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| Titel |
Testing the D / H ratio of alkenones and palmitic acid as salinity proxies in the Amazon Plume |
| VerfasserIn |
C. Häggi, C. M. Chiessi, E. Schefuß |
| 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. 23 ; Nr. 12, no. 23 (2015-12-10), S.7239-7249 |
| Datensatznummer |
250118209
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| Publikation (Nr.) |
 copernicus.org/bg-12-7239-2015.pdf |
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| Zusammenfassung |
| The stable hydrogen isotope composition of lipid biomarkers, such as
alkenones, is a promising new tool for the improvement of palaeosalinity
reconstructions. Laboratory studies confirmed the correlation between lipid
biomarker δD composition (δDLipid), water δD
composition (δDH2O) and salinity; yet there is limited insight
into the applicability of this proxy in oceanic environments. To fill this
gap, we test the use of the δD composition of alkenones (δDC37) and palmitic acid (δDPA) as salinity proxies using
samples of surface suspended material along the distinct salinity gradient
induced by the Amazon Plume. Our results indicate a positive correlation
between salinity and δDH2O, while the relationship between
δDH2O and δDLipid is more complex: δDPAM correlates strongly with δDH2O (r2 = 0.81) and
shows a salinity-dependent isotopic fractionation factor. δDC37 only correlates with δDH2O in a small number (n = 8) of
samples with alkenone concentrations > 10 ng L−1, while
there is no correlation if all samples are taken into account. These
findings are mirrored by alkenone-based temperature reconstructions, which
are inaccurate for samples with low alkenone concentrations. Deviations in
δDC37 and temperature are likely to be caused by limited
haptophyte algae growth due to low salinity and light limitation imposed by
the Amazon Plume. Our study confirms the applicability of δDLipid as a salinity proxy in oceanic environments. But it raises a
note of caution concerning regions where low alkenone production can be
expected due to low salinity and light limitation, for instance, under
strong riverine discharge. |
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