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Title: Reduced bed material stability and increased bedload transport caused by foraging fish: a flume study with juvenile Barbel (Barbus barbus)
Authors: Pledger, Andrew G.
Rice, Stephen P.
Millett, Jonathan
Keywords: Ecosystem engineering
Bedload transport
Barbel
Imbrication
Zoogeomorphology
Issue Date: 2014
Publisher: © John Wiley & Sons, Ltd
Citation: PLEDGER, A.G., RICE, S.P. and MILLETT, J., 2014. Reduced bed material stability and increased bedload transport caused by foraging fish: a flume study with juvenile Barbel (Barbus barbus). Earth Surface Processes and Landforms, 39 (11), pp. 1500 - 1513.
Abstract: The plants and animals that inhabit river channels may act as zoogeomorphic agents affecting the nature and rates of sediment recruitment, transport and deposition. The impact of benthic-feeding fish, which disturb bed material sediments during their search for food, has received very little attention, even though benthic feeding species are widespread in rivers and may collectively expend significant amounts of energy foraging across the bed. An ex situ experiment was conducted to investigate the impact of a benthic feeding fish (Barbel Barbus barbus) on particle displacements, bed sediment structures, gravel entrainment and transport fluxes. In a laboratory flume changes in bed surface topography were measured and grain displacements examined when an imbricated, water-worked bed of 5.6 to 16 mm gravels was exposed to feeding juvenile Barbel (on average, 0.195 m in length). Grain entrainment rates and bedload fluxes were measured under a moderate transport regime for substrates that had been exposed to feeding fish and control substrates which had not. On average, approximately 37% of the substrate, by area, was modified by foraging fish during a four-hour treatment period, resulting in increased microtopographic roughness and reduced particle imbrication. Structural changes by fish corresponded with an average increase in bedload flux of 60% under entrainment flows, whilst on average the total number of grains transported during the entrainment phase was 82% higher from substrates that had been disturbed by Barbel. Together, these results indicate that by increasing surface microtopography and undoing the naturally stable structures produced by water working, foraging can increase the mobility of gravel-bed materials. An interesting implication of this result is that by increasing the quantity of available, transportable sediment and lowering entrainment thresholds, benthic feeding might affect bedload fluxes in gravel-bed rivers. The evidence presented here is sufficient to suggest that further investigation of this possibility is warranted
Description: This is the peer reviewed version of the following article: PLEDGER, A.G., RICE, S.P. and MILLETT, J., 2014. Reduced bed material stability and increased bedload transport caused by foraging fish: a flume study with juvenile Barbel (Barbus barbus). Earth Surface Processes and Landforms, 39 (11), pp. 1500 - 1513, which has been published in final form at http://dx.doi.org/10.1002/esp.3592 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Sponsor: The authors would like to thank the Barbel Society for providing financial support. AGP was in receipt of a Loughborough University Faculty Studentship.
Version: Accepted for publication
DOI: 10.1002/esp.3592
URI: https://dspace.lboro.ac.uk/2134/16460
Publisher Link: http://dx.doi.org/10.1002/esp.3592
ISSN: 0197-9337
Appears in Collections:Published Articles (Geography)

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