The availability of data, their long-term maintenance, and careful documentation are essential for actors in coastal zone management and coastal marine research. Within the KüNO Programme a joint data portal for national North Sea - Baltic Sea research was developed. It combines metadata from previous and current KüNO projects as well as corresponding metadata from MDI-DE (Marine Data Infrastructure Germany). The KüNO data portal ensures the continuous availability and distribution of metadata for georeferenced data sets of the national North Sea and Baltic Sea research. Its aim is to provide sound scientific and independant information as a basis for decision makers of public authorities in charge of the implementation of environmental policies.