This dataset is part of the 2018 Belgian submission for the Marine Strategy Framework Directive (MSFD) linked to descriptor 5, criterion 1. This dataset contains the nutrient concentrations (ammonia, nitrate, nitrite, total nitrogen, phosphorus) measured on water samples taken in the BPNS between 2011 and 2016. The analysis of nutrients (N and P) is ensured by the national monitoring programme at ten sampling locations that are representative for the surrounding water masses. Based on all 2011-2016 results, the relationship with the salt content was calculated and, for each year, the value derived corresponding to a salt content of 33.5. The surface of the area where the nutrient concentrations exceed the respective thresholds was calculated on the basis of the relationship with the winter salt content and a climatology of the spatial distribution of the salt content (see annex D5 of the Belgian MSFD report). The resulting maps give a good overview of nutrient concentrations in the Belgian zone. In order to take into account the coastal-sea gradient and to illustrate the temporal trends in detail, the concentrations were also evaluated in three different areas of the BPNS: the coastal zone, the territorial zone and the open-sea zone. The long-term trends of nutrient concentrations in the three zones were assessed statistically.