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Weiner T, Tamburini F, Keren N, Keinan J, Angert A. Does metabolic water control the phosphate oxygen isotopes of microbial cells? Front Microbiol 2023; 14:1277349. [PMID: 38053558 PMCID: PMC10694195 DOI: 10.3389/fmicb.2023.1277349] [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: 08/14/2023] [Accepted: 10/30/2023] [Indexed: 12/07/2023] Open
Abstract
The oxygen isotopes ratio (δ18O) of microbial cell water strongly controls the δ18O of cell phosphate and of other oxygen-carrying moieties. Recently it was suggested that the isotopic ratio in cell water is controlled by metabolic water, which is the water produced by cellular respiration. This potentially has important implications for paleoclimate reconstruction, and for measuring microbial carbon use efficiency with the 18O-water method. Carbon use efficiency strongly controls soil organic matter preservation. Here, we directly tested the effect of metabolic water on microbial cells, by conducting experiments with varying the δ18O of headspace O2 and the medium water, and by measuring the δ18O of cell phosphate. The latter is usually assumed to be in isotopic equilibrium with the cell's water. Our results showed no correlation between the δ18O of O2 and that of the cell phosphate, contradicting the hypothesis that metabolic water is an important driver of δ18O of microbial cell water. However, our labeled 18O water experiments indicated that only 43% of the oxygen in the cell's phosphate is derived from equilibration with the medium water, during late-log to early-stationary growing phase. This could be explained by the isotopic effects of intra-and extra-cellular hydrolysis of organic compounds containing phosphate.
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Affiliation(s)
- Tal Weiner
- The Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | | | - Nir Keren
- Department of Plant and Environmental Science, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Jonathan Keinan
- The Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Alon Angert
- The Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
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2
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Nuber S, Rae JWB, Zhang X, Andersen MB, Dumont MD, Mithan HT, Sun Y, de Boer B, Hall IR, Barker S. Indian Ocean salinity build-up primes deglacial ocean circulation recovery. Nature 2023; 617:306-311. [PMID: 37165236 DOI: 10.1038/s41586-023-05866-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 02/17/2023] [Indexed: 05/12/2023]
Abstract
The Indian Ocean provides a source of salt for North Atlantic deep-water convection sites, via the Agulhas Leakage, and may thus drive changes in the ocean's overturning circulation1-3. However, little is known about the salt content variability of Indian Ocean and Agulhas Leakage waters during past glacial cycles and how this may influence circulation. Here we show that the glacial Indian Ocean surface salt budget was notably different from the modern, responding dynamically to changes in sea level. Indian Ocean surface salinity increased during glacial intensification, peaking in glacial maxima. We find that this is due to rapid land exposure in the Indonesian archipelago induced by glacial sea-level lowering, and we suggest a mechanistic link via reduced input of relatively fresh Indonesian Throughflow waters into the Indian Ocean. Using climate model results, we show that the release of this glacial Indian Ocean salinity via the Agulhas Leakage during deglaciation can directly impact the Atlantic Meridional Overturning Circulation and global climate.
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Affiliation(s)
- Sophie Nuber
- School of Earth and Environmental Sciences, Cardiff University, Cardiff, UK.
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK.
- Department of Geosciences, National Taiwan University, Taipei City, Taiwan.
| | - James W B Rae
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - Xu Zhang
- State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment (TPESRE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China
| | - Morten B Andersen
- School of Earth and Environmental Sciences, Cardiff University, Cardiff, UK
| | - Matthew D Dumont
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK
| | - Huw T Mithan
- Department of Geosciences, National Taiwan University, Taipei City, Taiwan
| | - Yuchen Sun
- Alfred Wegener Institute, Bremerhaven, Germany
| | - Bas de Boer
- Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Ian R Hall
- School of Earth and Environmental Sciences, Cardiff University, Cardiff, UK
| | - Stephen Barker
- School of Earth and Environmental Sciences, Cardiff University, Cardiff, UK
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3
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Adams A, Daval D, Baumgartner LP, Bernard S, Vennemann T, Cisneros-Lazaro D, Stolarski J, Baronnet A, Grauby O, Guo J, Meibom A. Rapid grain boundary diffusion in foraminifera tests biases paleotemperature records. COMMUNICATIONS EARTH & ENVIRONMENT 2023; 4:144. [PMID: 38665181 PMCID: PMC11041775 DOI: 10.1038/s43247-023-00798-2] [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: 05/20/2022] [Accepted: 04/06/2023] [Indexed: 04/28/2024]
Abstract
The oxygen isotopic compositions of fossil foraminifera tests constitute a continuous proxy record of deep-ocean and sea-surface temperatures spanning the last 120 million years. Here, by incubating foraminifera tests in 18O-enriched artificial seawater analogues, we demonstrate that the oxygen isotopic composition of optically translucent, i.e., glassy, fossil foraminifera calcite tests can be measurably altered at low temperatures through rapid oxygen grain-boundary diffusion without any visible ultrastructural changes. Oxygen grain boundary diffusion occurs sufficiently fast in foraminifera tests that, under normal upper oceanic sediment conditions, their grain boundaries will be in oxygen isotopic equilibrium with the surrounding pore fluids on a time scale of <100 years, resulting in a notable but correctable bias of the paleotemperature record. When applied to paleotemperatures from 38,400 foraminifera tests used in paleoclimate reconstructions, grain boundary diffusion can be shown to bias prior paleotemperature estimates by as much as +0.86 to -0.46 °C. The process is general and grain boundary diffusion corrections can be applied to other polycrystalline biocarbonates composed of small nanocrystallites (<100 nm), such as those produced by corals, brachiopods, belemnites, and molluscs, the fossils of which are all highly susceptible to the effects of grain boundary diffusion.
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Affiliation(s)
- Arthur Adams
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Damien Daval
- ISTerre, Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS, IRD, IFSTTAR, 38058 Grenoble, France
| | - Lukas P. Baumgartner
- Institute of Earth Surface Dynamics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Sylvain Bernard
- Museum National d’Histoire Naturelle, Sorbonne Université, CNRS UMR 7590, IMPMC, 75005 Paris, France
| | - Torsten Vennemann
- Institute of Earth Surface Dynamics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Deyanira Cisneros-Lazaro
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Jarosław Stolarski
- Institute of Paleobiology, Polish Academy of Sciences, PL-00-818 Warsaw, Poland
| | - Alain Baronnet
- CNRS, CINaM, Aix-Marseille Université, 13009 Marseille, France
| | - Olivier Grauby
- CNRS, CINaM, Aix-Marseille Université, 13009 Marseille, France
| | - Jinming Guo
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Anders Meibom
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
- Center for Advanced Surface Analysis, Institute of Earth Science, University of Lausanne, CH−1015 Lausanne, Switzerland
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4
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Lacey JH, Sloane HJ, Leng MJ, Crowley SF. Improving the routine analysis of siderite for δ 13 C and δ 18 O in environmental change research. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2023; 37:e9456. [PMID: 36515622 PMCID: PMC10078271 DOI: 10.1002/rcm.9456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Revised: 12/07/2022] [Accepted: 12/09/2022] [Indexed: 06/17/2023]
Abstract
RATIONALE The carbon (δ13 C) and oxygen (δ18 O) isotope composition of siderite (FeCO3 ) is used widely to understand and quantify geochemical processes to reconstruct past climate and environmental change. However, few laboratories follow precisely the same protocol for the preparation and analysis of siderite-bearing materials, which combined with the absence of international reference materials and mineral-specific acid fractionation factors, leads potentially to significant differences in isotope data generated by individual laboratories. Here we examine procedures for the isotope analysis of siderite and discuss factors potentially contributing to inconsistencies in sample measurement data. METHODS Isotope analysis of siderite is first assessed using similar versions of the classical off-line, sealed vessel acid digestion method by comparing data sets obtained from intercomparison materials measured at two participating laboratories. We then compare data from the classical method against those generated using an automated preparation technique using data produced from an independent set of test materials. RESULTS Measurement of siderite δ13 C is generally both repeatable and reproducible, but measurement of δ18 O may be subject to large (~1‰), method-dependent bias for siderite reacted at differing temperatures (70°C and 100°C) under classical and automated CO2 preparation conditions. The potential for poor oxygen isotope measurement reproducibility is amplified by local differences in sample preparation protocols and procedures used to calibrate measurement data to international reference scales. CONCLUSIONS We offer suggestions for improving the repeatability and reproducibility of δ13 C and δ18 O analysis on siderite. The challenge of producing consistent isotope data from siderite can only be resolved by ensuring the availability of siderite reference materials to facilitate identical treatment as a basis for minimising method-dependent contributions to data inconsistency between laboratories.
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Affiliation(s)
- Jack H. Lacey
- National Environmental Isotope Facility, British Geological SurveyNottinghamUK
| | - Hilary J. Sloane
- National Environmental Isotope Facility, British Geological SurveyNottinghamUK
| | - Melanie J. Leng
- National Environmental Isotope Facility, British Geological SurveyNottinghamUK
- Centre for Environmental Geochemistry, School of Biosciences, Sutton Bonington CampusUniversity of NottinghamLoughboroughUK
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5
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van der Ploeg R, Cramwinckel MJ, Kocken IJ, Leutert TJ, Bohaty SM, Fokkema CD, Hull PM, Meckler AN, Middelburg JJ, Müller IA, Penman DE, Peterse F, Reichart GJ, Sexton PF, Vahlenkamp M, De Vleeschouwer D, Wilson PA, Ziegler M, Sluijs A. North Atlantic surface ocean warming and salinization in response to middle Eocene greenhouse warming. SCIENCE ADVANCES 2023; 9:eabq0110. [PMID: 36696500 PMCID: PMC9876553 DOI: 10.1126/sciadv.abq0110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 12/22/2022] [Indexed: 06/17/2023]
Abstract
Quantitative reconstructions of hydrological change during ancient greenhouse warming events provide valuable insight into warmer-than-modern hydrological cycles but are limited by paleoclimate proxy uncertainties. We present sea surface temperature (SST) records and seawater oxygen isotope (δ18Osw) estimates for the Middle Eocene Climatic Optimum (MECO), using coupled carbonate clumped isotope (Δ47) and oxygen isotope (δ18Oc) data of well-preserved planktonic foraminifera from the North Atlantic Newfoundland Drifts. These indicate a transient ~3°C warming across the MECO, with absolute temperatures generally in accordance with trace element (Mg/Ca)-based SSTs but lower than biomarker-based SSTs for the same interval. We find a transient ~0.5‰ shift toward higher δ18Osw, which implies increased salinity in the North Atlantic subtropical gyre and potentially a poleward expansion of its northern boundary in response to greenhouse warming. These observations provide constraints on dynamic ocean response to warming events, which are consistent with theory and model simulations predicting an enhanced hydrological cycle under global warming.
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Affiliation(s)
- Robin van der Ploeg
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Margot J. Cramwinckel
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Ilja J. Kocken
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Thomas J. Leutert
- Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Bergen, Norway
| | - Steven M. Bohaty
- University of Southampton, Waterfront Campus, National Oceanography Centre, Southampton, UK
| | - Chris D. Fokkema
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Pincelli M. Hull
- Department of Geology and Geophysics, Yale University, New Haven, CT, USA
| | - A. Nele Meckler
- Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Bergen, Norway
| | - Jack J. Middelburg
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Inigo A. Müller
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Donald E. Penman
- Department of Geosciences, Utah State University, Logan, UT, USA
| | - Francien Peterse
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Gert-Jan Reichart
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
- NIOZ Royal Netherlands Institute for Sea Research and Utrecht University, Den Burg, Texel, Netherlands
| | - Philip F. Sexton
- School of Environment, Earth & Ecosystem Sciences, The Open University, Milton Keynes, UK
| | - Maximilian Vahlenkamp
- MARUM – Center for Marine and Environmental Sciences, University of Bremen, Bremen, Germany
| | - David De Vleeschouwer
- MARUM – Center for Marine and Environmental Sciences, University of Bremen, Bremen, Germany
- Institute of Geology and Paleontology, University of Münster, Münster, Germany
| | - Paul A. Wilson
- University of Southampton, Waterfront Campus, National Oceanography Centre, Southampton, UK
| | - Martin Ziegler
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
| | - Appy Sluijs
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands
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6
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The latitudinal temperature gradient and its climate dependence as inferred from foraminiferal δ
18
O over the past 95 million years. Proc Natl Acad Sci U S A 2022; 119:e2111332119. [PMID: 35254906 PMCID: PMC8931236 DOI: 10.1073/pnas.2111332119] [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] [Indexed: 12/03/2022] Open
Abstract
The temperature difference between low and high latitudes is one measure of the efficiency of the global climate system in redistributing heat and is used to test the ability of models to represent the climate system through time. Here, we show that the latitudinal temperature gradient has exhibited a consistent inverse relationship with global mean sea-surface temperature for at least the past 95 million years. Our results help reduce conflicts between climate models and empirical estimates of temperature and argue for a fundamental consistency in the dynamics of heat transport and radiative transfer across vastly different background states. The latitudinal temperature gradient is a fundamental state parameter of the climate system tied to the dynamics of heat transport and radiative transfer. Thus, it is a primary target for temperature proxy reconstructions and global climate models. However, reconstructing the latitudinal temperature gradient in past climates remains challenging due to the scarcity of appropriate proxy records and large proxy–model disagreements. Here, we develop methods leveraging an extensive compilation of planktonic foraminifera δ18O to reconstruct a continuous record of the latitudinal sea-surface temperature (SST) gradient over the last 95 million years (My). We find that latitudinal SST gradients ranged from 26.5 to 15.3 °C over a mean global SST range of 15.3 to 32.5 °C, with the highest gradients during the coldest intervals of time. From this relationship, we calculate a polar amplification factor (PAF; the ratio of change in >60° S SST to change in global mean SST) of 1.44 ± 0.15. Our results are closer to model predictions than previous proxy-based estimates, primarily because δ18O-based high-latitude SST estimates more closely track benthic temperatures, yielding higher gradients. The consistent covariance of δ18O values in low- and high-latitude planktonic foraminifera and in benthic foraminifera, across numerous climate states, suggests a fundamental constraint on multiple aspects of the climate system, linking deep-sea temperatures, the latitudinal SST gradient, and global mean SSTs across large changes in atmospheric CO2, continental configuration, oceanic gateways, and the extent of continental ice sheets. This implies an important underlying, internally driven predictability of the climate system in vastly different background states.
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7
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Cisneros-Lazaro D, Adams A, Guo J, Bernard S, Baumgartner LP, Daval D, Baronnet A, Grauby O, Vennemann T, Stolarski J, Escrig S, Meibom A. Fast and pervasive diagenetic isotope exchange in foraminifera tests is species-dependent. Nat Commun 2022; 13:113. [PMID: 35013292 PMCID: PMC8748890 DOI: 10.1038/s41467-021-27782-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 12/10/2021] [Indexed: 11/22/2022] Open
Abstract
Oxygen isotope compositions of fossil foraminifera tests are commonly used proxies for ocean paleotemperatures, with reconstructions spanning the last 112 million years. However, the isotopic composition of these calcitic tests can be substantially altered during diagenesis without discernible textural changes. Here, we investigate fluid-mediated isotopic exchange in pristine tests of three modern benthic foraminifera species (Ammonia sp., Haynesina germanica, and Amphistegina lessonii) following immersion into an 18O-enriched artificial seawater at 90 °C for hours to days. Reacted tests remain texturally pristine but their bulk oxygen isotope compositions reveal rapid and species-dependent isotopic exchange with the water. NanoSIMS imaging reveals the 3-dimensional intra-test distributions of 18O-enrichment that correlates with test ultra-structure and associated organic matter. Image analysis is used to quantify species level differences in test ultrastructure, which explains the observed species-dependent rates of isotopic exchange. Consequently, even tests considered texturally pristine for paleo-climatic reconstruction purposes may have experienced substantial isotopic exchange; critical paleo-temperature record re-examination is warranted. Paleoclimate reconstructions commonly use oxygen isotope compositions from fossil foraminifera tests as proxies. Here, the authors show that these tests exchange O-isotopes with surrounding fluids, with implications for paleotemperature records.
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Affiliation(s)
- Deyanira Cisneros-Lazaro
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
| | - Arthur Adams
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Jinming Guo
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Sylvain Bernard
- Museum National d'Histoire Naturelle, Sorbonne Université, CNRS UMR 7590, IMPMC, 75005, Paris, France
| | - Lukas P Baumgartner
- Center for Advanced Surface Analysis, Institute of Earth Science, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Damien Daval
- ISTerre, Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, 38058, Grenoble, France
| | - Alain Baronnet
- CNRS, CINaM, Aix-Marseille Université, 13009, Marseille, France
| | - Olivier Grauby
- CNRS, CINaM, Aix-Marseille Université, 13009, Marseille, France
| | - Torsten Vennemann
- Institute of Earth Surface Dynamics, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Jarosław Stolarski
- Institute of Paleobiology, Polish Academy of Sciences, PL-00-818, Warsaw, Poland
| | - Stéphane Escrig
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Anders Meibom
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland. .,Center for Advanced Surface Analysis, Institute of Earth Science, University of Lausanne, CH-1015, Lausanne, Switzerland.
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8
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Huck S, Heimhofer U. Early Cretaceous sea surface temperature evolution in subtropical shallow seas. Sci Rep 2021; 11:19765. [PMID: 34611212 PMCID: PMC8492702 DOI: 10.1038/s41598-021-99094-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 09/20/2021] [Indexed: 02/08/2023] Open
Abstract
Late Cretaceous sea surface temperatures (SST) are, amongst others, traditionally reconstructed by compiling oxygen isotope records of planktonic foraminifera obtained from globally distributed pelagic IODP drill cores. In contrast, the evolution of Early Cretaceous SSTs is essentially based on the organic TEX86 palaeothermometer, as oxygen-isotope data derived from well-preserved 'glassy' foraminifer calcite are currently lacking. In order to evaluate the extraordinary warm TEX86-derived SSTs of the Barremian to Aptian (130-123 Ma) subtropics, we present highly resolved sclerochemical profiles of pristine rudist bivalve shells from Tethyan and proto-North Atlantic shallow water carbonate platforms. An inverse correlation of seasonal ontogenetic variations in δ18Orudist and Mg/Ca ratios demonstrates the fidelity of oxygen isotopes as palaeotemperature proxy. The new data shows moderate mean annual SSTs (22-26 °C) for large parts of the Barremian and Aptian and transient warm pulses for the so-called Mid-Barremian Event and Oceanic Anoxic Event 1a (reaching mean annual SSTs of 28 to 30 °C). A positive shift in mean annual oxygen-isotope values (δ18O: ≤ - 0.3‰) coupled with invariant Mg/Ca ratios at the Barremian-Aptian boundary points to a significant net loss of 16O in Tethyan shallow-marine settings. As the positive oxygen-isotope rudist shell values are recorded immediately beneath a major superregional hiatal surface, they are interpreted to be related to a major cooling phase and potential glacio-eustatic sea-level lowering. Our new sclerochemical findings are in clear contrast to open ocean SST records based on TEX86, which indicate exceptionally warm Barremian to earliest Aptian subtropical oceans and weak meridional SST gradients.
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Affiliation(s)
- Stefan Huck
- grid.9122.80000 0001 2163 2777Institut für Geologie, Leibniz Universität Hannover, Callinstraße 30, 30167 Hannover, Germany
| | - Ulrich Heimhofer
- grid.9122.80000 0001 2163 2777Institut für Geologie, Leibniz Universität Hannover, Callinstraße 30, 30167 Hannover, Germany
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9
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Kearns LE, Bohaty SM, Edgar KM, Nogué S, Ezard THG. Searching for Function: Reconstructing Adaptive Niche Changes Using Geochemical and Morphological Data in Planktonic Foraminifera. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.679722] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dead species remain dead. The diversity record of life is littered with examples of declines and radiations, yet no species has ever re-evolved following its true extinction. In contrast, functional traits can transcend diversity declines, often develop iteratively and are taxon-free allowing application across taxa, environments and time. Planktonic foraminifera have an unrivaled, near continuous fossil record for the past 200 million years making them a perfect test organism to understand trait changes through time, but the functional role of morphology in determining habitat occupation has been questioned. Here, we use single specimen stable isotopes to reconstruct the water depth habitat of individual planktonic foraminifera in the genus Subbotina alongside morphological measurements of the tests to understand trait changes through the Middle Eocene Climatic Optimum [MECO: ∼40 Myr ago (mega annum, Ma)]. The MECO is a geologically transient global warming interval that marks the beginning of widespread biotic reorganizations in marine organisms spanning a size spectrum from diatoms to whales. In contrast to other planktonic foraminiferal genera, the subbotinids flourished through this interval despite multiple climatic perturbations superimposed on a changing background climate. Through coupled trait and geochemical analysis, we show that Subbotina survival through this climatically dynamic interval was aided by trait plasticity and a wider ecological niche than previously thought for a subthermocline dwelling genus supporting a generalist life strategy. We also show how individually resolved oxygen isotopes can track shifts in depth occupancy through climatic upheaval. During and following the MECO, temperature changes were substantial in the thermocline and subthermocline in comparison to the muted responses of the surface ocean. In our post-MECO samples, we observe restoration of planktonic foraminifera depth stratification. Despite these changing temperatures and occupied depths, we do not detect a contemporaneous morphological response implying that readily available traits such as test size and shape do not have a clear functional role in this generalist genus. Modern imaging measurement technologies offer a promising route to gather more informative morphological traits for functional analysis, rather than the traditional candidates that are most easily measured.
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10
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Pearson PN, Penny L. Coiling directions in the planktonic foraminifer Pulleniatina: A complex eco-evolutionary dynamic spanning millions of years. PLoS One 2021; 16:e0249113. [PMID: 33848285 PMCID: PMC8043407 DOI: 10.1371/journal.pone.0249113] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 03/11/2021] [Indexed: 12/27/2022] Open
Abstract
Planktonic foraminifera are heterotrophic sexually reproducing marine protists with an exceptionally complete fossil record that provides unique insights into long-term patterns and processes of evolution. Populations often exhibit strong biases towards either right (dextral) or left (sinistral) shells. Deep-sea sediment cores spanning millions of years reveal that some species show large and often rapid fluctuations in their dominant coiling direction through time. This is useful for biostratigraphic correlation but further work is required to understand the population dynamical processes that drive these fluctuations. Here we address the case of coiling fluctuations in the planktonic foraminifer genus Pulleniatina based on new high-resolution counts from two recently recovered sediment cores from either side of the Indonesian through-flow in the tropical west Pacific and Indian Oceans (International Ocean Discovery Program Sites U1486 and U1483). We use single-specimen stable isotope analyses to show that dextral and sinistral shells from the same sediment samples can show significant differences in both carbon and oxygen isotopes, implying a degree of ecological separation between populations. In one case we detect a significant difference in size between dextral and sinistral specimens. We suggest that major fluctuations in coiling ratio are caused by cryptic populations replacing one another in competitive sweeps, a mode of evolution that is more often associated with asexual organisms than with the classical 'biological species concept'.
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Affiliation(s)
- Paul N. Pearson
- School of Earth and Ocean Sciences, Cardiff University, Cardiff, United Kingdom
| | - Luke Penny
- School of Earth and Ocean Sciences, Cardiff University, Cardiff, United Kingdom
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11
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Ball MR, Taylor RJM, Einsle JF, Khanom F, Guillermier C, Harrison RJ. Helium ion microscope - secondary ion mass spectrometry for geological materials. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2020; 11:1504-1515. [PMID: 33083198 PMCID: PMC7537380 DOI: 10.3762/bjnano.11.133] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 09/09/2020] [Indexed: 06/11/2023]
Abstract
The helium ion microscope (HIM) is a focussed ion beam instrument with unprecedented spatial resolution for secondary electron imaging but has traditionally lacked microanalytical capabilities. With the addition of the secondary ion mass spectrometry (SIMS) attachment, the capabilities of the instrument have expanded to microanalysis of isotopes from Li up to hundreds of atomic mass units, effectively opening up the analysis of all natural and geological systems. However, the instrument has thus far been underutilised by the geosciences community, due in no small part to a lack of a thorough understanding of the quantitative capabilities of the instrument. Li represents an ideal element for an exploration of the instrument as a tool for geological samples, due to its importance for economic geology and a green economy, and the difficult nature of observing Li with traditional microanalytical techniques. Also Li represents a "best-case" scenario for isotopic measurements. Here we present details of sample preparation, instrument sensitivity, theoretical, and measured detection limits for both elemental and isotopic analysis as well as practicalities for geological sample analyses of Li alongside a discussion of potential geological use cases of the HIM-SIMS instrument.
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Affiliation(s)
- Matthew R Ball
- Department of Earth Sciences, University of Cambridge, UK
| | | | - Joshua F Einsle
- School of Geographical and Earth Sciences, University of Glasgow, UK
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12
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Stainbank S, Kroon D, Rüggeberg A, Raddatz J, de Leau ES, Zhang M, Spezzaferri S. Controls on planktonic foraminifera apparent calcification depths for the northern equatorial Indian Ocean. PLoS One 2019; 14:e0222299. [PMID: 31513624 PMCID: PMC6767952 DOI: 10.1371/journal.pone.0222299] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 08/26/2019] [Indexed: 11/19/2022] Open
Abstract
Within the world's oceans, regionally distinct ecological niches develop due to differences in water temperature, nutrients, food availability, predation and light intensity. This results in differences in the vertical dispersion of planktonic foraminifera on the global scale. Understanding the controls on these modern-day distributions is important when using these organisms for paleoceanographic reconstructions. As such, this study constrains modern depth habitats for the northern equatorial Indian Ocean, for 14 planktonic foraminiferal species (G. ruber, G. elongatus, G. pyramidalis, G. rubescens, T. sacculifer, G. siphonifera, G. glutinata, N. dutertrei, G. bulloides, G. ungulata, P. obliquiloculata, G. menardii, G. hexagonus, G. scitula) using stable isotopic signatures (δ18O and δ13C) and Mg/Ca ratios. We evaluate two aspects of inferred depth habitats: (1) the significance of the apparent calcification depth (ACD) calculation method/equations and (2) regional species-specific ACD controls. Through a comparison with five global, (sub)tropical studies we found the choice of applied equation and δ18Osw significant and an important consideration when comparing with the published literature. The ACDs of the surface mixed layer and thermocline species show a tight clustering between 73-109 m water depth coinciding with the deep chlorophyll maximum (DCM). Furthermore, the ACDs for the sub-thermocline species are positioned relative to secondary peaks in the local primary production. We surmise that food source plays a key role in the relative living depths for the majority of the investigated planktonic foraminifera within this oligotrophic environment of the Maldives and elsewhere in the tropical oceans.
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Affiliation(s)
| | - Dick Kroon
- School of GeoSciences, Grant Institute, University of Edinburgh,
Edinburgh, United Kingdom
| | - Andres Rüggeberg
- Department of Geosciences, University of Fribourg, Fribourg,
Switzerland
| | - Jacek Raddatz
- Institute of Geosciences, Goethe University Frankfurt, Frankfurt am Main,
Germany
- Frankfurt Isotope and Element Research Center (FIERCE), Goethe University
Frankfurt, Frankfurt am Main, Germany
| | - Erica S. de Leau
- School of GeoSciences, Grant Institute, University of Edinburgh,
Edinburgh, United Kingdom
| | - Manlin Zhang
- School of GeoSciences, Grant Institute, University of Edinburgh,
Edinburgh, United Kingdom
| | - Silvia Spezzaferri
- Department of Geosciences, University of Fribourg, Fribourg,
Switzerland
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13
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Ausín B, Haghipour N, Wacker L, Voelker AHL, Hodell D, Magill C, Looser N, Bernasconi SM, Eglinton TI. Radiocarbon Age Offsets Between Two Surface Dwelling Planktonic Foraminifera Species During Abrupt Climate Events in the SW Iberian Margin. PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY 2019; 34:63-78. [PMID: 30854509 PMCID: PMC6392128 DOI: 10.1029/2018pa003490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2018] [Revised: 12/23/2018] [Accepted: 12/30/2018] [Indexed: 06/09/2023]
Abstract
This study identifies temporal biases in the radiocarbon ages of the planktonic foraminifera species Globigerina bulloides and Globigerinoides ruber (white) in a sediment core from the SW Iberian margin (so-called Shackleton site). Leaching of the outer shell and measurement of the radiocarbon content of both the leachate and leached sample enabled us to identify surface contamination of the tests and its impact on their 14C ages. Incorporation of younger radiocarbon on the outer shell affected both species and had a larger impact downcore. Interspecies comparison of the 14C ages of the leached samples reveal systematic offsets with 14C ages for G. ruber being younger than G. bulloides ages during the last deglaciation and part of the Early and mid-Holocene. The greatest offsets (up to 1,030 years) were found during Heinrich Stadial 1, the Younger Dryas, and part of the Holocene. The potential factors differentially affecting these two planktonic species were assessed by complementary 14C, oxygen and carbon isotopes, and species abundance determinations. The coupled effect of bioturbation with changes in the abundance of G. ruber is invoked to account for the large age offsets. Our results highlight that 14C ages of planktonic foraminifera might be largely compromised even in settings characterized by high sediment accumulation rates. Thus, a careful assessment of potential temporal biases must be performed prior to using 14C ages for paleoclimate investigations or radiocarbon calibrations (e.g., marine calibration curve Marine13, Reimer et al., 2013, https://doi.org/10.2458/azu_js_rc.55.16947).
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Affiliation(s)
| | | | | | - Antje H. L. Voelker
- Centre of Marine Sciences (CCMAR)Universidade do AlgarveFaroPortugal
- Instituto Português do Mar e da AtmosferaLisbonPortugal
| | - David Hodell
- Department of Earth SciencesUniversity of CambridgeCambridgeUK
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14
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Bernard S, Daval D, Ackerer P, Pont S, Meibom A. Reply to 'No substantial long-term bias in the Cenozoic benthic foraminifera oxygen-isotope record'. Nat Commun 2018; 9:2874. [PMID: 30038223 PMCID: PMC6056461 DOI: 10.1038/s41467-018-05304-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 06/28/2018] [Indexed: 11/09/2022] Open
Affiliation(s)
- S Bernard
- Muséum National d'Histoire Naturelle, Sorbonne Université, CNRS UMR 7590, IRD, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Paris, 75005, France.
| | - D Daval
- LHyGeS, CNRS UMR 7517, Université de Strasbourg/EOST, 1 Rue Blessig, Strasbourg, 67084, France
| | - P Ackerer
- LHyGeS, CNRS UMR 7517, Université de Strasbourg/EOST, 1 Rue Blessig, Strasbourg, 67084, France
| | - S Pont
- Muséum National d'Histoire Naturelle, Sorbonne Université, CNRS UMR 7590, IRD, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Paris, 75005, France
| | - A Meibom
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, 1015, Switzerland
- Center for Advanced Surface Analysis, Institute of Earth Sciences, University of Lausanne, Lausanne, 1015, Switzerland
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15
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Hearing TW, Harvey THP, Williams M, Leng MJ, Lamb AL, Wilby PR, Gabbott SE, Pohl A, Donnadieu Y. An early Cambrian greenhouse climate. SCIENCE ADVANCES 2018; 4:eaar5690. [PMID: 29750198 PMCID: PMC5942912 DOI: 10.1126/sciadv.aar5690] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 03/23/2018] [Indexed: 06/08/2023]
Abstract
The oceans of the early Cambrian (~541 to 509 million years ago) were the setting for a marked diversification of animal life. However, sea temperatures-a key component of the early Cambrian marine environment-remain unconstrained, in part because of a substantial time gap in the stable oxygen isotope (δ18O) record before the evolution of euconodonts. We show that previously overlooked sources of fossil biogenic phosphate have the potential to fill this gap. Pristine phosphatic microfossils from the Comley Limestones, UK, yield a robust δ18O signature, suggesting sea surface temperatures of 20° to 25°C at high southern paleolatitudes (~65°S to 70°S) between ~514 and 509 million years ago. These sea temperatures are consistent with the distribution of coeval evaporite and calcrete deposits, peak continental weathering rates, and also our climate model simulations for this interval. Our results support an early Cambrian greenhouse climate comparable to those of the late Mesozoic and early Cenozoic, offering a framework for exploring the interplay between biotic and environmental controls on Cambrian animal diversification.
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Affiliation(s)
- Thomas W. Hearing
- School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester LE1 7RH, UK
- British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
| | - Thomas H. P. Harvey
- School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Mark Williams
- School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Melanie J. Leng
- NERC Isotope Geoscience Facilities, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
- Centre for Environmental Geochemistry, School of Biosciences, Sutton Bonington Campus, University of Nottingham, Loughborough LE12 5RD, UK
| | - Angela L. Lamb
- NERC Isotope Geoscience Facilities, British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
| | - Philip R. Wilby
- British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
| | - Sarah E. Gabbott
- School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester LE1 7RH, UK
| | - Alexandre Pohl
- Aix Marseille Université, CNRS, IRD, Coll France, CEREGE, Aix-en-Provence, France
| | - Yannick Donnadieu
- Aix Marseille Université, CNRS, IRD, Coll France, CEREGE, Aix-en-Provence, France
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16
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Luciani V, D'Onofrio R, Dickens GR, Wade BS. Did Photosymbiont Bleaching Lead to the Demise of Planktic Foraminifer Morozovella at the Early Eocene Climatic Optimum? PALEOCEANOGRAPHY 2017; 32:1115-1136. [PMID: 29398777 PMCID: PMC5784393 DOI: 10.1002/2017pa003138] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 09/24/2017] [Accepted: 09/27/2017] [Indexed: 06/07/2023]
Abstract
The symbiont-bearing mixed-layer planktic foraminiferal genera Morozovella and Acarinina were among the most important calcifiers of early Paleogene tropical-subtropical oceans. A marked and permanent switch in the abundance of these genera is known to have occurred at low-latitude sites at the beginning of the Early Eocene Climatic Optimum (EECO), such that the relative abundance of Morozovella permanently and significantly decreased along with a progressive reduction in the number of species; concomitantly, the genus Acarinina almost doubled its abundance and diversified. Here we examine planktic foraminiferal assemblages and stable isotope compositions of their tests at Ocean Drilling Program Site 1051 (northwest Atlantic) to detail the timing of this biotic event, to document its details at the species level, and to test a potential cause: the loss of photosymbionts (bleaching). We also provide stable isotope measurements of bulk carbonate to refine the stratigraphy at Site 1051 and to determine when changes in Morozovella species composition and their test size occurred. We demonstrate that the switch in Morozovella and Acarinina abundance occurred rapidly and in coincidence with a negative carbon isotope excursion known as the J event (~53 Ma), which marks the start of the EECO. We provide evidence of photosymbiont loss after the J event from a size-restricted δ13C analysis. However, such inferred bleaching was transitory and also occurred in the acarininids. The geologically rapid switch in planktic foraminiferal genera during the early Eocene was a major evolutionary change within marine biota, but loss of photosymbionts was not the primary causal mechanism.
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Affiliation(s)
- Valeria Luciani
- Department of Physics and Earth SciencesFerrara UniversityFerraraItaly
| | - Roberta D'Onofrio
- Department of Physics and Earth SciencesFerrara UniversityFerraraItaly
| | | | - Bridget S. Wade
- Department of Earth SciencesUniversity College LondonLondonUK
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17
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Bernard S, Daval D, Ackerer P, Pont S, Meibom A. Burial-induced oxygen-isotope re-equilibration of fossil foraminifera explains ocean paleotemperature paradoxes. Nat Commun 2017; 8:1134. [PMID: 29070888 PMCID: PMC5656689 DOI: 10.1038/s41467-017-01225-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 08/25/2017] [Indexed: 11/13/2022] Open
Abstract
Oxygen-isotope compositions of fossilised planktonic and benthic foraminifera tests are used as proxies for surface- and deep-ocean paleotemperatures, providing a continuous benthic record for the past 115 Ma. However, visually imperceptible processes can alter these proxies during sediment burial. Here, we investigate the diffusion-controlled re-equilibration process with experiments exposing foraminifera tests to elevated pressures and temperatures in isotopically heavy artificial seawater (H218O), followed by scanning electron microscopy and quantitative NanoSIMS imaging: oxygen-isotope compositions changed heterogeneously at submicrometer length scales without any observable modifications of the test ultrastructures. In parallel, numerical modelling of diffusion during burial shows that oxygen-isotope re-equilibration of fossil foraminifera tests can cause significant overestimations of ocean paleotemperatures on a time scale of 107 years under natural conditions. Our results suggest that the late Cretaceous and Paleogene deep-ocean and high-latitude surface-ocean temperatures were significantly lower than is generally accepted, thereby explaining the paradox of the low equator-to-pole surface-ocean thermal gradient inferred for these periods. The oxygen-isotope composition of fossil foraminifera tests is an established proxy for ocean paleotemperatures. Here, the authors show that isotope re-equilibration can occur during sediment burial without structural modification of the tests and cause a substantial overestimation of ocean paleotemperatures.
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Affiliation(s)
- S Bernard
- IMPMC, Sorbonne Universités, CNRS UMR 7590, MNHN, UPMC, IRD UMR 206, 61 Rue Buffon, 75005, Paris, France.
| | - D Daval
- LHyGeS, CNRS UMR 7517, Université de Strasbourg/EOST, 1 Rue Blessig, 67084, Strasbourg, France
| | - P Ackerer
- LHyGeS, CNRS UMR 7517, Université de Strasbourg/EOST, 1 Rue Blessig, 67084, Strasbourg, France
| | - S Pont
- IMPMC, Sorbonne Universités, CNRS UMR 7590, MNHN, UPMC, IRD UMR 206, 61 Rue Buffon, 75005, Paris, France
| | - A Meibom
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.,Center for Advanced Surface Analysis, Institute of Earth Sciences, University of Lausanne, 1015, Lausanne, Switzerland
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18
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Prasanna K, Ghosh P, Bhattacharya SK, Mohan K, Anilkumar N. Isotopic disequilibrium in Globigerina bulloides and carbon isotope response to productivity increase in Southern Ocean. Sci Rep 2016; 6:21533. [PMID: 26903274 PMCID: PMC4763226 DOI: 10.1038/srep21533] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 01/14/2016] [Indexed: 11/17/2022] Open
Abstract
Oxygen and carbon isotope ratios in planktonic foraminifera Globigerina bulloides collected from tow samples along a transect from the equatorial Indian ocean to the Southern Ocean (45°E and 80°E and 10°N to 53°S) were analysed and compared with the equilibrium δ18O and δ13C values of calcite calculated using the temperature and isotopic composition of the water column. The results agree within ~0.25‰ for the region between 10°N and 40°S and 75–200 m water depth which is considered to be the habitat of Globigerina bulloides. Further south (from 40°S to 55°S), however, the measured δ18O and δ13C values are higher than the expected values by ~2‰ and ~1‰ respectively. These enrichments can be attributed to either a ‘vital effect’ or a higher calcification rate. An interesting pattern of increase in the δ13C(DIC) value of the surface water with latitude is observed between 35°S and~ 60°S, with a peak at~ 42°S. This can be caused by increased organic matter production and associated removal. A simple model accounting for the increase in the δ13C(DIC) values is proposed which fits well with the observed chlorophyll abundance as a function of latitude.
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Affiliation(s)
- K Prasanna
- Centre for Earth Sciences (CEaS), Indian Institute of Science, Bangalore-560012, India
| | - Prosenjit Ghosh
- Centre for Earth Sciences (CEaS), Indian Institute of Science, Bangalore-560012, India.,Divecha Centre for Climate Change, Indian Institute of Science, Bangalore-560012, India
| | - S K Bhattacharya
- Centre for Earth Sciences (CEaS), Indian Institute of Science, Bangalore-560012, India
| | - K Mohan
- Geology and Geotechnical Engineering Division, School of Mechanical and Building Sciences, VIT University (Chennai Campus), Chennai-600127, India
| | - N Anilkumar
- National Centre for Antarctic and Ocean Research, Vasco da Gama, Goa-403 804, India
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