Details

Autor(en) / Beteiligte

• Hamersley, M. Robert
• Howes, Brian L.

Titel

Contribution of denitrification to nitrogen, carbon, and oxygen cycling in tidal creek sediments of a New England salt marsh

Ist Teil von

• Marine ecology. Progress series (Halstenbek), 2003-11, Vol.262, p.55-69

Ort / Verlag

Oldendorf: Inter-Research

Erscheinungsjahr

2003

Link zum Volltext

Quelle

Electronic Journals Library

Beschreibungen/Notizen

• The contribution of denitrification to sediment metabolism was studied at 2 sites (muddy and sandy) in unvegetated tidal creek sediments from a small Cape Cod, USA, salt marsh receiving nitrate-enriched groundwater flows (32 mmol m–2d–1). Simultaneous measurements of sediment N₂, CO₂, O₂, and dissolved inorganic N fluxes were made over annual cycles. A total of 46% of the ammonium remineralized within the sediments was transformed to N₂ by coupled nitrification-denitrification (D n). Denitrifying and nitrifying bacteria contributed 15 and 18% to total sediment C and O cycling, respectively. C, N, and O₂ cycling rates were limited by both temperature and the availability of labile organic matter. Muddy sediment C content was twice that of sandy sediments, but was half as labile, resulting in similar mean metabolic rates between sediment types (mean muddy and sandy O₂ consumption rates were 62 and 58 mmol m–2d–1, respectively; CO₂ production was 58 and 46 mmol m–2d–1; andD nwas 5.4 and 4.9 mmol N m–2d–1). Sediment δ13C (–18.5 and –20.8‰) and the molar CO₂:N flux ratio (6.1) at both sites are consistent with a sediment metabolism based on algal rather than macrophytic biomass, and groundwater nitrate was the dominant source of N supporting algal growth. Annually,D naccounted for 72% of total denitrification, with the remainder accounted for by water column-supported denitrification. Since all the denitrified N originated from groundwater nitrate, algal uptake must have initially out-competed denitrification for water column nitrate, but nearly half of this algal N was subsequently remineralized and denitrified.