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| Titel |
Bioavailability of organically bound Fe to model phytoplankton of the Southern Ocean |
| VerfasserIn |
C. S. Hassler, V. Schoemann |
| 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 ; 6, no. 10 ; Nr. 6, no. 10 (2009-10-30), S.2281-2296 |
| Datensatznummer |
250004045
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| Publikation (Nr.) |
 copernicus.org/bg-6-2281-2009.pdf |
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| Zusammenfassung |
| Iron (Fe) is known to be mostly bound to organic ligands and to limit
primary productivity in the Southern Ocean. It is thus important to
investigate the bioavailability of organically bound Fe. In this study, we
used four phytoplankton species of the Southern Ocean (Phaeocystis sp.,
Chaetoceros sp., Fragilariopsis kerguelensis and
Thalassiosira antarctica Comber) to measure the influence of various organic ligands on Fe solubility and
bioavailability. Short-term uptake Fe:C ratios were inversely related to the
surface area to volume ratios of the phytoplankton. The ratio of
extracellular to intracellular Fe is used to discuss the relative importance
of diffusive supply and uptake to control Fe bioavailability. The effect of
excess organic ligands on Fe bioavailability cannot be solely explained by
their effect on Fe solubility. For most strains studied, the bioavailability
of Fe can be enhanced relative to inorganic Fe in the presence of porphyrin,
catecholate siderophore and saccharides whereas it was decreased in presence
of hydroxamate siderophore and organic amine. For Thalassiosira, iron bioavailability was
not affected by the presence of porphyrin, catecholate siderophore and
saccharides. The enhancement of Fe bioavailability in presence of
saccharides is presented as the result from both the formation of
bioavailable (or chemically labile) organic form of Fe and the stabilisation
of Fe within the dissolved phase. Given the ubiquitous presence of
saccharides in the ocean, these compounds might represent an important
factor to control the basal level of soluble and bioavailable Fe. Results
show that the use of model phytoplankton is promising to improve mechanistic
understanding of Fe bioavailability and primary productivity in HNLC regions
of the ocean. |
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