Functional diversity as an early indicator of anthropogenic disturbances on insular sandy beaches within a protected...

Island habitats provide valuable natural laboratories for addressing questions about biodiversity dynamics. However, studies examining anthropogenic pressures on insular sandy beaches remain scarce. Furthermore, the functional diversity of macrobenthic communities has received little attention in these dynamic ecosystems. The main objective of this study was to evaluate taxonomic and functional diversity patterns of macrobenthic communities on insular sandy beaches and to assess how environmental features, seasonality, and anthropogenic factors shape these patterns within a marine protected area (MPA) network. Surveys were conducted on sheltered and exposed beaches of Ilha Grande Island during summer and winter. Community structure was analyzed using PERMANOVAs and SIMPER, while univariate diversity descriptors (species richness, total abundance, Simpson's diversity, functional richness, functional evenness, and functional divergence) were modeled against environmental (grain size, beach slope, organic matter, water temperature, and beach area) and anthropogenic predictors (urbanization and conservation indices) using GLMs/GLMMs. Environmental gradients on Ilha Grande's beaches were primarily defined by grain size, beach area, and conservation status. Sheltered beaches were generally smaller in area, featured coarser sediments, and were subject to higher levels of urbanization. In contrast, exposed beaches were larger, had finer sediments, and were better conserved. Exposed beaches supported higher abundance, species richness, and functional divergence. Model results indicated that abundance increased with beach area and conservation, richness declined with grain size, functional divergence was negatively associated with grain size and urbanization, and functional evenness declined with conservation. Overall, functional diversity proved effective in detecting early signals of anthropogenic disturbance within the MPA network.