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| Titel |
Detection of low bottom water oxygen concentrations in the North Sea; implications for monitoring and assessment of ecosystem health |
| VerfasserIn |
N. Greenwood, E. R. Parker, L. Fernand, D. B. Sivyer, K. Weston, S. J. Painting, S. Kröger, R. M. Forster, H. E. Lees, D. K. Mills, R. W. P. M. Laane |
| 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 ; 7, no. 4 ; Nr. 7, no. 4 (2010-04-29), S.1357-1373 |
| Datensatznummer |
250004673
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| Publikation (Nr.) |
 copernicus.org/bg-7-1357-2010.pdf |
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| Zusammenfassung |
This paper presents new results from high temporal resolution observations
over two years (2007 and 2008) from instrumented moorings deployed in the
central North Sea, at the Oyster Grounds and on the northern slope of Dogger
Bank (North Dogger). The water column was stratified in the summer at both
sites, leading to limited exchange of the water in the bottom mixed layer.
Data from these moorings revealed the variable nature of summer oxygen
depletion at the Oyster Grounds. The combination of in situ and ship-based
measurements allowed the physical and biological conditions leading to
decreasing dissolved oxygen concentrations in bottom water to be examined.
In 2007 and 2008, the concentration of dissolved oxygen in the bottom water
at both sites was observed to decrease throughout the summer period after
the onset of stratification. Depleted dissolved oxygen concentration
(6.5 mg l−1, 71% saturation) was measured at the North Dogger, a site which
is not significantly influenced by anthropogenic nutrient inputs. Lower
oxygen saturation (5.2 mg l−1, 60% saturation) was measured for
short durations at the Oyster Grounds. The seasonal increase in bottom water
temperature accounted for 55% of the decrease in dissolved oxygen
concentration at the Oyster Grounds compared to 10% at North Dogger.
Dissolved oxygen concentration in bottom water at the Oyster Grounds was
shown to be strongly influenced by short term events including storms and
pulses of particulate organic matter input. In contrast, dissolved oxygen
concentration in bottom water at the North Dogger reflected longer seasonal
processes such as a gradual temperature increase over the summer and a more
steady supply of particulate organic matter to the bottom mixed layer. The
differences between the study sites shows the need for an improved
understanding of the mechanisms driving these processes if the use of oxygen
in marine management and ensuring ecosystem health is to be meaningful and
successful in the future. These high frequency observations provide greater
understanding of the nature of the depletion in bottom oxygen concentration
in the North Sea. |
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