This thesis deals with sediments and their influence on the oxygen balance of the tidal Elbe River. The study area is the upper Elbe estuary, including the Port of Hamburg. In this area, minimal oxygen content zones are frequently formed during the summer months, where the oxygen content falls below the critical value of 3 mg O2 l-1 for fish. The biogeochemical processes that lead to this oxygen depletion are well known in the water phase. However, the influence of sediments with their spatially and temporally variable composition on the oxygen balance is largely unknown. The way sediments consume oxygen varies. Under resuspension, large amounts of oxygen-consuming substances are quickly released into the water phase and can negatively affect the oxygen balance. Under stable conditions, oxygen diffusely penetrates the sediment surface and is slowly but continuously consumed in the oxic sediment layer. The aim of this thesis is to clarify how strong the sediment-induced influence on oxygen consumption is, which processes play a major role in this and how much the sediments and their oxygen consumption potential (OCP) differ on a spatial and seasonal level during resuspension. In two approaches, the spatial and seasonal variability of sediment composition and OCP during sediment resuspension was determined. In a third approach, the oxygen consumption of sediments under stable conditions and its temperature dependence was determined. The OCP was quantified by seven-day incubation experiments, in which the sediment samples were kept in resuspension. To identify the oxygen-consuming sub-processes, the CO2 formed, and the pore water concentration of relevant anions and cations were determined before and after the experiments. From this information, the most important oxygen-consuming sub-processes could be distinguished, and their respective shares of the total oxygen consumption were calculated stoichiometrically. Based on the analysed sediment properties and the quantified sub-processes, we developed a prognosis ...