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Sample records for hydrocarbons diatoms show

  1. Diatom, cyanobacterial and microbial mats as indicators of hydrocarbon contaminated Arctic streams and waters

    Energy Technology Data Exchange (ETDEWEB)

    Ziervogel, H.; Selann, J.; Adeney, B. [EBA Engineering Consultants Ltd., Edmonton, AB (Canada); Nelson, J.A. [J.B. Services, Sarnia, ON (Canada); Murdock, E. [Nunavut Power, Iqaluit (Canada)

    2003-07-01

    An environmental assessment conducted at Repulse Bay, Nunavut in the summer of 2001 revealed a recent diesel spill flowing from the groundwater into a creek. The spill had not been reported. When Arctic surface waters mix with hydrocarbon impacted groundwater and sediments, distinctive mats of diatom, cyanobacteria and other bacteria are formed. These mats have the potential for phytoremediation of hydrocarbons. This paper explained the apparent dominance of mats in contaminated Arctic waters and why they promote biodegradation of hydrocarbons. Hydrocarbon-contaminated soils and groundwater are generally anaerobic. The higher dissolved carbon dioxide in polluted soils and groundwater can benefit photosynthetic cyanobacteria and diatom found in oligotrophic, lower alkalinity Arctic waters. The anaerobic and aerobic bacteria can potentially take advantage of the hydrogen substrate and the nitrogen fixing abilities of the cyanobacteria. Zooplankton predators may be killed off by the toxicity of the polluted groundwater. The paper provides examples where a microbial mat reduced the sulfate content of a hydrocarbon-impacted Arctic stream by 100 ppm, and where a pond covered in a benthic microbial mat showed no evidence of hydrocarbons in the water overlying sediments contaminated with hydrocarbons at concentrations measured at 30,000 ppm. 19 refs., 3 tabs., 8 figs.

  2. Method for depth referencing hydrocarbon gas shows on mud logs

    International Nuclear Information System (INIS)

    Dion, E.P.

    1986-01-01

    A method is described for identifying hydrocarbon formations surrounding a borehole, comprising the steps of: a. measuring hydrocarbon gas in the entrained formation cuttings obtained during drilling operations in which a drilling mud is continually circulated past a drill bit to carry the cuttings to the earth's surface, b. simultaneously measuring natural gamma radiation in the cuttings, c. identifying the depths at which the cuttings were obtained within the borehole, d. measuring natural gamma radiation within the borehole following completion of the drilling operations, e. correlating the natural gamma radiation measurements in steps (b) and (d), and f. identifying the depths within the borehole from which the entrained cuttings containing hydrocarbon gas were obtained during drilling operations when there is correlation between the natural gamma radiation measurements in steps (b) and (d)

  3. Paleolimnological studies of Laguna Chica of San Pedro (VIII Region: Diatoms, hydrocarbons and fatty acid records Estudio Paleolimnológico de Laguna Chica de San Pedro (VIII Región: Diatomeas, hidrocarburos y ácidos grasos

    Directory of Open Access Journals (Sweden)

    ROBERTO URRUTIA

    2000-12-01

    Full Text Available Diatom, hydrocarbons and fatty acid sedimentary records were used for reconstructing the recent (last 150 years palaeolimnological history of Laguna Chica of San Pedro (Concepción, VIII Región, Chile. Cluster analyses (Constrained Incremental Sum of Squares on the diatom data revealed three distinct periods. The first period (1883-1940's showed a pronounced increase in sedimentation rate and a slight increase in organic matter accumulation. In this period, eutrophic species (Aulacoseira granulata and Staurosira construens became increasingly dominant. From the 1940s until the 1970s the diatom signal is more equivocal: after the initial decrease in the relative abundance of A. granulata and S. construens their numbers fluctuate without a clear pattern. Sedimentation rates strongly fluctuate in this period. From 1978 onwards eutrophic species are in decline while indicators of oligotrophic conditions, such as Cyclotella stelligera and Aulacoseira distans, become more abundant. This shift in the lake trophic status could not be attributed to a reduction in the nutrient load from the catchment and we hypothesize that the invasion of the lake by the submersed macrophyte Egeria densa has altered nutrient availability to the plankton communities. This is in agreement with the hydrocarbons and fatty acid analyses which demonstrate a shift in carbon number distributions from short chain alkanes and alkanoic acids (typical for microalgae to long chain molecules (characteristic for higher plants in the upper layers of the lake sedimentSe realizó la reconstrucción histórica de los últimos 150 años de Laguna Chica de San Pedro (Concepción, VIII Región, Chile, a través de la utilización de los restos de diatomeas, hidrocarburos y ácidos grasos contenidos en la columna de sedimento. El análisis estratigráfico de las diatomeas reveló la presencia de tres períodos diferentes. El primer período (1883-1940's, mostró un marcado aumento de las

  4. Towards a representative periphytic diatom sample

    Directory of Open Access Journals (Sweden)

    2007-01-01

    Full Text Available The need to acquire a representative periphytic diatom sample for river water quality monitoring has been recognised in the development of existing diatom indices, important in the development and employment of diatom monitoring tools for the Water Framework Directive. In this study, a nested design with replication is employed to investigate the magnitude of variation in diatom biomass, composition and Trophic Diatom Index at varying scales within a small chalk river. The study shows that the use of artificial substrates may not result in diatom communities that are typical of the surrounding natural substrates. Periphytic diatom biomass and composition varies between artificial and natural substrates, riffles and glides and between two stretches of the river channel. The study also highlights the existence of high variation in diatom frustule frequency and biovolume at the individual replicate scale which may have implications for the use of diatoms in routine monitoring.

  5. Hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    1927-02-22

    Coal tar, mineral oils, bitumens, coal extraction products, hydrogenation products of coal, oil schists can be atomized and heated with steam to decompose pyrogenetically and form gases rich in olefins which may be heated with or without pressure and with or without catalysts to produce liquid hydrocarbons of low boiling point, some of which may be aromatic. The apparatus should be lined with copper, silica, or ferrosilicon to prevent contact of the bases with iron which causes deposition of soot. Catalysts used may be metal oxides, silica, graphite, active charcoal, mica, pumice, porcelain, barium carbonate, copper, silver, gold, chromium, boron, or their compounds. At temperatures from 300 to 400/sup 0/C, olefins are produced. At higher temperatures, naphthenes and benzene hydrocarbons are produced.

  6. Luminescence properties of a nanoporous freshwater diatom.

    Science.gov (United States)

    Goswami, Bondita; Choudhury, Amarjyoti; Buragohain, Alak K

    2012-01-01

    Freshwater diatom frustules show special optical properties. In this paper we observed luminescence properties of the freshwater diatom Cyclotella meneghiniana. To confirm the morphological properties we present scanning electron microscopy (SEM) images. X-ray diffraction (XRD) studies were carried out to visualize the structural properties of the frustules, confirming that silica present in diatom frustules crystallizes in an α-quartz structure. Study of the optical properties of the silica frustules of diatoms using ultra-violet-visible (UV-vis) spectroscopy and photoluminescence spectroscopy confirmed that the diatom C. meneghiniana shows luminescence in the blue region of the electromagnetic spectrum when irradiated with UV light. This property of diatoms can be exploited to obtain many applications in day-to-day life. Also, using time-resolved photoluminescence spectroscopy (TRPL) it was confirmed that this species of diatom shows bi-exponential decay. Copyright © 2011 John Wiley & Sons, Ltd.

  7. Diatoms and the nanotechnology

    International Nuclear Information System (INIS)

    Toekesi, K.; Bereczky, R.J.; Lakatos, Gy.; Cserhati, C.

    2004-01-01

    Complete text of publication follows. During the last decade studies of interactions between highly charged ions (HCI) and solid surfaces are at the center of interest which is partly stimulated by potential future technical application such as nanofabrication. The investigation of the interactions of highly charged ions with internal surfaces recently become available due to the advances in the fabrication of micro- and nanocapillaries. These target materials offer the opportunity to observe 'hollow atom' formation in free space. Hollow atoms are an exotic form of matter where the atomic charge cloud resides in shells with large diameters while the core is virtually empty. In the past there has been an increasing amount of indirect evidence for the existence of this atomic state. Microcapillary transmission promises to provide direct evidence for the hollow atom formation for the first time. Our earlier theoretical descriptions rely on metallic microcapillaries which have proven to be quite successful in comparison with experimental data. However, since very detailed measurements have recently become available for insulator nanocapillaries, critical and precise tests of theory are only now being possible. We note, that the theoretical description of the interaction between the HCI and insulator nanocapillaries is far from being well understood. One of the key point of the experimental investigations is the preparation of the nanocapillaries. In this work we propose an alternative way to prepare insulator nanocapillaries. We take an advantage of the nature that during the evolution the cylindrical shape nanostructure was developed as a truss of diatoms. The truss of the diatoms contains roughly 99 % SiO 2 and in some cases of diatoms it form almost ideal cylindrical shape. As an example Fig. 1 shows the scanning electron micrograph of the diatom. The size of the holes in the truss are in the nanometer range (see Fig. 1a). On the basis of these properties the

  8. Biophotonics of diatoms

    DEFF Research Database (Denmark)

    Gössling, Johannes Wilhelm

    Diatoms are unicellular microalgae present in all aquatic environments on earth. Due to their high photosynthetic productivity and abundance, diatoms are main components of aquatic food webs and among the main contributors of global photosynthetic carbon fixation. A unique feature of diatoms...

  9. Selective silicate-directed motility in diatoms

    DEFF Research Database (Denmark)

    Bondoc, Karen Grace V.; Heuschele, Jan; Gillard, Jeroen

    2016-01-01

    the major sink in the global Si cycle. Dissolved silicic acid (dSi) availability frequently limits diatom productivity and influences species composition of communities. We show that benthic diatoms selectively perceive and behaviourally react to gradients of dSi. Cell speed increases under d...

  10. Diatomic gasdynamic lasers.

    Science.gov (United States)

    Mckenzie, R. L.

    1972-01-01

    Predictions from a numerical model of the vibrational relaxation of anharmonic diatomic oscillators in supersonic expansions are used to show the extent to which the small anharmonicity of gases like CO can cause significant overpopulations of upper vibrational states. When mixtures of CO and N2 are considered, radiative gain on many of the vibration-rotation transitions of CO is predicted. Experiments are described that qualitatively verify the predictions by demonstrating laser oscillation in CO-N2 expansions. The resulting CO-N2 gasdynamic laser displays performance characteristics that equal or exceed those of similar CO2 lasers.

  11. Diatomic gasdynamic lasers

    International Nuclear Information System (INIS)

    McKenzie, R.L.

    1971-12-01

    Predictions from a numerical model of the vibrational relaxation of anharmonic diatomic oscillators in supersonic expansions are used to show the extent to which the small anharmonicity of gases like CO can cause significant over-populations of upper vibrational states. When mixtures of CO and N 2 are considered, radiative gain on many of the vibration-rotation transitions of CO is predicted. Experiments are described that qualitatively verify the predictions by demonstrating laser oscillation in CO-N 2 expansions. The resulting CO-N 2 gasdynamic laser displays performance characteristics that equal or exceed those of similar CO 2 lasers

  12. Automated measurement of diatom size

    Science.gov (United States)

    Spaulding, Sarah A.; Jewson, David H.; Bixby, Rebecca J.; Nelson, Harry; McKnight, Diane M.

    2012-01-01

    Size analysis of diatom populations has not been widely considered, but it is a potentially powerful tool for understanding diatom life histories, population dynamics, and phylogenetic relationships. However, measuring cell dimensions on a light microscope is a time-consuming process. An alternative technique has been developed using digital flow cytometry on a FlowCAM® (Fluid Imaging Technologies) to capture hundreds, or even thousands, of images of a chosen taxon from a single sample in a matter of minutes. Up to 30 morphological measures may be quantified through post-processing of the high resolution images. We evaluated FlowCAM size measurements, comparing them against measurements from a light microscope. We found good agreement between measurement of apical cell length in species with elongated, straight valves, including small Achnanthidium minutissimum (11-21 µm) and largeDidymosphenia geminata (87–137 µm) forms. However, a taxon with curved cells, Hannaea baicalensis (37–96 µm), showed differences of ~ 4 µm between the two methods. Discrepancies appear to be influenced by the choice of feret or geodesic measurement for asymmetric cells. We describe the operating conditions necessary for analysis of size distributions and present suggestions for optimal instrument conditions for size analysis of diatom samples using the FlowCAM. The increased speed of data acquisition through use of imaging flow cytometers like the FlowCAM is an essential step for advancing studies of diatom populations.

  13. Oceanographic and Biogeochemical Insights from Diatom Genomes

    Science.gov (United States)

    Bowler, Chris; Vardi, Assaf; Allen, Andrew E.

    2010-01-01

    Diatoms are the most successful group of eukaryotic phytoplankton in the modern ocean and have risen to dominance relatively quickly over the last 100 million years. Recently completed whole genome sequences from two species of diatom, Thalassiosira pseudonana and Phaeodactylum tricornutum, have revealed a wealth of information about the evolutionary origins and metabolic adaptations that have led to their ecological success. A major finding is that they have incorporated genes both from their endosymbiotic ancestors and by horizontal gene transfer from marine bacteria. This unique melting pot of genes encodes novel capacities for metabolic management, for example, allowing the integration of a urea cycle into a photosynthetic cell. In this review we show how genome-enabled approaches are being leveraged to explore major phenomena of oceanographic and biogeochemical relevance, such as nutrient assimilation and life histories in diatoms. We also discuss how diatoms may be affected by climate change-induced alterations in ocean processes.

  14. The effects of oil pollution on Antarctic benthic diatom communities over 5 years

    International Nuclear Information System (INIS)

    Polmear, R.; Stark, J.S.; Roberts, D.; McMinn, A.

    2015-01-01

    Highlights: • We examine the impact of hydrocarbon pollution on Antarctic benthic diatoms. • The effect of standard synthetic lubricant oil and a biodegradable oil were examined. • There were significant effects from both treatments for over 5 years. • There was little difference between the different types of oil. - Abstract: Although considered pristine, Antarctica has not been impervious to hydrocarbon pollution. Antarctica’s history is peppered with oil spills and numerous abandoned waste disposal sites. Both spill events and constant leakages contribute to previous and current sources of pollution into marine sediments. Here we compare the response of the benthic diatom communities over 5 years to exposure to a commonly used standard synthetic lubricant oil, an alternative lubricant marketed as more biodegradable, in comparison to a control treatment. Community composition varied significantly over time and between treatments with some high variability within contaminated treatments suggesting community stress. Both lubricants showed evidence of significant effects on community composition after 5 years even though total petroleum hydrocarbon reduction reached approximately 80% over this time period. It appears that even after 5 years toxicity remains high for both the standard and biodegradable lubricants revealing the temporal scale at which pollutants persist in Antarctica

  15. Diatom-inspired templates for 3D replication: natural diatoms versus laser written artificial diatoms

    International Nuclear Information System (INIS)

    Belegratis, M R; Schmidt, V; Nees, D; Stadlober, B; Hartmann, P

    2014-01-01

    The diatoms are ubiquitous, exist in large numbers and show a great diversity of features on their porous silica structures. Therefore, they inspire the fabrication of nanostructured templates for nanoimprint processes (NIL), where large structured areas with nanometer precision are required. In this study, two approaches regarding the respective challenges and potential exploitations are followed and discussed: the first one takes advantage of a template that is directly made of natural occurring diatoms. Here, two replication steps via soft lithography are needed to obtain a template which is subsequently used for NIL. The second approach exploits the technical capabilities of the precise 3D laser lithography (3DLL) based on two-photon polymerization of organic materials. This method enables the fabrication of arbitrary artificial diatom-inspired micro- and nanostructures and the design of an inverse structure. Therefore, only one replication step is needed to obtain a template for NIL. In both approaches, a replication technique for true 3D structures is shown. (paper)

  16. Diatom distribution in the surficial sediments of Lake Fuxian, Yunnan ...

    African Journals Online (AJOL)

    ajl yemi

    2011-11-30

    Nov 30, 2011 ... The diatom abundances per gram dry weight sediment vary between 18.4 × 106 and 66.9 × 106 valves (Figure 2). Abundances per gram dry weight of the eight most abundant diatom taxa are shown in Figure 3. The DCA diagram shows centroids of ecoregions in the ordination space of the first axes.

  17. The effects of oil pollution on Antarctic benthic diatom communities over 5 years.

    Science.gov (United States)

    Polmear, R; Stark, J S; Roberts, D; McMinn, A

    2015-01-15

    Although considered pristine, Antarctica has not been impervious to hydrocarbon pollution. Antarctica's history is peppered with oil spills and numerous abandoned waste disposal sites. Both spill events and constant leakages contribute to previous and current sources of pollution into marine sediments. Here we compare the response of the benthic diatom communities over 5 years to exposure to a commonly used standard synthetic lubricant oil, an alternative lubricant marketed as more biodegradable, in comparison to a control treatment. Community composition varied significantly over time and between treatments with some high variability within contaminated treatments suggesting community stress. Both lubricants showed evidence of significant effects on community composition after 5 years even though total petroleum hydrocarbon reduction reached approximately 80% over this time period. It appears that even after 5 years toxicity remains high for both the standard and biodegradable lubricants revealing the temporal scale at which pollutants persist in Antarctica. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Fabrication of insulator nanocapillaries from diatoms

    International Nuclear Information System (INIS)

    Bereczky, R.J.; Tokesi, K.

    2006-01-01

    Complete text of publication follows. Diatoms are unicellular microscopic organisms with silicon-dioxide based skeleton enveloped with an organic material, which composes essentially polysaccharides and proteins (see Fig. 1a.). As it was shown, the valva of the diatoms build up almost from clean silicondioxide [1]. Therefore, removing the organic compounds from the diatom, we can have in our hand an ideal, about 100 μ m-sized, and almost cylindrical shaped insulating nanostructure. There are various techniques available to disembarrass the diatom from its organic compounds. We used the so called hydrogen peroxide method. The advantageous properties of this method are the followings: a) this is one of the fastest procedures among the possible methods, b) do not require special equipment, c) cheap, and last but not least it is less harmful for health compared to other methods. This procedure can be an alternative way of the fabrication of insulator nanocapillaries. In this case the preparation of the nanocapillaries is simple and quick. Moreover, we do not need to invest expensive special techniques, (like micromachining-, electrochemical etching technique, moulding process etc) as it was necessary for the case of previously developed method producing insulator nanocapillaries [2,3]. Fig. 1b and Fig. 1c. show the scanning electron micrograph of the skeleton of the diatoms. The size of the cylindrical holes are roughly 200 nm (see Fig. 1c). (author)

  19. Fluxes of diatoms in the Dona Paula Bay, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Garg, A.; Bhaskar, P.V.

    of POC and diatom carbon was 251 and 0.39 mg C m sup(-2) day sup(-1), respectively. The diatom carbon accounted for 0.15% of the POC flux. Mass flux of diatoms showed significant negative correlation with the concentration of nitrate and phosphate...

  20. Environmental investigations using diatom microfossils

    Science.gov (United States)

    Smith, Kathryn E.L.; Flocks, James G.

    2010-01-01

    Diatoms are unicellular phytoplankton (microscopic plant-like organisms) with cell walls made of silica (called a frustule). They live in both freshwater and saltwater and can be found in just about every place on Earth that is wet. The shape and morphology of the diatom frustule unique to each species are used for identification. Due to the microscopic size of diatoms, high-power microscopy is required for diatom identification. Diatoms are vital to life on Earth. They are photosynthetic primary producers, using sunlight to create oxygen and organic carbon from carbon dioxide and water. They are a significant source of the oxygen we breathe, have a major impact on the global carbon cycle (Smetacek, 1999), and are a food source for many aquatic organisms (Mann, 1993). Diatom abundance has even been demonstrated to have an influence on the diversity of larger marine mammals, including whales (Marx and Uhen, 2010). Data on diatom abundance and diversity are extremely useful in environmental studies.

  1. Influence of diatom diversity on the ocean biological carbon pump

    Science.gov (United States)

    Tréguer, Paul; Bowler, Chris; Moriceau, Brivaela; Dutkiewicz, Stephanie; Gehlen, Marion; Aumont, Olivier; Bittner, Lucie; Dugdale, Richard; Finkel, Zoe; Iudicone, Daniele; Jahn, Oliver; Guidi, Lionel; Lasbleiz, Marine; Leblanc, Karine; Levy, Marina; Pondaven, Philippe

    2018-01-01

    Diatoms sustain the marine food web and contribute to the export of carbon from the surface ocean to depth. They account for about 40% of marine primary productivity and particulate carbon exported to depth as part of the biological pump. Diatoms have long been known to be abundant in turbulent, nutrient-rich waters, but observations and simulations indicate that they are dominant also in meso- and submesoscale structures such as fronts and filaments, and in the deep chlorophyll maximum. Diatoms vary widely in size, morphology and elemental composition, all of which control the quality, quantity and sinking speed of biogenic matter to depth. In particular, their silica shells provide ballast to marine snow and faecal pellets, and can help transport carbon to both the mesopelagic layer and deep ocean. Herein we show that the extent to which diatoms contribute to the export of carbon varies by diatom type, with carbon transfer modulated by the Si/C ratio of diatom cells, the thickness of the shells and their life strategies; for instance, the tendency to form aggregates or resting spores. Model simulations project a decline in the contribution of diatoms to primary production everywhere outside of the Southern Ocean. We argue that we need to understand changes in diatom diversity, life cycle and plankton interactions in a warmer and more acidic ocean in much more detail to fully assess any changes in their contribution to the biological pump.

  2. Isolation and biochemical characterization of underwater adhesives from diatoms.

    Science.gov (United States)

    Poulsen, Nicole; Kröger, Nils; Harrington, Matthew J; Brunner, Eike; Paasch, Silvia; Buhmann, Matthias T

    2014-01-01

    Many aquatic organisms are able to colonize surfaces through the secretion of underwater adhesives. Diatoms are unicellular algae that have the capability to colonize any natural and man-made submerged surfaces. There is great technological interest in both mimicking and preventing diatom adhesion, yet the biomolecules responsible have so far remained unidentified. A new method for the isolation of diatom adhesive material is described and its amino acid and carbohydrate composition determined. The adhesive materials from two model diatoms show differences in their amino acid and carbohydrate compositions, but also share characteristic features including a high content of uronic acids, the predominance of hydrophilic amino acid residues, and the presence of 3,4-dihydroxyproline, an extremely rare amino acid. Proteins containing dihydroxyphenylalanine, which mediate underwater adhesion of mussels, are absent. The data on the composition of diatom adhesives are consistent with an adhesion mechanism based on complex coacervation of polyelectrolyte-like biomolecules.

  3. Photosynthetic Pigments in Diatoms

    OpenAIRE

    Kuczynska, Paulina; Jemiola-Rzeminska, Malgorzata; Strzalka, Kazimierz

    2015-01-01

    Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvestin...

  4. Photosynthetic Pigments in Diatoms.

    Science.gov (United States)

    Kuczynska, Paulina; Jemiola-Rzeminska, Malgorzata; Strzalka, Kazimierz

    2015-09-16

    Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvesting pigments such as chlorophyll a, chlorophyll c, and fucoxanthin, there is a group of photoprotective carotenoids which includes β-carotene and the xanthophylls, diatoxanthin, diadinoxanthin, violaxanthin, antheraxanthin, and zeaxanthin, which are engaged in the xanthophyll cycle. Additionally, some intermediate products of biosynthetic pathways have been identified in diatoms as well as unusual pigments, e.g., marennine. Marine algae have become widely recognized as a source of unique bioactive compounds for potential industrial, pharmaceutical, and medical applications. In this review, we summarize current knowledge on diatom photosynthetic pigments complemented by some new insights regarding their physico-chemical properties, biological role, and biosynthetic pathways, as well as the regulation of pigment level in the cell, methods of purification, and significance in industries.

  5. Photosynthetic Pigments in Diatoms

    Directory of Open Access Journals (Sweden)

    Paulina Kuczynska

    2015-09-01

    Full Text Available Photosynthetic pigments are bioactive compounds of great importance for the food, cosmetic, and pharmaceutical industries. They are not only responsible for capturing solar energy to carry out photosynthesis, but also play a role in photoprotective processes and display antioxidant activity, all of which contribute to effective biomass and oxygen production. Diatoms are organisms of a distinct pigment composition, substantially different from that present in plants. Apart from light-harvesting pigments such as chlorophyll a, chlorophyll c, and fucoxanthin, there is a group of photoprotective carotenoids which includes β-carotene and the xanthophylls, diatoxanthin, diadinoxanthin, violaxanthin, antheraxanthin, and zeaxanthin, which are engaged in the xanthophyll cycle. Additionally, some intermediate products of biosynthetic pathways have been identified in diatoms as well as unusual pigments, e.g., marennine. Marine algae have become widely recognized as a source of unique bioactive compounds for potential industrial, pharmaceutical, and medical applications. In this review, we summarize current knowledge on diatom photosynthetic pigments complemented by some new insights regarding their physico-chemical properties, biological role, and biosynthetic pathways, as well as the regulation of pigment level in the cell, methods of purification, and significance in industries.

  6. Electron transport through a diatomic molecule

    International Nuclear Information System (INIS)

    Imran, Muhammad

    2014-01-01

    Electron transport through a diatomic molecular tunnel junction shows wave like interference phenomenon. By using Keldysh non-equilibrium Green's function (NEGF) theory, we have explicitly presented current and differential conductance calculation for a diatomic molecular and two isolated atoms (two atoms having zero hybridization between their energy orbitals) tunnel junctions. In case of a diatomic molecular tunnel junction, Green's function propagators entering into current and differential conductance formula interfere constructively for a molecular anti-bonding state and destructively for bonding state. Consequently, conductance through a molecular bonding state is suppressed, and to conserve current, conductance through anti-bonding state is enhanced. Therefore, current steps and differential conductance peaks amplitude show asymmetric correspondence between molecular bonding and anti-bonding states. Interestingly, for a diatomic molecule, comprising of two atoms of same energy level, these propagators interfere completely destructively for molecular bonding state and constructively for molecular anti-bonding state. Hence under such condition, a single step or a single peak is shown up in current versus voltage or differential conductance versus voltage studies.

  7. Effect of the Silica Content of Diatoms on Protozoan Grazing

    Directory of Open Access Journals (Sweden)

    Shuwen Zhang

    2017-06-01

    Full Text Available This study examined the effect that silica content in diatom cells has on the behavior of protists. The diatoms Thalassiosira weissflogii and T. pseudonana were cultured in high or low light conditions to achieve low and high silica contents, respectively. These cells were then fed to a heterotrophic dinoflagellate Noctiluca scintillans and a ciliate Euplotes sp. in single and mixed diet experiments. Our results showed that in general, N. scintillans and Euplotes sp. both preferentially ingested the diatoms with a low silica content rather than those with a high silica content. However, Euplotes sp. seemed to be less influenced by the silica content than was N. scintillans. In the latter case, the clearance and ingestion rate of the low silica diatoms were significantly higher, both in the short (6-h and long (1-d duration grazing experiments. Our results also showed that N. scintillans required more time to digest the high silica-containing cells. As the high silica diatoms are harder to digest, this might explain why N. scintillans exhibits a strong preference for the low silica prey. Thus, the presence of high silica diatoms might limit the ability of the dinoflagellate to feed. Our findings suggest that the silica content of diatoms affects their palatability and digestibility and, consequently, the grazing activity and selectivity of protozoan grazers.

  8. Controlling dynamics in diatomic systems

    Indian Academy of Sciences (India)

    WINTEC

    Abstract. Controlling molecular energetics using laser pulses is exemplified for nuclear motion in two different diatomic systems. The problem of finding the optimized field for maximizing a desired quantum dynamical target is formulated using an iterative method. The method is applied for two diatomic sys- tems, HF and OH.

  9. Codon adaptation and synonymous substitution rate in diatom plastid genes.

    Science.gov (United States)

    Morton, Brian R; Sorhannus, Ulf; Fox, Martin

    2002-07-01

    Diatom plastid genes are examined with respect to codon adaptation and rates of silent substitution (Ks). It is shown that diatom genes follow the same pattern of codon usage as other plastid genes studied previously. Highly expressed diatom genes display codon adaptation, or a bias toward specific major codons, and these major codons are the same as those in red algae, green algae, and land plants. It is also found that there is a strong correlation between Ks and variation in codon adaptation across diatom genes, providing the first evidence for such a relationship in the algae. It is argued that this finding supports the notion that the correlation arises from selective constraints, not from variation in mutation rate among genes. Finally, the diatom genes are examined with respect to variation in Ks among different synonymous groups. Diatom genes with strong codon adaptation do not show the same variation in synonymous substitution rate among codon groups as the flowering plant psbA gene which, previous studies have shown, has strong codon adaptation but unusually high rates of silent change in certain synonymous groups. The lack of a similar finding in diatoms supports the suggestion that the feature is unique to the flowering plant psbA due to recent relaxations in selective pressure in that lineage.

  10. Automated Diatom Classification (Part A: Handcrafted Feature Approaches

    Directory of Open Access Journals (Sweden)

    Gloria Bueno

    2017-07-01

    Full Text Available This paper deals with automatic taxa identification based on machine learning methods. The aim is therefore to automatically classify diatoms, in terms of pattern recognition terminology. Diatoms are a kind of algae microorganism with high biodiversity at the species level, which are useful for water quality assessment. The most relevant features for diatom description and classification have been selected using an extensive dataset of 80 taxa with a minimum of 100 samples/taxon augmented to 300 samples/taxon. In addition to published morphological, statistical and textural descriptors, a new textural descriptor, Local Binary Patterns (LBP, to characterize the diatom’s valves, and a log Gabor implementation not tested before for this purpose are introduced in this paper. Results show an overall accuracy of 98.11% using bagging decision trees and combinations of descriptors. Finally, some phycological features of diatoms that are still difficult to integrate in computer systems are discussed for future work.

  11. Acidification counteracts negative effects of warming on diatom silicification

    KAUST Repository

    Coello-Camba, Alexandra

    2016-10-24

    Diatoms are a significant group contributing up to 40 % of annual primary production in the oceans. They have a special siliceous cell wall that, acting as a ballast, plays a key role in the sequestration of global carbon and silica. Diatoms dominate primary production in the Arctic Ocean, where global climate change is causing increases in water temperature and in the partial pressure of CO2 (pCO2). Here we show that as water temperature increases diatoms become stressed, grow to smaller sizes, and decrease their silicification rates. But at higher pCO2, as the pH of seawater decreases, silica incorporation rates are increased. In a future warmer Arctic ocean diatoms may have a competitive advantage under increased ocean acidification, as increased pCO2 counteracts the adverse effects of increasing temperature on silicification and buffers its consequences in the biogeochemical cycles of carbon and silica.

  12. Acidification counteracts negative effects of warming on diatom silicification

    KAUST Repository

    Coello-Camba, Alexandra; Agusti, Susana

    2016-01-01

    Diatoms are a significant group contributing up to 40 % of annual primary production in the oceans. They have a special siliceous cell wall that, acting as a ballast, plays a key role in the sequestration of global carbon and silica. Diatoms dominate primary production in the Arctic Ocean, where global climate change is causing increases in water temperature and in the partial pressure of CO2 (pCO2). Here we show that as water temperature increases diatoms become stressed, grow to smaller sizes, and decrease their silicification rates. But at higher pCO2, as the pH of seawater decreases, silica incorporation rates are increased. In a future warmer Arctic ocean diatoms may have a competitive advantage under increased ocean acidification, as increased pCO2 counteracts the adverse effects of increasing temperature on silicification and buffers its consequences in the biogeochemical cycles of carbon and silica.

  13. A simple digestion method with a Lefort aqua regia solution for diatom extraction.

    Science.gov (United States)

    Wang, Huipin; Liu, Yan; Zhao, Jian; Hu, Sunlin; Wang, Yuzhong; Liu, Chao; Zhang, Yanji

    2015-01-01

    Presence of diatoms in tissues has been considered as a significant sign of drowning. However, there are limitations in the present extraction methods. We developed a new digestion method using the Lefort aqua regia solution (3:1 nitric acid to hydrochloric acid) for diatom extraction and evaluated the digestive capability, diatom destruction, and diatoms' recovery of this new method. The kidney tissues from rabbit mixed with water rich in diatoms were treated by the Lefort aqua regia digestion method (n = 10) and the conventional acid digestion method (n = 10). The results showed that the digestive capability of Lefort aqua regia digestion method was superior to conventional acid digestion method (p 0.05). The Lefort aqua regia reagent is an improvement over the conventional acid digestion for recovery of diatoms from tissue samples. © 2014 American Academy of Forensic Sciences.

  14. Processing and characterization of diatom nanoparticles and microparticles as potential source of silicon for bone tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Le, Thi Duy Hanh [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Bonani, Walter [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Interuniversity Consortium for Science and Technology of Materials, Trento Research Unit, Trento (Italy); Speranza, Giorgio [Center for Materials and Microsystems, PAM-SE, Fondazione Bruno Kessler, Trento (Italy); Sglavo, Vincenzo; Ceccato, Riccardo [Department of Industrial Engineering, University of Trento, Trento (Italy); Maniglio, Devid; Motta, Antonella [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Interuniversity Consortium for Science and Technology of Materials, Trento Research Unit, Trento (Italy); Migliaresi, Claudio, E-mail: claudio.migliaresi@unitn.it [Department of Industrial Engineering, University of Trento, Trento (Italy); BIOtech Research Center and European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Trento (Italy); Interuniversity Consortium for Science and Technology of Materials, Trento Research Unit, Trento (Italy)

    2016-02-01

    Silicon plays an important role in bone formation and maintenance, improving osteoblast cell function and inducing mineralization. Often, bone deformation and long bone abnormalities have been associated with silica/silicon deficiency. Diatomite, a natural deposit of diatom skeleton, is a cheap and abundant source of biogenic silica. The aim of the present study is to validate the potential of diatom particles derived from diatom skeletons as silicon-donor materials for bone tissue engineering applications. Raw diatomite (RD) and calcined diatomite (CD) powders were purified by acid treatments, and diatom microparticles (MPs) and nanoparticles (NPs) were produced by fragmentation of purified diatoms under alkaline conditions. The influence of processing on the surface chemical composition of purified diatomites was evaluated by X-ray photoelectron spectroscopy (XPS). Diatoms NPs were also characterized in terms of morphology and size distribution by transmission electron microscopy (TEM) and Dynamic light scattering (DLS), while diatom MPs morphology was analyzed by scanning electron microscopy (SEM). Surface area and microporosity of the diatom particles were evaluated by nitrogen physisorption methods. Release of silicon ions from diatom-derived particles was demonstrated using inductively coupled plasma optical emission spectrometry (ICP/OES); furthermore, silicon release kinetic was found to be influenced by diatomite purification method and particle size. Diatom-derived microparticles (MPs) and nanoparticles (NPs) showed limited or no cytotoxic effect in vitro depending on the administration conditions. - Highlights: • Diatomite is a natural source of silica and has a potential as silicon-donor for bone regenerative applications. • Diatom particles derived from purified diatom skeletons were prepared by fragmentation under extreme alkaline condition. • Dissolution of diatom particles derived from diatom skeletons in DI water depend on purification method

  15. Comparison between sedimentary and living diatoms in Lago Maggiore (N. Italy: implications of using transfer functions

    Directory of Open Access Journals (Sweden)

    Simona MUSAZZI

    2001-02-01

    Full Text Available We compared the recent history of living planktonic diatom assemblages in Lago Maggiore with the remains found in the topmost section of 14 sediment cores taken from the lake. Sediment samples showed a marked domination of planktonic taxa, but a significant proportion of benthic taxa was found in cores collected close to river mouths. Between-core variability in diatom assemblage and in diatom-inferred total phosphorus concentration was also estimated. The implications of our results for calibration data sets relating environmental variables to diatom assemblages are also discussed.

  16. Responses of diatom communities to hydrological processes during rainfall events

    Science.gov (United States)

    Wu, Naicheng; Faber, Claas; Ulrich, Uta; Fohrer, Nicola

    2015-04-01

    The importance of diatoms as a tracer of hydrological processes has been recently recognized (Pfister et al. 2009, Pfister et al. 2011, Tauro et al. 2013). However, diatom variations in a short-term scale (e.g., sub-daily) during rainfall events have not been well documented yet. In this study, rainfall event-based diatom samples were taken at the outlet of the Kielstau catchment (50 km2), a lowland catchment in northern Germany. A total of nine rainfall events were caught from May 2013 to April 2014. Non-metric multidimensional scaling (NMDS) revealed that diatom communities of different events were well separated along NMDS axis I and II, indicating a remarkable temporal variation. By correlating water level (a proxy of discharge) and different diatom indices, close relationships were found. For example, species richness, biovolume (μm3), Shannon diversity and moisture index01 (%, classified according to van Dam et al. 1994) were positively related with water level at the beginning phase of the rainfall (i.e. increasing limb of discharge peak). However, in contrast, during the recession limb of the discharge peak, diatom indices showed distinct responses to water level declines in different rainfall events. These preliminary results indicate that diatom indices are highly related to hydrological processes. The next steps will include finding out the possible mechanisms of the above phenomena, and exploring the contributions of abiotic variables (e.g., hydrologic indices, nutrients) to diatom community patterns. Based on this and ongoing studies (Wu et al. unpublished data), we will incorporate diatom data into End Member Mixing Analysis (EMMA) and select the tracer set that is best suited for separation of different runoff components in our study catchment. Keywords: Diatoms, Rainfall event, Non-metric multidimensional scaling, Hydrological process, Indices References: Pfister L, McDonnell JJ, Wrede S, Hlúbiková D, Matgen P, Fenicia F, Ector L, Hoffmann L

  17. Diatoms as water quality indicators in the upper reaches of the Great ...

    African Journals Online (AJOL)

    All index scores showed the Great Fish River to be impacted, and showed significant correlations of diatom species abundance with pH, NO3-N, electrical conductivity, NH4-N and CaCO3. Analysis revealed EC and NO3-N as the main environmental drivers affecting diatom commnity composition, followed by pH and ...

  18. The effect of antibiotics on diatom communities

    Digital Repository Service at National Institute of Oceanography (India)

    DeCosta, P.M.; Anil, A.C.

    Effect of antibiotics (penicillin (P), streptomycin (S) and chloramphenicol (C)) on benthic diatom communities was evaluated using a modified extinction–dilution method. The high antibiotic combinations (2PSC and PSC) reduced diatoms by 99...

  19. Diatom genomics: genetic acquisitions and mergers.

    Science.gov (United States)

    Nisbet, R Ellen R; Kilian, Oliver; McFadden, Geoffrey I

    2004-12-29

    Diatom algae arose by two-step endosymbiosis. The complete genome of the diatom Thalassiosira pseudonana has now been sequenced, allowing us to reconstruct the remarkable intracellular gene transfers that occurred during this convoluted cellular evolution.

  20. Diatom flora in subterranean ecosystems: a review

    Directory of Open Access Journals (Sweden)

    Elisa Falasco

    2014-09-01

    Full Text Available In scarcity of light and primary producers, subterranean ecosystems are generally extremely oligotrophic habitats, receiving poor supplies of degradable organic matter from the surface. Human direct impacts on cave ecosystems mainly derive from intensive tourism and recreational caving, causing important alterations to the whole subterranean environment. In particular, artificial lighting systems in show caves support the growth of autotrophic organisms (the so-called lampenflora, mainly composed of cyanobacteria, diatoms, chlorophytes, mosses and ferns producing exocellular polymeric substances (EPSs made of polysaccharides, proteins, lipids and nucleic acids. This anionic EPSs matrix mediates to the intercellular communications and participates to the chemical exchanges with the substratum, inducing the adsorption of cations and dissolved organic molecules from the cave formations (speleothems. Coupled with the metabolic activities of heterotrophic microorganisms colonising such layer (biofilm, this phenomenon may lead to the corrosion of the mineral surfaces. In this review, we investigate the formation of biofilms, especially of diatom-dominated ones, as a consequence of artificial lighting and its impacts on speleothems. Whenever light reaches the subterranean habitat (both artificially and naturally a relative high number of species of diatoms may indeed colonise it. Cave entrances, artificially illuminated walls and speleothems inside the cave are generally the preferred substrates. This review focuses on the diatom flora colonising subterranean habitats, summarizing the information contained in all the scientific papers published from 1900 up to date. In this review we provide a complete checklist of the diatom taxa recorded in subterranean habitats, including a total of 363 taxa, belonging to 82 genera. The most frequent and abundant species recorded in caves and other low light subterranean habitats are generally aerophilic and

  1. Diatomic interaction potential theory applications

    CERN Document Server

    Goodisman, Jerry

    2013-01-01

    Diatomic Interaction Potential Theory, Volume 2: Applications discusses the variety of applicable theoretical material and approaches in the calculations for diatomic systems in their ground states. The volume covers the descriptions and illustrations of modern calculations. Chapter I discusses the calculation of the interaction potential for large and small values of the internuclear distance R (separated and united atom limits). Chapter II covers the methods used for intermediate values of R, which in principle means any values of R. The Hartree-Fock and configuration interaction schemes des

  2. Energy transfer in diatom/diatom molecular collisions

    International Nuclear Information System (INIS)

    Sohlberg, K.W.

    1992-01-01

    In a collision of two molecules, the translational energy of the collision may be redistributed into internal energy of rotation, vibration, or electron motion, in one or both of the colliding partners. In addition, internal energy in one or more of these modes may be open-quotes quenchedclose quotes into translation, leading to a superelastic collision. Such energy transfer may take place by a number of mechanisms. This energy transfer is of fundamental importance in understanding chemical reaction dynamics. Nearly all chemical reactions take place through a bimolecular collision process (or multiple bimolecular collisions) and the quantum state specificity of the reaction can have a major role in determining the kinetics of the reaction, In particular, the author has investigated vibrational energy transfer in collisions between two diatomic molecules. In addition to serving as models for all molecular collision process, gas phase collisions of these species are ubiquitous in atmospheric phenomena which are of critical importance in answering the current questions about the human induced degradation of the earth's atmospheric. Classical trajectory methods have been used to explore the excitation of vibrations in gas-phase collisions of the nitrogen molecular ion with its parent molecule. The near symmetry of the reactants is shown to result in a high probability that the two molecules are excited by an equal amount of energy. This provides a possible explanation of the molecular beam measurements which show that the total number of vibrational energy quanta excited in the collision is, with a high probability that the two molecules are excited by an equal amount of energy. This provides a possible explanation of the molecular beam measurements which show that the total number of vibrational energy quanta excited in the collision is, with a high probability, even

  3. Adaptive significance of phytoplankton stickiness with emphasis on the diatom Skeletonema costatum

    DEFF Research Database (Denmark)

    Hansen, J.L.S.; Timm, U.; Kiørboe, Thomas

    1995-01-01

    Diatom aggregate formation was analyzed using coagulation theory. Population dynamics models show that coagulation has an important impact on species succession during diatom blooms. When different species collide and form mixed aggregates this process causes interspecific interference competitio...... was tested on field data, and the predicted dynamics of a spring bloom was very similar to that observed...

  4. Diatom feeding across trophic guilds in tidal flat nematodes, and the importance of diatom cell size

    Science.gov (United States)

    Moens, Tom; Vafeiadou, Anna-Maria; De Geyter, Ellen; Vanormelingen, Pieter; Sabbe, Koen; De Troch, Marleen

    2014-09-01

    We examine the capacity of nematodes from three feeding types (deposit feeder, epistrate feeder, predator) to utilize microphytobenthos (MPB), and assess whether diatom cell size and consumer body size are important drivers of their feeding. We analyzed natural stable isotope ratios of carbon and nitrogen in abundant nematode genera and a variety of carbon sources at an estuarine intertidal flat. All nematodes had δ13C indicating that MPB is their major carbon source. δ15N, however, demonstrated that only one deposit and one epistrate feeder genus obtained most of their carbon from direct grazing on MPB, whereas other deposit feeders and predators obtained at least part of their carbon by predation on MPB grazers. We then performed a microcosm experiment in which equal cell numbers of each of three differently sized strains of the pennate diatom Seminavis were offered as food to four, one and one genera of deposit feeders, epistrate feeders and predators, respectively. Previous studies have shown that all but the epistrate feeder ingest whole diatoms, whereas the epistrate feeder pierces cells and sucks out their contents. Most genera showed markedly higher carbon absorption from medium and large cells than from small ones. When considering the number of cells consumed, however, none of the nematodes which ingest whole cells exhibited a clear preference for any specific diatom size. The epistrate feeder was the smallest nematode taxon considered here, yet it showed a marked preference for large cells. These results highlight that the feeding mechanism is much more important than consumer size as a driver of particle size selection in nematodes grazing MPB.

  5. Aromatic hydrocarbons

    International Nuclear Information System (INIS)

    Roder, M.

    1985-01-01

    Papers dealing with radiolysis of aromatic hydrocarbons of different composition (from benzene to terphenyls and hydrocarbons with condensed rings) as well as their mixtures (with alkanes, alkenes, other aromatic hydrocarbons) are reviewed. High radiation stability of aromatic hydrocarbons in condensed phases associated with peculiarities of molecular structure of compounds is underlined. Mechanisms of radiolytic processes, vaues of product yields are considered

  6. Computation of diatomic molecular spectra for selected transitions of aluminum monoxide, cyanide, diatomic carbon, and titanium monoxide

    Energy Technology Data Exchange (ETDEWEB)

    Parigger, Christian G., E-mail: cparigge@tennessee.edu [The University of Tennessee/University of Tennessee Space Institute, Center for Laser Applications, 411 B.H. Goethert Parkway, Tullahoma, TN 37388-9700 (United States); Woods, Alexander C.; Surmick, David M.; Gautam, Ghaneshwar; Witte, Michael J. [The University of Tennessee/University of Tennessee Space Institute, Center for Laser Applications, 411 B.H. Goethert Parkway, Tullahoma, TN 37388-9700 (United States); Hornkohl, James O. [Hornkohl Consulting, Tullahoma, TN 37388 (United States)

    2015-05-01

    Laser ablation studies with laser-induced breakdown spectroscopy (LIBS) typically emphasize atomic species yet fingerprints from molecular species can occur subsequently or concurrently. In this work, selected molecular transitions of aluminum monixide (AlO), diatomic carbon (C{sub 2}), cyanide (CN), and titanium monoxide (TiO) are accurately computed. Line strength tables are used to describe the radiative transitions of diatomic molecules primarily in the visible, optical region. Details are elaborated of the computational procedure that allows one to utilize diatomic spectra as a predictive and as a diagnostic tool. In order to create a computed spectrum, the procedure requires information regarding the temperature of the diatomic transitions along with other input such as the spectral resolution. When combined with a fitting algorithm to optimize such parameters, this procedure is used to infer information from an experimentally obtained spectrum. Furthermore, the programs and data files are provided for LIBS investigations that also reveal AlO, C{sub 2}, CN, and TiO diatomic spectra. - Highlights: • We present a program for fitting of molecular spectra. • This includes data base for AlO, C{sub 2}, CN, and TiO. • We discuss the details of the program including fitting. • We show computed examples and reference current work.

  7. Circular random motion in diatom gliding under isotropic conditions

    International Nuclear Information System (INIS)

    Gutiérrez-Medina, Braulio; Maldonado, Ana Iris Peña; Guerra, Andrés Jiménez; Rubio, Yadiralia Covarrubias; Meza, Jessica Viridiana García

    2014-01-01

    How cells migrate has been investigated primarily for the case of trajectories composed by joined straight segments. In contrast, little is known when cellular motion follows intrinsically curved paths. Here, we use time-lapse optical microscopy and automated trajectory tracking to investigate how individual cells of the diatom Nitzschia communis glide across surfaces under isotropic environmental conditions. We find a distinct kind of random motion, where trajectories are formed by circular arcs traveled at constant speed, alternated with random stoppages, direction reversals and changes in the orientation of the arcs. Analysis of experimental and computer-simulated trajectories show that the circular random motion of diatom gliding is not optimized for long-distance travel but rather for recurrent coverage of limited surface area. These results suggest that one main biological role for this type of diatom motility is to efficiently build the foundation of algal biofilms. (paper)

  8. Bioactive glass 45S5 from diatom biosilica

    Directory of Open Access Journals (Sweden)

    Luqman A. Adams

    2017-12-01

    Full Text Available A major draw-back to large scale production of bioactive glasses is the high cost of the standard silica precursor, usually tetraethyl orthosilicate (TEOS. The current study describes a novel sol–gel preparation of 45S5 bioactive glass using diatom biosilica from cultured cells of the diatom, Aulacoseira granulata as substitute to TEOS. The glass formed was characterized using mechanical tester, scanning electron microscopy (SEM, energy dispersive X-ray analysis (EDX, X-ray diffraction (XRD and Fourier transform infrared (FTIR spectroscopy. Results showed that the glass possessed a compressive strength of 3.75 ± 0.18 and formed carbonated hydroxyapatite (HCA within 7 days in simulated body fluid (SBF, attributable to good surface chemistry. The performance of the glass was compared with that of those formed using TEOS. Diatom biosilica could be a potential economically friendly starting material for large scale fabrication of bioactive glasses.

  9. Cenozoic planktonic marine diatom diversity and correlation to climate change

    Science.gov (United States)

    Lazarus, David; Barron, John; Renaudie, Johan; Diver, Patrick; Türke, Andreas

    2014-01-01

    Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂18O (climate) and carbon cycle records (∂13C, and 20-0 Ma pCO2). Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p2 were only moderately higher than today. Diversity is strongly correlated to both ∂13C and pCO2 over the last 15 my (for both: r>.9, detrended r>.6, all p<.001), but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

  10. Cenozoic planktonic marine diatom diversity and correlation to climate change.

    Directory of Open Access Journals (Sweden)

    David Lazarus

    Full Text Available Marine planktonic diatoms export carbon to the deep ocean, playing a key role in the global carbon cycle. Although commonly thought to have diversified over the Cenozoic as global oceans cooled, only two conflicting quantitative reconstructions exist, both from the Neptune deep-sea microfossil occurrences database. Total diversity shows Cenozoic increase but is sample size biased; conventional subsampling shows little net change. We calculate diversity from a separately compiled new diatom species range catalog, and recalculate Neptune subsampled-in-bin diversity using new methods to correct for increasing Cenozoic geographic endemism and decreasing Cenozoic evenness. We find coherent, substantial Cenozoic diversification in both datasets. Many living cold water species, including species important for export productivity, originate only in the latest Miocene or younger. We make a first quantitative comparison of diatom diversity to the global Cenozoic benthic ∂(18O (climate and carbon cycle records (∂(13C, and 20-0 Ma pCO2. Warmer climates are strongly correlated with lower diatom diversity (raw: rho = .92, p.9, detrended r>.6, all p<.001, but only weakly over the earlier Cenozoic, suggesting increasingly strong linkage of diatom and climate evolution in the Neogene. Our results suggest that many living marine planktonic diatom species may be at risk of extinction in future warm oceans, with an unknown but potentially substantial negative impact on the ocean biologic pump and oceanic carbon sequestration. We cannot however extrapolate our my-scale correlations with generic climate proxies to anthropogenic time-scales of warming without additional species-specific information on proximate ecologic controls.

  11. Hydrocarbons and air pollution

    International Nuclear Information System (INIS)

    Herz, O.

    1992-01-01

    This paper shows the influence of hydrocarbons vapors, emitted by transports or by volatile solvents using, on air pollution. Hydrocarbons are the principal precursors of photochemical pollution. After a brief introduction on atmospheric chemistry and photochemical reactions, the author describes the french prevention program against hydrocarbons emissions. In the last chapter, informations on international or european community programs for photochemical pollution study are given. 5 figs., 10 tabs

  12. Importance of sampling frequency when collecting diatoms

    KAUST Repository

    Wu, Naicheng

    2016-11-14

    There has been increasing interest in diatom-based bio-assessment but we still lack a comprehensive understanding of how to capture diatoms’ temporal dynamics with an appropriate sampling frequency (ASF). To cover this research gap, we collected and analyzed daily riverine diatom samples over a 1-year period (25 April 2013–30 April 2014) at the outlet of a German lowland river. The samples were classified into five clusters (1–5) by a Kohonen Self-Organizing Map (SOM) method based on similarity between species compositions over time. ASFs were determined to be 25 days at Cluster 2 (June-July 2013) and 13 days at Cluster 5 (February-April 2014), whereas no specific ASFs were found at Cluster 1 (April-May 2013), 3 (August-November 2013) (>30 days) and Cluster 4 (December 2013 - January 2014) (<1 day). ASFs showed dramatic seasonality and were negatively related to hydrological wetness conditions, suggesting that sampling interval should be reduced with increasing catchment wetness. A key implication of our findings for freshwater management is that long-term bio-monitoring protocols should be developed with the knowledge of tracking algal temporal dynamics with an appropriate sampling frequency.

  13. Sampler collection gadget for epilithic diatoms.

    Science.gov (United States)

    Salomoni, S E; Torgan, L C; Rocha, O

    2007-11-01

    This work present a new gadget for sampling epilithic diatoms from both lentic and lotic enviroments. The sampler consists of a polystyrene cylinder, left to float on the surface of the water, to which stone substrates are attached. This epilithic diatom sampler (EDS) can be used to detect spatial and temporal richness and density variation in the study of the diatom community, as well as in water quality monitoring.

  14. Sampler collection gadget for epilithic diatoms

    Directory of Open Access Journals (Sweden)

    SE. Salomoni

    Full Text Available This work present a new gadget for sampling epilithic diatoms from both lentic and lotic enviroments. The sampler consists of a polystyrene cylinder, left to float on the surface of the water, to which stone substrates are attached. This epilithic diatom sampler (EDS can be used to detect spatial and temporal richness and density variation in the study of the diatom community, as well as in water quality monitoring.

  15. Low-Molecular-Weight Metabolites from Diatoms: Structures, Biological Roles and Biosynthesis

    Directory of Open Access Journals (Sweden)

    Valentin Stonik

    2015-06-01

    Full Text Available Diatoms are abundant and important biological components of the marine environment that biosynthesize diverse natural products. These microalgae are rich in various lipids, carotenoids, sterols and isoprenoids, some of them containing toxins and other metabolites. Several groups of diatom natural products have attracted great interest due to their potential practical application as energy sources (biofuel, valuable food constituents, and prospective materials for nanotechnology. In addition, hydrocarbons, which are used in climate reconstruction, polyamines which participate in biomineralization, new apoptotic agents against tumor cells, attractants and deterrents that regulate the biochemical communications between marine species in seawaters have also been isolated from diatoms. However, chemical studies on these microalgae are complicated by difficulties, connected with obtaining their biomass, and the influence of nutrients and contaminators in their environment as well as by seasonal and climatic factors on the biosynthesis of the corresponding natural products. Overall, the number of chemically studied diatoms is lower than that of other algae, but further studies, particularly those connected with improvements in the isolation and structure elucidation technique as well as the genomics of diatoms, promise both to increase the number of studied species with isolated biologically active natural products and to provide a clearer perception of their biosynthesis.

  16. Diatom-induced silicon isotopic fractionation in Antarctic sea ice

    Science.gov (United States)

    Francois, F.; Damien, C.; Jean-Louis, T.; Anthony, W.; Luc, A.

    2006-12-01

    grown in a semi-closed system in which the dissolved silicon pool (i.e. brines) is partially replenished. Finally, we show that the average silicon-isotopic composition of the sea-ice diatoms (+0.63 p.mil) is very distinct from the one of biogenic silica in the seasonal ice zone mixed layer (+0.08 p.mil) indicating that sea- ice diatoms either contribute to an insignificant part of the whole diatoms biomass in the upper water layer (without affecting the silicon-isotopic budget), and/or that they are directly exported below the mixed layer. In this latter case, we will study the possibility to use the distinct signature of the sea ice diatoms as a tracer of paleo-sea ice extension in oceanic sediments.

  17. A Zeeman slower for diatomic molecules

    Science.gov (United States)

    Petzold, M.; Kaebert, P.; Gersema, P.; Siercke, M.; Ospelkaus, S.

    2018-04-01

    We present a novel slowing scheme for beams of laser-coolable diatomic molecules reminiscent of Zeeman slowing of atomic beams. The scheme results in efficient compression of the one-dimensional velocity distribution to velocities trappable by magnetic or magneto-optical traps. We experimentally demonstrate our method in an atomic testbed and show an enhancement of flux below v = 35 m s‑1 by a factor of ≈20 compared to white light slowing. 3D Monte Carlo simulations performed to model the experiment show excellent agreement. We apply the same simulations to the prototype molecule 88Sr19F and expect 15% of the initial flux to be continuously compressed in a narrow velocity window at around 10 m s‑1. This is the first experimentally shown continuous and dissipative slowing technique in molecule-like level structures, promising to provide the missing link for the preparation of large ultracold molecular ensembles.

  18. Suggestions for diatom-based monitoring in intermittent streams

    Directory of Open Access Journals (Sweden)

    Falasco Elisa

    2016-01-01

    Full Text Available Over the last decades, river lentification processes and droughts have been dramatically spreading worldwide, due to global and local drastic changes due to human activities. Under this scenario, the evaluation of physical disturbance caused by intermittency and droughts has become more and more relevant. In this research, we compare samples collected in Mediterranean streams following both traditional and experimental approaches with the aim of understanding if diatom indices calculated from a new sampling strategy could provide additional information for the physical disturbance assessment. Moreover, we also evaluated the response of functional metrics. Our results demonstrated that even though an enhanced sampling method better reflects hydrological disturbance than the traditional one, diatom indices do not detect it. Conversely, functional traits proved to be important metrics for the hydrological disturbance assessment. In particular, benthic diatom chlorophyll a showed significantly lower values in sections more subject to droughts. With respect to ecological guilds, the motile taxa proved to be linked to depositional areas, which resulted important microhabitats (MHs to be explored in rivers affected by lentification. Including different MHs in the sampling process improves the information we can obtain from the analysis of the diatom community and presents important implications in documenting species distribution and autecology.

  19. Evolutionary genomics of the cold-adapted diatom Fragilariopsis cylindrus

    KAUST Repository

    Mock, Thomas; Otillar, Robert P.; Strauss, Jan; McMullan, Mark; Paajanen, Pirita; Schmutz, Jeremy; Salamov, Asaf; Sanges, Remo; Toseland, Andrew; Ward, Ben J.; Allen, Andrew E.; Dupont, Christopher L.; Frickenhaus, Stephan; Maumus, Florian; Veluchamy, Alaguraj; Wu, Taoyang; Barry, Kerrie W.; Falciatore, Angela; Ferrante, Maria I.; Fortunato, Antonio E.; Glö ckner, Gernot; Gruber, Ansgar; Hipkin, Rachel; Janech, Michael G.; Kroth, Peter G.; Leese, Florian; Lindquist, Erika A.; Lyon, Barbara R.; Martin, Joel; Mayer, Christoph; Parker, Micaela; Quesneville, Hadi; Raymond, James A.; Uhlig, Christiane; Valas, Ruben E.; Valentin, Klaus U.; Worden, Alexandra Z.; Armbrust, E. Virginia; Clark, Matthew D.; Bowler, Chris; Green, Beverley R.; Moulton, Vincent; Oosterhout, Cock van; Grigoriev, Igor V.

    2017-01-01

    The Southern Ocean houses a diverse and productive community of organisms. Unicellular eukaryotic diatoms are the main primary producers in this environment, where photosynthesis is limited by low concentrations of dissolved iron and large seasonal fluctuations in light, temperature and the extent of sea ice. How diatoms have adapted to this extreme environment is largely unknown. Here we present insights into the genome evolution of a cold-adapted diatom from the Southern Ocean, Fragilariopsis cylindrus, based on a comparison with temperate diatoms. We find that approximately 24.7 per cent of the diploid F. cylindrus genome consists of genetic loci with alleles that are highly divergent (15.1 megabases of the total genome size of 61.1 megabases). These divergent alleles were differentially expressed across environmental conditions, including darkness, low iron, freezing, elevated temperature and increased CO2. Alleles with the largest ratio of non-synonymous to synonymous nucleotide substitutions also show the most pronounced condition-dependent expression, suggesting a correlation between diversifying selection and allelic differentiation. Divergent alleles may be involved in adaptation to environmental fluctuations in the Southern Ocean.

  20. Evolutionary genomics of the cold-adapted diatom Fragilariopsis cylindrus

    KAUST Repository

    Mock, Thomas

    2017-01-17

    The Southern Ocean houses a diverse and productive community of organisms. Unicellular eukaryotic diatoms are the main primary producers in this environment, where photosynthesis is limited by low concentrations of dissolved iron and large seasonal fluctuations in light, temperature and the extent of sea ice. How diatoms have adapted to this extreme environment is largely unknown. Here we present insights into the genome evolution of a cold-adapted diatom from the Southern Ocean, Fragilariopsis cylindrus, based on a comparison with temperate diatoms. We find that approximately 24.7 per cent of the diploid F. cylindrus genome consists of genetic loci with alleles that are highly divergent (15.1 megabases of the total genome size of 61.1 megabases). These divergent alleles were differentially expressed across environmental conditions, including darkness, low iron, freezing, elevated temperature and increased CO2. Alleles with the largest ratio of non-synonymous to synonymous nucleotide substitutions also show the most pronounced condition-dependent expression, suggesting a correlation between diversifying selection and allelic differentiation. Divergent alleles may be involved in adaptation to environmental fluctuations in the Southern Ocean.

  1. Functionalized diatom silica microparticles for removal of mercury ions

    International Nuclear Information System (INIS)

    Yu Yang; Addai-Mensah, Jonas; Losic, Dusan

    2012-01-01

    Diatom silica microparticles were chemically modified with self-assembled monolayers of 3-mercaptopropyl-trimethoxysilane (MPTMS), 3-aminopropyl-trimethoxysilane (APTES) and n-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS), and their application for the adsorption of mercury ions (Hg(II)) is demonstrated. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses revealed that the functional groups (–SH or –NH 2 ) were successfully grafted onto the diatom silica surface. The kinetics and efficiency of Hg(II) adsorption were markedly improved by the chemical functionalization of diatom microparticles. The relationship among the type of functional groups, pH and adsorption efficiency of mercury ions was established. The Hg(II) adsorption reached equilibrium within 60 min with maximum adsorption capacities of 185.2, 131.7 and 169.5 mg g -1 for particles functionalized with MPTMS, APTES and AEAPTMS, respectively. The adsorption behavior followed a pseudo-second-order reaction model and Langmuirian isotherm. These results show that mercapto- or amino-functionalized diatom microparticles are promising natural, cost-effective and environmentally benign adsorbents suitable for the removal of mercury ions from aqueous solutions.

  2. Autofluorescence imaging system to discriminate and quantify the distribution of benthic cyanobacteria and diatoms

    DEFF Research Database (Denmark)

    Carreira, Cátia; Staal, Marc Jaap; Middelboe, Mathias

    2015-01-01

    successfully to (mixed) laboratory cultures as well as natural photosynthetic microbial mats. Cultures of the diatom Nitzschia capitellata and the cyanobacterium Geitlerinema sp. showed close correlation between autofluorescence and cell abundance. This simple and cheap imaging system allows fast observations...

  3. Relationship between diatom communities and environmental ...

    African Journals Online (AJOL)

    ajl yemi

    2011-11-30

    Nov 30, 2011 ... The relationship between diatom species and measured environmental variables was explored at different sites of Honghe wetland region located in northeastern China. Planktonic and epiphytic diatom assemblages in the wetland were identified from May to October of 2007 and 2008. Their relationships.

  4. Colloquium on diatom-copepod interactions

    DEFF Research Database (Denmark)

    Paffenhofer, G.A.; Ianora, A.; Miralto, A.

    2005-01-01

    in situ were also addressed. During the plenary session, the most recent advances on this topic were presented. The plenary session was followed by 3 working groups on (1) production of aldehydes by phytoplankton, (2) toxic and nutritional effects of diatoms on zooplankton, and (3) the chemistry of diatom...

  5. Relationship between diatom communities and environmental ...

    African Journals Online (AJOL)

    Abstract. The relationship between diatom species and measured environmental variables was explored at different sites of Honghe wetland region located in northeastern China. Planktonic and epiphytic diatom assemblages in the wetland were identified from May to October of 2007 and 2008. Their relationships with ...

  6. Diatoms dominate the eukaryotic metatranscriptome during spring in coastal 'dead zone' sediments.

    Science.gov (United States)

    Broman, Elias; Sachpazidou, Varvara; Dopson, Mark; Hylander, Samuel

    2017-10-11

    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. © 2017 The Author(s).

  7. Seasonal and daily fluctuation of diatoms during spring tide periods in Kerkennah Islands

    Directory of Open Access Journals (Sweden)

    Mounir Ben brahim

    2015-06-01

    Full Text Available Objective: To study seasonal and the daily distribution of diatoms in the three tidal periods (flood, slack and ebb period during the spring tide. Methods: Water samples were taken and environmental variables were measured three times in each tidal period during 10 days of spring tide. Sampling was done in 2007 in Cercina station located in the western coast of Kerkennah (34°41'27'' N; 11°07'45'' E (Southern Tunisia. Results: Nutrients showed significant variation between seasons, increasing in spring and decreasing noticeably in autumn and winter. About 36 diatom species were found. Results revealed a remarkable abundance increase in spring and summer. Irregular differences in diatom abundances were revealed over the tidal periods, with the highest rates being detected during the flood and the ebb period, while the abundance rate was lowest during the slack period. This could presumably be attributed to the increase of nutrient supply of suspended particulate matter during water motion. The results revealed a correlation between diatom abundance and temperature, NO2 - , NO3 - , Si(OH4 and PO4 3 . Temperature seemed to be the most important factors which may influence the distribution and diatom abundance. Conclusions: Tide has various effects on the nutrients status and diatoms community (in terms of species composition, succession and abundance between different tidal periods. Fluctuation of diatoms was correlated with changes in the circulation of water bodies and changes in nutrient regime.

  8. Architecture and material properties of diatom shells provide effective mechanical protection

    Science.gov (United States)

    Hamm, Christian E.; Merkel, Rudolf; Springer, Olaf; Jurkojc, Piotr; Maier, Christian; Prechtel, Kathrin; Smetacek, Victor

    2003-02-01

    Diatoms are the major contributors to phytoplankton blooms in lakes and in the sea and hence are central in aquatic ecosystems and the global carbon cycle. All free-living diatoms differ from other phytoplankton groups in having silicified cell walls in the form of two `shells' (the frustule) of manifold shape and intricate architecture whose function and role, if any, in contributing to the evolutionary success of diatoms is under debate. We explored the defence potential of the frustules as armour against predators by measuring their strength. Real and virtual loading tests (using calibrated glass microneedles and finite element analysis) were performed on centric and pennate diatom cells. Here we show that the frustules are remarkably strong by virtue of their architecture and the material properties of the diatom silica. We conclude that diatom frustules have evolved as mechanical protection for the cells because exceptional force is required to break them. The evolutionary arms race between diatoms and their specialized predators will have had considerable influence in structuring pelagic food webs and biogeochemical cycles.

  9. Displacement functions for diatomic materials

    International Nuclear Information System (INIS)

    Panrkin, D.M.; Coulter, C.A.

    1979-01-01

    An extension of the methods of Lindhard et at. was used to calculate the total displacement function n/sub ij/(E) for a number of diatomic materials, where n/sub ij/(E) is defined to be the average number of atoms of type j which are displaced from their sites in a displacement cascade initiated by a PKA of type i and energy E. From the n/sub ij/(E) one can calculate the fraction n/sub ij/(E) of the displacements produced by a type i PKA with energy E which are of type j. Values of the n/sub ij/ for MgO, CaO, Al 2 O 3 , and TaO are presented. It is shown that for diatomic materials with mass ratios reasonably near one (e.g., MgO, Al 2 O 3 ) and equal displacement thresholds for the two species the n/sub ij/ become independent of the PKA type i at energies only a few times threshold. However, for larger mass ratios the n/sub ij/ do not become independent of i until much larger, energies are reached - e.g. > 10 5 eV for TaO. In addition, it is found that the n/sub ij/ depend sensitively on the displacement thresholds, with very dramatic charges occuring when the two thresholds become significantly different from one another

  10. Diatom Transcriptional and Physiological Responses to Changes in Iron Bioavailability across Ocean Provinces

    Directory of Open Access Journals (Sweden)

    Natalie R. Cohen

    2017-11-01

    Full Text Available Changes in iron (Fe bioavailability influence diatom physiology and community composition, and thus have a profound impact on primary productivity and ecosystem dynamics. Iron limitation of diatom growth rates has been demonstrated in both oceanic and coastal waters of the Northeast Pacific Ocean and is predicted to become more pervasive in future oceans. However, it is unclear how the strategies utilized by phytoplankton to cope with low Fe bioavailability and resupply differ across these ocean provinces. We investigated the response of diatom communities to variable Fe conditions through incubation experiments performed in the Fe mosaic of the California Upwelling Zone and along a natural Fe gradient in the Northeast Pacific Ocean. Through coupling gene expression of two dominant diatom taxa (Pseudo-nitzschia and Thalassiosira with biological rate process measurements, we provide an in-depth examination of the physiological and molecular responses associated with varying Fe status. Following Fe enrichment, oceanic diatoms showed distinct differential expression of gene products involved in nitrogen assimilation, photosynthetic carbon fixation, and vitamin production compared to diatoms from low-Fe coastal sites, possibly driven by the chronic nature of Fe stress at the oceanic site. Genes of interest involved in Fe and N metabolism additionally exhibited divergent expression patterns between the two diatom taxa investigated, demonstrating that diverse diatoms may invoke alternative strategies when dealing with identical changes in their environment. We report here several mechanisms used distinctly by coastal or oceanic diatom communities as well as numerous taxa-specific strategies for coping with Fe stress and rearranging nutrient metabolism following Fe enrichment.

  11. Relationships between diatoms and tidal environments in Oregon and Washington, USA

    Science.gov (United States)

    Sawai, Yuki; Horton, Benjamin P.; Kemp, Andrew C.; Hawkes, Andrea D.; Nagumo, Tamostsu; Nelson, Alan R.

    2016-01-01

    A new regional dataset comprising 425 intertidal diatom taxa from 175 samples from 11 ecologically diverse Oregon and Washington estuaries illustrates the importance of compiling a large modern dataset from a range of sites. Cluster analyses and detrended correspondence analysis of the diatom assemblages identify distinct vertical zones within supratidal, intertidal and subtidal environments at six of the 11 study sites, but the abundance of some of the most common species varies widely among and within sites. Canonical correspondence analysis of the regional dataset shows relationships between diatom species and tidal exposure, salinity and substratum (grain size and organic content). Correspondence analyses of local datasets show higher values of explained variation than the analysis of the combined regional dataset. Our results emphasize that studies of the autecology of diatom species require many samples from a range of modern environments to adequately characterize species–environment relationships.

  12. Thraustochytrid protists degrade hydrocarbons

    Digital Repository Service at National Institute of Oceanography (India)

    Raikar, M.T.; Raghukumar, S.; Vani, V.; David, J.J.; Chandramohan, D.

    isolation tubes with crude oil. Three isolates tested showed positive hydrophobicity of cell walls as judged by the Microbial Adhesion to Hydrocarbons (MATH) assay. Addition of Bombay High crude oil to nutrient broth slightly enhanced growth of the protists...

  13. Role of Diatoms in the Spatial-Temporal Distribution of Intracellular Nitrate in Intertidal Sediment

    DEFF Research Database (Denmark)

    Stief, P.; Kamp, A.; de Beer, D.

    2013-01-01

    Intracellular nitrate storage allows microorganisms to survive fluctuating nutrient availability and anoxic conditions in aquatic ecosystems. Here we show that diatoms, ubiquitous and highly abundant microalgae, represent major cellular reservoirs of nitrate in an intertidal flat of the German Wa...... in anaerobic nitrate respiration. Due to the widespread dominance of diatoms in microphytobenthos, the total nitrate pool in coastal marine sediments may generally be at least two times larger than derived from porewater measurements and partially be recycled to ammonium....

  14. Diatomic Metasurface for Vectorial Holography.

    Science.gov (United States)

    Deng, Zi-Lan; Deng, Junhong; Zhuang, Xin; Wang, Shuai; Li, Kingfai; Wang, Yao; Chi, Yihui; Ye, Xuan; Xu, Jian; Wang, Guo Ping; Zhao, Rongkuo; Wang, Xiaolei; Cao, Yaoyu; Cheng, Xing; Li, Guixin; Li, Xiangping

    2018-05-09

    The emerging metasurfaces with the exceptional capability of manipulating an arbitrary wavefront have revived the holography with unprecedented prospects. However, most of the reported metaholograms suffer from limited polarization controls for a restrained bandwidth in addition to their complicated meta-atom designs with spatially variant dimensions. Here, we demonstrate a new concept of vectorial holography based on diatomic metasurfaces consisting of metamolecules formed by two orthogonal meta-atoms. On the basis of a simply linear relationship between phase and polarization modulations with displacements and orientations of identical meta-atoms, active diffraction of multiple polarization states and reconstruction of holographic images are simultaneously achieved, which is robust against both incident angles and wavelengths. Leveraging this appealing feature, broadband vectorial holographic images with spatially varying polarization states and dual-way polarization switching functionalities have been demonstrated, suggesting a new route to achromatic diffractive elements, polarization optics, and ultrasecure anticounterfeiting.

  15. Phenotypic plasticity of southern ocean diatoms: key to success in the sea ice habitat?

    Directory of Open Access Journals (Sweden)

    Olivia Sackett

    Full Text Available Diatoms are the primary source of nutrition and energy for the Southern Ocean ecosystem. Microalgae, including diatoms, synthesise biological macromolecules such as lipids, proteins and carbohydrates for growth, reproduction and acclimation to prevailing environmental conditions. Here we show that three key species of Southern Ocean diatom (Fragilariopsis cylindrus, Chaetoceros simplex and Pseudo-nitzschia subcurvata exhibited phenotypic plasticity in response to salinity and temperature regimes experienced during the seasonal formation and decay of sea ice. The degree of phenotypic plasticity, in terms of changes in macromolecular composition, was highly species-specific and consistent with each species' known distribution and abundance throughout sea ice, meltwater and pelagic habitats, suggesting that phenotypic plasticity may have been selected for by the extreme variability of the polar marine environment. We argue that changes in diatom macromolecular composition and shifts in species dominance in response to a changing climate have the potential to alter nutrient and energy fluxes throughout the Southern Ocean ecosystem.

  16. Petroleum hydrocarbons

    International Nuclear Information System (INIS)

    Farrington, J.W.; Teal, J.M.; Parker, P.L.

    1976-01-01

    Methods for analysis of petroleum hydrocarbons in marine samples are presented. Types of hydrocarbons present and their origins are discussed. Principles and methods of analysis are outlined. Infrared spectrometry, uv spectrometry, gas chromatography, mass spectroscopy, and carbon 14 measurements are described

  17. Molecular fossils of diatoms. Applications in petroleum geochemistry and palaeoenvironmental studies

    Energy Technology Data Exchange (ETDEWEB)

    Rampen, S.W.

    2009-06-11

    different Proboscia species and culture experiments showed increasing chain-lengths and a decreasing degree of unsaturation for 1,14-diols with increasing growth temperature. Lipid analyses from surface sediments from the eastern South Atlantic suggested a significant relationship between long-chain 1,14-diol chain-length and sea surface temperature, but the degree of unsaturation for 1,14-diols seems also determined by other factors. Sediment trap data from the Arabian Sea confirmed that Proboscia lipids can be used as proxies for upwelling conditions and also showed that long-chain 1,15-diols are not limited to upwelling conditions. A sediment core taken from the Somali continental slope showed strong fluctuations of long-chain 1,14- and 1,15-diols with time; 1,14-diols were relatively high during the Holocene when upwelling occurred and much lower during the Late Glacial Maximum and the last Glacial when upwelling was suppressed. Elevated 1,14-diol concentrations during the first half of Marine Isotope Stage 3 and at the end of Marine Isotope Stage 5.1 suggest intensified glacial upwelling during those periods. Analyses of long-chain diols in a sediment core from the North Western Antarctic Peninsula suggest that Proboscia diatom productivity in this area is associated with upwelling of Upper Circumpolar Deep Water at the shelf break. Comparison of the diol record with melt events in Siple Dome ice core indicates that this upwelling is driven by the same climatic processes that are responsible for changes in regional climate.

  18. Diatom algae of the Guni river (Pamir)

    International Nuclear Information System (INIS)

    Kurbonova, P.A.; Hisoriev, H.H.

    2006-01-01

    There are presented the dates of the results of diatom algae (Bacillariophyta) of the Gunt river. There was found 107 species and 9 subspecies which belong to 3 classics, 12 ordos, 13 families and 28 genus

  19. Importance of sampling frequency when collecting diatoms

    KAUST Repository

    Wu, Naicheng; Faber, Claas; Sun, Xiuming; Qu, Yueming; Wang, Chao; Ivetic, Snjezana; Riis, Tenna; Ulrich, Uta; Fohrer, Nicola

    2016-01-01

    There has been increasing interest in diatom-based bio-assessment but we still lack a comprehensive understanding of how to capture diatoms’ temporal dynamics with an appropriate sampling frequency (ASF). To cover this research gap, we collected

  20. Analytic vibrational matrix elements for diatomic molecules

    International Nuclear Information System (INIS)

    Bouanich, J.P.; Ogilvie, J.F.; Tipping, R.H.

    1986-01-01

    The vibrational matrix elements and expectation values for a diatomic molecule, including the rotational dependence, are calculated for powers of the reduced displacement in terms of the parameters of the Dunham potential-energy function. (orig.)

  1. Kinetic control on Zn isotope signatures recorded in marine diatoms

    Science.gov (United States)

    Köbberich, Michael; Vance, Derek

    2017-08-01

    Marine diatoms dominate the oceanic cycle of the essential micronutrient zinc (Zn). The stable isotopes of zinc and other metals are increasingly used to understand trace metal micronutrient cycling in the oceans. One clear feature of the early isotope data is the heavy Zn isotope signature of the average oceanic dissolved pool relative to the inputs, potentially driven by uptake of light isotopes into phytoplankton cells and export to sediments. However, despite the fact that diatoms strip Zn from surface waters across the Antarctic polar front in the Southern Ocean, the local upper ocean is not isotopically heavy. Here we use culturing experiments to quantify the extent of Zn isotope fractionation by diatoms and to elucidate the mechanisms driving it. We have cultured two different open-ocean diatom species (T. oceanica and Chaetoceros sp.) in a series of experiments at constant medium Zn concentration but at bioavailable medium Fe ranging from limiting to replete. We find that T. oceanica can maintain high growth rates and Zn uptake rates over the full range of bioavailable iron (Fe) investigated, and that the Zn taken up has a δ66Zn that is unfractionated relative to that of the bioavailable free Zn in the medium. The studied representative of the genus Chaetoceros, on the other hand, shows more significantly reduced Zn uptake rates at low Fe and records more variable biomass δ66Zn signatures, of up to 0.85‰ heavier than the medium. We interpret the preferential uptake of heavy isotopes at extremely low Zn uptake rates as potentially due to either of the following two mechanisms. First, the release of extracellular polymeric substances (EPS), at low Fe levels, may preferentially scavenge heavy Zn isotopes. Second, the Zn uptake rate may be slow enough to establish pseudo-equilibrium conditions at the transporter site, with heavy Zn isotopes forming more stable surface complexes. Thus we find that, in our experiments, Fe-limitation exerts a key control that

  2. Soliton solutions in a diatomic lattice system

    International Nuclear Information System (INIS)

    Yajima, Nobuo; Satsuma, Junkichi.

    1979-04-01

    A continuum limit is considered for a diatomic lattice system with a cubic nonlinearity. A long wave equation describing the interaction of acoustic and optical modes is obtained. It reduces, in certain approximations, to equations having coupled wave solutions. The solutions exhibit trapping of an optical mode by an acoustic soliton. The form of the trapped optical wave depends on the mass ratio of adjacent particles in the diatomic lattice. (author)

  3. Diatom. A potential bio-accumulator of gold

    International Nuclear Information System (INIS)

    Chakraborty, N.; Pal, R.; Ramaswami, A.; Nayak, D.; Lahiri, S.

    2006-01-01

    The bioaccumulation of gold in trace concentration by Nitzschia obtusa and Navicula minima, two members of bacillariophyceae, has been studied. It has been observed that Nitzschia obtusa showed better accumulation of gold in acidic pH in comparison to neutral and basic pH. Maximum accumulation was observed with 1 mg x kg -1 or less gold concentration. However, the accumulation by the living cells was reduced when the matrix concentration was higher. Navicula minima, on the other hand, found to be a better accumulator of gold in wide ranges of pH and substrate concentration of the media. It was also inferred that the gold accumulation by diatom was mainly due to adsorption by biosilica (siliceous frustules of dead diatom cells). Accumulated gold was recovered with conc. HNO 3 . (author)

  4. Development of a diatom-based multimetric index for acid mine drainage impacted depressional wetlands.

    Science.gov (United States)

    Riato, Luisa; Leira, Manel; Della Bella, Valentina; Oberholster, Paul J

    2018-01-15

    Acid mine drainage (AMD) from coal mining in the Mpumalanga Highveld region of South Africa has caused severe chemical and biological degradation of aquatic habitats, specifically depressional wetlands, as mines use these wetlands for storage of AMD. Diatom-based multimetric indices (MMIs) to assess wetland condition have mostly been developed to assess agricultural and urban land use impacts. No diatom MMI of wetland condition has been developed to assess AMD impacts related to mining activities. Previous approaches to diatom-based MMI development in wetlands have not accounted for natural variability. Natural variability among depressional wetlands may influence the accuracy of MMIs. Epiphytic diatom MMIs sensitive to AMD were developed for a range of depressional wetland types to account for natural variation in biological metrics. For this, we classified wetland types based on diatom typologies. A range of 4-15 final metrics were selected from a pool of ~140 candidate metrics to develop the MMIs based on their: (1) broad range, (2) high separation power and (3) low correlation among metrics. Final metrics were selected from three categories: similarity to reference sites, functional groups, and taxonomic composition, which represent different aspects of diatom assemblage structure and function. MMI performances were evaluated according to their precision in distinguishing reference sites, responsiveness to discriminate reference and disturbed sites, sensitivity to human disturbances and relevancy to AMD-related stressors. Each MMI showed excellent discriminatory power, whether or not it accounted for natural variation. However, accounting for variation by grouping sites based on diatom typologies improved overall performance of MMIs. Our study highlights the usefulness of diatom-based metrics and provides a model for the biological assessment of depressional wetland condition in South Africa and elsewhere. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Novel sex cells and evidence for sex pheromones in diatoms.

    Science.gov (United States)

    Sato, Shinya; Beakes, Gordon; Idei, Masahiko; Nagumo, Tamotsu; Mann, David G

    2011-01-01

    Diatoms belong to the stramenopiles, one of the largest groups of eukaryotes, which are primarily characterized by a presence of an anterior flagellum with tubular mastigonemes and usually a second, smooth flagellum. Based on cell wall morphology, diatoms have historically been divided into centrics and pennates, of which only the former have flagella and only on the sperm. Molecular phylogenies show the pennates to have evolved from among the centrics. However, the timing of flagellum loss--whether before the evolution of the pennate lineage or after--is unknown, because sexual reproduction has been so little studied in the 'araphid' basal pennate lineages, to which Pseudostaurosira belongs. Sexual reproduction of an araphid pennate, Pseudostaurosira trainorii, was studied with light microscopy (including time lapse observations and immunofluorescence staining observed under confocal scanning laser microscopy) and SEM. We show that the species produces motile male gametes. Motility is mostly associated with the extrusion and retrieval of microtubule-based 'threads', which are structures hitherto unknown in stramenopiles, their number varying from one to three per cell. We also report experimental evidence for sex pheromones that reciprocally stimulate sexualization of compatible clones and orientate motility of the male gametes after an initial 'random walk'. The threads superficially resemble flagella, in that both are produced by male gametes and contain microtubules. However, one striking difference is that threads cannot beat or undulate and have no motility of their own, and they do not bear mastigonemes. Threads are sticky and catch and draw objects, including eggs. The motility conferred by the threads is probably crucial for sexual reproduction of P. trainorii, because this diatom is non-motile in its vegetative stage but obligately outbreeding. Our pheromone experiments are the first studies in which gametogenesis has been induced in diatoms by cell

  6. Novel sex cells and evidence for sex pheromones in diatoms.

    Directory of Open Access Journals (Sweden)

    Shinya Sato

    Full Text Available BACKGROUND: Diatoms belong to the stramenopiles, one of the largest groups of eukaryotes, which are primarily characterized by a presence of an anterior flagellum with tubular mastigonemes and usually a second, smooth flagellum. Based on cell wall morphology, diatoms have historically been divided into centrics and pennates, of which only the former have flagella and only on the sperm. Molecular phylogenies show the pennates to have evolved from among the centrics. However, the timing of flagellum loss--whether before the evolution of the pennate lineage or after--is unknown, because sexual reproduction has been so little studied in the 'araphid' basal pennate lineages, to which Pseudostaurosira belongs. METHODS/PRINCIPAL FINDING: Sexual reproduction of an araphid pennate, Pseudostaurosira trainorii, was studied with light microscopy (including time lapse observations and immunofluorescence staining observed under confocal scanning laser microscopy and SEM. We show that the species produces motile male gametes. Motility is mostly associated with the extrusion and retrieval of microtubule-based 'threads', which are structures hitherto unknown in stramenopiles, their number varying from one to three per cell. We also report experimental evidence for sex pheromones that reciprocally stimulate sexualization of compatible clones and orientate motility of the male gametes after an initial 'random walk'. CONCLUSIONS/SIGNIFICANCE: The threads superficially resemble flagella, in that both are produced by male gametes and contain microtubules. However, one striking difference is that threads cannot beat or undulate and have no motility of their own, and they do not bear mastigonemes. Threads are sticky and catch and draw objects, including eggs. The motility conferred by the threads is probably crucial for sexual reproduction of P. trainorii, because this diatom is non-motile in its vegetative stage but obligately outbreeding. Our pheromone experiments

  7. A C-25 highly branched isoprenoid alkene and C-25 and C-27 n-polyenes in the marine diatom Rhizosolenia setigera

    NARCIS (Netherlands)

    Sinninghe Damste, J.S; Rijpstra, W.I C; Schouten, S; Peletier, H.; van der Maarel, M.J.E.C.; Gieskes, W.W C

    1999-01-01

    A North Atlantic strain of the marine diatom Rhizosolenia setigera was examined for the presence of hydrocarbons. This strain biosynthesizes a highly branched isoprenoid (HBI) C-25 pentaene, in contrast to Australian strains of R. setigera which produce HBI C-30 alkenes. The more widespread

  8. Diatom-Specific Oligosaccharide and Polysaccharide Structures Help to Unravel Biosynthetic Capabilities in Diatoms

    Directory of Open Access Journals (Sweden)

    Bruno Gügi

    2015-09-01

    Full Text Available Diatoms are marine organisms that represent one of the most important sources of biomass in the ocean, accounting for about 40% of marine primary production, and in the biosphere, contributing up to 20% of global CO2 fixation. There has been a recent surge in developing the use of diatoms as a source of bioactive compounds in the food and cosmetic industries. In addition, the potential of diatoms such as Phaeodactylum tricornutum as cell factories for the production of biopharmaceuticals is currently under evaluation. These biotechnological applications require a comprehensive understanding of the sugar biosynthesis pathways that operate in diatoms. Here, we review diatom glycan and polysaccharide structures, thus revealing their sugar biosynthesis capabilities.

  9. Rotation harmonics for a numerical diatomic potential

    International Nuclear Information System (INIS)

    Kobeissi, H.; Korek, M.

    1983-01-01

    The problem of the determination of the rotation harmonics phi 1 , phi 2 , ... for the case of a numerical diatomic potential is considered. These harmonics defined in a recent work by psisub(vJ) = psisub(vO) + lambda 2 phi 2 + ... (where psisub(vJ) is the wave function of the vibration level v and the rotation level J, and lambda = J(J+1)) are studied for the case of the Dunham potential and for a numerical potential defined by the coordinates of its turning points with polynomial interpolations and extrapolations. It is proved that the analytical expressions of the harmonics phi 1 , phi 2 , ... reduce to polynomials where the coefficients are simply related to those of the potential in the case of the Dunham potential, and to the coordinates of the turning points in the case of the numerical potential. The numerical application is simple. The examples presented show that the vibration-rotation wave function psisub(vJ) calculated by using two harmonics only is ''exact'' up to eight significant figures

  10. Diatoms as a fingerprint of sub-catchment contributions to meso-scale catchment runoff

    Science.gov (United States)

    Klaus, Julian; Wetzel, Carlos E.; Martinez-Carreras, Nuria; Ector, Luc; Pfister, Laurent

    2014-05-01

    In recent years, calls were made for new eco-hydrological approaches to improve understanding of hydrological processes. Recently diatoms, one of the most common and diverse algal groups that can be easily transported by flowing water due to their small size (~10-200 µm), were used to detect the onset and cessation of surface runoff to small headwater streams and constrain isotopic and hydro-chemical hydrograph separation methods. While the method showed its potential in the hillslope-riparian zone-stream continuum of headwater catchments, the behavior of diatoms and their use for hydrological process research in meso-scale catchments remains uncertain. Diatoms can be a valuable support for isotope and hydro-chemical tracer methods when these become ambiguous with increasing scale. Distribution and abundance of diatom species is controlled by various environmental factors (pH, soil type, moisture conditions, exposition to sunlight, etc.). We therefore hypothesize that species abundance and composition can be used as a proxy for source areas. This presentation evaluates the potential for diatoms to trace source-areas in the nested meso-scale Attert River basin (250 km2, Luxembourg, Europe). We sampled diatom populations in streamwater during one flood event in Fall 2011 in 6 sub-catchments and the basin outlet - 17 to 28 samples/catchment for the different sampling locations. Diatoms were classified and counted in every individual sample. In total more than 400 diatom species were detected. Ordination analysis revealed a clear distinction between communities sampled in different sub-catchments. The species composition at the catchment outlet reflects a mixing of the diatom composition originating from different sub-catchments. This data suggests that diatoms indeed can reflect the geographic origin of stream water at the catchment outlet. The centroids of the ordination analysis might be linked to the physiographic characteristics (geology and land use) of the

  11. Large variation in the Rubisco kinetics of diatoms reveals diversity among their carbon-concentrating mechanisms

    Science.gov (United States)

    Young, Jodi N.; Heureux, Ana M.C.; Sharwood, Robert E.; Rickaby, Rosalind E.M.; Morel, François M.M.; Whitney, Spencer M.

    2016-01-01

    While marine phytoplankton rival plants in their contribution to global primary productivity, our understanding of their photosynthesis remains rudimentary. In particular, the kinetic diversity of the CO2-fixing enzyme, Rubisco, in phytoplankton remains unknown. Here we quantify the maximum rates of carboxylation (k cat c), oxygenation (k cat o), Michaelis constants (K m) for CO2 (K C) and O2 (K O), and specificity for CO2 over O2 (SC/O) for Form I Rubisco from 11 diatom species. Diatom Rubisco shows greater variation in K C (23–68 µM), SC/O (57–116mol mol−1), and K O (413–2032 µM) relative to plant and algal Rubisco. The broad range of K C values mostly exceed those of C4 plant Rubisco, suggesting that the strength of the carbon-concentrating mechanism (CCM) in diatoms is more diverse, and more effective than previously predicted. The measured k cat c for each diatom Rubisco showed less variation (2.1–3.7s−1), thus averting the canonical trade-off typically observed between K C and k cat c for plant Form I Rubisco. Uniquely, a negative relationship between K C and cellular Rubisco content was found, suggesting variation among diatom species in how they allocate their limited cellular resources between Rubisco synthesis and their CCM. The activation status of Rubisco in each diatom was low, indicating a requirement for Rubisco activase. This work highlights the need to better understand the correlative natural diversity between the Rubisco kinetics and CCM of diatoms and the underpinning mechanistic differences in catalytic chemistry among the Form I Rubisco superfamily. PMID:27129950

  12. Quantification of diatoms in biofilms: Standardisation of methods

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Anil, A.C.

    of the difficulty in sampling and enumeration. Scraping or brushing are the traditional methods used for removal of diatoms from biofilms developed on solid substrata. The method of removal is the most critical step in enumerating the biofilm diatom community...

  13. 9 Records of Diatoms and Physicochemical.cdr

    African Journals Online (AJOL)

    Administrator

    between some physicochemical parameters and diatom species in these ponds. ..... Diversity and relative abundance (%) of diatoms species in selected seasonal ponds in Zaria, Nigeria ..... connection with reference conditions of the water.

  14. Preparation and method of study of fossil diatoms

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    Two methods of chemical concentration of diatoms occurring in fresh-water sediments, and one chemico-mechanical method of concentration for diatoms occurring in marine sediments are outlined, with emphasis on the extreme care that needs...

  15. Purifying hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Demoulins, H D; Garner, F H

    1923-02-07

    Hydrocarbon distillates, including natural gases and vapors produced by cracking hydrocarbon oils, are desulfurized etc. by treating the vapor with an aqueous alkaline solution of an oxidizing agent. The hydrocarbons may be previously purified by sulfuric acid. In examples aqueous solutions of sodium or calcium hydrochlorite containing 1.5 to 5.0 grams per liter of available chlorine and sufficient alkali to give an excess of 0.1 percent in the spent reagent are preheated to the temperature of the vapor, and either sprayed or atomized into the vapors near the outlet of the dephlegmator or fractionating tower, or passed in countercurrent to the vapors through one or a series of scrubbers.

  16. Diatoms: a fossil fuel of the future.

    Science.gov (United States)

    Levitan, Orly; Dinamarca, Jorge; Hochman, Gal; Falkowski, Paul G

    2014-03-01

    Long-term global climate change, caused by burning petroleum and other fossil fuels, has motivated an urgent need to develop renewable, carbon-neutral, economically viable alternatives to displace petroleum using existing infrastructure. Algal feedstocks are promising candidate replacements as a 'drop-in' fuel. Here, we focus on a specific algal taxon, diatoms, to become the fossil fuel of the future. We summarize past attempts to obtain suitable diatom strains, propose future directions for their genetic manipulation, and offer biotechnological pathways to improve yield. We calculate that the yields obtained by using diatoms as a production platform are theoretically sufficient to satisfy the total oil consumption of the US, using between 3 and 5% of its land area. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Silica diatom shells tailored with Au nanoparticles enable sensitive analysis of molecules for biological, safety and environment applications

    KAUST Repository

    Onesto, V.; Villani, M.; Coluccio, M. L.; Majewska, R.; Alabastri, A.; Battista, E.; Schirato, A.; Calestani, D.; Coppedé , N.; Cesarelli, M.; Amato, F.; Di Fabrizio, Enzo M.; Gentile, F.

    2018-01-01

    Diatom shells are a natural, theoretically unlimited material composed of silicon dioxide, with regular patterns of pores penetrating through their surface. For their characteristics, diatom shells show promise to be used as low cost, highly efficient drug carriers, sensor devices or other micro-devices. Here, we demonstrate diatom shells functionalized with gold nanoparticles for the harvesting and detection of biological analytes (bovine serum albumin—BSA) and chemical pollutants (mineral oil) in low abundance ranges, for applications in bioengineering, medicine, safety, and pollution monitoring.

  18. Silica diatom shells tailored with Au nanoparticles enable sensitive analysis of molecules for biological, safety and environment applications

    KAUST Repository

    Onesto, V.

    2018-04-19

    Diatom shells are a natural, theoretically unlimited material composed of silicon dioxide, with regular patterns of pores penetrating through their surface. For their characteristics, diatom shells show promise to be used as low cost, highly efficient drug carriers, sensor devices or other micro-devices. Here, we demonstrate diatom shells functionalized with gold nanoparticles for the harvesting and detection of biological analytes (bovine serum albumin—BSA) and chemical pollutants (mineral oil) in low abundance ranges, for applications in bioengineering, medicine, safety, and pollution monitoring.

  19. Diatoms in Liyu Lake, Eastern Taiwan

    Directory of Open Access Journals (Sweden)

    Liang-Chi Wang

    2010-09-01

    Full Text Available This study described the diatoms appeared in the sediments of Liyu Lake, a lowland natural lake situated at Hualen, eastern Taiwan. A total of 50 species was found in the sediments of this eutrophic lake. In them, 8 species were reported for the first time in Taiwan. They are: Cymbella thienemannii, Navicula absoluta, Navicula bacillum, Frustulia rhomboides var. crassinervia, Gyrosigma procerum, Nitzschia paleacea Epithemia smithii and Eunotia subarcuatioides. The ultrastructures of each species were described on the basis of observations under a scanning electron microscope. The ecological implications of the occurrence of these diatom species in this lake were inferred.

  20. Purifying hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Dunstan, A E

    1918-06-03

    Ligroin, kerosene, and other distillates from petroleum and shale oil, are purified by treatment with a solution of a hypochlorite containing an excess of alkali. The hydrocarbon may be poured into brine, the mixture stirred, and an electric current passed through. Heat may be applied.

  1. Epibiotic Diatoms Are Universally Present on All Sea Turtle Species

    Science.gov (United States)

    Majewska, Roksana; Lazo-Wasem, Eric A.; Nel, Ronel; Paladino, Frank V.; Rojas, Lourdes; Zardus, John D.; Pinou, Theodora

    2016-01-01

    The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtle species hosting at least two diatom taxa. We recommend that future research is undertaken to confirm whether diatom communities vary between sea turtle species and whether these diatom taxa are facultative or obligate commensals. PMID:27257972

  2. Genetic and metabolic engineering in diatoms.

    Science.gov (United States)

    Huang, Weichao; Daboussi, Fayza

    2017-09-05

    Diatoms have attracted considerable attention due to their success in diverse environmental conditions, which probably is a consequence of their complex origins. Studies of their metabolism will provide insight into their adaptation capacity and are a prerequisite for metabolic engineering. Several years of investigation have led to the development of the genome engineering tools required for such studies, and a profusion of appropriate tools is now available for exploring and exploiting the metabolism of these organisms. Diatoms are highly prized in industrial biotechnology, due to both their richness in natural lipids and carotenoids and their ability to produce recombinant proteins, of considerable value in diverse markets. This review provides an overview of recent advances in genetic engineering methods for diatoms, from the development of gene expression cassettes and gene delivery methods, to cutting-edge genome-editing technologies. It also highlights the contributions of these rapid developments to both basic and applied research: they have improved our understanding of key physiological processes; and they have made it possible to modify the natural metabolism to favour the production of specific compounds or to produce new compounds for green chemistry and pharmaceutical applications.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Author(s).

  3. Experimental toxicity and bioaccumulation of cadmium in freshwater periphytic diatoms in relation with biofilm maturity

    International Nuclear Information System (INIS)

    Duong, Thi Thuy; Morin, Soizic; Coste, Michel; Herlory, Olivier; Feurtet-Mazel, Agnes; Boudou, Alain

    2010-01-01

    A study was undertaken to examine cadmium accumulation in freshwater biofilm, its effects on biofilm development and on diatom community structure in laboratory experimental conditions. A suspension of a biofilm originated from the Riou-Mort River (South West France) was inoculated into three experimental units containing clean glass substrates under laboratory conditions. Settling and already developed biofilms were exposed to a Cd concentration of 100 μg L -1 . Metal accumulation (total and intracellular metal content) in biofilms, dry weight and ash-free dry mass, diatom cell density and diatom community composition were analyzed. Both total and intracellular Cd accumulated by the biofilm throughout the experiment increased with duration of metal exposure. Biofilms in the course of maturation were showed higher Cd content and less effective development than settled biofilms. However diatom communities in younger biofilms exposed to Cd increased their tolerance to Cd by a highly significant development of Nitzschia palea. In contrast, Cd exposure had different effect in installed biofilm and taxonomic composition. These results indicate that mature biofilm may limit Cd accumulation into its architecture and protect diatom communities from the effects of metals.

  4. Cadmium sensitivity, uptake, subcellular distribution and thiol induction in a marine diatom: Exposure to cadmium

    International Nuclear Information System (INIS)

    Wang Mengjiao; Wang Wenxiong

    2011-01-01

    The aims of this study were to (1) evaluate the changes in the Cd tolerance of a marine diatom after exposure under different Cd concentrations for various durations and (2) to explore the potential subcellular and biochemical mechanisms underlying these changes. The 72-h toxicity, short-term Cd uptake, subcellular Cd distribution, as well as the synthesis of phytochelatins (PCs) were measured in a marine diatom Thalassiosira nordenskioeldii after exposure to a range of free Cd ion concentrations ([Cd 2+ ], 0.01-84 nM) for 1-15 days. Surprisingly, the diatoms did not acquire higher resistance to Cd after exposure; instead their sensitivity to Cd increased with a higher exposed [Cd 2+ ] and a longer exposure period. The underlying mechanisms could be traced to the responses of Cd cellular accumulation and the intrinsic detoxification ability of the preconditioned diatoms. Generally, exposure to a higher [Cd 2+ ] and for a longer period increased the Cd uptake rate, cellular accumulation, as well as the Cd concentration in metal-sensitive fraction (MSF) in these diatoms. In contrast, although PCs were induced by the environmental Cd stress (with PC 2 being the most affected), the increased intracellular Cd to PC-SH ratio implied that the PCs' detoxification ability had reduced after Cd exposure. All these responses resulted in an elevated Cd sensitivity as exposed [Cd 2+ ] and duration increased. This study shows that the physiological/biochemical and kinetic responses of phytoplankton upon metal exposure deserve further investigation.

  5. Diatom diversity and response in metal-polluted river environment: preliminary reports from Gromolo Torrent (Liguria, Italy)

    Science.gov (United States)

    Capello, Marco; Tolotti, Raffaella; Bernabè, Dimitri; Carbone, Cristina; Consani, Sirio; Vagge, Greta; Cutroneo, Laura

    2016-04-01

    riverbed from the hard surface of selected cobblestone by scraping. In laboratory all the samples were washed (by digestion with hydrogen peroxide) and mounted according to the protocol used by the DISTAV Laboratories (University of Genoa). Identification and enumeration of diatom valves was performed using an LM Reichert Jung-Polyvar microscope with 1000x oil-immersion lens. Moreover, a representative subsample of each preparation was observed using SEM images providing an interesting iconographic dataset. Preliminary results show that diatom assemblages are characteristic (in both quality and quantity) in the three different environmental conditions highlighted: a) in AMD environment diatoms are quantitatively scarcely, represented by both typically pioneer and highly tolerant species; b) in the Gromolo torrent diatoms are well represented with fairly well-structured communities, but present specific types and different frequencies in teratological frustula, whereas c) in marine environment they are very poorly represented.

  6. Optimizing CRISPR/Cas9 for the Diatom Phaeodactylum tricornutum

    Directory of Open Access Journals (Sweden)

    Daniel Stukenberg

    2018-06-01

    Full Text Available CRISPR/Cas9 is a powerful tool for genome editing. We constructed an easy-to-handle expression vector for application in the model organism Phaeodactylum tricornutum and tested its capabilities in order to apply CRISPR/Cas9 technology for our purpose. In our experiments, we targeted two different genes, screened for mutations and analyzed mutated diatoms in a three-step process. In the end, we identified cells, showing either monoallelic or homo-biallelic targeted mutations. Thus, we confirm that application of the CRISPR/Cas9 system for P. tricornutum is very promising, although, as discussed, overlooked pitfalls have to be considered.

  7. Biosilica from Living Diatoms: Investigations on Biocompatibility of Bare and Chemically Modified Thalassiosira weissflogii Silica Shells

    Directory of Open Access Journals (Sweden)

    Stefania Roberta Cicco

    2016-12-01

    Full Text Available In the past decade, mesoporous silica nanoparticles (MSNs with a large surface area and pore volume have attracted considerable attention for their application in drug delivery and biomedicine. Here we propose biosilica from diatoms as an alternative source of mesoporous materials in the field of multifunctional supports for cell growth: the biosilica surfaces were chemically modified by traditional silanization methods resulting in diatom silica microparticles functionalized with 3-mercaptopropyl-trimethoxysilane (MPTMS and 3-aminopropyl-triethoxysilane (APTES. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that the –SH or –NH2 were successfully grafted onto the biosilica surface. The relationship among the type of functional groups and the cell viability was established as well as the interaction of the cells with the nanoporosity of frustules. These results show that diatom microparticles are promising natural biomaterials suitable for cell growth, and that the surfaces, owing to the mercapto groups, exhibit good biocompatibility.

  8. A mesoscale iron enrichment in the western subarctic Pacific induces a large centric diatom bloom.

    Science.gov (United States)

    Tsuda, Atsushi; Takeda, Shigenobu; Saito, Hiroaki; Nishioka, Jun; Nojiri, Yukihiro; Kudo, Isao; Kiyosawa, Hiroshi; Shiomoto, Akihiro; Imai, Keiri; Ono, Tsuneo; Shimamoto, Akifumi; Tsumune, Daisuke; Yoshimura, Takeshi; Aono, Tatsuo; Hinuma, Akira; Kinugasa, Masatoshi; Suzuki, Koji; Sohrin, Yoshiki; Noiri, Yoshifumi; Tani, Heihachiro; Deguchi, Yuji; Tsurushima, Nobuo; Ogawa, Hiroshi; Fukami, Kimio; Kuma, Kenshi; Saino, Toshiro

    2003-05-09

    We have performed an in situ test of the iron limitation hypothesis in the subarctic North Pacific Ocean. A single enrichment of dissolved iron caused a large increase in phytoplankton standing stock and decreases in macronutrients and dissolved carbon dioxide. The dominant phytoplankton species shifted after the iron addition from pennate diatoms to a centric diatom, Chaetoceros debilis, that showed a very high growth rate, 2.6 doublings per day. We conclude that the bioavailability of iron regulates the magnitude of the phytoplankton biomass and the key phytoplankton species that determine the biogeochemical sensitivity to iron supply of high-nitrate, low-chlorophyll waters.

  9. Anaerobic nitrogen turnover by sinking diatom aggregates at varying ambient oxygen levels

    DEFF Research Database (Denmark)

    Stief, Peter; Kamp, Anja; Thamdrup, Bo

    2016-01-01

    nitrate supply. Sinking diatom aggregates can contribute directly to fixed-nitrogen loss in low-oxygen environments in the ocean and vastly expand the ocean volume in which anaerobic nitrogen turnover is possible, despite relatively high ambient oxygen levels. Depending on the extent of intracellular......In the world’s oceans, even relatively low oxygen levels inhibit anaerobic nitrogen cycling by free-living microbes. Sinking organic aggregates, however, might provide oxygen-depleted microbial hotspots in otherwise oxygenated surface waters. Here, we show that sinking diatom aggregates can host...

  10. Red and green algal origin of diatom membrane transporters: insights into environmental adaptation and cell evolution.

    Directory of Open Access Journals (Sweden)

    Cheong Xin Chan

    Full Text Available Membrane transporters (MTs facilitate the movement of molecules between cellular compartments. The evolutionary history of these key components of eukaryote genomes remains unclear. Many photosynthetic microbial eukaryotes (e.g., diatoms, haptophytes, and dinoflagellates appear to have undergone serial endosymbiosis and thereby recruited foreign genes through endosymbiotic/horizontal gene transfer (E/HGT. Here we used the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum as models to examine the evolutionary origin of MTs in this important group of marine primary producers. Using phylogenomics, we used 1,014 diatom MTs as query against a broadly sampled protein sequence database that includes novel genome data from the mesophilic red algae Porphyridium cruentum and Calliarthron tuberculosum, and the stramenopile Ectocarpus siliculosus. Our conservative approach resulted in 879 maximum likelihood trees of which 399 genes show a non-lineal history between diatoms and other eukaryotes and prokaryotes (at the bootstrap value ≥70%. Of the eukaryote-derived MTs, 172 (ca. 25% of 697 examined phylogenies have members of both red/green algae as sister groups, with 103 putatively arising from green algae, 19 from red algae, and 50 have an unresolved affiliation to red and/or green algae. We used topology tests to analyze the most convincing cases of non-lineal gene history in which red and/or green algae were nested within stramenopiles. This analysis showed that ca. 6% of all trees (our most conservative estimate support an algal origin of MTs in stramenopiles with the majority derived from green algae. Our findings demonstrate the complex evolutionary history of photosynthetic eukaryotes and indicate a reticulate origin of MT genes in diatoms. We postulate that the algal-derived MTs acquired via E/HGT provided diatoms and other related microbial eukaryotes the ability to persist under conditions of fluctuating ocean chemistry, likely

  11. [Research advances in heavy metals pollution ecology of diatom].

    Science.gov (United States)

    Ding, Teng-Da; Ni, Wan-Min; Zhang, Jian-Ying

    2012-03-01

    Diatom, due to its high sensitivity to environmental change, is one of the bio-indicators of aquatic ecosystem health, and some typical diatom species have been applied to indicate the heavy metals pollution of water body. With the focus on the surface water heavy metals pollution, this paper reviewed the research advances in the toxic effect of heavy metals pollution on diatom, biosorption and bioaccumulation of heavy metals by diatom, ecological adaptation mechanisms of diatom to heavy metals pollution, and roles of diatom as bio-indicator and in ecological restoration of heavy metals pollution. The growth tendency of diatom and the morphological change of frustule under heavy metals pollution as well as the differences in heavy metals biosorption and bioaccumulation by diatom, the ecological adaptation mechanisms of diatom on heavy metals surface complexation and ion exchange, and the roles of diatom as bio-indicator and in ecological restoration of heavy metals polluted water body were also discussed. This review could provide scientific evidences for the prevention of aquatic ecosystems heavy metals pollution and related early warning techniques.

  12. Toxic Diatom Aldehydes Affect Defence Gene Networks in Sea Urchins.

    Directory of Open Access Journals (Sweden)

    Stefano Varrella

    Full Text Available Marine organisms possess a series of cellular strategies to counteract the negative effects of toxic compounds, including the massive reorganization of gene expression networks. Here we report the modulated dose-dependent response of activated genes by diatom polyunsaturated aldehydes (PUAs in the sea urchin Paracentrotus lividus. PUAs are secondary metabolites deriving from the oxidation of fatty acids, inducing deleterious effects on the reproduction and development of planktonic and benthic organisms that feed on these unicellular algae and with anti-cancer activity. Our previous results showed that PUAs target several genes, implicated in different functional processes in this sea urchin. Using interactomic Ingenuity Pathway Analysis we now show that the genes targeted by PUAs are correlated with four HUB genes, NF-κB, p53, δ-2-catenin and HIF1A, which have not been previously reported for P. lividus. We propose a working model describing hypothetical pathways potentially involved in toxic aldehyde stress response in sea urchins. This represents the first report on gene networks affected by PUAs, opening new perspectives in understanding the cellular mechanisms underlying the response of benthic organisms to diatom exposure.

  13. Anaerobic Nitrogen Turnover by Sinking Diatom Aggregates at Varying Ambient Oxygen Levels

    Directory of Open Access Journals (Sweden)

    Peter eStief

    2016-02-01

    Full Text Available In the world’s oceans, even relatively low oxygen (O2 levels inhibit anaerobic nitrogen cycling by free-living microbes. Sinking organic aggregates, however, might provide oxygen-depleted microbial hotspots in otherwise oxygenated surface waters. Here we show that sinking diatom aggregates can host anaerobic nitrogen cycling at ambient O2 levels well above the hypoxic threshold. Aggregates were produced from the ubiquitous diatom Skeletonema marinoi and the natural microbial community of seawater. Microsensor profiling through the center of sinking aggregates revealed internal anoxia at ambient 40% air saturation (~100 µmol O2 L-1 and below. Accordingly, anaerobic nitrate turnover inside the aggregates was evident within this range of ambient O2 levels. In incubations with 15N-labeled nitrate, individual Skeletonema aggregates produced NO2- (up to 10.7 nmol N h-1 per aggregate, N2 (up to 7.1 nmol N h-1, NH4+ (up to 2.0 nmol N h-1, and N2O (up to 0.2 nmol N h-1. Intriguingly, nitrate stored inside the diatom cells served as an additional, internal nitrate source for N2 production, which may partially uncouple anaerobic nitrate turnover by diatom aggregates from direct ambient nitrate supply. Sinking diatom aggregates can contribute directly to fixed-nitrogen loss in low-oxygen environments in the ocean and vastly expand the ocean volume in which anaerobic nitrogen turnover is possible, despite relatively high ambient O2 levels. Depending on the extent of intracellular nitrate consumption during the sinking process, diatom aggregates may also be involved in the long-distance export of nitrate to the deep ocean.

  14. Feeding, growth, and survival of post-larval abalone Haliotis asinina on different benthic diatoms

    Directory of Open Access Journals (Sweden)

    Emmanuel C. Capinpin, Jr.

    2007-12-01

    Full Text Available The feeding behavior, digestive efficiency, growth, and survival of post-larval abalone Haliotis asininafed with 5 species of locally isolated benthic diatom strains (Navicula mollis, N. ramosissima, Stauroneissp., Pleurosigma sp., and Cocconeis sp. were examined in the laboratory. Two 15-day feeding trialsusing 1 mm post-larvae were conducted. No significant differences were observed in sizes of post-larvalabalone after 15 days in all diatom treatments (P>0.05. However, in both trials, Cocconeis sp. resulted inhigh survival rates (88.9±5.6% and 80.0±20.0% for Trials 1 and 2, respectively. Cocconeis sp. wasefficiently digested by post-larval abalone, with most of the cells being ruptured during ingestion and/orpassage through the gut. One diatom strain, Pleurosigma sp., resulted to a high survival but producedthe slowest growth rate (<10 ìm.d-1 SL. It was probably not ingested easily during the experiment due toits large size or mobility. For the other diatom strains, N. mollis and N. ramosissima, most cells passedthrough the gut with the cells left intact. Stauroneis sp. is highly digestible, but did not result to highsurvival, although the remaining live post-larval abalone fed on this diatom as well as on N. mollis grewfaster during the second week of both feeding trials. N. ramosissima resulted to poorest survival rate(<10% due to its poor digestibility. Only Cocconeis sp. showed a fairly high growth rate, digestionefficiency, and survival rate. N. mollis which gave a fairly high survival rate and Stauroneis may be addedtowards the later stages of post-larval rearing as well as other large diatoms. The digestion efficiency ofdiatom strains is considered an important factor determining its dietary value, but other factors may alsobe important such as volume contents, biochemical composition, and other physical characteristics.

  15. Distribution of Epilithic Diatoms in Estuaries of the Korean Peninsula in Relation to Environmental Variables

    Directory of Open Access Journals (Sweden)

    Ha-Kyung Kim

    2015-11-01

    Full Text Available This study explores the relationships between environmental factors and the distribution of epilithic diatoms in 161 estuaries of three coastal areas on the Korean peninsula. We investigated epilithic diatoms, water quality, and land use in the vicinities of the estuaries during the months of May 2012, 2013 and 2014, because Korea is relatively free from the influences of rainfall at that time of year. We recorded 327 diatom taxa from the study sites, and the assemblage was dominated by members of the Naviculaceae. Bacillariaceae accounted for the largest proportion of diatoms, and Nitzschia inconspicua (18% and N. frustulum (9.6% were the most dominant species. A cluster analysis based on epilithic diatom abundance suggested that the epilithic diatom communities of Korean estuaries can be classified into four large groups (G according to geography, as follows: Ia—the East Sea watershed, Ib—the eastern watershed of the South Sea, IIa—the West Sea watershed, and IIb—the western watershed of the South Sea. The former two groups, Ia and Ib, showed higher proportions of forest land cover and use, higher species occurrence, lower salinity, lower turbidity, and lower concentrations of nutrients than the latter two groups, while the latter groups, IIa and IIb, had higher proportions of agricultural land cover and use, higher electrical conductivity, higher turbidity, higher concentrations of nutrients, and lower species occurrence. The environmental factors underlying the distribution of epilithic diatoms, representative of each region, are as follows: dissolved oxygen and forest land cover and use for Reimeria sinuate and Rhoicosphenia abbreviate of the East Sea (ES, salinity and turbidity for Tabularia fasciculate of the West Sea (WS, and biochemical oxygen demand (BOD and nutrients for Cyclotella meneghiniana of the WS. On the other hand, the most influential environmental factors affecting the occurrence of indicator species showing the

  16. Diatomic infrared gas-dynamic laser

    International Nuclear Information System (INIS)

    Mckenzie, R.L.

    1971-01-01

    A laser is provided which utilizes the infrared vibration rotation transitions of a diatomic gas such as carbon monoxide. The laser action is produced by an active diatomic gas such as carbon monoxide mixed with a vibrationally resonant pumping gas such as nitrogen. In addition, a noble gas such as argon may be employed as a third gas in the mixture. The gas mixture contains from 1 to 80 vol percent of the active gas based on the pumping gas, and the third gas, if used, can constitute up to 90 percent of the total gas volume. A number of significantly different wavelengths can be produced by the laser. A single laser may contain several optical resonators at different locations, so that the desired wave length can be selected at will

  17. Cracking hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Forwood, G F; Lane, M; Taplay, J G

    1921-10-07

    In cracking and hydrogenating hydrocarbon oils by passing their vapors together with steam over heated carbon derived from shale, wood, peat or other vegetable or animal matter, the gases from the condenser are freed from sulfuretted hydrogen, and preferably also from carbon dioxide, and passed together with oil vapors and steam through the retort. Carbon dioxide may be removed by passage through slaked lime, and sulfuretted hydrogen by means of hydrated oxide of iron. Vapors from high-boiling oils and those from low-boiling oils are passed alternately through the retort, so that carbon deposited from the high-boiling oils is used up during treatment of low-boiling oils.

  18. Distilling hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Bataafsche, N V; de Brey, J H.C.

    1918-10-30

    Hydrocarbons containing a very volatile constituent and less volatile constituents, such as casing-head gases, still gases from the distillation of crude petroleum and bituminous shale are separated into their constituents by rectification under pressure; a pressure of 20 atmospheres and limiting temperatures of 150/sup 0/C and 40/sup 0/C are mentioned as suitable. The mixture may be subjected to a preliminary treatment consisting in heating to a temperature below the maximum rectification temperature at a pressure greater than that proposed to be used in the rectification.

  19. Late holocene trends of phytoplankton productivity and anoxia as inferred from diatom and geochemical proxies in Lake Victoria, Eastern Africa

    Science.gov (United States)

    Andama, M.; Lejju, J. B.; Tolo, C. U.

    2013-11-01

    Lake Victoria ecosystem has undergone major ecological changes in the recent decades. Sedimentary diatom analysis and Fe / Mn determined by Energy Dispersive X-ray Fluorescence (EDXRF) have provided phytoplankton (diatom) productivity and the resultant anoxia (Fe / Mn) in Lake Victoria at Napoleon Gulf during the late Holocene (1778 cal yr BP (calibrated years before present) to 2008 AD) with radiocarbon dates determined using Accelerator Mass Spectrometry standard method. The results showed that increased total diatom counts in Napoleon Gulf during the late Holocene correspond with increased Fe / Mn ratio (anoxia) in some of the profiles and not in others and in most cases those that correspond correlate very well with increased eutrophication from nitrate input (Total Nitrogen, TN). Therefore slightly increased anoxia not related to increased diatom productivity was recorded in Lake Victoria at Napoleon Gulf from the period 1778 to 1135 cal yr BP. There was slightly increased diatom productivity at Napoleon Gulf from the period 857 to 758 cal yr BP but it did not increase anoxia in the lake. The period 415 cal yr BP to 2008 AD recorded increased anoxia at Napoleon Gulf related to high diatom productivity especially from 415 to 390 cal yr BP and 191 cal yr BP to 2008 AD.

  20. Silicon diatom frustules as nanostructured photoelectrodes.

    Science.gov (United States)

    Chandrasekaran, Soundarrajan; Sweetman, Martin J; Kant, Krishna; Skinner, William; Losic, Dusan; Nann, Thomas; Voelcker, Nicolas H

    2014-09-18

    In the quest for solutions to meeting future energy demands, solar fuels play an important role. A particularly promising example is photocatalysis since even incremental improvements in performance in this process are bound to translate into significant cost benefits. Here, we report that semiconducting and high surface area 3D silicon replicas prepared from abundantly available diatom fossils sustain photocurrents and enable solar energy conversion.

  1. Collision-induced dissociation of diatomic ions

    International Nuclear Information System (INIS)

    Los, J.; Govers, T.R.

    1978-01-01

    An attempt is made to illustrate how mass spectrometric studies of dissociation in diatomic molecular ions can provide information on the dynamics of these collisions and on the predissociative states involved. Restriction is made to primary beam energies of the order of at least keV. The review covers the dynamics of dissociation, experimental techniques, direct dissociation in heavy-particle collisions, and translational spectroscopy. 120 references

  2. Electric dipole moment of diatomic molecules

    International Nuclear Information System (INIS)

    Rosato, A.

    1983-01-01

    The electric dipole moment of some diatomic molecules is calculated using the Variational Cellular Method. The results obtained for the molecules CO, HB, HF and LiH are compared with other calculations and with experimental data. It is shown that there is strong dependence of the electric dipole moment with respect to the geometry of the cells. It is discussed the possibility of fixing the geometry of the problem by giving the experimental value of the dipole moment. (Author) [pt

  3. Electric dipole moment of diatomic molecules

    International Nuclear Information System (INIS)

    Rosato, A.

    1983-01-01

    The electric dipole moment of some diatomic molecules is calculated using the Variational Cellular Method. The results obtained for the CO, HB, HF and LiH molecules are compared with other calculations and with experimental data. It is shown that there is strong dependence of the electric dipole moment with respect to the geometry of the cells. The possibility of fixing the geometry of the problem by giving the experimental value of the dipole moment is discussed. (Author) [pt

  4. Autofluorescence imaging system to discriminate and quantify the distribution of benthic cyanobacteria and diatoms

    NARCIS (Netherlands)

    Carreira, C.; Staal, M.; Middelboe, M.; Brussaard, C.P.D.

    2015-01-01

    Observation of benthic photoautotrophs on sediment surfaces shows a single algal layer without distinction between photosynthetic groups. Until now it has not been possible to distinguish between benthic photosynthetic microorganisms, i.e. cyanobacteria and diatoms, at μm to mm scales using a single

  5. Solution of the Schrodinger Equation for a Diatomic Oscillator Using Linear Algebra: An Undergraduate Computational Experiment

    Science.gov (United States)

    Gasyna, Zbigniew L.

    2008-01-01

    Computational experiment is proposed in which a linear algebra method is applied to the solution of the Schrodinger equation for a diatomic oscillator. Calculations of the vibration-rotation spectrum for the HCl molecule are presented and the results show excellent agreement with experimental data. (Contains 1 table and 1 figure.)

  6. Interaction of a dinoflagellate neurotoxin with voltage-activated ion channels in a marine diatom.

    Science.gov (United States)

    Kitchen, Sheila A; Bourdelais, Andrea J; Taylor, Alison R

    2018-01-01

    The potent neurotoxins produced by the harmful algal bloom species Karenia brevis are activators of sodium voltage-gated channels (VGC) in animals, resulting in altered channel kinetics and membrane hyperexcitability. Recent biophysical and genomic evidence supports widespread presence of homologous sodium (Na + ) and calcium (Ca 2+ ) permeable VGCs in unicellular algae, including marine phytoplankton. We therefore hypothesized that VGCs of these phytoplankton may be an allelopathic target for waterborne neurotoxins produced by K. brevis blooms that could lead to ion channel dysfunction and disruption of signaling in a similar manner to animal Na + VGCs. We examined the interaction of brevetoxin-3 (PbTx-3), a K. brevis neurotoxin, with the Na + /Ca 2+ VGC of the non-toxic diatom Odontella sinensi s using electrophysiology. Single electrode current- and voltage- clamp recordings from O. sinensis in the presence of PbTx-3 were used to examine the toxin's effect on voltage gated Na + /Ca 2+ currents. In silico analysis was used to identify the putative PbTx binding site in the diatoms. We identified Na + /Ca 2+ VCG homologs from the transcriptomes and genomes of 12 diatoms, including three transcripts from O. sinensis and aligned them with site-5 of Na + VGCs, previously identified as the PbTx binding site in animals. Up to 1 µM PbTx had no effect on diatom resting membrane potential or membrane excitability. The kinetics of fast inward Na + /Ca 2+ currents that underlie diatom action potentials were also unaffected. However, the peak inward current was inhibited by 33%, delayed outward current was inhibited by 25%, and reversal potential of the currents shifted positive, indicating a change in permeability of the underlying channels. Sequence analysis showed a lack of conservation of the PbTx binding site in diatom VGC homologs, many of which share molecular features more similar to single-domain bacterial Na + /Ca 2+ VGCs than the 4-domain eukaryote channels

  7. Diatom diversity in chronically versus episodically acidified adirondack streams

    Science.gov (United States)

    Passy, S.I.; Ciugulea, I.; Lawrence, G.B.

    2006-01-01

    The relationship between algal species richness and diversity, and pH is controversial. Furthermore, it is still unknown how episodic stream acidification following atmospheric deposition affects species richness and diversity. Here we analyzed water chemistry and diatom epiphyton dynamics and showed their contrasting behavior in chronically vs. episodically acidic streams in the Adirondack region. Species richness and diversity were significantly higher in the chronically acidic brown water stream, where organic acidity was significantly higher and the ratio of inorganic to organic monomeric aluminum significantly lower. Conversely, in the episodically acidic clear water stream, the inorganic acidity and pH were significantly higher and the diatom communities were very species-poor. This suggests that episodic acidification in the Adirondacks may be more stressful for stream biota than chronic acidity. Strong negative linear relationships between species diversity, Eunotia exigua, and dissolved organic carbon against pH were revealed after the influence of non-linear temporal trends was partialled out using a novel way of temporal modeling. ?? 2006 WILEY-VCH Verlag GmbH & Co. KGaA.

  8. Applications of Diatoms as Potential Microalgae in Nanobiotechnology

    OpenAIRE

    Ahmad Yari Khosroushahi; Miguel de la Guardia; Mohamad Moradi Ghorakhlu; Ali Akbar Jamali; Fariba Akbari

    2012-01-01

    Introduction: Diatoms are single cell eukaryotic microalgae, which present in nearly every water habitat make them ideal tools for a wide range of applications such as oil explora­tion, forensic examination, environmental indication, biosilica pattern generation, toxicity testing and eutrophication of aqueous ecosystems. Methods: Essential information on diatoms were reviewed and discussed towards impacts of diatoms on biosynthesis and bioremediation. Results: In this review, we present the ...

  9. Seasonal variations in fouling diatom communities on the Yantai coast

    Science.gov (United States)

    Yang, Cuiyun; Wang, Jianhua; Yu, Yang; Liu, Sujing; Xia, Chuanhai

    2015-03-01

    Fouling diatoms are a main component of biofilm, and play an important role in marine biofouling formation. We investigated seasonal variations in fouling diatom communities that developed on glass slides immersed in seawater, on the Yantai coast, northern Yellow Sea, China, using microscopy and molecular techniques. Studies were conducted during 2012 and 2013 over 3, 7, 14, and 21 days in each season. The abundance of attached diatoms and extracellular polymeric substances increased with exposure time of the slides to seawater. The lowest diatom density appeared in winter and the highest species richness and diversity were found in summer and autumn. Seasonal variation was observed in the structure of fouling diatom communities. Pennate diatoms Cylindrotheca, Nitzschia, Navicula, Amphora, Gomphonema, and Licmophora were the main fouling groups. Cylindrotheca sp. dominated in the spring. Under laboratory culture conditions, we found that Cylindrotheca grew very fast, which might account for the highest density of this diatom in spring. The lower densities in summer and autumn might result from the emergence of fouling animals and environmental factors. The Cylindrotheca sp. was identified as Cylindrotheca closterium using18S rDNA sequencing. The colonization process of fouling diatoms and significant seasonal variation in this study depended on environmental and biological factors. Understanding the basis of fouling diatoms is essential and important for developing new antifouling techniques.

  10. Inorganic carbon availability in benthic diatom communities: photosynthesis and migration.

    Science.gov (United States)

    Marques da Silva, Jorge; Cruz, Sónia; Cartaxana, Paulo

    2017-09-05

    Diatom-dominated microphytobenthos (MPB) is the main primary producer of many intertidal and shallow subtidal environments, being therefore of critical importance to estuarine and coastal food webs. Owing to tidal cycles, intertidal MPB diatoms are subjected to environmental conditions far more variable than the ones experienced by pelagic diatoms (e.g. light, temperature, salinity, desiccation and nutrient availability). Nevertheless, benthic diatoms evolved adaptation mechanisms to these harsh conditions, including the capacity to move within steep physical and chemical gradients, allowing them to perform photosynthesis efficiently. In this contribution, we will review present knowledge on the effects of dissolved inorganic carbon (DIC) availability on photosynthesis and productivity of diatom-dominated MPB. We present evidence of carbon limitation of photosynthesis in benthic diatom mats and highly productive MPB natural communities. Furthermore, we hypothesize that active vertical migration of epipelic motile diatoms could overcome local depletion of DIC in the photic layer, providing the cells alternately with light and inorganic carbon supply. The few available longer-term experiments on the effects of inorganic carbon enrichment on the productivity of diatom-dominated MPB have yielded inconsistent results. Therefore, further studies are needed to properly assess the response of MPB communities to increased CO 2 and ocean acidification related to climate change.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Author(s).

  11. An improved coupled-states approximation including the nearest neighbor Coriolis couplings for diatom-diatom inelastic collision

    Science.gov (United States)

    Yang, Dongzheng; Hu, Xixi; Zhang, Dong H.; Xie, Daiqian

    2018-02-01

    Solving the time-independent close coupling equations of a diatom-diatom inelastic collision system by using the rigorous close-coupling approach is numerically difficult because of its expensive matrix manipulation. The coupled-states approximation decouples the centrifugal matrix by neglecting the important Coriolis couplings completely. In this work, a new approximation method based on the coupled-states approximation is presented and applied to time-independent quantum dynamic calculations. This approach only considers the most important Coriolis coupling with the nearest neighbors and ignores weaker Coriolis couplings with farther K channels. As a result, it reduces the computational costs without a significant loss of accuracy. Numerical tests for para-H2+ortho-H2 and para-H2+HD inelastic collision were carried out and the results showed that the improved method dramatically reduces the errors due to the neglect of the Coriolis couplings in the coupled-states approximation. This strategy should be useful in quantum dynamics of other systems.

  12. Continuous gene flow contributes to low global species abundance and distribution of a marine model diatom

    KAUST Repository

    Rastogi, Achal

    2017-08-15

    Unlike terrestrial ecosystems where geographical isolation often leads to a restricted gene flow between species, genetic admixing in aquatic micro-eukaryotes is likely to be frequent. Diatoms inhabit marine ecosystems since the Mesozoic period and presently constitute one of the major primary producers in the world ocean. They are a highly diversified group of eukaryotic phytoplankton with estimates of up to 200,000 species. Since decades, Phaeodactylum tricornutum is used as a model diatom species to characterize the functional pathways, physiology and evolution of diatoms in general. In the current study, using whole genome sequencing of ten P. tricornutum strains, sampled at broad geospatial and temporal scales, we show a continuous dispersal and genetic admixing between geographically isolated strains. We also describe a very high level of heterozygosity and propose it to be a consequence of frequent ancestral admixture. Our finding that P. tricornutum sequences are plausibly detectable at low but broadly distributed levels in the world ocean further suggests that high admixing between geographically isolated strains may create a significant bottleneck, thus influencing their global abundance and distribution in nature. Finally, in an attempt to understand the functional implications of genetic diversity between different P. tricornutum ecotypes, we show the effects of domestication in inducing changes in the selection pressure on many genes and metabolic pathways. We propose these findings to have significant implications for understanding the genetic structure of diatom populations in nature and provide a framework to assess the genomic underpinnings of their ecological success.

  13. Continuous gene flow contributes to low global species abundance and distribution of a marine model diatom

    KAUST Repository

    Rastogi, Achal; Deton-Cabanillas, Anne-Flore; Rocha Jimenez Vieira, Fabio; Veluchamy, Alaguraj; Cantrel, Catherine; Wang, Gaohong; Vanormelingen, Pieter; Bowler, Chris; Piganeau, Gwenael; Tirichine, Leila; Hu, Hanhua

    2017-01-01

    Unlike terrestrial ecosystems where geographical isolation often leads to a restricted gene flow between species, genetic admixing in aquatic micro-eukaryotes is likely to be frequent. Diatoms inhabit marine ecosystems since the Mesozoic period and presently constitute one of the major primary producers in the world ocean. They are a highly diversified group of eukaryotic phytoplankton with estimates of up to 200,000 species. Since decades, Phaeodactylum tricornutum is used as a model diatom species to characterize the functional pathways, physiology and evolution of diatoms in general. In the current study, using whole genome sequencing of ten P. tricornutum strains, sampled at broad geospatial and temporal scales, we show a continuous dispersal and genetic admixing between geographically isolated strains. We also describe a very high level of heterozygosity and propose it to be a consequence of frequent ancestral admixture. Our finding that P. tricornutum sequences are plausibly detectable at low but broadly distributed levels in the world ocean further suggests that high admixing between geographically isolated strains may create a significant bottleneck, thus influencing their global abundance and distribution in nature. Finally, in an attempt to understand the functional implications of genetic diversity between different P. tricornutum ecotypes, we show the effects of domestication in inducing changes in the selection pressure on many genes and metabolic pathways. We propose these findings to have significant implications for understanding the genetic structure of diatom populations in nature and provide a framework to assess the genomic underpinnings of their ecological success.

  14. The Effects of Salinity on Growth and Distribution of Four Freshwater Diatom Species

    International Nuclear Information System (INIS)

    Hayati, Attayeb A

    2007-01-01

    The upper and lower salinity limits of Nitzschia acicularis, Nitzschia pusilla, Nitzschia palea and Synedra acus, which were isolated from the Damour River, Lebanon, were determined from laboratory cultures. Growth responses of the investigated diatoms showed maximum growth in the enriched Damour River natural water (salinity = 0.24 ppt). With an increase in salinity there was a gradual decrease in the growth until the upper limit was reached. At higher salt concentrations near the upper limit a lag phase was observed, during the first two days of the growing culture, where the growth was greatly declined. This reduction in growth can be attributed to high osmotic stress experienced by the investigated diatoms when transferred to flasks containing salinities near the extremes of their tolerance. The investigated diatoms appear to be very resistant and capable of adaptation to new situations because they grew better after this two days lag period. The results of this study also showed that all the investigated diatom species have broader salinity tolerance limits than those reported in the literature and this would enable their distribution at localities with higher or lower salinities than those typical of the Damour River, Lebanon. (author)

  15. Hydrocarbon oils

    Energy Technology Data Exchange (ETDEWEB)

    Foorwood, G F; Taplay, J G

    1916-12-12

    Hydrocarbon oils are hydrogenated, cracked, or treated for the removal of sulfur by bringing their vapors mixed with steam at temperatures between 450 and 600/sup 0/C into contact with a form of carbon that is capable of decomposing steam with the production of nascent hydrogen at those temperatures. The forms of carbon used include lamp-black, soot, charcoals derived from wood, cellulose, and lignite, and carbons obtained by carbonizing oil residues and other organic bodies at temperatures below 600/sup 0/C. The process is applied to the treatment of coal oil, shale oil, petroleum, and lignite oil. In examples, kerosene is cracked at 570/sup 0/C, cracked spirit is hydrogenated at 500/sup 0/C, and shale spirit is desulfurized at 530/sup 0/C. The products are led to a condenser and thence to a scrubber, where they are washed with creosote oil. After desulfurization, the products are washed with dilute caustic soda to remove sulfurretted hydrogen.

  16. Hydrocarbon exploration

    Energy Technology Data Exchange (ETDEWEB)

    Lerche, I. (South Carolina Univ., Columbia, SC (United States). Dept. of Geological Sciences)

    1993-01-01

    This special issue of the journal examines various aspects of the on-going search for hydrocarbons, ranging from frontier basins where little data are available, to more mature areas where considerable data are available. The incentives underlying the search for oil are roughly: the social, economic and industrial needs of a nation; the incentive of a corporation to be profitable; and the personal incentives of individuals in the oil industry and governments, which range from financial wealth to power and which are as diverse as the individuals who are involved. From a geopolitical perspective, the needs, requirements, goals, strategies, and philosophies of nations, and groups of nations, also impact on the oil exploration game. Strategies that have been employed have ranged from boycott to austerity and rationing, to physical intervention, to global ''flooding'' with oil by over-production. (author)

  17. Transparent Exopolymeric Particles (TEP Selectively Increase Biogenic Silica Dissolution From Fossil Diatoms as Compared to Fresh Diatoms

    Directory of Open Access Journals (Sweden)

    Jordan Toullec

    2018-03-01

    Full Text Available Diatom production is mainly supported by the dissolution of biogenic silica (bSiO2 within the first 200 m of the water column. The upper oceanic layer is enriched in dissolved and/or colloidal organic matter, such as exopolymeric polysaccharides (EPS and transparent exopolymeric particles (TEP excreted by phytoplankton in large amounts, especially at the end of a bloom. In this study we explored for the first time the direct influence of TEP-enriched diatom excretions on bSiO2 dissolution. Twelve dissolution experiments on fresh and fossil diatom frustules were carried out on seawater containing different concentrations of TEP extracted from diatom cultures. Fresh diatom frustules were cleaned from the organic matter by low ash temperature, and fossil diatoms were made from diatomite powder. Results confirm that newly formed bSiO2 dissolved at a faster rate than fossil diatoms due to a lower aluminum (Al content. Diatom excretions have no effect on the dissolution of the newly formed bSiO2 from Chaetoceros muelleri. Reversely, the diatomite specific dissolution rate constant and solubility of the bSiO2 were positively correlated to TEP concentrations, suggesting that diatom excretion may provide an alternative source of dSi when limitations arise.

  18. The possible role of bacterial signal molecules N-acyl homoserine lactones in the formation of diatom-biofilm (Cylindrotheca sp.)

    International Nuclear Information System (INIS)

    Yang, Cuiyun; Fang, Shengtao; Chen, Dehui; Wang, Jianhua; Liu, Fanghua; Xia, Chuanhai

    2016-01-01

    Bacterial quorum sensing signal molecules N-acyl homoserine lactones (AHLs) (C10-HSL, 3-OXO-C10-HSL and 3-OH-C10-HSL) as possible chemical cues were employed to investigate the role in the formation of fouling diatom-biofilm (Cylindrotheca sp.). Results showed that AHLs promoted Chlorophyll a (Chl.a) and extracellular polymeric substance (EPS) contents in the diatom-biofilm. In the presence of AHLs-inhibitor 3, 4-Dibromo-2(5)H-furanone, which was used to avoid the possible interference of AHLs from bacteria, AHLs also increased the Chl.a and EPS contents. Scanning electron microscope and confocal laser scanning microscope analysis further demonstrated that AHLs promoted the formation of the diatom-biofilm. Non-invasive micro-test technique showed that AHLs promoted Ca 2+ efflux in Cylindrotheca sp., which implied that Ca 2+ might be correlated with AHLs-induced positive effect on the formation of diatom-biofilm. This study provides direct evidences that AHLs play an important role in developing the diatom-biofilm and AHLs-inhibitors might be promising active agents in marine antifouling. - Highlights: •AHLs effectively increase Chl.a and EPS contents in diatom-biofilm. •SEM and CLSM further demonstrate that AHLs promote the formation of diatom-biofilm. •AHLs trigger algal cellular Ca 2+ efflux. •AHLs-inhibitors might be promising active agents in marine antifouling.

  19. Diatom community structure on in-service cruise ship hulls.

    Science.gov (United States)

    Hunsucker, Kelli Zargiel; Koka, Abhishek; Lund, Geir; Swain, Geoffrey

    2014-10-01

    Diatoms are an important component of marine biofilms found on ship hulls. However, there are only a few published studies that describe the presence and abundance of diatoms on ships, and none that relate to modern ship hull coatings. This study investigated the diatom community structure on two in-service cruise ships with the same cruise cycles, one coated with an antifouling (AF) system (copper self-polishing copolymer) and the other coated with a silicone fouling-release (FR) system. Biofilm samples were collected during dry docking from representative areas of the ship and these provided information on the horizontal and vertical zonation of the hull, and intact and damaged coating and niche areas. Diatoms from the genera Achnanthes, Amphora and Navicula were the most common, regardless of horizontal ship zonation and coating type. Other genera were abundant, but their presence was more dependent on the ship zonation and coating type. Samples collected from damaged areas of the hull coating had a similar community composition to undamaged areas, but with higher diatom abundance. Diatom fouling on the niche areas differed from that of the surrounding ship hull and paralleled previous studies that investigated differences in diatom community structure on static and dynamically exposed coatings; niche areas were similar to static immersion and the hull to dynamic immersion. Additionally, diatom richness was greater on the ship with the FR coating, including the identification of several new genera to the biofouling literature, viz. Lampriscus and Thalassiophysa. These results are the first to describe diatom community composition on in-service ship hulls coated with a FR system. This class of coatings appears to have a larger diatom community compared to copper-based AF systems, with new diatom genera that have the ability to stick to ship hulls and withstand hydrodynamic forces, thus creating the potential for new problematic species in the biofilm.

  20. Molecular evidence of the toxic effects of diatom diets on gene expression patterns in copepods.

    Directory of Open Access Journals (Sweden)

    Chiara Lauritano

    Full Text Available Diatoms are dominant photosynthetic organisms in the world's oceans and are considered essential in the transfer of energy through marine food chains. However, these unicellular plants at times produce secondary metabolites such as polyunsaturated aldehydes and other products deriving from the oxidation of fatty acids that are collectively termed oxylipins. These cytotoxic compounds are responsible for growth inhibition and teratogenic activity, potentially sabotaging future generations of grazers by inducing poor recruitment in marine organisms such as crustacean copepods.Here we show that two days of feeding on a strong oxylipin-producing diatom (Skeletonema marinoi is sufficient to inhibit a series of genes involved in aldehyde detoxification, apoptosis, cytoskeleton structure and stress response in the copepod Calanus helgolandicus. Of the 18 transcripts analyzed by RT-qPCR at least 50% were strongly down-regulated (aldehyde dehydrogenase 9, 8 and 6, cellular apoptosis susceptibility and inhibitor of apoptosis IAP proteins, heat shock protein 40, alpha- and beta-tubulins compared to animals fed on a weak oxylipin-producing diet (Chaetoceros socialis which showed no changes in gene expression profiles.Our results provide molecular evidence of the toxic effects of strong oxylipin-producing diatoms on grazers, showing that primary defense systems that should be activated to protect copepods against toxic algae can be inhibited. On the other hand other classical detoxification genes (glutathione S-transferase, superoxide dismutase, catalase, cytochrome P450 were not affected possibly due to short exposure times. Given the importance of diatom blooms in nutrient-rich aquatic environments these results offer a plausible explanation for the inefficient use of a potentially valuable food resource, the spring diatom bloom, by some copepod species.

  1. Spatio-temporal distribution of the dominant Diatom and Dinoflagellate species in the Bay of Tunis (SW Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    O. DALY YAHIA-KEFI

    2005-06-01

    Full Text Available Microphytoplankton composition and its relationships with hydrology and nutrient distributions were investigated over 24 months (December 1993 - November 1995 in the Bay of Tunis ( SW Mediterranean Sea. A new index, the ‘Specific Preference Index’ (SPI obtained by computing the median value of each parameter weighed by the numerical value of each species density was developed. Using this index, the relationships between each species and temperature, salinity and major nutrients were analysed. The distribution of chlorophyll a did not show a clear correlation with microplankton abundance suggesting that other factors contribute to chlorophyll concentration, such as smaller phytoplankton size fractions or detritus. The winter-spring diatom blooms did not show a regular pattern during both years. High nutrient inputs in late summer, associated with mild meteorological conditions, contributed to the development of a large diatom bloom in autumn 1995 where significant silicate depletion was witnessed. Generally, diatoms were more stenotherm than dinoflagellates in the Bay, whereas dinoflagellates were more stenohaline than diatoms. The statistical analyses showed that the two species, Bellerochea horologicalis , and Lithodesmioides polymorpha, var., tunisiense, appeared in a wide range of environmental conditions. An excess of phosphateversus nitrate appeared to be associated with red tides of, Gymnodinium spp, whereas Peridinium quinquecorne, showed the opposite. Phosphate concentrations appear to be crucial in this coastal environment, where diatom blooms are often limited by low silicate availability.

  2. Attraction Pheromone of The Benthic Diatom Seminavis robusta: Studies on Structure-Activity Relationships.

    Science.gov (United States)

    Lembke, Christine; Stettin, Daniel; Speck, Franziska; Ueberschaar, Nico; De Decker, Sam; Vyverman, Wim; Pohnert, Georg

    2018-04-01

    Recently the first pheromone of a marine diatom was identified to be the diketopiperazine (S,S)-diproline. This compound facilitates attraction between mating partners in the benthic diatom Seminavis robusta. Interestingly, sexualized S. robusta cells are attracted to both the natural pheromone (S,S)-diproline as well as to its enantiomer (R,R)-diproline. Usually stereospecificity is a prerequisite for successful substrate-receptor interactions, and especially pheromone perception is often highly enantioselective. Here we introduce a structure-activity relationship study, to learn more about the principles of pheromone reception in diatoms. We analyzed the activity of nine different diketopiperazines in attraction and interference assays. The pheromone diproline itself, as well as a pipecolic acid derived diketopiperazine with two expanded aliphatic ring systems, showed the highest attractivity. Hydroxylatoin of the aliphatic rings abolished any bioactivity. Diketopiperazines derived from acyclic amino acids were not attrative as well. All stereoisomers of both the diproline and the pipecolic acid derived diketopiperazine were purified by enantioselective high-performance liquid chromatography, and application in bioactivity tests confirmed that attraction pheromone perception in this diatom is indeed not stereospecific. However, the lack of activity of diketopiperazines derived from acyclic amino acids suggests a specificity that prevents misguidance to sources of other naturally occurring diketopiperazines.

  3. Role of Diatoms in marine biofouling

    Digital Repository Service at National Institute of Oceanography (India)

    Anil, A; Patil, J.S..; Mitbavkar, S.; DeCosta, P.M.; DeSilva, S.; Hegde, S.; Naik, R.

    . Ltd., New Delhi, pp. 293-6. de Nys, R., Leya, T., Maximilien, R., Afsar, A., Nair, P. S. R. & Steinberg, P. D. 1996. The need for standardized broad scale bioassay testing: a case study using the red alga Laurencia rigida. Biofouling 10:213-24. de...-1 Content-Type text/plain; charset=ISO-8859-1 Recent Advances on Applied Aspects of Indian Marine Algae with Reference to Global Scenario, Volume 1, A. Tewari (Ed.), 2006 Central Salt & Marine Chemicals Research Institute Role of Diatoms...

  4. Digitisation of the South African diatom collection

    CSIR Research Space (South Africa)

    Van

    2008-06-01

    Full Text Available stream_source_info van der Molen_2008.pdf.txt stream_content_type text/plain stream_size 1285 Content-Encoding UTF-8 stream_name van der Molen_2008.pdf.txt Content-Type text/plain; charset=UTF-8 Digitisation... of the South African Diatom Collection Johan van der Molen, CSIR Background ➲ Since 1950 ➲ Properly curated ➲ In dis-use since ~1990 ➲ Renewed interest since ~2004 ➲ Water bodies in Southern Africa, mostly rivers ➲ Supports taxonomic work and biological...

  5. Dissociation Energies of Diatomic Molecules

    International Nuclear Information System (INIS)

    Qun-Chao, Fan; Wei-Guo, Sun

    2008-01-01

    Molecular dissociation energies of 10 electronic states of alkali molecules of KH, 7 LiD, 7 LiH, 6 LiH, NaK, NaLi and NaRb are studied using the highest three accurate vibrational energies of each electronic state, and an improved parameter-free analytical formula which is obtained starting from the LeRoy–Bernstein vibrational energy expression near the dissociation limit. The results show that as long as the highest three vibrational energies are accurate, the current analytical formula will give accurate theoretical dissociation energies D e theory , which are in excellent agreement with the experimental dissociation energies D e expt . (atomic and molecular physics)

  6. Displacement cascades in diatomic materials

    International Nuclear Information System (INIS)

    Parkin, D.M.; Coulter, C.A.

    1981-01-01

    A new function, the specified-projectile displacement function p/sub ijk/ (E), is introduced to describe displacement cascades in polyatomic materials. This function describes the specific collision events that produce displacements and hence adds new information not previously available. Calculations of p/sub ijk/ (E) for MgO, Al 2 O 3 and TaO are presented and discussed. Results show that the parameters that have the largest effect on displacement collision events are the PKA energy and the mass ratio of the atom types in the material. It is further shown that the microscopic nature of the displacement events changes over the entire recoil energy range relevant to fusion neutron spectra and that these changes are different in materials whose mass ratio is near one than in those where it is far from one

  7. The relevance of diatoms for water quality assessment in South ...

    African Journals Online (AJOL)

    Water quality assessment protocols based on the use of diatoms are now well developed and their value substantiated at an international level. The use of diatoms is not designed or intended to be a “rapid” technology. The detailed level of information generated from the procedure outweighs perceived disadvantages of ...

  8. Epiphytic Diatoms along Environmental Gradients in Western European Shallow Lakes

    NARCIS (Netherlands)

    Blanco, Saul; Cejudo-Figueiras, Cristina; Alvarez-Blanco, Irene; van Donk, Ellen|info:eu-repo/dai/nl/069838593; Gross, Elisabeth M.; Hansson, Lars-Anders; Irvine, Kenneth; Jeppesen, Erik; Kairesalo, Timo; Moss, Brian; Noges, Tiina; Becares, Eloy

    Diatom-based assays have been successfully associated worldwide with the tropic status of lakes. Several studies have demonstrated a correlation between epiphytic diatoms and nutrient load in shallow lakes and wetlands. We examine the relative importance of environmental factors in explaining the

  9. Colonization of diatom aggregates by the dinoflagellate Noctiluca scintillans

    DEFF Research Database (Denmark)

    Tiselius, P.; Kiørboe, Thomas

    1998-01-01

    coagulation of diatom cells and not by mucus feeding behavior of N. scintillans. N. scintillans can be positively buoyant, and estimates of encounter rates between N. scintillans and diatom aggregates during ascent demonstrates that this mechanism is sufficient to account for the observed colonization...

  10. Diatom-based water quality monitoring in southern Africa ...

    African Journals Online (AJOL)

    The purpose of this review is to summarise the challenges and future prospects associated with biological water quality monitoring using diatoms with special focus on southern Africa. Much work still needs to be carried out on diatom tolerances, ecological preferences and ecophysiology. It is recommended that past ...

  11. Interference patterns and extinction ratio of the diatom Coscinodiscus granii

    DEFF Research Database (Denmark)

    Maibohm, Christian; Friis, Søren Michael Mørk; Ellegaard, M.

    2015-01-01

    We report experimental and theoretical verification of the nature and position of multiple interference points of visible light transmitted through the valve of the centric diatom species Coscinodiscus granii. Furthermore, by coupling the transmitted light into an optical fiber and moving...... the diatom valve between constructive and destructive interference points, an extinction ratio of 20 dB is shown...

  12. The health of benthic diatom assemblages in lower stretch

    Indian Academy of Sciences (India)

    This study examines the ecological state of epilithic diatom assemblages along the lower stretch of Mandakini, a glacier-fed Himalayan river. The diatoms were sampled at four stations during winter and summer, only once in each season. Valve counts were obtained from Naphrax mounts prepared from each sample.

  13. Isolation of diatom Navicula cryptocephala and characterization of ...

    African Journals Online (AJOL)

    sjce

    synthesis to the storage of neutral lipids (Qiang et al.,. 2008). Diatoms were shown ... chemical analysis of the oil inside diatom oil droplets, a method for separating ... 120°C for 20 min. 0.1 mg.L. −1. Thiamine, 0.5 μg.L. −1. Biotin and 0.5 μg.L−1.

  14. Variations in diatom communities at genus and species levels in peatlands (central China) linked to microhabitats and environmental factors.

    Science.gov (United States)

    Chen, Xu; Bu, Zhaojun; Stevenson, Mark A; Cao, Yanmin; Zeng, Linghan; Qin, Bo

    2016-10-15

    Peatlands are a specialized type of organic wetlands, fulfilling essential roles as global carbon sinks, headwaters of rivers and biodiversity hotspots. Despite their importance, peatlands are being lost at an alarming rate due to human disturbance and climatic variability. Both the scientific and regulatory communities have focused considerable attention on developing tools for assessing environmental changes in peatlands. Diatoms are widely used in biomonitoring studies of lakes, rivers and streams as they have high abundance, specific ecological preferences and can respond rapidly to environmental change. However, diatom-based assessment studies in peatlands remain limited. The aims of this study were to identify indicator species and genus for three types of habitats (hummocks, hollows and ditch edges) in peatlands (central China), to examine the effects of physiochemical factors on diatom composition at genus and species levels, and to compare the efficiency of species- and genus-level identification in environmental assessment. Our results revealed that hummocks were characterized by drought-tolerant diatoms, while hollows were dominated by species and genus preferring wet conditions. Ditch edges were characterized by diatoms with different life strategies. Depth to water table, redox potential, conductivity and calcium were significant predictors of both genus- and species-level composition. According to ordination analyses, pH was not correlated with species composition while it was a significant factor associated with genus-level composition. Genus-level composition outperformed species composition in describing the response of diatoms to environmental variables. Our results indicate that diatoms can be useful environmental indicators of peatlands, and show that genus-level taxonomic analysis can be a potential tool for assessing environmental change in peatlands. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Applications of Diatoms as Potential Microalgae in Nanobiotechnology

    Directory of Open Access Journals (Sweden)

    Ahmad Yari Khosroushahi

    2012-05-01

    Full Text Available Introduction: Diatoms are single cell eukaryotic microalgae, which present in nearly every water habitat make them ideal tools for a wide range of applications such as oil explora­tion, forensic examination, environmental indication, biosilica pattern generation, toxicity testing and eutrophication of aqueous ecosystems. Methods: Essential information on diatoms were reviewed and discussed towards impacts of diatoms on biosynthesis and bioremediation. Results: In this review, we present the recent progress in this century on the application of diatoms in waste degradation, synthesis of biomaterial, biomineraliza­tion, toxicity and toxic effects of mineral elements evaluations. Conclusion: Diatoms can be considered as metal toxicity bioindicators and they can be applied for biomineralization, synthesis of biomaterials, and degradation of wastes.

  16. Epibiotic Diatoms Are Universally Present on All Sea Turtle Species.

    Directory of Open Access Journals (Sweden)

    Nathan J Robinson

    Full Text Available The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtle species hosting at least two diatom taxa. We recommend that future research is undertaken to confirm whether diatom communities vary between sea turtle species and whether these diatom taxa are facultative or obligate commensals.

  17. Limits to gene flow in a cosmopolitan marine planktonic diatom.

    Science.gov (United States)

    Casteleyn, Griet; Leliaert, Frederik; Backeljau, Thierry; Debeer, Ann-Eline; Kotaki, Yuichi; Rhodes, Lesley; Lundholm, Nina; Sabbe, Koen; Vyverman, Wim

    2010-07-20

    The role of geographic isolation in marine microbial speciation is hotly debated because of the high dispersal potential and large population sizes of planktonic microorganisms and the apparent lack of strong dispersal barriers in the open sea. Here, we show that gene flow between distant populations of the globally distributed, bloom-forming diatom species Pseudo-nitzschia pungens (clade I) is limited and follows a strong isolation by distance pattern. Furthermore, phylogenetic analysis implies that under appropriate geographic and environmental circumstances, like the pronounced climatic changes in the Pleistocene, population structuring may lead to speciation and hence may play an important role in diversification of marine planktonic microorganisms. A better understanding of the factors that control population structuring is thus essential to reveal the role of allopatric speciation in marine microorganisms.

  18. Aggregate Formation During the Viral Lysis of a Marine Diatom

    Directory of Open Access Journals (Sweden)

    Yosuke Yamada

    2018-05-01

    Full Text Available Recent studies have suggested that the viral lysis of microbes not only facilitates the conversion of particulate organic matter into dissolved organic matter, but also promotes the formation of organic aggregates, which enhance the export of organic carbon from the surface ocean to the deep sea. However, experimental data supporting this proposition are limited. Here, we tested the hypothesis that the viral infection of marine diatoms enhances aggregate formation. We used a model system consisting of Chaetoceros tenuissimus, a bloom-forming diatom with an approximate cell size of 3–10 μm, and a DNA virus, CtenDNAV type II, which replicates in the nucleus of C. tenuissimus. The volume of large particles (50–400 μm in equivalent spherical diameters, determined from photographic images was measured over time (up to 15 days in the diatom-alone control and a virus-added diatom culture. We also determined the concentrations of Coomassie-stainable particles (CSP, proteinaceous particles and transparent exopolymeric particles (TEP, acid-polysaccharide-rich particles with colorimetric methods. The total volume of large particles was significantly higher (5–59 fold in the virus-added diatoms than in the diatom-alone control during the period in which the viral lysis of the diatoms proceeded. One class of large particles produced in the virus-added diatoms was flake-shaped. The flakes were tightly packed and dense, and sank rapidly, possibly playing an important role in the vertical delivery of materials from the surface to the deep sea. The bulk CSP concentrations tended to be higher in the virus-added diatoms than in the diatom-alone control, whereas the reverse was true for the TEP. These results suggest that proteinaceous polymers are involved in aggregate formation. Our data support the emerging notion that the viral lysis of microbes facilitates aggregate formation and the export of organic carbon in the ocean.

  19. Coupled states approximation for scattering of two diatoms

    International Nuclear Information System (INIS)

    Heil, T.G.; Green, S.; Kouri, D.J.

    1978-01-01

    The coupled states (CS) approximation is developed in detail for the general case of two colliding diatomic molecules. The high energy limit of the exact Lippmann-Schwinger equation is used to obtain the CS equations so that the sufficiency conditions of Kouri, Heil, and Shimoni apply. In addition, care is taken to ensure correct treatment of parity in the CS, as well as correct labeling of the CS by an effective orbital angular momentum. The analysis follows that given by Shimoni and Kouri for atom-diatom collisions where the coupled rotor angular momentum j 12 and projection lambda 12 replace the single diatom angular momentum j and projection lambda. The result is an expression for the differential scattering amplitude which is a generalization of the highly successful McGuire-Kouri differential scattering amplitude for atom-diatom collisions. Also, the opacity function is found to be a generalization of the Clebsch-Gordon weight atom-diatom expression of Shimoni and Kouri. The diatom-diatom CS body frame T matrix T/sup J/(j 1 'j 2 'j 12 'lambda 12 'vertical-bar j 1 j 2 j 12 lambda 12 ) is also found to be nondiagonal in lambda' 12 ,lambda 12 , just as in the atom-diatom case. The parity and identical molecule interchange symmetries are also considered in detail in both the exact close coupling and CS approximations. Symmetrized expressions for all relevant quantities are obtained, along with the symmetrized coupled equations one must solve. The properly labeled and symmetrized CS equations have not been derived before this present work. The present correctly labeled CS theory is tested computationally by applications to three different diatom-diatom potentials. First we carry out calculations for para-para, ortho-ortho, and ortho-para H 2 -H 2 collisions using the experimental potential of Farrar and Lee

  20. Variation partitioning of diatom species data matrices: Understanding the influence of multiple factors on benthic diatom communities in tropical streams

    Energy Technology Data Exchange (ETDEWEB)

    Bere, Taurai, E-mail: tbere2015@gmail.com; Mangadze, Tinotenda; Mwedzi, Tongai

    2016-10-01

    Elucidating the confounding influence of multiple environmental factors on benthic diatom communities is important in developing water quality predictive models for better guidance of stream management efforts. The objective of this study was to explore the relative impact of metal pollution and hydromorphological alterations in, addition to nutrient enrichment and organic pollution, on diatom taxonomic composition with the view to improve stream diatom-based water quality inference models. Samples were collected twice at 20 sampling stations in the tropical Manyame Catchment, Zimbabwe. Diatom, macroinvertebrate communities and environmental factors were sampled and analysed. The variations in diatom community composition explained by different categories of environmental factors were analysed using canonical correspondence analysis using variance partitioning (partial CCA). The following variations were explained by the different predictor matrices: nutrient levels and organic pollution - 10.4%, metal pollution - 8.3% and hydromorphological factors - 7.9%. Thus, factors other than nutrient levels and organic pollution explain additional significant variation in these diatom communities. Development of diatom-based stream water quality inference models that incorporate metal pollution and hydromorphological alterations, where these are key issues, is thus deemed necessary. - Highlights: • Confounding influences of multiple environmental factors on diatom communities are elucidated. • Variation explained: nutrients + organic pollution - 10.4%, metals - 8.3% and hydromorphological factors - 7.9%. • Calibration of existing or development of new indices may be necessary.

  1. Variation partitioning of diatom species data matrices: Understanding the influence of multiple factors on benthic diatom communities in tropical streams

    International Nuclear Information System (INIS)

    Bere, Taurai; Mangadze, Tinotenda; Mwedzi, Tongai

    2016-01-01

    Elucidating the confounding influence of multiple environmental factors on benthic diatom communities is important in developing water quality predictive models for better guidance of stream management efforts. The objective of this study was to explore the relative impact of metal pollution and hydromorphological alterations in, addition to nutrient enrichment and organic pollution, on diatom taxonomic composition with the view to improve stream diatom-based water quality inference models. Samples were collected twice at 20 sampling stations in the tropical Manyame Catchment, Zimbabwe. Diatom, macroinvertebrate communities and environmental factors were sampled and analysed. The variations in diatom community composition explained by different categories of environmental factors were analysed using canonical correspondence analysis using variance partitioning (partial CCA). The following variations were explained by the different predictor matrices: nutrient levels and organic pollution - 10.4%, metal pollution - 8.3% and hydromorphological factors - 7.9%. Thus, factors other than nutrient levels and organic pollution explain additional significant variation in these diatom communities. Development of diatom-based stream water quality inference models that incorporate metal pollution and hydromorphological alterations, where these are key issues, is thus deemed necessary. - Highlights: • Confounding influences of multiple environmental factors on diatom communities are elucidated. • Variation explained: nutrients + organic pollution - 10.4%, metals - 8.3% and hydromorphological factors - 7.9%. • Calibration of existing or development of new indices may be necessary.

  2. The velocity of light intensity increase modulates the photoprotective response in coastal diatoms.

    Directory of Open Access Journals (Sweden)

    Vasco Giovagnetti

    Full Text Available In aquatic ecosystems, the superimposition of mixing events to the light diel cycle exposes phytoplankton to changes in the velocity of light intensity increase, from diurnal variations to faster mixing-related ones. This is particularly true in coastal waters, where diatoms are dominant. This study aims to investigate if coastal diatoms differently activate the photoprotective responses, xanthophyll cycle (XC and non-photochemical fluorescence quenching (NPQ, to cope with predictable light diel cycle and unpredictable mixing-related light variations. We compared the effect of two fast light intensity increases (simulating mixing events with that of a slower increase (corresponding to the light diel cycle on the modulation of XC and NPQ in the planktonic coastal diatom Pseudo-nitzschia multistriata. During each light treatment, the photon flux density (PFD progressively increased from darkness to five peaks, ranging from 100 to 650 µmol photons m-2 s-1. Our results show that the diel cycle-related PFD increase strongly activates XC through the enhancement of the carotenoid biosynthesis and induces a moderate and gradual NPQ formation over the light gradient. In contrast, during mixing-related PFD increases, XC is less activated, while higher NPQ rapidly develops at moderate PFD. We observe that together with the light intensity and its increase velocity, the saturation light for photosynthesis (Ek is a key parameter in modulating photoprotection. We propose that the capacity to adequately regulate and actuate alternative photoprotective 'safety valves' in response to changing velocity of light intensity increase further enhances the photophysiological flexibility of diatoms. This might be an evolutionary outcome of diatom adaptation to turbulent marine ecosystems characterized by unpredictable mixing-related light changes over the light diel cycle.

  3. Collision cross section calculations for polyatomic ions considering rotating diatomic/linear gas molecules

    International Nuclear Information System (INIS)

    Larriba-Andaluz, Carlos; Hogan, Christopher J.

    2014-01-01

    Structural characterization of ions in the gas phase is facilitated by measurement of ion collision cross sections (CCS) using techniques such as ion mobility spectrometry. Further information is gained from CCS measurement when comparison is made between measurements and accurately predicted CCSs for model ion structures and the gas in which measurements are made. While diatomic gases, namely molecular nitrogen and air, are being used in CCS measurement with increasingly prevalency, the majority of studies in which measurements are compared to predictions use models in which gas molecules are spherical or non-rotating, which is not necessarily appropriate for diatomic gases. Here, we adapt a momentum transfer based CCS calculation approach to consider rotating, diatomic gas molecule collisions with polyatomic ions, and compare CCS predictions with a diatomic gas molecule to those made with a spherical gas molecular for model spherical ions, tetra-alkylammonium ions, and multiply charged polyethylene glycol ions. CCS calculations are performed using both specular-elastic and diffuse-inelastic collisions rules, which mimic negligible internal energy exchange and complete thermal accommodation, respectively, between gas molecule and ion. The influence of the long range ion-induced dipole potential on calculations is also examined with both gas molecule models. In large part we find that CCSs calculated with specular-elastic collision rules decrease, while they increase with diffuse-inelastic collision rules when using diatomic gas molecules. Results clearly show the structural model of both the ion and gas molecule, the potential energy field between ion and gas molecule, and finally the modeled degree of kinetic energy exchange between ion and gas molecule internal energy are coupled to one another in CCS calculations, and must be considered carefully to obtain results which agree with measurements

  4. Nitrogen deposition effects on diatom communities in lakes from three National Parks in Washington State

    Science.gov (United States)

    Sheibley, Richard W.; Enache, Mihaela; Swarzenski, Peter W.; Moran, Patrick W.; Foreman, James R.

    2014-01-01

    The goal of this study was to document if lakes in National Parks in Washington have exceeded critical levels of nitrogen (N) deposition, as observed in other Western States. We measured atmospheric N deposition, lake water quality, and sediment diatoms at our study lakes. Water chemistry showed that our study lakes were ultra-oligotrophic with ammonia and nitrate concentrations often at or below detection limits with low specific conductance (−1 year−1 and were variable both within and across the parks. Diatom assemblages in a single sediment core from Hoh Lake (Olympic National Park) displayed a shift to increased relative abundances of Asterionella formosa and Fragilaria tenera beginning in the 1969–1975 timeframe, whereas these species were not found at the remaining (nine) sites. These diatom species are known to be indicative of N enrichment and were used to determine an empirical critical load of N deposition, or threshold level, where changes in diatom communities were observed at Hoh Lake. However, N deposition at the remaining nine lakes does not seem to exceed a critical load at this time. At Milk Lake, also in Olympic National Park, there was some evidence that climate change might be altering diatom communities, but more research is needed to confirm this. We used modeled precipitation for Hoh Lake and annual inorganic N concentrations from a nearby National Atmospheric Deposition Program station, to calculate elevation-corrected N deposition for 1980–2009 at Hoh Lake. An exponential fit to this data was hindcasted to the 1969–1975 time period, and we estimate a critical load of 1.0 to 1.2 kg N ha−1 year−1 for wet deposition for this lake.

  5. Predicting hydrocarbon release from soil

    International Nuclear Information System (INIS)

    Poppendieck, D.; Loehr, R.C.

    2002-01-01

    'Full text:' The remediation of hazardous chemicals from soils can be a lengthy and costly process. As a result, recent regulatory initiatives have focused on risk-based corrective action (RBCA) approaches. Such approaches attempt to identify the amount of chemical that can be left at a site with contaminated soil and still be protective of human health and the environment. For hydrocarbons in soils to pose risk to human heath and the environment, the hydrocarbons must be released from the soil and accessible to microorganisms, earthworms, or other higher level organisms. The sorption of hydrocarbons to soil can reduce the availability of the hydrocarbon to receptors. Typically in soils and sediments, there is an initial fast release of a hydrocarbon from the soil to the aqueous phase followed by a slower release of the remaining hydrocarbon to the aqueous phase. The rate and extent of slow release can influence aqueous hydrocarbon concentrations and the fate and transport of hydrocarbons in the subsurface. Once the fast fraction of the chemical has been removed from the soil, the remaining fraction of a chemical may desorb at a rate that natural mechanisms can attenuate the released hydrocarbon. Hence, active remediation may be needed only until the fast fraction has been removed. However, the fast fraction is a soil and chemical specific parameter. This presentation will present a tier I type protocol that has been developed to quickly estimate the fraction of hydrocarbons that are readily released from the soil matrix to the aqueous phase. Previous research in our laboratory and elsewhere has used long-term desorption (four months) studies to determine the readily released fraction. This research shows that a single short-term (less than two weeks) batch extraction procedure provides a good estimate of the fast released fraction derived from long-term experiments. This procedure can be used as a tool to rapidly evaluate the release and bioavailability of

  6. Modification of the physical and optical properties of the frustule of the diatom Coscinodiscus wailesii by nickel sulfate

    Energy Technology Data Exchange (ETDEWEB)

    Townley, Helen E [Department of Zoology, Oxford University, Tinbergen Building, South Parks Road, Oxford OX1 3PS (United Kingdom); Woon, Kai Lin [Department of Engineering, Oxford University, Parks Road, Oxford OX1 3PJ (United Kingdom); Payne, Frank P [Department of Engineering, Oxford University, Parks Road, Oxford OX1 3PJ (United Kingdom); White-Cooper, Helen [Department of Zoology, Oxford University, Tinbergen Building, South Parks Road, Oxford OX1 3PS (United Kingdom); Parker, Andrew R [Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD (United Kingdom)

    2007-07-25

    In this paper we demonstrate how the photonic properties of a diatom can be altered by growth with a metal pollutant. Both the optical and physical properties of the silica frustule of the diatom Coscinodiscus wailesii were affected by the presence of nickel sulfate in sea water. It was found that a sublethal concentration of the metal both significantly modified the size of the pores of the valves and quenched the intrinsic PL of the amorphous silica. Since cytoplasmic structures may be involved in determining the frustule architecture, we also present TEMs of nickel-grown diatoms and show the affected organelles. The ability to modify the properties of the frustule shows that mechanisms exist for the alteration of existing structures in nature to optimize specific characteristics for exploitation in biotechnological applications.

  7. Modification of the physical and optical properties of the frustule of the diatom Coscinodiscus wailesii by nickel sulfate

    International Nuclear Information System (INIS)

    Townley, Helen E; Woon, Kai Lin; Payne, Frank P; White-Cooper, Helen; Parker, Andrew R

    2007-01-01

    In this paper we demonstrate how the photonic properties of a diatom can be altered by growth with a metal pollutant. Both the optical and physical properties of the silica frustule of the diatom Coscinodiscus wailesii were affected by the presence of nickel sulfate in sea water. It was found that a sublethal concentration of the metal both significantly modified the size of the pores of the valves and quenched the intrinsic PL of the amorphous silica. Since cytoplasmic structures may be involved in determining the frustule architecture, we also present TEMs of nickel-grown diatoms and show the affected organelles. The ability to modify the properties of the frustule shows that mechanisms exist for the alteration of existing structures in nature to optimize specific characteristics for exploitation in biotechnological applications

  8. Assessing the effects of climate and volcanism on diatom and chironomid assemblages in an Andean lake near Quito, Ecuador

    Directory of Open Access Journals (Sweden)

    Neal Michelutti

    2015-12-01

    Full Text Available The tropical Andes are undergoing climate changes that rival those occurring anywhere else on the planet, and are likely to have profound consequences for ecosystems. Paleolimnological investigations of remote mountain lakes can provide details of past environmental change, especially where monitoring data are absent. Here, we reconstruct fossil diatom and chironomid communities spanning the last several hundred years from an Andean lake located in an ecological reserve near Quito, Ecuador. Both diatoms and chironomids recorded assemblage shifts reflective of changing climate conditions. The diatoms are likely responding primarily to temperature-related limnological changes, recording an increase in the number of planktonic taxa in the most recent sediments. This change is consistent with warmer conditions that result in enhanced periods of thermal stratification, allowing planktonic species to proliferate. The chironomids appear to respond mainly to a change in precipitation regime, recording a greater number of terrestrial and semi-terrestrial taxa that have been transported to the lake. A thick tephra deposit at the base of the sediment core affected both diatom and chironomid assemblages. The diatoms registered a change in species composition highlighting the ability of certain taxa to rapidly colonize new environments. In contrast, the chironomids showed a marked drop in abundance immediately following the tephra, but no change in species composition. In both cases the ecological response was short-lived, illustrating the resiliency of the lake to return to baseline conditions following volcanic inputs.

  9. Diatoms from a peat bog on the Pešter plateau (southwestern Serbia: New records for diatom flora of Serbia

    Directory of Open Access Journals (Sweden)

    Vidaković Danijela

    2016-01-01

    Full Text Available The distribution of diatoms was studied in three types of diatom communities (epiphytes, benthos and plankton of a peat bog on the Pešter plateau. The observed diatom flora inhabited all investigated communities, comprising in total 250 taxa in 53 genera. Among them, 45 taxa were new records for the Serbian diatom flora. Identified taxa belonged to different groups of algae, however alkaliphile diatoms were dominant. New ecological data for Encyonopsis minuta, Pinnularia isostauron and P. marchica are presented here. All the diatoms were documented by light micrographs, and brief notes on their morphology, distribution and ecology are provided. [Projekat Ministarstva nauke Republike Srbije, br. TR 037009

  10. TRIGLYCERIDE COMPOSITION OF SIXTEEN STRAINS OF MARINE DIATOM

    Directory of Open Access Journals (Sweden)

    Lily M.G. Panggabean

    2013-07-01

    Full Text Available Trigliceride or triacylglicerol (TAG composition in crude oil of sixteen strain of marine diatom has been detected by spectra analyses on an Electrospray - Ion Trap – Mass Spectrometry (ESI-IT-MS HCT Bruker-Daltonic GmbH instrument with AgNO3 used as coordination ionization agent. Biomass samples of each microalga strain were taken from early and late stationary cultures in f/2 enriched seawater and algal oils were extracted according to Bligh and Dyer. Results from spectra analysis showed that P-Pt-P (C16:0-C16:1-C16:0 were distinguished in TAG from diatom strains Chaetoceros sp.1, Chaetoceros sp.2, Thalasiossira sp.1, Thalasiossira sp.2, Thalasiossira sp.3, Navicula sp. 1, Navicula sp. 2, Navicula sp. 3, Navicula sp. 4, Nitzschia sp. 2 and Amphora sp. In contrast, TAGs in Melosira sp. included P-P-P (C16:0-C16:0-C16:0 and P-P-O (C16:0-C16:0-C18:1 were identified. TAGs from Chaetoceros sp. were the most varies among samples, i.e. P-Pt-P (C16:0-C16:1-C16:0, A-P-M (C20:4-C16:0-C14:0, P-Pt-Lt (C16:0-C16:1-C18:3, P-Pt-A (C16:0-C16:1-C20:4, D-P-P (C22:6-C16:0-C16:0, A-Ln-P (C20:4-C18:2-C16:0. Various TAGs were also detected in Nitzschia sp.2, i.e. P-Pt-M (C16:0-C16:1-C14:0, P-Pt-P (C16:0-C16:1-C16:0, P-Pt-S (C16:0-C16:1-C18:0, P-Pt-A (C16:0-C16:1-C20:4. TAGs composition in Skeletonema strains that similar to those in Nitzschia sp.1 has longer carbon, i.e. P-P-O (C16:0-C16:0-C18:1, P-O-O (C16:0-C18:1-C18:1 and O-O-O (C18:1-C18:1-C18:1. TAGs with longer carbon chain and more double bond including highly unsaturated fatty acid C20:4 were increased with culture age in diatoms Chaetoceros sp.1, Chaetoceros sp.2, Thalasiossira sp.2, Navicula sp.1 and Nitzschia sp. 2.Keywords: diatom, TAG, ESI-IT-MS, f/2, early and late stationary

  11. Comparing optical properties of different species of diatoms

    DEFF Research Database (Denmark)

    Maibohm, Christian; Friis, Søren Michael Mørk; Su, Y.

    2015-01-01

    species dependent with huge variety in size, shape, and micro- structure. We have experimentally investigated optical properties of frustules of several species of diatoms to further understand light harvesting properties together with commo n traits, effects and differences between the different...... analysis software. The software uses parameters which are extracted from experimental im ages as basis for simulation and allows us to extract the influence of the different elements of the frustule. The information could be used both for predicting optical properties of diatoms and by changing frustule...... parameters, maybe by altering growth conditions of the diatoms tailor their optical properties....

  12. Hydrogen production from hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Docekal, J

    1986-01-01

    Hydrogen is an important feed stock for chemical and petroleum industries, in addition to being considered as the energy carrier of the future. At the present time the feed stock hydrogen is mainly manufactured from hydrocarbons using steam reforming. In steam reforming two processes are employed, the conventional process and PSA (pressure swing adsorption) process. These two processes are described and compared. The results show that the total costs and the maintenance costs are lower for the PSA process, the capital outlay is lower for the conventional process, and the operating costs are similar for the two processes.

  13. Converting high boiling hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Terrisse, H; DuFour, L

    1929-02-12

    A process is given for converting high boiling hydrocarbons into low boiling hydrocarbons, characterized in that the high boiling hydrocarbons are heated to 200 to 500/sup 0/C in the presence of ferrous chloride and of such gases as hydrogen, water gas, and the like gases under a pressure of from 5 to 40 kilograms per square centimeter. The desulfurization of the hydrocarbons occurs simultaneously.

  14. Relaxed geometries and dipole moments of positron complexes with diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Assafrao, Denise; Mohallem, Jose R, E-mail: rachid@fisica.ufmg.b [Laboratorio de Atomos e Moleculas Especiais, Departamento de Fisica, ICEx, Universidade Federal de Minas Gerais, CP 702, 30123-970, Belo Horizonte, MG (Brazil)

    2010-01-01

    Relaxed geometries and dipole moments of diatomic molecules interacting with a slow positron are reported as functions of the positron distance to the more electronegative atom. A molecular model for the complex that allows applications to large systems is used. The electron population on the positron is proposed as a weighting function to calculate the average quantities. Results show Self-Consistent-Field quality or better.

  15. Emissions of hydrocarbons from marine phytoplankton—Some results from controlled laboratory experiments

    Science.gov (United States)

    McKay, W. A.; Turner, M. F.; Jones, B. M. R.; Halliwell, C. M.

    Laboratory experiments have been carried out to help assess and quantify the role of marine phytoplankton in the production of non-methane hydrocarbons. Evidence is presented here that supports the hypothesis that some short-chain hydrocarbons are produced during diatom and dinoflagellate lifecycles. The pattern of their emissions to the air above axenic unicultures of diatoms and dinoflagellates has been followed. The results suggest that ethane, ethene, propane and propene are produced during the autolysis of some phytoplankton, possibly by the oxidation of polyunsaturated lipids released into their culture medium. In contrast, isoprene and hexane appear during phytoplankton growth and are thus most likely produced either directly by the plankton or through the oxidation of exuded dissolved organic carbon.

  16. The effects of hydrological dynamics on benthic diatom community structure in a highly stratified estuary: The case of the Ebro Estuary (Catalonia, Spain)

    Science.gov (United States)

    Rovira, L.; Trobajo, R.; Leira, M.; Ibáñez, C.

    2012-04-01

    This study of the distribution of benthic diatom assemblages and their relationship with environmental factors in a highly stratified Mediterranean estuary, i.e. the Ebro Estuary, shows the importance of hydrological dynamics to explain the features of the diatom community in such an estuary, where river flow magnitude and fluctuations imply strong physicochemical variability especially in sites close to the sea. Eight sites along the estuary were sampled during 2007-2008 both at superficial and deep water layers, in order to gather both horizontal and vertical estuarine physicochemical and hydrological gradients. Canonical Variates Analysis and Hierarchical Cluster Analysis segregated diatom community in two assemblages depending on the dynamics of the salt-wedge. The diatom assemblages of riverine conditions (i.e. without salt-wedge influence) where characterised by high abundances of Cocconeis placentula var. euglypta and Amphora pediculus, meanwhile high abundances of Nizschia frustulum and Nitzschia inconspicua were characteristic of estuarine conditions (i.e. under salt-wedge influence). Redundancy Analysis showed that both diatom assemblages responded seasonally to Ebro River flows, especially in estuarine conditions, where fluctuating conditions affected diatom assemblages both at spatial and temporal scale.

  17. The upstream regulatory sequence of the light harvesting complex Lhcf2 gene of the marine diatom Phaeodactylum tricornutum enhances transcription in an orientation- and distance-independent fashion.

    Science.gov (United States)

    Russo, Monia Teresa; Annunziata, Rossella; Sanges, Remo; Ferrante, Maria Immacolata; Falciatore, Angela

    2015-12-01

    Diatoms are a key phytoplankton group in the contemporary ocean, showing extraordinary adaptation capacities to rapidly changing environments. The recent availability of whole genome sequences from representative species has revealed distinct features in their genomes, like novel combinations of genes encoding distinct metabolisms and a significant number of diatom-specific genes. However, the regulatory mechanisms driving diatom gene expression are still largely uncharacterized. Considering the wide variety of fields of study orbiting diatoms, ranging from ecology, evolutionary biology to biotechnology, it is thus essential to increase our understanding of fundamental gene regulatory processes such as transcriptional regulation. To this aim, we explored the functional properties of the 5'-flanking region of the Phaeodatylum tricornutum Lhcf2 gene, encoding a member of the Light Harvesting Complex superfamily and we showed that this region enhances transcription of a GUS reporter gene in an orientation- and distance-independent fashion. This represents the first example of a cis-regulatory sequence with enhancer-like features discovered in diatoms and it is instrumental for the generation of novel genetic tools and diatom exploitation in different areas of study. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Primary biodegradation of petroleum hydrocarbons in seawater

    Energy Technology Data Exchange (ETDEWEB)

    Comber, M.I.H.; Den Haan, K.H.; Djemel, N.; Eadsforth, C.V.; King, D.; Paumen, M.L.; Parkerton, T.; Dmytrasz, B.

    2012-12-15

    This report describes primary biodegradation experiments performed to determine the persistence of higher molecular weight petroleum hydrocarbons in seawater. Results from the biodegradation experiments show that the majority of tested petroleum hydrocarbons have half-lives in seawater less than 60 days.

  19. Identification and Characterisation of Major Hydrocarbons in ...

    African Journals Online (AJOL)

    Identification and Characterisation of Major Hydrocarbons in Thermally Degraded Low Density Polyethylene Films. ... There were alkanes, alkenes, halogenated alkanes, and very few aromatics in the liquid product and, the hydrocarbons were observed to range between C10 - C27. The FTIR and GC-MS results show the ...

  20. Diatoms - nature materials with great potential for bioapplications

    Directory of Open Access Journals (Sweden)

    Medarević Đorđe P.

    2016-01-01

    Full Text Available Diatoms are widespread unicellular photosynthetic algae that produce unique highly ordered siliceous cell wall, called frustule. Micro- to nanoporous structure with high surface area that can be easily modified, high mechanical resistance, unique optical features (light focusing and luminescence and biocompatibility make diatom frustule as a suitable raw material for the development of devices such as bio- and gas sensors, microfluidic particle sorting devices, supercapacitors, batteries, solar cells, electroluminescent devices and drug delivery systems. Their wide availability in the form of fossil remains (diatomite or diatomaceous earth as well as easy cultivation in the artificial conditions further supports use of diatoms in many different fields of application. This review focused on the recent achievements in the diatom bioapplications such as drug delivery, biomolecules immobilization, bio- and gas sensing, since great progress was made in this field over the last several years.

  1. Abundance of bacterial and diatom fouling on various surfaces

    Digital Repository Service at National Institute of Oceanography (India)

    PrabhaDevi

    Abundance of bacterial and diatom fouling on aluminium, fibreglass and stainless steel were studied from Dona Paula waters of the Zuari Estuary. Both these forms were reversibly attached in large numbers to surfaces during the initial 24 hr...

  2. A Simplified Quantum Mechanical Model of Diatomic Molecules

    Science.gov (United States)

    Nielsen, Lars Drud

    1978-01-01

    Introduces a simple one-dimensional model of a diatomic molecule that can explain all the essential features of a real two particle quantum mechanical system and gives quantitative results in fair agreement with those of a hydrogen molecule. (GA)

  3. Studies on new antifreeze protein from the psychrophilic diatom ...

    African Journals Online (AJOL)

    Studies on new antifreeze protein from the psychrophilic diatom, Fragilariopsis cylindrus. ... African Journal of Biotechnology. Journal Home · ABOUT THIS ... The predicted gene product, AfpA, had a molecular mass of 27 kDa. Expression of ...

  4. Analytic vibration-rotational matrix elements for diatomic molecules

    International Nuclear Information System (INIS)

    Bouanich, J.P.

    1987-01-01

    The vibration-rotational matrix elements for infrared or Raman transitions vJ → v'J' of diatomic molecules are calculated for powers of the reduced displacement X from parameters of the Dunham potential-energy function. (orig.)

  5. Modified Ribose Receptor Response in Isolated Diatom Frustules

    Energy Technology Data Exchange (ETDEWEB)

    Fairbanks, Carly R.

    2011-08-26

    Diatoms are a distinctive group of microalgae with the unique ability to produce a highly-ordered biosilica matrix, known as the frustule. Diatoms hold significant potential in the biotechnology field as a silica scaffold for embedding proteins. In this study, we analyzed the funtionalization of biosilica with a receptor complex through genetic modification of the diatom, Thalassiosira pseudonana. Through the use of Foerster Resonance Energy Transfer (FRET), the receptor was shown to remain active in transformed frustules after the inner cellular contents were removed. In addition to protein functionality, growth conditions for T. pseudonana were optimized. Untransformed cultures receiving aeration grew more rapidly than stagnant untransformed cultures. Surprisingly, transformed cultures grew more quickly than untransformed cultures. This study demonstrates isolated diatom frustules provide an effective scaffold for embedded receptor complexes. Through this research, we provide the groundwork for the development of new biosensors for use in diagnostics and environmental remediation.

  6. Pliocene diatoms from the Bryce Canyon Area, Utah

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    habitat. The fragmentary condition of these indicated agitation during sedimentation. The ratio between the planktonic and benthonic diatoms indicated near-shore deposition. The two extinct species (?), @iSurirella craticula@@ (= @iStictodesmis craticula...

  7. Resonant inelastic collisions of electrons with diatomic molecules

    International Nuclear Information System (INIS)

    Houfek, Karel

    2012-01-01

    In this contribution we give a review of applications of the nonlocal resonance theory which has been successfully used for treating the nuclear dynamics of low-energy electron collisions with diatomic molecules over several decades. We give examples and brief explanations of various structures observed in the cross sections of vibrational excitation and dissociative electron attachment to diatomic molecules such as threshold peaks, boomerang oscillations below the dissociative attachment threshold, or outer-well resonances.

  8. Resonant inelastic collisions of electrons with diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Houfek, Karel, E-mail: karel.houfek@gmail.com [Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University, V Holesovickach 2, 180 00 Prague 8 (Czech Republic)

    2012-05-15

    In this contribution we give a review of applications of the nonlocal resonance theory which has been successfully used for treating the nuclear dynamics of low-energy electron collisions with diatomic molecules over several decades. We give examples and brief explanations of various structures observed in the cross sections of vibrational excitation and dissociative electron attachment to diatomic molecules such as threshold peaks, boomerang oscillations below the dissociative attachment threshold, or outer-well resonances.

  9. Epibiotic Diatoms Are Universally Present on All Sea Turtle Species

    OpenAIRE

    Robinson, Nathan J.; Majewska, Roksana; Lazo-Wasem, Eric A.; Nel, Ronel; Paladino, Frank V.; Rojas, Lourdes; Zardus, John D.; Pinou, Theodora

    2016-01-01

    The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtl...

  10. Radiational and energetic characteristics of diatomic molecules (data base)

    International Nuclear Information System (INIS)

    Kuznetsova, L.A.; Pazyuk, E.A.; Stolyarov, A.V.

    1993-01-01

    Data base on radiational and energetic characteristics of diatomic molecules was created. The base consists of two parts: reference system and recommended data system. The reference system contains the information about studies of radiational and energetic parameters of more than 1500 electronic states and 1700 electron transfers for ∼ 350 diatomic molecules and their ions. The base bibliography includes ∼ 3000 publications. 11 refs., 1 figs

  11. Porous silicon and diatoms micro-shells: an example of inverse biomimetic

    Science.gov (United States)

    De Tommasi, Edoardo; Rea, Ilaria; Rendina, Ivo; De Stefano, Luca

    2011-05-01

    Porous silicon (PSi) is by far a very useful technological platform for optical monitoring of chemical and biological substances and due to its peculiar physical and morphological properties it is worldwide used in sensing experiments. On the other hand, we have discovered a natural material, the micro-shells of marine diatoms, ubiquitous unicellular algae, which are made of hydrated amorphous silica, but, most of all, show geometrical structures made of complex patterns of pores which are surprisingly similar to those of porous silicon. Moreover, under laser irradiation, this material is photoluminescent and the photoluminescence is very sensitive to the surrounding atmosphere, which means that the material can act as a transducer. Starting from our experience on PSi devices, we explore the optical and photonic properties of marine diatoms micro-shells in a sort of inverse biomimicry.

  12. Diatoms from lentic and lotic systems in Antioquia, Choco and Santander Departments in Colombia

    International Nuclear Information System (INIS)

    Sala, Silvia E.; Ramirez, John J.; Plata, Yasmin

    2008-01-01

    In the tropical and subtropical regions, there is a large number of species which has not been yet described. The high possibility of extinction makes their inventory a priority. 23 diatoms taxa from Andean lotic systems and lentic waterbodies localized in the Departments of Antioquia, Santander and Choco, Colombia, are analyzed with light and scanning electron microscopy. Each taxon is described and information about environmental characteristic of the sites where they were collected and distribution in Colombia is given. The studied taxa belong to the orders Thalassiosirales (1), Aulacoseirales (1), Fragilariales (4), Cymbellales (7), Achnanthales (2), Naviculales (7), and Thalassiophysales (1). Fifteen of them are recorded for the first time in Colombia and Encyonema jemtlandicum in America del Sur. A comparison with the diatom flora of the Colombian Amazonia showed that there were only three taxa in common to these two equatorial regions probably due to the influence of altitudinal gradient. (author)

  13. Effects of the oxylipin-producing diatom Skeletonema marinoi on gene expression levels of the calanoid copepod Calanus sinicus.

    Science.gov (United States)

    Lauritano, Chiara; Carotenuto, Ylenia; Vitiello, Valentina; Buttino, Isabella; Romano, Giovanna; Hwang, Jiang-Shiou; Ianora, Adrianna

    2015-12-01

    Diatoms are eukaryotic unicellular plants that constitute one of the major components of marine phytoplankton, comprising up to 40% of annual productivity at sea and representing 25% of global carbon-fixation. Diatoms have traditionally been considered a preferential food for zooplankton grazers such as copepods, but, in the last two decades, this beneficial role has been challenged after the discovery that many species of diatoms produce toxic metabolites, collectively termed oxylipins, that induce reproductive failure in zooplankton grazers. Diatoms are the dominant natural diet of Calanus sinicus, a cold-temperate calanoid copepod that supports secondary production of important fisheries in the shelf ecosystems of the Northwest Pacific Ocean, Yellow Sea, Sea of Japan and South China Sea. In this study, the effect of the oxylipin-producing diatom Skeletonema marinoi on C. sinicus has been evaluated by analyzing expression level changes of genes involved in defense and detoxification systems. Results show that C. sinicus is more resistant to a diet of this diatom species in terms of gene expression patterns, compared to the congeneric species Calanus helgolandicus which is an important constituent of the temperate waters of the Atlantic Ocean and northern Mediterranean Sea. These findings contribute to the better understanding of genetic and/or phenotypic flexibility of copepod species and their capabilities to cope with stress by identifying molecular markers (such as stress and detoxification genes) as biosensors for environmental perturbations (e.g. toxins and contaminants) affecting marine copepods. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  14. THE INFLUENCE OF SUBMERGED MACROPHYTES ON SEDIMENTARY DIATOM ASSEMBLAGES(1).

    Science.gov (United States)

    Vermaire, Jesse C; Prairie, Yves T; Gregory-Eaves, Irene

    2011-12-01

    Submerged macrophytes are a central component of lake ecosystems; however, little is known regarding their long-term response to environmental change. We have examined the potential of diatoms as indicators of past macrophyte biomass. We first sampled periphyton to determine whether habitat was a predictor of diatom assemblage. We then sampled 41 lakes in Quebec, Canada, to evaluate whether whole-lake submerged macrophyte biomass (BiomEpiV) influenced surface sediment diatom assemblages. A multivariate regression tree (MRT) was used to construct a semiquantitative model to reconstruct past macrophyte biomass. We determined that periphytic diatom assemblages on macrophytes were significantly different from those on wood and rocks (ANOSIM R = 0.63, P macrophyte, nutrient-limited lakes (BiomEpiV ≥525 μg · L(-1) ; total phosphorus [TP] macrophyte, nutrient-limited lakes (BiomEpiV macrophytes have a significant influence on diatom community structure and that sedimentary diatom assemblages can be used to infer past macrophyte abundance. © 2011 Phycological Society of America.

  15. Current trends to comprehend lipid metabolism in diatoms.

    Science.gov (United States)

    Zulu, Nodumo Nokulunga; Zienkiewicz, Krzysztof; Vollheyde, Katharina; Feussner, Ivo

    2018-04-01

    Diatoms are the most dominant phytoplankton species in oceans and they continue to receive a great deal of attention because of their significant contributions in ecosystems and the environment. Due to triacylglycerol (TAG) profiles that are abundant in medium-chain fatty acids, diatoms have emerged to be better feed stocks for biofuel production, in comparison to the commonly studied green microalgal species (chlorophytes). Importantly, diatoms are also known for their high levels of the essential ω3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and are considered to be a promising alternative source of these components. The two most commonly exploited diatoms include Thalassiosira pseudonana and Phaeodactylum tricornutum. Although obvious similarities between diatoms and chlorophytes exist, there are some substantial differences in their lipid metabolism. This review provides an overview on lipid metabolism in diatoms, with P. tricornutum as the most explored model. Special emphasis is placed on the synthesis and incorporation of very long chain ω3 fatty acids into lipids. Furthermore, current approaches including genetic engineering and biotechnological methods aimed at improving and maximizing lipid production in P. tricornutum are also discussed. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  16. Some aspects of water quality in a polluted lowland river in relation to the intracellular chemical levels in planktonic and epilithic diatoms.

    Science.gov (United States)

    Tien, Chien-Jung

    2004-04-01

    Changes in elemental concentrations of diatoms and river water from the river Erh-Jen were determined using scanning electron microscopy energy-dispersive X-ray microanalysis and inductively coupled plasma mass spectrometry. Relatively large amounts of copper and lead found in both planktonic and epilithic diatoms implied these algae might play an important role in biogeochemical cycles and in the transfer of those elements to higher trophic levels in the aquatic environment. Changes in elemental concentrations within diatom cells were found to vary with other elements within cells and the same or different elements in water. Planktonic and epilithic cells showed different correlation patterns. For epilithic diatoms, negative correlations were found between concentrations of total phosphorus and phosphate in water and those of phosphorus within cells, and between concentrations of lead in water and in cells. Concentrations of chromium and mercury within planktonic cells and those of phosphorus, manganese and lead within epilithic ones were found to be easily influenced by other elements in river water, indicating appearance of the competitive manner on uptake of such elements by algal cells. Relatively high concentration factors (CFs) for cadmium, mercury and lead by diatoms in this study suggested they are good accumulators for these heavy metals. Significant negative corrections were found between the CFs of diatoms and the concentrations of elements in river water.

  17. An integrative analysis of post-translational histone modifications in the marine diatom Phaeodactylum tricornutum

    KAUST Repository

    Veluchamy, Alaguraj

    2015-05-20

    Background: Nucleosomes are the building blocks of chromatin where gene regulation takes place. Chromatin landscapes have been profiled for several species, providing insights into the fundamental mechanisms of chromatin-mediated transcriptional regulation of gene expression. However, knowledge is missing for several major and deep-branching eukaryotic groups, such as the Stramenopiles, which include the diatoms. Diatoms are highly diverse and ubiquitous species of phytoplankton that play a key role in global biogeochemical cycles. Dissecting chromatin-mediated regulation of genes in diatoms will help understand the ecological success of these organisms in contemporary oceans. Results: Here, we use high resolution mass spectrometry to identify a full repertoire of post-translational modifications on histones of the marine diatom Phaeodactylum tricornutum, including eight novel modifications. We map five histone marks coupled with expression data and show that P. tricornutum displays both unique and broadly conserved chromatin features, reflecting the chimeric nature of its genome. Combinatorial analysis of histone marks and DNA methylation demonstrates the presence of an epigenetic code defining activating or repressive chromatin states. We further profile three specific histone marks under conditions of nitrate depletion and show that the histone code is dynamic and targets specific sets of genes. Conclusions: This study is the first genome-wide characterization of the histone code from a stramenopile and a marine phytoplankton. The work represents an important initial step for understanding the evolutionary history of chromatin and how epigenetic modifications affect gene expression in response to environmental cues in marine environments. © 2015 Veluchamy et al.

  18. Risk assessment of excessive CO{sub 2} emission on diatom heavy metal consumption

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fengjiao; Li, Shunxing, E-mail: shunxing_li@aliyun.com; Zheng, Fengying; Huang, Xuguang

    2016-10-01

    Diatoms are the dominant group of phytoplankton in the modern ocean, accounting for approximately 40% of oceanic primary productivity and critical foundation of coastal food web. Rising dissolution of anthropogenic CO{sub 2} in seawater may directly/indirectly cause ocean acidification and desalination. However, little is known about dietary diatom-associated changes, especially for diatom heavy metal consumption sensitivity to these processes, which is important for seafood safety and nutrition assessment. Here we show some links between ocean acidification/desalination and heavy metal consumption by Thalassiosira weissflogii. Excitingly, under desalination stress, the relationships between Cu, Zn, and Cd were all positively correlated, especially between Cu and Zn (r = 0.989, total intracellular concentration) and between Zn and Cd (r = 0.962, single-cell intracellular concentration). Heavy metal consumption activity in decreasing order was acidification < acidification + desalination < desalination for Zn, acidification < desalination < acidification + desalination for Cu and Cd, i.e., heavy metal uptake (or release) were controlled by environmental stress. Our findings showed that heavy metal uptake (or release) was already responded to ongoing excessive CO{sub 2} emission-driven acidification and desalination, which was important for risk assessment of climate change on diatom heavy metal consumption, food web and then seafood safety in future oceans. - Highlights: • Excessive CO{sub 2} in seawater may causes ocean acidification and desalination. • The relationships between Cu, Zn, and Cd were all positively correlated by desalination. • Significant effects of salinity on intracellular concentration of Cu and Cd • Cu and Cd in marine phytoplankton could be regulated by metal excretion. • Heavy metal consumption was affect by excessive CO{sub 2}.

  19. Risk assessment of excessive CO_2 emission on diatom heavy metal consumption

    International Nuclear Information System (INIS)

    Liu, Fengjiao; Li, Shunxing; Zheng, Fengying; Huang, Xuguang

    2016-01-01

    Diatoms are the dominant group of phytoplankton in the modern ocean, accounting for approximately 40% of oceanic primary productivity and critical foundation of coastal food web. Rising dissolution of anthropogenic CO_2 in seawater may directly/indirectly cause ocean acidification and desalination. However, little is known about dietary diatom-associated changes, especially for diatom heavy metal consumption sensitivity to these processes, which is important for seafood safety and nutrition assessment. Here we show some links between ocean acidification/desalination and heavy metal consumption by Thalassiosira weissflogii. Excitingly, under desalination stress, the relationships between Cu, Zn, and Cd were all positively correlated, especially between Cu and Zn (r = 0.989, total intracellular concentration) and between Zn and Cd (r = 0.962, single-cell intracellular concentration). Heavy metal consumption activity in decreasing order was acidification < acidification + desalination < desalination for Zn, acidification < desalination < acidification + desalination for Cu and Cd, i.e., heavy metal uptake (or release) were controlled by environmental stress. Our findings showed that heavy metal uptake (or release) was already responded to ongoing excessive CO_2 emission-driven acidification and desalination, which was important for risk assessment of climate change on diatom heavy metal consumption, food web and then seafood safety in future oceans. - Highlights: • Excessive CO_2 in seawater may causes ocean acidification and desalination. • The relationships between Cu, Zn, and Cd were all positively correlated by desalination. • Significant effects of salinity on intracellular concentration of Cu and Cd • Cu and Cd in marine phytoplankton could be regulated by metal excretion. • Heavy metal consumption was affect by excessive CO_2.

  20. Electrophoretic protein profiles of mid-sized copepod Calanoides patagoniensis steadily fed bloom-forming diatoms

    Directory of Open Access Journals (Sweden)

    Victor M Aguilera

    2015-09-01

    Full Text Available Recent field and experimental evidence collected in the southern upwelling region off Concepción (36°5'S, 73°3'W showed an abrupt reduction (<72 h in the egg production rates (EPR of copepods when they were fed steadily and solely with the local bloom-forming diatom Thalassiosira rotula. Because diatoms were biochemically similar to dinoflagellate Prorocentrum minimum, a diet which supported higher reproductive outcomes, the fecundity reduction observed in copepod females fed with the diatom may have obeyed to post-ingestive processes, giving rise to resources reallocation. This hypothesis was tested by comparing feeding (clearance and ingestion rates, reproduction (EPR and hatching success and the structure of protein profiles (i.e., number and intensity of electrophoretic bands of copepods (adults and eggs incubated during 96 h with the two food conditions. The structure of protein profiles included molecular sizes that were calculated from the relative mobility of protein standards against the logarithm of their molecular sizes. After assessing the experimental conditions, feeding decreased over time for those females fed with T. rotula, while reproduction was higher in females fed with P. minimum. Electrophoretic profiles resulted similar mostly at a banding region of 100 to 89-kDa, while they showed partial differences around the region of 56-kDa band, especially in those females fed and eggs produced with T. rotula. Due to reproductive volume was impacted while larvae viability, a physiological processes with specific and high nutritional requirements, was independent on food type; post-ingestive processes, such as expression of stress-related proteins deviating resources to metabolic processes others than reproduction, are discussed under framework of nutritional-toxic mechanisms mediating copepod-diatoms relationships in productive upwelling areas.

  1. Distribution of hydrocarbon-utilizing microorganisms and hydrocarbon biodegradation potentials in Alaskan continental shelf areas

    International Nuclear Information System (INIS)

    Roubal, G.; Atlas, R.M.

    1978-01-01

    Hydrocarbon-utilizing microogranisms were enumerated from Alaskan continental shelf areas by using plate counts and a new most-probable-number procedure based on mineralization of 14 C-labeled hydrocarbons. Hydrocarbon utilizers were ubiquitously distributed, with no significant overall concentration differences between sampling regions or between surface water and sediment samples. There were, however, significant seasonal differences in numbers of hydrocarbon utilizers. Distribution of hydrocarbon utilizers within Cook Inlet was positively correlated with occurrence of hydrocarbons in the environment. Hydrocarbon biodegradation potentials were measured by using 14 C-radiolabeled hydrocarbon-spiked crude oil. There was no significant correlation between numbers of hydrocarbon utilizers and hydrocarbon biodegradation potentials. The biodegradation potentials showed large seasonal variations in the Beaufort Sea, probably due to seasonal depletion of available nutrients. Non-nutrient-limited biodegradation potentials followed the order hexadecane > naphthalene >> pristane > benzanthracene. In Cook Inlet, biodegradation potentials for hexadecane and naphthalene were dependent on availability of inorganic nutrients. Biodegradation potentials for pristane and benzanthracene were restricted, probably by resistance to attack by available enzymes in the indigenous population

  2. Characterization of hydrocarbon utilizing fungi from hydrocarbon ...

    African Journals Online (AJOL)

    Prof. Ogunji

    isolated fungi could be useful in the bioremediation of hydrocarbon polluted sites. Keywords: ... Technologies such as mechanical force, burying, evaporation, dispersant application, and ..... The effects of drilling fluids on marine bacteria from a.

  3. Diatomic molecule vibrational potentials: Accuracy of representations

    International Nuclear Information System (INIS)

    Engelke, R.

    1978-01-01

    A method is presented for increasing the radius of convergence of certain representations of diatomic molecule vibrational potentials. The method relies on using knowledge of the analytic structure of such potentials to the maximum when attempting to approximate them. The known singular point (due to the centrifugal and/or Coulomb potentials) at zero internuclear separation should be included in its exact form in an approximate representation. The efficacy of this idea is tested [using Peek's ''exact'' numerical Born-Oppenheimer potential for the (1ssigma/sub g/) 2 Σ + /sub g/ state of H + 2 as a test problem] when the representational form is the series of (1) Dunham, (2) Simons, Parr, and Finlan, (3) Thakkar, and (4) Ogilvie-Tipping, and also (5) when the form is a [2, 2] or a [3, 3] Pade approximant. Significant improvements in accuracy are obtained in some of these cases, particularly on the inner wall of the potential. A comparison of the effectiveness of the five methods is made both with and without the origin behavior being included exactly. This is useful in itself as no comprehensive accuracy comparison of the standard representations seems to have appeared in the literature. The Ogilvie-Tipping series, corrected at the origin for singular behavior, is the best representation presently available for states analogous to the (1ssigma/sub g/) 2 Σ + /sub g/ state of H + 2

  4. Enhanced adsorption of trivalent arsenic from water by functionalized diatom silica shells.

    Directory of Open Access Journals (Sweden)

    Jianying Zhang

    Full Text Available The potential of porous diatom silica shells as a naturally abundant low-cost sorbent for the removal of arsenic in aqueous solutions was investigated in a batch study. The objective of this work was to chemically modify the silica shells of a diatom Melosira sp. with bifunctional (thiol and amino groups to effectively remove arsenic in its toxic As(III form (arsenite predominant in the aquatic environment. Sorption experiments with this novel sorbent were conducted under varying conditions of pH, time, dosage, and As(III concentration. A maximum adsorption capacity of 10.99 mg g-1 was achieved within 26 h for a solution containing 12 mg L-1 As(III at pH 4 and sorbent dosage of 2 g L-1. The functionalized diatom silica shells had a surface morphological change which was accompanied by increased pore size at the expense of reduced specific surface area and total pore volume. As(III adsorption was best fitted with the Langmuir-Freundlich model, and the adsorption kinetic data using pore surface diffusion model showed that both the external (film and internal (intraparticle diffusion can be rate-determining for As(III adsorption. Fourier transform infrared spectroscopy (FTIR indicated that the thiol and amino groups potentially responsible for As(III adsorption were grafted on the surface of diatom silica shells. X-ray photoelectron spectroscopy (XPS further verified that this unique sorbent proceeded via a chemisorption mechanism through the exchange between oxygen-containing groups of neutral As(III and thiol groups, and through the surface complexation between As(III and protonated nitrogen and hydroxyl groups. Results indicate that this functionalized bioadsorbent with a high As(III adsorption capacity holds promise for the treatment of As(III containing wastewater.

  5. Carbonate-sensitive phytotransferrin controls high-affinity iron uptake in diatoms

    Science.gov (United States)

    McQuaid, Jeffrey B.; Kustka, Adam B.; Oborník, Miroslav; Horák, Aleš; McCrow, John P.; Karas, Bogumil J.; Zheng, Hong; Kindeberg, Theodor; Andersson, Andreas J.; Barbeau, Katherine A.; Allen, Andrew E.

    2018-03-01

    In vast areas of the ocean, the scarcity of iron controls the growth and productivity of phytoplankton. Although most dissolved iron in the marine environment is complexed with organic molecules, picomolar amounts of labile inorganic iron species (labile iron) are maintained within the euphotic zone and serve as an important source of iron for eukaryotic phytoplankton and particularly for diatoms. Genome-enabled studies of labile iron utilization by diatoms have previously revealed novel iron-responsive transcripts, including the ferric iron-concentrating protein ISIP2A, but the mechanism behind the acquisition of picomolar labile iron remains unknown. Here we show that ISIP2A is a phytotransferrin that independently and convergently evolved carbonate ion-coordinated ferric iron binding. Deletion of ISIP2A disrupts high-affinity iron uptake in the diatom Phaeodactylum tricornutum, and uptake is restored by complementation with human transferrin. ISIP2A is internalized by endocytosis, and manipulation of the seawater carbonic acid system reveals a second-order dependence on the concentrations of labile iron and carbonate ions. In P. tricornutum, the synergistic interaction of labile iron and carbonate ions occurs at environmentally relevant concentrations, revealing that carbonate availability co-limits iron uptake. Phytotransferrin sequences have a broad taxonomic distribution and are abundant in marine environmental genomic datasets, suggesting that acidification-driven declines in the concentration of seawater carbonate ions will have a negative effect on this globally important eukaryotic iron acquisition mechanism.

  6. Isolation and Characterization of Silaffin that Catalyze Biosilica Formation from Marine Diatom Chaetoceros gracilis

    Directory of Open Access Journals (Sweden)

    AGNES IMELDA MANURUNG

    2007-09-01

    Full Text Available The method of making silica in industries requires extreme conditions. The finding of proteins involved in the formation of biosilica from diatoms, has opened up an alternative way of production. Chaetoceros gracilis is one of the diatoms, which is potential in producing silaffin protein. This study aimed to isolate and to characterize the protein. We also analyzed the protein activity toward tetraethoxyorthosilicate (TEOS substrate in in vitro reaction. Diatom biomass was harvested and further kept in 2% SDS/100 mM EDTA solution. Protein isolation was conducted by dissolving the silica and separating the protein by soaking in 2 M HF/8 M NH4F. Protein concentration was analyzed using Bradford method and the molecular weight was estimated through SDS-PAGE. Protein activity was observed by reacting it with TEOS substrate to form silica polymer and measured by colorimetric molibdate assay. Protein concentration was 1.20 mg/ml and appeared filamentous. The apparent molecular weights consisted of 12, 23, 42, 44 kDa. These protein was able to polymerize the silica at room temperature within 10 min. As much as 85.65 μmol TEOS was polymerized per 1.4 × 106 silaffin protein per min. SEM analysis showed the formation of spherical, aggregate biosilica.

  7. Isolation and Characterization of Silaffin that Catalyze Biosilica Formation from Marine Diatom Chaetoceros gracilis

    Directory of Open Access Journals (Sweden)

    AGNES IMELDA MANURUNG

    2007-09-01

    Full Text Available The method of making silica in industries requires extreme conditions. The finding of proteins involved in the formation of biosilica from diatoms, has opened up an alternative way of production. Chaetoceros gracilis is one of the diatoms, which is potential in producing silaffin protein. This study aimed to isolate and to characterize the protein. We also analyzed the protein activity toward tetraethoxyorthosilicate (TEOS substrate in in vitro reaction. Diatom biomass was harvested and further kept in 2% SDS/100 mM EDTA solution. Protein isolation was conducted by dissolving the silica and separating the protein by soaking in 2 M HF/8 M NH4F. Protein concentration was analyzed using Bradford method and the molecular weight was estimated through SDS-PAGE. Protein activity was observed by reacting it with TEOS substrate to form silica polymer and measured by colorimetric molibdate assay. Protein concentration was 1.20 mg/ml and appeared filamentous. The apparent molecular weights consisted of 12, 23, 42, 44 kDa. These protein was able to polymerize the silica at room temperature within 10 min. As much as 85.65 mol TEOS was polymerized per 1.4 x 106 silaffin protein per min. SEM analysis showed the formation of spherical, aggregate biosilica.

  8. Effect of UV-B radiation on biomass production, pigmentation and protein content of marine diatoms

    International Nuclear Information System (INIS)

    Doehler, G.

    1984-01-01

    Several species of marine diatoms were grown at + 18 0 C and + 22 0 C under normal air conditions (0.035 vol.% CO 2 ) at a light/dark alteration of 14.8 h. Intensity of white light was 1 mW (approx.= 5000 lux). An artifical nutrient solution of 35per mille salinity was used. Algae - harvested during exponential growth - were exposed to different intensities of UV-B radiation (439, 717 and 1230 J m -2 m -1 ) for 2 days. UV-B radiation depressed the growth of all tested marine diatoms. Low levels of UV-B resulted in a slight increase of the biomass production (dry weight) compared to not UV-B treated cells. Enhanced UV-B doses caused a diminution of the primary productivity in all species. Algae exposed to UV-B stress showed a marked decrease in the protein and pigment content (chlorophyll a, chlorophyll c 1 + c 2 and carotenoids). In + 22 0 C grown cells of Lauderia annulata and Thalassiosira rotula were more sensitive to UV-B radiation than those cultures grown at + 18 0 C. Bellerochea yucatanensis cells grown at + 22 0 C were less affected after UV-B exposure than at + 18 0 C grown algae. The UV-B sensibility and growth of the individual species varied in a mixture of several marine diatoms. Results were discussed with reference to the UV-B effect on metabolic processes. (orig.)

  9. Cytoplasmic inheritance of parent-offspring cell structure in the clonal diatom Cyclotella meneghiniana.

    Science.gov (United States)

    Shirokawa, Yuka; Shimada, Masakazu

    2016-11-16

    In cytoplasmic inheritance, structural states of a parent cell could be transmitted to offspring cells via two mechanisms. The first is referred to as the hangover of parent structure, where the structure itself remains and faithfully transmits within offspring cells; the second is structural inheritance, wherein the parent structure functions as a template for development of new offspring structure. We estimated to what extent the parent structure affects the development of offspring structure by structural inheritance, using a clone of the diatom Cyclotella meneghiniana The cell has two siliceous valves (a cell wall part at both cell poles): one is inherited from the parent and the other is newly formed. We estimated cytoplasmic heritability by comparing valve traits (central fultoportulae (CTFP), striae, central area, and cell diameter) of parent and new offspring valves, using single-cell isolation and valve labelling. Parent-offspring valve trait regressions showed that all traits, except CTFP, were significantly correlated. We formulated a quantitative genetic model considering the diatom inheritance system and revealed short-term rapid evolution compared with other inheritance systems. Diatom structural inheritance will have evolved to enable clonal populations to rapidly acquire and maintain suitable structures for temporal changes in environments and life-cycle stages. © 2016 The Author(s).

  10. The role of diatom nanostructures in biasing diffusion to improve uptake in a patchy nutrient environment.

    Directory of Open Access Journals (Sweden)

    James G Mitchell

    Full Text Available BACKGROUND: Diatoms are important single-celled autotrophs that dominate most lit aquatic environments and are distinguished by surficial frustules with intricate designs of unknown function. PRINCIPAL FINDINGS: We show that some frustule designs constrain diffusion to positively alter nutrient uptake. In nutrient gradients of 4 to 160 times over <5 cm, the screened-chambered morphology of Coscincodiscus sp. biases the nutrient diffusion towards the cell by at least 3.8 times the diffusion to the seawater. In contrast, the open-chambers of Thalassiosira eccentrica produce at least a 1.3 times diffusion advantage to the membrane over Coscincodiscus sp. when nutrients are homogeneous. SIGNIFICANCE: Diffusion constraint explains the success of particular diatom species at given times and the overall success of diatoms. The results help answer the unresolved question of how adjacent microplankton compete. Furthermore, diffusion constraint by supramembrane nanostructures to alter molecular diffusion suggests that microbes compete via supramembrane topology, a competitive mechanism not considered by the standard smooth-surface equations used for nutrient uptake nor in microbial ecology and cell physiology.

  11. Distribution and abundance of diatom species from coastal waters of Karachi, Pakistan

    International Nuclear Information System (INIS)

    Khokhar, F. N.; Burhan, Z.; Iqbal, P.; Abbasi, J.; Siddiqui, P.

    2016-01-01

    This is the first comprehensive study on the distribution and abundance of diatom species from the coastal and nearshore waters of Karachi, Pakistan, bordering northern Arabian Sea. A total of 20 genera are recorded in high abundance (Cerataulina, Chaetoceros, Coscinodiscus, Cylindrotheca, Eucampia, Guinardia, Haslea, Hemiaulus, Lauderia, Lennoxia, Leptocylindrus, Navicula, Nitzschia, Trieres, Planktoniella, Pleurosigma, Pseudo-nitzschia, Rhizosolenia, Thalassionema and Thalassiosira). The most abundant genera were observed Guinardia, Chaetoceros, Leptocylindrus, Nitzschia and Lennoxia at all stations. Manora coastal station (MI-1) had high abundance corresponding with high Chlorophyll a (130 meu gL- l) values. Minimum abundance and low chlorophyll a value (0.05μgL-l) were observed at Mubarak Village coastal station (MV-1). Diatom abundance showed significant correlation with Chlorophyll a. In present study 12 centric and 8 pennate forms were recorded and similarly high diversity of centric taxa was observed compared to pennate forms. A total of 134 species are recorded of which 40 species were observed at four stations, 31species at three stations, 23 at two stations and 40 species only at one station. The total phytoplankton and diatom peak abundance was observed during NE monsoon (winter season) associated with nutrient loading through up-sloping of nutrient rich water upwelled off of Oman during South West monsoon. Overall higher diversity was observed at Manora coastal and nearshore stations (MI-1, MI-2) indicating the influence of organic pollution loading from Layari and Malir rivers. (author)

  12. Effect of hypochlorite on the planktonic and attached (biofilm) diatom cells

    International Nuclear Information System (INIS)

    Nancharaiah, Y.V.; Vinnitha, E.; Venugopalan, V.P.

    2008-01-01

    Rapid, sensitive, multi-species and multi-parametric techniques are desirable for determining treatment efficacy and environmentally realistic toxicity assessment of oxidizing biocides. In this work, the effect of in-use levels the antifouling biocide chlorine was studied using attached and freely suspended cultures of the diatom Cocconeis scutellum. Using confocal microscopy, in vivo chlorophyll fluorescence was collected in x, y and z dimensions for determining mean fluorescence intensity (MFI) per individual cell and related to hypochlorite treatment. The inhibition in the chlorophyll fluorescence of C. scutellum cells was almost 50% after 1 hour of treatment with 2 mg l -1 of added hypochlorite (1.2 mg l -1 total residual oxidant, TRO) and increased to 68 % during recovery period (18 h). On the contrary, attached Cocconeis cells did not show any significant reduction in their chlorophyll fluorescence after treatment with up to 3 mg l -1 hypochlorite for up to 3 h. Reduction in the chlorophyll fluorescence in the attached Cocconeis cells was observed after prolonged (18 h) incubation in seawater dosed with 2.3 or 3.8 mg I-I hypochlorite (1.5 and 3 mg l -1 TRO). The data obtained in this study clearly suggest that (i) hypochlorite treated diatom cells do not recover in terms of chlorophyll fluorescence in short-term assays and (ii) attached diatom cells exhibit enhanced resistance to chlorination-induced cellular injury. (author)

  13. FRET Response of a Modified Ribose Receptor Expressed in the Diatom Thalassiosira pseudonana

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Hanna

    2011-08-26

    The ability to insert complex proteins into silica has many applications including biosensing. Previous research has demonstrated how to direct proteins to the biosilica of diatoms [1]. Here, we show that a complex fusion protein that includes an enzyme, a bacterial ribose periplasmic binding protein, flanked by fluorescent proteins constituting a FRET pair can remain functional in the frustules of living diatoms. A Sil3 tag is attached to the N-terminal end to localize the fusion protein to frustules of the diatom Thalassiosira pseudonana. When ribose was applied, a larger decrease in FRET response was seen in transformed cells than in untransformed cells. Multiple forms of the expression vector were tested to find the optimal system; specifically, a one-vector system was compared to a two-vector system and the gDNA version of the Sil3 localization tag was compared to the cDNA version. The optimal system was found to be a one-vector system with the genomic version of the Sil3 tag to direct the protein to the frustules. Localization of the enzyme to the frustules was further confirmed through cell fluorescence imaging.

  14. The diatom flora of Lake Kinneret (Israel) - Paleolimnological evidence for Holocene climate change and human impact in the southeastern Mediterranean

    Science.gov (United States)

    Vossel, Hannah; Reed, Jane M.; Litt, Thomas

    2015-04-01

    The Mediterranean basin is a region of highly complex topography and climatic variability, such that our understanding of the past environmental variability is still limited. Diatoms (single-celled siliceous algae, Bacillariophyceae) are abundant, diverse and sensitive to a wide range of environmental parameters. They are often well preserved in lake sediment records, and have well-recognised potential to generate high-quality paleolimnological data. Diatoms remain one of the least-exploited proxies in Mediterranean palaeoclimate research. Here, we present results of diatom analysis of an 18 m sediment core from Lake Kinneret (Israel) as part of a multi-proxy study of Holocene climate change and human impact in the Levant (http://www.sfb806.uni-koeln.de). Results are compared with other proxy data including pollen, and with output data from regional climate modelling, to strengthen interpretation of environmental change in the southeastern Mediterranean. The results show remarkable shifts in the diatom flora over the last ca. 8,000 years. Preliminary investigations show that 98% of the diatom taxa can be classified as oligohalobous-indifferent and as alkaliphilous, as is typical of freshwater, alkaline lakes of open hydrology in limestone, karst-dominated catchments. Changes in the diatom data over time can be interpreted mainly in terms of productivity shifts, with a clear trend from oligotrophic at the base to hypereutrophic in the modern lake. The eutrophication trend accelerates after ca. 3,000 cal. yrs. BP, indicating the influence of increased human activity in the catchment, identified previously by analysis of the vegetational history (Schiebel, 2013). The analysis of the composition of the diatom flora also provides some evidence for lake-level fluctuations, as a proxy for shifts in moisture availability. Low lake-level stands are characterized by low diatom concentration and increased relative abundance of littoral taxa. High lake-level stands are marked

  15. Production of hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Day, D T; Day, R E

    1920-04-27

    A process is disclosed of converting hydro-carbon oils having high boiling points to hydro-carbon oils having low boiling points, which process comprises adding the oil to be treated to a mass of hydro-carbon oil bearing shale, passing the shale with the oil through a conveyor retort and subjecting the material while in the retort to a heat treatment involving a temperature of at least 500/sup 0/F.

  16. The Diatom Staurosirella pinnata for Photoactive Material Production.

    Directory of Open Access Journals (Sweden)

    Roberta De Angelis

    Full Text Available A native isolate of the colonial benthic diatom Staurosirella pinnata was cultivated for biosilica production. The silicified cell walls (frustules were used as a source of homogeneous and structurally predictable porous biosilica for dye trapping and random laser applications. This was coupled with the extraction of lipids from biomass showing potential to fabricate photoactive composite materials sustainably. The strain was selected for its ease of growth in culture and harvesting. Biosilica and lipids were obtained at the end of growth in indoor photobioreactors. Frustules were structurally characterized microscopically and their chemistry analyzed with Fourier Transform Infrared Spectroscopy. Frustule capacity of binding laser dyes was evaluated on a set of frustules/Rhodamine B (Rho B solutions and with respect to silicon dioxide and diatomite by Fluorescence Spectroscopy demonstrating a high affinity for the organic dye. The effect of dye trapping property in conveying Rho B emission to frustules, with enhancement of scattering events, was analyzed on Rho B doped polyacrylamide gels filled or not with frustules. Amplified spontaneous emission was recorded at increasing pump power indicating the onset of a random laser effect in frustule filled gels at lower power threshold compared to unfilled matrices.

  17. The Diatom Staurosirella pinnata for Photoactive Material Production

    Science.gov (United States)

    Prosposito, Paolo; Casalboni, Mauro; Lamastra, Francesca Romana; Nanni, Francesca; Congestri, Roberta

    2016-01-01

    A native isolate of the colonial benthic diatom Staurosirella pinnata was cultivated for biosilica production. The silicified cell walls (frustules) were used as a source of homogeneous and structurally predictable porous biosilica for dye trapping and random laser applications. This was coupled with the extraction of lipids from biomass showing potential to fabricate photoactive composite materials sustainably. The strain was selected for its ease of growth in culture and harvesting. Biosilica and lipids were obtained at the end of growth in indoor photobioreactors. Frustules were structurally characterized microscopically and their chemistry analyzed with Fourier Transform Infrared Spectroscopy. Frustule capacity of binding laser dyes was evaluated on a set of frustules/Rhodamine B (Rho B) solutions and with respect to silicon dioxide and diatomite by Fluorescence Spectroscopy demonstrating a high affinity for the organic dye. The effect of dye trapping property in conveying Rho B emission to frustules, with enhancement of scattering events, was analyzed on Rho B doped polyacrylamide gels filled or not with frustules. Amplified spontaneous emission was recorded at increasing pump power indicating the onset of a random laser effect in frustule filled gels at lower power threshold compared to unfilled matrices. PMID:27828985

  18. Species interactions within a fouling diatom community: Roles of nutrients, initial inoculum and competitive strategies

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Anil, A

    Diatoms constitute an important component of the fouling community. Although a lot of work has dealt with the fouling diatom community structure, work on the species interactions within the community is still meager. In this regard, a study...

  19. Genotoxicity of cadmium in marine diatom Chaetoceros tenuissimus using the alkaline Comet assay

    Digital Repository Service at National Institute of Oceanography (India)

    Desai, S.R.; Verlecar, X.N.; Nagarajappa; Goswami, U.

    of Cd increased growth of the diatom decreased. Alkaline single-cell gel electrophoresis (Comet assay) method, which is highly sensitive in detection of DNA damage in eukaryotic cells, was used to observe genomic changes in marine diatom cells. DNA...

  20. Diatom community dynamics in a tropical, monsoon-influenced environment: West coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    DeCosta, P.M.; Anil, A.C.

    Diatom communities are influenced by environmental perturbations, such as the monsoon system that impact the niche opportunities of species. To discern the influence of the monsoon system on diatom community structure, we sampled during two...

  1. Fouling diatom community with reference to substratum variability in tropical marine environment

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Desai, D.V.; Khandeparker, L.; Anil, A.C.; Wagh, A.B.

    form encountered. The paper deals with the qualitative and quantitative aspects of diatom colonization, their community structure, and correlation between the prevailing diatom population in the environment and that in the fouling community...

  2. Growth inhibition of periphytic diatoms by methanol extracts of sponges and holothurians

    Digital Repository Service at National Institute of Oceanography (India)

    Mokashe, S.S.; Garg, A; Anil, A; Wagh, A

    Crude methanol extracts of a holothurian Holothuria leucospilota, and two sponges Craniella sp. and Ircinia ramosa were tested for their inhibitory effects on the growth of two marine diatoms, Navicula subinflata and N. crucicula, by diatom plating...

  3. The application and testing of diatom-based indices of stream water ...

    African Journals Online (AJOL)

    The application and testing of diatom-based indices of stream water quality in Chinhoyi Town, Zimbabwe. ... PROMOTING ACCESS TO AFRICAN RESEARCH ... test the applicability of foreign diatom-based water quality assessment indices to ...

  4. Epipsammic diatoms in streams influenced by urban pollution, São Carlos, SP, Brazil

    Directory of Open Access Journals (Sweden)

    T. Bere

    Full Text Available Epipsammic diatoms have important implications for ecosystem processes in lotic environments. Most of the studies on benthic diatoms concentrate on epilithic diatoms and very little is known about epipsammic diatoms. The objective of this study was to assess epipsammic diatom communities in streams in relation to environmental conditions. Epipsammic diatoms and water quality sampling was done at 7 sites during summer base flow period (2008. Forward stepwise multiple regression and canonical correspondence analysis (CCA were used to determine environmental gradients along which species vary with physical and chemical variables. A total of 112 diatom species distributed among 44 genera were recorded. Altitude and the process of eutrophication played a significant role in structuring diatom communities in the study region.

  5. Plasma devices for hydrocarbon reformation

    KAUST Repository

    Cha, Min

    2017-01-01

    Plasma devices for hydrocarbon reformation are provided. Methods of using the devices for hydrocarbon reformation are also provided. The devices can include a liquid container to receive a hydrocarbon source, and a plasma torch configured

  6. A new cell primo-culture method for freshwater benthic diatom communities

    OpenAIRE

    Debenest, Timothée; Silvestre, Jérôme; Coste, Michel; Delmas, François; Pinelli, Eric

    2009-01-01

    A new cell primo-culture method was developed for the benthic diatom community isolated from biofilm sampled in rivers. The approach comprised three steps: (1) scraping biofilm from river pebbles, (2) diatom isolation from biofilm, and (3) diatom community culture. With a view to designing a method able to stimulate the growth of diatoms, to limit the development of other microorganisms, and to maintain in culture a community similar to the original natural one, different factors were test...

  7. Using biodiversity of diatoms to identify hydrological connectivity in the hillslope-riparian zone-stream system

    Science.gov (United States)

    Wetzel, C. E.; Martínez-Carreras, N.; Ector, L.; Hlubikova, D.; Frentress, J.; McDonnell, J. J.; Hoffmann, L.; Pfister, L.

    2012-04-01

    In recent years, there have been increasingly calls for new eco-hydrological approaches to answer questions on water source and connectivity in the landscape. Diatoms are one of the most common and diverse algal groups, and offer the potential for the identification of reproducible flow patterns and a link to underlying watershed behaviour. Our preliminary investigations on the potential for terrestrial diatoms to detect the onset/cessation of surface runoff suggested that diatoms can contribute to confirm or reject the existence of a surface runoff component in total runoff, thereby helping to constrain assumptions made on a potential surface runoff component in a conventional tracer based hydrograph separation. Our investigations currently focus on the Attert River basin (Luxembourg, Europe) and the HJ Andrews experimental forest (Oregon, USA). Here we show results from the schistose Weierbach experimental catchment (0.45 km2), located in the Attert River basin. Ordination analysis revealed a clear distinction between communities belonging to the river bed substrate and the riparian zone. Drift samples corresponding to stream water show a mixed composition of diatoms stemming from the river bed substrate and the riparian zone. Ongoing investigations focus on the composition of hillslope communities. In winter, long-lasting low intensity rainfall events generate a two-tailed hydrograph response of the Weierbach, consisting in an immediate reaction to precipitation, followed by a delayed and much more significant rise of the hydrograph. For these events, mixing diagrams (SiO2 & Absorbance) suggest a substantial contribution of the soil water component to total runoff, with groundwater and especially overland flow remaining insignificant. Terrestrial diatom abundance appeared to be very sensitive to incident precipitation (rising to +/- 15% of the total diatom population), suggesting a rapid connectivity between the soil surface and the stream. In summer, short and

  8. Effect of ageing on survival of benthic diatom propagules

    Digital Repository Service at National Institute of Oceanography (India)

    Anil, A.C.; Mitbavkar, S.; De; Hegde, S.; De; Meher, S.S.; Banerjee, D.

    unfavorable for vegetative growth, many diatoms form resting stages to survive cell degradation or death (Anderson, 1975; Malone, 1980; Hargraves and French, 1983; Fryxell, 1990). Various external factors like availability of nutrients (N, P, Fe, Si.... 128, 497-508. 15 Lewis, J., Harris, A.S.D., Jones, K.J., Edmonds, R.L., 1999. Long-term survival of marine planktonic diatoms and dinoflagellates in stored sediment samples. J. Plank. Res. 21, 343- 354. Malone, T.C., 1980. Algal size. In...

  9. Diatom Assemblage in the Lake of Gaber Oun, Southern Libya

    Directory of Open Access Journals (Sweden)

    Abdelkader Elzen

    2012-07-01

    Full Text Available The lake of Gaber Oun in the southern district of Libya was studied to assess the diatom community composition in the littoral zone. Planktic and attached diatoms were listed and information on the constituent species made known (images are shown. Some criteria of the water characteristics are also given such as the pH, which is an average of 8.3, electrical conductivity which accounted for 1.4 µSim/cm1- and total dissolved salts (TDS of 189.0 mg/L1-.

  10. Biological monitoring of lotic ecosystems: the role of diatoms

    Directory of Open Access Journals (Sweden)

    T. Bere

    Full Text Available Increasing anthropogenic influence on lotic environments as a result of civilisation has captured public interest because of the consequent problems associated with deterioration of water quality. Various biological monitoring methods that provide a direct measure of ecological integrity by using the response of biota to environmental changes have been developed to monitor the ecological status of lotic environments. Diatoms have been used extensively in this regard and this review attempts to summarise the basic concepts associated with biological monitoring using benthic diatoms. Where possible, examples from work carried out in Brazil are used.

  11. Biological monitoring of lotic ecosystems: the role of diatoms.

    Science.gov (United States)

    Bere, T; Tundisi, J G

    2010-08-01

    Increasing anthropogenic influence on lotic environments as a result of civilisation has captured public interest because of the consequent problems associated with deterioration of water quality. Various biological monitoring methods that provide a direct measure of ecological integrity by using the response of biota to environmental changes have been developed to monitor the ecological status of lotic environments. Diatoms have been used extensively in this regard and this review attempts to summarise the basic concepts associated with biological monitoring using benthic diatoms. Where possible, examples from work carried out in Brazil are used.

  12. Detection of irradiated meats by hydrocarbon method

    International Nuclear Information System (INIS)

    Goto, Michiko; Miyakawa, Hiroyuki; Fujinuma, Kenji; Ozawa, Hideki

    2005-01-01

    Meats, for example, lamb, razorback, wild duck and turkey were irradiated by gamma ray, and the amounts of hydrocarbons formed from fatty acids were measured. Since C 20:0 was found from wild duck and turkey. C 1-18:1 was recommended for internal standard. Good correlation was found between the amount of hydrocarbons and the doses of gamma irradiation. This study shows that such hydrocarbons induced after radiation procedure as C 1,7-16:2 , C 8-17:1 , C 1-14:1 , and C 15:0 may make it possible to detect irradiated lamb, razorback, wild duck and turkey. (author)

  13. The UV filtering potential of drop-casted layers of frustules of three diatom species

    DEFF Research Database (Denmark)

    Su, Yanyan; Lenau, Torben Anker; Gundersen, Emil

    2018-01-01

    Diatoms are in focus as biological materials for a range of photonic applications. Many of theseapplications would require embedding a multitude of diatoms in a matrix (e.g. paint, crème or lacquer); however, most studies on the photonic and spectral properties of diatoms frustules (silica walls)...

  14. Plasma devices for hydrocarbon reformation

    KAUST Repository

    Cha, Min Suk

    2017-02-16

    Plasma devices for hydrocarbon reformation are provided. Methods of using the devices for hydrocarbon reformation are also provided. The devices can include a liquid container to receive a hydrocarbon source, and a plasma torch configured to be submerged in the liquid. The plasma plume from the plasma torch can cause reformation of the hydrocarbon. The device can use a variety of plasma torches that can be arranged in a variety of positions in the liquid container. The devices can be used for the reformation of gaseous hydrocarbons and/or liquid hydrocarbons. The reformation can produce methane, lower hydrocarbons, higher hydrocarbons, hydrogen gas, water, carbon dioxide, carbon monoxide, or a combination thereof.

  15. Diatom species composition and indices for determining the ecological status of coastal Mediterranean Spanish lakes

    Directory of Open Access Journals (Sweden)

    Antón-Garrido, Beatriz

    2013-12-01

    Full Text Available Diatom indices have been used and tested mainly for assessing the ecological status of rivers and deep lakes, but there are scarce studies that determine their effectiveness in shallow lakes and in coastal Mediterranean lakes. This study evaluates the validity of several common diatom indices (SPI, BDI, CEC and TDIL for the determination of the ecological quality of three coastal lakes (Valencia, Spain and presents descriptions and ecological data of the main diatom species recorded. Diatom samples were collected from phytobenthos, both from epiphyton of the dominant submerged macrophytes and the sediment. The ecological status of the systems was determined according to different physico-chemical variables and was compared with the results obtained from epiphytic diatom communities. The results showed discrepancies among diatom indices and also with the state determined by the environmental variables. The effectiveness of the indices depended on the number of species assessed for each index with respect to the total species recorded and the suitability of the weight assigned to each species. The results reveal the need to gather more information about the composition and ecology of the diatoms and microalgae characteristic of coastal Mediterranean standing waters. This work contributes to their better knowledge.Los índices de diatomeas han sido aplicados y contrastados principalmente en la evaluación del estado ecológico de los sistemas lóticos y lagos profundos, pero son escasos los estudios sobre su eficacia en lagos someros y lagunas litorales mediterráneas. Este trabajo evalúa la validez de varios índices conocidos de diatomeas (IPS, IBD, CEE y TDIL para la determinación de la calidad ecológica de tres lagunas litorales (Valencia, España y presenta las descripciones y datos ecológicos de las principales especies de diatomeas registradas. Las muestras de diatomeas se recogieron del fitobentos, tanto del epifiton desarrollado sobre

  16. Response of the diatom Phaeodactylum tricornutum to photooxidative stress resulting from high light exposure.

    Directory of Open Access Journals (Sweden)

    Nuno Domingues

    Full Text Available The response of microalgae to photooxidative stress resulting from high light exposure is a well-studied phenomenon. However, direct analyses of photosystem II (PSII D1 protein (the main target of photoinhibition in diatoms are scarce. In this study, the response of the diatom model species Phaeodactylum tricornutum to short-term exposure to high light was examined and the levels of D1 protein determined immunochemically. Low light (LL acclimated cells (40 µmol photons m(-2 s(-1 subjected to high light (HL, 1,250 µmol photons m(-2 s(-1 showed rapid induction of non-photochemical quenching (NPQ and ca. 20-fold increase in diatoxanthin (DT concentration. This resulted from the conversion of diadinoxanthin (DD to DT through the activation of the DD-cycle. D1 protein levels under LL decreased about 30% after 1 h of the addition of lincomycin (LINC, a chloroplast protein synthesis inhibitor, showing significant D1 degradation and repair under low irradiance. Exposure to HL lead to a 3.2-fold increase in D1 degradation rate, whereas average D1 repair rate was 1.3-x higher under HL than LL, leading to decreased levels of D1 protein under HL. There were significant effects of both HL and LINC on P. tricornutum maximum quantum yield of PSII (F(v/F(m, showing a reduction of active PSII reaction centres. Partial recovery of F(v/F(m in the dark demonstrates the photosynthetic resilience of this diatom to changes in the light regime. P. tricornutum showed high allocation of total protein to D1 and an active D1-repair cycle to limit photoinhibition.

  17. Hydrocarbon-degradation by Isolate Pseudomonas lundensis UTAR FPE2

    Directory of Open Access Journals (Sweden)

    Adeline, S. Y. Ting

    2009-01-01

    Full Text Available In this study, the potential of isolate Pseudomonas lundensis UTAR FPE2 as a hydrocarbon degrader was established. Their biodegradation activity was first detected with the formation of clearing zones on Bushnell-Hass agar plates, with the largest diameter observed on plates supplemented with paraffin, followed by mineral oil and petrol. Utilization of hydrocarbon sources were again detected in broth cultures supplemented with similar hydrocarbon substrates, where the mean viable cell count recovered from hydrocarbon-supplemented broth cultures were higher than the initial inoculum except for napthalene. In both tests, the isolate showed higher degradability towards aliphatic hydrocarbon sources, and the least activity towards the aromatic hydrocarbon naphthalene. The isolate P. lundensis UTAR FPE2 (8 log10 cfu/mL also degraded crude diesel sample, with 69% degradation during the first three days. To conclude, this study suggests the potential use of this isolate for bioremediation of hydrocarbon-contaminated environments.

  18. Effect of Industrial Effluent on the Growth of Marine Diatom ...

    African Journals Online (AJOL)

    The marine centric diatom,Chaetoceros simplex (Ostenfeld, 1901) was exposed to five different concentrations of industrial effluent for 96 hrs to investigate the effect on growth. The physico-chemical parameters viz. colour, odour, temperature, salinity, dissolved oxygen, turbidity, pH, alkalinity, hardness, ammonia, nitrite, ...

  19. Copepod reproduction is unaffected by diatom aldehydes or lipid composition

    DEFF Research Database (Denmark)

    Dutz, Jörg; Koski, Marja; Jonasdottir, Sigrun

    2008-01-01

    We investigated whether reduced reproductive success of copepods fed with diatoms was related to nutritional imbalances with regard to essential lipids or to the production of inhibitory aldehydes. In 10-d laboratory experiments, feeding, egg production, egg hatching success, and fecal pellet...

  20. Colonisation and community structure of benthic diatoms on artificial ...

    African Journals Online (AJOL)

    This was undertaken using tiles as artificial substrates so that we could study how the communities developed after the flood disturbance. The diatom community structure was assessed over a 28-day period following a flood event in October 2012. The Mann Whitney test indicated that there was a statistically significant ...

  1. Diatom distribution in the surficial sediments of Lake Fuxian, Yunnan ...

    African Journals Online (AJOL)

    ajl yemi

    2011-11-30

    Nov 30, 2011 ... (18.2%); there were some phosphorus post-mines which led to higher total phosphorus concentration than that in southern part. The most outstanding characteristic of diatom ... (212 km2 in surface area) is located in the central Yunnan. Province; it is a oligotrophic freshwater lake. It is the second deepest ...

  2. Mercury-induced genotoxicity in marine diatom (Chaetoceros tenuissimus)

    Digital Repository Service at National Institute of Oceanography (India)

    Sarker, S.; Desai, S.R.; Verlecar, X.N.; Sarker, M.S.; Sarkar, A.

    In this paper, we present an evaluation of genotoxic responses in marine diatom, Chaetoceros tenuissimus, isolated from Kandla Creek (lat 23.03° N, long 70.22° E), Gujarat, India, in terms of impairment of DNA integrity as a function...

  3. Temperature affects the silicate morphology in a diatom

    NARCIS (Netherlands)

    Javaheri, N.; Dries, R; Burson, A.; Stal, L.J.; Sloot, P.M.A.; Kaandorp, J.A.

    2015-01-01

    Silica deposition by diatoms, a common component of the phytoplankton, has attracted considerable interest given the importance in ecology and materials science. There has recently been a great deal of research into the biological control of biosilicifcation, yet the in vivo physical and chemical

  4. Temperature affects the silicate morphology in a diatom

    NARCIS (Netherlands)

    Javaheri, N.; Dries, R.; Burson, A.; Stal, L.J.; Sloot, P.M.A.; Kaandorp, J.A.

    2015-01-01

    Silica deposition by diatoms, a common component of the phytoplankton, has attracted considerable interest given the importance in ecology and materials science. There has recently been a great deal of research into the biological control of biosilicifcation, yet the in vivo physical and

  5. Enhancement of the reactive iron pool by marine diatoms

    NARCIS (Netherlands)

    Rijkenberg, Micha J. A.; Gerringa, Loes J. A.; Timmermans, Klaas R.; Fischer, Astrid C.; Kroon, Koos J.; Buma, Anita G. J.; Wolterbeek, Bert Th.; de Baar, Hein J. W.

    2008-01-01

    Short term (2 days) laboratory experiments were performed to study the change in irradiance induced production of Fe(II) in seawater in the presence of two open oceanic Southern Ocean diatom species, Thalassiosira sp. and Chaetoceros brevis. Three irradiance conditions were applied: 1) UVB+UVA+VIS,

  6. The Phaeodactylum genome reveals the evolutionary history of diatom genomes

    Czech Academy of Sciences Publication Activity Database

    Bowler, Ch.; Allen, A. E.; Badger, J. H.; Grimwood, J.; Jabbari, K.; Kuo, A.; Maheswari, U.; Martens, C.; Maumus, F.; Otillar, R. P.; Rayko, E.; Salamov, A.; Vandepoele, K.; Beszteri, B.; Gruber, A.; Heijde, M.; Katinka, M.; Mock, T.; Valentin, K.; Verret, F.; Berges, J. A.; Brownlee, C.; Cadoret, J.-P.; Chiovitti, A.; Choi, Ch. J.; Coesel, S.; De Martino, A.; Detter, J. Ch.; Durkin, C.; Falciatore, A.; Fournet, J.; Haruta, M.; Huysman, M. J. J.; Jenkins, B. D.; Jiroutová, Kateřina; Jorgensen, R. E.; Joubert, Y.; Kaplan, A.; Kröger, N.; Kroth, P. G.; La Roche, J.; Lindquist, E.; Lommer, M.; Martin–Jézéquel, V.; Lopez, P. J.; Lucas, S.; Mangogna, M.; McGinnis, K.; Medlin, L. K.; Montsant, A.; Oudot–Le Secq, M.-P.; Napoli, C.; Oborník, Miroslav; Schnitzler Parker, M.; Petit, J.-L.; Porcel, B. M.; Poulsen, N.; Robison, M.; Rychlewski, L.; Rynearson, T. A.; Schmutz, J.; Shapiro, H.; Siaut, M.; Stanley, M.; Sussman, M. R.; Taylor, A. R.; Vardi, A.; von Dassow, P.; Vyverman, W.; Willis, A.; Wyrwicz, L. S.; Rokhsar, D. S.; Weissenbach, J.; Armbrust, E. V.; Green, B. R.; Van de Peer, Y.; Grigoriev, I. V.

    2008-01-01

    Roč. 456, 13-11-2008 (2008), s. 239-244 ISSN 0028-0836 Institutional research plan: CEZ:AV0Z60220518 Keywords : Phaeodactylum * genome * evolution * diatom Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 31.434, year: 2008

  7. Models for calculation of dissociation energies of homonuclear diatomic molecules

    International Nuclear Information System (INIS)

    Brewer, L.; Winn, J.S.

    1979-08-01

    The variation of known dissociation energies of the transition metal diatomics across the Periodic Table is rather irregular like the bulk sublimation enthalpy, suggesting that the valence-bond model for bulk metallic systems might be applicable to the gaseous diatomic molecules and the various intermediate clusters. Available dissociation energies were converted to valence-state bonding energies considering various degrees of promotion to optimize the bonding. The degree of promotion of electrons to increase the number of bonding electrons is smaller than for the bulk, but the trends in bonding energy parallel the behavior found for the bulk metals. Thus using the established trends in bonding energies for the bulk elements, it was possible to calculate all unknown dissociation energies to provide a complete table of dissociation energies for all M 2 molecules from H 2 to Lr 2 . For solids such as Mg, Al, Si and most of the transition metals, large promotion energies are offset by strong bonding between the valence state atoms. The main question is whether bonding in the diatomics is adequate to sustain extensive promotion. The most extreme example for which a considerable difference would be expected between the bulk and the diatomics would be that of the Group IIA and IIB metals. The first section of this paper which deals with the alkaline earths Mg and Ca demonstrates a significant influence of the excited valence state even for these elements. The next section then expands the treatment to transition metals

  8. Diatoms in peat – dominant producers in a changing environment?

    DEFF Research Database (Denmark)

    Kokfelt, Ulla; Struyf, Eric; Randsalu, Linda

    2009-01-01

    to another, the old vegetation may be suppressed, die out or start to decay, and some time may pass until a new mire vegetation is fully established. Here, we demonstrate that diatoms may thrive during such transitions, creating isolated and shallow peat layers with significantly elevated biogenic silica...

  9. Molecular basis of chromatic adaptation in pennate diatom Phaeodactylum tricornutum

    Czech Academy of Sciences Publication Activity Database

    Herbstová, Miroslava; Bína, David; Koník, P.; Gardian, Zdenko; Vácha, František; Litvín, Radek

    2015-01-01

    Roč. 1847, 6-7 (2015), s. 534-543 ISSN 0005-2728 R&D Projects: GA ČR GBP501/12/G055 Institutional support: RVO:60077344 Keywords : Chromatic adaptation * Diatom * Heterokonta * Light harvesting antenna Subject RIV: CE - Biochemistry Impact factor: 4.864, year: 2015

  10. The effects of phosphorus limitation on carbon metabolism in diatoms.

    Science.gov (United States)

    Brembu, Tore; Mühlroth, Alice; Alipanah, Leila; Bones, Atle M

    2017-09-05

    Phosphorus is an essential element for life, serving as an integral component of nucleic acids, lipids and a diverse range of other metabolites. Concentrations of bioavailable phosphorus are low in many aquatic environments. Microalgae, including diatoms, apply physiological and molecular strategies such as phosphorus scavenging or recycling as well as adjusting cell growth in order to adapt to limiting phosphorus concentrations. Such strategies also involve adjustments of the carbon metabolism. Here, we review the effect of phosphorus limitation on carbon metabolism in diatoms. Two transcriptome studies are analysed in detail, supplemented by other transcriptome, proteome and metabolite data, to gain an overview of different pathways and their responses. Phosphorus, nitrogen and silicon limitation responses are compared, and similarities and differences discussed. We use the current knowledge to propose a suggestive model for the carbon flow in phosphorus-replete and phosphorus-limited diatom cells.This article is part of the themed issue 'The peculiar carbon metabolism in diatoms'. © 2017 The Authors.

  11. Improvement of Neutral Lipid and Polyunsaturated Fatty Acid Biosynthesis by Overexpressing a Type 2 Diacylglycerol Acyltransferase in Marine Diatom Phaeodactylum tricornutum

    Directory of Open Access Journals (Sweden)

    Ying-Fang Niu

    2013-11-01

    Full Text Available Microalgae have been emerging as an important source for the production of bioactive compounds. Marine diatoms can store high amounts of lipid and grow quite quickly. However, the genetic and biochemical characteristics of fatty acid biosynthesis in diatoms remain unclear. Glycerophospholipids are integral as structural and functional components of cellular membranes, as well as precursors of various lipid mediators. In addition, diacylglycerol acyltransferase (DGAT is a key enzyme that catalyzes the last step of triacylglyceride (TAG biosynthesis. However, a comprehensive sequence-structure and functional analysis of DGAT in diatoms is lacking. In this study, an isoform of diacylglycerol acyltransferase type 2 of the marine diatom Phaeodactylum tricornutum was characterized. Surprisingly, DGAT2 overexpression in P. tricornutum stimulated more oil bodies, and the neutral lipid content increased by 35%. The fatty acid composition showed a significant increase in the proportion of polyunsaturated fatty acids; in particular, EPA was increased by 76.2%. Moreover, the growth rate of transgenic microalgae remained similar, thereby maintaining a high biomass. Our results suggest that increased DGAT2 expression could alter fatty acid profile in the diatom, and the results thus represent a valuable strategy for polyunsaturated fatty acid production by genetic manipulation.

  12. The importance of Rydberg orbitals in dissociative ionization of small hydrocarbon molecules in intense laser fields.

    Science.gov (United States)

    Jochim, Bethany; Siemering, R; Zohrabi, M; Voznyuk, O; Mahowald, J B; Schmitz, D G; Betsch, K J; Berry, Ben; Severt, T; Kling, Nora G; Burwitz, T G; Carnes, K D; Kling, M F; Ben-Itzhak, I; Wells, E; de Vivie-Riedle, R

    2017-06-30

    Much of our intuition about strong-field processes is built upon studies of diatomic molecules, which typically have electronic states that are relatively well separated in energy. In polyatomic molecules, however, the electronic states are closer together, leading to more complex interactions. A combined experimental and theoretical investigation of strong-field ionization followed by hydrogen elimination in the hydrocarbon series C 2 D 2 , C 2 D 4 and C 2 D 6 reveals that the photofragment angular distributions can only be understood when the field-dressed orbitals rather than the field-free orbitals are considered. Our measured angular distributions and intensity dependence show that these field-dressed orbitals can have strong Rydberg character for certain orientations of the molecule relative to the laser polarization and that they may contribute significantly to the hydrogen elimination dissociative ionization yield. These findings suggest that Rydberg contributions to field-dressed orbitals should be routinely considered when studying polyatomic molecules in intense laser fields.

  13. Doping of magnetite nanoparticles facilitates clean harvesting of diatom oil as biofuel for sustainable energy

    Science.gov (United States)

    Kumar, Vikas; Singh, Ramesh; Thakur, Shipra; Ballabh Joshi, Khashti; Vinayak, Vandana

    2018-04-01

    Photosynthetic unicellular brown algae diatoms are considered as photobioreactors (PBRs) that synthesize and store oil in the form of lipid droplets and the much of the crude oil we use comes from fossil diatoms. The clean extraction of this crude oil from diatoms is difficult task. The construction of green chemical protocols for the clean separation of diatom oil from cells without killing or to harm the diatom cells is still in its primitive stage. In this report we would like to propose that facile doping of magnetite on diatoms can be used for clean oil separation in PBRs. We doped magnetite nanoparticles onto the surface of diatom Diadesmis confervaceae a diatom which oozes oil naturally. Doping magnetite onto diatoms can also facilitate easy separation of oil when cells are kept in an electromagnetic field. The cell wall of diatom besides having SiOH group has 281 amino acids of which 187–188 amino acids are conserved and are known for metal binding sites. The magnetite nanoparticles bind to the SiOH groups and metal binding sites of amino acids. The presence of appropriate amine functionalized linkers forming peptide aminosilane shells can further facilitate the binding of peptide/polypeptides which can be used in drug delivery. Besides this the magnetite doped diatoms have wide applications in removal of phosphates and chromium from waste water too.

  14. Teratogenic Effects of Diatom Metabolites on Sea Urchin Paracentrotus lividus Embryos

    Directory of Open Access Journals (Sweden)

    Giovanna Romano

    2010-03-01

    Full Text Available The diatom-derived polyunsaturated aldehydes (PUAs, 2-trans,4-trans-decadienal, 2-trans,4-trans-octadienal, 2-trans,4-trans,7-octatrienal, 2-trans,4-trans-heptadienal, as well as tridecanal were tested on early and later larval development in the sea urchin Paracentrotus lividus. We also tested the effect of some of the more abundant diatom polyunsaturated fatty acids (PUFAs on development, in particular 5,8,11,14,17-eicosapentaenoic acid (EPA, one of the main precursors of diatom PUAs, as well as 4,7,10,13,16,19-docosahexaenoic acid (DHA, 6,9,12,15-octadecatetraenoic acid (stearidonic acid, 6,9,12-octadecatrienoic acid (γ-linolenic acid and 9,12-octadecadienoic acid (linoleic acid. PUAs blocked sea urchin cell cleavage in a dose dependent manner and with increasing chain length from C7 to C10 PUAs, with arrest occurring at 27.27 µM with heptadienal, 16.13 µM with octadienal, 11.47 µM with octatrienal and 5.26 mM with decadienal. Of the PUFAs tested, only EPA and stearidonic acid blocked cleavage, but at much higher concentrations compared to PUAs (331 μM for EPA and 181 μM for stearidonic acid. Sub-lethal concentrations of decadienal (1.32–5.26 μM delayed development of embryos and larvae which showed various degrees of malformations depending on the concentrations tested. Sub-lethal concentrations also increased the proportion of TUNEL-positive cells indicating imminent death in embryos and larvae. Using decadienal as a model PUA, we show that this aldehyde can be detected spectrophotometrically for up to 14 days in f/2 medium.

  15. Toxicity of dissolved and precipitated aluminium to marine diatoms.

    Science.gov (United States)

    Gillmore, Megan L; Golding, Lisa A; Angel, Brad M; Adams, Merrin S; Jolley, Dianne F

    2016-05-01

    Localised aluminium contamination can lead to high concentrations in coastal waters, which have the potential for adverse effects on aquatic organisms. This research investigated the toxicity of 72-h exposures of aluminium to three marine diatoms (Ceratoneis closterium (formerly Nitzschia closterium), Minutocellus polymorphus and Phaeodactylum tricornutum) by measuring population growth rate inhibition and cell membrane damage (SYTOX Green) as endpoints. Toxicity was correlated to the time-averaged concentrations of different aluminium size-fractions, operationally defined as aluminium exposure varied between diatom species. C. closterium was the most sensitive species (10% inhibition of growth rate (72-h IC10) of 80 (55-100)μg Al/L (95% confidence limits)) while M. polymorphus (540 (460-600)μg Al/L) and P. tricornutum (2100 (2000-2200)μg Al/L) were less sensitive (based on measured total aluminium). Dissolved aluminium was the primary contributor to toxicity in C. closterium, while a combination of dissolved and precipitated aluminium forms contributed to toxicity in M. polymorphus. In contrast, aluminium toxicity to the most tolerant diatom P. tricornutum was due predominantly to precipitated aluminium. Preliminary investigations revealed the sensitivity of C. closterium and M. polymorphus to aluminium was influenced by initial cell density with aluminium toxicity significantly (paluminium toxicity to diatoms do not involve compromising the plasma membrane. These results indicate that marine diatoms have a broad range in sensitivity to aluminium with toxic mechanisms related to both dissolved and precipitated aluminium. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Effect of petroleum hydrocarbons on algae

    International Nuclear Information System (INIS)

    Bhadauria, S.; Sengar, R.M.S.; Mittal, S.; Bhattacharjee, S.

    1992-01-01

    Algal species (65) were isolated from oil refinery effluent. Twenty-five of these species were cultured in Benecke's medium in a growth chamber, along with controls. Retardation in algal growth, inhibition in algal photosynthesis, and discoloration was observed in petroleum enriched medium. Few forms, viz. Cyclotella sp., Cosmarium sp., and Merismopedia sp. could not survive. The lag phase lengthened by several days and slope of exponential phase was also depressed. Chlamydomonas sp., Scenedesmus sp., Ankistrodesmus sp., Nitzschia sp. and Navicula sp. were comparatively susceptible to petroleum. Depression in carbon fixation, cell numbers, and total dry algal mass was noticeable, showing toxicity to both diatoms and green algae

  17. Volatilisation of aromatic hydrocarbons from soil

    DEFF Research Database (Denmark)

    Lindhardt, B.; Christensen, T.H.

    1996-01-01

    The non-steady-state fluxes of aromatic hydrocarbons were measured in the laboratory from the surface of soils contaminated with coal tar Four soil samples from a former gasworks site were used for the experiments. The fluxes were quantified for 11 selected compounds, 4 mono- and 7 polycyclic...... aromatic hydrocarbons, for a period of up to 8 or 16 days. The concentrations of the selected compounds in the soils were between 0.2 and 3,100 mu g/g. The study included the experimental determination of the distribution coefficient of the aromatic hydrocarbons between the sorbed phase and the water under...... saturated conditions. The determined distribution coefficients showed that the aromatic hydrocarbons were more strongly sorbed to the total organic carbon including the coal tar pitch - by a factor of 8 to 25 - than expected for natural organic matter. The fluxes were also estimated using an analytical...

  18. Purifying hydrocarbon oils

    Energy Technology Data Exchange (ETDEWEB)

    Rostin, H

    1938-08-11

    A process is described for continuously purifying hydrocarbon oils consisting in conducting the vapors of the same at a temperature of 300 to 400/sup 0/C over the oelitic ore minette together with reducing gases in presence of steam the proportion of the reducing gases and steam being such that the sulfur of the hydrocarbons escapes from the reaction chamber in the form of sulfuretted hydrogen without permanent sulfide of iron being formed.

  19. Process for refining hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Risenfeld, E H

    1924-11-26

    A process is disclosed for the refining of hydrocarbons or other mixtures through treatment in vapor form with metal catalysts, characterized by such metals being used as catalysts, which are obtained by reduction of the oxide of minerals containing the iron group, and by the vapors of the hydrocarbons, in the presence of the water vapor, being led over these catalysts at temperatures from 200 to 300/sup 0/C.

  20. Light intensity modulates the response of two Antarctic diatom species to ocean acidification

    Directory of Open Access Journals (Sweden)

    Jasmin Pascale Heiden

    2016-12-01

    Full Text Available It is largely unknown how rising atmospheric CO2 concentrations and changes in the upper mixed layer depth, with its subsequent effects on light availability will affect phytoplankton physiology in the Southern Ocean. Linking seasonal variations in the availability of CO2 and light to abundances and physiological traits of key phytoplankton species could aid to understand their abilities to acclimate to predicted future climatic conditions. To investigate the combined effects of CO2 and light on two ecologically relevant Antarctic diatoms (Fragilariopsis curta and Odontella weisflogii a matrix of three light intensities (LL=20, ML=200, HL=500 µmol photons m-2 s-1 and three pCO2 levels (low=180, ambient=380, high=1000 µatm was applied assessing their effects on growth, particulate organic carbon (POC fixation and photophysiology. Under ambient pCO2, POC production rates were highest already at low light in Fragilariopsis, indicating saturation of photosynthesis, while in Odontella highest rates were only reached at medium irradiances. In both species ocean acidification did not stimulate, but rather inhibited, growth and POC production under low and medium light. This effect was, however, amended under high growth irradiances. Low pCO2 levels inhibited growth and POC production in both species at low and medium light, and further decreased absETRs under high light. Our results suggest that Southern Ocean diatoms were sensitive to changes in pCO2, showing species-specific responses, which were further modulated by light intensity. The two diatom species represent distinct ecotypes and revealed discrete physiological traits that matched their seasonal occurrence with the related physical conditions in Antarctic coastal waters.

  1. Impact of multispecies diatom bloom on plankton community structure in Sundarban mangrove wetland, India

    International Nuclear Information System (INIS)

    Biswas, Sejuti Naha; Rakshit, Dibyendu; Sarkar, Santosh Kumar; Sarangi, Ranjit Kumar; Satpathy, Kamala Kanta

    2014-01-01

    Highlights: • A multispecies algal bloom was studied in coastal regions of Sundarban wetland. • Sharp changes in plankton community structure and hydrological parameters observed. • Chlorophyll a showed highest cell density (11.4 × 10 5 cells l −1 ) during bloom phase. • MODIS Aqua derived chlorophyll maps have been interpreted. - Abstract: A multispecies bloom caused by the centric diatoms, viz. Coscinodiscus radiatus, Chaetoceros lorenzianus and the pennate diatom Thalassiothrix frauenfeldii was investigated in the context of its impact on phytoplankton and microzooplankton (the loricate ciliate tintinnids) in the coastal regions of Sagar Island, the western part of Sundarban mangrove wetland, India. Both number (15–18 species) and cell densities (12.3 × 10 3 cells l −1 to 11.4 × 10 5 cells l −1 ) of phytoplankton species increased during peak bloom phase, exhibiting moderately high species diversity (H′ = 2.86), richness (R′ = 6.38) and evenness (E′ = 0.80). The diatom bloom, which existed for a week, had a negative impact on the tintinnid community in terms of drastic changes in species diversity index (1.09–0.004) and population density (582.5 × 10 3 to 50 × 10 3 ind m −3 ). The bloom is suggested to have been driven by the aquaculture activities and river effluents resulting high nutrient concentrations in this region. An attempt has been made to correlate the satellite remote sensing-derived information to the bloom conditions. MODIS-Aqua derived chlorophyll maps have been interpreted

  2. A single peroxisomal targeting signal mediates matrix protein import in diatoms.

    Directory of Open Access Journals (Sweden)

    Nicola H Gonzalez

    Full Text Available Peroxisomes are single membrane bound compartments. They are thought to be present in almost all eukaryotic cells, although the bulk of our knowledge about peroxisomes has been generated from only a handful of model organisms. Peroxisomal matrix proteins are synthesized cytosolically and posttranslationally imported into the peroxisomal matrix. The import is generally thought to be mediated by two different targeting signals. These are respectively recognized by the two import receptor proteins Pex5 and Pex7, which facilitate transport across the peroxisomal membrane. Here, we show the first in vivo localization studies of peroxisomes in a representative organism of the ecologically relevant group of diatoms using fluorescence and transmission electron microscopy. By expression of various homologous and heterologous fusion proteins we demonstrate that targeting of Phaeodactylum tricornutum peroxisomal matrix proteins is mediated only by PTS1 targeting signals, also for proteins that are in other systems imported via a PTS2 mode of action. Additional in silico analyses suggest this surprising finding may also apply to further diatoms. Our data suggest that loss of the PTS2 peroxisomal import signal is not reserved to Caenorhabditis elegans as a single exception, but has also occurred in evolutionary divergent organisms. Obviously, targeting switching from PTS2 to PTS1 across different major eukaryotic groups might have occurred for different reasons. Thus, our findings question the widespread assumption that import of peroxisomal matrix proteins is generally mediated by two different targeting signals. Our results implicate that there apparently must have been an event causing the loss of one targeting signal even in the group of diatoms. Different possibilities are discussed that indicate multiple reasons for the detected targeting switching from PTS2 to PTS1.

  3. Assessing the influence of multiple stressors on stream diatom metrics in the upper Midwest, USA

    Science.gov (United States)

    Munn, Mark D.; Waite, Ian R.; Konrad, Christopher P.

    2018-01-01

    Water resource managers face increasing challenges in identifying what physical and chemical stressors are responsible for the alteration of biological conditions in streams. The objective of this study was to assess the comparative influence of multiple stressors on benthic diatoms at 98 sites that spanned a range of stressors in an agriculturally dominated region in the upper Midwest, USA. The primary stressors of interest included: nutrients, herbicides and fungicides, sediment, and streamflow; although the influence of physical habitat was incorporated in the assessment. Boosted Regression Tree was used to examine both the sensitivity of various diatom metrics and the relative importance of the primary stressors. Percent Sensitive Taxa, percent Highly Motile Taxa, and percent High Phosphorus Taxa had the strongest response to stressors. Habitat and total phosphorous were the most common discriminators of diatom metrics, with herbicides as secondary factors. A Classification and Regression Tree (CART) model was used to examine conditional relations among stressors and indicated that fine-grain streams had a lower percentage of Sensitive Taxa than coarse-grain streams, with Sensitive Taxa decreasing further with increased water temperature (>30 °C) and triazine concentrations (>1500 ng/L). In contrast, streams dominated by coarse-grain substrate contained a higher percentage of Sensitive Taxa, with relative abundance increasing with lower water temperatures (water depth (water temperature appears to be a major limiting factor in Midwest streams; whereas both total phosphorus and percent fines showed a slight subsidy-stress response. While using benthic algae for assessing stream quality can be challenging, field-based studies can elucidate stressor effects and interactions when the response variables are appropriate, sufficient stressor resolution is achieved, and the number and type of sites represent a gradient of stressor conditions and at least a quasi

  4. Diatom assemblage in a tropical lake of northeastern Brazil

    Directory of Open Access Journals (Sweden)

    Lilian Rodrigues do Nascimento

    2010-02-01

    Full Text Available The composition and spatial variation of diatom assemblage in surface sediments of Caçó Lake (shallow, mesotrophic and weakly acid lake - Maranhão State, Brazil were analyzed in order to know the distribution pattern of the species along the lake during rainy season (April 1999. Four zones were established in the lake based on 21 diatoms species and habitat affinities. The first three zones (prime three meters deep to six meters deep were marked by the occurrence of Pinnularia gigas, Frustulia rhomboides, Encyonopsis krasskei, Eunotia camelus, E. femoriformis and E. monodon. Zone IV (seven to nine meters deep was inhabited mainly by Surirella biseriata and Fragilariforma floridana. During the beginning of the rainy season, the diatom assemblage in Caçó Lake was composed mainly by benthic and epiphytic forms that reflected the low lake levels and the abundance of littoral vegetation present in this lake.Com o objetivo de se conhecer a dinâmica espacial e a distribuição das diatomáceas contidas no sedimento superficial do lago Caçó, durante o período de chuvas (abril de 1999 foram realizadas coletas em um "transect" horizontal. A partir da observação destas coletas efetuadas a cada 1 metro pode-se observar que a distribuição das diatomáceas esteve fortemente ligada a ocorrência do banco de macrófitas da sua margem, com a ocorrência maciça das espécies epifíticas e bentônicas. A análise de agrupamento de dados permitiu uma melhor visualização, da sua distribuição a cada profundidade e também das associações específicas em cada zona. Os resultados deste estudo permitiram concluir que a ocorrência e distribuição das diatomáceas do Lago Caçó está fortemente ligada ao banco de macrófitas localizado em suas margens, definindo assim zonas características dentro do lago.

  5. Trophic Cascading of Medusae on the Relationships between Copepods and Diatoms in a Subtropical Coastal Ecosystem

    Directory of Open Access Journals (Sweden)

    Jia-Lu Chung

    2009-01-01

    Full Text Available To investigate the spatial and temporal variation of phytoplankton and copepods, eight seasonal cruises (January 2005 ~ Oc to ber 2006 were conducted in a subtropical coast site that encom passed 19 sampling stations. The results in dicated that the temperature (18.4 - 29.7°C varied more than 10°C seasonally, while nutrient concentrations (ni trate: 0.4 - 6.3 mM, phosphate: 0.1 - 0.8 mM, and silicate 2.1 - 12.1 mM were in versely corre lated with temperature. Diatoms (2792 - 1602437 cells m-3 constituted > 90% of the phytoplankton as semblages and dinoflagellates (226 - 10029 cells m-3 represented only ~10% of the algaebiomass. Copepod abun dance (8 - 1031 ind. m-3 varied positively with that of diatom and tempeature. Therelative abundance of Temora spp. (1 - 712 ind. m-3 varied from 69% in summer; that of Paracalanus spp. (0.1 - 176 ind. m-3 were > 25% in spring and au tumn and Calanus spp. (0.5 - 24 ind. m-3 dom i nated in win ter and spring, but ac counted for only ~10% of the to tal copepods. Both di a tom den sity and copepod abun dance were positively correlated with temperature, indicating these two plank tongroups were left bot tom-up control. The copepod abun dance positively co-aried with diatoms in 2005, but not in 2006. Fur ther sea son-to-sea son analysis showed that the diatomvs. copepodratios changed positively only when the medusa abun dance changed greatly (> 40-fold between consecutive sea sons. During periods when the medusa abundance varied less than 10-fold between seasons, there is no relationship between the ratios and the medusa abun dance. This study suggests that the stability of the medusa abundance from season to season could be important in regulating the ecological linkage between diatoms and their predators ¡V copepods.

  6. A Quantitative Proxy for Sea-Ice Based on Diatoms: A Cautionary Tale.

    Science.gov (United States)

    Nesterovich, A.; Caissie, B.

    2016-12-01

    Sea ice in the Polar Regions supports unique and productive ecosystems, but the current decline in the Arctic sea ice extent prompts questions about previous sea ice declines and the response of ice related ecosystems. Since satellite data only extend back to 1978, the study of sea ice before this time requires a proxy. Being one of the most productive, diatom-dominated regions in the world and having a wide range of sea ice concentrations, the Bering and Chukchi seas are a perfect place to find a relationship between the presence of sea ice and diatom community composition. The aim of this work is to develop a diatom-based proxy for the sea ice extent. A total of 473 species have been identified in 104 sediment samples, most of which were collected on board the US Coast Guard Cutter Healy ice breaker (2006, 2007) and the Norseman II (2008). The study also included some of the archived diatom smear slides made from sediments collected in 1969. The assemblages were compared to satellite-derived sea ice extent data averaged over the 10 years preceding the sampling. Previous studies in the Arctic and Antarctic regions demonstrated that the Generalized Additive Model (GAM) is one of the best choices for proxy construction. It has the advantage of using only several species instead of the whole assemblage, thus including only sea ice-associated species and minimizing the noise created by species responding to other environmental factors. Our GAM on three species (Connia compita, Fragilariopsis reginae-jahniae, and Neodenticula seminae) has low standard deviation, high level of explained variation, and holds under the ten-fold cross-validation; the standard residual analysis is acceptable. However, a spatial residual analysis revealed that the model consistently over predicts in the Chukchi Sea and under predicts in the Bering Sea. Including a spatial model into the GAM didn't improve the situation. This has led us to test other methods, including a non-parametric model

  7. Climatic and lacustrine morphometric controls of diatom paleoproductivity in a tropical Andean lake

    Science.gov (United States)

    Bao, R.; Hernández, A.; Sáez, A.; Giralt, S.; Prego, R.; Pueyo, J. J.; Moreno, A.; Valero-Garcés, B. L.

    2015-12-01

    . The subsequent net increase in lake level introduced modifications in the area of the epilimnion sediments versus the total volume of the epilimnion, preventing complete overturn. Surpassing a certain depth threshold at approx. 8300 cal yr BP caused cessation of the morphometric eutrophy conditions associated with Cyclostephanos cf. andinus superblooms. After 7300 cal yr BP, the lake experienced a decrease in biosiliceous productivity and a change of state that involved a stronger dependence on precipitation variability, with a lesser contribution of diatoms to the total primary productivity. Our results show that the interpretation of lacustrine paleoproductivity records as paleoclimatic archives needs to take into account the effects of changes in the epilimnion sediment area to epilimnion volume ratio in association with lake ontogeny.

  8. Diatom diet selectivity by early post-larval abalone Haliotis diversicolor supertexta under hatchery conditions

    Science.gov (United States)

    Zhang, Yuyu; Gao, Yahui; Liang, Junrong; Chen, Changping; Zhao, Donghai; Li, Xuesong; Li, Yang; Wu, Wenzhong

    2010-11-01

    Benthic diatoms constitute the primary diet of abalone during their early stages of development. To evaluate the dietary preferences of early post-larval abalone, Haliotis diversicolor supertexta, we analyzed the gut contents of post-larvae that settled on diatom films. We compared the abundance and species diversity of diatom assemblages in the gut to those of the epiphytic diatom assemblages on the attachment films, and identified 40 benthic diatom species in the gut contents of post-larvae 12 to 24 d after settlement. The most abundant taxa in the gut contents were Navicula spp., Amphora copulate, and Amphora coffeaeformis. Navicula spp. accounted for 64.0% of the cell density. In the attachment films, we identified 110 diatom species belonging to 38 genera. Pennate diatoms were the dominant members including the species Amphiprora alata, Cocconeis placentula var. euglypta, Cylindrotheca closterium, Navicula sp. 2, and A. coffeaeformis. Nano-diatoms (abalone seed. The difference of the composition and abundance of diatoms between in the guts and on the biofilms suggests that early post-larval grazing was selective. An early post-larval abalone preferred nano-diatoms and the genera Navicula and Amphora during the month after settlement.

  9. Ocean acidification modulates expression of genes and physiological performance of a marine diatom

    Science.gov (United States)

    Li, Y.; Zhuang, S.; Wu, Y.; Ren, H.; Cheng, F.; Lin, X.; Wang, K.; Beardall, J.; Gao, K.

    2015-09-01

    Ocean Acidification (OA) is known to affect various aspects of the physiological performance of diatoms, but there is little information on the underlining molecular mechanisms involved. Here, we show that in the model diatom Phaeodactylum tricornutum expression of the genes related to light harvesting, carbon acquisition and carboxylation, nitrite assimilation and ATP synthesis are modulated by OA. Growth and photosynthetic carbon fixation were enhanced by elevated CO2 (1000 μatm) under both constant indoor and fluctuating outdoor light regimes. The genetic expression of nitrite reductase (NiR) was up-regulated by OA regardless of light levels and/or regimes. The transcriptional expression of fucoxanthin chlorophyll a/c protein (lhcf type (FCP)) and mitochondrial ATP synthase (mtATP synthase) genes were also enhanced by OA, but only under high light intensity. OA treatment decreased the expression of β-carbonic anhydrase (β-CA) along with down-regulation of CO2 concentrating mechanisms (CCMs). Additionally, the genes for these proteins (NiR, FCP, mtATP synthase, β-CA) showed diel expressions either under constant indoor light or fluctuating sunlight. Thus, OA enhanced photosynthetic and growth rates by stimulating nitrogen assimilation and indirectly by down-regulating the energy-costly inorganic carbon acquisition process.

  10. Momentum autocorrelation function of a classic diatomic chain

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Ming B., E-mail: mingbyu@gmail.com

    2016-10-23

    A classical harmonic diatomic chain is studied using the recurrence relations method. The momentum autocorrelation function results from contributions of acoustic and optical branches. By use of convolution theorem, analytical expressions for the acoustic and optical contributions are derived as even-order Bessel function expansions with coefficients given in terms of integrals of elliptic functions in real axis and a contour parallel to the imaginary axis, respectively. - Highlights: • Momentum autocorrelation function of a classic diatomic chain is studied. • It is derived as even-order Bessel function expansion using the convolution theorem. • The expansion coefficients are integrals of elliptic functions. • Addition theorem is used to reduce complex elliptic function to complex sum of real ones.

  11. Diatom-derived oxylipins induce cell death in sea urchin embryos activating caspase-8 and caspase 3/7.

    Science.gov (United States)

    Ruocco, Nadia; Varrella, Stefano; Romano, Giovanna; Ianora, Adrianna; Bentley, Matt G; Somma, Domenico; Leonardi, Antonio; Mellone, Stefano; Zuppa, Antonio; Costantini, Maria

    2016-07-01

    Diatoms are an important class of unicellular algae that produce bioactive secondary metabolites with cytotoxic activity collectively termed oxylipins, including polyunsaturated aldehydes (PUAs), hydroxyacids (HEPEs), oxo-acids and epoxyalcohols. Previous results showed that at higher concentrations, the PUA decadienal induced apoptosis on copepods and sea urchin embryos via caspase-3 activation; at lower concentrations decadienal affected the expression levels of the caspase-8 gene in embryos of the sea urchin Paracentrotus lividus. In the present work, we studied the effects of other common oxylipins produced by diatoms: two PUAs (heptadienal and octadienal) and four hydroxyacids (5-, 9- 11- and 15-HEPE) on P. lividus cell death and caspase activities. Our results showed that (i) at higher concentrations PUAs and HEPEs induced apoptosis in sea urchin embryos, detected by microscopic observation and through the activation of caspase-3/7 and caspase-8 measured by luminescent assays; (ii) at low concentrations, PUAs and HEPEs affected the expression levels of caspase-8 and caspase-3/7 (isolated for the first time here in P. lividus) genes, detected by Real Time qPCR. These findings have interesting implications from the ecological point of view, given the importance of diatom blooms in nutrient-rich aquatic environments. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Eruptive and environmental processes recorded by diatoms in volcanically-dispersed lake sediments from the Taupo Volcanic Zone, New Zealand

    Science.gov (United States)

    Harper, Margaret A.; Pledger, Shirley A.; Smith, Euan G. C.; Van Eaton, Alexa; Wilson, Colin J. N.

    2015-01-01

    Late Pleistocene diatomaceous sediment was widely dispersed along with volcanic ash (tephra) across and beyond New Zealand by the 25.4 ka Oruanui supereruption from Taupo volcano. We present a detailed analysis of the diatom populations in the Oruanui tephra and the newly discovered floras in two other eruptions from the same volcano: the 28.6 ka Okaia and 1.8 ka Taupo eruptions. For comparison, the diatoms were also examined in Late Pleistocene and Holocene lake sediments from the Taupo Volcanic Zone (TVZ). Our study demonstrates how these microfossils provide insights into the lake history of the TVZ since the Last Glacial Maximum. Morphometric analysis of Aulacoseira valve dimensions provides a useful quantitative tool to distinguish environmental and eruptive processes within and between individual tephras. The Oruanui and Okaia diatom species and valve dimensions are highly consistent with a shared volcanic source, paleolake and eruption style (involving large-scale magma-water interaction). They are distinct from lacustrine sediments sourced elsewhere in the TVZ. Correspondence analysis shows that small, intact samples of erupted lake sediment (i.e., lithic clasts in ignimbrite) contain heterogeneous diatom populations, reflecting local variability in species composition of the paleolake and its shallowly-buried sediments. Our analysis also shows a dramatic post-Oruanui supereruption decline in Cyclostephanos novaezelandiae, which likely reflects a combination of (1) reorganisation of the watershed in the aftermath of the eruption, and (2) overall climate warming following the Last Glacial Maximum. This decline is reflected in substantially lower proportions of C. novaezelandiae in the 1.8 ka Taupo eruption deposits, and even fewer in post-1.8 ka sediments from modern (Holocene) Lake Taupo. Our analysis highlights how the excellent preservation of siliceous microfossils in volcanic tephra may fingerprint the volcanic source region and retain a valuable record

  13. Interface states in a class of heterojunctions between diatomic semiconductors

    International Nuclear Information System (INIS)

    Kandilarov, B.D.; Detcheva, V.

    1979-09-01

    The theory of interface state in heterojunctions between diatomic semiconductors is developed in the framework of the S-matrix approach and on the basis of a one-dimensional model. The condition for the existence of interface states is explicitly derived for undeformed and deformed herterojunctions. Numerical analysis is performed and several particular cases are discussed in order to clarify the general features of the problem. (author)

  14. Bacterial colonization of the freshwater planktonic diatom Fragilaria crotonensis

    Czech Academy of Sciences Publication Activity Database

    Znachor, Petr; Šimek, Karel; Nedoma, Jiří

    2012-01-01

    Roč. 66, č. 1 (2012), s. 87-94 ISSN 0948-3055 R&D Projects: GA ČR(CZ) GA206/08/0015; GA ČR(CZ) GAP504/11/2177; GA ČR(CZ) GAP504/11/2182 Institutional research plan: CEZ:AV0Z60170517 Keywords : PDMPO * bacterial colonization * diatoms * Fragilaria crotonensis * flood * reservoir Subject RIV: DA - Hydrology ; Limnology Impact factor: 2.037, year: 2012

  15. Interactions of bacteria with diatoms: Influence on natural marine biofilms.

    Digital Repository Service at National Institute of Oceanography (India)

    Khandeparker, L.; DeCosta, P.M.; Anil, A.C.; Sawant, S.S.

    therein). In fact, biofilms are considered a reservoir and source of dissemination for V. cholerae (Shikuma & Hadfield 2010). Nutrient concentrations in the surrounding waters also affect the progression of the biofilm community (Qian et al. 2007... to render diatom monocultures near axenic (Patil & Anil 2005c). The following diluents were used – Aged Sea Water (ASW; unenriched control), ASW+streptomycin (ASW+S), ASW+chloramphenicol (ASW+C), f/2 medium (Guillard and Ryther, 1962) prepared in ASW [f...

  16. Recombinational laser employing electron transitions of diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Biriukov, A S; Prokhorov, A M; Shelepin, L A; Shirokov, N N

    1974-12-01

    Conditions are established for obtaining laser action in the visible and uv regions of the spectrum, using transitions between electronic states of diatomic molecules during recombination of a dissociated gas. The mechanism of population inversion was studied for the oxygen molecule, and gain estimates were obtained for laser action at a wavelength of 4881 A. The feasibility of laser action at other wavelengths was examined.

  17. Single ionization of diatomic molecules by bare ion impact

    International Nuclear Information System (INIS)

    Purkait, M; Mandal, C R

    2014-01-01

    The molecular three-Coulomb wave model (M3CW) has been extensively used to study the double-differential ionization cross sections (DDCS) of diatomic molecules by the impact of bare ions at intermediate and high energies. In this model, the distortion of the initial channel by the incoming projectile is also included. The present DDCS results are found to be in good accord both with the experiment of Baran et al 2008 as well as with other theory

  18. Radiation damage in diatomic materials at high doses

    International Nuclear Information System (INIS)

    Hobbs, L.W.; Hughes, A.E.

    1975-10-01

    Radiation effects in diatomic materials can differ structurally from those in metals because of the need to take into account different displacement rates on the two sublattices and the inevitable stoichiometric implications; in most diatomic insulators the anion species has the greater displacement cross section. Anion point defect stabilisation in heavily-irradiated (0.1 to 10 dpa) diatomic insulators has been studied using radiolysis of alkali and alkaline earth halides. A temperatures > 0.3 Tsub(m), all anion defects are mobile and can aggregate. Aggregation of anion interstitials results in creation of perfect dislocation loops without the need for primary cation displacements; simultaneous formation of substitutional anion molecular centres provides the necessary cation interstitials. Aggregation of anion vacancies leads to formation of metallic inclusions of the cation species, in some cases in an ordered array, which is the analogue, on a single sublattice, to the void lattice in metals. Availability of sinks for both anion interstitials and anion vacancies yields defect growth kinetics similar to those observed during formation of voids in irradiated metals, and a very high level of damage (approximately 10%) can be sustained in the lattice. The width of the temperature region concerned is much narrower, however, due to the possibility of recombination of aggregated or re-emitted anion vacancies with mobile or dispersed anion molecular defects; the latter can also aggregate to form fluid anion molecular inclusions and so complete the decomposition of the solid into separate phases of its constituent elements. (author)

  19. A Rapid Method for the Determination of Fucoxanthin in Diatom

    Directory of Open Access Journals (Sweden)

    Li-Juan Wang

    2018-01-01

    Full Text Available Fucoxanthin is a natural pigment found in microalgae, especially diatoms and Chrysophyta. Recently, it has been shown to have anti-inflammatory, anti-tumor, and anti-obesityactivity in humans. Phaeodactylum tricornutum is a diatom with high economic potential due to its high content of fucoxanthin and eicosapentaenoic acid. In order to improve fucoxanthin production, physical and chemical mutagenesis could be applied to generate mutants. An accurate and rapid method to assess the fucoxanthin content is a prerequisite for a high-throughput screen of mutants. In this work, the content of fucoxanthin in P. tricornutum was determined using spectrophotometry instead of high performance liquid chromatography (HPLC. This spectrophotometric method is easier and faster than liquid chromatography and the standard error was less than 5% when compared to the HPLC results. Also, this method can be applied to other diatoms, with standard errors of 3–14.6%. It provides a high throughput screening method for microalgae strains producing fucoxanthin.

  20. Models of the delayed nonlinear Raman response in diatomic gases

    International Nuclear Information System (INIS)

    Palastro, J. P.; Antonsen, T. M. Jr.; Pearson, A.

    2011-01-01

    We examine the delayed response of a diatomic gas to a polarizing laser field with the goal of obtaining computationally efficient methods for use with laser pulse propagation simulations. We demonstrate that for broadband pulses, heavy molecules such as O 2 and N 2 , and typical atmospheric temperatures, the initial delayed response requires only classical physics. The linear kinetic Green's function is derived from the Boltzmann equation and shown to be in excellent agreement with full density-matrix calculations. A straightforward perturbation approach for the fully nonlinear, kinetic impulse response is also presented. With the kinetic theory a reduced fluid model of the diatomic gas' orientation is derived. Transport coefficients are introduced to model the kinetic phase mixing of the delayed response. In addition to computational rapidity, the fluid model provides intuition through the use of familiar macroscopic quantities. Both the kinetic and the fluid descriptions predict a nonlinear steady-state alignment after passage of the laser pulse, which in the fluid model is interpreted as an anisotropic temperature of the diatomic fluid with respect to motion about the polarization axis.

  1. Nature engineered diatom biosilica as drug delivery systems.

    Science.gov (United States)

    Uthappa, U T; Brahmkhatri, Varsha; Sriram, G; Jung, Ho-Young; Yu, Jingxian; Kurkuri, Nikita; Aminabhavi, Tejraj M; Altalhi, Tariq; Neelgund, Gururaj M; Kurkuri, Mahaveer D

    2018-05-14

    Diatoms, unicellular photosynthetic algae covered with siliceous cell wall, are also called frustule. These are the most potential naturally available materials for the development of cost-effective drug delivery systems because of their excellent biocompatibility, high surface area, low cost and ease of surface modification. Mesoporous silica materials such as MCM-41 and SBA-15 have been extensively used in drug delivery area. Their synthesis is challenging, time consuming, requires toxic chemicals and are energy intensive, making the entire process expensive and non-viable. Therefore, it is necessary to explore alternative materials. Surprisingly, nature has provided some exciting materials called diatoms; biosilica is one such a material that can be potentially used as a drug delivery vehicle. The present review focuses on different types of diatom species used in drug delivery with respect to their structural properties, morphology, purification process and surface functionalization. In this review, recent advances along with their limitations as well as the future scope to develop them as potential drug delivery vehicles are discussed. Copyright © 2018. Published by Elsevier B.V.

  2. Process for desulfurizing hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    1937-04-12

    A process is described for the desulfurization of a mixture of hydrocarbons, and in particular hydrocarbons containing less than 7 atoms of carbon and sulfur compounds of the type of sulfur carbonyl, characterized by the fact that the mixture, preferably in the liquid phase, is brought in contact with a solution of caustic alkali, essentially anhydrous or preferably with a solution of alkali hydroxide in an organic hydroxy nonacid solvent, for example, an alcohol, or with an alkaline alcoholate, under conditions suitable to the formation of hydrogen sulfide which produces a hydrocarbon mixture free from sulfur compounds of the sulfur carbonyl type but containing hydrogen sulfide, and that it is treated, following mixing, having beem submitted to the first treatment, by means of aqueous alkaline hydroxide to eliminate the hydrogen sulfide.

  3. Hydrocarbon Plume Dynamics in the Worldś Most Spectacular Hydrocarbon Seeps, Santa Barbara Channel, California

    Science.gov (United States)

    Mau, S.; Reed, J.; Clark, J.; Valentine, D.

    2006-12-01

    Large quantities of natural gas are emitted from the seafloor into the coastal ocean near Coal Oil Point, Santa Barbara Channel (SBC), California. Methane, ethane, and propane were quantified in the surface water at 79 stations in a 270 km2 area in order to map the surficial hydrocarbon plume and to quantify air-sea exchange of these gases. A time series was initiated for 14 stations to identify the variability of the mapped plume, and biologically-mediated oxidation rates of methane were measured to quantify the loss of methane in surface water. The hydrocarbon plume was found to comprise ~70 km2 and extended beyond study area. The plume width narrowed from 3 km near the source to 0.7 km further from the source, and then expanded to 6.7 km at the edge of the study area. This pattern matches the cyclonic gyre which is the normal current flow in this part of the Santa Barbara Channel - pushing water to the shore near the seep field and then broadening the plume while the water turns offshore further from the source. Concentrations of gaseous hydrocarbons decrease as the plume migrates. Time series sampling shows similar plume width and hydrocarbon concentrations when normal current conditions prevail. In contrast, smaller plume width and low hydrocarbon concentrations were observed when an additional anticyclonic eddy reversed the normal current flow, and a much broader plume with higher hydrocarbon concentrations was observed during a time of diminished speed within the current gyre. These results demonstrate that surface currents control hydrocarbon plume dynamics in the SBC, though hydrocarbon flux to the atmosphere is likely less dependent on currents. Estimates of air- sea hydrocarbon flux and biological oxidation rates will also be presented.

  4. Recovery of hydrocarbon oils

    Energy Technology Data Exchange (ETDEWEB)

    1941-02-10

    A process is disclosed for recovery of hydrocarbon oils, especially lubricating oils or diesel oils, through pressure hydrogenation of distillation, extraction of hydrogenation products from coal or coaly materials or from oils such as mineral oils or tars in liquid phase by use in a reaction vessel of fixed-bed catalysts, characterized in that as starting material is employed material which has been freed of asphaltic and resinous material by hydrogenation refining, vacuum-steam distillation, treatment with hydrogen-rich hydrocarbons (hydroforming), or sulfuric acid.

  5. Diatom Valve Three-Dimensional Representation: A New Imaging Method Based on Combined Microscopies

    Science.gov (United States)

    Ferrara, Maria Antonietta; De Tommasi, Edoardo; Coppola, Giuseppe; De Stefano, Luca; Rea, Ilaria; Dardano, Principia

    2016-01-01

    The frustule of diatoms, unicellular microalgae, shows very interesting photonic features, generally related to its complicated and quasi-periodic micro- and nano-structure. In order to simulate light propagation inside and through this natural structure, it is important to develop three-dimensional (3D) models for synthetic replica with high spatial resolution. In this paper, we present a new method that generates images of microscopic diatoms with high definition, by merging scanning electron microscopy and digital holography microscopy or atomic force microscopy data. Starting from two digital images, both acquired separately with standard characterization procedures, a high spatial resolution (Δz = λ/20, Δx = Δy ≅ 100 nm, at least) 3D model of the object has been generated. Then, the two sets of data have been processed by matrix formalism, using an original mathematical algorithm implemented on a commercially available software. The developed methodology could be also of broad interest in the design and fabrication of micro-opto-electro-mechanical systems. PMID:27690008

  6. Specificity of lipoxygenase pathways supports species delineation in the marine diatom genus Pseudo-nitzschia.

    Directory of Open Access Journals (Sweden)

    Nadia Lamari

    Full Text Available Oxylipins are low-molecular weight secondary metabolites derived from the incorporation of oxygen into the carbon chains of polyunsaturated fatty acids (PUFAs. Oxylipins are produced in many prokaryotic and eukaryotic lineages where they are involved in a broad spectrum of actions spanning from stress and defense responses, regulation of growth and development, signaling, and innate immunity. We explored the diversity in oxylipin patterns in the marine planktonic diatom Pseudo-nitzschia. This genus includes several species only distinguishable with the aid of molecular markers. Oxylipin profiles of cultured strains were obtained by reverse phase column on a liquid chromatograph equipped with UV photodiode detector and q-ToF mass spectrometer. Lipoxygenase compounds were mapped on phylogenies of the genus Pseudo-nitzschia inferred from the nuclear encoded hyper-variable region of the LSU rDNA and the plastid encoded rbcL. Results showed that the genus Pseudo-nitzschia exhibits a rich and varied lipoxygenase metabolism of eicosapentaenoic acid (EPA, with a high level of specificity for oxylipin markers that generally corroborated the genotypic delineation, even among genetically closely related cryptic species. These results suggest that oxylipin profiles constitute additional identification tools for Pseudo-nitzschia species providing a functional support to species delineation obtained with molecular markers and morphological traits. The exploration of the diversity, patterns and plasticity of oxylipin production across diatom species and genera will also provide insights on the ecological functions of these secondary metabolites and on the selective pressures driving their diversification.

  7. Whole-cell response to nitrogen deprivation in the diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Alipanah, Leila; Rohloff, Jens; Winge, Per; Bones, Atle M; Brembu, Tore

    2015-10-01

    Algal growth is strongly affected by nitrogen (N) availability. Diatoms, an ecologically important group of unicellular algae, have evolved several acclimation mechanisms to cope with N deprivation. In this study, we integrated physiological data with transcriptional and metabolite data to reveal molecular and metabolic modifications in N-deprived conditions in the marine diatom Phaeodactylum tricornutum. Physiological and metabolite measurements indicated that the photosynthetic capacity and chlorophyll content of the cells decreased, while neutral lipids increased in N-deprived cultures. Global gene expression analysis showed that P. tricornutum responded to N deprivation through an increase in N transport, assimilation, and utilization of organic N resources. Following N deprivation, reduced biosynthesis and increased recycling of N compounds like amino acids, proteins, and nucleic acids was observed at the transcript level. The majority of the genes associated with photosynthesis and chlorophyll biosynthesis were also repressed. Carbon metabolism was restructured through downregulation of the Calvin cycle and chrysolaminarin biosynthesis, and co-ordinated upregulation of glycolysis, the tricarboxylic acid cycle, and pyruvate metabolism, leading to funnelling of carbon sources to lipid metabolism. Finally, reallocation of membrane lipids and induction of de novo triacylglycerol biosynthesis directed cells to accumulation of neutral lipids. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  8. Bio-remediation of hydrocarbons in coastal regions; Bioremediation des hydrocarbures en milieu cotier

    Energy Technology Data Exchange (ETDEWEB)

    Guyoneaud, R. [IBEAS, LEM - Lab. d' Ecologie Moleculaire - JE 159, 64 - Pau (France)

    2001-07-01

    Coasts are exposed to chronic or accidental pollutions by hydrocarbons. The aim of this study is to show the importance of the microbial layers (stratified sedimentary systems) in the biodegradation of the hydrocarbons. (A.L.B.)

  9. Using transcriptomic profiles in the diatom Phaeodactylum tricornutum to identify and prioritize stressors

    International Nuclear Information System (INIS)

    Osborn, Hannah L.; Hook, Sharon E.

    2013-01-01

    Highlights: •Exposure to stressors with different modes of action generated unique gene expression profiles in the diatom Phaeodactylum tricornutum. •The gene expression profile generated by a multiple stressor exposure reflected exposure to individual components of the mixture. •Quantitative PCR assays were generated that could be used to identify exposure to individual stressors. -- Abstract: The transcriptomic profile of the marine diatom, Phaeodactylum tricornutum, exposed to several ecologically relevant stressors, was used to develop toxicity identification evaluation (TIE)-like gene expression assays. Algal growth inhibition was measured by flow cytometry to determine exposure concentrations that elicited a sublethal toxic response. P. tricornutum was exposed to concentrations of copper (2 μg L −1 ), cadmium (5 μg L −1 ), silver (20 μg L −1 ), simazine (75 μg L −1 ), the water accommodated fraction (WAF) of weathered crude oil (5 mg L −1 ), 50 μg L −1 ammonia, a decreased salinity treatment (15‰), and a mixture exposure of ammonia, decreased salinity and cadmium (10 μg L −1 ). Analysis of the gene expression via microarray indicated that unique transcriptomic signals were generated for each of the individual treatments. Transcriptomic profiles of ammonia and the mixture treatment overlapped substantially. Photosynthesis related transcripts were altered in the simazine (herbicide) treatment. A transcript involved in degrading hydrocarbons, dioxygenase, had increased abundance after crude oil exposure. Overall, transcriptomic responses in the different treatments were associated with stress responses, membrane transport, transcription and translation and could be linked to contaminant mode of action. The transcriptomic profiles were used to design real-time (quantitative) polymerase chain reaction (qPCR) assays that would link changes in transcript abundance to a particular stressor in a TIE-based approach. At least one transcript

  10. Using transcriptomic profiles in the diatom Phaeodactylum tricornutum to identify and prioritize stressors

    Energy Technology Data Exchange (ETDEWEB)

    Osborn, Hannah L., E-mail: Hannah.Osborn@csiro.au; Hook, Sharon E., E-mail: Sharon.Hook@csiro.au

    2013-08-15

    Highlights: •Exposure to stressors with different modes of action generated unique gene expression profiles in the diatom Phaeodactylum tricornutum. •The gene expression profile generated by a multiple stressor exposure reflected exposure to individual components of the mixture. •Quantitative PCR assays were generated that could be used to identify exposure to individual stressors. -- Abstract: The transcriptomic profile of the marine diatom, Phaeodactylum tricornutum, exposed to several ecologically relevant stressors, was used to develop toxicity identification evaluation (TIE)-like gene expression assays. Algal growth inhibition was measured by flow cytometry to determine exposure concentrations that elicited a sublethal toxic response. P. tricornutum was exposed to concentrations of copper (2 μg L{sup −1}), cadmium (5 μg L{sup −1}), silver (20 μg L{sup −1}), simazine (75 μg L{sup −1}), the water accommodated fraction (WAF) of weathered crude oil (5 mg L{sup −1}), 50 μg L{sup −1} ammonia, a decreased salinity treatment (15‰), and a mixture exposure of ammonia, decreased salinity and cadmium (10 μg L{sup −1}). Analysis of the gene expression via microarray indicated that unique transcriptomic signals were generated for each of the individual treatments. Transcriptomic profiles of ammonia and the mixture treatment overlapped substantially. Photosynthesis related transcripts were altered in the simazine (herbicide) treatment. A transcript involved in degrading hydrocarbons, dioxygenase, had increased abundance after crude oil exposure. Overall, transcriptomic responses in the different treatments were associated with stress responses, membrane transport, transcription and translation and could be linked to contaminant mode of action. The transcriptomic profiles were used to design real-time (quantitative) polymerase chain reaction (qPCR) assays that would link changes in transcript abundance to a particular stressor in a TIE

  11. Diatoms in acid mine drainage and their role in the formation of iron-rich stromatolites

    Energy Technology Data Exchange (ETDEWEB)

    Brake, S.S.; Hasiotis, S.T.; Dannelly, H.K. [Indiana State University, Terre Haute, IN (United States)

    2004-08-01

    Adverse conditions in the acid mine drainage (AMD) system at the Green Valley mine, Indiana, limit diatom diversity to one species, Nitzschia tubicola. It is present in three distinct microbial consortia: Euglena mutabilis-dominated biofilm, diatom-dominated biofilm, and diatom-exclusive biofilm. E. mutabilis dominates the most extensive biofilm, with lesser numbers of N. tubicola, other eukaryotes, and bacteria. Diatom-dominated biofilm occurs as isolated patches containing N. tubicola with minor fungal hyphae, filamentous algae, E. mutabilis, and bacteria. Diatom-exclusive biofilm is rare, composed entirely of N. tubicola. Diatom distribution is influenced by seasonal and intraseasonal changes in water temperature and chemistry. Diatoms are absent in winter due to cool water temperatures. In summer, isolated patchy communities are present due to warmer water temperatures. In 2001, the diatom community expanded its distribution following a major rainfall that temporarily diluted the effluent, creating hospitable conditions for diatom growth. After several weeks when effluent returned to preexisting conditions, the diatom biofilm retreated to isolated patches, and E. mutabilis biofilm flourished. Iron-rich stromatolites underlie the biofilms and consist of distinct laminae, recording spatial and temporal oscillations in physicochemical conditions and microbial activity. The stromatolites are composed of thin, wavy laminae with partially decayed E. mutabilis biofilm, representing microbial activity and iron precipitation under normal AMD conditions. Alternating with the wavy layers are thicker, porous, spongelike laminae composed of iron precipitated on and incorporated into radiating colonies of diatoms. These layers indicate episodic changes in water chemistry, allowing diatoms to temporarily dominate the system.

  12. Studies on fouling diatoms from the Zuari Estuary, Goa (west coast of India)

    Digital Repository Service at National Institute of Oceanography (India)

    Redekar, P.D.; Wagh, A.B.

    from offshore waters of Bombay High area using aluminium panels and recorded 58 species of fouling diatoms Of these Navicula Coscinodiscus Rhizosolenia and Chaetoceros were found to be common The dominance of Centrales over Pennales in water column... on fouling diatoms from the Zuari estuary, Goa (West coast of India) 119 Pangu (1993) used mild steel, aluminium, fiberglass and glass test panels and the immersion period of panels was long (1 month to 11 months) The fouling diatoms from Waghotana...

  13. Complex dynamics in diatomic molecules. Part II: Quantum trajectories

    International Nuclear Information System (INIS)

    Yang, C.-D.; Weng, H.-J.

    2008-01-01

    The second part of this paper deals with quantum trajectories in diatomic molecules, which has not been considered before in the literature. Morse potential serves as a more accurate function than a simple harmonic oscillator for illustrating a realistic picture about the vibration of diatomic molecules. However, if we determine molecular dynamics by integrating the classical force equations derived from a Morse potential, we will find that the resulting trajectories do not consist with the probabilistic prediction of quantum mechanics. On the other hand, the quantum trajectory determined by Bohmian mechanics [Bohm D. A suggested interpretation of the quantum theory in terms of hidden variable. Phys. Rev. 1952;85:166-179] leads to the conclusion that a diatomic molecule is motionless in all its vibrational eigen-states, which also contradicts probabilistic prediction of quantum mechanics. In this paper, we point out that the quantum trajectory of a diatomic molecule completely consistent with quantum mechanics does exist and can be solved from the quantum Hamilton equations of motion derived in Part I, which is based on a complex-space formulation of fractal spacetime [El Naschie MS. A review of E-Infinity theory and the mass spectrum of high energy particle physics. Chaos, Solitons and Fractals 2004;19:209-36; El Naschie MS. E-Infinity theory - some recent results and new interpretations. Chaos, Solitons and Fractals 2006;29:845-853; El Naschie MS. The concepts of E-infinity. An elementary introduction to the cantorian-fractal theory of quantum physics. Chaos, Solitons and Fractals 2004;22:495-511; El Naschie MS. SU(5) grand unification in a transfinite form. Chaos, Solitons and Fractals 2007;32:370-374; Nottale L. Fractal space-time and microphysics: towards a theory of scale relativity. Singapore: World Scientific; 1993; Ord G. Fractal space time and the statistical mechanics of random works. Chaos, Soiltons and Fractals 1996;7:821-843] approach to quantum

  14. Reconstruction of Oceanographic Changes Based on the Diatom Records of the Central Okhotsk Sea over the last 500000 Years

    Directory of Open Access Journals (Sweden)

    Wei-Lung Wang Liang-Chi Wang

    2008-01-01

    Full Text Available This study provides insight into changes in sea ice conditions and the oceanographic environment over the past 500 kyr through analysis of the diatom record. Based on the relative abundance of 13 diatoms species in piston core MD012414, four types of environmental conditions in the central Okhotsk Sea over the last 330 ka BP have been distinguished: (1 open-ocean alternating with seasonal sea-ice cover in Stages 9, 5, and 1; (2 almost open-ocean free of sea-ice cover in Stages 7 and 3; (3 perennial sea-ice cover in Stages 6, 4, and 2; and (4 a warm ice-age dominated by open ocean assemblages in Stage 8. The littoral diatom species, Paralia sulcata, showed a sudden increase from the glacial period to the nterglacial period over the last 330 ka BP, except during Stage 8. Such a result implies that melting sea-ice transported terrigenous materials from the north Okhotsk Sea continental shelves to the central ocean during eglaciation. From Stage 13 to Stage 10, however, cold and warm marine conditions unexpectedly occurred in the late interglacial periods and the glacial periods, respectively. One possible reason for this is a lack of age control points from Stage 13 to Stage 10, and the different sediment accumulation rates between glacial and interglacial periods. This study suggests not only the process by which oceanographic variation of sea ice occurred, but also new significance for Paralia sulcata as an indicator in the diatom record of the Okhotsk Sea.

  15. Paleoenvironmental inference models from sediment diatom assemblages in Baffin Island lakes (Nunavut, Canada) and reconstruction of summer water temperature

    Energy Technology Data Exchange (ETDEWEB)

    Joynt, E. H. III; Wolfe, A. P. [Colorado Univ., Inst. of Arctic and Alpine Research, Boulder, CO (United States)

    2001-06-01

    Lake sediments are attractive repositories for paleoclimate proxy data because they are temporally continuous, undisturbed and datable. It is particularly true of lakes which are ubiquitous throughout the Arctic regions, enabling dense spatial coverage of sampling sites. In more recent times diatoms have been applied to a a variety of paleoenvironmental questions. However, these studies have been of limited usefulness because they lack a regional training set that would facilitate making quantitative paleoenvironmental inferences. This article provides this inferential tool, together with an example of its application. Conductivity, pH, summer lake water temperature, and mean annual air temperature have been identified as the significant controls over diatom assemblages from the surface sediments of 61 lakes on Baffin Island. Using weighted-averaging regression and calibration, predictive models for these parameters have been developed. Results show that the summer lake water temperature model provides realistic reconstructions when compared with other paleoenvironmental records. Over the past 5000 years the amplitude of reconstructed summer lake water temperature was found to be on the order of 4 degrees C, expressed primarily as progressive neoglacial cooling culminating in the Little Ice Age. Diatom-inferred summer water temperatures have increased by about 2 degrees C in the past 150 years, which is also in agreement with independent paleoclimatic reconstructions. The data obtained in this study complements similar efforts from the western Canadian Arctic and the northern reaches of Scandinavia, however, this is the first training set developed for lakes situated entirely north of the tree line. As such, it extends the applicability of diatoms for paleotemperature reconstructions well into the Arctic tundra biome. 45 refs., 1 tab., 10 figs., 1 appendix.

  16. Effect of diatom morphology on the small-scale behavior of the copepod Temora stylifera (Dana, 1849)

    KAUST Repository

    Mahadik, Gauri A.; Castellani, Claudia; Mazzocchi, Maria Grazia

    2017-01-01

    We explored the small-scale behavior of the calanoid copepod Temora stylifera in relation to the diatoms Chaetoceros socialis, Leptocylindrus aporus, Leptocylindrus danicus and Pseudo-nitzschia calliantha offered as monospecific diets at similar carbon concentrations. These four diatoms are characterized by distinct size, shape and colony forming ability and are important components of the autumnal bloom co-occurring with the seasonal peak of T. stylifera abundance in Mediterranean coastal waters. High-speed video recordings showed that T. stylifera acquired cells in a suspension feeding mode while creating feeding currents. Copepod behavior was quantified in terms of feeding, motion, and grooming activities. T. stylifera spent more time in hovering than cruising in presence of all diets. The solitary L. aporus and P. calliantha elicited longer feeding bouts, lower appendage beat frequency and shorter grooming events compared to the colonial L. danicus and C. socialis. Overall the present results indicate that the behavioral responses of T. stylifera to different diatom diets were species-specific. The observed behavioral plasticity may help T. stylifera to adjust rapidly to changes in the food environment and this can be advantageous in exploiting short-lived phytoplankton blooms.

  17. Assessment of river quality in a subtropical Austral river system: a combined approach using benthic diatoms and macroinvertebrates

    Science.gov (United States)

    Nhiwatiwa, Tamuka; Dalu, Tatenda; Sithole, Tatenda

    2017-12-01

    River systems constitute areas of high human population densities owing to their favourable conditions for agriculture, water supply and transportation network. Despite human dependence on river systems, anthropogenic activities severely degrade water quality. The main aim of this study was to assess the river health of Ngamo River using diatom and macroinvertebrate community structure based on multivariate analyses and community metrics. Ammonia, pH, salinity, total phosphorus and temperature were found to be significantly different among the study seasons. The diatom and macroinvertebrate taxa richness increased downstream suggesting an improvement in water as we moved away from the pollution point sources. Canonical correspondence analyses identified nutrients (total nitrogen and reactive phosphorus) as important variables structuring diatom and macroinvertebrate community. The community metrics and diversity indices for both bioindicators highlighted that the water quality of the river system was very poor. These findings indicate that both methods can be used for water quality assessments, e.g. sewage and agricultural pollution, and they show high potential for use during water quality monitoring programmes in other regions.

  18. Carbon isotope ratios of organic matter in Bering Sea settling particles. Extremely high remineralization of organic carbon derived from diatoms

    International Nuclear Information System (INIS)

    Yasuda, Saki; Akagi, Tasuku; Naraoka, Hiroshi; Kitajima, Fumio; Takahashi, Kozo

    2016-01-01

    The carbon isotope ratios of organic carbon in settling particles collected in the highly-diatom-productive Bering Sea were determined. Wet decomposition was employed to oxidize relatively fresh organic matter. The amount of unoxidised organic carbon in the residue following wet decomposition was negligible. The δ 13 C of organic carbon in the settling particles showed a clear relationship against SiO 2 /CaCO 3 ratio of settling particles: approximately -26‰ and -19‰ at lower and higher SiO 2 /CaCO 3 ratios, respectively. The δ 13 C values were largely interpreted in terms of mixing of two major plankton sources. Both δ 13 C and compositional data can be explained consistently only by assuming that more than 98% of diatomaceous organic matter decays and that organic matter derived from carbonate-shelled plankton may remain much less remineralized. A greater amount of diatom-derived organic matter is discovered to be trapped with the increase of SiO 2 /CaCO 3 ratio of the settling particles. The ratio of organic carbon to inorganic carbon, known as the rain ratio, therefore, tends to increase proportionally with the SiO 2 /CaCO 3 ratio under an extremely diatom-productive condition. (author)

  19. Effect of diatom morphology on the small-scale behavior of the copepod Temora stylifera (Dana, 1849)

    KAUST Repository

    Mahadik, Gauri A.

    2017-05-12

    We explored the small-scale behavior of the calanoid copepod Temora stylifera in relation to the diatoms Chaetoceros socialis, Leptocylindrus aporus, Leptocylindrus danicus and Pseudo-nitzschia calliantha offered as monospecific diets at similar carbon concentrations. These four diatoms are characterized by distinct size, shape and colony forming ability and are important components of the autumnal bloom co-occurring with the seasonal peak of T. stylifera abundance in Mediterranean coastal waters. High-speed video recordings showed that T. stylifera acquired cells in a suspension feeding mode while creating feeding currents. Copepod behavior was quantified in terms of feeding, motion, and grooming activities. T. stylifera spent more time in hovering than cruising in presence of all diets. The solitary L. aporus and P. calliantha elicited longer feeding bouts, lower appendage beat frequency and shorter grooming events compared to the colonial L. danicus and C. socialis. Overall the present results indicate that the behavioral responses of T. stylifera to different diatom diets were species-specific. The observed behavioral plasticity may help T. stylifera to adjust rapidly to changes in the food environment and this can be advantageous in exploiting short-lived phytoplankton blooms.

  20. Contrasting Photo-physiological Responses of the Haptophyte Phaeocystis Antarctica and the Diatom Pseudonitzschia sp. in the Ross Sea (Antarctica

    Directory of Open Access Journals (Sweden)

    Sasha Tozzi

    2017-05-01

    Full Text Available The Antarctic is a unique environment in which substantial variations in irradiance occur over a number of time scales, and as a result phytoplankton need to acclimate and adapt to these changes. We conducted field and laboratory manipulations in the Ross Sea, Antarctica to examine photophysiological differences between Phaeocystis antarctica and Pseudonitzschia sp. a diatom that commonly occurrs in the Ross Sea, since these are the two functional groups that dominate abundance and productivity. Both exhibited reduced quantum yields due to high irradiances. P. antarctica, a haptophyte, displays a distinct photophysiological response to irradiance when compared to diatoms. P. antarctica showed a rapid recovery from high light exposure, as indicated by the rapid return to initial, high quantum yields, in contrast to diatoms, which responded more slowly. Absorption cross sections were high in both forms, but those in P. antarctica were significantly higher. Both organisms recovered within 24 h to initial quantum yields, suggesting that high irradiance exposure does not have a permanent effect on these organisms. Among all micronutrient additions (iron, cobalt, zinc and vitamin B12, only iron additions resulted in rapid impacts on quantum yields. Iron limitation also can result in reduced photosynthetic efficiency. Understanding these photophysiologial responses and the impact of oceanographic conditions provides constraints on modeling efforts of photosynthesis and primary productivity in the Antarctic.

  1. Molecular Characterisation and Co-cultivation of Bacterial Biofilm Communities Associated with the Mat-Forming Diatom Didymosphenia geminata.

    Science.gov (United States)

    Brandes, Josephin; Kuhajek, Jeanne M; Goodwin, Eric; Wood, Susanna A

    2016-10-01

    Didymosphenia geminata (Lyngbye) M. Schmidt is a stalked freshwater diatom that is expanding its range globally. In some rivers, D. geminata forms thick and expansive polysaccharide-dominated mats. Like other stalked diatoms, D. geminata cells attach to the substratum with a pad of adhesive extracellular polymeric substance. Research on D. geminata and other diatoms suggests that bacterial biofilm composition may contribute to successful attachment. The aim of this study was to investigate the composition and role of bacterial biofilm communities in D. geminata attachment and survival. Bacterial biofilms were collected at four sites in the main stem of a river (containing D. geminata) and in four tributaries (free of D. geminata). Samples were characterised using automated rRNA intergenic spacer analysis and high-throughput sequencing (HTS). Mat-associated bacteria were isolated and their effect on the early establishment of D. geminata cells assessed using co-culturing experiments. ARISA and HTS data showed differences in bacterial communities between samples with and without D. geminata at two of the four sites. Samples with D. geminata had a higher relative abundance of Sphingobacteria (p geminata reduced survival (p geminata. Attachment was enhanced by Micrococcus sp. and Pseudomonas sp. (p geminata, and may partly explain observed distribution patterns.

  2. Diatom community and palaeoenvironmental properties of Karacaören diatomite deposits (Nevşehir, Central Anatolia, Turkey)

    Science.gov (United States)

    Yıldız, Ayşegül; Gürel, Ali; Dursun, Yusuf Gökhan

    2017-10-01

    The diatom community and palaeoenvironmental properties of volcano genetic diatomite deposits that outcrop in the Karacaören (Nevşehir) area are described. Two stratigraphic sections were measured in the study area. One of these sections was measured in Quaternary lake units (K1), and the other in lacustrine sediments of the late Miocene-Pliocene Ürgüp Formation's Bayramhacılı Member (K2). According to stratigraphic and chemical characteristics of the sections, two distinct paleogeographic domains were determined in the study area. One of these, the shallow lacustrine to fluvial area (Quaternary) which is represented by an alternating sequence of diatomite, silt/mud, and tuffite. The other was the deeper lacustrine stage (late Miocene) which is represented by diatomites with some interbedded mud facies, chert and volcanics. From the diatomite samples of these sections, twenty-five species of 10 different diatom genera were identified. When evaluated together, the ecological properties and the distribution of numerical values of the determined diatom genera and species, showed that the study area's diatomite was generally deposited in shallow, high temperature, nutrient-rich water, where nitrogen and phosphorus were abundant and which was an alkaline (pH > 7) freshwater lake environment. Over time the pH value of the environment decreased (pH < 7), and the environment became acidic.

  3. Transformation techniques for metabolic engineering of diatoms and haptophytes: current state and prospects.

    Science.gov (United States)

    Velmurugan, Natarajan; Deka, Deepi

    2018-05-01

    Diatoms and haptophytes represent a key segment of the dominant phytoplankton communities that frequently form massive blooms in the photic zone of the ocean and are considered indicators of global climate changes. Diatoms and haptophytes also play a vital role in the biological carbon fixation in the carbon cycles. Carbon partitioning within diatoms and haptophytes possesses a wide range of chemical compounds and storage materials, such as lipids, carbohydrates, and chlorophyll. Among the marine microorganisms, diatoms and haptophytes have been recognized as promising sources of long- and very long-chain polyunsaturated fatty acids (PUFA). So far, a variety of approaches have been employed for genetic modification in the nuclei of diatoms and haptophytes. Studies on transformation and metabolic engineering in various intracellular genomes, such as chloroplast and mitochondria, are scarce. Particle bombardment, Agrobacterium and PEG-mediated gene transfer, and electroporation have been reported for foreign gene transformation into the diatoms and haptophytes. Antibiotics (G418 and chloramphenicol) and herbicides (zeocin, hygromycin, and norflurazon) have been successfully demonstrated as the best selection markers. Despite the availability of a wide range of molecular tools for foreign gene expression in microalgae, very few promoters (lhcf1, nr, h4, ef2, fcp, and pds) have been reported for diatoms and haptophytes. Therefore, in this review, we first summarize the significant progress that has been achieved in transgene expression in diatoms and haptophytes and highlight the importance and availability of recently developed novel tools that are suitable for transgenic expression in diatoms and haptophytes.

  4. Diatom Attachment at Aquatic Interfaces: Molecular Interactions, Mechanisms, and Physiology of Adhesion

    National Research Council Canada - National Science Library

    Gretz, Michael

    1997-01-01

    .... those more hydrophobic and that bacterial 'preconditioning' has variable effects on adhesion; (3) developed methodology for mass culture of fouling diatoms and isolation of adhesive components; (4...

  5. Optrode for sensing hydrocarbons

    Science.gov (United States)

    Miller, H.; Milanovich, F.P.; Hirschfeld, T.B.; Miller, F.S.

    1988-09-13

    A two-phase system employing the Fujiwara reaction is provided for the fluorometric detection of halogenated hydrocarbons. A fiber optic is utilized to illuminate a column of pyridine trapped in a capillary tube coaxially attached at one end to the illuminating end of the fiber optic. A strongly alkaline condition necessary for the reaction is maintained by providing a reservoir of alkali in contact with the column of pyridine, the surface of contact being adjacent to the illuminating end of the fiber optic. A semipermeable membrane caps the other end of the capillary tube, the membrane being preferentially permeable to the halogenated hydrocarbon and but preferentially impermeable to water and pyridine. As the halogenated hydrocarbon diffuses through the membrane and into the column of pyridine, fluorescent reaction products are formed. Light propagated by the fiber optic from a light source, excites the fluorescent products. Light from the fluorescence emission is also collected by the same fiber optic and transmitted to a detector. The intensity of the fluorescence gives a measure of the concentration of the halogenated hydrocarbons. 5 figs.

  6. Catalyst for hydrocarbon conversion

    International Nuclear Information System (INIS)

    Duhaut, P.; Miquel, J.

    1975-01-01

    A description is given for a catalyst and process for hydrocarbon conversions, e.g., reforming. The catalyst contains an alumina carrier, platinum, iridium, at least one metal selected from uranium, vanadium, and gallium, and optionally halogen in the form of metal halide of one of the aforesaid components. (U.S.)

  7. Application of fission track analysis to hydrocarbon exploration

    International Nuclear Information System (INIS)

    Duddy, I.R.; Green, P.F.; Gleadow, A.J.W.; Marshallsea, S.; Tingate, P.; Laslett, G.M.; Hegarty, K.A.; Lovering, J.F.

    1985-01-01

    The temperature range over which fission tracks in apatite show observable annealing effects coincides with that responsible for the maximum generation of liquid hydrocarbons. Work is currently in progress in a number of Australian and overseas sedimentary basins, applying Apatite Fission Track Analysis (AFTA) to investigate the thermal evolution of these hydrocarbon prospective regions

  8. Depositional environment, organic matter characterization and hydrocarbon potential of Middle Miocene sediments from northeastern Bulgaria (Varna-Balchik Depression

    Directory of Open Access Journals (Sweden)

    Zdravkov Alexander

    2015-10-01

    Full Text Available The depositional environments and hydrocarbon potential of the siliciclastic, clayey and carbonate sediments from the Middle Miocene succession in the Varna-Balchik Depression, located in the south-eastern parts of the Moesian Platform, were studied using core and outcrop samples. Based on the lithology and resistivity log the succession is subdivided from base to top into five units. Siliciclastic sedimentation prevailed in the lower parts of units I and II, whereas their upper parts are dominated by carbonate rocks. Unit III is represented by laminated clays and biodetritic limestone. Units IV and V are represented by aragonitic sediments and biomicritic limestones, correlated with the Upper Miocene Topola and Karvuna Formations, respectively. Biogenic silica in the form of diatom frustules and sponge spicules correlates subunit IIa and unit III to the lower and upper parts of the Middle Miocene Euxinograd Formation. Both (subunits contain organic carbon contents in the order of 1 to 2 wt. % (median: 0.8 for subunit IIa; 1.3 for unit III, locally up to 4 wt. %. Based on Hydrogen Index values (HI and alkane distribution pattern, the kerogen is mainly type II in subunit IIa (average HI= 324 mg HC/g TOC and type III in unit III (average HI ~200 mg HC/g TOC. TOC and Rock Eval data show that subunit IIa holds a fair (to good hydrocarbon generative potential for oil, whereas the upper 5 m of unit III holds a good (to fair potential with the possibility to generate gas and minor oil. The rocks of both units are immature in the study area. Generally low sulphur contents are probably due to deposition in environments with reduced salinity. Normal marine conditions are suggested for unit III. Biomarker composition is typical for mixed marine and terrestrial organic matter and suggests deposition in dysoxic to anoxic environments.

  9. Automated Diatom Analysis Applied to Traditional Light Microscopy: A Proof-of-Concept Study

    Science.gov (United States)

    Little, Z. H. L.; Bishop, I.; Spaulding, S. A.; Nelson, H.; Mahoney, C.

    2017-12-01

    Diatom identification and enumeration by high resolution light microscopy is required for many areas of research and water quality assessment. Such analyses, however, are both expertise and labor-intensive. These challenges motivate the need for an automated process to efficiently and accurately identify and enumerate diatoms. Improvements in particle analysis software have increased the likelihood that diatom enumeration can be automated. VisualSpreadsheet software provides a possible solution for automated particle analysis of high-resolution light microscope diatom images. We applied the software, independent of its complementary FlowCam hardware, to automated analysis of light microscope images containing diatoms. Through numerous trials, we arrived at threshold settings to correctly segment 67% of the total possible diatom valves and fragments from broad fields of view. (183 light microscope images were examined containing 255 diatom particles. Of the 255 diatom particles present, 216 diatoms valves and fragments of valves were processed, with 170 properly analyzed and focused upon by the software). Manual analysis of the images yielded 255 particles in 400 seconds, whereas the software yielded a total of 216 particles in 68 seconds, thus highlighting that the software has an approximate five-fold efficiency advantage in particle analysis time. As in past efforts, incomplete or incorrect recognition was found for images with multiple valves in contact or valves with little contrast. The software has potential to be an effective tool in assisting taxonomists with diatom enumeration by completing a large portion of analyses. Benefits and limitations of the approach are presented to allow for development of future work in image analysis and automated enumeration of traditional light microscope images containing diatoms.

  10. All New Faces of Diatoms: Potential Source of Nanomaterials and Beyond

    Directory of Open Access Journals (Sweden)

    Meerambika Mishra

    2017-07-01

    Full Text Available Nature’s silicon marvel, the diatoms have lately astounded the scientific community with its intricate designs and lasting durability. Diatoms are a major group of phytoplanktons involved in the biogeochemical cycling of silica and are virtually inherent in every environment ranging from water to ice to soil. The usage of diatoms has proved prudently cost effective and its handling neither requires costly materials nor sophisticated instruments. Diatoms can easily be acquired from the environment, their culture requires ambient condition and does not involve any costly media or expensive instruments, besides, they can be transported in small quantities and proliferated to a desirable confluence from that scratch, thus are excellent cost effective industrial raw material. Naturally occurring diatom frustules are a source of nanomaterials. Their silica bio-shells have raised curiosity among nanotechnologists who hope that diatoms will facilitate tailoring minuscule structures which are beyond the capabilities of material scientists. Additionally, there is a colossal diversity in the dimensions of diatoms as the frustule shape differs from species to species; this provides a scope for the choice of a particular species of diatom to be tailored to an exacting requisite, thus paving the way to create desired three dimensional nanocomposites. The present article explores the use of diatoms in various arenas of science, may it be in nanotechnology, biotechnology, environmental science, biophysics or biochemistry and summarizes facets of diatom biology under one umbrella. Special emphasis has been given to biosilicification, biomineralization and use of diatoms as nanomaterials’, drug delivery vehicles, optical and immune-biosensors, filters, immunodiagnostics, aquaculture feeds, lab-on-a-chip, metabolites, and biofuels.

  11. Diatom species abundance and morphologically-based dissolution proxies in coastal Southern Ocean assemblages

    Science.gov (United States)

    Warnock, Jonathan P.; Scherer, Reed P.

    2015-07-01

    Taphonomic processes alter diatom assemblages in sediments, thus potentially negatively impacting paleoclimate records at various rates across space, time, and taxa. However, quantitative taphonomic data is rarely included in diatom-based paleoenvironmental reconstructions and no objective standard exists for comparing diatom dissolution in sediments recovered from marine depositional settings, including the Southern Ocean's opal belt. Furthermore, identifying changes to diatom dissolution through time can provide insight into the efficiency of both upper water column nutrient recycling and the biological pump. This is significant in that reactive metal proxies (e.g. Al, Ti) in the sediments only account for post-depositional dissolution, not the water column where the majority of dissolution occurs. In order to assess the range of variability of responses to dissolution in a typical Southern Ocean diatom community and provide a quantitative guideline for assessing taphonomic variability in diatoms recovered from core material, a sediment trap sample was subjected to controlled, serial dissolution. By evaluating dissolution-induced changes to diatom species' relative abundance, three preservational categories of diatoms have been identified: gracile, intermediate, and robust. The relative abundances of these categories can be used to establish a preservation grade for diatom assemblages. However, changes to the relative abundances of diatom species in sediment samples may reflect taphonomic or ecological factors. In order to address this complication, relative abundance changes have been tied to dissolution-induced morphological change to the areolae of Fragilariopsis curta, a significant sea-ice indicator in Southern Ocean sediments. This correlation allows differentiation between gracile species loss to dissolution versus ecological factors or sediment winnowing. These results mirror a similar morphological dissolution index from a parallel study utilizing

  12. Direct electroreduction of CO2 into hydrocarbon

    International Nuclear Information System (INIS)

    Winea, Gauthier; Ledoux, Marc-Jacques; Pham-Huu, Cuong; Gangeri, Miriam; Perathoner, Siglinda; Centi, Gabriele

    2006-01-01

    A lot of methods exist to directly reduce carbon dioxide into hydrocarbons: the photoelectrochemical process is certainly the most interesting, essentially due to the similarities with photosynthesis. As the human activities produce a great quantity of CO 2 , this one can then be considered as an infinite source of carbon. The products of this reaction are identical to those obtained during a Fischer-Tropsch reaction, that is to say hydrocarbons, alcohols and carboxylic acids. These works deal with the electrochemical reduction of CO 2 in standard conditions of temperature and pressure. The photochemical part has been replaced by a current generator as electrons source and a KHCO 3 aqueous solution as protons source. The first catalytic results clearly show that it is possible to reduce CO 2 into light hydrocarbons, typically from C1 to C9. (O.M.)

  13. Diatom Communities and Metrics as Indicators of Urbanization Effects on Streams and Potential Moderation by Landscape Green Infrastructure

    Science.gov (United States)

    Diatoms are very useful and important indicators of anthropogenic impacts on streams because they are the foundation of primary production and are responsive to nutrients, conductivity, and habitat conditions. We characterized relationships of diatom assemblages with water chemis...

  14. Growth inhibition of fouling bacteria and diatoms by extract of terrestrial plant, @iDerris scandens@@ (Dicotyledonae:Leguminocae)

    Digital Repository Service at National Institute of Oceanography (India)

    Sawant, S.S.; Sonak, S.; Garg, A.

    Methanol extract of terrestrial plant, @iDerris scandens@@ Benth, was found to inhibit growth of four diatoms and 7 bacterial species of fouling community. The concentrations required to bring about 100% inhibition of growth of the diatoms ranged...

  15. Growth inhibition of fouling bacteria and diatoms by extract of terrestrial plant, Derris scandens (Dicotyledonae:Leguminocae)

    Digital Repository Service at National Institute of Oceanography (India)

    Sawant, S.S.; Sonak, S.; Garg, A.

    Methanol extract of terrestrial plant, Derris scandens Benth, was found to inhibit growth of four diatoms and 7 bacterial species of fouling community. The concentrations required to bring about 100% inhibition of growth of the diatoms ranged...

  16. Action Spectrum of Photoinhibition in the Diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Havurinne, Vesa; Tyystjärvi, Esa

    2017-12-01

    Light-dependent electron transfer is necessary for photosynthesis, but light also damages PSII. Light-induced damage to PSII is called photoinhibition, and the damaging reactions of photoinhibition are still under debate. Diatoms possess an exotic combination of light-harvesting pigments, Chls a/c and fucoxanthin, making them an interesting platform for studying the photoreceptors of photoinhibition. We first confirmed the direct proportionality of photoinhibition to the photon flux density of incident light in the diatom Phaeodactylum tricornutum. Phaeodactylum is known for its efficient non-photochemical quenching, and the effect of this photoprotective mechanism on photoinhibition was tested. Photoinhibition proceeded essentially at the same rate in blue-light-grown Phaeodactylum cells that are capable of non-photochemical quenching and in red-light-grown, non-photochemical quenching-deficient cells. To obtain more insight into how the pigment composition of diatoms affects photoinhibition, we measured the action spectrum of photoinhibition in Phaeodactylum. In visible light, the action spectrum resembled the absorption spectrum of Phaeodactylum, and UV radiation caused much more photoinhibition than visible light. Comparison of the action spectrum of photoinhibition with the absorption spectrum and the excitation spectrum of 77 K PSII fluorescence emission confirmed that photosynthetic pigments are involved in photoinhibition, but the photoinhibitory efficiency of red light is weak, suggesting that the role of light-harvesting pigments as light receptors of photoinhibition is secondary. Finally, we compared photoinhibition in Phaeodactylum with that in other photosynthetic organisms, and our data indicate that the PSII reaction centers of Phaeodactylum are not particularly well protected against the primary damage of photoinhibition. © The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights

  17. Atom-diatom processes in helium

    International Nuclear Information System (INIS)

    Haftel, M.I.; Lim, T.K.

    1981-09-01

    Elastic and dissociative scattering of He on He 2 are studied for an incident laboratory energy of 1 0 K. We apply Faddeev-AGS multiple-scattering theory in momentum space to the analysis. We show that this leads to a simple justification for the importance of the 'complex-formation mechanism' in termolecular recombination, the time reverse of collision-induced dissociation. Our work, in which separable expansions of two phenomenological He-He potentials are used, predicts significant magnitude differences in the cross sections derived from the interactions and also verifies the validity of the 'peaking approximation' for hyperthermal-energy elastic collisions. (orig.)

  18. Distilling hydrocarbons, etc

    Energy Technology Data Exchange (ETDEWEB)

    Turner, C

    1917-11-23

    In the fractional or destructive distillation of hydrocarbon oils or other liquids, the pressure in the still is raised and lowered alternately. The still is closed to raise the pressure, and is opened to lower the pressure rapidly solely by expansion of the vapors. The operation is effected without intermittent cooling, except such as may occur during the lowering of the pressure. In distilling hydrocarbon oil, pressure steam is blown into the oil until the pressure reaches 5 lb/in./sup 2/. The vapor outlet is then opened until the pressure falls to 2 lb/in./sup 2/, whereupon the vapor outlet is closed and steam is again admitted. The operation is continued until the steam, which is of 20 lb pressure, no longer effects distillation; after this stage, superheated steam is used.

  19. Distilling hydrocarbon oils

    Energy Technology Data Exchange (ETDEWEB)

    Tausz, J

    1924-07-16

    Hydrocarbon oils such as petroleum, shale oils, lignite or coal tar oils are purified by distilling them and collecting the distillate in fractions within narrow limits so that all the impurities are contained in one or more of the narrow fractions. In distilling ligroin obtained by destructive distillation of brown coal, it is found that the coloring and resin-forming constituents are contained in the fractions distilling over at 62 to 86/sup 0/C and 108/sup 0/C. The ligroin is purified, therefore, by distillating in an apparatus provided with an efficient dephlegmotor and removing these two fractions. The distillation may be carried out wholly or in part under reduced pressure, and fractions separated under ordinary pressure may be subsequently distilled under reduced pressure. The hydrocarbons may be first separated into fractions over wider limits and the separate fractions be subjected to a further fractional distillation.

  20. Seasonal effects of cadmium accumulation in periphytic diatom communities of freshwater biofilms

    International Nuclear Information System (INIS)

    Thi Thuy Duong; Morin, Soizic; Herlory, Olivier; Feurtet-Mazel, Agnes; Coste, Michel; Boudou, Alain

    2008-01-01

    The relationships between diatom species and cadmium (Cd) accumulated in biofilms of the Riou-Mort River (SW, France) were studied in July 2004 and March 2005. Biofilms were sampled from artificial substrates immersed along a metallic pollution gradient during 20 days. Dynamics of diatom communities and cadmium accumulation were followed by collecting samples after 4, 7, 14 and 20 days of biofilm colonization. Cd accumulation in biofilms during experiment was significantly higher in Cd polluted station (Joanis) than in reference station (Firmi) for both seasons. Periphytic diatom composition varied between sites and seasons. At Firmi station, seasonal dynamics of diatom communities were stable with the dominance of Cyclotella meneghiniana and Melosira varians in July and Surirellabrebissonnii and Navicula gregaria in March. At Joanis station, diatom communities mainly responded to high levels of metal by a high proportion of small, adnate species. Positive correlations between Eolimna minima, Nitzschia palea, Encyonema minutum, Surirella angusta, and Gomphonema parvulum and cadmium accumulation were observed, indicating that these species are tolerant to high levels of cadmium. On the other hand, negative correlations of C. meneghiniana, N. gregaria, Navicula lanceolata, M. varians and Nitzschia dissipata with cadmium qualify them as sensitive diatom species. Periphytic diatom composition through the presence of specific species highlight metal tolerant indicator diatom groups which will be meaningful for biomonitoring pollution in natural aquatic systems

  1. The influence of land use on water quality and diatom community ...

    African Journals Online (AJOL)

    Epilithic diatom communities offer a holistic and integrated approach for assessing water quality as they remain in one place for a number of months and reflect an ecological memory of water quality over a period of time. The objective of this study is to use diatom assemblages to distinguish between particular land types ...

  2. Grazer-induced transcriptomic and metabolomic response of the chain-forming diatom Skeletonema marinoi

    DEFF Research Database (Denmark)

    Amato, Alberto; Sabatino, Valeria; Nylund, Göran M.

    2018-01-01

    Diatoms and copepods are main actors in marine food webs. The prey-predator interactions between them affect bloom dynamics, shape marine ecosystems and impact the energy transfer to higher trophic levels. Recently it has been demonstrated that the presence of grazers may affect the diatom prey b...

  3. Rotation-vibrational spectra of diatomic molecules and nuclei with Davidson interactions

    CERN Document Server

    Rowe, D J

    1998-01-01

    Complete rotation-vibrational spectra and electromagnetic transition rates are obtained for Hamiltonians of diatomic molecules and nuclei with Davidson interactions. Analytical results are derived by dynamical symmetry methods for diatomic molecules and a liquid-drop model of the nucleus. Numerical solutions are obtained for a many-particle nucleus with quadrupole Davidson interactions within the framework of the microscopic symplectic model. (author)

  4. Influence of land-use patterns on benthic diatom communities and ...

    African Journals Online (AJOL)

    The objective of this study was to determine the effects of land-use patterns on both diatom community composition and water quality in tropical streams during the dry season. Benthic diatom collections and water quality sampling were done 4 times at 10 sites. A suite of environmental variables that varied with human ...

  5. A stress surveillance system based on calcium and nitric oxide in marine diatoms

    NARCIS (Netherlands)

    Vardi, A.; Formiggini, F.; Casotti, R.; De Martino, A.; Ribalet, F.; Miralto, A.; Bowler, C.

    2006-01-01

    Diatoms are an important group of eukaryotic phytoplankton, responsible for about 20% of global primary productivity. Study of the functional role of chemical signaling within phytoplankton assemblages is still in its infancy although recent reports in diatoms suggest the existence of chemical-based

  6. A stress surveillance system based on calcium and nitric oxide in marine diatoms.

    NARCIS (Netherlands)

    Vardi, A.; Formiggini, F.; Casotti, R.; De Martino, A.; Ribalet, F.; Miralto, A.; Bowler, C.

    2006-01-01

    Diatoms are an important group of eukaryotic phytoplankton, responsible for about 20% of global primary productivity. Study of the functional role of chemical signaling within phytoplankton assemblages is still in its infancy although recent reports in diatoms suggest the existence of chemical-based

  7. Contribution to the Study of the flora diatomic Nahr Yahfufah (Lebanon)

    International Nuclear Information System (INIS)

    SLIM, K.; ALOUF, N.

    1984-01-01

    Contribution to the study of Diatomic flora on Nahr Yahfufah Lebanon. From October 1980 to June 1982 a hydrobiologic study has taken place on the river of Yahfufah situated to the west of anti Lebanon. From the diatomic population 52 species and varieties were designated. Further more the physico-chemical parameters were followed and studied. (author).

  8. Impact of marine influence and cultivation on the diatom flora of ...

    African Journals Online (AJOL)

    During a limnological and palaeolimnological study of the western part of the Great Coast of Senegal, an analysis of diatoms was carried out in Thiaroye Pond in the suburbs of Dakar. Current diatom flora in the water and on floating plants, and subfossil flora in two cores were sampled in 1996 and 2003. A total of 104 ...

  9. Seasonal effects of cadmium accumulation in periphytic diatom communities of freshwater biofilms

    Energy Technology Data Exchange (ETDEWEB)

    Thi Thuy Duong [Institute of Environmental Technology, Vietnamese Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay, Hanoi (Viet Nam); Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France)], E-mail: duongthuy0712@yahoo.com; Morin, Soizic [Cemagref, UR REBX, 50 avenue de Verdun, F-33612 Cestas cedex (France); Herlory, Olivier [Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France); Feurtet-Mazel, Agnes [Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France)], E-mail: a.feurtet-mazel@epoc.u-bordeaux1.fr; Coste, Michel [Cemagref, UR REBX, 50 avenue de Verdun, F-33612 Cestas cedex (France); Boudou, Alain [Universite de Bordeaux 1, CNRS, UMR 5805 EPOC, Place du Dr Peyneau, 33120 Arcachon (France)

    2008-10-20

    The relationships between diatom species and cadmium (Cd) accumulated in biofilms of the Riou-Mort River (SW, France) were studied in July 2004 and March 2005. Biofilms were sampled from artificial substrates immersed along a metallic pollution gradient during 20 days. Dynamics of diatom communities and cadmium accumulation were followed by collecting samples after 4, 7, 14 and 20 days of biofilm colonization. Cd accumulation in biofilms during experiment was significantly higher in Cd polluted station (Joanis) than in reference station (Firmi) for both seasons. Periphytic diatom composition varied between sites and seasons. At Firmi station, seasonal dynamics of diatom communities were stable with the dominance of Cyclotella meneghiniana and Melosira varians in July and Surirellabrebissonnii and Navicula gregaria in March. At Joanis station, diatom communities mainly responded to high levels of metal by a high proportion of small, adnate species. Positive correlations between Eolimna minima, Nitzschia palea, Encyonema minutum, Surirella angusta, and Gomphonema parvulum and cadmium accumulation were observed, indicating that these species are tolerant to high levels of cadmium. On the other hand, negative correlations of C. meneghiniana, N. gregaria, Navicula lanceolata, M. varians and Nitzschia dissipata with cadmium qualify them as sensitive diatom species. Periphytic diatom composition through the presence of specific species highlight metal tolerant indicator diatom groups which will be meaningful for biomonitoring pollution in natural aquatic systems.

  10. Paleoceanographic, and paleoclimatic constraints on the global Eocene diatom and silicoflagellate record

    Science.gov (United States)

    Barron, John A.; Stickley, Catherine E.; Bukry, David

    2015-01-01

    Eocene diatom and silicoflagellate biostratigraphy are summarized and correlated with the most recent geologic time scale as well as with the global oxygen isotope and eustatic sea level curves. The global distribution of Eocene diatom/silicoflagellate-bearing sediments varies considerably, reflecting changing oceanic gateways and paleoceanography with changing patterns that are punctuated by four major depositional events.

  11. An integrated analysis of molecular acclimation to high light in the marine diatom Phaeodactylum tricornutum

    DEFF Research Database (Denmark)

    Nymark, Marianne; Valle, Kristin C; Brembu, Tore

    2009-01-01

    Photosynthetic diatoms are exposed to rapid and unpredictable changes in irradiance and spectral quality, and must be able to acclimate their light harvesting systems to varying light conditions. Molecular mechanisms behind light acclimation in diatoms are largely unknown. We set out to investiga...

  12. Nuclear explosives and hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, P

    1971-10-01

    A nuclear explosive 12 in. in diam and producing very little tritium is feasible in France. Such a device would be well adapted for contained nuclear explosions set off for the purpose of hydrocarbon storage or stimulation. The different aspects of setting off the explosive are reviewed. In the particular case of gas storage in a nuclear cavity in granite, it is demonstrated that the dose of irradiation received is extremely small. (18 refs.)

  13. Treatment of hydrocarbon oils

    Energy Technology Data Exchange (ETDEWEB)

    1936-02-22

    A process is described for refining a mixture of liquid hydrocarbons containing harmful substances, this process permitting the operation, which consists in treating the liquid mixture at a temperature higher than 200/sup 0/C with a solid catalyst of phosphoric acid, consisting of phosphoric acid deposited on a solid support of the type of metallurgical coke, for a time sufficient to convert the harmful components to inoffensive substances.

  14. Biogeochemistry of Halogenated Hydrocarbons

    Science.gov (United States)

    Adriaens, P.; Gruden, C.; McCormick, M. L.

    2003-12-01

    Halogenated hydrocarbons originate from both natural and industrial sources. Whereas direct anthropogenic emissions to the atmosphere and biosphere are often easy to assess, particularly when they are tied to major industrial activities, the attribution of emissions to other human activities (e.g., biomass burning), diffuse sources (e.g., atmospheric discharge, run off), and natural production (e.g., soils, fungi, algae, microorganisms) are difficult to quantify. The widespread occurrence of both alkyl and aryl halides in groundwater, surface water, soils, and various trophic food chains, even those not affected by known point sources, suggests a substantial biogeochemical cycling of these compounds (Wania and Mackay, 1996; Adriaens et al., 1999; Gruden et al., 2003). The transport and reactive fate mechanisms controlling their reactivity are compounded by the differences in sources of alkyl-, aryl-, and complex organic halides, and the largely unknown impact of biogenic processes, such as enzymatically mediated halogenation of organic matter, fungal production of halogenated hydrocarbons, and microbial or abiotic transformation reactions (e.g., Asplund and Grimvall, 1991; Gribble, 1996; Watling and Harper, 1998; Oberg, 2002). The largest source may be the natural halogenation processes in the terrestrial environment, as the quantities detected often exceed the amount that can be explained by human activities in the surrounding areas ( Oberg, 1998). Since biogeochemical processes result in the distribution of a wide range of halogenated hydrocarbon profiles, altered chemical structures, and isomer distributions in natural systems, source apportionment (or environmental forensics) can often only be resolved using multivariate statistical methods (e.g., Goovaerts, 1998; Barabas et al., 2003; Murphy and Morrison, 2002).This chapter will describe the widespread occurrence of halogenated hydrocarbons, interpret their distribution and biogeochemical cycling in light of

  15. Cracking hydrocarbon oils

    Energy Technology Data Exchange (ETDEWEB)

    Seigle, A A.F.M.

    1922-12-20

    Hydrocarbon oils such as petroleum, peat, shale, or lignite oils, heavy tars, resin oils, naphthalene oils, etc., are vaporized by being fed from a tank through a preheater to the lower part of a vertical annular retort heated by a flame projected down the central cavity from a burner. The oil vapors rise through annular passages formed by disks, on which are placed chips of copper, iron, aluminum, etc., to act as catalysts.

  16. High boiling point hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Pier, M

    1929-04-29

    A process is given for the production of hydrocarbons of high boiling point, such as lubricating oils, from bituminous substances, such as varieties of coal, shale, or other solid distillable carbonaceous materials. The process consists of treating the initial materials with organic solvents and then subjecting the products extracted from the initial materials, preferably directly, to a reducing treatment in respect to temperature, pressure, and time. The reduction treatment is performed by means of hydrogen under pressure.

  17. Direct hydrocarbon fuel cells

    Science.gov (United States)

    Barnett, Scott A.; Lai, Tammy; Liu, Jiang

    2010-05-04

    The direct electrochemical oxidation of hydrocarbons in solid oxide fuel cells, to generate greater power densities at lower temperatures without carbon deposition. The performance obtained is comparable to that of fuel cells used for hydrogen, and is achieved by using novel anode composites at low operating temperatures. Such solid oxide fuel cells, regardless of fuel source or operation, can be configured advantageously using the structural geometries of this invention.

  18. Hydrocarbon production with nuclear explosives

    International Nuclear Information System (INIS)

    Wade Watkins, J.

    1970-01-01

    The tremendous energy of nuclear explosives and the small dimensions of the explosive package make an ideal combination for drill-hole explosive emplacement in deep, thick hydrocarbon deposits. Potential applications exist in fracturing low permeability natural-gas and petroleum formations for stimulating production, fracturing oil shale to permit in situ retorting, and creating storage chimneys for natural gas, liquefied petroleum gas, petroleum, petroleum products, helium, and other fluids. Calculations show, for example, that less than 100 shots per year would be needed to stabilize the natural gas reserves to production ratio. Under the Government-industry Plowshare program, two experiments, Projects Gasbuggy and Rulison, were conducted to stimulate natural gas production from low-permeability formations. Incomplete information indicates that both were technically successful. Potential problems associated with the use of nuclear explosives for underground engineering applications are radioactive contamination, maximum yield limitations, high costs of detonating contained nuclear explosives, and adverse public opinion. Results at Project Gasbuggy and other considerations indicated that the problem of radioactive contamination was about as predicted and not an insurmountable one. Also, it was demonstrated that shots at adequate depths could be detonated without appreciable damage to existing surface and subsurface buildings, natural features, and equipment. However, costs must be reduced and the public must be better informed before these techniques can be widely used in field operations. On the basis of present knowledge, the potential of nuclear-explosive stimulation of hydrocarbon production appears good. Additional field experiments will be required to adequately explore that potential. (author)

  19. Hydrocarbon production with nuclear explosives

    Energy Technology Data Exchange (ETDEWEB)

    Wade Watkins, J [Petroleum Research, Bureau of Mines, U.S. Department of the Interior, Washington, DC (United States)

    1970-05-01

    The tremendous energy of nuclear explosives and the small dimensions of the explosive package make an ideal combination for drill-hole explosive emplacement in deep, thick hydrocarbon deposits. Potential applications exist in fracturing low permeability natural-gas and petroleum formations for stimulating production, fracturing oil shale to permit in situ retorting, and creating storage chimneys for natural gas, liquefied petroleum gas, petroleum, petroleum products, helium, and other fluids. Calculations show, for example, that less than 100 shots per year would be needed to stabilize the natural gas reserves to production ratio. Under the Government-industry Plowshare program, two experiments, Projects Gasbuggy and Rulison, were conducted to stimulate natural gas production from low-permeability formations. Incomplete information indicates that both were technically successful. Potential problems associated with the use of nuclear explosives for underground engineering applications are radioactive contamination, maximum yield limitations, high costs of detonating contained nuclear explosives, and adverse public opinion. Results at Project Gasbuggy and other considerations indicated that the problem of radioactive contamination was about as predicted and not an insurmountable one. Also, it was demonstrated that shots at adequate depths could be detonated without appreciable damage to existing surface and subsurface buildings, natural features, and equipment. However, costs must be reduced and the public must be better informed before these techniques can be widely used in field operations. On the basis of present knowledge, the potential of nuclear-explosive stimulation of hydrocarbon production appears good. Additional field experiments will be required to adequately explore that potential. (author)

  20. Fossil diatoms imply common cometary origin of space-dust and the Polonnaruwa meteorite

    Science.gov (United States)

    Miyake, N.; Wallis, M. K.; Wickramasinghe, N. C.

    2013-09-01

    IDPs collected in 2001 at 40km altitude by cryosamplers studied via scanning electron microscopy and EDX were found to contain siliceous fibres and whiskers, some isolated but often embedded in a mineral matrix. The newly-arrived Polonnaruwa meteorite gives strong evidence for the hypothesis that they are fragments of diatoms agglomerating on solar system icy bodies. Diatom frustules and even whole diatom skeletons are identifiable within the meteorite. Specimens of a siliceous exoskeleton with multiple spines/whiskers have also been found, thought to be freshwater diatoms. As diatoms are dependent on a source of nitrogenous organics, the siliceous whiskers within IDPs would be an indicator of a photosynthesizing ecosystem, probably on a comet.

  1. Intensive aggregate formation with low vertical flux during an upwelling-induced diatom bloom

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Tiselius, P.; Mitchell-Innes, B.

    1998-01-01

    of turbulent shear in the ocean such stickiness coefficients predict very high specific coagulation rates (0.3 d(-1)). In situ video observation demonstrated the occurrence of abundant diatom aggregates with surface water concentrations between 1,000 and 3,000 ppm. Despite the very high concentration......The surfaces of most pelagic diatoms are sticky at times and may therefore form rapidly settling aggregates by physical coagulation. Stickiness and aggregate formation may be particularly adaptive in upwelling systems by allowing the retention of diatom populations in the vicinity of the upwelling...... center. We therefore hypothesized that upwelling diatom blooms are terminated by aggregate formation and rapid sedimentation. We monitored the development of a maturing diatom (mainly Chaetoceros spp.) bloom in the Benguela upwelling current during 7 d in February. Chlorophyll concentrations remained...

  2. Growth of fouling diatoms from the Zuari estuary, Goa (west coast of India) under different salinities in the laboratory

    Digital Repository Service at National Institute of Oceanography (India)

    Redekar, P.D.; Wagh, A.B.

    Diatoms take part in the initial process of fouling i.e. primary film formation. In order to understand the growth of the diatoms under different salinity conditions in the laboratory, this work was undertaken. Fouling diatoms on glass slides were...

  3. Structure of deformable diatomic molecules: a modified n-butane liquid

    International Nuclear Information System (INIS)

    Jang, Seanea; Kim, Soonchul; Lee, Songhi

    2005-01-01

    The density functional approximation for polyatomic molecules, which is based on the bridge function of the intermolecular interaction, was developed and applied to investigate the thermodynamic and the structural properties of deformable diatomic molecules. The Percus trick was employed to calculate the uniform structure of modified n-butane. The calculated static correlation functions were used to predict the density behaviors of a modified n-butane liquid at liquid-solid interfaces. The theoretical results show that (i) at low densities, the hypernetted-chain (HNC) equation compares with the density functional approximation based on the bridge function and that (ii) the relative population between the gauche and the trans states strongly affects the liquid structure at liquid-solid interfaces.

  4. Diatomáceas de tanques do cactário do Jardim Botânico, Guanabara, Brasil

    Directory of Open Access Journals (Sweden)

    Luis Tavares de Lyra

    1974-01-01

    Full Text Available O autor analisou a microflora de três tanques situados no Cactário do Jardim Botânico, Rio de Janeiro, Guanabara. Tanque nº 1. Apresentou desenvolvimento muito intenso da microfibra nos mseses mais frios. As diatomáceas foram muito freqüentes. As espécies indicadoras de saprobidade foram as seguintes: Gomphonema gracile Ehr., pinnularia maior. (kutz Cleve, Gomphonema parvulum (kutz Grunow, Navicula mutica Kutz., Pinnularia borealis Ehr., Pinnularia microstauron (Ehr Cleve, Pinnularia acrospheria Breb., Hantzschia amphioxys (Ehr Grunow, Nitzschia palea Kutz., Eutonia pectinalis (Kutz Rabenh. Tanque nº 2. As diatomáceas indicadoras de águas contaminadas, anotamos como segue: Eutonia pectinalis (Kutz Rabenh., Gomphonema parvulum (kutz Grunow, Hanstzschia amphioxys (Ehr Grunow, Navicula mutica Kutz, Pinnularia borealis Ehr., Pinnularia maior (Kutz Cleve, Pinnularia microstauron (Ehr Cleve. Tanque nº 3. Foi bastante reduzida a freqüência da microflora. Comparando-o com os tanques nº 1 e 2, as diatomáceas e clorofícias observadas, mostraram-se diminuídas nos meses mais quentes. Encontramos as seguintes espécies oligosaprobias: Eunotia pectinalis (Kutz Rabenh., Gomphonema gracile ehr., Gomphonema parvulum (Kutz Grunow Hantzschia amphioxys (Ehr Grunow, Pinnularia borealis Ehr., Pinnularia maior (Kutz Cleve. Foram consideradas também as clorofíceas quanto ao regime de saprobidade do material estudado. Eutonia augusta f. crenulata Cleve-Euler e Eutonia veneris var. exsecta Clever-Euler encontradas em nossas amostras, são novas para o Brasil. Um total de 71 espécies foram determinadas de 21 coletas realizadas durante o período de 36 meses.The author analysed the microflorafrom three ponds situated in the Cactarium from the Botanical Garden of Rio de Janeiro, Guanabara. Pond nº 1 - This pond showed a very intensive development of the microflora in the coldermonths. The diatoms were very frequent. Those diatoms that indicate saprobic

  5. A caveat regarding diatom-inferred nitrogen concentrations in oligotrophic lakes

    Science.gov (United States)

    Arnett, Heather A.; Saros, Jasmine E.; Mast, M. Alisa

    2012-01-01

    Atmospheric deposition of reactive nitrogen (Nr) has enriched oligotrophic lakes with nitrogen (N) in many regions of the world and elicited dramatic changes in diatom community structure. The lakewater concentrations of nitrate that cause these community changes remain unclear, raising interest in the development of diatom-based transfer functions to infer nitrate. We developed a diatom calibration set using surface sediment samples from 46 high-elevation lakes across the Rocky Mountains of the western US, a region spanning an N deposition gradient from very low to moderate levels (phosphorus, and hypolimnetic water temperature were related to diatom distributions. A transfer function was developed for nitrate and applied to a sedimentary diatom profile from Heart Lake in the central Rockies. The model coefficient of determination (bootstrapping validation) of 0.61 suggested potential for diatom-inferred reconstructions of lakewater nitrate concentrations over time, but a comparison of observed versus diatom-inferred nitrate values revealed the poor performance of this model at low nitrate concentrations. Resource physiology experiments revealed that nitrogen requirements of two key taxa were opposite to nitrate optima defined in the transfer function. Our data set reveals two underlying ecological constraints that impede the development of nitrate transfer functions in oligotrophic lakes: (1) even in lakes with nitrate concentrations below quantification (<1 μg L−1), diatom assemblages were already dominated by species indicative of moderate N enrichment; (2) N-limited oligotrophic lakes switch to P limitation after receiving only modest inputs of reactive N, shifting the controls on diatom species changes along the length of the nitrate gradient. These constraints suggest that quantitative inferences of nitrate from diatom assemblages will likely require experimental approaches.

  6. In vivo exposure to northern diatoms arrests sea urchin embryonic development.

    Science.gov (United States)

    Gudimova, Elena; Eilertsen, Hans C; Jørgensen, Trond Ø; Hansen, Espen

    2016-01-01

    There are numerous reports indicating that marine diatoms may act harmful to early developmental stages of invertebrates. It is believed that the compounds responsible for these detrimental effects are oxylipins resulting from oxidized polyunsaturated fatty acids, and that they may function as grazing deterrents. Most studies reporting these effects have exposed test organisms to diatom extracts or purified toxins, but data from in vivo exposure to intact diatoms are scarce. We have conducted sea urchin egg incubation and plutei feeding experiments to test if intact diatom cells affected sea urchin embryo development and survival. This was done by exposing the common northern sea urchins Strongylocentrotus droebachiensis and Echinus acutus to northern strains of the diatoms Chaetoceros socialis, Skeletonema marinoi, Chaetoceros furcellatus, Attheya longicornis, Thalassiosira gravida and Porosira glacialis. The intact diatom cell suspensions were found to inhibit sea urchin egg hatching and embryogenesis. S. marinoi was the most potent one as it caused acute mortality in S. droebachiensis eggs after only four hours exposure to high (50 μg/L Chla) diatom concentrations, as well as 24 h exposure to normal (20 μg/L Chla) and high diatom concentrations. The second most potent species was T. gravida that caused acute mortality after 24 h exposure to both diatom concentrations. A. longicornis was the least harmful of the diatom species in terms of embryo development arrestment, and it was the species that was most actively ingested by S. droebachiensis plutei. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  7. Symmetries and rotational line intensities in diatomic molecules

    International Nuclear Information System (INIS)

    Veseth, L.

    1986-02-01

    The general theory of angular momenta and the full rotation group is used to reconsider the theory of the intensity factors of rotational lines in the spectra of diatomic molecules (Hoenl-London factors). It is shown that the use of the rotational symmetry (rotation matrices) leads to compact derivations of the symmetry properties of the molecular wave functions, as well as the matrix elements of the transitions operator. The present work is restricted to spin-allowed electric dipole transitions, and the general sum rule characteristic of this type of transitions is rederived by use of the general angular momentum theory. A main purpose of the present work has been to provide a unified theoretical basis for exact numerical computations of Hoenl-London factors for all types of spin-allowed electric dipole transitions in diatomic molecules. The computed Hoenl-London factors are then in the next step intended to be the basis for construction of synthetic molecular band spectra, with particular applications to upper atmosperic emissions (aurora)

  8. Study on the excited diatomic molecules of rare gas

    International Nuclear Information System (INIS)

    Kasama, Kunihiko; Arai, Shigeyoshi

    1981-01-01

    The study on the excited diatomic molecules of rare gas is presented. The absorption spectra, the mechanism of formation and attenuation and the reactions with other molecules are described. The excitation of rare gas was made by using a pulsed electron beam generator. The absorption of excited diatomic molecules was measured as the functions of time. Two absorption peaks were observed. The electron states of rare gases were estimated. The observed and calculated transition values were given for each peak. The absorption spectra of Ne change with time. The spectra of Ar do not change with time. Four and eleven absorption maxima were seen in the spectra of Kr and Xe, respectively. In the case of Ar, the thermal equilibrium existed. The constants of the production and attenuation rates were obtained as the functions of Ar gas pressure. In the case of Ne, there wad definitely the time dependence of absorption spectra. The attenuation constant was obtained for each transition between various vibration levels. It is necessary to consider the relaxation from high vibrational levels. The energy transfer between vibrational levels hardly occurred in Ne because the intervals are large. When there are other molecules, the attnuation was accelerated. (Kato, T.)

  9. Study on surface geochemistry and microbiology for hydrocarbon exploration

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-01

    The test results of the experimental device for extraction of dissolved gases from water show that the device can be utilized for the gas geochemistry of water. The device is capable of determining hydrocarbon gases in water to the concentration of less than 5 x 10{sup -4} ml/l of water. According to the results of microbiological studies, the plate count technique can be a useful supplementary method for hydrocarbon exploration. This is based on the facts that the average survival rate to hydrocarbons (pentane, hexane) for heterotrophs is higher in the area known as containing considerable hydrocarbon gases than other areas in the Pohang region. However, it is still necessary to develop techniques to treat the bacteria with gaseous hydrocarbons. (author). 2 figs., 41 tabs.

  10. Imaging fluid/solid interactions in hydrocarbon reservoir rocks.

    Science.gov (United States)

    Uwins, P J; Baker, J C; Mackinnon, I D

    1993-08-01

    The environmental scanning electron microscope (ESEM) has been used to image liquid hydrocarbons in sandstones and oil shales. Additionally, the fluid sensitivity of selected clay minerals in hydrocarbon reservoirs was assessed via three case studies: HCl acid sensitivity of authigenic chlorite in sandstone reservoirs, freshwater sensitivity of authigenic illite/smectite in sandstone reservoirs, and bleach sensitivity of a volcanic reservoir containing abundant secondary chlorite/corrensite. The results showed the suitability of using ESEM for imaging liquid hydrocarbon films in hydrocarbon reservoirs and the importance of simulating in situ fluid-rock interactions for hydrocarbon production programmes. In each case, results of the ESEM studies greatly enhanced prediction of reservoir/borehole reactions and, in some cases, contradicted conventional wisdom regarding the outcome of potential engineering solutions.

  11. Degradation of petroleum hydrocarbons in a laboratory aquifer column

    International Nuclear Information System (INIS)

    Billowits, M.; Whyte, L.; Greer, C.; Ramsay, J.

    1998-01-01

    One of the primary mechanisms for eliminating hydrocarbon pollutants from the environment is degradation of hydrocarbons by indigenous microorganisms. This report describes a study in which samples from a petroleum polluted shallow aquifer in the Yukon were used which contained a hundred times greater concentration of psychrotropic bacteria than mesophilic bacteria. Results showed a maximum degradation of 47 per cent of the total petroleum hydrocarbon in columns which simulated the aquifer conditions and to which nutrients were added. It was concluded that although in this case bioaugmentation of the columns with a psychrotropic hydrocarbon-degrading consortium increased microbial numbers, total petroleum hydrocarbon degradation was not much greater than could be achieved by remediation with nutrients alone

  12. Performance estimation of ejector cycles using heavier hydrocarbon refrigerants

    International Nuclear Information System (INIS)

    Kasperski, Jacek; Gil, Bartosz

    2014-01-01

    Computer software basing on theoretical model of Huang et al. with thermodynamic properties of hydrocarbons was prepared. Investigation was focused on nine hydrocarbons: propane, butane, iso-butane, pentane, iso-pentane, hexane, heptane and octane. A series of calculations was carried out for the generator temperature between 70 and 200 °C, with assumed temperatures of evaporation 10 °C and condensation 40 °C. Calculation results show that none of the hydrocarbons enables high efficiency of a cycle in a wide range of temperature. Each hydrocarbon has its own maximal entrainment ratio at its individual temperature of optimum. Temperatures of entrainment ratios optimum increase according to the hydrocarbon heaviness with simultaneous increase of entrainment ratio peak values. Peak values of the COP do not increase according to the hydrocarbons heaviness. The highest COP = 0.32 is achieved for iso-butane at 102 °C and the COP = 0.28 for pentane at 165 °C. Heptane and octane can be ignored. - Highlights: • Advantages of use of higher hydrocarbons as ejector refrigerants were presumed. • Computer software basing on theoretical model of Huang et al. (1999) was prepared. • Optimal temperature range of vapor generation for each hydrocarbon was calculated

  13. Measuring Trace Hydrocarbons in Silanes

    Science.gov (United States)

    Lesser, L. A.

    1984-01-01

    Technique rapid and uses standard analytical equipment. Silane gas containing traces of hydrocarbons injected into carrier gas of moist nitrogen having about 0.2 percent water vapor. Carrier, water and silane pass through short column packed with powdered sodium hydroxide which combines moisture and silane to form nonvolatile sodium silicate. Carrier gas free of silane but containing nonreactive hydrocarbons, pass to silica-gel column where chromatographic separation takes place. Hydrocarbons measured by FID.

  14. Gamma-radiation induced polymerization of methyl methacrylate in aliphatic hydrocarbons: kinetics and evidence for incorporation of hydrocarbon in the polymer chain

    International Nuclear Information System (INIS)

    Mohan, H.; Iyer, R.M.

    1989-01-01

    On γ-radiolysis, the rate of polymerization of methyl methacrylate in hydrocarbon solvents is observed to decrease. It is explained by hydrocarbon entry into the polymer chains. The hydrocarbon entry into the polymer chains is observed to take place at later stages of polymerization and increases with hydrocarbon chain length. The extent of hydrocarbon entry into the polymer chains is estimated by NMR and GLC analysis. It is observed to be equal to ∼ 12% corresponding to ∼ 97 hexadecane molecules in each polymer chain. The IR, DSC, MW determination and radiation effects on the polymer showed evidences for hydrocarbon entry into the polymer. It is explained by chain transfer from the growing polymer radical to the hydrocarbon molecules. The chain transfer constant is determined to be equal to 1 x 10 -2 . (author)

  15. Fractional separation of hydrocarbon vapours

    Energy Technology Data Exchange (ETDEWEB)

    1937-07-10

    A process is described for converting higher boiling hydrocarbons to lower boiling hydrocarbons by subjecting them at elevated temperatures to a conversion operation, then separating the higher and lower boiling fractions. The separation takes place while the reaction products are maintained in the vapor phase by contact with a mass of solid porous material which has little or no catalytic activity but does have a preferential absorption property for higher boiling hydrocarbons so that the lower boiling part of the reaction products pass through the separation zone while the heavier hydrocarbons are retained. The separation is accomplished without substantial loss of heat of these reaction products.

  16. Ecophysiological and biochemical variation of the surf zone diatom asterionellopsis glacialis sensu lato from Santa Catarina, Southern Brazil

    Directory of Open Access Journals (Sweden)

    Leonardo Rubi Rörig

    Full Text Available Abstract Patches formed by dense accumulations of diatoms in the surf zone (surf diatoms are common on sandy beaches with intermediate to dissipative morphodynamic states. Their appearances are correlated with environmental factors such as the passage of cold fronts when onshore winds increase beach hydrodynamics, resuspending epibenthic stocks and accumulating them through the inner surf zone. In Santa Catarina state, Southern Brazil, two beaches are known to have frequent occurrence of accumulations of the surf diatom Asterionellopsis glacialis sensu lato: Rincão Beach (28°50' S and Navegantes Beach (26°52' S. The high biomass of this alga and its central importance in the trophic structure of the coastal ecosystems suggest studies about its potential applications. In the present study, strains of A. glacialis were isolated, cultured under different conditions and evaluated for ecophysiological aspects: growth rate under different conditions, potential biological activities of exudates, biomass and lipid content, and fatty acid profile. A. glacialis cells in culture showed deformation, which were ameliorated by using agitation and silicon and phosphorus enriched culture media. Exudates of the strains showed no allelopathic effects, although previous studies have indicated activity. Lipid content showed variation depending on the strain and culture media. Values ranged from 9% to 13.6% by dry weight. In all strains saturated fatty acids and polyunsaturated fatty acids were identified. Some hypotheses were proposed to explain the variation of the lipid contents, fatty acid profiles and physiological features between strains of the same species. We believe that the fatty acids profile of this primary producer has important consequences in the sandy beach ecology.

  17. Identification and functional analysis of delta-9 desaturase, a key enzyme in PUFA Synthesis, isolated from the oleaginous diatom Fistulifera.

    Directory of Open Access Journals (Sweden)

    Masaki Muto

    Full Text Available Oleaginous microalgae are one of the promising resource of nonedible biodiesel fuel (BDF feed stock alternatives. Now a challenge task is the decrease of the long-chain polyunsaturated fatty acids (PUFAs content affecting on the BDF oxidative stability by using gene manipulation techniques. However, only the limited knowledge has been available concerning the fatty acid and PUFA synthesis pathways in microalgae. Especially, the function of Δ9 desaturase, which is a key enzyme in PUFA synthesis pathway, has not been determined in diatom. In this study, 4 Δ(9 desaturase genes (fD9desA, fD9desB, fD9desC and fD9desD from the oleaginous diatom Fistulifera were newly isolated and functionally characterized. The putative Δ(9 acyl-CoA desaturases in the endoplasmic reticulum (ER showed 3 histidine clusters that are well-conserved motifs in the typical Δ(9 desaturase. Furthermore, the function of these Δ(9 desaturases was confirmed in the Saccharomyces cerevisiae ole1 gene deletion mutant (Δole1. All the putative Δ(9 acyl-CoA desaturases showed Δ(9 desaturation activity for C16∶0 fatty acids; fD9desA and fD9desB also showed desaturation activity for C18∶0 fatty acids. This study represents the first functional analysis of Δ(9 desaturases from oleaginous microalgae and from diatoms as the first enzyme to introduce a double bond in saturated fatty acids during PUFA synthesis. The findings will provide beneficial insights into applying metabolic engineering processes to suppressing PUFA synthesis in this oleaginous microalgal strain.

  18. Identification and functional analysis of delta-9 desaturase, a key enzyme in PUFA Synthesis, isolated from the oleaginous diatom Fistulifera.

    Science.gov (United States)

    Muto, Masaki; Kubota, Chihiro; Tanaka, Masayoshi; Satoh, Akira; Matsumoto, Mitsufumi; Yoshino, Tomoko; Tanaka, Tsuyoshi

    2013-01-01

    Oleaginous microalgae are one of the promising resource of nonedible biodiesel fuel (BDF) feed stock alternatives. Now a challenge task is the decrease of the long-chain polyunsaturated fatty acids (PUFAs) content affecting on the BDF oxidative stability by using gene manipulation techniques. However, only the limited knowledge has been available concerning the fatty acid and PUFA synthesis pathways in microalgae. Especially, the function of Δ9 desaturase, which is a key enzyme in PUFA synthesis pathway, has not been determined in diatom. In this study, 4 Δ(9) desaturase genes (fD9desA, fD9desB, fD9desC and fD9desD) from the oleaginous diatom Fistulifera were newly isolated and functionally characterized. The putative Δ(9) acyl-CoA desaturases in the endoplasmic reticulum (ER) showed 3 histidine clusters that are well-conserved motifs in the typical Δ(9) desaturase. Furthermore, the function of these Δ(9) desaturases was confirmed in the Saccharomyces cerevisiae ole1 gene deletion mutant (Δole1). All the putative Δ(9) acyl-CoA desaturases showed Δ(9) desaturation activity for C16∶0 fatty acids; fD9desA and fD9desB also showed desaturation activity for C18∶0 fatty acids. This study represents the first functional analysis of Δ(9) desaturases from oleaginous microalgae and from diatoms as the first enzyme to introduce a double bond in saturated fatty acids during PUFA synthesis. The findings will provide beneficial insights into applying metabolic engineering processes to suppressing PUFA synthesis in this oleaginous microalgal strain.

  19. Formation of polycyclic aromatic hydrocarbons by ionizing radiations

    International Nuclear Information System (INIS)

    Perez, G.; Lilia, E.; Cristalli, A.

    1986-01-01

    Gaseous 0-terphenyl, 1-phenylnaphthalene, and 9-phenylanthracene were submitted to gamma rays. The yields of cyclization products, polycyclic aromatic hydrocarbons, show that at least one twentieth of the intermediates formed undergo intramolecular reaction. (author)

  20. Identification of the meiotic toolkit in diatoms and exploration of meiosis-specific SPO11 and RAD51 homologs in the sexual species Pseudo-nitzschia multistriata and Seminavis robusta.

    Science.gov (United States)

    Patil, Shrikant; Moeys, Sara; von Dassow, Peter; Huysman, Marie J J; Mapleson, Daniel; De Veylder, Lieven; Sanges, Remo; Vyverman, Wim; Montresor, Marina; Ferrante, Maria Immacolata

    2015-11-14

    Sexual reproduction is an obligate phase in the life cycle of most eukaryotes. Meiosis varies among organisms, which is reflected by the variability of the gene set associated to the process. Diatoms are unicellular organisms that belong to the stramenopile clade and have unique life cycles that can include a sexual phase. The exploration of five diatom genomes and one diatom transcriptome led to the identification of 42 genes potentially involved in meiosis. While these include the majority of known meiosis-related genes, several meiosis-specific genes, including DMC1, could not be identified. Furthermore, phylogenetic analyses supported gene identification and revealed ancestral loss and recent expansion in the RAD51 family in diatoms. The two sexual species Pseudo-nitzschia multistriata and Seminavis robusta were used to explore the expression of meiosis-related genes: RAD21, SPO11-2, RAD51-A, RAD51-B and RAD51-C were upregulated during meiosis, whereas other paralogs in these families showed no differential expression patterns, suggesting that they may play a role during vegetative divisions. An almost identical toolkit is shared among Pseudo-nitzschia multiseries and Fragilariopsis cylindrus, as well as two species for which sex has not been observed, Phaeodactylum tricornutum and Thalassiosira pseudonana, suggesting that these two may retain a facultative sexual phase. Our results reveal the conserved meiotic toolkit in six diatom species and indicate that Stramenopiles share major modifications of canonical meiosis processes ancestral to eukaryotes, with important divergences in each Kingdom.

  1. Process for preparing hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Krauch, C; Anther, E; Pier, M

    1926-04-07

    A process is described for the conversion of coal of all kinds, wood, oil, shale, as well as other carbonaceous materials into liquid hydrocarbons in two steps, characterized by treatment of the coal and so forth with a stream of hydrogen or hydrogen-containing gases at raised temperatures and raised pressures and producing a tarry product which, after separation of the ashlike residue, is converted by a further treatment, in the presence of catalysts, with hydrogen or hydrogen-containing gases at raised temperature and pressure, largely into low-boiling products.

  2. Recovering valuable liquid hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Pier, M

    1931-06-11

    A process for recovering valuable liquid hydrocarbons from coking coal, mineral coal, or oil shale through treatment with hydrogen under pressure at elevated temperature is described. Catalysts and grinding oil may be used in the process if necessary. The process provides for deashing the coal prior to hydrogenation and for preventing the coking and swelling of the deashed material. During the treatment with hydrogen, the coal is either mixed with coal low in bituminous material, such as lean coal or active coal, as a diluent or the bituminous constituents which cause the coking and swelling are removed by extraction with solvents. (BLM)

  3. Evidence for middle Eocene Arctic sea ice from diatoms and ice-rafted debris.

    Science.gov (United States)

    Stickley, Catherine E; St John, Kristen; Koç, Nalân; Jordan, Richard W; Passchier, Sandra; Pearce, Richard B; Kearns, Lance E

    2009-07-16

    Oceanic sediments from long cores drilled on the Lomonosov ridge, in the central Arctic, contain ice-rafted debris (IRD) back to the middle Eocene epoch, prompting recent suggestions that ice appeared in the Arctic about 46 million years (Myr) ago. However, because IRD can be transported by icebergs (derived from land-based ice) and also by sea ice, IRD records are restricted to providing a history of general ice-rafting only. It is critical to differentiate sea ice from glacial (land-based) ice as climate feedback mechanisms vary and global impacts differ between these systems: sea ice directly affects ocean-atmosphere exchanges, whereas land-based ice affects sea level and consequently ocean acidity. An earlier report assumed that sea ice was prevalent in the middle Eocene Arctic on the basis of IRD, and although somewhat preliminary supportive evidence exists, these data are neither comprehensive nor quantified. Here we show the presence of middle Eocene Arctic sea ice from an extraordinary abundance of a group of sea-ice-dependent fossil diatoms (Synedropsis spp.). Analysis of quartz grain textural characteristics further supports sea ice as the dominant transporter of IRD at this time. Together with new information on cosmopolitan diatoms and existing IRD records, our data strongly suggest a two-phase establishment of sea ice: initial episodic formation in marginal shelf areas approximately 47.5 Myr ago, followed approximately 0.5 Myr later by the onset of seasonally paced sea-ice formation in offshore areas of the central Arctic. Our data establish a 2-Myr record of sea ice, documenting the transition from a warm, ice-free environment to one dominated by winter sea ice at the start of the middle Eocene climatic cooling phase.

  4. Direct fit of spectroscopic data of diatomic molecules by using genetic algorithms: II. The ground state of RbCs

    International Nuclear Information System (INIS)

    Almeida, Marcos M; Prudente, Frederico V; Fellows, Carlos E; Marques, Jorge M C; Pereira, Francisco B

    2011-01-01

    We extend our previous methodology based on genetic algorithms (Marques et al 2008 J. Phys. B: At. Mol. Opt. Phys. 41 085103) to carry out the challenging fit of the RbCs potential curve to spectroscopic data. Specifically, we have fitted an analytic functional form to line positions of the high-resolution Fourier transform spectrum of RbCs obtained by a laser-induced fluorescence technique. The results for the ground electronic state of RbCs show that the present method provides an efficient way to obtain diatomic potentials with great accuracy.

  5. What if the Diatoms of the Deep Chlorophyll Maximum Can Ascend?

    Science.gov (United States)

    Villareal, T. A.

    2016-02-01

    Buoyancy regulation is an integral part of diatom ecology via its role in sinking rates and is fundamental to understanding their distribution and abundance. Numerous studies have documented the effects of size and nutrition on sinking rates. Many pelagic diatoms have low intrinsic sinking rates when healthy and nutrient-replete (deep chlorophyll maximum. The potential for ascending behavior adds an additional layer of complexity by allowing both active depth regulation similar to that observed in flagellated taxa and upward transport by some fraction of deep euphotic zone diatom blooms supported by nutrient injection. In this talk, I review the data documenting positive buoyancy in small diatoms, offer direct visual evidence of ascending behavior in common diatoms typical of both oceanic and coastal zones, and note the characteristics of sinking rate distributions within a single species. Buoyancy control leads to bidirectional movement at similar rates across a wide size spectrum of diatoms although the frequency of ascending behavior may be only a small portion of the individual species' abundance. While much remains to be learned, the paradigm of unidirectional downward movement by diatoms is both inaccurate and an oversimplification.

  6. Review--Interactions between diatoms and stainless steel: focus on biofouling and biocorrosion.

    Science.gov (United States)

    Landoulsi, J; Cooksey, K E; Dupres, V

    2011-11-01

    There is a considerable body of information regarding bacterially enhanced corrosion, however, this review focuses on diatoms (unicellular algae) whose contribution to biocorrosion is less well studied. The reasons why diatoms have been neglected in studies of biocorrosion in natural waters are discussed and the question whether diatoms should be considered as inert with respect of electrochemical processes is considered. A particular focus is given to the case of stainless steels (SS), which are widely used in variety of applications in natural waters. Basic information on the cell biology of diatoms is included in the review, particularly with respect to their ability to 'sense' and adhere to surfaces. Investigations at the nanoscale are reviewed as these studies provide information about the behavior of cells at interfaces. Recent advances include the use of atomic force microscopy (AFM), although only a few studies have been applied to diatoms. Regarding the electrochemical behavior of SS, the mechanisms by which diatoms influence the potential ennoblement process is discussed. Such studies reveal the association of diatoms, in addition to bacteria, with biocorrosion processes.

  7. Investigation of the hydrodynamic behavior of diatom aggregates using particle image velocimetry.

    Science.gov (United States)

    Xiao, Feng; Li, Xiaoyan; Lam, Kitming; Wang, Dongsheng

    2012-01-01

    The hydrodynamic behavior of diatom aggregates has a significant influence on the interactions and flocculation kinetics of algae. However, characterization of the hydrodynamics of diatoms and diatom aggregates in water is rather difficult. In this laboratory study, an advanced visualization technique in particle image velocimetry (PIV) was employed to investigate the hydrodynamic properties of settling diatom aggregates. The experiments were conducted in a settling column filled with a suspension of fluorescent polymeric beads as seed tracers. A laser light sheet was generated by the PIV setup to illuminate a thin vertical planar region in the settling column, while the motions of particles were recorded by a high speed charge-coupled device (CCD) camera. This technique was able to capture the trajectories of the tracers when a diatom aggregate settled through the tracer suspension. The PIV results indicated directly the curvilinear feature of the streamlines around diatom aggregates. The rectilinear collision model largely overestimated the collision areas of the settling particles. Algae aggregates appeared to be highly porous and fractal, which allowed streamlines to penetrate into the aggregate interior. The diatom aggregates have a fluid collection efficiency of 10%-40%. The permeable feature of aggregates can significantly enhance the collisions and flocculation between the aggregates and other small particles including algal cells in water.

  8. First Morphological and Molecular Evidence of the Negative Impact of Diatom-Derived Hydroxyacids on the Sea Urchin Paracentrotus lividus

    Science.gov (United States)

    Varrella, Stefano; Romano, Giovanna; Ruocco, Nadia; Ianora, Adrianna; Bentley, Matt G.; Costantini, Maria

    2016-01-01

    Oxylipins (including polyunsaturated aldehydes [PUAs], hydoxyacids, and epoxyalcohols) are the end-products of a lipoxygenase/hydroperoxide lyase metabolic pathway in diatoms. To date, very little information is available on oxylipins other than PUAs, even though they represent the most common oxylipins produced by diatoms. Here, we report, for the first time, on the effects of 2 hydroxyacids, 5- and 15-HEPE, which have never been tested before, using the sea urchin Paracentrotus lividus as a model organism. We show that HEPEs do induce developmental malformations but at concentrations higher when compared with PUAs. Interestingly, HEPEs also induced a marked developmental delay in sea urchin embryos, which has not hitherto been reported for PUAs. Recovery experiments revealed that embryos do not recover following treatment with HEPEs. Finally, we report the expression levels of 35 genes (involved in stress, development, differentiation, skeletogenesis, and detoxification processes) to identify the molecular targets affected by HEPEs. We show that the 2 HEPEs have very few common molecular targets, specifically affecting different classes of genes and at different times of development. In particular, 15-HEPE switched on fewer genes than 5-HEPE, upregulating mainly stress-related genes at a later pluteus stage of development. 5-HEPE was stronger than 15-HEPE, targeting 24 genes, mainly at the earliest stages of embryo development (at the blastula and swimming blastula stages). These findings highlight the differences between HEPEs and PUAs and also have important ecological implications because many diatom species do not produce PUAs, but rather these other chemicals are derived from the oxidation of fatty acids. PMID:26984781

  9. Winter atmospheric circulation signature for the timing of the spring bloom of diatoms in the North Sea

    Science.gov (United States)

    Lohmann, Gerrit; Wiltshire, Karen

    2015-04-01

    Analysing long-term diatom data from the German Bight and observational climate data for the period 1962-2005, we found a close connection of the inter-annual variation of the timing of the spring bloom with the boreal winter atmospheric circulation. We examined the fact that high diatom counts of the spring bloom tended to occur later when the atmospheric circulation was characterized by winter blocking over Scandinavia. The associated pattern in the sea level pressure showed a pressure dipole with two centres located over the Azores and Norway and was tilted compared to the North Atlantic Oscillation. The bloom was earlier when the cyclonic circulation over Scandinavia allowed an increased inflow of Atlantic water into the North Sea which is associated with clearer, more marine water, and warmer conditions. The bloom was later when a more continental atmospheric flow from the east was detected. At Helgoland Roads, it seems that under turbid water conditions (= low light) zooplankton grazing can affect the timing of the phytoplankton bloom negatively. Warmer water temperatures will facilitate this. Under clear water conditions, light will be the main governing factor with regard to the timing of the spring bloom. These different water conditions are shown here to be mainly related to large-scale weather patterns. We found that the mean diatom bloom could be predicted from the sea level pressure one to three months in advance. Using historical pressure data, we derived a proxy for the timing of the spring bloom over the last centuries, showing an increased number of late (proxy-) blooms during the eighteenth century when the climate was considerably colder than today. We argue that these variations are important for the interpretation of inter-annual to centennial variations of biological processes. This is of particular interest when considering future scenarios, as well to considerations on past and future effects on the primary production and food webs.

  10. Diatoms as an indicator for tile drainage flow in a German lowland catchment.

    Science.gov (United States)

    Wu, Naicheng; Faber, Claas; Ulrich, Uta; Fohrer, Nicola

    2018-01-01

    The separation of runoff components within a model simulation is of great importance for a successful implementation of management measures. Diatoms could be a promising indicator for tile drainage flow due to their diverse preferences to different aquatic habitats. In this study, we collected diatom samples of 9 sites (4 tile drainage, TD, and 5 river sites, Ri) in a German lowland catchment at a weekly or biweekly time step from March to July 2013 with the aim of testing the suitability of diatoms for tile drainage flow, which is typical for lowland catchment. Planothidium lanceolatum , Ulnaria biceps , and Navicula gregaria dominated in TD sites with relative abundances of 22.2, 21.5, and 10.9%, respectively. For Ri sites, the most abundant species was Navicula lanceolata (20.5%), followed by Ulnaria biceps (12.9%), Cyclotella meneghiniana (9.5%), and Planothidium lanceolatum (9.3%). Compared with Ri sites, TD had a lower diatom density, biomass, species richness, and percentage of Aquatic/Riparian diatoms (AqRi%). However, the proportion of Riparian diatoms (RiZo%) increased at TD. Indicator value method (IndVal) revealed that the two groups (Ri and TD) were characterized by different indicator species. Fifteen taxa, including Cocconeis placentula , Cyclotella meneghiniana , N. lanceolata , and U. biceps , were significant indicators for Ri sites. Planothidium lanceolatum , Achnanthidium minutissimum , and Navicula gregaria were significant indicators for TD sites. A pronounced variation was found in the species lists of diatom community between Ri and TD water body types associated with different indicator species. With respect to hydrograph separation, these findings highlight the suitability of diatoms as an indicator for tile drainage flow. However, spatial and temporal variations of diatoms should be considered in future surveys.

  11. Determination of polynuclear hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Lodge, Jr, J P

    1963-01-01

    At the present time, the method of choice for the determination of polynuclear hydrocarbons appears to be the following, (a) extraction of the benzene-soluble fraction from the gross collected particulate matter, (b) one pass through a chromatographic column of partially deactivated alumina, (c) spectral examination of the fractions and (d) the application of appropriate chemical tests as indicated by the previous step. Using this method, the presence of pyrene, fluoranthene, one of the benzofluorenes, chrysens, benz(a)anthracene, benzo(a)pyrene, benzo(e)pyrene, benzo(k)fluoranthene, anthanthrene, and coronene was demonstrated in the air of numerous American cities, and benzo(a)pyrene was measured at some 130 sites. Invaluable as such accurate determinations may be for research purposes, they are still too costly and time-consuming for routine survey purposes. While studies on the subject are by no means complete, they indicate the validity of piperonal chloride test as a general index of polycyclic hydrocarbons. This procedure is described in this paper. 7 references.

  12. Hydrocarbons: source of energy

    International Nuclear Information System (INIS)

    Imarisio, G.; Frias, M.; Bemtgen, J.M.

    1989-01-01

    Hydrocarbons are at present the single most important source of energy, since they are the most versatile and widely used. It is expected that their importance will extend well into the next century and therefore it is essential to provide for all those improvements which will extend their availability and usefulness. The sub-programme ''Optimization of the production and utilization of hydrocarbons'' (within the Non-Nuclear Energy R and D Programme of the European Communities) is pursuing a number of R and D topics aimed at the above-mentioned results. It is implemented by means of shared-cost R and D contracts. At this first Seminar held in Lyon (France) from 21-23 September, 1988, all contractors of the sub-programme presented the state of progress of their R and D projects. These proceedings comprise all the papers presented at the Seminar. The section on oilfield exploration includes a report of work on the interpretation of nuclear logs by means of mathematical models. (author)

  13. THE RESPONSE OF THE PERIPHYTIC DIATOM COMMUNITY TO ACID MINE DRAINAGE POLLUTION

    Directory of Open Access Journals (Sweden)

    Andreea Ciorba

    2004-01-01

    Full Text Available This paper proposes to relate the principal characteristics of diatom community (species richness, biodiversity, community biomass, diatom indices to the stress induced by acidification and high levels of metal. The study was done in a mine drainage affected area in Galicia (NW Spain by comparing periphytic diatom communities from polluted streams to ones in supposedly clean waters. The change in the dominant species was the clearest response to AMD pollution while species richness and diversity were sensitive only to high levels of pollution.

  14. Do diatoms percolate through soil and can they be used for tracing the origin of runoff?

    Science.gov (United States)

    De Graaf, Lenka; Cammeraat, Erik; Pfister, Laurent; Wetzel, Carlos; Klaus, Julian; Hissler, Christophe

    2015-04-01

    Tracers are widely used to study the movement of water in a catchment. Because of depletion of scientific possibilities with most common tracer types, we proposed the use of diatoms as a natural tracer. Paradoxical results on the contribution of surface runoff to the storm hydrograph were obtained in pioneer research on this idea. Diatom transport via the subsurface flow to the stream would explain this paradox. Prerequisite for this is vertical transport of diatoms through soils, which is the topic of this study. Emphasis is on percolation behavior (speed of percolation, speed of percolation over time, and species distribution) of Pseudostaurosira sp. and Melosira sp. (Bacillariophyceae) through undisturbed soil columns of contrasting substrates. Co-objective is to study the flowpaths of water through the soil columns. Natural undisturbed soil columns were sampled in the Attert basin (Luxembourg) on schist, marl and sandstone substrates. Rain simulation experiments were performed to study vertical diatom transport. Rhodamine dye experiments were carried out to gain insight in the active flowpaths of water, and breakthrough experiments were performed to study the responses of the soil columns to applied water. Diatoms were transported through the soil columns of the three substrates. A vast majority of diatom percolation took place within the first 15 minutes, percolation hereafter was marginal but nevertheless present. Peaks in diatom percolation corresponded with a high flux caused by the addition of the diatom culture, but seepage of diatoms along the sides is unlikely according to the species distribution and the rhodamine dye experiment. Pseudostaurosira sp. percolated significantly better than Melosira sp. Significantly more diatoms percolated through the marl columns compared to the schist columns and variance within the sandstone group was very high. Absolute differences between substrates however, were marginal. Most preferential flowpaths were observed in

  15. Sorption of 237Pu by the diatom Asterionella formosa

    International Nuclear Information System (INIS)

    Conway, H.L.; Wahlgren, M.A.; Peterson, N.; Nelson, D.M.

    1976-01-01

    Knowledge of the behavior of the man-made radionuclide plutonium within aquatic environments is of fundamental importance in assessing its potential hazards and ecological impact. The sorption of plutonium by phytoplankton and other algae is the dominant factor in the biological transport of plutonium in the aquatic environment, and it has been suggested that sorption by phytoplankton may be responsible for the seasonal loss of plutonium from the epilimnion of Lake Michigan. A unialgal diatom culture was spiked with 237 Pu tracer solution in an attempt to simulate the behavior of fallout plutonium observed in field studies. The results were encouraging in that the 237 Pu in the filtered lake water medium exhibited strongly anionic properties similar to fallout plutonium in Lake Michigan, with limited sorption on container walls. The purpose of the present study was to extend the investigations of the sorption of plutonium by phytoplankton in a controlled environment using continuous culture techniques

  16. Quantum work distribution for a driven diatomic molecule

    International Nuclear Information System (INIS)

    Leonard, Alison; Deffner, Sebastian

    2015-01-01

    Highlights: • A method for calculating the time-dependent solution for a driven system is proposed. • These solutions are used to compute the quantum work distribution. • This distribution is calculated for the Morse potential mimicking a diatomic molecule. • Due to bound and scattering states distribution exhibits continuous and discrete part. • Result is compared with that of a harmonic approximation. - Abstract: We compute the quantum work distribution for a driven Morse oscillator. To this end, we solve the time-dependent dynamics for a scale-invariant process, from which the exact expressions for the transition probabilities are found. Special emphasis is put on the contributions to the work distribution from discrete (bound) and continuous (scattering) parts of the spectrum. The analysis is concluded by comparing the work distribution for the exact Morse potential and the one resulting from a harmonic approximation

  17. Sedimentation of phytoplankton during a diatom bloom : Rates and mechanisms

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Hansen, J.L.S.; Alldredge, A.L.

    1996-01-01

    Phytoplankton blooms are uncoupled from grazing and are normally terminated by sedimentation. There are several potential mechanisms by which phytoplankton cells may settle out of the photic zone: sinking of individual cells or chains, coagulation of cells into aggregates with high settling...... velocities, settling of cells attached to marine snow aggregates formed from discarded larvacean houses or pteropod feeding webs, and packaging of cells into rapidly falling zooplankton fecal pellets. We quantified the relative significance of these different mechanisms during a diatom bloom in a temperate...... to marine snow aggregates formed from discarded larvacean houses, whereas settling of unaggregated cells was insignificant. Formation rates of phytoplankton aggregates by physical coagulation was very low, and losses by this mechanism were much less than 0.07 d(-1); phytoplankton aggregates were neither...

  18. Shedding light on diatom photonics by means of digital holography.

    Science.gov (United States)

    Di Caprio, Giuseppe; Coppola, Giuseppe; De Stefano, Luca; De Stefano, Mario; Antonucci, Alessandra; Congestri, Roberta; De Tommasi, Edoardo

    2014-05-01

    Diatoms are among the dominant phytoplankters in the world's oceans, and their external silica investments, resembling artificial photonic crystals, are expected to play an active role in light manipulation. Digital holography allowed studying the interaction with light of Coscinodiscus wailesii cell wall reconstructing the light confinement inside the cell cytoplasm, condition that is hardly accessible via standard microscopy. The full characterization of the propagated beam, in terms of quantitative phase and intensity, removed a long-standing ambiguity about the origin of the light confinement. The data were discussed in the light of living cell behavior in response to their environment. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Steam hydrocarbon cracking and reforming

    NARCIS (Netherlands)

    Golombok, M.

    2004-01-01

    Many industrial chemical processes are taught as distinct contrasting reactions when in fact the unifying comparisons are greater than the contrasts. We examine steam hydrocarbon reforming and steam hydrocarbon cracking as an example of two processes that operate under different chemical reactivity

  20. Nonlinear quantum dynamics in diatomic molecules: Vibration, rotation and spin

    International Nuclear Information System (INIS)

    Yang, Ciann-Dong; Weng, Hung-Jen

    2012-01-01

    Highlights: ► This paper reveals the internal nonlinear dynamics embedded in a molecular quantum state. ► Analyze quantum molecular dynamics in a deterministic way, while preserving the consistency with probability interpretation. ► Molecular vibration–rotation interaction and spin–orbital coupling are considered simultaneously. ► Spin is just the remnant angular motion when orbital angular momentum is zero. ► Spin is the “zero dynamics” of nonlinear quantum dynamics. - Abstract: For a given molecular wavefunction Ψ, the probability density function Ψ ∗ Ψ is not the only information that can be extracted from Ψ. We point out in this paper that nonlinear quantum dynamics of a diatomic molecule, completely consistent with the probability prediction of quantum mechanics, does exist and can be derived from the quantum Hamilton equations of motion determined by Ψ. It can be said that the probability density function Ψ ∗ Ψ is an external representation of the quantum state Ψ, while the related Hamilton dynamics is an internal representation of Ψ, which reveals the internal mechanism underlying the externally observed random events. The proposed internal representation of Ψ establishes a bridge between nonlinear dynamics and quantum mechanics, which allows the methods and tools already developed by the former to be applied to the latter. Based on the quantum Hamilton equations of motion derived from Ψ, vibration, rotation and spin motions of a diatomic molecule and the interactions between them can be analyzed simultaneously. The resulting dynamic analysis of molecular motion is compared with the conventional probability analysis and the consistency between them is demonstrated.

  1. Structure-based optics of centric diatom frustules: modulation of the in vivo light field for efficient diatom photosynthesis.

    Science.gov (United States)

    Goessling, Johannes W; Su, Yanyan; Cartaxana, Paulo; Maibohm, Christian; Rickelt, Lars F; Trampe, Erik C L; Walby, Sandra L; Wangpraseurt, Daniel; Wu, Xia; Ellegaard, Marianne; Kühl, Michael

    2018-07-01

    The optical properties of diatom silicate frustules inspire photonics and nanotechnology research. Whether light interaction with the nano-structure of the frustule also affects diatom photosynthesis has remained unclear due to lack of information on frustule optical properties under more natural conditions. Here we demonstrate that the optical properties of the frustule valves in water affect light harvesting and photosynthesis in live cells of centric diatoms (Coscinodiscus granii). Microscale cellular mapping of photosynthesis around localized spot illumination demonstrated optical coupling of chloroplasts to the valve wall. Photonic structures of the three-layered C. granii valve facilitated light redistribution and efficient photosynthesis in cell regions distant from the directly illuminated area. The different porous structure of the two sides of the valve exhibited photon trapping and forward scattering of blue light enhancing photosynthetic active radiation inside the cell. Photonic structures of diatom frustules thus alter the cellular light field with implications on diatom photobiology. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

  2. Nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance in the diatom Phaeodactylum tricornutum

    Science.gov (United States)

    Li, W.; Gao, K.; Beardall, J.

    2015-04-01

    It has been proposed that ocean acidification (OA) will interact with other environmental factors to influence the overall impact of global change on biological systems. Accordingly we investigated the influence of nitrogen limitation and OA on the physiology of diatoms by growing the diatom Phaeodactylum tricornutum Bohlin under elevated (1000 μatm; high CO2 - HC) or ambient (390 μatm; low CO2 - LC) levels of CO2 with replete (110 μmol L-1; high nitrate - HN) or reduced (10 μmol L-1; low nitrate - LN) levels of NO3- and subjecting the cells to solar radiation with or without UV irradiance to determine their susceptibility to UV radiation (UVR, 280-400 nm). Our results indicate that OA and UVB induced significantly higher inhibition of both the photosynthetic rate and quantum yield under LN than under HN conditions. UVA or/and UVB increased the cells' non-photochemical quenching (NPQ) regardless of the CO2 levels. Under LN and OA conditions, activity of superoxide dismutase and catalase activities were enhanced, along with the highest sensitivity to UVB and the lowest ratio of repair to damage of PSII. HC-grown cells showed a faster recovery rate of yield under HN but not under LN conditions. We conclude therefore that nutrient limitation makes cells more prone to the deleterious effects of UV radiation and that HC conditions (ocean acidification) exacerbate this effect. The finding that nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance of the diatom P. tricornutum implies that ocean primary production and the marine biological C pump will be affected by OA under multiple stressors.

  3. Climate, catchment runoff and limnological drivers of carbon and oxygen isotope composition of diatom frustules from the central andean altiplano during the Lateglacial and Early Holocene

    OpenAIRE

    Hernández, Armand; Bao, Roberto; Giralt, Santiago; Sáez, Alberto; Leng, Melanie J.; Barker, Philips A.; Kendrick, C.P.; Sloane, Hilary J.

    2013-01-01

    Diatom-based carbon and oxygen isotope analyses (δ13Cdiatom and δ18Odiatom) were performed on diatomrich laminated sediments of Lake Chungará (Andean Altiplano, northern Chile) deposited during the Lateglacial and Early Holocene (12,400e8300 cal years BP) to reconstruct climate change and environmental response across this major climate transition. The δ13Cdiatom data show both centennial-tomillennial scale changes related to fluctuations in lake productivity and CO2 concentration in the lake...

  4. Saturated versus unsaturated hydrocarbon interactions with carbon nanostructures

    Directory of Open Access Journals (Sweden)

    Deivasigamani eUmadevi

    2014-09-01

    Full Text Available The interactions of various acyclic and cyclic hydrocarbons in both saturated and unsaturated forms with the carbon nanostructures (CNSs have been explored by using density functional theory (DFT calculations. Model systems representing armchair and zigzag carbon nanotubes (CNTs and graphene have been considered to investigate the effect of chirality and curvature of the CNSs towards these interactions. Results of this study reveal contrasting binding nature of the acyclic and cyclic hydrocarbons towards CNSs. While the saturated molecules show stronger binding affinity in acyclic hydrocarbons; the unsaturated molecules exhibit higher binding affinity in cyclic hydrocarbons. In addition, acyclic hydrocarbons exhibit stronger binding affinity towards the CNSs when compared to their corresponding cyclic counterparts. The computed results excellently corroborate the experimental observations. The interaction of hydrocarbons with graphene is more favourable when compared with CNTs. Bader’s theory of atoms in molecules has been invoked to characterize the noncovalent interactions of saturated and unsaturated hydrocarbons. Our results are expected to provide useful insights towards the development of rational strategies for designing complexes with desired noncovalent interaction involving CNSs.

  5. Canada's hydrocarbon processing evolution

    International Nuclear Information System (INIS)

    Wise, T.H.; Horton, R.

    2000-01-01

    The development of petroleum refining, petrochemicals and natural gas industries in Canada are discussed together with future issues and prospects. Figures give data on (a) refined products trade 1998; (b) refining capacity; (c) product demand 1980-1999; (d) refinery crude runs and capacity; (e) refining and marketing, historical returns 1993-1999; (f) processing power index for Canada and USA; (g) ethylene capacity; (eye) Montreal petrochemical capacities; (j) Sarnia petrochemical capacities in 2000; (k) Alberta petrochemicals capacities 2001; (l) ethylene net equivalent trade; (m) ethylene costs 1999 for W. Canada and other countries. It was concluded that the hydrocarbon processing business continues to expand in Canada and natural gas processing is likely to increase. Petrochemicals may expand in W. Canada, possibly using feed stock from the Far North. Offshore developments may stimulate new processing on the E. Coast

  6. Hydrogenating gaseous hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Nicolardot, P L.F.

    1930-08-06

    Gaseous hydrocarbons obtained by the destructive distillation of carbonaceous materials are simultaneously desulfurized and hydrogenated by passing them at 350 to 500/sup 0/C, mixed with carbon monoxide and water vapor over lime mixed with metallic oxides present in sufficient amount to absorb the carbon dioxide as it is formed. Oxides of iron, copper, silver, cobalt, and metals of the rare earths may be used and are mixed with the lime to form a filling material of small pieces filling the reaction vessel which may have walls metallized with copper and zinc dust. The products are condensed and fixed with absorbents, e.g. oils, activated carbon, silica gels. The metallic masses may be regenerated by a hot air stream and by heating in inert gases.

  7. Treating hydrocarbon oils

    Energy Technology Data Exchange (ETDEWEB)

    Scott, R; MacIvor, W

    1869-09-01

    The treatment of hydrocarbon oils, such as coal or shale oils, paraffin oils, and petroleum, either in the crude or more or less refined state has the object of reducing the specific gravity and otherwise improving the qualities of such oils. The oil to be treated is put into any ordinary still and distilled. The vapor escaping during the distillation is passed through one or more heating vessels or chambers and exposed to the heat necessary to produce the change. The heating vessels or chambers may be made of metal, clay, or any other material adapted to endure heat, and they may be made of any desired form, or they may be constituted of a coil of metal pipes or a series of tubes such as are used for heating air for blast furnaces.

  8. Epiphytic diatoms in lotic and lentic waters - diversity and representation of species complexes

    Czech Academy of Sciences Publication Activity Database

    Kollár, J.; Fránková, Markéta; Hašler, P.; Letáková, M.; Poulíčková, A.

    2015-01-01

    Roč. 15, č. 2 (2015), s. 259-271 ISSN 1802-5439 Institutional support: RVO:67985939 Keywords : diatoms * epiphyton * species comlexes * lotic and lentic waters Subject RIV: EF - Botanics Impact factor: 2.026, year: 2015

  9. Seasonal variations in the fouling diatom community structure from a monsoon influenced tropical estuary

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Anil, A.C.

    Seasonal variations in the fouling diatom community from a monsoon influenced tropical estuary were investigated. The community composition did not differ significantly between stainless steel and polystyrene substrata due to dominance by Navicula...

  10. Morphometry and cell volumes of diatoms from a tropical estuary of India

    Digital Repository Service at National Institute of Oceanography (India)

    RaviKumar, M.S.; Ramaiah, N.; Tang, D.

    Cell volumes and per cell carbon contents of different diatoms (10 centric, 14 pennate and 1 dinoflagellate) collected from Dona Paula Bay in the central west coast of India have been analyzed. Morphometric information on the phytoplankton types...

  11. A diatom functional-based approach to assess changing environmental conditions in temporary depressional wetlands

    CSIR Research Space (South Africa)

    Riato, L

    2017-07-01

    Full Text Available is limited although important for the development of temporary wetland biological assessments. We assessed how diatom life-form and ecological guilds responded to a seasonal hydrological and hydrochemical gradient in three least human-disturbed, temporary...

  12. Effect of holothurian and zoanthid extracts on growth of some bacterial and diatom species

    Digital Repository Service at National Institute of Oceanography (India)

    Gonsalves, C.

    The antifouling properties of the extracts from two zoanthids, viz. Zoanthus sp, Protopalythoa sp and one holothurian species, viz. Holothuria leucospilota occurring in the coastal waters off Goa were tested against 5 bacteria and 2 diatom species...

  13. Effect of chlorination on the development of marine biofilms dominated by diatoms

    Digital Repository Service at National Institute of Oceanography (India)

    Patil, J.S.; Jagadeesan, V.

    , and Thalassionema did not increase in density after chlorine treatment. It was also demonstrated that diatoms can colonize, grow and photosynthesize on chlorine-treated surfaces. Under pulse chlorination (treatment every 6 h), irrespective of chlorine concentration...

  14. An integrative analysis of post-translational histone modifications in the marine diatom Phaeodactylum tricornutum

    KAUST Repository

    Veluchamy, Alaguraj; Rastogi, Achal; Lin, Xin; Lombard, Bé rangè re; Murik, Omer; Thomas, Yann; Dingli, Florent; Rivarola, Maximo; Ott, Sandra; Liu, Xinyue; Sun, Yezhou; Rabinowicz, Pablo D.; McCarthy, James; Allen, Andrew E.; Loew, Damarys; Bowler, Chris; Tirichine, Leï la

    2015-01-01

    in global biogeochemical cycles. Dissecting chromatin-mediated regulation of genes in diatoms will help understand the ecological success of these organisms in contemporary oceans. Results: Here, we use high resolution mass spectrometry to identify a full

  15. Tidal Channel Diatom Assemblages Reflect within Wetland Environmental Conditions and Land Use at Multiple Scales

    Science.gov (United States)

    We characterized regional patterns of the tidal channel benthic diatom community and examined the relative importance of local wetland and surrounding landscape level factors measured at multiple scales in structuring this assemblage. Surrounding land cover was characterized at ...

  16. Influence of land-use patterns on benthic diatom communities and ...

    African Journals Online (AJOL)

    2010-03-01

    Mar 1, 2010 ... for management of Brazilian and other tropical lotic systems. The objective of this ... ity, floods and inundations, which affect diatom development, especially ...... Sociedade Brasileira de Ficologia, CETESB, São Paulo. 34-55.

  17. New and interesting small-celled naviculoid diatoms (Bacillariophyta) from the Maritime Antarctic Region

    Czech Academy of Sciences Publication Activity Database

    Van de Vijver, B.; Kopalová, Kateřina; Zidarova, R.; Cox, E. J.

    2013-01-01

    Roč. 97, 1-2 (2013), s. 189-208 ISSN 0029-5035 Institutional support: RVO:67985939 Keywords : Bacillariophyta * Diatoms * Maritime Antarctic Region Subject RIV: EF - Botanics Impact factor: 0.989, year: 2013

  18. Identification automatique des diatomées de la Merja fouarate : Une ...

    African Journals Online (AJOL)

    SARAH

    30 sept. 2015 ... Automatic identification of Fouarate Merja diatoms: An alternative to manual determination and classification .... 21 genres, avec une erreur de 4% car plusieurs organismes .... Electronic, Technologies of Information and.

  19. Intracellular nitrate of marine diatoms as a driver of anaerobic nitrogen cycling in sinking aggregates

    DEFF Research Database (Denmark)

    Kamp, Anja; Stief, Peter; Bristow, Laura A.

    2016-01-01

    % was recovered as nitrite. Hence, aggregate-associated diatoms accumulate nitrate from the surrounding water and sustain complex nitrogen transformations, including loss of fixed nitrogen, in anoxic, pelagic microniches. Additionally, it may be expected that intracellular nitrate not converted before...... store nitrate intracellularly, we explored the fate of intracellular nitrate and its availability for microbial metabolism within anoxic diatom-bacteria aggregates. The ubiquitous nitrate-storing diatom Skeletonema marinoi was studied as both axenic cultures and laboratory-produced diatom......-bacteria aggregates. Stable 15N isotope incubations under dark and anoxic conditions revealed that axenic S. marinoi is able to reduce intracellular nitrate to ammonium that is immediately excreted by the cells. When exposed to a light:dark cycle and oxic conditions, S. marinoi stored nitrate intracellularly...

  20. Aulacoseira kruegeriana (Bacillariophyta, Coscinodiscophyceae): a new centric diatom from high-elevation Andean streams of Bolivia

    Czech Academy of Sciences Publication Activity Database

    Morales, E. A.; Rivera, S. F.; Rubin, S. D. C.; Vis, M. L.; Houk, Václav

    2015-01-01

    Roč. 30, č. 3 (2015), s. 269-277 ISSN 0269-249X Institutional support: RVO:67985939 Keywords : centric diatoms * taxonomy * valve ultrastructure Subject RIV: EF - Botanics Impact factor: 1.868, year: 2015

  1. Diatom species composition in the Raška river (Southwestern Serbia

    Directory of Open Access Journals (Sweden)

    Vidaković Danijela P.

    2015-01-01

    Full Text Available The paper presents data on the composition of epilithic diatoms in the Raška River. Samples were collected by scraping stone surfaces with a brush from 5 localities along the Raška River in April, June, August and November 2011 and March and May 2012. Diatom frustules were cleaned using cold acid method, and mounted on permanent slides. An investigation of the Raška River resulted in description of 106 diatom taxa. The most species rich genera are Navicula (10, Gomphonema (10 and Nitzschia (9, while other genera are presented with one or more species. Detailed floristic analysis of the benthic diatom flora in this river has not been conducted before. Therefore, this paper provides a groundwork for future researches. [Projekat Ministarstva nauke Republike Srbije, br. TR 037009

  2. Diatom production in the marine environment : implications for larval fish growth and condition

    DEFF Research Database (Denmark)

    St. John, Michael; Clemmesen, C.; Lund, T.

    2001-01-01

    To test the effects of diatom production on larval fish growth and condition. laboratory experiments were performed with larval North Sea cod reared on different algal food chains. These food chains were based on cultures of (a) the diatoms Skeletonema costatum and Thalassiosira weissflogii: (b....../omega6 fatty acids in the algal source had no significant effect. The highest and lowest growth rates were observed in food chains based on H. triquetra and T. weissflogii. respectively (means for days 14-16 of 4.0 and - 4.7). The mixed diatom/dinoflagellate diet resulted in inter- mediate growth rates...... and condition. Regressions of growth rates against EPA and DHA content indicated no inhibitory effect of diatom production on growth in larval cod...

  3. Deep carbon export from a Southern Ocean iron-fertilized diatom bloom

    Digital Repository Service at National Institute of Oceanography (India)

    Smetacek, V.; Klaas, C.; Strass, V.H.; Assmy, P.; Montresor, M.; Cisewski, B.; Savoye, N.; Webb, A.; d’Ovidio, F.; Arrieta, J.M.; Bathmann, U.; Bellerby, R.; Berg, G.M.; Croot, P.; Gonzalez, S.; Henjes, J.; Herndl, G.J.; Hoffmann, L.J.; Leach, H.; Losch, M.; Mills, M.M.; Neill, C.; Peeken, I.; Rottgers, R.; Sachs, O.; Sauter, E.; Schmidt, M.M.; Schwarz, J.; Terbruggen, A.; Wolf-Gladrow, D.

    Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately...

  4. Photophysiological variability of microphytobenthic diatoms after growth in different types of culture conditions

    NARCIS (Netherlands)

    Forster, R.M.; Martin-Jézéquel, V.R.

    2005-01-01

    Microphytobenthic diatoms have great ecological importance in estuarine and coastal marine ecosystenis, yet many aspects of their physiology have not been investigated under controlled conditions. This work describes patterns in growth rates and photosynthesis in different types of culture for

  5. The reponse of epilithic diatom assemblages to sewage pollution in mountain streams of the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Moravcová, A.; Rauch, Ota; Lukavský, Jaromír; Nedbalová, Linda

    2013-01-01

    Roč. 146, č. 2 (2013), s. 153-166 ISSN 2032-3913 Institutional support: RVO:67985939 Keywords : epilitic diatoms * mountain streams * sewage polllution Subject RIV: EH - Ecology, Behaviour Impact factor: 0.960, year: 2013

  6. Occurrence of cyanobacteria - diatom symbiosis in the Bay of Bengal: Implications in biogeochemistry

    Digital Repository Service at National Institute of Oceanography (India)

    Kulkarni, V.V.; Chitari, R.R.; Narale, D.D.; Patil, J.S.; Anil, A.C.

    cyanobacterial endosymbiont of several diatom genera, are the most important diazotrophs accounting for approx. 63% of pelagic N sub(2) -fixation in the world’s oceans. However, information on R. intracellularis is lacking, even though its distribution...

  7. USE OF DIATOMS TO ASSES WATER QUALITY OF ANTHROPOGENICALLY MODIFIED MATYSÓWKA STREAM

    Directory of Open Access Journals (Sweden)

    Teresa Noga

    2013-04-01

    Full Text Available Matysówka stream is small, under 6 km long watercourse, which is a right-bank tributary of Strug River. In 2009–2011studies on the subject of diversity of diatom communities using diatom indices IPS, GDI and TDI for water quality assessment were conducted. On the stream 271 diatom taxa were identified, among which: Achnanthidium minutissimum var. minutissimum, Navicula cryptotenella, N. gregaria, N. lanceolata, N. tripunctata, Nitzschia linearis, N. pusilla, N. recta, Planothidium frequentissimum, Rhoicosphenia abbreviata were the most frequent. Middle and lower section of Matysówka stream was characterized by increased concentrations of phosphates, nitrites, ammonium, total phosphorus and nitrogen, BOD5. On the basis of diatom indices IPS and GDI waters were characterized as III–IV quality classes, while the TDI index revealed the worst water quality classes (IV–V.

  8. Diatom-based models for inferring water chemistry and hydrology in temporary depressional wetlands

    CSIR Research Space (South Africa)

    Riato, L

    2017-08-01

    Full Text Available Information on the response of temporary depressional wetland diatoms to human-induced disturbances is a limited and important component for the development of temporary wetland biological assessments in human-modified landscapes. Establishing a...

  9. PtAUREO1a and PtAUREO1b knockout mutants of the diatom Phaeodactylum tricornutum are blocked in photoacclimation to blue light.

    Science.gov (United States)

    Mann, Marcus; Serif, Manuel; Jakob, Torsten; Kroth, Peter G; Wilhelm, Christian

    2017-10-01

    Aureochromes are blue light receptors specifically found in photosynthetic Stramenopiles (algae). Four different Aureochromes have been identified in the marine diatom Phaeodactylum tricornutum (PtAUREO 1a, 1b, 1c, and 2). Since blue light is necessary for high light acclimation in diatoms, it has been hypothesized that Aureochromes might play an important role in the light acclimation capacity of diatoms. This hypothesis was supported by an RNAi knockdown line of PtAUREO1a, which showed a phenotype different from wild type cells when grown in either blue or red light. Here, we show for the first time the phenotype and the photoacclimation reaction of TALEN-mediated knockout mutants of PtAUREO1a and PtAUREO1b, clearly proving the necessity of Aureochromes for light acclimation under blue light. However, both mutants do also show specific differences in their respective phenotypes. Hence, PtAUREO1a and 1b are not functionally redundant in photoacclimation to blue light, and their specific contribution needs to be clarified further. Copyright © 2017 Elsevier GmbH. All rights reserved.

  10. The role of fluid migration system in hydrocarbon accumulation in Maichen Sag, Beibuwan Basin

    Science.gov (United States)

    Liu, Hongyu; Yang, Jinxiu; Wu, Feng; Chen, Wei; Liu, Qianqian

    2018-02-01

    Fluid migration system is of great significance for hydrocarbon accumulation, including the primary migration and secondary migration. In this paper, the fluid migration system is analysed in Maichen Sag using seismic, well logging and core data. Results show that many factors control the hydrocarbon migration process, including hydrocarbon generation and expulsion period from source rocks, microfractures developed in the source rocks, the connected permeable sand bodies, the vertical faults cutting into/through the source rocks and related fault activity period. The spatial and temporal combination of these factors formed an effective network for hydrocarbon expulsion and accumulation, leading to the hydrocarbon reservoir distribution at present. Generally, a better understanding of the hydrocarbon migration system can explain the present status of hydrocarbon distribution, and help select future target zones for oil and gas exploration.

  11. Distribution and origin of hydrocarbons in water and sediment in Sao Sebastiao, SP, Brazil

    International Nuclear Information System (INIS)

    Zanardi, Eliete; Bicego, Marcia Caruso; Miranda, Luiz Bruner de; Weber, Rolf Roland

    1999-01-01

    This study describes the dissolved/dispersed petroleum hydrocarbons (DDPH) in surface water and the origin and distribution of aliphatic and aromatic hydrocarbons in samples from the surface bottom sediments. The main objective was to verify the anthropogenic contribution on the adjacent inner shelf of Sao Sebastiao, taking into account the distribution of hydrographic properties and knowledge of the main circulation. The DDPH concentration range of the 20 samples were from 0.35 to 2.50 m u g . L -1 , characterising this region as slightly affected by the contribution of petroleum hydrocarbons. Considering sediment hydrocarbon results, sites located in the inner shelf were divided into three groups: one with mainly biogenic hydrocarbons, a second one with biogenic and petroleum hydrocarbons and a third with significant contribution of petroleum hydrocarbons. These results show an influence of human activities in the Sao Sebastiao Channel on the surrounding areas of the inner shelf. (Author)

  12. Distribution and origin of hydrocarbons in water and sediment in Sao Sebastiao, SP, Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Zanardi, Eliete [Universidade de Sao Paulo, Instituto Oceanografico, Sao Paulo, SP (Brazil); Bicego, Marcia Caruso; Miranda, Luiz Bruner de; Weber, Rolf Roland [Miami Univ., RSMAS/NAC, Miami, FL (United States)

    1999-04-01

    This study describes the dissolved/dispersed petroleum hydrocarbons (DDPH) in surface water and the origin and distribution of aliphatic and aromatic hydrocarbons in samples from the surface bottom sediments. The main objective was to verify the anthropogenic contribution on the adjacent inner shelf of Sao Sebastiao, taking into account the distribution of hydrographic properties and knowledge of the main circulation. The DDPH concentration range of the 20 samples were from 0.35 to 2.50 {sup m}u{sup g}. L{sup -1}, characterising this region as slightly affected by the contribution of petroleum hydrocarbons. Considering sediment hydrocarbon results, sites located in the inner shelf were divided into three groups: one with mainly biogenic hydrocarbons, a second one with biogenic and petroleum hydrocarbons and a third with significant contribution of petroleum hydrocarbons. These results show an influence of human activities in the Sao Sebastiao Channel on the surrounding areas of the inner shelf. (Author)

  13. Comparative Genomics of the Ubiquitous, Hydrocarbon-degrading Genus Marinobacter

    Science.gov (United States)

    Singer, E.; Webb, E.; Edwards, K. J.

    2012-12-01

    The genus Marinobacter is amongst the most ubiquitous in the global oceans and strains have been isolated from a wide variety of marine environments, including offshore oil-well heads, coastal thermal springs, Antarctic sea water, saline soils and associations with diatoms and dinoflagellates. Many strains have been recognized to be important hydrocarbon degraders in various marine habitats presenting sometimes extreme pH or salinity conditions. Analysis of the genome of M. aquaeolei revealed enormous adaptation versatility with an assortment of strategies for carbon and energy acquisition, sensation, and defense. In an effort to elucidate the ecological and biogeochemical significance of the Marinobacters, seven Marinobacter strains from diverse environments were included in a comparative genomics study. Genomes were screened for metabolic and adaptation potential to elucidate the strategies responsible for the omnipresence of the Marinobacter genus and their remedial action potential in hydrocarbon-polluted waters. The core genome predominantly encodes for key genes involved in hydrocarbon degradation, biofilm-relevant processes, including utilization of external DNA, halotolerance, as well as defense mechanisms against heavy metals, antibiotics, and toxins. All Marinobacter strains were observed to degrade a wide spectrum of hydrocarbon species, including aliphatic, polycyclic aromatic as well as acyclic isoprenoid compounds. Various genes predicted to facilitate hydrocarbon degradation, e.g. alkane 1-monooxygenase, appear to have originated from lateral gene transfer as they are located on gene clusters of 10-20% lower GC-content compared to genome averages and are flanked by transposases. Top ortholog hits are found in other hydrocarbon degrading organisms, e.g. Alcanivorax borkumensis. Strategies for hydrocarbon uptake encoded by various Marinobacter strains include cell surface hydrophobicity adaptation via capsular polysaccharide biosynthesis and attachment

  14. Decadal variations in diatoms and dinoflagellates on the inner shelf of the East China Sea, China

    Science.gov (United States)

    Abate, Rediat; Gao, Yahui; Chen, Changping; Liang, Junrong; Mu, Wenhua; Kifile, Demeke; Chen, Yanghang

    2017-11-01

    Diatoms and dinoflagellates are two major groups of phytoplankton that flourish in the oceans, particularly in coastal zone and upwelling systems, and their contrasting production have been reported in several world seas. However, this information is not available in the coastal East China Sea (ECS). Thus, to investigate and compare the decadal trends in diatoms and dinoflagellates, a sediment core, 47 cm long, was collected from the coastal zone of the ECS. Sediment chlorophyll- a (Chl- a), phytoplankton-group specific pigment signatures of diatoms and dinoflagellates, and diatom valve concentrations were determined. The sediment core covered the period from 1961 to 2011 AD. The chlorophyll- a contents ranged from 2.32 to 73 µg/g dry sediment (dw) and averaged 9.81 µg/g dw. Diatom absolute abundance ranged from 29152 to 177501 valve/gram (v/g) dw and averaged 72137 v/g dw. Diatom valve and diatom specific pigment marker concentrations were not significantly correlated. Peridinin increased after the 1980s in line with intensified use of fertilizer and related increases in nutrient inputs into the marine environment. The increased occurrence of dinoflagellate dominance after the 1980s can be mostly explained by the increase in nutrients. However, the contribution of dinoflagellates to total phytoplankton production (Chl- a) decreased during the final decade of this study, probably because of the overwhelming increase in diatom production that corresponded with the construction of the Three Gorges Dam (TGD) and related light availability. Similarly, the mean ratio of fucoxanthin/peridinin for the period from 1982 to 2001 was 6% less than for 1961 to 1982, while the ratio for 2001 to 2011 was 45.3% greater than for 1982 to 2001. The decadal variation in the fucoxanthin/peridinin ratio implies that dinoflagellate production had been gradually increasing until 2001. We suggest that the observed changes can be explained by anthropogenic impacts, such as nutrient

  15. Hierarchical and Size Dependent Mechanical Properties of Silica and Silicon Nanostructures Inspired by Diatom Algae

    Science.gov (United States)

    2010-09-01

    Chaniotakis. The physical and mechanical properties of composite cements manufactured with cal- careous and clayey greek diatomite mixtures. Cement and...Hierarchical and size dependent mechanical properties of silica and silicon nanostructures inspired by diatom algae by Andre Phillipe Garcia B.S...dependent mechanical properties of silica and silicon nanostructures inspired by diatom algae 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM

  16. Biosynthesis of gold nanoparticles using diatoms-silica-gold and EPS-gold bionanocomposite formation

    OpenAIRE

    Schröfel, Adam; Kratošová, Gabriela; Bohunická, Markéta; Dobročka, Edmund; Vávra, Ivo

    2011-01-01

    Novel synthesis of gold nanoparticles, EPS-gold, and silica-gold bionanocomposites by biologically driven processes employing two diatom strains (Navicula atomus, Diadesmis gallica) is described. Transmission electron microscopy (TEM) and electron diffraction analysis (SAED) revealed a presence of gold nanoparticles in the experimental solutions of the diatom culture mixed with tetrachloroaureate. Nature of the gold nanoparticles was confirmed by X-ray diffraction studies. Scanning electron m...

  17. Evolutionary origins and functions of the carotenoid biosynthetic pathway in marine diatoms.

    Directory of Open Access Journals (Sweden)

    Sacha Coesel

    Full Text Available Carotenoids are produced by all photosynthetic organisms, where they play essential roles in light harvesting and photoprotection. The carotenoid biosynthetic pathway of diatoms is largely unstudied, but is of particular interest because these organisms have a very different evolutionary history with respect to the Plantae and are thought to be derived from an ancient secondary endosymbiosis between heterotrophic and autotrophic eukaryotes. Furthermore, diatoms have an additional xanthophyll-based cycle for dissipating excess light energy with respect to green algae and higher plants. To explore the origins and functions of the carotenoid pathway in diatoms we searched for genes encoding pathway components in the recently completed genome sequences of two marine diatoms. Consistent with the supplemental xanthophyll cycle in diatoms, we found more copies of the genes encoding violaxanthin de-epoxidase (VDE and zeaxanthin epoxidase (ZEP enzymes compared with other photosynthetic eukaryotes. However, the similarity of these enzymes with those of higher plants indicates that they had very probably diversified before the secondary endosymbiosis had occurred, implying that VDE and ZEP represent early eukaryotic innovations in the Plantae. Consequently, the diatom chromist lineage likely obtained all paralogues of ZEP and VDE genes during the process of secondary endosymbiosis by gene transfer from the nucleus of the algal endosymbiont to the host nucleus. Furthermore, the presence of a ZEP gene in Tetrahymena thermophila provides the first evidence for a secondary plastid gene encoded in a heterotrophic ciliate, providing support for the chromalveolate hypothesis. Protein domain structures and expression analyses in the pennate diatom Phaeodactylum tricornutum indicate diverse roles for the different ZEP and VDE isoforms and demonstrate that they are differentially regulated by light. These studies therefore reveal the ancient origins of several

  18. Evolutionary origins and functions of the carotenoid biosynthetic pathway in marine diatoms.

    Science.gov (United States)

    Coesel, Sacha; Oborník, Miroslav; Varela, Joao; Falciatore, Angela; Bowler, Chris

    2008-08-06

    Carotenoids are produced by all photosynthetic organisms, where they play essential roles in light harvesting and photoprotection. The carotenoid biosynthetic pathway of diatoms is largely unstudied, but is of particular interest because these organisms have a very different evolutionary history with respect to the Plantae and are thought to be derived from an ancient secondary endosymbiosis between heterotrophic and autotrophic eukaryotes. Furthermore, diatoms have an additional xanthophyll-based cycle for dissipating excess light energy with respect to green algae and higher plants. To explore the origins and functions of the carotenoid pathway in diatoms we searched for genes encoding pathway components in the recently completed genome sequences of two marine diatoms. Consistent with the supplemental xanthophyll cycle in diatoms, we found more copies of the genes encoding violaxanthin de-epoxidase (VDE) and zeaxanthin epoxidase (ZEP) enzymes compared with other photosynthetic eukaryotes. However, the similarity of these enzymes with those of higher plants indicates that they had very probably diversified before the secondary endosymbiosis had occurred, implying that VDE and ZEP represent early eukaryotic innovations in the Plantae. Consequently, the diatom chromist lineage likely obtained all paralogues of ZEP and VDE genes during the process of secondary endosymbiosis by gene transfer from the nucleus of the algal endosymbiont to the host nucleus. Furthermore, the presence of a ZEP gene in Tetrahymena thermophila provides the first evidence for a secondary plastid gene encoded in a heterotrophic ciliate, providing support for the chromalveolate hypothesis. Protein domain structures and expression analyses in the pennate diatom Phaeodactylum tricornutum indicate diverse roles for the different ZEP and VDE isoforms and demonstrate that they are differentially regulated by light. These studies therefore reveal the ancient origins of several components of the

  19. Intracellular Nitrate of Marine Diatoms as a Driver of Anaerobic Nitrogen Cycling in Sinking Aggregates

    Directory of Open Access Journals (Sweden)

    Anja Kamp

    2016-11-01

    Full Text Available Diatom-bacteria aggregates are key for the vertical transport of organic carbon in the ocean. Sinking aggregates also represent pelagic microniches with intensified microbial activity, oxygen depletion in the center, and anaerobic nitrogen cycling. Since some of the aggregate-forming diatom species store nitrate intracellularly, we explored the fate of intracellular nitrate and its availability for microbial metabolism within anoxic diatom-bacteria aggregates. The ubiquitous nitrate-storing diatom Skeletonema marinoi was studied as both axenic cultures and laboratory-produced diatom-bacteria aggregates. Stable 15N isotope incubations under dark and anoxic conditions revealed that axenic S. marinoi is able to reduce intracellular nitrate to ammonium that is immediately excreted by the cells. When exposed to a light:dark cycle and oxic conditions, S. marinoi stored nitrate intracellularly in concentrations > 60 mmol L-1 both as free-living cells and associated to aggregates. Intracellular nitrate concentrations exceeded extracellular concentrations by three orders of magnitude. Intracellular nitrate was used up within 2-3 days after shifting diatom-bacteria aggregates to dark and anoxic conditions. Thirty-one percent of the diatom-derived nitrate was converted to nitrogen gas, indicating that a substantial fraction of the intracellular nitrate pool of S. marinoi becomes available to the aggregate-associated bacterial community. Only 5% of the intracellular nitrate was reduced to ammonium, while 59% was recovered as nitrite. Hence, aggregate-associated diatoms accumulate nitrate from the surrounding water and sustain complex nitrogen transformations, including loss of fixed nitrogen, in anoxic, pelagic microniches. Additionally, it may be expected that intracellular nitrate not converted before the aggregates have settled onto the seafloor could fuel benthic nitrogen transformations.

  20. Large centric diatoms allocate more cellular nitrogen to photosynthesis to counter slower RUBISCO turnover rates

    Directory of Open Access Journals (Sweden)

    Yaping eWu

    2014-12-01

    Full Text Available Diatoms contribute ~40% of primary production in the modern ocean and encompass the largest cell size range of any phytoplankton group. Diatom cell size influences their nutrient uptake, photosynthetic light capture, carbon export efficiency, and growth responses to increasing pCO2. We therefore examined nitrogen resource allocations to the key protein complexes mediating photosynthesis across six marine centric diatoms, spanning 5 orders of magnitude in cell volume, under past, current and predicted future pCO2 levels, in balanced growth under nitrogen repletion. Membrane bound photosynthetic protein concentrations declined with cell volume in parallel with cellular concentrations of total protein, total nitrogen and chlorophyll. Larger diatom species, however, allocated a greater fraction (by 3.5 fold of their total cellular nitrogen to the soluble RUBISCO carbon fixation complex than did smaller species. Carbon assimilation per unit of RUBISCO large subunit (C RbcL-1 s-1 decreased with cell volume, from ~8 to ~2 C RbcL-1 s-1 from the smallest to the largest cells. Whilst a higher allocation of cellular nitrogen to RUBISCO in larger cells increases the burden upon their nitrogen metabolism, the higher RUBISCO allocation buffers their lower achieved RUBISCO turnover rate to enable larger diatoms to maintain carbon assimilation rates per total protein comparable to small diatoms. Individual species responded to increased pCO2, but cell size effects outweigh pCO2 responses across the diatom species size range examined. In large diatoms a higher nitrogen cost for RUBISCO exacerbates the higher nitrogen requirements associated with light absorption, so the metabolic cost to maintain photosynthesis is a cell size-dependent trait.

  1. Diatoms as an indicator of bottom surface sediment dynamics in the southern Scotia sea

    Directory of Open Access Journals (Sweden)

    Олег Сергеевич Огиенко

    2015-05-01

    Full Text Available The study of diatoms from the sediments of the lower interval of column K97-18 in Scotia Sea it is revealed the combination of Late-Holocene and Miocene species in complexes, due to the abundance of inclusions of Middle Miocene diatoms in the rock. Age of re-deposition, transporters and ways of transportation are determined, and it is suggested possible localization of diatomite layers

  2. Iron Availability Influences Silicon Isotope Fractionation in Two Southern Ocean Diatoms (Proboscia inermis and Eucampia antarctica and a Coastal Diatom (Thalassiosira pseudonana

    Directory of Open Access Journals (Sweden)

    Scott Meyerink

    2017-07-01

    Full Text Available The fractionation of silicon (Si isotopes was measured in two Southern Ocean diatoms (Proboscia inermis and Eucampia Antarctica and a coastal diatom (Thalassiosira pseudonana that were grown under varying iron (Fe concentrations. Varying Fe concentrations had no effect on the Si isotope enrichment factor (ε in T. pseudonana, whilst E. Antarctica and P. inermis exhibited significant variations in the value of ε between Fe-replete and Fe-limited conditions. Mean ε values in P. inermis and E. Antarctica decreased from (± 1SD −1.11 ± 0.15‰ and −1.42 ± 0.41 ‰ (respectively under Fe-replete conditions, to −1.38 ± 0.27 ‰ and −1.57 ± 0.5 ‰ (respectively under Fe-limiting conditions. These variations likely arise from adaptations in diatoms arising from the nutrient status of their environment. T. pseudonana is a coastal clone typically accustomed to low Si but high Fe conditions whereas E. Antarctica and P. inermis are typically accustomed to High Si, High nitrate low Fe conditions. Growth induced variations in silicic acid (Si(OH4 uptake arising from Fe-limitation is the likely mechanism leading to Si-isotope variability in E. Antarctica and P. inermis. The multiplicative effects of species diversity and resource limitation (e.g., Fe on Si-isotope fractionation in diatoms can potentially alter the Si-isotope composition of diatom opal in diatamaceous sediments and sea surface Si(OH4. This work highlights the need for further in vitro studies into intracellular mechanisms involved in Si(OH4 uptake, and the associated pathways for Si-isotope fractionation in diatoms.

  3. Polycyclovorans algicola gen. nov., sp. nov., an aromatic-hydrocarbon-degrading marine bacterium found associated with laboratory cultures of marine phytoplankton.

    Science.gov (United States)

    Gutierrez, Tony; Green, David H; Nichols, Peter D; Whitman, William B; Semple, Kirk T; Aitken, Michael D

    2013-01-01

    A strictly aerobic, halotolerant, rod-shaped bacterium, designated strain TG408, was isolated from a laboratory culture of the marine diatom Skeletonema costatum (CCAP1077/1C) by enrichment with polycyclic aromatic hydrocarbons (PAHs) as the sole carbon source. 16S rRNA gene sequence analysis placed this organism within the order Xanthomonadales of the class Gammaproteobacteria. Its closest relatives included representatives of the Hydrocarboniphaga-Nevskia-Sinobacter clade (compounds and small organic acids. Notably, it displayed versatility in degrading two- and three-ring PAHs. Moreover, catechol 2,3-dioxygenase activity was detected in lysates, indicating that this strain utilizes the meta-cleavage pathway for aromatic compound degradation. Cells produced surface blebs and contained a single polar flagellum. The predominant isoprenoid quinone of strain TG408 was Q-8, and the dominant fatty acids were C(16:0), C(16:1) ω7c, and C(18:1) ω7c. The G+C content of the isolate's DNA was 64.3 mol% ± 0.34 mol%. On the basis of distinct phenotypic and genotypic characteristics, strain TG408 represents a novel genus and species in the class Gammaproteobacteria for which the name Polycyclovorans algicola gen. nov., sp. nov., is proposed. Quantitative PCR primers targeting the 16S rRNA gene of this strain were developed and used to show that this organism is found associated with other species of marine phytoplankton. Phytoplankton may be a natural biotope in the ocean where new species of hydrocarbon-degrading bacteria await discovery and which contribute significantly to natural remediation processes.

  4. Biofuel and Biochemical Analysis of Amphora coffeaeformis RR03, a Novel Marine Diatom, Cultivated in an Open Raceway Pond

    Directory of Open Access Journals (Sweden)

    Muthu Ganesan Rajaram

    2018-05-01

    Full Text Available (1 Background: To increase the biochemical productivity and to reduce the production cost of microalgal biodiesel, this study aimed to investigate the effects of CO2 on biomass, fatty acids, carbon-hydrogen, and biochemical accumulation of the marine diatom, Amphora coffeaeformis RR03 (A. coffeaeformis RR03. (2 Methods: Fatty acid composition of the dry biomass of A. coffeaeformis RR03 was analysed using Gas chromatography-mass spectrometry (GC-MS. (3 Results: The results showed that A. coffeaeformis RR03 contained high biomass productivity and biochemical composition in different cultivation conditions. A. coffeaeformis RR03 showed maximum growth of 5.2 × 106/mL on 21st day cultivation under CO2 supply. The bio-crude oil production from A. coffeaeformis RR03 was 36.19 megajoule (MJ. GC-MS analysis found that the dry biomass of A. coffeaeformis RR03 contained maximum of 47.72% fatty acids of 16-octadecanoic acid methyl ester (10:12 and 19.58% pentadecanoic acid, 13-methyl-, and methyl ester (9.24. (4 Conclusion: The results of this study may suggest that a novel diatom of A. coffeaeformis RR03 could be a suitable candidate for biocrude production in order to meet the future demand of energy.

  5. High Pressure Preignition Chemistry of Hydrocarbons and Hydrocarbon Mixtures

    National Research Council Canada - National Science Library

    Cernansky, N.P

    1998-01-01

    .... The research program entailed mechanistic studies examining the oxidation chemistry of single-component hydrocarbons and ignition studies examining the overall ignition of pure single component fuels and fuel blends...

  6. Diatoms on the carapace of common snapping turtles: Luticola spp. dominate despite spatial variation in assemblages.

    Directory of Open Access Journals (Sweden)

    Shelly C Wu

    Full Text Available Filamentous algae are often visible on the carapaces of freshwater turtles and these algae are dominated by a few species with varying geographic distributions. Compared to filamentous algae, little is known about the much more speciose microalgae on turtles. Our objectives were to compare the diatom flora on a single turtle species (the common snapping turtle, Chelydra serpentina across part of its range to examine spatial patterns and determine whether specific diatom taxa were consistently associated with turtles (as occurs in the filamentous alga Basicladia spp.. Using preserved turtle specimens from museums, we systematically sampled diatoms on the carapaces of 25 snapping turtles across five states. The diverse diatom assemblages formed two groups-the southern Oklahoma group and the northern Illinois/Wisconsin/New York group, with Arkansas not differing from either group. Of the six diatom species found in all five states, four species are widespread, whereas Luticola cf. goeppertiana and L. cf. mutica are undescribed species, known only from turtles in our study. L. cf. goeppertiana comprised 83% of the diatom abundance on Oklahoma turtles and was relatively more abundant on southern turtles (Oklahoma and Arkansas than on northern turtles (where mean abundance/state was > 10%. L. cf. mutica was the most abundant species (40% on New York turtles. Some Luticola species are apparently turtle associates and results support a pattern of spatial variation in Luticola species, similar to that in Basicladia. Using museum specimens is an efficient and effective method to study the distribution of micro-epibionts.

  7. Diatoms on the carapace of common snapping turtles: Luticola spp. dominate despite spatial variation in assemblages

    Science.gov (United States)

    Wu, Shelly C.; Bergey, Elizabeth A.

    2017-01-01

    Filamentous algae are often visible on the carapaces of freshwater turtles and these algae are dominated by a few species with varying geographic distributions. Compared to filamentous algae, little is known about the much more speciose microalgae on turtles. Our objectives were to compare the diatom flora on a single turtle species (the common snapping turtle, Chelydra serpentina) across part of its range to examine spatial patterns and determine whether specific diatom taxa were consistently associated with turtles (as occurs in the filamentous alga Basicladia spp.). Using preserved turtle specimens from museums, we systematically sampled diatoms on the carapaces of 25 snapping turtles across five states. The diverse diatom assemblages formed two groups–the southern Oklahoma group and the northern Illinois/Wisconsin/New York group, with Arkansas not differing from either group. Of the six diatom species found in all five states, four species are widespread, whereas Luticola cf. goeppertiana and L. cf. mutica are undescribed species, known only from turtles in our study. L. cf. goeppertiana comprised 83% of the diatom abundance on Oklahoma turtles and was relatively more abundant on southern turtles (Oklahoma and Arkansas) than on northern turtles (where mean abundance/state was > 10%). L. cf. mutica was the most abundant species (40%) on New York turtles. Some Luticola species are apparently turtle associates and results support a pattern of spatial variation in Luticola species, similar to that in Basicladia. Using museum specimens is an efficient and effective method to study the distribution of micro-epibionts. PMID:28192469

  8. Accumulation of {sup 241}Am by suspended matter, diatoms and aquatic weeds of the Yenisei River

    Energy Technology Data Exchange (ETDEWEB)

    Zotina, T.A., E-mail: t_zotina@ibp.r [Institute of Biophysics SB RAS, Akademgorodok, Krasnoyarsk 660036 (Russian Federation); Bolsunovsky, A.Ya.; Bondareva, L.G. [Institute of Biophysics SB RAS, Akademgorodok, Krasnoyarsk 660036 (Russian Federation)

    2010-02-15

    In this work we experimentally estimated the capacities of the key components of the Yenisei River (Russia): particulate suspended matter (seston), diatom microalgae, and submerged macrophytes for accumulating {sup 241}Am from water. In our experiments large particles of seston (>8 mum), comparable in size with diatoms, took up most of americium from water. The accumulation of americium by isolated diatom algae (Asterionella formosa and Diatoma vulgare) was lower than by total seston. The concentration factors (CFs) of {sup 241}Am for seston of the Yenisei River in our experiments were (2.8-6.9).10{sup 5}; for diatoms - (1.5-4.2).10{sup 4}. The CFs for aquatic plant Elodea canadensis were within the same order of magnitude as those for diatoms. Activity concentration and CFs of {sup 241}Am were nearly the same in experiments under dark and light conditions. This is indicative of an energy independent mechanism of americium uptake from the water by diatoms and submerged macrophytes.

  9. Biofilm and capsule formation of the diatom Achnanthidium minutissimum are affected by a bacterium.

    Science.gov (United States)

    Windler, Miriam; Leinweber, Katrin; Bartulos, Carolina Rio; Philipp, Bodo; Kroth, Peter G

    2015-04-01

    Photoautotrophic biofilms play an important role in various aquatic habitats and are composed of prokaryotic and/or eukaryotic organisms embedded in extracellular polymeric substances (EPS). We have isolated diatoms as well as bacteria from freshwater biofilms to study organismal interactions between representative isolates. We found that bacteria have a strong impact on the biofilm formation of the pennate diatom Achnanthidium minutissimum. This alga produces extracellular capsules of insoluble EPS, mostly carbohydrates (CHO), only in the presence of bacteria (xenic culture). The EPS themselves also have a strong impact on the aggregation and attachment of the algae. In the absence of bacteria (axenic culture), A. minutissimum did not form capsules and the cells grew completely suspended. Fractionation and quantification of CHO revealed that the diatom in axenic culture produces large amounts of soluble CHO, whereas in the xenic culture mainly insoluble CHO were detected. For investigation of biofilm formation by A. minutissimum, a bioassay was established using a diatom satellite Bacteroidetes bacterium that had been shown to induce capsule formation of A. minutissimum. Interestingly, capsule and biofilm induction can be achieved by addition of bacterial spent medium, indicating that soluble hydrophobic molecules produced by the bacterium may mediate the diatom/bacteria interaction. With the designed bioassay, a reliable tool is now available to study the chemical interactions between diatoms and bacteria with consequences for biofilm formation. © 2015 Phycological Society of America.

  10. Marennine, Promising Blue Pigments from a Widespread Haslea Diatom Species Complex

    Directory of Open Access Journals (Sweden)

    Romain Gastineau

    2014-05-01

    Full Text Available In diatoms, the main photosynthetic pigments are chlorophylls a and c, fucoxanthin, diadinoxanthin and diatoxanthin. The marine pennate diatom Haslea ostrearia has long been known for producing, in addition to these generic pigments, a water-soluble blue pigment, marennine. This pigment, responsible for the greening of oysters in western France, presents different biological activities: allelopathic, antioxidant, antibacterial, antiviral, and growth-inhibiting. A method to extract and purify marennine has been developed, but its chemical structure could hitherto not be resolved. For decades, H. ostrearia was the only organism known to produce marennine, and can be found worldwide. Our knowledge about H. ostrearia-like diatom biodiversity has recently been extended with the discovery of several new species of blue diatoms, the recently described H. karadagensis, H. silbo sp. inedit. and H. provincialis sp. inedit. These blue diatoms produce different marennine-like pigments, which belong to the same chemical family and present similar biological activities. Aside from being a potential source of natural blue pigments, H. ostrearia-like diatoms thus present a commercial potential for aquaculture, cosmetics, food and health industries.

  11. Spectral radiation dependent photoprotective mechanism in the diatom Pseudo-nitzschia multistriata.

    Directory of Open Access Journals (Sweden)

    Christophe Brunet

    Full Text Available Phytoplankton, such as diatoms, experience great variations of photon flux density (PFD and light spectrum along the marine water column. Diatoms have developed some rapidly-regulated photoprotective mechanisms, such as the xanthophyll cycle activation (XC and the non-photochemical chlorophyll fluorescence quenching (NPQ, to protect themselves from photooxidative damages caused by excess PFD. In this study, we investigate the role of blue fluence rate in combination with red radiation in shaping photoacclimative and protective responses in the coastal diatom Pseudo-nitzschia multistriata. This diatom was acclimated to four spectral light conditions (blue, red, blue-red, blue-red-green, each of them provided with low and high PFD. Our results reveal that the increase in the XC pool size and the amplitude of NPQ is determined by the blue fluence rate experienced by cells, while cells require sensing red radiation to allow the development of these processes. Variations in the light spectrum and in the blue versus red radiation modulate either the photoprotective capacity, such as the activation of the diadinoxanthin-diatoxanthin xanthophyll cycle, the diadinoxanthin de-epoxidation rate and the capacity of non-photochemical quenching, or the pigment composition of this diatom. We propose that spectral composition of light has a key role on the ability of diatoms to finely balance light harvesting and photoprotective capacity.

  12. GROWTH AND PHOTOPROTECTION IN THREE DINOFLAGELLATES (INCLUDING TWO STRAINS OF ALEXANDRIUM TAMARENSE) AND ONE DIATOM EXPOSED TO FOUR WEEKS OF NATURAL AND ENHANCED ULTRAVIOLET-B RADIATION(1).

    Science.gov (United States)

    Laurion, Isabelle; Roy, Suzanne

    2009-02-01

    Long-term growth response to natural solar radiation with enhanced ultraviolet-B (UVB) exposure was examined in two species of dinoflagellates [Alexandrium tamarense (M. Lebour) Balech, At, and Heterocapsa triquetra (Ehrenb.) F. Stein, Ht], including two strains of A. tamarense, one from Spain and another from UK, and one diatom species (Thalassiosira pseudonana Hasle et Heimdal). We examined whether variable photoprotection (mycosporine-like amino acids [MAAs] and xanthophyll-cycle pigments) affected photosynthetic performance, phytoplankton light absorption, and growth. Growth rate was significantly reduced under enhanced UVB for the UK strain of At and for Ht (both grew very little) as well as for the diatom (that maintained high growth rates), but there was no effect for the Spanish strain of At. MAA concentration was high in the dinoflagellates, but undetectable in the diatom, which instead used the xanthophyll cycle for photoprotection. The highest cell concentrations of MAAs and photoprotective pigments were observed in the UK strain of At, along with lowest growth rates and Fv /Fm , indicating high stress levels. In contrast, the Spanish strain showed progressive acclimation to the experimental conditions, with no significant difference in growth between treatments. Increase in total MAAs followed linearly the cumulative UVB of the preceding day, and both total and primary MAAs were maintained at higher constitutive levels in this strain. Acclimation to enhanced UVB in the diatom resulted in an increase in PSII activity and reduction in nonphotochemical quenching, indicating an increased resistance to photoinhibition after a few weeks. All four species showed increased phytoplankton light absorption under enhanced UVB. Large intrastrain differences suggest a need to consider more closely intraspecific variability in UV studies. © 2009 Phycological Society of America.

  13. Show-Bix &

    DEFF Research Database (Denmark)

    2014-01-01

    The anti-reenactment 'Show-Bix &' consists of 5 dias projectors, a dial phone, quintophonic sound, and interactive elements. A responsive interface will enable the Dias projectors to show copies of original dias slides from the Show-Bix piece ”March på Stedet”, 265 images in total. The copies are...

  14. Molecular Characterization of CTR-type Copper Transporters in an Oceanic Diatom, Thalassiosira oceanica 1005

    Science.gov (United States)

    Kong, L.; Price, N. M.

    2016-02-01

    Copper is an essential micronutrient for phytoplankton growth because of its role as a redox cofactor in electron transfer proteins in photosynthesis and respiration, and a potentially limiting resource in parts of the open sea. Thalassiosira oceanica 1005 can grow at inorganic copper concentrations varying from 10 fmol/L to 10 nmol/L by regulating copper uptake across plasma membrane. Four putative CTR-type copper transporter genes (ToCTR1, ToCTR2, ToCTR3.1 and ToCTR3.2) were identified by BLASTP search against the T. oceanica genome. Predicted gene models were revised by assembled mRNA sequencing transcripts and updated gene models contained all conserved features of characterized CTR-type copper transporters. ToCTR3.1 and ToCTR3.2 may arise from one another by gene duplication as they shared a sequence similarity of 97.6% with a peptide insertion of 5 amino acids at N-terminus of ToCTR3.1. The expression of ToCTR1, ToCTR2 and ToCTR3.1/3.2 was upregulated in low copper concentrations, but only ToCTR3.1/3.2 showed a significant increase (2.5 fold) in copper-starved cells. Both ToCTR3.1 and ToCTR3.2 restored growth of a yeast double mutant, Saccharomyces cerevisiae ctr1Δctr3Δ, in copper deficient medium. GFP-fused ToCTR expression showed that some ToCTR3.1 localized to the plasma membrane but a large portion was retained in the endoplasmic reticulum. Inefficient targeting of ToCTR3.1 to the yeast outer membrane may explain poorer growth compared to the Saccharomyces native ScCTR1 transformant. Thus, diatom CTR genes encoding CTR-type copper transporters show high-affinity copper uptake and their regulation may enable diatoms to survive in ocean environments containing a wide range of copper concentrations.

  15. Probing physics beyond the standard model in diatomic molecules

    International Nuclear Information System (INIS)

    Denis, M.

    2017-01-01

    Nowadays, the incompleteness of the Standard Model of particles (SM) is largely acknowledged. One of its most obvious shortcomings is the lack of explanation for the huge surplus of matter over antimatter in the universe, the so-called baryon asymmetry of the universe. New CP (charge conjugation and spatial parity) violations absent in the SM are assumed to be responsible for this asymmetry. Such a violation could be observed, in ordinary matter through a set of interactions violating both parity and time-reversal symmetries (P, T -odd) among which the preponderant ones are the electron Electric Dipole Moment (eEDM), the electron-nucleon scalar-pseudoscalar (enSPS) and the nuclear magnetic quadrupole moment (nMQM) interactions. Hence, an experimental evidence of a non-zero P, T -odd interaction constant would be a probe of this New Physics beyond the Standard Model. The calculation of the corresponding molecular parameters is performed by making use of an elaborate four-component relativistic configuration interaction approach in polar diatomic molecules containing an actinide, that are particularly adequate systems for eEDM experiments, such as ThO that allowed for assigning the most constraining upper bound on the eEDM and ThF"+ that will be used in a forthcoming experiment. Those results will be of crucial importance in the interpretation of the measurements since the fundamental constants can only be evaluated if one combines both experimental energy shift measurements and theoretical molecular parameters. This manuscript proceeds as follows, after an introduction to the general background of the search of CP-violations and its consequences for the understanding of the Universe (Chapter 1), a presentation of the underlying theory of the evidence of such violation in ordinary matter, namely the P, T -odd sources of the Electric Dipole Moment of a many-electron system, as well as the relevant molecular parameters is given in Chapter 2. A similar introduction to

  16. Nestmate recognition in social insects and the role of hydrocarbons

    DEFF Research Database (Denmark)

    van Zweden, Jelle Stijn; D'Ettorre, Patrizia

    2010-01-01

    A unique and critical analysis of the wealth of research conducted on the biology, biochemistry and chemical ecology of the rapidly growing field of insect cuticular hydrocarbons. Authored by leading experts in their respective fields, the twenty chapters show the complexity that has been...... discovered in the nature and role of hydrocarbons in entomology. Covers, in great depth, aspects of chemistry (structures, qualitative and quantitative analysis), biochemistry (biosynthesis, molecular biology, genetics, evolution), physiology, taxonomy, and ecology. Clearly presents to the reader the array...... of data, ideas, insights and historical disagreements that have been accumulated during the past half century. An emphasis is placed on the role of insect hydrocarbons in chemical communication, especially among the social insects. Includes the first review on the chemical synthesis of insect hydrocarbons...

  17. Short-term toxicity of hexavalent-chromium to epipsammic diatoms of a microtidal estuary (Río de la Plata): Responses from the individual cell to the community structure

    International Nuclear Information System (INIS)

    Licursi, M.; Gómez, N.

    2013-01-01

    biofilm composition, however, did change, as reflected in a decline in cyanophytes and an increment in the proportions of diatoms and chlorophytes; with Hippodonta hungarica, Navicula novaesiberica, Nitzschia palea, and Sellaphora pupula being the most frequent and abundant species. The most notable shifts related to chromium exposure were a decrease in the relative abundance of H. hungarica and a significant increase in the proportion of N. palea. Moreover, the species analyzed in the treatment microcosms showed higher growth rates than in the controls – N. palea grew faster, while H. hungarica replicated more slowly. The total nuclear abnormalities – as recorded in Fallacia pygmaea and N. novaesiberica – were significantly higher in the treatment microcosms; whereas in N. palea, the dominant species in treatment microcosms, neither nuclear alterations nor abnormal frustules were observed

  18. Short-term toxicity of hexavalent-chromium to epipsammic diatoms of a microtidal estuary (Río de la Plata): Responses from the individual cell to the community structure

    Energy Technology Data Exchange (ETDEWEB)

    Licursi, M., E-mail: malena@ilpla.edu.ar; Gómez, N.

    2013-06-15

    biofilms. The biofilm composition, however, did change, as reflected in a decline in cyanophytes and an increment in the proportions of diatoms and chlorophytes; with Hippodonta hungarica, Navicula novaesiberica, Nitzschia palea, and Sellaphora pupula being the most frequent and abundant species. The most notable shifts related to chromium exposure were a decrease in the relative abundance of H. hungarica and a significant increase in the proportion of N. palea. Moreover, the species analyzed in the treatment microcosms showed higher growth rates than in the controls – N. palea grew faster, while H. hungarica replicated more slowly. The total nuclear abnormalities – as recorded in Fallacia pygmaea and N. novaesiberica – were significantly higher in the treatment microcosms; whereas in N. palea, the dominant species in treatment microcosms, neither nuclear alterations nor abnormal frustules were observed.

  19. Growth of hydrocarbon utilizing microorganisms

    Digital Repository Service at National Institute of Oceanography (India)

    Bhosle, N.B.; Mavinkurve, S.

    Two isolates from marine mud having broad spectrum hydrocarbon utilizing profile were identified as Arthrobacter simplex and Candida tropicalis.Both the organisms grew exponentially on crude oil. The cell yield of the organisms was influenced...

  20. Process for treating hydrocarbons, etc

    Energy Technology Data Exchange (ETDEWEB)

    1933-09-15

    A process is described for treating simultaneously bituminous substances and hydrocarbon oils for the production of low-boiling hydrocarbons and volatilization of the bituminous substances, characterized by the fact that it consists of heating a current of charge constituted by a mixture of the bituminous substances and hydrocarbon oils, to a high temperature, passing the heated current into a zone of extended reaction where the vapors are separated from the liquid or solid residue to favor transformation of the liquid hydrocarbons and volatilization of the bituminous substances, owing to the utilization of a heating agent carried to a high temperature being brought in contact with the heated charge in order to communicate its heat to the charge, while this later presents itself as relatively fine pellet or in the condition of distinct particles, particularly separated from one another.

  1. Coherent control of atoms and diatomic molecules with shaped ultrashort pulses

    International Nuclear Information System (INIS)

    Degert, J.

    2002-12-01

    This thesis deals with the theoretical and experimental study of coherent control of atomic and molecular systems with shaped pulses. At first, we present several experiments of control of coherent transients in rubidium. These transients appear when a two-level system is excited by a perturbative chirped pulse, and are characterized by oscillations in the excited state population. For a strong chirp, we show that a phase step in the spectrum modifies the phase of the oscillations. Then, by direct analogy with Fresnel zone lens, we conceive a chirped pulse with a highly modulated amplitude, allowing to suppress destructive contributions to the population transfer. In a second set of experiments, we focus on quantum path interferences in two-photon transitions excited by linearly chirped pulses. Owing to the broad bandwidth of ultrashort pulses, sequential and direct excitation paths contribute to the excited state population. Oscillations resulting from interferences between these two paths are observed in atomic sodium. Moreover, we show that they are observable whatever the sign of chirp. Theoretically, we study the control of the predissociation of a benchmark diatomic molecule: NaI. Predissociation leads to matter wave interferences in the fragments distribution. First, we show that a suitably chosen probe pulse allows the observation of theses interferences. Next, using a sequence of control pulse inducing electronic transition, we demonstrate the possibility to manipulate fragment energy distribution. (author)

  2. An engineered diatom acting like a plasma cell secreting human IgG antibodies with high efficiency

    Directory of Open Access Journals (Sweden)

    Hempel Franziska

    2012-09-01

    Full Text Available Abstract Background Although there are many different expression systems for recombinant production of pharmaceutical proteins, many of these suffer from drawbacks such as yield, cost, complexity of purification, and possible contamination with human pathogens. Microalgae have enormous potential for diverse biotechnological applications and currently attract much attention in the biofuel sector. Still underestimated, though, is the idea of using microalgae as solar-fueled expression system for the production of recombinant proteins. Results In this study, we show for the first time that completely assembled and functional human IgG antibodies can not only be expressed to high levels in algal systems, but also secreted very efficiently into the culture medium. We engineered the diatom Phaeodactylum tricornutum to synthesize and secrete a human IgG antibody against the Hepatitis B Virus surface protein. As the diatom P. tricornutum is not known to naturally secrete many endogenous proteins, the secreted antibodies are already very pure making extensive purification steps redundant and production extremely cost efficient. Conclusions Microalgae combine rapid growth rates with all the advantages of eukaryotic expression systems, and offer great potential for solar-powered, low cost production of pharmaceutical proteins.

  3. Theoretical study of quantum molecular reaction dynamics and of the effects of intense laser radiation on a diatomic molecule

    International Nuclear Information System (INIS)

    Dardi, P.S.

    1984-11-01

    Within the very broad field of molecular dynamics, we have concentrated on two simple yet important systems. The systems are simple enough so that they are adequately described with a single Born-Oppenheimer potential energy surface and that the dynamics can be calculated accurately. They are important because they give insight into solving more complicated systems. First we discuss H + H 2 reactive scattering. We present an exact formalism for atom-diatom reactive scattering which avoids the problem of finding a coordinate system appropriate for both reactants and products. We present computational results for collinear H + H 2 reactive scattering which agree very well with previous calculations. We also present a coupled channel distorted wave Born approximation for atom-diatom reactive scattering which we show is a first order approximation to our exact formalism. We present coupled channel DWBA results for three dimensional H + H 2 reactive scattering. The second system is an isolated HF molecule in an intense laser field. Using classical trajectories and quantum dynamics, we look at energy absorbed and transition probabilities as a function of the laser pulse time and also averaged over the pulse time. Calculations are performed for both rotating and nonrotating HF. We examine one and two photon absorption about the fundamental frequency, multiphoton absorption, and overtone absorption. 127 references, 31 figures, 12 tables

  4. A conceptual model for the growth, persistence, and blooming behavior of the benthic mat-forming diatom Didymosphenia geminata (Invited)

    Science.gov (United States)

    Cullis, J. D.; Gillis, C.; Bothwell, M.; Kilroy, C.; Packman, A. I.; Hassan, M. A.

    2010-12-01

    The nuisance diatom Didymosphenia geminata (didymo) presents an ecological paradox. How can this benthic algae produce such large amounts of biomass in cold, fast flowing, low nutrient streams? The aim of this paper is to present a conceptual model for the growth, persistence, and blooming behavior of this benthic mat-forming diatom that may help to explain this paradox. The conceptual model highlights the importance of distinguishing between mat thickness and cell growth. It presents evidence gathered from a range of existing studies around the world to support the proposed relationship between growth and light, nutrients and temperature as well as the importance of flood events and bed disturbance in mat removal. It is anticipated that this conceptual model will not only help in identifying the key controlling variables and set a framework for future studies but also support the future management of this nuisance algae. Summary of the conceptual model for didymo growth showing the proposed relationships for the growth of cells and mats with nutrients, radiation and water temperature and the dependence of removal on bed shear stress and the potential for physical bed disturbance.

  5. Uptake and depuration of 131I from labelled diatoms (Skeletonema costatum) to the edible periwinkle (Littorina littorea)

    International Nuclear Information System (INIS)

    Wilson, R.C.; Vives i Batlle, J.; Watts, S.J.; McDonald, P.; Parker, T.G.

    2007-01-01

    Uptake and depuration of 131 I into winkles through consumption of the diatom Skeletonema costatum is described. The work follows on from previous studies that investigated the uptake of iodine into winkles from seawater and seaweed. Incorporation of 131 I in S. costatum from labelled seawater followed linear first-order kinetics with an uptake half-time of 0.40 days. Iodine uptake in winkles from labelled S. costatum also followed linear first-order kinetics, with a calculated equilibrium concentration (C ∞ ) of 42 Bq kg -1 and a transfer factor (TF) of 1.1 x 10 -4 with respect to labelled diatom food. This TF is lower than that observed for uptake of 131 I in winkles from labelled seaweed. For the depuration stage, a biphasic sequence with biological half-lives of 1.3 and 255 days was determined. The first phase is biokinetically important, given that winkles can lose two-thirds of their activity during that period. This study shows that, whilst winkles can obtain radioactive iodine from phytoplankton consumption, they do not retain the majority of that activity for very long. Hence, compared with other exposure pathways, such as uptake from seawater and macroalgae, incorporation from phytoplankton is a relatively minor exposure route

  6. Theoretical study of quantum molecular reaction dynamics and of the effects of intense laser radiation on a diatomic molecule

    Energy Technology Data Exchange (ETDEWEB)

    Dardi, P.S.

    1984-11-01

    Within the very broad field of molecular dynamics, we have concentrated on two simple yet important systems. The systems are simple enough so that they are adequately described with a single Born-Oppenheimer potential energy surface and that the dynamics can be calculated accurately. They are important because they give insight into solving more complicated systems. First we discuss H + H/sub 2/ reactive scattering. We present an exact formalism for atom-diatom reactive scattering which avoids the problem of finding a coordinate system appropriate for both reactants and products. We present computational results for collinear H + H/sub 2/ reactive scattering which agree very well with previous calculations. We also present a coupled channel distorted wave Born approximation for atom-diatom reactive scattering which we show is a first order approximation to our exact formalism. We present coupled channel DWBA results for three dimensional H + H/sub 2/ reactive scattering. The second system is an isolated HF molecule in an intense laser field. Using classical trajectories and quantum dynamics, we look at energy absorbed and transition probabilities as a function of the laser pulse time and also averaged over the pulse time. Calculations are performed for both rotating and nonrotating HF. We examine one and two photon absorption about the fundamental frequency, multiphoton absorption, and overtone absorption. 127 references, 31 figures, 12 tables.

  7. Effect of different CO2 concentrations on biomass, pigment content, and lipid production of the marine diatom Thalassiosira pseudonana.

    Science.gov (United States)

    Sabia, Alessandra; Clavero, Esther; Pancaldi, Simonetta; Salvadó Rovira, Joan

    2018-02-01

    The marine diatom Thalassiosira pseudonana grown under air (0.04% CO 2 ) and 1 and 5% CO 2 concentrations was evaluated to determine its potential for CO 2 mitigation coupled with biodiesel production. Results indicated that the diatom cultures grown at 1 and 5% CO 2 showed higher growth rates (1.14 and 1.29 div day -1 , respectively) and biomass productivities (44 and 48 mg AFDW L -1  day -1 ) than air grown cultures (with 1.13 div day -1 and 26 mg AFDW L -1  day -1 ). The increase of CO 2 resulted in higher cell volume and pigment content per cell of T. pseudonana. Interestingly, lipid content doubled when air was enriched with 1-5% CO 2 . Moreover, the analysis of the fatty acid composition of T. pseudonana revealed the predominance of monounsaturated acids (palmitoleic-16:1 and oleic-18:1) and a decrease of the saturated myristic acid-14:0 and polyunsaturated fatty acids under high CO 2 levels. These results suggested that T. pseudonana seems to be an ideal candidate for biodiesel production using flue gases.

  8. Hydrocarbon removal with constructed wetlands

    OpenAIRE

    Eke, Paul Emeka

    2008-01-01

    Wetlands have long played a significant role as natural purification systems, and have been effectively used to treat domestic, agricultural and industrial wastewater. However, very little is known about the biochemical processes involved, and the use of constructed treatment wetlands in the removal of petroleum aromatic hydrocarbons from produced and/or processed water. Wastewaters from the oil industry contain aromatic hydrocarbons such as benzene, toluene, ethylbenzene and x...

  9. Bioassay of polycyclic aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Van Kirk, E.A.

    1980-08-01

    A positive relationship was found between the photodynamic activity of 24 polycyclic aromatic hydrocarbons versus published results on the mutagenicity, carcinogenicity, and initiation of unscheduled DNA synthesis. Metabolic activation of benzo(a)pyrene resulted in detection of increased mutagenesis in Paramecium tetraurelia as found also in the Ames Salmonella assay. The utility of P. tetraurelia as a biological detector of hazardous polycyclic aromatic hydrocarbons is discussed.

  10. Diatom paleoecology Pass Key core 37, Everglades National Park, Florida Bay

    Science.gov (United States)

    Pyle, Laura; Cooper, S.R.; Huvane, J.K.

    1998-01-01

    During the 20th century, there have been large-scale anthropogenic modifications to the South Florida ecosystem. The effects of these changes on Florida Bay and its biological communities are currently of political and scientific interest. This study is part of a larger effort to reconstruct the history of environmental changes in the bay, using paleoecological techniques. We are using diatom indicators preserved in Florida Bay sediments to infer long-term water quality, productivity, nutrient, and salinity changes. We are also obtaining information concerning the natural variability of the ecosystem. Diatoms are microscopic algae, the remains of which are generally well preserved in sediments, and their distributions are closely linked to water quality. Diatoms were extracted from a 70-cm sediment core collected from the Pass Key mudbank of Florida Bay by the U.S. Geological Survey. Between 300-500 diatom valves from each of 15 core samples were identified and counted. Estimates of absolute abundance, species richness, Shannon-Wiener diversity, and centric:pennate ratios were calculated for each sample that was counted. Information on the ecology of the diatom species is presented, and changes in diatom community composition are evaluated. Samples contained an average of four million diatom valves per gram of sediment. Major changes in the diatom community are evident down core. These include increases in the percent abundance of marine diatoms in the time period represented by the core, probably the result of increasing salinity at Pass Key. Benthic diatoms become less abundant in the top half of the core. This may be related to a number of factors including the die-off of sea grass beds or increased turbidity of the water column. Once the chronology of the Pass Key core 37 is established, these down-core changes can be related to historical events and compared with other indicators in the sedimentary record that are currently being investigated by U.S Geological

  11. The Attribute for Hydrocarbon Prediction Based on Attenuation

    International Nuclear Information System (INIS)

    Hermana, Maman; Harith, Z Z T; Sum, C W; Ghosh, D P

    2014-01-01

    Hydrocarbon prediction is a crucial issue in the oil and gas industry. Currently, the prediction of pore fluid and lithology are based on amplitude interpretation which has the potential to produce pitfalls in certain conditions of reservoir. Motivated by this fact, this work is directed to find out other attributes that can be used to reduce the pitfalls in the amplitude interpretation. Some seismic attributes were examined and studies showed that the attenuation attribute is a better attribute for hydrocarbon prediction. Theoretically, the attenuation mechanism of wave propagation is associated with the movement of fluid in the pore; hence the existence of hydrocarbon in the pore will be represented by attenuation attribute directly. In this paper we evaluated the feasibility of the quality factor ratio of P-wave and S-wave (Qp/Qs) as hydrocarbon indicator using well data and also we developed a new attribute based on attenuation for hydrocarbon prediction -- Normalized Energy Reduction Stack (NERS). To achieve these goals, this work was divided into 3 main parts; estimating the Qp/Qs on well log data, testing the new attribute in the synthetic data and applying the new attribute on real data in Malay Basin data. The result show that the Qp/Qs is better than Poisson's ratio and Lamda over Mu as hydrocarbon indicator. The curve, trend analysis and contrast of Qp/Qs is more powerful at distinguishing pore fluid than Poisson ratio and Lamda over Mu. The NERS attribute was successful in distinguishing the hydrocarbon from brine on synthetic data. Applying this attribute on real data on Malay basin, the NERS attribute is qualitatively conformable with the structure and location where the gas is predicted. The quantitative interpretation of this attribute for hydrocarbon prediction needs to be investigated further

  12. Catalytic pyrolysis of hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Vail' eva, N A; Buyanov, R A

    1979-01-01

    Catalytic pyrolysis of petroleum fractions (undecane) was performed with the object of clarifying such questions as the mechanism of action of the catalyst, the concepts of activity and selectivity of the catalyst, the role of transport processes, the temperature ranges and limitations of the catalytic process, the effect of the catalyst on secondary processes, and others. Catalysts such as quartz, MgO, Al/sub 2/O/sub 3/, were used. Analysis of the experimental findings and the fact that the distribution of products is independent of the nature of the surface, demonstrate that the pyrolysis of hydrocarbons in the presence of catalysts is based on the heterogeneous-homogeneous radical-chain mechanism of action, and that the role of the catalysts reduces to increasing the concentration of free radicals. The concept of selectivity cannot be applied to catalysts here, since they do not affect the mechanism of the unfolding of the process of pyrolysis and their role consists solely in initiating the process. In catalytic pyrolysis the concepts of kinetic and diffusive domains of unfolding of the catalytic reaction do not apply, and only the outer surface of the catalyst is engaged, whereas the inner surface merely promotes deletorious secondary processes reducing the selectivity of the process and the activity of the catalyst. 6 references, 2 figures.

  13. Electrostatically atomised hydrocarbon sprays

    Energy Technology Data Exchange (ETDEWEB)

    Yule, A.J.; Shrimpton, J.S.; Watkins, A.P.; Balachandran, W.; Hu, D. [UMIST, Manchester (United Kingdom). Thermofluids Division, Dept. of Mechanical Engineering

    1995-07-01

    A burner using an electrostatic method to produce and control a fuel spray is investigated for non-burning sprays. The burner has a charge injection nozzle and the liquid flow rate and charge injection rate are varied using hydrocarbon liquids of differing viscosities, surface tensions and electrical conductivities (kerosene, white spirit and diesel oil). Droplet size distributions are measured and it is shown how the dropsize, spray pattern, breakup mechanism and breakup length depend on the above variables, and in particular on the specific charge achieved in the spray. The data are valuable for validating two computer models under development. One predicts the electric field and flow field inside the nozzle as a function of emitter potential, geometry and flow rate. The other predicts the effect of charge on spray dispersion, with a view to optimizing spray combustion. It is shown that electrostatic disruptive forces can be used to atomize oils at flow rates commensurate with practical combustion systems and that the charge injection technique is particularly suitable for highly resistive liquids. Possible limitations requiring further research include the need to control the wide spray angle, which may provide fuel-air mixtures too lean near the nozzle, and the need to design for maximum charge injection rate, which is thought to be limited by corona breakdown in the gas near the nozzle orifice. 30 refs., 15 figs., 1 tab.

  14. HYDROCARBONS RESERVES IN VENEZUELA

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez Cruz, D.J.

    2007-07-01

    Venezuela is an important player in the energy world, because of its hydrocarbons reserves. The process for calculating oil and associated gas reserves is described bearing in mind that 90% of the gas reserves of Venezuela are associated to oil. Likewise, an analysis is made of the oil reserves figures from 1975 to 2003. Reference is also made to inconsistencies found by international experts and the explanations offered in this respect by the Ministry of Energy and Petroleum (MENPET) and Petroleos de Venezuela (PDVSA) regarding the changes that took place in the 1980s. In turn, Hubbert's Law is explained to determine peak production of conventional oil that a reservoir or field will reach, as well as its relationship with remaining reserves. Emphasis is placed on the interest of the United Nations on this topic. The reserves of associated gas are presented along with their relationship with the different crude oils that are produced and with injected gas, as well as with respect to the possible changes that would take place in the latter if oil reserves are revised. Some recommendations are submitted so that the MENPET starts preparing the pertinent policies ruling reserves. (auth)

  15. Evaluation of hydrocarbon potential

    International Nuclear Information System (INIS)

    Cashman, P.H.; Trexler, J.H. Jr.

    1992-01-01

    Task 8 is responsible for assessing the hydrocarbon potential of the Yucca Mountain vincinity. Our main focus is source rock stratigraphy in the NTS area in southern Nevada. (In addition, Trexler continues to work on a parallel study of source rock stratigraphy in the oil-producing region of east central Nevada, but this work is not funded by Task 8.) As a supplement to the stratigraphic studies, we are studying the geometry and kinematics of deformation at NTS, particularly as these pertain to reconstructing Paleozoic stratigraphy and to predicting the nature of the Late Paleozoic rocks under Yucca Mountain. Our stratigraphic studies continue to support the interpretation that rocks mapped as the open-quotes Eleana Formationclose quotes are in fact parts of two different Mississippian units. We have made significant progress in determining the basin histories of both units. These place important constraints on regional paleogeographic and tectonic reconstructions. In addition to continued work on the Eleana, we plan to look at the overlying Tippipah Limestone. Preliminary TOC and maturation data indicate that this may be another potential source rock

  16. Quantum entanglement and the dissociation process of diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Esquivel, Rodolfo O; Molina-Espiritu, Moyocoyani [Departamento de Quimica, Universidad Autonoma Metropolitana, 09340-Mexico DF (Mexico); Flores-Gallegos, Nelson [Unidad Profesional Interdisciplinaria de IngenierIa, Campus Guanajuato del Instituto Politecnico Nacional, 36275-Guanajuato (Mexico); Plastino, A R; Angulo, Juan Carlos; Dehesa, Jesus S [Instituto Carlos I de Fisica Teorica y Computacional, and Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, 18071-Granada (Spain); Antolin, Juan, E-mail: esquivel@xanum.uam.mx, E-mail: arplastino@ugr.es [Departamento de Fisica Aplicada, EUITIZ, Universidad de Zaragoza, 50018-Zaragoza (Spain)

    2011-09-14

    In this work, we investigate quantum entanglement-related aspects of the dissociation process of some selected, representative homo- and heteronuclear diatomic molecules. This study is based upon high-quality ab initio calculations of the (correlated) molecular wavefunctions involved in the dissociation processes. The values of the electronic entanglement characterizing the system in the limit cases corresponding to (i) the united-atom representation and (ii) the asymptotic region when atoms dissociate are discussed in detail. It is also shown that the behaviour of the electronic entanglement as a function of the reaction coordinate R exhibits remarkable correspondences with the phenomenological description of the physically meaningful regimes comprising the processes under study. In particular, the extrema of the total energies and the electronic entanglement are shown to be associated with the main physical changes experienced by the molecular spatial electronic density, such as charge depletion and accumulation or bond cleavage regions. These structural changes are characterized by several selected descriptors of the density, such as the Laplacian of the electronic molecular distributions (LAP), the molecular electrostatic potential (MEP) and the atomic electric potentials fitted to the MEP.

  17. Heat conduction in diatomic chains with correlated disorder

    Science.gov (United States)

    Savin, Alexander V.; Zolotarevskiy, Vadim; Gendelman, Oleg V.

    2017-01-01

    The paper considers heat transport in diatomic one-dimensional lattices, containing equal amounts of particles with different masses. Ordering of the particles in the chain is governed by single correlation parameter - the probability for two neighboring particles to have the same mass. As this parameter grows from zero to unity, the structure of the chain varies from regular staggering chain to completely random configuration, and then - to very long clusters of particles with equal masses. Therefore, this correlation parameter allows a control of typical cluster size in the chain. In order to explore different regimes of the heat transport, two interatomic potentials are considered. The first one is an infinite potential wall, corresponding to instantaneous elastic collisions between the neighboring particles. In homogeneous chains such interaction leads to an anomalous heat transport. The other one is classical Lennard-Jones interatomic potential, which leads to a normal heat transport. The simulations demonstrate that the correlated disorder of the particle arrangement does not change the convergence properties of the heat conduction coefficient, but essentially modifies its value. For the collision potential, one observes essential growth of the coefficient for fixed chain length as the limit of large homogeneous clusters is approached. The thermal transport in these models remains superdiffusive. In the Lennard-Jones chain the effect of correlation appears to be not monotonous in the limit of low temperatures. This behavior stems from the competition between formation of long clusters mentioned above, and Anderson localization close to the staggering ordered state.

  18. Scattering and stopping of swift diatomic molecules under Coulomb explosion

    International Nuclear Information System (INIS)

    Sigmund, P.

    1992-01-01

    The scattering and stopping of the fragments of a fast diatomic molecule under Coulomb explosion has been analysed theoretically. The central assumption in the scheme is the dominance of Coulomb explosion, while electronic stopping (including wake forces) and elastic scattering are treated as perturbations. Charge exchange has been neglected. Coulomb images of penetration phenomena are heavily distorted. For small penetrated layer thicknesses, images appear contracted in the direction of the molecular axis, and expanded perpendicular to it. This distortion is described quantitatively by a linear transformation. General expressions have been derived for the effect of continuous and stochastic forces on the distribution of fragment velocities from Coulomb explosion (the ''ring pattern''). Moreover, relations have been found that allow to scale velocity distributions valid in the absence of Coulomb explosion into distributions allowing for Coulomb explosion. Applications concern the shift in ring pattern due to electronic stopping, the lateral broadening due to multiple scattering, and the effect of zero-point motion on the Coulomb image of a molecule. (orig.)

  19. Steady-state growth of the marine diatom Thalassiosira pseudonana

    International Nuclear Information System (INIS)

    Olson, R.J.; SooHoo, J.B.; Kiefer, D.A.

    1980-01-01

    Seasonal studies of the vertical distribution of nitrate, nitrite, and phytoplankton in the oceans and studies using 15 N as a tracer of nitrate metabolism indicate that the reduction of nitrate by phytoplankton is a source of nitrite in the upper waters of the ocean. To better understand this process, the relationship between nitrate uptake and nitrite production has been examined with continuous cultures of the small marine diatom Thalassiosira pseudonana. In a turbidostat culture, the rates of nitrite production by T. Pseudonana increase with light intensity. This process is only loosely coupled to rates of nitrate assimilation since the ratio of net nitrite production to total nitrate assimilation increases with increased rates of growth. In continuous cultures where steady-state concentrations of nitrate and nitrite were varied, T. pseudonana produced nitrite at rates which increased with increasing concentrations of nitrate. Again, the rates of nitrite production were uncoupled from rates of nitrate assimilation. The study was used to derive a mathematical description of nitrate and nitrite metabolism by T. pseudonana. The validity of this model was supported by the results of a study in which 15 N-labeled nitrite was introduced into the continuous culture, and the model was used to examine patterns in distribution of nitrite in the Antarctic Ocean and the Sargasso Sea

  20. Scattering and stopping of swift diatomic molecules under Coulomb explosion

    International Nuclear Information System (INIS)

    Sigmund, P.

    1991-01-01

    The scattering and stopping of the fragments of a fast diatomic molecule under Coulomb explosion has been analyzed theoretically. The central assumption in the scheme is the dominance of Coulomb explosion, while electronic stopping (including wake forces) and elastic scattering are treated as perturbations. Charge exchange has been neglected. Coulomb images of penetration phenomena are heavily distorted. For small penetrated layer thicknesses, images appear contracted in the direction of the molecular axis, and expanded perpendicular to it. This distortion is described quantitatively by a linear transformation. General expressions have been derived for the effect of continuous and stochastic forces on the distribution of fragment velocities from Coulomb explosion (the ''ring pattern''). Moreover, relations have been found that allow to scale velocity distributions valid in the absence of Coulomb explosion into distributions allowing for Coulomb explosion. Applications concern the shift in ring pattern due to electronic stopping, the lateral broadening due to multiple scattering and the effect of zero-point motion on the Coulomb image of a molecule. 14 refs., 5 figs

  1. Response of the marine diatom Thalassiosira weissflogii to iron stress

    International Nuclear Information System (INIS)

    Harrison, G.I.; Morel, F.M.M.

    1986-01-01

    The coastal diatom Thalassiosira weissflogii responds to iron limitation with decreasing growth rate, decreasing quotas of cellular iron, and increasing rates of maximum short term uptake. Growth response to steady iron limitation can be modeled according to the equations of Droop and Monod. The cellular iron quota varies from about 2 to 25 x 10 -1 mol iron per liter-cell with increasing iron; the half-saturation constant for growth, Kμ, is 1.1 x 10 -21 M (free ferric ion). In contrast, the half-saturation constant for 59 I iron uptake, K/sub rho/ is about 3 x 10 -19 M; the maximum iron uptake rate (rho/sub max/) is increased several-fold under iron limitation, resulting in a potential short term uptake rate that is a few hundred times the steady state rate. At a fixed concentration of free manganese ion, the cellular manganese quota is increased several-fold in iron-limited cultures compared to iron-sufficient cultures

  2. Behavior of the Position-Spread Tensor in Diatomic Systems.

    Science.gov (United States)

    Brea, Oriana; El Khatib, Muammar; Angeli, Celestino; Bendazzoli, Gian Luigi; Evangelisti, Stefano; Leininger, Thierry

    2013-12-10

    The behavior of the Position-Spread Tensor (Λ) in a series of light diatomic molecules (either neutral or negative ions) is investigated at a Full Configuration Interaction level. This tensor, which is the second moment cumulant of the total position operator, is invariant with respect to molecular translations, while its trace is also rotationally invariant. Moreover, the tensor is additive in the case of noninteracting subsystems and can be seen as an intrinsic property of a molecule. In the present work, it is shown that the longitudinal component of the tensor, Λ∥, which is small for internuclear distances close to the equilibrium, tends to grow if the bond is stretched. A maximum is reached in the region of the bond breaking, then Λ∥ decreases and converges toward the isolated-atom value. The degenerate transversal components, Λ⊥, on the other hand, usually have a monotonic growth toward the atomic value. The Position Spread is extremely sensitive to reorganization of the molecular wave function, and it becomes larger in the case of an increase of the electron mobility, as illustrated by the neutral-ionic avoided crossing in LiF. For these reasons, the Position Spread can be an extremely useful property that characterizes the nature of the wave function in a molecular system.

  3. Heat conduction in diatomic chains with correlated disorder

    Energy Technology Data Exchange (ETDEWEB)

    Savin, Alexander V., E-mail: asavin@center.chph.ras.ru [Semenov Institute of Chemical Physics, Russian Academy of Sciences, 4 Kosygin str., 119991 Moscow (Russian Federation); Zolotarevskiy, Vadim; Gendelman, Oleg V. [Faculty of Mechanical Engineering, Technion – Israel Institute of Technology, Haifa 32000 (Israel)

    2017-01-23

    The paper considers heat transport in diatomic one-dimensional lattices, containing equal amounts of particles with different masses. Ordering of the particles in the chain is governed by single correlation parameter – the probability for two neighboring particles to have the same mass. As this parameter grows from zero to unity, the structure of the chain varies from regular staggering chain to completely random configuration, and then – to very long clusters of particles with equal masses. Therefore, this correlation parameter allows a control of typical cluster size in the chain. In order to explore different regimes of the heat transport, two interatomic potentials are considered. The first one is an infinite potential wall, corresponding to instantaneous elastic collisions between the neighboring particles. In homogeneous chains such interaction leads to an anomalous heat transport. The other one is classical Lennard–Jones interatomic potential, which leads to a normal heat transport. The simulations demonstrate that the correlated disorder of the particle arrangement does not change the convergence properties of the heat conduction coefficient, but essentially modifies its value. For the collision potential, one observes essential growth of the coefficient for fixed chain length as the limit of large homogeneous clusters is approached. The thermal transport in these models remains superdiffusive. In the Lennard–Jones chain the effect of correlation appears to be not monotonous in the limit of low temperatures. This behavior stems from the competition between formation of long clusters mentioned above, and Anderson localization close to the staggering ordered state.

  4. Deceleration and Trapping of Heavy Diatomic Molecules for Precision Measurements

    Science.gov (United States)

    Berg, J. E. Van Den; Turkesteen, S. N. Hoekman; Prinsen, E. B.; Hoekstra, S.

    2011-06-01

    We are setting up a novel type of Stark-decelerator optimized for the deceleration and trapping of heavy diatomic molecules. Aim of these experiments is to prepare a trapped sample of ultracold molecules for precision studies of fundamental symmetries. The decelerator uses ring-shaped electrodes to create a moving trapping potential, a prototype of which has been shown to work for CO molecules. Molecules can be decelerated and trapped in the weak-field seeking part of excited rotational states. The alkaline-earth monohalide molecules (currently we focus on the SrF molecule) are prime candidates for next generation parity violation and electron-EDM studies. We plan to combine the Stark deceleration with molecular laser cooling to create a trapped sample of molecules at a final temperature of ˜ 200 μK. A. Osterwalder, S. A. Meek, G. Hammer, H. Haak and G. Meijer Phys. Rev. A 81 (51401), 2010. T. A. Isaev, S. Hoekstra, R. Berger Phys. Rev. A 82 (52521), 2010

  5. The genome of the diatom Thalassiosira pseudonana: Ecology,evolution, and metabolism

    Energy Technology Data Exchange (ETDEWEB)

    Ambrust, E.V.; Berges, J.; Bowler, C.; Green, B.; Martinez, D.; Putnam, N.; Zhou, S.; Allen, A.; Apt, K.; Bechner, M.; Brzezinski, M.; Chaal, B.; Chiovitti, A.; Davis, A.; Goodstein, D.; Hadi, M.; Hellsten,U.; Hildebrand, M.; Jenkins, B.; Jurka, J.; Kapitonov, V.; Kroger, N.; Lau, W.; Lane, T.; Larimer, F.; Lippmeier, J.; Lucas, S.; Medina, M.; Montsant, A.; Obornik, M.; Parker, M. Schnitzler; Palenik, B.; Pazour,G.; Richardson, P.; Rynearson, T.; Saito, M.; Schwartz, D.; Thamatrakoln,K.; Valentin, K.; Vardi, A.; Wilkerson, F.; Rokhsar, D.; Vardi, A.; Wilkerson, F.P.; Rokhsar, D.S.

    2004-09-01

    Diatoms are unicellular algae with plastids acquired by secondary endosymbiosis. They are responsible for {approx}20% of global carbon fixation. We report the 34 Mbp draft nuclear genome of the marine diatom, Thalassiosira pseudonana and its 129 Kbp plastid and 44 Kbp mitochondrial genomes. Sequence and optical restriction mapping revealed 24 diploid nuclear chromosomes. We identified novel genes for silicic acid transport and formation of silica-based cell walls, high-affinity iron uptake, biosynthetic enzymes for several types of polyunsaturated fatty acids, utilization of a range of nitrogenous compounds and a complete urea cycle, all attributes that allow diatoms to prosper in the marine environment. Diatoms are unicellular, photosynthetic, eukaryotic algae found throughout the world's oceans and freshwater systems. They form the base of short, energetically-efficient food webs that support large-scale coastal fisheries. Photosynthesis by marine diatoms generates as much as 40% of the 45-50 billion tonnes of organic carbon produced each year in the sea (1), and their role in global carbon cycling is predicted to be comparable to that of all terrestrial rainforests combined (2, 3). Over geological time, diatoms may have influenced global climate by changing the flux of atmospheric carbon dioxide into the oceans (4). A defining feature of diatoms is their ornately patterned silicified cell wall or frustule, which displays species-specific nano-structures of such fine detail that diatoms have long been used to test the resolution of optical microscopes. Recent attention has focused on biosynthesis of these nano-structures as a paradigm for future silica nanotechnology (5). The long history (over 180 million years) and dominance of diatoms in the oceans is reflected by their contributions to vast deposits of diatomite, most cherts and a significant fraction of current petroleum reserves (6). As photosynthetic heterokonts, diatoms reflect a fundamentally

  6. System responses to equal doses of photosynthetically usable radiation of blue, green, and red light in the marine diatom Phaeodactylum tricornutum.

    Directory of Open Access Journals (Sweden)

    Kristin Collier Valle

    Full Text Available Due to the selective attenuation of solar light and the absorption properties of seawater and seawater constituents, free-floating photosynthetic organisms have to cope with rapid and unpredictable changes in both intensity and spectral quality. We have studied the transcriptional, metabolic and photo-physiological responses to light of different spectral quality in the marine diatom Phaeodactylum tricornutum through time-series studies of cultures exposed to equal doses of photosynthetically usable radiation of blue, green and red light. The experiments showed that short-term differences in gene expression and profiles are mainly light quality-dependent. Transcription of photosynthesis-associated nuclear genes was activated mainly through a light quality-independent mechanism likely to rely on chloroplast-to-nucleus signaling. In contrast, genes encoding proteins important for photoprotection and PSII repair were highly dependent on a blue light receptor-mediated signal. Changes in energy transfer efficiency by light-harvesting pigments were spectrally dependent; furthermore, a declining trend in photosynthetic efficiency was observed in red light. The combined results suggest that diatoms possess a light quality-dependent ability to activate photoprotection and efficient repair of photodamaged PSII. In spite of approximately equal numbers of PSII-absorbed quanta in blue, green and red light, the spectral quality of light is important for diatom responses to ambient light conditions.

  7. Shared Epizoic Taxa and Differences in Diatom Community Structure Between Green Turtles (Chelonia mydas) from Distant Habitats.

    Science.gov (United States)

    Majewska, Roksana; de Vijver, Bart Van; Nasrolahi, Ali; Ehsanpour, Maryam; Afkhami, Majid; Bolaños, Federico; Iamunno, Franco; Santoro, Mario; De Stefano, Mario

    2017-11-01

    The first reports of diatoms growing on marine mammals date back to the early 1900s. However, only recently has direct evidence been provided for similar associations between diatoms and sea turtles. We present a comparison of diatom communities inhabiting carapaces of green turtles Chelonia mydas sampled at two remote sites located within the Indian (Iran) and Atlantic (Costa Rica) Ocean basins. Diatom observations and counts were carried out using scanning electron microscopy. Techniques involving critical point drying enabled observations of diatoms and other microepibionts still attached to sea turtle carapace and revealed specific aspects of the epizoic community structure. Species-poor, well-developed diatom communities were found on all examined sea turtles. Significant differences between the two host sea turtle populations were observed in terms of diatom abundance and their community structure (including growth form structure). A total of 12 and 22 diatom taxa were found from sea turtles in Iran and Costa Rica, respectively, and eight of these species belonging to Amphora, Chelonicola, Cocconeis, Navicula, Nitzschia and Poulinea genera were observed in samples from both locations. Potential mechanisms of diatom dispersal and the influence of the external environment, sea turtle behaviour, its life stage, and foraging and breeding habitats, as well as epibiotic bacterial flora on epizoic communities, are discussed.

  8. Diatoms of the jukskei-crocodile river system (transvaal, republic of South Africa): a preliminary check list

    CSIR Research Space (South Africa)

    Schoeman, FR

    1982-01-01

    Full Text Available : V & R Printers. SCHOEMAN, F. R., 1976. Diatom indicator groups in the assessment of water quality in the Jukskei-Crocodile River system (Transvaal, Republic of South Afri ca). J. Limnol. Soc. yth. Afr. 2: 21?24. SCHOEMAN, F. R., 1979. Diatoms... groups of diatom spe cies have been successfully used as an index of the quality of running waters (Lange-Bertalot, 1978a; 1979a; 1979b; Schoeman, 1976; 1979). However, the successful determination of water quality using diatoms as indicators...

  9. Biological monitoring of lotic ecosystems: the role of diatoms Biomonitoramento dos ecossistemas lóticos: o papel das diatomáceas

    Directory of Open Access Journals (Sweden)

    T. Bere

    2010-08-01

    Full Text Available Increasing anthropogenic influence on lotic environments as a result of civilisation has captured public interest because of the consequent problems associated with deterioration of water quality. Various biological monitoring methods that provide a direct measure of ecological integrity by using the response of biota to environmental changes have been developed to monitor the ecological status of lotic environments. Diatoms have been used extensively in this regard and this review attempts to summarise the basic concepts associated with biological monitoring using benthic diatoms. Where possible, examples from work carried out in Brazil are used.O aumento da influência antropogênica sobre ambientes lóticos como resultado da civilização conquistou o interesse público por causa de problemas relacionados com a consequente deterioração da qualidade da água. Vários métodos de biomonitoramento que fornecem uma medida direta da integridade ecológica usando a resposta da biota a alterações ambientais têm sido desenvolvidos para monitorar o estado ecológico de ecossistemas lóticos. Diatomáceas têm sido amplamente utilizadas e esta revisão tenta resumir os conceitos básicos associados ao monitoramento biológico utilizando diatomáceas bentônicas. Sempre que possível, exemplos de trabalhos realizados no Brasil serão utilizados.

  10. Static vs dynamic settlement and adhesion of diatoms to ship hull coatings.

    Science.gov (United States)

    Zargiel, Kelli A; Swain, Geoffrey W

    2014-01-01

    Many experiments utilize static immersion tests to evaluate the performance of ship hull coatings. These provide valuable data; however, they do not accurately represent the conditions both the hull and fouling organisms encounter while a ship is underway. This study investigated the effect of static and dynamic immersion on the adhesion and settlement of diatoms to one antifouling coating (BRA 640), four fouling-release coatings (Intersleek(®) 700, Intersleek(®) 900, Hempasil X3, and Dow Corning 3140) and one standard surface (Intergard(®) 240 Epoxy). Differences in community composition were observed between the static and dynamic treatments. Achnanthes longipes was present on all coatings under static immersion, but was not present under dynamic immersion. This was also found for diatoms in the genera Bacillaria and Gyrosigma. Melosira moniformis was the only diatom present under dynamic conditions, but not static conditions. Several common fouling diatom genera were present on panels regardless of treatment: Amphora, Cocconeis, Entomoneis Cylindrotheca, Licmophora, Navicula, Nitzschia, Plagiotropis, and Synedra. Biofilm adhesion, diatom abundance and diatom diversity were found to be significantly different between static and dynamic treatments; however, the difference was dependent on coating and sampling date. Several coatings (Epoxy, DC 3140 and IS 700) had significantly higher biofilm adhesion on dynamically treated panels on at least one of the four sampling dates, while all coatings had significantly higher diatom abundance on at least one sampling date. Diversity was significantly greater on static panels than dynamic panels for Epoxy, IS 700 and HX3 at least once during the sampling period. The results demonstrate how hydrodynamic stress will significantly influence the microfouling community. Dynamic immersion testing is required to fully understand how antifouling surfaces will respond to biofilm formation when subjected to the stresses experienced

  11. Insights into global diatom distribution and diversity in the world’s ocean

    KAUST Repository

    Malviya, Shruti; Scalco, Eleonora; Audic, Sté phane; Vincent, Flora; Veluchamy, Alaguraj; Poulain, Julie; Wincker, Patrick; Iudicone, Daniele; de Vargas, Colomban; Bittner, Lucie; Zingone, Adriana; Bowler, Chris

    2016-01-01

    Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of ∼12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 sizefractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron. We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.

  12. Molecular Tools for the Selective Detection of Nine Diatom Species Biomarkers of Various Water Quality Levels

    Directory of Open Access Journals (Sweden)

    Lucia Cimarelli

    2015-05-01

    Full Text Available Our understanding of the composition of diatom communities and their response to environmental changes is currently limited by laborious taxonomic identification procedures. Advances in molecular technologies are expected to contribute more efficient, robust and sensitive tools for the detection of these ecologically relevant microorganisms. There is a need to explore and test phylogenetic markers as an alternative to the use of rRNA genes, whose limited sequence divergence does not allow the accurate discrimination of diatoms at the species level. In this work, nine diatom species belonging to eight genera, isolated from epylithic environmental samples collected in central Italy, were chosen to implement a panel of diatoms covering the full range of ecological status of freshwaters. The procedure described in this work relies on the PCR amplification of specific regions in two conserved diatom genes, elongation factor 1-a (eEF1-a and silicic acid transporter (SIT, as a first step to narrow down the complexity of the targets, followed by microarray hybridization experiments. Oligonucleotide probes with the potential to discriminate closely related species were designed taking into account the genetic polymorphisms found in target genes. These probes were tested, refined and validated on a small-scale prototype DNA chip. Overall, we obtained 17 highly specific probes targeting eEF1-a and SIT, along with 19 probes having lower discriminatory power recognizing at the same time two or three species. This basic array was validated in a laboratory setting and is ready for tests with crude environmental samples eventually to be scaled-up to include a larger panel of diatoms. Its possible use for the simultaneous detection of diatoms selected from the classes of water quality identified by the European Water Framework Directive is discussed.

  13. Insights into global diatom distribution and diversity in the world’s ocean

    KAUST Repository

    Malviya, Shruti

    2016-03-01

    Diatoms (Bacillariophyta) constitute one of the most diverse and ecologically important groups of phytoplankton. They are considered to be particularly important in nutrient-rich coastal ecosystems and at high latitudes, but considerably less so in the oligotrophic open ocean. The Tara Oceans circumnavigation collected samples from a wide range of oceanic regions using a standardized sampling procedure. Here, a total of ∼12 million diatom V9-18S ribosomal DNA (rDNA) ribotypes, derived from 293 sizefractionated plankton communities collected at 46 sampling sites across the global ocean euphotic zone, have been analyzed to explore diatom global diversity and community composition. We provide a new estimate of diversity of marine planktonic diatoms at 4,748 operational taxonomic units (OTUs). Based on the total assigned ribotypes, Chaetoceros was the most abundant and diverse genus, followed by Fragilariopsis, Thalassiosira, and Corethron. We found only a few cosmopolitan ribotypes displaying an even distribution across stations and high abundance, many of which could not be assigned with confidence to any known genus. Three distinct communities from South Pacific, Mediterranean, and Southern Ocean waters were identified that share a substantial percentage of ribotypes within them. Sudden drops in diversity were observed at Cape Agulhas, which separates the Indian and Atlantic Oceans, and across the Drake Passage between the Atlantic and Southern Oceans, indicating the importance of these ocean circulation choke points in constraining diatom distribution and diversity. We also observed high diatom diversity in the open ocean, suggesting that diatoms may be more relevant in these oceanic systems than generally considered.

  14. Adsorption of asymmetric rigid rods or heteronuclear diatomic moleculeson homogeneous surfaces

    Science.gov (United States)

    Engl, W.; Courbin, L.; Panizza, P.

    2004-10-01

    We treat the adsorption on homogeneous surfaces of asymmetric rigid rods (like for instance heteronuclear diatomic molecules). We show that the n→0 vector spin formalism is well suited to describe such a problem. We establish an isomorphism between the coupling constants of the magnetic Hamiltonian and the adsorption parameters of the rigid rods. By solving this Hamiltonian within a mean-field approximation, we obtain analytical expressions for the densities of the different rod’s configurations, both isotherm and isobar adsorptions curves. The most probable configurations of the molecules (normal or parallel to the surface) which depends on temperature and energy parameters are summarized in a diagram. We derive that the variation of Qv , the heat of adsorption at constant volume, with the temperature is a direct signature of the adsorbed molecules configuration change. We show that this formalism can be generalized to more complicated problems such as for instance the adsorption of symmetric and asymmetric rigid rods mixtures in the presence or not of interactions.

  15. The role of ro-vibrational coupling in the revival dynamics of diatomic molecular wave packets

    International Nuclear Information System (INIS)

    Banerji, J; Ghosh, Suranjana

    2006-01-01

    We study the revival and fractional revivals of a diatomic molecular wave packet of circular states whose weighing coefficients are peaked about a vibrational quantum number ν-bar and a rotational quantum number j-bar. Furthermore, we show that the interplay between the rotational and vibrational motion is determined by a parameter γ =√D/C, where D is the dissociation energy and C is inversely proportional to the reduced mass of the two nuclei. Using I 2 and H 2 as examples, we show, both analytically and visually (through animations), that for γ>>ν-bar, j-bar, the rotational and vibrational time scales are so far apart that the ro-vibrational motion gets decoupled and the revival dynamics depends essentially on one time scale. For γ∼ν-bar, j-bar, on the other hand, the evolution of the wave packet depends crucially on both the rotational and vibrational time scales of revival. In the latter case, an interesting rotational-vibrational fractional revival is predicted and explained

  16. Structure and intensities of microwave lines in the spectra of diatomic molecules

    International Nuclear Information System (INIS)

    Tatum, J.B.

    1986-01-01

    The structure of the rotational levels in a diatomic molecule, and the intensities of microwave transitions between them, are reviewed. Attention is given to the statistical weights of levels that may have hyperfine structure on account of one or two nuclear spins, in the case of heteronuclear molecules and of homonuclear molecules. A new treatment is given, involving the concept of energy surfaces in a ternary diagram in the form of a triangular prism, in which the three vertices represent three limiting cases, while the interior of the prism displays energy levels where all three intermediate coupling parameters are of comparable magnitude. An example is given of a simple J = 2 to J = 1 transition in a molecule with nuclear spins 3/2 and 1, showing the 56 hyperhyperfine components into which the rotational line is split, and a movie film is described which shows how the resulting ''fingerprint'' varies with the relative strengths of the interactions between the nuclear and electronic angular momenta

  17. Ellipticity and the offset angle of high harmonics generated by homonuclear diatomic molecules

    International Nuclear Information System (INIS)

    Odzak, S; Milosevic, D B

    2011-01-01

    In our recent paper (2010 Phys. Rev. A 82 023412) we introduced a theory of high-order harmonic generation by diatomic molecules exposed to an elliptically polarized laser field and have shown that the nth harmonic emission rate has contributions of the components of the T-matrix element in the direction of the laser-field polarization and in the direction perpendicular to it. Using both components of the T-matrix element we now develop a theoretical approach for calculating ellipticity and the offset angle of high harmonics. We show that the emitted harmonics generated by aligned molecules are elliptically polarized even if the applied field is linearly polarized. Using examples of N 2 , O 2 and Ar 2 molecules we show the existence of extrema and sudden changes of the harmonic ellipticity and the offset angle for particular molecular alignment and explain them by the destructive two-centre interference. Taking into account that the aligned molecules are an anisotropic medium for high harmonic generation, we introduce elliptic dichroism as a measure of this anisotropy, for both components of the T-matrix element. We propose that the measurement of the elliptic dichroism may reveal further information about the molecular structure.

  18. Radiolytic degradation of chlorinated hydrocarbons in water

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xing-Zheng; Yamamoto, Takeshi [Fukui Univ., Faculty of Engineering, Dept. of Materials Science and Engineering, Fukui (Japan); Hatashita, Masanori [The Wakasa Wan Energy Research Center, Research Dept., Tsuruga, Fukui (Japan)

    2002-11-01

    Radiolytic degradation of chlorinated hydrocarbons (chloroform, trichloroethylene, and tetrachloroethylene) in water was carried out. Water solutions of the chlorinated hydrocarbons with different concentrations were irradiated with {gamma} rays. Concentrations of methane, ethane, CO, CO{sub 2}, H{sub 2}, and O{sub 2} after the irradiation were determined by gas chromatography. Concentration of chloride ion in the irradiated sample was determined by ion chromatography. Experimental results show that radiolytic degradation of the chlorinated hydrocarbon increased with the radiation dose. Methane, ethane, CO{sub 2}, H{sub 2}, and Cl{sup -} concentrations increased with the radiation dose and the sample concentration. On the other hand, O{sub 2} concentration decreased with the radiation dose and the sample concentration. When sample concentration was high, dissolved oxygen might be not enough for converting most of the C atoms in the sample into CO{sub 2}. This resulted in a low decomposition ratio. Addition of H{sub 2}O{sub 2} as an oxygen resource could increase the decomposition ratio greatly. Furthermore, gas chromatography-mass spectroscopy was applied to identify some intermediates of the radiolytic dehalogenation. Radiolytic degradation mechanisms are also discussed. (author)

  19. Polycyclic Aromatic Hydrocarbons

    Science.gov (United States)

    Salama, Farid

    2010-01-01

    Carbonaceous materials play an important role in space. Polycyclic Aromatic Hydrocarbons (PAHs) are a ubiquitous component of the carbonaceous materials. PAHs are the best-known candidates to account for the IR emission bands. They are also thought to be among the carriers of the diffuse interstellar absorption bands (DIBs). PAH ionization states reflect the ionization balance of the medium while PAH size, composition, and structure reflect the energetic and chemical history of the medium. A major challenge is to reproduce in the laboratory the physical conditions that exist in the emission and absorption interstellar zones. The harsh physical conditions of the ISM -low temperature, collisionless, strong UV radiation fields- are simulated in the laboratory by associating a molecular beam with an ionizing discharge to generate a cold plasma expansion. PAH ions and radicals are formed from the neutral precursors in an isolated environment at low temperature and probed with high-sensitivity cavity ringdown spectroscopy in the NUV-NIR range. Carbon nanoparticles are also formed during the short residence time of the precursors in the plasma and are characterized with time-offlight mass spectrometry. These experiments provide unique information on the spectra of large carbonaceous molecules and ions in the gas phase that can now be directly compared to interstellar and circumstellar observations (IR emission bands, DIBs, extinction curve). These findings also hold great potential for understanding the formation process of interstellar carbonaceous grains. We will review recent progress in the experimental and theoretical studies of PAHs, compare the laboratory data with astronomical observations and discuss the global implications.

  20. Bioremediation: Technology for treating hydrocarbon-contaminated wastewater

    Energy Technology Data Exchange (ETDEWEB)

    Towprayoon, S.; Kuntrangwattana, S. [King Mongkut`s Institute of Technology, Bangkok (Thailand)

    1996-12-31

    Cutting oil wastewater from an iron and steel factory was applied to the soil windrow. Self-remediation was then compared with remediation with acclimatized indigenous microbes. The incremental reduction rate of the microorganisms and hydrocarbon-degradable microbes was slower in self-remediation than in the latter treatment. Within 30 days, when the acclimatized indigenous microbes were used, there was a significant reduction of the contaminated hydrocarbons, while self-remediation took longer to reduce to the same concentration. Various nitrogen sources were applied to the soil pile, namely, organic compost, chemical fertilizer, ammonium sulfate, and urea. The organic compost induced a high yield of hydrocarbon-degradable microorganisms, but the rate at which the cutting oil in the soil decreased was slower than when other nitrogen sources were used. The results of cutting oil degradation studied by gas chromatography showed the absence of some important hydrocarbons. The increment of the hydrocarbon-degradable microbes in the land treatment ecosystem does not necessarily correspond to the hydrocarbon reduction efficiency. 3 refs., 3 figs.

  1. Effect of hydrocarbons on plasma treatment of NOx

    Energy Technology Data Exchange (ETDEWEB)

    Penetrante, B.M.; Pitz, W.J.; Hsaio, M.C.; Merritt, B.T.; Vogtlin, G.E. [Lawrence Livermore National Lab., CA (United States)

    1997-12-31

    Lean burn gasoline engine exhausts contain a significant amount of hydrocarbons in the form of propene. Diesel engine exhausts contain little gaseous hydrocarbon; however, they contain a significant amount of liquid-phase hydrocarbons (known as the volatile organic fraction) in the particulates. The objective of this paper is to examine the fate of NO{sub x} when an exhaust gas mixture that contains hydrocarbons is subjected to a plasma. The authors will show that the hydrocarbons promote the oxidation of NO to NO{sub 2}, but not the reduction of NO to N{sub 2}. The oxidation of NO to NO{sub 2} is strongly coupled with the hydrocarbon oxidation chemistry. This result suggests that gas-phase reactions in the plasma alone cannot lead to the chemical reduction of NO{sub x}. Any reduction of NO{sub x} to N{sub 2} can only be accomplished through heterogeneous reactions of NO{sub 2} with surfaces or particulates.

  2. Age estimation of Calliphora (Diptera: Calliphoridae) larvae using cuticular hydrocarbon analysis and Artificial Neural Networks

    OpenAIRE

    Moore, H E; Butcher, J B; Adam, C D; Day, C R; Falko, P D

    2016-01-01

    Cuticular hydrocarbons were extracted daily from the larvae of two closely related blowflies Calliphora vicina and Calliphora vomitoria (Diptera: Calliphoridae). The hydrocarbons were then analysed using Gas Chromatography–Mass Spectrometry (GC–MS), with the aim of observing changes within their chemical profiles in order to determine the larval age. The hydrocarbons were examined daily for each species from 1 day old larvae until pupariation. The results show significant chemical changes occ...

  3. Talking with TV shows

    DEFF Research Database (Denmark)

    Sandvik, Kjetil; Laursen, Ditte

    2014-01-01

    User interaction with radio and television programmes is not a new thing. However, with new cross-media production concepts such as X Factor and Voice, this is changing dramatically. The second-screen logic of these productions encourages viewers, along with TV’s traditional one-way communication...... mode, to communicate on interactive (dialogue-enabling) devices such as laptops, smartphones and tablets. Using the TV show Voice as our example, this article shows how the technological and situational set-up of the production invites viewers to engage in new ways of interaction and communication...

  4. Sedimentary facies and lithologic characters as main factors controlling hydrocarbon accumulations and their critical conditions

    Directory of Open Access Journals (Sweden)

    Jun-Qing Chen

    2015-10-01

    Full Text Available Taking more than 1000 clastic hydrocarbon reservoirs of Bohai Bay Basin, Tarim Basin and Junggar Basin, China as examples, the paper has studied the main controlling factors of hydrocarbon reservoirs and their critical conditions to reveal the hydrocarbon distribution and to optimize the search for favorable targets. The results indicated that the various sedimentary facies and lithologic characters control the critical conditions of hydrocarbon accumulations, which shows that hydrocarbon is distributed mainly in sedimentary facies formed under conditions of a long-lived and relatively strong hydrodynamic environment; 95% of the hydrocarbon reservoirs and reserves in the three basins is distributed in siltstones, fine sandstones, lithified gravels and pebble-bearing sandstones; moreover, the probability of discovering conventional hydrocarbon reservoirs decreases with the grain size of the clastic rock. The main reason is that the low relative porosity and permeability of fine-grained reservoirs lead to small differences in capillary force compared with surrounding rocks small and insufficiency of dynamic force for hydrocarbon accumulation; the critical condition for hydrocarbon entering reservoir is that the interfacial potential in the surrounding rock (Φn must be more than twice of that in the reservoir (Φs; the probability of hydrocarbon reservoirs distribution decreases in cases where the hydrodynamic force is too high or too low and when the rocks have too coarse or too fine grains.

  5. A synthesis of post-glacial diatom records from Lake Baikal

    Science.gov (United States)

    Bradbury, J. Platt; Bezrukova, E.; Chernyaeva, G.; Colman, S.M.; Khursevich, G.; King, J.W.; Likoshway, Ye. V.

    1994-01-01

    The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake.Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub — steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence.On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During

  6. Dinoflagellate blooms in upwelling systems: Seeding, variability, and contrasts with diatom bloom behaviour

    Science.gov (United States)

    Smayda, T. J.; Trainer, V. L.

    2010-04-01

    The influence of diatom bloom behaviour, dinoflagellate life cycles, propagule type and upwelling bloom cycles on the seeding of dinoflagellate blooms in eastern boundary current upwelling systems is evaluated. Winter-spring diatom bloom behaviour is contrasted with upwelling bloom behaviour because their phenology impacts dinoflagellate blooms. The winter-spring diatom bloom is usually sustained, whereas the classical upwelling diatom bloom occurs as a series of separate, recurrent mini-blooms intercalated by upwelling-relaxation periods, during which dinoflagellates often bloom. Four sequential wind-regulated phases characterize upwelling cycles, with each phase having different effects on diatom and dinoflagellate bloom behaviour: bloom “spin up”, bloom maximum, bloom “spin down”, and upwelling relaxation. The spin up - bloom maximum is the period of heightened diatom growth; the spin down - upwelling-relaxation phases are the periods when dinoflagellates often bloom. The duration, intensity and ratio of the upwelling and relaxation periods making up upwelling cycles determine the potential for dinoflagellate blooms to develop within a given upwelling cycle and prior to the subsequent “spin up” of upwelling that favours diatom blooms. Upwelling diatoms and meroplanktonic dinoflagellates have three types of propagules available to seed blooms: vegetative cells, resting cells and resting cysts. However, most upwelling dinoflagellates are holoplanktonic, which indicates that the capacity to form resting cysts is not an absolute requirement for growth and survival in upwelling systems. The long-term (decadal) gaps in bloom behaviour of Gymnodinium catenatum and Lingulodinium polyedrum, and the unpredictable bloom behaviour of dinoflagellates generally, are examined from the perspective of seeding strategies. Mismatches between observed and expected in situ bloom behaviour and resting cyst dynamics are common among upwelling dinoflagellates. This

  7. Talk Show Science.

    Science.gov (United States)

    Moore, Mitzi Ruth

    1992-01-01

    Proposes having students perform skits in which they play the roles of the science concepts they are trying to understand. Provides the dialog for a skit in which hot and cold gas molecules are interviewed on a talk show to study how these properties affect wind, rain, and other weather phenomena. (MDH)

  8. Obesity in show cats.

    Science.gov (United States)

    Corbee, R J

    2014-12-01

    Obesity is an important disease with a high prevalence in cats. Because obesity is related to several other diseases, it is important to identify the population at risk. Several risk factors for obesity have been described in the literature. A higher incidence of obesity in certain cat breeds has been suggested. The aim of this study was to determine whether obesity occurs more often in certain breeds. The second aim was to relate the increased prevalence of obesity in certain breeds to the official standards of that breed. To this end, 268 cats of 22 different breeds investigated by determining their body condition score (BCS) on a nine-point scale by inspection and palpation, at two different cat shows. Overall, 45.5% of the show cats had a BCS > 5, and 4.5% of the show cats had a BCS > 7. There were significant differences between breeds, which could be related to the breed standards. Most overweight and obese cats were in the neutered group. It warrants firm discussions with breeders and cat show judges to come to different interpretations of the standards in order to prevent overweight conditions in certain breeds from being the standard of beauty. Neutering predisposes for obesity and requires early nutritional intervention to prevent obese conditions. Journal of Animal Physiology and Animal Nutrition © 2014 Blackwell Verlag GmbH.

  9. Honored Teacher Shows Commitment.

    Science.gov (United States)

    Ratte, Kathy

    1987-01-01

    Part of the acceptance speech of the 1985 National Council for the Social Studies Teacher of the Year, this article describes the censorship experience of this honored social studies teacher. The incident involved the showing of a videotape version of the feature film entitled "The Seduction of Joe Tynan." (JDH)

  10. Geochemical assessment of light gaseous hydrocarbons in near-surface soils of Kutch-Saurashtra: Implication for hydrocarbon prospects

    Science.gov (United States)

    Rao, P. Lakshmi Srinivasa; Madhavi, T.; Srinu, D.; Kalpana, M. S.; Patil, D. J.; Dayal, A. M.

    2013-02-01

    Light hydrocarbons in soil have been used as direct indicators in geochemical hydrocarbon exploration, which remains an unconventional path in the petroleum industry. The occurrence of adsorbed soil gases, methane and heavier homologues were recorded in the near-surface soil samples collected from Kutch-Saurashtra, India. Soil gas alkanes were interpreted to be derived from deep-seated hydrocarbon sources and have migrated to the surface through structural discontinuities. The source of hydrocarbons is assessed to be thermogenic and could have been primarily derived from humic organic matter with partial contribution from sapropelic matter. Gas chromatographic analyses of hydrocarbons desorbed from soil samples through acid extraction technique showed the presence of methane through n-butane and the observed concentrations (in ppb) vary from: methane (C1) from 4-291, ethane (C2) from 0-84, propane (C3) from 0-37, i-butane (iC4) from 0-5 and n-butane (nC4) from 0-4. Carbon isotopes measured for methane and ethane by GC-C-IRMS, range between -42.9‰ to -13.3‰ (Pee Dee Belemnite - PDB) and -21.2‰ to -12.4‰ (PDB), respectively. The increased occurrence of hydrocarbons in the areas near Anjar of Kutch and the area south to Rajkot of Saurashtra signifies the area potential for oil and gas.

  11. Taxonomic studies of centric diatoms (Diatomeae: unusual nanoplanktonic forms and new records for Brazil

    Directory of Open Access Journals (Sweden)

    Kaoli Pereira Cavalcante

    2013-06-01

    Full Text Available There have been few taxonomic studies of centric diatoms in lotic freshwater environments in Brazil, especially in terms of those including nanoplanktonic forms, which are often neglected in studies of local floras, because of their small size or confusing taxonomy. This is the first study focusing on centric diatoms in the flora of the state of Bahia, in northeastern Brazil. Plankton and periphyton attached to Eichornia crassipes were collected in the winter of 2009 in the Cachoeira River. The diatoms were analyzed and described under light and electron microscopies. Seventeen infrageneric taxa were identified. Cyclotella was represented by five taxa, and concerning of similarities between diacritical features of species in this genus, their descriptions were thoroughly detailed. This was the first time that Cyclotella atomus var. marina, previously recorded only in coastal areas of Japan and Korea, has been documented in a river in South America. We also identified two diatom taxa previously unrecorded in the flora of Brazil: C. cryptica and C. meduanae. Finally, we present a detailed light, transmission and scanning electron microscopy analysis of Skeletonema potamos, a diatom rarely found in the Brazilian literature.

  12. A stress surveillance system based on calcium and nitric oxide in marine diatoms.

    Directory of Open Access Journals (Sweden)

    Assaf Vardi

    2006-03-01

    Full Text Available Diatoms are an important group of eukaryotic phytoplankton, responsible for about 20% of global primary productivity. Study of the functional role of chemical signaling within phytoplankton assemblages is still in its infancy although recent reports in diatoms suggest the existence of chemical-based defense strategies. Here, we demonstrate how the accurate perception of diatom-derived reactive aldehydes can determine cell fate in diatoms. In particular, the aldehyde (2E,4E/Z-decadienal (DD can trigger intracellular calcium transients and the generation of nitric oxide (NO by a calcium-dependent NO synthase-like activity, which results in cell death. However, pretreatment of cells with sublethal doses of aldehyde can induce resistance to subsequent lethal doses, which is reflected in an altered calcium signature and kinetics of NO production. We also present evidence for a DD-derived NO-based intercellular signaling system for the perception of stressed bystander cells. Based on these findings, we propose the existence of a sophisticated stress surveillance system in diatoms, which has important implications for understanding the cellular mechanisms responsible for acclimation versus death during phytoplankton bloom successions.

  13. Signal, Uncertainty, and Conflict in Phylogenomic Data for a Diverse Lineage of Microbial Eukaryotes (Diatoms, Bacillariophyta)

    Science.gov (United States)

    Parks, Matthew B; Wickett, Norman J; Alverson, Andrew J

    2018-01-01

    Abstract Diatoms (Bacillariophyta) are a species-rich group of eukaryotic microbes diverse in morphology, ecology, and metabolism. Previous reconstructions of the diatom phylogeny based on one or a few genes have resulted in inconsistent resolution or low support for critical nodes. We applied phylogenetic paralog pruning techniques to a data set of 94 diatom genomes and transcriptomes to infer perennially difficult species relationships, using concatenation and summary-coalescent methods to reconstruct species trees from data sets spanning a wide range of thresholds for taxon and column occupancy in gene alignments. Conflicts between gene and species trees decreased with both increasing taxon occupancy and bootstrap cutoffs applied to gene trees. Concordance between gene and species trees was lowest for short internodes and increased logarithmically with increasing edge length, suggesting that incomplete lineage sorting disproportionately affects species tree inference at short internodes, which are a common feature of the diatom phylogeny. Although species tree topologies were largely consistent across many data treatments, concatenation methods appeared to outperform summary-coalescent methods for sparse alignments. Our results underscore that approaches to species-tree inference based on few loci are likely to be misled by unrepresentative sampling of gene histories, particularly in lineages that may have diversified rapidly. In addition, phylogenomic studies of diatoms, and potentially other hyperdiverse groups, should maximize the number of gene trees with high taxon occupancy, though there is clearly a limit to how many of these genes will be available. PMID:29040712

  14. The transcriptome and proteome of the diatom Thalassiosira pseudonana reveal a diverse phosphorus stress response.

    Directory of Open Access Journals (Sweden)

    Sonya T Dyhrman

    Full Text Available Phosphorus (P is a critical driver of phytoplankton growth and ecosystem function in the ocean. Diatoms are an abundant class of marine phytoplankton that are responsible for significant amounts of primary production. With the control they exert on the oceanic carbon cycle, there have been a number of studies focused on how diatoms respond to limiting macro and micronutrients such as iron and nitrogen. However, diatom physiological responses to P deficiency are poorly understood. Here, we couple deep sequencing of transcript tags and quantitative proteomics to analyze the diatom Thalassiosira pseudonana grown under P-replete and P-deficient conditions. A total of 318 transcripts were differentially regulated with a false discovery rate of <0.05, and a total of 136 proteins were differentially abundant (p<0.05. Significant changes in the abundance of transcripts and proteins were observed and coordinated for multiple biochemical pathways, including glycolysis and translation. Patterns in transcript and protein abundance were also linked to physiological changes in cellular P distributions, and enzyme activities. These data demonstrate that diatom P deficiency results in changes in cellular P allocation through polyphosphate production, increased P transport, a switch to utilization of dissolved organic P through increased production of metalloenzymes, and a remodeling of the cell surface through production of sulfolipids. Together, these findings reveal that T. pseudonana has evolved a sophisticated response to P deficiency involving multiple biochemical strategies that are likely critical to its ability to respond to variations in environmental P availability.

  15. Aldehyde suppression of copepod recruitment in blooms of a ubiquitous planktonic diatom

    Science.gov (United States)

    Ianora, Adrianna; Miralto, Antonio; Poulet, Serge A.; Carotenuto, Ylenia; Buttino, Isabella; Romano, Giovanna; Casotti, Raffaella; Pohnert, Georg; Wichard, Thomas; Colucci-D'Amato, Luca; Terrazzano, Giuseppe; Smetacek, Victor

    2004-05-01

    The growth cycle in nutrient-rich, aquatic environments starts with a diatom bloom that ends in mass sinking of ungrazed cells and phytodetritus. The low grazing pressure on these blooms has been attributed to the inability of overwintering copepod populations to track them temporally. We tested an alternative explanation: that dominant diatom species impair the reproductive success of their grazers. We compared larval development of a common overwintering copepod fed on a ubiquitous, early-blooming diatom species with its development when fed on a typical post-bloom dinoflagellate. Development was arrested in all larvae in which both mothers and their larvae were fed the diatom diet. Mortality remained high even if larvae were switched to the dinoflagellate diet. Aldehydes, cleaved from a fatty acid precursor by enzymes activated within seconds after crushing of the cell, elicit the teratogenic effect. This insidious mechanism, which does not deter the herbivore from feeding but impairs its recruitment, will restrain the cohort size of the next generation of early-rising overwinterers. Such a transgenerational plant-herbivore interaction could explain the recurringly inefficient use of a predictable, potentially valuable food resource-the spring diatom bloom-by marine zooplankton.

  16. Syntrophic biodegradation of hydrocarbon contaminants.

    Science.gov (United States)

    Gieg, Lisa M; Fowler, S Jane; Berdugo-Clavijo, Carolina

    2014-06-01

    Anaerobic environments are crucial to global carbon cycling wherein the microbial metabolism of organic matter occurs under a variety of redox conditions. In many anaerobic ecosystems, syntrophy plays a key role wherein microbial species must cooperate, essentially as a single catalytic unit, to metabolize substrates in a mutually beneficial manner. Hydrocarbon-contaminated environments such as groundwater aquifers are typically anaerobic, and often methanogenic. Syntrophic processes are needed to biodegrade hydrocarbons to methane, and recent studies suggest that syntrophic hydrocarbon metabolism can also occur in the presence of electron acceptors. The elucidation of key features of syntrophic processes in defined co-cultures has benefited greatly from advances in 'omics' based tools. Such tools, along with approaches like stable isotope probing, are now being used to monitor carbon flow within an increasing number of hydrocarbon-degrading consortia to pinpoint the key microbial players involved in the degradative pathways. The metagenomic sequencing of hydrocarbon-utilizing consortia should help to further identify key syntrophic features and define microbial interactions in these complex communities. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. The energy show

    International Nuclear Information System (INIS)

    1988-01-01

    The Energy Show is a new look at the problems of world energy, where our supplies come from, now and in the future. The programme looks at how we need energy to maintain our standards of living. Energy supply is shown as the complicated set of problems it is - that Fossil Fuels are both raw materials and energy sources, that some 'alternatives' so readily suggested as practical options are in reality a long way from being effective. (author)

  18. Diatomic-molecule vibrational potentials. II. New representationsa)

    International Nuclear Information System (INIS)

    Engelke, R.

    1979-01-01

    Two new representations of diatomic-molecule vibrational potentials are presented. One of these includes most of the previously employed series approximations as special cases. The new representations are tested against older ones by using Peek's ''exact'' numerical Born--Oppenheimer potentials for the 1ssigma/sub g/, 2pπ/sub u/, and 3dsigma/sub g/ states of H 2 + as test problems. Accuracy comparisons are made with Dunham, Thakkar, Ogilvie--Tipping, Coulomb-subtracted Ogilvie--Tipping, and Pade representations. A central idea of the new treatment is that it is not necessary to use a global representation of the potential over the region 0 or =1 and then match them smoothly to each other and to the Dunham expansion at R/R/sub e/=1. Attention is focused on finding improved approximations for R/R/sub e/>1, since this region exerts strong control on the vibrational eigenvalue spectrum and it is here, perhaps, where the older techniques are at their weakest. Known properties of the exact potential such as the R→infinity behavior and the dissociation energy can be built into the new forms a priori. If the dissociation energy is not known, the new methods allow it to be estimated with better accuracy then could be done previously. If one knows only Dunham coefficients, the Coulomb-subtracted Ogilvie--Tipping series is the superior representation. If one knows, in addition, the dissociation energy, the new representations are superior and give more accurate results on the interval R/R/sub e/> or =1

  19. Defensome against toxic diatom aldehydes in the sea urchin Paracentrotus lividus.

    Directory of Open Access Journals (Sweden)

    Vincenzo Marrone

    Full Text Available Many diatom species produce polyunsaturated aldehydes, such as decadienal, which compromise embryonic and larval development in benthic organisms. Here newly fertilized Paracentrotus lividus sea urchins were exposed to low concentration of decadienal and the expression levels of sixteen genes, implicated in a broad range of functional responses, were followed by Real Time qPCR in order to identify potential decadienal targets. We show that at low decadienal concentrations the sea urchin Paracentrotus lividus places in motion different classes of genes to defend itself against this toxic aldehyde, activating hsp60 and two proteases, hat and BP10, at the blastula stage and hsp56 and several other genes (14-3-3ε, p38 MAPK, MTase, and GS at the prism stage. At this latter stage all genes involved in skeletogenesis (Nec, uni, SM50 and SM30 were also down-expressed, following developmental abnormalities that mainly affected skeleton morphogenesis. Moreover, sea urchin embryos treated with increasing concentrations of decadienal revealed a dose-dependent response of activated target genes. Finally, we suggest that this orchestrated defense system against decadienal represents part of the chemical defensome of P. lividus affording protection from environmental toxicants.

  20. The role of ultraviolet-adaptation of a marine diatom in photoenhanced toxicity of acridine.

    Science.gov (United States)

    Wiegman, Saskia; Barranguet, Christiane; Spijkerman, Elly; Kraak, Michiel Harm Steven; Admiraal, Wim

    2003-03-01

    Cultures of the marine diatom Phaeodactylum tricornutum were grown under laboratory light with a different fraction of ultraviolet radiation (UV) to study the potential role of photoadaptation in determining the sensitivity to photoenhanced toxicity of acridine. In short-term experiments, a higher acridine concentration was needed to inhibit the photosynthetic electron flux, monitored with chlorophyll a fluorescence, in algae exposed to fluorescent light (low UV) than to mercury light (high UV), consistent with the expected role of UV. The two types of light in long-term exposures led to changes in the pigment composition and photosystem I (PS I) to photosystem II (PS II) stoichiometry to optimize the utilization of fluorescent and mercury light. Despite the adaptation of the photosynthetic apparatus to a small fraction of UV, long-term exposure to mercury light did show a constant sensitivity of the photosynthetic efficiency of P. tricornutum to the phototoxic acridine. It is concluded that the prime receptor of photoenhanced toxicity may be unrelated to the photosynthetic machinery.