BIOLOGICAL SURFACES AND FINE SEDIMENT TRAPPING IN DELTAIC WETLANDS

It is commonly believed that wetland vegetation can be a significant control acting to increase sediment deposition in coastal wetlands, but this effect is poorly understood and quantified. Field observations and limited flume studies with model vegetation have suggested possible mechanisms by which this effect may occur. Here, I describe new experiments inspired by field observations of substantial amounts of fine sediment collected on vegetation stems and leaves. Sediment is allowed to collect on surfaces in a stirred container, and the sediment-retaining properties of different surfaces are investigated. Early results suggest that sticky microbial biofilms, combined with the extremely high surface area provided by dense marsh vegetation, may be responsible for a significant amount of wetland deposition. Such an effect would be in addition to, and complimentary to, any purely fluid-mechanical effect caused by baffling or trapping of flow through vegetation leading to reduction in sediment transport. Results may have implication for restoring sediment-starved deltas.