Lab-grown corals help restore critically endangered reefs

Scientists have for the first time successfully raised laboratory-bred colonies of a critically endangered Caribbean coral species to their reproductive age, a step towards sustainable restoration of degraded reefs.

An estimated 80 per cent of all Caribbean corals have disappeared over the last four decades. The elkhorn coral (Acropora palmata) was one species whose decline was so severe that it was one of the first coral species to be listed as critically endangered under The International Union for Conservation of Nature (IUCN) Red List of Threatened species.

Due to its large size and branching shape, elkhorn corals created vast forests in shallow reef waters that protect shores from incoming storms and provide a critical habitat for a myriad of reef organisms, including ecologically and economically important fish species.

Elkhorn corals reproduce only once or twice a year, synchronously releasing their gametes (reproductive cells) into the water column. SECORE International researchers collected a small proportion of these gametes and produced coral embryos by in-vitro fertilisation. Coral embryos develop into swimming larvae within days and eventually settle onto specifically designed substrates. After a short nursery period, researchers outplanted the substrates with the newly-settled corals onto the reef