Facilitating the facilitators: advance coral reef restoration using the services of natural reef inhabitants

Despite the evident services coral reefs provide, failing local management and global climate change are rapidly annihilating these ecosystems. To restore reefs, coral is maricultured in nurseries and outplanted onto degraded reefs to kick-start recovery (coral gardening). However, coral gardening is often inefficient, for the nurseries need regular cleaning of biofouling, and success of coral outplanting is low due to space competition with other benthic life forms and coral predation. Coral gardening can be optimized by using biological assistance to: (1) reduce cleaning time in nurseries by facilitating herbivores’ grazing on biofouling, (2) improve performance of outplanted corals by facilitating grazing on competing benthic life forms and (3) reduce coral predation by facilitating predators of corallivorous invertebrates. This thesis aims to increase our understanding on bio-assistance at natural reefs, and use this knowledge to facilitate the facilitators to optimize coral reef restoration by creating favourable conditions for beneficial key organisms. Five research questions are investigated using field experiments and surveys on coral reefs in southern Kenya: 1. What are key herbivores and is their grazing associated with reef condition? 2. What are key corallivores and is their impact associated with reef condition? 3. Does reef condition influence grazing of herbivorous fish on nearby coral in mariculture? 4. Can the local reef-bound fish community facilitate coral mariculture? 5. How can artificial reefs be optimized to accommodate grazers and reduce corallivores? This thesis aspires to improve restoration methods by using the assistance of reef inhabitants to restore their own habitat. Such efficient coral reef restoration will have a long-term positive impact on coastal communities, for the additional habitat will increase fish populations and thereby improve fishing as well as tourism opportunities. The combination of fundamental and applied research resulting in a benefit to local communities promises to suit the WIAS mission.