Biofilm contribution to the deposition of suspended particles in a stream

概要

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Microorganisms growing in a stream often form biofilm draping the surface of riverbed gravels. The biofilm develops a particular interface between stream water and riverbed, which seems to control the hydrodynamic condition and the retention time of particles within the zone of interface. We made a series of experiment on the deposition of inorganic suspended particles from flowing water on the bed with/without biofilm using an open flume. Grain-size analyses of the deposits were done after experiments, and cross-section of the biofilm was observed. The increase of the sediment on the biofilm was proportional to the flow velocity, while that on no-biofilm bottom was decreased with the increase of the flow velocity. When the velocity increased, grain-size distribution of the sediment on the biofilm becomes coarser. The results indicate that the biofilm has a great advantage on the deposition of fine clastics from flowing water through sieving the particles by its mesh structure within biofilm.
日本堆積学会の論文