1
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Beerling DJ, Epihov DZ, Kantola IB, Masters MD, Reershemius T, Planavsky NJ, Reinhard CT, Jordan JS, Thorne SJ, Weber J, Val Martin M, Freckleton RP, Hartley SE, James RH, Pearce CR, DeLucia EH, Banwart SA. Enhanced weathering in the US Corn Belt delivers carbon removal with agronomic benefits. Proc Natl Acad Sci U S A 2024; 121:e2319436121. [PMID: 38386712 PMCID: PMC10907306 DOI: 10.1073/pnas.2319436121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 12/30/2023] [Indexed: 02/24/2024] Open
Abstract
Terrestrial enhanced weathering (EW) of silicate rocks, such as crushed basalt, on farmlands is a promising scalable atmospheric carbon dioxide removal (CDR) strategy that urgently requires performance assessment with commercial farming practices. We report findings from a large-scale replicated EW field trial across a typical maize-soybean rotation on an experimental farm in the heart of the United Sates Corn Belt over 4 y (2016 to 2020). We show an average combined loss of major cations (Ca2+ and Mg2+) from crushed basalt applied each fall over 4 y (50 t ha-1 y-1) gave a conservative time-integrated cumulative CDR potential of 10.5 ± 3.8 t CO2 ha-1. Maize and soybean yields increased significantly (P < 0.05) by 12 to 16% with EW following improved soil fertility, decreased soil acidification, and upregulation of root nutrient transport genes. Yield enhancements with EW were achieved with significantly (P < 0.05) increased key micro- and macronutrient concentrations (including potassium, magnesium, manganese, phosphorus, and zinc), thus improving or maintaining crop nutritional status. We observed no significant increase in the content of trace metals in grains of maize or soybean or soil exchangeable pools relative to controls. Our findings suggest that widespread adoption of EW across farming sectors has the potential to contribute significantly to net-zero greenhouse gas emissions goals while simultaneously improving food and soil security.
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Affiliation(s)
- David J. Beerling
- Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, SheffieldS10 2TN, United Kingdom
| | - Dimitar Z. Epihov
- Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, SheffieldS10 2TN, United Kingdom
| | - Ilsa B. Kantola
- Institute for Sustainability, Energy, and Environment, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Michael D. Masters
- Institute for Sustainability, Energy, and Environment, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Tom Reershemius
- Yale Center for Natural Carbon Capture, Department of Earth & Planetary Sciences, Yale University, New Haven, CT 06511
| | - Noah J. Planavsky
- Yale Center for Natural Carbon Capture, Department of Earth & Planetary Sciences, Yale University, New Haven, CT 06511
| | - Christopher T. Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332
| | | | - Sarah J. Thorne
- Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, SheffieldS10 2TN, United Kingdom
| | - James Weber
- Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, SheffieldS10 2TN, United Kingdom
| | - Maria Val Martin
- Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, SheffieldS10 2TN, United Kingdom
| | - Robert P. Freckleton
- Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, SheffieldS10 2TN, United Kingdom
| | - Sue E. Hartley
- Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, SheffieldS10 2TN, United Kingdom
| | - Rachael H. James
- School of Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, SouthamptonSO14 3ZH, United Kingdom
| | | | - Evan H. DeLucia
- Institute for Sustainability, Energy, and Environment, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Steven A. Banwart
- Global Food and Environment Institute, University of Leeds, LeedsLS2 9JT, United Kingdom
- School of Earth and Environment, University of Leeds, Leeds LS2 9JT, United Kingdom
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2
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Reershemius T, Kelland ME, Jordan JS, Davis IR, D'Ascanio R, Kalderon-Asael B, Asael D, Suhrhoff TJ, Epihov DZ, Beerling DJ, Reinhard CT, Planavsky NJ. Initial Validation of a Soil-Based Mass-Balance Approach for Empirical Monitoring of Enhanced Rock Weathering Rates. Environ Sci Technol 2023; 57:19497-19507. [PMID: 37961896 DOI: 10.1021/acs.est.3c03609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Enhanced rock weathering (ERW) is a promising scalable and cost-effective carbon dioxide removal (CDR) strategy with significant environmental and agronomic co-benefits. A major barrier to large-scale implementation of ERW is a robust monitoring, reporting, and verification (MRV) framework. To successfully quantify the amount of carbon dioxide removed by ERW, MRV must be accurate, precise, and cost-effective. Here, we outline a mass-balance-based method in which analysis of the chemical composition of soil samples is used to track in situ silicate rock weathering. We show that signal-to-noise issues of in situ soil analysis can be mitigated by using isotope-dilution mass spectrometry to reduce analytical error. We implement a proof-of-concept experiment demonstrating the method in controlled mesocosms. In our experiment, a basalt rock feedstock is added to soil columns containing the cereal crop Sorghum bicolor at a rate equivalent to 50 t ha-1. Using our approach, we calculate rock weathering corresponding to an average initial CDR value of 1.44 ± 0.27 tCO2eq ha-1 from our experiments after 235 days, within error of an independent estimate calculated using conventional elemental budgeting of reaction products. Our method provides a robust time-integrated estimate of initial CDR, to feed into models that track and validate large-scale carbon removal through ERW.
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Affiliation(s)
- Tom Reershemius
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut 06511, United States
| | - Mike E Kelland
- Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
| | - Jacob S Jordan
- Porecast Research, Lawrence, Kansas 66049, United States
| | - Isabelle R Davis
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut 06511, United States
- School of Ocean and Earth Science, University of Southampton Waterfront Campus, Southampton SO14 3ZH, U.K
| | - Rocco D'Ascanio
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut 06511, United States
| | - Boriana Kalderon-Asael
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut 06511, United States
| | - Dan Asael
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut 06511, United States
| | - T Jesper Suhrhoff
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut 06511, United States
- Yale Center for Natural Carbon Capture, Yale University, New Haven, Connecticut 06511, United States
| | - Dimitar Z Epihov
- Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
| | - David J Beerling
- Leverhulme Centre for Climate Change Mitigation, School of Biosciences, University of Sheffield, Sheffield S10 2TN, U.K
| | - Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Noah J Planavsky
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut 06511, United States
- Yale Center for Natural Carbon Capture, Yale University, New Haven, Connecticut 06511, United States
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3
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Anbar AD, Buick R, Gordon GW, Johnson AC, Kendall B, Lyons TW, Ostrander CM, Planavsky NJ, Reinhard CT, Stüeken EE. Technical comment on "Reexamination of 2.5-Ga 'whiff' of oxygen interval points to anoxic ocean before GOE". Sci Adv 2023; 9:eabq3736. [PMID: 37027472 PMCID: PMC10081836 DOI: 10.1126/sciadv.abq3736] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 03/03/2023] [Indexed: 06/19/2023]
Abstract
Many lines of inorganic geochemical evidence suggest transient "whiffs" of environmental oxygenation before the Great Oxidation Event (GOE). Slotznick et al. assert that analyses of paleoredox proxies in the Mount McRae Shale, Western Australia, were misinterpreted and hence that environmental O2 levels were persistently negligible before the GOE. We find these arguments logically flawed and factually incomplete.
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Affiliation(s)
- Ariel D. Anbar
- School of Earth and Space Exploration, Arizona State University. Tempe, AZ, USA
- School of Molecular Sciences, Arizona State University, Tempe, AZ, USA
| | - Roger Buick
- Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA
| | - Gwyneth W. Gordon
- School of Earth and Space Exploration, Arizona State University. Tempe, AZ, USA
| | | | - Brian Kendall
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON, Canada
| | - Timothy W. Lyons
- Department of Earth and Planetary Sciences, University of California Riverside, Riverside, CA, USA
| | - Chadlin M. Ostrander
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Falmouth, MA, USA
| | - Noah J. Planavsky
- Department of Earth and Planetary Sciences, Yale University, New Haven, CT, USA
| | - Christopher T. Reinhard
- Department of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Eva E. Stüeken
- School of Earth and Environmental Sciences, University of St. Andrews, Scotland, UK
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4
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Kanzaki Y, Planavsky NJ, Reinhard CT. New estimates of the storage permanence and ocean co-benefits of enhanced rock weathering. PNAS Nexus 2023; 2:pgad059. [PMID: 37096198 PMCID: PMC10122414 DOI: 10.1093/pnasnexus/pgad059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 01/26/2023] [Accepted: 02/06/2023] [Indexed: 04/26/2023]
Abstract
Avoiding many of the most severe consequences of anthropogenic climate change in the coming century will very likely require the development of "negative emissions technologies"-practices that lead to net carbon dioxide removal (CDR) from Earth's atmosphere. However, feedbacks within the carbon cycle place intrinsic limits on the long-term impact of CDR on atmospheric CO2 that are likely to vary across CDR technologies in ways that are poorly constrained. Here, we use an ensemble of Earth system models to provide new insights into the efficiency of CDR through enhanced rock weathering (ERW) by explicitly quantifying long-term storage of carbon in the ocean during ERW relative to an equivalent modulated emissions scenario. We find that although the backflux of CO2 to the atmosphere in the face of CDR is in all cases significant and time-varying, even for direct removal and underground storage, the leakage of initially captured carbon associated with ERW is well below that currently assumed. In addition, net alkalinity addition to the surface ocean from ERW leads to significant increases in seawater carbonate mineral saturation state relative to an equivalent emissions trajectory, a co-benefit for calcifying marine organisms. These results suggest that potential carbon leakage from the oceans during ERW is a small component of the overall ERW life cycle and that it can be rigorously quantified and incorporated into technoeconomic assessments of ERW at scale.
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Affiliation(s)
- Yoshiki Kanzaki
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30318, USA
| | - Noah J Planavsky
- Department of Earth and Planetary Sciences, Yale University, New Haven, CT 06511, USA
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5
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Planavsky NJ, Asael D, Rooney AD, Robbins LJ, Gill BC, Dehler CM, Cole DB, Porter SM, Love GD, Konhauser KO, Reinhard CT. A sedimentary record of the evolution of the global marine phosphorus cycle. Geobiology 2023; 21:168-174. [PMID: 36471206 DOI: 10.1111/gbi.12536] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 08/25/2022] [Accepted: 11/11/2022] [Indexed: 06/17/2023]
Abstract
Phosphorus (P) is typically considered to be the ultimate limiting nutrient for Earth's biosphere on geologic timescales. As P is monoisotopic, its sedimentary enrichment can provide some insights into how the marine P cycle has changed through time. A previous compilation of shale P enrichments argued for a significant change in P cycling during the Ediacaran Period (635-541 Ma). Here, using an updated P compilation-with more than twice the number of samples-we bolster the case that there was a significant transition in P cycling moving from the Precambrian into the Phanerozoic. However, our analysis suggests this state change may have occurred earlier than previously suggested. Specifically in the updated database, there is evidence for a transition ~35 million years before the onset of the Sturtian Snowball Earth glaciation in the Visingsö Group, potentially divorcing the climatic upheavals of the Neoproterozoic from changes in the Earth's P cycle. We attribute the transition in Earth's sedimentary P record to the onset of a more modern-like Earth system state characterized by less reducing marine conditions, higher marine P concentrations, and a greater predominance of eukaryotic organisms encompassing both primary producers and consumers. This view is consistent with organic biomarker evidence for a significant eukaryotic contribution to the preserved sedimentary organic matter in this succession and other contemporaneous Tonian marine sedimentary rocks. However, we stress that, even with an expanded dataset, we are likely far from pinpointing exactly when this transition occurred or whether Earth's history is characterized by a single or multiple transitions in the P cycle.
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Affiliation(s)
- Noah J Planavsky
- The Department of Earth & Planetary Sciences, Yale University, New Haven, Connecticut, USA
| | - Dan Asael
- The Department of Earth & Planetary Sciences, Yale University, New Haven, Connecticut, USA
| | - Alan D Rooney
- The Department of Earth & Planetary Sciences, Yale University, New Haven, Connecticut, USA
| | - Leslie J Robbins
- The Department of Earth & Planetary Sciences, Yale University, New Haven, Connecticut, USA
| | - Benjamin C Gill
- Department of Geosciences, Virginia Institute of Technology, Blacksburg, Virginia, USA
| | - Carol M Dehler
- Department of Geology, Utah State University, Logan, Utah, USA
| | - Devon B Cole
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Susannah M Porter
- Department of Earth Sciences, University of California, Santa Barbara, California, USA
| | - Gordon D Love
- Department of Earth Sciences, University of California, Riverside, California, USA
| | - Kurt O Konhauser
- Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
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6
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Abstract
The large-scale dynamics of ocean oxygenation have changed dramatically throughout Earth's history, in step with major changes in the abundance of O2 in the atmosphere and changes to marine nutrient availability. A comprehensive mechanistic understanding of this history requires insights from oceanography, marine geology, geochemistry, geomicrobiology, evolutionary ecology, and Earth system modeling. Here, we attempt to synthesize the major features of evolving ocean oxygenation on Earth through more than 3 billion years of planetary history. We review the fundamental first-order controls on ocean oxygen distribution and summarize the current understanding of the history of ocean oxygenation on Earth from empirical and theoretical perspectives-integrating geochemical reconstructions of oceanic and atmospheric chemistry, genomic constraints on evolving microbial metabolism, and mechanistic biogeochemical models. These changes are used to illustrate primary regimes of large-scale ocean oxygenation and to highlight feedbacks that can act to stabilize and destabilize the ocean-atmosphere system in anoxic, low-oxygen, and high-oxygen states.
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Affiliation(s)
- Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332, USA;
- Alternative Earths Team, Interdisciplinary Consortia for Astrobiology Research, National Aeronautics and Space Administration, Riverside, California 92521, USA
- Nexus for Exoplanet System Science (NExSS), National Aeronautics and Space Administration, Washington, DC 20546, USA
| | - Noah J Planavsky
- Alternative Earths Team, Interdisciplinary Consortia for Astrobiology Research, National Aeronautics and Space Administration, Riverside, California 92521, USA
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut 06511, USA
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7
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Johnson AC, Ostrander CM, Romaniello SJ, Reinhard CT, Greaney AT, Lyons TW, Anbar AD. Reconciling evidence of oxidative weathering and atmospheric anoxia on Archean Earth. Sci Adv 2021; 7:eabj0108. [PMID: 34586856 PMCID: PMC8480925 DOI: 10.1126/sciadv.abj0108] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 08/09/2021] [Indexed: 05/23/2023]
Abstract
Evidence continues to emerge for the production and low-level accumulation of molecular oxygen (O2) at Earth’s surface before the Great Oxidation Event. Quantifying this early O2 has proven difficult. Here, we use the distribution and isotopic composition of molybdenum in the ancient sedimentary record to quantify Archean Mo cycling, which allows us to calculate lower limits for atmospheric O2 partial pressures (PO2) and O2 production fluxes during the Archean. We consider two end-member scenarios. First, if O2 was evenly distributed throughout the atmosphere, then PO2 > 10–6.9 present atmospheric level was required for large periods of time during the Archean eon. Alternatively, if O2 accumulation was instead spatially restricted (e.g., occurring only near the sites of O2 production), then O2 production fluxes >0.01 Tmol O2/year were required. Archean O2 levels were vanishingly low according to our calculations but substantially above those predicted for an abiotic Earth system.
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Affiliation(s)
- Aleisha C. Johnson
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
- Department of Geophysical Sciences, University of Chicago, Chicago, IL, USA
| | - Chadlin M. Ostrander
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Stephen J. Romaniello
- Department of Earth and Planetary Sciences, University of Tennessee—Knoxville, Knoxville, TN, USA
| | | | | | - Timothy W. Lyons
- Department of Earth and Planetary Sciences, University of California, Riverside, Riverside, CA, USA
| | - Ariel D. Anbar
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
- School of Molecular Sciences, Arizona State University, Tempe, AZ, USA
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8
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Szeinbaum N, Toporek Y, Reinhard CT, Glass JB. Microbial helpers allow cyanobacteria to thrive in ferruginous waters. Geobiology 2021; 19:510-520. [PMID: 33871172 PMCID: PMC8349797 DOI: 10.1111/gbi.12443] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 03/15/2021] [Accepted: 03/28/2021] [Indexed: 06/12/2023]
Abstract
The Great Oxidation Event (GOE) was a rapid accumulation of oxygen in the atmosphere as a result of the photosynthetic activity of cyanobacteria. This accumulation reflected the pervasiveness of O2 on the planet's surface, indicating that cyanobacteria had become ecologically successful in Archean oceans. Micromolar concentrations of Fe2+ in Archean oceans would have reacted with hydrogen peroxide, a byproduct of oxygenic photosynthesis, to produce hydroxyl radicals, which cause cellular damage. Yet, cyanobacteria colonized Archean oceans extensively enough to oxygenate the atmosphere, which likely required protection mechanisms against the negative impacts of hydroxyl radical production in Fe2+ -rich seas. We identify several factors that could have acted to protect early cyanobacteria from the impacts of hydroxyl radical production and hypothesize that microbial cooperation may have played an important role in protecting cyanobacteria from Fe2+ toxicity before the GOE. We found that several strains of facultative anaerobic heterotrophic bacteria (Shewanella) with ROS defence mechanisms increase the fitness of cyanobacteria (Synechococcus) in ferruginous waters. Shewanella species with manganese transporters provided the most protection. Our results suggest that a tightly regulated response to prevent Fe2+ toxicity could have been important for the colonization of ancient ferruginous oceans, particularly in the presence of high manganese concentrations and may expand the upper bound for tolerable Fe2+ concentrations for cyanobacteria.
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Affiliation(s)
- Nadia Szeinbaum
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA
| | - Yael Toporek
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA
| | | | - Jennifer B. Glass
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA
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9
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Lyons TW, Diamond CW, Planavsky NJ, Reinhard CT, Li C. Oxygenation, Life, and the Planetary System during Earth's Middle History: An Overview. Astrobiology 2021; 21:906-923. [PMID: 34314605 PMCID: PMC8403206 DOI: 10.1089/ast.2020.2418] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The long history of life on Earth has unfolded as a cause-and-effect relationship with the evolving amount of oxygen (O2) in the oceans and atmosphere. Oxygen deficiency characterized our planet's first 2 billion years, yet evidence for biological O2 production and local enrichments in the surface ocean appear long before the first accumulations of O2 in the atmosphere roughly 2.4 to 2.3 billion years ago. Much has been written about this fundamental transition and the related balance between biological O2 production and sinks coupled to deep Earth processes that could buffer against the accumulation of biogenic O2. However, the relationship between complex life (eukaryotes, including animals) and later oxygenation is less clear. Some data suggest O2 was higher but still mostly low for another billion and a half years before increasing again around 800 million years ago, potentially setting a challenging course for complex life during its initial development and ecological expansion. The apparent rise in O2 around 800 million years ago is coincident with major developments in complex life. Multiple geochemical and paleontological records point to a major biogeochemical transition at that time, but whether rising and still dynamic biospheric oxygen triggered or merely followed from innovations in eukaryotic ecology, including the emergence of animals, is still debated. This paper focuses on the geochemical records of Earth's middle history, roughly 1.8 to 0.5 billion years ago, as a backdrop for exploring possible cause-and-effect relationships with biological evolution and the primary controls that may have set its pace, including solid Earth/tectonic processes, nutrient limitation, and their possible linkages. A richer mechanistic understanding of the interplay between coevolving life and Earth surface environments can provide a template for understanding and remotely searching for sustained habitability and even life on distant exoplanets.
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Affiliation(s)
- Timothy W. Lyons
- Department of Earth and Planetary Sciences, University of California, Riverside, California, USA
- Address correspondence to: Timothy W. Lyons, Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA
| | - Charles W. Diamond
- Department of Earth and Planetary Sciences, University of California, Riverside, California, USA
| | - Noah J. Planavsky
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut, USA
| | - Christopher T. Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Chao Li
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, China
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10
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Abstract
Atmospheric oxygen is thought to have played a vital role in the evolution of large, complex multicellular organisms. Challenging the prevailing theory, we show that the transition from an anaerobic to an aerobic world can strongly suppress the evolution of macroscopic multicellularity. Here we select for increased size in multicellular 'snowflake' yeast across a range of metabolically-available O2 levels. While yeast under anaerobic and high-O2 conditions evolved to be considerably larger, intermediate O2 constrained the evolution of large size. Through sequencing and synthetic strain construction, we confirm that this is due to O2-mediated divergent selection acting on organism size. We show via mathematical modeling that our results stem from nearly universal evolutionary and biophysical trade-offs, and thus should apply broadly. These results highlight the fact that oxygen is a double-edged sword: while it provides significant metabolic advantages, selection for efficient use of this resource may paradoxically suppress the evolution of macroscopic multicellular organisms.
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Affiliation(s)
- G. Ozan Bozdag
- grid.213917.f0000 0001 2097 4943School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA USA
| | - Eric Libby
- grid.12650.300000 0001 1034 3451Integrated Science Lab, Umeå University, Umeå, Sweden ,grid.12650.300000 0001 1034 3451Department of Mathematics and Mathematical Statistics, Umeå University, Umeå, Sweden ,grid.209665.e0000 0001 1941 1940Santa Fe Institute, Santa Fe, NM USA
| | - Rozenn Pineau
- grid.213917.f0000 0001 2097 4943School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA USA ,grid.213917.f0000 0001 2097 4943Interdisciplinary Graduate Program in Quantitative Biosciences, Georgia Institute of Technology, Georgia, USA
| | - Christopher T. Reinhard
- grid.213917.f0000 0001 2097 4943School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA USA ,NASA Astrobiology Institute, Alternative Earths Team, Riverside, CA USA
| | - William C. Ratcliff
- grid.213917.f0000 0001 2097 4943School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA USA ,NASA Astrobiology Institute, Reliving the Past Team, Atlanta, GA USA
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11
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Zhao M, Zhang S, Tarhan LG, Reinhard CT, Planavsky N. Publisher Correction: The role of calcium in regulating marine phosphorus burial and atmospheric oxygenation. Nat Commun 2020; 11:3046. [PMID: 32528111 PMCID: PMC7289855 DOI: 10.1038/s41467-020-16793-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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12
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Szeinbaum N, Nunn BL, Cavazos AR, Crowe SA, Stewart FJ, DiChristina TJ, Reinhard CT, Glass JB. Novel insights into the taxonomic diversity and molecular mechanisms of bacterial Mn(III) reduction. Environ Microbiol Rep 2020; 12:583-593. [PMID: 32613749 PMCID: PMC7775658 DOI: 10.1111/1758-2229.12867] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 06/27/2020] [Accepted: 06/29/2020] [Indexed: 05/23/2023]
Abstract
Soluble ligand-bound Mn(III) can support anaerobic microbial respiration in diverse aquatic environments. Thus far, Mn(III) reduction has only been associated with certain Gammaproteobacteria. Here, we characterized microbial communities enriched from Mn-replete sediments of Lake Matano, Indonesia. Our results provide the first evidence for the biological reduction of soluble Mn(III) outside the Gammaproteobacteria. Metagenome assembly and binning revealed a novel betaproteobacterium, which we designate 'Candidatus Dechloromonas occultata.' This organism dominated the enrichment and expressed a porin-cytochrome c complex typically associated with iron-oxidizing Betaproteobacteria and a novel cytochrome c-rich protein cluster (Occ), including an undecaheme putatively involved in extracellular electron transfer. This occ gene cluster was also detected in diverse aquatic bacteria, including uncultivated Betaproteobacteria from the deep subsurface. These observations provide new insight into the taxonomic and functional diversity of microbially driven Mn(III) reduction in natural environments.
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Affiliation(s)
- Nadia Szeinbaum
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- NASA Astrobiology Institute, Alternative Earths Team, Mountain View, CA, USA
| | - Brook L. Nunn
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Amanda R. Cavazos
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Sean A. Crowe
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
- Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada
| | - Frank J. Stewart
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Department of Microbiology and Immunology, Montana State University, Bozeman, MT, USA
| | | | - Christopher T. Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- NASA Astrobiology Institute, Alternative Earths Team, Mountain View, CA, USA
| | - Jennifer B. Glass
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- NASA Astrobiology Institute, Alternative Earths Team, Mountain View, CA, USA
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13
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Zhao M, Zhang S, Tarhan LG, Reinhard CT, Planavsky N. The role of calcium in regulating marine phosphorus burial and atmospheric oxygenation. Nat Commun 2020; 11:2232. [PMID: 32376824 PMCID: PMC7203231 DOI: 10.1038/s41467-020-15673-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 03/18/2020] [Indexed: 11/09/2022] Open
Abstract
The marine phosphorus cycle plays a critical role in controlling the extent of global primary productivity and thus atmospheric pO2 on geologic time scales. However, previous attempts to model carbon–phosphorus-oxygen feedbacks have neglected key parameters that could shape the global P cycle. Here we present new diagenetic models to fully parameterize marine P burial. We have also coupled this diagenetic framework to a global carbon cycle model. We find that seawater calcium concentration, by strongly influencing carbonate fluorapatite (CFA) formation, is a key factor controlling global phosphorus cycling, and therefore plays a critical role in shaping the global oxygen cycle. A compilation of Cenozoic deep-sea sedimentary phosphorus speciation data provides empirical support for the idea that CFA formation is strongly influenced by marine Ca concentrations. Therefore, we propose a previously overlooked coupling between Phanerozoic tectonic cycles, the major-element composition of seawater, the marine phosphorus cycle, and atmospheric pO2. Previous work suggests that marine oxygen levels and bioturbation are important factors that shape phosphorus burial and the size of the marine biosphere. Here the authors show that seawater calcium concentration is a key factor in controlling marine P burial, and thus the global oxygen cycle.
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Affiliation(s)
- Mingyu Zhao
- Department of Geology and Geophysics, Yale University, 210 Whitney Ave, New Haven, CT, 06511, USA.
| | - Shuang Zhang
- Department of Geology and Geophysics, Yale University, 210 Whitney Ave, New Haven, CT, 06511, USA
| | - Lidya G Tarhan
- Department of Geology and Geophysics, Yale University, 210 Whitney Ave, New Haven, CT, 06511, USA
| | - Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, GA, 30332, USA
| | - Noah Planavsky
- Department of Geology and Geophysics, Yale University, 210 Whitney Ave, New Haven, CT, 06511, USA.
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14
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Planavsky NJ, Reinhard CT, Isson TT, Ozaki K, Crockford PW. Large Mass-Independent Oxygen Isotope Fractionations in Mid-Proterozoic Sediments: Evidence for a Low-Oxygen Atmosphere? Astrobiology 2020; 20:628-636. [PMID: 32228301 DOI: 10.1089/ast.2019.2060] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Earth's ocean-atmosphere system has undergone a dramatic but protracted increase in oxygen (O2) abundance. This environmental transition ultimately paved the way for the rise of multicellular life and provides a blueprint for how a biosphere can transform a planetary surface. However, estimates of atmospheric oxygen levels for large intervals of Earth's history still vary by orders of magnitude-foremost for Earth's middle history. Historically, estimates of mid-Proterozoic (1.9-0.8 Ga) atmospheric oxygen levels are inferred based on the kinetics of reactions occurring in soils or in the oceans, rather than being directly tracked by atmospheric signatures. Rare oxygen isotope systematics-based on quantifying the rare oxygen isotope 17O in addition to the conventionally determined 16O and 18O-provide a means to track atmospheric isotopic signatures and thus potentially provide more direct estimates of atmospheric oxygen levels through time. Oxygen isotope signatures that deviate strongly from the expected mass-dependent relationship between 16O, 17O, and 18O develop during ozone formation, and these "mass-independent" signals can be transferred to the rock record during oxidation reactions in surface environments that involve atmospheric O2. The magnitude of these signals is dependent upon pO2, pCO2, and the overall extent of biospheric productivity. Here, we use a stochastic approach to invert the mid-Proterozoic Δ17O record for a new estimate of atmospheric pO2, leveraging explicit coupling of pO2 and biospheric productivity in a biogeochemical Earth system model to refine the range of atmospheric pO2 values that is consistent with a given observed Δ17O. Using this approach, we find new evidence that atmospheric oxygen levels were less than ∼1% of the present atmospheric level (PAL) for at least some intervals of the Proterozoic Eon.
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Affiliation(s)
- Noah J Planavsky
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut, USA
| | - Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Terry T Isson
- Environmental Research Institute, University of Waikato, Tauranga, New Zealand
| | - Kazumi Ozaki
- Department of Environmental Science, Toho University, Funabashi, Chiba, Japan
| | - Peter W Crockford
- Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, Israel
- Department of Geosciences, Princeton University, Princeton, New Jersey, USA
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15
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Cole DB, Mills DB, Erwin DH, Sperling EA, Porter SM, Reinhard CT, Planavsky NJ. On the co-evolution of surface oxygen levels and animals. Geobiology 2020; 18:260-281. [PMID: 32175670 DOI: 10.1111/gbi.12382] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 01/04/2020] [Accepted: 01/22/2020] [Indexed: 05/22/2023]
Abstract
Few topics in geobiology have been as extensively debated as the role of Earth's oxygenation in controlling when and why animals emerged and diversified. All currently described animals require oxygen for at least a portion of their life cycle. Therefore, the transition to an oxygenated planet was a prerequisite for the emergence of animals. Yet, our understanding of Earth's oxygenation and the environmental requirements of animal habitability and ecological success is currently limited; estimates for the timing of the appearance of environments sufficiently oxygenated to support ecologically stable populations of animals span a wide range, from billions of years to only a few million years before animals appear in the fossil record. In this light, the extent to which oxygen played an important role in controlling when animals appeared remains a topic of debate. When animals originated and when they diversified are separate questions, meaning either one or both of these phenomena could have been decoupled from oxygenation. Here, we present views from across this interpretive spectrum-in a point-counterpoint format-regarding crucial aspects of the potential links between animals and surface oxygen levels. We highlight areas where the standard discourse on this topic requires a change of course and note that several traditional arguments in this "life versus environment" debate are poorly founded. We also identify a clear need for basic research across a range of fields to disentangle the relationships between oxygen availability and emergence and diversification of animal life.
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Affiliation(s)
- Devon B Cole
- School of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, Georgia
| | - Daniel B Mills
- Department of Geological Sciences, Stanford University, Stanford, California
| | - Douglas H Erwin
- Department of Paleobiology, National Museum of Natural History, Washington, District of Columbia
- Santa Fe Institute, Santa Fe, New Mexico
| | - Erik A Sperling
- Department of Geological Sciences, Stanford University, Stanford, California
| | - Susannah M Porter
- Department of Earth Science, University of California Santa Barbara, Santa Barbara, California
| | - Christopher T Reinhard
- School of Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, Georgia
| | - Noah J Planavsky
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut
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16
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Reinhard CT, Planavsky NJ, Ward BA, Love GD, Le Hir G, Ridgwell A. The impact of marine nutrient abundance on early eukaryotic ecosystems. Geobiology 2020; 18:139-151. [PMID: 32065509 DOI: 10.1111/gbi.12384] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 11/05/2019] [Indexed: 06/10/2023]
Abstract
The rise of eukaryotes to ecological prominence represents one of the most dramatic shifts in the history of Earth's biosphere. However, there is an enigmatic temporal lag between the emergence of eukaryotic organisms in the fossil record and their much later ecological expansion. In parallel, there is evidence for a secular increase in the availability of the key macronutrient phosphorus (P) in Earth's oceans. Here, we use an Earth system model equipped with a size-structured marine ecosystem to explore relationships between plankton size, trophic complexity, and the availability of marine nutrients. We find a strong dependence of planktonic ecosystem structure on ocean nutrient abundance, with a larger ocean nutrient inventory leading to greater overall biomass, broader size spectra, and increasing abundance of large Zooplankton. If existing estimates of Proterozoic marine nutrient levels are correct, our results suggest that increases in the ecological impact of eukaryotic algae and trophic complexity in eukaryotic ecosystems were directly linked to restructuring of the global P cycle associated with the protracted rise of surface oxygen levels. Our results thus suggest an indirect but potentially important mechanism by which ocean oxygenation may have acted to shape marine ecological function during late Proterozoic time.
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Affiliation(s)
- Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
| | - Noah J Planavsky
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut
| | - Ben A Ward
- Ocean and Earth Science, University of Southampton, Southampton, UK
| | - Gordon D Love
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- Department of Earth and Planetary Sciences, University of California, Riverside, California
| | | | - Andy Ridgwell
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- Department of Earth and Planetary Sciences, University of California, Riverside, California
- School of Geographical Sciences, University of Bristol, Bristol, UK
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17
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Colwyn DA, Sheldon ND, Maynard JB, Gaines R, Hofmann A, Wang X, Gueguen B, Asael D, Reinhard CT, Planavsky NJ. A paleosol record of the evolution of Cr redox cycling and evidence for an increase in atmospheric oxygen during the Neoproterozoic. Geobiology 2019; 17:579-593. [PMID: 31436043 DOI: 10.1111/gbi.12360] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 07/05/2019] [Accepted: 07/29/2019] [Indexed: 06/10/2023]
Abstract
Atmospheric oxygen levels control the oxidative side of key biogeochemical cycles and place limits on the development of high-energy metabolisms. Understanding Earth's oxygenation is thus critical to developing a clearer picture of Earth's long-term evolution. However, there is currently vigorous debate about even basic aspects of the timing and pattern of the rise of oxygen. Chemical weathering in the terrestrial environment occurs in contact with the atmosphere, making paleosols potentially ideal archives to track the history of atmospheric O2 levels. Here we present stable chromium isotope data from multiple paleosols that offer snapshots of Earth surface conditions over the last three billion years. The results indicate a secular shift in the oxidative capacity of Earth's surface in the Neoproterozoic and suggest low atmospheric oxygen levels (<1% PAL pO2 ) through the majority of Earth's history. The paleosol record also shows that localized Cr oxidation may have begun as early as the Archean, but efficient, modern-like transport of hexavalent Cr under an O2 -rich atmosphere did not become common until the Neoproterozoic.
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Affiliation(s)
| | - Nathan D Sheldon
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
| | - J Barry Maynard
- Department of Geology, University of Cincinnati, Cincinnati, OH, USA
| | - Robert Gaines
- Geology Department, Pomona College, Claremont, CA, USA
| | - Axel Hofmann
- Department of Geology, University of Johannesburg, Johannesburg, South Africa
| | - Xiangli Wang
- Department of Geology and Geophysics, Yale University, New Haven, CT, USA
- Department of Marine Sciences, University of South Alabama, Mobile, AL, USA
- Dauphin Island Sea Lab, Dauphin Island, AL, USA
| | - Bleuenn Gueguen
- Department of Geology and Geophysics, Yale University, New Haven, CT, USA
- Institut Universitaire Européen de la Mer, CNRS UMS 3113, Université de Brest, Plouzané, France
| | - Dan Asael
- Department of Geology and Geophysics, Yale University, New Haven, CT, USA
| | - Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Noah J Planavsky
- Department of Geology and Geophysics, Yale University, New Haven, CT, USA
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18
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Thompson KJ, Kenward PA, Bauer KW, Warchola T, Gauger T, Martinez R, Simister RL, Michiels CC, Llirós M, Reinhard CT, Kappler A, Konhauser KO, Crowe SA. Photoferrotrophy, deposition of banded iron formations, and methane production in Archean oceans. Sci Adv 2019; 5:eaav2869. [PMID: 31807693 PMCID: PMC6881150 DOI: 10.1126/sciadv.aav2869] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 09/18/2019] [Indexed: 06/10/2023]
Abstract
Banded iron formation (BIF) deposition was the likely result of oxidation of ferrous iron in seawater by either oxygenic photosynthesis or iron-dependent anoxygenic photosynthesis-photoferrotrophy. BIF deposition, however, remains enigmatic because the photosynthetic biomass produced during iron oxidation is conspicuously absent from BIFs. We have addressed this enigma through experiments with photosynthetic bacteria and modeling of biogeochemical cycling in the Archean oceans. Our experiments reveal that, in the presence of silica, photoferrotroph cell surfaces repel iron (oxyhydr)oxides. In silica-rich Precambrian seawater, this repulsion would separate biomass from ferric iron and would lead to large-scale deposition of BIFs lean in organic matter. Excess biomass not deposited with BIF would have deposited in coastal sediments, formed organic-rich shales, and fueled microbial methanogenesis. As a result, the deposition of BIFs by photoferrotrophs would have contributed fluxes of methane to the atmosphere and thus helped to stabilize Earth's climate under a dim early Sun.
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Affiliation(s)
- Katharine J. Thompson
- Departments of Microbiology and Immunology and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Paul A. Kenward
- Departments of Microbiology and Immunology and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Kohen W. Bauer
- Departments of Microbiology and Immunology and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Tyler Warchola
- Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
| | - Tina Gauger
- Center for Applied Geosciences, University of Tuebingen, 72076 Tuebingen, Germany
| | - Raul Martinez
- Institut für Geo- und Umweltnaturwissenschaften, Albert-Ludwigs-Universität, Mineralogie-Geochemie, 79104 Freiburg, Germany
| | - Rachel L. Simister
- Departments of Microbiology and Immunology and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Céline C. Michiels
- Departments of Microbiology and Immunology and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Marc Llirós
- Department of Genetics and Microbiology, BioSciences Faculty, Universitat Autònoma de Barcelona, Catalunya, Spain
| | | | - Andreas Kappler
- Center for Applied Geosciences, University of Tuebingen, 72076 Tuebingen, Germany
| | - Kurt O. Konhauser
- Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
| | - Sean A. Crowe
- Departments of Microbiology and Immunology and Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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19
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Zaharescu DG, Burghelea CI, Dontsova K, Presler JK, Hunt EA, Domanik KJ, Amistadi MK, Sandhaus S, Munoz EN, Gaddis EE, Galey M, Vaquera-Ibarra MO, Palacios-Menendez MA, Castrejón-Martinez R, Roldán-Nicolau EC, Li K, Maier RM, Reinhard CT, Chorover J. Ecosystem-bedrock interaction changes nutrient compartmentalization during early oxidative weathering. Sci Rep 2019; 9:15006. [PMID: 31628373 PMCID: PMC6800431 DOI: 10.1038/s41598-019-51274-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 09/03/2019] [Indexed: 01/11/2023] Open
Abstract
Ecosystem-bedrock interactions power the biogeochemical cycles of Earth's shallow crust, supporting life, stimulating substrate transformation, and spurring evolutionary innovation. While oxidative processes have dominated half of terrestrial history, the relative contribution of the biosphere and its chemical fingerprints on Earth's developing regolith are still poorly constrained. Here, we report results from a two-year incipient weathering experiment. We found that the mass release and compartmentalization of major elements during weathering of granite, rhyolite, schist and basalt was rock-specific and regulated by ecosystem components. A tight interplay between physiological needs of different biota, mineral dissolution rates, and substrate nutrient availability resulted in intricate elemental distribution patterns. Biota accelerated CO2 mineralization over abiotic controls as ecosystem complexity increased, and significantly modified the stoichiometry of mobilized elements. Microbial and fungal components inhibited element leaching (23.4% and 7%), while plants increased leaching and biomass retention by 63.4%. All biota left comparable biosignatures in the dissolved weathering products. Nevertheless, the magnitude and allocation of weathered fractions under abiotic and biotic treatments provide quantitative evidence for the role of major biosphere components in the evolution of upper continental crust, presenting critical information for large-scale biogeochemical models and for the search for stable in situ biosignatures beyond Earth.
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Affiliation(s)
- Dragos G Zaharescu
- Department of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA.
- Alternative Earths Team, NASA Astrobiology Institute, University of California, Riverside, CA, USA.
- Biosphere 2, The University of Arizona, Tucson, AZ, USA.
| | | | - Katerina Dontsova
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
- Department of Environmental Science, The University of Arizona, Tucson, AZ, USA
| | | | - Edward A Hunt
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
| | - Kenneth J Domanik
- Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ, USA
| | - Mary K Amistadi
- Arizona Laboratory for Emerging Contaminants, The University of Arizona, Tucson, AZ, USA
| | - Shana Sandhaus
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
- Honor's College, The University of Arizona, Tucson, AZ, USA
| | - Elise N Munoz
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
- Honor's College, The University of Arizona, Tucson, AZ, USA
| | - Emily E Gaddis
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
- Williams College, Williamstown, MA, USA
| | - Miranda Galey
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
- Biology Department, The University of Minnesota, Duluth, MN, USA
| | - María O Vaquera-Ibarra
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
- University of the Americas Puebla, Puebla, Mexico
| | | | - Ricardo Castrejón-Martinez
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
- National Autonomous University of Mexico, Mexico City, Mexico
| | - Estefanía C Roldán-Nicolau
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
- National Autonomous University of Mexico, Mexico City, Mexico
| | - Kexin Li
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
- Department of Computer Sciences, University of Wisconsin-Madison, Madison, WI, USA
| | - Raina M Maier
- Department of Environmental Science, The University of Arizona, Tucson, AZ, USA
| | - Christopher T Reinhard
- Department of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Alternative Earths Team, NASA Astrobiology Institute, University of California, Riverside, CA, USA
| | - Jon Chorover
- Biosphere 2, The University of Arizona, Tucson, AZ, USA
- Department of Environmental Science, The University of Arizona, Tucson, AZ, USA
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20
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Ozaki K, Thompson KJ, Simister RL, Crowe SA, Reinhard CT. Anoxygenic photosynthesis and the delayed oxygenation of Earth's atmosphere. Nat Commun 2019; 10:3026. [PMID: 31289261 PMCID: PMC6616575 DOI: 10.1038/s41467-019-10872-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 05/28/2019] [Indexed: 12/03/2022] Open
Abstract
The emergence of oxygenic photosynthesis created a new niche with dramatic potential to transform energy flow through Earth's biosphere. However, more primitive forms of photosynthesis that fix CO2 into biomass using electrons from reduced species like Fe(II) and H2 instead of water would have competed with Earth's early oxygenic biosphere for essential nutrients. Here, we combine experimental microbiology, genomic analyses, and Earth system modeling to demonstrate that competition for light and nutrients in the surface ocean between oxygenic phototrophs and Fe(II)-oxidizing, anoxygenic photosynthesizers (photoferrotrophs) translates into diminished global photosynthetic O2 release when the ocean interior is Fe(II)-rich. These results provide a simple ecophysiological mechanism for inhibiting atmospheric oxygenation during Earth's early history. We also find a novel positive feedback within the coupled C-P-O-Fe cycles that can lead to runaway planetary oxygenation as rising atmospheric pO2 sweeps the deep ocean of the ferrous iron substrate for photoferrotrophy.
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Affiliation(s)
- Kazumi Ozaki
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, CA, USA
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, MD, 21046, USA
- Department of Environmental Science, Toho University, Funabashi, Chiba, 274-8510, Japan
| | - Katharine J Thompson
- Departments of Microbiology & Immunology and Earth, Ocean, & Atmospheric Sciences, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Rachel L Simister
- Departments of Microbiology & Immunology and Earth, Ocean, & Atmospheric Sciences, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Sean A Crowe
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
- Departments of Microbiology & Immunology and Earth, Ocean, & Atmospheric Sciences, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, CA, USA.
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21
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Ozaki K, Reinhard CT, Tajika E. A sluggish mid-Proterozoic biosphere and its effect on Earth's redox balance. Geobiology 2019; 17:3-11. [PMID: 30281196 PMCID: PMC6585969 DOI: 10.1111/gbi.12317] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 08/27/2018] [Indexed: 05/20/2023]
Abstract
The possibility of low but nontrivial atmospheric oxygen (O2 ) levels during the mid-Proterozoic (between 1.8 and 0.8 billion years ago, Ga) has important ramifications for understanding Earth's O2 cycle, the evolution of complex life and evolving climate stability. However, the regulatory mechanisms and redox fluxes required to stabilize these O2 levels in the face of continued biological oxygen production remain uncertain. Here, we develop a biogeochemical model of the C-N-P-O2 -S cycles and use it to constrain global redox balance in the mid-Proterozoic ocean-atmosphere system. By employing a Monte Carlo approach bounded by observations from the geologic record, we infer that the rate of net biospheric O2 production was 3 . 5 - 1.1 + 1.4 Tmol year-1 (1σ), or ~25% of today's value, owing largely to phosphorus scarcity in the ocean interior. Pyrite burial in marine sediments would have represented a comparable or more significant O2 source than organic carbon burial, implying a potentially important role for Earth's sulphur cycle in balancing the oxygen cycle and regulating atmospheric O2 levels. Our statistical approach provides a uniquely comprehensive view of Earth system biogeochemistry and global O2 cycling during mid-Proterozoic time and implicates severe P biolimitation as the backdrop for Precambrian geochemical and biological evolution.
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Affiliation(s)
- Kazumi Ozaki
- School of Earth and Atmospheric SciencesGeorgia Institute of TechnologyAtlantaGeorgia
- NASA Astrobiology InstituteAlternative Earths TeamMountain ViewCalifornia
- NASA Postdoctoral ProgramUniversities Space Research AssociationColumbiaMaryland
- Present address:
Department of Environmental ScienceToho UniversityChibaJapan
| | - Christopher T. Reinhard
- School of Earth and Atmospheric SciencesGeorgia Institute of TechnologyAtlantaGeorgia
- NASA Astrobiology InstituteAlternative Earths TeamMountain ViewCalifornia
| | - Eiichi Tajika
- Department of Earth and Planetary ScienceGraduate School of ScienceThe University of TokyoBunkyo‐kuJapan
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22
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Stanton CL, Reinhard CT, Kasting JF, Ostrom NE, Haslun JA, Lyons TW, Glass JB. Nitrous oxide from chemodenitrification: A possible missing link in the Proterozoic greenhouse and the evolution of aerobic respiration. Geobiology 2018; 16:597-609. [PMID: 30133143 DOI: 10.1111/gbi.12311] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 06/23/2018] [Accepted: 07/02/2018] [Indexed: 05/26/2023]
Abstract
The potent greenhouse gas nitrous oxide (N2 O) may have been an important constituent of Earth's atmosphere during Proterozoic (~2.5-0.5 Ga). Here, we tested the hypothesis that chemodenitrification, the rapid reduction of nitric oxide by ferrous iron, would have enhanced the flux of N2 O from ferruginous Proterozoic seas. We empirically derived a rate law, d N 2 O d t = 7.2 × 10 - 5 [ Fe 2 + ] 0.3 [ NO ] 1 , and measured an isotopic site preference of +16‰ for the reaction. Using this empirical rate law, and integrating across an oceanwide oxycline, we found that low nM NO and μM-low mM Fe2+ concentrations could have sustained a sea-air flux of 100-200 Tg N2 O-N year-1 , if N2 fixation rates were near-modern and all fixed N2 was emitted as N2 O. A 1D photochemical model was used to obtain steady-state atmospheric N2 O concentrations as a function of sea-air N2 O flux across the wide range of possible pO2 values (0.001-1 PAL). At 100-200 Tg N2 O-N year-1 and >0.1 PAL O2 , this model yielded low-ppmv N2 O, which would produce several degrees of greenhouse warming at 1.6 ppmv CH4 and 320 ppmv CO2 . These results suggest that enhanced N2 O production in ferruginous seawater via a previously unconsidered chemodenitrification pathway may have helped to fill a Proterozoic "greenhouse gap," reconciling an ice-free Mesoproterozoic Earth with a less luminous early Sun. A particularly notable result was that high N2 O fluxes at intermediate O2 concentrations (0.01-0.1 PAL) would have enhanced ozone screening of solar UV radiation. Due to rapid photolysis in the absence of an ozone shield, N2 O is unlikely to have been an important greenhouse gas if Mesoproterozoic O2 was 0.001 PAL. At low O2 , N2 O might have played a more important role as life's primary terminal electron acceptor during the transition from an anoxic to oxic surface Earth, and correspondingly, from anaerobic to aerobic metabolisms.
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Affiliation(s)
- Chloe L Stanton
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
- Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania
| | - Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - James F Kasting
- Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania
| | - Nathaniel E Ostrom
- Department of Integrative Biology, Michigan State University, East Lansing, Michigan
- DOE Great Lakes Bioenergy Research Institute, Michigan State University, East Lansing, Michigan
| | - Joshua A Haslun
- Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan
| | - Timothy W Lyons
- Department of Earth Sciences, University of California, Riverside, California
| | - Jennifer B Glass
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
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23
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Bellefroid EJ, Hood AVS, Hoffman PF, Thomas MD, Reinhard CT, Planavsky NJ. Constraints on Paleoproterozoic atmospheric oxygen levels. Proc Natl Acad Sci U S A 2018; 115:8104-8109. [PMID: 30038009 PMCID: PMC6094116 DOI: 10.1073/pnas.1806216115] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The oxygenation of Earth's surface environment dramatically altered key biological and geochemical cycles and ultimately ushered in the rise of an ecologically diverse biosphere. However, atmospheric oxygen partial pressures (pO2) estimates for large swaths of the Precambrian remain intensely debated. Here we evaluate and explore the use of carbonate cerium (Ce) anomalies (Ce/Ce*) as a quantitative atmospheric pO2 proxy and provide estimates of Proterozoic pO2 using marine carbonates from a unique Precambrian carbonate succession-the Paleoproterozoic Pethei Group. In contrast to most previous work, we measure Ce/Ce* on marine carbonate precipitates that formed in situ across a depth gradient, building on previous detailed sedimentology and stratigraphy to constrain the paleo-depth of each sample. Measuring Ce/Ce* across a full platform to basin depth gradient, we found only minor depleted Ce anomalies restricted to the platform and upper slope facies. We combine these results with a Ce oxidation model to provide a quantitative constraint on atmospheric pO2 1.87 billion years ago (Ga). Our results suggest Paleoproterozoic atmospheric oxygen concentrations were low, near 0.1% of the present atmospheric level. This work provides another crucial line of empirical evidence that atmospheric oxygen levels returned to low concentrations following the Lomagundi Event, and remained low enough for large portions of the Proterozoic to have impacted the ecology of the earliest complex organisms.
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Affiliation(s)
- Eric J Bellefroid
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511;
| | - Ashleigh V S Hood
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511
| | - Paul F Hoffman
- School of Earth and Ocean Sciences, University of Victoria, Victoria, BC, V8P 3E6 Canada;
| | - Matthew D Thomas
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511
| | - Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Tech, Atlanta, GA 30332
- NASA Astrobiology Institute Alternative Earths Team, University of California, Riverside, CA, 92521
| | - Noah J Planavsky
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511
- NASA Astrobiology Institute Alternative Earths Team, University of California, Riverside, CA, 92521
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24
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Isson TT, Love GD, Dupont CL, Reinhard CT, Zumberge AJ, Asael D, Gueguen B, McCrow J, Gill BC, Owens J, Rainbird RH, Rooney AD, Zhao MY, Stueeken EE, Konhauser KO, John SG, Lyons TW, Planavsky NJ. Tracking the rise of eukaryotes to ecological dominance with zinc isotopes. Geobiology 2018; 16:341-352. [PMID: 29869832 DOI: 10.1111/gbi.12289] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Accepted: 03/31/2018] [Indexed: 05/19/2023]
Abstract
The biogeochemical cycling of zinc (Zn) is intimately coupled with organic carbon in the ocean. Based on an extensive new sedimentary Zn isotope record across Earth's history, we provide evidence for a fundamental shift in the marine Zn cycle ~800 million years ago. We discuss a wide range of potential drivers for this transition and propose that, within available constraints, a restructuring of marine ecosystems is the most parsimonious explanation for this shift. Using a global isotope mass balance approach, we show that a change in the organic Zn/C ratio is required to account for observed Zn isotope trends through time. Given the higher affinity of eukaryotes for Zn relative to prokaryotes, we suggest that a shift toward a more eukaryote-rich ecosystem could have provided a means of more efficiently sequestering organic-derived Zn. Despite the much earlier appearance of eukaryotes in the microfossil record (~1700 to 1600 million years ago), our data suggest a delayed rise to ecological prominence during the Neoproterozoic, consistent with the currently accepted organic biomarker records.
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Affiliation(s)
- Terry T Isson
- Geology and Geophysics, Yale University, New Haven, Connecticut
| | - Gordon D Love
- Earth Science, University of California, Riverside, Riverside, California
| | - Christopher L Dupont
- Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, California
| | | | - Alex J Zumberge
- Earth Science, University of California, Riverside, Riverside, California
| | - Dan Asael
- Geology and Geophysics, Yale University, New Haven, Connecticut
| | - Bleuenn Gueguen
- Earth Science, Université de Bretagne Occidentale, Brest, France
| | - John McCrow
- J. Craig Venter Institute, Rockville, Maryland
| | - Ben C Gill
- Geosciences, Virginia Tech, Blacksburg, Virginia
| | | | | | - Alan D Rooney
- Geology and Geophysics, Yale University, New Haven, Connecticut
| | - Ming-Yu Zhao
- Geology and Geophysics, Yale University, New Haven, Connecticut
| | - Eva E Stueeken
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, Scotland, UK
| | - Kurt O Konhauser
- Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada
| | - Seth G John
- Earth Science, University of Southern Carolina, Los Angeles, California
| | - Timothy W Lyons
- Earth Science, University of California, Riverside, Riverside, California
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25
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Walker SI, Bains W, Cronin L, DasSarma S, Danielache S, Domagal-Goldman S, Kacar B, Kiang NY, Lenardic A, Reinhard CT, Moore W, Schwieterman EW, Shkolnik EL, Smith HB. Exoplanet Biosignatures: Future Directions. Astrobiology 2018; 18:779-824. [PMID: 29938538 PMCID: PMC6016573 DOI: 10.1089/ast.2017.1738] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 03/13/2018] [Indexed: 05/08/2023]
Abstract
We introduce a Bayesian method for guiding future directions for detection of life on exoplanets. We describe empirical and theoretical work necessary to place constraints on the relevant likelihoods, including those emerging from better understanding stellar environment, planetary climate and geophysics, geochemical cycling, the universalities of physics and chemistry, the contingencies of evolutionary history, the properties of life as an emergent complex system, and the mechanisms driving the emergence of life. We provide examples for how the Bayesian formalism could guide future search strategies, including determining observations to prioritize or deciding between targeted searches or larger lower resolution surveys to generate ensemble statistics and address how a Bayesian methodology could constrain the prior probability of life with or without a positive detection. Key Words: Exoplanets-Biosignatures-Life detection-Bayesian analysis. Astrobiology 18, 779-824.
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Affiliation(s)
- Sara I. Walker
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
- Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, Arizona
- ASU-Santa Fe Institute Center for Biosocial Complex Systems, Arizona State University, Tempe, Arizona
- Blue Marble Space Institute of Science, Seattle, Washington
| | - William Bains
- EAPS (Earth, Atmospheric and Planetary Science), MIT, Cambridge, Massachusetts
- Rufus Scientific Ltd., Royston, United Kingdom
| | - Leroy Cronin
- School of Chemistry, University of Glasgow, Glasgow, United Kingdom
| | - Shiladitya DasSarma
- Department of Microbiology and Immunology, Institute of Marine and Environmental Technology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Sebastian Danielache
- Department of Materials and Life Science, Faculty of Science and Technology, Sophia University, Tokyo, Japan
- Earth Life Institute, Tokyo Institute of Technology, Tokyo, Japan
| | - Shawn Domagal-Goldman
- NASA Goddard Space Flight Center, Greenbelt, Maryland
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, University of Washington, Seattle, Washington
| | - Betul Kacar
- Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts
- NASA Astrobiology Institute, Reliving the Past Team, University of Montana, Missoula, Montana
- Department of Molecular and Cell Biology, University of Arizona, Tucson, Arizona
- Department of Astronomy and Steward Observatory, University of Arizona, Tucson, Arizona
| | - Nancy Y. Kiang
- NASA Goddard Institute for Space Studies, New York, New York
| | - Adrian Lenardic
- Department of Earth Science, Rice University, Houston, Texas
| | - Christopher T. Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
- NASA Astrobiology Institute, Alternative Earths Team, University of California, Riverside, California
| | - William Moore
- Department of Atmospheric and Planetary Sciences, Hampton University, Hampton, Virginia
- National Institute of Aerospace, Hampton, Virginia
| | - Edward W. Schwieterman
- Blue Marble Space Institute of Science, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Alternative Earths Team, University of California, Riverside, California
- Department of Earth Sciences, University of California, Riverside, California
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
| | - Evgenya L. Shkolnik
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
| | - Harrison B. Smith
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
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26
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Schwieterman EW, Kiang NY, Parenteau MN, Harman CE, DasSarma S, Fisher TM, Arney GN, Hartnett HE, Reinhard CT, Olson SL, Meadows VS, Cockell CS, Walker SI, Grenfell JL, Hegde S, Rugheimer S, Hu R, Lyons TW. Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life. Astrobiology 2018; 18:663-708. [PMID: 29727196 PMCID: PMC6016574 DOI: 10.1089/ast.2017.1729] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 12/10/2017] [Indexed: 05/04/2023]
Abstract
In the coming years and decades, advanced space- and ground-based observatories will allow an unprecedented opportunity to probe the atmospheres and surfaces of potentially habitable exoplanets for signatures of life. Life on Earth, through its gaseous products and reflectance and scattering properties, has left its fingerprint on the spectrum of our planet. Aided by the universality of the laws of physics and chemistry, we turn to Earth's biosphere, both in the present and through geologic time, for analog signatures that will aid in the search for life elsewhere. Considering the insights gained from modern and ancient Earth, and the broader array of hypothetical exoplanet possibilities, we have compiled a comprehensive overview of our current understanding of potential exoplanet biosignatures, including gaseous, surface, and temporal biosignatures. We additionally survey biogenic spectral features that are well known in the specialist literature but have not yet been robustly vetted in the context of exoplanet biosignatures. We briefly review advances in assessing biosignature plausibility, including novel methods for determining chemical disequilibrium from remotely obtainable data and assessment tools for determining the minimum biomass required to maintain short-lived biogenic gases as atmospheric signatures. We focus particularly on advances made since the seminal review by Des Marais et al. The purpose of this work is not to propose new biosignature strategies, a goal left to companion articles in this series, but to review the current literature, draw meaningful connections between seemingly disparate areas, and clear the way for a path forward. Key Words: Exoplanets-Biosignatures-Habitability markers-Photosynthesis-Planetary surfaces-Atmospheres-Spectroscopy-Cryptic biospheres-False positives. Astrobiology 18, 663-708.
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Affiliation(s)
- Edward W. Schwieterman
- Department of Earth Sciences, University of California, Riverside, California
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- Blue Marble Space Institute of Science, Seattle, Washington
| | - Nancy Y. Kiang
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Goddard Institute for Space Studies, New York, New York
| | - Mary N. Parenteau
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Ames Research Center, Exobiology Branch, Mountain View, California
| | - Chester E. Harman
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Goddard Institute for Space Studies, New York, New York
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York
| | - Shiladitya DasSarma
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland
- Institute of Marine and Environmental Technology, University System of Maryland, Baltimore, Maryland
| | - Theresa M. Fisher
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
| | - Giada N. Arney
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland
| | - Hilairy E. Hartnett
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
- School of Molecular Sciences, Arizona State University, Tempe, Arizona
| | - Christopher T. Reinhard
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Stephanie L. Olson
- Department of Earth Sciences, University of California, Riverside, California
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
| | - Victoria S. Meadows
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- Astronomy Department, University of Washington, Seattle, Washington
| | - Charles S. Cockell
- University of Edinburgh School of Physics and Astronomy, Edinburgh, United Kingdom
- UK Centre for Astrobiology, Edinburgh, United Kingdom
| | - Sara I. Walker
- Blue Marble Space Institute of Science, Seattle, Washington
- School of Earth and Space Exploration, Arizona State University, Tempe, Arizona
- Beyond Center for Fundamental Concepts in Science, Arizona State University, Tempe, Arizona
- ASU-Santa Fe Institute Center for Biosocial Complex Systems, Arizona State University, Tempe, Arizona
| | - John Lee Grenfell
- Institut für Planetenforschung (PF), Deutsches Zentrum für Luft und Raumfahrt (DLR), Berlin, Germany
| | - Siddharth Hegde
- Carl Sagan Institute, Cornell University, Ithaca, New York
- Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, New York
| | - Sarah Rugheimer
- Department of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, United Kingdom
| | - Renyu Hu
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California
| | - Timothy W. Lyons
- Department of Earth Sciences, University of California, Riverside, California
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
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27
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Meadows VS, Reinhard CT, Arney GN, Parenteau MN, Schwieterman EW, Domagal-Goldman SD, Lincowski AP, Stapelfeldt KR, Rauer H, DasSarma S, Hegde S, Narita N, Deitrick R, Lustig-Yaeger J, Lyons TW, Siegler N, Grenfell JL. Exoplanet Biosignatures: Understanding Oxygen as a Biosignature in the Context of Its Environment. Astrobiology 2018; 18:630-662. [PMID: 29746149 PMCID: PMC6014580 DOI: 10.1089/ast.2017.1727] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 12/15/2017] [Indexed: 05/04/2023]
Abstract
We describe how environmental context can help determine whether oxygen (O2) detected in extrasolar planetary observations is more likely to have a biological source. Here we provide an in-depth, interdisciplinary example of O2 biosignature identification and observation, which serves as the prototype for the development of a general framework for biosignature assessment. Photosynthetically generated O2 is a potentially strong biosignature, and at high abundance, it was originally thought to be an unambiguous indicator for life. However, as a biosignature, O2 faces two major challenges: (1) it was only present at high abundance for a relatively short period of Earth's history and (2) we now know of several potential planetary mechanisms that can generate abundant O2 without life being present. Consequently, our ability to interpret both the presence and absence of O2 in an exoplanetary spectrum relies on understanding the environmental context. Here we examine the coevolution of life with the early Earth's environment to identify how the interplay of sources and sinks may have suppressed O2 release into the atmosphere for several billion years, producing a false negative for biologically generated O2. These studies suggest that planetary characteristics that may enhance false negatives should be considered when selecting targets for biosignature searches. We review the most recent knowledge of false positives for O2, planetary processes that may generate abundant atmospheric O2 without a biosphere. We provide examples of how future photometric, spectroscopic, and time-dependent observations of O2 and other aspects of the planetary environment can be used to rule out false positives and thereby increase our confidence that any observed O2 is indeed a biosignature. These insights will guide and inform the development of future exoplanet characterization missions. Key Words: Biosignatures-Oxygenic photosynthesis-Exoplanets-Planetary atmospheres. Astrobiology 18, 630-662.
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Affiliation(s)
- Victoria S. Meadows
- Department of Astronomy, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
| | - Christopher T. Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
| | - Giada N. Arney
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- Planetary Systems Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland
| | - Mary N. Parenteau
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Ames Research Center, Exobiology Branch, Mountain View, California
| | - Edward W. Schwieterman
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- Department of Earth Sciences, University of California, Riverside, California
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
- Blue Marble Space Institute of Science, Seattle, Washington
| | - Shawn D. Domagal-Goldman
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
- Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland
| | - Andrew P. Lincowski
- Department of Astronomy, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
| | - Karl R. Stapelfeldt
- NASA Exoplanet Exploration Program, Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California
| | - Heike Rauer
- German Aerospace Center, Institute of Planetary Research, Extrasolar Planets and Atmospheres, Berlin, Germany
| | - Shiladitya DasSarma
- Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, Maryland
- Institute of Marine and Environmental Technology, University System of Baltimore, Maryland
| | - Siddharth Hegde
- Carl Sagan Institute, Cornell University, Ithaca, New York
- Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, New York
| | - Norio Narita
- Department of Astronomy, The University of Tokyo, Tokyo, Japan
- Astrobiology Center, NINS, Tokyo, Japan
- National Astronomical Observatory of Japan, NINS, Tokyo, Japan
| | - Russell Deitrick
- Department of Astronomy, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
| | - Jacob Lustig-Yaeger
- Department of Astronomy, University of Washington, Seattle, Washington
- NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington
| | - Timothy W. Lyons
- NASA Astrobiology Institute, Alternative Earths Team, Riverside, California
- Department of Earth Sciences, University of California, Riverside, California
| | - Nicholas Siegler
- NASA Exoplanet Exploration Program, Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California
| | - J. Lee Grenfell
- German Aerospace Center, Institute of Planetary Research, Extrasolar Planets and Atmospheres, Berlin, Germany
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28
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Saad EM, Wang X, Planavsky NJ, Reinhard CT, Tang Y. Redox-independent chromium isotope fractionation induced by ligand-promoted dissolution. Nat Commun 2017; 8:1590. [PMID: 29150598 PMCID: PMC5693864 DOI: 10.1038/s41467-017-01694-y] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 10/09/2017] [Indexed: 11/24/2022] Open
Abstract
The chromium (Cr) isotope system has emerged as a potential proxy for tracing the Earth’s atmospheric evolution based on a redox-dependent framework for Cr mobilization and isotope fractionation. Although studies have demonstrated that redox-independent pathways can also mobilize Cr, no quantitative constraints exist on the associated isotope fractionations. Here we survey the effects of common environmental ligands on the dissolution of Cr(III)-(oxy)hydroxide solids and associated Cr isotope fractionation. For a variety of organic acids and siderophores, δ53Cr values of dissolved Cr(III) are −0.27 to 1.23‰, within the range of previously observed Cr isotope signatures in rock records linked to Cr redox cycling. Thus, ligand-promoted dissolution of Cr-containing solids, a redox-independent process, must be taken into account when using sedimentary Cr isotope signatures to diagnose atmospheric oxygen levels. This work provides a step towards establishing a more robust framework for using Cr isotopes to track the evolution of the Earth’s atmosphere. The chromium (Cr) isotope system has emerged as a potential proxy for tracing Earth’s atmospheric evolution based on a redox-dependent framework. Here the authors show that ligand-complexation, a redox-independent process, must be considered when using Cr isotope signatures to diagnose atmospheric oxygen levels.
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Affiliation(s)
- Emily M Saad
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Xiangli Wang
- Department of Geology and Geophysics, Yale University, New Haven, CT, 06511, USA
| | - Noah J Planavsky
- Department of Geology and Geophysics, Yale University, New Haven, CT, 06511, USA
| | - Christopher T Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Yuanzhi Tang
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA.
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29
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Reinhard CT, Olson SL, Schwieterman EW, Lyons TW. False Negatives for Remote Life Detection on Ocean-Bearing Planets: Lessons from the Early Earth. Astrobiology 2017; 17:287-297. [PMID: 28418704 PMCID: PMC5399744 DOI: 10.1089/ast.2016.1598] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 01/23/2017] [Indexed: 05/04/2023]
Abstract
Ocean-atmosphere chemistry on Earth has undergone dramatic evolutionary changes throughout its long history, with potentially significant ramifications for the emergence and long-term stability of atmospheric biosignatures. Though a great deal of work has centered on refining our understanding of false positives for remote life detection, much less attention has been paid to the possibility of false negatives, that is, cryptic biospheres that are widespread and active on a planet's surface but are ultimately undetectable or difficult to detect in the composition of a planet's atmosphere. Here, we summarize recent developments from geochemical proxy records and Earth system models that provide insight into the long-term evolution of the most readily detectable potential biosignature gases on Earth-oxygen (O2), ozone (O3), and methane (CH4). We suggest that the canonical O2-CH4 disequilibrium biosignature would perhaps have been challenging to detect remotely during Earth's ∼4.5-billion-year history and that in general atmospheric O2/O3 levels have been a poor proxy for the presence of Earth's biosphere for all but the last ∼500 million years. We further suggest that detecting atmospheric CH4 would have been problematic for most of the last ∼2.5 billion years of Earth's history. More broadly, we stress that internal oceanic recycling of biosignature gases will often render surface biospheres on ocean-bearing silicate worlds cryptic, with the implication that the planets most conducive to the development and maintenance of a pervasive biosphere will often be challenging to characterize via conventional atmospheric biosignatures. Key Words: Biosignatures-Oxygen-Methane-Ozone-Exoplanets-Planetary habitability. Astrobiology 17, 287-297.
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Affiliation(s)
- Christopher T. Reinhard
- NASA Astrobiology Institute
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Stephanie L. Olson
- NASA Astrobiology Institute
- Department of Earth Sciences, University of California, Riverside, California
| | - Edward W. Schwieterman
- NASA Astrobiology Institute
- Department of Earth Sciences, University of California, Riverside, California
- NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland
- Blue Marble Space Institute of Science, Seattle, Washington
| | - Timothy W. Lyons
- NASA Astrobiology Institute
- Department of Earth Sciences, University of California, Riverside, California
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30
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Abstract
The redox landscape of Earth's ocean-atmosphere system has changed dramatically throughout Earth history. Although Earth's protracted oxygenation is undoubtedly the consequence of cyanobacterial oxygenic photosynthesis, the relationship between biological O2 production and Earth's redox evolution remains poorly understood. Existing models for Earth's oxygenation cannot adequately explain the nearly 2.5 billion years delay between the origin of oxygenic photosynthesis and the oxygenation of the deep ocean, in large part owing to major deficiencies in our understanding of the coevolution of O2 and Earth's key biogeochemical cycles (e.g., the N cycle). For example, although possible links between O2 and N scarcity have been previously explored, the consequences of N2 limitation for net biological O2 production have not been examined thoroughly. Here, we revisit the prevailing view that N2 fixation has always been able to keep pace with P supply and discuss the possibility that bioavailable N, rather than P, limited export production for extended periods of Earth's history. Based on the observation that diazotrophy occurs at the expense of oxygenesis in the modern ocean, we suggest that an N-limited biosphere may be inherently less oxygenic than a P-limited biosphere-and that cyanobacterial diazotrophy was a primary control on the timing and tempo of Earth's oxygenation by modulating net biogenic O2 fluxes. We further hypothesize that negative feedbacks inhibit the transition between N and P limitation, with the implication that the pervasive accumulation of O2 in Earth's ocean-atmosphere system may not have been an inevitable consequence of oxygenic photosynthesis by marine cyanobacteria.
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Affiliation(s)
- Stephanie L. Olson
- Department of Earth Sciences, University of California, Riverside, Riverside, CAUSA
| | | | - Timothy W. Lyons
- Department of Earth Sciences, University of California, Riverside, Riverside, CAUSA
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Kendall B, Creaser RA, Reinhard CT, Lyons TW, Anbar AD. Transient episodes of mild environmental oxygenation and oxidative continental weathering during the late Archean. Sci Adv 2015; 1:e1500777. [PMID: 26702438 PMCID: PMC4681338 DOI: 10.1126/sciadv.1500777] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 10/16/2015] [Indexed: 05/18/2023]
Abstract
It is not known whether environmental O2 levels increased in a linear fashion or fluctuated dynamically between the evolution of oxygenic photosynthesis and the later Great Oxidation Event. New rhenium-osmium isotope data from the late Archean Mount McRae Shale, Western Australia, reveal a transient episode of oxidative continental weathering more than 50 million years before the onset of the Great Oxidation Event. A depositional age of 2495 ± 14 million years and an initial (187)Os/(188)Os of 0.34 ± 0.19 were obtained for rhenium- and molybdenum-rich black shales. The initial (187)Os/(188)Os is higher than the mantle/extraterrestrial value of 0.11, pointing to mild environmental oxygenation and oxidative mobilization of rhenium, molybdenum, and radiogenic osmium from the upper continental crust and to contemporaneous transport of these metals to seawater. By contrast, stratigraphically overlying black shales are rhenium- and molybdenum-poor and have a mantle-like initial (187)Os/(188)Os of 0.06 ± 0.09, indicating a reduced continental flux of rhenium, molybdenum, and osmium to seawater because of a drop in environmental O2 levels. Transient oxygenation events, like the one captured by the Mount McRae Shale, probably separated intervals of less oxygenated conditions during the late Archean.
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Affiliation(s)
- Brian Kendall
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
- Corresponding author. E-mail:
| | - Robert A. Creaser
- Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
| | - Christopher T. Reinhard
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Timothy W. Lyons
- Department of Earth Sciences, University of California, Riverside, Riverside, CA 92521, USA
| | - Ariel D. Anbar
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA
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Planavsky NJ, Reinhard CT, Wang X, Thomson D, McGoldrick P, Rainbird RH, Johnson T, Fischer WW, Lyons TW. Earth history. Low mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals. Science 2014; 346:635-8. [PMID: 25359975 DOI: 10.1126/science.1258410] [Citation(s) in RCA: 180] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The oxygenation of Earth's surface fundamentally altered global biogeochemical cycles and ultimately paved the way for the rise of metazoans at the end of the Proterozoic. However, current estimates for atmospheric oxygen (O2) levels during the billion years leading up to this time vary widely. On the basis of chromium (Cr) isotope data from a suite of Proterozoic sediments from China, Australia, and North America, interpreted in the context of data from similar depositional environments from Phanerozoic time, we find evidence for inhibited oxidation of Cr at Earth's surface in the mid-Proterozoic (1.8 to 0.8 billion years ago). These data suggest that atmospheric O2 levels were at most 0.1% of present atmospheric levels. Direct evidence for such low O2 concentrations in the Proterozoic helps explain the late emergence and diversification of metazoans.
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Affiliation(s)
| | | | - Xiangli Wang
- Department Geology and Geophysics, Yale University, CT, USA. Department of Geology, University of Illinois, Champaign, IL, USA
| | - Danielle Thomson
- Department of Earth Science, Carleton University, Ottawa, ON, Canada
| | - Peter McGoldrick
- Centre for Ore Deposit and Exploration Science, University of Tasmania, TAS, Australia
| | | | - Thomas Johnson
- Department of Geology, University of Illinois, Champaign, IL, USA
| | - Woodward W Fischer
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
| | - Timothy W Lyons
- Department of Earth Sciences, University of California, Riverside, CA, USA
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Lyons TW, Reinhard CT, Planavsky NJ. The rise of oxygen in Earth’s early ocean and atmosphere. Nature 2014; 506:307-15. [DOI: 10.1038/nature13068] [Citation(s) in RCA: 1516] [Impact Index Per Article: 151.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 01/21/2014] [Indexed: 11/09/2022]
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Planavsky NJ, McGoldrick P, Scott CT, Li C, Reinhard CT, Kelly AE, Chu X, Bekker A, Love GD, Lyons TW. Widespread iron-rich conditions in the mid-Proterozoic ocean. Nature 2011; 477:448-51. [DOI: 10.1038/nature10327] [Citation(s) in RCA: 322] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Accepted: 06/23/2011] [Indexed: 11/09/2022]
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Abstract
Iron speciation data for the late Archean Mount McRae Shale provide evidence for a euxinic (anoxic and sulfidic) water column 2.5 billion years ago. Sulfur isotope data compiled from the same stratigraphic section suggest that euxinic conditions were stimulated by an increase in oceanic sulfate concentrations resulting from weathering of continental sulfide minerals exposed to an atmosphere with trace amounts of photosynthetically produced oxygen. Variability in local organic matter flux likely confined euxinic conditions to midportions of the water column on the basin margin. These findings indicate that euxinic conditions may have been common on a variety of spatial and temporal scales both before and immediately after the Paleoproterozoic rise in atmospheric oxygen, hinting at previously unexplored texture and variability in deep ocean chemistry during Earth's early history.
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Affiliation(s)
- Christopher T Reinhard
- University of California-Riverside, Department of Earth Sciences, Riverside, CA 92521, USA
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