The pervasive role of biological cohesion in bedform development

Malarkey, Jonathan; Baas, Jaco H.; Hope, Julie A.; Aspden, Rebecca J.; Parsons, Daniel R.; Peakall, Jeff; Paterson, David M.; Schindler, Robert J.; Ye, Leiping; Lichtman, Ian D.; Bass, Sarah J.; Davies, Alan G.; Manning, Andrew J.; Thorne, Peter D.

Abstract

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.

Citation

Malarkey, J., Baas, J. H., Hope, J. A., Aspden, R. J., Parsons, D. R., Peakall, J., …Thorne, P. D. (2015). The pervasive role of biological cohesion in bedform development. Nature communications, 6(1), Article ARTN 6257. https://doi.org/10.1038/ncomms7257

• Journal Article Type: Article
• Acceptance Date: Jan 9, 2015
• Online Publication Date: Feb 6, 2015
• Publication Date: Feb 6, 2015
• Deposit Date: Dec 21, 2016
• Publicly Available Date: Dec 21, 2016
• Journal: Nature communications
• Electronic ISSN: 2041-1723
• Publisher: Nature Publishing Group
• Peer Reviewed: Peer Reviewed
• Volume: 6
• Issue: 1
• Article Number: ARTN 6257
• DOI: https://doi.org/10.1038/ncomms7257
• Keywords: Sedimentology, Extracellular polymeric substances (EPS), Bedform development
• Public URL: https://hull-repository.worktribe.com/output/446462
• Publisher URL: http://www.nature.com/articles/ncomms7257
• Additional Information: Copy of article first published in: Nature communications, 2015, v.6, article number 6257.