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Institut für Wasser- und Umweltsystemmodellierung - IWS



"The effect of seasonality upon the development of lotic biofilms and microbial biostabilisation"

1. Fine sediments (fine sands or silts) are significantly impacted by microbial biostabilisation. This process complicates precise modelling solutions for sediment dynamics and management strategies for riverine sediment. The present publication investigates the effect of seasonality upon biostabilisation.
2. In total, five straight flume experiments with fluvial water were performed during spring, summer and autumn under identical boundary conditions. The extracellular polymeric substances (EPS), microbial biomass and microbial community composition of the developing biofilms were analysed. In addition, biofilm adhesiveness was measured.
3. Highest biostabilisation occurred during spring (up to six times greater than during autumn) and coincided with maximal EPS production – especially extracellular proteins indicating the essential role of adhesive proteins for the stability of the biofilm matrix. Furthermore, not biomass but microbial community composition significantly differed between seasons. For instance, during minimal biostabilszation in autumn, the diatom community was dominated by the motile diatoms Nitzschia fonticola and Nitzschia dissipata var. dissipata. Concurrently, the highest rates of change within the bacterial community were detected. This suggests a disruptive impact of diatom movement upon the biofilm matrix and overall biofilm stability.
4. These findings emphasise the importance of detailed analyses of the microbial community and demonstrate the complex interactions of distinct biofilm features influencing the functionality of the overall biofilm system.
Keywords: Biofilm, biostabilisation, diatoms, fine sediment, Magnetic Particle Induction