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dc.contributor.author
Ladd, Sarah Nemiah
dc.contributor.author
Dubois, Nathalie
dc.contributor.author
Schubert, Carsten J.
dc.contributor.contactPerson
Ladd, Sarah Nemiah
dc.contributor.dataCollector
Ladd, Sarah Nemiah
dc.contributor.researchGroup
Schubert, Carsten J.
dc.date.accessioned
2018-02-09T12:56:59Z
dc.date.available
2017-08-14T13:33:21Z
dc.date.available
2018-02-02T13:57:11Z
dc.date.available
2018-02-09T12:56:59Z
dc.date.issued
2017
dc.identifier.uri
http://hdl.handle.net/20.500.11850/176730
dc.identifier.doi
10.3929/ethz-b-000176730
dc.description.abstract
The hydrogen isotopic composition (δ2H) of lipid biomarkers has diverse applications in the fields of paleoclimatology, biogeochemistry, and microbial community dynamics. Large changes in hydrogen isotope fractionation have been observed among microbes with differing core metabolisms, while environmental factors including temperature and nutrient availability can affect isotope fractionation by photoautotrophs. Much effort has gone into studying these effects under laboratory conditions with single species cultures. Moving beyond controlled environments and quantifying the natural extent of these changes in freshwater lacustrine settings and identifying their causes is essential for robust application of δ2H values of common short-chain fatty acids as a proxy of net community metabolism, and of phytoplankton specific biomarkers as a paleohydrologic proxy. This work targets the effect of community dynamics, temperature, and productivity on 2H/1H fractionation in lipid biomarkers through a comparative time series in two central Swiss lakes: eutrophic Lake Greifen and oligotrophic Lake Lucerne. Particulate organic matter was collected from surface waters at six time points throughout the spring and summer of 2015, and δ2H values of short chain fatty acids, as well as chlorophyll-derived phytol and the diatom biomarker brassicasterol, were measured. We paired these measurements with in situ incubations conducted with NaH13CO3, which were used to calculate the production rates of individual lipids in lake surface water. As algal productivity increased from April to June, net discrimination against 2H in Lake Greifen increased by as much as 148 ‰ for individual fatty acids. During the same time period in Lake Lucerne, net discrimination against 2H increased by as much as 58 ‰ for individual fatty acids. A large portion of this signal is likely due to a greater proportion of heterotrophically derived fatty acids in the winter and early spring, which are displaced by more 2H-depleted fatty acids as phytoplankton productivity increases. Smaller increases in 2H discrimination for phytol and brassicasterol suggest that a portion of the signal is due to changes in net photoautotrophic 2H fractionation, which may be caused by increasing temperatures, a shift from maintenance to high growth, or changes in the community assemblage. The fractionation factors for brassicasterol were significantly different between the two lakes, suggesting that its hydrogen isotope composition may be more sensitive to nutrient regime than is the case for fatty acids or phytol.
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dc.format
text/csv
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dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.rights.uri
http://creativecommons.org/licenses/by/4.0/
dc.subject
ORGANIC GEOCHEMISTRY
en_US
dc.subject
FATTY ACIDS (BIOCHEMISTRY)
en_US
dc.subject
Hydrogen isotopes
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dc.subject
Sterols
en_US
dc.title
Data set for paper "Interplay of community dynamics, temperature, and productivity on the hydrogen isotope signatures of lipid biomarkers"
en_US
dc.type
Dataset
dc.rights.license
Creative Commons Attribution 4.0 International
dc.date.published
2018-02-01
ethz.size
0.078 MB
en_US
ethz.date.collected
04-2015/09-2015
en_US
ethz.code.ddc
5 - Science::550 - Earth sciences
en_US
ethz.code.ddc
DDC - DDC::5 - Science
en_US
ethz.geolocation.pointlong
8.679
ethz.geolocation.pointlong
8.437
ethz.geolocation.pointlat
47.351
ethz.geolocation.pointlat
47.014
ethz.geolocation.placename
Lake Greifen
ethz.geolocation.placename
Lake Luzern
ethz.publication.place
Zurich
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02330 - Dep. Erdwissenschaften / Dep. of Earth Sciences::09596 - Dubois, Nathalie (SNF-Professur) / Dubois, Nathalie (SNF-Professur)
en_US
ethz.date.retentionend
indefinite
en_US
ethz.date.retentionendDate
n/a
ethz.date.deposited
2017-08-14T13:33:22Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.description.methods
Particulate material in each lake was collected at approximately monthly intervals throughout the spring and summer of 2015 (mid-April through early September). Surface water (~0.5 m water depth) was filtered onto a pre-combusted 142 mm diameter GF/F filter (0.7 μm pore size) using a WTS-LV Large Volume Pump (McLane, Massachusetts, USA). Water samples were collected from surface water before and after pumping began. Samples were collected in 4 mL screw cap vials, sealed with electrical tape, and stored at room temperature prior to analysis. On the morning of each sampling day, 4 x 12.5 L of surface water was collected in acid-rinsed, autoclaved, transparent carboys for in situ incubations. In two of the four carboys, 1 mL of concentrated NaH13CO3 solution was added. The other two carboys were not isotopically labelled. Carboys were mixed and attached to a fixed, floating line so that they stayed in the upper 50 cm of lake water throughout the day. After 6 hours, they were retrieved and the contents were filtered onto a pre-combusted 142 mm diameter GF/F filter using a peristaltic pump. Water δ2H and δ18O values were measured by Cavity Ring Down Spectroscopy (CRDS) on a L-2120i Water Isotope Analyzer (Picarro, Santa Clara, CA, USA) at ETH-Zurich. DIC concentrations were measured on a TOC-LCSH/CHN Total Organic Carbon Analyzer (Shimadzu, Kyoto, Japan). Carbon isotope values of DIC were measured on an Isotope Ratio Mass Spectrometer (IRMS) (Isoprime, Stockport, United Kingdom). Dry sediment samples were extracted in 30 mL of 9:1 Dichloromethane (DCM)/Methanol (MeOH) in a SOLVpro Microwave Reaction System (Anton Paar, Graz, Austria) at 70 °C for 5 minutes. The total lipid extract was saponified with 3 mL of 1 N KOH in MeOH and 2 mL of solvent-extracted nanopure H2O for 3 hours at 80 °C , after which the neutral fraction was extracted with hexane. Subsequently, the aqueous phase was acidified to pH = 2, and the protonated fatty acids were extracted with hexane. Neutral fractions were further purified using silica gel column chromatography. The alcohol fraction was acetylated with 25 μL of acetic anhydride and 25 μL of pyridine for 30 minutes at 70 °C, and further purified by silver nitrate silica gel chromatography. The δ2H and δ13C values of the added acetyl group were determined by analyzing acetylated and unacetylated nC10-alkanol. Fatty acid fractions were methylated with 1 mL of BF3 in MeOH (14% by volume, Sigma Aldrich) for 2 hours at 100 °C. The δ2H and δ13C values of the added methyl group were determined by methylating phthalic acid of known isotopic composition (Arndt Schimmelmann, Indiana University). FAMEs and brassicasterol were quantified by gas chromatography – flame ionization detection (GC-FID) (Shimazdu, Kyoto, Japan). Samples were injected by an AOC-20i autosampler (Shimadzu) through a split/splitless injector operated in splitless mode at 280 °C. The GC column was an InertCap 5MS/NP (0.25 mm x 30 m x 0.25 μm) (GL Sciences, Japan) and it was heated from 70 °C to 130 °C at 20 °C/min, then to 320 °C at 4 °C/min, and held at 320 °C for 20 minutes. In order to determine how much of the compound was in the original sample, peak areas were normalized to those of the internal standard. The stable isotope values of individual FAMEs and brassicasterol were measured by gas chromatography – isotope ratio mass spectrometry (GC-IRMS). A GC-1310 gas chromatograph (Thermo Scientific, Bremen, Germany) equipped with an InertCap 5MS/NP (0.25 mm x 30 m x 0.25 μm) (GL Sciences, Japan) was interfaced to a Delta Advantage IRMS (Thermo Scientific) with a ConFlow IV interface (Thermo Scientific). Samples were injected with a TriPlusRSH autosampler to a PTV inlet operated in splitless mode at 280 °C. The oven was heated from 80 °C to 215 °C at 15 °C/min, then to 320 °C at 5 °C/min, and then was held at 320 °C for 10 minutes. Hydrogen isotope samples were pyrolyzed at 1420 °C after they eluted from the GC column. Carbon isotope samples were combusted at 1020 °C after elution. Raw isotope values were converted to the VSMOW (hydrogen) and VPDB (carbon) scales using Thermo Isodat 3.0 software and pulses of a reference gas that was measured at the beginning and end of each analysis. Sample δ2H and δ13C values were further corrected using the slope and intercept of measured and known values of isotopic standards (nC17, 19, 21, 23, 25, 28, and 34-alkanes, Arndt Schimmelmann, Indiana University), which were run at the beginning and end of each sequence, as well as after every 6 to 8 sample injections. Offsets between measured and known values for these standards were used to correct for any drift over the course of the sequence or any isotope effects associated with peak area or retention time. The H3+ factor was measured at the beginning of each sequence and averaged 3.6 ± 0.3 during the analysis period. Samples were corrected for hydrogen and carbon added during derivatization using isotopic mass balance, and reported errors represent propagated errors from replicate measurements and the uncertainties associated with the added hydrogen.
en_US
ethz.rosetta.installDate
2018-02-09T12:57:01Z
ethz.rosetta.lastUpdated
2018-11-06T08:52:14Z
ethz.rosetta.versionExported
true
ethz.COinS
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