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Aquatic insect bioconstructions modify fine-sediment entrainment and mobility
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  • Richard J Mason,
  • Stephen P. P Rice,
  • Matthew Frederick Johnson,
  • Paul Wood,
  • Davide Vettori
Richard J Mason
UmeƄ University

Corresponding Author:richard.mason@umu.se

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Stephen P. P Rice
Loughborough University
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Matthew Frederick Johnson
University of Nottingham
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Paul Wood
Loughborough University
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Davide Vettori
Politecnico di Torino
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The importance of animals within fluvial geomorphology (zoogeomorphology) is increasingly recognized. Caddisflies (Trichoptera) are a group of aquatic insects known for their bioconstructions. Many caddisfly construct cases from fine sediment and silk. Caddisfly cases differ in size, shape and density from the incorporated sediment and case construction may therefore affect the mobility of these sediments in rivers. However, even though communities of caddisfly often use substantial quantities of sediment in case construction, the effect of these bioconstructions on sediment transport in rivers is unknown. We use a flume experiment to compare the bed shear stress required to transport (1) empty caddisfly cases and (2) individual sediment particles following disaggregation from the case. The cases of three species were considered; two that construct different styles of tubular case (Potamophlax latipennis and Sericostoma personatum) and one that builds a domed case (Agapetus fuscipes). P. latipennis and S. personatum cases were easier to entrain than the sediment grains incorporated into them, whilst A. fuscipes cases were not. Despite their low mass, A. fuscipes cases required the most shear stress to transport them because their domed shape impeded rolling. These findings are important for understanding how caddisfly affect sediment mobility in rivers and how differences in case design reflect case function to the larvae. These results suggest that un-attached tubular caddisfly cases may be preferentially transported over other particles on the river bed and thus caddisfly may increase fluvial entrainment of sand where they occur in high abundance.
Feb 2022Published in Journal of Geophysical Research: Earth Surface volume 127 issue 2. 10.1029/2021JF006399