Description: Prior to 1975, average winter water nutrient concentrations at station Bokniseck in Kieler Bucht (Western Baltic} were 1.23 mmol/m3 total phosphorus and 12.7 mmol/m3 dissolved inorganic nitrogen. Nitrogen concentrations did not change until 1984. The mean of a few total phosphorus data from 1980-1984 is 1.94 mmol/m3. Mean nutrient concentrations in the area between the southern entrance of the Great Belt and Darss Sill increased between 1975 and 1984 from 0.8 to 1.6 mmol/m3 total phosphorus and from about 6 to 10 mmol/m3 inorganic nitrogen. Comparatively higher nutrient concentrations at Bokniseck station are correlated to higher salinity. However, no data are available on nutrient imports into Kieler Bucht with saline deep water. Unchanged nutrient concentrations at Bokniseck prior to 1975 are an argument against any dominant influence of anthroprogenic inputs which until 1974 increased to annually 1500 t of total phosphorus and 12700 t of total nitrogen, plus 5000 t of nitrogen from the atmosphere. Higher phosphorus concentrations 1980-1984 are correlated to severe oxygen deficiency in the deep water. Mobilization of phosphorus from sediments becoming anoxic could be the reason. Biota could be such sources and sinks of nutrients that influence the nutrient balance of Kieler Bucht. To sum up, there are several processes besides anthropogenic inputs that influence nutrient concentrations in water. An assessment of winter water nutrient concentrations alone is no adequate tool for the evaluation of the effects of anthropogenic nutrient inputs via rivers, sewage, land runoff, groundwater and from the atmosphere.