Whole ecosystem 15N labeling to identify nitrogen cycling in marshes
Gribsholt, B.; Dehairs, F.A.; Struyf, E.; Boschker, E. (2002). Whole ecosystem 15N labeling to identify nitrogen cycling in marshes, in: ECSA Local Meeting: ecological structures and functions in the Scheldt Estuary: from past to future, Antwerp, Belgium October 7-10, 2002: abstract book. pp. 25
In: (2002). ECSA Local Meeting: Ecological structures and functions in the Scheldt Estuary: from past to future, Antwerp, Belgium October 7-10, 2002: abstract book. University of Antwerp: Antwerp. 73 + 1 cd-rom pp.
It is generally thought that fringing marshes act as a filter for the estuarine water by removing inorganic and organic forms of nitrogen from the floodwaters. We studied this process in an integrated in situ study on the processing and retention of nitrogen in a tidal freshwater marsh. The study is a combination of a whole ecosystem 15N pulse labeling study with a classical exchange study. 15N-ammonium was added to the incoming tidal water in a small creek feeding an isolated freshwater marsh area (app. 3500 m2). The processing of the 15N label by the marsh was subsequently followed in the flood and ebb water of several consecutive tides as well as in important sinks within the marsh (sediment and plants). Furthermore, the incorporation and transfer of 15N into the benthic marsh food web was studied. Discharge characteristics of the creek such as tidal height, water movement and concentrations of the different N pools were assessed over the entire study period. The first results reveal that label was successfully distributed within the entire marsh. In the water phase the 15N label was recovered in all the pools analyzed (NH4, NO3, N2O, N2 and PN) suggesting nitrification to be an important process. The long term objective of the project is to construct an integrated view of the role of tidal marshes in the nitrogen retention and processing of ammonium and nitrate in a typical marsh system.
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