Substrate-specific macroinvertebrate diversity patterns following stream restoration

Abstract.

We examined the effects of stream restoration efforts that re-established multiple-channel sections in otherwise single-channel streams on aquatic habitat diversity and macroinvertebrate assemblages. At seven pairs of sites (single- vs. multiple-channel) we analysed the diversity of aquatic habitat parameters at various spatial scales (e.g. shore length, channel features, substrate diversity, flow variability). We also sampled macroinvertebrates in all available substrates individually and compared alpha- and beta-diversity and nestedness patterns on substrates between single- and multiple-channel sections. Multiple-channel sections showed a considerably more diverse hydromorphology. Taxa number, abundance, and evenness of macroinvertebrate assemblages did not differ significantly. Ten Coleoptera and seven Trichoptera taxa were present exclusively in multiple-channel sections on loam, sand, living parts of terrestrial plants (LPTP), coarse particulate organic matter (CPOM) or large wood. Non-metric Multidimensional Scaling showed that macroinvertebrate assemblages were substrate-specific rather than section-specific. Nestedness did not differ for samples from single- and multiple-channel sections, nor for individual substrates from different sections. We did not observe differences in alpha-diversity from substrates at single- and multiple-channel sections. However, different substrates host different assemblages and the increased substrate diversity in multiple-channel sections might result in higher beta-diversity in these sections. Our results indicate that stream restoration projects aimed at redeveloping near-natural macroinvertebrate diversity should focus on generating several long multiple-channel stretches with large areas of high quality habitats (e.g. large wood), creating stepping stone habitats for re-colonisation, and should allow sufficient time for new assemblages to establish.