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| Titel |
Balance of assimilative and dissimilative nitrogen processes in a diatom-rich tidal flat sediment |
| VerfasserIn |
K. Dähnke, A. Moneta, B. Veuger, K. Soetaert, J. J. Middelburg |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 10 ; Nr. 9, no. 10 (2012-10-22), S.4059-4070 |
| Datensatznummer |
250007338
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| Publikation (Nr.) |
 copernicus.org/bg-9-4059-2012.pdf |
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| Zusammenfassung |
Tidal flat sediments are subject to repetitive mixing and resuspension
events. In a short-term (24 h) 15N-labelling experiment, we investigated
reactive nitrogen cycling in a tidal flat sediment following an
experimentally induced resuspension event. We focused on (a) the relative
importance of assimilatory versus dissimilatory processes and (b) the role
of benthic microalgae therein. 15N-labelled substrate was added to
homogenized sediment, and 15N was subsequently traced into sediment and
dissolved inorganic nitrogen (DIN) pools. Integration of results in a
N-cycle model allowed us to quantify the proportion of major assimilatory
and dissimilatory processes in the sediment.
Upon sediment disturbance, rates of dissimilatory processes like
nitrification and denitrification were very high, but declined rapidly
towards a steady state. Once this was reached, the balance between
assimilation and dissimilation in this tidal mudflat was mainly dependent on
the nitrogen source: nitrate was utilized almost exclusively dissimilatory
via denitrification, whereas ammonium was rapidly assimilated, with about a
quarter of this assimilation due to benthic microalgae (BMA). Benthic
microalgae significantly affected the nitrogen recycling balance in
sediments, because in the absence of BMA activity the recovering sediment
turned from a net ammonium sink to a net source.
The driving mechanisms for assimilation or dissimilation accordingly appear
to be ruled to a large extent by external physical forcing, with the entire
system being capable of rapid shifts following environmental changes.
Assimilatory pathways gain importance under stable conditions, with a
substantial contribution of BMA to total assimilation. |
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