1
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Anderson RP, Mughal S, Wedlake GO. Proterozoic microfossils continue to provide new insights into the rise of complex eukaryotic life. ROYAL SOCIETY OPEN SCIENCE 2024; 11:240154. [PMID: 39170929 PMCID: PMC11336685 DOI: 10.1098/rsos.240154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 07/11/2024] [Accepted: 07/12/2024] [Indexed: 08/23/2024]
Abstract
Eukaryotes have evolved to dominate the biosphere today, accounting for most documented living species and the vast majority of the Earth's biomass. Consequently, understanding how these biologically complex organisms initially diversified in the Proterozoic Eon over 539 million years ago is a foundational question in evolutionary biology. Over the last 70 years, palaeontologists have sought to document the rise of eukaryotes with fossil evidence. However, the delicate and microscopic nature of their sub-cellular features affords early eukaryotes diminished preservation potential. Chemical biomarker signatures of eukaryotes and the genetics of living eukaryotes have emerged as complementary tools for reconstructing eukaryote ancestry. In this review, we argue that exceptionally preserved Proterozoic microfossils are critical to interpreting these complementary tools, providing crucial calibrations to molecular clocks and testing hypotheses of palaeoecology. We highlight recent research on their preservation and biomolecular composition that offers new ways to enhance their utility.
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Affiliation(s)
- Ross P. Anderson
- Museum of Natural History, University of Oxford, OxfordOX1 3PW, UK
- All Souls College, University of Oxford, OxfordOX1 4AL, UK
| | - Sanaa Mughal
- Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AlbertaT6G 2E3, Canada
| | - George O. Wedlake
- Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK
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2
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Hoshino Y, Gaucher EA. Impact of steroid biosynthesis on the aerobic adaptation of eukaryotes. GEOBIOLOGY 2024; 22:e12612. [PMID: 38967402 PMCID: PMC11234327 DOI: 10.1111/gbi.12612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 06/20/2024] [Accepted: 06/24/2024] [Indexed: 07/06/2024]
Abstract
Steroids are indispensable components of the eukaryotic cellular membrane and the acquisition of steroid biosynthesis was a key factor that enabled the evolution of eukaryotes. The polycyclic carbon structures of steroids can be preserved in sedimentary rocks as chemical fossils for billions of years and thus provide invaluable clues to trace eukaryotic evolution from the distant past. Steroid biosynthesis consists of (1) the production of protosteroids and (2) the subsequent modifications toward "modern-type" steroids such as cholesterol and stigmasterol. While protosteroid biosynthesis requires only two genes for the cyclization of squalene, complete modification of protosteroids involves ~10 additional genes. Eukaryotes universally possess at least some of those additional genes and thus produce modern-type steroids as major final products. The geological biomarker records suggest a prolonged period of solely protosteroid production in the mid-Proterozoic before the advent of modern-type steroids in the Neoproterozoic. It has been proposed that mid-Proterozoic protosteroids were produced by hypothetical stem-group eukaryotes that presumably possessed genes only for protosteroid production, even though in modern environments protosteroid production as a final product is found exclusively in bacteria. The host identity of mid-Proterozoic steroid producers is crucial for understanding the early evolution of eukaryotes. In this perspective, we discuss how geological biomarker data and genetic data complement each other and potentially provide a more coherent scenario for the evolution of steroids and associated early eukaryotes. We further discuss the potential impacts that steroids had on the evolution of aerobic metabolism in eukaryotes, which may have been an important factor for the eventual ecological dominance of eukaryotes in many modern environments.
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Affiliation(s)
- Yosuke Hoshino
- GFZ German Research Centre for Geosciences, Potsdam, Germany
- Institute for Advanced Research, Nagoya University, Nagoya, Japan
- Synchrotron Radiation Research Center, Nagoya University, Nagoya, Japan
| | - Eric A Gaucher
- Department of Biology, Georgia State University, Atlanta, Georgia, USA
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3
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Slagter S, Konhauser KO, Briggs DEG, Tarhan LG. Controls on authigenic mineralization in experimental Ediacara-style preservation. GEOBIOLOGY 2024; 22:e12615. [PMID: 39149974 DOI: 10.1111/gbi.12615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 06/20/2024] [Accepted: 07/26/2024] [Indexed: 08/17/2024]
Abstract
The earliest evidence of complex macroscopic life on Earth is preserved in Ediacaran-aged siliciclastic deposits as three-dimensional casts and molds, known as Ediacara-style preservation. The mechanisms that led to this extraordinary preservation of soft-bodied organisms in fine- to medium-grained sandstones have been extensively debated. Ediacara-style fossilization is recorded in a variety of sedimentary facies characterized by clean quartzose sandstones (as in the eponymous Ediacara Member) as well as less compositionally mature, clay-rich sandstones and heterolithic siliciclastic deposits. To investigate this preservational process, we conducted experiments using different mineral substrates (quartzose sand, kaolinite, and iron oxides), a variety of soft-bodied organisms (microalgae, cyanobacteria, marine invertebrates), and a range of estimates for Ediacaran seawater dissolved silica (DSi) levels (0.5-2.0 mM). These experiments collectively yielded extensive amorphous silica and authigenic clay coatings on the surfaces of organisms and in intergranular pore spaces surrounding organic substrates. This was accompanied by a progressive drawdown of the DSi concentration of the experimental solutions. These results provide evidence that soft tissues can be rapidly preserved by silicate minerals precipitated under variable substrate compositions and a wide range of predicted scenarios for Ediacaran seawater DSi concentrations. These observations suggest plausible mechanisms explaining how interactions between sediments, organic substrates, and seawater DSi played a significant role in the fossilization of the first complex ecosystems on Earth.
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Affiliation(s)
- Silvina Slagter
- Department of Earth & Planetary Sciences, Yale University, New Haven, Connecticut, USA
- Instituto de Ciencias de la Ingeniería, Universidad de O'Higgins, Rancagua, Chile
| | - Kurt O Konhauser
- Department of Earth & Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Derek E G Briggs
- Department of Earth & Planetary Sciences, Yale University, New Haven, Connecticut, USA
| | - Lidya G Tarhan
- Department of Earth & Planetary Sciences, Yale University, New Haven, Connecticut, USA
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4
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Yu Y, Li YP, Ren K, Hao X, Fru EC, Rønn R, Rivera WL, Becker K, Feng R, Yang J, Rensing C. A brief history of metal recruitment in protozoan predation. Trends Microbiol 2024; 32:465-476. [PMID: 38103995 DOI: 10.1016/j.tim.2023.11.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 11/20/2023] [Accepted: 11/23/2023] [Indexed: 12/19/2023]
Abstract
Metals and metalloids are used as weapons for predatory feeding by unicellular eukaryotes on prokaryotes. This review emphasizes the role of metal(loid) bioavailability over the course of Earth's history, coupled with eukaryogenesis and the evolution of the mitochondrion to trace the emergence and use of the metal(loid) prey-killing phagosome as a feeding strategy. Members of the genera Acanthamoeba and Dictyostelium use metals such as zinc (Zn) and copper (Cu), and possibly metalloids, to kill their bacterial prey after phagocytosis. We provide a potential timeline on when these capacities first evolved and how they correlate with perceived changes in metal(loid) bioavailability through Earth's history. The origin of phagotrophic eukaryotes must have postdated the Great Oxidation Event (GOE) in agreement with redox-dependent modification of metal(loid) bioavailability for phagotrophic poisoning. However, this predatory mechanism is predicted to have evolved much later - closer to the origin of the multicellular metazoans and the evolutionary development of the immune systems.
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Affiliation(s)
- Yanshuang Yu
- Institute of Environmental Microbiology, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Yuan-Ping Li
- Institute of Environmental Microbiology, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Kexin Ren
- Aquatic EcoHealth Group, Fujian Key Laboratory of Watershed Ecology, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
| | - Xiuli Hao
- Hubei Key Laboratory of Soil Environment and Pollution Remediation, Huazhong Agricultural University, Wuhan 430070, China
| | - Ernest Chi Fru
- Centre for Geobiology and Geochemistry, School of Earth and Ocean Sciences, Cardiff University, CF10 3AT Cardiff, UK
| | - Regin Rønn
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Windell L Rivera
- Pathogen-Host-Environment Interactions Research Laboratory, Institute of Biology, College of Science, University of the Philippines Diliman, Quezon City 1101, Philippines
| | - Karsten Becker
- Friedrich Loeffler-Institute for Medical Microbiology, University Medicine Greifswald, D-17489 Greifswald, Germany
| | - Renwei Feng
- Institute of Environmental Microbiology, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Jun Yang
- Aquatic EcoHealth Group, Fujian Key Laboratory of Watershed Ecology, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
| | - Christopher Rensing
- Institute of Environmental Microbiology, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China.
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5
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Maloney KM, Halverson GP, Lechte M, Gibson TM, Bui TH, Schiffbauer JD, Laflamme M. The paleoredox context of early eukaryotic evolution: insights from the Tonian Mackenzie Mountains Supergroup, Canada. GEOBIOLOGY 2024; 22:e12598. [PMID: 38700417 DOI: 10.1111/gbi.12598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 03/18/2024] [Accepted: 03/27/2024] [Indexed: 05/05/2024]
Abstract
Tonian (ca. 1000-720 Ma) marine environments are hypothesised to have experienced major redox changes coinciding with the evolution and diversification of multicellular eukaryotes. In particular, the earliest Tonian stratigraphic record features the colonisation of benthic habitats by multicellular macroscopic algae, which would have been powerful ecosystem engineers that contributed to the oxygenation of the oceans and the reorganisation of biogeochemical cycles. However, the paleoredox context of this expansion of macroalgal habitats in Tonian nearshore marine environments remains uncertain due to limited well-preserved fossils and stratigraphy. As such, the interdependent relationship between early complex life and ocean redox state is unclear. An assemblage of macrofossils including the chlorophyte macroalga Archaeochaeta guncho was recently discovered in the lower Mackenzie Mountains Supergroup in Yukon (Canada), which archives marine sedimentation from ca. 950-775 Ma, permitting investigation into environmental evolution coincident with eukaryotic ecosystem evolution and expansion. Here we present multi-proxy geochemical data from the lower Mackenzie Mountains Supergroup to constrain the paleoredox environment within which these large benthic macroalgae thrived. Two transects show evidence for basin-wide anoxic (ferruginous) oceanic conditions (i.e., high FeHR/FeT, low Fepy/FeHR), with muted redox-sensitive trace metal enrichments and possible seasonal variability. However, the weathering of sulfide minerals in the studied samples may obscure geochemical signatures of euxinic conditions. These results suggest that macroalgae colonized shallow environments in an ocean that remained dominantly anoxic with limited evidence for oxygenation until ca. 850 Ma. Collectively, these geochemical results provide novel insights into the environmental conditions surrounding the evolution and expansion of benthic macroalgae and the eventual dominance of oxygenated oceanic conditions required for the later emergence of animals.
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Affiliation(s)
- Katie M Maloney
- Department of Earth and Planetary Sciences/GEOTOP, McGill University, Montréal, Québec, Canada
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Galen P Halverson
- Department of Earth and Planetary Sciences/GEOTOP, McGill University, Montréal, Québec, Canada
| | - Maxwell Lechte
- Department of Earth and Planetary Sciences/GEOTOP, McGill University, Montréal, Québec, Canada
| | - Timothy M Gibson
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut, USA
| | - Thi Hao Bui
- Department of Earth and Planetary Sciences/GEOTOP, McGill University, Montréal, Québec, Canada
| | - James D Schiffbauer
- Department of Geological Sciences, University of Missouri, Columbia, Missouri, USA
- X-ray Microanalysis Core, University of Missouri, Columbia, Missouri, USA
| | - Marc Laflamme
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada
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6
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Crockford PW, Bar On YM, Ward LM, Milo R, Halevy I. The geologic history of primary productivity. Curr Biol 2023; 33:4741-4750.e5. [PMID: 37827153 DOI: 10.1016/j.cub.2023.09.040] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 09/11/2023] [Accepted: 09/18/2023] [Indexed: 10/14/2023]
Abstract
The rate of primary productivity is a keystone variable in driving biogeochemical cycles today and has been throughout Earth's past.1 For example, it plays a critical role in determining nutrient stoichiometry in the oceans,2 the amount of global biomass,3 and the composition of Earth's atmosphere.4 Modern estimates suggest that terrestrial and marine realms contribute near-equal amounts to global gross primary productivity (GPP).5 However, this productivity balance has shifted significantly in both recent times6 and through deep time.7,8 Combining the marine and terrestrial components, modern GPP fixes ≈250 billion tonnes of carbon per year (Gt C year-1).5,9,10,11 A grand challenge in the study of the history of life on Earth has been to constrain the trajectory that connects present-day productivity to the origin of life. Here, we address this gap by piecing together estimates of primary productivity from the origin of life to the present day. We estimate that ∼1011-1012 Gt C has cumulatively been fixed through GPP (≈100 times greater than Earth's entire carbon stock). We further estimate that 1039-1040 cells have occupied the Earth to date, that more autotrophs than heterotrophs have ever existed, and that cyanobacteria likely account for a larger proportion than any other group in terms of the number of cells. We discuss implications for evolutionary trajectories and highlight the early Proterozoic, which encompasses the Great Oxidation Event (GOE), as the time where most uncertainty exists regarding the quantitative census presented here.
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Affiliation(s)
- Peter W Crockford
- Department of Earth Sciences, Carleton University, Ottawa, ON K1S 5B6, Canada; Department of Earth and Planetary Sciences, Weizmann Institute of Science, 7610001 Rehovot, Israel; Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA.
| | - Yinon M Bar On
- Department of Earth and Planetary Sciences, Weizmann Institute of Science, 7610001 Rehovot, Israel; Division of Geological Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - Luce M Ward
- Department of Geosciences, Smith College, Northampton, MA 01063, USA
| | - Ron Milo
- Department of Earth and Planetary Sciences, Weizmann Institute of Science, 7610001 Rehovot, Israel
| | - Itay Halevy
- Department of Earth and Planetary Sciences, Weizmann Institute of Science, 7610001 Rehovot, Israel
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7
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Yang Z, Ma X, Wang Q, Tian X, Sun J, Zhang Z, Xiao S, De Clerck O, Leliaert F, Zhong B. Phylotranscriptomics unveil a Paleoproterozoic-Mesoproterozoic origin and deep relationships of the Viridiplantae. Nat Commun 2023; 14:5542. [PMID: 37696791 PMCID: PMC10495350 DOI: 10.1038/s41467-023-41137-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 08/23/2023] [Indexed: 09/13/2023] Open
Abstract
The Viridiplantae comprise two main clades, the Chlorophyta (including a diverse array of marine and freshwater green algae) and the Streptophyta (consisting of the freshwater charophytes and the land plants). Lineages sister to core Chlorophyta, informally refer to as prasinophytes, form a grade of mainly planktonic green algae. Recently, one of these lineages, Prasinodermophyta, which is previously grouped with prasinophytes, has been identified as the sister lineage to both Chlorophyta and Streptophyta. Resolving the deep relationships among green plants is crucial for understanding the historical impact of green algal diversity on marine ecology and geochemistry, but has been proven difficult given the ancient timing of the diversification events. Through extensive taxon and gene sampling, we conduct large-scale phylogenomic analyses to resolve deep relationships and reveal the Prasinodermophyta as the lineage sister to Chlorophyta, raising questions about the necessity of classifying the Prasinodermophyta as a distinct phylum. We unveil that incomplete lineage sorting is the main cause of discordance regarding the placement of Prasinodermophyta. Molecular dating analyses suggest that crown-group green plants and crown-group Prasinodermophyta date back to the Paleoproterozoic-Mesoproterozoic. Our study establishes a plausible link between oxygen levels in the Paleoproterozoic-Mesoproterozoic and the origin of Viridiplantae.
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Affiliation(s)
- Zhiping Yang
- College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Xiaoya Ma
- College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Qiuping Wang
- College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Xiaolin Tian
- College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Jingyan Sun
- College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Zhenhua Zhang
- College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Shuhai Xiao
- Department of Geosciences and Global Change Center, Virginia Tech, Blacksburg, VA, USA
| | - Olivier De Clerck
- Phycology Research Group and Center for Molecular Phylogenetics and Evolution, Ghent University, Ghent, Belgium
| | | | - Bojian Zhong
- College of Life Sciences, Nanjing Normal University, Nanjing, China.
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8
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Kenig F. Infancy of sterol biosynthesis hints at extinct eukaryotic species. Nature 2023:10.1038/d41586-023-01816-1. [PMID: 37286675 DOI: 10.1038/d41586-023-01816-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
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9
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Brocks JJ, Nettersheim BJ, Adam P, Schaeffer P, Jarrett AJM, Güneli N, Liyanage T, van Maldegem LM, Hallmann C, Hope JM. Lost world of complex life and the late rise of the eukaryotic crown. Nature 2023:10.1038/s41586-023-06170-w. [PMID: 37286610 DOI: 10.1038/s41586-023-06170-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 05/04/2023] [Indexed: 06/09/2023]
Abstract
Eukaryotic life appears to have flourished surprisingly late in the history of our planet. This view is based on the low diversity of diagnostic eukaryotic fossils in marine sediments of mid-Proterozoic age (around 1,600 to 800 million years ago) and an absence of steranes, the molecular fossils of eukaryotic membrane sterols1,2. This scarcity of eukaryotic remains is difficult to reconcile with molecular clocks that suggest that the last eukaryotic common ancestor (LECA) had already emerged between around 1,200 and more than 1,800 million years ago. LECA, in turn, must have been preceded by stem-group eukaryotic forms by several hundred million years3. Here we report the discovery of abundant protosteroids in sedimentary rocks of mid-Proterozoic age. These primordial compounds had previously remained unnoticed because their structures represent early intermediates of the modern sterol biosynthetic pathway, as predicted by Konrad Bloch4. The protosteroids reveal an ecologically prominent 'protosterol biota' that was widespread and abundant in aquatic environments from at least 1,640 to around 800 million years ago and that probably comprised ancient protosterol-producing bacteria and deep-branching stem-group eukaryotes. Modern eukaryotes started to appear in the Tonian period (1,000 to 720 million years ago), fuelled by the proliferation of red algae (rhodophytes) by around 800 million years ago. This 'Tonian transformation' emerges as one of the most profound ecological turning points in the Earth's history.
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Affiliation(s)
- Jochen J Brocks
- Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory, Australia.
| | - Benjamin J Nettersheim
- Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory, Australia.
- MARUM-Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Bremen, Germany.
| | - Pierre Adam
- Université de Strasbourg, CNRS, Institut de Chimie de Strasbourg UMR 7177, Strasbourg, France
| | - Philippe Schaeffer
- Université de Strasbourg, CNRS, Institut de Chimie de Strasbourg UMR 7177, Strasbourg, France
| | - Amber J M Jarrett
- Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory, Australia
- Northern Territory Geological Survey, Darwin, Northern Territory, Australia
| | - Nur Güneli
- Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Tharika Liyanage
- Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Lennart M van Maldegem
- Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory, Australia
| | | | - Janet M Hope
- Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory, Australia
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10
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Tingle KE, Porter SM, Raven MR, Czaja AD, Webb SM, Bloeser B. Organic preservation of vase-shaped microfossils from the late Tonian Chuar Group, Grand Canyon, Arizona, USA. GEOBIOLOGY 2023; 21:290-309. [PMID: 36651474 DOI: 10.1111/gbi.12544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 12/08/2022] [Accepted: 01/05/2023] [Indexed: 06/17/2023]
Abstract
Vase-shaped microfossils (VSMs) are found globally in middle Neoproterozoic (800-730 Ma) marine strata and represent the earliest evidence for testate (shell-forming) amoebozoans. VSM tests are hypothesized to have been originally organic in life but are most commonly preserved as secondary mineralized casts and molds. A few reports, however, suggest possible organic preservation. Here, we test the hypothesis that VSMs from shales of the lower Walcott Member of the Chuar Group, Grand Canyon, Arizona, contain original organic material, as reported by B. Bloeser in her pioneering studies of Chuar VSMs. We identified VSMs from two thin section samples of Walcott Member black shales in transmitted light microscopy and used scanning electron microscopy to image VSMs. Carbonaceous material is found within the internal cavity of all VSM tests from both samples and is interpreted as bitumen mobilized from Walcott shales likely during the Cretaceous. Energy dispersive X-ray spectroscopy (EDS) and wavelength dispersive X-ray spectroscopy (WDS) reveal that VSM test walls contain mostly carbon, iron, and sulfur, while silica is present only in the surrounding matrix. Raman spectroscopy was used to compare the thermal maturity of carbonaceous material within the samples and indicated the presence of pyrite and jarosite within fossil material. X-ray absorption spectroscopy revealed the presence of reduced organic sulfur species within the carbonaceous test walls, the carbonaceous material found within test cavities, and in the sedimentary matrix, suggesting that organic matter sulfurization occurred within the Walcott shales. Our suite of spectroscopic analyses reveals that Walcott VSM test walls are organic and sometimes secondarily pyritized (with the pyrite variably oxidized to jarosite). Both preservation modes can occur at a millimeter spatial scale within sample material, and at times even within a single specimen. We propose that sulfurization within the Walcott Shales promoted organic preservation, and furthermore, the ratio of iron to labile VSM organic material controlled the extent of pyrite replacement. Based on our evidence, we conclude that the VSMs are preserved with original organic test material, and speculate that organic VSMs may often go unrecognized, given their light-colored, translucent appearance in transmitted light.
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Affiliation(s)
- Kelly E Tingle
- Department of Earth Science, University of California, Santa Barbara, California, USA
| | - Susannah M Porter
- Department of Earth Science, University of California, Santa Barbara, California, USA
| | - Morgan R Raven
- Department of Earth Science, University of California, Santa Barbara, California, USA
| | - Andrew D Czaja
- Department of Geology, University of Cincinnati, Cincinnati, Ohio, USA
| | - Samuel M Webb
- Stanford Synchrotron Radiation Lightsource, Stanford University, Menlo Park, California, USA
| | - Bonnie Bloeser
- Department of Geological Sciences, San Diego State University, San Diego, California, USA
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11
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Kang J, Gill B, Reid R, Zhang F, Xiao S. Nitrate limitation in early Neoproterozoic oceans delayed the ecological rise of eukaryotes. SCIENCE ADVANCES 2023; 9:eade9647. [PMID: 36947611 PMCID: PMC10032604 DOI: 10.1126/sciadv.ade9647] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 02/17/2023] [Indexed: 06/18/2023]
Abstract
The early Neoproterozoic Era witnessed the initial ecological rise of eukaryotes at ca. 800 Ma. To assess whether nitrate availability played an important role in this evolutionary event, we measured nitrogen isotope compositions (δ15N) of marine carbonates from the early Tonian (ca. 1000 Ma to ca. 800 Ma) Huaibei Group in North China. The data reported here fill a critical gap in the δ15N record and indicate nitrate limitation in early Neoproterozoic oceans. A compilation of Proterozoic sedimentary δ15N data reveals a stepwise increase in δ15N values at ~800 Ma. Box model simulations indicate that this stepwise increase likely represents a ~50% increase in marine nitrate availability. Limited nitrate availability in early Neoproterozoic oceans may have delayed the ecological rise of eukaryotes until ~800 Ma when increased nitrate supply, together with other environmental and ecological factors, may have contributed to the transition from prokaryote-dominant to eukaryote-dominant marine ecosystems.
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Affiliation(s)
- Junyao Kang
- Department of Geosciences, Virginia Tech, Blacksburg, VA, USA
- Global Change Center, Virginia Tech, Blacksburg, VA, USA
| | - Benjamin Gill
- Department of Geosciences, Virginia Tech, Blacksburg, VA, USA
- Global Change Center, Virginia Tech, Blacksburg, VA, USA
| | - Rachel Reid
- Department of Geosciences, Virginia Tech, Blacksburg, VA, USA
- Global Change Center, Virginia Tech, Blacksburg, VA, USA
| | - Feifei Zhang
- State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing 210023, China
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, VA, USA
- Global Change Center, Virginia Tech, Blacksburg, VA, USA
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12
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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] [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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13
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Maloney KM, Schiffbauer JD, Halverson GP, Xiao S, Laflamme M. Preservation of early Tonian macroalgal fossils from the Dolores Creek Formation, Yukon. Sci Rep 2022; 12:6222. [PMID: 35418588 PMCID: PMC9007953 DOI: 10.1038/s41598-022-10223-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 04/04/2022] [Indexed: 11/30/2022] Open
Abstract
The rise of eukaryotic macroalgae in the late Mesoproterozoic to early Neoproterozoic was a critical development in Earth’s history that triggered dramatic changes in biogeochemical cycles and benthic habitats, ultimately resulting in ecosystems habitable to animals. However, evidence of the diversification and expansion of macroalgae is limited by a biased fossil record. Non-mineralizing organisms are rarely preserved, occurring only in exceptional environments that favor fossilization. Investigating the taphonomy of well-preserved macroalgae will aid in identifying these target environments, allowing ecological trends to be disentangled from taphonomic overprints. Here we describe the taphonomy of macroalgal fossils from the Tonian Dolores Creek Formation (ca. 950 Ma) of northwestern Canada (Yukon Territory) that preserves cm-scale macroalgae. Analytical microscopy, including scanning electron microscopy and tomographic x-ray microscopy, was used to investigate fossil preservation, which was the result of a combination of pyritization and aluminosilicification, similar to accessory mineralization observed in Paleozoic Burgess Shale-type fossils. These new Neoproterozoic fossils help to bridge a gap in the fossil record of early algae, offer a link between the fossil and molecular record, and provide new insights into evolution during the Tonian Period, when many eukaryotic lineages are predicted to have diversified.
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Affiliation(s)
- Katie M Maloney
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada.
| | - James D Schiffbauer
- Department of Geological Sciences, University of Missouri, Columbia, MO, 65211, USA.,X-Ray Microanalysis Core, University of Missouri, Columbia, MO, 65211, USA
| | - Galen P Halverson
- Department of Earth and Planetary Sciences/GEOTOP, McGill University, Montréal, QC, H3A 0E8, Canada
| | - Shuhai Xiao
- Department of Geosciences, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Marc Laflamme
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, ON, L5L 1C6, Canada
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14
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15
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Strong evidence for a weakly oxygenated ocean–atmosphere system during the Proterozoic. Proc Natl Acad Sci U S A 2022; 119:2116101119. [PMID: 35101984 PMCID: PMC8833159 DOI: 10.1073/pnas.2116101119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/16/2021] [Indexed: 11/18/2022] Open
Abstract
Earth’s transition from anoxic oceans and atmosphere to a well-oxygenated state led to major changes in nearly every surficial system. However, estimates of surface oxygen levels in the billion years preceding this shift span two orders of magnitude, suggesting a poor understanding of the evolution of the oxygen cycle. We use the isotopic record of iron oxides deposited in ancient shallow marine environments to show that oxygen remained at extremely low levels in the ocean–atmosphere system for most of Earth’s history, and that a rise in oxygen occurred in step with the expansion of complex, eukaryotic ecosystems. These results indicate that Earth is capable of stabilizing at low atmospheric oxygen levels, with important implications for exploration of exoplanet biosignatures. Earth’s surface has undergone a protracted oxygenation, which is commonly assumed to have profoundly affected the biosphere. However, basic aspects of this history are still debated—foremost oxygen (O2) levels in the oceans and atmosphere during the billion years leading up to the rise of algae and animals. Here we use isotope ratios of iron (Fe) in ironstones—Fe-rich sedimentary rocks deposited in nearshore marine settings—as a proxy for O2 levels in shallow seawater. We show that partial oxidation of dissolved Fe(II) was characteristic of Proterozoic shallow marine environments, whereas younger ironstones formed via complete oxidation of Fe(II). Regardless of the Fe(II) source, partial Fe(II) oxidation requires low O2 in the shallow oceans, settings crucial to eukaryotic evolution. Low O2 in surface waters can be linked to markedly low atmospheric O2—likely requiring less than 1% of modern levels. Based on our records, these conditions persisted (at least periodically) until a shift toward higher surface O2 levels between ca. 900 and 750 Ma, coincident with an apparent rise in eukaryotic ecosystem complexity. This supports the case that a first-order shift in surface O2 levels during this interval may have selected for life modes adapted to more oxygenated habitats.
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16
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A largely invariant marine dissolved organic carbon reservoir across Earth's history. Proc Natl Acad Sci U S A 2021; 118:2103511118. [PMID: 34580216 DOI: 10.1073/pnas.2103511118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/28/2021] [Indexed: 11/18/2022] Open
Abstract
Marine dissolved organic carbon (DOC), the largest pool of reduced carbon in the oceans, plays an important role in the global carbon cycle and contributes to the regulation of atmospheric oxygen and carbon dioxide abundances. Despite its importance in global biogeochemical cycles, the long-term history of the marine DOC reservoir is poorly constrained. Nonetheless, significant changes to the size of the oceanic DOC reservoir through Earth's history have been commonly invoked to explain changes to ocean chemistry, carbon cycling, and marine ecology. Here, we present a revised view of the evolution of marine DOC concentrations using a mechanistic carbon cycle model that can reproduce DOC concentrations in both oxic and anoxic modern environments. We use this model to demonstrate that the overall size of the marine DOC reservoir has likely undergone very little variation through Earth's history, despite major changes in the redox state of the ocean-atmosphere system and the nature and efficiency of the biological carbon pump. A relatively static marine DOC reservoir across Earth's history renders it unlikely that major changes in marine DOC concentrations have been responsible for driving massive repartitioning of surface carbon or the large carbon isotope excursions observed in Earth's stratigraphic record and casts doubt on previously hypothesized links between marine DOC levels and the emergence and radiation of early animals.
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17
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Pehr K, Bisquera R, Bishop AN, Ossa Ossa F, Meredith W, Bekker A, Love GD. Preservation and Distributions of Covalently Bound Polyaromatic Hydrocarbons in Ancient Biogenic Kerogens and Insoluble Organic Macromolecules. ASTROBIOLOGY 2021; 21:1049-1075. [PMID: 34030461 DOI: 10.1089/ast.2020.2338] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The likelihood of finding pristine molecular biosignatures preserved in Earth's oldest rocks or on other planetary bodies is low, and new approaches are needed to assess the origins of highly altered and recalcitrant organic matter. In this study, we aim to understand the distributions and systematics of preservation of ancient polycyclic aromatic hydrocarbons (PAHs), as both free hydrocarbons and bound within insoluble macromolecules. We report the distributions of bound PAHs generated by catalytic hydropyrolysis from ancient biogenic kerogens and from insoluble organic matter (IOM) in high-temperature carbonaceous residues from pyrobitumens and synthetic coke. For biogenic kerogens, the degree of thermal maturity exerts the primary control on the preservation and distributions of the major five-ring and six-ring PAH compounds. This holds for both Precambrian and Phanerozoic rocks, thus source variation in primary biogenic organic matter inputs does not exert the major control on bound PAH. The IOM samples, predominantly residues from hydrocarbon cracking at high temperatures, preserve a bound PAH profile significantly distinct from ancient biogenic kerogens and characterized by an absence of perylene and higher abundance of large-ring condensed PAHs. Covalently bound PAH profiles offer promise as "last resort" molecular biosignatures for aiding the astrobiological search for ancient life.
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Affiliation(s)
- Kelden Pehr
- Department of Earth and Planetary Sciences, University of California-Riverside, Riverside, California, USA
| | - Rose Bisquera
- Department of Earth and Planetary Sciences, University of California-Riverside, Riverside, California, USA
| | | | - Frantz Ossa Ossa
- Department of Geosciences, University of Tübingen, Tübingen, Germany
| | - William Meredith
- Department of Chemical and Environmental Engineering, University of Nottingham, Nottingham, United Kingdom
| | - Andrey Bekker
- Department of Earth and Planetary Sciences, University of California-Riverside, Riverside, California, USA
| | - Gordon D Love
- Department of Earth and Planetary Sciences, University of California-Riverside, Riverside, California, USA
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18
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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] [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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19
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Rivera-Valentín EG, Filiberto J, Lynch KL, Mamajanov I, Lyons TW, Schulte M, Méndez A. Introduction-First Billion Years: Habitability. ASTROBIOLOGY 2021; 21:893-905. [PMID: 34406807 PMCID: PMC8403211 DOI: 10.1089/ast.2020.2314] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 12/22/2020] [Indexed: 06/13/2023]
Abstract
The physical processes active during the first billion years (FBY) of Earth's history, such as accretion, differentiation, and impact cratering, provide constraints on the initial conditions that were conducive to the formation and establishment of life on Earth. This motivated the Lunar and Planetary Institute's FBY topical initiative, which was a four-part conference series intended to look at each of these physical processes to study the basic structure and composition of our Solar System that was set during the FBY. The FBY Habitability conference, held in September 2019, was the last in this series and was intended to synthesize the initiative; specifically, to further our understanding of the origins of life, planetary and environmental habitability, and the search for life beyond Earth. The conference included discussions of planetary habitability and the potential emergence of life on bodies within our Solar System, as well as extrasolar systems by applying our knowledge of the Solar System's FBY, and in particular Earth's early history. To introduce this Special Collection, which resulted from work discussed at the conference, we provide a review of the main themes and a synopsis of the FBY Habitability conference.
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Affiliation(s)
| | - Justin Filiberto
- Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, USA
| | - Kennda L. Lynch
- Lunar and Planetary Institute, Universities Space Research Association, Houston, Texas, USA
| | - Irena Mamajanov
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
| | - Timothy W. Lyons
- Department of Earth and Planetary Sciences, University of California Riverside, Riverside, California, USA
| | - Mitch Schulte
- Planetary Science Division, NASA Headquarters, Washington, District of Columbia, USA
| | - Abel Méndez
- Planetary Habitability Laboratory, University of Puerto Rico Arecibo, Arecibo, Puerto Rico
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20
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van Maldegem LM, Nettersheim BJ, Leider A, Brocks JJ, Adam P, Schaeffer P, Hallmann C. Geological alteration of Precambrian steroids mimics early animal signatures. Nat Ecol Evol 2020; 5:169-173. [PMID: 33230255 DOI: 10.1038/s41559-020-01336-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 09/23/2020] [Indexed: 11/09/2022]
Abstract
The absence of unambiguous animal body fossils in rocks older than the late Ediacaran has rendered fossil lipids the most promising tracers of early organismic complexity. Yet much debate surrounds the various potential biological sources of putative metazoan steroids found in Precambrian rocks. Here we show that 26-methylated steranes-hydrocarbon structures currently attributed to the earliest animals-can form via geological alteration of common algal sterols, which carries important implications for palaeo-ecological interpretations and inhibits the use of such unconventional 'sponge' steranes for reconstructing early animal evolution.
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Affiliation(s)
- Lennart M van Maldegem
- Max Planck Institute for Biogeochemistry, Jena, Germany. .,MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany. .,The Australian National University, Canberra, Australian Capital Territory, Australia.
| | - Benjamin J Nettersheim
- Max Planck Institute for Biogeochemistry, Jena, Germany. .,MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
| | - Arne Leider
- Max Planck Institute for Biogeochemistry, Jena, Germany.,MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Jochen J Brocks
- The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Pierre Adam
- University of Strasbourg, CNRS-UMR 7177, Strasbourg, France
| | | | - Christian Hallmann
- Max Planck Institute for Biogeochemistry, Jena, Germany. .,MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany.
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21
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Eckford-Soper LK, Canfield DE. The global explosion of eukaryotic algae: The potential role of phosphorus? PLoS One 2020; 15:e0234372. [PMID: 33091058 PMCID: PMC7580907 DOI: 10.1371/journal.pone.0234372] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 10/04/2020] [Indexed: 11/24/2022] Open
Abstract
There arose one of the most important ecological transitions in Earth's history approximately 750 million years ago during the middle Neoproterozoic Era (1000 to 541 million years ago, Ma). Biomarker evidence suggests that around this time there was a rapid shift from a predominantly bacterial-dominated world to more complex ecosystems governed by eukaryotic primary productivity. The resulting 'Rise of the algae' led to dramatically altered food webs that were much more efficient in terms of nutrient and energy transfer. Yet, what triggered this ecological shift? In this study we examined the theory that it was the alleviation of phosphorus (P) deficiency that gave eukaryotic alga the prime opportunity to flourish. We performed laboratory experiments on the cyanobacterium Synechocystis salina and the eukaryotic algae Tetraselmis suecica and examined their ability to compete for phosphorus. Both these organisms co-occur in modern European coastal waters and are not known to have any allelopathic capabilities. The strains were cultured in mono and mixed cultures in chemostats across a range of dissolved inorganic phosphorus (DIP) concentrations to reflect modern and ancient oceanic conditions of 2 μM P and 0.2 μM P, respectively. Our results show that the cyanobacteria outcompete the algae at the low input (0.2 μM P) treatment, yet the eukaryotic algae were not completely excluded and remained a constant background component in the mixed-culture experiments. Also, despite their relatively large cell size, the algae T. suecica had a high affinity for DIP. With DIP input concentrations resembling modern-day levels (2 μM), the eukaryotic algae could effectively compete against the cyanobacteria in terms of total biomass production. These results suggest that the availability of phosphorus could have influenced the global expansion of eukaryotic algae. However, P limitation does not seem to explain the complete absence of eukaryotic algae in the biomarker record before ca. 750 Ma.
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Affiliation(s)
| | - Donald E. Canfield
- Nordcee, Department of Biology, University of Southern Denmark, Odense M, Denmark
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22
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Abstract
Phagocytosis, or 'cell eating', is a eukaryote-specific process where particulate matter is engulfed via invaginations of the plasma membrane. The origin of phagocytosis has been central to discussions on eukaryogenesis for decades-, where it is argued as being either a prerequisite for, or consequence of, the acquisition of the ancestral mitochondrion. Recently, genomic and cytological evidence has increasingly supported the view that the pre-mitochondrial host cell-a bona fide archaeon branching within the 'Asgard' archaea-was incapable of phagocytosis and used alternative mechanisms to incorporate the alphaproteobacterial ancestor of mitochondria. Indeed, the diversity and variability of proteins associated with phagosomes across the eukaryotic tree suggest that phagocytosis, as seen in a variety of extant eukaryotes, may have evolved independently several times within the eukaryotic crown-group. Since phagocytosis is critical to the functioning of modern marine food webs (without it, there would be no microbial loop or animal life), multiple late origins of phagocytosis could help explain why many of the ecological and evolutionary innovations of the Neoproterozoic Era (e.g. the advent of eukaryotic biomineralization, the 'Rise of Algae' and the origin of animals) happened when they did.
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Affiliation(s)
- Daniel B. Mills
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA
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23
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Niche expansion for phototrophic sulfur bacteria at the Proterozoic-Phanerozoic transition. Proc Natl Acad Sci U S A 2020; 117:17599-17606. [PMID: 32647063 PMCID: PMC7395447 DOI: 10.1073/pnas.2006379117] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Carotenoid pigments afford valuable clues about the chemistry and biology of both modern and ancient aquatic environments. This study reveals that fossil aromatic carotenoids—long considered biomarkers for anoxygenic, phototrophic sulfur bacteria and their physiological requirement for hydrogen sulfide and illumination—can also be biosynthesized by oxygen-producing cyanobacteria. Cyanobacterial aromatic carotenoids, which are distinct in their chemical structures and occurrence patterns, are the most commonly encountered compounds in Proterozoic marine settings as well as in lakes from more recent eras. In contrast, carotenoids diagnostic for green sulfur bacteria of the family Chlorobiaceae became both prevalent and abundant in marine paleoenvironments beginning in the Phanerozoic Eon. This expansion occurs as marine sulfate inventories increased toward the end of the Proterozoic Eon. Fossilized carotenoid hydrocarbons provide a window into the physiology and biochemistry of ancient microbial phototrophic communities for which only a sparse and incomplete fossil record exists. However, accurate interpretation of carotenoid-derived biomarkers requires detailed knowledge of the carotenoid inventories of contemporary phototrophs and their physiologies. Here we report two distinct patterns of fossilized C40 diaromatic carotenoids. Phanerozoic marine settings show distributions of diaromatic hydrocarbons dominated by isorenieratane, a biomarker derived from low-light-adapted phototrophic green sulfur bacteria. In contrast, isorenieratane is only a minor constituent within Neoproterozoic marine sediments and Phanerozoic lacustrine paleoenvironments, for which the major compounds detected are renierapurpurane and renieratane, together with some novel C39 and C38 carotenoid degradation products. This latter pattern can be traced to cyanobacteria as shown by analyses of cultured taxa and laboratory simulations of sedimentary diagenesis. The cyanobacterial carotenoid synechoxanthin, and its immediate biosynthetic precursors, contain thermally labile, aromatic carboxylic-acid functional groups, which upon hydrogenation and mild heating yield mixtures of products that closely resemble those found in the Proterozoic fossil record. The Neoproterozoic–Phanerozoic transition in fossil carotenoid patterns likely reflects a step change in the surface sulfur inventory that afforded opportunities for the expansion of phototropic sulfur bacteria in marine ecosystems. Furthermore, this expansion might have also coincided with a major change in physiology. One possibility is that the green sulfur bacteria developed the capacity to oxidize sulfide fully to sulfate, an innovation which would have significantly increased their capacity for photosynthetic carbon fixation.
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24
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Tang Q, Pang K, Yuan X, Xiao S. A one-billion-year-old multicellular chlorophyte. Nat Ecol Evol 2020; 4:543-549. [PMID: 32094536 PMCID: PMC8668152 DOI: 10.1038/s41559-020-1122-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 01/20/2020] [Indexed: 11/09/2022]
Abstract
Chlorophytes (representing a clade within the Viridiplantae and a sister group of the Streptophyta) probably dominated marine export bioproductivity and played a key role in facilitating ecosystem complexity before the Mesozoic diversification of phototrophic eukaryotes such as diatoms, coccolithophorans and dinoflagellates. Molecular clock and biomarker data indicate that chlorophytes diverged in the Mesoproterozoic or early Neoproterozoic, followed by their subsequent phylogenetic diversification, multicellular evolution and ecological expansion in the late Neoproterozoic and Palaeozoic. This model, however, has not been rigorously tested with palaeontological data because of the scarcity of Proterozoic chlorophyte fossils. Here we report abundant millimetre-sized, multicellular and morphologically differentiated macrofossils from rocks approximately 1,000 million years ago. These fossils are described as Proterocladus antiquus new species and are interpreted as benthic siphonocladalean chlorophytes, suggesting that chlorophytes acquired macroscopic size, multicellularity and cellular differentiation nearly a billion years ago, much earlier than previously thought.
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Affiliation(s)
- Qing Tang
- Department of Geosciences and Global Change Center, Virginia Tech, Blacksburg, VA, USA.
| | - Ke Pang
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Xunlai Yuan
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Shuhai Xiao
- Department of Geosciences and Global Change Center, Virginia Tech, Blacksburg, VA, USA.
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