Effects of water depth and water level fluctuation on the total and bio-available element concentrations in riverine reed stands

•Chemical composition in riverine reed stands depends on water depth and water level fluctuation.•Both the total and the bio-available element concentrations increase towards the deep water.•Floods homogenize the surface layer of the sediment, but water depth gradient influences the bio-available fractions.•Chemistry in reed stands can indicate redox conditions in the rhizosphere and anthropogenic pollution sources.