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Kevin M Sutherland - One of the best experts on this subject based on the ideXlab platform.
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ferromanganese crusts as recorders of marine dissolved Oxygen
Earth and Planetary Science Letters, 2020Co-Authors: Kevin M Sutherland, Jordan A G Wostbrock, Colleen M Hansel, Zachary D Sharp, James R Hein, Scott D WankelAbstract:Abstract The distinct triple Oxygen isotope composition of tropospheric O2 relative to seawater is the result of biogeochemical reactions (e.g. primary productivity, respiration), exchange with the stratosphere, and the relative size of different Oxygen-containing reservoirs, namely O2, O3, and CO2. This difference in isotopic composition gives tropospheric O2 utility as a record of biogeochemical and atmospheric processes and may also be used for determining where in the rock record isotopic fingerprints of tropospheric Oxygen may be preserved. The isotopic record of tropospheric Oxygen in previous studies is largely limited to analyses of gas trapped in continental glaciers and a patchwork of other proxies, most notably the triple Oxygen signature of sulfate. Here we show the uppermost layers of hydrogenetic, deep-ocean ferromanganese crusts from each of the major ocean basins have a triple Oxygen isotope composition consistent with the direct incorporation of dissolved Oxygen. The range of δ18O and Δ ′ 17O in ferromanganese crusts suggests the Mn oxide endmember contains a near 50:50 mixture of Oxygen from water and dissolved O2. Our data indicate this signal also persists into older layers of the crusts, potentially preserving near 75 million years of the Oxygen isotopic composition of the lower troposphere and subsequent deep-ocean respiration. Our analysis of Oxygen isotope values, bulk chemistry, and estimated local dissolved Oxygen for crust top samples reveals that variations in bulk chemistry ultimately exhibit more influence on the Oxygen mass balance than changes in dissolved Oxygen, presenting a challenge for unambiguous determination of local dissolved Oxygen. Although analytical challenges remain, these widespread, layered deposits of ferromanganese crust may offer a viable path for future interrogation of the history or relative history of the Oxygen Cycle of the troposphere and deep ocean millions of years into the past.
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dark biological superoxide production as a significant flux and sink of marine dissolved Oxygen
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Kevin M Sutherland, Scott D Wankel, Colleen M HanselAbstract:The balance between sources and sinks of molecular Oxygen in the oceans has greatly impacted the composition of Earth's atmosphere since the evolution of Oxygenic photosynthesis, thereby exerting key influence on Earth's climate and the redox state of (sub)surface Earth. The canonical source and sink terms of the marine Oxygen budget include photosynthesis, respiration, photorespiration, the Mehler reaction, and other smaller terms. However, recent advances in understanding cryptic Oxygen cycling, namely the ubiquitous one-electron reduction of O2 to superoxide by microorganisms outside the cell, remains unexplored as a potential player in global Oxygen dynamics. Here we show that dark extracellular superoxide production by marine microbes represents a previously unconsidered global Oxygen flux and sink comparable in magnitude to other key terms. We estimate that extracellular superoxide production represents a gross Oxygen sink comprising about a third of marine gross Oxygen production, and a net Oxygen sink amounting to 15 to 50% of that. We further demonstrate that this total marine dark extracellular superoxide flux is consistent with concentrations of superoxide in marine environments. These findings underscore prolific marine sources of reactive Oxygen species and a complex and dynamic Oxygen Cycle in which Oxygen consumption and corresponding carbon oxidation are not necessarily confined to cell membranes or exclusively related to respiration. This revised model of the marine Oxygen Cycle will ultimately allow for greater reconciliation among estimates of primary production and respiration and a greater mechanistic understanding of redox cycling in the ocean.
Colleen M Hansel - One of the best experts on this subject based on the ideXlab platform.
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ferromanganese crusts as recorders of marine dissolved Oxygen
Earth and Planetary Science Letters, 2020Co-Authors: Kevin M Sutherland, Jordan A G Wostbrock, Colleen M Hansel, Zachary D Sharp, James R Hein, Scott D WankelAbstract:Abstract The distinct triple Oxygen isotope composition of tropospheric O2 relative to seawater is the result of biogeochemical reactions (e.g. primary productivity, respiration), exchange with the stratosphere, and the relative size of different Oxygen-containing reservoirs, namely O2, O3, and CO2. This difference in isotopic composition gives tropospheric O2 utility as a record of biogeochemical and atmospheric processes and may also be used for determining where in the rock record isotopic fingerprints of tropospheric Oxygen may be preserved. The isotopic record of tropospheric Oxygen in previous studies is largely limited to analyses of gas trapped in continental glaciers and a patchwork of other proxies, most notably the triple Oxygen signature of sulfate. Here we show the uppermost layers of hydrogenetic, deep-ocean ferromanganese crusts from each of the major ocean basins have a triple Oxygen isotope composition consistent with the direct incorporation of dissolved Oxygen. The range of δ18O and Δ ′ 17O in ferromanganese crusts suggests the Mn oxide endmember contains a near 50:50 mixture of Oxygen from water and dissolved O2. Our data indicate this signal also persists into older layers of the crusts, potentially preserving near 75 million years of the Oxygen isotopic composition of the lower troposphere and subsequent deep-ocean respiration. Our analysis of Oxygen isotope values, bulk chemistry, and estimated local dissolved Oxygen for crust top samples reveals that variations in bulk chemistry ultimately exhibit more influence on the Oxygen mass balance than changes in dissolved Oxygen, presenting a challenge for unambiguous determination of local dissolved Oxygen. Although analytical challenges remain, these widespread, layered deposits of ferromanganese crust may offer a viable path for future interrogation of the history or relative history of the Oxygen Cycle of the troposphere and deep ocean millions of years into the past.
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dark biological superoxide production as a significant flux and sink of marine dissolved Oxygen
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Kevin M Sutherland, Scott D Wankel, Colleen M HanselAbstract:The balance between sources and sinks of molecular Oxygen in the oceans has greatly impacted the composition of Earth's atmosphere since the evolution of Oxygenic photosynthesis, thereby exerting key influence on Earth's climate and the redox state of (sub)surface Earth. The canonical source and sink terms of the marine Oxygen budget include photosynthesis, respiration, photorespiration, the Mehler reaction, and other smaller terms. However, recent advances in understanding cryptic Oxygen cycling, namely the ubiquitous one-electron reduction of O2 to superoxide by microorganisms outside the cell, remains unexplored as a potential player in global Oxygen dynamics. Here we show that dark extracellular superoxide production by marine microbes represents a previously unconsidered global Oxygen flux and sink comparable in magnitude to other key terms. We estimate that extracellular superoxide production represents a gross Oxygen sink comprising about a third of marine gross Oxygen production, and a net Oxygen sink amounting to 15 to 50% of that. We further demonstrate that this total marine dark extracellular superoxide flux is consistent with concentrations of superoxide in marine environments. These findings underscore prolific marine sources of reactive Oxygen species and a complex and dynamic Oxygen Cycle in which Oxygen consumption and corresponding carbon oxidation are not necessarily confined to cell membranes or exclusively related to respiration. This revised model of the marine Oxygen Cycle will ultimately allow for greater reconciliation among estimates of primary production and respiration and a greater mechanistic understanding of redox cycling in the ocean.
Scott D Wankel - One of the best experts on this subject based on the ideXlab platform.
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ferromanganese crusts as recorders of marine dissolved Oxygen
Earth and Planetary Science Letters, 2020Co-Authors: Kevin M Sutherland, Jordan A G Wostbrock, Colleen M Hansel, Zachary D Sharp, James R Hein, Scott D WankelAbstract:Abstract The distinct triple Oxygen isotope composition of tropospheric O2 relative to seawater is the result of biogeochemical reactions (e.g. primary productivity, respiration), exchange with the stratosphere, and the relative size of different Oxygen-containing reservoirs, namely O2, O3, and CO2. This difference in isotopic composition gives tropospheric O2 utility as a record of biogeochemical and atmospheric processes and may also be used for determining where in the rock record isotopic fingerprints of tropospheric Oxygen may be preserved. The isotopic record of tropospheric Oxygen in previous studies is largely limited to analyses of gas trapped in continental glaciers and a patchwork of other proxies, most notably the triple Oxygen signature of sulfate. Here we show the uppermost layers of hydrogenetic, deep-ocean ferromanganese crusts from each of the major ocean basins have a triple Oxygen isotope composition consistent with the direct incorporation of dissolved Oxygen. The range of δ18O and Δ ′ 17O in ferromanganese crusts suggests the Mn oxide endmember contains a near 50:50 mixture of Oxygen from water and dissolved O2. Our data indicate this signal also persists into older layers of the crusts, potentially preserving near 75 million years of the Oxygen isotopic composition of the lower troposphere and subsequent deep-ocean respiration. Our analysis of Oxygen isotope values, bulk chemistry, and estimated local dissolved Oxygen for crust top samples reveals that variations in bulk chemistry ultimately exhibit more influence on the Oxygen mass balance than changes in dissolved Oxygen, presenting a challenge for unambiguous determination of local dissolved Oxygen. Although analytical challenges remain, these widespread, layered deposits of ferromanganese crust may offer a viable path for future interrogation of the history or relative history of the Oxygen Cycle of the troposphere and deep ocean millions of years into the past.
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dark biological superoxide production as a significant flux and sink of marine dissolved Oxygen
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Kevin M Sutherland, Scott D Wankel, Colleen M HanselAbstract:The balance between sources and sinks of molecular Oxygen in the oceans has greatly impacted the composition of Earth's atmosphere since the evolution of Oxygenic photosynthesis, thereby exerting key influence on Earth's climate and the redox state of (sub)surface Earth. The canonical source and sink terms of the marine Oxygen budget include photosynthesis, respiration, photorespiration, the Mehler reaction, and other smaller terms. However, recent advances in understanding cryptic Oxygen cycling, namely the ubiquitous one-electron reduction of O2 to superoxide by microorganisms outside the cell, remains unexplored as a potential player in global Oxygen dynamics. Here we show that dark extracellular superoxide production by marine microbes represents a previously unconsidered global Oxygen flux and sink comparable in magnitude to other key terms. We estimate that extracellular superoxide production represents a gross Oxygen sink comprising about a third of marine gross Oxygen production, and a net Oxygen sink amounting to 15 to 50% of that. We further demonstrate that this total marine dark extracellular superoxide flux is consistent with concentrations of superoxide in marine environments. These findings underscore prolific marine sources of reactive Oxygen species and a complex and dynamic Oxygen Cycle in which Oxygen consumption and corresponding carbon oxidation are not necessarily confined to cell membranes or exclusively related to respiration. This revised model of the marine Oxygen Cycle will ultimately allow for greater reconciliation among estimates of primary production and respiration and a greater mechanistic understanding of redox cycling in the ocean.
Zhongyuan Ren - One of the best experts on this subject based on the ideXlab platform.
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a nephelinitic component with unusual δ56fe in cenozoic basalts from eastern china and its implications for deep Oxygen Cycle
Earth and Planetary Science Letters, 2019Co-Authors: Xunan Meng, Chuanwei Zhu, Fangzhen Teng, Jochen Hoefs, Jian Huang, Wei Yang, Zhenhui Hou, Zhongyuan RenAbstract:Abstract Cycling of elements with multiple valences (e.g., Fe, C, and S) through subduction and magmatism may dictate the redox evolution of the deep mantle and atmosphere. To investigate the potential of Fe isotopes as a tracer of such Cycles, here we report Fe isotopic compositions of thirty-seven Cenozoic basalts from eastern China. A nephelinitic melt component with δ 56 Fe up to 0.29 has been identified, which cannot be explained by weathering, alteration, magma differentiation, or chemical diffusion. Its low Fe/Mn ∼58, relatively low TiO2 and high Na2O + K2O argue against a significant contribution of pyroxenite melting. Instead, the heavy Fe component requires enhanced isotope fractionation during partial melting of a peridotitic source with Fe3+/ΣFe ≥ 0.15. Low Ba/Th ∼ 50 and depleted 87Sr/86Sr(i) and eNd(t) suggest that the source was insignificantly affected by hydrous fluids and reCycled terrigenous sediments. The heavy Fe component is known to be unique in its low δ 26 Mg and high δ 66 Zn and indicates hybridization by reCycled carbonates. The source Fe3+/ΣFe was most likely enhanced at cost of reduction of reCycled carbonates to diamonds in a mantle depth ≥300 km. The origin of the heavy Fe component illustrates a pathway with net transportation of oxidizer back to Earth's surface: CO2 (in carbonates) → C (as diamond frozen in the deep mantle) + O2 (ferric Fe being scavenged by melt extraction). Secular cooling of global subduction zones may have stepwisely increased the efficiency of this carbon driven deep Oxygen Cycle in the past, providing an alternative explanation for the rise of atmospheric O2.
Linda Godfrey - One of the best experts on this subject based on the ideXlab platform.
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the geochemical record of the ancient nitrogen Cycle nitrogen isotopes and metal cofactors
Methods in Enzymology, 2011Co-Authors: Linda Godfrey, Jennifer B GlassAbstract:Abstract The nitrogen (N) Cycle is the only global biogeochemical Cycle that is driven by biological functions involving the interaction of many microorganisms. The N Cycle has evolved over geological time and its interaction with the Oxygen Cycle has had profound effects on the evolution and timing of Earth's atmosphere Oxygenation (Falkowski and Godfrey, 2008). Almost every enzyme that microorganisms use to manipulate N contains redox-sensitive metals. Bioavailability of these metals has changed through time as a function of varying redox conditions, and likely influenced the biological underpinnings of the N Cycle. It is possible to construct a record through geological time using N isotopes and metal concentrations in sediments to determine when the different stages of the N Cycle evolved and the role metal availability played in the development of key enzymes. The same techniques are applicable to understanding the operation and changes in the N Cycle through geological time. However, N and many of the redox-sensitive metals in some of their oxidation states are mobile and the isotopic composition or distribution can be altered by subsequent processes leading to erroneous conclusions. This chapter reviews the enzymology and metal cofactors of the N Cycle and describes proper utilization of methods used to reconstruct evolution of the N Cycle through time.
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electrons life and the evolution of earth s Oxygen Cycle
Philosophical Transactions of the Royal Society B, 2008Co-Authors: Paul G Falkowski, Linda GodfreyAbstract:The biogeochemical Cycles of H, C, N, O and S are coupled via biologically catalysed electron transfer (redox) reactions. The metabolic processes responsible for maintaining these Cycles evolved over the first ca 2.3 Ga of Earth's history in prokaryotes and, through a sequence of events, led to the production of Oxygen via the photobiologically catalysed oxidation of water. However, geochemical evidence suggests that there was a delay of several hundred million years before Oxygen accumulated in Earth's atmosphere related to changes in the burial efficiency of organic matter and fundamental alterations in the nitrogen Cycle. In the latter case, the presence of free molecular Oxygen allowed ammonium to be oxidized to nitrate and subsequently denitrified. The interaction between the Oxygen and nitrogen Cycles in particular led to a negative feedback, in which increased production of Oxygen led to decreased fixed inorganic nitrogen in the oceans. This feedback, which is supported by isotopic analyses of fixed nitrogen in sedimentary rocks from the Late Archaean, continues to the present. However, once sufficient Oxygen accumulated in Earth's atmosphere to allow nitrification to out-compete denitrification, a new stable electron ‘market’ emerged in which Oxygenic photosynthesis and aerobic respiration ultimately spread via endosymbiotic events and massive lateral gene transfer to eukaryotic host cells, allowing the evolution of complex (i.e. animal) life forms. The resulting network of electron transfers led a gas composition of Earth's atmosphere that is far from thermodynamic equilibrium (i.e. it is an emergent property), yet is relatively stable on geological time scales. The early coevolution of the C, N and O Cycles, and the resulting non-equilibrium gaseous by-products can be used as a guide to search for the presence of life on terrestrial planets outside of our Solar System.
