Coral restoration Bonaire. An evaluation of growth, regeneration and survival.
The Coral restoration of Staghorn (Acropora cervicornis) and Elkhorn (A. palmata) as practiced by the Coral Restoration Foundation Bonaire (CRFB) is shown to be highly successful in terms of growth and survival of new colonies, in both nurseries and transplant locations. Coral restoration is expected to contribute to ecosystem services and increase coastal protection, biodiversity, fish biomass, and tourism.
Staghorn fields once covered the bottom of the shallow reefs of Bonaire for up to 70%. Most of Bonaire’s Staghorn and Elkhorn populations have been decimated by white band disease (WBD), leaving the shallow terraces around this popular diving destination as biologically barren sandy plains. The CRFB restoration project attempts to restore these populations by actively (with help from volunteers) rebuilding the once so attractive Staghorn fields. The coral restoration project of CRF Bonaire needed scientific assessment of important aspects of the restoration methodology such as growth, regeneration and survival of CRFB’s corals recruits.
Fragments are created from mother colonies by cutting and these cuts are short‐term wounds that need to be regenerated by the living tissue on both the ‘parent’ and the fragment. Results of a series of field experiments in the CRFB coral nurseries indicated that recovery of cut fragments was 99.6% (n=234). Time until recovery of tissue was extremely fast within approximately 1 week. Full pigmentation and apical polyp formation was generally achieved within two weeks and depended on the origin of parental colonies and the current growing location.
Over 200 colonies were transplanted from the nurseries on to attachment structures at different locations on the reef to determine growth rates and potential effects of location, attachment structure, and parental origin (genetic identity). Transplant sites (several kms apart) differing in environmental conditions and type of attachment structure were not found to impact transplant growth which was exceptionally high (almost 14 cm per year per branch tip and). An average fragment of 25 gram will grow to approximately 12 times its weight within one year. Nursery grown Staghorn fragments developed more side branches compared to their wild counterparts. While the exact mechanism behind side branch formation is not yet understood, several possible explanations are provided. The results of this research generate many follow‐up suggestions and exciting ideas for future coral restoration practices.
Results show clearly that current restoration practices by CRFB of transplanting Staghorn colonies to different locations is likely to be an excellent way to restore the Staghorn fields of Bonaire and probably in the wider Caribbean. Parental origin of the transplanted fragments significantly affected damage regeneration and growth rate, opening up the possibilities for active selection of specific genotypes to increase transplantation success. However, genetic diversity of the population should be studied and safeguarded. The measured survival, regeneration, and growth rates indicate that current restoration practices of CRFB are highly sustainable and may create viable clusters of Staghorn colonies which may initiate the regrow of Staghorn corals into thick fields. Coral restoration through fragmentation can create a very large number of viable fragments in a very short time (one fragment can be cut into two fragments within 6 months without influencing survival rate). It is recommended to also monitor the long‐term development of these restored Staghorn colonies in order to determine the recovery of the total community associated with these colonies.