Scientists Have Begun Conserving Coral by Slicing and Freezing It 

Scientists Have Begun Conserving Coral by Slicing and Freezing It 

Researchers have done something groundbreaking. They froze pieces of grown-up coral and then brought them back to life using a special method involving antifreeze and colder-than-normal liquid. These revived corals then acted just like normal ones for a whole day after coming back to life; a good discovery for conservation. 

This new method might someday be used to keep other living things, even human organs, preserved for many years. However, this finding is crucial now because it comes at a time when coral reefs are in serious trouble due to the warming of the oceans. 

“Coral reefs are essential to the baseline health of our oceans, and cryo-conservation of endangered coral species can help to ensure that these invaluable and marvelous organisms do not go extinct,” Matthew Powell-Palm, a mechanical engineer at Texas A&M University and the paper’s lead author, said. 

Getting the specimens 

The development of this novel cryopreservation method has been a long process. Before this achievement, marine biologist and the research co-author Mary Hagedorn and her team had already made advancements in preserving coral sperm, using methods similar to those done in human sperm banks. 

There’s a difference, though. Unlike sperm, which consist of single cells and are generally simpler to freeze, collecting them can be exceptionally challenging. Usually, corals live in remote and inaccessible regions on the seafloor, and they only release their sperm on a few days each year.  

This leaves researchers with only a narrow chance to gather the specimens. 

Hagedorn said, “It can be very, very challenging to get there at the right time. One year, we missed it by a whole month, because they spawned early because the water was warm.”  

And unfortunately, in another year, the team was hit by a hurricane, and they had to temporarily discontinue their work. 


Picture of branched finger coral by James St. John Wikimedia Commons



The urgency to save more corals  

Corals are particularly challenging in conservation because they’re sensitive to changes in temperature. When it gets hot, corals get rid of algae that live in their bodies, which then make them turn completely white. We know this process as coral bleaching, and it has caused a lot of stress on the corals, exposing them to more diseases and mortality. 

As we know, overfishing, pollution, and climate change have caused half of the world’s coral reefs to vanish since 1950. Moreover, within a decade from 2009 to 2018, our planet has lost 14% of its coral reefs. That’s bigger than all the corals in Australia now. And experts believe that this issue will get worse without intervention. 

According to a 2018 report from the Intergovernmental Panel on Climate Change, if Earth got to the point of being 1.5 degrees Celsius warmer (from before the industrial revolution and beyond), coral reefs could reduce by 70 to 90 percent.  

With how things are right now, and if there’s no effort to change the warming, we can fit that temperature between 2030 and 2052. Then, if our planet got 2 degrees C warmer, coral reefs could be gone entirely.  

Our planet can’t lose coral reefs. According to Joe Pollock, a senior coral reef resilience scientist with the Nature Conservancy’s Hawaii who was not involved in the research, “Coral reefs are simply too valuable to lose. They support over a quarter of marine life, protect our coastlines during storms and contribute an estimated $375 billion to the global economy annually.” 

In 2023, we’ve seen record-breaking high temperatures. Back in July this year, we had hottest month ever recorded. And in Florida, the temperature in the ocean reached above 100F, which resulted in coral bleaching.  

Hagedorn said that as the ocean gets heated up continually, coral bleaching can become a common, frequent phenomenon. 



Cryopreserving other species? 

Although corals do need attention because they’re important for the future, some scientists think that we can apply this conservation method to other species.  

Dr Sue Walker, head of science at Chester Zoo and co-founder of Nature’s SAFE said, “With gene pools and animal populations continually shrinking in the wild, the work of modern conservation zoos like ours has never been more important. 

“Technologies, such as cryopreservation, offer us a new, critical piece of the conservation puzzle and help us provide a safeguard for many of the world’s animals that, right now, we’re sadly on track to lose.” 

In Chester Zoo, animals that pass away are still capable to valuable contributions to the survival of their species. As an example, the Javan green magpie; an animal that has been pushed to the brink of extinction due to poaching. The unique genetic code of this bird is preserved in vials stored at a biobank located in Shropshire. 

This process involves extracting sperm cells from an animal’s testes after castration. After extraction, sperm cells are then placed in test tubes and given cell-friendly antifreeze and stored in containers filled with liquid nitrogen. 

When it’s needed, scientists will thaw the cells and use them to fertilize a frozen egg. This will result in an embryo which the scientists can then place in a surrogate mother. 

Freezing and preserving 

Given the rising stress on coral reefs, the scientists realized the need for a cryopreservation approach that goes beyond concentrating solely on preserving sperm. 

“We felt like we needed to go faster. We’re going too slow. … It’s important that we get the genetic diversity and biodiversity while it still exists,” Hagedorn said. 

So, in 2019, Hagedorn and her colleagues—including researchers at the University of California, Berkeley, and Texas A&M University—began their effort to cryopreserve and revive entire pieces of finger coral (Porites compressa) from Hawaii.  

The process is relatively simple, Hagedorn stated. First, researchers find a healthy adult coral and harvest off a thinly sliced chunk about the size of a human thumbnail. They bleach the coral and place the fragment into a small aluminum cylinder filled with an antifreeze solution.  


finger coral, lobe coral, and auliflower coral. Picture by U.S. Fish & Wildlife Service – Pacific Region’s Wikimedia Commons


While the goal is to freeze the coral piece, the team must avoid ice formation, which would damage the animal’s tissue. Finally, the cylinder is placed into liquid nitrogen and cooled to nearly minus 321 degrees Fahrenheit, causing the coral to rapidly freeze.  

To revive the coral, scientists don’t need a surrogate mother. They simply need to place the cylinder in a warm water bath for two minutes, then remove the coral fragment and put it back into seawater.  

“It’s conceptually complicated because of thermodynamics. But the actual process itself is really dead easy,” Hagedorn said.  

Simplicity was part of the team’s goal; they wanted a process that could be quick and economical for coral reef managers to use in the field around the world. 

Ensuring survival of some species 

In the new study, the team only tested the coral’s survival for 24 hours after its revival, but Hagedorn said that they were working on refining some of their processes to allow the corals survive up to three weeks.  

Down the line, Hagedorn predicted that the technique could be adapted to preserve human organs, as mentioned. “I think it’s going to have an amazing trajectory in terms of doing … more whole pieces of organisms. It’s very, very cool technology, and it is the wave of the future,” Hagedorn said. 

Other than cryopreservation, researchers are actively exploring methods to create cultures from this tissue that can generate egg and sperm cells for future breeding efforts. With science, every skin cell has the ability to transform into various types of body cells. 

From this innovative discovery, even a skin taken from the ear of an Eastern black rhino could hold the key to preserving the species. 



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