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| Titel |
Oxygen, a regulating factor for nitrogen cycling in continental shelf sediments? |
| VerfasserIn |
E. Neubacher, R. Parker, M. Trimmer |
| 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 |
250028605
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| Zusammenfassung |
| Oxygen is a fundamental parameter in regulating the cycling of carbon and nitrogen in
continental shelf seas. Recent studies and models have shown that some regions of coastal
seas are prone to a lack of oxygen and under such conditions, the dynamics of the nitrogen
cycle could be altered. We measured rates of denitrification, anaerobic ammonium oxidation
(anammox), oxygen uptake, nutrient exchange and pore water profiles of oxygen in sediments
of the southern North Sea experimentally exposed to different oxygen saturations. The
incubation of sediment at 33% (of air-saturation) for oxygen reduced the penetration and
consumption of oxygen by the sediment by of approximately 50%, with a new steady state
being reached after approximately 75 min. The rates of the various processes showed strong
seasonality over the survey period (2007-2008), with denitrification ranging from 0.6 to
21.2 μmol N m-2 h-1, anammox 0.2 to 4.4 μmol N m-2 h-1 and oxygen uptake
46.5 to 631.8 μmol O2 m-2 h-1. At the reduced saturation for oxygen (~ 33%),
denitrification increased significantly (30%) while anammox remained constant. On average
anammox accounted for 14-28% of the total production of di-nitrogen (N2) gas. Under
ambient oxygen saturation, the rates of oxygen uptake and total production of N2 were
positively correlated with each other (r = 0.73, p = 0.01, n = 230). The increase in
denitrification was coupled to a change in NO3- flux. Under ambient oxygen there was a
net release of 10.5 μmol NO3- m-2 h-1 from the sediment to the water column,
whereas under reduced oxygen, the sediments became a sink for NO3- (-1.2 μmol
NO3- m-2 h-1) from the overlaying water. These results suggest that facultative
denitrifying bacteria were able to exploit the newly extended suboxic sediment
layer, while the monophyletic group of anammox bacteria were not as flexible. |
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