A new method to measure substrate coherent strength of Stenopsyche marmorata

Abstract

We developed a method for estimating the substrate coherent strength of a net-spinning caddis larva, Stenopsyche marmorata, in the field. Plastic experimental cages (prefabricated containers with 5-mm mesh; 0.1 m high, 0.12 m wide, 0.2 m long) that enclosed gravel substrate and an objective stone (5-6 cm in diameter) were prepared. We expected the caddisflies to build a retreat(s) between the objective stone and cage substrate when submerged in a riffle channel reach for 6 days. Ten final-instar larvae (4-5 cm long) were placed in the cage and allowed to form retreats. Two treatments (cages with and without larvae) with 15 replicates each were used in two experimental trials. The vertical lift-force of objective stones associated with a retreat (coherent strength) was measured using a spring weighing scale. In 87% of 30 cages of with-larvae treatment, retreats were formed between the objective stone and cage substrate. Coherent strength ranged from 0.0 to 1.6 kg. Our approach can be used under varying flow velocities, substrate conditions, and larval biomass, all of which are normally difficult to test in flume experiments. Findings based on our field method provide unique physical properties of the caddisfly retreats in stream ecosystems.

Physical and biological controls on fine sediment transport and storage in rivers

“…Hydropsychidae is one of the most abundant families of lotic insects worldwide, often accounting for as much as 80% of invertebrate biomass in some rivers and, consequently, exerting substantial controls on geomorphic processes (Nunokawa, Gomi, Negishi, & Nakahara, 2008;Statzner, Arens, Champagne, Morel, & Herouin, 1999;Takao, Negishi, Nunokawa, Gomi, & Nakahara, 2006). Hydropsychids construct nets to filter FPOM from the water column, increasing the force required to entrain bed sediments by 10-30% (Cardinale, Gelmann, & Palmer, 2004;Rice et al, 2014).…”

Meta‐analysis: abundance, behavior, and hydraulic energy shape biotic effects on sediment transport in streams

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Geomorphological implications of engineering bed sediments by lotic animals

“…Clears the upper interstitial space among cobbles from fine sediments (up to 7 cm deep), thereby increasing τ c of cobble by perhaps 50% I.6, caddisfly: Stenopsyche marmorata (up to 0.3 g/Asia)/ Takao et al, 2006 Field observation across natural biomass gradient Riffle/autumn Spinning with silk: larval-retreat and filter-net building Increase of force to dislodge stones (1-3 kg) by up to 50-260% I.7, caddisfly: Stenopsyche marmorata (0.5 g/Asia)/ Nunokawa et al, 2008 Field experiment, mimicking low natural larval density Riffle/perhaps all seasons Spinning with silk: particularly larval-retreat building…”