scholarly journals Dark biological superoxide production as a significant flux and sink of marine dissolved oxygen

2020 ◽  
Vol 117 (7) ◽  
pp. 3433-3439 ◽  
Author(s):  
Kevin M. Sutherland ◽  
Scott D. Wankel ◽  
Colleen M. Hansel
Keyword(s):  
Superoxide Production ◽  
Oxygenic Photosynthesis ◽  
Marine Microbes ◽  
Sources And Sinks ◽  
Oxygen Budget ◽  
Oxygen Cycle ◽  
Oxygen Cycling ◽  
Electron Reduction ◽  
Earth’S Climate ◽  
Key Terms

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.

Quantifying sources and sinks of trace gases using space-borne measurements: current and future science

2008 ◽  
Vol 366 (1885) ◽  
pp. 4509-4528 ◽  
Author(s):  
Paul I Palmer
Keyword(s):  
Trace Gases ◽  
Lower Troposphere ◽  
Biological Interactions ◽  
Satellite Measurements ◽  
Sources And Sinks ◽  
The Past ◽  
Fundamental Understanding ◽  
Earth’S Climate ◽  
New Generation

We have been observing the Earth's upper atmosphere from space for several decades, but only over the past decade has the necessary technology begun to match our desire to observe surface air pollutants and climate-relevant trace gases in the lower troposphere, where we live and breathe. A new generation of Earth-observing satellites, capable of probing the lower troposphere, are already orbiting hundreds of kilometres above the Earth's surface with several more ready for launch or in the planning stages. Consequently, this is one of the most exciting times for the Earth system scientists who study the countless current-day physical, chemical and biological interactions between the Earth's land, ocean and atmosphere. First, I briefly review the theory behind measuring the atmosphere from space, and how these data can be used to infer surface sources and sinks of trace gases. I then present some of the science highlights associated with these data and how they can be used to improve fundamental understanding of the Earth's climate system. I conclude the paper by discussing the future role of satellite measurements of tropospheric trace gases in mitigating surface air pollution and carbon trading.

The oxygen budget of two closed, dimictic lakes in the vicinity of Bytów (West Pomeranian Lake District, northern Poland)

2010 ◽  
Vol 39 (2) ◽  
Author(s):  
Zbigniew Witek ◽  
Anna Jarosiewicz
Keyword(s):  
Oxygen Release ◽  
Key Factors ◽  
Lake District ◽  
Trophic Conditions ◽  
Phytoplankton Primary Production ◽  
Stratified Lakes ◽  
Oxygen Budget ◽  
Northern Poland ◽  
Oxygen Cycle ◽  
Turn Over

The oxygen budget of two closed, dimictic lakes in the vicinity of Bytów (West Pomeranian Lake District, northern Poland)The aim of this work was to identify key factors governing the oxygen fluxes in two thermally stratified lakes of different morphology. Oxygen and temperature profiles in lakes Jeleń and Mały Borek, as well as phytoplankton primary production in Mały Borek (oxygen-method) were measured in monthly intervals, except for periods of ice cover. Rates of oxygen release due to photosynthesis, consumption in the water column, loss to atmosphere, depletion in the hypolimnion, and restoration during periods of turn-over were roughly estimated. It was discovered that trophic conditions and morphometry may substantially influence not only the intensity, but also the timing, of particular events in the oxygen cycle of the lakes.

scholarly journals Cryptic oxygen cycling in anoxic marine zones

2017 ◽  
Vol 114 (31) ◽  
pp. 8319-8324 ◽  
Author(s):  
Emilio Garcia-Robledo ◽  
Cory C. Padilla ◽  
Montserrat Aldunate ◽  
Frank J. Stewart ◽  
Osvaldo Ulloa ◽  
...  
Keyword(s):  
Surface Layer ◽  
Carbon Fixation ◽  
Nitrogen Loss ◽  
Biogeochemical Cycling ◽  
Oxygenic Photosynthesis ◽  
Nitrite Oxidation ◽  
Tight Coupling ◽  
Expression Of Genes ◽  
Aerobic Processes ◽  
Oxygen Cycling

Oxygen availability drives changes in microbial diversity and biogeochemical cycling between the aerobic surface layer and the anaerobic core in nitrite-rich anoxic marine zones (AMZs), which constitute huge oxygen-depleted regions in the tropical oceans. The current paradigm is that primary production and nitrification within the oxic surface layer fuel anaerobic processes in the anoxic core of AMZs, where 30–50% of global marine nitrogen loss takes place. Here we demonstrate that oxygenic photosynthesis in the secondary chlorophyll maximum (SCM) releases significant amounts of O2to the otherwise anoxic environment. The SCM, commonly found within AMZs, was dominated by the picocyanobacteriaProchlorococcusspp. Free O2levels in this layer were, however, undetectable by conventional techniques, reflecting a tight coupling between O2production and consumption by aerobic processes under apparent anoxic conditions. Transcriptomic analysis of the microbial community in the seemingly anoxic SCM revealed the enhanced expression of genes for aerobic processes, such as nitrite oxidation. The rates of gross O2production and carbon fixation in the SCM were found to be similar to those reported for nitrite oxidation, as well as for anaerobic dissimilatory nitrate reduction and sulfate reduction, suggesting a significant effect of local oxygenic photosynthesis on Pacific AMZ biogeochemical cycling.

scholarly journals The effect of one-electron reduced drugs on hepatic aconitase activity and triglycerides level

2015 ◽  
Vol 28 (1) ◽  
pp. 5-7
Author(s):  
Magdalena Wnukowska ◽  
Slawomir Mandziuk ◽  
Agnieszka Korga ◽  
Barbara Jodlowska-Jedrych ◽  
Wlodzimierz Matysiak ◽  
...  
Keyword(s):  
Anticancer Agents ◽  
Wistar Rats ◽  
Biochemical Analysis ◽  
Superoxide Production ◽  
Redox Cycle ◽  
Redox Equilibrium ◽  
Aconitase Activity ◽  
Male Wistar Rats ◽  
Electron Reduction ◽  
Doxorubicin Administration

Abstract The redox cycle triggered by one electron reduction of doxorubicin and tirapazamine - both anticancer agents - leads to superoxide production. This superoxide production itself removes one iron atom from the [4Fe-4S] cluster, being an active center of aconitase. In addition, the incurred changes in cell redox equilibrium may affect lipid metabolism. The aim of the study was to evaluate a concomitant effect of both drugs on hepatic aconitase activity and triglycerides level. In our study, doxorubicin (1.8 mg/kg b.w.) was administered intraperitoneal (i.p.) six times, once a week, within male Wistar rats, to achieve a cumulative dose of 10.8 mg/kg b.w. Two hours before every doxorubicin administration, tirapazamine in the dose of either 5 or 10 mg/kg b.w. was also i.p. injected. A week after withdrawing drug administration, the liver was taken for biochemical analysis. Therein, an increase in aconitase activity and a decrease in triglycerides level was seen in all groups exposed to doxorubicin. Our work demonstrated that tirapazamine administration had no influence on both tested parameters, but its higher dose rate normalized aconitase activity affected by doxorubicin.

scholarly journals Photoferrotrophy, deposition of banded iron formations, and methane production in Archean oceans

2019 ◽  
Vol 5 (11) ◽  
pp. eaav2869 ◽  
Author(s):  
Katharine J. Thompson ◽  
Paul A. Kenward ◽  
Kohen W. Bauer ◽  
Tyler Warchola ◽  
Tina Gauger ◽  
...  
Keyword(s):  
Large Scale ◽  
Iron Oxidation ◽  
Coastal Sediments ◽  
Oxygenic Photosynthesis ◽  
Iron Formation ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Earth’S Climate ◽  
Iron Formations ◽  
Scale Deposition

Banded iron formation (BIF) deposition was the likely result of oxidation of ferrous iron in seawater by either oxygenic photosynthesis or iron-dependent anoxygenic photosynthesis—photoferrotrophy. BIF deposition, however, remains enigmatic because the photosynthetic biomass produced during iron oxidation is conspicuously absent from BIFs. We have addressed this enigma through experiments with photosynthetic bacteria and modeling of biogeochemical cycling in the Archean oceans. Our experiments reveal that, in the presence of silica, photoferrotroph cell surfaces repel iron (oxyhydr)oxides. In silica-rich Precambrian seawater, this repulsion would separate biomass from ferric iron and would lead to large-scale deposition of BIFs lean in organic matter. Excess biomass not deposited with BIF would have deposited in coastal sediments, formed organic-rich shales, and fueled microbial methanogenesis. As a result, the deposition of BIFs by photoferrotrophs would have contributed fluxes of methane to the atmosphere and thus helped to stabilize Earth’s climate under a dim early Sun.

The Impact of Inorganic Trace Gases on Ozone in the Atmosphere

2015 ◽  
Author(s):  
Jack G. Calvert ◽  
John J. Orlando ◽  
William R. Stockwell ◽  
Timothy J. Wallington
Keyword(s):  
Radiative Forcing ◽  
Marine Boundary Layer ◽  
Global Climate ◽  
Deep Ocean ◽  
Co2 Concentration ◽  
Tropospheric Chemistry ◽  
Sources And Sinks ◽  
Organic Sulfur Compounds ◽  
Earth’S Climate ◽  
Carbon Dioxide Co2

A major focus of the previous six chapters has been on the chemistry and interactions of the HOx, NOx, and volatile organic compound (VOC) families. Details of the reactions of O3 NO3, and HO that act to initiate VOC oxidation have been presented, as has the ensuing chemistry involving organic peroxy and alkoxy radicals and their interactions with NOx. In this chapter, we complete our discussion of thermal chemical reactions that impact tropospheric ozone. The chapter begins with a discussion of the budgets of two simple (inorganic) carbon-containing species not yet discussed, carbon dioxide (CO2) and carbon monoxide (CO). Although CO2 is not directly involved in ozone-related tropospheric chemistry, it is of course the species most critical to discussions of global climate change, and thus a very brief overview of its concentrations, sources, and sinks is presented. CO is a ubiquitous global pollutant, and its reaction with HO is an essential part of the tropospheric background chemistry. This is followed by a presentation of the tropospheric chemistry of halogen species, beginning with a discussion of inorganic halogen cycles that impact (in particular) the ozone chemistry of the marine boundary layer (MBL) and concluding with a detailed presentation of the reactions of Cl atoms and Br atoms with VOC species. The chapter concludes with an overview of tropospheric sulfur chemistry. The reactions leading to the oxidation of inorganic (SO2 and SO3) as well as organic sulfur compounds (e.g., DMS, CH3SCH3) are detailed, and a brief discussion of the effects of the oxidation of sulfur species on aerosol production in the troposphere and stratosphere is also given. The abundance of CO2 in the atmosphere has obviously received a great deal of attention in recent decades due to the influence of this gas on Earth’s climate system. Indeed, changes in the atmospheric CO2 concentration represent the single largest contributor to changes in radiative forcing since preindustrial times (c. 1750). The atmospheric burden of CO2 is controlled by the processes that make up the global carbon cycle—the exchanges of carbon (mostly in the form of CO2) between various “reservoirs,” including the atmosphere, land (vegetation and soil), the surface ocean, the intermediate and deep ocean, sediment on the ocean floor, and the fossil fuel reservoir (IPCC, 2007).

scholarly journals Numerical simulations of oceanic oxygen cycling in the FAMOUS Earth-System model: FAMOUS-ES, version 1.0

2014 ◽  
Vol 7 (1) ◽  
pp. 1453-1476
Author(s):  
J. H. T. Williams ◽  
I. J. Totterdell ◽  
P. R. Halloran ◽  
P. J. Valdes
Keyword(s):  
Climate Model ◽  
Coupled Model ◽  
System Model ◽  
Temperature Structure ◽  
Model Intercomparison ◽  
Oxygen Cycle ◽  
Surface Productivity ◽  
Intercomparison Project ◽  
Oxygen Cycling ◽  
Good Agreement

Abstract. Addition and validation of an oxygen cycle to the ocean component of the FAMOUS climate model are described. Surface validation is carried out with respect to HadGEM2-ES where good agreement is found and where discrepancies are mainly attributed to disagreement in surface temperature structure between the models. The agreement between the models at depth (where observations are also used in the comparison) in the Southern Hemisphere is less encouraging than in the Northern Hemisphere. This is attributed to a combination of excessive surface productivity in FAMOUS' equatorial waters (and its concomitant effect on remineralisation at depth) and its reduced overturning circulation compared to HadGEM2-ES. For the entire Atlantic basin FAMOUS has a circulation strength of 12.7 ± 0.4 Sv compared to 15.0 ± 0.9 for HadGEM2-ES. The HadGEM2-ES data used in this paper were obtained from the online database of the fifth Coupled Model Intercomparison Project, CMIP5 (Taylor et al., 2012).

scholarly journals Mechanism of Enhanced Superoxide Production in the Cytochrome b6f Complex of Oxygenic Photosynthesis

Biochemistry ◽  
2013 ◽  
Vol 52 (50) ◽  
pp. 8975-8983 ◽  
Author(s):  
Danas Baniulis ◽  
S. Saif Hasan ◽  
Jason T. Stofleth ◽  
William A. Cramer
Keyword(s):  
Superoxide Production ◽  
Oxygenic Photosynthesis ◽  
Cytochrome B6f Complex ◽  
Cytochrome B6f ◽  
B6f Complex

Job Validation Studies and Physical Agility Testing: Is the Vendor Telling You What They Think You Want or Are You Telling Them What You Need?

2016 ◽  
Vol 21 (6) ◽  
pp. 5-11
Author(s):  
E. Randolph Soo Hoo ◽  
Stephen L. Demeter
Keyword(s):  
Equal Employment Opportunity Commission ◽  
Job Analysis ◽  
Specific Work ◽  
Test Protocol ◽  
Systematic Method ◽  
Technical Standards ◽  
Work Related ◽  
Physical Abilities ◽  
Specific Factors ◽  
Key Terms

Abstract Referring agents may ask independent medical evaluators if the examinee can return to work in either a normal or a restricted capacity; similarly, employers may ask external parties to conduct this type of assessment before a hire or after an injury. Functional capacity evaluations (FCEs) are used to measure agility and strength, but they have limitations and use technical jargon or concepts that can be confusing. This article clarifies key terms and concepts related to FCEs. The basic approach to a job analysis is to collect information about the job using a variety of methods, analyze the data, and summarize the data to determine specific factors required for the job. No single, optimal job analysis or validation method is applicable to every work situation or company, but the Equal Employment Opportunity Commission offers technical standards for each type of validity study. FCEs are a systematic method of measuring an individual's ability to perform various activities, and results are matched to descriptions of specific work-related tasks. Results of physical abilities/agilities tests are reported as “matching” or “not matching” job demands or “pass” or “fail” meeting job criteria. Individuals who fail an employment physical agility test often challenge the results on the basis that the test was poorly conducted, that the test protocol was not reflective of the job, or that levels for successful completion were inappropriate.

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