Abstract Summary
The widespread bleaching event in 1998 caused significant disturbance to coral reefs within the Western Indian Ocean, resulting in up to 95% coral mortality within the Seychelles. In 2011, a large-scale coral reef restoration project was implemented to facilitate reef recovery and enhance ecosystem services within the Cousin Island Special Reserve. Between December 2012 and June 2014, a total of 24,431 nursery-grown coral colonies from 9 different species were transplanted in 5,225 m2 (0.52 ha) of degraded reef at the no-take marine reserve. Coral nubbins, collected from survivors of the 1998 event and corals of opportunity, were raised in in-situ midwater rope and net nurseries. To measure the effects of restoration on natural recovery, ecological monitoring was completed before and after initial transplantation, at the transplanted site and at the adjacent control sites (degraded and healthy). In 2012, before intervention, live coral cover, juvenile coral density (< 5 cm in diameter) and fish density at the transplanted and degraded sites were similar. In 2014, live coral cover, juvenile coral density and fish density at the transplanted site were 5.5, 1.6 and 1.4 times higher than at the degraded control site, respectively. Following a series of natural disturbances throughout 2015 and 2016 (including a severe bleaching event) live coral cover decreased dramatically across all sites. Surviving corals (i.e. thermally resilient) were identified, stocked and transplanted (1,837 colonies between 2017 and 2018) in an ongoing effort to repopulate the reef. Preliminary results from ongoing monitoring show significant signs of reef recovery and the positive effects of transplantation are still apparent, whereby juvenile coral density and fish density at the transplantation site remain higher than at the degraded control site. This work highlights that the positive effects of large-scale reef restoration continue even after the occurrence of natural disturbances, which may be related to prevailing structural complexity following coral mortality. The next phase of the project aims to utilise ex-situ nurseries to microfragment massive and encrusting species and cultivate heat resilient corals based on genetic markers.
