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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Endress MGA, Penn JL, Boag TH, Burford BP, Sperling EA, Deutsch CA. Thermal optima in the hypoxia tolerance of marine ectotherms: Physiological causes and biogeographic consequences. PLoS Biol 2024; 22:e3002443. [PMID: 38227580 PMCID: PMC10790991 DOI: 10.1371/journal.pbio.3002443] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 11/21/2023] [Indexed: 01/18/2024] Open
Abstract
The minimum O2 needed to fuel the demand of aquatic animals is commonly observed to increase with temperature, driven by accelerating metabolism. However, recent measurements of critical O2 thresholds ("Pcrit") reveal more complex patterns, including those with a minimum at an intermediate thermal "optimum". To discern the prevalence, physiological drivers, and biogeographic manifestations of such curves, we analyze new experimental and biogeographic data using a general dynamic model of aquatic water breathers. The model simulates the transfer of oxygen from ambient water through a boundary layer and into animal tissues driven by temperature-dependent rates of metabolism, diffusive gas exchange, and ventilatory and circulatory systems with O2-protein binding. We find that a thermal optimum in Pcrit can arise even when all physiological rates increase steadily with temperature. This occurs when O2 supply at low temperatures is limited by a process that is more temperature sensitive than metabolism, but becomes limited by a less sensitive process at warmer temperatures. Analysis of published species respiratory traits suggests that this scenario is not uncommon in marine biota, with ventilation and circulation limiting supply under cold conditions and diffusion limiting supply at high temperatures. Using occurrence data, we show that species with these physiological traits inhabit lowest O2 waters near the optimal temperature for hypoxia tolerance and are restricted to higher O2 at temperatures above and below this optimum. Our results imply that hypoxia tolerance can decline under both cold and warm conditions and thus may influence both poleward and equatorward species range limits.
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Affiliation(s)
- Martin-Georg A. Endress
- School of Oceanography, University of Washington, Seattle, Washington, United States of America
- Institute of Zoology, University of Cologne, Cologne, Germany
| | - Justin L. Penn
- School of Oceanography, University of Washington, Seattle, Washington, United States of America
- Department of Geosciences, Princeton University, Princeton, New Jersey, United States of America
| | - Thomas H. Boag
- Department of Geosciences, Princeton University, Princeton, New Jersey, United States of America
| | - Benjamin P. Burford
- Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
- National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southwest Fisheries Science Center, Santa Cruz, California, United States of America
| | - Erik A. Sperling
- Department of Earth and Planetary Sciences, Stanford University, Stanford, California, United States of America
| | - Curtis A. Deutsch
- School of Oceanography, University of Washington, Seattle, Washington, United States of America
- Department of Geosciences, Princeton University, Princeton, New Jersey, United States of America
- High Meadows Environmental Institute, Princeton University, Princeton, New Jersey, United States of America
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Duncan MI, Micheli F, Boag TH, Marquez JA, Deres H, Deutsch CA, Sperling EA. Oxygen availability and body mass modulate ectotherm responses to ocean warming. Nat Commun 2023; 14:3811. [PMID: 37369654 DOI: 10.1038/s41467-023-39438-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 06/13/2023] [Indexed: 06/29/2023] Open
Abstract
In an ocean that is rapidly warming and losing oxygen, accurate forecasting of species' responses must consider how this environmental change affects fundamental aspects of their physiology. Here, we develop an absolute metabolic index (ΦA) that quantifies how ocean temperature, dissolved oxygen and organismal mass interact to constrain the total oxygen budget an organism can use to fuel sustainable levels of aerobic metabolism. We calibrate species-specific parameters of ΦA with physiological measurements for red abalone (Haliotis rufescens) and purple urchin (Strongylocentrotus purpuratus). ΦA models highlight that the temperature where oxygen supply is greatest shifts cooler when water loses oxygen or organisms grow larger, providing a mechanistic explanation for observed thermal preference patterns. Viable habitat forecasts are disproportionally deleterious for red abalone, revealing how species-specific physiologies modulate the intensity of a common climate signal, captured in the newly developed ΦA framework.
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Affiliation(s)
- Murray I Duncan
- Earth and Planetary Science, Stanford University, Stanford, CA, USA.
- Oceans Department, Hopkins Marine Station, Stanford University, Pacific Grove, CA, USA.
- Department of Environment, University of Seychelles, Anse Royale, Seychelles.
- Blue Economy Research Institute, University of Seychelles, Anse Royale, Seychelles.
- Department of Ichthyology and Fisheries Science, Rhodes University, Makhanda, South Africa.
| | - Fiorenza Micheli
- Oceans Department, Hopkins Marine Station, Stanford University, Pacific Grove, CA, USA
- Stanford Center for Ocean Solutions, Stanford University, Pacific Grove, CA, USA
| | - Thomas H Boag
- Earth and Planetary Science, Stanford University, Stanford, CA, USA
- Department of Earth and Planetary Sciences, Yale University, New Haven, CT, 06511, USA
| | - J Andres Marquez
- Earth and Planetary Science, Stanford University, Stanford, CA, USA
| | - Hailey Deres
- Earth Systems, Stanford University, Stanford, CA, USA
| | - Curtis A Deutsch
- Department of Geosciences and the High Meadows Environmental Institute, Princeton, NJ, USA
| | - Erik A Sperling
- Earth and Planetary Science, Stanford University, Stanford, CA, 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. Biol Bull 2022; 243:184-206. [PMID: 36548971 DOI: 10.1086/721754] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [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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Farrell ÚC, Samawi R, Anjanappa S, Klykov R, Adeboye OO, Agic H, Ahm AC, Boag TH, Bowyer F, Brocks JJ, Brunoir TN, Canfield DE, Chen X, Cheng M, Clarkson MO, Cole DB, Cordie DR, Crockford PW, Cui H, Dahl TW, Mouro LD, Dewing K, Dornbos SQ, Drabon N, Dumoulin JA, Emmings JF, Endriga CR, Fraser TA, Gaines RR, Gaschnig RM, Gibson TM, Gilleaudeau GJ, Gill BC, Goldberg K, Guilbaud R, Halverson GP, Hammarlund EU, Hantsoo KG, Henderson MA, Hodgskiss MS, Horner TJ, Husson JM, Johnson B, Kabanov P, Brenhin Keller C, Kimmig J, Kipp MA, Knoll AH, Kreitsmann T, Kunzmann M, Kurzweil F, LeRoy MA, Li C, Lipp AG, Loydell DK, Lu X, Macdonald FA, Magnall JM, Mänd K, Mehra A, Melchin MJ, Miller AJ, Mills NT, Mwinde CN, O'Connell B, Och LM, Ossa Ossa F, Pagès A, Paiste K, Partin CA, Peters SE, Petrov P, Playter TL, Plaza‐Torres S, Porter SM, Poulton SW, Pruss SB, Richoz S, Ritzer SR, Rooney AD, Sahoo SK, Schoepfer SD, Sclafani JA, Shen Y, Shorttle O, Slotznick SP, Smith EF, Spinks S, Stockey RG, Strauss JV, Stüeken EE, Tecklenburg S, Thomson D, Tosca NJ, Uhlein GJ, Vizcaíno MN, Wang H, White T, Wilby PR, Woltz CR, Wood RA, Xiang L, Yurchenko IA, Zhang T, Planavsky NJ, Lau KV, Johnston DT, Sperling EA. The Sedimentary Geochemistry and Paleoenvironments Project. Geobiology 2021; 19:545-556. [PMID: 34219351 PMCID: PMC9291056 DOI: 10.1111/gbi.12462] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 06/05/2021] [Indexed: 06/13/2023]
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Boag TH, Gearty W, Stockey RG. Metabolic tradeoffs control biodiversity gradients through geological time. Curr Biol 2021; 31:2906-2913.e3. [PMID: 33961786 DOI: 10.1016/j.cub.2021.04.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 02/24/2021] [Accepted: 04/09/2021] [Indexed: 11/26/2022]
Abstract
The latitudinal gradient of increasing marine biodiversity from the poles to the tropics is one of the most conspicuous biological patterns in modern oceans.1-3 Low-latitude regions of the global ocean are often hotspots of animal biodiversity, yet they are set to be most critically affected by anthropogenic climate change.4 As ocean temperatures rise and deoxygenation proceeds in the coming centuries, the volume of aerobically viable habitat is predicted to decrease in these zones.5,6 In contrast to the slightly asymmetrical modern latitudinal biodiversity gradient,7 compilations of fossil occurrences indicate peaks in biodiversity may have existed much further away from the equator in the past, with transitions between climate states hypothesized to explain this trend.8-13 We combine a new compilation of fossil mollusc occurrences, paleotemperature proxies, and biogeographic data to reveal a non-monotonic relationship between temperature and diversity in the paleontological record over the last 145 million years. We derive a metabolic model that integrates the kinetic effects of temperature on biodiversity14 with the recently described Metabolic Index that calculates aerobic habitat availability based on the effect of temperature on hypoxia sensitivity.5,15,16 Although factors such as coastal habitat area and homeothermy are important,17,18 we find strong congruence between our metabolic model and our fossil and paleotemperature meta-analysis. We therefore suggest that the effects of ocean temperature on the aerobic scope of marine ectotherms is a primary driver of migrating biodiversity peaks through geologic time and will likely play a role in the restructuring of biodiversity under projected future climate scenarios.
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Affiliation(s)
- Thomas H Boag
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA; Department of Earth and Planetary Sciences, Yale University, New Haven, CT 06511, USA.
| | - William Gearty
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA; School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Richard G Stockey
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA
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Cribb AT, Kenchington CG, Koester B, Gibson BM, Boag TH, Racicot RA, Mocke H, Laflamme M, Darroch SAF. Increase in metazoan ecosystem engineering prior to the Ediacaran-Cambrian boundary in the Nama Group, Namibia. R Soc Open Sci 2019; 6:190548. [PMID: 31598294 PMCID: PMC6774933 DOI: 10.1098/rsos.190548] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 08/23/2019] [Indexed: 05/20/2023]
Abstract
The disappearance of the soft-bodied Ediacara biota at the Ediacaran-Cambrian boundary potentially represents the earliest mass extinction of complex life, although the precise driver(s) of this extinction remain unresolved. The 'biotic replacement' model proposes that an evolutionary radiation of metazoan ecosystem engineers in the latest Ediacaran profoundly altered marine palaeoenvironments, resulting in the extinction of Ediacara biota and setting the stage for the subsequent Cambrian Explosion. However, metazoan ecosystem engineering across the Ediacaran-Cambrian transition has yet to be quantified. Here, we test this key tenet of the biotic replacement model by characterizing the intensity of metazoan bioturbation and ecosystem engineering in trace fossil assemblages throughout the latest Ediacaran Nama Group in southern Namibia. The results illustrate a dramatic increase in both bioturbation and ecosystem engineering intensity in the latest Ediacaran, prior to the Cambrian boundary. Moreover, our analyses demonstrate that the highest-impact ecosystem engineering behaviours were present well before the onset of the Cambrian. These data provide the first support for a fundamental prediction of the biotic replacement model, and evidence for a direct link between the early evolution of ecosystem engineering and the extinction of the Ediacara biota.
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Affiliation(s)
- Alison T. Cribb
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
- Earth Sciences, University of Southern California, Los Angeles, CA 90089-0740, USA
| | | | - Bryce Koester
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
- Department of Biodiversity, Drexel University, Philadelphia, PA, 19104, USA
| | - Brandt M. Gibson
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
| | - Thomas H. Boag
- Geological Sciences, Stanford University, Stanford, CA 94304, USA
| | - Rachel A. Racicot
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
| | - Helke Mocke
- Geological Survey of Namibia, Ministry of Mines and Energy, Windhoek, Namibia
| | - Marc Laflamme
- Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, CanadaL5L 1C6
| | - Simon A. F. Darroch
- Earth and Environmental Science, Vanderbilt University, Nashville, TN 37235-1805, USA
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Muscente AD, Bykova N, Boag TH, Buatois LA, Mángano MG, Eleish A, Prabhu A, Pan F, Meyer MB, Schiffbauer JD, Fox P, Hazen RM, Knoll AH. Ediacaran biozones identified with network analysis provide evidence for pulsed extinctions of early complex life. Nat Commun 2019; 10:911. [PMID: 30796215 PMCID: PMC6384941 DOI: 10.1038/s41467-019-08837-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 01/28/2019] [Indexed: 12/05/2022] Open
Abstract
Rocks of Ediacaran age (~635–541 Ma) contain the oldest fossils of large, complex organisms and their behaviors. These fossils document developmental and ecological innovations, and suggest that extinctions helped to shape the trajectory of early animal evolution. Conventional methods divide Ediacaran macrofossil localities into taxonomically distinct clusters, which may represent evolutionary, environmental, or preservational variation. Here, we investigate these possibilities with network analysis of body and trace fossil occurrences. By partitioning multipartite networks of taxa, paleoenvironments, and geologic formations into community units, we distinguish between biostratigraphic zones and paleoenvironmentally restricted biotopes, and provide empirically robust and statistically significant evidence for a global, cosmopolitan assemblage unique to terminal Ediacaran strata. The assemblage is taxonomically depauperate but includes fossils of recognizable eumetazoans, which lived between two episodes of biotic turnover. These turnover events were the first major extinctions of complex life and paved the way for the Cambrian radiation of animals. The Ediacara biota—the first large, complex organisms to evolve on Earth—disappeared prior to the radiation of animals during the Cambrian Period. Here, Muscente et al. perform network analysis of Ediacaran fossils and show that there were two global extinction events before the Cambrian radiation.
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Affiliation(s)
- A D Muscente
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, 02138, USA. .,Department of Geological Sciences, Jackson School of Geoscience, University of Texas at Austin, Austin, TX, 78712, USA.
| | - Natalia Bykova
- Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch Russian Academy of Sciences, Novosibirsk, 630090, Russia
| | - Thomas H Boag
- Department of Geological Sciences, Stanford University, Stanford, CA, 94305, USA
| | - Luis A Buatois
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, S7n 5E2, Canada
| | - M Gabriela Mángano
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, S7n 5E2, Canada
| | - Ahmed Eleish
- Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Jonsson-Rowland Science Center, 1W19, 110 8th Street, Troy, NY, 12180, USA
| | - Anirudh Prabhu
- Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Jonsson-Rowland Science Center, 1W19, 110 8th Street, Troy, NY, 12180, USA
| | - Feifei Pan
- Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Jonsson-Rowland Science Center, 1W19, 110 8th Street, Troy, NY, 12180, USA
| | - Michael B Meyer
- Earth and Environmental Science Program, Harrisburg University of Science and Technology, Harrisburg, PA, 17101, USA
| | - James D Schiffbauer
- Department of Geological Sciences, University of Missouri, Columbia, MO, 65211, USA.,X-ray Microanalysis Core Facility, University of Missouri, Columbia, MO, 65211, USA
| | - Peter Fox
- Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Jonsson-Rowland Science Center, 1W19, 110 8th Street, Troy, NY, 12180, USA
| | - Robert M Hazen
- Geophysical Laboratory, Carnegie Institution for Science, 5251 Broad Branch Road, Washington, D.C, 20015, USA
| | - Andrew H Knoll
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, 02138, USA.,Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
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Boag TH, Stockey RG, Elder LE, Hull PM, Sperling EA. Oxygen, temperature and the deep-marine stenothermal cradle of Ediacaran evolution. Proc Biol Sci 2018; 285:20181724. [PMID: 30963899 PMCID: PMC6304043 DOI: 10.1098/rspb.2018.1724] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 11/13/2018] [Indexed: 11/12/2022] Open
Abstract
Ediacaran fossils document the early evolution of complex megascopic life, contemporaneous with geochemical evidence for widespread marine anoxia. These data suggest early animals experienced frequent hypoxia. Research has thus focused on the concentration of molecular oxygen (O2) required by early animals, while also considering the impacts of climate. One model, the Cold Cradle hypothesis, proposed the Ediacaran biota originated in cold, shallow-water environments owing to increased O2 solubility. First, we demonstrate using principles of gas exchange that temperature does have a critical role in governing the bioavailability of O2-but in cooler water the supply of O2 is actually lower. Second, the fossil record suggests the Ediacara biota initially occur approximately 571 Ma in deep-water facies, before appearing in shelf environments approximately 555 Ma. We propose an ecophysiological underpinning for this pattern. By combining oceanographic data with new respirometry experiments we show that in the shallow mixed layer where seasonal temperatures fluctuate widely, thermal and partial pressure ( pO2) effects are highly synergistic. The result is that temperature change away from species-specific optima impairs tolerance to low pO2. We hypothesize that deep and particularly stenothermal (narrow temperature range) environments in the Ediacaran ocean were a physiological refuge from the synergistic effects of temperature and low pO2.
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Affiliation(s)
- Thomas H. Boag
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA
| | - Richard G. Stockey
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA
| | - Leanne E. Elder
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA
| | - Pincelli M. Hull
- Department of Geology and Geophysics, Yale University, New Haven, CT 06511, USA
| | - Erik A. Sperling
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA
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10
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Darroch SAF, Sperling EA, Boag TH, Racicot RA, Mason SJ, Morgan AS, Tweedt S, Myrow P, Johnston DT, Erwin DH, Laflamme M. Biotic replacement and mass extinction of the Ediacara biota. Proc Biol Sci 2016; 282:rspb.2015.1003. [PMID: 26336166 DOI: 10.1098/rspb.2015.1003] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The latest Neoproterozoic extinction of the Ediacara biota has been variously attributed to catastrophic removal by perturbations to global geochemical cycles, 'biotic replacement' by Cambrian-type ecosystem engineers, and a taphonomic artefact. We perform the first critical test of the 'biotic replacement' hypothesis using combined palaeoecological and geochemical data collected from the youngest Ediacaran strata in southern Namibia. We find that, even after accounting for a variety of potential sampling and taphonomic biases, the Ediacaran assemblage preserved at Farm Swartpunt has significantly lower genus richness than older assemblages. Geochemical and sedimentological analyses confirm an oxygenated and non-restricted palaeoenvironment for fossil-bearing sediments, thus suggesting that oxygen stress and/or hypersalinity are unlikely to be responsible for the low diversity of communities preserved at Swartpunt. These combined analyses suggest depauperate communities characterized the latest Ediacaran and provide the first quantitative support for the biotic replacement model for the end of the Ediacara biota. Although more sites (especially those recording different palaeoenvironments) are undoubtedly needed, this study provides the first quantitative palaeoecological evidence to suggest that evolutionary innovation, ecosystem engineering and biological interactions may have ultimately caused the first mass extinction of complex life.
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Affiliation(s)
- Simon A F Darroch
- Smithsonian Institution, PO Box 37012, MRC 121, Washington, DC 20013-7012, USA Department of Earth and Environmental Sciences, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235-1805, USA
| | - Erik A Sperling
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA Department of Geological Sciences, Stanford University, 450 Serra Mall Bldg. 320, Stanford, CA 94305, USA
| | - Thomas H Boag
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Road, Ontario, Canada L5 L 1C6
| | - Rachel A Racicot
- Department of Biology, Howard University, 415 College Street NW, Washington, DC 20059, USA
| | - Sara J Mason
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Road, Ontario, Canada L5 L 1C6
| | - Alex S Morgan
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA
| | - Sarah Tweedt
- Smithsonian Institution, PO Box 37012, MRC 121, Washington, DC 20013-7012, USA Department of Behavior, Ecology, Evolution & Systematics, University of Maryland, College Park, MD 20742, USA
| | - Paul Myrow
- Geology Department, Colorado College, 14 E. Cache La Poudre, Colorado Springs, CO 80903, USA
| | - David T Johnston
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA
| | - Douglas H Erwin
- Smithsonian Institution, PO Box 37012, MRC 121, Washington, DC 20013-7012, USA
| | - Marc Laflamme
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Road, Ontario, Canada L5 L 1C6
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