Coastal wetlands provide important ecological and economic services but are also threatened by sea level rise and pollution. To preserve their benefits, restoration projects have been undertaken in several parts of the world. The objective of this study was to assess the impacts of restoring and reconnecting a freshwater marsh to the sea on contamination dynamics. This study focused on the urban coastal marsh of Tasdon (La Rochelle, France), which was restored between April 2020 and April 2021. Several species representing the trophic web (algae, oligochaetes, crayfish, crabs and fish) were collected before and after, i.e. in autumn 2019 and 2021. N and C isotopic ratios, toxic trace metals (mercury (Hg), cadmium, lead and arsenic) were measured in each species and environmental variables (including salinity, particulate organic matter (POM) and chlorophyll a (Chl a)) were recorded in the surface water. The results showed that, contrary to other metals, Hg concentrations in the species significantly increased through the food chain in both years and at higher levels in 2021 than in 2019. For instance, Hg concentrations measured in the muscles of European eels, increased by a factor of 2. In parallel, the salinity, POM and Chl a increased. Moreover, contaminated fish species from saline waters such as the 3-spined stickleback, colonized the marsh in 2021. If an increase in salinity can modify the bioavailable form of metals, other chemical, physical or biological factors can interfere with their accumulation. The influence of environmental parameters and the restoration works on metal accumulation and transfer through the food web will be discussed. Finally, this pilot study provides new data on the dynamics of aquatic contamination under salinization and restoration scenarios.