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| Titel |
Particle size distribution and estimated carbon flux across the Arabian Sea oxygen minimum zone |
| VerfasserIn |
F. Roullier, L. Berline, L. Guidi, X. Durrieu de Madron, M. Picheral, A. Sciandra, S. Pesant, L. Stemmann |
| 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 ; 11, no. 16 ; Nr. 11, no. 16 (2014-08-28), S.4541-4557 |
| Datensatznummer |
250117566
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| Publikation (Nr.) |
 copernicus.org/bg-11-4541-2014.pdf |
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| Zusammenfassung |
| The goal of the Arabian Sea section of the TARA oceans expedition was to
study large particulate matter (LPM > 100 μm) distributions and
possible impact of associated midwater biological processes on vertical
carbon export through the oxygen minimum zone (OMZ) of this region. We
propose that observed spatial patterns in LPM distribution resulted from the
timing and location of surface phytoplankton bloom, lateral transport,
microbial processes in the core of the OMZ, and enhanced biological processes
mediated by bacteria and zooplankton at the lower oxycline. Indeed,
satellite-derived net primary production maps showed that the northern
stations of the transect were under the influence of a previous major bloom
event while the most southern stations were in a more oligotrophic situation.
Lagrangian simulations of particle transport showed that deep particles of
the northern stations could originate from the surface bloom while the
southern stations could be considered as driven by 1-D vertical processes. In
the first 200 m of the OMZ core, minima in nitrate concentrations and the
intermediate nepheloid layer (INL) coincided with high concentrations of
100 μm < LPM < 200 μm. These particles could
correspond to colonies of bacteria or detritus produced by anaerobic
microbial activity. However, the calculated carbon flux through this layer
was not affected. Vertical profiles of carbon flux indicate low flux
attenuation in the OMZ, with a Martin model b exponent value of 0.22. At
three stations, the lower oxycline was associated to a deep nepheloid layer, an
increase of calculated carbon flux and an increase in mesozooplankton
abundance. Enhanced bacterial activity and zooplankton feeding in the deep
OMZ is proposed as a mechanism for the observed deep particle aggregation.
Estimated lower flux attenuation in the upper OMZ and re-aggregation at the
lower oxycline suggest that OMZ may be regions of enhanced carbon flux to the
deep sea relative to non OMZ regions. |
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