Nutrient concentrations during winter from the starting conditions for the annual phytoplankton development beginning in spring and reaching its maximum during summer. For this reason nutrient data were collected from the central north Sea during winter and summer, to calculate long-time means, interannual variability and local trends. These data are needed for the understanding of fluxes of matter in the system as well as for the assessment of the eutrophication status of the North Sea (OSPARCOM). (with CD-ROM)