Field performance of innovative wood protection treatments on early successional macrofouling communities

Marine biofouling has long threatened the integrity of wooden structures commonly used in coastal and sensitive lagoon areas. To improve softwood durability while minimising environmental impacts, innovative antifouling treatments (i.e. Silvanolin® and thermal modification (TM)) have been developed as alternatives to traditional copper-based products. In this study, we assessed and compared the in-situ performance of these innovative treatments with the commercially available copper-based chromated copper borate (CCB) on the early stages of macrofouling community development. A total of 72 Picea abies panels, divided into four groups (12 samples per treatment: CCB, Silvanolin, TM, and controls), were immersed for 20 and 40 days at two sites in the Grado Lagoon, characterised by diverse hydrodynamic conditions. Overall, 36 macrofouling species were found. According to PERMANOVA test, communities differed significantly between the two sites, highlighting the key role of local hydrodynamics in influencing both treatment effectiveness and fouling settlement dynamics. The high-flow site showed greater macrofouling colonisation and recruitment, indicating reduced performance of treatments. In contrast, the enclosed site exhibited lower overall colonisation and dominance of copper-tolerant species such as cirripeds and tubeworms indicating a longer but still limited treatment efficacy. Taxonomic composition also varied among treatments, with TM having a major effect in selecting certain species over others. This study highlights the multifaceted role of local hydrodynamics in affecting wood treatment performance and structuring macrofouling communities. It also provides valuable field-based insights and a practical methodological framework for testing innovative, environmentally compatible antifouling solutions in highly sensitive coastal areas.