Coral Restoration Via Sexual Coral Reproduction

Is sexual coral reproduction — coral sex — the future for helping to restore the world’s coral reefs? Is it more effective than current coral restoration methods?

The world’s coral reefs are in immediate danger of destruction from human activities. Deforestation, agricultural activities, pollution, coastal development, overfishing, boat damage and mining have all led to coral-reef decline. The biggest threat facing coral reefs is global warming, which is a main contributor to mass-bleaching events. As sea temperatures continue to rise, so too will we lose huge expanses of coral reefs around the world. Is coral restoration via sexual coral reproduction a solution?

Rehabilitating Coral Reefs

Apart from trying to reverse or slow these negative impacts to reefs, scientists, conservationists and scuba divers have been taking steps to help rehabilitate coral reefs around the world. Building coral nurseries and growing fragments of corals has proven successful on the local level. Divers and scientists attach fragments to manmade structures where they can grow. The scientists then plant them back into areas where reefs need some help. The resulting coral reefs are now spawning, reproducing and helping to restore even larger areas in turn.

Most common for this type of restoration work in the Caribbean are the Acroporid corals, such as Acropora palmata (elkhorn coral) and Acropora cervicornis (staghorn coral). These are not only the building blocks of Caribbean reefs, but have also suffered dramatic decline across the region. The IUCN Red List classifies both elkhorn and staghorn corals as Critically Endangered. These branching corals grow fast so they work well in these coral gardens.

Sexual Coral Reproduction

Gaining popularity when it comes to coral restoration is sexual coral reproduction. SECORE (SExual COral REproduction) a global network of scientists, public aquarium professionals and local stakeholders, is a pioneer in this area. The organization uses a multidisciplinary strategy, which combines research, education, outreach and active reef restoration. Here’s a brief video, explaining SECORE’s work and vision.

The agency held its first workshop in 2010 in Curacao. Since then, SECORE has begun collaborations in other parts of the world, holding workshops in Belize, Guam, Mexico and the Philippines. Most recently they held a workshop at the Cape Eleuthera Institute in the Bahamas, which I attended representing Stuart Cove’s Dive Bahamas conservation efforts. Theoretical background lectures focused primarily on elkhorn coral conservation, and featured hands-on practice in the lab. Participants also trained in fieldwork and learned how to observe coral spawning at night on the reef. The process of sexual coral reproduction, as shown in the video, can be done in a few ways.

Types of Sexual Coral Reproduction

Some corals are “broadcast spawners,” which release bundles of sperm and eggs (gametes) into the water during an annual event. Divers can collect the gametes using special nets and take them to a lab. Here, scientists put the gametes into tanks where the embryos will develop into coral larvae, called planulae. Scientists give the larvae a substrate to settle on, where they start to grow. Once large enough, the larvae are then planted back onto a reef.

Other corals are “brooders,” featuring internal fertilization and embryogenesis before they release settlement-competent larvae. Scientists can take these larvae into a lab and allow them to grow in controlled conditions as well, until they’re big enough to plant back onto a reef. Raising the larvae in the lab gives them the best chance of survival to develop without surrounding stressors, such as predators, sediment and pollution.

Coral Sex vs. Coral Nurseries

Sexual coral reproduction restoration differs from coral-nursery restoration efforts in that it is much more labor efficient and, apparently, more cost effective. Coral nurseries require materials to build, lots of manpower to set up, and many hours to clean algae off the structures. Nursery workers must follow up by out-planting the corals with a nail, zip-tie or epoxy. Sexual coral also needs a lab setup and expertise in creating the labs. But this method can also produce higher quantities of recruits and requires significantly less labor as there’s no cleaning involved. With the SECORE-designed substrate, there are also no extensive out-planting costs.

Get Involved

Many groups are starting local conservation projects using SECORE techniques. Get involved by educating yourself on when and where different species of corals spawn in your country. Data around the world on these events is limited but crucial if coral sexual reproduction is to be a successful means of restoration. Divers are the main worker bees for many conservation activities, so contact SECORE or similar coral-restoration agencies to determine what information they’re looking for and then pop on your fins and go out searching.

At Stuart Cove’s Dive Bahamas, we have a successful coral nursery and are excited at the prospect of developing a lab to start coral sexual restoration efforts. Right now, we are busy night diving to record local spawning events.

Although coral restoration is crucial, remember that this is not the only answer to the problems facing coral reefs. Continuously rising water temperatures and destruction of reefs via manmade or natural occurrences means these structures are in constant peril. Reef restoration is just one part of a much bigger puzzle that we must solve before it’s too late.

If you would like to become a Coral Nursery & Restoration Diver or Instructor, contact Hayley-Jo Carr at Stuart Cove’s Dive Bahamas.