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Lüdemann, Heiner, Inko Arth, and Werner Liesack. "Spatial Changes in the Bacterial Community Structure along a Vertical Oxygen Gradient in Flooded Paddy Soil Cores." Applied and Environmental Microbiology 66, no. 2 (February 1, 2000): 754–62. http://dx.doi.org/10.1128/aem.66.2.754-762.2000.
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ABSTRACT Molecular ecology techniques were applied to assess changes in the bacterial community structure along a vertical oxygen gradient in flooded paddy soil cores. Microsensor measurements showed that oxygen was depleted from 140 μM at the floodwater/soil interface to nondetectable amounts at a depth of approximately 2.0 mm and below. Bacterial 16S rRNA gene (rDNA)-based community fingerprint patterns were obtained from 200-μm-thick soil slices of both the oxic and anoxic zones by using the T-RFLP (terminal restriction fragment length polymorphism) technique. The fingerprints revealed a tremendous shift in the community patterns in correlation to the oxygen depletion measured with depth. 16S rDNA clone sequences recovered from the oxic or anoxic zone directly corresponded to those terminal restriction fragments which were highly characteristic of the respective zone. Comparative sequence analysis of these clones identified members of the α and β subclasses of Proteobacteria as the abundant populations in the oxic zone. In contrast, members of clostridial cluster I were determined to be the predominant bacterial group in the oxygen-depleted soil. The extraction of total RNA followed by reverse transcription-PCR of the bacterial 16S rRNA and T-RFLP analysis resulted for both oxic and anoxic zones of flooded soil cores in community fingerprint patterns similar to those obtained by the rDNA-based analysis. This finding suggests that the microbial groups detected on the rDNA level are the metabolically active populations within the oxic and anoxic soil slices examined.
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Wanner, Jiri, and Petr Grau. "Filamentous Bulking in Nutrient Removal Activated Sludge Systems." Water Science and Technology 20, no. 4-5 (April 1, 1988): 1–8. http://dx.doi.org/10.2166/wst.1988.0149.
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Behaviour of filamentous microorganisms under anaerobic, anoxic, and oxic conditions has been reviewed from the point of view of filamentous bulking in nutrient removal activated sludge systems. It was concluded that the growth of most filamentous microorganisms is considerably suppressed under anaerobic and anoxic conditions and that the filamentous bulking in nutrient removal systems is chiefly caused by the growth of filamentous microorganisms in oxic zones. The role of particulate substrate hydrolysis was also discussed and the necessity of compartmentalization of oxic zones was shown.
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Lichtschlag, A., D. Donis, F. Janssen, G. L. Jessen, M. Holtappels, F. Wenzhöfer, S. Mazlumyan, N. Sergeeva, C. Waldmann, and A. Boetius. "Effects of fluctuating hypoxia on benthic oxygen consumption in the Black Sea (Crimean shelf)." Biogeosciences 12, no. 16 (August 27, 2015): 5075–92. http://dx.doi.org/10.5194/bg-12-5075-2015.
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Abstract. The outer western Crimean shelf of the Black Sea is a natural laboratory to investigate effects of stable oxic versus varying hypoxic conditions on seafloor biogeochemical processes and benthic community structure. Bottom-water oxygen concentrations ranged from normoxic (175 μmol O2 L−1) and hypoxic (< 63 μmol O2 L−1) or even anoxic/sulfidic conditions within a few kilometers' distance. Variations in oxygen concentrations between 160 and 10 μmol L−1 even occurred within hours close to the chemocline at 134 m water depth. Total oxygen uptake, including diffusive as well as fauna-mediated oxygen consumption, decreased from 15 mmol m−2 d−1 on average in the oxic zone, to 7 mmol m−2 d−1 on average in the hypoxic zone, correlating with changes in macrobenthos composition. Benthic diffusive oxygen uptake rates, comprising respiration of microorganisms and small meiofauna, were similar in oxic and hypoxic zones (on average 4.5 mmol m−2 d−1), but declined to 1.3 mmol m−2 d−1 in bottom waters with oxygen concentrations below 20 μmol L−1. Measurements and modeling of porewater profiles indicated that reoxidation of reduced compounds played only a minor role in diffusive oxygen uptake under the different oxygen conditions, leaving the major fraction to aerobic degradation of organic carbon. Remineralization efficiency decreased from nearly 100 % in the oxic zone, to 50 % in the oxic–hypoxic zone, to 10 % in the hypoxic–anoxic zone. Overall, the faunal remineralization rate was more important, but also more influenced by fluctuating oxygen concentrations, than microbial and geochemical oxidation processes.
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Wielinga, Bruce, Juliette K. Lucy, Johnnie N. Moore, October F. Seastone, and James E. Gannon. "Microbiological and Geochemical Characterization of Fluvially Deposited Sulfidic Mine Tailings." Applied and Environmental Microbiology 65, no. 4 (April 1, 1999): 1548–55. http://dx.doi.org/10.1128/aem.65.4.1548-1555.1999.
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ABSTRACT The fluvial deposition of mine tailings generated from historic mining operations near Butte, Montana, has resulted in substantial surface and shallow groundwater contamination along Silver Bow Creek. Biogeochemical processes in the sediment and underlying hyporheic zone were studied in an attempt to characterize interactions consequential to heavy-metal contamination of shallow groundwater. Sediment cores were extracted and fractionated based on sediment stratification. Subsamples of each fraction were assayed for culturable heterotrophic microbiota, specific microbial guilds involved in metal redox transformations, and both aqueous- and solid-phase geochemistry. Populations of cultivable Fe(III)-reducing bacteria were most prominent in the anoxic, circumneutral pH regions associated with a ferricrete layer or in an oxic zone high in organic carbon and soluble iron. Sulfur- and iron-oxidizing bacteria were distributed in discrete zones throughout the tailings and were often recovered from sections at and below the anoxic groundwater interface. Sulfate-reducing bacteria were also widely distributed in the cores and often occurred in zones overlapping iron and sulfur oxidizers. Sulfate-reducing bacteria were consistently recovered from oxic zones that contained high concentrations of metals in the oxidizable fraction. Altogether, these results suggest a highly varied and complex microbial ecology within a very heterogeneous geochemical environment. Such physical and biological heterogeneity has often been overlooked when remediation strategies for metal contaminated environments are formulated.
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van der Wielen, P. W. J. J., M. Blokker, and G. J. Medema. "Modelling the length of microbiological protection zones around phreatic sandy aquifers in The Netherlands." Water Science and Technology 54, no. 3 (August 1, 2006): 63–69. http://dx.doi.org/10.2166/wst.2006.449.
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The aim of the current study was to calculate the size of protection zones around (sub)oxic and anoxic sandy aquifers without confining layers using a virus infection and transport model. The maximum allowable virus infection risk was 10−4/person/year at the 95% confidence level. Model results demonstrated that phreatic (sub)oxic sandy aquifers in The Netherlands required protection areas with a residence time of 43–117 d to ensure that the maximum virus infection risk would not be exceeded. This was 0.7–2× the current guideline of 60 d. In contrast, phreatic anoxic sandy aquifers without confining layers needed protection zones of 555–898 d to stay below the maximum virus infection risk, 9.5–15× the current guideline. A sensitivity analysis of the model demonstrated that the calculated protection zone was most sensitive for virus inactivation rate and collision efficiency. Values of both parameters were predicted from values obtained from previously published field and laboratory studies. At present, as it is unknown if these values can also be used at other locations, model results should be interpreted with care.
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Haberstroh, P. R., and F. J. Sansone. "Reef framework diagenesis across wave-flushed oxic-suboxic-anoxic transition zones." Coral Reefs 18, no. 3 (September 23, 1999): 229–40. http://dx.doi.org/10.1007/s003380050187.
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Jakobs, G., G. Rehder, G. Jost, K. Kießlich, M. Labrenz, and O. Schmale. "Comparative studies of pelagic microbial methane oxidation within two anoxic basins of the central Baltic Sea (Gotland Deep and Landsort Deep)." Biogeosciences Discussions 10, no. 7 (July 20, 2013): 12251–84. http://dx.doi.org/10.5194/bgd-10-12251-2013.
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Abstract. Pelagic methane oxidation was investigated in dependence on differing environmental conditions within the redox zone of the Gotland Deep (GD) and Landsort Deep (LD), central Baltic Sea. The redox zone of both deeps, which indicates the transition between oxic and anoxic conditions, was characterized by a pronounced methane concentration gradient between the deep water (GD: 1233 nM, LD: 2935 nM) and the surface water (GD and LD < 10 nM), together with a 13C CH4 enrichment (δ13C CH4 deep water: GD −84‰, LD −71‰ ; redox zone: GD −60‰, LD −20‰ ; δ13C CH4 vs. Vienna Pee Dee Belemnite standard), clearly indicating microbial methane consumption in that specific depth interval. Expression analysis of the methane monooxygenase identified one active type I methanotrophic bacterium in both redox zones. In contrast, the turnover of methane within the redox zones showed strong differences between the two basins (GD: max. 0.12 nM d–1 and LD: max. 0.61 nM d–1), with a four times higher turnover rate constant (k) in the LD (GD: 0.0022 d–1, LD: 0.0079 d–1). Vertical mixing rates for both deeps were calculated on the base of the methane concentration profile and the consumption of methane in the redox zone (GD: 2.5 × 10–6 m2 s–1 LD: 1.6 × 10–5 m2 s–1). Our study identified vertical transport of methane from the deep water body towards the redox zone as well as differing hydrographic conditions within the oxic/anoxic transition zone of these deeps as major factors that determine the pelagic methane oxidation.
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Berndmeyer, C., V. Thiel, O. Schmale, N. Wasmund, and M. Blumenberg. "Biomarkers in the stratified water column of the Landsort Deep (Baltic Sea)." Biogeosciences 11, no. 23 (December 11, 2014): 7009–23. http://dx.doi.org/10.5194/bg-11-7009-2014.
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Abstract. The water column of the Landsort Deep, central Baltic Sea, is stratified into an oxic, suboxic, and anoxic zone. This stratification controls the distributions of individual microbial communities and biogeochemical processes. In summer 2011, particulate organic matter was filtered from these zones using an in situ pump. Lipid biomarkers were extracted from the filters to establish water-column profiles of individual hydrocarbons, alcohols, phospholipid fatty acids, and bacteriohopanepolyols (BHPs). As a reference, a cyanobacterial bloom sampled in summer 2012 in the central Baltic Sea Gotland Deep was analyzed for BHPs. The biomarker data from the surface layer of the oxic zone showed major inputs from cyanobacteria, dinoflagellates, and ciliates, while the underlying cold winter water layer was characterized by a low diversity and abundance of organisms, with copepods as a major group. The suboxic zone supported bacterivorous ciliates, type I aerobic methanotrophic bacteria, sulfate-reducing bacteria, and, most likely, methanogenic archaea. In the anoxic zone, sulfate reducers and archaea were the dominating microorganisms as indicated by the presence of distinctive branched fatty acids: archaeol and pentamethylicosane (PMI) derivatives, respectively. Our study of in situ biomarkers in the Landsort Deep thus provided an integrated insight into the distribution of relevant compounds and describes useful tracers to reconstruct stratified water columns in the geological record.
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Canfield, D. E. "Models of oxic respiration, denitrification and sulfate reduction in zones of coastal upwelling." Geochimica et Cosmochimica Acta 70, no. 23 (December 2006): 5753–65. http://dx.doi.org/10.1016/j.gca.2006.07.023.
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Berndmeyer, C., V. Thiel, O. Schmale, N. Wasmund, and M. Blumenberg. "Biomarkers in the stratified water column of the Landsort Deep (Baltic Sea)." Biogeosciences Discussions 11, no. 6 (June 25, 2014): 9853–87. http://dx.doi.org/10.5194/bgd-11-9853-2014.
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Abstract. The water column of the Landsort Deep, central Baltic Sea, is stratified into an oxic, suboxic and anoxic zone. This stratification controls the distributions of individual microbial communities and biogeochemical processes. In summer 2011, particulate organic matter was filtered from these zones using an in~situ pump. Lipid biomarkers were extracted from the filters to establish water column profiles of individual hydrocarbons, alcohols, phospholipid fatty acids, and bacteriohopanepolyols (BHPs). As a reference, a cyanobacterial bloom sampled in summer 2012 in the central Baltic Sea Gotland Deep was analyzed for BHPs. The biomarker data from the surface layer of the oxic zone showed major inputs from different cyanobacteria and eukaryotes such as dinoflagellates and ciliates, while the underlying cold winter water layer was characterized by a low diversity and abundance of organisms, with copepods as a major group. The suboxic zone supported bacterivorous ciliates, type I aerobic methanotrophic bacteria, sulfate reducing bacteria, and, most likely, methanogenic archaea. In the anoxic zone, sulfate reducers and archaea were the dominating microorganisms as indicated by the presence of distinctive branched fatty acids, archaeol and PMI derivatives, respectively. Our study of in situ biomarkers in the Landsort Deep thus provided an integrated insight into the distribution of relevant players and the related biogeochemical processes in stratified water columns of marginal seas.
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Wolke, Philipp, Yoni Teitelbaum, Chao Deng, Jörg Lewandowski, and Shai Arnon. "Impact of Bed Form Celerity on Oxygen Dynamics in the Hyporheic Zone." Water 12, no. 1 (December 22, 2019): 62. http://dx.doi.org/10.3390/w12010062.
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Oxygen distribution and uptake in the hyporheic zone regulate various redox-sensitive reactions and influence habitat conditions. Despite the fact that fine-grain sediments in streams and rivers are commonly in motion, most studies on biogeochemistry have focused on stagnant sediments. In order to evaluate the effect of bed form celerity on oxygen dynamics and uptake in sandy beds, we conducted experiments in a recirculating indoor flume. Oxygen distribution in the bed was measured under various celerities using 2D planar optodes. Bed morphodynamics were measured by a surface elevation sensor and time-lapse photography. Oxygenated zones in stationary beds had a conchoidal shape due to influx through the stoss side of the bed form, and upwelling anoxic water at the lee side. Increasing bed celerity resulted in the gradual disappearance of the upwelling anoxic zone and flattening of the interface between the oxic (moving fraction of the bed) and the anoxic zone (stationary fraction of the bed), as well as in a reduction of the volumetric oxygen uptake rates due shortened residence times in the hyporheic zone. These results suggest that including processes related to bed form migration are important for understanding the biogeochemistry of hyporheic zones.
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Ha, J. H., and S. K. Ong. "Nitrification and denitrification in partially aerated biological aerated filter (BAF) with dual size sand media." Water Science and Technology 55, no. 1-2 (January 1, 2007): 9–17. http://dx.doi.org/10.2166/wst.2007.025.
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A 104-mm (4-inch) diameter pilot-scale biological aerated filter (BAF) with a media depth of 2.5 m (8.3 feet) was operated with an anaerobic, anoxic and oxic zone at a temperature of 23°C. The medium for the anaerobic and anoxic zones was 10 mm diameter sand while the medium for the oxic zone was 5 mm diameter sand. The influent sCOD and total nitrogen concentrations in the feedwater were approximately 250 mg/L and 35 mg N/L, respectively. sCOD removal at optimum hydraulic retention time (HRT) of 3 h with recirculation rates of 100, 200 and 300% in the column was above 96%. Nitrification was found to be more than 96% for 3 h HRT at 200 and 300% recirculation. Total nitrogen removal was consistent at more than 80% for 4 and 6 h HRT at 300% recirculation. For 3 h HRT and 300% recirculation, total nitrogen removal was approximately 79%. The ammonia loading rates for maximum ammonia removed were 0.15 and 0.19 kg NH3-N/m3-day for 100 and 200% recirculation, respectively. The experimental results demonstrated that the BAF can be operated at an HRT of 3 h with 200–300% recirculation rates with more than 96% removal of sCOD and ammonia and at least 75% removal of total nitrogen.
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Chao, Yeong-Nan, Jui-Hsien Lin, Kok-Kwang Ng, Chung-Hsin Wu, Pui-Kwan Andy Hong, and Cheng-Fang Lin. "Improving total nitrogen removal in aeration basin retrofitted with entrapped biomass." Water Science and Technology 69, no. 7 (February 4, 2014): 1558–64. http://dx.doi.org/10.2166/wst.2014.053.
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This study presented a method to upgrade existing aeration tanks to remove total nitrogen (TN). Bioplates carrying entrapped biomass were installed in an aeration basin to create anoxic/anaerobic zones where denitrification can proceed. In a reactor that coupled bioplates containing entrapped biomass (equivalent to as high as 7,500 mg/L of biomass) and an activated sludge suspension (at mixed liquor suspended solids of 1,300–2,400 mg/L), nitrification efficiency exceeded 95% for an influent wastewater containing 21–54 mg/L of NH3-N. In all cases amended with alkalinity and with or without added methanol as an electron source, TN removal was between 60 and 70%. The results demonstrated anoxic/oxic or anaerobic/anoxic/oxic processes could be incorporated in a conventional aeration basin, requiring no substantial modifications of the vessel and operation, and thus providing improved treatment in terms of nitrogen removal in the conventional suspended-growth process.
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Garcia-Robledo, Emilio, Cory C. Padilla, Montserrat Aldunate, Frank J. Stewart, Osvaldo Ulloa, Aurélien Paulmier, Gerald Gregori, and Niels Peter Revsbech. "Cryptic oxygen cycling in anoxic marine zones." Proceedings of the National Academy of Sciences 114, no. 31 (July 17, 2017): 8319–24. http://dx.doi.org/10.1073/pnas.1619844114.
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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.
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Fontugne, Michel, François Guichard, Ilham Bentaleb, Claudia Strechie, and Gilles Lericolais. "Variations in 14C Reservoir Ages of Black Sea Waters and Sedimentary Organic Carbon During Anoxic Periods: Influence of Photosynthetic Versus Chemoautotrophic Production." Radiocarbon 51, no. 3 (2009): 969–76. http://dx.doi.org/10.1017/s0033822200034044.
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Radiocarbon activity of dissolved inorganic carbon has been measured in the northwestern Black Sea. Both continental shelf and open-sea profiles show that surface waters are in equilibrium with the atmosphere. The observed distribution of 14C activity shows a weak contribution of the deep 14C-depleted CO2 to the photic zone. Such a distribution of 14C within the water column is unable to explain the aging of sedimentary organic matter and reservoir ages greater than 500 yr. A contribution of production by chemoautotrophic bacteria feeding on 14C-depleted methane at the boundary of the oxic and anoxic zones is a realistic hypothesis. Also, a contribution to sedimentary organic carbon estimated at <15% of the photosynthetic primary production could explain 14C reservoir ages greater than 1300 yr.
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Bishop, Janice L., Brandy L. Anglen, Lisa M. Pratt, Howell G. M. Edwards, David J. Des Marais, and Peter T. Doran. "A spectroscopy and isotope study of sediments from the Antarctic Dry Valleys as analogues for potential paleolakes on Mars." International Journal of Astrobiology 2, no. 4 (October 2003): 273–87. http://dx.doi.org/10.1017/s1473550403001654.
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A spectroscopy and isotope study has been performed on igneous sediments from Lake Hoare, a nearly isolated ecosystem in the Dry Valleys region of Antarctica. The mineralogy and chemistry of these sediments were studied in order to gain insights into the biogeochemical processes occurring in a permanently ice-covered lake and to assist in characterizing potential habitats for life in paleolakes on Mars. Obtaining visible/near-infrared, mid-infrared and Raman spectra of such sediments provides the ground truth needed for using reflectance, emittance and Raman spectroscopy for exploration of geology, and perhaps biology, on Mars. Samples measured in this study include a sediment from the ice surface, lake bottom sediment cores from oxic and anoxic zones of the lake and the magnetic fractions of two samples.These sediments are dominated by quartz, pyroxene, plagioclase and K-feldspar, but also contain calcite, organics, clays, sulphides and iron oxides/hydroxides that resulted from chemical and biological alteration processes. Chlorophyll-like bands are observed in the spectra of the sediment-mat layers on the surface of the lake bottom, especially in the deep anoxic region. Layers of high calcite concentration in the oxic sediments and layers of high pyrite concentration in the anoxic sediments are indicators of periods of active biogeochemical processing in the lake. Micro-Raman spectra revealed the presence of ~5 μm-sized pyrite deposits on the surface of quartz grains in the anoxic sediments. C, N and S isotope trends are compared with the chemistry and spectral properties. The δ13C and δ15N trends highlight the differences in the balance of microbial processes in the anoxic sediments versus the oxic sediments. The biogenic pyrite found in the sediments from the anoxic zone is associated with depleted δ34S values, high organic C levels and chlorophyll spectral bands and could be used as a potential biomarker mineral for paleolakes on Mars.
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Schmale, Oliver, Stefan Krause, Peter Holtermann, Nicole C. Power Guerra, and Lars Umlauf. "Dense bottom gravity currents and their impact on pelagic methanotrophy at oxic/anoxic transition zones." Geophysical Research Letters 43, no. 10 (May 27, 2016): 5225–32. http://dx.doi.org/10.1002/2016gl069032.
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Versteegh, Gerard J. M., Andrea Koschinsky, Thomas Kuhn, Inken Preuss, and Sabine Kasten. "Geochemical consequences of oxygen diffusion from the oceanic crust into overlying sediments and its significance for biogeochemical cycles based on sediments of the northeast Pacific." Biogeosciences 18, no. 17 (September 13, 2021): 4965–84. http://dx.doi.org/10.5194/bg-18-4965-2021.
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Abstract. Exchange of dissolved substances at the sediment–water interface provides an important link between the short-term and long-term geochemical cycles in the ocean. A second, as yet poorly understood sediment–water exchange is supported by low-temperature circulation of seawater through the oceanic basement underneath the sediments. From the basement, upwards diffusing oxygen and other dissolved species modify the sediment, whereas reaction products diffuse from the sediment down into the basement where they are transported by the basement fluid and released to the ocean. Here, we investigate the impact of this “second” route with respect to transport, release and consumption of oxygen, nitrate, manganese, nickel and cobalt on the basis of sediment cores retrieved from the Clarion Clipperton Zone (CCZ) in the equatorial Pacific Ocean. We show that in this abyssal ocean region characterised by low organic carbon burial and sedimentation rates vast areas exist where the downward- and upward-directed diffusive fluxes of oxygen meet so that the sediments are oxic throughout. This is especially the case where sediments are thin or in the proximity of faults. Oxygen diffusing upward from the basaltic crust into the sediment contributes to the degradation of sedimentary organic matter. Where the sediments are entirely oxic, nitrate produced in the upper sediment by nitrification is lost both by upward diffusion into the bottom water and by downward diffusion into the fluids circulating within the basement. Where the oxygen profiles do not meet, they are separated by a suboxic sediment interval characterised by Mn2+ in the porewater. Where porewater Mn2+ in the suboxic zones remains low, nitrate consumption is low and the sediment continues to deliver nitrate to the ocean bottom waters and basement fluid. We observe that at elevated porewater manganese concentrations, nitrate consumption exceeds production and nitrate diffuses from the basement fluid into the sediment. Within the suboxic zone, not only manganese but also cobalt and nickel are released into the porewater by reduction of Mn oxides, diffusing towards the oxic–suboxic fronts above and below where they precipitate, effectively removing these metals from the suboxic zone and concentrating them at the two oxic–suboxic redox boundaries. We show that not only do diffusive fluxes in the top part of deep-sea sediments modify the geochemical composition over time but also diffusive fluxes of dissolved constituents from the basement into the bottom layers of the sediment. Hence, the palaeoceanographic interpretation of sedimentary layers should carefully consider such deep secondary modifications in order to prevent the misinterpretation of primary signatures.
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Homoky, William B., Tim M. Conway, Seth G. John, Daniela König, FeiFei Deng, Alessandro Tagliabue, and Rachel A. Mills. "Iron colloids dominate sedimentary supply to the ocean interior." Proceedings of the National Academy of Sciences 118, no. 13 (March 26, 2021): e2016078118. http://dx.doi.org/10.1073/pnas.2016078118.
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Dissolution of marine sediment is a key source of dissolved iron (Fe) that regulates the ocean carbon cycle. Currently, our prevailing understanding, encapsulated in ocean models, focuses on low-oxygen reductive supply mechanisms and neglects the emerging evidence from iron isotopes in seawater and sediment porewaters for additional nonreductive dissolution processes. Here, we combine measurements of Fe colloids and dissolved δ56Fe in shallow porewaters spanning the full depth of the South Atlantic Ocean to demonstrate that it is lithogenic colloid production that fuels sedimentary iron supply away from low-oxygen systems. Iron colloids are ubiquitous in these oxic ocean sediment porewaters and account for the lithogenic isotope signature of dissolved Fe (δ56Fe = +0.07 ± 0.07‰) within and between ocean basins. Isotope model experiments demonstrate that only lithogenic weathering in both oxic and nitrogenous zones, rather than precipitation or ligand complexation of reduced Fe species, can account for the production of these porewater Fe colloids. The broader covariance between colloidal Fe and organic carbon (OC) abundance suggests that sorption of OC may control the nanoscale stability of Fe minerals by inhibiting the loss of Fe(oxyhydr)oxides to more crystalline minerals in the sediment. Oxic ocean sediments can therefore generate a large exchangeable reservoir of organo-mineral Fe colloids at the sediment water interface (a “rusty source”) that dominates the benthic supply of dissolved Fe to the ocean interior, alongside reductive supply pathways from shallower continental margins.
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Mammitzsch, K., G. Jost, and K. Jürgens. "Influence of increasing dissolved inorganic carbon concentrations and decreasing pH on chemolithoautrophic bacteria from oxic-sulfidic interfaces." Biogeosciences Discussions 9, no. 12 (December 17, 2012): 18371–95. http://dx.doi.org/10.5194/bgd-9-18371-2012.
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Abstract. Increases in the dissolved inorganic carbon (DIC) concentration are expected to cause a decrease in the pH of ocean waters, a process known as ocean acidification. In oxygen-deficient zones this will add to already increased DIC and decreased pH values. It is not known how this might affect microbial communities and microbially mediated processes. In this study, the potential effects of ocean acidification on chemolithoautotrophic prokaryotes of marine oxic-anoxic transition zones were investigated, using the chemoautotrophic denitrifying ε-proteobacterium "Sulfurimonas gotlandica" strain GD1 as a model organism. This and related taxa use reduced sulfur compounds, e.g. sulfide and thiosulfate, as electron donors and were previously shown to be responsible for nitrate removal and sulfide detoxification in redox zones of the Baltic Sea water column but occur also in other oxygen-deficient marine systems. Bacterial cell growth within a broad range of DIC concentrations and pH values was monitored and substrate utilization was determined. The results showed that the DIC saturation concentration for growth was already reached at 800 μM, which is well below in situ DIC levels. The pH optimum was between 6.6 and 8.0. Within a pH range of 6.6–7.1 there was no significant difference in substrate utilization; however, at lower pH values cell growth decreased sharply and cell-specific substrate consumption increased. These findings suggest that a direct effect of ocean acidification, with the predicted changes in pH and DIC, on chemolithoautotrophic bacteria such as "S. gotlandica" str. GD1 is generally not very probable.
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Hoffman, H. "Influence of Oxic and Anoxic Mixing Zones in Compartment Systems on Substrate Removal and Sludge Characteristics in Activated Sludge Plants." Water Science and Technology 19, no. 5-6 (May 1, 1987): 897–910. http://dx.doi.org/10.2166/wst.1987.0268.
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During a research program the influence of activated sludge compartment systems with and without anoxic mixing zone on the efficiency of the system and the settleability and dewatering characteristics of the activated sludge was tested. COD-load, number and volume of the compartments and the mixing zones were varied. Experiments were carried out with two pilot plants, a compartment system and a totally mixed system. The tests clearly indicate that a four-stage cascade system with a BOD-load of about 1.0 kg/(m3.d) could improve settleability and dewatering characteristics, but bulking sludge could not be avoided. Using a nonaerated upstream zone with a volume load of 4.0 kg/(m3.d)the settling properties in the compartment system(total BOD-load 1.0 kg/(m3.d)) could be improved to such an extent that the formation of bulking sludge was prevented. Better settleability leads to the higher solids concentration in the cascade system and to a lower sludge load. Therefore lower BOD-outflow-concentrations and higher efficiency of the activated sludge system were available.
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Albertson, Orris E. "Bulking Sludge Control–Progress, Practice and Problems." Water Science and Technology 23, no. 4-6 (February 1, 1991): 835–46. http://dx.doi.org/10.2166/wst.1991.0535.
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Since bulking sludges are the primary cause of failure of activated sludge systems, the first obligation of the designer is to minimize the possibility of such an occurrence. This paper traces the evolution of bulking control concepts from the earliest date when batch and semi-continuous selectors were employed, to more recent experiences with anaerobic, anoxic, oxic and high F/M biological selectors. This paper also summarizes recent results obtained from 12 USA facilities employing various selectors. Preliminary conclusions support high to low F/M gradient as a dominant selector factor. Whether the system is aerated or not, the available oxygen in the initial contact zones (ICZs) should be substantially less than the oxygen demand in the zone to ensure that anaerobic functions occur within the cell mass. In addition, F/M gradients should be provided in each environment.
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Noutsopoulos, C., D. Mamais, and A. D. Andreadakis. "The effect of reactor configuration and operational mode on Microthrix parvicella bulking and foaming in nutrient removal activated sludge systems." Water Science and Technology 46, no. 1-2 (July 1, 2002): 61–64. http://dx.doi.org/10.2166/wst.2002.0457.
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Three bench-scale nutrient removal activated sludge units were used to examine the effect of the reactor configuration and the intermittent aeration mode on the growth of Microthrix parvicella. According to the results, the plug flow configuration seems to achieve satisfactory Microthrix parvicella control. The imposed concentration gradient for both RBCOD and SBCOD creates a selective advantage for the floc forming bacteria throughout the system (both the anoxic and oxic zones) and limits Microthrix parvicella growth. In terms of the operational mode, the intermittent aeration CSTR nutrient removal system promotes the growth of M.parvicella and deteriorates the settling characteristics of the activated sludge.
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Willscher, Sabine, Doreen Knippert, Heiko Ihling, Denise Kühn, and Sophie Starke. "Underground Degradation of Lignite Coal Spoil Material by a Mixed Microbial Community under Acid Mine Drainage Conditions." Advanced Materials Research 825 (October 2013): 46–49. http://dx.doi.org/10.4028/www.scientific.net/amr.825.46.
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In a field study, biogeochemical processes in a large lignite coal spoil area with moderate AMD generation were investigated. Underneath this area, large amounts of groundwater are impacted by degradation and transformation processes of coal remainders in the former open pit mining area. An investigation was performed to find out the sources for the ground and surface water contaminations of larger areas. Samples were taken from different places and different depths of the coal spoil area and were investigated for different metabolic groups of microorganisms. As a result, fungi are able to degrade humic matter in coal spoil heaps in a first step to oligomers. Other microorganisms do a further degradation of first intermediates in a commensalic community. Streptomycetes do a cleavage of lignocelluloses, strepto- and other actinomycetes also degrade cellobiose and xylose related parts of the humic coal spoil matter. The different members of the microbial community exist in different “floors” of the spoil area: fungi and most Actinomycetes prefer the oxic zone, whereas degraders of aromatic and heterocyclic compounds can also exist in the capillary and ground water zones; here more frequently Arthrobacter, Pseudomonas, Rhodococcus and Mycobacterium strains were detected. Ferric iron formed in biooxidation of pyrite seems to play an important role as a catalyst for oxic as well as anaerobic degradation of complex organic matter in the underground. A complex linkage between microbial Fe-, S-, C- and N-cycles was figured out on this site that induces a high and long-term impact on ground water contamination in this area.
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Sheppard, Samuel Keir, Manfred Beckmann, and David Lloyd. "The effect of temperature on methane dynamics in soil and peat cores: Calculations from membrane inlet mass spectrometry." Canadian Journal of Soil Science 87, no. 1 (January 1, 2007): 11–22. http://dx.doi.org/10.4141/s06-021.
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Methanogenesis and methane oxidation, fundamental microbial processes in the global carbon cycle, are mediated by numerous factors in terrestrial soil and wetland ecosystems. Accurate quantification of CH4 and CO2 concentrations in soils and wetlands is now possible using membrane inlet mass spectrometry. Below-ground production and headspace exchange of O2, CO2 and CH4 were monitored in microcosms from an upland Soil (Scotland) and three different peat bog systems (Sweden, Iceland and Scotland) by membrane inlet mass spectrometry. A comparison of cores from the different locations revealed that temperature, soil structure, plant cover and water table level are associated with the regulation of the depth of oxygen available for methanotrophic processes in the oxic zone and therefore gas emission rates. In aerobic soil cores, all the methane produced in anaerobic sites is oxidised rather than being emitted from the soil surface. In peat cores, molar CH4:CO2-ratios of around 1:10 indicate the boundary between the oxic and the anoxic zones. Changes in dissolved gas concentrations with depth and especially the molar CH4 :CO2-ratios are discussed. We also demonstrate that inconsistencies in dissolved gas profiles, along with higher localized molar CH4:CO2-ratios, indicate bubble formation at depths greater than 10 cm; gas emission by ebullition was promoted at these sites. Increase in temperature had a particularly strong effect upon gas dynamics in soil and peat cores. Gas solubilities were reduced and elevated CO2 and CH4 emission rates were observed potentially due to increased microbial activity. Key words: Methane, CO2, membrane inlet mass spectrometry, soil
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Stott, R., and C. C. Tanner. "Influence of biofilm on removal of surrogate faecal microbes in a constructed wetland and maturation pond." Water Science and Technology 51, no. 9 (May 1, 2005): 315–22. http://dx.doi.org/10.2166/wst.2005.0343.
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The effect of biofilm on the attenuation of pathogen-sized particles from wastewater was compared for biofilms cultivated in a surface flow constructed wetland (SFW) and maturation pond (MP) The fate of fluorescently labelled microspheres (FLM) as surrogates for viruses (0.1 μm), bacteria (1 μm) and parasitic protozoa (4.5 μm dia) was investigated in microcosms in the presence or absence of biofilms. Rates of FLM removal from suspension were higher in the presence of biofilms for all particle sizes (kd 0.02–0.11 h−1) in MP and SFW microcosms with removal efficiency related to particle size and biofilm thickness and structure. Greater removal of 0.1 μm (79–81%), 1 μm FLM (92–96%) and 4.5 μm FLM (up to 98%) from suspension were found for microcosms containing thicker (autotrophic) biofilms grown in the MP or open water zone of the SFW. Lower removal of 43% (0.1 μm), 59% (1 μm) and 84% (4.5 μm) occurred in microcosms containing thinner heterotrophic biofilms from SFW vegetated zones. Providing surfaces for attachment of photosynthetic biofilms offers potential to enhance pathogen removal in open water systems. In vegetated systems, linkage to more oxic openwater zones may allow thicker and ‘stickier’ epiphytic biofilms to develop, improving pathogen interception and removal.
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Kenneke, John F., and Steven C. McCutcheon. "Use of Pretreatment Zones and Zero-Valent Iron for the Remediation of Chloroalkenes in an Oxic Aquifer." Environmental Science & Technology 37, no. 12 (June 2003): 2829–35. http://dx.doi.org/10.1021/es0207302.
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Kim, H., D. Rhu, H. Hwang, and E. Choi. "Performance of a hybrid SBR with fixed bed and suspended growth." Water Science and Technology 48, no. 11-12 (December 1, 2004): 309–17. http://dx.doi.org/10.2166/wst.2004.0868.
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A hybrid SBR system combined with fixed bed (media) and suspended growth zones was developed to improve both nitrogen and phosphorus removal. About 27% of the tank volume was filled with clay media to make a fixed bed in this system, and additional air was applied under the bed to wash the microbes from the media during the oxic stage to prevent the bed from clogging. This hybrid SBR system could eliminate the backwashing requirement for SBBR (sequencing batch biofilm reactor). This system showed a stable nitrification even at low temperature and shock load conditions. The specific reaction rates indicated the fixed bed zone had higher microbial activities for nitrification and denitrification, while the suspended growth zone had higher microbial activities for phosphorus release and uptake. In addition, the use of external sludge storage also increased both phosphorus and nitrogen removal. The effluent COD, nitrogen and phosphorus concentrations were respectively less than 15, 10.5 and 0.6 mg/L with weak sewage of 230 mg/L COD, 35 mg/L TKN and 5.3 mg/L TP.
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Jakobs, G., G. Rehder, G. Jost, K. Kießlich, M. Labrenz, and O. Schmale. "Comparative studies of pelagic microbial methane oxidation within the redox zones of the Gotland Deep and Landsort Deep (central Baltic Sea)." Biogeosciences 10, no. 12 (December 3, 2013): 7863–75. http://dx.doi.org/10.5194/bg-10-7863-2013.
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Abstract. Pelagic methane oxidation was investigated in dependence on differing hydrographic conditions within the redox zone of the Gotland Deep (GD) and Landsort Deep (LD), central Baltic Sea. The redox zone of both deeps, which indicates the transition between oxic and anoxic conditions, was characterized by a pronounced methane concentration gradient between the deep water (GD: 1233 nM, 223 m; LD: 2935 nM, 422 m) and the surface water (GD and LD < 10 nM). This gradient together with a 13C CH4 enrichment (δ13C CH4 deep water: GD −84‰, LD −71‰; redox zone: GD −60‰, LD −20‰; surface water: GD −47‰, LD −50‰; δ13C CH4 vs. Vienna Pee Dee Belemnite standard), clearly indicating microbial methane consumption within the redox zone. Expression analysis of the methane monooxygenase identified one active type I methanotrophic bacterium in both redox zones. In contrast, the turnover of methane within the redox zones showed strong differences between the two basins (GD: max. 0.12 nM d−1, LD: max. 0.61 nM d−1), with a nearly four-times-lower turnover time of methane in the LD (GD: 455 d, LD: 127 d). Vertical mixing rates for both deeps were calculated on the base of the methane concentration profile and the consumption of methane in the redox zone (GD: 2.5 × 10–6 m2 s−1, LD: 1.6 × 10–5 m2 s−1). Our study identified vertical transport of methane from the deep-water body towards the redox zone as well as differing hydrographic conditions (lateral intrusions and vertical mixing) within the redox zone of these deeps as major factors that determine the pelagic methane oxidation.
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Chen, Jianfei, Tianli Tong, Xinshu Jiang, and Shuguang Xie. "Biodegradation of sulfonamides in both oxic and anoxic zones of vertical flow constructed wetland and the potential degraders." Environmental Pollution 265 (October 2020): 115040. http://dx.doi.org/10.1016/j.envpol.2020.115040.
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Buchshtav, Tamir, and Alexey Kamyshny. "Decomposition of dimethyl polysulfides under solar irradiation in oxic aqueous solutions." Environmental Chemistry 17, no. 5 (2020): 377. http://dx.doi.org/10.1071/en19252.
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Environmental contextThe quality of drinking water can be greatly compromised by the presence of dimethyl polysulfides. We studied the rate and mechanism of decomposition of dimethyl polysulfides in aqueous solution under solar irradiation, and found that they decompose photochemically in seconds to minutes, i.e. much faster than under dark conditions. These results suggest that photochemical pathways of dimethyl polysulfide decomposition may prevail in euphotic zones of natural aquatic systems. AbstractThe presence of malodorous dimethyl polysulfides (DMPSs) has been documented in marine and limnic systems as well as in tap water distribution systems. These compounds compromise the quality of drinking water. Under oxic conditions and in the absence of radiation, DMPSs with n ≥ 3 sulfur atoms disproportionate into DMPSs with n+1 and n−1 sulfur atoms, and, finally, to dimethyl disulfide (DMDS) and S8. DMDS, in turn, decomposes to methyl mercaptan (MT) and methanesulfinic acid. Under these conditions, the half-lives of DMPSs vary from months for dimethyl pentasulfide (DM5S) to hundreds of thousands of years for DMDS. In this work, we studied the kinetics and mechanisms of the decomposition reactions of DMPSs with 2–5 sulfur atoms in aqueous solutions in the presence of oxygen and under exposure to solar radiation. The quantum yields of decomposition of DMPSs with 2, 3, 4 and 5 sulfur atoms do not depend on either the concentration of DMPSs or pH, and are 40±10, 2.0±0.2, 35±10 and 10±4 respectively. The quantum yields, which are higher than unity, suggest that under exposure to solar radiation the photochemical decomposition of DMPSs proceeds by a radical chain reaction mechanism. Half-lives of DMPSs in oxic aquatic solutions exposed to solar radiation under a very clear atmosphere and a solar elevation angle of 90° were calculated from the quantum yields and were found to be as low as 43±13s for DMDS, 40±4s for dimethyl trisulfide (DMTS), 2.1±0.6s for dimethyl tetrasulfide (DM4S) and 4.2±1.7s for DM5S.
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Kamngam, Sittikorn, Thammarat Koottatep, Nawatch Surinkul, Chawalit Chaiwong, and Chongrak Polprasert. "Performance evaluation of anoxic–oxic–anoxic processes in illuminated biofilm reactor (AOA-IBR) treating septic tank effluent." Journal of Water, Sanitation and Hygiene for Development 10, no. 4 (October 19, 2020): 874–84. http://dx.doi.org/10.2166/washdev.2020.145.
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Abstract This study was conducted to evaluate the treatment performance of the anoxic–oxic–anoxic processes in illuminated biofilm reactor (AOA-IBR) in removing organics and nitrogen contained in septic tank effluent. The 27 L of the AOA-IBR was illuminated with red light-emitting diode (LED) lamps (peak wavelength of 635 nm, intensity of 100 μmol/(m2s)). Three types of biofilm media, namely ball ring®, plastic sheets and zeolite beads, were placed in the anoxic, oxic and anoxic zones, respectively, of the reactor to support the growth of microalgal–bacterial biofilm. The AOA-IBR was continuously fed with septic tank effluent and operated at hydraulic retention times (HRTs) of 24, 48 and 72 h. The experimental results found the increases in chemical oxygen demand (COD), total nitrogen (TN) and ammonia nitrogen (NH4-N) removal efficiencies with increasing HRTs in which the HRT of 72 h resulted in 78.6, 72.8 and 90.6% removals of COD, TN and NH4-N, respectively. The effluent quality of the AOA-IBR could meet the ISO 30500 effluent standards for Non-Sewered Sanitation Systems. The predominant microalgal biofilm species was observed to be Oscillatoria sp., while Proteobacteria was the predominant bacterial phylum found in the biofilm growing in the reactor. The above results suggested the applicability of the AOA-IBR in improving septic tank treatment performance which should result in better water pollution control.
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Bravidor, Jenny, Julika Kreling, Andreas Lorke, and Matthias Koschorreck. "Effect of fluctuating oxygen concentration on iron oxidation at the pelagic ferrocline of a meromictic lake." Environmental Chemistry 12, no. 6 (2015): 723. http://dx.doi.org/10.1071/en14215.
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Environmental context The cycling of iron plays an important role in pelagic boundary zones such as the oxic–anoxic interface where physical and chemical gradients occur. The turnover of iron in this zone depends on oxygen fluctuation and the duration of the fluctuation event. This study increases the understanding of biogeochemical iron transformation in such hotspots. Abstract In stratified iron-rich lakes, the interface between oxic and anoxic water bodies, the oxycline, is accompanied by a steep gradient of dissolved iron, the ferrocline. It is a hotspot of biogeochemical transformations, namely the cycling of iron (Fe). The rate of iron oxidation, both chemical and microbial, depends on pH, iron and oxygen concentration, and microbial activity. We investigated the ferrocline of the meromictic Lake Waldsee to find out how the ferrocline is influenced by fluctuating oxygen concentrations. We measured diurnal fluctuations of Fe2+, O2 and pH along vertical profiles during two campaigns in July and September 2011 as well as rates of iron oxidation in laboratory incubations. The oxygen content of the water column varied both between the campaigns and diurnally. We observed a diurnal intrusion of O2 into the ferrocline. The diurnal signal was visible in the iron profile in July but not in September. Iron oxidation rates determined in the laboratory demonstrate the importance of microbial iron reduction and the strong pH dependency. We related the reaction timescales for iron oxidation to the characteristic timescale of oxygen fluctuations by calculating non-dimensional numbers. This analysis showed that an oxygenation event had to last at least 10h in order to affect the depth and vertical extent of the ferrocline, which was the case in July but not in September. Our results show that the duration of events can be an important parameter regulating biogeochemical interactions in pelagic redoxclines.
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Lin, Donglin, Shuheng Tang, Zhaodong Xi, Bing Zhang, and Yapei Ye. "Geochemical Characteristics of Late Ordovician Shales in the Upper Yangtze Platform, South China: Implications for Redox Environmental Evolution." Minerals 11, no. 7 (June 30, 2021): 710. http://dx.doi.org/10.3390/min11070710.
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Changes to the redox environment of seawater in the Late Ordovician affect the process of organic matter enrichment and biological evolution. However, the evolution of redox and its underlying causes remain unclear. This paper analyzed the vertical variability of main, trace elements and δ34Spy from a drill core section (well ZY5) in the Upper Yangtze Platform, and described the redox conditions, paleoproductivity and paleoclimate variability recorded in shale deposits of the P. pacificus zone and M. extraordinarius zone that accumulated during Wufeng Formation. The results showed that shale from well ZY5 in Late Ordovician was deposited under oxidized water environment, and there are more strongly reducing bottom water conditions of the M. extraordinarius zone compared with the P. pacificus zone. Excess silica (SiO2(exc)) and substitution index of paleoproductivity (Y) indicated that the P. pacificus zone had higher paleoproductivity whereas the M. extraordinarius zone was lower. The high productivity level controlled O2 release in the shallow water area as well as the oxidation degree of the P. pacificus zone. The decrease of productivity and the relatively stagnant water mass of the inner Yangtze Sea controlled the formation of relatively reduced water conditions in the M. extraordinarius zone. The chemical index of alteration (CIA) results suggested that palaeoclimatic conditions changed from warm and humid to cold and dry climate from the P. pacificus to the M. extraordinarius zones in the study area. A comparative analysis of the published Fe-S-C data for the Xiushan Datianba section showed that in the P. pacificus zone of the inner Yangtze Sea, warm and humid climate conditions drove high productivity, sulphate flux and low reactive iron flux, which promoted the expansion of oxic ocean-surface waters and mid-depth euxinic waters. In the M. extraordinarius zone, the cold and dry climate with significant uplift of the Xiang’e Submarine High led to the relative sea level decline, resulting in low productivity, sulfate flux and high reactive iron flux, which promoted the expansion of the mid-depth ferruginous waters and the shrinkage of oxic ocean-surface waters. The results offered new insights into the co-evolution of continents and oceans, and explained the role of continental weathering and uplift of the Xiang’e Submarine High in the exchange of sulfate flux and nutrients in the redox environment change of inner Yangtze Sea during the Late Ordovician.
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Briggs, Martin A., Judson W. Harvey, Stephen T. Hurley, Donald O. Rosenberry, Timothy McCobb, Dale Werkema, and John W. Lane Jr. "Hydrogeochemical controls on brook trout spawning habitats in a coastal stream." Hydrology and Earth System Sciences 22, no. 12 (December 10, 2018): 6383–98. http://dx.doi.org/10.5194/hess-22-6383-2018.
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Abstract. Brook trout (Salvelinus fontinalis) spawn in fall and overwintering egg development can benefit from stable, relatively warm temperatures in groundwater-seepage zones. However, eggs are also sensitive to dissolved oxygen concentration, which may be reduced in discharging groundwater (i.e., seepage). We investigated a 2 km reach of the coastal Quashnet River in Cape Cod, Massachusetts, USA, to relate preferred fish spawning habitats to geology, geomorphology, and discharging groundwater geochemistry. Thermal reconnaissance methods were used to locate zones of rapid groundwater discharge, which were predominantly found along the central channel of a wider stream valley section. Pore-water chemistry and temporal vertical groundwater flux were measured at a subset of these zones during field campaigns over several seasons. Seepage zones in open-valley sub-reaches generally showed suboxic conditions and higher dissolved solutes compared to the underlying glacial outwash aquifer. These discharge zones were cross-referenced with preferred brook trout redds and evaluated during 10 years of observation, all of which were associated with discrete alcove features in steep cutbanks, where stream meander bends intersect the glacial valley walls. Seepage in these repeat spawning zones was generally stronger and more variable than in open-valley sites, with higher dissolved oxygen and reduced solute concentrations. The combined evidence indicates that regional groundwater discharge along the broader valley bottom is predominantly suboxic due to the influence of near-stream organic deposits; trout show no obvious preference for these zones when spawning. However, the meander bends that cut into sandy deposits near the valley walls generate strong oxic seepage zones that are utilized routinely for redd construction and the overwintering of trout eggs. Stable water isotopic data support the conclusion that repeat spawning zones are located directly on preferential discharges of more localized groundwater. In similar coastal systems with extensive valley peat deposits, the specific use of groundwater-discharge points by brook trout may be limited to morphologies such as cutbanks, where groundwater flow paths do not encounter substantial buried organic material and remain oxygen-rich.
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Harrold, Zoë R., Mark L. Skidmore, Trinity L. Hamilton, Libby Desch, Kirina Amada, Will van Gelder, Kevin Glover, Eric E. Roden, and Eric S. Boyd. "Aerobic and Anaerobic Thiosulfate Oxidation by a Cold-Adapted, Subglacial Chemoautotroph." Applied and Environmental Microbiology 82, no. 5 (December 28, 2015): 1486–95. http://dx.doi.org/10.1128/aem.03398-15.
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ABSTRACTGeochemical data indicate that protons released during pyrite (FeS2) oxidation are important drivers of mineral weathering in oxic and anoxic zones of many aquatic environments, including those beneath glaciers. Oxidation of FeS2under oxic, circumneutral conditions proceeds through the metastable intermediate thiosulfate (S2O32−), which represents an electron donor capable of supporting microbial metabolism. Subglacial meltwaters sampled from Robertson Glacier (RG), Canada, over a seasonal melt cycle revealed concentrations of S2O32−that were typically below the limit of detection, despite the presence of available pyrite and concentrations of the FeS2oxidation product sulfate (SO42−) several orders of magnitude higher than those of S2O32−. Here we report on the physiological and genomic characterization of the chemolithoautotrophic facultative anaerobeThiobacillussp. strain RG5 isolated from the subglacial environment at RG. The RG5 genome encodes genes involved with pathways for the complete oxidation of S2O32−, CO2fixation, and aerobic and anaerobic respiration with nitrite or nitrate. Growth experiments indicated that the energy required to synthesize a cell under oxygen- or nitrate-reducing conditions with S2O32−as the electron donor was lower at 5.1°C than 14.4°C, indicating that this organism is cold adapted. RG sediment-associated transcripts ofsoxB, which encodes a component of the S2O32−-oxidizing complex, were closely affiliated withsoxBfrom RG5. Collectively, these results suggest an active sulfur cycle in the subglacial environment at RG mediated in part by populations closely affiliated with RG5. The consumption of S2O32−by RG5-like populations may accelerate abiotic FeS2oxidation, thereby enhancing mineral weathering in the subglacial environment.
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Wilkinson, M., R. S. Haszeldine, A. E. Fallick, and M. J. Osborne. "Siderite zonation within the Brent Group: microbial influence or aquifer flow?" Clay Minerals 35, no. 1 (March 2000): 107–17. http://dx.doi.org/10.1180/000985500546512.
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AbstractA three-fold zonation can be imaged within authigenic siderite from sandstones of the Brent Group using back-scatter SEM techniques. We interpret this zonation in terms of the biogeochemical zonation of shallow buried sediment. The innermost siderite crystal zone is very Fe rich (95.0±0.5 mol.% FeCO3), with high Mn levels relative to Ca and Mg. This is interpreted as forming within the Fe reduction zone, with Mn from the closely associated Mn reduction zone. The second siderite crystal zone is frequently represented either by an episode of dissolution, or is impure (80±1 mol.% FeCO3), and this corresponds to the sulphate reduction zone. The outer crystal zone is intermediate in composition, and is equated with the zone of methanogenesis (88±1 mol.% FeCO3). Isotopic values cannot be assigned to individual crystal zones. Bulk δ18O values (−2.7 to −13.0‰ V-PDB) are not consistent with precipitation from seawater at low temperatures, but suggest meteoric pore-waters. δ13C data (−4.3 to −15.7‰ V-PDB) are consistent with microbially-mediated precipitation.Pyrite and siderite are usually mutually exclusive within a single sample. Sedimentary conditions which favour the development of a strong sulphate reduction zone, and hence the formation of pyrite, do not favour the formation of a strong sub-oxic zone, where siderite is preferentially precipitated, and vice versa. There is a strong facies control upon siderite formation, with ripple cross-laminated sands being most strongly siderite cemented.
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Broman, Elias, Varvara Sachpazidou, Mark Dopson, and Samuel Hylander. "Diatoms dominate the eukaryotic metatranscriptome during spring in coastal ‘dead zone’ sediments." Proceedings of the Royal Society B: Biological Sciences 284, no. 1864 (October 4, 2017): 20171617. http://dx.doi.org/10.1098/rspb.2017.1617.
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An important characteristic of marine sediments is the oxygen concentration that affects many central metabolic processes. There has been a widespread increase in hypoxia in coastal systems (referred to as ‘dead zones’) mainly caused by eutrophication. Hence, it is central to understand the metabolism and ecology of eukaryotic life in sediments during changing oxygen conditions. Therefore, we sampled coastal ‘dead zone’ Baltic Sea sediment during autumn and spring, and analysed the eukaryotic metatranscriptome from field samples and after incubation in the dark under oxic or anoxic conditions. Bacillariophyta (diatoms) dominated the eukaryotic metatranscriptome in spring and were also abundant during autumn. A large fraction of the diatom RNA reads was associated with the photosystems suggesting a constitutive expression in darkness. Microscope observation showed intact diatom cells and these would, if hatched, represent a significant part of the pelagic phytoplankton biomass. Oxygenation did not significantly change the relative proportion of diatoms nor resulted in any major shifts in metabolic ‘signatures’. By contrast, diatoms rapidly responded when exposed to light suggesting that light is limiting diatom development in hypoxic sediments. Hence, it is suggested that diatoms in hypoxic sediments are on ‘standby’ to exploit the environment if they reach suitable habitats.
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Zhang, Yan Qiu, Ang Li, and Yan Li. "Study on Water Qualities Change along ECOSUNIDE Process." Advanced Materials Research 243-249 (May 2011): 4783–87. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4783.
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By distributing influent to different action zones, a high sludge concentration and high sludge concentration gradient were carried out in ECOSUNIDE treatment system. Carbon source was respectively supplied to anaerobic and anoxic tanks, meeting the demand of PAOs for phosphorus release and denirifiers for denitrification. The operation mode of muliple A/O (anoxic/oxic) was employed to avoid the inhibition of nitrate on nitrification and phosphorus accumulation, improving the nutrient removal efficiency without internal reflux. In the paper, the experiments were performed on ECOSUNIDE to investigate the change law of water qualities in the whole system by monitoring MLSS and every index including CODCr, ammonia nitrogen, total nitrogen and total phosphorous, etc. From the results, the removal rates of CODCr, ammonia nitrogen, total nitrogen and total phosphorous were 87.28%, 96.99%, 77.97% and 79.92% reseparately and there was a consistency of the removal rule for every kind of pollutant in the system.
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Nam, Duong Van, Nguyen Hoai Chau, Hamasaki Tatsuhide, Dinh Van Vien, and Phan Do Hung. "EFFECTS OF COD/TN RATIO AND LOADING RATES ON PERFORMANCE OF MODIFIED SBRs IN SIMULTANEOUS REMOVAL OF ORGANIC MATTER AND NITROGEN FROM RUBBER LATEX PROCESSING WASTEWATER." Vietnam Journal of Science and Technology 56, no. 2 (April 12, 2018): 236. http://dx.doi.org/10.15625/2525-2518/56/2/10816.
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Two modified sequencing batch reactors (SBRs) specially configured to consist of both oxic and anoxic zones, and be operated with only a single simultaneous oxic/anoxic phase in each treatment batch were tested to evaluate their applicability in treatment of rubber latex processing (RLP) wastewater. The former, R1 was operated with constant aeration, whereas the latter, R2 was operated with air flow varied from lower rate in the early period of the reaction phase to higher rate in the later one. Effects of the chemical oxygen demand (COD) to total nitrogen (TN) ratio and their loading rates on performance of the modified SBRs in simultaneous removal of organic matter and nitrogen from RLP wastewater were investigated. It was observed that performance of the two reactors in removal of COD and ammonium nitrogen was similar, and did not remarkably change when varying COD/TN ratio, as well as COD and TN loading rates in the ranges of 3.4 – 6.0 gCOD/gN, 0.8 – 1.7 kgCOD×m-3×d-1 and 0.15 – 0.34 kgN×m-3×d-1, respectively. The average COD removal efficiencies were over 95%. Ammonium nitrogen was almost completely eliminated in both reactors with effluent concentrations lower than 1.0 mg/L. Nevertheless, TN removal efficiencies of both reactors were significantly increased with increasing the COD/TN ratio from 3.4 to 6.0, and slightly decreased when increasing the TN loading rate from 0.15 to 0.34 kgN×m-3×d-1. The most effective COD/TN ratios were in the range of 5 – 6, at which the maximal TN removal efficiencies of R1 and R2 were 92% and 97%, respectively.
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Atashgahi, Siavash, Yue Lu, Javier Ramiro-Garcia, Peng Peng, Farai Maphosa, Detmer Sipkema, Winnie Dejonghe, Hauke Smidt, and Dirk Springael. "Geochemical Parameters and Reductive Dechlorination Determine Aerobic Cometabolic vs Aerobic Metabolic Vinyl Chloride Biodegradation at Oxic/Anoxic Interface of Hyporheic Zones." Environmental Science & Technology 51, no. 3 (January 11, 2017): 1626–34. http://dx.doi.org/10.1021/acs.est.6b05041.
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BERNASCONI, EMILIANA. "Ecological study based on the distribution of recent foraminifers from southeast of Buenos Aires province, Argentinean Continental Shelf." Zootaxa 4821, no. 1 (July 30, 2020): 135–47. http://dx.doi.org/10.11646/zootaxa.4821.1.7.
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The study about the distribution of benthic foraminifers in relationship with the type of substrate is presented. Samples of surface sediments from 15 to 60 m of depth from the southeast coast of the province of Buenos Aires (40º 30´ - 42ºS), Argentina were analysed. The foraminiferal assemblage was constituted by forty-eight species that belong to 22 genera. It was characterized mostly by the free-living style, epifaunal microhabitats, oxic levels and a detritivore trophic strategy. Based on statistical analysis, three zones were determinated: at 15 m depth , characterized mainly by Buccella peruviana (d´Orbigny), and species of Bolivina reflected a littoral environment with sandy sediments and the most important clay contribution, whereas it also presented the lowest oxygen levels were determinated; between 24-48 m depth, associted by Ammonia parkinsoniana (d´Orbigny), Buccella peruviana and Quinqueloculina seminula (Linné), this zone displayed an oxygenated environment with coarse grainsize from inner shelf where local water circulation may explain the high energy observed; and the last one located between 36 to 58 m of depth was characterized by Buccella peruviana, Ammonia parkinsoniana, Elphidium macellum (Fichtel & Moll), Cibicides dispars (d´Orbigny) and Cibicides aknerianus (d´Orbigny) regflecting an inner shelf environment with sandy sediments, the lowest water temperature and the highest oxygen levels.
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Okabe, Satoshi, Hisashi Satoh, Tsukasa Itoh, and Yoshimasa Watanabe. "Microbial ecology of sulfate-reducing bacteria in wastewater biofilms analyzed by microelectrodes and fish (fluorescent in situ hybridization) technique." Water Science and Technology 39, no. 7 (April 1, 1999): 41–47. http://dx.doi.org/10.2166/wst.1999.0323.
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The vertical distribution of sulfate-reducing bacteria (SRB) in microaerophilic wastewater biofilms grown on fully submerged rotating disk reactors (RDR) was determined by the conventional culture-dependent MPN method and in situ hybridization of fluorescently-labelled 16S rRNA-targeted oligonucleotide probes for SRB in parallel. Chemical concentration profiles within the biofilm were also measured using microelectrodes for O2, S2-, NO3- and pH. In situ hybridization revealed that the SRB probe-stained cells were distributed throughout the biofilm even in the oxic surface zone in all states from single scattered cells to clustered cells. The higher fluorescence intensity and abundance of SRB probe-stained cells were found in the middle part of the biofilm. This result corresponded well with O2 and H2S concentration profiles measured by microelectrodes, showing sulfate reduction was restricted to a narrow anaerobic zone located about 500 μm below the biofilm surface. Results of the MPN and potential sulfate reducing activity (culture-dependent approaches) indicated a similar distribution of cultivable SRB in the biofilm. The majority of the general SRB probe-stained cells were hybridized with SRB 660 probe, suggesting that one important member of the SRB in the wastewater biofilm could be the genus Desulfobulbus. An addition of nitrate forced the sulfate reduction zone deeper in the biofilm and reduced the specific sulfate reduction rate as well. The sulfate reduction zone was consequently separated from O2 and NO3- respiration zones. Anaerobic H2S oxidation with NO3- was also induced by addition of nitrate to the medium.
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Santegoeds, Cecilia M., Timothy G. Ferdelman, Gerard Muyzer, and Dirk de Beer. "Structural and Functional Dynamics of Sulfate-Reducing Populations in Bacterial Biofilms." Applied and Environmental Microbiology 64, no. 10 (October 1, 1998): 3731–39. http://dx.doi.org/10.1128/aem.64.10.3731-3739.1998.
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ABSTRACT We describe the combined application of microsensors and molecular techniques to investigate the development of sulfate reduction and of sulfate-reducing bacterial populations in an aerobic bacterial biofilm. Microsensor measurements for oxygen showed that anaerobic zones developed in the biofilm within 1 week and that oxygen was depleted in the top 200 to 400 μm during all stages of biofilm development. Sulfate reduction was first detected after 6 weeks of growth, although favorable conditions for growth of sulfate-reducing bacteria (SRB) were present from the first week. In situ hybridization with a 16S rRNA probe for SRB revealed that sulfate reducers were present in high numbers (approximately 108 SRB/ml) in all stages of development, both in the oxic and anoxic zones of the biofilm. Denaturing gradient gel electrophoresis (DGGE) showed that the genetic diversity of the microbial community increased during the development of the biofilm. Hybridization analysis of the DGGE profiles with taxon-specific oligonucleotide probes showed thatDesulfobulbus and Desulfovibrio were the main sulfate-reducing bacteria in all biofilm samples as well as in the bulk activated sludge. However, different Desulfobulbus andDesulfovibrio species were found in the 6th and 8th weeks of incubation, respectively, coinciding with the development of sulfate reduction. Our data indicate that not all SRB detected by molecular analysis were sulfidogenically active in the biofilm.
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Canfield, Don E., Beate Kraft, Carolin R. Löscher, Richard A. Boyle, Bo Thamdrup, and Frank J. Stewart. "The regulation of oxygen to low concentrations in marine oxygen-minimum zones." Journal of Marine Research 77, no. 3 (May 1, 2019): 297–324. http://dx.doi.org/10.1357/002224019828410548.
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The Bay of Bengal hosts persistent, measurable, but sub-micromolar, concentrations of oxygen in its oxygen-minimum zone (OMZ). Such low-oxygen conditions are not necessarily rare in the global ocean and seem also to characterize the OMZ of the Pescadero Basin in the Gulf of California, as well as the outer edges of otherwise anoxic OMZs, such as can be found, for example, in the Eastern Tropical North Pacific. We show here that biological controls on oxygen consumption are required to allow the semistable persistence of low-oxygen conditions in OMZ settings; otherwise, only small changes in physical mixing or rates of primary production would drive the OMZ between anoxic and oxic states with potentially large swings in oxygen concentration. We propose that two controls are active: an oxygen-dependent control on oxygen respiration and an oxygen inhibition of denitrification. These controls, working alone and together, can generate low-oxygen concentrations over a wide variability in ocean mixing parameters. More broadly, we discuss the oxygen regulation of organic matter cycling and N2 production in OMZ settings. Modern biogeochemical models of nitrogen and oxygen cycling in OMZ settings do contain some of the parameterizations that we explore here. However, these models have not been applied to understanding the persistence of low, but measurable, concentrations of oxygen in settings like the Bay of Bengal, nor have they been applied to understanding what biological/physical processes control the transition from a weakly oxygenated state to a “functionally” anoxic state with implications for nitrogen cycling. Therefore, we believe that the approach here illuminates the relationship between oxygen and the biogeochemical cycling of carbon and nitrogen in settings like the Bay of Bengal. Furthermore, we believe that our results could further inform large-scale ocean models seeking to explore how global warming might influence the spread of low-oxygen waters, influencing the cycles of oxygen, carbon, and nitrogen in OMZ settings.
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Löscher, C. R., H. W. Bange, R. A. Schmitz, C. M. Callbeck, A. Engel, H. Hauss, T. Kanzow, et al. "Water column biogeochemistry of oxygen minimum zones in the eastern tropical North Atlantic and eastern tropical South Pacific Oceans." Biogeosciences Discussions 12, no. 6 (March 17, 2015): 4495–556. http://dx.doi.org/10.5194/bgd-12-4495-2015.
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Abstract. Recent modeling results suggest that oceanic oxygen levels will decrease significantly over the next decades to centuries in response to climate change and altered ocean circulation. Hence the future ocean may experience major shifts in nutrient cycling triggered by the expansion and intensification of tropical oxygen minimum zones (OMZs). There are numerous feedbacks between oxygen concentrations, nutrient cycling and biological productivity; however, existing knowledge is insufficient to understand physical, chemical and biological interactions in order to adequately assess past and potential future changes. We investigated the pelagic biogeochemistry of OMZs in the eastern tropical North Atlantic and eastern tropical South Pacific during a series of cruise expeditions and mesocosm studies. The following summarizes the current state of research on the influence of low environmental oxygen conditions on marine biota, viruses, organic matter formation and remineralization with a particular focus on the nitrogen cycle in OMZ regions. The impact of sulfidic events on water column biogeochemistry, originating from a specific microbial community capable of highly efficient carbon fixation, nitrogen turnover and N2O production is further discussed. Based on our findings, an important role of sinking particulate organic matter in controlling the nutrient stochiometry of the water column is suggested. These particles can enhance degradation processes in OMZ waters by acting as microniches, with sharp gradients enabling different processes to happen in close vicinity, thus altering the interpretation of oxic and anoxic environments.
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Lachkar, Zouhair, Marina Lévy, and Shafer Smith. "Intensification and deepening of the Arabian Sea oxygen minimum zone in response to increase in Indian monsoon wind intensity." Biogeosciences 15, no. 1 (January 10, 2018): 159–86. http://dx.doi.org/10.5194/bg-15-159-2018.
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Abstract. The decline in oxygen supply to the ocean associated with global warming is expected to expand oxygen minimum zones (OMZs). This global trend can be attenuated or amplified by regional processes. In the Arabian Sea, the world's thickest OMZ is highly vulnerable to changes in the Indian monsoon wind. Evidence from paleo-records and future climate projections indicates strong variations of the Indian monsoon wind intensity over climatic timescales. Yet, the response of the OMZ to these wind changes remains poorly understood and its amplitude and timescale unexplored. Here, we investigate the impacts of perturbations in Indian monsoon wind intensity (from −50 to +50 %) on the size and intensity of the Arabian Sea OMZ, and examine the biogeochemical and ecological implications of these changes. To this end, we conducted a series of eddy-resolving simulations of the Arabian Sea using the Regional Ocean Modeling System (ROMS) coupled to a nitrogen-based nutrient–phytoplankton–zooplankton–detritus (NPZD) ecosystem model that includes a representation of the O2 cycle. We show that the Arabian Sea productivity increases and its OMZ expands and deepens in response to monsoon wind intensification. These responses are dominated by the perturbation of the summer monsoon wind, whereas the changes in the winter monsoon wind play a secondary role. While the productivity responds quickly and nearly linearly to wind increase (i.e., on a timescale of years), the OMZ response is much slower (i.e., a timescale of decades). Our analysis reveals that the OMZ expansion at depth is driven by increased oxygen biological consumption, whereas its surface weakening is induced by increased ventilation. The enhanced ventilation favors episodic intrusions of oxic waters in the lower epipelagic zone (100–200 m) of the western and central Arabian Sea, leading to intermittent expansions of marine habitats and a more frequent alternation of hypoxic and oxic conditions there. The increased productivity and deepening of the OMZ also lead to a strong intensification of denitrification at depth, resulting in a substantial amplification of fixed nitrogen depletion in the Arabian Sea. We conclude that changes in the Indian monsoon can affect, on longer timescales, the large-scale biogeochemical cycles of nitrogen and carbon, with a positive feedback on climate change in the case of stronger winds. Additional potential changes in large-scale ocean ventilation and stratification may affect the sensitivity of the Arabian Sea OMZ to monsoon intensification.
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Chang, Hsuan-Fang, Wei-Chin Chang, Shun-Hsing Chuang, and Ya-Lan Fang. "Comparison of polyhydroxyalkanoates production by activated sludges from anaerobic and oxic zones of an enhanced biological phosphorus removal system: effect of sludge retention time." Bioresource Technology 102, no. 9 (May 2011): 5473–78. http://dx.doi.org/10.1016/j.biortech.2010.10.097.
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Aldilla Fajri, Joni, Tomonari Fujisawa, Yenni Trianda, Yasushi Ishiguro, Guangyu Cui, Fusheng Li, and Toshiro Yamada. "Effect of Aeration Rates on Removals of Organic Carbon and Nitrogen in Small Onsite Wastewater Treatment System (Johkasou)." MATEC Web of Conferences 147 (2018): 04008. http://dx.doi.org/10.1051/matecconf/201814704008.
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Onsite application of oxygen supply in domestic wastewater system may be influenced by several factors that can inhibit the oxidation and nitrification processes. In this study, the influence of aeration rate on the Johkasou performance was focused using two Johkasou facilities serving up to five persons household. In the Johkasou A (JO-A) system, we increased the aeration rate from 30 to 63 L.min-1 whereas, in the Johkasou B (JO-B), it was decreased from 59 to 34 L.min-1. Water and sludge samples were collected from the anaerobic-anoxic-oxic zones before and after adjustment of the aeration rate measured for organic matters and nitrogen parameters. Increasing the aeration rate in JO-A resulted in a high removal of organic matter (82.5%) and nitrogen (60.3%) compared to decreasing of aeration rate in JO-B (52.0% and 33.0%, respectively). Simultaneous nitrification and denitrification (SND) exhibited a maximum percentage when the aeration rate was increased compared to decreasing of aeration rate. These results indicate that application of a high aeration rate increases removal of organic matter and nitrogen and enhances ammonia transformation. It is therefore recommended to apply high aeration rates in Johkasou system.
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Findlay, Alyssa J., Alexa J. Bennett, Thomas E. Hanson, and George W. Luther. "Light-Dependent Sulfide Oxidation in the Anoxic Zone of the Chesapeake Bay Can Be Explained by Small Populations of Phototrophic Bacteria." Applied and Environmental Microbiology 81, no. 21 (August 21, 2015): 7560–69. http://dx.doi.org/10.1128/aem.02062-15.
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ABSTRACTMicrobial sulfide oxidation in aquatic environments is an important ecosystem process, as sulfide is potently toxic to aerobic organisms. Sulfide oxidation in anoxic waters can prevent the efflux of sulfide to aerobic water masses, thus mitigating toxicity. The contribution of phototrophic sulfide-oxidizing bacteria to anaerobic sulfide oxidation in the Chesapeake Bay and the redox chemistry of the stratified water column were investigated in the summers of 2011 to 2014. In 2011 and 2013, phototrophic sulfide-oxidizing bacteria closely related toProsthecochlorisspecies of the phylumChlorobiwere cultivated from waters sampled at and below the oxic-anoxic interface, where measured light penetration was sufficient to support populations of low-light-adapted photosynthetic bacteria. In 2012, 2013, and 2014, light-dependent sulfide loss was observed in freshly collected water column samples. In these samples, extremely low light levels caused 2- to 10-fold increases in the sulfide uptake rate over the sulfide uptake rate under dark conditions. An enrichment, CB11, dominated byProsthecochlorisspecies, oxidized sulfide with aKsvalue of 11 μM and aVmaxvalue of 51 μM min−1(mg protein−1). Using these kinetic values within situsulfide concentrations and light fluxes, we calculated that a small population ofChlorobisimilar to those in enrichment CB11 can account for the observed anaerobic light-dependent sulfide consumption activity in natural water samples. We conclude thatChlorobiplay a far larger role in the Chesapeake Bay than currently appreciated. This result has potential implications for coastal anoxic waters and expanding oxygen-minimum zones as they begin to impinge on the photic zone.