Insights from multispecies coral seeding deployments on turbid nearshore reefs

Coral seeding may help sustain coral populations in a warming ocean; however, key knowledge gaps currently temper the successful application of this method across varied reef environments. This study investigated the survival and growth of three common coral species seeded on two device designs and deployed across a broad range of benthic communities in the Keppel Islands, southern inshore Great Barrier Reef. We examined the influence of algal cover and biomass, sedimentation, water flow, and temperature on seeding success after one year. Benthic communities at deployment sites ranged from coral- to macroalgal-dominated, yet site-level differences in survival were only detected for Acropora millepora on one device type. Coral survival and size were related to macroalgal biomass and/or cover (particularly Sargassum ), sedimentation, water temperature, and water flow, and the patterns were species-specific. Overall, Montipora aequituberculata demonstrated higher survival than Acropora millepora and A. muricata , consistent with a previous deployment in the region. Higher survival and growth on a device fixed above the substrate versus a tethered device on the substrate may reflect higher pre-deployment spat numbers, differences in device composition and design, and/or negative interactions with the benthos. Higher survival was also observed in a side compared to an upward facing orientation. Survival increased with the number of A. millepora spat on fixed devices and A. muricata spat on tethered devices, suggesting positive density-dependent effects. This study highlights the complex, taxa-dependent ways in which seeded-coral survival is influenced by device design, pre-deployment spat numbers and deployment environment.