Sustained modulation of microbial communities by high-performance DCOIT microcapsules for enhanced antifouling and anticorrosion performance of submerged marine infrastructure.

Marine corrosion and biofouling significantly compromise the safety and durability of marine infrastructures. Biofilms on submerged structures exhibit a dual nature, providing physical barrier protection while potentially exacerbating corrosion. Conventional protective strategies relying on biocidal and physical barrier mechanisms are often limited by the burst release of antifouling agents, which undermines biofilm protection and accelerates corrosion, thereby reducing coating longevity and environmental compatibility. To address this challenge in marine coating engineering, we developed a DCOIT-loaded microcapsule/epoxy glass flake composite coating and conducted a 90-day field immersion test in the South China Sea. The composite coating achieved an initial impedance modulus of (9.49 ± 1.25) × 108 Ω·cm2 and maintained an impedance 1.4 times higher than that of the control after 90 days. It reduced bacterial biomass and barnacle attachment to 38.6% and 26.3% of control levels, respectively. Microbial community analysis revealed that sustained DCOIT release effectively modulated microbial communities, decreasing key carbon-fixing Cyanobacteria and biofilm-forming Bacteroidota by 88.13% and 67.97%, respectively. Enhanced positive interspecies interactions (93.83%, 1.07 times that of the control) and a narrowed ecological niche width (from 1.499 to 1.293) indicated decreased community stability and the formation of cooperative survival strategies under stress. This study confirms that DCOIT-loaded microcapsules enhance the performance of epoxy glass flake coatings and provides new insights for developing next-generation marine protective coatings based on ecological regulation strategies.