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| Titel |
Microbial iron uptake in the naturally fertilized waters in the vicinity of the Kerguelen Islands: phytoplankton–bacteria interactions |
| VerfasserIn |
M. Fourquez, I. Obernosterer, D. M. Davies, T. W. Trull, 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 ; 12, no. 6 ; Nr. 12, no. 6 (2015-03-23), S.1893-1906 |
| Datensatznummer |
250117875
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| Publikation (Nr.) |
 copernicus.org/bg-12-1893-2015.pdf |
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| Zusammenfassung |
| Iron (Fe) uptake by the microbial community and the contribution of three
different size fractions was determined during spring phytoplankton blooms in
the naturally Fe-fertilized area off the Kerguelen Islands (KEOPS2). Total Fe
uptake in surface waters was on average 34 ± 6 pmol Fe L-1 d-1, and microplankton (> 25 μm
size fraction; 40–69%) and pico-nanoplankton (0.8–25 μm
size fraction; 29–59%) were the main contributors. The contribution of
heterotrophic bacteria (0.2–0.8 μm size fraction) to total Fe
uptake was low at all stations (1–2%). Iron uptake rates normalized to
carbon biomass were highest for pico-nanoplankton above the Kerguelen Plateau
and for microplankton in the downstream plume. We also investigated the
potential competition between heterotrophic bacteria and phytoplankton for
the access to Fe. Bacterial Fe uptake rates normalized to carbon biomass were
highest in incubations with bacteria alone, and dropped in incubations
containing other components of the microbial community. Interestingly, the
decrease in bacterial Fe uptake rate (up to 26-fold) was most pronounced in
incubations containing pico-nanoplankton and bacteria, while the bacterial Fe
uptake was only reduced by 2- to 8-fold in incubations containing the whole
community (bacteria + pico-nanoplankton + microplankton). In
Fe-fertilized waters, the bacterial Fe uptake rates normalized to carbon
biomass were positively correlated with primary production. Taken together,
these results suggest that heterotrophic bacteria are outcompeted by small-sized phytoplankton cells for the access to Fe during the spring bloom
development, most likely due to the limitation by organic matter. We conclude
that the Fe and carbon cycles are tightly coupled and driven by a complex
interplay of competition and synergy between different members of the
microbial community. |
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