Description of the study site: the Seine River from Paris (km 0) to the mouth of the estuary (km 356). Numbers 1 to 18 represent the sampling stations, as follows: 1, Saint Maurice; 2, Maison Laffites; 3, Conflans; 4, Triel; 5, Porcheville; 6, Vernon; 7, Les Andelys; 8, Poses; 9, Pont Arche; 10, Elbeuf; 11, Oissel; 12, Bassin des Docks; 13, La Bouille; 14, Duclair; 15, Heurtauville; 16, Caudebec; 17, Tancarville; 18, Honfleur. Caudebec represents the limit of saline intrusion.