Microbial nitrogen transformations in sediments and inorganic nitrogen fluxes across the sediment/water interface on the South Island West Coast, New Zealand

• Published in: Estuarine, coastal and shelf science Vol. 21; no. 2; pp. 245 - 255
• Main Authors: Kaspar, Heinrich F., Asher, Rodney A., Boyer, Ian C.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.1985
• Subjects: denitrification; diffusion; Marine; mineralization; New Zealand; nitrate reduction; nitrogen cycle; sediments; PSE, New Zealand, South I; New Zealand; nitrate reduction; mineralization; diffusion; nitrogen cycle; denitrification; sediments
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1016/0272-7714(85)90100-3

In January 1982, sediment microbial N transformations and inorganic N fluxes across the sediment/water interface were studied at nine sites off the South Island West Coast, New Zealand. The sediments showed a great variety in physical, chemical and biological properties. The sediment organic matter had a molar C N ratio of 5.9–10.9, and the total N P ratio was 1.2–4.0. The denitrification capacity in the top 7.5 cm of sediment was 0.1–77.2 mmol N m −2 day −1 and generally declined with increasing sediment depth. The in situ denitrification rate was 0.02–1.84 mmol N m −2 day −1 and highest activities were generally found in surface sediments and at 6–7.5 cm depth. Denitrification accounted for 82–100% of total nitrate reduction. Net N mineralization was indirectly estimated at 0.6–2.4 mmol N m −2 day −1, and the experimental determination of this N transformation gave 0.6–3.2 mmol N m −2 day −1. Denitrification accounted for 3–75% of net N mineralization. The diffusive flux of ammonium and nitrate across the sediment/water interface was 0.1–0.7 and 0.1–0.6 mmol N m −2 day −1, respectively.