Effect of near-bed turbulence on chronic detachment of epilithic biofilm: Experimental and modeling approaches

The biomass dynamics of epilithic biofilm, a collective term for a complex microorganism community that grows on gravel bed rivers, was investigated by coupling experimental and numerical approaches focusing on epilithic biofilm‐flow interactions. The experiment was conducted during 65 days in an ar...

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Bibliographic Details
Published in:Water resources research 2010-11, Vol.46 (11), p.1-n/a
Main Authors: Graba, Myriam, Moulin, Frédéric Y., Boulêtreau, Stéphanie, Garabétian, Frédéric, Kettab, Ahmed, Eiff, Olivier, Sánchez-Pérez, José Miguel, Sauvage, Sabine
Format: Article
Language:English
Subjects:
Biodegradable materials
Biodiversity and Ecology
Biofilms
Biogeochemistry
Biomass
biomass dynamics
Boundary layers
Creeks & streams
Environmental Sciences
Experiments
Friction
friction velocity
Geobiology
Gravel
Hydrology
Laboratories
Open channel flow
Reynolds number
Rivers
roughness
Running waters
turbulent boundary layer
Velocity
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Summary:The biomass dynamics of epilithic biofilm, a collective term for a complex microorganism community that grows on gravel bed rivers, was investigated by coupling experimental and numerical approaches focusing on epilithic biofilm‐flow interactions. The experiment was conducted during 65 days in an artificial rough open‐channel flow, where filtered river water circulated at a constant discharge. To characterize the effect of near‐bed turbulence on the chronic detachment process in the dynamics of epilithic biofilm, local hydrodynamic conditions were measured by laser Doppler anemometry and turbulent boundary layer parameters inferred from double‐averaged quantities. Numerical simulations of the EB biomass dynamics were performed using three different models of chronic detachment based upon three different descriptors for the flow conditions: Discharge Q, friction velocity u*, and roughness Reynolds number k+. Comparisons of numerical simulation results with experimental data revealed chronic detachment to be better simulated by taking the roughness Reynolds number as the external physical variable forcing chronic detachment. Indeed, the loss of epilithic matter through the chronic detachment process is related not only to hydrodynamic conditions, but also to change in bottom roughness. This suggests that changes in the behavior and dimensions of river bed roughness must be considered when checking the dynamics of epilithic biofilm in running waters.
ISSN:0043-1397
1944-7973
DOI:10.1029/2009WR008679