Metabolic and ecological controls on the stable carbon isotopic composition of archaeal (isoGDGT and BDGT) and bacterial (brGDGT) lipids in wetlands and lignites

Blewett, Jerome; Elling, Felix J.; Naafs, B. David A.; Kattein, Laura; Evans, Thomas W.; Lauretano, Vittoria; Gallego‐Sala, Angela; Pancost, Richard D.; Pearson, Ann

doi:10.1016/j.gca.2021.12.023

Cited by 7 publications

(6 citation statements)

References 175 publications

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“…2d), further highlighting multiple sources of brGDGTs in cold seeps. Moreover, the absence of a clear isotopic offset between hydrocarbon “a” and TOC supports the ubiquitously heterotrophic lifestyles of brGDGT‐producing bacteria (Weijers et al 2010; Huguet et al 2017; Blewett et al 2022). Interestingly, hydrocarbon “b” and “c” are substantially more 13 C‐depleted than TOC (up to 49‰ more negative than TOC, Fig.…”

Section: Resultsmentioning

confidence: 79%

“…To test this, we further investigated carbon isotopes of brGDGT‐derived alkanes (Fig. 2), which could provide insight into the C‐substrate that was utilized by brGDGT producers (Pancost and Sinninghe Damsté 2003; Weijers et al 2010; Colcord et al 2017; Huguet et al 2017; Lu et al 2018; Weber et al 2018; Blewett et al 2022). 13,16‐Dimethyloctacosane (hydrocarbon “a”) is the most abundant brGDGT‐derived hydrocarbon through ether cleavage.…”

Section: Resultsmentioning

confidence: 99%

“…Noteworthy, the GBM_SEEP model was developed to differentiate the marine-type, seep-type, and soil-type brGDGTs in marine sediments, which could capture potential ancient AOM signals. This model may not work in terrestrial settings, including (ancient) wetlands (Naafs et al 2017(Naafs et al , 2018Inglis et al 2020;Lauretano et al 2021;Blewett et al 2022) and lake environments (Colcord et al 2017;Weber et al 2018) where AOM might also occur. Future studies in classifying methaneimpacted samples and normal background samples in such settings may shed new light on terrestrial methane cycling.…”

Section: Supervised Machine Learning Algorithmsmentioning

confidence: 99%

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Bacterial glycerol tetraethers as a potential tool to trace marine methane cycling

Zhang,

Li,

et al. 2023

Limnology & Oceanography

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Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial lipids that can be preserved in sedimentary archives for tens of millions of years and are ubiquitous in diverse environments, including cold seep systems. Their potential implications for detecting methane activity in deep time are, however, hampered by the multiple sources of brGDGTs in cold seeps and the lack of evidence of their stable carbon isotopes. Here, we show that brGDGTs in cold seeps are characterized by depleted stable carbon isotopic compositions of the alkyl moieties (δ13C = −32.9‰ to −82.7‰), indicating a methane metabolizing community origin, which is supported by the association between 16S rRNA genes and brGDGTs. We further identify unique seep‐derived brGDGT signals from the global published dataset by a tree‐based machine‐learning algorithm. This trained model, named light gradient‐boosting machine classification for paleoSEEP (GBM_SEEP), is further applied on a paleorecord across the Paleocene–Eocene Thermal Maximum (PETM), which suggests potential methane emission events during the PETM recovery phase. Collectively, our study links brGDGT production in cold seeps with methane metabolizing communities and provides a potential strategy to capture significant methane emission events using the machine‐learning model, which warrants further investigation.

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Section: Resultsmentioning

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Supervised Machine Learning Algorithmsmentioning

confidence: 99%

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Bacterial glycerol tetraethers as a potential tool to trace marine methane cycling

Zhang,

Li,

et al. 2023

Limnology & Oceanography

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“…This high phytoplankton biomass might consequently create an environment that accelerates the growth and production of heterotrophic bacteria, which can in turn transform phytoplankton-derived organic matter (Buchan et al, 2014). As the brGDGT-producers were suggested to have a heterotrophic lifestyle (Weijers et al, 2010;Huguet et al, 2017;Blewett et al, 2022), they may transform phytoplankton-derived organic matter and thus participate in N cycling during blooms. Hence, the co-variation of all the parameters (IR 6Me , TN, δ 15 N, and Chl a concentration), which peak in the low-salinity area during the lowflow season, suggests that a low salinity range and high phytoplankton productivity represent favorable conditions for 6methyl brGDGT production.…”

Section: Environmental Controls On the Brgdgt Distributionmentioning

confidence: 99%

Environmental controls on the distribution of brGDGTs and brGMGTs across the Seine River basin (NW France): implications for bacterial tetraethers as a proxy for riverine runoff

Zhang,

Parlanti,

Anquetil

et al. 2024

Biogeosciences

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Abstract. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial lipids that have been widely used as environmental proxies in continental paleorecords. Another group of related lipids, branched glycerol monoalkyl glycerol tetraethers (brGMGTs), has recently been proposed as a potential paleotemperature proxy. Nevertheless, the sources and environmental dependencies of both brGDGTs and brGMGTs along the river–sea continuum are still poorly understood, complicating their application as paleoenvironmental proxies in some aquatic settings. In this study, the sources of brGDGTs and brGMGTs and the potential factors controlling their distributions are explored across the Seine River basin (NW France), which encompasses the freshwater-to-seawater continuum. BrGDGTs and brGMGTs were analyzed in soils, suspended particulate matter (SPM), and sediments (n=237) collected along the land–sea continuum of the Seine basin. Both types of compounds (i.e., brGDGTs and brGMGTs) are shown to be produced in situ, in freshwater and saltwater, based on their high concentrations and distinct distributions in aquatic settings (SPM and sediments) vs. soils. Redundancy analysis further shows that both salinity and nitrogen dominantly control the brGDGT distributions. Furthermore, the relative abundance of 6-methyl vs. that of 5-methyl brGDGTs (the IR6Me ratio), the total nitrogen (TN), the δ15N, and the chlorophyll a concentration co-vary in a specific geographical zone with low salinity, suggesting that 6-methyl brGDGTs are preferentially produced under low-salinity and high-productivity conditions. In contrast to brGDGTs, the brGMGT distribution appears to be primarily regulated by salinity, with a distinct influence on the individual homologues. Salinity is positively correlated with homologues H1020a and H1020b and negatively correlated with compounds H1020c and H1034b in SPM. This suggests that bacteria living in freshwater preferentially produce compounds H1020c and H1034b, whereas bacteria that primarily grow in saltwater appear to be predominantly responsible for the production of homologues H1020a and H1020b. Based on the abundance ratio of the freshwater-derived compounds (H1020c and H1034b) vs. their saltwater-derived homologues (H1020a and H1020b), a novel proxy, the Riverine IndeX (RIX), is proposed to trace riverine organic matter inputs, with high values (>0.5) indicating a higher riverine contribution. We successfully applied RIX to the Godavari River basin (India) and a paleorecord across the upper Paleocene and lower Eocene from the Arctic Coring Expedition at Lomonosov Ridge, showing its potential applicability to both modern samples and paleorecords.

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“…Tropical peats also contain abundant BDGTs (butanetriol dialkyl glycerol tetraethers) produced by the methanogenic archaeon Methanomassiliicoccus luminyensis; however, BDGTs are also abundant in some temperate and even boreal peats, especially sedge-dominated peatland. We have previously speculated that the low  13 C values of BDGTs in freshwater wetlands reflects their utilization of methyl substrates (Blewett et al, 2022). If so, we anticipate greater proportions of BDGTs in peats comprised of organic substrates rich in oxidized methyl moieties (lignin, pectin), and these are abundant in all of the SSPS cores.…”

mentioning

confidence: 90%

The Tropical Peatland Archaeal Lipidome – Influence of Vegetation and Redox on Diversity

Pancost,

Blewett,

Naafs

et al. 2023

Imog 2023

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Metabolic and ecological controls on the stable carbon isotopic composition of archaeal (isoGDGT and BDGT) and bacterial (brGDGT) lipids in wetlands and lignites

Cited by 7 publications

References 175 publications

Bacterial glycerol tetraethers as a potential tool to trace marine methane cycling

Bacterial glycerol tetraethers as a potential tool to trace marine methane cycling

Environmental controls on the distribution of brGDGTs and brGMGTs across the Seine River basin (NW France): implications for bacterial tetraethers as a proxy for riverine runoff

The Tropical Peatland Archaeal Lipidome – Influence of Vegetation and Redox on Diversity

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