Response of macrophyte communities to flow regulation in mountain streams. Environmental Monitoring and Assessment

River macrophytes are widely used in fresh- tation procedure. Plant similarity between sites was water ecosystem assessment because of their sensitivity evaluated at the level of phylum, and indicator species to anthropogenic pressures, even if there are only a few analysis was performed to identify the taxa most sensi- studies that investigated how macrophytes respond to tive or tolerant to water regulation. We found that the water regime alterations. In this study, we analyzed the effects of dams on river macrophyte communities overall environmental setting overwhelms the dam im- pact and that the influence of hydrological alteration through a comparison between upstream and down- became apparent when comparing upstream and down- stream sides from 18 dams located in Alps and stream assemblages at the same dam. In particular, we Apennines. A co-inertia analysis and a Mantel test were found that most of taxa had a higher affinity with the applied to assess if the analysis of environmental pa- downstream side and that in general, stream regulation rameters could be effective in predicting macrophyte increases plant richness and coverage, but reduces com- community structure. We analyzed morphological and physicochemical inter-site differences and tested the munity evenness. Analyses based on higher taxonomic groups (phyla) demonstrated that this community can be influence of dams on various aspects of community effectively used in bioassessment even at phylum level structure (composition, richness, diversity, dominance, analysis. In particular, we found that bryophytes, strictly linked with changes in substrate stability, show particu- Electronic supplementary material The online version of this lar sensitivity to water regulation in mountain streams.