Long-term N-nitrogen retention in tidal freshwater marsh sediment: Elucidating the microbial contribution

Abstract The long-term retention of nitrogen in sediment,of a tidal freshwater marsh in the Scheldt estuary (Belgium) was,investigated by an in situ ,N. This study shows,the strong potential of reed roots and especially bacteria to retain nitrogen in tidal freshwater sediment,over longer periods of time. Tidal freshwater marshes,are diverse habitats that differ widely in terms of plant community composition, sediment type, marsh elevation, and nutrient availability. They often occur where,estuaries are most,enriched,in particles and nutrients and are hotspots,of biogeochemical,transforma- tions (Bowden,et al. 1991; Struyf et al. 2006). Tidal freshwater marshes provide a range of ecosystem services, including acting as water quality filters, and are often regarded,as seasonal,or long-term sinks for nutrients (Bowden 1987; Fisher and,Acreman,2004; Neubauer,et al. 2005). Despite their ecological significance, tidal freshwater,marshes,have not been studied nearly as well as their brackish and salt marsh,counterparts. Traditionally, tidal freshwater marsh studies have focused,on nutrient exchange,between,marshes,and,tidal