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Lacustrine in situ production and stable carbon isotope dynamics of branched GDGTs

English title Lacustrine in situ production and stable carbon isotope dynamics of branched GDGTs
Applicant Niemann Helge
Number 162414
Funding scheme Project funding (Div. I-III)
Research institution Institut für Umweltgeowissenschaften Universität Basel
Institution of higher education University of Basel - BS
Main discipline Other disciplines of Environmental Sciences
Start/End 01.10.2015 - 30.09.2016
Approved amount 65'546.00
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All Disciplines (5)

Discipline
Other disciplines of Environmental Sciences
Organic Chemistry
Pedology
Climatology. Atmospherical Chemistry, Aeronomy
Hydrology, Limnology, Glaciology

Keywords (9)

Proxy indicator; Paleotemperature; Switzerland; Sediments; Lipid Biomarker; branched GDGT; MBT/CBT-paleothermometer; Lakes; compound specific stable isotopes

Lay Summary (German)

Lead
Bakterielle Membranlipide für die Rekonstruktion von Temperatur in der Erdgeschichte
Lay summary

In Böden ist die Verteilung bestimmter bakterieller Membranlipide (verzweigte Glycerol-Dialkyl-Glycerol-Tetraether - brGDGTs) abhängig von der Umgebungstemperatur und des pH-Wertes der Böden. Aufgrund von Bodenerosion vwerden diese Komponenten über Bäche und Flüsse in Seen eingetragen, wo sie sich als teil des Seesediments ablagern und als mikrobielle “Fossilien” erhalten bleiben. Die Sequenz von Seesedimenten kann mehrere hundert bis tausend, manchmal sogar zehntausende bis Millionen Jahre zurück reichen. Somit stellen brGDGTs  vielversprechende Proxyindikatoren für die Rekonstruktion von Paleotemperatur und Boden pH dar und können einen wertvollen Beitrag für das Verständnis vergangener Klimavariationen in der Erdgeschichte leisten. Die Ziele des Projektes sind (i) die globale Datenbasis von brGDGTs in Böden und Seesedimenten zu erweitern, (ii) die Rolle einer möglichen aquatischen Produktion von brGDGTs in deren Ablagerung im  Sedimentarchiv zu untersuchen und (iii) die kontinentale Temperatur und den Boden-pH während des Holozäns zu rekonstruieren. Für diese Ziele haben wir verschiedene Schweizer Seesedimente und Böden beprobt und die Verteilung der brGDGTs mithilfe einer verbesserten HPLC Methode analysiert. Dabei konnten wir eine neuartige brGDGT-Komponente finden (Weber et al., 2015), die auf eine bisher unterschätze Produktion von brGDGTs in lakustrinen Systemen hindeutet. Die unterschiedlichen brGDGT Quellen konnten auch in der komponentenspezifischen Zusammensetzung der stabilen Kohlenstoffisotope der brGDGTs nachgewiesen werden. Somit konnten wir zeigen, dass Isotopemessungen eine eindeutige Unterscheidung  zwischen brGDGTs aquatischer und terrestrischer Herkunft ermöglichen. Für diese Projektphase haben wir vorgeschlagen, die Zusammensetzung der stabilen Kohlenstoffisotope von brGDGTs in den bereits beprobten Seesedimenten und Böden zu untersuchen um mögliche Zusammenhänge zwischen Umweltfaktoren und der lakustrinen Produktion von brGDGTs aufzudecken. 

 

Direct link to Lay Summary Last update: 25.09.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Redox-dependent niche differentiation provides evidence for multiple bacterial sources of glycerol tetraether lipids in lakes
Weber Yuki, Sinninghe Damsté Jaap S., Zopfi Jakob, De Jonge Cindy, Gilli Adrian, Schubert Carsten J., Lepori Fabio, Lehmann Moritz F., Niemann Helge (2018), Redox-dependent niche differentiation provides evidence for multiple bacterial sources of glycerol tetraether lipids in lakes, in Proceedings of the National Academy of Sciences, 115(43), 10926-10931.
Incomplete recovery of intact polar glycerol dialkyl glycerol tetraethers from lacustrine suspended biomassIncomplete recovery of intact polar GDGTs
Weber Yuki, Sinninghe Damsté Jaap S., Hopmans Ellen C., Lehmann Moritz F., Niemann Helge (2017), Incomplete recovery of intact polar glycerol dialkyl glycerol tetraethers from lacustrine suspended biomassIncomplete recovery of intact polar GDGTs, in Limnology and Oceanography: Methods, 15(9), 782-793.
Identification and carbon isotope composition of a novel branched GDGT isomer in lake sediments: Evidence for lacustrine branched GDGT production
Weber Yuki, De Jonge Cindy, Rijpstra W. Irene C., Hopmans Ellen C., Stadnitskaia Alina, Schubert Carsten J., Lehmann Moritz F., Sinninghe Damsté Jaap S., Niemann Helge (2015), Identification and carbon isotope composition of a novel branched GDGT isomer in lake sediments: Evidence for lacustrine branched GDGT production, in Geochimica et Cosmochimica Acta, 154, 118-129.

Collaboration

Group / person Country
Types of collaboration
Organic Geochmistry Group at NIOZ (Prof. J. S. Sinninghe Damsté) Netherlands (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Awards

Title Year
Hydrology/Limnology prize by the Swiss Society for Hydrology and Limnology (SGHL) 2018

Associated projects

Number Title Start Funding scheme
121909 FloodAlp! Frequency and intensity of extreme floods in the Alps through the Holocene and implications for natural hazards in future climate scenarios 01.12.2008 Project funding (Div. I-III)
121861 Biogeochemical fluxes in South-Alpine Lakes: Linking nitrogen and methane dynamics in lacustrine redox-transition zones using a combined stable isotope and molecular approach 01.12.2008 Project funding (Div. I-III)
131407 Holocene Paleoclimate Reconstruction of Southern Switzerland: Testing the MBT/CBT Paleothermometer on Lake Sediments (Lake Cadagno, Switzerland) 01.03.2010 International short research visits
140662 Validation and application of a novel, terrestrial biomarker-based paleo thermometer to Holocene Swiss lake sediments and soils 01.10.2012 Project funding (Div. I-III)

Abstract

The distribution of specific bacterial membrane lipids (branched glycerol dialkyl glycerol tetraethers, brGDGTs) in soils correlate with air temperature and soil pH. brGDGTs in lacustrine sediment archives are thus potentially valuable paleo climate proxy indicators. The accuracy of the brGDGT paleoproxy, however, may be compromised by lacustrine in situ production of brGDGTs, masking the primary soil signal. The initial aims of the PhD project were (i) to expand the available data sets for brGDGTs for modern lacustrine sediments and catchment soils and to validate their use as a reliable paleothermometer for lake sediments under various environmental conditions and depositional settings, to (ii) assess the role of in situ brGDGT production and early diagenesis and to (iii) apply the brGDGT paleothermometer to Holocene sediments from Lake Soppensee in order to reconstruct climate variations during the last centuries/millennia. For investigating brGDGTs in lacustrine sediments and catchment soils, we chose a wide variety of Swiss lakes covering almost 2000 m of altitudinal range, which translates to variations in mean annual air temperature of ~10°C . For these lakes we determined the brGDGT composition and observed a rather weak correlation with environmental temperature. In order to better understand the mechanisms that apparently bias the brGDGT-paleothermometer, we chose two lakes for in-depth investigations of brGDGT sources in lacustrine systems: Lake Hinterburg and Lake Lugano. During the first two years of the project, we were able to assemble a comprehensive data set on the identity, relative abundance, and carbon isotopic composition of single brGDGT in these two lakes (sediments and/or water column), which allowed us to asses the role of brGDGT in situ production in the lake system itself. Applying an improved HPLC setup, we found a novel brGDGT isomer in sediments of Lake Hinterburg, which was not present in the lake’s catchment. Furthermore, the novel isomer, as well as all other major brGDGTs in the sediment, were characterised by very low stable carbon isotope ratios, contrasting the significantly higher values of brGDGT in catchment soils. For the first time, these results provide proof for dominant in situ production of brGDGTs in a lake system. The results from this study were recently published in Gochimica et Cosmochimica Acta (Weber et al., 2015)*, a high ranking scientific journal. Here, we propose additional analyses of already collected and new samples, to complement the already exiting data sets. Our investigations revealed that the novel brGDGT isomer was present in 36% of the analysed lakes but never in catchment soils. This provides evidence for the widespread occurrence of brGDGT in situ production in lacustrine systems and, furthermore, attests to the suitability of the novel isomer as a biomarker for brGDGT in situ production. We propose to additionally analyse the stable carbon isotope composition of single brGDGTs from sediments and catchment soils of all lakes for which we already measured brGDGT contents in order to gain further insights into the isotope dynamics and sources of brGDGTs in the studies lakes, and to evaluate possible links to limnological parameters (e.g., productivity, redox dynamics, temperature). In the water column of Lake Lugano, for example, we found the novel brGDGT isomer exclusively in anoxic bottom waters indicating in situ production of this compound is restricted to reduced conditions. (in greater detail) the distribution of specific brGDGTs in suspended particulate matter from the lake Lugano water column in order to test whether distinct bacterial communities with different redox requirements may produce distinct brGDGT distributions. We also have access to sediment trap material collected from Lake Lugano between 1990 - 1993, which we will analyse to gain information about temporally averaged brGDGT fluxes and potential seasonal controls on in situ brGDGT production. Finally, we propose to analyse samples from long-term incubation experiments, which we started in 2013 (Lake Lugano water samples with amendments of 13C-labelled glucose) in an attempt to trace brGDGT production and associated brGDGT compositional changes during simulated early diagenesis.The proposed study will represent an important step forward in our efforts to understand the sources and production of brGDGT in lacustrine environments, with important implications for the use of brGDGT-based reconstructions of past climate variations from lacustrine sediments.* Weber, Y., C. De Jonge, W.I.C. Rijpstra, E.C. Hopmans, A. Stadnitskaia, C.J. Schubert, M.F. Lehmann, J.S.S. Damsté, and H. Niemann. 2015. Identification and carbon isotope composition of a novel branched GDGT isomer in lake sediments: Evidence for lacustrine branched GDGT production. Geochim. Cosmochim. Acta 154: 118-12
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