Artificial reefs vs coral transplantation as restoration tools for mitigating coral reef deterioration: benefits, concerns, and proposed guidelines

Restoration of degraded reefs is considered one of the major reef management strategies to help remedy the negative effects of human activities on coral reef eco-systems. Degraded coral reefs may not respond readily to restoration efforts due to our incomplete understanding of various ecological dynamics such as loss of source sites, decline in species richness, shifts in species dominance, trophic interactions, and bioinvasion. Coral reef restoration techniques are at an experimental stage. There are two major approaches to reef restoration: coral transplantation and artificial reefs. Coral transplantation is appealing because it is an efficient means of turning a bare reef into a highly covered reef and there is a scientific basis for the technique. By contrast, artificial reef implementation is widely used and apparently accepted by the public and some resource managers, yet its scientific foundation is far from complete. Even so, there are major potential benefits of artificial reefs, which make them an essential tool in reef restoration. I suggest that the focus on artificial reefs and coral transplantation be shifted to combined approaches that use aspects of both in conjunction with other methods such as re-introduction of algal grazers. This review examines the advantages, disadvantages, and general guidelines for coral reef restoration.