The pervasive role of biological cohesion in bedform development
MetadataShow full item record
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.
Malarkey , J , Baas , J , Hope , J A , Aspden , R J , Parsons , D R , Peakall , J , Paterson , D M , Schindler , R , Ye , L , Lichtman , I D , Bass , S J , Davies , A G , Manning , A J & Thorne , P D 2015 , ' The pervasive role of biological cohesion in bedform development ' Nature Communications , vol 6 , 6257 . DOI: 10.1038/ncomms7257
© 2015. The Authors. Published by Nature Publishing Group. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
DescriptionDate of Acceptance: 09/01/2015
Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.