Academic literature on the topic 'Oxic zones'
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Journal articles on the topic "Oxic zones"
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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.
Dissertations / Theses on the topic "Oxic zones"
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Trouwborst, Robert Elisa. "Geochemistry of manganese and iron across both stable and dynamic natural oxic-anoxic transition zones." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.64 Mb., 177 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3200548.
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Conway, Carol Leza, and n/a. "Oxic and anoxic transformations of leaf derived organic matter in freshwater systems." University of Canberra. Resource, Environmental & Heritage Sciences, 2005. http://erl.canberra.edu.au./public/adt-AUC20060519.105559.
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In Australia, significant effort goes into reducing the amount of nitrogen and phosphorus
entering inland waters from point sources. However, little is known of the extent to
which riparian organic matter may act as a source of these nutrients. Also, whilst the relationships
between the nitrogen, phosphorus and carbon cycles are broadly known, there
is little quantitative data regarding the release of these elements from Australian riparian
organic matter and their subsequent microbial mineralisation within aquatic environments.
In particular, comparatively little is known of their comparative role in nutrient and organic
matter cycling within anoxic zones, and the influence that different riparian organic matter
may have on stream water quality. This lack of such data presently hampers the ability of
water managers to make educated decisions regarding the management of riparian zones
in Australia. In order to improve understanding in this area, a combination of laboratory
and in situ experiments were carried out in order to compare the abiotic release and aerobic/
anaerobic mineralisation of leaf derived dissolved organic carbon (DOC), dissolved
nitrate/nitrite (NOx) and soluble reactive phosphorus (SRP) under different environmental
conditions. Four plants common to Australian riparian zones were investigated: two native
species, Eucalyptus camaldulensis (gum) and Phragmites australis (common reed), and
two exotic species, Salix babylonica (willow) and Lolium multiflorum (rye grass). After 30
days, formaldehyde inhibited 1g willow and rye grass extracts contained the most SRP (0.7
mg/L), whilst gum extracts contained 0.3 mg/L and common reed 0.1 mg/L of SRP.Willow
and rye grass abiotically released twice as much NOx than gum and common reed, although
concentrations were only between 0.05-0.1 mg/L. Gum and common reed released the most
DOC per gram of leaf matter (14 and 12 mmol/g of leaf matter respectively), but based on
the initial carbon content of each leaf type, the largest percentage contributor of DOC under
abiotic conditions was common reed and rye grass (both 38% mass/mass), with gum (33%
mass/mass) and willow (30% mass/mass) being smaller contributors. The most bioavailable
DOC was released by rye grass and common reed, with between 83 and 94% of this
DOC microbially mineralised after 30 days in oxic conditions. When conditions were not
inhibited, microbial growth was evident almost immediately in willow, rye grass and common
reed leaf extracts. However, microbial growth was suppressed for the first 48 hours
in gum leaf extracts. After this suppression period, the rate of DOC mineralisation was
equal in willow and gum leaf extracts (0.1 day-1). Under anoxic conditions, the rate and
extent of DOC mineralisation of willow and gum leaves depended on the type of electron
acceptor provided. Added nitrate and iron III enhanced the mineralisation of both willow
and gum leaves relative to no terminal electron acceptors (from zero to 0.01-0.04 and 0.002-
0.004 moles/day respectively), but added sulphate only enhanced the mineralisation of gum
leaves (0.04 moles/day). When no additional electron acceptors were provided, particulate
leaf mineralisation was more extensive under oxic than anoxic conditions. However, the
mineralisation of leaf derived DOC were the same regardless of oxygen availability, and
after 35 days in either condition the percentage of leaf DOC mineralised for each leaf type
was of the order common reed > rye grass > willow > gum. All the leaf types tested were
able to sustain the caddis fly larvae Triplectides australis under controlled laboratory conditions,
and survival rates were high using all four leaf types as a food source. Triplectides
australis did not significantly increase the amount of DOC released from each type of leaf
matter, but they did consistently increase the proportion of simple carbohydrates present
within the DOC fraction. The results of these experiments suggest that changes to riparian
vegetation, particularly from the native to exotic species used in this study, will inherently
alter in-stream concentrations of dissolved carbon and nutrients (particularly SRP). This
potentially will affect in-stream, hyporheic and subsurface processes, particularly in areas
where surface water flow is low and riparian leaf inputs are high.
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Montes-Herrera, Enrique. "Seasonal Changes in the Sinking Particulate Flux and in the Nitrogen Cycle within the Euphotic and Twilight Zones of the Cariaco Basin, Venezuela." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3253.
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This study explored the effects of seasonal variability on the geochemistry of sinking pthesiss and on the nitrogen cycle of the Cariaco Basin. Pthesis fluxes were measured at the base of the euphotic zone (the depth of 1% of photosynthetically active radiation - PAR) with drifting sediment traps during months of upwelling and non-upwelling regimes from March 2007 to November 2009. Flux estimates were analyzed in the context of seasonal variations in sea surface temperature, primary productivity, and chlorophyll a concentrations using data generated by the CARIACO Time-series Program as well as satellite data. Additionally, nine years (1996-2000 and 2004-2007) of nutrients, phytoplankton taxonomy and δ15N of sinking pthesis data within the twilight zone (225 m) from the CARIACO Time-series Program were examined. Results showed that the flux of organic matter responded to changes in surface chlorophyll a but not to primary production. Sinking organic matter decreased by an order of magnitude from the base of the euphotic zone to the oxic-anoxic interface; most of the organic matter produced in surface waters was remineralized before leaving the upper 50-100 m. Lithogenic material often represented a large fraction of the flux. Isotopic analyses showed that 13C/12C ratios of sinking organic carbon were enriched (~-19‰) during the upwelling period and depleted during relaxation (~-23‰). This reflects seasonal changes in inorganic carbon utilization by phytoplankton and suggests that the δ13C of organic carbon in Cariaco sediments can be used as a proxy for carbon fixation by primary producers. The δ15N of the settling flux was influenced by the strength of the upwelling and the presence of the nitrogen fixer Trichodesmium thiebautii in the basin in different seasons; the 15N/14N ratio of sinking nitrogen reflects both imported and local nitrogen fixation signals. This result argues against previous interpretations of the δ15N from the basin's sedimentary record, which suggested that the nitrogen isotopic composition of flux is influenced by denitrification at the oxic-anoxic interface.
Dissolved gas samples from the Cariaco eastern and western sub-basins from September 2008 (non-upwelling) and March 2009 (upwelling) were studied to assess the production of biogenic nitrogen gas through mass spectrometric N2/Ar ratiometry. Excess nitrogen gas indicated that upwelling affects the intensity of denitrification at the oxic-anoxic interface. In four of the six stations the concentration of biogenic nitrogen gas at the oxic-anoxic interface was 2.7-6.1 µM N higher during the upwelling period than during the relaxation season (p< 0.001), implying that denitrification in the basin was stimulated by the vertical flux of organic matter and/or the ventilation of the oxic-anoxic interface by oxygenated and nutrient-rich intermediate Caribbean waters.
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Terrisse, Fanny. "Influence des oscillations anoxie/oxie sur des communautés microbiennes hydrocarbonoclastes de sédiments intertidaux." Thesis, Pau, 2014. http://www.theses.fr/2014PAUU3056/document.
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Les écosystèmes côtiers sont des milieux complexes au sein desquels les communautés microbiennes, jouant un rôle majeur dans leur fonctionnement et leur maintien, s’adaptent et sont tolérantes à des conditions environnementales fluctuantes. En effet, au rythme des marées et de l'activité de la macrofaune, des oscillations oxie/anoxie influencent la composition et la dynamique des communautés microbiennes et par conséquent leur implication métabolique. Afin d’appréhender le devenir du pétrole dans ces écosystèmes, il est donc indispensable d’apporter des connaissances sur l’écologie des microorganismes intervenant dans son élimination, notamment dans des conditions oscillantes anoxie/oxie. Ainsi, ce travail de thèse a eu pour objectif de décrypter l’assemblage de communautés microbiennes hydrocarbonoclastesde sédiments intertidaux soumises à des oscillations anoxie/oxie en présence de pétrole lors d’une expérience en bioréacteurs. Les réponses écologiques des communautés bactériennes globales et de micro-organismes sulfato-réducteurs en conditions oscillantes ont pu être décrites en comparaison avec celles obtenues en conditions d’oxie ou d’anoxie permanentes, par l’analyse des données obtenues par séquençage haut-débit des gènes de l’ARN 16S et dsrB au niveau transcriptionnel. Ces études comparatives ont mis en évidence des profils écologiques en réponseaux conditions oscillantes, pouvant être répandus dans différents environnements marins côtiers. En réponse à ces conditions particulières, de nombreux microorganismes semblent avoir le potentiel à tolérer et/ou s’adapter aux différentes conditions d'oxygénation. Cette capacité d’acclimatation rapide des communautés bactériennes aux conditions oscillantes se sont accompagnées de capacités de dégradation équivalentes ou supérieures dans ces conditions par rapport à la condition d’oxie permanente montrant l’influence des oscillations anoxie/oxie sur le devenir du polluant dans les environnements pollués soumis à ces conditionsCoastal ecosystems are complex environments in which microbial communities, playing a major role in their functioning and maintain, are tolerant and adapt to changing environmental conditions. Indeed, the tides and the macrofauna’s activity generate oxic/anoxic oscillations which influence the composition and dynamics of microbial communities and consequently their metabolic in volvement. To understand the fate of oil in these ecosystems, it is essential to provide knowledge on the ecology of microorganisms involved in these systems, taking into account anoxic/oxicoscillating conditions. Thus, this thesis aimed to decipher the organization of hydrocarbonoclastic microbial communities inhabiting intertidal sediments, when they are subjected to anoxic/oxic oscillations in an experiment in bioreactors with oil addition. Ecological responses of bacterial communities and sulfate-reducing microorganisms in oscillating conditions have been described comparing with those obtained with permanent oxic or anoxic conditions, using high-throughputsequencing analyses of the 16S rRNA and dsrB genes at the transcriptional level. These comparatives studies have highlighted ecological profiles in response to the oscillating conditions, which can be prevalent in different coastal marine environments. In response to these particular conditions, many organisms seem to have the potential to tolerate and / or adapt to the different conditions of oxygenation. This rapid acclimation capacity of bacterial communities tothese changing conditions have been accompanied by equivalent or greater degradation capacity under these conditions compared to the permanent oxic condition, showing the influence of the anoxic/oxic oscillations on the fate of pollutant in environments subjected tothese conditions
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Souptel, Dmitri. "Crystal growth and perfection of selected intermetallic and oxide compounds." Doctoral thesis, [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=973879408.
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Souptel, Dmitri. "Crystal growth and perfection of selected intermetallic and oxide compounds." Doctoral thesis, Technische Universität Dresden, 2004. https://tud.qucosa.de/id/qucosa%3A24461.
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The aim of the present work is to clarify the interplay between the complex technological chain of crystal preparation, chemical and structural perfection of grown crystals of intermetallic compounds and oxides and their physical properties. This technological chain includes detailed studies of unknown or insufficiently known phase diagrams, their correlation with growth conditions and optimisation of process parameters for obtaining single crystals with high chemical and physical perfection. The measurements of the physical properties of the grown crystals such as superconductivity, thermoelectric or dielectric properties not only show new features and properties for application of the materials obtained, but also allow conclusions of the crystal perfection. The studies are focused on the following systems: RENi2B2C borocarbides (RE=Y, Tb or Ho) displaying superconductivity, magnetic order and a strong interplay between magnetic and superconducting properties for YNi2B2C, TbNi2B2C, HoNi2B2C, respectively; CeSi2-?Ô and Ru2Si3 as examples of systems with magnetic and promising thermoelectric properties, respectively; MgB2 and LiBC to test of theoretical predictions of the new superconducting intermetallic compounds discovered in the last years; SrTiO3 and SrZrO3 oxide compounds with special dielectric and optical properties. For this wide spectrum of substances necessarily different growth techniques were applied. That is mainly the floating zone (FZ) or travelling solvent floating zone (TSFZ) techniques with optical heating. Flux techniques were used if the vapour pressure of composing elements is high such as for Mg and Li. The crucible free FZ technique is very attractive for the crystal growth of these intermetallic and oxide compounds to avoid contamination with the crucible material, if the melts have very high chemical reactivity, high melting temperatures and if a large crystal size (at least 3-5 mm) is desired for corresponding physical measurements. One special aim in the presented work is the optimisation of the preparation and growth process features with respect to crystal perfection, establishing new relationships between process parameters, crystal perfection, crystallographic structure, composition of grown crystals and the related physical properties. Optimisation of crystal growth process requires own constitutional studies of growth relevant parts of corresponding multicomponent phase diagrams. Therefore, parts of the phase diagrams were experimentally revealed by differential thermal analysis (DTA), optical metallography and EPMA and partially combined with CALPHAD calculations.
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Chang, Fang-Wen, and 張芳文. "By Use of Anoxic/Oxic Treatment System to Remove Ammonium Nitrogen from Industrial Zone Wastewater." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/6gtrq5.
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碩士龍華科技大學
化工與材料工程系碩士班
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Ammonia nitrogen refers to the compound in the form of free ammonia (NH3) and nitrogen ion (NH4+). When excess ammonia nitrogen is discharged into the water body, the water body will be eutrophicated and the ornamental value of the water body will be reduced. The ammonia nitrogen will dissolve dissolved oxygen in the water during the nitrification process. In addition to the deterioration of water quality, the formation of nitrates and nitrites can also affect the growth of aquatic organisms and even human health. This study is aimed at the wastewater from an industrial wastewater treatment plant, using AO: Anoxic/Oxic method to remove ammonia nitrogen from wastewater, data collection, water quality testing, field operation observation and adjustment analysis, etc. , comprehensively explore the processing effect of the AO system. From this study, it is known that there is no significant correlation between ammonia and nitrogen removal efficiency when pH is between 6 and 9. Dissolved oxygen (DO) has a highly positive correlation with total nitrogen/ammonia nitrogen removal rate, and wastewater water temperature is in the range of 10 to 35 °C. Does not directly affect the total nitrogen / ammonia nitrogen removal rate. After analyzing the data of pH, chemical oxygen demand (COD), suspended solids (SS), biochemical oxygen demand (BOD5), ammonia nitrogen (NH3-N), etc., it can be used as a wastewater treatment plant efficiency evaluation. The basic parameters and the improvement of the failure assessment of the sampling points are based on the improvement of the ammonia nitrogen removal efficiency of the AO treatment program under normal conditions by more than 90%.
Book chapters on the topic "Oxic zones"
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Bazylinski, Dennis A., Christopher T. Lefèvre, and Richard B. Frankel. "Magnetotactic Protists at the Oxic–Anoxic Transition Zones of Coastal Aquatic Environments." In Cellular Origin, Life in Extreme Habitats and Astrobiology, 131–43. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-1896-8_7.
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Gaines, Susan M., Geoffrey Eglinton, and Jürgen Rullkötter. "Weird Molecules, Inconceivable Microbes, and Unlikely Environmental Proxies: Marine Ecology Revised." In Echoes of Life. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780195176193.003.0014.
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Anaerobic methanotrophs are not the only ecologically important archaea to surprise microbiologists in the last decade. And their isoprenoid ethers are not the only useful lipids—and certainly not the strangest—to have joined the lexicon of microbial biomarkers. Though much of that lexicon is still too generic to be of much use in understanding geologic history, some of these structures have allowed geochemists to transcend biological complexity and garner clues to past climates and environments. In the 1990s, when Stefan Schouten first started finding ring-containing biphytanyl ethers in his sediment samples, he was still working on his doctorate at NIOZ. Like everyone else at the time, he assumed that they derived from the lipids of methanogenic archaea and that it was only a matter of time before ring-containing biphytanyl tetraethers would be identified among the lipids of some newly isolated culture of methanogens, as Guy Ourisson had predicted. Schouten was studying oxygen- and sulfur-bound biomarkers, which meant he treated his sediment extracts chemically to cleave the ether and sulfur bonds, and the treatments often turned up biphytanes. But then, he says, he and another student started finding the ring-containing compounds in some really unlikely places, such as the oxic surface layer of marine sediments where neither methanogens nor extreme thermophilic and halophilic archaea were likely to make a home. The only thing they could think of at the time was that the tetraethers had come from methanogens that lived in the oxygen minimum zone, the layer of water beneath the photic zone where heterotrophic bacteria are active, sometimes to the point of using up all of the oxygen. When Schouten presented these ideas at the 1995 organic geochemistry meeting, Stuart Wakeham immediately piped up with the suggestion that they look for the lipids in the water column—and offered the perfect samples for the enterprise. He had collected particulate matter at different depths in the Black Sea and Cariaco Basin, just the sort of anoxic environments where one might expect to find methanogens in the water column. . . .
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Hallam, Tony. "Oxygen deficiency in the oceans." In Catastrophes and Lesser Calamities. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780198524977.003.0009.
Full textAbstract:
We are all very much aware that oxygen deprivation leads quickly to death, and this is true not just of our own species but of virtually the whole organic world. There are indeed very few exceptions, such as the anaerobic bacteria that derive their energy from reducing sulphates to sulphides, which flourish in the absence of free oxygen. (As these organisms do not leave a fossil record they provide no clues for the geological detective.) Today the atmosphere never lacks oxygen, except in artificially enclosed conditions, but oxygen deficiency can be lethal in certain marine environments and thus must be explored as a possible factor in causing mass extinctions. Mixing with atmospheric winds ensures that the surface waters of the ocean, down to the greatest depth attained by storm waves, always contain plenty of oxygen. Most of the oceans and marginal seas today contain oxygen throughout their depth, but in certain circumstances an oxygen deficiency can occur in the lower parts of the ocean. In parts of some tropical oceans, for instance, the oxygen content decreases with depth until near the ocean bottom, where under the influence of currents driven by cold water from around Antarctica, the oxygen content increases again. This gives rise to a zone in the ocean known as the oxygen minimum zone. The rapid deep ocean circulation is today driven ultimately by the presence of polar ice on Antarctica, which is the main cause of the strong sea-water temperature gradient from the tropics to the poles. For long periods in the Earth’s history substantial polar ice caps were lacking, and many geologists believe that during those periods latitudinal ocean currents were more sluggish. The deep ocean must then have been largely deficient in oxygen, if not completely lacking in oxygen (anoxic). (Sea water with a content of one or more millilitres of oxygen per litre of water is called oxic; 0.1 ml or less is anoxic; and for any intermediate value the water is dysoxic.) Certain parts of the sea bed where the overlying water is deficient in oxygen are enriched in organic matter derived principally from the plankton.