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Scientists hope to preserve coral by deep freezing it as climate change heats oceans


Oceans around the world have been extremely hot this summer, which has been devastating for some coral reefs. As climate change takes a toll on corals, scientists are finding new ways to preserve them by putting them in a deep freeze. Lauren Sommer from NPR's climate desk has more.

LAUREN SOMMER, BYLINE: Mary Hagedorn is a cryopreservationist, and she says when people hear that, they think science fiction.

MARY HAGEDORN: Yeah. They think of head freezers. They think of all this weird stuff. But think human fertility techniques.

SOMMER: Like freezing eggs and sperm - Hagedorn does that but for coral. She's a senior scientist at the Smithsonian's National Zoo and Conservation Biology Institute. Coral need help, she says, because marine heatwaves like the ones this summer are causing corals to bleach and turn ghostly white, which can kill them.

HAGEDORN: Our oceans are not doing well. Bleaching is going to be something that we will struggle with for many, many years, and it's only going to get worse.

SOMMER: So scientists are trying to collect the genetic material to breed new corals, but getting corals' sperm is tricky. They only spawn one or two days per year.

HAGEDORN: It's almost always at night, and it's around the full moon, and they're in very remote locations.

SOMMER: So Hagedorn and her colleagues developed a way to preserve the coral itself. They took living pieces of coral from a reef in Hawaii and got them really cold, down to minus-196 degrees Celsius. Normally, that would kill a living thing, but they found a way to thaw it out so the coral is still alive, as they published in the journal Nature Communications. Hagedorn says they're working on how to make the coral healthy after it thaws. But if it works, the idea is to create a frozen library of coral from around the world, basically a Noah's Ark.

HAGEDORN: We have to get through this. We have to do what is ever necessary to maintain the ecosystems on our planet.

SOMMER: That could be helpful for people like Jennifer Moore. She's trying to protect Florida's coral reefs with the National Oceanic and Atmospheric Administration. This summer, water temperatures there hit 100 degrees.

JENNIFER MOORE: This is, at least in my career so far, the most severe bleaching event that I have witnessed.

SOMMER: She says they rushed to collect and preserve coral samples as the temperatures rose. They'll be keeping those in tanks to help restore the reef when the ocean cools down again. And she says cryopreservation could be a big help with that in the future.

MOORE: Corals will continue to die, and unless we are replacing them with restoration, there won't be corals available in the future, even if we were to fix all of the threats.

SOMMER: Still, Moore says, there's only so far restoration can go if the planet keeps getting hotter. And coral reefs are a vital ecosystem, not just for marine life but to protect coastal cities from waves and storms.

MOORE: It is not a foregone conclusion. There are still things that can be done to combat climate change so that it's - we are not forced to be on a trajectory to a place where there are no more coral reefs.

SOMMER: In the meantime, she says, collecting a living library of coral is a necessary insurance policy. Lauren Sommer, NPR News.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.

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Lauren Sommer covers climate change for NPR's Science Desk, from the scientists on the front lines of documenting the warming climate to the way those changes are reshaping communities and ecosystems around the world.