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| Titel |
Rapid formation of large aggregates during the spring bloom of Kerguelen Island: observations and model comparisons |
| VerfasserIn |
M.-P. Jouandet, G. A. Jackson, F. Carlotti, M. Picheral, L. Stemmann, S. Blain |
| 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 (2014-08-20), S.4393-4406 |
| Datensatznummer |
250117555
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| Publikation (Nr.) |
 copernicus.org/bg-11-4393-2014.pdf |
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| Zusammenfassung |
| While production of aggregates and their subsequent sinking is known to be one
pathway for the downward movement of organic matter from the euphotic zone,
the rapid transition from non-aggregated to aggregated particles has not been
reported previously. We made one vertical profile of particle size
distributions (PSD; sizes ranging from 0.052 to several millimeters in equivalent
spherical diameter) at pre-bloom stage and seven vertical profiles 3 weeks later over a 48 h period at early bloom stage using the Underwater
Vision Profiler during the Kerguelen Ocean and Plateau Compared Study cruise
2 (KEOPS2, October–November 2011). In these naturally iron-fertilized waters
southeast of Kerguelen Island (Southern Ocean), the total particle numerical
abundance increased by more than fourfold within this time period. A massive
total volume increase associated with particle size distribution changes was
observed over the 48 h survey, showing the rapid formation of large particles
and their accumulation at the base of the mixed layer. The results of a one-dimensional particle dynamics model support coagulation as the mechanism
responsible for the rapid aggregate formation and the development of the
VT subsurface maxima. The comparison of VT profiles
between early bloom stage and pre-bloom stage indicates an increase of
particulate export below 200 m when bloom has developed. These results
highlight the role of coagulation in forming large particles and triggering carbon export at the early stage of a naturally iron-fertilized bloom, while
zooplankton grazing may dominate later in the season. The rapid changes
observed illustrate the critical need to measure carbon export flux with high
sampling temporal resolution. Our results are the first published in situ
observations of the rapid accumulation of marine aggregates and their export
and the general agreement of this rapid event with a model of phytoplankton
growth and coagulation. |
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