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Earth Surface Dynamics An interactive open-access journal of the European Geosciences Union
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Volume 6, issue 1 | Copyright
Earth Surf. Dynam., 6, 203-215, 2018
https://doi.org/10.5194/esurf-6-203-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 16 Mar 2018

Research article | 16 Mar 2018

Quantifying biostabilisation effects of biofilm-secreted and extracted extracellular polymeric substances (EPSs) on sandy substrate

Wietse I. van de Lageweg1,a, Stuart J. McLelland1, and Daniel R. Parsons1 Wietse I. van de Lageweg et al.
  • 1Geography and Geology, School of Environmental Sciences, University of Hull, Cottingham Road, Kingston upon Hull, HU6 7RX, UK
  • anow at: Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands

Abstract. Microbial assemblages (biofilms) preferentially develop at water–sediment interfaces and are known to have a considerable influence on sediment stability and erodibility. There is potential for significant impacts on sediment transport and morphodynamics, and hence on the longer-term evolution of coastal and fluvial environments. However, the biostabilisation effects remain poorly understood and quantified due to the inherent complexity of biofilms and the large spatial and temporal (i.e. seasonality) variations involved. Here, we use controlled laboratory tests to systematically quantify the effects of natural biofilm colonisation as well as extracted extracellular polymeric substances (EPSs) on sediment stability. Extracted EPSs may be useful to simulate biofilm-mediated biostabilisation and potentially provide a method of speeding up timescales of physical modelling experiments investigating biostabilisation effects. We find a mean biostabilisation effect due to natural biofilm colonisation and development of almost 4 times that of the uncolonised sand. The presented cumulative probability distribution of measured critical threshold for erosion of colonised sand reflects the large spatial and temporal variations generally seen in natural biostabilised environments. For identical sand, engineered sediment stability from the addition of extracted EPSs compares well across the measured range of the critical threshold for erosion and behaves in a linear and predictable fashion. Yet, the effectiveness of extracted EPSs to stabilise sediment is sensitive to the preparation procedure, time after application and environmental conditions such as salinity, pH and temperature. These findings are expected to improve biophysical experimental models in fluvial and coastal environments and provide much-needed quantification of biostabilisation to improve predictions of sediment dynamics in aquatic ecosystems.

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Sticky sediments are an important component of many rivers and coasts. Stickiness depends on many factors including the presence of micro-organisms, also known as biofilms. We performed a laboratory study to better understand the role of biofilms in controlling sediment transport and dynamics. We find that sand with biofilms requires significantly higher flow velocities to be mobilised compared to uncolonised sand. This will help improve predictions of sediment in response to currents and waves.
Sticky sediments are an important component of many rivers and coasts. Stickiness depends on...
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