In the brackish water lagoon of Neustädt (Lübeck Bay/Southern Baltic Sea) hydrological, sedimentological and geochemical measurements were carried out to quantify the retention of nutrients and harmful substances. The exchange of water masses between Neustädt Kanal and the lagoon is dominated by aperiodic sea level fluctuations of the Baltic Sea. In the contact zone saltwater/freshwater muddy sediments occurred. The distribution of heavy metals in the surface sediments in the S part of the lagoon can be referred to the vicinity of the harbour, in the N part to the influence of the sewage plant
