To help ensure the future of Florida’s Coral Reef, 12 organizations came together for one of nature’s most elusive events: coral spawning.

Scientists worked in early August to propagate and conserve the next generation of corals by collecting eggs and sperm, fertilizing embryos and cryopreserving sperm to safeguard invaluable genetic diversity for generations to come.

Coral spawning is exceedingly rare, occurring once a year and within a narrow window dependent on lunar cues and environmental conditions.

The event involves synchronized breeding when millions of egg and sperm bundles are released simultaneously. The bundles must encounter other bundles of the same species for fertilization to occur.

But after decades of decline, coral colonies have become so sparse and widely dispersed that the bundles often cannot find one another in the water, making natural reproduction increasingly difficult, and leaving some species functionally extinct in Florida.

Now, fewer than 150 unique elkhorn corals and 300 staghorn corals remain on Florida’s Coral Reef — just one percent of their former numbers.

Threats to coral reefs include extreme heat, pesticides and other chemical pollution, overfishing and other damaging human activities. Coral reef loss disrupts marine food webs, reducing fish populations that people depend on for food. Reefs also absorb wave energy from storms, helping protect coastlines from erosion, flooding and property damage.

So scientists have many reasons not to give up.

Last month dive teams collected millions of gametes from elkhorn and staghorn corals at offshore nurseries operated by Reef Renewal USA and Mote Marine Laboratory near Key Largo. The gametes were then rapidly transported to a temporary laboratory at John Pennekamp Coral Reef State Park through a partnership with Mote Marine Laboratory, where experts across organizations determined desirable genetic crosses to create fertilized embryos that would prove most resilient to environmental stressors.

At the same time, another team worked to cryopreserve additional sperm for future restoration purposes.

Florida has the only living coral barrier reef in the continental U.S. It stretches nearly 350 miles running from the Dry Tortugas to St. Lucie Inlet in Martin County.

“This project aims to incorporate new innovative approaches into coral restoration while also bringing together many years of experience of coral spawning that is dispersed across several institutions working on Florida’s Coral Reef,” said Andrew Baker, professor of marine biology and ecology at the University of Miami Rosenstiel School.

“Our reef is in trouble, and we need to take urgent action to scale up efforts to help restore and rebuild one of the state’s most valuable environmental and economic resources,” he said.

Throughout seven days, scientists observed 25 elkhorn genotypes and 36 staghorn genotypes spawning, resulting in 116 unique, directional crosses using assisted fertilization.

The scientists ultimately produced more than 1,500,000 total embryos resulting in over 61,000 elkhorn larvae and 47,000 staghorn larvae divided between The University of Miami Rosenstiel School, Mote Marine Laboratory, The Florida Aquarium, The Reef Institute and The Smithsonian Marine Station.

The organizations will continue nurturing and growing the larvae, and within two years return the new corals to the same nurseries before finding a permanent home on reef sites nearby, including Mission: Iconic Reefs locations in the Florida Keys National Marine Sanctuary and the Kristin Jacobs Coral Aquatic Preserve.

“What we have done over a few weeks would have never happened without human intervention,” said Celia Leto, biologist and manager of the Coral Reproduction Laboratory at Mote Marine Laboratory.

“The sheer number of gametes collected, and larvae produced is a testament to the preparation, expertise, and collaboration of everyone involved. It was amazing to see all the partners come together for this effort and make this remarkable achievement possible.”

Participating partners included the University of Miami Rosenstiel School, Reef Renewal USA, Mote Marine Laboratory, The Florida Aquarium, The Reef Institute, SECORE International, Phillip and Patricia Frost Museum of Science, Nova Southeastern University, Smithsonian Marine Station, John Pennekamp Coral Reef State Park, Biscayne National Park, and AECOM.

“Collaboration allows us to push the boundaries of what is possible in coral restoration,” said Keri O’Neil, director of the Coral Conservation Program at The Florida Aquarium. “This effort brought together people from across the coral restoration community to seize a rare opportunity and turn it into something with tremendous potential for the future of Florida’s Coral Reef.”