Material for direct coral transplantation can be obtained through nurseries or from a natural reef, where there are two main sources of transplants.
- “Corals of opportunity” which are fragments broken off from colonies by natural processes (e.g., storms) or human activity that can be found lying on the seabed. There may also be individual coral colonies that are at risk – badly bio-eroded or being overgrown (e.g., by algae or sponges, etc.). These corals can be “rescued” and either reared in nurseries prior to transplantation or directly transplanted to a restoration site.
- Donor colonies from which fragments can be obtained. Research suggests that as a precautionary measure, no more than 10% of a donor colony should be removed.1
Some development projects may have already taken the decision to severely impact or destroy an area of reef, such that any corals not moved will probably die. In such projects where corals are being relocated, as much of the reef community as possible (not just corals) should be saved, with priority given to species that do not rapidly colonize bare sites.
A key issue for such mitigation projects, in which threatened corals are to be relocated to a new site, is to find a suitable site to which to move them. If corals are not naturally present at a destination site, conditions for coral survival are unlikely to be conducive there.
What Species to Transplant?
Careful selection of coral species to transplant is one of the most crucial steps in successful restoration. When considering which species to use, the most logical choice is one that occurs naturally at the rehabilitation site and is relatively common on nearby potential source reefs. Species that are known to have occurred naturally at the rehabilitation site in the recent past may also be considered. Fast-growing branching species may provide a rapid increase in coral cover and topographic complexity, but they tend to be more susceptible to bleaching, disease and coral predators.
What Time of Year Should Transplantation Occur?
Times to avoid transplanting:
- immediately before the stormy season
- when sea temperatures are highest, as bleaching is more likely and disease more prevalent
Aim to carry out transplantation during the coolest months in sheltered reef environments (e.g., within protected lagoons) where corals will be protected from storm waves, and prior to the calmest months in more exposed environments where water flushing will hopefully prevent corals from becoming heat stressed soon after transplantation.