CO2 and CH4 fluxes measured under controlled laboratory conditions (i.e. potential aerobic respiration and methanogenesis rates), from riverbed sediment collected from the 6 European DRNs in 3 sampling campaigns; together with sediment characteristics including humidity, organic matter, carbon and nitrogen content. The following environmental variables measured in the field when collecting the sediment samples are included: flow state, habitat where sample was collected (flowing waters, dry riverbed, isolated pool, water pH, conductivity, temperature, dissolved oxygen (absolute concentration), discharge.