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| Titel |
Oxygen, carbon, and nutrients in the oligotrophic eastern subtropical North Atlantic |
| VerfasserIn |
P. Kähler, A. Oschlies, H. Dietze, W. Koeve |
| 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. 3 ; Nr. 7, no. 3 (2010-03-26), S.1143-1156 |
| Datensatznummer |
250004599
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| Publikation (Nr.) |
 copernicus.org/bg-7-1143-2010.pdf |
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| Zusammenfassung |
The Beta Triangle, a region of the oligotrophic subtropical eastern
North Atlantic Ocean, is notorious for its enigmatic oxygen, carbon,
and nitrogen balances, in which nutrient supply is said to explain
only a fraction of production necessary for estimated carbon
export. Rates of dissolved organic carbon accumulation and dissolved
organic nitrogen utilization in surface water and an assessment of
oxygen utilized, organic matter consumed, and nitrate and phosphate
regenerated in subsurface water, show that conventional production
estimates miss substantial shares of biotic production.
The shallow export of total organic carbon, predominantly dissolved (DOC), by
subduction is responsible for about 50–70% of apparent oxygen utilization
in subsurface water between the base of the surface layer at ca.
140 m and ca. 195 m depth, but it is insignificant below.
Additionally, there is an estimated accumulation of 1.0 to
1.75 mol DOC m−2 a−1 in surface water. Including DOC dynamics
in its carbon balance reveals the surface of this ultra-oligotrophic part of
the ocean to be net autotrophic.
Increasing subsurface values of excess nitrogen (DINxs) imply the export of
nitrogen from surface water stemming from production not exclusively fuelled
by new nitrate supplied from below. Total organic nitrogen (almost
exclusively dissolved, DON) is consumed in the surface layer at a rate
estimated at 0.13 to 0.23 mol m−2 a−1. There is no variation in
dissolved organic phosphorus (DOP) in the same direction. DON utilization
thus contributes to the pronounced subsurface DINxs signature.
DOC export and accumulation are important in the carbon balance in
surface and near-surface water. DON utilization and, probably,
N2 fixation contribute significant amounts to the nitrogen
supply of surface water. These processes can close part of the
enigmatic carbon and nitrogen balances in the Beta Triangle. There
are, however, no comparable processes which can explain the equally
enigmatic situation concerning phosphorus supply in this area. |
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