The world’s first cryo-born baby corals have been successfully settled into their new and natural homes on the Great Barrier Reef, marking perhaps the start of a groundbreaking new era for science and the conservation and restoration of coral reefs in Australia.

Reproductive biologists from Taronga Conservation Society Australia used cutting-edge cryopreservation techniques to successfully fertilise fresh coral eggs – collected during the October coral spawning event on the Great Barrier Reef – using cryopreserved coral sperm.

In an astonishing world-first, these researchers, working alongside specialists from the Australian Institute of Marine Science within the world’s most advanced research aquarium – the National Sea Simulator – have successfully grown and now transported these cryo-born coral babies into specially designed ‘coral cradles’ on the Barrier Reef.

The design of these ‘cradles’ allows researchers to track how well the babies grow throughout their critical first year of life.

Scientists from both Taronga Conservation Society Australia (TCSA) and the Australian Institute of Marine Science (AIMS) suggest that this innovative advance in science will “help pave the way to safeguard reefs” currently under pressure from climate change, by deploying “millions of heat-tolerant corals onto the Reef every year.”

To prepare for increasingly warmer ocean temperatures, researchers at TCSA have been working alongside its partners at the Reef Restoration and Adaptation Programme to develop ways to plant millions of heat tolerant corals onto not only the Great Barrier Reef but coral reefs around the world.

The Taronga CryDiversity Bank currently holds the world’s largest frozen bio-repository of living coral cells, with trillions of sperm across 32 coral species, collected annually from the Great Barrier Reef since 2011. It’s intended for these cells to be used in future reproduction efforts to aid restoration and “completely revolutionise the approach to it”.

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,” said the project’s lead researcher, Dr Jonathan Daly, from the Taronga Conservation Society.

So, how does this all work? Coral cryopreservation is, quite simply, 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 that keep corals and their cells alive while they’re frozen. This is done by adding what is 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 place it immediately in liquid nitrogen at -196 degrees Celsius.

At this temperature, the metabolic processes stop allowing the cells to be frozen in such a state indefinitely, easing the logistics around their safe transportation to ‘seed banks’ at Taronga Zoo Sydney or to Taronga Western Plains Zoo in Dubbo. Here, they are cared for in biosecure and alarmed chambers of liquid nitrogen until they are required.

When they are needed for future Reef restoration efforts, different types of warming and thawing methods are used to revive them.

According to specialists at the Great Barrier Reef Foundation, this breakthrough now “opens the door to scaling up 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 resilience of coral reefs around the world,” said the Foundation.

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