BIOLOGICAL CONSEQUENCES OF TIDAL STIRRING GRADIENTS IN THE NORTH-SEA

Tidal stirring gradients, interacting with seasonal variation in photo synthetically active radiation, sea-surface heating , and wind stirrin g, are proposed as the most important controls on plankton in the sout hern North Sea. The hypothesis, in the form of a numerical model, is t ested against observations during 1988/89 of seasonal cycles and spati al variation in phyto- and zoo-plankton. The importance of the tidal m ixing front, and the effects of residual circulation and nutrient-rich river discharges, are discussed, and estimates given of microplankton community production and its fate.