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The effects of non-native signal crayfish (Pacifastacus leniusculus) on fine sediment and sediment-biomonitoring

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posted on 2017-06-20, 09:03 authored by Matt D. Turley, Gary S. Bilotta, Antonio Gasparrini, Francesco Sera, Kate MathersKate Mathers, Ian Humpheryes, J. England
© 2017 The Authors The North American signal crayfish (Pacifastacus leniusculus) has invaded freshwater ecosystems across Europe. Recent studies suggest that predation of macroinvertebrates by signal crayfish can affect the performance of freshwater biomonitoring tools used to assess causes of ecological degradation. Given the reliance on biomonitoring globally, it is crucial that the potential influence of invasive species is better understood. Crayfish are also biogeomorphic agents, and therefore, the aim of this study was to investigate whether sediment-biomonitoring tool outputs changed following signal crayfish invasions, and whether these changes reflected post-invasion changes to deposited fine sediment, or changes to macroinvertebrate community compositions unrelated to fine sediment. A quasi-experimental study design was employed, utilising interrupted time series analysis of long-term environmental monitoring data and a hierarchical modelling approach. The analysis of all sites (n = 71) displayed a small, but statistically significant increase between pre- and post-invasion index scores for the Proportion of Sediment-sensitive Invertebrates (PSI) index biomonitoring tool (4.1, p <  0.001, 95%CI: 2.1, 6.2), which can range from 0 to 100, but no statistically significant difference was observed for the empirically-weighted PSI (0.4, p = 0.742, 95%CI: − 2.1, 2.9), or fine sediment (− 2.3, p = 0.227, 95%CI: − 6.0, 1.4). Subgroup analyses demonstrated changes in biomonitoring tool scores ranging from four to 10 percentage points. Importantly, these subgroup analyses showed relatively small changes to fine sediment, two of which were statistically significant, but these did not coincide with the expected responses from biomonitoring tools. The results suggest that sediment-biomonitoring may be influenced by signal crayfish invasions, but the effects appear to be context dependent, and perhaps not the result of biogeomorphic activities of crayfish. The low magnitude changes to biomonitoring scores are unlikely to result in an incorrect diagnosis of sediment pressure, particularly as these tools should be used alongside a suite of other pressure-specific indices.


This article arises, in part, from research co-funded by the Natural Environment Research Council (NERC grant number: NE/P012264/1 and NE/K00722X/1) and the Environment Agency (Project number: SC 130021).



  • Social Sciences and Humanities


  • Geography and Environment

Published in

Science of The Total Environment




186 - 193


TURLEY, M.D. ...et al, 2017. The effects of non-native signal crayfish (Pacifastacus leniusculus) on fine sediment and sediment-biomonitoring. Science of The Total Environment, 601-602, pp. 186-193.


© The Authors. Published by Elsevier


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This work is made available according to the conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/

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This is an Open Access Article. It is published by Elsevier under the Creative Commons Attribution 4.0 Unported Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/






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