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| Titel |
Distribution of lipid biomarkers and carbon isotope fractionation in contrasting trophic environments of the South East Pacific |
| VerfasserIn |
I. Tolosa, J.-C. Miquel, B. Gasser, P. Raimbault, C. Goyet, H. Claustre |
| 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 (2008-06-30), S.949-968 |
| Datensatznummer |
250002533
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| Publikation (Nr.) |
 copernicus.org/bg-5-949-2008.pdf |
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| Zusammenfassung |
The distribution of lipid biomarkers and their stable carbon isotope
composition was investigated on suspended particles from different
contrasting trophic environments at six sites in the South East Pacific.
High algal biomass with diatom-related lipids
(24-methylcholesta-5,24(28)-dien-3β-ol, C25 HBI alkenes,
C16:4 FA, C20:5 FA) was characteristic in the upwelling zone,
whereas haptophyte lipids (long-chain (C37-C39) unsaturated
ketones) were proportionally most abundant in the nutrient-poor settings
of the centre of the South Pacific Gyre and on its easter edge. The
dinoflagellate–sterol, 4α-23,24-trimethylcholest-22(E)-en-3β-ol, was a minor contributor in all of the studied area and the
cyanobacteria-hydrocarbon, C17n-alkane, was at maximum in the high
nutrient low chlorophyll regime of the subequatorial waters near the
Marquesas archipelago.
The taxonomic and spatial variability of the relationships between carbon
photosynthetic fractionation and environmental conditions for four specific
algal taxa (diatoms, haptophytes, dinoflagellates and cyanobacteria) was
also investigated. The carbon isotope fractionation factor (εp) of the 24-methylcholesta-5,24(28)-dien-3β-ol diatom marker,
varied over a range of 16% along the different trophic systems. In contrast,
εp of dinoflagellate, cyanobacteria and alkenone markers
varied only by 7–10‰. The low fractionation factors and small variations
between the different phytoplankton markers measured in the upwelling area
likely reveals uniformly high specific growth rates within the four
phytoplankton taxa, and/or that transport of inorganic carbon into
phytoplankton cells may not only occur by diffusion but also by other carbon
concentrating mechanisms (CCM). In contrast, in the oligotrophic zone, i.e. gyre and eastgyre, relatively high εp values, especially
for the diatom marker, indicate diffusive CO2 uptake by the eukaryotic
phytoplankton. At these nutrient-poor sites, the lower εp values for haptophytes, dinoflagellates and cyanobacteria indicate
higher growth rates or major differences on the carbon uptake mechanisms
compared to diatoms. |
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