Now that we have either divided, or moved the coral fragment, we will need to apply a substrate to keep it upright. This, so that the coral (depending on the type) may either continue feedinf with microorganisms in the water or continue on doing fotosynthesis. Susbtrate is the surface on which an organism grows or is attached. In coral reef rehabilitation, the substrate is simply the material used to keep it upright and thus not function as a resource from which nutrients are gathered (unlike with conventional plants).

Applying substrate[edit | edit source]

With coral propogation, the primary substrate we use is generally the glue (or concrete) to attach the coral to a secondary substrate. This secondary substrate is a heavier material (such as limestone, rock, ...). With coral reef balls, the whole is often called a coral plug and is used for insertion into a module. PS:Note that in some cases, primary and secondary substrate are concrete

With coral rescue's, enough substrate (eg soil, limestone, ...) can still be present on the coral to not require the adding of secondary substrate. Thus, only the primary substrate (glue) is added and simply reattached to the sea bed (soil, rocks, ...). The seabed is also referred to as "tertiary substrate" in this manual for the purpose of clarity. Note that sometimes (with certain species of coral such as gorgonians), it may not require any primary substrate (glue, concrete) neither and it is instead inmediatelly inserted into a crevice of the sea bed or in a module (in the next step). Also note that in the modules chapter, limestone boulder modules are noted, but this differs from regular boulders in the fact that they have coral plug adapters drilled into them.

Different styles of Reef ball artificial reef modules equipped with coral plug adapters indicated with red arrows.

Coral plug adapters are depressions in the material of a uniform size and shape (see Figure 10). Coral fragments or colonies can be attached into coral plugs made of cement which fit into the coral plug adapters, and can be fastened in place underwater.

Substrate Requirements[edit | edit source]

Coral propagation and coral rescue is best accomplished using a fresh clean base substrate. Typically, this means limestone boulders, or sterilized hard bottom (without a fouling community). If necessary, clean hard bottom with a minor fouling community can also be used for re-stabilization techniques that don’t require coral basing. These requirements are necessary to be efficient, to provide a clean (non-competitive) substrate for long term coral basing, and to avoid mature fouling communities with abundant coral predators. As a rule of thumb, all coral planting activity must be completed between 30-90 days after the substrate is deployed, depending upon season. The same is true for recently exposed sterilized hard bottom. Experiments with planting coral after that time indicate that the fouling community competes too heavily for the basing space and that there are increases in coral predation from members of the fouling community. Less competition for newly transplanted corals results in higher survival rates, and more rapid growth.

pH neutralized concrete and a roughened surface texture, (patented features of Reef Balls) are NOT necessary to support propagated or transplanted coral colonies, but without them, there will be less natural coral settlement on the base substrate in areas not planted with coral.

Mixing concrete[edit | edit source]

As mentioned before, one of the primary substrates is concrete. When using the traditional hydrostatic cement mixing method, practice mixing very carefully before hand. A slight misformulation can create a very weak bond that will break during the first storm. Pick your attachment spots wisely and make sure to get a mechanical bond on both surfaces; don’t rely on the adhesion of the cement alone.

Tertiary substrate types[edit | edit source]

Besides attaching the substrate+coral to a module, it can also be attached directly to the seabed (as discussed above). The options here are:

Piles of natural limestone boulders can be used to create an artificial reef.
  1. Natural Limestone Boulders: Natural boulders can be drilled to accept coral adapter plugs for coral rehabilitation projects. From our experience we recommend that boulders be at least 3 tons, and be deployed in a stable configuration, in order to prevent shifting in storms.
  2. Pilings: Note that coral adapter plug holes can be drilled into the substrate, or added during construction. When using this method, ensure that all corals are planted below the coral biological tide line.
  3. Sterilized Hard Bottom: It is possible to transplant or propagate corals directly onto sterilized hard bottom environments (for example, in response to a ship grounding which exposes large amounts of sterilized bottom). While this method does not require the use of artificial reef modules, and can be accomplished by drilling holes for coral adapter plugs, the development of EPVS from a project of this nature is extremely slow, as it depends exclusively on the growth of transplanted and propagated coral colonies.
  4. Natural Live Bottom: This is not a recommended option because planting on natural live bottom can displace or damage existing marine life. Furthermore, planting on live bottom exposes recently transplanted corals to an increased risk of predation, competition, and disease, all of which lower initial transplant success rate by stressing the corals. Re-stabilizing colonies on Sterilized Hard Bottom is a safer alternative in all respects. Whatever base substrate you choose, conduct thorough research into the available materials and choose wisely. A good place to start your research is by reviewing material on the websites of various artificial reef manufacturers. Make sure that you also review the goals and resources of your project to help guide your decision. Remember that a healthy unmolested coral colony can live for hundreds, even thousands of years, so if you are planting corals, be sure that your chosen substrate is sufficiently durable. Whether you choose to use Reef Balls or another type of substrate, we hope you will find many of the methods and suggestions in this manual to be useful. There is also an appendix with our concrete mix design for coral friendly concrete that you may find useful for any base substrate creation project.

Disclaimer[edit | edit source]

This information was Reef Ball's Draftguide document.

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