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| Titel |
Degradation state of organic matter in surface sediments from the Southern Beaufort Sea: a lipid approach |
| VerfasserIn |
J.-F. Rontani, B. Charrière, M. Petit, F. Vaultier, H. J. Heipieper, H. Link, G. Chaillou, R. Sempéré |
| 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. 9 ; Nr. 9, no. 9 (2012-09-05), S.3513-3530 |
| Datensatznummer |
250007285
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| Publikation (Nr.) |
 copernicus.org/bg-9-3513-2012.pdf |
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| Zusammenfassung |
| For the next decades significant climatic changes should occur in the Arctic
zone. The expected destabilisation of permafrost and its consequences for
hydrology and plant cover should increase the input of terrigenous carbon to
coastal seas. Consequently, the relative importance of the fluxes of
terrestrial and marine organic carbon to the seafloor will likely change,
strongly impacting the preservation of organic carbon in Arctic marine
sediments. Here, we investigated the lipid content of surface sediments
collected on the Mackenzie basin in the Beaufort Sea. Particular attention
was given to biotic and abiotic degradation products of sterols and
monounsaturated fatty acids. By using sitosterol and campesterol degradation
products as tracers of the degradation of terrestrial higher plant inputs
and brassicasterol degradation products as tracers of degradation of
phytoplanktonic organisms, it could be observed that autoxidation,
photooxidation and biodegradation processes act much more intensively on
higher plant debris than on phytoplanktonic organisms. Examination of
oxidation products of monounsaturated fatty acids showed that photo- and
autoxidation processes act more intensively on bacteria than on
phytodetritus. Enhanced damages induced by singlet oxygen (transferred from
senescent phytoplanktonic cells) in bacteria were attributed to the lack of
an adapted antioxidant system in these microorganisms. The strong oxidative
stress observed in the sampled sediments resulted in the production of
significant amounts of epoxy acids and unusually high proportions of
monounsaturated fatty acids with a trans double bond. The formation of epoxy acids
was attributed to peroxygenases (enzymes playing a protective role against
the deleterious effects of fatty acid hydroperoxides in vivo), while cis/trans isomerisation
was probably induced by thiyl radicals produced during the reaction of
thiols with hydroperoxides. Our results confirm the important role
played by abiotic oxidative processes in the degradation of marine bacteria
and do not support the generally expected refractory character of
terrigenous material deposited in deltaic systems. |
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