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| Titel |
Towards an organic palaeosalinity proxy: the effect of salinity, growth rate and growth phase on the hydrogen isotopic composition of alkenones produced by haptophyte algae |
| VerfasserIn |
David Chivall, Daniela M'Boule, Stefan Schouten, Jaap S. Sinninghe Damsté, Marcel T. J. van der Meer |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078296
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| Zusammenfassung |
| Palaeosalinity is one of the most important oceanographic parameters which currently cannot
be quantified with reasonable accuracy from sedimentary records. Schouten et al.1
established that the fractionation of hydrogen isotopes between growth water and alkenones
produced by the haptophyte algae Emiliania huxleyi and Gephyrocapsa oceanica is salinity
dependent. As such, the δD values of alkenones recovered from sediment cores can be used to
reconstruct variations in palaeo- sea surface salinity.2 However, to accurately determine
absolute palaeosalinity requires a better constraining of the relationship between this
hydrogen fractionation, salinity and other parameters such as growth rate and growth
phase.
Here, we present results from our ongoing work to constrain the relationship between the
fractionation factor αalkenone-water, salinity, growth rate and growth phase for the major
alkenone-producing haptophytes.
In batch cultures of different strains of the open-ocean haptophyte E. huxleyi sampled
during the exponential growth phase, αC37alkenone-growthwater increases by between 0.0022
and 0.0033 per unit increase in salinity. A similar relationship is observed in batch cultures of
the coastal haptophyte Isochrysis galbana, where α increases with each unit of salinity by
0.0019 — slightly less than for E. huxleyi. However, absolute αC37alkenone-growthwater
values vary strongly between species suggesting that species composition has a strong impact
on the δD value of alkenones.
The fractionation factor for alkenones produced by batch cultures of I. galbana is affected
by growth phase: the rate of change of αC37alkenone-growthwater with each unit of salinity
decreases from 0.0019 in the exponential phase to 0.0010 during the stationary phase.
We also show the effect of varying growth rate over the range 0.2–0.8 day-1 on
the fractionation factor for alkenones produced by E. huxleyi grown in continuous
culture.
These data show that alkenone δD can be used to reconstruct relative shifts in
palaeosalinity in coastal as well as open ocean environments; however, for absolute salinity
reconstructions changes in species composition, growth rate and growth phase effects will
have to be constrained.
References
1. Schouten, S., Ossebaar, J., Schreiber, K., Kienhuis, M. V. M., Langer, G., Benthien, A.,
Bijma, J. Biogeosciences 3, 113, 2006
2. van der Meer, M. T. J., Baas, M., Rijpstra, W. I. C., Marino, G., Rohling, E. J.,
Sinninghe Damsté, J S., Schouten, S., Earth and Planetary Science Letters 262, 594, 2007 |
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