Abstract
Early post-settlement mortality is a major bottleneck in larval-based coral restoration, largely driven by competitive overgrowth from benthic fouling organisms. Non-biocidal fouling-release coatings (FRCs) may reduce fouling pressure and enhance spat survival, but their efficacy in situ remains poorly quantified. We evaluated whether a commercial FRC could reduce benthic fouling and improve survival of Acropora loripes spat on a mid-shelf Great Barrier Reef. Larvae were settled onto ceramic seeding devices containing either FRC-treated or untreated (control) cores. Devices were deployed on the reef and monitored for fouling cover and spat survival over 46 weeks (~12 months). Relationships between spat survival, fouling, and benthic community composition were assessed. Fouling was substantially lower on FRC-treated devices, with only 25% fouling cover, compared to near-total overgrowth on controls. Importantly, spat survival remained consistently higher on FRC devices (68%) compared to controls (59%) at 46 weeks. Spat survival was negatively associated with device fouling, independent of immediate benthic community composition. This study provides the first in situ mechanistic evidence that FRCs indirectly enhance coral spat survival by mitigating competitive fouling pressure during the critical early growth period. Although the greatest benefit occurred in the first six months, fouling protection persisted throughout the deployment, suggesting that FRCs could provide a scalable solution to improve restoration outcomes. Integration of FRCs into seeding device design represents a promising strategy to support large-scale coral reef restoration under ongoing climate stress.