Taxonomic differentiation but functional convergence in metaphyton and phytoplankton across eutrophic lakes

Abstract This study aimed to test whether metaphyton and phytoplankton in shallow lakes represent functionally distinct communities shaped by habitat-specific environmental filtering or whether connectivity between them leads to functional overlap. We combined taxonomic and trait-based approaches across multiple standing waters using diversity metrics, multivariate analyses, and regression-based models to assess community differences and the influence of shoreline development and vegetation cover. Taxonomic composition differed clearly between communities, with higher richness in metaphyton, whereas trait composition showed only weak separation. Functional richness and dispersion were higher in phytoplankton, indicating greater functional space, while higher taxonomic richness in metaphyton was consistent with functional redundancy. Differences in individual traits were primarily morphological, with metaphyton characterized by more elongated and structurally complex forms and phytoplankton by higher proportions of mobile taxa. These differences are consistent with adaptations to contrasting habitat conditions. Shoreline development and vegetation cover had limited influence on overall patterns, although intermediate vegetation cover was associated with higher diversity and patterns of functional richness suggested increased functional redundancy. The observed functional overlap is consistent with a potential role of dispersal-driven connectivity or mass effects between littoral and pelagic habitats, highlighting the importance of considering both compartments in freshwater biodiversity assessments.