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AME 14:69-80 (1998)
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Abstract
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Budgets of sediment nitrogen and carbon cycling in the shallow water of Knebel Vig, Denmark
Bente Aa. Lomstein1,*, Anna-Grethe U. Jensen1, Jens W. Hansen1, Jane B. Andreasen1, Lars S. Hansen1, Jørgen Berntsen1, Helmar Kunzendorf2
1Department of Microbial Ecology, Institute of Biological Sciences, Aarhus University, Building 540, Ny Munkegade, DK-8000 Aarhus C, Denmark 2Environmental Science & Technology Department, Gamma Dating Center, Risø National
Laboratory, PO Box 49, MIL-124, DK-4000 Roskilde, Denmark
*E-mail: bente@pop.bio.aau.dk
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ABSTRACT: Sediment was sampled from a shallow coastal area (Knebel Vig, Denmark). The vertical distribution of pigments, Pb-210 and Cs-137 indicated that organic matter was mixed into the sediment. On an area basis, sediment acid hydrolyzable amino acids accounted
for 24% of the particulate organic carbon pool and 53% of the particulate organic nitrogen pool. Similarly, porewater acid hydrolyzable amino acids were an important component of dissolved organic carbon and dissolved organic nitrogen (9 and 27%,
respectively). It was inferred that ribonucleic acids potentially were an important component of dissolved organic nitrogen. The estimated efflux of dissolved organic nitrogen from the sediment was higher (3.9 mmol N m-2 d-1) than
the estimated efflux of dissolved inorganic nitrogen (<2 mmol N m-2 d-1). The high efflux of dissolved organic nitrogen was explained by organic matter hydrolysis close to the sediment surface. The low rates of inorganic nitrogen
efflux together with a high carbon oxidation rate suggested degradation of organic matter with a low average nitrogen content and possible bacterial nitrogen assimilation. This was further supported by mass balance calculations on nitrogen incorporation
into microbial biomass. The calculated average C/N ratio in the organic matter degraded suggested that only part of the sediment acid hydrolyzable amino acids were available for bacterial degradation. The efficiency of bacterial carbon incorporation was
0.33 and within the range previously encountered in sediments of Danish waters.
KEY WORDS: Sediment · Nitrogen · Carbon · Cycling · Fluxes · Urea · Amino acids
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Published in AME Vol.
14, No. 1
(1998) on January 2
Print ISSN: 0948-3055; Online ISSN: 1616-1564.
Copyright © Inter-Research, Oldendorf/Luhe, 1998
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