A survey of current trends and suggested future directions in coral transplantation for reef restoration

Abstract

Coral transplantation has been used in reef restoration for several decades, but information on the type of projects, their scope, scale, and success is mostly limited to published scientific studies and technical reports. Many practitioners do not have the capacity to share their progress in peer-reviewed literature, yet likely have a wealth of information to share on how to improve the efficiency of transplantation efforts. In order to incorporate non-published data on coral transplantation projects and gain an overview of the general features of these projects, we conducted an initial systematic online survey of projects run by various practitioners. Surveyed projects (n = 50) covered most of the tropical belt and ranged in size from a few hundred transplanted corals to >5000 transplants. The most frequent source of coral fragments were corals already broken from some previous impact ("corals of opportunity"; 58% of projects), followed by fragments stored in different types of aquaculture systems (42% of projects). The use of sexual reproduction was very limited. Fast-growing, branching corals were used in 96% of projects, being by far the most common transplanted growth form. About half of the projects mentioned undertaking maintenance of the transplantation plots. The majority of projects undertook subsequent monitoring (80%), yet the available data indicates that duration of monitoring efforts was not adequate to evaluate long-term success. The findings underline that while some general principles for successful coral restoration projects are reasonably well established, others need to be mainstreamed better in order to improve the effectiveness of coral transplantation for reef restoration. This relates in particular to sustainable funding, adequate site assessment, and long-term monitoring using established protocols. Additional information is needed to better understand and address potential challenges with regards to the sourcing of transplants and use of slow-growing species. A better integration of practitioners is necessary to improve the understanding of coral transplantation effectiveness. The results underline a need to develop and use monitoring protocols that allow gauging and comparing the effectiveness of coral transplantation among various projects, as well as for accessible platform(s) to allow the exchange of experiences made in different projects. Regular surveys of restoration projects are recommended to collate and share information among practitioners. We provide a number of recommendations for items to include in future surveys.

Fig 1. Map showing the 50 coral transplantation projects covered in this survey.

Symbols represent the different types of organizations running the projects, and size of the symbols corresponds to the number of corals transplanted in each project (small/light blue: <500 corals, intermediate/medium blue: 1000–5000 corals, large/dark blue: >5000 corals). The NGO project in Malaysia used between 500 and 1000 fragments, but was grouped with the <500 corals projects for further analysis. Made with Natural Earth.

Fig 2. Funding sources for the transplantation projects.

Multiple responses were possible for each project.

Fig 3. Overall main objectives of the different transplantation projects.

Respondents were asked to provide multiple answers if several objectives were deemed equally important.

Fig 4. Sources of information used in projects.

The types of assessments and sources of information used to gauge a) the cause of coral degradation prior to transplantation of corals, and b) environmental conditions at the target site for transplantation.

Fig 5. Measures in addition to coral transplantation carried out in the different projects.

Multiple responses were possible for each project.