A very high resolution model for a small area in Roskilde Fjord around the outlet of Hove å was set up, to examine the potential nutrient removal by eelgrass and musselbeds. This was done by introducing a tracer to the freshwater input and inserting area of tracer depletion in the very shallow near shore areas. When the freshwater flux an low and the hydrodynamic conditions are calm, the residiense time of the tracer in the depletion areas are high and hence the depletion also large. Visa versa, when the fresh water flux is high and the hydrodynamic conditions vigorous, the residence time is low and the depletion also low. This study was part of the project "Kystzonen som renselanlæg" funded by VELUX and a popular scientific paper was published in "Aktuel Naturvidenskab" (in Danish): https://aktuelnaturvidenskab.dk/fileadmin/Aktuel_Naturvidenskab/nr-4/AN4-2019-kystzonefilter.pdf