Nutrient release and storm induced particle resuspension in the Eastern and Western Scheldt
Mast, I. (2020). Nutrient release and storm induced particle resuspension in the Eastern and Western Scheldt. MSc Thesis. NIOZ Royal Netherlands Institute for Sea Research: Yerseke. 58 pp.
Global climate change is expected to increase storm frequency in the Scheldt estuary. Mud flats, intertidal wetland areas, are prone to particle resuspension as induced by storms. Particle resuspension disturbs the sediment and nutrients from the porewater or bound in complexes, suddenly interact with the water column. A possible consequence is that this process could contribute to eutrophication. This raises the question how storm induced resuspension affects nutrient release in mudflats of the Scheldt estuary? Gaining insight in these nutrient - water interactions provides the opportunity to better understand the nutrient cycling in this area under influence of climate change. Within this research the effects of sudden particle resuspension on nutrient release in two systems of the Scheldt estuary, Eastern and Western Scheldt, were studied. The nutrients under study were NH4+, NO3-, NO2-, DSi and PO43-. An extensive sampling campaign was conducted over seven field sites (4 in Western Scheldt, 3 in Eastern Scheldt). Porewater and grain size samples were taken next to an experimental setup, in which a storm event was simulated. Differences in grainsize and porewater nutrient concentration were tested between the Eastern and Western Scheldt, and between sheltered and exposed locations. The concentrations found during the flume experiment were compared to the porewater nutrient concentrations. Effects of particle resuspension on nutrient release seemed to be more dependent in which system it occurred, rather than if it happened in a sheltered or exposed site. NH4+ and NO2- concentrations increased as a result of resuspension in both systems. NO3- and DSi did not show clear increases or decreases at increased resuspension. PO43- increased with augmented resuspension at the Western Scheldt and decreased with increasing resuspension at the Eastern Scheldt. This indicates a difference in complex formation with this nutrient between the two systems. The outcomes of this research imply that nutrient management should be addressed rather on system level than on estuary scale.
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