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| Titel |
Towards a palaeosalinity proxy: hydrogen isotopic fractionation between source water and lipids produced via different biosynthetic pathways in haptophyte algae |
| VerfasserIn |
David Chivall, Daniela M'Boule, Sandra M. Heinzelmann, Sebastian Kasper, Daniëlle Sinke-Schoen, Jaap S. Sininnghe-Damsté, Stefan Schouten, Marcel T. J. van der Meer |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096557
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| Publikation (Nr.) |
 EGU/EGU2014-12066.pdf |
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| Zusammenfassung |
| Palaeosalinity is one of the most important oceanographic parameters that cannot
currently be quantified with reasonable accuracy from sedimentary records. Hydrogen
isotopic fractionation between water and alkenones is dependent, amongst other
factors, upon the salinity in which alkenone-producing haptophyte algae grow and is
represented by the fractionation factor, α, increasing with salinity.1 As such, the
hydrogen isotopic composition of alkenones is emerging as a palaeosalinity proxy.
Understanding the mechanism behind the sensitivity of fractionation to salinity is
important for the correct application of the proxy, however this mechanism is currently
unknown.
Here we present hydrogen isotopic compositions of lipids produced via different
biosynthetic pathways from batch cultures of Emiliania huxleyi CCMP 1516 and
Isochrysis galbana CCMP 1323 grown over a range of salinities and discuss the
possible sources of the sensitivity of hydrogen isotope fractionation to salinity. α for
C37 alkenones (produced via an unknown biosynthetic pathway but assumed to be
acetogenic; e.g.2) and that for C14:0, C16:0, and C18:1 fatty acids (acetogenic) from
exponential growth phase I. galbana show a similar sensitivity to salinity, increasing at
0.0013-0.0019 per salinity unit (S-1). Meanwhile, in exponential growth phase E. huxleyi,
α for C37 alkenones and α for brassicasterol (mevalonate pathway) increase at
0.0015-0.0022 S-1, but α for phytol (methylerythritol pathway) shows no significant
relationship with salinity. These results suggest that fractionation is sensitive to salinity
for lipids formed both in the chloroplast and cytosol. They also suggest that the
sensitivity may either originate in glyceralde-3-phosphate or pyruvate but is then lost
through hydrogen exchange with cell water during sugar rearrangements in the
methylerythritol pathway or sensitivity originates with the production and consumption of
acetate.
References
Schouten, S., Ossebaar, J., Schreiber, K., Kienhuis, M. V. M., Langer, G.,
Benthien, A., and Bijma, J.: The effect of temperature, salinity and growth rate
on the stable hydrogen isotopic composition of long chain alkenones produced
by Emiliania huxleyi and Gephyrocapsa oceanica, Biogeosciences, 3, 113-119,
doi:10.5194/bg-3-113-2006, 2006.
Rontani, J. F., Prahl, F. G., and Volkman, J. K.: Re-examination of the
double bond positions in alkenones and derivatives: Biosynthetic implications, J
Phycol., 42, 800-813, doi:10.1111/j.1529-8817.2006.00251.x, 2006. |
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