Augmenting coral adaptation to climate change via coral gardening (the nursery phase).

Unceasing climate change and anthropogenic impacts on coral reefs worldwide lead the needs for augmenting adaptive potential of corals. Currently, the most successful approach for restoring degraded reefs is 'coral gardening', where corals are farmed in underwater nurseries, then outplanted to damaged reefs. Dealing with enhanced coral adaptation, the 'coral gardening' approach is conceptually structured here within a hierarchical list of five encircling tiers that include all restoration activities, focusing on the nursery phase. Each tier encompasses all the activities performed in the levels below it hierarchically. The first is the 'coral mariculture' tier, followed by the 'ecological engineering' tier. The third is the adaptation-based reef restoration (ABRR) tier, preceding the fourth ('ecosystem seascape') and the fifth ('ecosystem services') tiers. The ABRR tier is further conceptualized and its constituent five classes (phenotypic plasticity, assisted migration, epigenetics, coral chimerism, holobiont modification) are detailed. It is concluded that the nursery phase of the 'gardening' tenet may further serve as a platform to enhance the adaptation capacities of corals to climate change through the five ABBR classes. Employing the 'gardening' tiers in reef restoration without considering ABRR will scarcely be able to meet global targets for healthy reef ecosystems in the future.