Carbon isotopic composition of intact branched GDGT core lipids in Greenland lake sediments and soils

Colcord, Devon E.; Pearson, Ann; Brassell, Simon C.

doi:10.1016/j.orggeochem.2017.04.008

Cited by 27 publications

(24 citation statements)

References 36 publications

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“…The more negative δ 13 C POM values encountered at the RTZ, in turn, are predominantly due to the presence of methanotrophic bacteria that oxidize and incorporate 13 C-depleted methane (−60‰) at and below the anoxic interface ( 27 ). We thus argue that at least some of the brGDGT producers thriving within the RTZ are part of a methane-based microbial food web ( 22 , 28 ), in which they assimilate organic matter that is derived either directly from methanotrophic bacteria and/or from other organisms that have previously incorporated methanotroph-derived carbon ( 29 – 31 ).…”

Section: Resultsmentioning

confidence: 99%

Redox-dependent niche differentiation provides evidence for multiple bacterial sources of glycerol tetraether lipids in lakes

Weber

Damsté

Zopfi

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

120

118

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SignificanceReliable prediction of future climate conditions requires a thorough understanding of climate variability throughout Earth’s history. Microbial molecular fossils, such as bacterial membrane-spanning tetraether lipids [branched glycerol dialkyl glycerol tetraethers (brGDGTs)], have proven to be particularly useful for the assessment of past climatic conditions, because they occur ubiquitously in the environment and show compositional changes related to temperature. However, the identity and ecology of brGDGT-producing bacteria is largely unknown, and a mechanistic basis for brGDGT-based paleoclimate reconstruction is still lacking. Here, we present insights into the ecological parameters that affect brGDGT synthesis in lakes, demonstrating that eutrophic lakes with oxygen-deprived bottom waters are the preferred sites for brGDGT-based reconstructions of continental climate.

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Section: Resultsmentioning

confidence: 99%

Redox-dependent niche differentiation provides evidence for multiple bacterial sources of glycerol tetraether lipids in lakes

Weber

Damsté

Zopfi

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

120

118

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“…In lake sediment records, the biological source of brGDGTs and interpretations of their reconstructed temperature is more complex. Lake sediment brGDGTs can originate from a combination of soil, water column, and/or surface sediment bacteria that may each respond to their own niche environmental conditions (Blaga et al, ; Colcord et al, ; Feng et al, ; Naeher et al, ; Russell et al, ; Weber et al, , ). To help reduce some of this complexity, end‐member sources can often be differentiated by the fractional abundances of individual brGDGTs (Martin et al, ; Niemann et al, ).…”

Section: Source Discrimination Of Brgdgtsmentioning

confidence: 99%

Lipid Biomarkers Quantify Holocene Summer Temperature and Ice Cap Sensitivity in Icelandic Lakes

Harning

Curtin

Geirsdóttir

et al. 2020

Geophysical Research Letters

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Although recent research has made significant advances in characterizing Iceland's Holocene environmental history, the region still lacks reliable and continuous records of corresponding paleotemperature. Here we merge bacterial and algal lipid biomarkers (branched glycerol dialkyl glycerol tetraethers and long‐chain alkenones, respectively) to quantify Holocene temperature change from a small lake in northwest Iceland. Our local proxy record shows that early Holocene and late Holocene temperatures ranged from 3.2 to −1.1 oC relative today, which are in close agreement with independent estimates from regional ice cap models. At 2.4 ka, we observe abrupt cooling across bacteria‐, algae‐, and glacier‐derived proxy records, which may have been initiated by extratropical volcanism and/or ocean/atmospheric climate variability of the North Atlantic region. Using early Holocene warmth and ice cap demise as an analog for modern climate change, Intergovernmental Panel on Climate Change temperature projections suggest that the local ice cap, Drangajökull, could vanish by ~2050 CE.

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“…Temperature calibrations based on brGDGTs in soils and peats have substantially improved following the identification and chromatographic separation of 5-methyl and 6methyl brGDGT isomers (De Jonge et al, 2014a;Naafs et al, 2017a, b;Dearing Crampton-Flood et al, 2020). Initial scanning of surficial bottom sediments from East African lakes revealed that especially 6-methyl brGDGTs behave differently in lakes compared to soils, suggesting that they are produced by different bacteria or that brGDGT producers in lakes respond differently to environmental changes than those in soils (Russell et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Seasonal variability and sources of in situ brGDGT production in a permanently stratified African crater lake

et al. 2020

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Abstract. Lake sediments are important archives of continental climate history, and their lipid biomarker content can be exploited to reconstruct paleoenvironmental conditions. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial membrane lipids widely used in paleoclimate studies to reconstruct past temperature. However, major gaps still exist in our understanding of the environmental controls on in situ (i.e. aquatic) production in lake systems. In Lake Chala, a permanently stratified tropical crater lake in East Africa, we determined the concentrations and fractional abundances of individual brGDGTs along depth profiles of suspended particulate matter collected monthly from September 2013 to January 2015 and in settling particles collected monthly at 35 m water depth from August 2010 to January 2015 and compared these brGDGT distributions with those in surficial lake bottom sediments and catchment soils. We find that brGDGTs are primarily produced within the water column and that their concentrations and distributions vary greatly with depth and over time. Comparison with concentration–depth profiles of the monthly distribution and abundance of bacterial taxa, based on 16S rRNA gene amplicon sequencing and quantification, indicates that Acidobacteria are likely not the main producers of brGDGTs in Lake Chala. Shallowing of the oxic–anoxic boundary during seasonal episodes of strong water column stratification promoted production of specific brGDGTs in the anoxic zone. BrGDGT distributions in the water column do not consistently relate with temperature, pH, or dissolved-oxygen concentration but do respond to transitions between episodes of strong stratification and deep (but partial) lake mixing, as does the aquatic bacterial community. Hence, the general link between brGDGT distributions and temperature in brGDGT-based paleothermometry is more likely driven by a change in bacterial community composition than by membrane adaptation of specific members of the bacterial community to changing environmental conditions. Although temperature is not the principal driver of distributional changes in aquatic brGDGTs in this system, at least not during the 17-month study period, abundance-weighted and time-integrated averages of brGDGT fractional abundance in the 53-month time series of settling particles reveal systematic variability over longer timescales that indirectly relates to temperature. Thus, although we do not as yet fully understand the drivers of modern-day brGDGT fluxes and distributions in Lake Chala, our data do support the application of brGDGT paleothermometry to time-integrated archives such as sediments. Highlights. BrGDGTs in the tropical African lake Chala are produced in situ. Acidobacteria are not the dominant source of aquatic brGDGTs. Stratification and mixing drive aquatic brGDGT production and their signature.

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Carbon isotopic composition of intact branched GDGT core lipids in Greenland lake sediments and soils

Cited by 27 publications

References 36 publications

Redox-dependent niche differentiation provides evidence for multiple bacterial sources of glycerol tetraether lipids in lakes

Redox-dependent niche differentiation provides evidence for multiple bacterial sources of glycerol tetraether lipids in lakes

Lipid Biomarkers Quantify Holocene Summer Temperature and Ice Cap Sensitivity in Icelandic Lakes

Seasonal variability and sources of in situ brGDGT production in a permanently stratified African crater lake

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