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Silica fluxes and wetlands: assessment of a missing processor in the global Si cycle


Recent estimates have shown that terrestrial silica cycling is strongly influenced by biota. Terrestrial silica transport is of utmost importance for the coastal zone: the ratio of the nutrients N-P and Si delivered to estuaries, is essential in influencing the occurrence of harmful eutrophication events in the coastal waters.

Despite the importance, very little research has focused on quantifying the terrestrial silica cycle. Lack of knowledge has also prevented the correct quantification of an important C O2 sink in the global carbon cycle: chemical weathering of lithogenic Si is a sink for atmospheric CO2.

This project will investigate the virtually unstudied role of wetlands in the biogeochemical cycle of Si. Recent research in tidal freshwater marshes ha s indicated that wetlands have a large potential to store and recycle big amounts of biogenic Si.

During this project, storage and processing of BSi in wetland vegetation and sediments will be investigated across a European gradient of wetland ecotypes, a t different flooding frequencies and drainage capacity. The analysed biogenic Si will be studied microscopically to determine if either vegetation or diatom biogenic Si are buried or processed preferentially.

The project is highly relevant to priority topics defined in the `6th Framework Programme. Proper knowledge of the terrestrial silica cycle and transport of Si towards the coastal zone, is essential for both the sustainable, integrated management of river basins and estuaries and the correct quantification of the lithogenic Si weathering sink for atmospheric CO2.

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