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| Titel |
Hidden biosphere in an oxygen-deficient Atlantic open-ocean eddy: future implications of ocean deoxygenation on primary production in the eastern tropical North Atlantic |
| VerfasserIn |
C. R. Löscher, M. A. Fischer, S. C. Neulinger, B. Fiedler, M. Philippi, F. Schütte, A. Singh, H. Hauss, J. Karstensen, A. Körtzinger, S. Künzel, R. A. Schmitz |
| 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 ; 12, no. 24 ; Nr. 12, no. 24 (2015-12-21), S.7467-7482 |
| Datensatznummer |
250118221
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| Publikation (Nr.) |
 copernicus.org/bg-12-7467-2015.pdf |
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| Zusammenfassung |
The eastern tropical North Atlantic (ETNA) is characterized by a highly
productive coastal upwelling system and a moderate oxygen minimum zone with
lowest open-ocean oxygen (O2) concentrations of approximately 40 μmol kg−1.
The recent discovery of re-occurring mesoscale eddies with
close to anoxic O2 concentrations (< 1 μmol kg−1)
located just below the mixed layer has challenged our understanding of
O2 distribution and biogeochemical processes in this area.
Here, we present the first microbial community study from a deoxygenated
anticyclonic modewater eddy in the open waters of the ETNA. In the eddy, we
observed significantly lower bacterial diversity compared to surrounding
waters, along with a significant community shift. We detected enhanced
primary productivity in the surface layer of the eddy indicated by elevated
chlorophyll concentrations and carbon uptake rates of up to three times as
high as in surrounding waters. Carbon uptake rates below the euphotic zone
correlated to the presence of a specific high-light ecotype of
Prochlorococcus, which is usually underrepresented in the ETNA. Our data indicate that high
primary production in the eddy fuels export production and supports enhanced
respiration in a specific microbial community at shallow depths, below the
mixed-layer base. The transcription of the key functional marker gene for dentrification, nirS, further indicated a potential for nitrogen loss processes in O2-depleted core waters of the eddy. Dentrification is usually
absent from the open ETNA waters.
In light of future projected ocean deoxygenation, our results show that even
distinct events of anoxia have the potential to alter microbial community
structure with critical impacts on primary productivity and biogeochemical
processes of oceanic water bodies. |
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