Short-term sedimentation in Tagus estuary, Portugal: the influence of salt marsh plants

Short-term sediment deposition was studied at four salt marsh areas in the Tagus estuary. In areas covered with Sarcocornia perennis, Sarcocornia fruticosa, Halimione portulacoides and Spartina maritima and also in the non-vegetated areas, sedimentation was measured as the monthly accumulation of sediments on nylon filters anchored on the soil surface, from August 2000 to May 2001. Our experiments were used also to determine the influence of the different plant species in vertical accretion rates. Short-term sedimentation rates (from 2.8 to 272.3 g m−2 d−1) did show significant differences when the four salt marshes studied in the Tagus estuary were compared to each others. Salt marshes closer to the sediment sources had higher sedimentation rates. Our results suggest that the salt marsh type and surface cover may provide small-scale variations in sedimentation and also that sediment deposition values do change according to the position of the different plant species within the salt marsh. Sedimentation is an essential factor in salt marsh vertical accretion studies and our investigation may provide support to help forecast the adaptative response of the Tagus estuary wetlands to future sea level rise.