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| Titel |
A laboratory experiment on the behaviour of soil-derived core and intact polar GDGTs in aquatic environments |
| VerfasserIn |
F. Peterse, C. M. Moy, T. I. Eglinton |
| 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. 4 ; Nr. 12, no. 4 (2015-02-16), S.933-943 |
| Datensatznummer |
250117816
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| Publikation (Nr.) |
 copernicus.org/bg-12-933-2015.pdf |
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| Zusammenfassung |
| We have performed incubation experiments in order to examine the behaviour of
soil-derived branched glycerol dialkyl glycerol tetraether (brGDGT) membrane
lipids upon entering an aquatic environment and to evaluate the processes
that potentially take place during their fluvial transport from land to sea.
We incubated a soil from the Rakaia River catchment on the South Island of
New Zealand using Rakaia River water and ocean water collected near the
river mouth as inocula for a period of up to 152 days. The concentrations,
as well as the relative distribution of brGDGTs derived from intact polar
("living"; IPL) lipids and core ("fossil"; CL) lipids remained unaltered
over the course of the experiment. Although the stability of the brGDGTs may
be a consequence of the higher than natural soil : water ratio used in the
laboratory experiment, the substantial increase (27–72%) in the total
pool of isoprenoid GDGTs (isoGDGTs) in all incubation setups, including the
control using distilled water, indicates that entering an aquatic
environment does influence the behaviour of soil-derived GDGTs. However, the
availability of water appears to be more important than its properties. As a
consequence of increasing isoGDGT concentrations, a decrease in Branched and
Isoprenoid Tetraether (BIT) index values – a proxy for the relative input of
fluvially discharged soil material into a marine system – became evident
after an incubation period of 30 days, with a maximum final decrease of 0.88
to 0.74 in the experiment with river water. The relative distribution within
the isoGDGT pool shows changes with time, suggesting that isoGDGT producers
may either have different rates of membrane adaptation or
production/degradation, or that preferential release from the soil matrix or
a shift in source organism(s) may take place. While the apparent stability
of soil brGDGTs during this incubation experiment reinforces their potential
as tracers for land–sea transport of soil organic carbon and their use in
paleoclimate reconstructions, the distributional differences between GDGTs
in river water and nearby soil, as well as in river and ocean water,
indicate that further research is needed to pinpoint the sources of GDGTs
that are ultimately discharged to the oceans and are subsequently archived
in continental margin sediments. |
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