coral gardening

Coral reef restoration requires efficient, effective and scalable techniques and methodologies to counteract the continued decline of coral reefs. Here we tested an in situ method to collect and settle fully developed planulae shed by the brooding coral species (Stylophora pistillata). Three devices called Coral Settlement Boxes (CSB; L × W × H: 50 × 40 × 6 cm; V: 4.5 L) were built from transparent Plexiglas and designed to be easily assembled and disassembled. Each CSB contained two integrated biofilm-covered nets (0.5 × 0.5 cm mesh size), which functioned as settlement substrate. The trap container of a traditional planulae trap was replaced by the CSB, and this new construction was used to collected planulae over 4 consecutive days. The CSBs were then transported to a mid-water coral nursery at 12 m depth. One CSB was disassembled immediately, the two settlement substrates were removed and each was placed in a protective cage (mesh size 4 cm²). The other two CSBs were opened after a 4-month period, leaving the four settlement substrates attached to the Plexiglas plates and covered by protective cages. None of the settlement substrates were cleaned of fouling organisms in the nursery. After 5 months in the mid-water nursery, a total of 120 healthy juvenile coral colonies had resulted from the estimated 2045 planulae initially trapped. This inexpensive and simple approach to producing sexually propagated stocks of colonies entirely in situ may enhance the efficiency, effectiveness and scalability of restoration activities that include brooding coral species.

Bachelor thesis research project

The previously dominant, reef-building Acropora cervicornis abundance decreased drastically across the greater Caribbean area since the 1970s. This is mainly due to the white band disease (WBD) and coral bleaching events. They have been considered a critically endangered species by the IUCN Red List since 2008 and restoration efforts are paramount to assist recovery of this species population. The exceptionally high growth rate and possibility of fragmenting this species, make it very suitable for coral gardening. This technique grows coral colonies from small fragments in ex- or in-situ coral nurseries before out-planting them into the natural reef. To test which locations are best suited for focusing future out-planting efforts, all previous out-planting trials have been analyzed to select three promising locations. In this research, two rebar frames have been installed at each of these locations. Per location, one frame was equipped with 20 fragments of the genotype ‘HiC’ and the other one with 20 fragments of the genotype ‘LL’. For the following 70 days fragment health, survival, growth rates, sediment settlement, and turbidity have been measured biweekly. The growth rates at location ‘Nursery’ and ‘Big Rock Market’ did not differ, however, at location ‘Hole in the Corner’ the genotype HiC had a significantly higher growth rate compared to the other locations and genotypes. The high amount and variation of turbidity and sedimentation at the Nursery make this location unsuitable for out-planting efforts. Sedimentation at Big Rock Market was exceptionally low and consistent, which could benefit out-planting efforts, but faster growth rates at Hole in the Corner will yield more coral. Because the locations are approximately 1.5km apart and both are considered suitable, it is recommended to outplant at and in between both locations instead of focusing out-planting efforts on one location, in order to increase the resilience of the out-planting efforts against natural stressors such as new outbreaks of the WBD.

Reef restoration activities have proliferated in response to the need to mitigate coral declines and recover lost reef structure, function, and ecosystem services. Here, we describe the recent shift from costly and complex engineering solutions to recover degraded reef structure to more economical and efficient ecological approaches that focus on recovering the living components of reef communities. We review the adoption and expansion of the coral gardening framework in the Caribbean and Western Atlantic where practitioners now grow and outplant 10,000’s of corals onto degraded reefs each year. We detail the steps for establishing a gardening program as well as long-term goals and direct and indirect benefits of this approach in our region. With a strong scientific basis, coral gardening activities now contribute significantly to reef and species recovery, provide important scientific, education, and outreach opportunities, and offer alternate livelihoods to local stakeholders. While challenges still remain, the transition from engineering to ecological solutions for reef degradation has opened the field of coral reef restoration to a wider audience poised to contribute to reef conservation and recovery in regions where coral losses and recruitment bottlenecks hinder natural recovery.