Eutrophication is a reoccurring problem in coastal regions, including the North-West European Shelf (NWES). By developing machine learning model from sparse observations, we reconstruct a gap-free, 7km and daily, bi-decadal (1998-2020), data-set for nitrate at the NWES, allowing for much more robust analyses than the sparse observational data. From the data-set we identify nitrate-limited coastal areas, which are potentially vulnerable to eutrophication. Apart from known eutrophication-problem areas, these include additional coastal zones, which could become problematic under sub-optimal policy, or management changes. Furthermore, we show only a limited link between winter nitrate and the size of phytoplankton growth the following year, suggesting winter inorganic nitrogen might not provide the best indicator for eutrophication (as used by OSPAR). Finally, we demonstrate that reduction of nitrate on the NWES in the 1998-2020 period has been mostly small, with the exception of specific areas, such as the Bay of Biscay.