Nitrogen exchange between a portion of vegetated salt marsh and the adjoining creek

Abstract

We measured net exchange of nitrogen between a portion of vegetated salt marsh (dominated by Spartina alterniflora) and the adjacent tidal creek. During tidal inundation, the marsh imported ammonium, nitrate + nitrite, and particulate nitrogen and exported dissolved organic nitrogen over an annual cycle. The low marsh (characterized by the tall form of S. alterniflora) had higher uptake and release rates compared to high marsh areas dominated by shorter forms of S. alterniflora. When creek‐water levels were below the marsh surface during the late ebb and early flood, residual water on the marsh surface drained into the tidal creek and exported substantial amounts of particulate and dissolved organic nitrogen but relatively small amounts of dissolved inorganic nitrogen. Rainfall during exposure of the marsh surface increased particulate nitrogen export to the tidal creek 40‐fold. With respect to tidal exchange via inundation and drainage, the vegetated marsh exported ~4.5 g N m−2 yr−1, largely as dissolved organic nitrogen.