The role of benthic microhabitats in determining the effects of hydromorphological river restoration on macroinvertebrates

Ralf C M Verdonschot,Jochem Kail,Piet F M Verdonschot,Brendan G Mckie

doi:10.1007/s10750-015-2575-8

Abstract

Despite the large number of river restoration projects carried out worldwide, evidence for strong and long-term positive ecological effects of hydromorphological restoration on macroinvertebrates is scarce. To improve the understanding of the success and failure of restoration measures, a standardized field study was carried out in nineteen paired restored and degraded river sections in mid-sized lowland and mountain rivers throughout Europe. We investigated if there were effects of restoration on macroinvertebrate biodiversity, and if these effects could be related to changes in microhabitat composition, diversity and patchiness. Effects were quantified for all taxa combined, as well as Ephemeroptera, Plecoptera and Trichoptera separately. Additionally, species trait classifications of microhabitat preference types were used as a functional indicator. Restoration had no overall positive effects on the selected macroinvertebrate metrics. Rather, we did find positive relationships between the macroinvertebrate responses and the effect of restoration on the diversity and patchiness of microhabitats. Furthermore, the effects on macroinvertebrates could be related to changes in the cover of specific substrate types in the restored sections. We conclude that the limited effect of restoration on macroinvertebrate diversity overall reflected, at least in part, the limited effect of most restoration measures on microhabitat composition and diversity.

Highlights

A large number of river restoration projects have been carried out worldwide, aiming at restoring natural flow patterns and enhancing habitat heterogeneity to increase biodiversity, including that of macroinvertebrates
Local restoration measures aiming at restoring specific channel features that are undertaken without addressing larger-scale hydromorphological processes are often not sustainable, as seen when restoration of gravel beds is undermined by deposition of silt which clogs interstitial spaces, hindering the recovery of macroinvertebrate populations (Mueller et al, 2014)
We expected that hydromorphological river restoration resulting in an increase in the number, diversity and/or patchiness of microhabitat types would have positive effects on both total and EPT richness and diversity

Summary

Introduction

A large number of river restoration projects have been carried out worldwide, aiming at restoring natural flow patterns and enhancing habitat heterogeneity to increase biodiversity, including that of macroinvertebrates. Palmer et al, 2010; Feld et al, 2011; Friberg et al, 2014), despite some notable exceptions (Miller et al, 2010; Kail et al, 2015) These findings partly reflect the lack of robust scientific assessments of restoration measures, but even where such assessments have been carried out, changes in invertebrate diversity and community composition have often been minimal In most restoration projects, diversity of habitats, including microhabitats, increases considerably, this does not automatically result in a strong positive response by macroinvertebrate assemblages (Jahnig & Lorenz, 2008; Louhi et al, 2011). We expected that hydromorphological river restoration resulting in an increase in the number, diversity and/or patchiness of microhabitat types would have positive effects on both total and EPT richness and diversity. An increase in the number or diversity of microhabitats in the restored section should be reflected in the microhabitat preferences of the assemblage recorded, given that part of the stream macroinvertebrates can be regarded as microhabitat specialists (Schroder et al, 2013)

Methods

Sampling methodology

Results