A new study suggests that creative interbreeding could save coral from extinction.
Breeder Wally Conron wanted to build a better dog—something smart and loyal that could work as a guide dog, but without all that allergy-triggering hair that most working pups grow. So he put a female Labrador retriever in a room with a male poodle, played a little romantic music, and voila. The first Labradoodle emerged a few months later, an offspring with all the desired traits.
Researchers from the University of Texas at Austin reported the results of a very similar experiment today in the journal Science. Except instead of dogs, it was coral. And instead of trying to prevent sneezing, they were trying to prevent extinction.
Coral reefs are the foundation of some of the most vibrant ecosystems on earth. They host 32 of the 34 animal phyla known to science, while tropical rainforests support a paltry nine. More than a quarter of fish biodiversity depends on coral reefs. Some experts estimate their value to the global economy at $5.5 billion. Losing that coral—or even a significant portion of it—would deal a powerful blow to the planet, and to humanity.
We are inching ever closer to that outcome. The conservative estimate is that one-third of reef-building coral species are at risk of extinction. Some experts think coral could be gone within a century. Pollution, overdevelopment of coastlines, bottom-trawling for seafood, and, most significantly, global warming have pushed coral to the brink.
Humanity’s excess carbon emissions affect coral in two ways: ocean acidification and overheating. Increasing carbon dioxide in the atmosphere elevates the carbon concentration in ocean water, because air and water exchange gases at the sea surface. Carbon dioxide acidifies the ocean. The altered water chemistry prevents coral from absorbing calcium carbonate, which is a building block for the stony skeleton that we identify with coral.
Global warming is also heating up the planet’s oceans, for rather obvious reasons. When temperatures are elevated for a prolonged period, the photosynthetic algae that coral rely on for food flee. The process is called bleaching, because coral rely on these algae for color. It ends with the coral white and dead.
Ocean acidification and bleaching are two different problems, and—unless we stop burning fossil fuels tomorrow—they will likely require two different solutions. The research in today’s paper addresses the bleaching issue.
We think of coral as a purely tropical species, because that’s where most humans like to snorkel and scuba dive, but they exist in subtropical regions as well. Based on the size of their range, scientists have always suspected that coral have genetic variations that make some species more heat-tolerant than others, but they have never been able to prove it.
The researchers produced a sort of Punnett square of coral. They created a generation of coral—some with both parents from the warm waters of the Great Barrier Reef, some with both parents from the cooler waters 300 miles to the south, and some with one parent from each area. Then they exposed the larvae to warm water. The researchers found that the coral with warm-water parents were up to 10 times more likely to survive the heat, proving that genetics play a significant role in the wide variation of heat tolerance observed in coral reefs.
The findings suggest that the future of coral may not be as dim as we thought. First, migration is actually a possibility. Many species have shifted their ranges to find cooler weather. According to one study of a select group of plants and animals, the average species has moved itself 36 feet uphill and 10 miles toward the poles per decade in response to global warming. Coral aren’t particularly mobile, but over the course of generations, they may be able to drift into cooler waters.
If the water is warming too fast for migration, conservationists might use a technique known as “genetic rescue” to combat the problem of bleaching. In its simplest form, genetic rescue would work just like the Labradoodle—introduce warm-water coral into cold-water communities and hope they spread their genes for heat tolerance. (The study further found that mitochondrial DNA, which is passed exclusively from mother to child, seems to be the most influential genetic segment, so eggs from warmer waters would be the key ingredient.) A more extreme form of genetic rescue would involve genetic editing, splicing the heat-tolerant genes into cold-loving coral.
There’s no guarantee this will work, of course. Just ask Wally Cornon, who now regrets creating the Labradoodle. “I released a Frankenstein,” he said in 2014. “So many of these dogs have physical problems, and a lot of them are just crazy.”
Still, crazy Franken-coral would probably be better than no coral at all.
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