Ecological impacts of coral gardening outplanting in the Maldives

As coral reefs continue to degrade at an alarming rate, coral restoration efforts are increasing worldwide in an attempt to keep up with the global challenge of preserving these iconic ecosystems and the many services they provide. Coral gardening, the farming and outplanting of coral fragments, is a commonly applied practice; however, regional validation is required before upscaling can be considered. This study follows up from the successful farming of fragments in mid-water rope nurseries, by reporting on the successive outplanting of these corals. Specifically, 60 Pocillopora verrucosa colonies were outplanted to a degraded reef at different depths (1–12 m), applying three arrangement patterns (equal, clustered, random). After 1 year, 72% were considered successfully outplanted (alive and still attached), with detachment being the main challenge at wave-impacted shallow depths, while loose coral rubble caused more partial mortality at depth. Outplanting stress was observed at 1–6 m depth, but had no impact on survival or growth. Drupella sp. predation was most common at 3 m and 79% of colonies hosted mutualistic fauna after 1 year. Outplanting significantly benefitted the reef environment with a higher fish abundance and diversity along with a higher increase in natural coral cover (H = 2.7; 6.2% increase) in comparison with the control sites. These are promising results, considering that the restoration site has shown little natural recovery in the last few years (coral cover <4%). We hope that our findings provide useful initial insights and help to guide effective restoration practices in the Maldives.