1
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Fourquez M, Janssen DJ, Conway TM, Cabanes D, Ellwood MJ, Sieber M, Trimborn S, Hassler C. Chasing iron bioavailability in the Southern Ocean: Insights from Phaeocystis antarctica and iron speciation. SCIENCE ADVANCES 2023; 9:eadf9696. [PMID: 37379397 DOI: 10.1126/sciadv.adf9696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 05/24/2023] [Indexed: 06/30/2023]
Abstract
Dissolved iron (dFe) availability limits the uptake of atmospheric CO2 by the Southern Ocean (SO) biological pump. Hence, any change in bioavailable dFe in this region can directly influence climate. On the basis of Fe uptake experiments with Phaeocystis antarctica, we show that the range of dFe bioavailability in natural samples is wider (<1 to ~200% compared to free inorganic Fe') than previously thought, with higher bioavailability found near glacial sources. The degree of bioavailability varied regardless of in situ dFe concentration and depth, challenging the consensus that sole dFe concentrations can be used to predict Fe uptake in modeling studies. Further, our data suggest a disproportionately major role of biologically mediated ligands and encourage revisiting the role of humic substances in influencing marine Fe biogeochemical cycling in the SO. Last, we describe a linkage between in situ dFe bioavailability and isotopic signatures that, we anticipate, will stimulate future research.
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Affiliation(s)
- Marion Fourquez
- Aix Marseille Univ., Université de Toulon, CNRS, IRD, MIO UMR 110, Marseille 13288, France
- University of Geneva, Department F.-A. Forel for Environmental and Aquatic Sciences, Geneva 1211, Switzerland
| | - David J Janssen
- Department Surface Waters, Eawag-Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
| | - Tim M Conway
- College of Marine Science, University of South Florida, St. Petersburg, FL 33701, USA
| | - Damien Cabanes
- University of Geneva, Department F.-A. Forel for Environmental and Aquatic Sciences, Geneva 1211, Switzerland
| | - Michael J Ellwood
- Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia
- Australian Centre for Excellence in Antarctic Science, Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia
| | - Matthias Sieber
- College of Marine Science, University of South Florida, St. Petersburg, FL 33701, USA
- Institute of Geochemistry and Petrology, ETH Zürich, Zürich, Switzerland
| | - Scarlett Trimborn
- Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Bremerhaven 27570, Germany
| | - Christel Hassler
- University of Geneva, Department F.-A. Forel for Environmental and Aquatic Sciences, Geneva 1211, Switzerland
- Institute of Earth Sciences, University of Lausanne, Lausanne 1015, Switzerland
- School of Architecture, Civil, and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Sion 1951, Switzerland
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2
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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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3
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Non-traditional stable isotopic analysis for source tracing of atmospheric particulate matter. Trends Analyt Chem 2023. [DOI: 10.1016/j.trac.2022.116866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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4
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Liu K, Schiff SL, Wu L, Molot LA, Venkiteswaran JJ, Paterson MJ, Elgood RJ, Tsuji JM, Neufeld JD. Large Fractionation in Iron Isotopes Implicates Metabolic Pathways for Iron Cycling in Boreal Shield Lakes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:14840-14851. [PMID: 36162065 DOI: 10.1021/acs.est.2c04247] [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: 06/16/2023]
Abstract
Stable Fe isotopes have only recently been measured in freshwater systems, mainly in meromictic lakes. Here we report the δ56Fe of dissolved, particulate, and sediment Fe in two small dimictic boreal shield headwater lakes: manipulated eutrophic Lake 227, with annual cyanobacterial blooms, and unmanipulated oligotrophic Lake 442. Within the lakes, the range in δ56Fe is large (ca. -0.9 to +1.8‰), spanning more than half the entire range of natural Earth surface samples. Two layers in the water column with distinctive δ56Fe of dissolved (dis) and particulate (spm) Fe were observed, despite differences in trophic states. In the epilimnia of both lakes, a large Δ56Fedis-spm fractionation of 0.4-1‰ between dissolved and particulate Fe was only observed during cyanobacterial blooms in Lake 227, possibly regulated by selective biological uptake of isotopically light Fe by cyanobacteria. In the anoxic layers in both lakes, upward flux from sediments dominates the dissolved Fe pool with an apparent Δ56Fedis-spm fractionation of -2.2 to -0.6‰. Large Δ56Fedis-spm and previously published metagenome sequence data suggest active Fe cycling processes in anoxic layers, such as microaerophilic Fe(II) oxidation or photoferrotrophy, could regulate biogeochemical cycling. Large fractionation of stable Fe isotopes in these lakes provides a potential tool to probe Fe cycling and the acquisition of Fe by cyanobacteria, with relevance for understanding biogeochemical cycling of Earth's early ferruginous oceans.
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Affiliation(s)
- Kai Liu
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
- Water Institute, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Sherry L Schiff
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
- Water Institute, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Lingling Wu
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
- Water Institute, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Lewis A Molot
- Faculty of Environmental and Urban Change, York University, Toronto, Ontario M3J 1P3, Canada
| | - Jason J Venkiteswaran
- Department of Geography and Environmental Studies, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
| | | | - Richard J Elgood
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
- Water Institute, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Jackson M Tsuji
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
| | - Josh D Neufeld
- Water Institute, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
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5
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König D, Conway TM, Hamilton DS, Tagliabue A. Surface Ocean Biogeochemistry Regulates the Impact of Anthropogenic Aerosol Fe Deposition on the Cycling of Iron and Iron Isotopes in the North Pacific. GEOPHYSICAL RESEARCH LETTERS 2022; 49:e2022GL098016. [PMID: 36245954 PMCID: PMC9539696 DOI: 10.1029/2022gl098016] [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: 01/26/2022] [Revised: 06/09/2022] [Accepted: 06/20/2022] [Indexed: 06/16/2023]
Abstract
Distinctively-light isotopic signatures associated with Fe released from anthropogenic activity have been used to trace basin-scale impacts. However, this approach is complicated by the way Fe cycle processes modulate oceanic dissolved Fe (dFe) signatures (δ56Fediss) post deposition. Here we include dust, wildfire, and anthropogenic aerosol Fe deposition in a global ocean biogeochemical model with active Fe isotope cycling, to quantify how anthropogenic Fe impacts surface ocean dFe and δ56Fediss. Using the North Pacific as a natural laboratory, the response of dFe, δ56Fediss, and primary productivity are spatially and seasonally variable and do not simply follow the footprint of atmospheric deposition. Instead, the effect of anthropogenic Fe is regulated by the biogeochemical regime, specifically the degree of Fe limitation and rates of primary production. Overall, we find that while δ56Fediss does trace anthropogenic input, the response is muted by fractionation during phytoplankton uptake, but amplified by other isotopically-light Fe sources.
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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
| | - D. S. Hamilton
- Department of Earth and Atmospheric ScienceCornell UniversityIthacaNYUSA
| | - A. Tagliabue
- School of Environmental SciencesUniversity of LiverpoolLiverpoolUK
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6
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Hasegawa N, Itai T, Kunisue T, Takahashi Y. Variation of Iron Stable Isotopes in a Marine Ecosystem from the Northwest Pacific Ocean. CHEM LETT 2022. [DOI: 10.1246/cl.220099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Nanako Hasegawa
- Department of Earth and Planetary Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takaaki Itai
- Department of Earth and Planetary Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Tatsuya Kunisue
- Center for Marine Environmental Studies (CMES), Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime, 790-8577, Japan
| | - Yoshio Takahashi
- Department of Earth and Planetary Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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7
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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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8
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Hunnestad AV, Vogel AIM, Armstrong E, Digernes MG, Ardelan MV, Hohmann-Marriott MF. From the Ocean to the Lab-Assessing Iron Limitation in Cyanobacteria: An Interface Paper. Microorganisms 2020; 8:E1889. [PMID: 33260337 PMCID: PMC7760322 DOI: 10.3390/microorganisms8121889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 11/25/2020] [Accepted: 11/26/2020] [Indexed: 12/22/2022] Open
Abstract
Iron is an essential, yet scarce, nutrient in marine environments. Phytoplankton, and especially cyanobacteria, have developed a wide range of mechanisms to acquire iron and maintain their iron-rich photosynthetic machinery. Iron limitation studies often utilize either oceanographic methods to understand large scale processes, or laboratory-based, molecular experiments to identify underlying molecular mechanisms on a cellular level. Here, we aim to highlight the benefits of both approaches to encourage interdisciplinary understanding of the effects of iron limitation on cyanobacteria with a focus on avoiding pitfalls in the initial phases of collaboration. In particular, we discuss the use of trace metal clean methods in combination with sterile techniques, and the challenges faced when a new collaboration is set up to combine interdisciplinary techniques. Methods necessary for producing reliable data, such as High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS), Flow Injection Analysis Chemiluminescence (FIA-CL), and 77K fluorescence emission spectroscopy are discussed and evaluated and a technical manual, including the preparation of the artificial seawater medium Aquil, cleaning procedures, and a sampling scheme for an iron limitation experiment is included. This paper provides a reference point for researchers to implement different techniques into interdisciplinary iron studies that span cyanobacteria physiology, molecular biology, and biogeochemistry.
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Affiliation(s)
- Annie Vera Hunnestad
- Department of Chemistry, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway; (A.V.H.); (M.G.D.)
| | - Anne Ilse Maria Vogel
- PhotoSynLab, Department of Biotechnology and Food Science, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway; (A.I.M.V.); (M.F.H.-M.)
| | - Evelyn Armstrong
- NIWA/University of Otago Research Centre for Oceanography, Department of Chemistry, University of Otago, 9054 Dunedin, New Zealand;
| | - Maria Guadalupe Digernes
- Department of Chemistry, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway; (A.V.H.); (M.G.D.)
| | - Murat Van Ardelan
- Department of Chemistry, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway; (A.V.H.); (M.G.D.)
| | - Martin Frank Hohmann-Marriott
- PhotoSynLab, Department of Biotechnology and Food Science, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway; (A.I.M.V.); (M.F.H.-M.)
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9
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Abstract
Fossil-fuel emissions may impact phytoplankton primary productivity and carbon cycling by supplying bioavailable Fe to remote areas of the ocean via atmospheric aerosols. However, this pathway has not been confirmed by field observations of anthropogenic Fe in seawater. Here we present high-resolution trace-metal concentrations across the North Pacific Ocean (158°W from 25°to 42°N). A dissolved Fe maximum was observed around 35°N, coincident with high dissolved Pb and Pb isotope ratios matching Asian industrial sources and confirming recent aerosol deposition. Iron-stable isotopes reveal in situ evidence of anthropogenic Fe in seawater, with low δ56Fe (-0.23‰ > δ56Fe > -0.65‰) observed in the region that is most influenced by aerosol deposition. An isotope mass balance suggests that anthropogenic Fe contributes 21-59% of dissolved Fe measured between 35° and 40°N. Thus, anthropogenic aerosol Fe is likely to be an important Fe source to the North Pacific Ocean.
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10
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Ellwood MJ, Strzepek RF, Strutton PG, Trull TW, Fourquez M, Boyd PW. Distinct iron cycling in a Southern Ocean eddy. Nat Commun 2020; 11:825. [PMID: 32047154 PMCID: PMC7012851 DOI: 10.1038/s41467-020-14464-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 01/07/2020] [Indexed: 11/09/2022] Open
Abstract
Mesoscale eddies are ubiquitous in the iron-limited Southern Ocean, controlling ocean-atmosphere exchange processes, however their influence on phytoplankton productivity remains unknown. Here we probed the biogeochemical cycling of iron (Fe) in a cold-core eddy. In-eddy surface dissolved Fe (dFe) concentrations and phytoplankton productivity were exceedingly low relative to external waters. In-eddy phytoplankton Fe-to-carbon uptake ratios were elevated 2–6 fold, indicating upregulated intracellular Fe acquisition resulting in a dFe residence time of ~1 day. Heavy dFe isotope values were measured for in-eddy surface waters highlighting extensive trafficking of dFe by cells. Below the euphotic zone, dFe isotope values were lighter and coincident with peaks in recycled nutrients and cell abundance, indicating enhanced microbially-mediated Fe recycling. Our measurements show that the isolated nature of Southern Ocean eddies can produce distinctly different Fe biogeochemistry compared to surrounding waters with cells upregulating iron uptake and using recycling processes to sustain themselves. Eddies are common ocean features that isolate large swaths of seawater, but it is unclear how they influence productivity of phytoplankton trapped inside. Here Ellwood and colleagues use stable and radiogenic isotopes to characterize a Southern Ocean eddy, finding vanishingly low iron concentrations that drive low productivity across the region.
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Affiliation(s)
- Michael J Ellwood
- Research School of Earth Sciences, Australian National University, Canberra, Australia.
| | - Robert F Strzepek
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
| | - Peter G Strutton
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia.,Australian Research Council Centre of Excellence for Climate Extremes, University of Tasmania, Hobart, Australia
| | | | - Marion Fourquez
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
| | - Philip W Boyd
- Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
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11
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Anderson RF. GEOTRACES: Accelerating Research on the Marine Biogeochemical Cycles of Trace Elements and Their Isotopes. ANNUAL REVIEW OF MARINE SCIENCE 2020; 12:49-85. [PMID: 31337253 DOI: 10.1146/annurev-marine-010318-095123] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The biogeochemical cycles of trace elements and their isotopes (TEIs) constitute an active area of oceanographic research due to their role as essential nutrients for marine organisms and their use as tracers of oceanographic processes. Selected TEIs also provide diagnostic information about the physical, geological, and chemical processes that supply or remove solutes in the ocean. Many of these same TEIs provide information about ocean conditions in the past, as their imprint on marine sediments can be interpreted to reflect changes in ocean circulation, biological productivity, the ocean carbon cycle, and more. Other TEIs have been introduced as the result of human activities and are considered contaminants. The development and implementation of contamination-free methods for collecting and analyzing samples for TEIs revolutionized marine chemistry, revealing trace element distributions with oceanographically consistent features and new insights about the processes regulating them. Despite these advances, the volume and geographic coverage of high-quality TEI data by the end of the twentieth century were insufficient to constrain their global biogeochemical cycles. To accelerate progress in this field of research, marine geochemists developed a coordinated international effort to systematically study the marine biogeochemical cycles of TEIs-the GEOTRACES program. Following a decade of planning and implementation, GEOTRACES launched its main field effort in 2010. This review, roughly midway through the field program, summarizes the steps involved in designing the program, its management structure, and selected findings.
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Affiliation(s)
- Robert F Anderson
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA;
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12
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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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13
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Central role for ferritin in the day/night regulation of iron homeostasis in marine phytoplankton. Proc Natl Acad Sci U S A 2015; 112:14652-7. [PMID: 26553998 DOI: 10.1073/pnas.1506074112] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In large regions of the open ocean, iron is a limiting resource for phytoplankton. The reduction of iron quota and the recycling of internal iron pools are among the diverse strategies that phytoplankton have evolved to allow them to grow under chronically low ambient iron levels. Phytoplankton species also have evolved strategies to cope with sporadic iron supply such as long-term storage of iron in ferritin. In the picophytoplanktonic species Ostreococcus we report evidence from observations both in the field and in laboratory cultures that ferritin and the main iron-binding proteins involved in photosynthesis and nitrate assimilation pathways show opposite diurnal expression patterns, with ferritin being maximally expressed during the night. Biochemical and physiological experiments using a ferritin knock-out line subsequently revealed that this protein plays a central role in the diel regulation of iron uptake and recycling and that this regulation of iron homeostasis is essential for cell survival under iron limitation.
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