Exploring the performance of mid-water lagoon nurseries for coral restoration in the Maldives

Small island nations like the Maldives are highly dependent on healthy coral reefs and the ecosystem services they provide. Lately, Maldivian reefs have experienced considerable degradation as a result of severe mass bleaching events and accumulating threats posed by pollution, human development, coral diseases, and outbreaks of corallivores. Coral restoration can be a useful mitigation tool in assisting natural recovery, especially when economically important reef areas such as resort reefs are in poor health with slow natural recovery. This study assesses the performance efficiency of lagoon mid-water rope nurseries for coral gardening in two different atolls in the Maldives for the first time. Three different coral genera, namely Acropora, Pocillopora, and Porites, were assessed applying a common monitoring protocol. Fragment survival was generally very high, exceeding 90% survivorship for the genus Acropora and Pocillopora, while nursing success for Porites was significantly lower (66%). We further report benchmark growth rates for these genera in mid-water rope nurseries in the Maldives. The study also identifies potential threats to coral nursing success, namely disease occurrence and predation, as we report the corallivorous nudibranch Phestilla on in situ nursing stock for the first time. Overall, our results suggest that the use of mid-water rope nurseries in lagoons is an efficient and widely applicable technique for rearing corals in the Maldives. We aim to provide useful insight into best practices for applying this coral gardening technique on a wider scale in the archipelago and highlight future research requirements.