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| Titel |
Factors limiting heterotrophic bacterial production in the southern Pacific Ocean |
| VerfasserIn |
F. Wambeke, S. Bonnet, T. Moutin, P. Raimbault, G. Alarcón, C. Guieu |
| 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 ; 5, no. 3 ; Nr. 5, no. 3 (2008-05-19), S.833-845 |
| Datensatznummer |
250002525
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| Publikation (Nr.) |
 copernicus.org/bg-5-833-2008.pdf |
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| Zusammenfassung |
| The role of potential factors limiting bacterial growth was investigated
along vertical and longitudinal gradients across the South Eastern Pacific
Gyre. The effects of glucose, nitrate, ammonium and phosphate additions on
heterotrophic bacterial production (using leucine technique) were studied in
parallel in unfiltered seawater samples incubated under natural daily
irradiance. The enrichments realized on the subsurface showed three types of
responses. From 141° W (Marquesas plateau) to approx 125° W, bacteria
were not bottom-up controlled, as confirmed by the huge potential of growth
in non-enriched seawater (median of enhancement factor×39 in 24 h). Within
the Gyre (125° W–95° W), nitrogen alone stimulated leucine
incorporation rates (median×4.2), but rapidly labile carbon (glucose)
became a second limiting factor (median×37) when the two elements were
added. Finally from the border of the gyre to the Chilean upwelling (95° W–73° W),
labile carbon was the only factor stimulating heterotrophic
bacterial production. Interaction between phytoplankton and heterotrophic
bacterial communities and the direct versus indirect effect of iron and
macronutrients on bacterial production were also investigated in four
selected sites: two sites on the vicinity of the Marquesas plateau, the
centre of the gyre and the Eastern border of the gyre. Both phytoplankton
and heterotrophic bacteria were limited by availability of nitrogen within
the gyre, but not by iron. Iron limited phytoplankton at Marquesas plateau
and at the eastern border of the gyre. However 48 h enrichment experiments
were not sufficient to show any clear limitation of heterotrophic bacteria
within Marquesas plateau and showed a limitation of these organisms by
labile carbon in the eastern border of the Gyre. |
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