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Freshwater mussels are bivalve mollusks that inhabit the substrates of rivers. Fully three-dimensional large eddy simulations are used to investigate flow, turbulence and the capacity of the flow to dislocate an isolated, partially-buried, isolated freshwater mussel placed in a ful-ly-developed incoming turbulent open channel flow. The mussel is aligned with the flow di-rection, which corresponds to normal conditions in rivers containing mussel beds. Its sub-mergence depth is about 60% of the mussel height. The paper focuses on quantifying the ef-fect of the active filtering flow through the incurring and excurring siphons. Simulation re-sults are discussed for two limiting cases with no active filtering and with a filtering flow dis-charge that is close to the maximum value recorded for the investigated freshwater mussel species. It is shown that the active filtering increases the turbulent kinetic energy in the wake and slightly decreases the mean streamwise drag acting on the mussel shell. The paper also discusses the main types of large-scale coherent structures generated by partially-burrowed mussels aligned with the flow, how they are affected by the filtered flow and the effects of these eddies on the bed shear stress, sediment entrainment/deposition phenomena and nutri-ent transport