Estimating regional and cross-boarder eutrophication problems, and the potential effects of management actions

Morten Skogen, Einar Svendsen, Henrik Søiland
Institute of Marine Research,
PB. 1870 Nordnes
5817 Bergen, Norway
morten@imr.no, einar@imr.no, henrik@imr.no

An environmental status for year 2000 of the North Sea and Skagerrak has been done based on outputs from a biophysical model (NORWECOM). The model results suggests that in year 2000 the mean annual primary production in the North Sea was the highest in the period 1985-2000, and that the net inflow through the English Channel, due to an extreme strong influx in the fourth quarter, was the highest on an annual basis in the period 1955-2000. Also the oxygen levels and sedimentation rates in the North Sea and Skagerrak have been examined, and a eutrophication assessment conclude that, except for the winter values of nitrate, eutrophication is not a big problem in most of the Skagerrak and Kattegat area.

The effects of reducing the nutrient inputs (either P or both P and N) by 50% on the spatial distribution of flagellate production and the practical use of the model system to predict harmful algae distribution and decay are demonstrated.