Smithsonian scientists help pave the way for large-scale coral reef restoration

As global warming, acidification and disease threaten a healthy future for the world’s coral reefs, conservationists have in recent years turned to the lab to study advanced reproductive methods, especially cryopreservation – or freezing. coral eggs, sperm and other materials – as a tool to produce coral larvae. A new article from the Smithsonian Conservation Biology Institute (SCBI) and partner organizations is the first to determine how conservationists can use cryopreserved sperm to grow corals in much higher numbers for large-scale restoration efforts in the future.

“This is the first major step for a lab to get these corals out of the reef,” said Mary Hagedorn, SCBI research scientist and lead author of the article, published Oct. 31 in the journal. Scientific reports. “In our previous work we have focused on producing small experimental samples, but for effective conservation we need to be able to produce tens or hundreds of thousands of larvae that can survive until the phase of. installation and, hopefully, beyond. This is critical proof that we will be able to take these techniques out of the lab and expand them in a way that allows us to effectively rebuild coral reefs in the event of a collapse. “

The study, which involved SCBI partners, the Hawaii Institute of Marine Biology, the Australian Institute of Marine Science and the Taronga Conservation Society Australia, examined small and large-scale techniques for using frozen sperm to fertilize fresh eggs from two fast growing reefs. species, the purple-tipped acropora (Acropora tenuis) and milli staghorn coral (A. millepora) in Australia. The Acropora coral group is one of the most widespread and responsible for much of large-scale reef building, but this group is also among the most threatened.

In addition to determining how to produce coral larvae on a larger scale with cryopreserved sperm, the study is also the first to discover that coral larvae produced with frozen sperm are equally successful in reaching the life stage when they metamorphose from a free-swimming larva. in a single polyp or in an installed “adolescent” or “juvenile” coral. The researchers found this to be true even using semen frozen for two years and transferred from one place to another hundreds of miles away.

To date, scientists have placed sperm from 16 species of corals around the world in frozen deposits. Because the banked cells are alive, researchers can thaw frozen material in 50 years or, in theory, even 1,000 years to help restore a species or diversify a population. Done correctly over time, samples of frozen material can be reared and placed back into ecosystems to infuse genes into natural populations, thus helping to improve the health and viability of wild stocks.

Hagedorn said the next step is to place the installed coral in a “nursery” in the ocean where it is protected but has access to natural water flow, natural light and natural food resources. Next, the team hopes to get permission to create such a nursery off the coast of Lady Elliot Island, the southernmost part of the Great Barrier Reef, where warming and bleaching may have less of an impact in because of the colder waters.

“We hope to release them on a scale large enough that thousands of corals will grow over the next five years,” Hagedorn said. “Ultimately, we want to prove that cryopreserved material can produce healthy, mature individuals capable of reproduction. Science is one step at a time, and this study brings us much closer to that success. “

These basic research studies, which can support subsequent restoration efforts, are important because coral reefs are living, dynamic ecosystems that provide invaluable services: they feed more than a quarter of all marine life, provide natural barriers. against storms for the coasts and maintain livelihoods by adding more than $ 300 billion a year to the global economy. Yet coral reefs are disappearing quickly. Locally, reefs are damaged by pollution, nutrients and sedimentation from poor land use, fishing and mining. Globally, increasing greenhouse gases are warming and acidifying the oceans, making corals more susceptible to stress, bleaching and emerging diseases, causing a widespread reef crisis.

The other authors of the article are Virginia L. Carter, SCBI; Michael Henley, Hawaii Institute of Marine Biology; Madeleine JH van Oppen, Australian Institute of Marine Sciences and University of Melbourne; Rebecca Hobbs and Rebecca E. Spindler, Taronga Conservation Society.

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