018, the world lost about 14% of its coral.

Assisted evolution was not widely accepted when first proposed.

Ms. van Oppen said there were concerns about losing genetic diversity and critics who said the scientists were 鈥減laying gods鈥� by tampering with the reef.

鈥淲ell, you know, [humans] have already intervened with the reef for very long periods of time,鈥� Ms. van Oppen said. 鈥淎ll we鈥檙e trying to do is to repair the damage.鈥�

Rather than editing genes or creating anything unnatural, researchers are just nudging what could already happen in the ocean, she said. 鈥淲e are really focusing first on as local a scale as possible to try and maintain and enhance what is already there.鈥�

Millions of years in the making聽

Still, there are lingering questions.

鈥淲e have discovered lots of reasons why corals don鈥檛 bleach,鈥� said Steve Palumbi, a marine biologist and professor at Stanford University. 鈥淛ust because you find a coral that isn鈥檛 bleaching in the field or in the lab doesn鈥檛 mean it鈥檚 permanently heat tolerant.鈥�

Corals have been on Earth for about 250 million years and their genetic code is not fully understood.

鈥淭his is not the first time any coral on the entire planet has ever been exposed to heat,鈥� Mr. Palumbi said. 鈥淪o the fact that all corals are not heat resistant tells you ... that there鈥檚 some disadvantage to it. And if there weren鈥檛 a disadvantage, they鈥檇 all be heat resistant.鈥�

But Mr. Palumbi thinks the assisted evolution work has a valuable place in coral management plans because 鈥渞eefs all over the world are in desperate, desperate, desperate trouble.鈥�

The project has gained broad support and spurred research around the world. Scientists in the United Kingdom, Saudi Arabia, Germany, and elsewhere are doing their own coral resilience work. The U.S. government also backs the effort.

Assisted evolution 鈥渋s really impressive and very consistent with a study that we conducted with the National Academies of Sciences,鈥� said Jennifer Koss, the director of NOAA鈥檚 Coral Reef Conservation Program.

鈥淲e asked them to gather all the most recent cutting-edge science that was really centered on innovative interventions in coral reef management,鈥� Ms. Koss said. 鈥淎nd certainly, this assisted gene flow fits right in.鈥�

Major hurdles

There are still serious challenges.

Scalability is one. Getting lab-bred corals out into the ocean and having them survive will be hard, especially since reintroduction has to happen on a local level to avoid bringing detrimental biological material from one region to another.

James Guest, a coral ecologist in the United Kingdom, leads a project to show selectively bred corals not only survive longer in warmer water, but can also be successfully reintroduced on a large scale.

鈥淚t鈥檚 great if we can do all this stuff in the lab, but we have to show that we can get very large numbers of them out onto the reef in a cost-effective way,鈥� Mr. Guest said.

Scientists are testing delivery methods, such as using ships to pump young corals into the ocean and deploying small underwater robots to plant coral.

No one is proposing assisted evolution alone will save the world鈥檚 reefs. The idea is part of a suite of measures 鈥� with proposals ranging from creating shades for coral to pumping cooler deep-ocean water onto reefs that get too warm.

The advantage of planting stronger corals is that after a generation or two, they should spread their traits naturally, without much human intervention.

Over the next several years, the Hawaii scientists will place selectively bred coral back into Kaneohe Bay and observe their behavior. Ms. van Oppen and her colleagues have already put some corals with modified symbiotic algae back on the Great Barrier Reef.

With the world鈥檚 oceans continuing to warm, scientists say they are up against the clock to save reefs.

鈥淎ll the work we are going to do here,鈥� said Hawaii鈥檚 Drury, 鈥渋s not going to make a difference if we don鈥檛 wind up addressing climate change on a global, systematic scale.

鈥淪o really, what we鈥檙e trying to do is buy time.鈥�

This story was reported by The Associated Press.聽