Step 2: Rearing Mature Coral Colonies Copy

After collecting coral fragments to create your restoration feedstock, the next step is to secure the corals and maintain their growth until they are mature and large enough to be transplanted to the reefs. We need to find a place to secure them where they will get respite from threats and be held in a place that is easy for us to regularly access and care for them.

Generally, this is done through the use of tables or mid-water coral nurseries placed in areas with good water quality, ideally within swimming distance from the fragment collection area and the final transplantation area. Although sometimes the nursery step is not required and fragments can be secured directly to the reefs, higher levels of success can be obtained using the nursery step as long as there is available manpower and resources for regular maintenance.

The coral fragments need to be prepared to be secured to the nurseries. This can be done either in the water (preferred) or on a boat/land. Higher success is generally found when the work is completely carried out in the water, but this requires more skilled manpower to be dedicated to underwater time, which can raise the cost of some projects.

Trimming corals out of the water

When SCUBA diving is not ideal due to cost issues, or when training non-divers (volunteers, school groups, local children, etc.), fragments may be removed from the water as long as the protocols below are followed:

  • Corals should be kept in buckets of seawater when not being handled or secured
  • Corals should be removed from the water for no more than 30 minutes
  • They should regularly be sprayed or misted with sea water (every 2-3minutes)
  • Handling the corals should be minimized
  • Participants should wash their hands thoroughly, be encouraged to wear gloves, and extra care should be taken to ensure that the corals are not exposed to sunscreen, lotions, hand creams, etc.
  • Tools, gloves, and hands should be rinsed or soaked in warm freshwater between fragments to reduce the possibility of disease transmission.
  • All work should be conducted in the shade.
  • Great care should be taken to prevent contamination or contact with fuels, chemicals, etc.

When we prepare corals fragments for the nursery, there are several things we need to do. First, any large dead pieces of the skeleton are removed to leave mostly just the living areas. This reduces the chances of introducing fouling or encrusting organisms into the nurseries. Often, a large pair of pliers or a hammer and chisel are the best tools for trimming the fragments.

Second, we want to look around the fragment for any macroalgae, sponges, or other competitors that could be growing on it or any corallivores or parasites that could be hitchhiking.

Lastly, we will also amputate diseased sections before moving the coral to a nursery for rehabilitation (the diseased section can be buried in the sand, or brought back to land and left in the sun to dry)

On rare occasions, some fragments may be too large or awkward to fit in the nurseries and can be divided into several pieces, but breaking the coral tissue should be minimized whenever possible. Corals too large for the nursery should be cleaned and secured in place instead of being broken up into smaller pieces for the nurseries.

In our programs, we never advocate the asexual propagation of corals to increase feedstocks as it can lead to reduced resilience and diminished long-term project success. We will go into this in more detail later, but for now, just be aware of issues involved in decreased genetic diversity, which include genetic bottlenecking, inbreeding depressions, and other reproductive failures.

Securing to the Nursery

The prepared coral fragments are then secured through various means to some type of growing substrate that can be secured to the floating or mid-water nurseries. Growing substrates utilized by community-based managers may be fixed and permanent such as concrete plugs, or temporary, as in the case of vinyl tubes.

When planning which method to use, managers should consider where and how the mature colonies will be transplanted after the nursery stage. Begin with the end in mind.

During the nursery stage, regular maintenance is required to remove predators, parasites, or macroalgae, reattach corals that may have fallen out, remove dead fragments, and monitor growth.

In many cases, projects experience low success because the managers did not understand the amount of maintenance necessary to successfully rear corals in a nursery or did not adequately budget or plan for the ongoing work needed. We advise not to begin such a project without first ensuring long-term staffing/volunteers and financial resources.

Coral nurseries can potentially assist in rehabilitating compromised corals, growing out small fragments, providing a feedstock for restoration, and creating a living bank of biodiversity. Once corals have grown large and healthy enough or are too large to keep in the nursery, they are ready to transplant.