Reef Renewal Foundation Bonaire (RRFB) is a non-profit organization funded in 2012, dedicated to protecting and restoring coral reefs in the small island of Bonaire, Dutch Caribbean.

Diver works in the nursery trees propagating new corals and maintaining the tree structures

Through large-scale propagation, outplanting, and monitoring of genetically diverse corals, RRFB works to assist the reefs’ natural recovery. To date RRFB oversees 8 nurseries, made up of 116 nursery trees for a total capacity of 13,650 corals. The focal coral species for the restoration project are the branching Acropora cervicornis and A. palmata, which population, once common in the Caribbean, has dramatically declined over the last 30 years. Since 2013, RRFB has outplanted more than 22,000 corals back to the reef at 11 different sites around Bonaire. The restored area, estimated using photomosaics and satellite pictures, currently extends for approximately 1 ha of degraded reef (~9,000m2).

Last year, in January 2018, RRFB, as part of a project funded by the BEST 2.0 Programme of the European Commission, installed a pop-up coral nursery at Oil Slick Leap, a reef that was documented to historically have abundant populations, but today has only a few, isolated coral colonies remaining. The coral nursery consisted of seven tree-like structures that float in mid-water and that were installed at the site temporarily and were removed at the end of the year-long project, leaving no visible trace of what was once there. Throughout the year, the coral nursery was maintained and surveyed by RRFB staff and volunteers, including several Marine Park Jr. Rangers who were trained in coral restoration.

Nursery-reared Elkhorn corals outplanted in the 2015

By October 2018, the nursery was full with over 750 Elkhorn corals (Acropora palmata) and the outplanting phase started. The pop-up nursery provided simplified logistics for the outplanting phase of the project because the nursery was situated just a few meters’ swim from the restoration site. This close proximity also eliminated the stress of transportation of the corals by boat, potentially increasing coral survival. Throughout the course of about 2 months, 763 Elkhorn corals were outplanted back to the reef at Oil Slick. Corals of different strains were strategically spaced and planted to maximize genetic diversity at the site and were attached to the bottom using a marine epoxy.

After outplanting, though, the work wasn’t done. To better assess the method and techniques, coral monitoring takes place at specific intervals over time. Before outplanting, an orthomosaic of the entire restoration site was created. This was done by swimming over the entire site while taking photographs and then using a dedicated software to stitch them all together, creating a high-resolution image of the area. The orthomosaic will be repeated after outplanting on a yearly basis and to measure changes in coral cover, expansion, and colony survival at a reef-wide scale.

3D model of a coral created to take more accurate measurements of surface area, volume, etc.

Photos taken during the dives were also used to create digital 3D models of the corals, to better assess coral health and measure growth. This easy-to-use, non-intrusive photogrammetry tool will save divers valuable underwater time and create snapshots in time of the corals to allow for researchers to re-analyze the models for years to come.

They proved to be a reliable monitoring tool for outplanted Elkhorn corals in order to collect additional important information, (i.e. volume, surface This easy-to-use, non-intrusive photogrammetry tool save divers valuable underwater time and create snapshots in time of the corals to allow for researchers to re-analyze the models for years to come.

Nursery-reared Elkhorn corals outplanted in the 2015

With all of the corals outplanted and the trees removed, the monitoring continues throughout the long-term to evaluate the success of the restoration efforts.

Since the 1980’s, Elkhorn coral populations have declined around the Caribbean, and recent studies in Bonaire show dramatic changes in the reef communities since then. This project was an important step toward restoring Elkhorn corals in Bonaire’s shallow waters by adding both more corals and more genetic diversity to Oil Slick Leap. The strategic outplanting of these different genotypes at the same site will ideally give the reef a helping hand by providing better chances for successful reproduction and fertilization at annual spawning events. By assisting the natural recovery of these corals and developing innovative nursery and monitoring techniques, this project has made important strides toward restoring Elkhorn corals in Bonaire and laid the groundwork for more successful reef restoration in the years to come.

Healthy and grown-up corals get selected in the nursery to be outplanted on the damaged reef area

To learn more about how to get involved or lend support, visit reefrenewalbonaire.org or email info@reefrenewalbonaire.org.

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