During the October coral spawning event on the Great Barrier Reef, reproductive biologists from Taronga Conservation Society Australia have used cutting-edge cryopreservation techniques to successfully fertilise fresh coral eggs using cryopreserved coral sperm.
Working alongside researchers from the Australian Institute of Marine Science in the world's most advanced research aquarium - the National Sea Simulator - they were able to collect fresh eggs from corals spawning in the lab to conduct this research.
Now, in a world-first, these cryo-born coral babies have been delivered into their natural habitat, the Great Barrier Reef, on specially designed coral cradles so researchers can track how well they grow in their critical first year of life.
This innovative achievement helps pave the way to safeguard reefs under pressure from climate change by deploying millions of heat-tolerant corals onto the Reef every year.
Taronga Conservation Society researcher conducting cryopreservation
Cryopreservation supporting next-gen Reef restoration
To prepare for increasingly warmer ocean temperatures, with our partners in the Reef Restoration and Adaptation Program we've been focused on developing solutions that will enable millions of heat tolerant corals to be planted on the Great Barrier Reef, and coral reefs around the world.
The Taronga CryoDiversity Bank holds the world's largest frozen biorepository of living coral cells with trillions of sperm across 32 coral species collected annually from the Great Barrier Reef since 2011. The intention is that these cells can be used in future reproduction efforts to aid restoration, completely revolutionising how we approach reef restoration.
The storage of cryopreserved living genetic material also supports crucial research into increasing heat-tolerance in coral.
"Through bypassing the challenges of aligning with the natural spawning event which happens once a year, we've got greater control over selective breeding processes, allowing colonies to be used for reproduction multiple times without disturbing wild populations" says lead researcher Dr Jonathan Daly, Taronga Conservation Society.
Dr Jonathan Daly delivering coral babies to a larval tank in the lab
How does cryopreservation work?
Coral cryopreservation is the process of preserving coral cells and tissues at very low temperatures.
Like all animal cells, coral cells and tissues contain lots of water which, when frozen, form ice crystals that can cause damage. Cryopreservation techniques aim to minimise ice crystal formation and keep corals and their cells alive while they're frozen. This is done by adding what's known as cryoprotectants, which remove water from the cells while they're being frozen and also support cell structures when samples are thawed.
When corals spawn, they release bundles of sperm and eggs. Researchers collect these bundles, separate the sperm and immediately place it in liquid nitrogen at a chilly -196 degrees Celsius.
The frozen coral sperm are then placed in travel-safe containers of nitrogen vapour and shipped to "seed banks" at Taronga Zoo Sydney on Cammeraigal Country, and at Taronga Western Plains Zoo in Dubbo on Wiradjuri Country. There they are cared for in biosecure and alarmed chambers of liquid nitrogen.
At -196 degrees Celsius, metabolic processes stop and the cells can be kept frozen in that state indefinitely. When they're needed for future Reef restoration efforts, different types of warming and thawing methods are used to revive them.
Coral sperm collected for cryopreservation
Hope for coral reefs
This breakthrough opens the door to scaling up coral restoration efforts, with the potential to deliver millions of corals with increased tolerance to heat on the Great Barrier Reef and beyond. By combining science, technology, and collaboration, we're taking a critical step toward building the resilience of coral reefs around the world.
The work is part of the Reef Restoration and Adaptation Program, funded by the partnership between the Australian Government's Reef Trust and the Great Barrier Reef Foundation.
