The oceans are heating up and bleaching corals in what is now being called a global bleaching event. However, some scientists are working to freeze corals to help save them from starving to death.

“We have to come up with another product, another thing that we can use, a tool for our conservation toolbox,” said Mary Hagedorn, a senior research scientist with the Smithsonian’s National Zoo and Conservation Biology Institute.

For the last two decades Hagedorn has worked to save the delicate corals that live on the ocean floor. In 2023, she and her team published a paper containing a breakthrough in coral cryopreservation.

The current method of freezing and preserving coral is to harvest the larvae and sperm, but the problem is that the window for gathering that material is only a couple days a year. Hagedorn’s proposal could change the field.

“We came up with the idea of trying to do coral fragment cryopreservation,” Hagedorn said. “Now, what this means is we’re actually freezing the whole coral organism. They’re tiny. Corals can grow from a thumbnail-sized piece. And so we’re using these very thumbnail-sized pieces to test our cryopreservation method. We’ve partnered with engineers around the country to use a process called isotope vitrification.”

This process eliminates the problems caused by ice crystals forming and damaging frozen material. 

Hagedorn described the process of cryopreserving the coral.

“We put them in highly concentrated cryoprotectants,” she said. “And think of them as kind of like a syrup, or if you’ve ever seen insects in amber. It’s not quite that viscous, but it’s the same sort of concept. We’re using these very viscous media that can go from a liquid state into a frozen state without any ice. So they turn into a glass.”

The National Oceanic and Atmospheric Administration announced this spring that the oceans are in the midst of a global coral bleaching event, making Hagedorn’s work all the more important.

“We’re very close now to having something that not only is going to be very helpful for coral cryopreservation and coral conservation, but what we hope will be very field-friendly as well, so that we can get it out into the field and train many professionals to do this so that we can quickly move across the oceans and start to take this biodiversity and bank it,” she said.

Hagedorn is part of the Coral Biobank Alliance, a group of scientists and conservationists who work together to either freeze or collect coral in aquariums around the world. They hope to preserve as many species as they can as the rising temperatures cause their wild counterparts to bleach and die.

“Given that climate change is causing this issue and we don’t have as much time as we would really like, this actually is a very good solution,” Hagedorn said. “I think we stand a very good chance in the next five years of capturing as much of the diversity as we can before certain ecosystems collapse in the coral world.”