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Thiagarajan N, Lepland A, Ryb U, Torsvik TH, Ainsaar L, Hints O, Eiler J. Reconstruction of Phanerozoic climate using carbonate clumped isotopes and implications for the oxygen isotopic composition of seawater. Proc Natl Acad Sci U S A 2024; 121:e2400434121. [PMID: 39186659 PMCID: PMC11388280 DOI: 10.1073/pnas.2400434121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 07/11/2024] [Indexed: 08/28/2024] Open
Abstract
The oxygen isotope ratio 18O/16O (expressed as a δ18OVSMOW value) in marine sedimentary rocks has increased by ~8‰ from the early Paleozoic to modern times. Interpretation of this trend is hindered by ambiguities in the temperature of formation of the carbonate, the δ18Oseawater, and the effects of postdepositional diagenesis. Carbonate clumped isotope measurements, a temperature proxy, offer constraints on this problem. This thermometer is thermodynamically controlled in cases where carbonate achieves an equilibrium internal distribution of isotopes and is independent of the δ18O of the water from which the carbonate grew; therefore, it has a relatively rigorous chemical-physics foundation and can be applied to settings where the δ18O of the water is not known. We apply this technique to an exceptionally well-preserved Ordovician carbonate record from the Baltic Basin and present a framework for interpreting clumped isotope results and for reconstructing past δ18Oseawater. We find that the seawater in the Ordovician had lower δ18Oseawater values than previously estimated, highlighting the need to reassess climate records based on oxygen-isotopes, particularly where interpretations are based on assumptions regarding either the δ18Oseawater or the temperature of deposition or diagenesis. We argue that an increase in δ18Oseawater contributed to the long-term rise in the δ18O of marine sedimentary rocks since the early Paleozoic. This rise might have been driven by a change in the proportion of high- versus low-temperature water-rock interaction in the earth's hydrosphere as a whole.
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Affiliation(s)
- Nivedita Thiagarajan
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
| | - Aivo Lepland
- Section for Marine Geology, Geological Survey of Norway, Trondheim 7040, Norway
- Department of Geology, University of Tartu, Tartu 50411, Estonia
- Department of Geology, Tallinn University of Technology, Tallinn 19086, Estonia
| | - Uri Ryb
- The Fredy & Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Trond H Torsvik
- Department of Geosciences, University of Oslo, Oslo 0316, Norway
| | - Leho Ainsaar
- Department of Geology, University of Tartu, Tartu 50411, Estonia
| | - Olle Hints
- Department of Geology, Tallinn University of Technology, Tallinn 19086, Estonia
| | - John Eiler
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
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2
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Boag TH, Busch JF, Gooley JT, Strauss JV, Sperling EA. Deep-water first occurrences of Ediacara biota prior to the Shuram carbon isotope excursion in the Wernecke Mountains, Yukon, Canada. GEOBIOLOGY 2024; 22:e12597. [PMID: 38700422 DOI: 10.1111/gbi.12597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 02/29/2024] [Accepted: 03/27/2024] [Indexed: 05/05/2024]
Abstract
Ediacara-type macrofossils appear as early as ~575 Ma in deep-water facies of the Drook Formation of the Avalon Peninsula, Newfoundland, and the Nadaleen Formation of Yukon and Northwest Territories, Canada. Our ability to assess whether a deep-water origination of the Ediacara biota is a genuine reflection of evolutionary succession, an artifact of an incomplete stratigraphic record, or a bathymetrically controlled biotope is limited by a lack of geochronological constraints and detailed shelf-to-slope transects of Ediacaran continental margins. The Ediacaran Rackla Group of the Wernecke Mountains, NW Canada, represents an ideal shelf-to-slope depositional system to understand the spatiotemporal and environmental context of Ediacara-type organisms' stratigraphic occurrence. New sedimentological and paleontological data presented herein from the Wernecke Mountains establish a stratigraphic framework relating shelfal strata in the Goz/Corn Creek area to lower slope deposits in the Nadaleen River area. We report new discoveries of numerous Aspidella hold-fast discs, indicative of frondose Ediacara organisms, from deep-water slope deposits of the Nadaleen Formation stratigraphically below the Shuram carbon isotope excursion (CIE) in the Nadaleen River area. Such fossils are notably absent in coeval shallow-water strata in the Goz/Corn Creek region despite appropriate facies for potential preservation. The presence of pre-Shuram CIE Ediacara-type fossils occurring only in deep-water facies within a basin that has equivalent well-preserved shallow-water facies provides the first stratigraphic paleobiological support for a deep-water origination of the Ediacara biota. In contrast, new occurrences of Ediacara-type fossils (including juvenile fronds, Beltanelliformis, Aspidella, annulated tubes, and multiple ichnotaxa) are found above the Shuram CIE in both deep- and shallow-water deposits of the Blueflower Formation. Given existing age constraints on the Shuram CIE, it appears that Ediacaran organisms may have originated in the deeper ocean and lived there for up to ~15 million years before migrating into shelfal environments in the terminal Ediacaran. This indicates unique ecophysiological constraints likely shaped the initial habitat preference and later environmental expansion of the Ediacara biota.
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Affiliation(s)
- Thomas H Boag
- Department of Earth and Planetary Science, Stanford University, Stanford, California, USA
- Department of Earth and Planetary Sciences, Yale University, New Haven, Connecticut, USA
- Department of Geosciences, Princeton University, Princeton, New Jersey, USA
| | - James F Busch
- Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | - Jared T Gooley
- Alaska Science Center, U.S. Geological Survey, Anchorage, Alaska, USA
| | - Justin V Strauss
- Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | - Erik A Sperling
- Department of Earth and Planetary Science, Stanford University, Stanford, California, USA
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3
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Isson T, Rauzi S. Oxygen isotope ensemble reveals Earth's seawater, temperature, and carbon cycle history. Science 2024; 383:666-670. [PMID: 38330122 DOI: 10.1126/science.adg1366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Accepted: 01/05/2024] [Indexed: 02/10/2024]
Abstract
Earth's persistent habitability since the Archean remains poorly understood. Using an oxygen isotope ensemble approach-comprising shale, iron oxide, carbonate, silica, and phosphate records-we reconcile a multibillion-year history of seawater δ18O, temperature, and marine and terrestrial clay abundance. Our results reveal a rise in seawater δ18O and a temperate Proterozoic climate distinct to interpretations of a hot early Earth, indicating a strongly buffered climate system. Precambrian sediments are enriched in marine authigenic clay, with prominent reductions occurring in concert with Paleozoic and Cenozoic cooling, the expansion of siliceous life, and the radiation of land plants. These findings support the notion that shifts in the locus and extent of clay formation contributed to seawater 18O enrichment, clement early Earth conditions, major climate transitions, and climate stability through the reverse weathering feedback.
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Affiliation(s)
- Terry Isson
- Te Aka Mātuatua, University of Waikato (Tauranga), Bay of Plenty, Tauranga, New Zealand
| | - Sofia Rauzi
- Te Aka Mātuatua, University of Waikato (Tauranga), Bay of Plenty, Tauranga, New Zealand
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4
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Ontiveros DE, Beaugrand G, Lefebvre B, Marcilly CM, Servais T, Pohl A. Impact of global climate cooling on Ordovician marine biodiversity. Nat Commun 2023; 14:6098. [PMID: 37816739 PMCID: PMC10564867 DOI: 10.1038/s41467-023-41685-w] [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: 12/16/2022] [Accepted: 09/14/2023] [Indexed: 10/12/2023] Open
Abstract
Global cooling has been proposed as a driver of the Great Ordovician Biodiversification Event, the largest radiation of Phanerozoic marine animal Life. Yet, mechanistic understanding of the underlying pathways is lacking and other possible causes are debated. Here we couple a global climate model with a macroecological model to reconstruct global biodiversity patterns during the Ordovician. In our simulations, an inverted latitudinal biodiversity gradient characterizes the late Cambrian and Early Ordovician when climate was much warmer than today. During the Mid-Late Ordovician, climate cooling simultaneously permits the development of a modern latitudinal biodiversity gradient and an increase in global biodiversity. This increase is a consequence of the ecophysiological limitations to marine Life and is robust to uncertainties in both proxy-derived temperature reconstructions and organism physiology. First-order model-data agreement suggests that the most conspicuous rise in biodiversity over Earth's history - the Great Ordovician Biodiversification Event - was primarily driven by global cooling.
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Affiliation(s)
| | - Gregory Beaugrand
- Univ. Littoral Côte d'Opale, CNRS, Univ. Lille, UMR 8187 LOG, F-62930, Wimereux, France
| | - Bertrand Lefebvre
- Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, F-69622, Villeurbanne, France
| | | | - Thomas Servais
- Univ. Lille, CNRS, UMR 8198-Evo-Eco-Paleo, F-59000, Lille, France
| | - Alexandre Pohl
- Biogéosciences, UMR 6282 CNRS, Université de Bourgogne, 6 Boulevard Gabriel, 21000, Dijon, France.
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5
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Rasmussen CMØ, Vandenbroucke TRA, Nogues-Bravo D, Finnegan S. Was the Late Ordovician mass extinction truly exceptional? Trends Ecol Evol 2023; 38:812-821. [PMID: 37183151 DOI: 10.1016/j.tree.2023.04.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 04/14/2023] [Accepted: 04/17/2023] [Indexed: 05/16/2023]
Abstract
The Late Ordovician mass extinction event is the oldest of the five great extinction events in the fossil record. It has long been regarded as an outlier among mass extinctions, primarily due to its association with a cooling climate. However, recent temporally better resolved fossil biodiversity estimates complicate this view, providing growing evidence for a prolonged but punctuated biodiversity decline modulated by changes in atmospheric composition, ocean chemistry, and viable habitat area. This evolving view invokes extinction drivers similar to those that occurred during other major extinctions; some are even factors in the current human-induced biodiversity crisis. Even this very ancient and, at first glance, exceptional event conveys important lessons about the intensifying 'sixth mass extinction'.
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Affiliation(s)
| | | | - David Nogues-Bravo
- Center for Macroecology, Evolution and Climate, Globe Institute, University of Copenhagen, Copenhagen, Denmark
| | - Seth Finnegan
- University of California Museum of Paleontology and Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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6
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Burton ZFM, McHargue T, Kremer CH, Bloch RB, Gooley JT, Jaikla C, Harrington J, Graham SA. Peak Cenozoic warmth enabled deep-sea sand deposition. Sci Rep 2023; 13:1276. [PMID: 36755039 PMCID: PMC9908870 DOI: 10.1038/s41598-022-27138-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 12/27/2022] [Indexed: 02/10/2023] Open
Abstract
The early Eocene (~ 56-48 million years ago) was marked by peak Cenozoic warmth and sea levels, high CO2, and largely ice-free conditions. This time has been described as a period of increased continental erosion and silicate weathering. However, these conclusions are based largely on geochemical investigation of marine mudstones and carbonates or study of intermontane Laramide basin settings. Here, we evaluate the marine coarse siliciclastic response to early Paleogene hothouse climatic and oceanographic conditions. We compile an inventory of documented sand-rich (turbidite) deep-marine depositional systems, recording 59 instances of early Eocene turbidite systems along nearly all continental margins despite globally-elevated sea levels. Sand-rich systems were widespread on active margins (42 instances), but also on passive margins (17 instances). Along passive margins, 13 of 17 early Eocene systems are associated with known Eocene-age fluvial systems, consistent with a fluvial clastic response to Paleogene warming. We suggest that deep-marine sedimentary basins preserve clastic records of early Eocene climatic extremes. We also suggest that in addition to control by eustasy and tectonism, climate-driven increases in sediment supply (e.g., drainage integration, global rainfall, denudation) may significantly contribute to the global distribution and volume of coarse-grained deep-marine deposition despite high sea level.
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Affiliation(s)
- Zachary F. M. Burton
- grid.168010.e0000000419368956Department of Geological Sciences, Stanford University, Stanford, CA 94305 USA
| | - Tim McHargue
- grid.168010.e0000000419368956Department of Geological Sciences, Stanford University, Stanford, CA 94305 USA
| | - Christopher H. Kremer
- grid.40263.330000 0004 1936 9094Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912 USA
| | - Roger B. Bloch
- grid.168010.e0000000419368956Department of Geological Sciences, Stanford University, Stanford, CA 94305 USA
| | - Jared T. Gooley
- grid.2865.90000000121546924U.S. Geological Survey, Alaska Science Center, Anchorage, AK 99508 USA
| | - Chayawan Jaikla
- grid.168010.e0000000419368956Department of Geological Sciences, Stanford University, Stanford, CA 94305 USA
| | - Jake Harrington
- grid.168010.e0000000419368956Department of Geological Sciences, Stanford University, Stanford, CA 94305 USA
| | - Stephan A. Graham
- grid.168010.e0000000419368956Department of Geological Sciences, Stanford University, Stanford, CA 94305 USA
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Sperling EA, Boag TH, Duncan MI, Endriga CR, Marquez JA, Mills DB, Monarrez PM, Sclafani JA, Stockey RG, Payne JL. Breathless through Time: Oxygen and Animals across Earth's History. THE BIOLOGICAL BULLETIN 2022; 243:184-206. [PMID: 36548971 DOI: 10.1086/721754] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
AbstractOxygen levels in the atmosphere and ocean have changed dramatically over Earth history, with major impacts on marine life. Because the early part of Earth's history lacked both atmospheric oxygen and animals, a persistent co-evolutionary narrative has developed linking oxygen change with changes in animal diversity. Although it was long believed that oxygen rose to essentially modern levels around the Cambrian period, a more muted increase is now believed likely. Thus, if oxygen increase facilitated the Cambrian explosion, it did so by crossing critical ecological thresholds at low O2. Atmospheric oxygen likely remained at low or moderate levels through the early Paleozoic era, and this likely contributed to high metazoan extinction rates until oxygen finally rose to modern levels in the later Paleozoic. After this point, ocean deoxygenation (and marine mass extinctions) is increasingly linked to large igneous province eruptions-massive volcanic carbon inputs to the Earth system that caused global warming, ocean acidification, and oxygen loss. Although the timescales of these ancient events limit their utility as exact analogs for modern anthropogenic global change, the clear message from the geologic record is that large and rapid CO2 injections into the Earth system consistently cause the same deadly trio of stressors that are observed today. The next frontier in understanding the impact of oxygen changes (or, more broadly, temperature-dependent hypoxia) in deep time requires approaches from ecophysiology that will help conservation biologists better calibrate the response of the biosphere at large taxonomic, spatial, and temporal scales.
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8
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Life rather than climate influences diversity at scales greater than 40 million years. Nature 2022; 607:307-312. [PMID: 35732740 DOI: 10.1038/s41586-022-04867-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 05/12/2022] [Indexed: 11/08/2022]
Abstract
The diversity of life on Earth is controlled by hierarchical processes that interact over wide ranges of timescales1. Here, we consider the megaclimate regime2 at scales ≥1 million years (Myr). We focus on determining the domains of 'wandering' stochastic Earth system processes ('Court Jester'3) and stabilizing biotic interactions that induce diversity dependence of fluctuations in macroevolutionary rates ('Red Queen'4). Using state-of-the-art multiscale Haar and cross-Haar fluctuation analyses, we analysed the global genus-level Phanerozoic marine animal Paleobiology Database record of extinction rates (E), origination rates (O) and diversity (D) as well as sea water palaeotemperatures (T). Over the entire observed range from several million years to several hundred million years, we found that the fluctuations of T, E and O showed time-scaling behaviour. The megaclimate was characterized by positive scaling exponents-it is therefore apparently unstable. E and O are also scaling but with negative exponents-stable behaviour that is biotically mediated. For D, there were two regimes with a crossover at critical timescale [Formula: see text] ≈ 40 Myr. For shorter timescales, D exhibited nearly the same positive scaling as the megaclimate palaeotemperatures, whereas for longer timescales it tracks the scaling of macroevolutionary rates. At scales of at least [Formula: see text] there is onset of diversity dependence of E and O, probably enabled by mixing and synchronization (globalization) of the biota by geodispersal ('Geo-Red Queen').
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Abstract
The Cambrian is the most poorly dated period of the past 541 million years. This hampers analysis of profound environmental and biological changes that took place during this period. Astronomically forced climate cycles recognized in sediments and anchored to radioisotopic ages provide a powerful geochronometer that has fundamentally refined Mesozoic-Cenozoic time scales but not yet the Palaeozoic. Here we report a continuous astronomical signal detected as geochemical variations (1 mm resolution) in the late Cambrian Alum Shale Formation that is used to establish a 16-Myr-long astronomical time scale, anchored by radioisotopic dates. The resulting time scale is biostratigraphically well-constrained, allowing correlation of the late Cambrian global stage boundaries with the 405-kyr astrochronological framework. This enables a first assessment, in numerical time, of the evolution of major biotic and abiotic changes, including the end-Marjuman extinctions and the Steptoean Positive Carbon Isotope Excursion, that characterized the late Cambrian Earth.
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Gilbert PUPA, Bergmann KD, Boekelheide N, Tambutté S, Mass T, Marin F, Adkins JF, Erez J, Gilbert B, Knutson V, Cantine M, Hernández JO, Knoll AH. Biomineralization: Integrating mechanism and evolutionary history. SCIENCE ADVANCES 2022; 8:eabl9653. [PMID: 35263127 PMCID: PMC8906573 DOI: 10.1126/sciadv.abl9653] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Calcium carbonate (CaCO3) biomineralizing organisms have played major roles in the history of life and the global carbon cycle during the past 541 Ma. Both marine diversification and mass extinctions reflect physiological responses to environmental changes through time. An integrated understanding of carbonate biomineralization is necessary to illuminate this evolutionary record and to understand how modern organisms will respond to 21st century global change. Biomineralization evolved independently but convergently across phyla, suggesting a unity of mechanism that transcends biological differences. In this review, we combine CaCO3 skeleton formation mechanisms with constraints from evolutionary history, omics, and a meta-analysis of isotopic data to develop a plausible model for CaCO3 biomineralization applicable to all phyla. The model provides a framework for understanding the environmental sensitivity of marine calcifiers, past mass extinctions, and resilience in 21st century acidifying oceans. Thus, it frames questions about the past, present, and future of CaCO3 biomineralizing organisms.
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Affiliation(s)
- Pupa U. P. A. Gilbert
- Departments of Physics, Chemistry, Geoscience, and Materials Science, University of Wisconsin-Madison, Madison, WI 53706, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Corresponding author. (P.U.P.A.G.); (A.H.K.)
| | - Kristin D. Bergmann
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Nicholas Boekelheide
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Sylvie Tambutté
- Centre Scientifique de Monaco, Department of Marine Biology, 98000 Monaco, Principality of Monaco
| | - Tali Mass
- University of Haifa, Marine Biology Department, Mt. Carmel, Haifa 31905, Israel
| | - Frédéric Marin
- Université de Bourgogne–Franche-Comté (UBFC), Laboratoire Biogéosciences, UMR CNRS 6282, Bâtiment des Sciences Gabriel, 21000 Dijon, France
| | - Jess F. Adkins
- Geological and Planetary Sciences, California Institute of Technology, MS 100-23, Pasadena, CA 91125, USA
| | - Jonathan Erez
- The Hebrew University of Jerusalem, Institute of Earth Sciences, Jerusalem 91904, Israel
| | - Benjamin Gilbert
- Energy Geoscience Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Vanessa Knutson
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Marjorie Cantine
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - Javier Ortega Hernández
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Andrew H. Knoll
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
- Corresponding author. (P.U.P.A.G.); (A.H.K.)
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11
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Decreasing Phanerozoic extinction intensity as a consequence of Earth surface oxygenation and metazoan ecophysiology. Proc Natl Acad Sci U S A 2021; 118:2101900118. [PMID: 34607946 DOI: 10.1073/pnas.2101900118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2021] [Indexed: 11/18/2022] Open
Abstract
The decline in background extinction rates of marine animals through geologic time is an established but unexplained feature of the Phanerozoic fossil record. There is also growing consensus that the ocean and atmosphere did not become oxygenated to near-modern levels until the mid-Paleozoic, coinciding with the onset of generally lower extinction rates. Physiological theory provides us with a possible causal link between these two observations-predicting that the synergistic impacts of oxygen and temperature on aerobic respiration would have made marine animals more vulnerable to ocean warming events during periods of limited surface oxygenation. Here, we evaluate the hypothesis that changes in surface oxygenation exerted a first-order control on extinction rates through the Phanerozoic using a combined Earth system and ecophysiological modeling approach. We find that although continental configuration, the efficiency of the biological carbon pump in the ocean, and initial climate state all impact the magnitude of modeled biodiversity loss across simulated warming events, atmospheric oxygen is the dominant predictor of extinction vulnerability, with metabolic habitat viability and global ecophysiotype extinction exhibiting inflection points around 40% of present atmospheric oxygen. Given this is the broad upper limit for estimates of early Paleozoic oxygen levels, our results are consistent with the relative frequency of high-magnitude extinction events (particularly those not included in the canonical big five mass extinctions) early in the Phanerozoic being a direct consequence of limited early Paleozoic oxygenation and temperature-dependent hypoxia responses.
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12
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Abstract
There can be no doubt that early land plant evolution transformed the planet but, until recently, how and when this was achieved was unclear. Coincidence in the first appearance of land plant fossils and formative shifts in atmospheric oxygen and CO2 are an artefact of the paucity of earlier terrestrial rocks. Disentangling the timing of land plant bodyplan assembly and its impact on global biogeochemical cycles has been precluded by uncertainty concerning the relationships of bryophytes to one another and to the tracheophytes, as well as the timescale over which these events unfolded. New genome and transcriptome sequencing projects, combined with the application of sophisticated phylogenomic modelling methods, have yielded increasing support for the Setaphyta clade of liverworts and mosses, within monophyletic bryophytes. We consider the evolution of anatomy, genes, genomes and of development within this phylogenetic context, concluding that many vascular plant (tracheophytes) novelties were already present in a comparatively complex last common ancestor of living land plants (embryophytes). Molecular clock analyses indicate that embryophytes emerged in a mid-Cambrian to early Ordovician interval, compatible with hypotheses on their role as geoengineers, precipitating early Palaeozoic glaciations.
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Affiliation(s)
- Philip C J Donoghue
- School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK.
| | - C Jill Harrison
- School of Biological Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Jordi Paps
- School of Biological Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Harald Schneider
- School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK; Center of Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Yunnan, China
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