On the wisdom of calculating annual material budgets in tidal wetlands

In the last decade, measurements of the tidal exchange of inorganic and organic materials, and their extrapolation for the calculation of annual budgets, have played an important role in assessing the ecological functioning and sedimentary status of coastal wetlands. Flux measurements, and their application to longer sequences of tidal flooding, for an enclosed back-barrier salt marsh in Norfolk, England, show how net import/export characteristics for a range of materials (total suspended sediment, inorganic suspended sediment, particulate organic carbon and dissolved organic carbon), and thus the interpretation of wetland function, are strongly dependent upon the method of budgetary calculation. Annual budgets should be evaluated in a broader context which explores differing combinations of flooding regime, sediment supply and surface accretion, and vegetation production and decay.