Since 1980, populations of Staghorn (Acropora cervicornis) and Elkhorn (Acropora palmata) corals have collapsed throughout the Caribbean from disease outbreaks with losses compounded locally by hurricanes, increased predation, bleaching, elevated temperatures, algae overgrowth, and other factors.
Once found in continuous stands that extended along the front side of most coral reefs, today these areas have been largely transformed into rubble fields with few, isolated living colonies facing local extinction.
In 2006 NOAA (National Oceanic and Atmospheric Administration) and NMFS (National Marine Fisheries Service) listed elkhorn and staghorn coral as “threatened” species under the Endangered Species Act (ESA) and in December 2012, NMFS proposed reclassifying the Elkhorn and Staghorn corals as endangered. Both Staghorn and Elkhorn corals are listed as Critically endangered by the IUCN (International Union for the Conservation of Nature and Natural Resources)
Coral Nursery Tree
The coral nurseries are rows of “trees” (PVC trunks with fiberglass rods running through the trunk) that are tethered to the bottom with sand anchors and buoyed with floats that sit just below the surface. This allows for free movement within the water and dissipates wave energy, preventing damage to the tree structure or corals. Each tree holds a unique genetic strain of coral (genotype), and a “full” tree can hold anywhere from 100 to 160 corals.
One of the primary benefits of coral nursery areas is the care provided to growing corals. Husbandry activities and maintenance of nursery sites are critical to maximizing coral health and minimizing incidence of disease, predation, breakage, and other damaging factors.
The Coral Tree nursery, has proved to be an efficient and effective way to grow second and third generations of corals, through fragmentation. In this way, the Coral Tree nurseries become a self-sustaining to grow corals.
At any given time, you can find over 12,000 corals, both Staghorn and Elkhorn, on our over 100 trees throughout our different nurseries around the island. It is thanks to the support of our dive shops, volunteers, and donors that we have been able to increase our nursery capacity.
Coral restoration means moving nursery-reared corals to restoration sites. After six to eight months growing in the nursery, corals are healthy and mature enough to be transplanted to a restoration site. These are reef sites that are degraded and damaged and would benefit from Staghorn and Elkhorn corals growing there.
Corals are taken from the nursery and are transplanted to restoration sites (damaged reef areas) using a couple of different methods. Corals are tagged to keep track of the genetic information and to allow for short and long-term monitoring.
There are many criteria for selecting a coral restoration site. Each of them plays an important role in helping to determine where we transplant and how many corals get placed at that site. A few we take into consideration are existing wild populations, depth, water quality, bottom type, size of the area, predator abundance, wave exposure, and the effects of human activities.
Maintenance and Monitoring
Both coral nursery and restoration site are monitored regularly to check survival, disease, damage, predation, tissue paling, and broken branches and more. In nurseries, this helps control and prevent issues before they occur. In restoration sites, maintenance can also give corals another chance at success. Without reattachment, the broken fragments would most likely be unable to attach to the reef substrate on their own and would not survive.
A subset of transplanted corals are also monitored at set intervals after transplanting to better understand the short and long-term success of transplanted corals. With this data, we can better understand the factors affecting the success of our transplanted corals at different restoration sites.
In addition to our data-collecting monitoring activities, Reef Renewal Bonaire is also involved in documenting our corals in another way. Project Baseline is an initiative that aims to monitor the change of our oceans through time. RRFB regularly updates its database and collaborates with this effort by photographing transplanted corals over time to show the change happening at our restoration sites. You can check the Reef Renewal Bonaire Project Baseline site to see how our corals are growing at different sites around the island.