The objective of the TRACES (2014, 2016) cruises is to help evaluate what proportion of a known quantity of released tracers will bind to the sediments, with what kinetics and to what extent these tracers can become bioavailable again for living species. The sampling strategy will be based on grab samples of sediments distributed evenly over the entire Brittany Normandy Gulf. Concurrently, regular collection of seawater samples will be used to test how representative the hydrodynamic models applied for this study are. Samples of seaweeds and limpets will be taken at two points which are inaccessible from shore (Chausey, Roches Douvres), in addition to regular monitoring. The results obtained will make it possible to specify the conditions for mobilizing the deposited sediments, the dynamics of their evolution and the marking induced within living species. This information will be utilized to assess the medium- and long-term consequences of environmental pollution. The ultimate objective is to have models simulating dispersion, transport and transfers of radionuclides within the marine ecosystem on a multiannual scale.