| dc.description.abstract | The environmental effects of river nutrient loads to the North Sea have been investigated
using a numerical biophysical model, NORWECOM, to perform different reduction scenarios.
The simulations demonstrate that the river nutrients have a significant contribution
on the annual primary production, both in the southern North Sea, in Skagerrak and along
the Norwegian west coast. A 50% reduction in the loads of N and P reduces the primary
production with 10-30% in the southern North Sea, and 5-10% in Skagerrak and along the
Norwegian west coast. Scandinavian rivers only contribute to the 1-2% level in these reductions,
thus continental rivers has the major effect on the environment in all downstream
areas. However, it should be noted that this reduction, even in the southern North Sea, is less
than the natural variability of the production of phytoplankton. A reduction only in the P
values, shows that the production regime in the southern North Sea is phosphorous limited,
while nitrogen is the limiting nutrient in the northern North Sea. Focusing on the N/P ratio
as a possible proxy for eutrophication, a reduction in the N and P loads reduces this ratio
by a similar factor, while a reduction in the P loads only, increases it. Based on this it is
proposed to use the N/P ratio for eutrophication assessment. | en |
