1
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Chen Y, Dong L, Sui W, Niu M, Cui X, Hinrichs KU, Wang F. Cycling and persistence of iron-bound organic carbon in subseafloor sediments. Nat Commun 2024; 15:6370. [PMID: 39075044 PMCID: PMC11286938 DOI: 10.1038/s41467-024-50578-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Accepted: 07/16/2024] [Indexed: 07/31/2024] Open
Abstract
Reactive iron (FeR) serves as an important sink of organic carbon (OC) in marine surface sediments, which preserves approximately 20% of total OC (TOC) as reactive iron-bound OC (FeR-OC). However, the fate of FeR-OC in subseafloor sediments and its availability to microorganisms, remain undetermined. Here, we reconstructed continuous FeR-OC records in two sediment cores of the northern South China Sea encompassing the suboxic to methanic biogeochemical zones and reaching a maximum age of ~100 kyr. The downcore FeR-OC contributes a relatively stable proportion of 13.3 ± 3.2% to TOC. However, distinctly lower values of less than 5% of TOC, accompanied by notable 13C depletion of FeR-OC, are observed in the sulfate-methane transition zone (SMTZ). FeR-OC is suggested to be remobilized by microbially mediated reductive dissolution of FeR and subsequently remineralized, the flux of which is 18-30% of the methane consumption in the SMTZ. The global reservoir of FeR-OC in microbially active Quaternary marine sediments could be 19-46 times the size of the atmospheric carbon pool. Thus, the FeR-OC pool may support subseafloor microorganisms and contribute to regulating Earth's carbon cycle.
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Affiliation(s)
- Yunru Chen
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
- MARUM-Center for Marine Environmental Sciences, University of Bremen, D-28359, Bremen, Germany
| | - Liang Dong
- Key Laboratory of Polar Ecosystem and Climate Change, Ministry of Education, and School of Oceanography, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Weikang Sui
- Key Laboratory of Polar Ecosystem and Climate Change, Ministry of Education, and School of Oceanography, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Mingyang Niu
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Xingqian Cui
- Key Laboratory of Polar Ecosystem and Climate Change, Ministry of Education, and School of Oceanography, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Kai-Uwe Hinrichs
- MARUM-Center for Marine Environmental Sciences, University of Bremen, D-28359, Bremen, Germany
- Faculty of Geosciences, University of Bremen, D-28359, Bremen, Germany
| | - Fengping Wang
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China.
- Key Laboratory of Polar Ecosystem and Climate Change, Ministry of Education, and School of Oceanography, Shanghai Jiao Tong University, Shanghai, 200240, China.
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519000, China.
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2
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Frinault BAV, Barnes DKA. Variability in zoobenthic blue carbon storage across a southern polar gradient. MARINE ENVIRONMENTAL RESEARCH 2024; 199:106621. [PMID: 38909538 DOI: 10.1016/j.marenvres.2024.106621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2024] [Revised: 06/19/2024] [Accepted: 06/20/2024] [Indexed: 06/25/2024]
Abstract
The seabed of the Antarctic continental shelf hosts most of Antarctica's known species, including taxa considered indicative of vulnerable marine ecosystems (VMEs). Nonetheless, the potential impact of climatic and environmental change, including marine icescape transition, on Antarctic shelf zoobenthos, and their blue carbon-associated function, is still poorly characterised. To help narrow knowledge gaps, four continental shelf study areas, spanning a southern polar gradient, were investigated for zoobenthic (principally epi-faunal) carbon storage (a component of blue carbon), and potential environmental influences, employing a functional group approach. Zoobenthic carbon storage was highest at the two southernmost study areas (with a mean estimate of 41.6 versus 7.2 g C m-2) and, at each study area, increased with morphotaxa richness, overall faunal density, and VME indicator density. Functional group mean carbon content varied with study area, as did each group's percentage contribution to carbon storage and faunal density. Of the environmental variables explored, sea-ice cover and primary production, both likely to be strongly impacted by climate change, featured in variable subsets most highly correlating with assemblage and carbon storage (by functional groups) structures. The study findings can underpin biodiversity- and climate-considerate marine spatial planning and conservation measures in the Southern Ocean.
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Affiliation(s)
- Bétina A V Frinault
- School of Geography and the Environment, Oxford University Centre for the Environment, University of Oxford, South Parks Road, Oxford, OX1 3QY, UK.
| | - David K A Barnes
- British Antarctic Survey, UK Research and Innovation, Madingley Road, Cambridge, CB3 0ET, UK
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3
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Ren X, Wang XL, Zhang FF, Du JQ, Du JZ, Hong GH. Utilities of environmental radioactivity tracers in assessing sequestration potential of carbon in the coastal wetland ecosystems. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2024; 277:107464. [PMID: 38851006 DOI: 10.1016/j.jenvrad.2024.107464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 05/28/2024] [Accepted: 05/28/2024] [Indexed: 06/10/2024]
Abstract
Demand for accurate estimation of coastal blue carbon sequestration rates in a regular interval has recently surged due to the increasing awareness of nature-based climate solutions to alleviate adverse impacts stemming from the recent global warming. The robust estimation method is, however, far from well-established. The international community requires, moreover, to quantify its effect of "management." This article tries to provide the environmental isotope community with basic biophysical features of coastal blue carbon ecosystems to identify a suitable set of environmental isotopes for promoting coastal ocean-based climate solutions. This article reviews (i) the primary biophysical characteristics of coastal blue carbon ecosystems and hydrology, (ii) their consequential impact on the accumulation and preservation of organic carbon (OC) in the sediment column, (iii) suitable environmental isotopes to quantifying the sedimentary organic carbon accumulation, outwelling of the carbon-containing byproducts of decomposition of biogenic organic matter and acid neutralizing alkalinity produced in situ sediment to the offshore. Above-ground biomass is not cumulative over the years except for mangrove forests within coastal blue carbon systems. Non-gaseous carbon sequestration and loss occur mainly as a form of sediment organic carbon (SOC) and dissolved carbon in an intertidal and subtidal bottom sediment body in a slow, patchy, and dispersive way, on which this article focuses. Investigating environmental radionuclides is probably the most cost-effective effort to contribute to defining the offshore spatial extent of coastal blue carbon systems except for seagrass beds (e.g., Ra isotopes), to quantify millimeter per year scale carbon accretion and loss within the systems (e.g., 7Be, 210Pb) and a liter per meter of coastline per a day scale water movement from the systems (Ra isotopes). A millimeter-scale spatial and an annual (or less) time-scale resolution offered by the use of environmental isotopes would equip us with a novel tool to enhance the carbon storage capacity of the coastal blue carbon system.
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Affiliation(s)
- X Ren
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China; Guangxi Key Laboratory of Marine Environmental Change and Disaster in Beibu Gulf, Beibu Gulf University, Qinzhou 535011, China
| | - X L Wang
- Guangxi Key Laboratory of Marine Environmental Change and Disaster in Beibu Gulf, Beibu Gulf University, Qinzhou 535011, China
| | - F F Zhang
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China
| | - J Q Du
- National Marine Environmental Monitoring Center, Dalian, 116023, China
| | - J Z Du
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China
| | - G H Hong
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China; Integrated Marine Biosphere Research International Project Office, State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200242, China.
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4
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Wang Y, Costa KM, Lu W, Hines SKV, Nielsen SG. Global oceanic oxygenation controlled by the Southern Ocean through the last deglaciation. SCIENCE ADVANCES 2024; 10:eadk2506. [PMID: 38241365 PMCID: PMC10798564 DOI: 10.1126/sciadv.adk2506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 12/19/2023] [Indexed: 01/21/2024]
Abstract
Ocean dissolved oxygen (DO) can provide insights on how the marine carbon cycle affects global climate change. However, the net global DO change and the controlling mechanisms remain uncertain through the last deglaciation. Here, we present a globally integrated DO reconstruction using thallium isotopes, corroborating lower global DO during the Last Glacial Maximum [19 to 23 thousand years before the present (ka B.P.)] relative to the Holocene. During the deglaciation, we reveal reoxygenation in the Heinrich Stadial 1 (~14.7 to 18 ka B.P.) and the Younger Dryas (11.7 to 12.9 ka B.P.), with deoxygenation during the Bølling-Allerød (12.9 to 14.7 ka B.P.). The deglacial DO changes were decoupled from North Atlantic Deep Water formation rates and imply that Southern Ocean ventilation controlled ocean oxygen. The coherence between global DO and atmospheric CO2 on millennial timescales highlights the Southern Ocean's role in deglacial atmospheric CO2 rise.
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Affiliation(s)
- Yi Wang
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
- NIRVANA Laboratories, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
- Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA 70118, USA
| | - Kassandra M. Costa
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Wanyi Lu
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Sophia K. V. Hines
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Sune G. Nielsen
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
- NIRVANA Laboratories, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
- Centre de Recherches Pétrographiques et Géochimiques, CNRS, Université de Lorraine, 15 rue Notre Dame des Pauvres, 54501 Vandoeuvre lès Nancy, France
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5
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Talling PJ, Hage S, Baker ML, Bianchi TS, Hilton RG, Maier KL. The Global Turbidity Current Pump and Its Implications for Organic Carbon Cycling. ANNUAL REVIEW OF MARINE SCIENCE 2024; 16:105-133. [PMID: 37487592 DOI: 10.1146/annurev-marine-032223-103626] [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: 07/26/2023]
Abstract
Submarine turbidity currents form the largest sediment accumulations on Earth, raising the question of their role in global carbon cycles. It was previously inferred that terrestrial organic carbon was primarily incinerated on shelves and that most turbidity current systems are presently inactive. Turbidity currents were thus not considered in global carbon cycles, and the burial efficiency of global terrestrial organic carbon was considered low to moderate (∼10-44%). However, recent work has shown that burial of terrestrial organic carbon by turbidity currents is highly efficient (>60-100%) in a range of settings and that flows occur more frequently than once thought, although they were far more active at sea-level lowstands. This leads to revised global estimates for mass flux (∼62-90 Mt C/year) and burial efficiency (∼31-45%) of terrestrial organic carbon in marine sediments. Greatly increased burial fluxes during sea-level lowstands are also likely underestimated; thus, organic carbon cycling by turbidity currents could play a role in long-term changes in atmospheric CO2 and climate.
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Affiliation(s)
- Peter J Talling
- Department of Geography, Durham University, Durham, United Kingdom; ,
- Department of Earth Sciences, Durham University, Durham, United Kingdom
| | - Sophie Hage
- Geo-Ocean, Université de Bretagne-Occidentale, IFREMER, CNRS UMR 6538, Plouzané, France;
| | - Megan L Baker
- Department of Geography, Durham University, Durham, United Kingdom; ,
| | - Thomas S Bianchi
- Department of Geological Sciences, University of Florida, Gainesville, Florida, USA;
| | - Robert G Hilton
- Department of Earth Sciences, University of Oxford, Oxford, United Kingdom;
| | - Katherine L Maier
- National Institute of Water and Atmospheric Research, Wellington, Aotearoa New Zealand;
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6
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Chang L, Hoogakker BAA, Heslop D, Zhao X, Roberts AP, De Deckker P, Xue P, Pei Z, Zeng F, Huang R, Huang B, Wang S, Berndt TA, Leng M, Stuut JBW, Harrison RJ. Indian Ocean glacial deoxygenation and respired carbon accumulation during mid-late Quaternary ice ages. Nat Commun 2023; 14:4841. [PMID: 37563128 PMCID: PMC10415292 DOI: 10.1038/s41467-023-40452-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 07/28/2023] [Indexed: 08/12/2023] Open
Abstract
Reconstructions of ocean oxygenation are critical for understanding the role of respired carbon storage in regulating atmospheric CO2. Independent sediment redox proxies are essential to assess such reconstructions. Here, we present a long magnetofossil record from the eastern Indian Ocean in which we observe coeval magnetic hardening and enrichment of larger, more elongated, and less oxidized magnetofossils during glacials compared to interglacials over the last ~900 ka. Our multi-proxy records of redox-sensitive magnetofossils, trace element concentrations, and benthic foraminiferal Δδ13C consistently suggest a recurrence of lower O2 in the glacial Indian Ocean over the last 21 marine isotope stages, as has been reported for the Atlantic and Pacific across the last glaciation. Consistent multi-proxy documentation of this repeated oxygen decline strongly supports the hypothesis that increased Indian Ocean glacial carbon storage played a significant role in atmospheric CO2 cycling and climate change over recent glacial/interglacial timescales.
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Affiliation(s)
- Liao Chang
- Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, 100871, Beijing, China.
- Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, 266071, Qingdao, China.
| | | | - David Heslop
- Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia
| | - Xiang Zhao
- Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia
| | - Andrew P Roberts
- Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia
| | - Patrick De Deckker
- Research School of Earth Sciences, The Australian National University, Canberra, ACT 2601, Australia
| | - Pengfei Xue
- Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, 100871, Beijing, China
| | - Zhaowen Pei
- Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, 100871, Beijing, China
| | - Fan Zeng
- Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, 100871, Beijing, China
| | - Rong Huang
- Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, 100871, Beijing, China
| | - Baoqi Huang
- Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, 100871, Beijing, China
| | - Shishun Wang
- Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, 100871, Beijing, China
| | - Thomas A Berndt
- Department of Geophysics, School of Earth and Space Sciences, Peking University, 100871, Beijing, China
| | - Melanie Leng
- National Environmental Isotope Facility, British Geological Survey, Keyworth, NG12 5GG, UK
- School of Biosciences, University of Nottingham, Sutton Bonington, LE12 5RD, UK
| | - Jan-Berend W Stuut
- NIOZ-Royal Netherlands Institute for Sea Research and Utrecht University, Texel, The Netherlands
| | - Richard J Harrison
- Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK
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7
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Li Z, Zhang YG, Torres M, Mills BJW. Neogene burial of organic carbon in the global ocean. Nature 2023; 613:90-95. [PMID: 36600067 DOI: 10.1038/s41586-022-05413-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 10/05/2022] [Indexed: 01/05/2023]
Abstract
Organic carbon buried in marine sediment serves as a net sink for atmospheric carbon dioxide and a source of oxygen1,2. The rate of organic carbon burial through geologic history is conventionally established by using the mass balance between inorganic and organic carbon, each with distinct carbon isotopic values (δ13C)3,4. This method is complicated by large uncertainties, however, and has not been tested with organic carbon accumulation data5,6. Here we report a 'bottom-up' approach for calculating the rate of organic carbon burial that is independent from mass balance calculations. We use data from 81 globally distributed sites to establish the history of organic carbon burial during the Neogene (roughly 23-3 Ma). Our results show larger spatiotemporal variability of organic carbon burial than previously estimated7-9. Globally, the burial rate is high towards the early Miocene and Pliocene and lowest during the mid-Miocene, with the latter period characterized by the lowest ratio of organic-to-carbonate burial rates. This is in contrast to earlier work that interpreted enriched carbonate 13C values of the mid-Miocene as massive organic carbon burial (that is, the Monterey Hypothesis)10,11. Suppressed organic carbon burial during the warm mid-Miocene is probably related to temperature-dependent bacterial degradation of organic matter12,13, suggesting that the organic carbon cycle acted as positive feedback of past global warming.
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Affiliation(s)
- Ziye Li
- College of Marine Geosciences, Key Laboratory of Submarine Geosciences and Prospecting Techniques, Ocean University of China, Qingdao, China.,Department of Oceanography, Texas A&M University, College Station, TX, USA.,MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Yi Ge Zhang
- Department of Oceanography, Texas A&M University, College Station, TX, USA.
| | - Mark Torres
- Department of Earth, Environmental, and Planetary Sciences, Rice University, Houston, TX, USA
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8
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Bradley JA, Hülse D, LaRowe DE, Arndt S. Transfer efficiency of organic carbon in marine sediments. Nat Commun 2022; 13:7297. [PMID: 36435937 PMCID: PMC9701188 DOI: 10.1038/s41467-022-35112-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 11/18/2022] [Indexed: 11/28/2022] Open
Abstract
Quantifying the organic carbon (OC) sink in marine sediments is crucial for assessing how the marine carbon cycle regulates Earth's climate. However, burial efficiency (BE) - the commonly-used metric reporting the percentage of OC deposited on the seafloor that becomes buried (beyond an arbitrary and often unspecified reference depth) - is loosely defined, misleading, and inconsistent. Here, we use a global diagenetic model to highlight orders-of-magnitude differences in sediment ages at fixed sub-seafloor depths (and vice-versa), and vastly different BE's depending on sediment depth or age horizons used to calculate BE. We propose using transfer efficiencies (Teff's) for quantifying sediment OC burial: Teff is numerically equivalent to BE but requires precise specification of spatial or temporal references, and emphasizes that OC degradation continues beyond these horizons. Ultimately, quantifying OC burial with precise sediment-depth and sediment-age-resolved metrics will enable a more consistent and transferable assessment of OC fluxes through the Earth system.
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Affiliation(s)
- James A. Bradley
- grid.4868.20000 0001 2171 1133Queen Mary University of London, London, UK ,grid.23731.340000 0000 9195 2461GFZ German Research Center for Geosciences, Potsdam, Germany
| | - Dominik Hülse
- grid.266097.c0000 0001 2222 1582University of California, Riverside, Riverside, CA USA ,grid.450268.d0000 0001 0721 4552Max-Planck-Institute for Meteorology, Hamburg, Germany
| | - Douglas E. LaRowe
- grid.42505.360000 0001 2156 6853University of Southern California, Los Angeles, CA USA
| | - Sandra Arndt
- grid.4989.c0000 0001 2348 0746Université Libre de Bruxelles, Brussels, Belgium
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9
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Le JT, Girguis PR, Levin LA. Using deep-sea images to examine ecosystem services associated with methane seeps. MARINE ENVIRONMENTAL RESEARCH 2022; 181:105740. [PMID: 36155343 DOI: 10.1016/j.marenvres.2022.105740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 08/27/2022] [Accepted: 08/31/2022] [Indexed: 06/16/2023]
Abstract
Deep-sea images are routinely collected during at-sea expeditions and represent a repository of under-utilized knowledge. We leveraged dive videos collected by the remotely-operated vehicle Hercules (deployed from E/V Nautilus, operated by the Ocean Exploration Trust), and adapted biological trait analysis, to develop an approach that characterizes ecosystem services. Specifically, fisheries and climate-regulating services related to carbon are assessed for three southern California methane seeps: Point Dume (∼725 m), Palos Verdes (∼506 m), and Del Mar (∼1023 m). Our results enable qualitative intra-site comparisons that suggest seep activity influences ecosystem services differentially among sites, and site-to-site comparisons that suggest the Del Mar site provides the highest relative contributions to fisheries and carbon services. This study represents a first step towards ecosystem services characterization and quantification using deep-sea images. The results presented herein are foundational, and continued development should help guide research and management priorities by identifying potential sources of ecosystem services.
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Affiliation(s)
- Jennifer T Le
- Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California San Diego, La Jolla, 92093, USA.
| | - Peter R Girguis
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, 02138, USA
| | - Lisa A Levin
- Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California San Diego, La Jolla, 92093, USA
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10
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Organic Matter Burial in Deep-Sea Fans: A Depositional Process-Based Perspective. JOURNAL OF MARINE SCIENCE AND ENGINEERING 2022. [DOI: 10.3390/jmse10050682] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Organic matter burial in the deep-sea fan sediments is an important component of the long-term carbon cycle. Although there is increasing recognition of the importance of organic matter in deep-sea sediments, a major focus has been on mudstones, commonly interpreted as the background sediments, deposited by pelagic or hemipelagic vertical suspension fallout in low-energy fan environments. Emerging evidence suggests that relatively coarse-grained sediment gravity flow deposits (e.g., turbidites and hybrid event beds) can also store a significant quantity of organic carbon, implying that a wide range of depositional processes can result in the concentration and enrichment of organic matter in submarine fans. However, the role of these processes on carbon burial is still not fully understood. This review aims to discuss the impact of three widely documented deep-sea depositional mechanisms/processes, namely vertical suspension settling, grain-by-grain (incremental aggradation), and the en-masse deposition on distribution, burial, and preservation of organic matter in deep-marine deposits. Organic matter accumulated from slowly settling suspension in mud caps (Te or H5 divisions of turbidites and hybrid beds, respectively) is prone to higher oxidation compared to the carbon buried in sandy components of turbidity currents (Ta-Tc units) and hybrid beds (H2/H3 divisions). The burial of organic matter in sandy parts of the deposits has important implications for understanding the fundamental physical processes that control carbon accumulation and preservation in deep-marine rock record.
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11
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Raja M, Rosell‐Melé A. Quantitative Link Between Sedimentary Chlorin and Sea-Surface Chlorophyll- a. JOURNAL OF GEOPHYSICAL RESEARCH. BIOGEOSCIENCES 2022; 127:e2021JG006514. [PMID: 35966617 PMCID: PMC9359122 DOI: 10.1029/2021jg006514] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 03/12/2022] [Accepted: 03/14/2022] [Indexed: 06/15/2023]
Abstract
Primary productivity in the ocean plays a major role in the global carbon cycle. To estimate its changes through geological time, different sedimentary proxies are used. However, the relative weights of the various processes driving the sedimentary accumulation of organic matter are not fully constrained or represent the flux of specific algal classes. Here, we compare sea-surface chlorophyll-a (SSchla) abundance estimated from remote sensing data over the last 20 years with the sedimentary concentration of its derivatives (i.e., chlorin) on a suite of 140 core-top sediments from different biogeochemical regions. We estimate with field data that only 0.33% of SSchla in tropical and subtropical regions is transferred to surface sediments in the form of chlorin. Despite the small fraction of chlorin that arrive to the sea-floor, the sedimentary spatial distribution of chlorin is driven primarily by SSchla concentration in high and moderate productivity locations (SSchla > 0.20 mg·m-3). Our calibration paves the way for the use of chlorin as quantitative proxies of primary productivity in paleoreconstructions and cautions on their use in low primary productivity settings.
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Affiliation(s)
- M. Raja
- Institut de Ciència i Tecnologia Ambientals (ICTA‐UAB)Universitat Autònoma de BarcelonaBellaterraSpain
- Present at: University of NottinghamGSK Centre for Sustainable ChemistryNottinghamUK
| | - A. Rosell‐Melé
- Institut de Ciència i Tecnologia Ambientals (ICTA‐UAB)Universitat Autònoma de BarcelonaBellaterraSpain
- Institució Catalana de Recerca i Estudis Avançats (ICREA)BarcelonaSpain
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12
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Persistent deep water anoxia in the eastern South Atlantic during the last ice age. Proc Natl Acad Sci U S A 2021; 118:2107034118. [PMID: 34873057 DOI: 10.1073/pnas.2107034118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/26/2021] [Indexed: 11/18/2022] Open
Abstract
During the last glacial interval, marine sediments recorded reduced current ventilation within the ocean interior below water depths of approximately >1,500 m [B. A. Hoogakker et al., Nat. Geosci. 8, 40-43 (2015)]. The degree of the associated oxygen depletion in the different ocean basins, however, is still poorly constrained. Here, we present sedimentary records of redox-sensitive metals from the southwest African margin. These records show evidence of continuous bottom water anoxia in the eastern South Atlantic during the last glaciation that led to enhanced carbon burial over a prolonged period of time. Our geochemical data indicate that upwelling-related productivity and the associated oxygen minimum zone in the eastern South Atlantic shifted far seaward during the last glacial period and only slowly retreated during deglaciation times. While increased productivity during the last ice age may have contributed to oxygen depletion in bottom waters, especially on the upper slope, slow-down of the Late Quaternary deep water circulation pattern [Rutberg et al., Nature 405, 935-938 (2000)] appears to be the ultimate driver of anoxic conditions in deep waters.
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13
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Zhang J, Li C, Zhang Y. Geological evidences and mechanisms for oceanic anoxic events during the Early Paleozoic. CHINESE SCIENCE BULLETIN-CHINESE 2021. [DOI: 10.1360/tb-2021-0535] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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14
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Abstract
Organic matter in the global ocean, soils, and sediments stores about five times more carbon than the atmosphere. Thus, the controls on the accumulation of organic matter are critical to global carbon cycling. However, we lack a quantitative understanding of these controls. This prevents meaningful descriptions of organic matter cycling in global climate models, which are required for understanding how changes in organic matter reservoirs provide feedbacks to past and present changes in climate. Currently, explanations for organic matter accumulation remain under debate, characterized by seemingly competing hypotheses. Here, we develop a quantitative framework for organic matter accumulation that unifies these hypotheses. The framework derives from the ecological dynamics of microorganisms, the dominant consumers of organic matter. Organic matter constitutes a key reservoir in global elemental cycles. However, our understanding of the dynamics of organic matter and its accumulation remains incomplete. Seemingly disparate hypotheses have been proposed to explain organic matter accumulation: the slow degradation of intrinsically recalcitrant substrates, the depletion to concentrations that inhibit microbial consumption, and a dependency on the consumption capabilities of nearby microbial populations. Here, using a mechanistic model, we develop a theoretical framework that explains how organic matter predictably accumulates in natural environments due to biochemical, ecological, and environmental factors. Our framework subsumes the previous hypotheses. Changes in the microbial community or the environment can move a class of organic matter from a state of functional recalcitrance to a state of depletion by microbial consumers. The model explains the vertical profile of dissolved organic carbon in the ocean and connects microbial activity at subannual timescales to organic matter turnover at millennial timescales. The threshold behavior of the model implies that organic matter accumulation may respond nonlinearly to changes in temperature and other factors, providing hypotheses for the observed correlations between organic carbon reservoirs and temperature in past earth climates.
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15
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Raja M, Rosell-Melé A. Appraisal of sedimentary alkenones for the quantitative reconstruction of phytoplankton biomass. Proc Natl Acad Sci U S A 2021; 118:e2014787118. [PMID: 33380457 PMCID: PMC7812761 DOI: 10.1073/pnas.2014787118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Marine primary productivity (PP) is the driving factor in the global marine carbon cycle. Its reconstruction in past climates relies on biogeochemical proxies that are not considered to provide an unequivocal signal. These are often based on the water column flux of biogenic components to sediments (organic carbon, biogenic opal, biomarkers), although other factors than productivity are posited to control the sedimentary contents of the components, and their flux is related to the fraction of export production buried in sediments. Moreover, most flux proxies have not been globally appraised. Here, we assess a proxy to quantify past phytoplankton biomass by correlating the concentration of C37 alkenones in a global suite of core-top sediments with sea surface chlorophyll-a (SSchla) estimates over the last 20 y. SSchla is the central metric to calculate phytoplankton biomass and is directly related to PP. We show that the global spatial distribution of sedimentary alkenones is primarily correlated to SSchla rather than diagenetic factors such as the oxygen concentration in bottom waters, which challenges previous assumptions on the role of preservation on driving concentrations of sedimentary organic compounds. Moreover, our results suggest that the rate of global carbon export to sediments is not regionally constrained, and that alkenones producers play a dominant role in the global export of carbon buried in the seafloor. This study shows the potential of using sedimentary alkenones to estimate past phytoplankton biomass, which in turn can be used to infer past PP in the global ocean.
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Affiliation(s)
- Maria Raja
- Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain;
| | - Antoni Rosell-Melé
- Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia, Spain
- Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Catalonia, Spain
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16
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Lai D, Hedlund BP, Xie W, Liu J, Phelps TJ, Zhang C, Wang P. Impact of Terrestrial Input on Deep-Sea Benthic Archaeal Community Structure in South China Sea Sediments. Front Microbiol 2020; 11:572017. [PMID: 33224115 PMCID: PMC7674655 DOI: 10.3389/fmicb.2020.572017] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 10/15/2020] [Indexed: 12/12/2022] Open
Abstract
Archaea are widespread in marine sediments and play important roles in the cycling of sedimentary organic carbon. However, factors controlling the distribution of archaea in marine sediments are not well understood. Here we investigated benthic archaeal communities over glacial-interglacial cycles in the northern South China Sea and evaluated their responses to sediment organic matter sources and inter-species interactions. Archaea in sediments deposited during the interglacial period Marine Isotope Stage (MIS) 1 (Holocene) were significantly different from those in sediments deposited in MIS 2 and MIS 3 of the Last Glacial Period when terrestrial input to the South China Sea was enhanced based on analysis of the long-chain n-alkane C31. The absolute archaeal 16S rRNA gene abundance in subsurface sediments was highest in MIS 2, coincident with high sedimentation rates and high concentrations of total organic carbon. Soil Crenarchaeotic Group (SCG; Nitrososphaerales) species, the most abundant ammonia-oxidizing archaea in soils, increased dramatically during MIS 2, likely reflecting transport of terrestrial archaea during glacial periods with high sedimentation rates. Co-occurrence network analyses indicated significant association of SCG archaea with benthic deep-sea microbes such as Bathyarchaeota and Thermoprofundales in MIS 2 and MIS 3, suggesting potential interactions among these archaeal groups. Meanwhile, Thermoprofundales abundance was positively correlated with total organic carbon (TOC), along with n-alkane C31 and sedimentation rate, indicating that Thermoprofundales may be particularly important in processing of organic carbon in deep-sea sediments. Collectively, these results demonstrate that the composition of heterotrophic benthic archaea in the South China Sea may be influenced by terrestrial organic input in tune with glacial-interglacial cycles, suggesting a plausible link between global climate change and microbial population dynamics in deep-sea marine sediments.
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Affiliation(s)
- Dengxun Lai
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China.,School of Life Sciences, University of Nevada, Las Vegas, NV, United States
| | - Brian P Hedlund
- School of Life Sciences, University of Nevada, Las Vegas, NV, United States.,Nevada Institute of Personalized Medicine, University of Nevada, Las Vegas, NV, United States
| | - Wei Xie
- School of Marine Sciences, Sun Yat-sen University, Zhuhai, China.,Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
| | - Jingjing Liu
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
| | - Tommy J Phelps
- Earth and Planetary Sciences, University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Chuanlun Zhang
- Shenzhen Key Laboratory of Marine Archaea Geo-Omics, Southern University of Science and Technology, Shenzhen, China.,Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen, China.,Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China.,Shanghai Sheshan National Geophysical Observatory, Shanghai, China
| | - Peng Wang
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, China
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17
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Marine nitrogen fixers mediate a low latitude pathway for atmospheric CO 2 drawdown. Nat Commun 2019; 10:4611. [PMID: 31601810 PMCID: PMC6787065 DOI: 10.1038/s41467-019-12549-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 09/16/2019] [Indexed: 02/02/2023] Open
Abstract
Roughly a third (~30 ppm) of the carbon dioxide (CO2) that entered the ocean during ice ages is attributed to biological mechanisms. A leading hypothesis for the biological drawdown of CO2 is iron (Fe) fertilisation of the high latitudes, but modelling efforts attribute at most 10 ppm to this mechanism, leaving ~20 ppm unexplained. We show that an Fe-induced stimulation of dinitrogen (N2) fixation can induce a low latitude drawdown of 7–16 ppm CO2. This mechanism involves a closer coupling between N2 fixers and denitrifiers that alleviates widespread nitrate limitation. Consequently, phosphate utilisation and carbon export increase near upwelling zones, causing deoxygenation and deeper carbon injection. Furthermore, this low latitude mechanism reproduces the regional patterns of organic δ15N deposited in glacial sediments. The positive response of marine N2 fixation to dusty ice age conditions, first proposed twenty years ago, therefore compliments high latitude changes to amplify CO2 drawdown. Iron fertilisation of the high latitude oceans is a well-established biological mechanism to explain the ice age drawdown of atmospheric CO2, yet modelling has so far struggled to account for a sufficient drawdown via this mechanism. Here, the authors propose that N2 fixers, which inhabit the lower latitude ocean, made a significant contribution to CO2 drawdown and so amplified the global response to iron fertilisation during ice ages.
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18
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Jørgensen BB, Findlay AJ, Pellerin A. The Biogeochemical Sulfur Cycle of Marine Sediments. Front Microbiol 2019. [DOI: 10.10.3389/fmicb.2019.00849] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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19
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Jørgensen BB, Findlay AJ, Pellerin A. The Biogeochemical Sulfur Cycle of Marine Sediments. Front Microbiol 2019; 10:849. [PMID: 31105660 PMCID: PMC6492693 DOI: 10.3389/fmicb.2019.00849] [Citation(s) in RCA: 203] [Impact Index Per Article: 40.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 04/02/2019] [Indexed: 11/13/2022] Open
Abstract
Microbial dissimilatory sulfate reduction to sulfide is a predominant terminal pathway of organic matter mineralization in the anoxic seabed. Chemical or microbial oxidation of the produced sulfide establishes a complex network of pathways in the sulfur cycle, leading to intermediate sulfur species and partly back to sulfate. The intermediates include elemental sulfur, polysulfides, thiosulfate, and sulfite, which are all substrates for further microbial oxidation, reduction or disproportionation. New microbiological discoveries, such as long-distance electron transfer through sulfide oxidizing cable bacteria, add to the complexity. Isotope exchange reactions play an important role for the stable isotope geochemistry and for the experimental study of sulfur transformations using radiotracers. Microbially catalyzed processes are partly reversible whereby the back-reaction affects our interpretation of radiotracer experiments and provides a mechanism for isotope fractionation. We here review the progress and current status in our understanding of the sulfur cycle in the seabed with respect to its microbial ecology, biogeochemistry, and isotope geochemistry.
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Affiliation(s)
- Bo Barker Jørgensen
- Department of Bioscience, Center for Geomicrobiology, Aarhus University, Aarhus, Denmark
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20
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Willeit M, Ganopolski A, Calov R, Brovkin V. Mid-Pleistocene transition in glacial cycles explained by declining CO 2 and regolith removal. SCIENCE ADVANCES 2019; 5:eaav7337. [PMID: 30949580 PMCID: PMC6447376 DOI: 10.1126/sciadv.aav7337] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 02/08/2019] [Indexed: 05/03/2023]
Abstract
Variations in Earth's orbit pace the glacial-interglacial cycles of the Quaternary, but the mechanisms that transform regional and seasonal variations in solar insolation into glacial-interglacial cycles are still elusive. Here, we present transient simulations of coevolution of climate, ice sheets, and carbon cycle over the past 3 million years. We show that a gradual lowering of atmospheric CO2 and regolith removal are essential to reproduce the evolution of climate variability over the Quaternary. The long-term CO2 decrease leads to the initiation of Northern Hemisphere glaciation and an increase in the amplitude of glacial-interglacial variations, while the combined effect of CO2 decline and regolith removal controls the timing of the transition from a 41,000- to 100,000-year world. Our results suggest that the current CO2 concentration is unprecedented over the past 3 million years and that global temperature never exceeded the preindustrial value by more than 2°C during the Quaternary.
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Affiliation(s)
- M. Willeit
- Potsdam Institute for Climate Impact Research, Potsdam, Germany
- Corresponding author.
| | - A. Ganopolski
- Potsdam Institute for Climate Impact Research, Potsdam, Germany
| | - R. Calov
- Potsdam Institute for Climate Impact Research, Potsdam, Germany
| | - V. Brovkin
- Max Planck Institute for Meteorology, Hamburg, Germany
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21
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Abrupt global-ocean anoxia during the Late Ordovician-early Silurian detected using uranium isotopes of marine carbonates. Proc Natl Acad Sci U S A 2018; 115:5896-5901. [PMID: 29784792 PMCID: PMC6003337 DOI: 10.1073/pnas.1802438115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Late Ordovician mass extinction (LOME) terminated one of the greatest biodiversity radiations in Earth history eliminating ∼85% of marine animals, and it is coincident with the first major glaciation of the Phanerozoic. To evaluate LOME origins, we use uranium isotopes from marine limestones as a proxy for global-ocean redox conditions. Our results provide evidence of an abrupt global-ocean anoxic event coincident with the LOME onset and its continuation after the biologic recovery, through peak glaciation, and the following early Silurian deglaciation. These results also provide evidence for widespread ocean anoxia initiating and continuing during icehouse conditions. Widespread marine anoxia is hypothesized as the trigger for the second pulse of the Late Ordovician (Hirnantian) mass extinction based on lithologic and geochemical proxies that record local bottom waters or porewaters. We test the anoxia hypothesis using δ238U values of marine limestones as a global seawater redox proxy. The δ238U trends at Anticosti Island, Canada, document an abrupt late Hirnantian ∼0.3‰ negative shift continuing through the early Silurian indicating more reducing seawater conditions. The lack of observed anoxic facies and no covariance among δ238U values and other local redox proxies suggests that the δ238U trends represent a global-ocean redox record. The Hirnantian ocean anoxic event (HOAE) onset is coincident with the extinction pulse indicating its importance in triggering it. Anoxia initiated during high sea levels before peak Hirnantian glaciation, and continued into the subsequent lowstand and early Silurian deglacial eustatic rise, implying that major climatic and eustatic changes had little effect on global-ocean redox conditions. The HOAE occurred during a global δ13C positive excursion, but lasted longer indicating that controls on the C budget were partially decoupled from global-ocean redox trends. U cycle modeling suggests that there was a ∼15% increase in anoxic seafloor area and ∼80% of seawater U was sequestered into anoxic sediments during the HOAE. Unlike other ocean anoxic events (OAE), the HOAE occurred during peak and waning icehouse conditions rather than during greenhouse climates. We interpret that anoxia was driven by global cooling, which reorganized thermohaline circulation, decreased deep-ocean ventilation, enhanced nutrient fluxes, stimulated productivity, which lead to expanded oxygen minimum zones.
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22
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He Z, Zhang Q, Feng Y, Luo H, Pan X, Gadd GM. Microbiological and environmental significance of metal-dependent anaerobic oxidation of methane. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 610-611:759-768. [PMID: 28830047 DOI: 10.1016/j.scitotenv.2017.08.140] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 07/22/2017] [Accepted: 08/14/2017] [Indexed: 06/07/2023]
Abstract
Anaerobic oxidation of methane (AOM) can be coupled to the reduction of sulfate, nitrate and nitrite, which effectively reduces methane emission into the atmosphere. Recently, metal-dependent AOM (metal-AOM, AOM coupled to metal reduction) was demonstrated to occur in both environmental samples and enrichment cultures. Anaerobic methanotrophs are capable of respiration using Fe(III) or Mn(IV), whether they are in the form of soluble metal species or insoluble minerals. Given the wide distribution of Fe(III)/Mn(IV)-bearing minerals in aquatic methane-rich environments, metal-AOM is considered to be globally important, although it has generally been overlooked in previous studies. In this article, we discuss the discovery of this process, the microorganisms and mechanisms involved, environmental significance and factors influencing metal-AOM. Since metal-AOM is poorly studied to date, some discussion is included on the present understanding of sulfate- and nitrate-AOM and traditional metal reduction processes using organic substrates or hydrogen as electron donors. Metal-AOM is a relatively new research field, and therefore more studies are needed to fully characterize the process. This review summarizes current studies and discusses the many unanswered questions, which should be useful for future research in this field.
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Affiliation(s)
- Zhanfei He
- College of Environment, Zhejiang University of Technology, Hangzhou, China; Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, Zhejiang University of Technology, Hangzhou, China
| | - Qingying Zhang
- College of Environment, Zhejiang University of Technology, Hangzhou, China
| | - Yudong Feng
- College of Environment, Zhejiang University of Technology, Hangzhou, China
| | - Hongwei Luo
- College of Environment, Zhejiang University of Technology, Hangzhou, China; Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, Zhejiang University of Technology, Hangzhou, China
| | - Xiangliang Pan
- College of Environment, Zhejiang University of Technology, Hangzhou, China; Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, Zhejiang University of Technology, Hangzhou, China.
| | - Geoffrey Michael Gadd
- Geomicrobiology Group, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
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23
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Torres MA, Moosdorf N, Hartmann J, Adkins JF, West AJ. Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks. Proc Natl Acad Sci U S A 2017; 114:8716-8721. [PMID: 28760954 PMCID: PMC5565423 DOI: 10.1073/pnas.1702953114] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Connections between glaciation, chemical weathering, and the global carbon cycle could steer the evolution of global climate over geologic time, but even the directionality of feedbacks in this system remain to be resolved. Here, we assemble a compilation of hydrochemical data from glacierized catchments, use this data to evaluate the dominant chemical reactions associated with glacial weathering, and explore the implications for long-term geochemical cycles. Weathering yields from catchments in our compilation are higher than the global average, which results, in part, from higher runoff in glaciated catchments. Our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals. To evaluate the effects of glacial weathering on atmospheric pCO2, we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon (DIC) generated by weathering reactions. Compared with nonglacial weathering, glacial weathering is more likely to yield alkalinity/DIC ratios less than 1, suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of CO2 to the atmosphere. Back-of-the-envelope calculations indicate that oxidative fluxes could change ocean-atmosphere CO2 equilibrium by 25 ppm or more over 10 ky. Over longer timescales, CO2 release could act as a negative feedback, limiting progress of glaciation, dependent on lithology and the concentration of atmospheric O2 Future work on glaciation-weathering-carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals.
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Affiliation(s)
- Mark A Torres
- Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
- Department of Earth, Environmental, and Planetary Sciences, Rice University, Houston, TX 77005
| | - Nils Moosdorf
- Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089
- Institute for Geology, Center for Earth System Research and Sustainability (CEN), Universität Hamburg, 20146 Hamburg, Germany
- Leibniz Center for Tropical Marine Research, 28359 Bremen, Germany
| | - Jens Hartmann
- Institute for Geology, Center for Earth System Research and Sustainability (CEN), Universität Hamburg, 20146 Hamburg, Germany
| | - Jess F Adkins
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
| | - A Joshua West
- Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089;
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24
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Oni OE, Friedrich MW. Metal Oxide Reduction Linked to Anaerobic Methane Oxidation. Trends Microbiol 2016; 25:88-90. [PMID: 27986381 DOI: 10.1016/j.tim.2016.12.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 12/01/2016] [Indexed: 11/28/2022]
Abstract
Microbial methanotrophy is important in mitigating methane emissions to the atmosphere. Geochemical evidence suggests the occurrence of anaerobic methane oxidation with metal oxides in natural environments. A study has now identified, for the first time, novel freshwater archaea of the order Methanosarcinales that can oxidize methane with Fe(III) and Mn(IV) minerals as electron acceptors.
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Affiliation(s)
- Oluwatobi E Oni
- Microbial Ecophysiology group, Faculty of Biology/Chemistry and MARUM, University of Bremen, Bremen, Germany.
| | - Michael W Friedrich
- Microbial Ecophysiology group, Faculty of Biology/Chemistry and MARUM, University of Bremen, Bremen, Germany
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