Abstract

Hydromorphological river restoration can significantly alter habitat configuration and modify invertebrate assemblages of rivers and floodplains. However, the consequences of these changes for ecosystem functioning and aquatic-terrestrial interactions are not known. As a restored shoreline has a more heterogeneous structure compared to a straightened river, restoration is likely to impact aquatic-terrestrial linkages in multiple ways, which might be captured based on biomarker indicators to characterize changes in food web functioning. We conducted a large scale comparative study targeting eleven river restoration projects in central and northern Europe to assess effects of river restoration on trophic patterns across the aquatic-terrestrial interface. We investigated the isotopic composition (delta C-13, delta N-15) of prey and of invertebrate consumers stratifying between the aquatic, riparian and terrestrial zones. The isotopic distance of riparian arthropods to instream macroinvertebrates and terrestrial arthropods was used as a measure of trophic linkage, and its variation with riparian habitat composition was quantified. Restoration enhanced aquatic-terrestrial linkages, indicated especially by differentiation in the delta N-15 isotopic signatures between aquatic, riparian and terrestrial consumers, rather than by delta C-13 signatures. The delta N-15 isotopic signatures of riparian arthropods revealed a higher relative trophic position in restored sections (delta N-15(Restored): 8.64 parts per thousand, n = 11) as compared to non-restored sections (delta N-15(Degraded): 8.05%, n = 11), lending support to the conjecture that restoration increased the proportion of more highly enriched aquatic prey (delta N-15(Restored): 10.01 parts per thousand; delta N-15(Degraded): 10.38 parts per thousand) while simultaneously reducing the share of lower enriched terrestrial prey (delta N-15(Restored): 4.88 parts per thousand; delta N-15(Degraded): 5.53 parts per thousand). Riparian habitat diversity and the share of exposed sand and gravel bars were positively related to the strength of aquatic-terrestrial linkages (R-2 = 0.28 and R-2 = 0.31, respectively), pointing to the importance of habitat diversification in the riparian zone in promoting trophic linkages between river and floodplain. These findings expand our understanding of the multifaceted outcomes of hydromorphological restoration, beyond biodiversity in the aquatic environment. It highlights the need to expand our current set of indicators in order to mechanistic understand restoration effects on ecological networks spanning across boundaries. This knowledge is highly relevant for the large restoration efforts driven by legislative frameworks such as the Water Framework Directive in Europe.

Keywords

Restoration assessment; Functional indicators; Habitat diversity; Food webs; Riparian buffer; Macroinvertebrates

Published in

Ecological Indicators
2020, Volume: 113, article number: 106242
Publisher: ELSEVIER

SLU Authors

• Mckie, Brendan

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

SDG15 Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss


UKÄ Subject classification

Ecology


Publication identifier

DOI: https://doi.org/10.1016/j.ecolind.2020.106242

Permanent link to this page (URI)

https://res.slu.se/id/publ/105262