GDGT distribution in tropical soils and its potential as a terrestrial paleothermometer revealed by Bayesian deep-learning models

Geochimica et Cosmochimica Acta, Journal Year: 2023, Volume and Issue: 362, P. 41 - 64

Published: Sept. 21, 2023

Branched and isoprenoidal glycerol dialkyl tetraethers (br- isoGDGTs) are membrane lipids produced by bacteria archaea, respectively. These form the basis of several frequently used paleoclimatic proxies. For example, degree methylation brGDGTs (MBT'5Me) preserved in mineral soils (as well as peats lakes) is one most important terrestrial paleothermometers, but features substantial variability that so far insufficiently constrained. The distribution isoGDGTs has received less attention applications have focused on use relative abundance isoGDGT crenarchaeol versus (BIT index) an indicator aridity. To expand our knowledge factors can impact br- soils, including MBT'5Me index, to improve isoGDGT-based precipitation reconstructions, we surveyed GDGT a large collection surface (n=229) soil profiles (n=22) across tropical South America. We find index significantly higher grassland compared forest even among sites with same mean annual air temperature. This likely result lack shading grasslands, leading warmer soils. also relationship between pH Together existing data from arid areas mid-latitudes, confirm BIT-index aridity, alone aridity dependent. combined strengthen reconstructions past archives. In terms site-specific variations, BIT larger at show average lower values. combination modelling results, suggest this pattern arises mathematical formulation these proxies amplifies for intermediate values mutes it close saturation (value 1). Soil relatively little variation depth brGDGT indices. On other hand, changes does isoGDGTs. especially pronounced isoGDGTIsomerIndex where deeper horizons near absence isomers. might be driven archaeal community different horizons, potentially difference aerobic anaerobic communities. Finally, extensive new dataset Bayesian neural networks (BNNs) establish brGDGT-based temperature models. provide calibration removes dependence (n=404; RMSE=2.0 °C) global peat models calibrated against months above freezing (n=1740; RMSE=2.4) RMSE=3.6). All correct bias found samples adjust cold river sediments. successfully test calibrations Chinese loess records. Overall, improved

Language: Английский

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Reconstructing warm-season temperatures using brGDGTs and assessing biases in Holocene temperature records in northern Fennoscandia

Quaternary Science Reviews, Journal Year: 2024, Volume and Issue: 329, P. 108555 - 108555

Published: March 5, 2024

Understanding Holocene climate variability is crucial for predicting future change, which will disproportionally affect high-latitude regions. Summer temperature (Tsummer) reconstructions in regions such as northern Finland are mainly derived from microfossil data. We reconstructed Tsummer spanning the interval 10-1 cal ka BP using branched glycerol dialkyl tetraethers (brGDGTs) lake-sediment record Lake Annan Juomusjärvi (AJU) Finland. The reconstruction shows cool early conditions, ∼2 °C below long-term mean (defined by last 8.5 kyr), followed persistent warming to a thermal maximum around ∼7.0 BP, relatively stable (∼0.5 above mean) 7.0 3.5 and then cooling trend (−0.1 °C·kyr−1) since BP. This history remarkably well replicated nearby pollen-TJuly Loitsana. However, Loitsana chironomid macrofossil data argue much earlier at ∼10 Comparison of versus pollen records across Fennoscandia confirms this inter-proxy discrepancy on timing peak warmth regional-scale phenomenon. Previous studies had raised possibility that non-climatic noise certain records, due local-scale overrepresentation types mid Holocene, may be contributing an artificial lag maximum. brGDGTs unaffected terrestrial flora corroborate mid-Holocene maximum, challenges notion generally prone misrepresenting history. Alternatively, proxy-specific environmental or seasonality biases explain discrepancies warmth. Continued diversification proxy network help better understand differences refine knowledge Fennoscandia.

Language: Английский

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BrGDGTs sources in eastern China marginal seas and their constraints on seawater temperature reconstruction

Chemical Geology, Journal Year: 2025, Volume and Issue: 676, P. 122624 - 122624

Published: Jan. 12, 2025

Language: Английский

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Pre-industrial Common Era temperature fluctuations in South China inferred based upon bacterial tetraether lipids from Lake Poyang

Quaternary Science Reviews, Journal Year: 2025, Volume and Issue: 352, P. 109206 - 109206

Published: Jan. 23, 2025

Language: Английский

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Discovering Hidden Archaeal and Bacterial Lipid Producers in a Euxinic Marine System

Environmental Microbiology, Journal Year: 2025, Volume and Issue: 27(3)

Published: Feb. 27, 2025

ABSTRACT Bacterial membrane lipids are typically characterised by fatty acid bilayers linked through ester bonds, whereas those of Archaea ether‐linked isoprenoids forming or monolayers membrane‐spanning known as isoprenoidal glycerol dialkyl tetraethers (isoGDGTs). However, this understanding has been reconsidered with the identification branched GDGTs (brGDGTs), which ether‐bound alkyl acids bacterial origin, though their producers often unidentified. The limited availability microbial cultures constrains biological sources these lipids, thus limiting use biomarkers. To address issue, we identified in Black Sea using high‐resolution accurate mass/mass spectrometry and inferred potential targeting lipid biosynthetic pathways encoded on metagenome, metagenome‐assembled genomes unbinned scaffolds. We also brGDGTs highly suboxic euxinic waters, potentially attributed to Planctomycetota, Cloacimonadota, Desulfobacterota, Chloroflexota, Actinobacteria Myxococcota—based genomic potential. These findings introduce new possibilities for specific biomarkers anoxic conditions marine environments highlight role adaptation.

Language: Английский

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Mid- to Late-Holocene branched GDGT-based air temperatures from a crater lake in Cameroon (Central Africa)

Organic Geochemistry, Journal Year: 2025, Volume and Issue: unknown, P. 104982 - 104982

Published: March 1, 2025

Language: Английский

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The Branched GDGT Isomer Ratio Refines Lacustrine Paleotemperature Estimates

Geochemistry Geophysics Geosystems, Journal Year: 2025, Volume and Issue: 26(3)

Published: March 1, 2025

Abstract Branched glycerol dialkyl tetraethers (brGDGTs) are membrane‐spanning lipids synthesized by bacteria in numerous substrates. The degree of methylation the five methyl brGDGTs both soils and lake sediments, described MBT′ 5Me index, is empirically related to surface atmospheric temperature. This relationship lakes generally assumed reflect temperatures captured brGDGT production water column exported index has been applied sediment successions reconstruct changes temperature through time. We analyzed between isomerization (IR 6Me ) globally distributed surficial sediments demonstrated that relationship, calibrations, middle high latitude sensitive incompletely understood factors IR . does not appear track a non‐thermal influence tropical lakes, but this could change as data set expanded. address ongoing challenges application paleothermometer with new ‐temperature calibrations based on grouping demonstrate how can distinguish samples significant targeting anomalously warm during Last Glacial Maximum from newly piston gravity core Lake Baikal, Russia.

Language: Английский

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New global lacustrine brGDGTs temperature calibrations based on machine learning

Quaternary Science Reviews, Journal Year: 2025, Volume and Issue: 357, P. 109319 - 109319

Published: March 26, 2025

Language: Английский

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Dynamic environment but no temperature change since the late Paleogene at Lühe Basin (Yunnan, China)

Palaeogeography Palaeoclimatology Palaeoecology, Journal Year: 2025, Volume and Issue: unknown, P. 112920 - 112920

Published: March 1, 2025

Language: Английский

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A novel method to advance the brGDGTs-based paleoclimate reconstruction applicable to different terrestrial environments

Quaternary Science Reviews, Journal Year: 2024, Volume and Issue: 328, P. 108540 - 108540

Published: Feb. 14, 2024

Language: Английский

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