These assisted gene flow studies produced 600 new genetic-assorted individuals of the threatened elkhorn coral Acropora palmata. As of early 2024, there are only about 150 elkhorn individuals left in the wild in the Florida population. If given the chance, these selectively bred corals held in captivity could significantly increase the wild elkhorn gene pool.

Preserving sperm cells and larvae is an important hedge against the loss of biodiversity and species extinctions. But we can only collect this material during fleeting spawning events when corals release egg and sperm into the water.

These episodes occur over just a few days a year – a small time window that poses logistical challenges for researchers and conservationists, and limits the speed at which we can successfully cryo-bank coral species.

To complicate matters further, warming oceans and increasingly frequent marine heat waves can biologically stress corals. This can make their reproductive material too weak to withstand the rigors of being cryopreserved and thawed.

To collect coral material faster, we are developing a cryopreservation process for whole coral fragments, using a method called isochoric vitrification. This technique is still developing. However, if fully successful, it will preserve whole coral fragments without causing ice to form in their tissues, thus producing viable fragments after they’ve thawed that thrive and can be placed back out on the reef.

To do this, we dehydrate the fragment by exposing it to a viscous cryoprotectant cocktail. Then we place it into a small aluminum cylinder and immerse the cylinder in liquid nitrogen, which has a temperature of minus 320 degrees Fahrenheit (minus 196 Celsius).

This process freezes the cylinder’s contents so fast that the cryoprotectant forms a clear glass instead of allowing ice crystals to develop. When we want to thaw the fragments, we place them into a warm water bath for a few minutes, then rehydrate them in seawater.

Using this method, we can collect and cryopreserve coral fragments year-round, since we don’t have to wait and watch for fleeting spawning events. This approach greatly accelerates our conservation efforts.

Protecting as many species as possible will require expanding and sharing our science to create robust cryopreserved-and-thawed coral material through multiple methods. My colleagues and I want the technology to be easy, fast and cheap so any professional can replicate our process and help us preserve corals across the globe.

We have created a video-based coral cryo-training program that includes directions for building simple, 3D-printed cryo-freezers, and have collaborated with engineers to develop new methods that now allow coral larvae to be frozen by the hundreds on simple, inexpensive metal meshes. These new tools will make it possible for labs around the world to significantly accelerate coral collection around the globe within the next five years.

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