Creating stocks of young colonies from brooding coral larvae, amenable to active reef restoration

Coral reefs are declining worldwide, even though traditional reef practices continuously underlie reef protection. This calls for exploration and integration of novel restoration techniques and tools, such as the "gardening" concept. The gardening approach, which has been successfully applied in various reef sites worldwide, is based on farming coral stocks in mid-water nurseries. To date, the farming of asexually produced coral material has chiefly been studied. Here, we test the performance of a novel spat-stocking tool for planulae of Stylophora pistillata, a brooding coral species. Two prototypes of a new settlement apparatus and one original apparatus made of Petri dishes lined with preconditioned transparency (Mailer's paper) disks had been stocked with >3730 planulae. After 96h, only 95.3% of >2080 settlers were found on the Mailer paper provided. One-month-old survivors (80.8% of initial settlements) that were kept ex situ in a flow through seawater table were detached from the papers, "transglued" onto plastic pins, and transferred to mid-water coral nursery, where the trays were covered with fitted plastic nets (1cm² mesh) to prevent predation and detachment. Four months later, more than 89% survivorship was documented, with colonies starting to form 3D structures. We estimate that 676 person-hours would be required to create 10,000 5-month-old genotypes of equal size to small branch fragments. This novel methodology allows farming of large quantities of colonies originating from sexually produced planulae and may enhance local populations' genetic variability within a short period. This method is inexpensive and easy to perform in remote places for incorporation in coral reef management practices.