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Institut für Wasser- und Umweltsystemmodellierung - IWS



"Microbial biomass and biofilm topography in a quasi natural experiment with varying hydrodynamics"

Studies on the obvious effects caused by varying flow regimes have been carried out by a number of reports on the biofilm properties and motion. The typical result being that the higher the velocity, the thinner and denser the biofilm will be (with higher content of EPS). Nonetheless, some journal article revealed different results, as they did not find any effects from varying flow on the microbial biofilm. Since neither microalgae nor bacteria exist independently in natural sediments, their cooperation and significance for EPS secretion and thus for sediment stability are crucial to analyse. The main purpose of this research is to provide an empirical analysis of the structure and dynamic behaviour of biofilm and its functionality, when grown under high and low flow velocities. Thereby, the biochemical properties (microbial biomass and EPS) as well adhesion stability were addressed. Biofilm were growing on noncohesive glass beads over 8 weeks and adjust the velocity to high and low flow for three weeks sampling time. The microbial biomass was determined by flow cytometry (bacterial cell numbers, cyanobacterial cell numbers, diatom cell numbers) and spectrophotometric (chlorophyll a and phaeopigment a). Results shows that the correlation test between microbial biomass parameter does not show significant differences for high and low velocity. However, in some point of the time they have strong significantly increase or decrease due to the treatment period. Moreover, further assessment on the behaviour of microbial biomass give explanations how that biofilm as micro elastic microorganism adapts to different conditions. The interaction between chlorophyll a with heterotrophic bacteria, shows an inversely significant correlation. Diatom and cyanobacteria show a strongly significant correlation. Similarly, chlorophyll a and phaeopigment a have a strongly positive correlation. While to related with EPS and adhesion, microbial biomass not is showing significantly correlation in quantitative way but might be in qualitative.