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Hoefs J, Harmon RS. Isotopic history of seawater: the stable isotope character of the global ocean at present and in the geological past. Isotopes Environ Health Stud 2023; 59:349-411. [PMID: 37877261 DOI: 10.1080/10256016.2023.2271127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Accepted: 09/10/2023] [Indexed: 10/26/2023]
Abstract
After the atmosphere, the ocean is the most well-mixed and homogeneous global geochemical reservoir. Both physical and biological processes generate elemental and isotope variations in seawater. Contrasting geochemical behaviors cause elements to be susceptible to different fractionation mechanisms, with their isotopes providing unique insights into the composition and evolution of the ocean over the course of geological history. Supplementing the traditional stable isotopes (H, C, O, N, S) that provide information about ocean processes and past environmental conditions, radiogenic isotope (Sr, Nd, Os, Pb, U) systems can be used as time markers, indicators of terrestrial weathering, and ocean water mass mixing. Recent instrumentation advances have made possible the measurement of natural stable isotope variations produced by both mass-dependent and mass-independent fractionation for an ever-increasing number of metal elements (e.g. Li, B, Mg, Si, Ca, V, Cr, Fe, Ni, Cu, Zn, Se, Mo, Cd, Tl, U). The major emphasis in this review is on the isotopic composition of the light elements based on a comparatively large literature. Unlike O, H and S, the stable isotopes of C, N and Si do not have a constant isotopic composition in the modern ocean. The major cations Ca, Mg, and Sr fixed in carbonate shells provide the best proxies for reconstruction of the composition of the ocean in the past. Exhibiting large isotope enrichments in ocean water, B and Li are suitable for the investigation of water/rock interactions and can act as monitors of former oceanic pH. The bioessential elements Zn, Cd, and Ni are indicators of paleoproductivity in the ocean. Characteristic isotope enrichments or depletions of the multivalent elements V, Cr, Fe, Se, Mo, and U record the past redox state of the ocean/atmosphere system. Case studies describe how isotopes have been used to define the seawater composition in the geological past.
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Affiliation(s)
- Jochen Hoefs
- Geowissenschaftliches Zentrum, Universität Göttingen, Göttingen, Germany
| | - Russell S Harmon
- Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC, USA
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Schimmenti D, Marcantonio F, Hayes CT, Hertzberg J, Schmidt M, Sarao J. Insights into the deglacial variability of phytoplankton community structure in the eastern equatorial Pacific Ocean using [ 231Pa/ 230Th]xs and opal-carbonate fluxes. Sci Rep 2022; 12:22258. [PMID: 36564500 PMCID: PMC9789155 DOI: 10.1038/s41598-022-26593-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 12/16/2022] [Indexed: 12/24/2022] Open
Abstract
Fully and accurately reconstructing changes in oceanic productivity and carbon export and their controls is critical to determining the efficiency of the biological pump and its role in the global carbon cycle through time, particularly in modern CO2 source regions like the eastern equatorial Pacific (EEP). Here we present new high-resolution records of sedimentary 230Th-normalized opal and nannofossil carbonate fluxes and [231Pa/230Th]xs ratios from site MV1014-02-17JC in the Panama Basin. We find that, across the last deglaciation, phytoplankton community structure is driven by changing patterns of nutrient (nitrate, iron, and silica) availability which, in turn, are caused by variability in the position of the Intertropical Convergence Zone (ITCZ) and associated changes in biogeochemical cycling and circulation in the Southern Ocean. Our multi-proxy work suggests greater scrutiny is required in the interpretation of common geochemical proxies of productivity and carbon export in the EEP.
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Affiliation(s)
- Danielle Schimmenti
- grid.264756.40000 0004 4687 2082Department of Geology and Geophysics, Texas A&M University, College Station, TX USA
| | - Franco Marcantonio
- grid.264756.40000 0004 4687 2082Department of Geology and Geophysics, Texas A&M University, College Station, TX USA
| | - Christopher T. Hayes
- grid.267193.80000 0001 2295 628XSchool of Ocean Science and Engineering, University of Southern Mississippi, Stennis Space Center, MS USA
| | | | - Matthew Schmidt
- grid.261368.80000 0001 2164 3177Department of Ocean and Earth Sciences, Old Dominion University, Norfolk, VA USA
| | - John Sarao
- grid.264756.40000 0004 4687 2082Department of Geology and Geophysics, Texas A&M University, College Station, TX USA
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Dumont M, Pichevin L, Geibert W, Crosta X, Michel E, Moreton S, Dobby K, Ganeshram R. The nature of deep overturning and reconfigurations of the silicon cycle across the last deglaciation. Nat Commun 2020; 11:1534. [PMID: 32210225 PMCID: PMC7093442 DOI: 10.1038/s41467-020-15101-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 02/14/2020] [Indexed: 12/02/2022] Open
Abstract
Changes in ocean circulation and the biological carbon pump have been implicated as the drivers behind the rise in atmospheric CO2 across the last deglaciation; however, the processes involved remain uncertain. Previous records have hinted at a partitioning of deep ocean ventilation across the two major intervals of atmospheric CO2 rise, but the consequences of differential ventilation on the Si cycle has not been explored. Here we present three new records of silicon isotopes in diatoms and sponges from the Southern Ocean that together show increased Si supply from deep mixing during the deglaciation with a maximum during the Younger Dryas (YD). We suggest Antarctic sea ice and Atlantic overturning conditions favoured abyssal ocean ventilation at the YD and marked an interval of Si cycle reorganisation. By regulating the strength of the biological pump, the glacial-interglacial shift in the Si cycle may present an important control on Pleistocene CO2 concentrations.
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Affiliation(s)
- M Dumont
- School of Geosciences, University of Edinburgh, Edinburgh, UK.
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, UK.
| | - L Pichevin
- School of Geosciences, University of Edinburgh, Edinburgh, UK
| | - W Geibert
- Alfred Wegener Institute, Bremerhaven, Germany
| | - X Crosta
- UMR 5805 EPOC, Universite de Bordeaux, Bordeaux, France
| | - E Michel
- Laboratoire des Sciences du Climat et l'Environnement/Institute Pierre-Simon Laplace, Laboratoire CNRS-CEA-UVSQ, Gif-sur-Yvette, France
| | - S Moreton
- Scottish Universities Environmental Research Centre, East Kilbride, UK
| | - K Dobby
- School of Geosciences, University of Edinburgh, Edinburgh, UK
| | - R Ganeshram
- School of Geosciences, University of Edinburgh, Edinburgh, UK
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Winckler G, Anderson RF, Jaccard SL, Marcantonio F. Ocean dynamics, not dust, have controlled equatorial Pacific productivity over the past 500,000 years. Proc Natl Acad Sci U S A 2016; 113:6119-24. [PMID: 27185933 DOI: 10.1073/pnas.1600616113] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Biological productivity in the equatorial Pacific is relatively high compared with other low-latitude regimes, especially east of the dateline, where divergence driven by the trade winds brings nutrient-rich waters of the Equatorial Undercurrent to the surface. The equatorial Pacific is one of the three principal high-nutrient low-chlorophyll ocean regimes where biological utilization of nitrate and phosphate is limited, in part, by the availability of iron. Throughout most of the equatorial Pacific, upwelling of water from the Equatorial Undercurrent supplies far more dissolved iron than is delivered by dust, by as much as two orders of magnitude. Nevertheless, recent studies have inferred that the greater supply of dust during ice ages stimulated greater utilization of nutrients within the region of upwelling on the equator, thereby contributing to the sequestration of carbon in the ocean interior. Here we present proxy records for dust and for biological productivity over the past 500 ky at three sites spanning the breadth of the equatorial Pacific Ocean to test the dust fertilization hypothesis. Dust supply peaked under glacial conditions, consistent with previous studies, whereas proxies of export production exhibit maxima during ice age terminations. Temporal decoupling between dust supply and biological productivity indicates that other factors, likely involving ocean dynamics, played a greater role than dust in regulating equatorial Pacific productivity.
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Costa KM, McManus JF, Anderson RF, Ren H, Sigman DM, Winckler G, Fleisher MQ, Marcantonio F, Ravelo AC. No iron fertilization in the equatorial Pacific Ocean during the last ice age. Nature 2016; 529:519-22. [PMID: 26819045 DOI: 10.1038/nature16453] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 11/09/2015] [Indexed: 11/08/2022]
Abstract
The equatorial Pacific Ocean is one of the major high-nutrient, low-chlorophyll regions in the global ocean. In such regions, the consumption of the available macro-nutrients such as nitrate and phosphate is thought to be limited in part by the low abundance of the critical micro-nutrient iron. Greater atmospheric dust deposition could have fertilized the equatorial Pacific with iron during the last ice age--the Last Glacial Period (LGP)--but the effect of increased ice-age dust fluxes on primary productivity in the equatorial Pacific remains uncertain. Here we present meridional transects of dust (derived from the (232)Th proxy), phytoplankton productivity (using opal, (231)Pa/(230)Th and excess Ba), and the degree of nitrate consumption (using foraminifera-bound δ(15)N) from six cores in the central equatorial Pacific for the Holocene (0-10,000 years ago) and the LGP (17,000-27,000 years ago). We find that, although dust deposition in the central equatorial Pacific was two to three times greater in the LGP than in the Holocene, productivity was the same or lower, and the degree of nitrate consumption was the same. These biogeochemical findings suggest that the relatively greater ice-age dust fluxes were not large enough to provide substantial iron fertilization to the central equatorial Pacific. This may have been because the absolute rate of dust deposition in the LGP (although greater than the Holocene rate) was very low. The lower productivity coupled with unchanged nitrate consumption suggests that the subsurface major nutrient concentrations were lower in the central equatorial Pacific during the LGP. As these nutrients are today dominantly sourced from the Subantarctic Zone of the Southern Ocean, we propose that the central equatorial Pacific data are consistent with more nutrient consumption in the Subantarctic Zone, possibly owing to iron fertilization as a result of higher absolute dust fluxes in this region. Thus, ice-age iron fertilization in the Subantarctic Zone would have ultimately worked to lower, not raise, equatorial Pacific productivity.
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Hendry KR, Robinson LF, McManus JF, Hays JD. Silicon isotopes indicate enhanced carbon export efficiency in the North Atlantic during deglaciation. Nat Commun 2015; 5:3107. [PMID: 24452197 DOI: 10.1038/ncomms4107] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 12/13/2013] [Indexed: 11/09/2022] Open
Abstract
Today's Sargasso Sea is nutrient starved, except for episodic upwelling events caused by wind-driven winter mixing and eddies. Enhanced diatom opal burial in Sargasso Sea sediments indicates that silicic acid, a limiting nutrient today, may have been more available in subsurface waters during Heinrich Stadials, millennial-scale climate perturbations of the last glacial and deglaciation. Here we use the geochemistry of opal-forming organisms from different water depths to demonstrate changes in silicic acid supply and utilization during the most recent Heinrich Stadial. We suggest that during the early phase (17.5-18 ka), wind-driven upwelling replenished silicic acid to the subsurface, resulting in low Si utilization. By 17 ka, stratification reduced the surface silicic acid supply leading to increased Si utilization efficiency. This abrupt shift in Si cycling would have contributed to high regional carbon export efficiency during the recent Heinrich Stadial, despite being a period of increasing atmospheric CO2.
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Affiliation(s)
- Katharine R Hendry
- 1] School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK [2] Department of Earth Sciences, Bristol University, Wills Building, Queen's Road, Bristol BS8 1RJ, UK [3] Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
| | - Laura F Robinson
- 1] Department of Earth Sciences, Bristol University, Wills Building, Queen's Road, Bristol BS8 1RJ, UK [2] Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
| | - Jerry F McManus
- Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, New York 10964, USA
| | - James D Hays
- Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, New York 10964, USA
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Martínez-botí MA, Marino G, Foster GL, Ziveri P, Henehan MJ, Rae JWB, Mortyn PG, Vance D. Boron isotope evidence for oceanic carbon dioxide leakage during the last deglaciation. Nature 2015; 518:219-22. [DOI: 10.1038/nature14155] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 12/11/2014] [Indexed: 11/09/2022]
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Abstract
Accounting for almost one-fifth of the primary production on Earth, the unicellular eukaryotic group of diatoms plays a key ecological and biogeochemical role in our contemporary oceans. Furthermore, as producers of various lipids and pigments, and characterized by their finely ornamented silica cell wall, diatoms hold great promise for different industrial fields, including biofuel production, nanotechnology, and pharmaceutics. However, in spite of their major ecological importance and their high commercial value, little is known about the mechanisms that control the diatom life and cell cycle. To date, both microscopic and genomic analyses have revealed that diatoms exhibit specific and unique mechanisms of cell division compared with those found in the classical model organisms. Here, we review the structural peculiarities of diatom cell proliferation, highlight the regulation of their major cell cycle checkpoints by environmental factors, and discuss recent progress in molecular cell division research.
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Affiliation(s)
- Marie J J Huysman
- Department of Plant Systems Biology, VIB, B-9052 Gent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, B-9052 Gent, Belgium
| | - Wim Vyverman
- Protistology and Aquatic Ecology, Department of Biology, Ghent University, B-9000 Gent, Belgium
| | - Lieven De Veylder
- Department of Plant Systems Biology, VIB, B-9052 Gent, Belgium Department of Plant Biotechnology and Bioinformatics, Ghent University, B-9052 Gent, Belgium
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Calvo E, Pelejero C, Pena LD, Cacho I, Logan GA. Eastern equatorial pacific productivity and related-CO2 changes since the last glacial period. Proc Natl Acad Sci U S A 2011; 108:5537-41. [PMID: 21422283 DOI: 10.1073/pnas.1009761108] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Understanding oceanic processes, both physical and biological, that control atmospheric CO(2) is vital for predicting their influence during the past and into the future. The Eastern Equatorial Pacific (EEP) is thought to have exerted a strong control over glacial/interglacial CO(2) variations through its link to circulation and nutrient-related changes in the Southern Ocean, the primary region of the world oceans where CO(2)-enriched deep water is upwelled to the surface ocean and comes into contact with the atmosphere. Here we present a multiproxy record of surface ocean productivity, dust inputs, and thermocline conditions for the EEP over the last 40,000 y. This allows us to detect changes in phytoplankton productivity and composition associated with increases in equatorial upwelling intensity and influence of Si-rich waters of sub-Antarctic origin. Our evidence indicates that diatoms outcompeted coccolithophores at times when the influence of Si-rich Southern Ocean intermediate waters was greatest. This shift from calcareous to noncalcareous phytoplankton would cause a lowering in atmospheric CO(2) through a reduced carbonate pump, as hypothesized by the Silicic Acid Leakage Hypothesis. However, this change does not seem to have been crucial in controlling atmospheric CO(2), as it took place during the deglaciation, when atmospheric CO(2) concentrations had already started to rise. Instead, the concomitant intensification of Antarctic upwelling brought large quantities of deep CO(2)-rich waters to the ocean surface. This process very likely dominated any biologically mediated CO(2) sequestration and probably accounts for most of the deglacial rise in atmospheric CO(2).
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Affiliation(s)
- Michael J. Ellwood
- Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
| | - Martin Wille
- Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia
| | - William Maher
- Institute for Applied Ecology, Faculty of Applied Science, University of Canberra, Canberra, ACT 2601, Australia
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Huysman MJ, Martens C, Vandepoele K, Gillard J, Rayko E, Heijde M, Bowler C, Inzé D, Van de Peer Y, De Veylder L, Vyverman W. Genome-wide analysis of the diatom cell cycle unveils a novel type of cyclins involved in environmental signaling. Genome Biol 2010; 11:R17. [PMID: 20146805 DOI: 10.1186/gb-2010-11-2-r17] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 02/01/2010] [Accepted: 02/08/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Despite the enormous importance of diatoms in aquatic ecosystems and their broad industrial potential, little is known about their life cycle control. Diatoms typically inhabit rapidly changing and unstable environments, suggesting that cell cycle regulation in diatoms must have evolved to adequately integrate various environmental signals. The recent genome sequencing of Thalassiosira pseudonana and Phaeodactylum tricornutum allows us to explore the molecular conservation of cell cycle regulation in diatoms. RESULTS By profile-based annotation of cell cycle genes, counterparts of conserved as well as new regulators were identified in T. pseudonana and P. tricornutum. In particular, the cyclin gene family was found to be expanded extensively compared to that of other eukaryotes and a novel type of cyclins was discovered, the diatom-specific cyclins. We established a synchronization method for P. tricornutum that enabled assignment of the different annotated genes to specific cell cycle phase transitions. The diatom-specific cyclins are predominantly expressed at the G1-to-S transition and some respond to phosphate availability, hinting at a role in connecting cell division to environmental stimuli. CONCLUSION The discovery of highly conserved and new cell cycle regulators suggests the evolution of unique control mechanisms for diatom cell division, probably contributing to their ability to adapt and survive under highly fluctuating environmental conditions.
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Marchetti A, Cassar N. Diatom elemental and morphological changes in response to iron limitation: a brief review with potential paleoceanographic applications. Geobiology 2009; 7:419-431. [PMID: 19659798 DOI: 10.1111/j.1472-4669.2009.00207.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Diatoms are a major group of phytoplankton that account for approximately 40% of the ocean carbon fixation and the vast majority of biogenic silica production through the construction of their cell walls (termed frustules). These frustules accumulate and are partially preserved in the ocean sediments. Diatom growth and nutrient utilization in high-nitrate, low-chlorophyll regions of the world's oceans are mostly regulated by iron availability. Diatoms acclimate to iron limitation by decreasing cell size. The associated increase in surface area-to-volume ratio and decrease in diffusive boundary layer thickness may improve nutrient uptake kinetics. In parallel, cellular silicon (Si) contents are elevated in iron-limited diatoms relative to nitrogen (N) and carbon (C). Variations in degree of silicification and nutritional requirements of iron-limited diatoms have been hypothesized to account for higher cellular Si and/or lower cellular N and C, respectively. However, in some diatoms, frustule silicification does not significantly change when cells are iron-limited. Instead, changes in the Si-containing valve surface area relative to volume within these diatoms is hypothesized to be responsible for the variations in the cellular Si : N and Si : C ratios. In particular, some examined iron-limited pennate diatoms have reduced widths relative to their lengths (i.e. lower length-normalized widths, LNW) compared to iron-replete cells. In the pennate diatom Fragilariopsis kerguelensis, the mean LNWs of valves preserved in sediments throughout the Southern Ocean (a well-characterized iron-limited region) is positively correlated with satellite-derived, climatological net primary productivity in the overlying waters. Because of the specific morphological changes in pennate diatom frustules in response to iron availability, the valve morphometerics (e.g. LNWs) can potentially be used as a diagnostic tool for iron-limited diatom growth and relative changes in the Si : N (and Si : C) ratios in extant diatom assemblages as well as those preserved in the sediments.
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Affiliation(s)
- A Marchetti
- School of Oceanography, University of Washington, Seattle, WA, USA.
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