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| Titel |
Aerobic denitrification in permeable intertidal sediments from the Wadden Sea |
| VerfasserIn |
H. Gao, Frank Schreiber, Gavin Collins, Marlene Mark Jensen, Gaute Lavik, Marcel M. M. Kuypers |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250028962
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| Zusammenfassung |
| Sandy sediments dominate the intertidal region of the Wadden Sea but so far little is known
about their role in the coastal N-cycle. We investigated the potential N-loss rates at a sandflat
(Janssand) in the central German Wadden Sea by using a modified version of the whole core
incubation technique used for fine-grained sediments. In view of the high permeability and
strong pore water advection in these sediments, the percolation method better represents the
in situ conditions than the conventional diffusive flux technique. Denitrification
assays with those permeable sediments incubated with 15NO3- indicate immediate
29N2 and 30N2 production. In contrast to the conventional views, our preliminary
results show that permeable Janssand sediments are characterized by some of the
highest denitrification rates in the marine environment. Moreover, our results from
gas-tight bag incubations indicate that denitrification immediately occurs even under
aerobic conditions, with rates of 2.03±0.06 at 0-2 cm and 2.30±0.09 mmol m-3
h-1 at 2-4 cm of the sediments with the starting O2concentrations of 90 and 30
μmol L-1, respectively. Additional evidence for denitrification in the presence
of free oxygen was obtained by simultaneous O2 and NOx measurements with
microsensors in percolated cores and Membrane Inlet Mass Spectrometer measurements.
We speculate that the observed high denitrification rates in the presence of free
oxygen might be an adaptation of the denitrifying bacteria to recurrent tidally-induced
oscillations in pore water oxygen concentrations in the permeable sediments of Janssand. |
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