The Sylt-Rømø Bight is one of the largest tidal catchments in the Wadden Sea characterized by a chain of near shore islands, separated by tidal inlets. Since the beginning of the last century two artificial causeways connect the mainland with the islands of Sylt and Rømø, thus creating a backbarrier environment. This coastal lagoon exchanges almost 50% of its water volume with the open German Bight during each tidal cycle and thus the pelagic community is strongly triggered by both local and open water influence. Since the early seventies the SYLT ROADS LTER pelagic time series have also included information about physical and hydrochemical parameters in the Sylt-Rømø Bight. The measurements of those have been performed twice a week. The spatial and temporal variations of the salinity in the area have complex pattern as they are largely triggered by the phase of tidal cycle and wind forcing and in a less extent by wave action and baroclinicity.