Early‐stage coral survivorship using wild larval assemblages on coral seeding devices for reef restoration

Following large‐scale disturbances, population recovery is often recruitment limited due to combinations of reduced propagule supply from remnant populations and the hostile state of the disturbed environment. To overcome recruitment limitation, restoring coral populations using coral larvae settled onto devices is an intervention approach being trialed in coral restoration efforts. This study utilized coral larvae from wild coral spawn slicks reared in situ in floating larval pools to compare the overall performance between engineered ceramic devices versus CaCO 3 travertine tiles. Six submersion time frames were tested to investigate larval settlement densities across competency windows. Travertine tiles supported greater than 2.5 times the mean settlement rates of engineered ceramic devices with densities greatest when submerged in culture pools for 24 hours, 3 days, and 4 days post‐spawning. Devices with settled coral larvae were deployed using two approaches (attached/unattached) across three unconsolidated rubble beds at a sheltered reef slope location at Lizard Island. After 21 months, 9% of engineered ceramic devices supported at least one recruit, all unattached and unconsolidated on the reef, whereas no recruits were present on any of the travertine tiles. Only one reef plot supported a positive device yield, with heavy sand deposition and unconsolidated reef substrata reducing recruit survival on the other two plots. Despite high settlement on both devices, our study shows a low yield of juvenile corals 21 months following deployment. This highlights the need to assess reef conditions prior to deploying seeded devices. Suboptimal habitats can result in low yields, making it crucial to ensure suitable conditions for effective restoration.