Flux of sediments and nutrients from low to deep water in a Danish Fjord

Investigations on the seasonal variations of the flux of sediments and nutrients from low to deep water were carried out in Vejle Fjord on the east coast of Jutland, Denmark in order to obtain a more detailed knowledge of the distribution of sediments and dynamics of sediment and nutrient transport in the fjord. Previous investigations show that there is a seasonal variation in the run-off from land. The purpose of this project was to see to what extent this variation includes nutrients. The results show that a wide variety of hydrographic processes are responsible for the water exchange and the mixing of the water throughout the year. One of the dominating features is an inward current along the north coast and out-flow along the south coast. As the main part of the run-off to Vejle Fjord is in the inner part of the fjord, the consequence is that the southern part of the fjord is more eutrophicated than the northern part due to flocculation and nutrient supply from land. Furthermore, occasional strong north-west winds lead to upwelling in the inner part of the fjord. One of the combined effects of these mixing processes is the formation of drifting “islands” of nutrient-rich water. These “islands” eventually form the basis for phytoplankton blooms.