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|Title: ||Stabilization of fine gravels by net-spinning caddisfly larvae|
|Authors: ||Johnson, Matthew F.|
Rice, Stephen P.
Wood, Paul J.
|Keywords: ||Ecosystem engineering|
|Issue Date: ||2009|
|Publisher: ||© John Wiley & Sons, Ltd.|
|Citation: ||JOHNSON, M.F. ... et al., 2009. Stabilization of fine gravels by net-spinning caddisfly larvae. Earth Surface Processes and Landforms, 34 (3), pp. 413 - 423.|
|Abstract: ||We examined the impact of Hydropsychidae caddisfly larvae on the incipient motion of two sizes of narrowly graded
fine-gravel (4–6 and 6–8 mm). This impact was assessed relative to the collective impact of other abiotic and biotic processes that
are potentially important conditioning agents of fine-gravels. Trays of gravel were placed in the River Soar, Leicestershire, UK,
where they were colonized to natural densities by caddisfly larvae. Identical trays that were surrounded by a 250 μm mesh were
also deployed, preventing colonization but allowing field conditioning of sediments, including minor reworking of grains and
biofilm development. After 21 days in the river, trays were removed to a laboratory flume where grain entrainment stresses were
established. In addition to the colonized and conditioned treatments, critical shear stresses were measured for identical sediments
that were not placed in the river (laboratory gravels). Gravels that were colonized by Hydropsychidae required significantly
greater shear stresses for entrainment than conditioned trays (p ≤ 0·002), however, there was no significant difference between
conditioned and laboratory gravels. This implies that the presence of caddisfly can be a more important influence on fine-gravel
stability than some conditioning processes. Shields parameter was compared across treatments and across the two gravel size-fractions
using two-way ANOVA. No significant differences or interactions were observed, indicating that 4–6 mm gravel was stabilized to
a similar degree as 6–8 mm gravel by conditioning and colonization processes. Our results extend earlier studies in two important
ways: (1) entrainment stresses were established for fine gravels that were colonized at natural densities, under natural stream
conditions; and (2) the caddisfly effect was measured relative to both field-conditioned and unconditioned laboratory controls.
The temporal and spatial distribution of silk-spinning caddisfly larvae suggests that they have the potential to influence fine-sediment
mobility in many rivers, worldwide.|
|Description: ||This article was submitted for publication in the journal, Earth Surface Processes and Landforms [© John Wiley & Sons, Ltd.] and the definitive version is available at: http://dx.doi.org/10.1002/esp.1750|
|Version: ||Submitted for publication|
|Publisher Link: ||http://dx.doi.org/10.1002/esp.1750|
|Appears in Collections:||Published Articles (Geography)|
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