The inner port of Zeebrugge is a genuine brackish-water-basin. The inlet of seawater and the drainage of fresh water by the purification plant for household effluents are determining for the character of the harbour water. Temperature at the surface fluctuates between 0 and 28.2 Â°C. The salinity near Bruges fluctuates between 12.7 and 30.3 9 Cl/kg and near the sea locks at Zeebrugge between 25.1 and 31.1 9 Cl/kg. Pollution is problematic in the Boudewijnkanaal. The situation is however much better in the docks near the sea locks, the latter is reflected in the abundance of species. Several parameters are compared with the national quality standards for surface water and fishing water. During the period 1996, 1997 and 1998, a small yearly improvement is noticeable.