Ecosystem Analysis - Exchange with the North Sea
Exchange with the North Sea
The Wadden Sea is a heterotrophic system: It remineralises more organic matter than is locally produced. The excess organic matter is mainly imported from the North Sea. During the remineralisation of the organic matter, nutrients are released and used within the Wadden Sea to sustain the high local primary production.
A conceptual model showing the interconnection between nutrient input into the coastal zone, primary production in the coastal zone and import of part of this organic matter into the Wadden Sea
This concept has been used to analyse long-term nutrient data from the Dutch Wadden Sea. It could be shown that a link exists between river input of nitrogen and the intensity of the remineralisation within the Wadden Sea.
Differences in the seasonal cycle of ammonium in the Western Dutch Wadden Sea
The autumn maximum of ammonium is not due to advective but due to local processes. In the Western Dutch Wadden Sea, the mean autumn concentrations of ammonium plus nitrite are significantly correlated with nitrogen input via the rivers Rhine and Meuse. We have suggested (publication) to use the above mentioned autumn values as in indicator of the eutrophication status of the Wadden Sea and as a measure to compare the eutrophication status in different parts of the Wadden Sea.
Our research of water column processes in the Sylt Rømø Bight is based on the above concept. Presently we focus on the following aspects:
- Seasonal dynamics of dissolved and particulate organic nutrients
- Composition of suspended matter
- Causes of interannual differences in the seasonal cycle of nutrients and suspended matter
- Exchange processes between sediment and water
- Si cycle in the Wadden Sea
These investigations are part of the long-term research in the Sylt Rømø Basin.
Selected literature:
van Beusekom, J. E. E. and V. N. de Jonge. (2002) Long-Term Changes in Wadden Sea Nutrient Cycles: Importance of organic matter import from the North Sea. Hydrobiologia . in press.
<van>van Beusekom J. E. E</van>., F. de Jong, H. Fock, S. Diel-Christiansen, B. Christiansen. (2001) Wadden Sea Specific Eutrophication Criteria. Wadden Sea Ecosystem 14, Common Wadden Sea Secretariat, Wilhelmshaven, Germany, 116 pp.