The pervasive role of biological cohesion in bedform development

Malarkey, J. and Baas, J.H. and Hope, J.A. and Aspenden, R.J. and Parsons, D.R. and Peakall, J. and Peterson, D.M. and Schindler, R.J. and Ye, L. and Lichtman, I.D. and Bass, S.J. and Davies, A.G. and Manning, A.J. and Thorne, P.D. (2015) The pervasive role of biological cohesion in bedform development. Nature Communications, 6 (6257). DOI: 10.1038/ncomms7257

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Sediment fluxes in aquatic environments are crucially dependent on bedform dynamics. However, sediment-flux predictions rely almost completely on clean-sand studies, despite most environments being composed of mixtures of non-cohesive sands, physically cohesive muds and biologically cohesive extracellular polymeric substances (EPS) generated by microorganisms. EPS associated with surficial biofilms are known to stabilize sediment and increase erosion thresholds. Here we present experimental data showing that the pervasive distribution of low levels of EPS throughout the sediment, rather than the high surficial levels of EPS in biofilms, is the key control on bedform dynamics. The development time for bedforms increases by up to two orders of magnitude for extremely small quantities of pervasively distributed EPS. This effect is far stronger than for physical cohesion, because EPS inhibit sand grains from moving independently. The results highlight that present bedform predictors are overly simplistic, and the associated sediment transport processes require re-assessment for the influence of EPS.

Item Type: Article
Subjects: Research Publications
Departments: College of Natural Sciences > School of Ocean Sciences
Date Deposited: 14 Feb 2015 03:28
Last Modified: 23 Sep 2015 02:49
ISSN: 2041-1723
URI: http://e.bangor.ac.uk/id/eprint/3464
Identification Number: DOI: 10.1038/ncomms7257
Publisher: Nature Publishing Group
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