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Köster M, Staubwasser M, Meixner A, Kasemann SA, Manners HR, Morono Y, Inagaki F, Heuer VB, Kasten S, Henkel S. Uniquely low stable iron isotopic signatures in deep marine sediments caused by Rayleigh distillation. Sci Rep 2023; 13:10281. [PMID: 37355766 DOI: 10.1038/s41598-023-37254-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 06/19/2023] [Indexed: 06/26/2023] Open
Abstract
Dissimilatory iron reduction (DIR) is suggested to be one of the earliest forms of microbial respiration. It plays an important role in the biogeochemical cycling of iron in modern and ancient sediments. Since microbial iron cycling is typically accompanied by iron isotope fractionation, stable iron isotopes are used as tracer for biological activity. Here we present iron isotope data for dissolved and sequentially extracted sedimentary iron pools from deep and hot subseafloor sediments retrieved in the Nankai Trough off Japan. Dissolved iron (Fe(II)aq) is isotopically light throughout the ferruginous sediment interval but some samples have exceptionally light isotope values. Such light values have never been reported in natural marine environments and cannot be solely attributed to DIR. We show that the light isotope values are best explained by a Rayleigh distillation model where Fe(II)aq is continuously removed from the pore water by adsorption onto iron (oxyhydr)oxide surfaces. While the microbially mediated Fe(II)aq release has ceased due to an increase in temperature beyond the threshold of mesophilic microorganisms, the abiotic adsorptive Fe(II)aq removal continued, leading to uniquely light isotope values. These findings have important implications for the interpretation of dissolved iron isotope data especially in deep subseafloor sediments.
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Affiliation(s)
- Male Köster
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
- Faculty of Geosciences, University of Bremen, Bremen, Germany.
| | | | - Anette Meixner
- Faculty of Geosciences, University of Bremen, Bremen, Germany
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Simone A Kasemann
- Faculty of Geosciences, University of Bremen, Bremen, Germany
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Hayley R Manners
- School of Geography, Earth and Environmental Sciences, University of Plymouth, Plymouth, UK
| | - Yuki Morono
- Kochi Institute for Core Sample Research, Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Sciences and Technology (JAMSTEC), Nankoku, Kochi, Japan
| | - Fumio Inagaki
- Institute for Marine-Earth Exploration and Engineering (MarE3), JAMSTEC, Yokohama, Japan
- Department of Earth Sciences, Graduate School of Science, Tohoku University, Sendai, Japan
| | - Verena B Heuer
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Sabine Kasten
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- Faculty of Geosciences, University of Bremen, Bremen, Germany
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Susann Henkel
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
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2
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Tang Y, Han G, Man L, Zeng J, Qu R. Fe contents and isotopes in suspended particulate matter of Lancang River in Southwest China. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 878:162964. [PMID: 36958553 DOI: 10.1016/j.scitotenv.2023.162964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/15/2023] [Accepted: 03/16/2023] [Indexed: 05/13/2023]
Abstract
Iron (Fe) isotope geochemistry in rivers is crucial for comprehending surficial weathering and geochemical cycle mechanisms. Lancang River is an important channel for material transport between the Tibet Plateau and the oceans of Southeast Asia. In this study, Fe contents and Fe isotope (δ56Fe) compositions in the suspended particulate matter (SPM) are investigated to discuss the rock weathering processes in the Lancang River Basin. The δ56Fe values of SPM range from 0.01 ‰ to 0.21 ‰, with an average of 0.12 ‰, close to the average δ56Fe value of continental crust (0.07 ‰). The results indicate that the fractionation of Fe isotopes is limited caused of weathering process in the Lancang River Basin. Due to the interception of dense dams in the middle and lower reaches (1000-2000 m), the dissolved oxygen (DO) values of river water and the Fe contents of SPM remain at a relatively highest level, whereas the δ56Fe values in SPM are more positive. The positive correlation between chemical index of alteration (CIA) values and the Fe contents suggest that Fe in the tributary SPM may represent the weathering degree of their source areas. The increase of DO in the mainstream water may promote the decomposition and dissolution of SPM, thus increasing the contents of Fe in the remaining SPM, and causing slight positive fractionation of Fe in SPM. This study presents a complete analysis of the Fe isotope's potential utility in identifying the source of SPM. In addition, the Fe isotope may represent some alterations encountered by SPM throughout the runoff process.
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Affiliation(s)
- Yang Tang
- Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550004, China
| | - Guilin Han
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing 100083, China.
| | - Liu Man
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing 100083, China
| | - Jie Zeng
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing 100083, China
| | - Rui Qu
- Institute of Earth Sciences, China University of Geosciences (Beijing), Beijing 100083, China
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3
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Fitzsimmons JN, Conway TM. Novel Insights into Marine Iron Biogeochemistry from Iron Isotopes. ANNUAL REVIEW OF MARINE SCIENCE 2023; 15:383-406. [PMID: 36100217 DOI: 10.1146/annurev-marine-032822-103431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The micronutrient iron plays a major role in setting the magnitude and distribution of primary production across the global ocean. As such, an understanding of the sources, sinks, and internal cycling processes that drive the oceanic distribution of iron is key to unlocking iron's role in the global carbon cycle and climate, both today and in the geologic past. Iron isotopic analyses of seawater have emerged as a transformative tool for diagnosing iron sources to the ocean and tracing biogeochemical processes. In this review, we summarize the end-member isotope signatures of different iron source fluxes and highlight the novel insights into iron provenance gained using this tracer. We also review ways in which iron isotope fractionation might be used to understand internal oceanic cycling of iron, including speciation changes, biological uptake, and particle scavenging. We conclude with an overview of future research needed to expand the utilization of this cutting-edge tracer.
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Affiliation(s)
| | - Tim M Conway
- College of Marine Science, University of South Florida, St. Petersburg, Florida, USA;
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4
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van de Velde SJ, Dale AW, Arndt S. Bioturbation and the δ 56Fe signature of dissolved iron fluxes from marine sediments. ROYAL SOCIETY OPEN SCIENCE 2023; 10:220010. [PMID: 36704258 PMCID: PMC9874279 DOI: 10.1098/rsos.220010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 01/05/2023] [Indexed: 06/18/2023]
Abstract
We developed a reaction-transport model capable of tracing iron isotopes in marine sediments to quantify the influence of bioturbation on the isotopic signature of the benthic dissolved (DFe) flux. By fitting the model to published data from marine sediments, we calibrated effective overall fractionation factors for iron reduction (-1.3‰), oxidation (+0.4‰), iron-sulfide precipitation (+0.5‰) and dissolution (-0.5‰) and pyrite precipitation (-0.7‰) that agree with literature values. Results show that for bottom-water oxygen concentrations greater than 50 µM, higher bioturbation increased the benthic DFe flux and its δ 56Fe signature. By contrast, for oxygen concentrations less than 50 µM, higher bioturbation decreased the benthic DFe flux and its δ 56Fe signature. The expressed overall fractionation of the benthic DFe flux relative to the δ 56Fe of the iron oxides entering the sediment ranges from -1.67‰ to 0.0‰. On a global scale, the presence of bioturbation increases sedimentary DFe release from approximately 70 G mol DFe yr-1 to approximately 160 G mol DFe yr-1 and decreases the δ 56Fe signature of the DFe flux.
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Affiliation(s)
- Sebastiaan J. van de Velde
- Department of Geoscience, Environment & Society, Université Libre de Bruxelles, Av. F. Roosevelt 50, CP160/02, 1050 Brussels, Belgium
- Operational Directorate Natural Environment, Royal Belgian Institute of Natural Sciences, Rue Vautier 29, Brussels, Belgium
| | - Andrew W. Dale
- GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1-3, D-24148 Kiel, Germany
| | - Sandra Arndt
- Department of Geoscience, Environment & Society, Université Libre de Bruxelles, Av. F. Roosevelt 50, CP160/02, 1050 Brussels, Belgium
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5
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König D, Conway TM, Ellwood MJ, Homoky WB, Tagliabue A. Constraints on the Cycling of Iron Isotopes From a Global Ocean Model. GLOBAL BIOGEOCHEMICAL CYCLES 2021; 35:e2021GB006968. [PMID: 35860342 PMCID: PMC9285799 DOI: 10.1029/2021gb006968] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 08/05/2021] [Accepted: 08/11/2021] [Indexed: 06/15/2023]
Abstract
Although iron (Fe) is a key regulator of primary production over much of the ocean, many components of the marine iron cycle are poorly constrained, which undermines our understanding of climate change impacts. In recent years, a growing number of studies (often part of GEOTRACES) have used Fe isotopic signatures (δ56Fe) to disentangle different aspects of the marine Fe cycle. Characteristic δ56Fe endmembers of external sources and assumed isotopic fractionation during biological Fe uptake or recycling have been used to estimate relative source contributions and investigate internal transformations, respectively. However, different external sources and fractionation processes often overlap and act simultaneously, complicating the interpretation of oceanic Fe isotope observations. Here we investigate the driving forces behind the marine dissolved Fe isotopic signature (δ56Fediss) distribution by incorporating Fe isotopes into the global ocean biogeochemical model PISCES. We find that distinct external source endmembers acting alongside fractionation during organic complexation and phytoplankton uptake are required to reproduce δ56Fediss observations along GEOTRACES transects. δ56Fediss distributions through the water column result from regional imbalances of remineralization and abiotic removal processes. They modify δ56Fediss directly and transfer surface ocean signals to the interior with opposing effects. Although attributing crustal compositions to sedimentary Fe sources in regions with low organic carbon fluxes improves our isotope model, δ56Fediss signals from hydrothermal or sediment sources cannot be reproduced accurately by simply adjusting δ56Fe endmember values. This highlights that additional processes must govern the exchange and/or speciation of Fe supplied by these sources to the ocean.
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Affiliation(s)
- D. König
- School of Environmental SciencesUniversity of LiverpoolLiverpoolUK
| | - T. M. Conway
- College of Marine ScienceUniversity of South FloridaSt PetersburgFLUSA
| | - M. J. Ellwood
- Research School of Earth SciencesAustralian National UniversityCanberraACTAustralia
| | - W. B. Homoky
- School of Earth and EnvironmentUniversity of LeedsLeedsUK
| | - A. Tagliabue
- School of Environmental SciencesUniversity of LiverpoolLiverpoolUK
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6
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Krisch S, Hopwood MJ, Schaffer J, Al-Hashem A, Höfer J, Rutgers van der Loeff MM, Conway TM, Summers BA, Lodeiro P, Ardiningsih I, Steffens T, Achterberg EP. The 79°N Glacier cavity modulates subglacial iron export to the NE Greenland Shelf. Nat Commun 2021; 12:3030. [PMID: 34031401 PMCID: PMC8144390 DOI: 10.1038/s41467-021-23093-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 04/14/2021] [Indexed: 02/04/2023] Open
Abstract
Approximately half of the freshwater discharged from the Greenland and Antarctic Ice Sheets enters the ocean subsurface as a result of basal ice melt, or runoff draining via the grounding line of a deep ice shelf or marine-terminating glacier. Around Antarctica and parts of northern Greenland, this freshwater then experiences prolonged residence times in large cavities beneath floating ice tongues. Due to the inaccessibility of these cavities, it is unclear how they moderate the freshwater associated supply of nutrients such as iron (Fe) to the ocean. Here, we show that subglacial dissolved Fe export from Nioghalvfjerdsbrae (the '79°N Glacier') is decoupled from particulate inputs including freshwater Fe supply, likely due to the prolonged ~162-day residence time of Atlantic water beneath Greenland's largest floating ice-tongue. Our findings indicate that the overturning rate and particle-dissolved phase exchanges in ice cavities exert a dominant control on subglacial nutrient supply to shelf regions.
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Affiliation(s)
- Stephan Krisch
- GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
| | | | - Janin Schaffer
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Ali Al-Hashem
- GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
| | - Juan Höfer
- Escuela de Ciencias del Mar, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | | | - Tim M Conway
- College of Marine Science, University of South Florida, St Petersburg, FL, USA
| | - Brent A Summers
- College of Marine Science, University of South Florida, St Petersburg, FL, USA
| | - Pablo Lodeiro
- GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
- Department of Chemistry, University of Lleida - Agrotecnio-Cerca Centre, Lleida, Spain
| | - Indah Ardiningsih
- NIOZ Royal Netherlands Institute for Sea Research, Utrecht University, Den Burg, Texel, The Netherlands
| | - Tim Steffens
- GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
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7
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Abstract
Dissolution of marine sediment is a key source of dissolved iron (Fe) that regulates the ocean carbon cycle. Currently, our prevailing understanding, encapsulated in ocean models, focuses on low-oxygen reductive supply mechanisms and neglects the emerging evidence from iron isotopes in seawater and sediment porewaters for additional nonreductive dissolution processes. Here, we combine measurements of Fe colloids and dissolved δ56Fe in shallow porewaters spanning the full depth of the South Atlantic Ocean to demonstrate that it is lithogenic colloid production that fuels sedimentary iron supply away from low-oxygen systems. Iron colloids are ubiquitous in these oxic ocean sediment porewaters and account for the lithogenic isotope signature of dissolved Fe (δ56Fe = +0.07 ± 0.07‰) within and between ocean basins. Isotope model experiments demonstrate that only lithogenic weathering in both oxic and nitrogenous zones, rather than precipitation or ligand complexation of reduced Fe species, can account for the production of these porewater Fe colloids. The broader covariance between colloidal Fe and organic carbon (OC) abundance suggests that sorption of OC may control the nanoscale stability of Fe minerals by inhibiting the loss of Fe(oxyhydr)oxides to more crystalline minerals in the sediment. Oxic ocean sediments can therefore generate a large exchangeable reservoir of organo-mineral Fe colloids at the sediment water interface (a "rusty source") that dominates the benthic supply of dissolved Fe to the ocean interior, alongside reductive supply pathways from shallower continental margins.
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8
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Lotfi-Kalahroodi E, Pierson-Wickmann AC, Rouxel O, Marsac R, Bouhnik-Le Coz M, Hanna K, Davranche M. More than redox, biological organic ligands control iron isotope fractionation in the riparian wetland. Sci Rep 2021; 11:1933. [PMID: 33479360 PMCID: PMC7820352 DOI: 10.1038/s41598-021-81494-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 12/21/2020] [Indexed: 11/17/2022] Open
Abstract
Although redox reactions are recognized to fractionate iron (Fe) isotopes, the dominant mechanisms controlling the Fe isotope fractionation and notably the role of organic matter (OM) are still debated. Here, we demonstrate how binding to organic ligands governs Fe isotope fractionation beyond that arising from redox reactions. The reductive biodissolution of soil Fe(III) enriched the solution in light Fe isotopes, whereas, with the extended reduction, the preferential binding of heavy Fe isotopes to large biological organic ligands enriched the solution in heavy Fe isotopes. Under oxic conditions, the aggregation/sedimentation of Fe(III) nano-oxides with OM resulted in an initial enrichment of the solution in light Fe isotopes. However, heavy Fe isotopes progressively dominate the solution composition in response to their binding with large biologically-derived organic ligands. Confronted with field data, these results demonstrate that Fe isotope systematics in wetlands are controlled by the OM flux, masking Fe isotope fractionation arising from redox reactions. This work sheds light on an overseen aspect of Fe isotopic fractionation and calls for a reevaluation of the parameters controlling the Fe isotopes fractionation to clarify the interpretation of the Fe isotopic signature.
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Affiliation(s)
| | | | - Olivier Rouxel
- IFREMER, Unité de Géosciences Marines, 29280, Plouzané, France
| | - Rémi Marsac
- Univ. Rennes, CNRS, Géosciences Rennes - UMR 6118, 35000, Rennes, France
| | | | - Khalil Hanna
- Univ. Rennes, Ecole Nationale Supérieure de Chimie de Rennes, CNRS ISCR UMR6226, 35000, Rennes, France
| | - Mélanie Davranche
- Univ. Rennes, CNRS, Géosciences Rennes - UMR 6118, 35000, Rennes, France
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9
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Major lithogenic contributions to the distribution and budget of iron in the North Pacific Ocean. Sci Rep 2019; 9:11652. [PMID: 31406147 PMCID: PMC6690902 DOI: 10.1038/s41598-019-48035-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 07/29/2019] [Indexed: 11/28/2022] Open
Abstract
Recent studies have elucidated that iron (Fe) is a critical trace metal that influences the productivity of marine ecosystems and the biogeochemical cycles of other elements in the modern ocean. However, our understanding of the biogeochemistry of Fe remains incomplete. Herein, we report basin-scale and full-depth sectional distributions of total dissolvable iron (tdFe), dissolved iron (dFe), and labile particulate iron (lpFe = tdFe – dFe) in the North Pacific Ocean, as observed during three cruises of the GEOTRACES Japan program. We found that lpFe dominates tdFe and is significantly correlated with labile particulate aluminum (lpAl): lpFe [nmol kg−1] = (0.544 ± 0.005) lpAl [nmol kg−1] + 0.11 ± 0.04, r2 = 0.968, n = 432. The results indicate a major lithogenic contribution to the distribution of particulate Fe. For dFe, the unique distribution is attributed to the combined effects of biogeochemical cycling, manganese reduction, and lithogenic contribution. Based on concurrent observations of Fe, Al, and manganese (Mn), we infer that the width of the boundary scavenging zone is approximately 500 km off the Aleutian shelf. We estimate the inventory of tdFe in the North Pacific as 1.1 × 1012 mol, which is approximately four times that of dFe. Our results emphasize the potential importance of lpFe in the ocean’s iron cycle.
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10
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Birchill AJ, Hartner NT, Kunde K, Siemering B, Daniels C, González-Santana D, Milne A, Ussher SJ, Worsfold PJ, Leopold K, Painter SC, Lohan MC. The eastern extent of seasonal iron limitation in the high latitude North Atlantic Ocean. Sci Rep 2019; 9:1435. [PMID: 30723260 PMCID: PMC6363741 DOI: 10.1038/s41598-018-37436-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 11/25/2018] [Indexed: 11/29/2022] Open
Abstract
The availability of iron (Fe) can seasonally limit phytoplankton growth in the High Latitude North Atlantic (HLNA), greatly reducing the efficiency of the biological carbon pump. However, the spatial extent of seasonal iron limitation is not yet known. We present autumn nutrient and dissolved Fe measurements, combined with microphytoplankton distribution, of waters overlying the Hebridean (Scottish) shelf break. A distinct biogeochemical divide was observed, with Fe deficient surface waters present beyond the shelf break, much further eastwards than previously recognised. Due to along and on-shelf circulation, the Hebridean shelf represents a much-localised source of Fe, which does not fertilise the wider HLNA. Shelf sediments are generally thought to supply large quantities of Fe to overlying waters. However, for this Fe to influence upper-ocean biogeochemical cycling, efficient off-shelf transport mechanisms are required. This work challenges the view that the oceanic surface waters in close proximity to continental margins are iron replete with respect to marine primary production demands.
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Affiliation(s)
- A J Birchill
- School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, United Kingdom.
- National Oceanography Centre, European Way, Southampton, SO14 3ZH, United Kingdom.
| | - N T Hartner
- School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, United Kingdom
- Institute of Analytical and Bioanalytical Chemistry, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - K Kunde
- Ocean and Earth Sciences, University of Southampton, Waterfront Campus, National Oceanography Centre, European Way, Southampton, SO14 3ZH, United Kingdom
| | - B Siemering
- Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA, United Kingdom
- Marine Institute, Rinville, Oranmore, Co., Galway, H91 R673, Ireland
| | - C Daniels
- National Oceanography Centre, European Way, Southampton, SO14 3ZH, United Kingdom
| | - D González-Santana
- Ocean and Earth Sciences, University of Southampton, Waterfront Campus, National Oceanography Centre, European Way, Southampton, SO14 3ZH, United Kingdom
| | - A Milne
- School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, United Kingdom
| | - S J Ussher
- School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, United Kingdom
| | - P J Worsfold
- School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, United Kingdom
| | - K Leopold
- Institute of Analytical and Bioanalytical Chemistry, University of Ulm, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - S C Painter
- National Oceanography Centre, European Way, Southampton, SO14 3ZH, United Kingdom
| | - M C Lohan
- School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, United Kingdom
- Ocean and Earth Sciences, University of Southampton, Waterfront Campus, National Oceanography Centre, European Way, Southampton, SO14 3ZH, United Kingdom
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11
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Thompson CEL, Silburn B, Williams ME, Hull T, Sivyer D, Amoudry LO, Widdicombe S, Ingels J, Carnovale G, McNeill CL, Hale R, Marchais CL, Hicks N, Smith HEK, Klar JK, Hiddink JG, Kowalik J, Kitidis V, Reynolds S, Woodward EMS, Tait K, Homoky WB, Kröger S, Bolam S, Godbold JA, Aldridge J, Mayor DJ, Benoist NMA, Bett BJ, Morris KJ, Parker ER, Ruhl HA, Statham PJ, Solan M. An approach for the identification of exemplar sites for scaling up targeted field observations of benthic biogeochemistry in heterogeneous environments. BIOGEOCHEMISTRY 2017; 135:1-34. [PMID: 32009689 PMCID: PMC6961521 DOI: 10.1007/s10533-017-0366-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 06/08/2017] [Indexed: 05/16/2023]
Abstract
Continental shelf sediments are globally important for biogeochemical activity. Quantification of shelf-scale stocks and fluxes of carbon and nutrients requires the extrapolation of observations made at limited points in space and time. The procedure for selecting exemplar sites to form the basis of this up-scaling is discussed in relation to a UK-funded research programme investigating biogeochemistry in shelf seas. A three-step selection process is proposed in which (1) a target area representative of UK shelf sediment heterogeneity is selected, (2) the target area is assessed for spatial heterogeneity in sediment and habitat type, bed and water column structure and hydrodynamic forcing, and (3) study sites are selected within this target area encompassing the range of spatial heterogeneity required to address key scientific questions regarding shelf scale biogeochemistry, and minimise confounding variables. This led to the selection of four sites within the Celtic Sea that are significantly different in terms of their sediment, bed structure, and macrofaunal, meiofaunal and microbial community structures and diversity, but have minimal variations in water depth, tidal and wave magnitudes and directions, temperature and salinity. They form the basis of a research cruise programme of observation, sampling and experimentation encompassing the spring bloom cycle. Typical variation in key biogeochemical, sediment, biological and hydrodynamic parameters over a pre to post bloom period are presented, with a discussion of anthropogenic influences in the region. This methodology ensures the best likelihood of site-specific work being useful for up-scaling activities, increasing our understanding of benthic biogeochemistry at the UK-shelf scale.
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Affiliation(s)
- C. E. L. Thompson
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH UK
| | - B. Silburn
- Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT UK
| | - M. E. Williams
- National Oceanography Centre, 6 Brownlow St, Liverpool, L3 5DA UK
| | - T. Hull
- Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT UK
| | - D. Sivyer
- Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT UK
| | - L. O. Amoudry
- National Oceanography Centre, 6 Brownlow St, Liverpool, L3 5DA UK
| | - S. Widdicombe
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - J. Ingels
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - G. Carnovale
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - C. L. McNeill
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - R. Hale
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH UK
| | - C. Laguionie Marchais
- National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH UK
| | - N. Hicks
- Scottish Association for Marine Science, Scottish Marine Institute, Oban, Argyll, PA37 1QA UK
| | - H. E. K. Smith
- National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH UK
| | - J. K. Klar
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH UK
- LEGOS, University of Toulouse, IRDm CNES, CNRS, UPS, 14 av. Edouard Belin, 31400 Toulouse, France
| | - J. G. Hiddink
- School of Ocean Sciences, Bangor University, Menai Bridge, LL59 5AB UK
| | - J. Kowalik
- Navama – Technology for Nature, Landshuter Allee 8, 80637 Munich, Germany
| | - V. Kitidis
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - S. Reynolds
- School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Road, Portsmouth, PO1 3QL UK
| | - E. M. S. Woodward
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - K. Tait
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - W. B. Homoky
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN UK
| | - S. Kröger
- Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT UK
| | - S. Bolam
- Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT UK
| | - J. A. Godbold
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH UK
- Biological Sciences, University of Southampton, Life Sciences Building, Highfield, Southampton SO17 1BJ UK
| | - J. Aldridge
- Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT UK
| | - D. J. Mayor
- National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH UK
| | - N. M. A. Benoist
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH UK
| | - B. J. Bett
- National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH UK
| | - K. J. Morris
- National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH UK
| | - E. R. Parker
- Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT UK
| | - H. A. Ruhl
- National Oceanography Centre, University of Southampton Waterfront Campus, European Way, Southampton, SO14 3ZH UK
| | - P. J. Statham
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH UK
| | - M. Solan
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH UK
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Persistent effects of the Yellow River on the Chinese marginal seas began at least ~880 ka ago. Sci Rep 2017; 7:2827. [PMID: 28588261 PMCID: PMC5460111 DOI: 10.1038/s41598-017-03140-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 05/02/2017] [Indexed: 11/08/2022] Open
Abstract
The Yellow River (or Huanghe and also known as China's Sorrow in ancient times), with the highest sediment load in the world, provides a key link between continental erosion and sediment accumulation in the western Pacific Ocean. However, the exact age of its influence on the marginal sea is highly controversial and uncertain. Here we present high-resolution records of clay minerals and lanthanum to samarium (La/Sm) ratio spanning the past ~1 million years (Myr) from the Bohai and Yellow Seas, the potential sedimentary sinks of the Yellow River. Our results show a climate-driven provenance shift from small, proximal mountain rivers-dominance to the Yellow River-dominance at ~880 ka, a time period consistent with the Mid-Pleistocene orbital shift from 41-kyr to 100-kyr cyclicity. We compare the age of this provenance shift with the available age data for Yellow River headwater integration into the marginal seas and suggest that the persistent influence of the Yellow River on the Chinese marginal seas must have occurred at least ~880 ka ago. To our knowledge, this study provides the first offshore evidence on the drainage history of the Yellow River within an accurate chronology framework.
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13
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Klar JK, Homoky WB, Statham PJ, Birchill AJ, Harris EL, Woodward EMS, Silburn B, Cooper MJ, James RH, Connelly DP, Chever F, Lichtschlag A, Graves C. Stability of dissolved and soluble Fe(II) in shelf sediment pore waters and release to an oxic water column. BIOGEOCHEMISTRY 2017; 135:49-67. [PMID: 32009691 PMCID: PMC6961528 DOI: 10.1007/s10533-017-0309-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 02/06/2017] [Indexed: 05/28/2023]
Abstract
Shelf sediments underlying temperate and oxic waters of the Celtic Sea (NW European Shelf) were found to have shallow oxygen penetrations depths from late spring to late summer (2.2-5.8 mm below seafloor) with the shallowest during/after the spring-bloom (mid-April to mid-May) when the organic carbon content was highest. Sediment porewater dissolved iron (dFe, <0.15 µm) mainly (>85%) consisted of Fe(II) and gradually increased from 0.4 to 15 μM at the sediment surface to ~100-170 µM at about 6 cm depth. During the late spring this Fe(II) was found to be mainly present as soluble Fe(II) (>85% sFe, <0.02 µm). Sub-surface dFe(II) maxima were enriched in light isotopes (δ56Fe -2.0 to -1.5‰), which is attributed to dissimilatory iron reduction (DIR) during the bacterial decomposition of organic matter. As porewater Fe(II) was oxidised to insoluble Fe(III) in the surface sediment layer, residual Fe(II) was further enriched in light isotopes (down to -3.0‰). Ferrozine-reactive Fe(II) was found in surface porewaters and in overlying core top waters, and was highest in the late spring period. Shipboard experiments showed that depletion of bottom water oxygen in late spring can lead to a substantial release of Fe(II). Reoxygenation of bottom water caused this Fe(II) to be rapidly lost from solution, but residual dFe(II) and dFe(III) remained (12 and 33 nM) after >7 h. Iron(II) oxidation experiments in core top and bottom waters also showed removal from solution but at rates up to 5-times slower than predicted from theoretical reaction kinetics. These data imply the presence of ligands capable of complexing Fe(II) and supressing oxidation. The lower oxidation rate allows more time for the diffusion of Fe(II) from the sediments into the overlying water column. Modelling indicates significant diffusive fluxes of Fe(II) (on the order of 23-31 µmol m-2 day-1) are possible during late spring when oxygen penetration depths are shallow, and pore water Fe(II) concentrations are highest. In the water column this stabilised Fe(II) will gradually be oxidised and become part of the dFe(III) pool. Thus oxic continental shelves can supply dFe to the water column, which is enhanced during a small period of the year after phytoplankton bloom events when organic matter is transferred to the seafloor. This input is based on conservative assumptions for solute exchange (diffusion-reaction), whereas (bio)physical advection and resuspension events are likely to accelerate these solute exchanges in shelf-seas.
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Affiliation(s)
- J. K. Klar
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
- Present Address: LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS, 14 Avenue Edouard Belin, 31400 Toulouse, France
| | - W. B. Homoky
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN UK
| | - P. J. Statham
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - A. J. Birchill
- School of Geography, Earth and Environmental Science, University of Plymouth, Drake Circus, Plymouth, PL4 8AA UK
| | - E. L. Harris
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - E. M. S. Woodward
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - B. Silburn
- Centre for Environment, Fisheries and Aquaculture Science, Pakefield Road, Lowestoft, NR33 0HT UK
| | - M. J. Cooper
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - R. H. James
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - D. P. Connelly
- Marine Geosciences, National Oceanography Centre, European Way, Southampton, SO14 3ZH UK
| | - F. Chever
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
| | - A. Lichtschlag
- Marine Geosciences, National Oceanography Centre, European Way, Southampton, SO14 3ZH UK
| | - C. Graves
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton, SO14 3ZH UK
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14
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Iron isotopes reveal distinct dissolved iron sources and pathways in the intermediate versus deep Southern Ocean. Proc Natl Acad Sci U S A 2017; 114:858-863. [PMID: 28096366 DOI: 10.1073/pnas.1603107114] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
As an essential micronutrient, iron plays a key role in oceanic biogeochemistry. It is therefore linked to the global carbon cycle and climate. Here, we report a dissolved iron (DFe) isotope section in the South Atlantic and Southern Ocean. Throughout the section, a striking DFe isotope minimum (light iron) is observed at intermediate depths (200-1,300 m), contrasting with heavier isotopic composition in deep waters. This unambiguously demonstrates distinct DFe sources and processes dominating the iron cycle in the intermediate and deep layers, a feature impossible to see with only iron concentration data largely used thus far in chemical oceanography. At intermediate depths, the data suggest that the dominant DFe sources are linked to organic matter remineralization, either in the water column or at continental margins. In deeper layers, however, abiotic non-reductive release of Fe (desorption, dissolution) from particulate iron-notably lithogenic-likely dominates. These results go against the common but oversimplified view that remineralization of organic matter is the major pathway releasing DFe throughout the water column in the open ocean. They suggest that the oceanic iron cycle, and therefore oceanic primary production and climate, could be more sensitive than previously thought to continental erosion (providing lithogenic particles to the ocean), particle transport within the ocean, dissolved/particle interactions, and deep water upwelling. These processes could also impact the cycles of other elements, including nutrients.
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15
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Homoky WB, Weber T, Berelson WM, Conway TM, Henderson GM, van Hulten M, Jeandel C, Severmann S, Tagliabue A. Quantifying trace element and isotope fluxes at the ocean-sediment boundary: a review. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2016.0246. [PMID: 29035270 PMCID: PMC5069539 DOI: 10.1098/rsta.2016.0246] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/24/2016] [Indexed: 05/23/2023]
Abstract
Quantifying fluxes of trace elements and their isotopes (TEIs) at the ocean's sediment-water boundary is a pre-eminent challenge to understand their role in the present, past and future ocean. There are multiple processes that drive the uptake and release of TEIs, and properties that determine their rates are unevenly distributed (e.g. sediment composition, redox conditions and (bio)physical dynamics). These factors complicate our efforts to find, measure and extrapolate TEI fluxes across ocean basins. GEOTRACES observations are unveiling the oceanic distributions of many TEIs for the first time. These data evidence the influence of the sediment-water boundary on many TEI cycles, and underline the fact that our knowledge of the source-sink fluxes that sustain oceanic distributions is largely missing. Present flux measurements provide low spatial coverage and only part of the empirical basis needed to predict TEI flux variations. Many of the advances and present challenges facing TEI flux measurements are linked to process studies that collect sediment cores, pore waters, sinking material or seawater in close contact with sediments. However, such sampling has not routinely been viable on GEOTRACES expeditions. In this article, we recommend approaches to address these issues: firstly, with an interrogation of emergent data using isotopic mass-balance and inverse modelling techniques; and secondly, by innovating pursuits of direct TEI flux measurements. We exemplify the value of GEOTRACES data with a new inverse model estimate of benthic Al flux in the North Atlantic Ocean. Furthermore, we review viable flux measurement techniques tailored to the sediment-water boundary. We propose that such activities are aimed at regions that intersect the GEOTRACES Science Plan on the basis of seven criteria that may influence TEI fluxes: sediment provenance, composition, organic carbon supply, redox conditions, sedimentation rate, bathymetry and the benthic nepheloid inventory.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.
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Affiliation(s)
- William B Homoky
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - Thomas Weber
- School of Oceanography, University of Washington, 1503 NE Boat Street, Seattle, WA 98105, USA
| | - William M Berelson
- Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Tim M Conway
- Department of Earth Sciences, ETH Zürich, Clausiusstrasse 25, 8092 Zürich, Switzerland
- College of Marine Science, University of South Florida, St Petersburg, FL 33701, USA
| | - Gideon M Henderson
- Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK
| | - Marco van Hulten
- Laboratoire des Sciences du Climat et de l'Environnement (LSCE), IPSL, CEA-Orme des Merisiers, 91191 Gif-sur-Yvette, France
| | - Catherine Jeandel
- Laboratoire d'Etudes en Géophysique et Océanographie Spatiales (LEGOS), 14 Avenue Edouard Belin, 31400 Toulouse, France
| | - Silke Severmann
- Department of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901, USA
| | - Alessandro Tagliabue
- School of Environmental Sciences, University of Liverpool, Jane Herdman Building, Liverpool L69 3GP, UK
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16
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Jeandel C. Overview of the mechanisms that could explain the 'Boundary Exchange' at the land-ocean contact. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2015.0287. [PMID: 29035253 PMCID: PMC5069524 DOI: 10.1098/rsta.2015.0287] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/10/2016] [Indexed: 05/23/2023]
Abstract
Land to ocean transfer of material largely controls the chemical composition of seawater and the global element cycles. Oceanic isotopic budgets of chemical species, macro- and micronutrients (e.g. Nd, Sr, Si, Mg, Zn, Mo and Ni) have revealed an imbalance between their sources and sinks. Radiogenic isotope budgets underlined the importance of taking into account continental margins as a source of elements to oceans. They also highlighted that the net land-ocean inputs of chemical species probably result from particle-dissolved exchange processes, named 'Boundary Exchange'. Yet, locations where 'Boundary Exchange' occurs are not clearly identified and reviewed here: discharge of huge amount of freshly weathered particles at the river mouths, submarine weathering of deposited sediments along the margins, submarine groundwater discharges and subterranean estuaries. As a whole, we conclude that all of them might contribute to 'Boundary Exchange'. Highlighting their specific roles and the processes at play is a key scientific issue for the second half of GEOTRACES.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.
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Affiliation(s)
- Catherine Jeandel
- Laboratoire d'Etudes en Géophysique et Océanographie Spatiale (LEGOS, Université de Toulouse/CNRS/CNES/IRD/Université Paul Sabatier), Observatoire Midi-Pyrénées, 14 Avenue Edouard Belin, 31400 Toulouse, France
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17
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Charette MA, Lam PJ, Lohan MC, Kwon EY, Hatje V, Jeandel C, Shiller AM, Cutter GA, Thomas A, Boyd PW, Homoky WB, Milne A, Thomas H, Andersson PS, Porcelli D, Tanaka T, Geibert W, Dehairs F, Garcia-Orellana J. Coastal ocean and shelf-sea biogeochemical cycling of trace elements and isotopes: lessons learned from GEOTRACES. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:20160076. [PMID: 29035267 PMCID: PMC5069537 DOI: 10.1098/rsta.2016.0076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/30/2016] [Indexed: 05/06/2023]
Abstract
Continental shelves and shelf seas play a central role in the global carbon cycle. However, their importance with respect to trace element and isotope (TEI) inputs to ocean basins is less well understood. Here, we present major findings on shelf TEI biogeochemistry from the GEOTRACES programme as well as a proof of concept for a new method to estimate shelf TEI fluxes. The case studies focus on advances in our understanding of TEI cycling in the Arctic, transformations within a major river estuary (Amazon), shelf sediment micronutrient fluxes and basin-scale estimates of submarine groundwater discharge. The proposed shelf flux tracer is 228-radium (T1/2 = 5.75 yr), which is continuously supplied to the shelf from coastal aquifers, sediment porewater exchange and rivers. Model-derived shelf 228Ra fluxes are combined with TEI/ 228Ra ratios to quantify ocean TEI fluxes from the western North Atlantic margin. The results from this new approach agree well with previous estimates for shelf Co, Fe, Mn and Zn inputs and exceed published estimates of atmospheric deposition by factors of approximately 3-23. Lastly, recommendations are made for additional GEOTRACES process studies and coastal margin-focused section cruises that will help refine the model and provide better insight on the mechanisms driving shelf-derived TEI fluxes to the ocean.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.
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Affiliation(s)
- Matthew A Charette
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Phoebe J Lam
- Department of Ocean Sciences, University of California-Santa Cruz, Santa Cruz, CA 95064, USA
| | - Maeve C Lohan
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK
| | - Eun Young Kwon
- Research Institute of Oceanography, Seoul National University, Seoul 151-742, Korea
| | - Vanessa Hatje
- Centro Interdisciplinar de Energia e Ambiente, Inst. de Química, Universidade Federal da Bahia, Salvador 40170-115, Brazil
| | - Catherine Jeandel
- University of Toulouse/CNRS/UPS/IRD/CNES, Observatoire Midi-Pyrénées, Toulouse 31400, France
| | - Alan M Shiller
- Department of Marine Science, University of Southern Mississippi, Stennis Space Center, MS 39529, USA
| | - Gregory A Cutter
- Department of Ocean, Earth, and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529, USA
| | - Alex Thomas
- School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FE, UK
| | - Philip W Boyd
- Institute of Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania 7005, Australia
| | - William B Homoky
- Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK
| | - Angela Milne
- School of Geography, Earth and Environmental Sciences, Plymouth University, Plymouth PL4 8AA, UK
| | - Helmuth Thomas
- Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2
| | - Per S Andersson
- Department of Geosciences, Swedish Museum of Natural History, Stockholm 104 05, Sweden
| | - Don Porcelli
- Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK
| | - Takahiro Tanaka
- Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa Chiba 277-8564, Japan
| | - Walter Geibert
- Marine Geochemistry Department, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
| | - Frank Dehairs
- Earth System Sciences and Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Brussels 1050, Belgium
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18
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Moore CM. Diagnosing oceanic nutrient deficiency. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:20150290. [PMID: 29035255 PMCID: PMC5069526 DOI: 10.1098/rsta.2015.0290] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/23/2016] [Indexed: 05/24/2023]
Abstract
The supply of a range of nutrient elements to surface waters is an important driver of oceanic production and the subsequent linked cycling of the nutrients and carbon. Relative deficiencies of different nutrients with respect to biological requirements, within both surface and internal water masses, can be both a key indicator and driver of the potential for these nutrients to become limiting for the production of new organic material in the upper ocean. The availability of high-quality, full-depth and global-scale datasets on the concentrations of a wide range of both macro- and micro-nutrients produced through the international GEOTRACES programme provides the potential for estimation of multi-element deficiencies at unprecedented scales. Resultant coherent large-scale patterns in diagnosed deficiency can be linked to the interacting physical-chemical-biological processes which drive upper ocean nutrient biogeochemistry. Calculations of ranked deficiencies across multiple elements further highlight important remaining uncertainties in the stoichiometric plasticity of nutrient ratios within oceanic microbial systems and caveats with regards to linkages to upper ocean nutrient limitation.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.
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Affiliation(s)
- C Mark Moore
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, European Way, Southampton SO14 3ZH, UK
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19
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Zhou H, Dang H, Klotz MG. Environmental Conditions Outweigh Geographical Contiguity in Determining the Similarity of nifH-Harboring Microbial Communities in Sediments of Two Disconnected Marginal Seas. Front Microbiol 2016; 7:1111. [PMID: 27489551 PMCID: PMC4951488 DOI: 10.3389/fmicb.2016.01111] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 07/04/2016] [Indexed: 12/20/2022] Open
Abstract
Ecological evidence suggests that heterotrophic diazotrophs fueled by organic carbon respiration in sediments play an important role in marine nitrogen fixation. However, fundamental knowledge about the identities, abundance, diversity, biogeography, and controlling environmental factors of nitrogen-fixing communities in open ocean sediments is still elusive. Surprisingly, little is known also about nitrogen-fixing communities in sediments of the more research-accessible marginal seas. Here we report on an investigation of the environmental geochemistry and putative diazotrophic microbiota in the sediments of Bohai Sea, an eutrophic marginal sea of the western Pacific Ocean. Diverse and abundant nifH gene sequences were identified and sulfate-reducing bacteria (SRB) were found to be the dominant putative nitrogen-fixing microbes. Community statistical analyses suggested bottom water temperature, bottom water chlorophyll a content (or the covarying turbidity) and sediment porewater Eh (or the covarying pH) as the most significant environmental factors controlling the structure and spatial distribution of the putative diazotrophic communities, while sediment Hg content, sulfide content, and porewater SiO32−-Si content were identified as the key environmental factors correlated positively with the nifH gene abundance in Bohai Sea sediments. Comparative analyses between the Bohai Sea and the northern South China Sea (nSCS) identified a significant composition difference of the putative diazotrophic communities in sediments between the shallow-water (estuarine and nearshore) and deep-water (offshore and deep-sea) environments, and sediment porewater dissolved oxygen content, water depth and in situ temperature as the key environmental factors tentatively controlling the species composition, community structure, and spatial distribution of the marginal sea sediment nifH-harboring microbiota. This confirms the ecophysiological specialization and niche differentiation between the shallow-water and deep-water sediment diazotrophic communities and suggests that the in situ physical and geochemical conditions play a more important role than geographical contiguity in determining the community similarity of the diazotrophic microbiota in marginal sea sediments.
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Affiliation(s)
- Haixia Zhou
- State Key Laboratory of Marine Environmental Science, Institute of Marine Microbes and Ecospheres, and College of Ocean and Earth Sciences, Xiamen UniversityXiamen, China; Centre for Bioengineering and Biotechnology, College of Chemical Engineering, China University of Petroleum (East China)Qingdao, China; Department of Food Quality and Safety, College of Life Science, Dezhou UniversityDezhou, China
| | - Hongyue Dang
- State Key Laboratory of Marine Environmental Science, Institute of Marine Microbes and Ecospheres, and College of Ocean and Earth Sciences, Xiamen University Xiamen, China
| | - Martin G Klotz
- State Key Laboratory of Marine Environmental Science, Institute of Marine Microbes and Ecospheres, and College of Ocean and Earth Sciences, Xiamen UniversityXiamen, China; Department of Biology and School of Earth and Environmental Sciences, Queens College, City University of New YorkQueens, NY, USA
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20
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Emerson D. The Irony of Iron - Biogenic Iron Oxides as an Iron Source to the Ocean. Front Microbiol 2016; 6:1502. [PMID: 26779157 PMCID: PMC4701967 DOI: 10.3389/fmicb.2015.01502] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 12/14/2015] [Indexed: 11/16/2022] Open
Abstract
Primary productivity in at least a third of the sunlit open ocean is thought to be iron-limited. Primary sources of dissolved iron (dFe) to the ocean are hydrothermal venting, flux from the sediments along continental margins, and airborne dust. This article provides a general review of sources of hydrothermal and sedimentary iron to the ocean, and speculates upon the role that iron-cycling microbes play in controlling iron dynamics from these sources. Special attention is paid to iron-oxidizing bacteria (FeOB) that live by oxidizing iron and producing biogenic iron oxides as waste products. The presence and ubiquity of FeOB both at hydrothermal systems and in sediments is only beginning to be appreciated. The biogenic oxides they produce have unique properties that could contribute significantly to the dynamics of dFe in the ocean. Changes in the physical and chemical characteristics of the ocean due to climate change and ocean acidification will undoubtedly impact the microbial iron cycle. A better understanding of the contemporary role of microbes in the iron cycle will help in predicting how these changes could ultimately influence marine primary productivity.
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Affiliation(s)
- David Emerson
- Bigelow Laboratory for Ocean Sciences East Boothbay, ME, USA
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21
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Jickells T, Moore CM. The Importance of Atmospheric Deposition for Ocean Productivity. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2015. [DOI: 10.1146/annurev-ecolsys-112414-054118] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Tim Jickells
- Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom;
| | - C. Mark Moore
- Ocean and Earth Science, National Oceanography Center Southampton, University of Southampton Waterfront Campus, Southampton SO14 3ZH, United Kingdom
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22
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Abstract
Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe-Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface.
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23
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Conway TM, John SG. Quantification of dissolved iron sources to the North Atlantic Ocean. Nature 2014; 511:212-5. [PMID: 25008528 DOI: 10.1038/nature13482] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 05/09/2014] [Indexed: 11/09/2022]
Abstract
Dissolved iron is an essential micronutrient for marine phytoplankton, and its availability controls patterns of primary productivity and carbon cycling throughout the oceans. The relative importance of different sources of iron to the oceans is not well known, however, and flux estimates from atmospheric dust, hydrothermal vents and oceanic sediments vary by orders of magnitude. Here we present a high-resolution transect of dissolved stable iron isotope ratios (δ(56)Fe) and iron concentrations ([Fe]) along a section of the North Atlantic Ocean. The different iron sources can be identified by their unique δ(56)Fe signatures, which persist throughout the water column. This allows us to calculate the relative contribution from dust, hydrothermal venting and reductive and non-reductive sedimentary release to the dissolved phase. We find that Saharan dust aerosol is the dominant source of dissolved iron along the section, contributing 71-87 per cent of dissolved iron. Additional sources of iron are non-reductive release from oxygenated sediments on the North American margin (10-19 per cent), reductive sedimentary dissolution on the African margin (1-4 per cent) and hydrothermal venting at the Mid-Atlantic Ridge (2-6 per cent). Our data also indicate that hydrothermal vents in the North Atlantic are a source of isotopically light iron, which travels thousands of kilometres from vent sites, potentially influencing surface productivity. Changes in the relative importance of the different iron sources through time may affect interactions between the carbon cycle and climate.
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Affiliation(s)
- Tim M Conway
- 1] Department of Earth and Ocean Sciences, University of South Carolina, Columbia, South Carolina 29208, USA [2] Institute of Geochemistry and Petrology, Eidgenössische Technische Hochschule Zürich, NW D81.4, Clausiusstrasse 25, 8092 Zürich, Switzerland
| | - Seth G John
- Department of Earth and Ocean Sciences, University of South Carolina, Columbia, South Carolina 29208, USA
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