Persistent organic matter in oxic subseafloor sediment

Estes, Emily R.; Pockalny, R. A.; Dhondt, Steven; Inagaki, Fumio; Morono, Yuki; Murray, Richard W; Nordlund, Dennis; Spivack, Arthur J.; Wankel, Scott D.; Xiao, Nan; Hansel, Colleen M.

doi:10.1038/s41561-018-0291-5

Cited by 67 publications

(54 citation statements)

References 60 publications

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“…It is of note that although the sediments buried in the YRE are episodically exposed to oxygen by physical and/or biological mixing, the effects of oxidation of C org on the efficiency of carbon preservation could be limited, mainly with respect to the physical protection offered by mineral association: CF strongly and positively correlates with C org (R 2 = 0.812, p < 0.001; Figure 8). This interpretation is consistent with the previously mentioned findings that under oxidation conditions in the seafloor, mineral surfaces adsorption of organic compounds are inaccessible to microbes or enzymes, which protects against remineralization and facilitates the presentation of sedimentary C org in the marine environment over million-year timescales (Estes et al, 2019;Hedges & Keil, 1995;Keil et al, 1994;Kennedy et al, 2002;Mayer, 1994). In addition, when a thick layer of eroded materials and/or fresh sediments are quickly deposited, the exposure time of C org buried in these estuarine sediments to O 2 in bottom water is limited to only few years or so, which is insufficient for effective C org oxidation (Galy et al, 2011).…”

Section: Journal Of Geophysical Research: Biogeosciencessupporting

confidence: 93%

Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary

et al. 2020

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Large river‐dominated margins play a potential key role in regulating global carbon cycle and budget due to high terrestrial organic carbon (Corg) inputs and sediment accumulation rates. Here bulk elements (Corg and TN), isotopic compositions (δ13Corg and δ15N), radioisotope 210Pb, sedimentary grain size, pH, Eh, and physicochemical properties were analyzed on samples from the Yangtze River Estuary to determine the mechanism involved in transporting sedimentary Corg offshore. In addition, nine box‐cores were analyzed to further reveal the potential effects of the declining sediment load on the modern depositional pattern of Corg. The statistical analyses indicate that the hydrodynamically driven sediment composition exerts a significant control on the transport, mobilization, and accumulation of sedimentary Corg from the river to the estuary, with respect to the redistribution of fine‐grained sediments. Furthermore, X‐radiographs and 210Pb indicate that reworked environment dominates carbon burial in the Yangtze proximal deposit, while a stable sedimentary environment of Corg (3.50–5.58 g cm−2 year−1) is observed in the Yangtze distal mud. Notably, the enhanced erosional inputs that contain terrestrial plant debris (mainly the coarse fractions) have tended to become important sources for Corg. Although reworked sediments in the Yangtze River Estuary are frequently exposed to oxygen during physical and biological processes, there appears to be a high potential for long‐term sedimentary Corg storage, due to its association with sediment particles (mainly the clay fractions) that provide physical protection against its degradation.

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Section: Journal Of Geophysical Research: Biogeosciencessupporting

confidence: 93%

Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary

et al. 2020

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“…It is not clear why certain compounds or pools of organic matter are readily remineralized by heterotrophic microbes, while others remain stable for millennial time scales (Middelburg et al ., ; Arndt et al ., ). The lability or availability of organic matter is dependent on intrinsic chemical and physical factors such as the molecular size and structure of the compounds as well as mineral content of the matrix (Hedges et al ., ; Rothman and Forney, ; Schmidt et al ., ; Lalonde et al ., ; Estes et al ., ; Hemingway et al ., ). However, it is becoming increasingly recognized that the lability and transformation of organic matter is also influenced by biological factors such as microbial community composition (Carlson et al ., ; Glassman et al ., ).…”

Section: Introductionmentioning

confidence: 97%

Illuminating microbial species‐specific effects on organic matter remineralization in marine sediments

Mahmoudi

Enke

Beaupré

et al. 2019

Environmental Microbiology

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Marine microorganisms play a fundamental role in the global carbon cycle by mediating the sequestration of organic matter in ocean waters and sediments. A better understanding of how biological factors, such as microbial community composition, influence the lability and fate of organic matter is needed. Here, we explored the extent to which organic matter remineralization is influenced by species-specific metabolic capabilities. We carried out aerobic time-series incubations of Guaymas Basin sediments to quantify the dynamics of carbon utilization by two different heterotrophic marine isolates (Vibrio splendidus 1A01; Pseudoalteromonas sp. 3D05). Continuous measurement of respiratory CO 2 production and its carbon isotopic compositions ( 13 C and 14 C) shows species-specific differences in the rate, quantity and type of organic matter remineralized. Each species was incubated with hydrothermally-influenced versus unimpacted sediments, resulting in a~2-fold difference in respiratory CO 2 yield across the experiments. Genomic analysis indicated that the observed carbon utilization patterns may be attributed in part to the number of gene copies encoding for extracellular hydrolytic enzymes. Our results demonstrate that the lability and remineralization of organic matter in marine environments is not only a function of chemical composition and/or environmental conditions, but also a function of the microorganisms that are present and active.

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“…Microbial activities can also be stimulated at redox interfaces deep below the seafloor over geological timescales (3,18). However, the capacity of microbes to reproduce in abyssal subseafloor ecosystems close to the energy limit to life (6,14) is particularly unconstrained, given the extreme scarcity of organic substrates in these settings (19).…”

Section: Introductionmentioning

confidence: 99%

Atribacteria reproducing over millions of years in the Atlantic abyssal subseafloor

Vuillemin

Vargas

Coskun

et al. 2020

Preprint

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How microbial metabolism is translated into cellular reproduction under energy-limited settings below the seafloor over long timescales is poorly understood. Here, we show that microbial abundance increases an order of magnitude over a five million-year-long sequence in anoxic subseafloor clay of the abyssal North Atlantic Ocean. This increase in biomass correlated with an increased number of transcribed protein-encoding genes that included those involved in cytokinesis, demonstrating that active microbial reproduction outpaces cell death in these ancient sediments. Metagenomes, metatranscriptomes, and 16S rRNA gene sequencing all show that the actively reproducing community was dominated by the candidate Phylum “Candidatus Atribacteria”, which exhibited patterns of gene expression consistent with a fermentative, and potentially acetogenic metabolism. “Ca. Atribacteria” dominated throughout the entire eight million-year-old cored sequence, despite the detection limit for gene expression being reached in five million-year-old sediments. The subseafloor reproducing “Ca. Atribacteria” also expressed genes encoding a bacterial micro-compartment that has potential to assist in secondary fermentation by recycling aldehydes and, thereby, harness additional power to reduce ferredoxin and NAD+. Expression of genes encoding the Rnf complex for generation of chemiosmotic ATP synthesis were also detected from the subseafloor “Ca. Atribacteria”, as well as the Wood-Ljungdahl pathway that could potentially have an anabolic or catabolic function. The correlation of this metabolism with cytokinesis gene expression and a net increase in biomass over the million-year-old sampled interval indicates that the “Ca. Atribacteria” can perform the necessary catabolic and anabolic functions necessary for cellular reproduction, even under energy limitation in millions of years old anoxic sediments.ImportanceThe deep subseafloor sedimentary biosphere is one of the largest ecosystems on Earth, where microbes subsist under energy-limited conditions over long timescales. It remains poorly understood how mechanisms of microbial metabolism promote increased fitness in these settings. We discovered that the candidate bacterial Phylum “Candidatus Atribacteria” dominated a deep-sea subseafloor ecosystem, where it exhibited increased transcription of genes associated with acetogenic fermentation and reproduction in million-year old sediment. We attribute its improved fitness after burial in the seabed to its capabilities to derive energy from increasingly oxidized metabolites via a bacterial micro-compartment and utilize a potentially reversible Wood-Ljungdahl pathway to help meet anabolic and catabolic requirements for growth. Our findings show that “Ca. Atribacteria” can perform all the necessary catabolic and anabolic functions necessary for cellular reproduction, even under energy limitation in anoxic sediments that are millions of years old.

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Persistent organic matter in oxic subseafloor sediment

Cited by 67 publications

References 60 publications

Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary

Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary

Illuminating microbial species‐specific effects on organic matter remineralization in marine sediments

Atribacteria reproducing over millions of years in the Atlantic abyssal subseafloor

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