The sites monitored by the Luc-sur-Mer marine station are located in the Channel, in the central part of the Bay of Seine (total surface area 4,000km2) to the north of Luc-sur-Mer. The Baie de Seine is a macrotidal system (maximum tidal range 7 m), largely influenced by river inflows from the Seine (mean annual flow = 442 m3 s-1) and, to a lesser extent, the Orne (30 m3 s-1). The Seine watershed, with a surface area of 76260 km2, is characterized by high population density and agricultural activity, which exert significant anthropogenic pressures that impact the estuary and Seine Bay. High levels of nutrient salts, particularly N and P, have been measured in the waters of the Seine (Morelle, 2020, Serre-Fredj et al 2021, Serre-Fredj et al 2023). SOMLIT is monitored by the Centre de Recherche en Environnement Côtier (CREC) - marine station of the Université de Caen Normandie, located in Luc-sur-Mer. Two sampling sites are monitored every 15 days, at open sea, during spring tides with coefficients of 90 ±10. Two boats are used for sampling: the Tiamat (7m) moored in the port of Courseulles-sur-Mer and a 6m semi-rigid, the Nausicaa III. CREC-Station Marine became part of the SOMLIT network in 2007, with its original site at the Wharf. Since April 2013, a second monitoring site was added further offshore, called SMILE in reference to the instrumented buoy located there. Sampling is carried out at a depth of 2 m at both sites.