Let’s talk about sexual coral restoration, baby!

Did you know that the Roatan Marine Park (RMP) is using some “sexy” new technology to scale up coral restoration efforts in Roatan? The local nonprofit is in its fourth year of partnering with SECORE International to bring cutting edge coral restoration to Roatan. And we’re proud to support their efforts! 

Since 2022, Sun Divers customers and team members have worked with restoration leaders from RMP to monitor coral spawning activity. The 4-6 day volunteer event is conducted annually to confirm spawning times for Diploria labyrinthiformis, commonly known as grooved brain coral.  When spawning occurs, it also provides the opportunity to collect the gamete (male & female germ cells) for coral breeding restoration efforts. 

Read on to learn more about the fascinating phenomenon of coral spawning and how SECORE’s exciting new technology is allowing us to take advantage of this natural process to restore more of Roatan’s reefs.

So, how do corals breed?!

Corals have a gift of growing and reproducing both sexually and asexually. 

Let’s talk about asexual reproduction first. When coral fragments break off from their primary colony either through natural causes or with intent for restoration, they can reattach to the reef and start a whole new colony.

Corals also reproduce sexually. This occurs through mass coral spawning events. Hard (or stony) corals release male & female germ cells called gamete all at the same time. The lucky gamete then fertilize. And, much like we learned about in junior high, they become an embryo that turns into coral larvae (also known as planula). Or if you want to keep the sex ed analogies going, you can think of these as little coral ‘babies.’ The planula can then attach to substrate and ultimately grow into a new colony. 

What is coral breeding restoration?

For decades, restoration practices, including those in Roatan, have taken advantage of coral’s asexual superpowers, and “propagated” corals by cutting fragments, growing them in a coral nursery, and then outplanting them onto the reef. 

While this restoration practice has a solid success rate, it is costly and time consuming. It also requires significant physical space, and manpower. 

New technologies are now allowing us to lend corals a helping hand when it comes to the success rate of their sexual reproduction. Specifically in Roatan, SECORE International, a global coral restoration organization, is bringing tools, techniques and talent to help our community increase its efforts in sexual coral restoration.

Most simply, the method used by SECORE International, RMP and local volunteers like ourselves involves these five primary steps:

1. Researchers and volunteers collect data to confirm coral spawning times for keystone species.

2. Once they confirm a particular species’ spawning time and a spawning event occurs, they collect gametes. They cover the corals with a net containing a plastic vial, which captures the gametes as they float upward.

3. Researchers and volunteers then take the gametes to a land-based lab, where they cross-breed them in hopes of fertilization—think of this as IVF for corals.

4. Coral larvae attach to substrate blocks that SECORE developed, and researchers place these blocks in Coral Rearing In-Situ Basins (CRIBs) in the ocean.

5. Once the blocks develop starter colonies (recruits), they are “seeded” them onto the reef. This process requires no manual attachment, which often makes traditional outplanting time-consuming and prone to error.

The in-situ cribs only require 5% of the labor that land based facilities require, and the substrate to seeding method allows major scaling of coral coverage.

How is Sun Divers supporting?

Sun Divers volunteers on their way to monitor. Photo credit: Gil Sassi

As part of our support of the Roatan Marine Park and local coral restoration efforts, every year Sun Divers contributes boats, tanks, captain time to coral spawning monitoring of Grooved Brain Coral (Diploria labyrinthiformis). Each year we monitor 15-20 colonies with around 20 volunteers. These volunteers train on how to properly net the corals and collect gamete in the event of a mass spawning event. 

Every year the results are different. In 2022, the first year of spawning monitoring, only one colony spawned. And we all know it takes two to tango. So while we were able to validate the spawning calendar, we weren’t able assist in fertilization. In 2023, we had witnessed the true magic of spawning and were able to collect a significant amount of gamete to fertilize in a lab with an astounding 95% success rate – much higher than what would occur in nature. This was one of two fertilizations that had occurred resulting in 1,188 coral recruits outplanted on substrate and onto Roatan’s reefs.

Last year was a tough year for coral spawning across the world with minimal spawning occurring likely due to stress caused by the global bleaching event. But, we’re very hopeful and excited for our participation in the 2025 Spawn Watch, happening mid-June.

“Conservation brings science and the community together, so monitoring coral spawning with the diving community is critical for long-term coral restoration efforts and giving our Roatan reef hope. We are grateful to the local dive shops on Roatan, such as Sun Divers, for collaborating with us on these sustainability efforts,” RMP Research Project Coordinator Damaris Dueñas said.

What’s involved in coral spawning monitoring? 

A coral spawning monitoring dive is both scientific and entertaining. It’s  basically a two-hour (yes, two full hours!) dusk or night dive conducted in a small area where the majority of your focus is on 1-2 coral colonies. You’re basically waiting for that after-dark magic to happen. But while you have one eye on your colonies, you can also focus more intently than on fun dives where you have to keep moving, and watch the reef come to life.

If you love macro diving, you’ll love this because you have all the time in the world to let your eyes adjust and discover the interconnected nature of corals, gobies, blennies, crabs, shrimps, pipehorses and more. See the slideshow below for some of our cool findings on one of the dives. Larger life will also pass you by including Eagle Rays, octopus and schools of fish – the butterfly fish seem particularly inquisitive!

Okay, but back to the work at hand. While you’re monitoring, you’ll be capturing important data on an underwater slate including documenting the start & stop time of spawning should it occur. 

If spawning occurs, volunteers collect gamete and that’s when the on-land cross-fertilization happens.

How can I get involved? 

RMP will continue to conduct coral spawning monitoring with the hopes of kicking off a concerted coral breeding restoration program. Contact the Roatan Marine Park to participate in Spawn Watch volunteer opportunities. 

We’ll also continue to offer the RMP Coral Restoration Ambassador certification to support the traditional coral nursery maintenance and outplanting. And this is a great way to volunteer when coral spawning is not occurring.

What’s next for sexual coral restoration? 

Substrates for sexual coral restoration at Overheat dive site. Photo credit: RMP

Coral spawning monitoring and gamete collection will continue into this year. If you see these substrates pictured right at sites like

Overheat, please do not touch or move them as they are part of the coral restoration efforts.

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