Oxygen Concentration In Sea Water Research Articles

Aerobic and anaerobic biodegradation of synthetic drilling fluids in marine deep-water offshore environments: Process variables and empirical investigations

In this study, the aerobic and anaerobic biodegradation tendencies of a newly developed synthetic ester drilling fluid named “SEEP Mixture synthetic fluid” in marine deep-water environment were experimentally studied. The results were compared with a GTL and LASF synthetic hydrocarbon fluids. A modified Oxygen (O2) Consumption and a gas pressure measurement technique were used for biodegradation evaluation in the aerobic and anaerobic digesters respectively. The tested drilling fluids were exposed to the sea water inoculum for a period of 28 and 60 days in the different digester designs. An empirical investigation of the influence of some paramount biodegradation factors among others such as reaction temperature, dissolved oxygen concentration, time, chemical and inoculum concentrations was conducted.The biodegradation levels in SEEP mixture synthetic fluid and reference chemical sample were already above 60% during the 10-day window period under aerobic condition which shows that the new ester fluid (SEEP mixture) is inherently-readily biodegradable under aerobic condition. The ultimate biodegradability degrees of the new fluid were 81.50% and 76.10 % in aerobic and anaerobic pathways respectively. The rates of biodegradation were higher in the aerobic than in anaerobic medium in all the tested fluid chemicals. However, the GTL and LASF fluids (SHBF & SEBF) were not readily biodegradable in both microbial consortia. The rate of aerobic and anaerobic biodegradation has a positive linear relationship with incubation time and temperature but an inverse relationship with substrate concentration. Finally, Lower oxygen concentration in sea water reduces aerobic biodegradation while anaerobic transformation is grossly dependent on the availability of alternative electron acceptor ions such as NO3−, SO42−, Fe3＋ Mn4+, and CO32− and methanogens in the sea water.

Dual‐Gate Organic Electrochemical Transistors for Marine Sensing

AbstractMonitoring dissolved oxygen is essential to marine research, but the high redox potentials required to drive sensing reactions have posed an ongoing instability issue in the sensors. Here, a novel dual‐gate configuration for organic electrochemical transistors that extends the device electrochemical stability window is demonstrated. This paper presents the sensor operating principle that relates the channel conductance to potentials on the two gates. This broadly applicable design allows a large potential to be applied between the gates for sensing analytes, while synergistically modulating the channel within a lower potential range to maintain the stability of the semiconductor. Specifically, the sensor achieves a detection limit of 0.3 ppm dissolved oxygen concentration in seawater, with a sensitivity of 222 µA cm−2 ppm−1 for concentrations below 5 ppm. The device demonstrates reliable operation over 5 days and is capable of monitoring oxygenation changes arising from the photosynthesis cycles of saltwater macro‐algae. This dual‐gate configuration serves to extend the sensor operating voltage window and improves device stability. Thus, this new configuration provides a new type of compact, robust sensor for marine research, and opportunities in other fields ranging from waste‐water management to bioelectronics.

Morphometric parameters of erythroid hemocytes of alien mollusc <i>Anadara kagoshimensis </i>(Bivalvia, Arcidae) under normoxia and anoxia

In the present work we investigated the influence of three days anoxia on hematological parameters, morphological and functional characteristics of eryhroid cells of alien bivalve Anadara kagoshimensis . Oxygen concentration in seawater was decreased by bubbling with nitrogen gas for 5 h. Temperature was maintained at 20±1oC and photoperiod was 12h day: 12h night. Extrapallial fluids were sampled by a puncture of extrapalial cavity. Three-day exposure to anoxia caused pronounced cellular responses. At the organismic level changes were not observed, as hemoglobin concentration the total number of erythroid cells and mean hemoglobin concentration ( МСН ) remained at the level of normoxia. We observed an increase of cellular anomalies, i.e. shistocytes and erythroid cells with polymorphic nuclei, and cells undergoing reactive amitotic division, which resulted in formation of binuclear cells. Nuclear volume ( V ) increased for more than 40 % compared to control level. This increase depended on the duration of anoxia. Changes in cellular volume ( V ) possessed a complicated manner. At the end of experimental period (3rd day of anoxia) nucleo- cytoplasmic ratio was 36% lower comparing to normoxia. Exposure to anoxia did not cause mortality of erythroid cells. The number or red blood cell shades observed on slides remained at control level.

A model for monitoring the evolution of the Black Sea ecosystem on the basis of remote sensing data assimilation

ABSTRACTThe study presents some results of the Black Sea ecosystem dynamics during about twenty years (1998–2016), based on numerical simulations with the assimilation of remote-sensing data. The 3D model of the lower trophic level marine ecosystem is a one-way, off-line coupled with circulation model. It describes processes in the layer from the sea surface to 200 m depth and includes 15 state variables. The ecosystem model assimilates the satellite measurements which are the maps of the surface chlorophyll concentration fields reconstructed based on the remote-sensing data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS, satellite OrbView) and Moderate Resolution Imaging Spectroradiometer (MODIS, satellites Aqua and Terra) using the regional optical model of the Black Sea. The assimilation technique is based on optimal interpolation and nudging procedure. The results of the simulation were validated using the Black Sea Oceanographic Database, which contains the direct measurements of chlorophyll, nitrates, and dissolved oxygen concentrations in seawater. Comparison of the simulation data with measurements showed that the simulated fields satisfactorily reproduce seasonal variability and vertical distribution. In addition to in situ measurements, the obtained surface chlorophyll distributions were also compared with the satellite data. The simulation results allowed analysing the inter-annual and seasonal variability of the main parameters of the Black Sea pelagic ecosystem. Evolution of the plankton biomass in the upper 50 m layer shows a negative linear trend, which is followed by reduction of the nitrates content in this layer.

Alternative mitochondrial respiratory chains from two crustaceans: Artemia franciscana nauplii and the white shrimp, Litopenaeus vannamei

Mitochondrial ATP is synthesized by coupling between the electron transport chain and complex V. In contrast, physiological uncoupling of these processes allows mitochondria to consume oxygen at high rates without ATP synthesis. Such uncoupling mechanisms prevent reactive oxygen species overproduction. One of these mechanisms are the alternative redox enzymes from the mitochondrial respiratory chain, which may help cells to maintain homeostasis under stress independently of ATP synthesis. To date, no reports have been published on alternative redox enzymes in crustaceans mitochondria. Specific inhibitors were used to identify alternative redox enzymes in mitochondria isolated from Artemia franciscana nauplii, and the white shrimp, Litopenaeus vannamei. We report the presence of two alternative redox enzymes in the respiratory chain of A. franciscana nauplii, whose isolated mitochondria used glycerol-3-phosphate as a substrate, suggesting the existence of a glycerol-3-phosphate dehydrogenase. In addition, cyanide and octyl-gallate were necessary to fully inhibit this species' mitochondrial oxygen consumption, suggesting an alternative oxidase is present. The in-gel activity analysis confirmed that additional mitochondrial redox proteins exist in A. franciscana. A mitochondrial glycerol-3-phosphate dehydrogenase oxidase was identified by protein sequencing as part of a branched respiratory chain, and an alternative oxidase was also identified in this species by western blot. These results indicate different adaptive mechanisms from artemia to face environmental challenges related to the changing levels of oxygen concentration in seawater through their life cycles. No alternative redox enzymes were found in shrimp mitochondria, further efforts will determine the existence of an uncoupling mechanism such as uncoupling proteins.

Formation of shallow-water glaucony in weakly oxygenated Precambrian ocean: An example from the Mesoproterozoic Tieling Formation in North China

Authigenic glaucony precipitation in Phanerozoic oceans takes place mostly in middle shelf to upper slope environments with low depositional rate or sediment starvation. Precambrian glaucony, however, is more common in stratigraphic successions deposited from shallower-water environments with high and variable depositional rates. This phenomenon has long been noticed in literature, but the controlling factors of shallow-water glaucony precipitation in Precambrian oceans have not been adequately investigated. To better understand the glauconitization processes in Precambrian oceans, we have conducted an integrated study of the glaucony in stromatolitic carbonates of the Mesoproterozoic Tieling Formation (ca. 1437Ma) in North China, using sedimentological, mineralogical, and geochemical data obtained from field observations, petrography, XRD, SEM, quantitative EDS and ICP-MS analyses. Macro- and microscopic observations show that the Tieling glaucony fills voids of varying sizes and shapes, and records different maturation stages of glauconitization. Geochemical analyses show that the Tieling glaucony has high K2O (avg.>8%) but low and variable total Fe2O3 (TFe2O3) contents (1.92–13.65wt%). The TFe2O3 contents increase with maturation of glaucony. Titration results show that the Tieling glaucony contains both Fe3+ and Fe2+ ions, but has Fe2+/Fe3+ ratios much higher than that of the Phanerozoic glaucony. REE results of glaucony-hosting carbonates show weak negative and positive Ce anomalies with average Ce/Ce∗ ratio close to 1.0, suggesting carbonate precipitation near the redoxcline of Fe-Mn oxides. All these features suggest that the Tieling glaucony was precipitated in seawater around the Fe-redoxcline, where both Fe2+ and Fe3+ were available throughout the glaucony maturation stages. High Fe2+/Fe3+ ratios in the depositional environments led to Fe2+ occupation at octahedral sites of glaucony and negative charges on octahedrons, which resulted in high K content (to balance the negative charges on octahedrons) and low TFe2O3 (limited by dioctahedral structure). The formation of the Tieling glaucony and other similar Precambrian glauconies is likely controlled by low oxygen concentration in seawater and a shallow redoxcline that controls the availability of Fe and K cations during initial precipitation and maturation of glaucony. The shift of authigenic glaucony precipitation from shallow water in the Precambrian to deep water in the Phanerozoic may record the deepening of ocean chemocline in response to increased ocean oxygenation.

Identification of an Archean marine oxygen oasis

The early Earth was essentially anoxic. A number of indicators suggest the presence of oxygenic photosynthesis ∼2700–3000 million years (Ma) ago, but direct evidence for molecular oxygen (O2) in seawater has remained elusive. Here we report rare earth element (REE) analyses of ∼2800 million year old shallow-marine limestones and deep-water iron-rich sediments at Steep Rock Lake, Canada. These show that the seawater from which extensive shallow-water limestones precipitated was oxygenated, whereas the adjacent deeper waters where iron-rich sediments formed were not. We propose that oxygen promoted limestone precipitation by oxidative removal of dissolved ferrous iron species, Fe(II), to insoluble Fe(III) oxyhydroxide, and estimate that at least 10.25μM oxygen concentration in seawater was required to accomplish this at Steep Rock. This agrees with the hypothesis that an ample supply of dissolved Fe(II) in Archean oceans would have hindered limestone formation. There is no direct evidence for the oxygen source at Steep Rock, but organic carbon isotope values and diverse stromatolites in the limestones suggest the presence of cyanobacteria. Our findings support the view that during the Archean significant oxygen levels first developed in protected nutrient-rich shallow marine habitats. They indicate that these environments were spatially restricted, transient, and promoted limestone precipitation. If Archean marine limestones in general reflect localized oxygenic removal of dissolved iron at the margins of otherwise anoxic iron-rich seas, then early oxygen oases are less elusive than has been assumed.

Redox condition during Ediacaran–Cambrian transition in the Lower Yangtze deep water basin, South China: constraints from iron speciation and δ 13Corg in the Diben section, Zhejiang

Cherts of the Piyuancun Formation and black mudstones of the Hetang Formation in Diben Town, Kaihua County, Zhejiang were deposited in a deep water basin of the Lower Yangtze area during the Ediacaran–Cambrian transition (E–C transition), offering an opportunity to reconstruct the ancient redox condition of the deep water basin. Total 53 samples were collected and analyzed for iron speciation, including pyrite iron (FePy), carbonate associated iron (FeCarb), iron oxide and hydroxide (FeOx), magnetite iron (FeMag) and total iron (FeT) as well as δ 13Corg to gain a deeper understanding of specific redox condition during the period. The results show that (1) most samples have pyrite concentration 0.5). (2) The E–C boundary in the Diben section occurred at the maximum negative excursion of organic carbon isotope within the Piyuancun Formation, which can be correlated with other sections by using δ 13Corg. We thus concluded that the relatively high content of highly reactive iron and low content of pyrite iron in the Diben section indicate a minor occurrence of H2S and a predominance of anoxic and ferruginous environment, which is similar to other reported sections such as the Longbizui and Yanwutan sections, western Hunan. In addition, oxygen concentration in sea water showed an increasing trend in the interval corresponding to the bottom and upper layer of the Hetang Formation as indicated by the FeHR/FeT ratio, which decreased from 0.7 to 0.38, however, it was not great enough to oxidize the whole deep water. Therefore, during the E–C transition deep water basin in South China was most likely an anoxic and ferruginous enrironment, which prevented metazoon from the evolution in the deep water basin. Our work offers an important reference to better understanding of the spatiotemporal occurrence and dynamic processes of the “Cambrian Explosion”.

Dispersed air flotation as a pretreatment process for seawater desalination

Pretreatment of seawater before reverse osmosis (RO) processes with dispersed air flotation involves a change in oxygen concentration in seawater. In order to understand this phenomenon, a series of experimental aeration studies was conducted. Aeration tests were performed under different operating conditions of seawater temperature, flow rate of the air and depth of the water in the aeration tank. The experimental results show that the overall mass transfer coefficient increases by increasing air flow rate. A measured increase in the overall mass transfer coefficient was observed with elevation of the temperature from 24 to 38 °C. The estimated value of activation energy of oxygen absorption in seawater is 42.5 kJ/mol. The value of the overall mass transfer coefficient is found to be affected by diffuser type and stirrer speed as these parameters influence the bubble size and the surface area available for mass transfer of oxygen from air bubbles to seawater.

Size-Frequency Distributions along a Latitudinal Gradient in Middle Permian Fusulinoideans

Geographic gradients in body size within and among living species are commonly used to identify controls on the long-term evolution of organism size. However, the persistence of these gradients over evolutionary time remains largely unknown because ancient biogeographic variation in organism size is poorly documented. Middle Permian fusulinoidean foraminifera are ideal for investigating the temporal persistence of geographic gradients in organism size because they were diverse and abundant along a broad range of paleo-latitudes during this interval (∼275–260 million years ago). In this study, we determined the sizes of Middle Permian fusulinoidean fossils from three different paleo-latitudinal zones in order to examine the relationship between the size of foraminifers and regional environment. We recovered the following results: keriothecal fusulinoideans are substantially larger than nonkeriothecal fusulinoideans; fusulinoideans from the equatorial zone are typically larger than those from the north and south transitional zones; neoschwagerinid specimens within a single species are generally larger in the equatorial zone than those in both transitional zones; and the nonkeriothecal fusulinoideans Staffellidae and Schubertellidae have smaller size in the north transitional zone. Fusulinoidean foraminifers differ from most other marine taxa in exhibiting larger sizes closer to the equator, contrary to Bergmann's rule. Meridional variation in seasonality, water temperature, nutrient availability, and carbonate saturation level are all likely to have favored or enabled larger sizes in equatorial regions. Temporal variation in atmospheric oxygen concentrations have been shown to account for temporal variation in fusulinoidean size during Carboniferous and Permian time, but oxygen availability appears unlikely to explain biogeographic variation in fusulinoidean sizes, because dissolved oxygen concentrations in seawater typically increase away from the equator due to declining seawater temperatures. Consequently, our findings highlight the fact that spatial gradients in organism size are not always controlled by the same factors that govern temporal trends within the same clade.

From Krill to Whale: an overview of marine fatty acids and lipid compositions

In this study, fatty acid compositions of phyto-zooplankton (calanoid copepod species, krill…) to fish species (mackerel, sardine anchovy, salmon, shark) are presented. Marine oils are essentially used for their high long-chain polyunsaturated fatty acids (LC-PUFA), namely eicosapentaenoic (EPA) and docosahexaenoic (DHA) for their good health impact. Due to health benefits of the omega-3, weekly fish consumption is today recommended by many authorities (FDA, AFSSA…). Capture fisheries and aquaculture supplied the world with about 110 million tonnes of food fish in 2006 (FAO 2009), providing an apparent per capita supply of 16.7 kg. It is well established that the lipid composition of fish muscle is influenced by the diet and also depends on the effects of environmental factors (temperature, oxygen concentration in sea water) and endogenous medium (physiological state and individual variability). In general, cultured fish have been reported to have a softer texture than wild fish, which has been related to the differences in muscle structure, proximate composition and nutritional value. New applications of typical compounds (wax esters, squalene …) or lipid classes (glycerophospholipids, ether glycerolipids, sphingophospholipids …) as cosmetics, functional foods and dietary supplements will become very important in the near future with nano-structured drug carriers in pharmaceutical and biomedical areas.

Erratum: Fully automated spectrophotometric approach to determine oxygen concentrations in seawater via continuous‐flow analysis

Erratum: Fully automated spectrophotometric approach to determine oxygen concentrations in seawater via continuous‐flow analysis

Fully automated spectrophotometric approach to determine oxygen concentrations in seawater via continuous-flow analysis

Oxygen consumption measurements are the most common approach to estimate the remineralization of organic carbon to CO2. A refined protocol of the spectrophotometric Winkler approach is presented, where a continuous-flow analyzer is coupled with a custom-made autosampler holding up to 30 oxygen bottles. The time required for analysis is 2 min per sample, and the precision is 0.05% at ~200 mmol O2 m−3. Thus, analysis speed and quality are significantly improved compared to the classic Winkler titration approach to determine O2 concentrations. The accuracy of the method is 99.7% ± 0.2% as determined by comparing the measured versus the theoretical oxygen concentration of saturated seawater at 20°C. The measured absorbance of the iodine at 460 nm wavelength was linear up to an equivalent of 320 mmol O2 m−3, which is within the range of open-ocean oxygen concentrations. The instrument was tested on a cruise in the subtropical North Atlantic where community respiration (CR) and bacterial respiration (BR) were determined. Both CR and BR decreased by ~85% from the Mauritanian upwelling region and the oligotrophic gyre. Along this transect, the contribution of BR to CR increased from 36% to 76%. The instrument proved highly suitable for work at sea and should allow more rapid and precise oxygen concentration measurements under open-ocean conditions.

The effect of oil films on water evaporation and oxygen content in sea water

The paper covers some results of laboratory and nature experiments on studying the effect of oil films on water evaporation rate and oxygen concentration in sea water. It is demonstrated that oil films on the sea surface reduce the rate of water evaporation by 15 to 33% due to diffusion resistance of oil film as well as energy resistance of monolayer of surface active substances at the film-water interface. Large oil spots may cause, in areas oversaturated with oxygen, increase of oxygen concentration in sea water under the oil spot due to decrease of gas exchange rate at the sea-atmosphere interface.

Hypoxia-induced respiratory changes in English sole ( Parophrys vetulus girard)

1. 1. Laboratory measurements were made of ventilation volume, ventilation rate, oxygen consumption rate, and oxygen uptake efficiency of English sole ( Parophrys vetulus Girard) subjected to a range of oxygen concentrations in seawater. 2. 2. Oxygen consumption was constant over various oxygen concentrations, and no critical oxygen tension was found. 3. 3. As oxygen concentration decreased, ventilation volume and ventilation rate increased, and the efficiency of oxygen extraction decreased (from 73 to 58% of oxygen extracted from ventilation stream). 4. 4. Results suggest a moderate degree of hypoxic tolerance in English sole.

Oxygen as a limiting factor in phototaxis and in intraclonal spacing of the sea anemone Anthopleura elegantissima

Phototaxis in Anthopleura elegantissima, a sea anemone symbiotic with zooxanthellae, was investigated with special reference to oxygen as a possible controlling factor. Under high oxygen concentrations in seawater, movement towards light was not observed for symbiotic anamones as it was under normal oxygen concentrations. Both aposymbiotic and symbiotic anemones demonstrated movement towards high oxygen concentrations in seawater. Oxygen is, therefore, implicated as a controlling factor in phototaxis. Under laboratory conditions, increased intraclonal spacing occurred with low oxygen concentrations in seawater. In the field, individuals in symbiotic clones were spaced significantly closer than in aposymbiotic clones. Since intraclonal spacing is controlled by oxygen in the laboratory, spacing may also be affected in the field by oxygen; symbiotic clones may be spaced closer because they have better oxygen availability than do aposymbiotic clones.

Effect of Oxygen Concentration and pH on Electrode Potential of Stainless Steels and Operation of Microcouples

Abstract Using Russian steels of 13 Cr and 18–9 analyses in general experiments are conducted varying pH and oxygen concentrations in sea water to determine the relative effect of these variables on corrosion rates in crevices. Effect of oxygen concentrations in the range 1–9 mg/1 and pH 8.3 to 2.3 are reported. Changes in pH were found to strongly and changes in oxygen concentration weakly influence the corrosion rate. Authors postulate that anodic passivity is effected after application of tenths of a milliampere per square centimeter whereas when the pH in the anodic space is lowered, critical current density required for passivation increases 40–50 fold. Heat treatment of the steel does not influence electrode potentials when solution pH is lowered.

Primary Organic Productivity of a Hawaiian Coral Reef1

Primary organic productivity was determined by measuring changes in oxygen concentration of sea water flowing over a fringing coral reef at Kapaa, Kauai, Hawaii. Prevalence of a rather strong, unidirectional current facilitated use of this method.Determinations were made both in summer (July) and winter (November). The reef is autotrophic, as were two previously studied atoll reefs in the Marshall Islands. Gross primary productivity is about 2,900 g C/m2/yr. This is in impressive agreement with results obtained on the atoll reefs, which are the only previous measurements of coral reef productivity.All three results are considerably higher than determinations of productivity of open ocean waters. The authors attribute this difference to photosynthesis by benthic algae on the coral reef platform.

STUDIES IN THE PHYSIOLOGY OF SPERMATOZOA

STUDIES IN THE PHYSIOLOGY OF SPERMATOZOA