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What drives the distribution of chemical fossils? Influence of microbial community dynamics on bacterial membrane lipid signatures. [MiCoDy-Lipids]

Applicant De Jonge Cindy
Number 179783
Funding scheme PRIMA
Research institution Geologisches Institut ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Other disciplines of Environmental Sciences
Start/End 01.12.2018 - 30.11.2023
Approved amount 1'286'736.00
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All Disciplines (4)

Discipline
Other disciplines of Environmental Sciences
Pedology
Other disciplines of Earth Sciences
Geochemistry

Keywords (3)

Palaeolimnology; BrGDGT lipids; Bacterial community dynamics

Lay Summary (German)

Lead
Die Rekonstruktion des vergangenen Klimas ist für die akkurate Bestimmung zukünftiger Temperaturveränderungen essentiell. BrGDGTs (Branched Glycerol Dialkyl Glycerol Tetraethers) sind bakterielle Membranumspannende Lipide welche sich in unterschiedlichen Geoarchiven (z.B. Seesedimente, Meeressedimente, Paläoböden) finden lassen und zur Bestimmung von vergangenen Klima und Umweltparametern herangezogen werden können. Um die quantitative Rekonstruktion zu ermöglichen, werden Kalibrierungen basierend auf der gegenwertigen Variabilität der Lipide unter verschiedenen Klimabedingungen, entwickelt.
Lay summary

Es bleibt jedoch unklar auf welchen Mechanismen diese Kalibrierungen basieren. Verändern sich die Lipide nur unter dem Einfluss des Klimas oder auch unter dem Einfluss der Zusammensetzung der bakteriellen Gemeinschaft? So zeigt z.B. die gegenwärtige Literatur, dass nichtlineare Veränderungen der mikrobiellen Gemeinschaft die Temperatursensibilität in Böden beeinflusst.

BrGDGT Lipide die hingegen in Flüssen und Seen anstatt in Böden produziert werden, zeigen eine unterschiedliche Abhängigkeit von Umweltparametern wie z.B. Temperatur, pH und Seetiefe. Daher wurden für Böden und Seen unterschiedliche brGDGTs Kalibrierungsmethoden entwickelt. Dies bedeutet allerdings, dass brGDGTs welche aus Seesedimenten extrahiert wurden und somit aus einem Mix aus See und Bodensedimenten bestehen, nicht uneingeschränkt zur Rekonstruktion von Paläotemperaturen genutzt werden können. Ich plane dieses Problem zu lösen indem ich brGDGTs aus verschiedenen Schweizerischen Wasserscheiden (z.B. Böden, Flüsse, Seewasserprofile und Seesedimente) extrahiere und daraufhin analysiere ob sich die Lipide aufgrund der Temperatur oder der Zusammensetzung der Bakteriellen Gemeinschaft verändern. Mit dieser Erkenntnis werde ich, basierend auf brGDGTs, einen verbesserten Klimaindikator entwickeln, welcher eine zuverlässigere Klimarekonstruktion nicht nur für die Schweiz sondern auch auf globaler Skala erlaubt.
Direct link to Lay Summary Last update: 21.01.2019

Lay Summary (English)

Lead
Reconstructing past continental temperatures is essential for the accurate prediction of temperature changes expected in the future. BrGDGTs (Branched Glycerol Dialkyl Glycerol Tetraethers) are bacterial membrane-spanning lipids preserved in a wide variety of geological archives (e.g. lake sediments, marine sediments, paleosoils) that find an application as climate (temperature) and environmental (pH) estimators. Using calibrations that are based on their current variation with the environment, these lipid biomarkers allow the quantitative reconstruction of temperature and pH over time.
Lay summary

However, it remains unclear what mechanism these calibrations are based on. Do the lipids vary directly with the environment (direct environmental effect)? Or do they follow a shift in the community composition of their bacterial producers (indirect environmental effect)? Recent work in soils fi. shows that nonlinear shifts in the microbial community composition determine a large part of the brGDGT temperature sensitivity along a temperature gradient in soils.

BrGDGT lipids produced in rivers and lakes however, follow a different dependency to environmental factors (temperature, pH, lake depth), compared to the brGDGTs produced in soils. Because of this, different calibrations were developed for brGDGTs produced in soils or in lakes. This also means that brGDGTs found in lake sedimentary archives, that reflect a mixture of soil and lacustrine sources, cannot be used with confidence to reconstruct changes in past temperatures. I propose to solve this problem by studying the brGDGTs variation encountered in two Swiss watersheds (i.e. soils with a different soil water moisture content, rivers, lakes water column and lake sediments). I will determine the influence of the indirect environmental effect (community effect) and separate this from the direct environmental effect, the physiological plasticity of the cell membrane, to developed a new climate proxy based on brGDGT lipids.

Direct link to Lay Summary Last update: 21.01.2019

Responsible applicant and co-applicants

Employees

Collaboration

Group / person Country
Types of collaboration
ETHZ - Paleolimnology group Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
ETHZ - Environmental Microbiology group Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
ETHZ - Biogeosciences group Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
EAWAG - Surface Waters Research and Management Switzerland (Europe)
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Swiss Geoscience Meeting 2021 Talk given at a conference SEASONAL TEMPERATURE VARIABILITY ON FRESHWATER BRANCHED GLYCEROL DIALKYL GLYCEROL TETRAETHERS: A MESOCOSM APPROACH 20.11.2021 virtual, Switzerland De Jonge Cindy; Ajallooeian Fatemeh;
30th International Meeting on Organic Geochemistry (IMOG 2021) Poster SEASONAL TEMPERATURE VARIABILITY ON FRESHWATER BRANCHED GLYCEROL DIALKYL GLYCEROL TETRAETHERS: A MESOCOSM APPROACH 13.09.2021 Virtual, France De Jonge Cindy; Ajallooeian Fatemeh;
30th International Meeting on Organic Geochemistry (IMOG 2021) Talk given at a conference Using supervised and unsupervised statistical approaches to elucidate the presence of environmental brGDGTs clusters that reflect different bacterial producers 12.09.2021 Montpellier, France De Jonge Cindy;
EGU General Assembly 2021 Poster Testing a thermometer of the past: abiotic and biotic drivers of the brGDGT-based temperature proxy along a subarctic elevation gradient. 19.04.2021 Vienna/virtual, Austria De Jonge Cindy;
18th Swiss Geoscience Meeting Talk given at a conference Using brGDGT lipids to determine Holocene climate variations in Swiss alpine Lake Cadagno 06.11.2020 virtual, Switzerland De Jonge Cindy; Rowan Sarah Ann;
EGU General Assembly 2020 Poster Biomarker (brGDGT) degradation and production in lacustrine surface sediments: Implications for paleoclimate reconstructions 04.05.2020 Vienna/ virtual, Austria De Jonge Cindy;


Abstract

Reconstructing past continental temperatures is essential for developing climate models that can accurately predict temperature changes expected in the future. BrGDGTs (Branched Glycerol Dialkyl Glycerol Tetraethers) are bacterial membrane-spanning lipids preserved in a wide variety of geological archives (e.g. lake sediments, marine sediments, paleosoils) that find an application as climate (temperature) and environmental (pH) proxies. Using calibrations that are based on modern settings (soils or lakes), these lipid biomarkers allow the quantitative reconstruction of temperature and pH over time.However, it remains unclear which mechanism underpins their observed variation with climatic gradients in modern environments, i.e. whether the lipids follow a shift in the community composition of their bacterial producers (indirect environmental effect), or whether the cell membrane composition varies directly with the environment (direct environmental effect). My recent work shows that nonlinear shifts in the microbial community composition determine a large part of the brGDGT temperature sensitivity along a temperature gradient in soils. Furthermore, the lipid fingerprint from different communities was shown to react in a separate way to the environment. Accounting for the community effect (indirect effect) thus allow to determine which environmental factors have a direct influence on the brGDGT lipids. BrGDGT lipids produced in freshwater environments have been shown to follow a different dependency to environmental factors (temperature, pH, lake depth), compared to the brGDGTs produced in soils. Because of this, different calibrations were developed for brGDGTs produced in soils or in lakes. In addition, brGDGTs found in lake sedimentary archives that reflect a mixture of soil and lacustrine sources cannot be used to reconstruct changes in past temperatures. I propose to solve this problem by studying the brGDGTs variation encountered on a watershed scale (i.e. soils with a different soil water moisture content, rivers, lakes water column and lake sediments). I will determine the influence of indirect environmental effect, caused by shifts in the bacterial community composition and separate this from the direct environmental effect, the physiological plasticity of the cell membrane. Sampling at high spatial (watershed soils, lacustrine sediments) and temporal (river and lake water) scale in two Swiss watersheds (Sihl River and Lake Rot) will allow tracing those environmental changes that are known to influence the composition of the bacterial community (i.e. type and concentration of cations and anions, nutrients, alkalinity and pH, oxygen content, organic carbon source). BrGDGT production and conservation will be determined in sediment cores from 4 lakes. The bacterial community composition will be determined by Illumina Miseq analysis of the 16S rDNA fragment. The fossil and the recently produced brGDGT lipids (core and intact polar lipids respectively) will be analyzed using HPLC-MS.The proposed research will significantly improve our understanding of the environmental controls on brGDGT production, and the influence of the community composition. By accounting for the indirect environmental effect, I will aim to construct a “universal brGDGT calibration”, targeting the environmental parameters temperature, pH, and moisture, that will be valid for brGDGTs produced in soils, rivers and lakes. With this, I will increase the confidence in and accuracy of continental paleoclimate reconstructions, both within Switzerland and on a global scale.
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