In a development reminiscent of science fiction, researchers have achieved the successful cryopreservation and revival of small colonies of mature corals. However, ensuring their long-term survival remains a challenge, according to a report published in Nature Communications on August 23. This breakthrough could hold the key to safeguarding corals from extinction in the face of rising ocean temperatures and acidification due to human-induced climate change.
Prior to this achievement, scientists had successfully cryopreserved and revived coral larvae, as reported in October 26, 2018. However, collecting coral larvae is only feasible during specific spawning events that occur a few nights each year, as explained by marine scientist Liza Roger of Arizona State University in Tempe. This limitation poses a significant risk given the challenges coral reproduction faces, with fewer larvae surviving in warming seas.
Given the difficulties associated with larvae collection, an alternative solution is to cryopreserve mature coral colonies, which are accessible year-round. Preserved adult corals could play a crucial role in the restoration of reef ecosystems if climate warming can be reversed. Nevertheless, cryopreserving larger specimens presents its own set of challenges, primarily the prevention of ice formation, which can damage tissues much like pipes cracking in winter.
Matthew Powell-Palm, a thermodynamicist from Texas A&M University in College Station, and his team conducted experiments using small fragments of a common Hawaiian finger coral known as Porites compressa. They employed menthol and light to eliminate interfering microbes and then sealed the fragments within robust metal chambers filled with a specialized chemical solution, partially dehydrating the corals and reducing ice growth. Subsequently, the samples were submerged in liquid nitrogen.
Exposing the corals to temperatures around -200°C, combined with chemical treatment and the containment provided by the chamber, caused the remaining water in the corals to solidify into a vitrified, glass-like state without forming ice crystals. Under such extreme cold conditions, metabolic processes and other life-sustaining activities slowed to an almost imperceptible pace, making it possible to preserve living specimens for potentially hundreds or even thousands of years.
The true test came after cryopreservation. Following a carefully monitored 24-hour thawing and recovery process, the researchers measured the corals' oxygen consumption. One day after thawing, the corals displayed signs of being alive and healthy.
While these results are promising, Liza Roger emphasizes that the work is far from complete. Several days after thawing, the corals remained vulnerable, as they were overwhelmed and killed by bacteria with which they typically coexist. The next steps in this research should focus on ensuring the long-term survival of the revived coral colonies.
Matthew Powell-Palm remains optimistic about the future. He believes that by applying appropriate antibiotics, the cryopreserved coral fragments can thrive in their new environment once revived, offering hope for the preservation and restoration of coral reefs in an ever-changing world.