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Scientists have achieved a first by growing adult corals from cryopreserved larvae, a potential boon for reef restoration. This breakthrough overcomes the significant challenges of freezing and thawing delicate coral cells.

In a groundbreaking achievement that echoes the revival of Captain America, scientists have successfully grown adult corals from cryopreserved larvae, a first in marine biology. This milestone, detailed in a recent study, could revolutionize coral reef restoration efforts worldwide.

For nearly two decades, the scientific community has been freezing corals at temperatures as low as -196 °C with the hope of one day repopulating reefs that are suffering from bleaching and acidification. However, the process has been fraught with challenges. Freezing and thawing inflict severe damage on the delicate cells of coral larvae. The water inside the cells forms ice, leaving them dehydrated and deflated. Moreover, if the thawing process is not conducted swiftly enough, ice can refreeze, causing the cells to rupture and die, much like a thawing frozen strawberry loses its firmness.

Arah Narida, a graduate student at National Sun Yat-sen University in Taiwan, has been at the forefront of overcoming these challenges. By washing the corals in antifreeze before freezing, she has managed to protect the larvae from ice damage. Although antifreeze is toxic, it displaces the water in the larvae's cells, allowing them to survive being submerged in liquid nitrogen.

In 2018, scientists first succeeded in having a coral larva survive the freeze-thaw cycle by incorporating gold nanoparticles into the antifreeze to ensure even warming. However, these larvae failed to mature into adulthood, dying after a period of aimless swimming.

For nearly 20 years, scientists have been cryopreserving corals—freezing them at temperatures as low as -196 °C for long-term storage. The goal has been to one day plant corals grown from cryopreserved samples on reefs plagued by bleaching and acidification.

Building on this work, Narida's experiments in 2021 included a blend of antifreeze chemicals and gold to reduce toxicity. She then employed a high-powered laser, typically used for welding jewelry, to rapidly thaw the larvae. This process was followed by a careful rinse with seawater to rehydrate the corals. The result was remarkable: 11 percent of the larvae not only survived the thawing but also settled and grew into adults.

Leandro Godoy, a coral cryobiologist at the Federal University of Rio Grande do Sul in Brazil, lauds the significant survival rate, especially considering that in the wild, only about five percent of corals reach adulthood. Narida's oldest revived coral has been thriving for nearly nine months, continuing to grow.

Despite this success, Narida and her colleagues acknowledge that the larvae surviving cryopreservation are extremely delicate and require intensive care, akin to ICU patients. According to Hakai Magazine, the next challenge is to enhance the survival rate further to make large-scale reef restoration from cryopreserved larvae a viable solution.

This scientific breakthrough not only represents a 'cool' factor likened to superhero revivals but also marks a significant stride toward the conservation and restoration of coral reefs, which are vital to marine ecosystems. The success story of these cryopreserved baby corals reaching adulthood offers a glimmer of hope for the future of our oceans.

Eunice is a sustainability writer whose passion is sharing accessible eco-friendly practices with GreenCitizen's global readership. She enjoys birdwatching during her downtime, often deriving inspiration from nature's resilience. An enthusiastic cyclist, she is also an ardent advocate of eco-friendly transport.

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