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The contribution of water radiolysis to marine sedimentary life (2021)

Sauvage, Justine ; Flinders, Ashton F. ; Spivack, Arthur J. ; [et al.]

Nature Research

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Publication Date: 2022-05-27

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sauvage, J. F., Flinders, A., Spivack, A. J., Pockalny, R., Dunlea, A. G., Anderson, C. H., Smith, D. C., Murray, R. W., & D'Hondt, S. The contribution of water radiolysis to marine sedimentary life. Nature Communications, 12(1), (2021): 1297, https://doi.org/10.1038/s41467-021-21218-z.

Description: Water radiolysis continuously produces H2 and oxidized chemicals in wet sediment and rock. Radiolytic H2 has been identified as the primary electron donor (food) for microorganisms in continental aquifers kilometers below Earth’s surface. Radiolytic products may also be significant for sustaining life in subseafloor sediment and subsurface environments of other planets. However, the extent to which most subsurface ecosystems rely on radiolytic products has been poorly constrained, due to incomplete understanding of radiolytic chemical yields in natural environments. Here we show that all common marine sediment types catalyse radiolytic H2 production, amplifying yields by up to 27X relative to pure water. In electron equivalents, the global rate of radiolytic H2 production in marine sediment appears to be 1-2% of the global organic flux to the seafloor. However, most organic matter is consumed at or near the seafloor, whereas radiolytic H2 is produced at all sediment depths. Comparison of radiolytic H2 consumption rates to organic oxidation rates suggests that water radiolysis is the principal source of biologically accessible energy for microbial communities in marine sediment older than a few million years. Where water permeates similarly catalytic material on other worlds, life may also be sustained by water radiolysis.

Description: This project was funded by the US National Science Foundation (through grant NSF-OCE-1130735 and the Center for Deep Dark Energy Biosphere Investigations [C-DEBI; grant NSF-OCE-0939564]); the National Aeronautics and Space Administration (grant NNX12AD65G); the U.S. Science Support Program, IODP; and a Schlanger Ocean Drilling Fellowship to J.F.S. This is a contribution to the Deep Carbon Observatory (DCO). It is C-DEBI publication 553.

Repository Name: Woods Hole Open Access Server

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Relationship of bacterial richness to organic degradation rate and sediment age in subseafloor sediment (2016)

Walsh, Emily A. ; Kirkpatrick, John B. ; Pockalny, Robert ; [et al.]

American Society for Microbiology

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Publication Date: 2022-05-26

Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Applied and Environmental Microbiology 82 (2016): 4994-4999, doi:10.1128/AEM.00809-16.

Description: Subseafloor sediment hosts a large, taxonomically rich and metabolically diverse microbial ecosystem. However, the factors that control microbial diversity in subseafloor sediment have rarely been explored. Here we show that bacterial richness varies with organic degradation rate and sediment age. At three open-ocean sites (in the Bering Sea and equatorial Pacific) and one continental margin site (Indian Ocean), richness decreases exponentially with increasing sediment depth. The rate of decrease in richness with depth varies from site to site. The vertical succession of predominant terminal electron acceptors correlates to abundance-weighted community composition, but does not drive the vertical decrease in richness. Vertical patterns of richness at the open-ocean sites closely match organic degradation rates; both properties are highest near the seafloor and decline together as sediment depth increases. This relationship suggests that (i) total catabolic activity and/or electron donor diversity exerts a primary influence on bacterial richness in marine sediment, and (ii) many bacterial taxa that are poorly adapted for subseafloor sedimentary conditions are degraded in the geologically young sediment where respiration rates are high. Richness consistently takes a few hundred thousand years to decline from near-seafloor values to much lower values in deep anoxic subseafloor sediment, regardless of sedimentation rate, predominant terminal electron acceptor, or oceanographic context.

Description: This work, including the efforts of Mitchell L. Sogin and Steven D’Hondt, was funded by Sloan Foundation (Census of Deep Life). This work, including the efforts of Steven D’Hondt, was funded by U.S. Science Support Program for IODP. This work, including the efforts of Steven D’Hondt, was funded by National Science Foundation (NSF) (OCE- 0752336 and OCE-0939564). The work of E. A. Walsh, J. B. Kirkpatrick, R. Pockalny, and J. Sauvage was funded by the grants to S. D’Hondt.

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Glacial to Holocene changes in trans-Atlantic Saharan dust transport and dust-climate feedbacks (2017)

Williams, Ross H. ; McGee, David ; Kinsley, Christopher W. ; [et al.]

American Association for the Advancement of Science

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Publication Date: 2022-05-26

Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Science Advances 2 (2016): e1600445, doi:10.1126/sciadv.1600445.

Description: Saharan mineral dust exported over the tropical North Atlantic is thought to have significant impacts on regional climate and ecosystems, but limited data exist documenting past changes in long-range dust transport. This data gap limits investigations of the role of Saharan dust in past climate change, in particular during the mid-Holocene, when climate models consistently underestimate the intensification of the West African monsoon documented by paleorecords. We present reconstructions of African dust deposition in sediments from the Bahamas and the tropical North Atlantic spanning the last 23,000 years. Both sites show early and mid-Holocene dust fluxes 40 to 50% lower than recent values and maximum dust fluxes during the deglaciation, demonstrating agreement with records from the northwest African margin. These quantitative estimates of trans-Atlantic dust transport offer important constraints on past changes in dust-related radiative and biogeochemical impacts. Using idealized climate model experiments to investigate the response to reductions in Saharan dust’s radiative forcing over the tropical North Atlantic, we find that small (0.15°C) dust-related increases in regional sea surface temperatures are sufficient to cause significant northward shifts in the Atlantic Intertropical Convergence Zone, increased precipitation in the western Sahel and Sahara, and reductions in easterly and northeasterly winds over dust source regions. Our results suggest that the amplifying feedback of dust on sea surface temperatures and regional climate may be significant and that accurate simulation of dust’s radiative effects is likely essential to improving model representations of past and future precipitation variations in North Africa.

Description: This study was supported, in part, by NSF awards OCE-1030784 (to D.M. and P.B.d.) and OCE-09277247 (to P.B.d.); NASA grant NN14AP38G (to C. Heald, Massachusetts Institute of Technology), which supports D.A.R.; and the Columbia University Center for Climate and Life. A.F. is supported by the NSF grant AGS-1116885 and the National Oceanic and Atmospheric Administration (NOAA) grant NA14OAR4310277. S.H. is supported by the NASA Earth and Space Sciences Fellowship. We also acknowledge computational support from the NSF/NCAR Yellowstone Supercomputing Center and the Yale University High Performance Computing Center.

Keywords: Mineral dust ; North Africa ; Paleoclimate ; African Humid Period

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Archaea dominate oxic subseafloor communities over multimillion-year time scales (2019)

Vuillemin, Aurèle ; Wankel, Scott D. ; Coskun, Ömer K. ; [et al.]

American Association for the Advancement of Science

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Publication Date: 2022-05-26

Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).. The definitive version was published in Vuillemin, A., Wankel, S. D., Coskun, Ö. K., Magritsch, T., Vargas, S., Estes, E. R., Spivack, A. J., Smith, D. C., Pockalny, R., Murray, R. W., D'Hondt, S., & Orsi, W. D. Archaea dominate oxic subseafloor communities over multimillion-year time scales. Science Advances, 5(6), (2019): eaaw4108, doi: 10.1126/sciadv.aaw4108.

Description: Ammonia-oxidizing archaea (AOA) dominate microbial communities throughout oxic subseafloor sediment deposited over millions of years in the North Atlantic Ocean. Rates of nitrification correlated with the abundance of these dominant AOA populations, whose metabolism is characterized by ammonia oxidation, mixotrophic utilization of organic nitrogen, deamination, and the energetically efficient chemolithoautotrophic hydroxypropionate/hydroxybutyrate carbon fixation cycle. These AOA thus have the potential to couple mixotrophic and chemolithoautotrophic metabolism via mixotrophic deamination of organic nitrogen, followed by oxidation of the regenerated ammonia for additional energy to fuel carbon fixation. This metabolic feature likely reduces energy loss and improves AOA fitness under energy-starved, oxic conditions, thereby allowing them to outcompete other taxa for millions of years.

Description: This work was supported primarily by the Deutsche Forschungsgemeinschaft (DFG) project OR 417/1-1 granted to W.D.O. Preliminary work was supported by the Center for Dark Energy Biosphere Investigations project OCE-0939564 also granted to W.D.O. Publication of the manuscript was supported by the LMU Mentoring Program. The expedition was funded by the US National Science Foundation through grant NSF-OCE-1433150 to A.J.S, S.D., and R.P. R.W.M. led the expedition. This is a contribution of the Deep Carbon Observatory (DCO). S.D.W. acknowledges partial support from NASA Exobiology (NNX15AM04G). This is Center for Dark Energy Biosphere Investigations (C-DEBI) publication number 463. Portions of this material are based on work supported while R.W.M. was serving at the National Science Foundation. A portion of this work was performed as part of the LMU Masters Program “Geobiology and Paleobiology” (MGAP).

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Atribacteria reproducing over millions of years in the Atlantic abyssal subseafloor (2020)

Vuillemin, Aurèle ; Vargas, Sergio ; Coskun, Ömer K. ; [et al.]

American Society for Microbiology

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Publication Date: 2022-10-26

Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Vuillemin, A., Vargas, S., Coskun, O. K., Pockalny, R., Murray, R. W., Smith, D. C., D'Hondt, S., & Orsi, W. D. Atribacteria reproducing over millions of years in the Atlantic abyssal subseafloor. Mbio, 11(5), (2020): e01937-20, doi:10.1128/mBio.01937-20.

Description: 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 5 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 fermentative, and potentially acetogenic, metabolism. “Ca. Atribacteria” dominated throughout the 8 million-year-old cored sequence, despite the detection limit for gene expression being reached in 5 million-year-old sediments. The subseafloor reproducing “Ca. Atribacteria” also expressed genes encoding a bacterial microcompartment 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.

Description: This work was supported primarily by the Deutsche Forschungsgemeinschaft (DFG) project OR 417/1-1 granted to W.D.O. Preliminary work was supported by the Center for Dark Energy Biosphere Investigations project OCE-0939564 also granted to W.D.O. The expedition was funded by the US National Science Foundation through grant NSF-OCE-1433150 to S.D. and R.P. R.W.M. led the expedition. Shipboard microbiology efforts were supported by the Center for Dark Energy Biosphere Investigations (C-DEBI grant NSF-OCE-0939564). This is C-DEBI publication 545. This is a contribution of the Deep Carbon Observatory (DCO).

Keywords: Deep biosphere ; Energy limit to life ; Atribacteria ; Acetogenesis ; Metagenomics ; Transcriptomics ; Fermentation ; Bacterial microcompartment ; Clade JS1 ; Metatranscriptomics ; Subseafloor life

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Co-seismic Slip and Early Afterslip of the 2015 Illapel, Chile Earthquake: Implications for Frictional Heterogeneity and Coastal Uplift (2016)

William D. Barnhart, Jessica R. Murray, Richard W. Briggs, Francisco Gomez, Charles P. J. Miles, Jerry Svarc, Sebastian Riquelme, Bryan J. Stressler

Wiley

In: Journal of Geophysical Research JGR - Solid Earth

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Publication Date: 2016-07-28

Description: Great subduction earthquakes are thought to rupture portions of the megathrust where interseismic coupling is high and velocity-weakening frictional behavior is dominant, releasing elastic deformation accrued over a seismic cycle. Conversely, post-seismic afterslip is assumed to occur primarily in regions of velocity-strengthening frictional characteristics that may correlate with lower interseismic coupling. However, it remains unclear if fixed frictional properties of the subduction interface, co-seismic or aftershock-induced stress redistribution, or other factors control the spatial distribution of afterslip. Here, we use InSAR and GPS observations to map the distribution of co-seismic slip of the 2015 M w 8.3 Illapel, Chile earthquake and afterslip within the first 38 days following the earthquake. We find that afterslip overlaps the co-seismic slip area and propagates along-strike into regions of both high and moderate interseismic coupling. The significance of these observations, however, is tempered by the limited resolution of geodetic inversions for both slip and coupling. Additional afterslip imaged deeper on the fault surface bounds a discrete region of deep co-seismic slip, and both contribute to net uplift of the Chilean Coastal Cordillera. A simple partitioning of the subduction interface into regions of fixed frictional properties cannot reconcile our geodetic observations. Instead, stress heterogeneities, either pre-existing or induced by the earthquake, likely provide the primary control on the afterslip distribution for this subduction zone earthquake. We also explore the occurrence of co- and post-seismic coastal uplift in this sequence and its implications for recent hypotheses concerning the source of permanent coastal uplift along subduction zones.

Print ISSN: 0148-0227

Topics: Geosciences , Physics