The zoogeomorphology of case‐building caddisfly: Quantifying sediment use

Richard J Mason,Stephen P Rice,Matthew F Johnson,Paul J Wood

doi:10.1002/esp.4670

Richard J Mason, Stephen P Rice + Show 2 more

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https://doi.org/10.1002/esp.4670

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Abstract

AbstractCaddisfly (Trichoptera) larvae are an abundant and widespread aquatic insect group characterized by the construction of silk structures, including nets and cases. Case‐building caddisfly have the potential to modify the sorting and mobility of sand and fine gravel via: (1) case construction, resulting in altered sediment properties; (2) transporting sediment incorporated into cases over the river bed; and (3) changing the structure of river beds via burrowing activity. To investigate these mechanisms, it is necessary to understand the mass, size distribution and spatial variability of sediment use by case‐building caddisfly larvae.We quantified the mineral sediment used by individuals and communities of case‐building caddisfly in 27 samples, from three sites on a gravel‐bed stream. The mass and size distribution of sediment in individual cases varied between taxa (mass = 0.001–0.83 g, D50 = 0.17–4 mm). The mean mass of sediment used by the caddisfly community was 38 g m−2 and varied locally. Sediment use was predominantly coarse sand (D50 = 1 mm). 64% of sediment use was attributable to Agapetus fuscipes (Glossosomatidae).Due to within‐species variability in case mass, the abundance of most taxa, including A. fuscipes, was only weakly associated with the mass of sediment used by this species, at the river scale. Whilst the caddisfly community used a small percentage of the total sediment available (average 2.99% of the 1–1.4 mm size fraction), A. fuscipes used more fine sediment in their cases at sites where it was more available. Despite variability in local habitat, all sites supported diverse case‐building caddisfly communities utilizing mineral sediment. Consequently, geomorphological effects of case‐building caddisfly are potentially widespread. The results provide novel insights into the specific grain sizes and quantities of fine sediment used by caddisfly larvae, which represents an important step towards understanding their zoogeomorphic activities. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.

Highlights

While sediment dynamics in rivers have traditionally been considered a largely physical phenomenon (Reinhardt et al, 2010), it is increasingly recognized that plants and animals can have substantial effects on hydraulics, bed sediment sorting and sediment transport processes (Rice et al, 2012; Statzner, 2012; Wilkes et al, 2018)
We investigated how sediment use varies in space, in relation to the abundance of caddisfly taxa and the availability of sediment in the bed; both likely to be important controls on case design and sediment use
This paper addresses three specific questions: 1. What is the mass and grain size of sediment used in cases by different caddisfly taxa and by the whole caddisfly community?

Summary

Introduction

While sediment dynamics in rivers have traditionally been considered a largely physical phenomenon (Reinhardt et al, 2010), it is increasingly recognized that plants and animals can have substantial effects on hydraulics, bed sediment sorting and sediment transport processes (Rice et al, 2012; Statzner, 2012; Wilkes et al, 2018). A growing body of research has demonstrated the importance of biogeomorphology (Viles, 1988) in rivers, for plants and larger animals, such as fish and mammals (Statzner, 2012). Both living plants and dead wood effect instream hydraulics and sediment stability Foraging by benthic-feeding fish can increase sediment mixing and fine sediment suspension (Pledger et al, 2014; Huser et al, 2016), affecting both gravel and sand substrates (Statzner et al, 2003; Pledger et al, 2017)

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