by These assisted gene flow studies produced 600 new genetically diverse 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. Given the chance, these selectively bred and captive elkhorn could significantly increase the wild elkhorn gene pool.
Conserving sprats and larvae is an important hedge against biodiversity loss and species extinction. But we can only collect this material during ship spawning events when corals release eggs and sperm into the water.
These episodes occur over a few days a year – a short period of time that creates logistical challenges for researchers and conservationists, and limits the speed at which we can recover cryobank coral species.
To further complicate matters, warming oceans and increasingly frequent marine heat waves can cause biological stress on corals. This can make their reproductive material too weak to withstand the rigors of cryopreservation and thawing.
Scaling up the rescue
To collect coral material faster, we are developing a cryo-preservation process for whole coral fragments, using a method called isochoric vitrification. This technique is still developing. However, if completely successful, it will preserve whole coral fragments without ice forming in their tissues, producing viable fragments after thawing that thrive and can be returned to the reef.
To do this, we dehydrate the fragment by exposing it to a viscous cocktail of cryoprotectant. Then we put it in a small aluminum cylinder and dip the cylinder in liquid nitrogen, which has a temperature of minus 320 degrees Fahrenheit (minus 196 Celsius).
This process freezes the contents of the cylinder so quickly that the cryoprotectant forms a clear glass rather than allowing ice crystals to develop. When we want to thaw the fragments, we put them in a hot water bath for a few minutes, then rehydrate them in sea water.
Using this method, we can collect and cryopreserve coral fragments all year round, since we don’t have to wait and watch for fleet spawning events. This approach greatly enhances 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 a variety of methods. My colleagues and I want the technology to be easy, fast and cheap so that any professional can replicate our process and help us conserve corals around the globe.
We created a video-based coral cryo-training program that includes instructions for building simple, 3D-printed cryo-freezers, and collaborated with engineers to develop new methods that allow hundreds of coral larvae to be frozen by the hundreds in a simple, inexpensive . metal mesh. With these new tools laboratories around the world will be able to significantly accelerate the collection of corals around the world in the next five years.
Protecting the future
Recent climate models estimate that if greenhouse gas emissions continue unabated, 95% or more of the world’s corals could die by the mid-2030s. This leaves little time to conserve the biodiversity and genetic diversity of the reefs.
One approach, which is already underway, is to bring all coral species under human care. The Smithsonian is part of the Coral Biobank Alliance, an international collaboration to conserve corals by collecting living colonies, skeletons and genetic samples and using scientific best practices to help rebuild reefs.
To date, over 200 coral species, out of approximately 1,000 known hard coral species, and thousands of colonies are under human care in institutions around the world, including organizations associated with the US and European armies of Association of Zoos and Aquariums. Although these are clones of the colonies from the wild, these individuals could be placed in coral breeding systems that could later be used to cryopreserve their genetically diverse larvae. Alternatively, their larvae could be used for reef restoration projects.
Until climate change is slowed and reversed, reefs will continue to degrade. To ensure a better future for coral reefs it will be necessary to build coral stores, establish nurseries on land to maintain coral colonies and develop new larval settlers, and train new cryoprofessionals.
For decades, zoos have used captive breeding and introductions to protect animal species that have fallen to critically low levels. Likewise, I believe our new solutions can create hope and help save coral reefs to reseed our oceans today and far into the future.
This article is republished from The Conversation, a non-profit, independent news organization that brings you facts and analysis to help you make sense of our complex world.
It was written by: Mary Hagedorn, Smithsonian Institution.
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Mary Hagedorn receives funding from Revive & Restore; Paul M. Angel Family Foundation; Volgenau Foundation; CORDAP Foundation; Zegar Family Foundation; Oceankind; The Mastriani Family; De Witt Family; Anela Kolohe Foundation; Cedar Hill Foundation; Sidney E. Frank Foundation; Scintilla Foundation; and the Smithsonian Women’s Committee. She is affiliated with the Smithsonian National Institute of Zoo and Conservation Biology and the Hawaii Institute of Marine Biology.
