In this study an overview is given of the time series analysis of monthly mean data of physical, chemical and biological parameters. The time series are available at eight locations on the Northwest European Shelf. The integrated evaluation of those time series gives the opportunity to look for connections between the different parts of the shelf. Temperature and salinity seem to be externally forced. For the nutrients and biological parameters the local forcing is dominating the time series. It is concluded that there are areas that are comparable to each other (freshwater dominated boxes along the Belgian and Dutch coasts and German Bight; Atlantic dominated boxes in the English Channel and off the Scottish coast), although significant cross-correlations are hardly found. The Irish Sea can be regarded as a separate ecosystem.

Mean seasonal cycles in time series of salinity, nutrients, chlorophyll and Zooplankton at 8 locations on the Northwest-European shelf were analysed in relation to each other and with respect to their timing and magnitude during a period most of the time series overlap (1980–1984). A relatively late spring bloom in April/May with low chlorophyll values (2–4 mg/m3) is observed in the Irish Sea, off the Scottish east coast and the Channel entrance. An early spring bloom in March/April and relatively high chlorophyll values (7–12 mg/m3) are found in the Southern Bight of the North Sea and in the Skagerrak, whereas a late spring bloom in April/May with chlorophyll concentrations of about 23 mg/m3 is found along the Dutch and Belgian coast. The peak of the phytoplankton carbon cycle in the German Bight (Helgoland) occurs during summer. This is caused by the dominance of large dinoflagellates in this period. The peak in the yearly abundance of copepods shifts from May-June in the south to July-August in the north of the shelf. In the Irish Sea and the Channel entrance two seasonal copepods peaks are observed. The January nitrate values in Irish Sea, the Southern Bight and the Skagerrak are, compared to the Atlantic input signal represented by the data from the Channel entrance and east of Scotland, about 20% higher. The values of dissolved inorganic phosphate in January are comparable to those of the Atlantic input signal. However, the Irish Sea forms an exception, here the level is increased by 10–20%. The January values for nitrate and dissolved inorganic phosphate at the Dutch and Belgium coast are about 10 and 4, and in the German Bight (Helgoland) 4 and 3 times higher then the Atlantic input signal. At most sites changes in the seasonal cycles of chlorophyll coincide with changes in nutrient concentrations, whereas the maximum level of the seasonal signal of chlorophyll is related to nutrient levels.

Seasonal cycles of salinity, nutrients, chlorophyll and Zooplankton at 8 locations on the W estEuropean shelf were analysed with respect to their timing and magnitude in the period 1980-1984. A late spring bloom with low chlorophyll values (2-4 mg.m '3) is observed in the Irish Sea, off the Scottish east coast and the Channel entrance. An early spring bloom and relatively high chlorophyll values (7-12 mg.m'3) are found in the southern Bight and the Skagerrak, whereas a late spring bloom with high chlorophyll concentrations (24 m g.m '3) is found along the Dutch and Belgian coast. In contrast to the other regions, the peak of the phytoplankton cycle in the German Bight (Helgoland) occurs in the summer period instead o f the spring period. The peak in the yearly abundance of copepods shifts from M ay-June in the south to July-August in the north of the shelf. In the Irish Sea and the Channel entrance two seasonal copepods peaks are observed. The January nitrate values in Irish Sea, the southern Bight and the Skagerrak are about 20 % higher than those in the Atlantic input signal in the Channel entrance and east off Scotland. The January DIP values in these regions are com parable to those of the input signal, but the Irish Sea forms an exception here the level is increased by 10-20%. If compared with the Atlantic input signal the January values for nitrate and DIP at the Dutch and Belgium coast are about 10 and 4, and in the German Bight This paper has been submitted to Deutsche Hydrographische Zeitschrift as part of a special issue on NOWESP NOWESP Final Report Bot ef al. (Helgoland) 4 and 3 times higher, respectively. At most sites changes in the seasonal cycles o f chlorophyll coincide with changes in nutrient concentrations, whereas the m aximum level of the seasonal signal is related to the nutrient levels.