The method of transplantation that will be most effective in a given case will depend on:
- the species of coral being transplanted
- the nature of the substrate at the transplantation site
- the environment at that site
Methods of transplantation vary for different environments, described below.
Unattached and loosely attached transplants in sheltered environments
Fungiids (mushroom corals), several species of Acropora (including A. palmata and A. cervicornis in the Caribbean) and Porites, some species of Montipora and eastern Pacific Pocillopora damicornis have been reported to reproduce successfully by fragmentation, typically as a result of storm damage or by the actions of other reef organisms. In some low-energy environments such as back-reef zones, lagoons and protected embayments, fragments of such species can survive and grow without being artificially attached to the substrate. In these limited situations, coral transplantation may be effected by the scattering of fragments of an appropriate species on the substratum.
Attached without adhesives or cement in relatively sheltered environments
In relatively sheltered environments where there are natural holes or crevices in the reef, smaller (< 10 cm) coral branches or fragments can be slotted into them. Holes can also be created artificially using a hand-held auger or hand drill or compressed-air drill if the reef substrate is very hard. Larger fragments will generally require adhesives and even initial support wires for stability while waiting for self-attachment to occur. Such areas with natural holes at sheltered shallow sites are particularly suitable for community restoration projects.
Attachment with cement and epoxy adhesives
The use of adhesives and cement for fixing corals directly onto hard substrate is the most common transplantation method. The technique is labor-intensive; analysis of a range of studies suggest that only about 5–10 fragments or colonies can be attached per person-hour once all necessary peripheral activities are taken into account. The choice of adhesive depends on local availability, the environmental conditions at the restoration site, the size and morphology of the corals, the amount of coral that needs to be attached, and the manpower and financial resources available to undertake the restoration.
The following adhesives can be used for transplantation:
- Cement, usually in the form of sand-cement concrete, is cheaper than epoxy and may be the best choice for large massive and submassive corals and for repairing reef framework damaged by ship groundings or tsunamis.
- Ordinary Portland cement mixed with sand and freshwater (try to avoid using saltwater as this may interfere with the setting process and strength of the concrete) has been widely used, sometimes with admixtures to alter the rate of setting of the concrete. Type II Portland cement or specialist sulphate resistant marine cements with microsilica-based additives are recommended for use in the marine environment and can be used if available locally.
- Two-party epoxy putty (e.g., AquaMend, Epoxyclay Aqua) appear the easiest to use and most cost effective. Epoxy putty comes in small sticks (e.g., 60–70 grams?) and the chemical reaction between the two parts does not begin until the two parts are mixed together. It has the advantage that for each transplant only the portion that is needed can be broken off from the stick.
Use of wire, fishing line and cable-ties
Insulated electrical wire, stainless steel wire, monofilament fishing line and cable-ties have all been used to attach coral transplants, usually either to artificial structures or to artificial substrates for nursery rearing (e.g. limestone slabs), which are later transferred to the reef once corals have grown. They may also be suitable for attaching fragments to thick dead coral branches or to nails or metal stakes fixed in the reef.