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| Titel |
Occurrence and distribution of ladderane oxidation products in different oceanic regimes |
| VerfasserIn |
D. Rush, E. C. Hopmans, S. G. Wakeham, S. Schouten, J. S. Sinninghe Damsté |
| 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 ; 9, no. 7 ; Nr. 9, no. 7 (2012-07-04), S.2407-2418 |
| Datensatznummer |
250007176
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| Publikation (Nr.) |
 copernicus.org/bg-9-2407-2012.pdf |
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| Zusammenfassung |
| Ladderane fatty acids are commonly used as biomarkers for bacteria involved
in anaerobic ammonium oxidation (anammox). These lipids have been
experimentally shown to undergo aerobic microbial degradation to form short
chain ladderane fatty acids. However, nothing is known of the production or
the distribution of these oxic biodegradation products in the natural
environment. In this study, we analysed marine water column particulate
matter and sediment from three different oceanic regimes for the presence of
ladderane oxidation products (C14 ladderane fatty acids) and of
original ladderane fatty acids (C18 and C20 ladderane fatty
acids). We found that ladderane oxidation products, i.e. C14 ladderane
fatty acids, are already produced within the water column of the Arabian Sea
oxygen minimum zone (OMZ) and thus only low amounts of oxygen (< 3 μM)
are needed for the β-oxidation of original ladderane fatty
acids to proceed. However, no short chain ladderane fatty acids were
detected in the Cariaco Basin water column, where oxygen concentrations were
below detection limit, suggesting that the β-oxidation pathway is
inhibited by the absence of molecular oxygen, or that the microbes
performing the degradation are not proliferating under these conditions.
Comparison of distributions of ladderane fatty acids indicates that short
chain ladderane fatty acids are mostly produced in the water column and at
the sediment surface, before being preserved deeper in the sediments. Short
chain ladderane fatty acids were abundant in Arabian Sea and Peru Margin
sediments (ODP Leg 201), often in higher concentrations than the original
ladderane fatty acids. In a sediment core taken from within the Arabian Sea
OMZ, short chain ladderanes made up more than 90% of the total ladderanes
at depths greater than 5 cm below sea floor. We also found short chain
ladderanes in higher concentrations in hydrolysed sediment residues compared
to those freely occurring in lipid extracts, suggesting that they had become
bound to the sediment matrix. Furthermore, these matrix-bound short chain
ladderanes were found at greater sediment depths than short chain ladderanes
in the lipid extract, suggesting that binding to the sediment matrix aids
the preservation of these lipids. Though sedimentary degradation of short
chain ladderane fatty acids did occur, it appeared to be at a slower rate
than that of the original ladderane fatty acids, and short chain ladderane
fatty acids were found in sediments from the Late Pleistocene
(~ 100 kyr). Together these results suggest that the oxic
degradation products of ladderane fatty acids may be suitable biomarkers for
past anammox activity in OMZs. |
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