We investigated nutrient input and retention in the Elbe River (Germany) at the river/estuarine transition with high agricultural loads of nitrogen. Surface water samples were taken at the weir Geesthacht (stream kilometre 585, 53°25'31''N, 10°20'10''E) from 2011 to 2021. In these samples, we analyzed nutrient concentrations, nitrate dual stable isotopes and suspended particulate matter composition. Usually, samples were taken once or twice per month. Aims of the study were to investigate 1) nitrate retention in the Elbe River and catchment, 2) seasonal dynamic of nitrate stable isotopes and 3) key nitrogen turnover processes and their respective controls over a ten year period.