Enhancement of coral recruitment by in situ mass culture of coral larvae

New technologies for culturing and settling scleractinian coral larvae in the field are required to elucidate the role of recruitment in population dynamics and to provide options for reef rehabilitation. Natural multi-species aggregations of coral embryos, which frequently form slicks on the sea surface after large-scale annual spawnings, were identified as a potential resource for mass coral culture. Slicks containing billions of embryos were found at sea and several million embryos were sub-sampled and successfully cultured in simple floating ponds, moored over the reef. Coral larvae were maintained in the floating ponds until competent to settle, and then seeded onto the reef environment via hoses from the ponds to mesh enclosures temporarily fixed to the reef substratum. Reefal areas exposed to the cultured larvae exhibited a dramatic enhancement of coral larval recruitment compared to natural rates. The results demonstrate the ability to seed defined areas of reef with controlled densities of recruits. We conclude that natural spawning slicks, which have been noted on numerous reefs throughout the world, provide opportunities for very large-scale culture of corals, which may have application in reef rehabilitation and management strategies where natural recruitment is limited.