The North Sea is part of the north-west European Shelf of the North Atlantic. The circulation is counterclockwise and shows a strong dependency on the open boundaries. Nutrient inputs from the Atlantic, the rivers, the sediments and the Wadden Sea cause areas of high productivity. Observations show low production zones in the stratified regions and higher production in the well-mixed areas. The minimum annual primary production observed was 40–79 gC m–2 y–1 off the British coast and the maximum values > 261 gC m–2 y–1 in the German Bight. Much higher values (> 370 gC m–2 y–1) were observed in the Wadden Sea. Although there have been large observational programs (Charnock et al., 1994: Stindermann 1994), the capacity of ship and man power is not enough to study the different regional primary production cycles. One way to estimate primary production is the use of a numerical model if all the necessary forcing is available.