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Published on: July 30, 2019
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Beaver effects on macroinvertebrate assemblages in two streams with contrasting morphology
C T Robinson1, P Schweizer2, A Larsen3
1Aquatic Ecology, Eawag, 8600 Dübendorf, Switzerland; Institute of Integrative Biology, ETH-Zürich, 8092 Zürich, Switzerland.
The Science of the Total Environment
|March 21, 2020
Summary
Beavers significantly alter river ecosystems, but topography shapes their impact. A Swiss study found beaver effects were more pronounced in a low-gradient wetland system than a high-gradient ravine system.
Area of Science:
- Ecology
- Freshwater Biology
- Environmental Science
Background:
- Beaver (Castor spp.) populations are expanding across Europe, including Switzerland.
- Beavers act as ecosystem engineers, profoundly impacting river morphology, hydrology, and biota.
- Understanding how beaver activity influences aquatic ecosystems is crucial for conservation and management.
Purpose of the Study:
- To compare macroinvertebrate assemblages and trophic structure in two Swiss beaver complexes with contrasting topography.
- To investigate the influence of beaver engineering on fluvial systems and resident biota across different topographical settings.
- To assess the role of topography in mediating beaver impacts on riverine ecosystems.
Main Methods:
- Annual monitoring of macroinvertebrate assemblages and water physico-chemistry at two beaver complexes (Marthalen: low gradient; Flaach: high gradient).
- Analysis of carbon/nitrogen stable isotopes to determine dietary shifts and resource use (autochthonous vs. allochthonous).
- Comparison of hydraulic residence time and nutrient retention between the two contrasting beaver-influenced sites.
Main Results:
- Water chemistry differed, with higher nutrients and dissolved organic carbon (DOC) at Marthalen. Nutrient retention was highest in summer at Marthalen.
- Macroinvertebrate assemblages varied seasonally and between complexes; Marthalen showed more lentic (still water) characteristics, while Flaach supported more lotic (flowing water) taxa.
- Dietary shifts occurred seasonally, with increased autochthonous resource use downstream, most pronounced at Marthalen. Resource use was similar across sites in winter.
- Beaver influence on fluvial dynamics and macroinvertebrates was more pronounced at Marthalen, leading to a more wetland-like character.
Conclusions:
- Beaver significantly alter fluvial systems, but the extent and nature of these impacts are modulated by landscape topography.
- Topography influences beaver effects on river systems, affecting water chemistry, macroinvertebrate communities, and trophic dynamics.
- The study highlights the importance of considering topographical context when evaluating beaver ecosystem engineering and its ecological consequences.
