Inter-linkages between in-stream plant diversity and macroinvertebrate communities

Abstract Evidence of freshwater biodiversity decline, species extinction and severe alterations in the biological structure and function of freshwater ecosystems is accumulating. Here we explore the role of macrophyte diversity in lowland streams for the abundance, taxon richness and composition of macroinvertebrate communities including also the abundance of different functional feeding groups. We applied a controlled in situ experiment in four small lowland stream reaches situated in rural landscapes in Denmark. We were able to explain a major fraction of variability in the macroinvertebrate communities by differences in total macrophyte surface areas among treatments, but the number of macrophyte species in the experimental treatment also played a highly significant role (i.e. one, two or three plant species) for both the abundance, richness and composition of the macroinvertebrate community. We strongly encourage managers to protect plant diversity in streams, not only because the plants in themselves constitute an important part of the biodiversity, but also because they positively affect the macroinvertebrate community. Moreover, macrophyte-friendly management can be seen as a nature-based solution to mitigate the degraded physical conditions characterising many streams in agricultural catchments.