Universität zu Köln

Pearson, Ann, Hurley, Sarah J., Walter, Sunita R. Shah, Kusch, Stephanie ORCID: 0000-0002-2708-4975, Lichtin, Samantha and Zhang, Yi Ge ORCID: 0000-0001-7331-1246 (2016). Stable carbon isotope ratios of intact GDGTs indicate heterogeneous sources to marine sediments. Geochim. Cosmochim. Acta, 181. S. 18 - 36. OXFORD: PERGAMON-ELSEVIER SCIENCE LTD. ISSN 1872-9533

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Abstract

Thaumarchaeota, the major sources of marine glycerol dibiphytanyl glycerol tetraether lipids (GDGTs), are believed to fix the majority of their carbon directly from dissolved inorganic carbon (DIC). The delta C-13 values of GDGTs (delta C-13(GDGT)) may be powerful tools for reconstructing variations in the ocean carbon cycle, including paleoproductivity and water mass circulation, if they can be related to values of delta C-13(DIC). To date, isotope measurements primarily are made on the C-40 biphytane skeletons of GDGTs, rather than on complete tetraether structures. This approach erases information revealed by the isotopic heterogeneity of GDGTs within a sample and may impart an isotopic fractionation associated with the ether cleavage. To circumvent these issues, we present delta C-13 values for GDGTs from twelve recent sediments representing ten continental margin locations. Samples are purified by orthogonal dimensions of HPLC, followed by measurement of delta C-13 values by Spooling Wire Microcombustion (SWiM)-isotope ratio mass spectrometry (IRMS) with 1 sigma precision and accuracy of +/- 0.25%. Using this approach, we confirm that GDGTs, generally around -19%, are isotopically heavy compared to other marine lipids. However, measured delta C-13(GDGT) values are inconsistent with predicted values based on the C-13 content of DIC in the overlying water column and the previously-published biosynthetic isotope fractionation for a pure culture of an autotrophic marine thaumarchaeon. In some sediments, the isotopic composition of individual GDGTs differs, indicating multiple source inputs. The data appear to confirm that crenarchaeol primarily is a biomarker for Thaumarchaeota, but its delta C-13 values still cannot be explained solely by autotrophic carbon fixation. Overall the complexity of the results suggests that both organic carbon assimilation (ca. 25% of total carbon) and multiple source(s) of exogenous GDGTs (contributing generally <30% of input to sediments) are necessary to explain the observed delta C-13(GDGT) values. The results suggest caution when interpreting the total inputs of GDGTs to sedimentary records. Biogenic or open-slope sediments, rather than clastic basinal or shallow shelf sediments, are preferred locations for generating minimally-biased GDGT proxy records. (C) 2016 Elsevier Ltd. All rights reserved.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Pearson, Ann UNSPECIFIED UNSPECIFIED UNSPECIFIED Hurley, Sarah J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Walter, Sunita R. Shah UNSPECIFIED UNSPECIFIED UNSPECIFIED Kusch, Stephanie UNSPECIFIED orcid.org/0000-0002-2708-4975 UNSPECIFIED Lichtin, Samantha UNSPECIFIED UNSPECIFIED UNSPECIFIED Zhang, Yi Ge UNSPECIFIED orcid.org/0000-0001-7331-1246 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-275696
DOI:	10.1016/j.gca.2016.02.034
Journal or Publication Title:	Geochim. Cosmochim. Acta
Volume:	181
Page Range:	S. 18 - 36
Date:	2016
Publisher:	PERGAMON-ELSEVIER SCIENCE LTD
Place of Publication:	OXFORD
ISSN:	1872-9533
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language AMMONIA-OXIDIZING ARCHAEON; ISOPRENOID TETRAETHER LIPIDS; COMPOUND-SPECIFIC DELTA-C-14; TERRESTRIAL ORGANIC-MATTER; BASIN SURFACE SEDIMENT; OXYGEN MINIMUM ZONE; ST-LAWRENCE ESTUARY; WATER-COLUMN; PLANKTONIC ARCHAEA; NITROSOSPHAERA-VIENNENSIS Multiple languages Geochemistry & Geophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/27569