The silica and inorganic carbon system in tidal marshes of the Elbe estuary, Germany : Fluxes and spatio-temporal patterns

VIII Zusammenfassung XI List of Publications XIV 1 General introduction 1 1.1 Identifying research gaps 3 1.2 Contribution of this thesis 5 2 Study area 6 2.1 The Elbe estuary 6 2.2 Tidal marshes of the Elbe estuary 9 2.2.1 Sampling sites 10 2.2.2 Hydrology of sampling sites 11 3 Silica dynamics of tidal marshes in the inner Elbe estuary, Germany 14 3.1 Abstract 14 3.2 Introduction 14 3.3 Material and Methods 16 3.3.1 Sampling and analysis 16 3.3.2 Digital elevation model and monitoring database 18 3.3.3 Statistics 20 3.4 Results 20 3.4.1 Physical characteristics of the sampling sites 20 3.4.2 Silica concentrations of the fresh, brackish and saline sampling site 20 3.5 Discussion 25 3.5.1 Temporal development of DSi concentrations along the salinity gradient 25 3.5.2 DSi export 31 3.6 Conclusion 34 4 The role of salt marshes in the silica budget of the North Sea 36 4.1 Abstract 36 4.2 Introduction 36 4.3 Materials and Methods 37 4.4 Results and Discussion 39 4.5 Conclusions 43 5 Silicon Isotopes in the Elbe estuary 45 5.1 Abstract 45 5.2 Introduction 45 5.3 Material and Methods 47 5.3.1 Sampling 47 5.3.2 Isotopic measurement 47 5.4 Results 50 5.4.1 Tidal marsh areas 50 5.4.2 Estuarine transects 51 5.5 Discussion 53