Sampling sites. The eight marshes included in this study are located in Northern France within the former French Administrative Region of Picardy. The French “Département de la Somme” comprises two Ramsar sites: “Baie de Somme”, a natural estuary, and “Marais et tourbières des vallées de la Somme et de l'Avre” which encompasses the lower stretches of the Somme River and its main tributary, the Avre River, as well as adjacent marshes and peatlands. Sampling sites are situated in the latter, except the National Nature Reserve “Marais d'Isles”, located amid the Saint-Quentin urban area. The inset in the top right corner depicts the position of Picardy on the map of France and its division into three “Départements”. The Département of Somme is located Northwest of Picardy.