What ecological and functional changes follow the positioning of an artificial barrier? Answers from a 4-year investigation on soft bottom benthic communities

Increasing employment of artificial barriers to combat coastal erosion is causing alterations of coastal ecosystems. Understanding their ecological functioning is key to planning management activities and minimising their negative impacts on the ecosystem. In this paper, changes in biodiversity and in functional traits of macrofaunal shallow communities were investigated throughout 4 years of study in the central Mediterranean. Biodiversity indices (S, d, H′) showed the highest mean values during in-operam phases (5.7, 1.99 and 2.07, respectively) whilst functional diversity (FDis) and functional redundancy (FDiv/H′) showed the highest mean values in ante-operam (4.34 and 2.44, respectively). The PERMANOVA showed differences both in species composition and functional traits between sampling periods. β-diversity was driven by the replacement of species over years. The non-indigenous polychaete Lumbrinerides neogesae, recorded for the first time during in-operam, supplied the highest differences between years (14.5%, SIMPER). During in and post-operam phases an increase of sub-surface deposit feeder, tolerant, and pioneer categories was recorded. When the classic taxonomic approach is combined with novel functional biodiversity attributes, a wide range of biota responses to a disturbance can be better described and the efficient mitigation solutions to minimize negative impacts of human activities proposed.