Coral Restoration Techniques

Since the 1980s, more than half of the world’s coral reefs have been lost. The current rates of change in our environment due to human activity are far outpacing the intrinsic capacity of coral reefs to survive. We need to act immediately or we risk losing more than 90% of all coral reefs by 2050.

RRFI trains network members to use proven restoration techniques designed and developed by Ken Nedimeyer (founder of Coral Restoration Foundation).

Explore the tabs below to learn more about some of the techniques used.

Coral restoration through fragmentation

Our current method of propagation begins with Coral Tree Nurseries. These nurseries are rows of PVC and fiberglass “trees” that are tethered to the bottom with sand anchors and buoyed with floats that sit just below the surface. This design allows the trees to move freely within the water column and dissipates wave energy, preventing damage both to the tree structure and the corals. Generally, each tree holds a unique genetic strain, or genotype, of coral, and a “full” tree can hold anywhere from 100 to 160 corals.

The Coral Tree nursery has proved to be an efficient and effective way to grow and propagate second, third, and future generations of corals through fragmentation. Fragmentation is a process that occurs naturally when corals reproduce asexually. When a large fish or wave breaks a branch off the coral, the branch will continue to grow into a new coral if the water conditions are favorable. We mimic this process in our nurseries by using pliers to cut smaller pieces from existing, large corals. Those fragments get hung back on the same tree, creating more corals of the same genotype. In this way, the Coral Tree nurseries become a self-sustaining approach to grow corals.

coral Outplanting
coral Maintenance and Monitoring

After six to eight months of growing in the nursery, the corals are healthy and mature enough to be outplanted to a restoration site. Coral outplanting means moving nursery reared corals to a restoration site. Restoration sites are reef sites that are degraded and damaged and would benefit from our healthy corals growing there.

Current outplanting methods include attaching corals to bamboo structures, adhering corals to solid substrate using a marine epoxy, and placing corals strategically in areas where conditions seem favorable. Whichever method is used, the corals are tagged to keep track of the genetic information and to allow for short and long-term monitoring.

reef Maintenance and Monitoring

Both coral nurseries and restoration sites are monitored regularly. Nurseries are checked for disease, predation, damage to nursery structures, and more, which helps to control and prevent issues before they occur. Nurseries also receive regular cleaning in order to prevent the overgrowth of algae and fire coral.

Restoration sites are monitored for survival rates, tissue paling, disease, and predation, among other factors. A subset of outplanted corals is also monitored at set intervals after outplanting to better understand the short and long-term success of those corals. This is achieved by taking a mosaic, a series of photos of a monitoring site and stitching them together to create one big picture of the site. Mosaics are taken annually to help represent the corals change over time.

Anne counting coral recruits

Corals in our Caribbean nurseries

Scientific name: Acropora cervicornis
Distinguishing features: A branching coral, where their branches are reminiscent of stag antlers, hence the name.
Growth: 4-8 in/10-20 cm per year. This coral species exhibits the fastest growth of all known western Atlantic corals.
Average depth: 0-100 ft/0-30 m. When their environment maintains a healthy status, they can live for hundreds of years and grow together to form dense thickets, meters across.

Staghorn coral (Acropora cervicornis)

Scientific name: Acropora palmata
Distinguishing features: A large, branching coral with thick and sturdy branches resembling elk antlers.
Growth: Colonies are fast-growing with branches increasing in length by 2-4 inches/5-10 cm per year and colonies reaching their maximum size in approximately 10-12 years.
Average depth: 3 ft-16 ft/1-5 m deep. Elkhorn coral was formerly the dominant species in shallow water throughout the Caribbean and Florida Reef tract.

Elkhorn coral (Acropora palmata)

Scientific name: Orbicella annularis
Distinguishing features: Large, bulbous columns or lobes clustered together.
Average size: 5 ft / 1.5 m. It has the largest average colony size of any coral species.
Average depth: 3-85 ft/1-25 m (can be found as deep as 80 m)

Mountainous star coral (Orbicella faveolata)

Scientific name: Orbicella faveolata
Distinguishing features: Large continuous cone-like lumps that are uniformly distributed in vertical rows, making it look like small mountain peaks and ridges.
Average depth: 30-60 ft/10-20 m (but can be found as deep as 40 m).

 

Mountainous star coral (Orbicella faveolata)

Scientific name: Monastraea cavernosa
Distinguishing features: Colonies are made up of large puffy looking polyps about the size of a thumbnail.
Average size: 2-8 ft/1-2 m
Average depth: 3-270+ ft / 1-90+ m. They are often the predominant coral species between depths 12-30 m.

Great star coral (Monastraea cavernosa)