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Sample records for bloom-forming diatom chaetoceros

  1. Global diversity of two widespread, colony-forming diatoms of the marine plankton, Chaetoceros socialis (syn. C. radians) and Chaetoceros gelidus sp. nov.

    Science.gov (United States)

    Chamnansinp, Atchaneey; Li, Yang; Lundholm, Nina; Moestrup, Øjvind

    2013-12-01

    Marine phytoplankton samples containing diatoms of the Chaetoceros socialis group were collected from Thailand, China, Denmark, and Greenland, and cells were isolated into culture for light and electron microscopy and DNA sequencing of D1-D3 of the LSU rDNA. Species of this lineage are characterized by three short and one long setae extending from each cell, the long setae from several cells joining into a common center to form large colonies, which are sometimes visible with the naked eye. Phylogenetic analyses including sequences from other parts of the world revealed segregation into three groups. Most sequences fell into two large clades, one comprising material from cold waters, whereas the other contained material from warmer waters. Strain CCMP 172 from the Strait of Georgia, Washington State, USA, formed a separate group. The warm-water species included Chinese and Thai material and therefore probably also material from the type locality of C. socialis, Hong Kong. It is characterized by all setae being covered by spines and the setae extending from the valve at some distance from the margin. In the resting spores, both valves are ornamented with spines. The cold-water material is characterized by three spiny and one mostly smooth long setae, and the setae extend from the valve near the margin. Both valves of the resting spore are smooth. This material is described as C. gelidus sp. nov. C. radians, described from the Baltic in 1894, is considered a synonym of C. socialis. CCMP172 is in many ways intermediate and probably constitutes a separate species. The published evidence on this globally distributed and sometimes bloom-forming group of species indicates higher species diversity than presently thought. PMID:27007633

  2. Isotopic discrimination and kinetic parameters of RubisCO from the marine bloom-forming diatom, Skeletonema costatum.

    Science.gov (United States)

    Boller, A J; Thomas, P J; Cavanaugh, C M; Scott, K M

    2015-01-01

    The cosmopolitan, bloom-forming diatom, Skeletonema costatum, is a prominent primary producer in coastal oceans, fixing CO2 with ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) that is phylogenetically distinct from terrestrial plant RubisCO. RubisCOs are subdivided into groups based on sequence similarity of their large subunits (IA-ID, II, and III). ID is present in several major oceanic primary producers, including diatoms such as S. costatum, coccolithophores, and some dinoflagellates, and differs substantially in amino acid sequence from the well-studied IB enzymes present in most cyanobacteria and in green algae and plants. Despite this sequence divergence, and differences in isotopic discrimination apparent in other RubisCO enzymes, stable carbon isotope compositions of diatoms and other marine phytoplankton are generally interpreted assuming enzymatic isotopic discrimination similar to spinach RubisCO (IB). To interpret phytoplankton δ(13) C values, S. costatum RubisCO was characterized via sequence analysis, and measurement of its KCO2 and Vmax , and degree of isotopic discrimination. The sequence of this enzyme placed it among other diatom ID RubisCOs. Michaelis-Menten parameters were similar to other ID enzymes (KCO2 = 48.9 ± 2.8 μm; Vmax = 165.1 ± 6.3 nmol min(-1 ) mg(-1) ). However, isotopic discrimination (ε = [(12) k/(13) k - 1] × 1000) was low (18.5‰; 17.0-19.9, 95% CI) when compared to IA and IB RubisCOs (22-29‰), though not as low as ID from coccolithophore, Emiliania huxleyi (11.1‰). Variability in ε-values among RubisCOs from primary producers is likely reflected in δ(13) C values of oceanic biomass. Currently, δ(13) C variability is ascribed to physical or chemical factors (e.g. illumination, nutrient availability) and physiological responses to these factors (e.g. carbon-concentrating mechanisms). Estimating the importance of these factors from δ(13) C measurements requires an accurate ε-value, and a mass

  3. Effect of Low ph on Carbohydrate Production by a Marine Planktonic Diatom (Chaetoceros muelleri)

    International Nuclear Information System (INIS)

    Rising carbon dioxide (CO2) concentrations in the atmosphere due to human activity are causing the surface ocean to become more acidic. Diatoms play a pivotal role in biogeochemical cycling and ecosystem function in the ocean. ph affected the quantum efficiency of photosystem II and carbohydrate metabolism in a planktonic diatom (Chaetoceros muelleri), representative of a widely distributed genus. In batch cultures grown at low ph, the proportion of total carbohydrate stored within the cells decreased and more dissolved carbohydrates were exuded from the cells into the surrounding medium. Changes in productivity and the way in which diatoms allocate carbon into carbohydrates may affect ecosystem function and the efficiency of the biological carbon pump in a low ph ocean.

  4. Effect of Low pH on Carbohydrate Production by a Marine Planktonic Diatom (Chaetoceros muelleri

    Directory of Open Access Journals (Sweden)

    Daniel C. O. Thornton

    2009-01-01

    Full Text Available Rising carbon dioxide (CO2 concentrations in the atmosphere due to human activity are causing the surface ocean to become more acidic. Diatoms play a pivotal role in biogeochemical cycling and ecosystem function in the ocean. pH affected the quantum efficiency of photosystem II and carbohydrate metabolism in a planktonic diatom (Chaetoceros muelleri, representative of a widely distributed genus. In batch cultures grown at low pH, the proportion of total carbohydrate stored within the cells decreased and more dissolved carbohydrates were exuded from the cells into the surrounding medium. Changes in productivity and the way in which diatoms allocate carbon into carbohydrates may affect ecosystem function and the efficiency of the biological carbon pump in a low pH ocean.

  5. Copper addition helps alleviate iron stress in a coastal diatom: Response of Chaetoceros gracilis from the Bay of Bengal to experimental Cu and Fe addition

    Digital Repository Service at National Institute of Oceanography (India)

    Biswas, H.; Bandyopadhyay, D.; Waite, A.

    . Coastal waters receive significant Cu input from a variety of anthropogenic sources which may affect fundamental biological processes including phytoplankton growth. We investigated the responses of the coastal diatom Chaetoceros gracilis to variable Cu...

  6. Induction of protease release of the resistant diatom Chaetoceros didymus in response to lytic enzymes from an algicidal bacterium.

    Science.gov (United States)

    Paul, Carsten; Pohnert, Georg

    2013-01-01

    Marine lytic bacteria can have a substantial effect on phytoplankton and are even capable to terminate blooms of microalgae. The bacterium Kordia algicida was reported to lyse cells of the diatom Skeletonema costatum and several other diatoms by a quorum sensing controlled excretion of proteases. However the diatom Chaetoceros didymus is fully resistant against the bacterial enzymes. We show that the growth curve of this diatom is essentially unaffected by addition of bacterial filtrates that are active against other diatoms. By monitoring proteases from the medium using zymography and fluorescence based activity assays we demonstrate that C. didymus responds to the presence of the lytic bacteria with the induced production of algal proteases. These proteases exhibit a substantially increased activity compared to the bacterial counterparts. The induction is also triggered by signals in the supernatant of a K. algicida culture. Size fractionation shows that only the >30 kD fraction of the bacterial exudates acts as an inducing cue. Implications for a potential induced defense of the diatom C. didymus are discussed. PMID:23469204

  7. Induction of protease release of the resistant diatom Chaetoceros didymus in response to lytic enzymes from an algicidal bacterium.

    Directory of Open Access Journals (Sweden)

    Carsten Paul

    Full Text Available Marine lytic bacteria can have a substantial effect on phytoplankton and are even capable to terminate blooms of microalgae. The bacterium Kordia algicida was reported to lyse cells of the diatom Skeletonema costatum and several other diatoms by a quorum sensing controlled excretion of proteases. However the diatom Chaetoceros didymus is fully resistant against the bacterial enzymes. We show that the growth curve of this diatom is essentially unaffected by addition of bacterial filtrates that are active against other diatoms. By monitoring proteases from the medium using zymography and fluorescence based activity assays we demonstrate that C. didymus responds to the presence of the lytic bacteria with the induced production of algal proteases. These proteases exhibit a substantially increased activity compared to the bacterial counterparts. The induction is also triggered by signals in the supernatant of a K. algicida culture. Size fractionation shows that only the >30 kD fraction of the bacterial exudates acts as an inducing cue. Implications for a potential induced defense of the diatom C. didymus are discussed.

  8. Efficient solvent extraction of antioxidant-rich extract from a tropical diatom,Chaetoceros calcitrans (Paulsen) Takano 1968简

    Institute of Scientific and Technical Information of China (English)

    Su; Chern; Foo; Fatimah; Md.Yusoff; Maznah; Ismail; Mahiran; Basri; Nicholas; Mun; Hoe; Khong; Kim; Wei; Chan; Sook; Kun; Yau

    2015-01-01

    Objective: To compare the in vitro antioxidant capacity of a diatom, Chaetoceros calcitrans(C. calcitrans) extracted using six types of solvents.Methods: Each extract was evaluated in terms of extraction yield, total carotenoid,fucoxanthin content, total phenolic and antioxidant capacities(DPPH and ABTS +scavenging activity and iron chelating activity).Results: The methanol extract exhibited the highest yield [(22.71 ± 0.96) g/100 g dry weight(DW)], total carotenoid [(4.46 ± 0.36) mg/g DW], total phenolic [(2.49 ± 0.08) mg gallic acid equivalents/g DW] and second highest fucoxanthin content [(2.08 ± 0.03) mg fucoxanthin/g DW] as compared to other solvent extracts. Methanolic extract also exhibited significantly higher(P < 0.05) scavenging(DPPH, ABTS +) and iron chelating activities.Conclusions: Methanol was the recommended solvent for the production of antioxidant rich extract from C. calcitrans. Both carotenoids and phenolic acids were found to be positively correlated to the antioxidant capacities of C. calcitrans. Lead bioactives confirmed by subsequent high performance liquid chromatography studies were fucoxanthin, gallic acid and protocatechuic acid.

  9. Efficient solvent extraction of antioxidant-rich extract from a tropical diatom,Chaetoceros calcitrans (Paulsen) Takano 1968

    Institute of Scientific and Technical Information of China (English)

    Su Chern Foo; Fatimah Md Yusoff; Maznah Ismail; Mahiran Basri; Nicholas Mun Hoe Khong; Kim Wei Chan; Sook Kun Yau

    2015-01-01

    Objective:To compare thein vitro antioxidant capacity of a diatom,Chaetoceros calcitrans (C. calcitrans) extracted using six types of solvents. Methods:Each extract was evaluated in terms of extraction yield, total carotenoid, fucoxanthin content, total phenolic and antioxidant capacities (DPPH• andABTS•+ scavenging activity and iron chelating activity). Results: The methanol extract exhibited the highest yield [(22.71 ± 0.96) g/100 g dry weight (DW)], total carotenoid [(4.46 ± 0.36) mg/g DW], total phenolic [(2.49 ± 0.08) mg gallic acid equivalents/g DW] and second highest fucoxanthin content [(2.08 ± 0.03) mg fucoxanthin/g DW] as compared to other solvent extracts. Methanolic extract also exhibited significantly higher (P Conclusions: Methanol was the recommended solvent for the production of antioxidant rich extract fromC. calcitrans. Both carotenoids and phenolic acids were found to be positively correlated to the antioxidant capacities ofC. calcitrans. Lead bioactives confirmed by subsequent high performance liquid chromatography studies were fucoxanthin, gallic acid and protocatechuic acid.

  10. Isolation and characterization of a single-stranded DNA virus infecting the marine diatom Chaetoceros sp. strain SS628-11 isolated from western Japan.

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    Kei Kimura

    Full Text Available Diatoms are significant organisms for primary production in the earth's aquatic environment. Hence, their dynamics are an important focus area in current studies. Viruses are a great concern as potential factors of diatom mortality, along with other physical, chemical, and biological factors. We isolated and characterized a new diatom virus (Csp07DNAV that lyses the marine planktonic diatom Chaetoceros sp. strain SS628-11. This paper examines the physiological, morphological, and genomic characteristics of Csp07DNAV. The virus was isolated from a surface water sample that was collected at Hiroshima Bay, Japan. It was icosahedral, had a diameter of 34 nm, and accumulated in the nuclei of host cells. Rod-shaped virus particles also coexisted in the host nuclei. The latent period and burst size were estimated to be <12 h and 29 infectious units per host cell, respectively. Csp07DNAV had a closed circular single-stranded DNA genome (5,552 nucleotides, which included a double-stranded region and 3 open reading frames. The monophyly of Csp07DNAV and other Bacilladnavirus group single-stranded DNA viruses was supported by phylogenetic analysis that was based on the amino acid sequence of each virus protein. On the basis of these results, we considered Csp07DNAV to be a new member of the genus Bacilladnavirus.

  11. Interaction Effects of Light, Temperature and Nutrient Limitations (N, P and Si on Growth, Stoichiometry and Photosynthetic Parameters of the Cold-Water Diatom Chaetoceros wighamii.

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    Kristian Spilling

    Full Text Available Light (20-450 μmol photons m(-2 s(-1, temperature (3-11 °C and inorganic nutrient composition (nutrient replete and N, P and Si limitation were manipulated to study their combined influence on growth, stoichiometry (C:N:P:Chl a and primary production of the cold water diatom Chaetoceros wighamii. During exponential growth, the maximum growth rate (~0.8 d(-1 was observed at high temperature and light; at 3 °C the growth rate was ~30% lower under similar light conditions. The interaction effect of light and temperature were clearly visible from growth and cellular stoichiometry. The average C:N:P molar ratio was 80:13:1 during exponential growth, but the range, due to different light acclimation, was widest at the lowest temperature, reaching very low C:P (~50 and N:P ratios (~8 at low light and temperature. The C:Chl a ratio had also a wider range at the lowest temperature during exponential growth, ranging 16-48 (weight ratio at 3 °C compared with 17-33 at 11 °C. During exponential growth, there was no clear trend in the Chl a normalized, initial slope (α* of the photosynthesis-irradiance (PE curve, but the maximum photosynthetic production (P(m was highest for cultures acclimated to the highest light and temperature. During the stationary growth phase, the stoichiometric relationship depended on the limiting nutrient, but with generally increasing C:N:P ratio. The average photosynthetic quotient (PQ during exponential growth was 1.26 but decreased to <1 under nutrient and light limitation, probably due to photorespiration. The results clearly demonstrate that there are interaction effects between light, temperature and nutrient limitation, and the data suggests greater variability of key parameters at low temperature. Understanding these dynamics will be important for improving models of aquatic primary production and biogeochemical cycles in a warming climate.

  12. Impact of elevated CO2 concentrations on the growth and ultrastructure of non-calcifying marine diatom (Chaetoceros gracilis F.Schütt

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    Hanan M. Khairy

    2014-01-01

    Full Text Available The impacts of different CO2 concentrations on the growth, physiology and ultrastructure of noncalcifying microalga Chaetoceros gracilis F.Schütt (Diatom were studied. We incubated Ch. gracilis under different CO2 concentrations, preindustrial and current ambient atmospheric concentrations (285 and 385 μatm, respectively or predicted year-2100 CO2 levels (550, 750 and 1050 μatm in continuous culture conditions. The growth of Ch. gracilis measured as cell number was decreased by increasing the pCO2 concentration from nowadays concentration (385 μatm to 1050 μatm. The lowest percentage changes of oxidizable organic matter, nitrite, nitrate, phosphate and silicate were recorded at a higher pCO2 (1050 μatm, and this is in consistence with the lowest recorded cell number indicating unsuitable conditions for the growth of Ch. gracilis. The minimum cell numbers obtained at higher levels of CO2 clearly demonstrate that, low improvement occurred when the carbon level was raised. This was confirmed by a highly negative correlation between cell number and carbon dioxide partial pressure (r = −0.742, p ⩽ 0.05. On the other hand, highest growth rate at pCO2 = 385 μatm was also confirmed by the maximum uptake of nutrient salts (NO3 = 68.96 μmol.l−1, PO4 = 29.75 μmol.l−1, Si2O3 = 36.99 μmol.l−1. Total protein, carbohydrate and lipid composition showed significant differences (p ⩽ 0.05 at different carbon dioxide concentrations during the exponential growth phase (day 8. Transmission Electron Microscopy of Ch. gracilis showed enlargement of the cell, chloroplast damage, disorganization and disintegration of thylakoid membranes; cell lysis occurs at a higher CO2 concentration (1050 μatm. It is concluded from this regression equation and from the results that the growth of Ch. gracilis is expected to decrease by increasing pCO2 and increasing ocean acidification.

  13. Dynamics of the marine planktonic diatom family Chaetocerotaceae in a Mediterranean coastal zone

    Science.gov (United States)

    Bosak, Sunčica; Godrijan, Jelena; Šilović, Tina

    2016-10-01

    The planktonic diatoms belonging to two genera Chaetoceros and Bacteriastrum, included within the family Chaetocerotaceae, are ecologically important as they represent an important component of the phytoplankton in the coastal regions and are often among bloom-forming taxa. We analysed the chaetocerotacean species composition and abundances in the coastal area of northeastern Adriatic in a biweekly study conducted from September 2008 to October 2009 with the aim of investigating seasonal dynamics and species succession on a fine temporal scale and determining the most important ecological factors influencing their distribution. The study identified seven Chaetoceros and three Bacteriastrum species as major phytoplankton components showing the clear annual succession and two types of blooms (one species/multi species) governed by differing ecological conditions. Autumn bloom was composed of 20 chaetocerotacean species with Chaetoceros contortus and Chaetoceros vixvisibilis alternating in dominance. The summer period was characterized by spreading of freshwater from the Po River up to the eastern coast increasing availability of phosphate which triggered the monospecific Chaetoceros vixvisibilis bloom. We explained the chaetocerotacean dominant species succession pattern by the environmental parameters, with the temperature, salinity and phosphate availability as most important factors driving the species seasonality.

  14. Fluorescent characteristics of dissolved organic matter produced by bloom-forming coastal phytoplankton

    OpenAIRE

    Fukuzaki, K; Imai, I.; Fukushima, K; Ishii, K.-I.; SAWAYAMA, S.; Yoshioka, T.

    2014-01-01

    Dynamics and sources of fluorescent dissolved organic matter (FDOM) are important for understanding biogeochemical processes in aquatic ecosystems. This study aimed to analyse direct production of FDOM by marine phytoplankton cultures and reveal fluorescent characteristics of exuded FDOM. Axenic cultures of eight species of bloom-forming marine phytoplankton, including two diatoms; a raphidophyte; two dinoflagellates; a chlorophyte; a cryptophyte and a haptophyte, were incubated in an artific...

  15. Comparison of acute toxicity of process chemicals used in the oil refinery industry, tested with the diatom Chaetoceros gracilis, the flagellate Isochrysis galbana, and the zebra fish, Brachydanio rerio

    Energy Technology Data Exchange (ETDEWEB)

    Roseth, S.; Edvardsson, T.; Botten, T.M.; Fuglestad, J.; Fonnum, F.; Stenersen, J. [Univ. of Oslo (Norway)

    1996-07-01

    Chemicals under the trade names Nalco 537-DA, Nalco 625, Nalco 7607, Nalco 5165, Ivamin, and technical monoethanolamine are used extensively in the oil refinery industry. Aquatic toxicity tests were conducted using zebra fish fry (Brachydanio rerio) and the unicellular algae Isochrysis galbana (a flagellate) and Chaetoceros gracilis (a diatom). Inhibition of cell division, chlorophyll content, and {sup 14}CO{sub 2} uptake in the algae were sensitive end points. The effective concentrations (EC50s) of growth inhibition were 0.1 mg/L (Ivamin; I. galbana), 0.8 mg/L (Nalco 7607; I. galbana), 6 mg/L (Nalco 625; I. galbana), 10 mg/L (Nalco 5165; C. gracilis), and 15 mg/L (Nalco 537-DA; C. gracilis). The lethal concentrations (LC50s) (96 h) toward zebra fish fry was 1 mg/L for Nalco 7607, 6.5 mg/L for Nalco 537-DA, 7.1 mg/L for Nalco 625, and 20 mg/L for Ivamin 803. Monoethanolamine had an LC50 higher than 5,000 mg/L. Nalco 5165 was not tested on fish fry. The heartbeat frequency of fish embryos was reduced by 2.5 mg/L Nalco 537-DA, but this was an insensitive end point for the other chemicals.

  16. Comparison of acute toxicity of process chemicals used in the oil refinery industry, tested with the diatom Chaetoceros gracilis, the flagellate Isochrysis galbana, and the zebra fish, Brachydanio rerio

    International Nuclear Information System (INIS)

    Chemicals under the trade names Nalco 537-DA, Nalco 625, Nalco 7607, Nalco 5165, Ivamin, and technical monoethanolamine are used extensively in the oil refinery industry. Aquatic toxicity tests were conducted using zebra fish fry (Brachydanio rerio) and the unicellular algae Isochrysis galbana (a flagellate) and Chaetoceros gracilis (a diatom). Inhibition of cell division, chlorophyll content, and 14CO2 uptake in the algae were sensitive end points. The effective concentrations (EC50s) of growth inhibition were 0.1 mg/L (Ivamin; I. galbana), 0.8 mg/L (Nalco 7607; I. galbana), 6 mg/L (Nalco 625; I. galbana), 10 mg/L (Nalco 5165; C. gracilis), and 15 mg/L (Nalco 537-DA; C. gracilis). The lethal concentrations (LC50s) (96 h) toward zebra fish fry was 1 mg/L for Nalco 7607, 6.5 mg/L for Nalco 537-DA, 7.1 mg/L for Nalco 625, and 20 mg/L for Ivamin 803. Monoethanolamine had an LC50 higher than 5,000 mg/L. Nalco 5165 was not tested on fish fry. The heartbeat frequency of fish embryos was reduced by 2.5 mg/L Nalco 537-DA, but this was an insensitive end point for the other chemicals

  17. Characterisation of algal organic matter produced by bloom-forming marine and freshwater algae

    KAUST Repository

    Villacorte, Loreen O.

    2015-04-01

    Algal blooms can seriously affect the operation of water treatment processes including low pressure (micro- and ultra-filtration) and high pressure (nanofiltration and reverse osmosis) membranes mainly due to accumulation of algal-derived organic matter (AOM). In this study, the different components of AOM extracted from three common species of bloom-forming algae (Alexandrium tamarense, Chaetoceros affinis and Microcystis sp.) were characterised employing various analytical techniques, such as liquid chromatography - organic carbon detection, fluorescence spectroscopy, fourier transform infrared spectroscopy, alcian blue staining and lectin staining coupled with laser scanning microscopy to indentify its composition and force measurement using atomic force microscopy to measure its stickiness. Batch culture monitoring of the three algal species illustrated varying characteristics in terms of growth pattern, cell concentration and AOM release. The AOM produced by the three algal species comprised mainly biopolymers (e.g., polysaccharides and proteins) but some refractory compounds (e.g., humic-like substances) and other low molecular weight acid and neutral compounds were also found. Biopolymers containing fucose and sulphated functional groups were found in all AOM samples while the presence of other functional groups varied between different species. A large majority (>80%) of the acidic polysaccharide components (in terms of transparent exopolymer particles) were found in the colloidal size range (<0.4μm). The relative stickiness of AOM substantially varied between algal species and that the cohesion between AOM-coated surfaces was much stronger than the adhesion of AOM on AOM-free surfaces. Overall, the composition as well as the physico-chemical characteristics (e.g., stickiness) of AOM will likely dictate the severity of fouling in membrane systems during algal blooms.

  18. Competition of bloom-forming marine phytoplankton at low nutrient concentrations

    Institute of Scientific and Technical Information of China (English)

    Hanhua Hu; Jun Zhang; Weidong Chen

    2011-01-01

    Competition of three bloom-forming marine phytoplankton (diatom Skeletonema costatum, and dinoflagellates Prorocentrum minimum and Alexandrium tamarense) was studied through a series of multispecies cultures with different nitrate (NaNO3) and phosphate (NaH2PO4) levels and excess silicate to interpret red tide algae succession. S. costatum outgrew the other two dinoflagellates in nitrate and phosphate replete cultures with 10 μmol/L Na2SiO3. Under nitrate limited (8.82 μ mol/L NaNO3) conditions, the growth of S. costatum was also dominant when phosphate concentrations were from 3.6 to 108 μmol/L. Cell density of the two dinoflagellates only increased slighfly, to less than 400 and 600 cells/mL, respectively. Cell density of S. costatum decreased with time before day 12, and then increased to 4000 cells/mL (1.5 mg/L dry biomass) at NaNO3 concentrations between 88.2 and 882 μmol/L with limited phosphate (0.36 μmol/L NaH2PO4) levels. In addition, P. minimum grew well with a maximal cell density of 1690-2100 cells/mL (0.5-0.6 mg/L dry biomass). Although S. costatum initially grew fast, its cell density decreased quickly with time later in the growth phase and the two dinoflagellates were dominant under the nitrate-limited and high nitrate conditions with limited phosphate. These results indicated that the diatom was a poor competitor compared to the two dinoflagellates under limited phosphate; however, it grew well under limited nitrate when growth of the dinoflagellates was near detection limits.

  19. Competition of bloom-forming marine phytoplankton at low nutrient concentrations.

    Science.gov (United States)

    Hu, Hanhua; Zhang, Jun; Chen, Weidong

    2011-01-01

    Competition of three bloom-forming marine phytoplankton (diatom Skeletonema costatum, and dinoflagellates Prorocentrum minimum and Alexandrium tamarense) was studied through a series of multispecies cultures with different nitrate (NaNO3) and phosphate (NaH2PO4) levels and excess silicate to interpret red tide algae succession. S. costatum outgrew the other two dinoflagellates in nitrate and phosphate replete cultures with 10 micromol/L Na2SiO3. Under nitrate limited (8.82 micromol/L NaNO3) conditions, the growth of S. costatum was also dominant when phosphate concentrations were from 3.6 to 108 micromol/L. Cell density of the two dinoflagellates only increased slightly, to less than 400 and 600 cells/mL, respectively. Cell density of S. costatum decreased with time before day 12, and then increased to 4000 cells/mL (1.5 mg/L dry biomass) at NaNO3 concentrations between 88.2 and 882 micromol/L with limited phosphate (0.36 micromol/L NaH2PO4) levels. In addition, P. minimum grew well with a maximal cell density of 1690-2100 cells/mL (0.5-0.6 mg/L dry biomass). Although S. costatum initially grew fast, its cell density decreased quickly with time later in the growth phase and the two dinoflagellates were dominant under the nitrate-limited and high nitrate conditions with limited phosphate. These results indicated that the diatom was a poor competitor compared to the two dinoflagellates under limited phosphate; however, it grew well under limited nitrate when growth of the dinoflagellates was near detection limits. PMID:21793409

  20. Natural and anthropogenic nitrogen uptake by bloom-forming macroalgae

    Energy Technology Data Exchange (ETDEWEB)

    Thornber, Carol S. [Department of Biological Sciences, 100 Flagg Road, University of Rhode Island, Kingston, RI 02881 (United States)], E-mail: thornber@uri.edu; DiMilla, Peter; Nixon, Scott W. [Graduate School of Oceanography, University of Rhode Island, South Ferry Road, Narragansett, RI 02881 (United States); McKinney, Richard A. [US Environmental Protection Agency, Atlantic Ecology Division, 27 Tarzwell Drive, Narragansett, RI 02882 (United States)

    2008-02-15

    The frequency and duration of macroalgal blooms have increased in many coastal waters over the past several decades. We used field surveys and laboratory culturing experiments to examine the nitrogen content and {delta}{sup 15}N values of Ulva and Gracilaria, two bloom-forming algal genera in Narragansett Bay, RI (USA). The northern end of this bay is densely populated with large sewage treatment plant nitrogen inputs; the southern end is more lightly populated and opens to the Atlantic Ocean. Field-collected Ulva varied in {delta}{sup 15}N among sites, but with two exceptions had {delta}{sup 15}N above 10 per mille , reflecting a significant component of heavy anthropogenic N. This variation was not correlated with a north-south gradient. Both Ulva and Gracilaria cultured in water from across Narragansett Bay also had high signals ({delta}{sup 15}N = {approx}14-17 per mille and 8-12 per mille , respectively). These results indicate that inputs of anthropogenic N can have far-reaching impacts throughout estuaries.

  1. MF/UF rejection and fouling potential of algal organic matter from bloom-forming marine and freshwater algae

    KAUST Repository

    Villacorte, Loreen O.

    2015-07-01

    Pretreatment with microfiltration (MF) or ultrafiltration (UF) membranes has been proposed for seawater reverse osmosis (SWRO) plants to address operational issues associated with algal blooms. Here, we investigated the MF/UF rejection and fouling potential of algal organic matter (AOM) released by common species of bloom-forming marine (Alexandrium tamarense and Chaetoceros affinis) and freshwater (Microcystis sp.) algae. Batch culture monitoring of the three algal species illustrated varying growth pattern, cell concentration, AOM released and membrane fouling potential. The high membrane fouling potential of the cultures can be directly associated (R2>0.85) with AOM such as transparent exopolymer particle (TEP) while no apparent relationship with algal cell concentration was observed. The AOM comprised mainly biopolymers (e.g., polysaccharides and proteins) and low molecular weight organic compounds (e.g., humic-like substances). The former were largely rejected by MF/UF membranes while the latter were poorly rejected. MF (0.4μm and 0.1μm pore size) rejected 14%-56% of biopolymers while conventional UF (100kDa) and tight UF (10kDa) rejected up to 83% and 97%, respectively. The retention of AOM resulted in a rapid increase in trans-membrane pressure (δP) over time, characterised by pore blocking followed by cake filtration with enhanced compression as illustrated by an exponential progression of δP. © 2015 Elsevier B.V.

  2. Bloom forming and toxic phytoplankton in transitional and coastal waters of Cantabria region coast (Southeastern Bay of Biscay, Spain).

    Science.gov (United States)

    Seoane, Sergio; Puente, Araceli; Guinda, Xabier; Juanes, Jose Antonio

    2012-12-01

    Phytoplankton monitoring has extended to practically all the regions of the European coast due to the implementation of the European Water Framework Directive. In this way, the study of phytoplankton taxonomic composition and dynamic is being performed in many areas poorly studied or not studied before. During the last years, a monitoring programme has been carried out at the coast of Cantabria region (SE Bay of Biscay); the presence of some potentially toxic and bloom forming species (>7.5 × 10⁵ cells per litre) has been observed. Diatoms and cryptophytes are the main blooming taxa in this region in the majority of the estuaries and in some of the coastal sites. All estuaries and coastal stations showed at least one potentially toxic species, being the dinoflagellates the group with the highest number of taxa observed. The potentially toxic species found in highest concentrations were the genera Pseudo-nitzschia and Chrysochromulina. PMID:23017945

  3. Inhibition effect of engineered silver nanoparticles to bloom forming cyanobacteria

    Science.gov (United States)

    Thuy Duong, Thi; Son Le, Thanh; Thu Huong Tran, Thi; Kien Nguyen, Trung; Ho, Cuong Tu; Hien Dao, Trong; Phuong Quynh Le, Thi; Chau Nguyen, Hoai; Dang, Dinh Kim; Thu Huong Le, Thi; Thu Ha, Phuong

    2016-09-01

    Silver nanoparticle (AgNP) has a wide range antibacterial effect and is extensively used in different aspects of medicine, food storage, household products, disinfectants, biomonitoring and environmental remediation etc. In the present study, we examined the growth inhibition effect of engineered silver nanoparticles against bloom forming cyanobacterial M. aeruginosa strain. AgNPs were synthesized by a chemical reduction method at room temperature and UV-Vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscope (TEM) showed that they presented a maximum absorption at 410 nm and size range between 10 and 18 nm. M. aeruginosa cells exposed during 10 d to AgNPs to a range of concentrations from 0 to 1 mg l-1. The changes in cell density and morphology were used to measure the responses of the M. aeruginosa to AgNPs. The control and treatment units had a significant difference in terms of cell density and growth inhibition (p < 0.05). Increasing the concentration of AgNPs, a reduction of the cell growths in all treatment was observed. The inhibition efficiency was reached 98.7% at higher concentration of AgNPs nanoparticles. The term half maximal effective concentration (EC50) based on the cell growth measured by absorbance at 680 nm (A680) was 0.0075 mg l-1. The inhibition efficiency was 98.7% at high concentration of AgNPs (1 mg l-1). Image of SEM and TEM reflected a shrunk and damaged cell wall indicating toxicity of silver nanoparticles toward M. aeruginosa.

  4. Biomass decay rates and tissue nutrient loss in bloom and non-bloom-forming macroalgal species

    Science.gov (United States)

    Conover, Jessie; Green, Lindsay A.; Thornber, Carol S.

    2016-09-01

    Macroalgal blooms occur in shallow, low-wave energy environments and are generally dominated by fast-growing ephemeral macroalgae. When macroalgal mats undergo senescence and decompose they can cause oxygen depletion and release nutrients into the surrounding water. There are relatively few studies that examine macroalgal decomposition rates in areas impacted by macroalgal blooms. Understanding the rate of macroalgal bloom decomposition is essential to understanding the impacts of macroalgal blooms following senescence. Here, we examined the biomass, organic content, nitrogen decay rates and δ15N values for five macroalgal species (the bloom-forming Agardhiella subulata, Gracilaria vermiculophylla, Ulva compressa, and Ulva rigida and the non-bloom-forming Fucus vesiculosus) in Narragansett Bay, Rhode Island, U.S.A. using a litterbag design. Bloom-forming macroalgae had similar biomass decay rates (0.34-0.51 k d-1) and decayed significantly faster than non-bloom-forming macroalgae (0.09 k d-1). Biomass decay rates also varied temporally, with a significant positive correlation between biomass decay rate and water temperature for U. rigida. Tissue organic content decreased over time in all species, although A. subulata and G. vermiculophylla displayed significantly higher rates of organic content decay than U. compressa, U. rigida, and F. vesiculosus. Agardhiella subulata had a significantly higher rate of tissue nitrogen decay (0.35 k d-1) than all other species. By contrast, only the δ15N of F. vesiculosus changed significantly over the decay period. Overall, our results indicate that bloom-forming macroalgal species decay more rapidly than non-bloom-forming species.

  5. 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.

    be accumulated within the tissues of various species of marine organisms pos- ing serious threat to the health of aquatic ecosystems (Yan et al. 1997). Among the heavy metals, Hg is well-known for its high toxicity and negative impact on the health of marine... of Veterinary Medicine, Veterinaerplatz 1, 1210 Vienna, Austria 2 National Institute of Oceanography, CSIR, Dona Paula, Goa 403004, India 3 Global Enviro-Care, Kevnem, Caranzalem, Goa 403002, India Environ Sci Pollut Res (2016) 23:2770–2777 DOI 10.1007/s11356...

  6. Integrating phylogeny, geographic niche partitioning, and secondary metabolite synthesis in bloom-forming Planktothrix

    OpenAIRE

    Kurmayer, Rainer; Blom, Judith F.; Deng, Li; Pernthaler, Jakob

    2015-01-01

    Toxic freshwater cyanobacteria form harmful algal blooms that can cause acute toxicity to humans and livestock. Globally distributed, bloom-forming cyanobacteria Planktothrix either retain or lose the mcy gene cluster (encoding the synthesis of the secondary metabolite hepatotoxin microcystin or MC), resulting in a variable spatial/temporal distribution of (non)toxic genotypes. Despite their importance to human well-being, such genotype diversity is not being mapped at scales relevant to natu...

  7. Extensive Chaetoceros curvisetus bloom in relation to water quality in Port Blair Bay, Andaman Islands.

    Science.gov (United States)

    Begum, Mehmuna; Sahu, Biraja Kumar; Das, Apurba Kumar; Vinithkumar, Nambali Valsalan; Kirubagaran, Ramalingam

    2015-05-01

    Blooming of diatom species Chaetoceros curvisetus (Cleve, 1889) was observed in Junglighat Bay and Haddo Harbour of Port Blair Bay of Andaman and Nicobar Islands during June 2010. Physico-chemical parameters, nutrient concentrations and phytoplankton composition data collected from five stations during 2010 were classified as bloom area (BA) and non-bloom area (NBA) and compared. Elevated values of dissolved oxygen were recorded in the BA, and it significantly varied (p parametric multidimensional scaling (nMDS) ordinations; cluster analysis powered by SIMPROF test also grouped the stations as BA and NBA.

  8. Extensive Chaetoceros curvisetus bloom in relation to water quality in Port Blair Bay, Andaman Islands.

    Science.gov (United States)

    Begum, Mehmuna; Sahu, Biraja Kumar; Das, Apurba Kumar; Vinithkumar, Nambali Valsalan; Kirubagaran, Ramalingam

    2015-05-01

    Blooming of diatom species Chaetoceros curvisetus (Cleve, 1889) was observed in Junglighat Bay and Haddo Harbour of Port Blair Bay of Andaman and Nicobar Islands during June 2010. Physico-chemical parameters, nutrient concentrations and phytoplankton composition data collected from five stations during 2010 were classified as bloom area (BA) and non-bloom area (NBA) and compared. Elevated values of dissolved oxygen were recorded in the BA, and it significantly varied (p parametric multidimensional scaling (nMDS) ordinations; cluster analysis powered by SIMPROF test also grouped the stations as BA and NBA. PMID:25838063

  9. Genetic Basis for Geosmin Production by the Water Bloom-Forming Cyanobacterium, Anabaena ucrainica

    Directory of Open Access Journals (Sweden)

    Zhongjie Wang

    2014-12-01

    Full Text Available Geosmin is a common, musty-smelling sesquiterpene, principally produced by cyanobacteria. Anabaena ucrainica (Schhorb. Watanabe, a water bloom-forming cyanobacterium, is the geosmin producer responsible for odor problems in Dianchi and Erhai lakes in China. In this study, the geosmin synthase gene (geo of A. ucrainica and its flanking regions were identified and cloned by polymerase chain reaction (PCR and genome walking. The geo gene was found to be located in a transcription unit with two cyclic nucleotide-binding protein genes (cnb. The two cnb genes were highly similar and were predicted members of the cyclic adenosine monophosphate (cAMP receptor protein/fumarate nitrate reductase regulator (Crp–Fnr family. Phylogenetic and evolutionary analyses implied that the evolution of the geosmin genes involved a horizontal gene transfer process in cyanobacteria. These genes showed a close relationship to 2-methylisoborneol genes in origin and evolution.

  10. Evaluation of genotoxic responses of Chaetoceros tenuissimus and Skeletonema costatum to water accommodated fraction of petroleum hydrocarbons as biomarker of exposure

    Digital Repository Service at National Institute of Oceanography (India)

    Desai, S.R.; Verlecar, X.N.; Ansari, Z.A.; Jagtap, T.G.; Sarkar, A.; Vashistha, D.; Dalal, S.G.

    method standardized in our laboratory, involves optimization of the alkaline unwinding assay using unialgal cultures of marine diatom C. tenuissimus and S. costatum as test species. 2. Material and methods Chaetoceros tenuissimus... of the analysis as less than 2.5%. Analysis was carried out by GC/MS Laboratory, National Institute of Oceanography, India. A typical chromatogram and a mass spectrum are shown in Fig 5a and 5b. 2.3 Preparation of test cultures for C. tenuissimus and S...

  11. Bioactivity effect of two macrophyte extracts on growth performance of two bloom-forming cyanophytes

    Directory of Open Access Journals (Sweden)

    M.G. Ghobrial

    2015-01-01

    Full Text Available Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have beneficial (positive allelopathy or detrimental (negative allelopathy effects on the target organisms. The current research aims at using selected brackish water adapted submerged aquatic macrophytes allelopathy to combat bloom-forming cyanophytes, in laboratory bioassay experiments. Dry matters of macrophytes were extracted in solvents and the initial cyanophytes inoculum, derived from unialgal culture media, was used. Therefore, aqueous extracts with 50% and 100% acetone and ethanol solvents of two freshwater macrophytes; Potamogeton pectinatus and Ceratophyllum demersum were used to test their growth performance exhibited on two bloom-forming cyanophytes, Microcystis aeruginosa and Oscillatoria tenuis. The results revealed insignificant difference between the overall total average growth performance at treatment with 50% and 100% Ceratophyllum acetone extracts expressed by optical density (OD as well as chlorophyll a (chl a. Results showed, also, stimulation of M. aeruginosa growth. The highest growth increase in 100 μl/100 ml treatment with 50% acetone extract had a percentage rate (R of 94.66. On the contrary, treatment with ethanol extract recorded the highest inhibitory effect, thus in 1.5 μl/100 ml treatment with 50% Ceratophyllum ethanol extract R recorded −87.54, sustaining LC50 value of 1.12 μl/100 ml. The highest stimulating effect in 105 μl/100 ml treatment with 50% Ceratophyllum acetone extracts against O. tenuis was; R, 169.4. The highest inhibition in 1500 μl/100 ml treatment with 50% Ceratophyllum ethanol extracts against O. tenuis was; R −74.32, with LC50 0.830 μl/100 ml. While, the highest inhibition by 50% and 100% Potamogeton acetone or ethanol extracts against M. aeruginosa was

  12. Differential effects of ocean acidification on carbon acquisition in two bloom-forming dinoflagellate species.

    Science.gov (United States)

    Eberlein, Tim; Van de Waal, Dedmer B; Rost, Björn

    2014-08-01

    Dinoflagellates represent a cosmopolitan group of phytoplankton with the ability to form harmful algal blooms. Featuring a Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) with very low CO2 affinities, photosynthesis of this group may be particularly prone to carbon limitation and thus benefit from rising atmospheric CO2 partial pressure (pCO2) under ocean acidification (OA). Here, we investigated the consequences of OA on two bloom-forming dinoflagellate species, the calcareous Scrippsiella trochoidea and the toxic Alexandrium tamarense. Using dilute batch incubations, we assessed growth characteristics over a range of pCO2 (i.e. 180-1200 µatm). To understand the underlying physiology, several aspects of inorganic carbon acquisition were investigated by membrane-inlet mass spectrometry. Our results show that both species kept growth rates constant over the tested pCO2 range, but we observed a number of species-specific responses. For instance, biomass production and cell size decreased in S. trochoidea, while A. tamarense was not responsive to OA in these measures. In terms of oxygen fluxes, rates of photosynthesis and respiration remained unaltered in S. trochoidea whereas respiration increased in A. tamarense under OA. Both species featured efficient carbon concentrating mechanisms (CCMs) with a CO2-dependent contribution of HCO3(-) uptake. In S. trochoidea, the CCM was further facilitated by exceptionally high and CO2-independent carbonic anhydrase activity. Comparing both species, a general trade-off between maximum rates of photosynthesis and respective affinities is indicated. In conclusion, our results demonstrate effective CCMs in both species, yet very different strategies to adjust their carbon acquisition. This regulation in CCMs enables both species to maintain growth over a wide range of ecologically relevant pCO2 .

  13. UVB radiation as a potential selective factor favoring microcystin producing bloom forming Cyanobacteria.

    Directory of Open Access Journals (Sweden)

    Yi Ding

    Full Text Available Due to the stratospheric ozone depletion, several organisms will become exposed to increased biologically active UVB (280-320 nm radiation, not only at polar but also at temperate and tropical latitudes. Bloom forming cyanobacteria are exposed to UVB radiation on a mass scale, particularly during the surface bloom and scum formation that can persist for long periods of time. All buoyant species of cyanobacteria are at least periodically exposed to higher irradiation during their vertical migration to the surface that usually occurs several times a day. The aim of this study is to assess the influence on cyanobacteria of UVB radiation at realistic environmental intensities. The effects of two UVB intensities of 0.5 and 0.99 W/m(2 in up to 0.5 cm water depth were studied in vitro on Microcystis aeruginosa strains, two microcystin producing and one non-producing. After UVB exposure their ability to proliferate was estimated by cell counting, while cell fitness and integrity were evaluated using light microscopy, autofluorescence and immunofluorescence. Gene damage was assessed by TUNEL assay and SYBR Green staining of the nucleoide area. We conclude that UVB exposure causes damage to the genetic material, cytoskeletal elements, higher sedimentation rates and consequent cell death. In contrast to microcystin producers (PCC7806 and FACHB905, the microcystin non-producing strain PCC7005 is more susceptible to the deleterious effects of radiation, with weak recovery ability. The ecological relevance of the results is discussed using data from eleven years' continuous UVB radiation measurements within the area of Ljubljana city (Slovenia, Central Europe. Our results suggest that increased solar radiation in temperate latitudes can have its strongest effect during cyanobacterial bloom formation in spring and early summer. UVB radiation in this period may significantly influence strain composition of cyanobacterial blooms in favor of microcystin producers.

  14. 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

    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...

  15. Genome-derived insights into the biology of the hepatotoxic bloom-forming cyanobacterium Anabaena sp. strain 90

    Directory of Open Access Journals (Sweden)

    Wang Hao

    2012-11-01

    Full Text Available Abstract Background Cyanobacteria can form massive toxic blooms in fresh and brackish bodies of water and are frequently responsible for the poisoning of animals and pose a health risk for humans. Anabaena is a genus of filamentous diazotrophic cyanobacteria commonly implicated as a toxin producer in blooms in aquatic ecosystems throughout the world. The biology of bloom-forming cyanobacteria is poorly understood at the genome level. Results Here, we report the complete sequence and comprehensive annotation of the bloom-forming Anabaena sp. strain 90 genome. It comprises two circular chromosomes and three plasmids with a total size of 5.3 Mb, encoding a total of 4,738 genes. The genome is replete with mobile genetic elements. Detailed manual annotation demonstrated that almost 5% of the gene repertoire consists of pseudogenes. A further 5% of the genome is dedicated to the synthesis of small peptides that are the products of both ribosomal and nonribosomal biosynthetic pathways. Inactivation of the hassallidin (an antifungal cyclic peptide biosynthetic gene cluster through a deletion event and a natural mutation of the buoyancy-permitting gvpG gas vesicle gene were documented. The genome contains a large number of genes encoding restriction-modification systems. Two novel excision elements were found in the nifH gene that is required for nitrogen fixation. Conclusions Genome analysis demonstrated that this strain invests heavily in the production of bioactive compounds and restriction-modification systems. This well-annotated genome provides a platform for future studies on the ecology and biology of these important bloom-forming cyanobacteria.

  16. Diatom associations in shelf waters off Paraná State, Southern Brazil: annual variation in relation to environmental factors

    OpenAIRE

    Luciano Felício Fernandes; Frederico Pereira Brandini

    2004-01-01

    The seasonal variation of diatoms in the inshore waters off Paraná State, Southern Brazil was investigated to analyse their temporal dynamics and to detect the main environmental constraints of the planktonic community. Biomass peaks occurred from May to August and from December to March. Among the microplanktonic diatoms, Cerataulina pelagica, Chaetoceros spp., Dactyliosolen fragilissimus, Guinardia striata, Lauderia annulata, Leptocylindrus spp., Pseudo-nitzschia cf. delicatissima, P. austr...

  17. Modulation of Medium-Chain Fatty Acid Synthesis in Synechococcus sp. PCC 7002 by Replacing FabH with a Chaetoceros ketoacyl-ACP synthase

    Directory of Open Access Journals (Sweden)

    Huiya eGu

    2016-05-01

    Full Text Available The isolation or engineering of algal cells synthesizing high levels of medium-chain fatty acids (MCFAs is attractive to mitigate the high clouding point of longer chain fatty acids in algal based biodiesel. To develop a more informed understanding of MCFA synthesis is photosynthetic microorganisms, we isolated several algae from Great Salt Lake and screened this collection for MCFA accumulation to identify strains naturally accumulating high levels of MCFA. A diatom, Chaetoceros sp. GSL56, accumulated particularly high levels of C14 (up to 40%, with the majority of C14 fatty acids (~2/3 allocated in triacylglycerols. Using whole cell transcriptome sequencing and de novo assembly, putative genes encoding fatty acid synthesis enzymes were identified. Enzymes from this Chaetoceros sp. were expressed in the cyanobacterium Synechococcus sp. PCC 7002 to validate gene function and to determine whether eukaryotic enzymes lacking bacteria evolutionary control mechanisms could be used to improve MCFA production in this promising production strains. Replacement of the Synechococcus 7002 native FabH with a Chaetoceros ketoacyl-ACP synthase III increased MCFA synthesis up to five fold. The level of increase is dependent on promoter strength and culturing conditions.

  18. Optimization of Alkaline Flocculation for Harvesting of Scenedesmus quadricauda #507 and Chaetoceros muelleri #862

    Directory of Open Access Journals (Sweden)

    Shuhao Huo

    2014-09-01

    Full Text Available A response surface methodology (RSM was used to evaluate the effects of pH and microalgal biomass concentration (BC on alkaline flocculating activity for harvesting one freshwater green algae Scenedesmus quadricauda #507 and one marine diatom Chaetoceros muelleri #862. The pH value and BC were in range of 9.0–12.0 and 0.20–2.30 g/L, respectively. Very high regression coefficient between the variables and the response indicates excellent evaluation of experimental data by second-order regressions. Optimum conditions for flocculating activity were estimated as follows: (i pH 11.6, BC 0.54 g/L for strain #507 and (ii pH 11.5, BC 0.42 g/L for strain #862. The maximum flocculating activity was around 94.7% and 100%, respectively. Furthermore, the addition of synthetic ocean water (SOW to the freshwater #507 culture can increase the flocculating activity from 82.13%–88.79% in low algae concentration (0.52 g/L and 82.92%–95.60% in high concentration (2.66 g/L.

  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.

    on the growth of C. tenuissimus. Data were statistically analysed by ANOVA and Student ?t? test was done (?t? table value at 0.01). Statistical 5 analysis revealed that growth in control and 2.4 mg/L Cd concentration was almost similar (p>0.... tenuissimus exposed to different Cd concentrations observed as percent nuclei with comets. Among the different Cd concentrations, statistical tests showed significantly higher DNA damage (p<0.01) in 10 mg/L (65% damage) and lowest in 2.4 mg/L (23% damage...

  20. Effects of iron limitation on photosynthesis and carbohydrate metabolism in the Antarctic diatom Chaetoceros brevis (Bacillariophyceae)

    NARCIS (Netherlands)

    van Oijen, T; van Leeuwe, MA; Gieskes, WWC; de Baar, HJW

    2004-01-01

    Iron, one of the structural elements of organic components that play an essential role in photosynthesis and nitrogen assimilation of plants, is available at extremely low concentrations in large parts of the Southern Ocean's surface waters. We tested the hypothesis that photosynthesis is the primar

  1. Effects of decabromodiphenyl ether (BDE-209 on inter-specific competition between two species of marine bloom-forming microalgae.

    Directory of Open Access Journals (Sweden)

    Xinxin Zhang

    Full Text Available Decabromodiphenyl ether (BDE-209, a new kind of persistent organic pollutants, was selected to investigate its influence on population growth and inter-specific competition between two species of marine bloom-forming microalgae, Heterosigma akashiwo and Karenia mikimotoi. (1BDE-209 showed acute toxic effects on both microalgae and H. akashiwo was more sensitive from view of 96 h-EC50 and the ultrastructure variation. (2The microalgal population growth patterns in mono-culture were density-dependent and the growth of both species in the normal co-culture was significantly depressed by competition (P<0.05 with different initial biomass ratios. BDE-209 exposure significantly changed the growth. (3 Lotka-Volterra competition model was used to simulate the interaction between the microalgae. BDE-209 exposure broke the competitive balance to make competition gradually shift in favor of H. akashiwo. Results suggested BDE-209 did have toxic effects on either microalgal growth or the inter-specific competition, which was quite different from previous reports. Further exploration of the mechanism is needed.

  2. Comparative genomics reveals diversified CRISPR-Cas systems of globally distributed Microcystis aeruginosa, a freshwater bloom-forming cyanobacterium

    Directory of Open Access Journals (Sweden)

    Chen eYang

    2015-05-01

    Full Text Available Microcystis aeruginosa is one of the most common and dominant bloom-forming cyanobacteria in freshwater lakes around the world. Microcystis cells can produce toxic secondary metabolites, such as microcystins, which are harmful to human health. Two M. aeruginosa strains were isolated from two highly eutrophic lakes in China and their genomes were sequenced. Comparative genomic analysis was performed with the 12 other available M. aeruginosa genomes and closely related unicellular cyanobacterium. Each genome of M. aeruginosa containing at least one clustered regularly interspaced short palindromic repeat (CRISPR locus and total 71 loci were identified, suggesting it is ubiquitous in M. aeruginosa genomes. In addition to the previously reported subtype I-D cas gene sets, three CAS subtypes I-A, III-A and III-B were identified and characterized in this study. Seven types of CRISPR direct repeat have close association with CAS subtype, confirming that different and specific secondary structures of CRISPR repeats are important for the recognition, binding and process of corresponding cas gene sets. Homology search of the CRISPR spacer sequences provides a history of not only resistance to bacteriophages and plasmids known to be associated with M. aeruginosa, but also the ability to target much more exogenous genetic material in the natural environment. These adaptive and heritable defense mechanisms play a vital role in keeping genomic stability and self-maintenance by restriction of horizontal gene transfer. Maintaining genomic stability and modulating genomic plasticity are both important evolutionary strategies for M. aeruginosa in adaptation and survival in various habitats.

  3. Proximate composition analysis posterior to the cryopreservation of Chaetoceros calcitrans

    Directory of Open Access Journals (Sweden)

    Joan Salas-Leiva

    2015-12-01

    Full Text Available Objective. The effect of cryopreservation on the proximate composition of microalgae Chaetoceros calcitrans was evaluated. Materials and methods. C. calcitrans was cultured and cryopreserved using 5% (v/v dimethylsulfoxide as cryoprotectant. The freezing was controlled at a rate of 3°C/min, up to -60°C and then the microalgae were immersed in liquid nitrogen (-196°C. After storage in liquid nitrogen, microalgae were rapidly thawed out and subcultured. The percentage of proteins, lipids and carbohydrates was analyzed using absorption spectrophotometry and the organic matter was studied by gravimetric analysis. Results. There was no significant variation between the proximate composition of C. calcitrans cryopreserved and the controls (p>0.05. Conclusion. Our results show that, despite low cell recovery after the preservation of this organism at low temperatures, there is no apparent loss of nutritional characteristics caused by the storing process at low temperatures.

  4. 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.

  5. Species-dependent silicon isotope fractionation in unialgal cultures of marine diatoms

    Science.gov (United States)

    Sutton, J. N.; Varela, D. E.; Brzezinski, M. A.; Beucher, C.

    2011-12-01

    Variations in the natural abundance of stable isotopes of silicon (expressed as δ30Si in %) are a key tool for studying the marine silicon (Si) cycle in modern and ancient oceans. In particular, this tool can be used to track relative differences in silicic acid drawdown in surface waters by siliceous microplankton. Diatoms are siliceous phytoplankton that dominate the cycling of Si in the oceans. They represent a major source of primary production and are important in the transfer of Si, nitrogen, phosphorus, and atmospheric carbon to the deep sea. Previous investigations of Si isotope fractionation in diatom cultures have ruled out the influence of temperature (12-22°C) and shown that Si fractionation was invariant in different species of temperate diatoms (De La Rocha et al. 1997). However, the application of this proxy for marine paleo-silicon reconstructions has typically only been used in polar regions, such as the Southern Ocean, where high primary production rates give rise to diatom-rich sediments. Here, we present results on the fractionation of Si isotopes by four species of polar diatoms grown in semi-continuous cultures (Chaetoceros brevis, Fragilariopsis kerguelensis, Porosira glacialis, and Thalassiosira antarctica). To compare with previous studies (De La Rocha et al, 1997), we also tested Si isotope fractionation by two species of temperate diatoms (Thalassiosira pseudonana and Thalassiosira weissflogii). The temperate species yielded Si isotope fractionation (Δ30Si) values of -0.81 % (±0.12, SD, n=11) for T. pseudonana and -1.03% (±0.09, SD, n=3) for T. weissflogii, that are identical to the previously reported fractionation of -1.1 % (±0.4, SD, n=6) (De La Rocha et al. 1997). Similarly, our data for polar species F. kerguelensis, P. glacialis and T. antarctica suggest a fractionation of -0.7 to -1.1 %. Interestingly, our preliminary results from Chaetoceros brevis cultures show a Si isotope fractionation value of about -2.61 % (±0.05, SD

  6. The Diatoms

    Science.gov (United States)

    Stoermer, E. F.; Smol, John P.

    2001-07-01

    Diatoms are microscopic algae which are found in virtually every habitat where water is present. This volume is an up-to-date summary of the expanding field of their uses in environmental and earth sciences. Their abundance and wide distribution, and their well-preserved glass-like walls make them ideal tools for a wide range of applications as both fossils and living organisms. Examples of their wide range of applications include environmental indicators, oil exploration, and forensic examination. The major emphasis is on their use in analyzing ecological problems such as climate change, acidification, and eutrophication. The contributors to the volume are leading researchers in their fields and are brought together for the first time to give a timely synopsis of a dynamic and important area. This book should be read by environmental scientists, phycologists, limnologists, ecologists and palaeoecologists, oceanographers, archaeologists and forensic scientists.

  7. Chemical Diversity as a Function of Temperature in Six Northern Diatom Species

    Directory of Open Access Journals (Sweden)

    Siv Huseby

    2013-10-01

    Full Text Available In this study, we investigate how metabolic fingerprints are related to temperature. Six common northern temperate diatoms (Attheya longicornis, Chaetoceros socialis, Chaetoceros furcellatus, Porosira glacialis, Skeletonema marinoi, and Thalassiosira gravida were cultivated at two different temperatures, 0.5 and 8.5 °C. To exclude metabolic variations due to differences in growth rates, the growth rates were kept similar by performing the experiments under light limited conditions but in exponential growth phase. Growth rates and maximum quantum yield of photosynthesis were measured and interpreted as physiological variables, and metabolic fingerprints were acquired by high-resolution mass spectrometry. The chemical diversity varied substantially between the two temperatures for the tested species, ranging from 31% similarity for C. furcellatus and P. glacialis to 81% similarity for A. longicornis. The chemical diversity was generally highest at the lowest temperature.

  8. Distribution of diatoms in the water and surface sediments of southern South China Sea

    Institute of Scientific and Technical Information of China (English)

    LU Jun; CHEN Muhong; CHEN Zhong

    2006-01-01

    The relationship of species and abundance between the diatoms in the water and sediments from the southern South China Sea (SCS) were discussed, and the key environmental controlling factors were also investigated. Studies show that the diatom abundance is high in both water and sediments in the southeast part of the southern SCS and the varying trend is similar, while in the northwest part, the abundance is low, and the varying trend is different. The dominant diatom species are Thalassionema nitzschioides and Nitzschia bicapitata in water, and T. nitzschioides and Chaetoceros messanensis in sediments. The diatom species of small size and thin shell in water are more than in the sediments, while the diatom species of large size and thick shell in water are less. The percentage of species T. nitzschioides is higher in water of southeast part than in that of northwest part, but it is similar in sediments of both areas. It is shown that the southwest monsoon is the important factor influencing diatom abundance and T. nitzschioides percentage,and when the southwest monsoon is well developed,the distribution of diatom abundance and T. nitzschioides percentage are consistent in both water and sediments of the study area.

  9. Strong Endemism of bloom-forming tubular Ulva in Indian West Coast, with description of Ulva paschima Sp. Nov. (Ulvales, Chlorophyta.

    Directory of Open Access Journals (Sweden)

    Felix Bast

    Full Text Available Ulva intestinalis and Ulva compressa are two bloom-forming morphologically-cryptic species of green seaweeds widely accepted as cosmopolitan in distribution. Previous studies have shown that these are two distinct species that exhibit great morphological plasticity with changing seawater salinity. Here we present a phylogeographic assessment of tubular Ulva that we considered belonging to this complex collected from various marine and estuarine green-tide occurrences in a ca. 600 km stretch of the Indian west coast. Maximum Likelihood and Bayesian Inference phylogenetic reconstructions using ITS nrDNA revealed strong endemism of Indian tubular Ulva, with none of the Indian isolates forming part of the already described phylogenetic clades of either U. compressa or U. intestinalis. Due to the straightforward conclusion that Indian isolates form a robust and distinct phylogenetic clade, a description of a new bloom-forming species, Ulva paschima Bast, is formally proposed. Our phylogenetic reconstructions using Neighbor-Joining method revealed evolutionary affinity of this new species with Ulva flexuosa. This is the first molecular assessment of Ulva from the Indian Subcontinent.

  10. PENGARUH PEMBERIAN FeCl3 TERHADAP PERTUMBUHAN Chaetoceros calcitrans

    Directory of Open Access Journals (Sweden)

    Cahya Laila Oktaviana Putri

    2009-04-01

    Full Text Available Besi termasuk unsur yang esensial bagi makhluk hidup. Pada tumbuhan termasuk algae, besi berperan sebagai penyusun sitokrom dan klorofil. Selain itu, besi juga berperan dalam sistem enzim dan transfer elektron pada proses fotosintesis. Namun, belum diketahui konsentrasi yang tepat untuk pengunaannya oleh algae sehingga diperlukan penelitian yang dapat mengetahui konsentrasi pemakaian FeCl3 untuk perkembangan algae terutama untuk C. calcitrans. Tujuan dari penelitian ini adalah untuk mengetahui pengaruh pemberian FeCl3 terhadap kepadatan C. calcitran sehingga dapat mengetahui konsentrasi FeCl3 yang paling baik terhadap kepadatan C. calcitran. Serta untuk Mengetahui kepadatan C. calcitran berdasarkan hari. Penelitian ini diawali dengan menyetock C. calcitran hingga kepadatan 400 ribu sel/ml kemudian dilanjutkan dengan mengkultur C. calcitran pada toples yang telah dibuat sama parameternya kecuali pemberian FeCl3 sesuai dengan perlakuan. Untuk menganalisa pengaruh pemberian FeCl3 pada konsentrasi yang bebeda terhadap kepadatan C. calcitrans digunakan analisa sidik ragam (ANOVA dua langkah dengan bantuan software SPSS 12 dan dilakukan uji lanjut Tukey (Multiple Comparisons untuk melihat perlakuan yang berbeda dengan membandingkan berbagai hasil perlakuan. Pada konsentrasi FeCl3 0 mg/l berbeda nyata (P<0,05 sedangkan konsentrai FeCl3 0,02 mg/l, 0,2  mg/l, 2 mg/l berbeda signifikan terhadap kepadatan C. calcitrans sehingga hanya konsentrasi FeCl3 0 mg/l yang mempengaruhi kepadatan C. calcitrans. Ini disebabkan karena pemberian konsentrasi terlalu sedikit dan selisih konsentrasi yang kecil sehingga tidak mempengaruhi kepadatan C. calcitrans. Sedangkan untuk hari  diperoleh hari ke-1 dan ke-7 merupakan hari yang signifikan terhadap kepadatan C. calcitrans.  Kata Kunci : Chaetoceros calcitrans, FeCl3 dan kepadatan

  11. Pyrolytic characteristics of biodiesel prepared from lipids accumulated in diatom cells with growth regulation.

    Science.gov (United States)

    Cheng, Jun; Feng, Jia; Ge, Tingting; Yang, Weijuan; Zhou, Junhu; Cen, Kefa

    2015-08-01

    Dynamic compositions of lipids accumulated in two diatoms Chaetoceros gracilis and Nitzschia closterium cultured with nitrogen and silicon deprivation were studied. It was found that short-chain fatty acids (C14-C16) content was much higher than long-chain fatty acids (C18-C20) content in lipids of two diatoms. The pyrolytic characteristics of biodiesel made from two diatoms and two plant seeds were compared by thermogravimetric analysis. The highest activation energy of 46.68 kJ mol(-1) and the minimum solid residue of 25.18% were obtained in the pyrolysis of biodiesel made from C. gracilis cells, which were cultured with 0.5 mmol L(-1) of nitrogen (no silicon) and accumulated the minimum polyunsaturated fatty acid (C20:5). The pyrolysis residue percentage of C. gracilis biodiesel was lower than that of N. closterium biodiesel and higher than those of plant (Cormus wilsoniana and Pistacia chinensis) biodiesels.

  12. Pyrolytic characteristics of biodiesel prepared from lipids accumulated in diatom cells with growth regulation.

    Science.gov (United States)

    Cheng, Jun; Feng, Jia; Ge, Tingting; Yang, Weijuan; Zhou, Junhu; Cen, Kefa

    2015-08-01

    Dynamic compositions of lipids accumulated in two diatoms Chaetoceros gracilis and Nitzschia closterium cultured with nitrogen and silicon deprivation were studied. It was found that short-chain fatty acids (C14-C16) content was much higher than long-chain fatty acids (C18-C20) content in lipids of two diatoms. The pyrolytic characteristics of biodiesel made from two diatoms and two plant seeds were compared by thermogravimetric analysis. The highest activation energy of 46.68 kJ mol(-1) and the minimum solid residue of 25.18% were obtained in the pyrolysis of biodiesel made from C. gracilis cells, which were cultured with 0.5 mmol L(-1) of nitrogen (no silicon) and accumulated the minimum polyunsaturated fatty acid (C20:5). The pyrolysis residue percentage of C. gracilis biodiesel was lower than that of N. closterium biodiesel and higher than those of plant (Cormus wilsoniana and Pistacia chinensis) biodiesels. PMID:25782618

  13. Composition of diatom communities and their contribution to plankton biomass in the naturally iron-fertilized region of Kerguelen in the Southern Ocean.

    Science.gov (United States)

    Lasbleiz, Marine; Leblanc, Karine; Armand, Leanne K; Christaki, Urania; Georges, Clément; Obernosterer, Ingrid; Quéguiner, Bernard

    2016-11-01

    In the naturally iron-fertilized surface waters of the northern Kerguelen Plateau region, the early spring diatom community composition and contribution to plankton carbon biomass were investigated and compared with the high nutrient, low chlorophyll (HNLC) surrounding waters. The large iron-induced blooms were dominated by small diatom species belonging to the genera Chaetoceros (Hyalochaete) and Thalassiosira, which rapidly responded to the onset of favorable light-conditions in the meander of the Polar Front. In comparison, the iron-limited HNLC area was typically characterized by autotrophic nanoeukaryote-dominated communities and by larger and more heavily silicified diatom species (e.g. Fragilariopsis spp.). Our results support the hypothesis that diatoms are valuable vectors of carbon export to depth in naturally iron-fertilized systems of the Southern Ocean. Furthermore, our results corroborate observations of the exported diatom assemblage from a sediment trap deployed in the iron-fertilized area, whereby the dominant Chaetoceros (Hyalochaete) cells were less efficiently exported than the less abundant, yet heavily silicified, cells of Thalassionema nitzschioides and Fragilariopsis kerguelensis Our observations emphasize the strong influence of species-specific diatom cell properties combined with trophic interactions on matter export efficiency, and illustrate the tight link between the specific composition of phytoplankton communities and the biogeochemical properties characterizing the study area.

  14. Diatom thanatocoenosis in a middle Galician Ría: Spatial patterns and their relationship to the seasonal diatom cycle in the water column and hydrographic conditions

    Science.gov (United States)

    Bernárdez, Patricia; Prego, Ricardo; Varela, Manuel; Francés, Guillermo

    2008-10-01

    Modern diatom distribution patterns in the surface sediment of the Ferrol Ría and their relationship to the hydrography and diatom patterns in the water column were studied to determine the hydrographic influence on the record of these biogenic components. Diatom abundance in the water column was assessed for different oceanographic periods and compared with the biosiliceous sedimentary record. Very low abundances were found in the water column during the winter, whereas in spring and summer, diatoms proliferated. Chaetoceros spp. formed the bulk of the water column community during spring and summer, followed by Thalassionema nitzschioides and Rhizosolenia spp. Nitzschia longissima represented a significant portion of the winter assemblage, together with Paralia sulcata and benthic taxa . Leptocylindrus danicus, N. longissima and Skeletonema costatum characterized the autumn campaign, when stratification of the waters occurs, with L. danicus being especially abundant in the outer ría. Seasonal hydrographic and associated productivity patterns govern the abundance and assemblage of the diatoms preserved in surface sediments. Samples located in the inner ría area and its margins exhibited the highest abundances of diatoms, and were primarily dominated by benthic species. The freshwater group, crysophycean cysts and phytoliths were present in the landward stations influenced by river runoff. The middle ría was characterized by P. sulcata and Thalassiosira spp., with minor occurrences of the benthic and freshwater group. Chaetoceros R.S., L. danicus R.S. and T. nitzschioides typified the outer ría, an assemblage that corresponds to nutrient-rich coastal areas of high productivity influenced by oceanic waters, demonstrating the impact of oceanic waters flowing into the embayment due to enhanced tidal mixing through the narrow channel. Therefore, sediment diatom assemblages reflect diatom production patterns in the water column of the Ría. However, we must proceed

  15. Temporal pattern in the bloom-forming macroalgae Chaetomorpha linum and Ulva pertusa in seagrass beds, Swan Lake lagoon, North China

    International Nuclear Information System (INIS)

    Highlights: • We conducted an annual survey of bloom-forming macroalgae in a lagoon. • C. linum biomass reached 1712 ± 780 g DW m−2 at the northern part of the lagoon. • Macroalgae δ15N values indicated a land-based source of N enrichment to the blooms. • High nutrient concentrations near the river mouth supported the blooms. • C. linum blooms induced the loss of seagrasses and benthic filter feeders. - Abstract: Seagrasses that are distributed over a large area of the Swan Lake, Weihai, China, support a productive ecosystem. In recent years, however, frequent macroalgal blooms have changed the ecosystem structure and threatened the seagrasses. To understand the bloom-forming macroalgae we conducted a yearly field survey of Swan Lake. Results indicated that the macroalgae Chaetomorpha linum and Ulva pertusa both exhibited a much higher productivity and attained a greater maximum biomass (of 1712 ± 780 g DW m−2 and 1511 ± 555 g DW m−2, respectively) than was the case for the seagrasses. The mean annual atomic ratios of C/N, C/P and N/P in C. linum were 14.31 ± 4.45, 402.82 ± 130.25, and 28.12 ± 2.08, respectively. The δ15N values (11.09 ± 0.91‰ for C. linum; 9.27 ± 2.83‰ for U. pertusa) indicated a land-based source of N enrichment to the macroalgal blooms. High concentrations of nitrogen and phosphorus in the lagoon, particularly near the river mouth, supported the blooms

  16. Fungal parasites infect marine diatoms in the upwelling ecosystem of the Humboldt current system off central Chile.

    Science.gov (United States)

    Gutiérrez, Marcelo H; Jara, Ana M; Pantoja, Silvio

    2016-05-01

    This is the first report of fungal parasitism of diatoms in a highly productive coastal upwelling ecosystem, based on a year-round time series of diatom and parasitic Chytridiomycota abundance in the Humboldt Current System off Chile (36°30.80'S-73°07.70'W). Our results show co-variation in the presence of Skeletonema, Thalassiosira and Chaetoceros diatoms with attached and detached chytrid sporangia. High abundance of attached sporangia was observed during the austral spring, coinciding with a predominance of Thalassiosira and Skeletonema under active upwelling conditions. Towards the end of austral spring, a decreasing proportion of attached sporangia was accompanied by a decline in abundance of Skeletonema and Thalassiosira and the predominance of Chaetoceros, suggesting specificity and host density dependence of chytrid infection. The new findings on fungal parasitism of diatoms provide further support for the inclusion of Fungi in the current model of the role played by the marine microbial community in the coastal ocean. We propose a conceptual model where Fungi contribute to controlling the dynamics of phytoplankton populations, as well as the release of organic matter and the transfer of organic carbon through the pelagic trophic web in coastal upwelling ecosystems. PMID:26914416

  17. Pigment signatures of some diatoms isolated from China seas

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The photosynthetic pigments of 12 species (14 strains) of cultured diatoms from six genera under specific conditions were examined by the HPLC. The diatom genera were Skeletonema, Thalassiosira, Chaetoceros, Nitzschia, Phaeodactylum and Meuniera. All strains were isolated from China seas and most of them were from the Jiaozhou Bay, China. Fifteen pigments were identified and eight of them were various chlorophyll a derivatives. Chlorophyll a, c2 and c1 and the carotenoids fucoxanthin, diadinoxanthin, diatoxanthin and β,β-carotene existed in all species. The ratios of each pigment to chlorophyll a were compared with the results in literatures. The pigment ratios of this study generally fall within the ranges reported by the literatures although the maximum ratio of fucoxanthin to chlorophyll a was higher and the ratios of chlorophyll c and diatoxanthin to chlorophyll a were low. The pigment ratios are useful to understanding the pigment signatures of diatoms in the Jiaozhou Bay, China, and to setting up the chemotaxonomic method ofphytoplankton in these sea areas.

  18. Benthic diatoms in lakes

    OpenAIRE

    Gottschalk, Steffi

    2014-01-01

    In order to protect or improve surface waters ecosystem response to pressures needs to be quantified. Diatoms are frequently used for assessing ecological status in streams and for reconstructing water quality of lakes. However, ecological status assessment of European lakes based on extant diatom assemblages is rare. The overall aim of this thesis is to facilitate the application of benthic diatoms in water quality assessment of boreal lakes, using methods developed for stream assessmen...

  19. Neither elevated nor reduced CO2 affects the photophysiological performance of the marine Antarctic diatom Chaetoceros brevis

    NARCIS (Netherlands)

    Boelen, Peter; de Poll, Willem H. van; van der Strate, Han J.; Neven, Ika A.; Beardall, John; Buma, Anita G. J.

    2011-01-01

    Enhanced or reduced pCO(2) (partial pressure of CO2) may affect the photosynthetic performance of marine microalgae since changes in pCO(2) can influence the activity of carbon concentrating mechanisms, modulate cellular RuBisCO levels or alter carbon uptake efficiency. In the present study we compa

  20. Effects of iron availability on pigment signature and biogenic silica production in the coastal diatom Chaetoceros gracilis

    Digital Repository Service at National Institute of Oceanography (India)

    Biswas, H.; Bandyopadhyay, D.

    , the principal physiological process in phytoplankton, requires almost 80% of the total Fe quota for photosynthetic electron transport chains [2]. In absence of sufficient Fe, the rate of carbon fixation can be largely hindered as the absorbed light energy... cannot be transferred further due to lack of electron carriers (mainly Fe containing proteins, such as ferredoxin) and the surplus energy can potentially form reactive oxygen species leading to photodamage of the cell [3]. Dissolved Fe has extremely...

  1. Regulation of chain length in two diatoms as a growth-fragmentation process

    Science.gov (United States)

    Gherardi, Marco; Amato, Alberto; Bouly, Jean-Pierre; Cheminant, Soizic; Ferrante, Maria Immacolata; d'Alcalá, Maurizio Ribera; Iudicone, Daniele; Falciatore, Angela; Cosentino Lagomarsino, Marco

    2016-08-01

    Chain formation in diatoms is relevant because of several aspects of their adaptation to the ecosystem. However, the tools to quantify the regulation of their assemblage and infer specific mechanisms in a laboratory setting are scarce. To address this problem, we define an approach based on a statistical physics model of chain growth and separation in combination with experimental evaluation of chain-length distributions. Applying this combined analysis to data from Chaetoceros decipiens and Phaeodactylum tricornutum, we find that cells of the first species control chain separation, likely through a cell-to-cell communication process, while the second species only modulates the separation rate. These results promote quantitative methods for characterizing chain formation in several chain-forming species and in diatoms in particular.

  2. Influence of elevated CO2 concentrations on cell division and nitrogen fixation rates in the bloom-forming cyanobacterium Nodularia spumigena

    Directory of Open Access Journals (Sweden)

    U. Riebesell

    2009-04-01

    Full Text Available The surface ocean currently absorbs about one-fourth of the CO2 emitted to the atmosphere from human activities. As this CO2 dissolves in seawater, it reacts with seawater to form carbonic acid, increasing ocean acidity and shifting the partitioning of inorganic carbon species towards increased CO2 at the expense of CO32− concentrations. While the decrease in [CO32−] and/or increase in [H+] has been found to adversely affect many calcifying organisms, some photosynthetic organisms appear to benefit from increasing [CO2]. Among these is the cyanobacterium Trichodesmium, a predominant diazotroph (nitrogen-fixing in large parts of the oligotrophic oceans, which responded with increased carbon and nitrogen fixation at elevated pCO2. With the mechanism underlying this CO2 stimulation still unknown, the question arises whether this is a common response of diazotrophic cyanobacteria. In this study we therefore investigate the physiological response of Nodularia spumigena, a heterocystous bloom-forming diazotroph of the Baltic Sea, to CO2-induced changes in seawater carbonate chemistry. N. spumigena reacted to seawater acidification/carbonation with reduced cell division rates and nitrogen fixation rates, accompanied by significant changes in carbon and phosphorus quota and elemental composition of the formed biomass. Possible explanations for the contrasting physiological responses of Nodularia compared to Trichodesmium may be found in the different ecological strategies of non-heterocystous (Trichodesmium and heterocystous (Nodularia cyanobacteria.

  3. Comparison of Quantitative PCR and Droplet Digital PCR Multiplex Assays for Two Genera of Bloom-Forming Cyanobacteria, Cylindrospermopsis and Microcystis.

    Science.gov (United States)

    Te, Shu Harn; Chen, Enid Yingru; Gin, Karina Yew-Hoong

    2015-08-01

    The increasing occurrence of harmful cyanobacterial blooms, often linked to deteriorated water quality and adverse public health effects, has become a worldwide concern in recent decades. The use of molecular techniques such as real-time quantitative PCR (qPCR) has become increasingly popular in the detection and monitoring of harmful cyanobacterial species. Multiplex qPCR assays that quantify several toxigenic cyanobacterial species have been established previously; however, there is no molecular assay that detects several bloom-forming species simultaneously. Microcystis and Cylindrospermopsis are the two most commonly found genera and are known to be able to produce microcystin and cylindrospermopsin hepatotoxins. In this study, we designed primers and probes which enable quantification of these genera based on the RNA polymerase C1 gene for Cylindrospermopsis species and the c-phycocyanin beta subunit-like gene for Microcystis species. Duplex assays were developed for two molecular techniques-qPCR and droplet digital PCR (ddPCR). After optimization, both qPCR and ddPCR assays have high linearity and quantitative correlations for standards. Comparisons of the two techniques showed that qPCR has higher sensitivity, a wider linear dynamic range, and shorter analysis time and that it was more cost-effective, making it a suitable method for initial screening. However, the ddPCR approach has lower variability and was able to handle the PCR inhibition and competitive effects found in duplex assays, thus providing more precise and accurate analysis for bloom samples. PMID:26025892

  4. Intricate interactions between the bloom-forming cyanobacterium Microcystis aeruginosa and foreign genetic elements, revealed by diversified clustered regularly interspaced short palindromic repeat (CRISPR) signatures.

    Science.gov (United States)

    Kuno, Sotaro; Yoshida, Takashi; Kaneko, Takakazu; Sako, Yoshihiko

    2012-08-01

    Clustered regularly interspaced short palindromic repeats (CRISPR) confer sequence-dependent, adaptive resistance in prokaryotes against viruses and plasmids via incorporation of short sequences, called spacers, derived from foreign genetic elements. CRISPR loci are thus considered to provide records of past infections. To describe the host-parasite (i.e., cyanophages and plasmids) interactions involving the bloom-forming freshwater cyanobacterium Microcystis aeruginosa, we investigated CRISPR in four M. aeruginosa strains and in two previously sequenced genomes. The number of spacers in each locus was larger than the average among prokaryotes. All spacers were strain specific, except for a string of 11 spacers shared in two closely related strains, suggesting diversification of the loci. Using CRISPR repeat-based PCR, 24 CRISPR genotypes were identified in a natural cyanobacterial community. Among 995 unique spacers obtained, only 10 sequences showed similarity to M. aeruginosa phage Ma-LMM01. Of these, six spacers showed only silent or conservative nucleotide mutations compared to Ma-LMM01 sequences, suggesting a strategy by the cyanophage to avert CRISPR immunity dependent on nucleotide identity. These results imply that host-phage interactions can be divided into M. aeruginosa-cyanophage combinations rather than pandemics of population-wide infectious cyanophages. Spacer similarity also showed frequent exposure of M. aeruginosa to small cryptic plasmids that were observed only in a few strains. Thus, the diversification of CRISPR implies that M. aeruginosa has been challenged by diverse communities (almost entirely uncharacterized) of cyanophages and plasmids.

  5. Synergistic algicidal effect and mechanism of two diketopiperazines produced by Chryseobacterium sp. strain GLY-1106 on the harmful bloom-forming Microcystis aeruginosa.

    Science.gov (United States)

    Guo, Xingliang; Liu, Xianglong; Pan, Jianliang; Yang, Hong

    2015-10-01

    A potent algicidal bacterium isolated from Lake Taihu, Chryseobacterium sp. strain GLY-1106, produces two algicidal compounds: 1106-A (cyclo(4-OH-Pro-Leu)) and 1106-B (cyclo(Pro-Leu)). Both diketopiperazines showed strong algicidal activities against Microcystis aeruginosa, the dominant bloom-forming cyanobacterium in Lake Taihu. Interestingly, these two algicidal compounds functioned synergistically. Compared with individual treatment, combined treatment with cyclo(4-OH-Pro-Leu) and cyclo(Pro-Leu) significantly enhanced algicidal activity, accelerated the increase in intracellular reactive oxygen species (ROS) levels in M. aeruginosa, and further decreased the activities of antioxidases, effective quantum yield and maximal electron transport rate of M. aeruginosa. The results also showed that the algicidal characteristics of cyclo(4-OH-Pro-Leu) are distinct from those of cyclo(Pro-Leu). Cyclo(4-OH-Pro-Leu) mainly interrupted the flux of electron transport in the cyanobacterial photosynthetic system, whereas cyclo(Pro-Leu) mainly inhibited the activity of cyanobacterial intracellular antioxidases. A possible algicidal mechanism for the synergism between cyclo(4-OH-Pro-Leu) and cyclo(Pro-Leu) is proposed, which is in accordance with their distinct algicidal characteristics in individual and combined treatment. These findings suggest that synergism between algicidal compounds might be used as an effective strategy for the future control of Microcystis blooms.

  6. Synergistic algicidal effect and mechanism of two diketopiperazines produced by Chryseobacterium sp. strain GLY-1106 on the harmful bloom-forming Microcystis aeruginosa

    Science.gov (United States)

    Guo, Xingliang; Liu, Xianglong; Pan, Jianliang; Yang, Hong

    2015-10-01

    A potent algicidal bacterium isolated from Lake Taihu, Chryseobacterium sp. strain GLY-1106, produces two algicidal compounds: 1106-A (cyclo(4-OH-Pro-Leu)) and 1106-B (cyclo(Pro-Leu)). Both diketopiperazines showed strong algicidal activities against Microcystis aeruginosa, the dominant bloom-forming cyanobacterium in Lake Taihu. Interestingly, these two algicidal compounds functioned synergistically. Compared with individual treatment, combined treatment with cyclo(4-OH-Pro-Leu) and cyclo(Pro-Leu) significantly enhanced algicidal activity, accelerated the increase in intracellular reactive oxygen species (ROS) levels in M. aeruginosa, and further decreased the activities of antioxidases, effective quantum yield and maximal electron transport rate of M. aeruginosa. The results also showed that the algicidal characteristics of cyclo(4-OH-Pro-Leu) are distinct from those of cyclo(Pro-Leu). Cyclo(4-OH-Pro-Leu) mainly interrupted the flux of electron transport in the cyanobacterial photosynthetic system, whereas cyclo(Pro-Leu) mainly inhibited the activity of cyanobacterial intracellular antioxidases. A possible algicidal mechanism for the synergism between cyclo(4-OH-Pro-Leu) and cyclo(Pro-Leu) is proposed, which is in accordance with their distinct algicidal characteristics in individual and combined treatment. These findings suggest that synergism between algicidal compounds might be used as an effective strategy for the future control of Microcystis blooms.

  7. Production of biodiesel from lipid of phytoplankton Chaetoceros calcitrans through ultrasonic method.

    Science.gov (United States)

    Kwangdinata, Raymond; Raya, Indah; Zakir, Muhammad

    2014-01-01

    A research on production of biodiesel from lipid of phytoplankton Chaetoceros calcitrans through ultrasonic method has been done. In this research, we carried out a series of phytoplankton cultures to determine the optimum time of growth and biodiesel synthesis process from phytoplankton lipids. Process of biodiesel synthesis consists of two steps, that is, isolation of phytoplankton lipids and biodiesel synthesis from those lipids. Oil isolation process was carried out by ultrasonic extraction method using ethanol 96%, while biodiesel synthesis was carried out by transesterification reaction using methanol and KOH catalyst under sonication. Weight of biodiesel yield per biomass Chaetoceros calcitrans is 35.35%. Characterization of biodiesel was well carried out in terms of physical properties which are density and viscosity and chemical properties which are FFA content, saponification value, and iodine value. These values meet the American Society for Testing and Materials (ASTM D6751) standard levels, except for the viscosity value which was 1.14 g · cm(-3).

  8. Production of Biodiesel from Lipid of Phytoplankton Chaetoceros calcitrans through Ultrasonic Method

    OpenAIRE

    Raymond Kwangdinata; Indah Raya; Muhammad Zakir

    2014-01-01

    A research on production of biodiesel from lipid of phytoplankton Chaetoceros calcitrans through ultrasonic method has been done. In this research, we carried out a series of phytoplankton cultures to determine the optimum time of growth and biodiesel synthesis process from phytoplankton lipids. Process of biodiesel synthesis consists of two steps, that is, isolation of phytoplankton lipids and biodiesel synthesis from those lipids. Oil isolation process was carried out by ultrasonic extracti...

  9. Phytoremediation of Cd2+ by Marine Phytoplanktons, Tetracelmis chuii and Chaetoceros calcitrans

    OpenAIRE

    Sjahrul, M

    2012-01-01

    The use of marine phytoplankton, Tetracelmis chuii and Chaetoceros calcitrans as phytoremediator has already been reported. However their use as phytoremediator on the cadmium polluted marine has not yet well understood. Therefore, this study was conducted to evaluate the influence of the Cd2+ concentration, interacting time, and medium pH on accumulation of Cd2+ in the phytoplankton. Methods of analysis and data collection were carried out on 1) the growth rate, the number of phy...

  10. PENGARUH MEDIA KULTIVASI Chaetoceros gracilis TERHADAP KANDUNGAN KIMIAWI DAN POTENSI INHIBITOR PROTEASE [Effect of Chaetoceros gracilis Cultivation Media to the Chemical Content and Protease Inhibitor Potential

    Directory of Open Access Journals (Sweden)

    Iriani Setyaningsih*

    2013-12-01

    Full Text Available Microalgae produce secondary metabolites with different characteristics for each genus, species or strain. A single species of microalgae can produce several bioactive compounds, including protease inhibitors which can prevent deterioration of fish. In this study, we observed the growth of Chaetoceros gracilis in the media NPSi and NPSi + NaHCO3 and determined the chemical content and the potency of protease inhibitor from Chaetoceros gracilis in both media. The culture was harvested at 8 and 15 days. Screening of protease inhibitor activity was performed by agar diffusion method. Protease inhibitor activity was tested on three pathogenic protease-producing bacteria, namely Staphylococcus aureus, Bacillus cereus and Escherichia coli. The pathogenic bacteria often contaminate foodstuffs. The results showed that media NPSi and NPSi + NaHCO3 affected protein and lipid content of C. gracilis, but the culture age did not affect them. The protein content of C. gracilis cultivated in NPSi media (34.75 and 32.94% was higher than in NPSi + NaHCO3 media (28.13 and 27.13%, while the lipid content was 16.36 and 18.06, 23.86 and 25.40% respectively. Extracts of C. gracilis grown in NPSi and NPSi+NaHCO3 media had inhibitory activity against the test bacteria. Inhibitory activity against E. coli was greater than S. aureus and B. cereus.

  11. Quantification of diatom gene expression in the sea by selecting uniformly transcribed mRNA as the basis for normalization.

    Science.gov (United States)

    Kang, Lee-Kuo; Tsui, Feng-Hsiu; Chang, Jeng

    2012-09-01

    To quantify gene expressions by quantitative reverse transcription-PCR (Q-RT-PCR) in natural diatom assemblages, it is necessary to seek a biomass reference specific to the target species. Two housekeeping genes, TBP (encoding the TATA box-binding protein) and EFL (encoding the translation elongation factor-like protein), were evaluated as candidates for reference genes in Q-RT-PCR assays. Transcript levels of TBP and EFL were relatively stable under various test conditions including growth stages, light-dark cycle phases, and nutrient stresses in Skeletonema costatum and Chaetoceros affinis, and TBP expression was more stable than that of EFL. Next, the sequence diversity of diatom assemblages was evaluated by obtaining 32 EFL and 29 TBP homologous gene fragments from the East China Sea (ECS). Based on sequence alignments, EFL and TBP primer sets were designed for Chaetoceros and Skeletonema groups in the ECS. An evaluation of primer specificity and PCR efficiency indicated that the EFL primer sets performed better. To demonstrate the applicability of EFL primer sets in the ECS, they were employed to measure mRNA levels of the FcpB (fucoxanthin-chlorophyll protein) gene in diatoms. The results correctly revealed prominent diel variations in FcpB expression and confirmed EFL as a good reference gene. PMID:22706063

  12. Evaluation of genotoxic responses of Chaetoceros tenuissimus and Skeletonema costatum to water accommodated fraction of petroleum hydrocarbons as biomarker of exposure.

    Science.gov (United States)

    Desai, S R; Deasi, S R; Verlecar, X N; Ansari, Z A; Jagtap, T G; Sarkar, A; Vashistha, Deepti; Dalal, S G

    2010-04-01

    Genotoxic responses towards chronic exposure of Chaetoceros tenuissimus and Skeletonema costatum to water accommodated fraction of petroleum hydrocarbons (WAF-P) were evaluated as biomarkers of petroleum hydrocarbons pollution. The DNA damage caused by water accommodated fraction of petroleum hydrocarbons was assessed in terms of the DNA integrity measured by alkaline unwinding assay. The comparative study of the growth pattern of C. tenuissimus with respect to DNA integrity and the DNA strand breaks in different concentrations of WAF-P showed sufficient tolerance. However, its toxicity increased proportionately with exposure to elevated levels of WAF-P. Although DNA damage in S. costatum was similar to C. tenuissimus, its tolerance level to WAF-P was at least 5 times lower than that of C. tenuissimus indicating its high sensitivity to petroleum hydrocarbons. Active growth was exhibited by C. tenuissimus between 10 and 20% WAF-P (ranging from 0.59 to 1.18mg/L petroleum hydrocarbons) which can be related to the polluted regions only, suggesting the tolerant nature of this organism. Considering the degree of sensitivity to petroleum products and good growth under laboratory conditions, these two diatoms could be recommended as model species for evaluating ecogenotoxic effects of wide range of petroleum hydrocarbon pollutants using alkaline unwinding assays. PMID:20096916

  13. Molecular identification of bloom-forming species Phaeocystis globosa (Prymnesiophyta) and its dispersal based on rDNA ITS sequence analysis

    Institute of Scientific and Technical Information of China (English)

    Chen Yueqin; Shao Peng; Wang Ning; Zhou Hui; Qu Lianghu; Linda K. Medlin

    2003-01-01

    The colony-forming Phaeocystis species are causative agents of dense bloom occurrences in coastal waters worldwide. It is difficult to separate them because of the different morphologies associated with their colonial stages. In this study we applied molecular approaches to analyze the genetic variation of Phaeocystis globosa and Phaeocystis pouchetii from several geographic regions, and to assist in tracing the dispersal of bloom-forming Phaeocystis species in coastal waters of China. The sequences of the internal transcribed spacers ( ITS1 and ITS2) of rDNA and the 5.8S ribosomal RNA gene of Phaeocystis strains were determined. Sequence comparison shows that P.globosa was the most divergent to P. pouchetii, exhibiting sequence divergence higher than 0.08. However, lower genetic divergences existed between strains of P. globosa. The sequence comparison of the Phaeocystis rDNA ITS clearly shows that the species isolated from the southeast coast of China is identified as P. globosa rather than P. cf. pouchetii or other species. Furthermore, the significance of rDNA variation in distinct global populations of P. globosa suggested it might have had sufficient time to accumulate detectable mutations at the rDNA locus, supporting the hypothesis of ancient dispersal of P.globosa to many areas, meaning that P. globosa blooms in the coastal waters of China are endemic rather than a newly introduced species or a foreign source. Finally, based on the high divergent region of rDNA ITS, a pair of species-specific primers for P. globosa were designed, they could be useful to detect the presence of this species in mixed plankton assemblages or flagellate stages that are recognized with diffculties by means of conventional microscopy.

  14. Insights into global diatom distribution and diversity in the world's ocean.

    Science.gov (United States)

    Malviya, Shruti; Scalco, Eleonora; Audic, Stéphane; Vincent, Flora; Veluchamy, Alaguraj; Poulain, Julie; Wincker, Patrick; Iudicone, Daniele; de Vargas, Colomban; Bittner, Lucie; Zingone, Adriana; Bowler, Chris

    2016-03-15

    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 size-fractionated 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.

  15. 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.

  16. Prospects in diatom research.

    Science.gov (United States)

    Lopez, Pascal J; Desclés, Julien; Allen, Andrew E; Bowler, Chris

    2005-04-01

    Diatoms are unicellular photosynthetic eukaryotes that play a major role in the global cycling of carbon and silicon. They are believed to have arisen from a secondary endosymbiotic event between two eukaryotes, a red alga and a flagellated heterotroph. Recent analysis of a diatom genome indeed reveals a 'mosaic' nature, with genes derived from plant, animal and bacterial lineages. Advances in molecular genomics are facilitating the use of diatom-specific genes or pathways for biotechnology. Another interest is in understanding the artistry of the amorphous silica shell and the underlying biomineralization process. Materials scientists and chemists are now exploiting diatoms to develop new biomimetic approaches and to create silicon-based microdevices with specific features. PMID:15831384

  17. 旋链角毛藻和中肋骨条藻间的他感作用%Allelopathic effects between Chaetoceros curvisetus and Skeletonema costatum

    Institute of Scientific and Technical Information of China (English)

    张议文; 王江涛

    2012-01-01

    选择两种常见硅藻——中肋骨条藻(Skeletonema costatum)和旋链角毛藻(Chaetoceros curvisetus)为研究对象,采用滤液培养的方法考察二者之间的他感效应,结果表明:f/2全营养培养条件下,旋链角毛藻指数后期无藻细胞滤液对中肋骨条藻的生长有显著抑制作用,抑制率随旋链角毛藻滤液比例的增大而增大,他感效应随作用时间消退后,中肋骨条藻生长速率提高,且随着旋链角毛藻滤液比例的增大,中肋骨条藻的细胞粒径有减小的趋势;中肋骨条藻指数后期无藻细胞滤液对旋链角毛藻的生长速率和细胞粒径均无影响,表明中肋骨条藻对旋链角毛藻无他感作用.本实验结果可为下一步提取他感物质、研究他感作用机理提供实验基础.%The two common types of diatom, respectively Chaetoceros curvisetus and Skeletonema costatum, were chosen to observe and study the allelopathic effect between them by means of cell-free filtrate culture. The observation showed that under the condition of enriched , cell-free filtrate of the C. curvisetus culture inhibited the growth of 5. costatum significantly in the later exponential growth phase. The inhibition rate was related to the proportion of C. curvisetus cell-free filtrate in the culture, in addition the diameter of S. costatum was affected as well. Allelochemical degraded as time went on, and then the relative growth rate of 5. costatum was increased. There was no influence on the relative growth rate and diameter of S. costatum by enriched C. cumsetus cell-free Citrate in the end of exponential growth phase, which showed that there was not allelopathic effect of S. costatum on C. curuisetus. The results provided the experimental basis for extracting allelochemical and researching allelopathic mechanism later.

  18. Interactions of the algicidal bacterium Kordia algicida with diatoms: regulated protease excretion for specific algal lysis.

    Directory of Open Access Journals (Sweden)

    Carsten Paul

    Full Text Available Interactions of planktonic bacteria with primary producers such as diatoms have great impact on plankton population dynamics. Several studies described the detrimental effect of certain bacteria on diatoms but the biochemical nature and the regulation mechanism involved in the production of the active compounds remained often elusive. Here, we investigated the interactions of the algicidal bacterium Kordia algicida with the marine diatoms Skeletonema costatum, Thalassiosira weissflogii, Phaeodactylum tricornutum, and Chaetoceros didymus. Algicidal activity was only observed towards the first three of the tested diatom species while C. didymus proved to be not susceptible. The cell free filtrate and the >30 kDa fraction of stationary K. algicida cultures is fully active, suggesting a secreted algicidal principle. The active supernatant from bacterial cultures exhibited high protease activity and inhibition experiments proved that these enzymes are involved in the observed algicidal action of the bacteria. Protease mediated interactions are not controlled by the presence of the alga but dependent on the cell density of the K. algicida culture. We show that protease release is triggered by cell free bacterial filtrates suggesting a quorum sensing dependent excretion mechanism of the algicidal protein. The K. algicida / algae interactions in the plankton are thus host specific and under the control of previously unidentified factors.

  19. Interactions of the algicidal bacterium Kordia algicida with diatoms: regulated protease excretion for specific algal lysis.

    Science.gov (United States)

    Paul, Carsten; Pohnert, Georg

    2011-01-01

    Interactions of planktonic bacteria with primary producers such as diatoms have great impact on plankton population dynamics. Several studies described the detrimental effect of certain bacteria on diatoms but the biochemical nature and the regulation mechanism involved in the production of the active compounds remained often elusive. Here, we investigated the interactions of the algicidal bacterium Kordia algicida with the marine diatoms Skeletonema costatum, Thalassiosira weissflogii, Phaeodactylum tricornutum, and Chaetoceros didymus. Algicidal activity was only observed towards the first three of the tested diatom species while C. didymus proved to be not susceptible. The cell free filtrate and the >30 kDa fraction of stationary K. algicida cultures is fully active, suggesting a secreted algicidal principle. The active supernatant from bacterial cultures exhibited high protease activity and inhibition experiments proved that these enzymes are involved in the observed algicidal action of the bacteria. Protease mediated interactions are not controlled by the presence of the alga but dependent on the cell density of the K. algicida culture. We show that protease release is triggered by cell free bacterial filtrates suggesting a quorum sensing dependent excretion mechanism of the algicidal protein. The K. algicida / algae interactions in the plankton are thus host specific and under the control of previously unidentified factors. PMID:21695044

  20. Effect of UV-B radiation on free amino acid pools of marine diatoms

    Energy Technology Data Exchange (ETDEWEB)

    Doehler, G. (Frankfurt Univ. (Germany, F.R.). Botanisches Institut)

    1985-01-01

    The marine diatoms Asterionella glacialis, Chaetoceros debilis, Ditylum brightwellii and Thalassiosira punctigera were grown for 2 d under different levels of UV-B radiation (439, 717 and 1230 Jm/sup -2/d/sup -1/) at 18 /sup 0/C bubbling with normal air (0.035 vol.% CO/sub 2/). Enhanced levels of UV-B radiation reduced biomass production (dry weight), protein and pigment contents of all tested diatoms. UV-B influence on amides and free amino acid pools - using reversed-phase high-performance liquid chromatography - was found to be species dependent. Thalassiosira cells exposed to UV-B radiation are characterized by an increase of glutamic acid and a reduction of glutamine. The effect of UV-B irradiance on the other diatoms resulted in a marked enhancement of glutamine and a diminution of the glutamic acid concentration. Aspartic acid pool was reduced in nearly all marine diatoms. Results are discussed with reference to the inhibition of the enzymes for the carbon and nitrogen pathway.

  1. Nutritional Content of Artemia sp. Fed with Chaetoceros calcitrans and Skeletonema costatum

    Directory of Open Access Journals (Sweden)

    VIVI ENDAR HERAWATI

    2014-12-01

    Full Text Available Artemia sp. is a natural food with high protein content, especially amino acid. Nowadays, Indonesia still relies on import for its supply. Hence, the utilization of local Artemia sp. as an alternative to the imported product is recommended as it contains more protein and less expensive. The advantages of local Artemia sp. is its better crystal quality as it is still fresh. It also provides better income for salt farmers because waste water from salt farm can be used to culture Artemia sp.. This research is aimed at determining the quality of locally-produced Artemia sp., by evaluation of its essential amino acid and fatty acid profiles after treatments. Our results indicated that Artemia sp. cysts with good quality were produced after 8 hours and Artemia sp. reaches a hatching rate of 1,320,000 cysts (95% after 27 hours. We also found an indication that the best feed concentration was a mix of 60% Chaetoceros calcitrans with 40% Skeletonema costatum. Fatty acid profile analyses showed that the highest SAFA (12.86% and PUFA (29.91% were gained after feeding with Chaetoceros calcitrans, whereas the highest HUFA (4.93% was gained after feeding with Skeletonemacostatum. Essential amino acid profile analyses revealed the highest content of amino acid (18912.62 ppm was after feeding with a combination of Chaetoceros calcitrans and Skeletonema costatum. Finally, the proper water quality during research was at 25-30 oC of temperature, 30-31 ppt of salinity, pH 7.8-8.9, and DO was at 3.0-4.4 mg/L.

  2. Production of Biodiesel from Lipid of Phytoplankton Chaetoceros calcitrans through Ultrasonic Method

    Directory of Open Access Journals (Sweden)

    Raymond Kwangdinata

    2014-01-01

    Full Text Available A research on production of biodiesel from lipid of phytoplankton Chaetoceros calcitrans through ultrasonic method has been done. In this research, we carried out a series of phytoplankton cultures to determine the optimum time of growth and biodiesel synthesis process from phytoplankton lipids. Process of biodiesel synthesis consists of two steps, that is, isolation of phytoplankton lipids and biodiesel synthesis from those lipids. Oil isolation process was carried out by ultrasonic extraction method using ethanol 96%, while biodiesel synthesis was carried out by transesterification reaction using methanol and KOH catalyst under sonication. Weight of biodiesel yield per biomass Chaetoceros calcitrans is 35.35%. Characterization of biodiesel was well carried out in terms of physical properties which are density and viscosity and chemical properties which are FFA content, saponification value, and iodine value. These values meet the American Society for Testing and Materials (ASTM D6751 standard levels, except for the viscosity value which was 1.14 g·cm−3.

  3. Diatom associations in shelf waters off Paraná State, Southern Brazil: annual variation in relation to environmental factors

    Directory of Open Access Journals (Sweden)

    Luciano Felício Fernandes

    2004-03-01

    Full Text Available The seasonal variation of diatoms in the inshore waters off Paraná State, Southern Brazil was investigated to analyse their temporal dynamics and to detect the main environmental constraints of the planktonic community. Biomass peaks occurred from May to August and from December to March. Among the microplanktonic diatoms, Cerataulina pelagica, Chaetoceros spp., Dactyliosolen fragilissimus, Guinardia striata, Lauderia annulata, Leptocylindrus spp., Pseudo-nitzschia cf. delicatissima, P. australis, Rhizosolenia spp., Skeletonema costatum and Thalassionema nitzschioides were dominant species. Nanoplanktonic diatoms were dominated by Naviculaceae, Nitzschia spp., Thalassiosira spp. and Chaetoceros cf. tenuissimus. Concentrations of most of the species decreased during and just after the blooms of Phaeocystis pouchetii in September and of Coscinodiscus wailesii in April. Based on cluster analysis and interpretations of the environmental parameters monitored, six diatom associations were discerned. Four main environmental factors were attributed as the determinants for the grouping: (a the stronger influence of the tropical oligotrophic waters of the Brazil Current in spring/summer, (b the alternation between dry and rainy (nutrient-richer seasons, (c the influence of subantarctic waters mixed with coastal ones in fall/winter, bringing cold species and promoting the growth of autochthonous species, and (d the blooms of nanoplanktonic (Phaeocystis and microplanktonic (C. wailesii species.A variação sazonal das diatomáceas em águas neríticas do estado do Paraná, Sul do Brasil, foi investigada para analisar sua dinâmica temporal e detectar as principais forçantes ambientais da comunidade planctônica. Picos de biomassa ocorreram de Maio a Agosto e de Dezembro a Março. As espécies dominantes foram Cerataulina pelagica, Chaetoceros spp., Dactyliosolen fragilissimus, Guinardia striata, Lauderia annulata, Leptocylindrus spp., Pseudo-nitzschia cf

  4. A comparison of morphological and molecular-based surveys to estimate the species richness of Chaetoceros and Thalassiosira (bacillariophyta, in the Bay of Fundy.

    Directory of Open Access Journals (Sweden)

    Sarah E Hamsher

    Full Text Available The goal of this study was to compare the ability of morphology and molecular-based surveys to estimate species richness for two species-rich diatom genera, Chaetoceros Ehrenb. and Thalassiosira Cleve, in the Bay of Fundy. Phytoplankton tows were collected from two sites at intervals over two years and subsampled for morphology-based surveys (2010, 2011, a culture-based DNA reference library (DRL; 2010, and a molecular-based survey (2011. The DRL and molecular-based survey utilized the 3' end of the RUBISCO large subunit (rbcL-3P to identify genetic species groups (based on 0.1% divergence in rbcL-3P, which were subsequently identified morphologically to allow comparisons to the morphology-based survey. Comparisons were compiled for the year (2011 by site (n = 2 and by season (n = 3. Of the 34 taxa included in the comparisons, 50% of taxa were common to both methods, 35% were unique to the molecular-based survey, and 12% were unique to the morphology-based survey, while the remaining 3% of taxa were unidentified genetic species groups. The morphology-based survey excelled at identifying rare taxa in individual tow subsamples, which were occasionally missed with the molecular approach used here, while the molecular methods (the DRL and molecular-based survey, uncovered nine cryptic species pairs and four previously overlooked species. The last mentioned were typically difficult to identify and were generically assigned to Thalassiosira spp. during the morphology-based survey. Therefore, for now we suggest a combined approach encompassing routine morphology-based surveys accompanied by periodic molecular-based surveys to monitor for cryptic and difficult to identify taxa. As sequencing technologies improve, molecular-based surveys should become routine, leading to a more accurate representation of species composition and richness in monitoring programs.

  5. Discovery of two novel viruses expands the diversity of single-stranded DNA and single-stranded RNA viruses infecting a cosmopolitan marine diatom.

    Science.gov (United States)

    Kimura, Kei; Tomaru, Yuji

    2015-02-01

    Recent studies have suggested that diatom viruses are an important factor affecting diatom population dynamics, which in turn are important in considering marine primary productivity. The marine planktonic diatom Chaetoceros tenuissimus Meunier is a cosmopolitan species and often causes blooms off the western coast of Japan. To date, two viruses, C. tenuissimus DNA virus (CtenDNAV) type I and CtenRNAV type I, have been identified that potentially affect C. tenuissimus population dynamics in the natural environment. In this study, we successfully isolated and characterized two additional novel viruses (CtenDNAV type II and CtenRNAV type II). This paper reports the basic characteristics of these new viruses isolated from surface water or sediment from the Hiroshima Bay, Japan. The physiological and morphological characteristics of the two new viruses were similar to those of the previously isolated viruses. However, the amino acid sequences of the structural proteins of CtenDNAV type II and CtenRNAV type II were clearly distinct from those of both type I viruses, with identity scores of 38.3% and 27.6%, respectively. Our results suggest that at least four genetically distinct viruses sharing the same diatom host are present in western Japan and affect the population dynamics of C. tenuissimus. Moreover, the result that CtenRNAV type II lysed multiple diatom species indicates that RNA viruses may affect various diatom populations in the natural environment.

  6. Effect of Growth Phase on the Fatty Acid Compositions of Four Species of Marine Diatoms

    Institute of Scientific and Technical Information of China (English)

    LIANG Ying; MAI Kangsen

    2005-01-01

    The fatty acid compositions of four species of marine diatoms (Chaetoceros gracilis MACC/B13, Cylindrotheca fusiformis MACC/B211, Phaeodactylum tricornutum MACC/B221 and Nitzschia closterium MACC/B222), cultivated at 22 ℃± 1 ℃ with the salinity of 28 in f/2 medium and harvested in the exponential growth phase, the early stationary phase and the late stationary phase, were determined. The results showed that growth phase has significant effect on most fatty acid contents in the four species of marine diatoms. The proportions of 16:0 and 16:1n-7 fatty acids increased while those of 16:3n-4 and eicosapentaenoic acid (EPA) decreased with increasing culture age in all species studied. The subtotal of saturated fatty acids (SFA) increased with the increasing culture age in all species with the exception of B13. The subtotal of monounsaturated fatty acids (MUFA) increased while that of polyunsaturated fatty acids (PUFA) decreased with culture age in the four species of marine diatoms. MUFA reached their lowest value in the exponential growth phase, whereas PUFA reached their highest value in the same phase.

  7. Impacta of CO2 enrichment on growth and photosynthesis in freshwater and marine diatoms

    Institute of Scientific and Technical Information of China (English)

    HU Hanhua; GAO Kunshan

    2008-01-01

    The physiological responses of Nitzschia palea Kiitzing, a freshwater diatom, to elevated CO2 were investigated and compared with those of a marine diatom, Chaetoceros muelleri Lemmermann previously reported. Elevated CO2 concentration to 700 μl/L increased the dissolved inorganic carbon (DIC) and lowered the pH in the cultures of N. palea, thus enhancing the growth by 4%-20% during the whole growth period. High CO2-grown N. palea cells showed lower levels of dark respiration rates and higher Ik values. Light-saturated photosynthetic rates and photosynthetic efficiencies decreased in N. palea with the doubling CO2 concentration in airflow to the bottom of cultures, although the doubling CO2 concentration in airflow to the surface cultures had few effects on these two photosynthetic parameters. N. palea cells were found to be capable of using HCO3- in addition to gaseous CO2, and the CO2 enrichment decreased their affinity for HCO3- and CO2. Although doubled CO2 level would enhance the biomass of N. palea and C. muelleri to different extents, compared with the marine diatom, it had a significant effect on the specific growth rates of N. palea. In addition, the responses of photosynthetic parameters of N. palea to doubled CO2 concentration were almost opposite to those of C. muelleri.

  8. 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

    different evolutionary history from the higher plants that dominate photosynthesis on land. Higher plants and green, red and glaucophyte algae are derived from a primary endosymbiotic event in which a non-photosynthetic eukaryote acquired a chloroplast by engulfing (or being invaded by) a prokaryotic cyanobacterium. In contrast, dominant bloom-forming eukaryotic phytoplankton in the ocean, such as diatoms and haptophytes, were derived by secondary endosymbiosis whereby a non-photosynthetic eukaryote acquired a chloroplast by engulfing a photosynthetic eukaryote, probably a red algal endosymbiont (Fig. 1). Each endosymbiotic event led to new combinations of genes derived from the hosts and endosymbionts (7). Prior to this project, relatively few diatom genes had been sequenced, few chromosome numbers were known, and genetic maps did not exist (8). The ecological and evolutionary importance of diatoms motivated our sequencing and analysis of the nuclear, plastid, and mitochondrial genomes of the marine centric diatom Thalassiosira pseudonana.

  9. The Genome of the Diatom Thalassiosira Pseudonana: Ecology, Evolution and Metabolism

    Energy Technology Data Exchange (ETDEWEB)

    Armbrust, E V; Berges, J A; Bowler, C; Green, B R; Martinez, D; Putnam, N H; Zhou, S; Allen, A E; Apt, K E; Bechner, M; Brzezinski, M A; Chaal, B K; Chiovitti, A; Davis, A K; Demarest, M S; Detter, J C; del Rio, T G; Goodstein, D; Hadi, M Z; Hellsten, U; Hildebrand, M; Jenkins, B D; Jurka, J; Kapitonov, V V; Kroger, N; Lau, W Y; Lane, T W; Larimer, F W; Lippmeier, J C; Lucas, S; Medina, M; Montsant, A; Obornik, M; Parker, M S; Palenik, B; Pazour, G J; Richardson, P M; Rynearson, T A; Saito, M A; Schwartz, D C; Thamatrakoln, K; Valentin, K; Vardi, A; Wilkerson, F P; Rokhsar, D S

    2005-11-14

    different evolutionary history from the higher plants that dominate photosynthesis on land. Higher plants and green, red and glaucophyte algae are derived from a primary endosymbiotic event in which a non-photosynthetic eukaryote acquired a chloroplast by engulfing (or being invaded by) a prokaryotic cyanobacterium. In contrast, dominant bloom-forming eukaryotic phytoplankton in the ocean, such as diatoms and haptophytes, were derived by secondary endosymbiosis whereby a non-photosynthetic eukaryote acquired a chloroplast by engulfing a photosynthetic eukaryote, probably a red algal endosymbiont (Fig. 1). Each endosymbiotic event led to new combinations of genes derived from the hosts and endosymbionts (7). Prior to this project, relatively few diatom genes had been sequenced, few chromosome numbers were known, and genetic maps did not exist (8). The ecological and evolutionary importance of diatoms motivated our sequencing and analysis of the nuclear, plastid, and mitochondrial genomes of the marine centric diatom Thalassiosira pseudonana.

  10. 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 BACKGROUND: 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. PRINCIPAL FINDINGS: 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. CONCLUSIONS: 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.

  11. Ecological composition and distribution of the diatoms from the Laguna Superior, Oaxaca, Mexico.

    Science.gov (United States)

    Moreno-Ruiz, José Luis; Tapia-Garcia, Margarito; Licea, Sergio; Figueroa-Torres, María Guadalupe; Esquivel, Alfonso; Herrera-Galindo, Jorge Eduardo; González-Fernández, José Manuel; González-Macias, Maria Del Carmen

    2011-07-01

    A taxonomic study of diatoms was carried out in a tropical coastal lagoon. Material for this study consists of water samples obtained from February-March 1992 to November-December 2000. Qualitative and quantitative analyses showed the presence of 373 taxa of which the families Bacillariaceae (67 species) and Chaetocerotaceae (37 species) were the most abundant groups. The species Skeletonema costatum, Chaetoceros curvisetus, Coscinodiscus radiatus var. radiatus, Ditylum brightwellii, Thalassiosira eccentrica and Entomoneis alata were found associated with moderate water quality and forming blooms. In addition, a regional comparison between Mexico and South America of the identified species is given. For practical handling, indicative values obtained from their ecological composition are incorporated as well as a code of the floristic list. Achecklist of the species and their occurrence are given. PMID:22315822

  12. Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia

    Science.gov (United States)

    Rembauville, M.; Manno, C.; Tarling, G. A.; Blain, S.; Salter, I.

    2016-09-01

    Biogeochemical and diatom export fluxes are presented from two bathypelagic sediment trap deployments in the Antarctic Zone of the Southern Ocean. One of the sediment traps was deployed in very productive, naturally iron-fertilized waters downstream of South Georgia (P3, 2000 m) and compared to a deployment in moderately productive waters upstream of the island system (P2, 1500 m). At both sites significant diatom export events occurred in spring (November) and contained mostly empty cells that were associated with low particulate organic carbon (POC) fluxes. A summer export pulse occurred one month later at P2 (end February/March) compared to P3 (end January). Diatom fluxes at P3 were one order of magnitude higher than at P2, a difference mainly attributed to the short and intense export of resting spores from Chaetoceros Hyalochaete and Thalassiosira antarctica species. Aside from these resting spores, diatom export assemblages at both sites were dominated by empty Fragilariopsis kerguelensis frustules. The fraction of diatoms exported as empty frustules was considerably lower at P3 (52%) than P2 (91%). This difference was related to the flux of intact diatom resting spores at P3 and may partially explain the lower Si:C export stoichiometry observed at P3 (1.1) compared to P2 (1.5). Through the enumeration of full diatom frustules and subsequent biomass calculations we estimate that diatom resting spores account for 42% of annual POC flux in the productive waters downstream of South Georgia. At both sites the contribution of diatom vegetative stages to POC fluxes was considerably lower (vector out of the mixed layer. Furthermore, the contribution or resting spores to POC flux in the bathypelagic ocean and sediments suggests they play a particularly important role in sequestering biologically fixed CO2 over climatically relevant timescales.

  13. The study on the effect of NO on the growth of Chaetoceros curvisetus

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhengbin; WU Zhenzhen; LIU Chunying; XING Lei

    2006-01-01

    This article studied nitric oxide (NO) effect on the growth of Chaetoceros curvisetus in chemistry for the first time. Nitric oxide was added into the media with 4 different nutrient concentrations f/2, f/50, f/100, and f/200 when the alga was growing. The growth of C. curvisetus could be obviously promoted or inhibited during the cultivation process in NO enriched media of different concentrations.The growth curve in such media showed a sharp single peak that is the optimal NO concentration for the alga growth, which is consistent with the influence of NO on the growth of high plants. In addition, C.curvisetus can produce NO by itself during the growth. Therefore, using NO could effectively regulate the algae growth, which is important in real tide control and remediation.

  14. Temporal variation of diatom benthic propagules in a monsoon-influenced tropical estuary

    Science.gov (United States)

    Patil, Jagadish S.; Anil, Arga Chandrashekar

    2008-10-01

    Temporal variations in the diatom benthic propagule (DBP) community and their role in the phytoplankton community in a monsoon-affected tropical estuary, Zuari estuary, Goa (India) are presented. The DBP from the sediments was enumerated using an extinction dilution method (most probable number method), which allows estimation of resting stages through examination of germinated vegetative cells in culture. The DBP community was dominated by planktonic species belonging to the genera Skeletonema, Fragilariopsis, Thalassiosira, and Chaetoceros. Benthic propagules (BPs) of Skeletonema costatum and Fragilariopsis sp. were dominant throughout the year. Between these two species, only S. costatum showed a linear relationship between the BP and planktonic cells, indicating that this species is particularly important in coupling of pelagic and benthic ecosystems. During the onset and restart of monsoon after an intermittent break, water column was stratified, with a low-salinity layer arising from riverine discharge and precipitation at the surface and relatively cold, saline, low-oxygen waters at the bottom. Stratification favored blooming of S. costatum and Fragilariopsis sp. in nutrient-rich surface and bottom waters, respectively. The decline in these blooms ensuing nitrate depletion and salinity change resulted in an increased abundance of BP. Chaetoceros bloom was observed during the monsoon break as well as during non-monsoon period and on both the occasions the decline in bloom was coupled with freshwater discharge. During the non-monsoon season, Thalassiosira blooms were encountered subsequent to high nitrate inputs. These findings suggest that in such shallow tropical regions, physical processes during monsoon (freshwater discharge) and non-monsoon seasons (currents, waves and tides) cause resuspension of diatom BP. Since light is not a limiting factor for germination in such regions, the blooming of resuspended BP depends on nutrient availability.

  15. 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.

  16. Diatomic gasdynamic lasers

    International Nuclear Information System (INIS)

    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 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

  17. Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia

    Science.gov (United States)

    Rembauville, M.; Manno, C.; Tarling, G. A.; Blain, S.; Salter, I.

    2016-09-01

    Biogeochemical and diatom export fluxes are presented from two bathypelagic sediment trap deployments in the Antarctic Zone of the Southern Ocean. One of the sediment traps was deployed in very productive, naturally iron-fertilized waters downstream of South Georgia (P3, 2000 m) and compared to a deployment in moderately productive waters upstream of the island system (P2, 1500 m). At both sites significant diatom export events occurred in spring (November) and contained mostly empty cells that were associated with low particulate organic carbon (POC) fluxes. A summer export pulse occurred one month later at P2 (end February/March) compared to P3 (end January). Diatom fluxes at P3 were one order of magnitude higher than at P2, a difference mainly attributed to the short and intense export of resting spores from Chaetoceros Hyalochaete and Thalassiosira antarctica species. Aside from these resting spores, diatom export assemblages at both sites were dominated by empty Fragilariopsis kerguelensis frustules. The fraction of diatoms exported as empty frustules was considerably lower at P3 (52%) than P2 (91%). This difference was related to the flux of intact diatom resting spores at P3 and may partially explain the lower Si:C export stoichiometry observed at P3 (1.1) compared to P2 (1.5). Through the enumeration of full diatom frustules and subsequent biomass calculations we estimate that diatom resting spores account for 42% of annual POC flux in the productive waters downstream of South Georgia. At both sites the contribution of diatom vegetative stages to POC fluxes was considerably lower (export contributes towards the slightly higher bathypelagic (POC) flux at P3 (40.6 mmol m-2 y-1) compared to P2 (26.4 mmol m-2 y-1). We compared our sediment trap records with previously published diatom assemblage data from the mixed layer and surface sediments (3760 m) around South Georgia. The relative proportion of diatom resting spores within diatom assemblages increases as a

  18. Diatom DNA as historical information

    Science.gov (United States)

    Stoof, K. R.; Epp, L. S.; Trauth, M. H.; Tiedemann, R.

    2009-04-01

    This survey is about the reconstruction of paleo environmental conditions in East Africa using recent and historic lakes sediments of shallow lakes in Kenya. This interdisciplinary approach combines the molecular analysis of ancient diatom DNA and the morphological analysis of diatom assemblages of short sediment cores to reveal the potential of molecular genetics in geosciences. This study comprises the investigation of two short sediment cores from Lake Naivasha (Kenya) taken in 2007, covering a stretch of ca. 80 years. Several sediment slices were analysed by molecular methods that concludes in species identification based on DNA fragments. Therefore total DNA was extracted and applied to a diatom DNA specific PCR amplifying a gene fragment that is frequently used for species identification. After cloning PCR products, clones were sequenced, sequences from different diatom species were analysed. As a comparison permanent slides were prepared for each sediment sample for counting diatom valves. The results suggest that DNA damage, perhaps species depended, and specific factors of PCR contribute to an overhang of two dominant diatom species (Aulacoseira ambigua and Aulacoseira granulata) represented by the molecular approach whereas rare species seen by light microscopy are not yet identifiable with molecular methods. Moreover changes in diatom assemblages and the reconstructed conductivity indicate a decrease of lake level around 1940. This shift seems to be also represented in the molecular approach as a decrease in the amount of diverse diatom DNA sequences found, what is probably caused by worse DNA preservation conditions at that time.

  19. Response of the ubiquitous pelagic diatom Thalassiosira weissflogii to darkness and anoxia.

    Directory of Open Access Journals (Sweden)

    Anja Kamp

    Full Text Available Thalassiosira weissflogii, an abundant, nitrate-storing, bloom-forming diatom in the world's oceans, can use its intracellular nitrate pool for dissimilatory nitrate reduction to ammonium (DNRA after sudden shifts to darkness and anoxia, most likely as a survival mechanism. T. weissflogii cells that stored 4 mM (15N-nitrate consumed 1.15 (±0.25 fmol NO3 (- cell(-1 h(-1 and simultaneously produced 1.57 (±0.21 fmol (15NH4 (+ cell(-1 h(-1 during the first 2 hours of dark/anoxic conditions. Ammonium produced from intracellular nitrate was excreted by the cells, indicating a dissimilatory rather than assimilatory pathway. Nitrite and the greenhouse gas nitrous oxide were produced at rates 2-3 orders of magnitude lower than the ammonium production rate. While DNRA activity was restricted to the first few hours of darkness and anoxia, the subsequent degradation of photopigments took weeks to months, supporting the earlier finding that diatoms resume photosynthesis even after extended exposure to darkness and anoxia. Considering the high global abundance of T. weissflogii, its production of ammonium and nitrous oxide might be of ecological importance for oceanic oxygen minimum zones and the atmosphere, respectively.

  20. Diatom and Geochemical Constraints on Pliocene Sea Surface Conditions on the Wilkes Land Margin, East Antarctica

    Science.gov (United States)

    Riesselman, C. R.; Taylor-Silva, B.

    2015-12-01

    The mid-Pliocene is the most recent interval in Earth's history to sustain global temperatures within the range of warming predicted for the 21st century, providing an appealing analog with which to examine the changes we might encounter in the coming century. Diatom-based Southern Ocean sea surface and sea ice reconstructions by the USGS Pliocene Research Interpretations and Synoptic Mapping (PRISM) Group suggest an average +2° summer SST anomaly during the 3.3-3.0 Ma interval relative to modern. Here, we present a reconstruction of Pliocene sea surface conditions from a marine sediment core collected at IODP Site U1361, on the continental rise of the Wilkes Land margin. U1361 biogenic silica concentrations document the alternation of diatom-rich and diatom-poor lithologies; we interpret 8 diatom-rich mudstones within this sequence to record interglacial conditions between 3.8 and 2.8 Ma, across the transition from obliquity control to precession control on East Antarctic ice volumes. This progression also preserves 3 packages of interglacial sediments within the 3.3-3.0 PRISM interval, providing an opportunity for direct comparison to proximal PRISM site Eltanin 50-28. Diatom assemblages in both cores are characterized by Fragilariopsis barronii and Rouxia antarctica, extinct species with an inferred ecological preference for waters south of the polar front. However F. weaveri, an extinct diatom with inferred preference for more northerly waters and moderate abundance in E50-28, has not been identified at U1361. This may indicate that the polar frontal zone migrated across E50-28 (62° 54'S) but remained north of U1361 (64° 25'S) during the mid-Pliocene. This interpretation is bolstered by the low abundance of extant polar front species (e.g., Thalassiosira oliverana, T. lentiginosa) at U1361; these diatoms dominate the E50-28 assemblage. In contrast, the U1361 assemblage includes a number of extant sea ice indicators (F. sublinearis, F. curta, Chaetoceros

  1. Biogenic silica dissolution in diatom aggregates: insights from reactive transport modelling

    KAUST Repository

    Moriceau, B

    2014-12-15

    © Inter-Research 2014. Diatom aggregates contribute significantly to the vertical sinking flux of particulate matter in the ocean. These fragile structures form a specific microhabitat for the aggregated cells, but their internal chemical and physical characteristics remain largely unknown. Studies on the impact of aggregation on the Si cycle led to apparent inconsistency. Despite a lower biogenic silica (bSiO2) dissolution rate and diffusion of the silicic acid (dSi) being similar in aggregates and in sea-water, dSi surprisingly accumulates in aggregates. A reaction-diffusion model helps to clarify this incoherence by reconstructing dSi accumulation measured during batch experiments with aggregated and non-aggregated Skeletonema marinoi and Chaetoceros decipiens. The model calculates the effective bSiO2 dissolution rate as opposed to the experimental apparent bSiO2 dissolution rate, which is the results of the effective dissolution of bSiO2 and transport of dSi out of the aggregate. In the model, dSi transport out of the aggregate is modulated by alternatively considering retention (decrease of the dSi diffusion constant) and adsorption (reversible chemical bonds between dSi and the aggregate matrix) processes. Modelled bSiO2 dissolution is modulated by the impact of dSi concentration inside aggregates and diatom viability, as enhanced persistence of metabolically active diatoms has been observed in aggregates. Adsorption better explains dSi accumulation within and outside aggregates, raising the possible importance of dSi travelling within aggregates to the deep sea (potentially representing 20% of the total silica flux). The model indicates that bSiO2 dissolution is effectively decreased in aggregates mainly due to higher diatom viability but also to other parameters discussed herein.

  2. Nutrient compositions of cultured Skeletonema costatum, Chaetoceros curvisetus, and Thalassiosira nordenskiöldii

    Science.gov (United States)

    Pan, Shengjun; Shen, Zhiliang; Liu, Wenping; Han, Xiaotian; Miao, Hui; Ma, Haiqing

    2010-11-01

    We cultured different-sized fractions of dominant phytoplankton species, Skeletonema costatum, Chaetoceros curvisetus, and Thalassiosira nordenskiöldii, collected in different sea areas in various seasons, and measured and compared their C, N, P, Si contents. The N content of these species is similar, while the C, P, and Si contents of S. costatum from eutrophic Changjiang (Yangtze River) estuary are higher than those from Jiaozhou Bay (JZB), particularly the content of Si. The C, N, P, and Si contents of cultured phytoplankton in JZB increase with size fraction augmentation, and the percentages of C, N, and P follow the same trend, while the percentage of Si remain constant. Moreover, S. costatum from small-sized fraction assimilated Si more easily than C. curvisetus and T. nordenskiöldii, which is explained by the dominance of S. costatum under the conditions of low SiO3-Si concentration in JZB. The C, N, P, and Si contents of cultured S. costatum collected during summer and winter are higher, which is consistent with the phytoplankton blooming seasons in JZB. The SiO3-Si concentration of seawater during spring restrain the growth of phytoplankton, supported by the fact that the N, P, and Si contents and their ratios in cells of cultured S. costatum are low in spring season.

  3. Snapshot prediction of carbon productivity, carbon and protein content in a Southern Ocean diatom using FTIR spectroscopy.

    Science.gov (United States)

    Sackett, Olivia; Petrou, Katherina; Reedy, Brian; Hill, Ross; Doblin, Martina; Beardall, John; Ralph, Peter; Heraud, Philip

    2016-02-01

    Diatoms, an important group of phytoplankton, bloom annually in the Southern Ocean, covering thousands of square kilometers and dominating the region's phytoplankton communities. In their role as the major food source to marine grazers, diatoms supply carbon, nutrients and energy to the Southern Ocean food web. Prevailing environmental conditions influence diatom phenotypic traits (for example, photophysiology, macromolecular composition and morphology), which in turn affect the transfer of energy, carbon and nutrients to grazers and higher trophic levels, as well as oceanic biogeochemical cycles. The paucity of phenotypic data on Southern Ocean phytoplankton limits our understanding of the ecosystem and how it may respond to future environmental change. Here we used a novel approach to create a 'snapshot' of cell phenotype. Using mass spectrometry, we measured nitrogen (a proxy for protein), total carbon and carbon-13 enrichment (carbon productivity), then used this data to build spectroscopy-based predictive models. The models were used to provide phenotypic data for samples from a third sample set. Importantly, this approach enabled the first ever rate determination of carbon productivity from a single time point, circumventing the need for time-series measurements. This study showed that Chaetoceros simplex was less productive and had lower protein and carbon content during short-term periods of high salinity. Applying this new phenomics approach to natural phytoplankton samples could provide valuable insight into understanding phytoplankton productivity and function in the marine system.

  4. Controlling dynamics in diatomic systems

    Indian Academy of Sciences (India)

    Praveen Kumar; Harjinder Singh

    2007-09-01

    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 systems, HF and OH. The power spectra of the fields and evolution of populations of different vibrational states during transitions are obtained.

  5. Stuart R. Stidolph diatom atlas

    Science.gov (United States)

    Stidolph, S.R.; Sterrenburg, F.A.S.; Smith, K.E.L.; Kraberg, A.

    2012-01-01

    The "Stuart R. Stidolph Diatom Atlas" is a comprehensive volume of diatom taxa identified and micrographed by Stuart R. Stidoph during the 1980s and 1990s. The samples were collected from marine coasts of various geographic regions within tropical and subtropical climates. The plates included within this report have never been published and are being published by the USGS as an online reference so that others may have access to this incredible collection.

  6. The influence of extracellular compounds produced by selected Baltic cyanobacteria, diatoms and dinoflagellates on growth of green algae Chlorella vulgaris

    Science.gov (United States)

    Żak, Adam; Kosakowska, Alicja

    2015-12-01

    Secondary metabolites produced by bacteria, fungi, algae and plants could affect the growth and development of biological and agricultural systems. This natural process that occurs worldwide is known as allelopathy. The main goal of this work was to investigate the influence of metabolites obtained from phytoplankton monocultures on the growth of green algae Chlorella vulgaris. We selected 6 species occurring in the Baltic Sea from 3 different taxonomic groups: cyanobacteria (Aphanizomenon flos-aquae; Planktothrix agardhii), diatoms (Thalassiosira pseudonana; Chaetoceros wighamii) and dinoflagellates (Alexandrium ostenfeldii; Prorocentrum minimum). In this study we have demonstrated that some of selected organisms caused allelopathic effects against microalgae. Both the negative and positive effects of collected cell-free filtrates on C. vulgaris growth, chlorophyll a concentration and fluorescence parameters (OJIP, QY, NPQ) have been observed. No evidence has been found for the impact on morphology and viability of C. vulgaris cells.

  7. 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.

  8. African diatom palaeoecology and biostratigraphy

    Science.gov (United States)

    Gasse, F.; Fourtanier, E.

    This paper illustrates the different types of information which can be deduced from African diatoms studies. The first section is devoted to the reconstruction of palaeoenvironments. The accuracy of ecological data (estimates of ecological variables e.g. types of habitats, water chemistry…) depends on the times scale and on the spatial scale considered: short-term environments in a given waterbody, environmental evolution during individual humid episodes considered locally or regionally, long-term changes in diatom flora induced by major climatic tendencies at a regional or continental scale. One then summarizes our present state of knowledge in diatom biostratigraphy in Africa. Several centric taxa, belonging to the genera Aulacoseira, Mesodictyon, Cyclotella, Stephanodiscus and Cyclostephanos appear to have limited stratigraphical ranges and to be good chronological markers.

  9. Persistent blooms of surf diatoms along the pacific coast U. S. A. I. physical characteristics of the coastal region in relation to the distribution and abundance of the species

    Energy Technology Data Exchange (ETDEWEB)

    Garver, J.L.; Lewin, J.

    1981-01-01

    The surf diatom populations at thirteen beaches along the Oregon and Washington coast were studied from June 1977 through August 1978. Chaetoceros armatum T. West and Asterionella socialis Lewin and Norris, the two species responsible for the blooms, were present in the surf along beaches between Point Grenville, Washington, and Cape Blanco, Oregon. On the basis of the cell densities of these two species, the beaches were arranged into four distinct groups. Discriminant analysis showed that the four groups could also be completely separated by three discriminant functions composed of four physical variables: offshore bottomslope, per cent chlorite, per cent montmorillonite and beach length. The absence of surf diatoms at two beaches south of Cape Blanco can probably be explained by the unsuitable physical conditions along the coast south of the Cape.

  10. The marine diatom and diazotroph under future climate: Role of Iron

    Science.gov (United States)

    Li, Xuefeng; Fonseca-batista, Debany; Brouwers, Julie; Roevros, Nathalie; Dehairs, Frank; Chou, Lei

    2016-04-01

    Diatoms constitute a major group of phytoplankton, accounting for one quarter of the world's net primary productivity. Diazotrophs provide the largest input of new nitrogen (N) to the ocean and control the marine N budgets. It has been shown that iron (Fe) can be the limiting factor for diatom growth, in particular, in the HNLC (High Nutrient Low Chlorophyll) regions. This trace element can also govern the development of marine diazotrophs due to the high Fe demand necessary for biological N2 fixation. Iron plays thus an essential role in governing the marine primary productivity and the efficiency of biological carbon pump. Ocean systems are undergoing continuous modifications at varying rates and magnitudes as a result of changing climate. The objectives of our research is to evaluate 1) how climate change (dust deposition, ocean warming and acidification) can affect Fe biogeochemistry and the growth of diatoms and diazotrophs, and 2) the role of Fe in the control of biological N2 fixation under future climate scenarios. Laboratory culture experiments using Chaetoceros socialis were examined at two temperatures (13°C and 18°C) and two CO2 conditions (400 μatm and 800 μatm). The present study demonstrates clearly the influence of ocean acidification on the release of Fe upon dust deposition. It also shows that dust particles could provide a readily utilizable source of Fe and other macronutrients (dissolved phosphate and silicate) for phytoplankton growth. Elevated pCO2 concentrations may have adverse impact on the diatom growth; seawater warming may cause poleward shifts in the biogeographic distribution of diatoms. The impact of Fe on the natural N2 fixation was tested via field incubation experiments using natureal phytoplankton assemblage in the Bay of Biscay and along the Iberian Margin. N2 fixation rates in oligotrophic waters were greatly stimulated through the addition of dissolved Fe compared to the control, demonstrating the limitation of N2 fixation

  11. 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

  12. Diatom preservation: differential preservation of sedimentary diatoms in two saline lakes

    OpenAIRE

    Flower, R. J.; D. B. Ryves

    2009-01-01

    The integrity of all sedimentary diatom assemblages is influenced to sonic degree by taphonomic processes. Recognising these processes with regard to preservation pathways for diatom assemblages and for individual species can be instructive for interpreting sediment core diatom records. Diatoms deposited in saline lakes are usually particularly exposed to both chemical and physical processes that promote poor preservation. Aspects of diatom preservation are explored in two markedly different ...

  13. Copepod grazing during spring blooms: Does Calanus pacificus avoid harmful diatoms?

    Science.gov (United States)

    Leising, Andrew W.; Pierson, James J.; Halsband-Lenk, Claudia; Horner, Rita; Postel, James

    2005-11-01

    During late winter and spring of 2002 and 2003, 24, 2-3 day cruises were conducted to Dabob Bay, Washington State, USA, to examine the grazing, egg production, and hatching success rates of adult female Calanus pacificus and Pseudocalanus newmani. The results of the copepod grazing experiments for C. pacificus are discussed here. Each week, copepod grazing incubation experiments from two different depth layers were conducted. Grazing was measured by both changes in chlorophyll concentration and cell counts. In 2002, there was one moderate bloom consisting mainly of Thalassiosira spp. in early February, and a larger bloom in April comprised of two Chaetoceros species and Phaeocystis sp. Similarly, in 2003, there were two blooms, an early one dominated by Thalassiosira spp., and a later one consisting of Chaetoceros spp. and Thalassiosira spp. Clearance rates on individual prey species, as calculated by cell counts, showed that C. pacificus are highly selective in their feeding, and may have much higher clearance rates on individual taxa than rates calculated from bulk chlorophyll disappearance. During weeks of high phytoplankton concentration, the copepods generally ate phytoplankton. However, they often rejected the most abundant phytoplankton species, particularly certain Thalassiosira spp., even though the rejected prey were often of the same genus and similar size to the preferred prey. It is speculated that this avoidance may be related to the possible deleterious effects that certain of these diatom species have on the reproductive success of these copepods. During weeks of medium to low phytoplankton concentration, the copepods selectively ate certain species of phytoplankton, and often had high electivity for microzooplankton. The selection mechanism must consist of active particle rejection most likely based on detection of surface chemical properties, since the diatoms that were selected were of the same genus, nearly the same size, and at lower numerical

  14. AEROSAKKONEMA, A NEWLY REPORTED GENUS OF WATER BLOOM FORMING CYANOBACTERIA IN THE POYANG LAKE OF CHINA%鄱阳湖的中国水华蓝藻新记录属-气丝藻属

    Institute of Scientific and Technical Information of China (English)

    李守淳; 黄静; 虞功亮; 李仁辉

    2014-01-01

    2012年4月和10月在江西省鄱阳湖进行野外调查时,发现一种浮游的丝状蓝藻。通过分离纯培养,获得了6个纯化藻株。根据藻株主要形态学特征及其16S rRNA基因序列与比较,鄱阳湖这些藻株与老挝的2株Aerosakkonema funiforme较为相近,其中16S rRNA基因序列的相似度达到98%。鉴于这些藻株不同于颤藻目中其他属的藻株,因此确定为我国一水华蓝藻新记录属--气丝藻属Aerosakkonema Nanda&Watanabe 2012,模式种为索状气丝藻Aerosakkonema funiforme Nanda&Watanabe 2012。%During a recent field survey of the water bloom forming cyanobacteria in the Poyang Lake, we collected a type of gas-vacuolated filamentous cyanobacterial. Six strains of this species were isolated and purified after the culture in the lab. The 16S rRNA gene sequence of this species showed a high similarity (98%) with those of two strains from the Nam Ngum Reservoir of Lao People’s Democratic Republic. This result, together with their morphological charac-teristics, suggested that these six strains were different from other Oscilatorialean cyanobacteria. Therefore this species was identified as Aerosakkonema funiforme that belonged to Aerosakkonema (Nanda & Watanabe 2012). Aero-sakkonema is a new record of cyanobacteria genus in China.

  15. "Dinoflagellate Sterols" in marine diatoms.

    Science.gov (United States)

    Giner, José-Luis; Wikfors, Gary H

    2011-10-01

    Sterol compositions for three diatom species, recently shown to contain sterols with side chains typically found in dinoflagellates, were determined by HPLC and ¹H NMR spectroscopic analyses. The centric diatom Triceratium dubium (=Biddulphia sp., CCMP 147) contained the highest percentage of 23-methylated sterols (37.2% (24R)-23-methylergosta-5,22-dienol), whereas the pennate diatom Delphineis sp. (CCMP 1095) contained the cyclopropyl sterol gorgosterol, as well as the 27-norsterol occelasterol. The sterol composition of Ditylum brightwellii (CCMP 358) was the most complex, containing Δ⁰- and Δ⁷-sterols, in addition to the predominant Δ⁵-sterols. A pair of previously unknown sterols, stigmasta-5,24,28-trienol and stigmasta-24,28-dienol, were detected in D. brightwellii and their structures were determined by NMR spectroscopic analysis and by synthesis of the former sterol from saringosterol. Also detected in D. brightwellii was the previously unknown 23-methylcholesta-7,22-dienol. PMID:21621802

  16. The effect of antibiotics on diatom communities

    Digital Repository Service at National Institute of Oceanography (India)

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

    viable diatoms were observed were scored as positive. Diatoms were identified based on standard taxonomic keys, detailed in D’Costa and Anil 24 . Diatoms < 10 μm which could not be identified to generic level were grouped together as unidentified... positive bacteria in a tidal flat ecosystem. Environ. Microbiol., 2007, 9, 1810–1822. 32. Stevenson, B. S., Eichorst, S. A., Wertz, J. T., Schmidt, T. M. and Breznak, J. A., New strategies for cultivation and detection of previously uncultured microbes...

  17. [Algal blooms of the toxigenic diatom Pseudo-Nitzschia (Bacillariophyceae) in the Golfo de Nicoya, Costa Rica].

    Science.gov (United States)

    Vargas-Montero, Maribelle; Freer, Enrique

    2004-09-01

    Water samples were collected during a red tide event in November 2001, near San Lucas Island (Gulf of Nicoya, Costa Rica). Superficial temperature was 27 degrees C and water was turbid, with no fetid smell. One sample was treated with negative staining and observed using a transmission electron microscope (TEM); another sample was observed using a scanning electron microscope (SEM). Samples had high concentrations of the diatom Pseudo-Nitzschia pungensf pungens (characterized by two rows of poroids in the external channel), and lower concentrations of Skeletonema costatum (chains joined by external microtubules) and Chaetoceros lorenzianus (oval apertures and long chains, having setae with distinctive transverse rows and spines). This is the first time that the first species was described producing red tides in Costa Rica. However, reports about red tides with high concentration of species like P. pungens (variety multiseries) are increasing. These species have been related to the production of domoic acid, a low molecular weight amino acid which in humans can cause amnesic intoxications with seafood. Previously, Costa Rican reports of toxic accidents only referred to seafood contaminated with Pyrodinium bahamense var. compressum and Gymnodinium catenatum dinoflagellates. The increase in the number of Pseudo-Nitzschia causing harmful algae blooms is of interest for scientists around the world and must be documented. Similarly, some Chaetoceros species have been reported to be harmful to fish. We strongly recommend the establishment of a permanent surveillance program monitoring the presence of these species new at Costa Rican Pacific coast. Since the amnesic toxin is soluble in water and heat-resistant, we want to stress the possibility of having human cases of amnesic intoxication. PMID:17465126

  18. The rise of the rhizosolenoid diatoms

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Muyzer, G.; Abbas, B.; Rampen, S.W.; Massé, G.; Allard, W.G.; Belt, S.T.; Robert, J.-M.; Rowland, S.J.; Moldowan, J.M.; Barbanti, S.M.; Fago, F.J.; Denisevich, P.; Dahl, J.; Trindade, L.A.F.; Schouten, S.

    2004-01-01

    The 18S ribosomal DNA molecular phylogeny and lipid composition of over 120 marine diatoms showed that the capability to biosynthesize highly branched isoprenoid (HBI) alkenes is restricted to two specific phylogenetic clusters, which independently evolved in centric and pennate diatoms. The molecul

  19. Selective silicate-directed motility in diatoms

    DEFF Research Database (Denmark)

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

    2016-01-01

    Diatoms are highly abundant unicellular algae that often dominate pelagic as well as benthic primary production in the oceans and inland waters. Being strictly dependent on silica to build their biomineralized cell walls, marine diatoms precipitate 240 × 10(12) mol Si per year, which makes them t...

  20. Automatic segmentation of diatom images for classification

    NARCIS (Netherlands)

    Jalba, Andrei C.; Wilkinson, Michael H.F.; Roerdink, Jos B.T.M.

    2004-01-01

    A general framework for automatic segmentation of diatom images is presented. This segmentation is a critical first step in contour-based methods for automatic identification of diatoms by computerized image analysis. We review existing results, adapt popular segmentation methods to this difficult p

  1. Taxonomic and Environmental Variability in the Elemental Composition and Stoichiometry of Individual Dinoflagellate and Diatom Cells from the NW Mediterranean Sea.

    Directory of Open Access Journals (Sweden)

    Mariona Segura-Noguera

    Full Text Available Here we present, for the first time, the elemental concentration, including C, N and O, of single phytoplankton cells collected from the sea. Plankton elemental concentration and stoichiometry are key variables in phytoplankton ecophysiology and ocean biogeochemistry, and are used to link cells and ecosystems. However, most field studies rely on bulk techniques that overestimate carbon and nitrogen because the samples include organic matter other than plankton organisms. Here we used X-ray microanalysis (XRMA, a technique that, unlike bulk analyses, gives simultaneous quotas of C, N, O, Mg, Si, P, and S, in single-cell organisms that can be collected directly from the sea. We analysed the elemental composition of dinoflagellates and diatoms (largely Chaetoceros spp. collected from different sites of the Catalan coast (NW Mediterranean Sea. As expected, a lower C content is found in our cells compared to historical values of cultured cells. Our results indicate that, except for Si and O in diatoms, the mass of all elements is not a constant fraction of cell volume but rather decreases with increasing cell volume. Also, diatoms are significantly less dense in all the measured elements, except Si, compared to dinoflagellates. The N:P ratio of both groups is higher than the Redfield ratio, as it is the N:P nutrient ratio in deep NW Mediterranean Sea waters (N:P = 20-23. The results suggest that the P requirement is highest for bacterioplankton, followed by dinoflagellates, and lowest for diatoms, giving them a clear ecological advantage in P-limited environments like the Mediterranean Sea. Finally, the P concentration of cells of the same genera but growing under different nutrient conditions was the same, suggesting that the P quota of these cells is at a critical level. Our results indicate that XRMA is an accurate technique to determine single cell elemental quotas and derived conversion factors used to understand and model ocean biogeochemical

  2. Offshore influence of coastal upwelling off Mauritania, NW Africa, as recorded by diatoms in sediment traps at 2195 m water depth

    Science.gov (United States)

    Lange, Carina B.; Romero, Oscar E.; Wefer, Gerold; Gabric, Albert J.

    1998-06-01

    taxa in the sediments. In an attempt to contrast coastal vs. oceanic upwelling, we compared the Cap Blanc trap results (a coastal/open-ocean transition site) with the patterns recorded previously in sediment traps from the Guinea Basin (GBN3; an open-ocean equatorial upwelling site). Enhanced fluxes at both sites corresponded in time with the occurrence of upwelling (i.e. spring and early summer for CB1, and early spring and summer for GBN3). Total, opal and lithogenic mean daily fluxes were 2.4, 1.6 and 6.3 times higher at CB1 than at GBN3. Diatom and silicoflagellate fluxes were 8.9 and 1.6 times higher at GBN3. On a yearly basis, the diatom flora for CB1 can be characterized as "coastal with oceanic influence", and for GBN3 as "open ocean with moderate coastal influence". Chain-forming and colonial diatoms with individual cell diameters of >5 μm dominated the coastal upwelling site ( Thalassionema nitzschioides and Chaetoceros), while small (<5 μm) solitary diatoms ( Nitzschia bicapitata) dominated the open ocean equatorial upwelling regime. Comparable relative abundances of freshwater diatoms were noted at both trap sites; their seasonal distribution within each geographical area was attributed to the Saharan dust transport patterns involved. While diatom indicators of coastal upwelling were readily preser ved in the surface sediments off Cap Blanc, the assemblage in the Guinea Basin sediments differed greatly from that in the traps with the summer signal for equatorial upwelling being removed from the sediment. We conclude that significant differences between the assemblages trapped at both sites support the usefulness of these data as sensitive indicators of dissimilar oceanographic settings.

  3. Characterization of marine diatom-infecting virus promoters in the model diatom Phaeodactylum tricornutum

    OpenAIRE

    Takashi Kadono; Arisa Miyagawa-Yamaguchi; Nozomu Kira; Yuji Tomaru; Takuma Okami; Takamichi Yoshimatsu; Liyuan Hou; Takeshi Ohama; Kazunari Fukunaga; Masanori Okauchi; Haruo Yamaguchi; Kohei Ohnishi; Angela Falciatore; Masao Adachi

    2015-01-01

    International audience Viruses are considered key players in phytoplankton population control in oceans. However, mechanisms that control viral gene expression in prominent microalgae such as diatoms remain largely unknown. In this study, potential promoter regions isolated from several marine diatom-infecting viruses (DIVs) were linked to the egfp reporter gene and transformed into the Pennales diatom Phaeodactylum tricornutum. We analysed their activity in cells grown under different con...

  4. 重金属离子胁迫对赤潮微藻的急性毒性%Acute Toxic Effects of Heavy Metal Ions on Growth of Marine Bloom-Forming Microalgae

    Institute of Scientific and Technical Information of China (English)

    于小娣; 师玥; 周斌; 王其翔; 张鑫鑫; 唐学玺; 王悠

    2012-01-01

    重金属污染和赤潮都是较为突出的海洋环境问题,为给相关研究提供基础试验数据,在实验室条件下研究了Cu2+、Cd2+、Zn2对米氏凯伦藻和微小原甲藻的急性毒性效应.通过2种藻的EC50(半数抑制浓度)比较了其敏感性差异,分析了不同浓度重金属胁迫对微藻的影响;同时,利用TEM(transmission electronic microscopy,透射电镜技术)和FCM(flow cytometry,流式细胞术)研究了重金属Cu2+的急性毒性胁迫在亚细胞水平上对米氏凯伦藻的损伤.其中,Cu2+、Cd2+、Zn2+对微小原甲藻的48 h EC50和96 h EC50分别为0.514和0.276 mg/L、0.835和1.215 mg/L及4.376和7.976 mg/L;对米氏凯伦藻的48 h EC50和96 h EC50分别为1.881和1.881 mg/L、5.405和6.268 mg/L及13.134和18.732 mg/L.结果表明:2种微藻的种群相对增长率随着胁迫浓度的增加而下降,3种重金属离子的毒性表现出Cu2+>Cd2+>Zn2+的趋势,微小原甲藻对重金属胁迫更敏感;Cu2+胁迫可使米氏凯伦藻细胞体积增大,内容物复杂程度增高,但叶绿素a的MFI(mean fluorescence intensity,平均荧光强度)的变化不明显;Cu2+胁迫对藻膜结构的损伤较明显,但对线粒体及叶绿体的结构影响不明显.%The acute toxic effects of Cu2+,Cd2+ and Zn2+ on growth of the marine microalga Karenia mikimotoi and Prorocentrum minimum were investigated. The sensitivity differences of the two alga were estimated,and the effects of different concentrations of heavy metals on growth of the bloom-forming microalga were analyzed. Moreover,a further study on toxicity of Cu2+ to K. mikimotoi at the sub-cellular level was conducted using the techniques of transmission electron microscope (TEM) and flow cytometry (FCM). The 48 h EC50/ 96 h EC50 of Cu2+ ,Cd2+ and Zn2+ stresses on P. minimum were 0. 514 and 0. 276 mg/L,0. 835 and 1. 215 mg/L,4. 376 and 7. 976 mg/L,respectively. The stresses on K. mikimotoi were 1.881 and 1.881 mg/L,5.405 and 6.268 mg/L,13. 134 and

  5. Role of Diatoms in marine biofouling

    Digital Repository Service at National Institute of Oceanography (India)

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

    &sim to form two new individuals within a single parent cell frustule. Each daughter cell receiv~ one parent cell theca as epitheca; formation of a new hypotheca for each of the daughter cells terminates cell division. Diatoms may also... methods are still practiced mainly because expensive equipment is not required. The advantage of brushing and scraping methods over direct methods is that quantification of larger areas of substratum is possible. The main disadvantages of Diatoms...

  6. Ocean acidification decreases the light-use efficiency in an Antarctic diatom under dynamic but not constant light.

    Science.gov (United States)

    Hoppe, Clara J M; Holtz, Lena-Maria; Trimborn, Scarlett; Rost, Björn

    2015-07-01

    There is increasing evidence that different light intensities strongly modulate the effects of ocean acidification (OA) on marine phytoplankton. The aim of the present study was to investigate interactive effects of OA and dynamic light, mimicking natural mixing regimes. The Antarctic diatom Chaetoceros debilis was grown under two pCO2 (390 and 1000 μatm) and light conditions (constant and dynamic), the latter yielding the same integrated irradiance over the day. To characterize interactive effects between treatments, growth, elemental composition, primary production and photophysiology were investigated. Dynamic light reduced growth and strongly altered the effects of OA on primary production, being unaffected by elevated pCO2 under constant light, yet significantly reduced under dynamic light. Interactive effects between OA and light were also observed for Chl production and particulate organic carbon quotas. Response patterns can be explained by changes in the cellular energetic balance. While the energy transfer efficiency from photochemistry to biomass production (Φe,C ) was not affected by OA under constant light, it was drastically reduced under dynamic light. Contrasting responses under different light conditions need to be considered when making predictions regarding a more stratified and acidified future ocean.

  7. Evaluation of the nutritional quality of Chaetoceros muelleri Schütt (Chaetocerotales: Chaetocerotaceae and Isochrysis sp. (Isochrysidales: isochrysidaceae grown outdoors for the larval development of Litopenaeus vannamei (Boone, 1931 (Decapoda: Penaeidae

    Directory of Open Access Journals (Sweden)

    Rodríguez Erika O.

    2012-01-01

    Full Text Available The biomass, proximal composition and fatty acid profile of Isochrysis sp., Chaetoceros muelleri and their mixture, grown under greenhouse conditions, were evaluated. The nutritional value of both species supplied as the monoalgal (Chaetoceros muelleri: Diet I, and Isochrysis sp. Diet II and mixed diet (Diet III for larval Litopenaeus vannamei was also assessed on the basis of the development and biochemical composition of the larvae. The highest protein levels were obtained in Diets I and II (40% and 35%, respectively. No significant differences in larval survival were found among the diets; however, larvae fed on Diet II had the lowest mean larval length.

  8. Extremophile Diatoms: Implications to the Drake Equation

    Science.gov (United States)

    Sterrenburg, Frithjof A. S.; Hoover, Richard B.

    2011-01-01

    Diatoms are unicellular Eukaryotes that (as a group and phylogenetically) are not strictly regarded as extremophiles , since the vast majority of diatoms are mesophilic photoautotrophs. However, among the terrestrial Eukaryotes, diatoms are by far the single group of organisms with the ability to inhabit the greatest range of hostile environments on Earth. They are the dominant eukaryotes in the polar regions; in fumaroles, hot springs and geysers; and in hypersaline and hyperalkaline lakes and pools. Cryophilic species such as Fragilaria sublinearis and Chaetoceras fragilis are able to carry out respiration at extremely low rates at low temperatures in darkness. The Drake Equation refers to the likelihood of there being intelligent life at the technological level of electromagnetic communication. However, consideration of the range of conditions suitable for the habitability of eukaryotic diatoms and prokaryotic extremophiles, the likelihood that life exists elsewhere in the cosmos becomes many orders of magnitude greater than that predicted by the classical Drake Equation. In this paper we review the characteristics of diatoms as eukaryotic extremophiles and consider the implications to adjustments needed to the Drake Equation to assess the possibility that life exists elsewhere in the Universe.

  9. Biofilm diatom community structure: Influence of temporal and substratum variability

    Digital Repository Service at National Institute of Oceanography (India)

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

    Diatoms, which are early autotrophic colonisers, are an important constituent of the biofouling community in the marine environment. The effects of substratum and temporal variations on the fouling diatom community structure in a monsooninfluenced...

  10. Characterization of marine diatom-infecting virus promoters in the model diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Kadono, Takashi; Miyagawa-Yamaguchi, Arisa; Kira, Nozomu; Tomaru, Yuji; Okami, Takuma; Yoshimatsu, Takamichi; Hou, Liyuan; Ohama, Takeshi; Fukunaga, Kazunari; Okauchi, Masanori; Yamaguchi, Haruo; Ohnishi, Kohei; Falciatore, Angela; Adachi, Masao

    2015-01-01

    Viruses are considered key players in phytoplankton population control in oceans. However, mechanisms that control viral gene expression in prominent microalgae such as diatoms remain largely unknown. In this study, potential promoter regions isolated from several marine diatom-infecting viruses (DIVs) were linked to the egfp reporter gene and transformed into the Pennales diatom Phaeodactylum tricornutum. We analysed their activity in cells grown under different conditions. Compared to diatom endogenous promoters, novel DIV promoter (ClP1) mediated a significantly higher degree of reporter transcription and translation. Stable expression levels were observed in transformants grown under both light and dark conditions, and high levels of expression were reported in cells in the stationary phase compared to the exponential phase of growth. Conserved motifs in the sequence of DIV promoters were also found. These results allow the identification of novel regulatory regions that drive DIV gene expression and further examinations of the mechanisms that control virus-mediated bloom control in diatoms. Moreover, the identified ClP1 promoter can serve as a novel tool for metabolic engineering of diatoms. This is the first report describing a promoter of DIVs that may be of use in basic and applied diatom research. PMID:26692124

  11. 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.

  12. 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

  13. Colloquium on diatom-copepod interactions

    DEFF Research Database (Denmark)

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

    2005-01-01

    From 3 to 6 November 2002, a colloquium was convened at the Benthos Laboratory of the Stazione Zoologica Anton Dohrn on Ischia, Italy, with the goal of evaluating the present status of the effects of diatoms on their main consumers, planktonic copepods, and to develop future research strategies...

  14. Electric dipole moment of diatomic molecules

    International Nuclear Information System (INIS)

    The calculation of the electric dipole moment of diatomic molecules by the Variational Cellular Method is presented, discussed and compared with the semiempirical CNDO/2 method. The molecule HF is taken as example. It is also shown that the value of the electric dipole moment by the VCM improves considerably when the electronegativity of the atoms of the molecule is taken into account. (Author)

  15. Evaluation of European diatom trophic indices.

    NARCIS (Netherlands)

    Lototskaya, A.A.; Verdonschot, P.F.M.; Coste, M.; Vijver, van de B.

    2011-01-01

    Freshwater diatoms are considered to be reliable indicators of the trophic status of rivers and lakes. In the past 30 years, a number of indicator indices have been developed and used for the assessment of trophic conditions all over Europe. It is however still not clear whether the ecologic signatu

  16. Equilibrium properties of linear diatomic chain

    International Nuclear Information System (INIS)

    The thermodynamic properties of a linear system of diatomic molecules are exactly found. The molecules interact via the sum of harmonic and quadrupole potentials. Results are given for equation of state, order parameter, specific heat, one- and two-particle orientational correlation functions. They show pseudo phase transition from hindered to rotational diffusion and generally agree with the predictions of molecular dynamics. (author)

  17. The effect of UV radiation on photosynthesis in an Antarctic diatom (Thalassiosira sp.): does vertical mixing matter?

    International Nuclear Information System (INIS)

    Full text: The reduction of the Antarctic stratospheric ozone resulted in significant increases in ultraviolet B radiation (UVBR, 280-320 nm) reaching the surface of the ocean. A series of laboratory and field experiments were conducted at Potter Cove (25 de Mayo Is., South Shetland Is., Antarctica) to study the effects of UVBR on photosynthesis of a typical Antarctic bloom forming diatom (Thalassiosira sp.) in fixed and moving incubations. There were three irradiance treatments: PART (with only photosynthetic active radiation, PAR, 400- 700 nm), UVAT (with PAR and ultraviolet A radiation, UVAR, 320-400 nm) and UVBT (with PAR, UVAR and UVBR). The three treatments were incubated in the field and laboratory with a solar simulator (SOLSI) in fixed frames at 0.5 and 5 m depth (Sfix and Bfix, respectively), while for the moving incubations were done within 6 h cycles (Mix). Considering the field and laboratory pooled data, results suggest an overall 45-50 % photosynthesis inhibition of Sfix incubations in relation with Mix ones. During SOLSI experiments no significant differences were found between irradiance treatments under normal and medium ozone concentrations. Under low ozone conditions, a 40 % reduction in photosynthesis was observed in the UVBT for Sfix . In contrast, no significant differences were observed between the irradiance treatments for Mix. Field experiment showed results similar to the laboratory ones, but in this case not only Sfix but Mix incubations presented a significant reduction in photosynthesis under low ozone. The differences between laboratory and field experiments are discussed in terms of the relative significance of UVBR dose and dose rate on both types of experiments. (author)

  18. Heteronuclear diatomics in diffuse and translucent clouds

    CERN Document Server

    Weselak, T

    2013-01-01

    Diffuse and translucent molecular clouds fill a vast majority of the interstellar space in the galactic disk being thus the most typical objects of the Interstellar Medium (ISM). Recent advances in observational techniques of modern optical and ultraviolet spectroscopy led to detection of many features of atomic and molecular origin in spectra of such clouds. Molecular spectra of heteronuclear diatomic molecules, ie. OH, OH+, CH CH+, CN, NH, CO play an important role in understanding chemistry and physical conditions in environments they do populate. A historical review of astronomical observations of interstellar molecules is presented. Recent results based on visual and ultraviolet observations of molecular features in spectra of reddened, early type OB-stars are presented and discussed. Appearance of vibrational-rotational spectra with observed transitions based on high-quality spectra, are also presented. Relations between column densities of heteronuclear diatomics (based on the recommended oscillator st...

  19. Mitosis in diatoms: rediscovering an old model for cell division.

    Science.gov (United States)

    De Martino, Alessandra; Amato, Alberto; Bowler, Chris

    2009-08-01

    Diatoms are important protists that generate one fifth of the oxygen produced annually on earth. These aquatic organisms likely derived from a secondary endosymbiosis event, and they display peculiar genomic and structural features that reflect their chimeric origin. Diatoms were one of the first models of cell division and these early studies revealed a range of interesting features including a unique acentriolar microtubule-organising centre. Unfortunately, almost nothing is known at the molecular level, in contrast to the advances in other experimental organisms. Recently the full genome sequences of two diatoms have been annotated and molecular tools have been developed. These resources offer new possibilities to re-investigate the mechanisms of cell division in diatoms by recruiting information from more intensively studied organisms. A renaissance of the topic is further justified by the current interest in diatoms as a source of biofuels and for understanding massive diatom proliferation events in response to environmental stimuli. PMID:19572334

  20. Export fluxes in a naturally iron-fertilized area of the Southern Ocean - Part 2: Importance of diatom resting spores and faecal pellets for export

    Science.gov (United States)

    Rembauville, M.; Blain, S.; Armand, L.; Quéguiner, B.; Salter, I.

    2015-06-01

    The biological composition of the material exported to a moored sediment trap located under the winter mixed layer of the naturally fertilized Kerguelen Plateau in the Southern Ocean was studied over an annual cycle. Despite iron availability in spring, the annual particulate organic carbon (POC) export (98.2 mmol m-2) at 289 m was low, but annual biogenic silica export was significant (114 mmol m-2). This feature was related to the abundance of empty diatom cells and the ratio of full to empty cells exerted a first-order control in BSi : POC export stoichiometry of the biological pump. Chaetoceros Hyalochaete spp. and Thalassiosira antarctica resting spores were responsible for more than 60% of the annual POC flux that occurred during two very short export events of 80%). The seasonal progression of faecal pellet types revealed a clear transition from small spherical shapes (small copepods) in spring, to larger cylindrical and ellipsoid shapes in summer (euphausiids and large copepods) and finally to large tabular shapes (salps) in autumn and winter. We propose in this high-biomass, low-export (HBLE) environment that small but highly silicified and fast-sinking resting spores are able to bypass the intense grazing pressure and efficient carbon transfer to higher trophic levels that are responsible for the low fluxes observed the during the remainder of the year. More generally our study also provides a statistical framework linking the ecological succession of diatom and zooplankton communities to the seasonality of carbon and silicon export within an iron-fertilized bloom region in the Southern Ocean.

  1. A suggested local regions in the Southern Gulf of Mexico using a diatom database (1979-2002) and oceanic hidrographic features.

    Science.gov (United States)

    Licea, Sergio; Zamudio, Ma E; Moreno-Ruiz, J L; Luna, R

    2011-07-01

    A diatom data-base of 255 species obtained from 14 oceanographic cruises (14801 entries of 647 sampling sites) together with the analysis of oceanic features were used to establish four local regions in the southern Gulf of Mexico. In addition, common species for each region were designated. This study is based on the application of cluster analysis and the species frequency data. Material for this undertaking consisted of water and net samples obtained between June 1979 and December 2002. Results show that the most frequent species (> 40%) were: Asterionellopsis glacialis, Bacteriastrum delicatulum, B. hyalinum, Chaetoceros affinis, C. coarctatus, C. compresus, C. curvisetus, C. danicus, C. decipiens, C. diversus, C. lorenzianus, C. pelagicus, C. peruvianus, Coscinodiscus radiatus, Cylindrotheca closterium, Guinardia flaccida, Hemiaulus hauckii, H. membranaceus, H. sinensis, Leptocylindrus danicus, Neocalyptrella robusta, Nitzschia bicapitata, Pleurosigma diverse-striatum, Proboscia alata, Pseudo-nitzschia pungens, Pseudosolenia calcar-avis, Rhizosolenia imbricata, R. setigera, Skeletonema costatum, Thalassionema bacillare, T frauenfeldii, T nitzschioides and Thalassiosira eccentrica. The species composition for each region and season are discussed. Itis concluded that sampling site assemblages are related to oceanographic conditions. A total list of species composition is given, forty-seven species taxa being new records for this area. PMID:22315823

  2. Effect of ageing on survival of benthic diatom propagules

    Digital Repository Service at National Institute of Oceanography (India)

    Anil, A.C.; Mitbavkar, S.; DeSilva, M.S.; Hegde, S.; DeCosta, P.M.; Meher, S.S.; Banerjee, D.

    of various diatom species (Peters, 1996). Dark survival has been highlighted as one possible reason for the survival of diatoms during the Cretaceous period with relatively slight generic loss as compared to other planktonic organisms (Gould, 1994.... Mar. Biol. Lett. 1, 185-195. Fryxell, G.A., 1983. Survival Strategies of the algae. Cambridge University Press Cambridge, pp. 160. Fryxell, G.A., 1990. Planktonic marine diatom winter stages. Antarctic alternatives to resting spores. In: Kocilek, K...

  3. 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

  4. Testing Prospects for Reliable Diatom Nanotechnology in Microgravity

    Science.gov (United States)

    Gordon, Richard; Hoover, Richard B.; Tuszynski, Jack A.; deLuis, Javier; Camp, Philip J.; Tiffany, Mary Ann; Nagy, Stephen S.; Lerner, Beatriz E.

    2007-01-01

    The worldwide effort to grow nanotechnology, rather than use lithography, focuses on diatoms, single cell eukaryotic algae with ornate silica shells, which can be replaced by oxides and ceramics, or reduced to elemental silicon, to create complex nanostructures with compositions of industrial and electronics importance. Diatoms produce an enormous variety of structures, some of which are microtubule dependent and perhaps sensitive to microgravity. The NASA Single Loop for Cell Culture (SLCC) for culturing and observing microorganisms permits inexpensive, low labor in-space experiments. We propose to send up to the International Space Station diatom cultures of the three diatom species whose genomes are being sequenced, plus the giant diatoms of Antarctica (up to 2 mm diameter for a single cell) and the unique colonial diatom, Bacillaria paradoxa. Bacillaria cells move against each other in partial synchrony, like a sliding deck of cards, by a microfluidics mechanism. Will normal diatoms have aberrant pattern and shape or motility compared to ground controls? The generation time is typically one day, so that many generations may be examined from one flight. Rapid, directed evolution may be possible running the SLCC as a compustat. The shell shapes and patterns are preserved in hard silica, so that the progress of normal and aberrant morphogenesis may be followed by drying samples on a moving filter paper "diatom tape recorder". With a biodiversity of 100,000 distinct species, diatom nanotechnology may offer a compact and portable nanotechnology toolkit for exploration anywhere.

  5. 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. PMID

  6. A toy model for a diatomic molecule

    Science.gov (United States)

    Hecker Denschlag, Johannes

    2016-08-01

    We introduce a toy model for a diatomic molecule which is based on coupling electronic and nuclear spins to a rigid rotor. Despite its simplicity, the model can be used scientifically to analyze and understand complex molecular hyperfine spectra. In addition, the model has educational value as a number of fundamental symmetries and conservation laws of the molecule can be studied. Because of its simple structure, the model can be readily implemented as a computer program with comparatively short computing times on the order of a few seconds.

  7. 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...

  8. The Central Carbon and Energy Metabolism of Marine Diatoms

    Directory of Open Access Journals (Sweden)

    Adriano Nunes-Nesi

    2013-05-01

    Full Text Available Diatoms are heterokont algae derived from a secondary symbiotic event in which a eukaryotic host cell acquired an eukaryotic red alga as plastid. The multiple endosymbiosis and horizontal gene transfer processes provide diatoms unusual opportunities for gene mixing to establish distinctive biosynthetic pathways and metabolic control structures. Diatoms are also known to have significant impact on global ecosystems as one of the most dominant phytoplankton species in the contemporary ocean. As such their metabolism and growth regulating factors have been of particular interest for many years. The publication of the genomic sequences of two independent species of diatoms and the advent of an enhanced experimental toolbox for molecular biological investigations have afforded far greater opportunities than were previously apparent for these species and re-invigorated studies regarding the central carbon metabolism of diatoms. In this review we discuss distinctive features of the central carbon metabolism of diatoms and its response to forthcoming environmental changes and recent advances facilitating the possibility of industrial use of diatoms for oil production. Although the operation and importance of several key pathways of diatom metabolism have already been demonstrated and determined, we will also highlight other potentially important pathways wherein this has yet to be achieved.

  9. A contribution to the epipsammic diatom flora of Estonia

    NARCIS (Netherlands)

    Cremer, H.

    2006-01-01

    A study of the modern epipsammic diatom flora in Lake Karujärv, Saaremaa Island, Estonia revealed seventy-one taxa representing thirty-one genera. The identity of all taxa is documented with light micrographs. Most abundant taxa of the epipsammic diatom community were Achnanthidium minutissimum sens

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

    NARCIS (Netherlands)

    Blanco, Saul; Cejudo-Figueiras, Cristina; Alvarez-Blanco, Irene; van Donk, Ellen; Gross, Elisabeth M.; Hansson, Lars-Anders; Irvine, Kenneth; Jeppesen, Erik; Kairesalo, Timo; Moss, Brian; Noges, Tiina; Becares, Eloy

    2014-01-01

    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 st

  11. Regulated growth of diatom cells on self-assembled monolayers

    Directory of Open Access Journals (Sweden)

    Kobayashi Koichi

    2007-03-01

    Full Text Available Abstract We succeeded in regulating the growth of diatom cells on chemically modified glass surfaces. Glass surfaces were functionalized with -CF3, -CH3, -COOH, and -NH2 groups using the technique of self-assembled monolayers (SAM, and diatom cells were subsequently cultured on these surfaces. When the samples were rinsed after the adhesion of the diatom cells on the modified surfaces, the diatoms formed two dimensional arrays; this was not possible without the rinsing treatment. Furthermore, we examined the number of cells that grew and their motility by time-lapse imaging in order to clarify the interaction between the cells and SAMs. We hope that our results will be a basis for developing biodevices using living photosynthetic diatom cells.

  12. 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.

  13. 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.

  14. 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.

  15. Nonnuclear Attractors in Heteronuclear Diatomic Systems.

    Science.gov (United States)

    Terrabuio, Luiz Alberto; Teodoro, Tiago Quevedo; Matta, Chérif F; Haiduke, Roberto Luiz Andrade

    2016-03-01

    Nonnuclear attractors (NNAs) are observed in the electron density of a variety of systems, but the factors governing their appearance and their contribution to the system's properties remain a mystery. The NNA occurring in homo- and heteronuclear diatomics of main group elements with atomic numbers up to Z = 38 is investigated computationally (at the UCCSD/cc-pVQZ level of theory) by varying internuclear separations. This was done to determine the NNA occurrence window along with the evolution of the respective pseudoatomic basin properties. Two distinct categories of NNAs were detected in the data analyzed by means of catastrophe theory. Type "a" implies electronic charge transfer between atoms mediated by a pseudoatom. Type "b" shows an initial relocation of some electronic charge to a pseudoatom, which posteriorly returns to the same atom that donated this charge in the first place. A small difference of polarizability between the atoms that compose these heteronuclear diatomics seems to favor NNA formation. We also show that the NNA arising tends to result in some perceptible effects on molecular dipole and/or quadrupole moment curves against internuclear distance. Finally, successive cationic ionization results in the fast disappearance of the NNA in Li2 indicating that its formation is mainly governed by the field generated by the quantum mechanical electronic density and only depends parametrically on the bare nuclear field/potential at a given molecular geometry. PMID:26842391

  16. Diatom Milking: A Review and New Approaches

    Directory of Open Access Journals (Sweden)

    Vandana Vinayak

    2015-04-01

    Full Text Available The rise of human populations and the growth of cities contribute to the depletion of natural resources, increase their cost, and create potential climatic changes. To overcome difficulties in supplying populations and reducing the resource cost, a search for alternative pharmaceutical, nanotechnology, and energy sources has begun. Among the alternative sources, microalgae are the most promising because they use carbon dioxide (CO2 to produce biomass and/or valuable compounds. Once produced, the biomass is ordinarily harvested and processed (downstream program. Drying, grinding, and extraction steps are destructive to the microalgal biomass that then needs to be renewed. The extraction and purification processes generate organic wastes and require substantial energy inputs. Altogether, it is urgent to develop alternative downstream processes. Among the possibilities, milking invokes the concept that the extraction should not kill the algal cells. Therefore, it does not require growing the algae anew. In this review, we discuss research on milking of diatoms. The main themes are (a development of alternative methods to extract and harvest high added value compounds; (b design of photobioreactors; (c biodiversity and (d stress physiology, illustrated with original results dealing with oleaginous diatoms.

  17. Copepod population-specific response to a toxic diatom diet.

    Directory of Open Access Journals (Sweden)

    Chiara Lauritano

    Full Text Available Diatoms are key phytoplankton organisms and one of the main primary producers in aquatic ecosystems. However, many diatom species produce a series of secondary metabolites, collectively termed oxylipins, that disrupt development in the offspring of grazers, such as copepods, that feed on these unicellular algae. We hypothesized that different populations of copepods may deal differently with the same oxylipin-producing diatom diet. Here we provide comparative studies of expression level analyses of selected genes of interest for three Calanus helgolandicus populations (North Sea, Atlantic Ocean and Mediterranean Sea exposed to the same strain of the oxylipin-producing diatom Skeletonema marinoi using as control algae the flagellate Rhodomonas baltica. Expression levels of detoxification enzymes and stress proteins (e.g. glutathione S-transferase, glutathione synthase, superoxide dismutase, catalase, aldehyde dehydrogenases and heat shock proteins and proteins involved in apoptosis regulation and cell cycle progression were analyzed in copepods after both 24 and 48 hours of feeding on the diatom or on a control diet. Strong differences occurred among copepod populations, with the Mediterranean population of C. helgolandicus being more susceptible to the toxic diet compared to the others. This study opens new perspectives for understanding copepod population-specific responses to diatom toxins and may help in underpinning the cellular mechanisms underlying copepod toxicity during diatom blooms.

  18. Copepod population-specific response to a toxic diatom diet.

    Science.gov (United States)

    Lauritano, Chiara; Carotenuto, Ylenia; Miralto, Antonio; Procaccini, Gabriele; Ianora, Adrianna

    2012-01-01

    Diatoms are key phytoplankton organisms and one of the main primary producers in aquatic ecosystems. However, many diatom species produce a series of secondary metabolites, collectively termed oxylipins, that disrupt development in the offspring of grazers, such as copepods, that feed on these unicellular algae. We hypothesized that different populations of copepods may deal differently with the same oxylipin-producing diatom diet. Here we provide comparative studies of expression level analyses of selected genes of interest for three Calanus helgolandicus populations (North Sea, Atlantic Ocean and Mediterranean Sea) exposed to the same strain of the oxylipin-producing diatom Skeletonema marinoi using as control algae the flagellate Rhodomonas baltica. Expression levels of detoxification enzymes and stress proteins (e.g. glutathione S-transferase, glutathione synthase, superoxide dismutase, catalase, aldehyde dehydrogenases and heat shock proteins) and proteins involved in apoptosis regulation and cell cycle progression were analyzed in copepods after both 24 and 48 hours of feeding on the diatom or on a control diet. Strong differences occurred among copepod populations, with the Mediterranean population of C. helgolandicus being more susceptible to the toxic diet compared to the others. This study opens new perspectives for understanding copepod population-specific responses to diatom toxins and may help in underpinning the cellular mechanisms underlying copepod toxicity during diatom blooms. PMID:23056617

  19. Diatom (Bacillariophyta) community response to water quality and land use

    Science.gov (United States)

    Stewart, Paul M.; Butcher, Jason T.; Gerovac, Paul J.

    1999-01-01

    Aquatic algal communities are sensitive to environmental stresses and are used as indicators of water quality. Diatoms were collected from three streams that drain the Great Marsh at Indiana Dunes National Lakeshore. Diatom communities, water chemistry, and land use were measured at each site to test the hypothesis that differences in land use indirectly affect diatom communities, through changes in water quality. Relationships among these variables were examined by correlation, cluster, and detrended correspondence analysis. Several water chemistry variables were correlated to several land-use categories. Diatom species diversity was most variable in disturbed areas with poorer water quality and was correlated with land use and total alkalinity, total hardness, and specific conductance. Sites within each stream were grouped in terms of their diatom assemblage by both cluster and detrended correspondence analysis with but two exceptions in Dunes Creek. Diatom communities in the three streams responded to land use through its effects on water quality. The results of this study demonstrate the use of diatom assemblages as indicators of water quality, which can be linked to land use in a watershed.

  20. Diatom assemblages promote ice formation in large lakes.

    Science.gov (United States)

    D'souza, N A; Kawarasaki, Y; Gantz, J D; Lee, R E; Beall, B F N; Shtarkman, Y M; Koçer, Z A; Rogers, S O; Wildschutte, H; Bullerjahn, G S; McKay, R M L

    2013-08-01

    We present evidence for the directed formation of ice by planktonic communities dominated by filamentous diatoms sampled from the ice-covered Laurentian Great Lakes. We hypothesize that ice formation promotes attachment of these non-motile phytoplankton to overlying ice, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for ice nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (T(c)) as high as -3 °C. Ice nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of ice nucleation activity, the resulting production of frazil ice may provide a means for the diatoms to be recruited to the overlying lake ice, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal ice cover around the world. PMID:23552624

  1. Molecular Detection of a Potentially Toxic Diatom Species

    Directory of Open Access Journals (Sweden)

    Bidhan Chandra Dhar

    2015-05-01

    Full Text Available A few diatom species produce toxins that affect human and animal health. Among these, members of the Pseudo-nitzschia genus were the first diatoms unambiguously identified as producer of domoic acid, a neurotoxin affecting molluscan shell-fish, birds, marine mammals, and humans. Evidence exists indicating the involvement of another diatom genus, Amphora, as a potential producer of domoic acid. We present a strategy for the detection of the diatom species Amphora coffeaeformis based on the development of species-specific oligonucleotide probes and their application in microarray hybridization experiments. This approach is based on the use of two marker genes highly conserved in all diatoms, but endowed with sufficient genetic divergence to discriminate diatoms at the species level. A region of approximately 450 bp of these previously unexplored marker genes, coding for elongation factor 1-a (eEF1-a and silicic acid transporter (SIT, was used to design oligonucleotide probes that were tested for specificity in combination with the corresponding fluorescently labeled DNA targets. The results presented in this work suggest a possible use of this DNA chip technology for the selective detection of A. coffeaeformis in environmental settings where the presence of this potential toxin producer may represent a threat to human and animal health. In addition, the same basic approach can be adapted to a wider range of diatoms for the simultaneous detection of microorganisms used as biomarkers of different water quality levels.

  2. Phylogenetic signal in diatom ecology: perspectives for aquatic ecosystems biomonitoring.

    Science.gov (United States)

    Keck, François; Rimet, Frédéric; Franc, Alain; Bouchez, Agnés

    2016-04-01

    Diatoms include a great diversity of taxa and are recognized as powerful bioindicators in rivers. However using diatoms for monitoring programs is costly and time consuming because most of the methodologies necessitate species-level identification. This raises the question of the optimal trade-off between taxonomic resolution and bioassessment quality. Phylogenetic tools may form the bases of new, more efficient approaches for biomonitoring if relationships between ecology and phylogeny can be demonstrated. We estimated the ecological optima of 127 diatom species for 19 environmental parameters using count data from 2119 diatom communities sampled during eight years in eastern France. Using uni- and multivariate analyses, we explored the relationships between freshwater diatom phylogeny and ecology (i.e., the phylogenetic signal). We found a significant phylogenetic signal for many of the ecological optima that were tested, but the strength of the signal varied significantly from one trait to another. Multivariate analysis also showed that the multidimensional ecological niche of diatoms can be strongly related to phylogeny. The presence of clades containing species that exhibit homogeneous ecology suggests that phylogenetic information can be useful for aquatic biomonitoring. This study highlights the presence of significant patterns of ecological optima for freshwater diatoms in relation to their phylogeny. These results suggest the presence of a signal above the species level, which is encouraging for the development of simplified methods for biomonitoring survey. PMID:27411256

  3. 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.

  4. Rotational structures of long-range diatomic molecules

    OpenAIRE

    Gao, Bo

    2004-01-01

    We present a systematic understanding of the rotational structure of a long-range (vibrationally highly-excited) diatomic molecule. For example, we show that depending on a quantum defect, the least-bound vibrational state of a diatomic molecule with $-C_n/r^n$ ($n>2$) asymptotic interaction can have only 1, 2, and up to a maximum of $n-2$ rotational states. A classification scheme of diatomic molecules is proposed, in which each class has a distinctive rotational structure and corresponds to...

  5. Spatial paradigms of lotic diatom distribution: A landscape ecology perspective

    Science.gov (United States)

    Passy, S.I.

    2001-01-01

    Spatial distributional patterns of benthic diatoms and their relation to current velocity were investigated in an unshaded cobble-bottom reach of White Creek (Washington County, NY). On 27 August 1999, diatoms were sampled and current velocity and depth were measured on a regular square sampling grid with a grain size of 0.01 m2, interval of 0.5 m, and extent of 16 m2. The relative abundance of the 18 common diatom species enumerated in the 81 samples was subjected to detrended correspondence analysis (DCA). The first axis (DCA1) explained 51% of the variance in diatom data and separated the samples according to current regimes. The spatial autocorrelation of DCA1 sample scores in deposition and erosion regions of White Creek was determined by Moran's I statistic to indicate patch size. In White Creek the patch length of all diatom communities was more than 3.1 m, whereas the patch width was 1 m in the deposition region and 0.5 m in the erosion region. There were 5 dominant diatom taxa, Achnanthes minutissima Ku??tz. et vars, Fragilaria capucina Dezmazie??res et vars, F. crotonensis Kitt., Diatoma vulgaris Bory, and Synedra ulna (Nitz.) Ehr. et vars. The patch length of the dominant species varied from 1 to more than 4.1 m, whereas the patch width, if defined, was 0.5 m. Achnanthes minutissima and F. capucina, the two diatom species with the highest relative abundance, displayed spatially structured patches of low abundance and comparatively random patches of high abundance, suggesting broad scale abiotic control of species performance in low abundance regions and finer scale biotic control of high abundance areas. Another objective of this study was to test the hypothesis that higher current velocities, which generally impede immigration, would increase randomness and complexity (i.e. homogeneity of diatom distributional patterns). The spatial complexity in low versus high velocity transects was determined by calculating the respective fractal dimension (D) of DCA

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

    Science.gov (United States)

    Bere, Taurai; 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. PMID:27320742

  7. The dilemma of disappearing diatoms: Incorporating diatom dissolution data into palaeoenvironmental modelling and reconstruction

    Science.gov (United States)

    Ryves, David B.; Battarbee, Richard W.; Fritz, Sherilyn C.

    2009-01-01

    Taphonomic issues pose fundamental challenges for Quaternary scientists to recover environmental signals from biological proxies and make accurate inferences of past environments. The problem of microfossil preservation, specifically diatom dissolution, remains an important, but often overlooked, source of error in both qualitative and quantitative reconstructions of key variables from fossil samples, especially those using relative abundance data. A first step to tackling this complex issue is establishing an objective method of assessing preservation (here, diatom dissolution) that can be applied by different analysts and incorporated into routine counting strategies. Here, we establish a methodology for assessment of diatom dissolution under standard light microscopy (LM) illustrated with morphological criteria for a range of major diatom valve shapes. Dissolution data can be applied to numerical models (transfer functions) from contemporary samples, and to fossil material to aid interpretation of stratigraphic profiles and taphonomic pathways of individual taxa. Using a surface sediment diatom-salinity training set from the Northern Great Plains (NGP) as an example, we explore a variety of approaches to include dissolution data in salinity inference models indirectly and directly. Results show that dissolution data can improve models, with apparent dissolution-adjusted error (RMSE) up to 15% lower than their unadjusted counterparts. Internal validation suggests improvements are more modest, with bootstrapped prediction errors (RMSEP) up to 10% lower. When tested on a short core from Devils Lake, North Dakota, which has a historical record of salinity, dissolution-adjusted models infer higher values compared to unadjusted models during peak salinity of the 1930s-1940s Dust Bowl but nonetheless significantly underestimate peak values. Site-specific factors at Devils Lake associated with effects of lake level change on taphonomy (preservation and re

  8. Comparing optical properties of different species of diatoms

    DEFF Research Database (Denmark)

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

    2015-01-01

    Diatoms are single cellular algae encapsulate d in an external wall of micro-structured porous silica called the frustule. Diatoms are present in all water environments and contribute with 20-25 % of the global primary production of oxygen by photosynthesis. The appearance of the frustule is very...... 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...

  9. 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.

  10. 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...

  11. 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 permeability were observed for any of the three diatoms suggesting that mechanisms of aluminium 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. PMID:26921729

  12. Windblown Pliocene diatoms and East Antarctic Ice Sheet retreat

    Science.gov (United States)

    Scherer, Reed P.; DeConto, Robert M.; Pollard, David; Alley, Richard B.

    2016-01-01

    Marine diatoms in tillites along the Transantarctic Mountains (TAMs) have been used to suggest a diminished East Antarctic Ice Sheet (EAIS) during Pliocene warm periods. Updated ice-sheet modelling shows significant Pliocene EAIS retreat, creating marine embayments into the Wilkes and Aurora basins that were conducive to high diatom productivity and rapid accumulation of diatomaceous sediments. Here we show that subsequent isostatic uplift exposed accumulated unconsolidated marine deposits to wind erosion. We report new atmospheric modelling utilizing Pliocene climate and derived Antarctic landscapes indicating that prevailing mid-altitude winds transported diatoms towards the TAMs, dominantly from extensive emerged coastal deposits of the Aurora Basin. This result unifies leading ideas from competing sides of a contentious debate about the origin of the diatoms in the TAMs and their link to EAIS history, supporting the view that parts of the EAIS are vulnerable to relatively modest warming, with possible implications for future sea-level rise. PMID:27649516

  13. Quantification of diatoms in biofilms: Standardisation of methods

    Digital Repository Service at National Institute of Oceanography (India)

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

    becomes coated by an organic layer, often referred as the conditioning film (Loeb & Neihof, 1975; Bakker et al. 2003; Bhosle et al. 2005). Formation of this film is immediately followed by an accumulation of microorganisms (bacteria, diatoms), which... it evidentthatthetoolsemployedfortheremovalofbio- film diatoms are critical. Although there was no signi- ficant variation between the nylon brush and ceramic scraper, the former was found to be a better tool than the latter. Sharma et al. (1990) also concluded that a...

  14. 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.

    influenced by monsoons: spatial and temporal variations. Marine Biology, 148, 693-709. Mitbavkar S., Anil A.C. (2007) Species interactions within a fouling diatom community: roles of nutrients, initial inoculum and competitive strategies. Biofouling, 23, 99... by bacteria that helps in competition and signaling processes. The changes in fouling diatom communities when treated with antibiotics indicate the relevance of bacteria in influencing the biofilm. Streptomycin and chloramphenicol (produced naturally...

  15. Transitional Description of Diatomic Molecules in U(4) Vibron Model

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xin; PAN Feng

    2004-01-01

    U(3)-O(4) transitional description of diatomic molecules in the U(4) vibron model is studied by using the algebraic Bethe ansatz, in which the O(4) limit is a special case of the theory. Vibrational band-heads of some typical diatornic molecules are fitted by both transitional theory and the O(4) limit within the same framework. The results show that there are evident deviations from the O(4) limit in description of vibrational spectra of some diatomic molecules.

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

    OpenAIRE

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

    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...

  17. Adsorption of diatoms at the oil-water interface

    Science.gov (United States)

    Fathollahi, Niloofar; Sheng, Jian

    2013-11-01

    Statistically robust experimental observations on 3D trajectory of diatoms approaching an oil-water interface is crucial for understanding sorption mechanisms of active particles, and interfacial rheology with over-arching implications in interfacial dynamics, droplet break and coalescence. Digital Holographic Cinematography is utilized to measure 3-D trajectories of diatoms, Thalassiosira pseudomona and T. weissflogii and simultaneously track the interface. Experiments are conducted in a 300 × 100 × 100 mm chamber containing 32 ppt artificial seawater. A stationary pendant drop is created on the tip of a needle located at the center of the chamber. Three oil samples, Louisiana crude, hexadecane, and mineral oil, are used. Diatoms are injected at a height above the drop with a negligible velocity, where Diatom precipitates freely on its excess weight. Holograms of diatom and drop are recorded at 5 fps with a magnification of 1.3X and are streamed in real time allowing for long-term study of sorption onto a slowly aging interface. A novel autofocus algorithm enables us to determine 3D locations within an uncertainty of 0.05 particle diameter. This allows us to perform super-resolution measurement to determine the effects of location and orientation of diatoms on the adsorption rate at the oil-water interface. Funded by GoMRI.

  18. Marine Polysaccharide Networks and Diatoms at the Nanometric Scale

    Directory of Open Access Journals (Sweden)

    Tea Mišić Radić

    2013-10-01

    Full Text Available Despite many advances in research on photosynthetic carbon fixation in marine diatoms, the biophysical and biochemical mechanisms of extracellular polysaccharide production remain significant challenges to be resolved at the molecular scale in order to proceed toward an understanding of their functions at the cellular level, as well as their interactions and fate in the ocean. This review covers studies of diatom extracellular polysaccharides using atomic force microscopy (AFM imaging and the quantification of physical forces. Following a brief summary of the basic principle of the AFM experiment and the first AFM studies of diatom extracellular polymeric substance (EPS, we focus on the detection of supramolecular structures in polysaccharide systems produced by marine diatoms. Extracellular polysaccharide fibrils, attached to the diatom cell wall or released into the surrounding seawater, form distinct supramolecular assemblies best described as gel networks. AFM makes characterization of the diatom polysaccharide networks at the micro and nanometric scales and a clear distinction between the self-assembly and self-organization of these complex systems in marine environments possible.

  19. Molecular Fossils as Time Indicators for the Evolution of Diatoms.

    Science.gov (United States)

    Rampen, S. W.; Schouten, S.; Muyzer, G.; Abbas, B.; Rowland, S. J.; Moldowan, M.; Sinninghe Damsté, J. S.

    2004-12-01

    Bacillariophyta (diatoms) are one of the most abundant divisions of phytoplankton, and contribute to almost 50% of the primary productivity of today's oceans. However, their ecological dominance is relatively young and little is known about the exact pace of their rapid evolution. DNA analyses on diatoms and the use of molecular clock calculations can help to reconstruct their evolution, but this molecular clock rate needs to be calibrated against the fossil record to determine the mutation rate. Until now, diatom silica skeletons have been used for reconstructing the evolution of diatoms, but their use is limited due to destruction by diagenesis. Molecular fossils may prove to be more useful for time reconstruction. To search for suitable compounds, we have analyzed both the lipid composition and 18S rRNA sequences of ca. 100 marine diatoms. This revealed that some specific phylogenetic clusters within the diatoms produce specific organic compounds, so-called diatom biomarkers. One group of diatom biomarkers are the C25 highly branched isoprenoid (HBI) alkenes (1,2). HBI biosynthesis evolved independently at least twice in the diatoms. The first group of HBI producers consists of the centric diatoms of the genus Rhizosolenia, the second group comprises pennate diatoms of the genera Haslea, Navicula and Pleurosigma. Based on the constructed phylogenetic tree it is likely that the HBI biosynthesis evolved first in the older group of centric diatoms (i.e. the Rhizosolenia genus). The fossil record was studied to determine the geological occurrence of C25 HBI alkenes, and this data set shows that HBI biosynthesis evolved ca. 91.5 My ago, so we can date the evolution of the genus Rizosolenia to ca. 91.5 My. With this information, we can now accurately predict the mutation rate of the 18S rDNA gene to 1% per 14.8 My for Rhizosolenia, which is substantially faster than the 1% per 18-26 My reported previously for diatoms in general. Another specific biomarker is 24

  20. 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

  1. The paleoclimatology of Lake Baikal: A diatom synthesis and prospectus

    Science.gov (United States)

    Mackay, Anson W.

    2007-06-01

    The paleoclimatic archive held in Lake Baikal sediments is of significant importance, given the lake's position in one of the world's most continental regions where there are few continuous, high quality records spanning the Quaternary. Here I review diatom and associated biogenic silica records from Lake Baikal sediments and provide a paleoclimatic synthesis of changes at various timescales over the Quaternary. I initially highlight major climatic and hydrological aspects of Lake Baikal, as understanding the contemporary system (both regionally and within the lake) are fundamental to understanding past change interpreted from the sedimentary archive. In this respect, special attention is given to factors that can affect the integrity of the diatom record, most notably dissolution processes. These mechanisms are likely to have had a relatively greater impact on the preservation of diatom valves during glacial periods because of overall lower diatom productivity. Lower diatom numbers and relative increased dissolution during cold periods explains the lack of diatoms and low biogenic silica concentrations found in the lake sediments during glacial periods. The biogenic record highlights the nature of the 100 ka cycle especially during the last 800 ka, although there is also a strong precessional component. Further work is needed to reassess biological responses in Lake Baikal with respect to different orbital forcing mechanisms, together with their impacts on evolution and speciation of diatoms. The biological record from Lake Baikal confirms that the last interglacial in central Asia lasted approximately 10.5 ka. Productivity in the lake (as inferred from diatom biovolume accumulation rates) exhibits millennial-scale variability with the occurrence of centennial-scale reductions in diatom biomass throughout the last interglacial period. The most severe reduction in diatom biomass (at c. 120 ka BP) is concurrent with millennial-scale cooling in the North Atlantic

  2. Seasonal changes of diatom species in the Hooghly estuary, India

    Science.gov (United States)

    Goswami, P. K.

    2013-12-01

    The Hooghly estuary is considered as one of the most important fishing ground of north-east India which is mainly because presence of large shallow parts of Bays, which provide extensive growths for benthic and planktonic community and also makes it a highly productive area .Anthropogenic effects induce intensive pressure to this ecosystem ;and consequently results in the eutrophication followed by rapid plankton growth, sometimes even bloom. Diatom comprises one of the most diverse and significant part of the biota of aquatic habitats. Ecologically they are of immense importance since they constitute the podium of food chain and are at pinnacle of the biomass pyramid. The present study was based on the diversity of most dominant diatom species found in the brackish waters of Hooghly estuarine region in three locations of Sagar islands - Gangasagar, Chemaguri and Kachuberia. In this study diatom distribution from post monsoon - pre monsoon period was studied on the specific assemblages of them.. There was wide diversity of diatom species in different locations and in different seasons. Maximum number of diatom species was found in post-monsoon period in Gangasagar and Chemaguri, while in Kachuberia maximum number was found in pre-monsoon period. In Gangasagar, Navicula socialis, Coscinodiscus spp. and Biddulphia spp. were the predominant species in early, mid and late post monsoon period respectively and Biddulphia spp. also continues as the predominant diatom in pre-monsoon period. In Chemaguri, Amphora ostrearia, Coscinodiscus perforatus and Nitzschia acuminate were the predominant species in early, mid and late post monsoon period respectively while Coscinodiscus radiates was the stable predominant diatom species in pre-monsoon period while Thalassionema spp., Ditylum spp., Proboscia spp. and Biddulphia spp. were also found in significantly increased numbers at different times of pre-monsoon period. In Kachuberia area although a wide range of diatoms are present

  3. Early Cretaceous Tectonism and Diatoms in Korea

    Institute of Scientific and Technical Information of China (English)

    Ki-Hong CHANG; Sun-Ok PARK

    2008-01-01

    The Early Cretaceous Sindong Group, a non-marine molasse, unconformably overlies the folded earliest Cretaceous Myogok Formation. The tectonism that folded the Jaseong Synthem including the Myogok and other formations is here called the Nakdong-Jaeryeonggang (N-J) tectonism. The Oknyeobong and Dabokni Formations are discussed to show that they belong to the Jaseong Synthem. The Dabokni Formation yielded fossil diatoms whose age has been referred as the "earliest Cretaceous" based on the geologically constrained age of the fossil-bearing deposit. The age of the N-J tectonism appears Barremian as it is between the Hauterivian Myogok Formation and the Aptian Sindong Group with the TPN (Trigonioides-Plicatounio-Nippononaia) fauna. The N-J tectonism, an orogeny, quite deformed pre-Aptian strata in Korea, but can hardly find its reported equivalent in NE China. A revised correlation table shows that the Jaseong- Sindong sequence corresponds to the Jehol Group of China. The Sindong-Hayang transition was characterized by basin migration and dextral rotation probably caused by the Tan-Lu fault system in a broad sense.

  4. Classification of marine diatoms using pigment ratio suites

    Institute of Scientific and Technical Information of China (English)

    YAO Peng; YU Zhigang; DENG Chunmei; LIU Shuxia; ZHEN Yu

    2011-01-01

    Diatoms are widely distributed in many temperate areas and some species frequently form extensive blooms in spring.Hence,monitoring the variations of specific genera or species of diatoms is necessary for studying phytoplankton population dynamics in marine ecosystems.To test whether pigment ratios can be used to identify diatoms at a below-class taxonomic level,we analyzed 14 species/strains of diatoms isolated from Chinese seas using high performance liquid chromatography (HPLC).We normalized all pigment concentrations to total chlorophyll a to calculate the ratios of pigment to chlorophyll a,and calculated the ratios between accessory pigments (or pigment sums).Cluster analysis indicated that these diatoms could be classified into four clusters in terms of three accessory pigment ratios:chlorophyll c2:chlorophyll c1,fucoxanthin:total chlorophyll c and diadinoxanthin:diatoxanthin.The classification results matched well with those of biological taxonomy.To test the stability of the classification,pigment data from one species,cultured under different light intensities,and five new species/strains were calculated and used for discriminant analysis.The results show that the classification of diatom species using pigment ratio suites was stable for the variations of pigment ratios of species cultured in different light intensities.The introduction of new species,however,may confuse the classification within the current scheme.Classification of marine diatoms using pigment ratio suites is potentially valuable for the fine chemotaxonomy of phytoplankton at taxonomic levels below class and would advance studies on phytoplankton population dynamics and marine ecology.

  5. 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.

  6. Duo: a general program for calculating spectra of diatomic molecules

    CERN Document Server

    Yurchenko, Sergei N; Tennyson, Jonathan; Stolyarov, Andrey V

    2016-01-01

    Duo is a general, user-friendly program for computing rotational, rovibrational and rovibronic spectra of diatomic molecules. Duo solves the Schr\\"{o}dinger equation for the motion of the nuclei not only for the simple case of uncoupled, isolated electronic states (typical for the ground state of closed-shell diatomics) but also for the general case of an arbitrary number and type of couplings between electronic states (typical for open-shell diatomics and excited states). Possible couplings include spin-orbit, angular momenta, spin-rotational and spin-spin. Corrections due to non-adiabatic effects can be accounted for by introducing the relevant couplings using so-called Born-Oppenheimer breakdown curves. Duo requires user-specified potential energy curves and, if relevant, dipole moment, coupling and correction curves. From these it computes energy levels, line positions and line intensities. Several analytic forms plus interpolation and extrapolation options are available for representation of the curves. ...

  7. Influence of cobalamin scarcity on diatom molecular physiology and identification of a cobalamin acquisition protein

    OpenAIRE

    Erin M Bertrand; Andrew E Allen; Dupont, Christopher L.; Norden-Krichmar, Trina M.; Bai, Jing; Valas, Ruben E.; Saito, Mak A.

    2012-01-01

    Diatoms are responsible for ∼40% of marine primary production and are key players in global carbon cycling. There is mounting evidence that diatom growth is influenced by cobalamin (vitamin B12) availability. This cobalt-containing micronutrient is only produced by some bacteria and archaea but is required by many diatoms and other eukaryotic phytoplankton. Despite its potential importance, little is known about mechanisms of cobalamin acquisition in diatoms or the impact of cobalamin scarcit...

  8. Genome size differentiates co-occurring populations of the planktonic diatom Ditylum brightwellii (Bacillariophyta)

    OpenAIRE

    von Dassow Peter; Swalwell Jarred E; Koester Julie A; Armbrust E Virginia

    2010-01-01

    Abstract Background Diatoms are one of the most species-rich groups of eukaryotic microbes known. Diatoms are also the only group of eukaryotic micro-algae with a diplontic life history, suggesting that the ancestral diatom switched to a life history dominated by a duplicated genome. A key mechanism of speciation among diatoms could be a propensity for additional stable genome duplications. Across eukaryotic taxa, genome size is directly correlated to cell size and inversely correlated to phy...

  9. Effect of alternative mediums on production and proximate composition of the microalgae Chaetoceros muelleri as food in culture of the copepod Acartia sp. Efecto de medios alternativos sobre la producción y composición proximal de la microalga Chaetoceros muelleri como alimento en cultivo del copépodo Acartia sp.

    Directory of Open Access Journals (Sweden)

    Luis R Martínez-Córdova

    2012-03-01

    Full Text Available Microalgae Chaetoceros muelleri was cultured in three different mediums consisting on an agricultural fertilizer (Agr-F, aquacultural fertilizer (Aq-F and a conventional medium (F/2, control. These microalgae were later used as natural food to culture the copepod Acartia sp. The productive response and chemical proximate composition of microalgae and copepods were monitored. Growth rate and final cell concentration were higher in microalgae cultured in Agr-F compared to the control. In addition, the final biomass and cellular concentration were also the highest in Agr-F. Microalgae from Agr-F and Aq-F had higher carbohydrate and lower protein contents than those in the control. No differences in lipid and ash contents were observed. Regarding copepod production, higher densities and fecundity indexes were observed for those fed with microalgae previously cultured in Agr-F and Aq-F, compared to the control. The adult-nauplii ratio was also higher in copepods fed on microalgae from Agr-F compared to Aq-F and control. Copepods fed on Agr-F and Aq-F microalgae, had higher protein content compared to those fed on control microalgae; carbohydrates were higher in copepods fed on Agr-F as compared to Aq-F microalgae. No differences in lipid and ash contents were registered. Agr-F and Aq-F were adequate alternative mediums to produce C. muelleri, which produced higher quality microalgae that increased the copepod production.La microalga Chaetoceros muelleri fue cultivada en tres medios diferentes basados en un fertilizante agrícola (Agr-F, un fertilizante acuícola (Aq-F y un medio convencional (F/2, control. Éstas microalgas fueron posteriormente utilizadas como alimento natural para cultivar el copépodo Acartia sp. La respuesta productiva y la composición proximal de las microalgas y copépodos fueron monitoreadas. La tasa de crecimiento y concentración final de células fueron mayores en la microalga cultivada en Agr-F, comparada con el control

  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. Prevalence of diatom frustules in non-vegetarian foodstuffs and its implications in interpreting identification of diatom frustules in drowning cases.

    Science.gov (United States)

    Yen, Law Yen; Jayaprakash, P T

    2007-07-20

    Detection of diatom frustules in bone marrow (diatom test) is used for diagnosing ante-mortem drowning where the usual signs of drowning are not present in dead bodies recovered from water. However, controversies over the reliability of diatom test results are continuing. There have been indications on the possibilities of diatoms entering into systemic circulation from atmospheric air, food and drink. While diatoms have been demonstrated in the gut content of edible marine forms such as shrimps and clams, the present study, for the first time, provides empirical evidence on the prevalence as well as abundance of diatom frustules in the samples of cooked non-vegetarian foodstuffs that impend human consumption in Kelantan, Malaysia. It is found that 50 g each of cleaned and cooked prawns and of clams impending human consumption contain about 8360 and 29,054 diatom frustules, respectively. A person accustomed to prawn and clam food would be ingesting an estimated 2 million diatoms in a single year. Considering the suggestion that detection of five diatom frustules in 10 g of bone marrow would suffice for concluding drowning as mode of death, and the fact that there is yet no proof that diatom frustules do not enter into the human systemic circulation through the digestive tract, the estimated number of diatom frustules routinely ingested acquires significance since entry of a few of such ingested frustules into the systemic circulation can lead to false positive test results. The findings of this research raise two important issues: first, population based routine food related diatom ingestion requires to be estimated, and, second, studies have to be initiated to categorically prove or disprove the possibility of entry of diatom frustules into the systemic circulation via the digestive tract.

  12. Relativistic Effects Break Periodicity in Group 6 Diatomic Molecules.

    Science.gov (United States)

    Wang, Yi-Lei; Hu, Han-Shi; Li, Wan-Lu; Wei, Fan; Li, Jun

    2016-02-01

    The finding of the periodic law is a milestone in chemical science. The periodicity of light elements in the Periodic Table is fully accounted for by quantum mechanics. Here we report that relativistic effects change the bond multiplicity of the group 6 diatomic molecules M2 (M = Cr, Mo, W, Sg) from hextuple bonds for Cr2, Mo2, W2 to quadruple bonds for Sg2, thus breaking the periodicity in the nonrelativistic domain. The same trend is also found for other superheavy-element diatomics Rf2, Db2, Bh2, and Hs2. PMID:26787134

  13. Effects of monomethylhydrazine on selected species of marine diatoms

    Energy Technology Data Exchange (ETDEWEB)

    Wendler, B.W.; Norris, D.R.

    1985-07-01

    A safe concentration (SC) and the mean effective concentration (EC) for hydrazine, MMH, and unsymmetrical dimethylhydrazine have been determined on species of green algae. The aqueous degradation of MMH is relatively rapid compared to the time green algae require to reach maximum standing crop. The diatoms Thalassiosira pseudonana and Skeletonema costatum reach maximum standing crop in 6 to 7 days in culture which makes them ideal for testing short-term effects of MMH. The objectives of this study were to determine the relative sensitivity of selected marine diatoms to MMH and whether species composition would be affected by MMH.

  14. Coherent control of mesoscopic superpositions in a diatomic molecule

    CERN Document Server

    Ghosh, Suranjana

    2011-01-01

    A phase controlled wave packet, recently used in experiment of wave packet interferometry of a diatomic molecule, is investigated to obtain mesoscopic superposition structures, useful in quantum metrology. This analysis provides a new way of obtaining sub-Planck scale structures at smaller time scale of revival dynamics. We study a number of situations for delineating the smallest interference structures and their control by tailoring the relative phase between two subsidiary wave packets. We also find the most appropriate state, so far, for high precision parameter estimation in a system of diatomic molecule.

  15. R-Syst::diatom: an open-access and curated barcode database for diatoms and freshwater monitoring.

    Science.gov (United States)

    Rimet, Frédéric; Chaumeil, Philippe; Keck, François; Kermarrec, Lenaïg; Vasselon, Valentin; Kahlert, Maria; Franc, Alain; Bouchez, Agnès

    2016-01-01

    Diatoms are micro-algal indicators of freshwater pollution. Current standardized methodologies are based on microscopic determinations, which is time consuming and prone to identification uncertainties. The use of DNA-barcoding has been proposed as a way to avoid these flaws. Combining barcoding with next-generation sequencing enables collection of a large quantity of barcodes from natural samples. These barcodes are identified as certain diatom taxa by comparing the sequences to a reference barcoding library using algorithms. Proof of concept was recently demonstrated for synthetic and natural communities and underlined the importance of the quality of this reference library. We present an open-access and curated reference barcoding database for diatoms, called R-Syst::diatom, developed in the framework of R-Syst, the network of systematic supported by INRA (French National Institute for Agricultural Research), see http://www.rsyst.inra.fr/en. R-Syst::diatom links DNA-barcodes to their taxonomical identifications, and is dedicated to identify barcodes from natural samples. The data come from two sources, a culture collection of freshwater algae maintained in INRA in which new strains are regularly deposited and barcoded and from the NCBI (National Center for Biotechnology Information) nucleotide database. Two kinds of barcodes were chosen to support the database: 18S (18S ribosomal RNA) and rbcL (Ribulose-1,5-bisphosphate carboxylase/oxygenase), because of their efficiency. Data are curated using innovative (Declic) and classical bioinformatic tools (Blast, classical phylogenies) and up-to-date taxonomy (Catalogues and peer reviewed papers). Every 6 months R-Syst::diatom is updated. The database is available through the R-Syst microalgae website (http://www.rsyst.inra.fr/) and a platform dedicated to next-generation sequencing data analysis, virtual_BiodiversityL@b (https://galaxy-pgtp.pierroton.inra.fr/). We present here the content of the library regarding the

  16. Surficial Sedimentary Diatoms in Okinawa Trough and Its Response to Kuroshio Current

    Institute of Scientific and Technical Information of China (English)

    Lan Dongzhao; Fang Qi; Liao Lianzhao

    2002-01-01

    This paper describes the relative contents of dominant diatom species and the distributive characteristics of tropical pelagic species and diatom assemblages, and also discusses the relations between the relative content of tropical pelagic species and Kuroshio Current and between the distribution of diatom assemblages and material sources. The results show that the limit of>20% relative content of tropical pelagic species is basically consistent with the demarcation of Kuroshio Current, and that the distributions of dominant diatom species and diatom assemblages reserve the records of their closer relations to material sources.

  17. Accurate vibrational energy spectra and dissociationenergies of some diatomic electronic states

    Institute of Scientific and Technical Information of China (English)

    Wei-guo SUN; Xiu-ying LIU; Yu-jie WANG; Yan ZHAN; Qun-chao FAN

    2008-01-01

    An algebraic method (AM) used to study the full vibrational spectra of diatomic systems, and an analytical formula used to calculate accurate molecular dissociation energies are applied to study the full vi-brational spectra and molecular dissociation energies of some electronic states of homonuclear and heteronuclear diatomic molecules and diatomic ions. Studies show that the AM method and the analytical expression are reli-able and economical physical methods for studying full vibrational spectra and molecular dissociation energies of diatomic electronic systems theoretically. They are par-ticularly useful for those diatomic systems whose high-lying vibrational energies may not be available.

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

    International Nuclear Information System (INIS)

    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 M2 molecules from H2 to Lr2. 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

  19. Origin and evolution of the canal raphe system in diatoms.

    Science.gov (United States)

    Ruck, Elizabeth C; Theriot, Edward C

    2011-11-01

    One lineage of pennate diatoms has a slit through the siliceous cell wall, called a "raphe," that functions in motility. Raphid pennate diatoms number in the perhaps tens of thousands of species, with the diversity of raphe forms potentially matching this number. Three lineages-the Bacillariales, Rhopalodiales, and Surirellales-possess a complex and presumably highly derived raphe that is physically separated from the cell interior, most often by a set of siliceous braces. Because the relationship among these three lineages is unclear, the number of origins of the canal raphe system and the homology of it and its constitutive parts among these lineages, is equally unclear. We reconstructed the phylogeny of raphid pennate diatoms and included, for the first time, members of all three canal raphid diatom lineages, and used the phylogeny to test specific hypotheses about the origin of the canal raphe. The canal raphe appears to have evolved twice, once in the common ancestor of Bacillariales and once in the common ancestor of Rhopalodiales and Surirellales, which form a monophyletic group in our analyses. These results recommend careful follow-up morphogenesis studies of the canal raphe in these two lineages to determine the underlying developmental basis for this remarkable case of parallel evolution.

  20. Diatoms respire nitrate to survive dark and anoxic conditions

    DEFF Research Database (Denmark)

    Kamp, Anja; de Beer, Dirk; Nitsch, Jana L.;

    2011-01-01

    − in their cells survived for 6–28 wk. After sudden shifts to dark, anoxic conditions, the benthic diatom Amphora coffeaeformis consumed 84–87% of its intracellular NO3− pool within 1 d. A stable-isotope labeling experiment proved that 15NO3− consumption was accompanied by the production and re- lease of 15NH4...

  1. 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 pimpact 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.

  2. The Kinker diatom collection: discovery – exploration – exploitation

    NARCIS (Netherlands)

    Sterrenburg, F.A.S.; Wolf, de H.

    2004-01-01

    Johannes Kinker (1823-1900) was a typical representative of the Victorian ‘amateur-savant’. As a wellto- do stockbroker he was able to invest considerable time and money into studies of nature, first entomology and subsequently diatoms. The latter subject flourished in the late 19th century and, amo

  3. Functionalized diatom silica microparticles for removal of mercury ions

    Directory of Open Access Journals (Sweden)

    Yang Yu, Jonas Addai-Mensah and Dusan Losic

    2012-01-01

    Full Text Available 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 –NH2 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.

  4. Dimethylsulfoniopropionate (DMSP) cell quota of key Southern North Sea spring diatoms and Phaeocystis globosa.

    Science.gov (United States)

    Speeckaert, Gaëlle; Gypens, Nathalie; Lancelot, Christiane; Borges, Alberto V.

    2015-04-01

    Dimethylsulfide (DMS) in the ocean results of complex transformations of dimethylsulfoniopropionate (DMSP) produced by phytoplankton under different controls, including microbial transformation pathways. The phytoplankton composition is an important factor of variability due to the species dependence of the DMSP production and conversion to DMS. To better appraise the link between phytoplankton diversity and the DMS(P) cycling in the Southern North Sea we present measurements of the DMSP cell quota of key spring phytoplankton species (Skeletonema costatum, Thalassiosira rotula, Rhizosolenia delicatula, Asterionella glacialis, Nitzschia closterium, Chaetoceros debilis, Chaetoceros socialis and Phaeocystis globosa) isolated from the North Sea and maintained in non-limiting and axenic laboratory culture conditions. Results are discussed with regards to literature data and hypothesis currently used in DMS(P) biogeochemical models.

  5. Fossilized diatoms in meteorites from recent falls in Sri Lanka

    Science.gov (United States)

    Hoover, Richard B.; Wallis, Jamie; Wickramarathne, Keerthi; Samaranayake, Anil; Williams, George; Jerman, Gregory; Wallis, D. H.; Wickramasinghe, N. C.

    2013-09-01

    On December 29, 2012, a bright yellow and green fireball was observed to disintegrate over the Polonnaruwa District of North Central, Sri Lanka. Many low density, black stones were recovered soon after the observed fall from rice paddy fields near the villages of Aralaganwila and Dimbulagala. These stones were initially studied by optical microscopy methods at the Medical Research Institute in Colombo, Sri Lanka. Soon thereafter, samples were sent to the UK and to the United States. More extensive Field Emission Scanning Electron Microscopy studies were then carried out at Cardiff University and the NASA/Marshall Space Flight Center. The physico-chemical properties, elemental abundances, mineralogy and stable isotope data clearly indicate that these stones are non-terrestrial. Freshly fractured interior surfaces of the black stones have also been observed to contain the remains of fossilized diatom. Many of the diatom frustules are clearly embedded in the meteorite rock matrix and exhibit nitrogen levels below the EDX detection limits. Some of the fossil diatoms are araphid marine pennates and planktonic forms that are inconsistent with conditions associated with rice paddy fields. These observations indicate the fossilized diatoms are indigenous to the meteorites rather than post-arrival biological contaminants. The carbon content and mineralogy suggests that these stones may represent a previously ungrouped clan of carbonaceous meteorites. The extremely low density (~0.6) of the stones and their observed mineralogy was inconsistent with known terrestrial rocks (e.g., pumice, diatomite and fulgurites). The minerals detected suggest that the parent body of the Polonnaruwa stones may have been the nucleus of a comet. These observations are interpreted as supporting the Hoyle-Wickramasinghe Panspermia hypothesis and the hypothesis that diatoms and other microorganisms might be capable of living and growing in water ice and brines in comets.

  6. Diatom proteomics reveals unique acclimation strategies to mitigate Fe limitation.

    Directory of Open Access Journals (Sweden)

    Brook L Nunn

    Full Text Available Phytoplankton growth rates are limited by the supply of iron (Fe in approximately one third of the open ocean, with major implications for carbon dioxide sequestration and carbon (C biogeochemistry. To date, understanding how alteration of Fe supply changes phytoplankton physiology has focused on traditional metrics such as growth rate, elemental composition, and biophysical measurements such as photosynthetic competence (Fv/Fm. Researchers have subsequently employed transcriptomics to probe relationships between changes in Fe supply and phytoplankton physiology. Recently, studies have investigated longer-term (i.e. following acclimation responses of phytoplankton to various Fe conditions. In the present study, the coastal diatom, Thalassiosira pseudonana, was acclimated (10 generations to either low or high Fe conditions, i.e. Fe-limiting and Fe-replete. Quantitative proteomics and a newly developed proteomic profiling technique that identifies low abundance proteins were employed to examine the full complement of expressed proteins and consequently the metabolic pathways utilized by the diatom under the two Fe conditions. A total of 1850 proteins were confidently identified, nearly tripling previous identifications made from differential expression in diatoms. Given sufficient time to acclimate to Fe limitation, T. pseudonana up-regulates proteins involved in pathways associated with intracellular protein recycling, thereby decreasing dependence on extracellular nitrogen (N, C and Fe. The relative increase in the abundance of photorespiration and pentose phosphate pathway proteins reveal novel metabolic shifts, which create substrates that could support other well-established physiological responses, such as heavily silicified frustules observed for Fe-limited diatoms. Here, we discovered that proteins and hence pathways observed to be down-regulated in short-term Fe starvation studies are constitutively expressed when T. pseudonana is

  7. Diatom Nanotechnology%硅藻纳米技术

    Institute of Scientific and Technical Information of China (English)

    夏嵩; 张成武

    2011-01-01

    硅藻是一类微小的单细胞藻类,具有由无定形氧化硅组成的坚硬细胞壁(硅壳).硅壳具有精致的形态和结构,且随硅藻种类和生长条件不同而千变万化.目前估算的硅藻种类超过200 000种,其独特的纳米结构对光子结构、化学生物传感器、新纳米材料和器件的开发具有启发意义.同时硅藻形态形成学和分子生物学的研究,可以推动硅质材料的仿生合成、化学转化及模板技术的发展.因此设计和生产特殊形态的硅壳,在纳米技术领域具有广泛应用前景.%Diatoms are microscopic , single-celled algae that possess rigid cell walls ( frustules) composed of amorphous silica. The intact diatom frustules possess intricate nanoscale features. Depending on the species of diatom and the growth conditions, the frustules can display different morphologies. The almost 200 000 different diatom species feature unique frustule architectures that are instructive for construction of photonic structures,chemo/biosensing and new nano-devices. The researches of diatom molecular biology and frustule formation are instructive for development of biomimetic synthesis of silica-based materials, chemical transformations and templating techniques. It is possible to design and produce specific frustules that have a wide rang of applications in nanotechnology.

  8. Understanding amine catalyzed silica polymerization : diatoms as bioarchitects.

    Energy Technology Data Exchange (ETDEWEB)

    Spoerke, Erik David; Aubry, Sylvie; Lane, Pamela; Robinson, David B; Bauer, Christina A.; Zendejas, Frank; Tran, Huu; Lane, Todd W.; Simmons, Blake Alexander

    2007-10-01

    Current state-of-the-art biomimetic methodologies employed worldwide for the realization of self-assembled nanomaterials are adequate for certain unique applications, but a major breakthrough is needed if these nanomaterials are to obtain their true promise and potential. These routes typically utilize a 'top-down' approach in terms of controlling the nucleation, growth, and deposition of structured nanomaterials. Most of these techniques are inherently limited to primarily 2D and simple 3D structures, and are therefore limited in their ultimate functionality and field of use. Zeolites, one of the best-known and understood synthetic silica structures, typically possess highly ordered silica domains over very small length scales. The development of truly organized and hierarchical zeolites over several length scales remains an intense area of research world wide. Zeolites typically require high-temperature and complex synthesis routes that negatively impact certain economic parameters and, therefore, the ultimate utility of these materials. Nonetheless, zeolite usage is in the tons per year worldwide and is quickly becoming ubiquitous in its applications. In addition to these more mature aspects of current practices in materials science, one of the most promising fields of nanotechnology lies in the advent and control of biologically self-assembled materials, especially those involved with silica and other ceramics such as hydroxyapatite. Nature has derived, through billions of years of evolutionary steps, numerous methods by which fault-tolerant and mechanically robust structures can be created with exquisite control and precision at relatively low temperature ranges and pressures. Diatoms are one of the best known examples that exhibit this degree of structure and control known that is involved with the biomineralization of silica. Diatoms are eukaryotic algae that are ubiquitous in marine and freshwater environments. They are a dominant form of

  9. Effects of growth and dissolution on the fractionation of silicon isotopes by estuarine diatoms

    Science.gov (United States)

    Sun, Xiaole; Olofsson, Martin; Andersson, Per S.; Fry, Brian; Legrand, Catherine; Humborg, Christoph; Mörth, Carl-Magnus

    2014-04-01

    Studies of silicon (Si) isotope fractionation during diatom growth in open ocean systems have documented lower Si isotopic values (δ30Si) in the biogenic silica of diatom frustules compared to dissolved silicon. Recent findings also indicate that Si isotope fractionation occurs during dissolution of diatom frustules, producing higher δ30Si values in the remaining biogenic silica. This study focuses on diatoms from high production areas in estuarine and coastal areas that represent approximately 30-50% of the global marine primary production. Two species of diatoms, Thalassiosira baltica and Skeletonema marinoi, were isolated from the brackish Baltic Sea, one of the largest estuarine systems in the world. These species were used for laboratory investigations of Si isotope fractionation during diatom growth and the subsequent dissolution of the diatom frustules. Both species of diatoms give an identical Si isotope fractionation factor during growth of -1.50 ± 0.36‰ (2σ) for 30Si, which falls in the range of -2.09‰ to -0.55‰ of published data. Our results also suggest a dissolution-induced Si isotope fractionation factor of -0.86‰ at early stage of dissolution, but this effect was observed only in DSi and no significant Si isotope change was observed for BSi. The growth and dissolution results are applied to a Baltic Sea sediment core to reconstruct DSi utilization by diatoms, and found to be in agreement with the observed DSi uptake rates in the overlying water column during diatom growth.

  10. Using benthic diatom assemblages to assess human impacts on streams across a rural to urban gradient.

    Science.gov (United States)

    Yang, Ying; Cao, Jin-Xiang; Pei, Guo-Feng; Liu, Guo-Xing

    2015-11-01

    Benthic diatom assemblages on the natural substrata were investigated at 21 sites of the Ganhe River watershed (China) once per season and in addition, early spring in 2013. A total of 487 diatom taxa from 36 genera were identified during five investigations. The assemblages were dominated by Achnanthidium minutissimum (Kützing) Czarnecki and Cocconeis placentula in the rural reach, whereas Navicula, Nitzschia, and Gomphonema species were characteristic of urbanized sites. Our results suggest that biodiversity was positively related to high nutrient levels and strongly negatively related to diatom-based indices. The periphyton biomass (expressed as chlorophyll a and ash-free dry mass) was not related to water quality. Canonical correspondence analysis (CCA) showed that the nutrient concentration gradient was the most important factor that affected the diatom assemblage composition and species distribution. The diatom-based indices (specific pollution sensitivity index (IPS), biological diatom index (IBD), and trophic diatom index (TDI)) were significantly positively correlated with water quality and are adequate for use in China. Slight changes in the biodiversity and diatom-based indices followed a temporal pattern. The species composition was less related to the season or hydrological characteristics of the river but more strongly related to differences in the trophic status. In this region, urbanization masked the impact of rural land use on benthic diatoms. The research will expand the understanding of using benthic diatom assemblages for water quality monitoring in urban streams and improve watershed-scale management and conservation efforts in the Ganhe River, China. PMID:26174985

  11. False-positive diatom test: a real challenge? A post-mortem study using standardized protocols.

    Science.gov (United States)

    Lunetta, Philippe; Miettinen, Arto; Spilling, Kristian; Sajantila, Antti

    2013-09-01

    The main criticism of the validity of the diatom test for the diagnosis of drowning is based on the potential ante- and post-mortem penetration of diatoms and the finding of diatoms in bodies of non-drowned human beings. However, qualitative and quantitative studies on diatoms in organs of the non-drowned have yielded both conflicting and contradictory results. In the present study, we have analysed under standardised methods the diatom content in several organs of 14 non-drowned human bodies. Overall, only 9 diatoms (6 entire, 3 fragmented) were disclosed in 6 of the 14 non-drowned bodies. Each of these 6 cadavers had only a single "positive" organ. Six diatoms were found in the bone marrow, 2 in the lung, and one in the pleural liquid. No diatoms were recovered from the brain, liver, kidney, or blood samples of any of these 14 bodies. Moreover, in five additional cadavers, whose lungs were injected, prior autopsy, with a 3.5L solution containing a bi-cellulate diatom culture (Thalassiosira baltica, Thalassiosira levanderi) via tracheostomy, a few diatoms appeared in the pleural cavity and in the blood from the left heart chamber, but none in any other internal organs investigated. The results of the presented study demonstrate that the issue of the false-positive diatom test should not be a logical impediment to the performance of the diatom method. However, strict and standardized protocols aimed at avoiding contamination during sample preparation must be used, appropriate separation values set and taxonomic analysis of all diatoms performed. PMID:23701706

  12. The Diatom Stratigraphy of Rawapening Lake, Implying Eutrophication History

    Directory of Open Access Journals (Sweden)

    Tri Retnaningsih Soeprobowati

    2012-01-01

    Full Text Available Problem statement: The use of diatoms to reconstruct past ecological conditions in lakes is well established. Diatoms are microscopic algae that forms siliceous frustules which allow them to preserve well in sediments. Rawapening Lake is one of 15 Indonesian lakes identified as 2010-2014 National Priority Lakes. Naturally, Rawapening is a tectono-volcanic lake. In the early 1900s, the sole outlet of the lake, Tuntang River, was impounded for hydroelectricity, irrigation and fisheries. Since then Rawapening had become a semi natural lake. The main problem of Rawapening Lake is blooming of water hyacinth that reduce lake function. This research was conducted in order to reconstruct the nutrient history of Rawapening Lake, Java. Approach: Sediment samples were taken from four sites and were sliced every 0.5 cm for diatom analysis and bulked across 2-5 cm for 210Pb radiometric dating of sediment. Diatom analysis consisted of three steps: the digestion process to separate the diatoms from the sediment; preparation and mounting of diatom residues onto slides and identification-enumeration. Results: The diatom-inferred condition of Rawapening Lake may be divided into four phases represented by zone 1 (1967-1974, zone 2 (1974-1983, zone 3 (1984-1990 and zone 4 (1990-2008. The predominance of Synedra from 1967 to present indicates that Rawapening Lake has been fresh and meso-eutrophic throughout. Zone 1 is also characterized by Fragilaria capucina Desm, Luticola goeppertiana (Bleisch Mann, Mayamae atomus (Kutzing Lange-Bertalot, Navicula radiosa Kutzing, Nitzschia palea (Kutzing W. Smith and in one site, Tryblionella apiculata Gregory, that reflect eutrophic, but clear waters. An increase in epiphytic Gomphonema spp. in zone 2 marks an increase in aquatic macrophyte plants, perhaps in response to high nutrient levels. This change is followed promptly by an increase in acidophilous Eunotia spp. reflecting high organic production. A transition to a diatom

  13. Asymptotic behavior of subradiant states in homonuclear diatomic molecules

    CERN Document Server

    McGuyer, Bart H; Iwata, Geoffrey Z; Tarallo, Marco G; Skomorowski, Wojciech; Moszynski, Robert; Zelevinsky, Tanya

    2014-01-01

    Weakly bound molecules have physical properties without atomic analogues, even as the bond length approaches dissociation. In particular, the internal symmetries of homonuclear diatomic molecules result in the formation of two-body superradiant and subradiant excited states. While superradiance has been demonstrated in a variety of systems, subradiance is more elusive due to the inherently weak interaction with the environment. Transition mechanisms that are strictly forbidden for atoms become allowed just below the dissociation asymptote due to new selection rules associated with the subradiant states. Here we directly probe deeply subradiant states in ultracold diatomic strontium molecules and characterize their properties near the intercombination atomic asymptote via optical spectroscopy of doubly-forbidden transitions with intrinsic quality factors exceeding 10^(13). This precision measurement of subradiance is made possible by tightly trapping the molecules in a state-insensitive optical lattice and ach...

  14. Neural Network predictions of Diatomic and Triatomic Molecular Data

    Science.gov (United States)

    Blake Laing, W.

    1997-11-01

    The arrangement of molecules in periodic systems offers an enhanced comprehension of trends in molecular properties, a more efficient method of sorting and searching of molecular databases, and bases for the prediction of new data. Neural networks have the ability to "learn" existing data and to forecast a large amount of new data without a smoothing equation.(R. Hefferlin, B. Davis, W. B. Laing, "The Learning and Prediction of Triatomic Molecular Data with Neural Networks," International Arctic Seminar 1997, Murmansk, Russia)(J. Wohlers, W. B. Laing, R. Hefferlin, and B. Daivs, "Least-Squares and Neural-Network Forecasting from Citical Data: Diatomic Molecular Internuclear Separations and Triatomic Heats of Atomization and Ionization Potentials," Advances in Molecular Similarity: JIA book series, in press) This report will present periodic systems of molecules as well as neural network predictions for additional properties of diatomic and triatomic molecules.

  15. Strong-field approximation for harmonic generation in diatomic molecules

    OpenAIRE

    Chirila, Ciprian C.; Lein, Manfred

    2005-01-01

    The generation of high-order harmonics in diatomic molecules is investigated within the framework of the strong-field approximation. We show that the conventional saddle-point approximation is not suitable for large internuclear distances. An adapted saddle-point method that takes into account the molecular structure is presented. We analyze the predictions for the harmonic-generation spectra in both the velocity and the length gauge. At large internuclear separations, we compare the resultin...

  16. Using diatom taxonomic diversity to assess herbicide contamination in rivers

    OpenAIRE

    Marcel, Rémy; Bouchez, Agnes; Rimet, Frédéric,

    2011-01-01

    The increasing contamination by micropollutants in freshwater systems has become a major problem in modern societies, giving rise to toxicological, sanitary and economical concerns. In 2010 the French government adopted a plan for a 50% reduction over 10 years in the use of pesticides which promotes research on contamination monitoring. Diatom bio-indication tools in rivers have been standardized and normalized (AFNOR NFT 90 354 ; CEN – EN 13946 & EN 14407) and are adapted to assess nutrient ...

  17. 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

  18. Diatom cooccurrence shows less segregation than predicted from niche modeling

    OpenAIRE

    Marius Bottin; Janne Soininen; Didier Alard; Juliette Rosebery

    2016-01-01

    Species cooccurrence patterns give significant insights into the processes shaping communities. While biotic interactions have been widely studied using cooccurrence analyses in animals and larger plants, studies about cooccurrences among micro-organisms are still relatively rare. We examined stream diatom cooccurrences in France through a national database of samples. In order to test the relative influence of environmental, biotic and spatial constraints on species’ incidence distribution, ...

  19. Diatom Cooccurrence Shows Less Segregation than Predicted from Niche Modeling.

    Science.gov (United States)

    Bottin, Marius; Soininen, Janne; Alard, Didier; Rosebery, Juliette

    2016-01-01

    Species cooccurrence patterns give significant insights into the processes shaping communities. While biotic interactions have been widely studied using cooccurrence analyses in animals and larger plants, studies about cooccurrences among micro-organisms are still relatively rare. We examined stream diatom cooccurrences in France through a national database of samples. In order to test the relative influence of environmental, biotic and spatial constraints on species' incidence distribution, cooccurrence and nestedness patterns of real communities were compared with the patterns generated from a set of standard and environmentally constrained null models. Real communities showed a higher level of segregation than the most conservative standard null models, but a general aggregation of cooccurrences when compared to environmentally constrained null models. We did not find any evidence of limiting similarity between cooccurring species. Aggregations of species cooccurrences were associated with the high levels of nestedness. Altogether, these results suggested that biotic interactions were not structuring cooccurrences of diatom species at our study scale. Instead, the patterns were more likely to be related with colonization patterns, mass effect, and local temporal dynamics of diatom biofilms. We further highlight that the association of standard and environmentally constrained null models may give realistic insight into the cooccurrence patterns of microbial communities. PMID:27128737

  20. Diatom Cooccurrence Shows Less Segregation than Predicted from Niche Modeling.

    Directory of Open Access Journals (Sweden)

    Marius Bottin

    Full Text Available Species cooccurrence patterns give significant insights into the processes shaping communities. While biotic interactions have been widely studied using cooccurrence analyses in animals and larger plants, studies about cooccurrences among micro-organisms are still relatively rare. We examined stream diatom cooccurrences in France through a national database of samples. In order to test the relative influence of environmental, biotic and spatial constraints on species' incidence distribution, cooccurrence and nestedness patterns of real communities were compared with the patterns generated from a set of standard and environmentally constrained null models. Real communities showed a higher level of segregation than the most conservative standard null models, but a general aggregation of cooccurrences when compared to environmentally constrained null models. We did not find any evidence of limiting similarity between cooccurring species. Aggregations of species cooccurrences were associated with the high levels of nestedness. Altogether, these results suggested that biotic interactions were not structuring cooccurrences of diatom species at our study scale. Instead, the patterns were more likely to be related with colonization patterns, mass effect, and local temporal dynamics of diatom biofilms. We further highlight that the association of standard and environmentally constrained null models may give realistic insight into the cooccurrence patterns of microbial communities.

  1. Multidimensional Chemical Modeling. III. Abundance and excitation of diatomic hydrides

    CERN Document Server

    Bruderer, Simon; Stäuber, P; Doty, Steven D

    2010-01-01

    The Herschel Space Observatory opens the sky for observations in the far infrared at high spectral and spatial resolution. A particular class of molecules will be directly observable; light diatomic hydrides and their ions (CH, OH, SH, NH, CH+, OH+, SH+, NH+). These simple constituents are important both for the chemical evolution of the region and as tracers of high-energy radiation. If outflows of a forming star erode cavities in the envelope, protostellar far UV (FUV; 6 100 K) for water ice to evaporate. If the cavity shape allows FUV radiation to penetrate this hot-core region, the abundance of FUV destroyed species (e.g. water) is decreased. In particular, diatomic hydrides and their ions CH$+, OH+ and NH+ are enhanced by many orders of magnitude in the outflow walls due to the combination of high gas temperatures and rapid photodissociation of more saturated species. The enhancement of these diatomic hydrides is sufficient for a detection using the HIFI and PACS instruments onboard Herschel. The effect...

  2. Crassostrea virginica grazing on toxic and non-toxic diatoms.

    Science.gov (United States)

    Thessen, A E; Soniat, T M; Dortch, Q; Doucette, G J

    2010-01-01

    Despite high abundances of toxic Pseudo-nitzschia spp. over Louisiana oyster beds (Crassostrea virginica; eastern oyster) there have been no documented cases of amnesic shellfish poisoning (ASP) in the state. Two possible explanations are that oysters do not readily feed on long pointed chains of Pseudo-nitzschia cells or they discriminate against toxic cells while grazing. To test these hypotheses, short-term grazing experiments were conducted with several diatoms, including the domoic acid (DA)-producing Pseudo-nitzschia multiseries (1.31+/-0.057 pg DA cell(-1)) and the non-toxic Pseudo-nitzschia delicatissima, Thalassiosira weissflogii, and Ditylum brightwellii. Grazing rates on the small centric species T. weissflogii were significantly higher than on the larger and pointier D. brightwellii and either Pseudo-nitzschia species. Grazing on toxic P. multiseries and non-toxic P. delicatissima was not significantly different. Pseudofeces production was higher and feces production was occasionally lower in oysters fed Pseudo-nitzschia spp. than in oysters fed the other two diatoms. Our data demonstrate lower filtration rates of C. virginica on Pseudo-nitzschia spp. relative to the other diatoms tested and comparable filtration on toxic and non-toxic Pseudo-nitzschia spp. These findings suggest that eastern oysters do not discriminate amongst food types due to DA content. PMID:19835902

  3. Metapopulation Structure in the Planktonic Diatom Ditylum brightwellii (Bacillariophyceae).

    Science.gov (United States)

    Rynearson, Tatiana A; Lin, Ellen O; Armbrust, E Virginia

    2009-02-01

    Approximately 200,000 diatom species are thought to exist and yet the underlying processes of speciation in diatoms are unknown. Because genetic subdivision within species can reveal potential speciation mechanisms, we examined genetic differentiation and patterns of gene flow among four populations of the diatom Ditylum brightwellii. Single-cell isolates were examined at two microsatellite markers and two rDNA loci (18S and internal transcribed spacer region I (ITSI)). Among isolates, rDNA sequences varied by 0.08+/-0.04% (18S) and 0.7+/-0.3% (ITSI) and there were no compensatory base pair changes in the predicted ITSI secondary structure, all suggesting that a single species was represented. Two numerically dominant ITSI sequence types were detected and their distribution among isolates from genetically distinct populations was significantly different. Two populations shared ITSI sequence type 1 and two shared ITSI sequence type 2, indicating differences in relatedness among populations. The signature of unequal gene flow among populations suggested that D. brightwellii exhibited a metapopulation structure: the species was subdivided into populations of populations. The identification of metapopulations suggests a possible mechanism of speciation through reduced levels of gene flow, providing newly evolved taxa with a large repository of genetic and physiological diversity and perhaps significant adaptive potential. PMID:19083268

  4. Population dynamics of phytoplankton, heterotrophic bacteria, and viruses during the spring bloom in the western subarctic Pacific

    Science.gov (United States)

    Suzuki, Koji; Kuwata, Akira; Yoshie, Naoki; Shibata, Akira; Kawanobe, Kyoko; Saito, Hiroaki

    2011-05-01

    We characterized the community composition of phytoplankton in the western subarctic Pacific from the pre-bloom to the decline phase of the spring bloom with special reference to decreases in the silicic acid concentration in surface waters as an index for diatom bloom development. Furthermore, responses of heterotrophic bacteria and viruses to the spring bloom were also concomitantly investigated. Under pre-bloom conditions when nutrients were abundant but the surface mixed layer depth was relatively deep, chlorophyll (Chl) a concentrations were consistently low and green algae (chlorophytes and prasinophytes), cryptophytes, and diatoms were predominant in the phytoplankton assemblages as estimated by algal pigment signatures. Together with the shallowing of the mixed layer depth and the decrease in silicic acid concentration, diatoms bloomed remarkably in the Oyashio region, though the magnitude of the bloom in the Kuroshio-Oyashio transition (hereafter Transition) region was relatively small. A total of 77 diatom species were identified, with the bloom-forming diatoms mainly consisting of Thalassiosira, Chaetoceros, and Fragilariopsis species. It has become evident that the carotenoid fucoxanthin can serve as a strong indicator of the diatom carbon biomass during the spring diatom bloom. Differences in the species richness of diatoms among stations generally enabled us to separate the Oyashio bloom stations from the Transition and the Oyashio pre-bloom stations. Relatively high values of the Shannon-Wiener index for the diatom species were also maintained during the Oyashio bloom, indicating that a wide variety of species then shared dominance. In the decline phase of the Oyashio bloom when surface nutrient concentrations decreased, senescent diatom cells increased, as inferred from the levels of chlorophyllide a. Although the cell density of heterotrophic bacteria changed little with the development of the diatom bloom, viral abundance increased toward the end

  5. Positive Selection within a Diatom Species Acts on Putative Protein Interactions and Transcriptional Regulation

    OpenAIRE

    Koester, Julie A.; Swanson, Willie J.; Armbrust, E. Virginia

    2012-01-01

    Diatoms are the most species-rich group of microalgae, and their contribution to marine primary production is important on a global scale. Diatoms can form dense blooms through rapid asexual reproduction; mutations acquired and propagated during blooms likely provide the genetic, and thus phenotypic, variability upon which natural selection may act. Positive selection was tested using genome and transcriptome-wide pair-wise comparisons of homologs in three genera of diatoms (Pseudo-nitzschia,...

  6. Patterns of diatom treatment in two coexisting species of filter-feeding freshwater gastropods

    Directory of Open Access Journals (Sweden)

    Sitnikova T.Ya.

    2014-03-01

    Full Text Available To assess trophic partitioning among sympatric gastropod species in ancient lakes, we quantified diatoms in the guts of two coexistent Baikal gastropod species and tested for differences in species, size, and fracturing of large and small diatoms by taenioglossan radulae. In May 2010, the diatom Synedra acus dominated the littoral phytoplankton and gut contents of Baicalia turriformis and Teratobaikalia ciliata (Baicaliidae, both inhabiting the rocky Baikal littoral. In laboratory experiments, both ctenidial filter-feeding gastropods were fed with two diets of cultivated Synedra acus of different cell sizes: >150 μm and <100 μm. Field and laboratory studies revealed intact diatom cells (often with green chromatophores and fragmented frustules of diatoms <60 μm in the guts of both species. The two baicaliids varied in the number of ingested microalgae. In addition, they exhibited significantly different efficiencies for breaking large diatoms; B. turriformis broke large diatoms into more fragments than T. ciliata. The differences in the utilization of large and small diatoms by gastropods are discussed in terms of the relationships among coexisting species. Small diatom survival is considered from the view of interactions between producers and their consumers in the freshwater food web.

  7. How-to-Do-It: Diatoms: The Ignored Alga in High School Biology.

    Science.gov (United States)

    Hungerford, James J.

    1988-01-01

    Provides historical background, descriptions, uses and basis for identification of diatoms. Explains collection, dry-mount cleaning, and preparation procedures of the algae. Cites additional resources. (RT)

  8. Bioengineered Silicon Diatoms: Adding Photonic Features to a Nanostructured Semiconductive Material for Biomolecular Sensing

    Science.gov (United States)

    Rea, Ilaria; Terracciano, Monica; Chandrasekaran, Soundarrajan; Voelcker, Nicolas H.; Dardano, Principia; Martucci, Nicola M.; Lamberti, Annalisa; De Stefano, Luca

    2016-09-01

    Native diatoms made of amorphous silica are first converted into silicon structures via magnesiothermic process, preserving the original shape: electron force microscopy analysis performed on silicon-converted diatoms demonstrates their semiconductor behavior. Wet surface chemical treatments are then performed in order to enhance the photoluminescence emission from the resulting silicon diatoms and, at the same time, to allow the immobilization of biological probes, namely proteins and antibodies, via silanization. We demonstrate that light emission from semiconductive silicon diatoms can be used for antibody-antigen recognition, endorsing this material as optoelectronic transducer.

  9. 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

  10. 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...

  11. Structure factors for tunneling ionization rates of diatomic molecules

    International Nuclear Information System (INIS)

    Within the leading-order, single-active-electron, and frozen-nuclei approximation of the weak-field asymptotic theory, the rate of tunneling ionization of a molecule in an external static uniform electric field is determined by the structure factor for the highest occupied molecular orbital. We present the results of systematic calculations of structure factors for 40 homonuclear and heteronuclear diatomic molecules by the Hartree–Fock method using a numerical grid-based approach implemented in the program X2DHF

  12. Cell damage and recovery in cryopreserved microphytobenthic diatoms

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Anil, A.C.

    .cryobiol.2006.05.002 CSIR Senior Research fellowship awarded to S.M. * Corresponding author. Fax: +91 0 832 2450704. E-mail address: acanil@nio.org (A.C. Anil). –147 www.elsevier.com/locate/ycryo unication cryopreserved ic diatoms H22845 andrashekar Anil.... Mitbavkar, A.C. Anil / Cr from room temperature to a holding temperature at a known cooling rate [1,12]. Both these methods were employed in the presence and absence of a cryoprotectant. Through the use of these techniques, one can understand the role...

  13. Resting stage cells of diatoms in deep waters in Kumano-

    OpenAIRE

    AKIRA, ISHIKAWA; Shingo, Kitami; Ken-Ichiro, Ishii; Toru, NAKAMURA; ICHIRO, IMAI

    2011-01-01

    The abundance and species composition of viable resting stage cells of diatoms were investigated in deep waters (200,500 and 1,000 m depths) collected at neighboring stations in Kumano-Nada, central part of Japan, in April, August and October 2006. Viable resting stage cells were enumerated by the modified extinction dilution method [most probable number (MPN) method] based on incubation. Resting stage cells were detected from all samples, except at 500 m depth in August, in a range of abunda...

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

    DEFF Research Database (Denmark)

    Kokfelt, Ulla; Struyf, Eric; Randsalu, Linda

    2009-01-01

    Changes in hydrology and temperature can induce rapid changes in boreal wetland ecosystems. Factors such as hydrosere, permafrost, climate and human interference may disturb the prevailing mire vegetation, whereby a new dominant assemblage can develop. At the transition from one vegetation type...... content. Biogenic silica and other nutrients that would otherwise be lost during mineralization in runoff are in this way retained in the ecosystem. Our results imply that silica storage originating from diatoms can be expected to increase in today's rapidly changing boreal wetlands. The impacts...

  15. Extraction of high quality DNA from bloodstains using diatoms.

    Science.gov (United States)

    Günther, S; Herold, J; Patzelt, D

    1995-01-01

    A simple method is described for the extraction of high quality DNA for PCR amplification. The DNA was extracted by using Chelex-100 ion exchange resin or a special cell lysis buffer containing proteinase K. For further purification the DNA was bound to silica in the presence of a chaotrophic agent. Hence it is possible to unlimitedly wash the bound DNA and inhibitory substances are removed. By using diatoms as a source of silicates, this method is very economical and can therefore be used as a routine method.

  16. Ratchet dynamics of large polarons in asymmetric diatomic molecular chains.

    OpenAIRE

    Brizhik, L.; Eremko, A.; Piette, B.; Zakrzewski, W. J.

    2010-01-01

    We study the dynamics of large polarons in diatomic molecular chains, at zero temperature, under the influence of an external, periodic in time, electric field of zero mean value. We show that in asymmetric chains, i.e. chains with two different atoms per unit cell, a harmonic unbiased field causes a drift of such polarons. Such a drift current, known as the ratchet phenomenon, depends strongly on the parameters of the chain; in particular, on the extent of the anisotropy of the chain and on ...

  17. 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)

  18. 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) ...

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

    NARCIS (Netherlands)

    Rampen, S.W.

    2009-01-01

    Diatoms are one of the major groups of algae which originated relatively recently and evolved in the Late Jurassic/Cretaceous. This thesis presents the results of a comprehensive study of diatom lipids in cultures and in the environment and their applications in the age determination of petroleum an

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

    NARCIS (Netherlands)

    Rampen, S.W.

    2009-01-01

    Diatoms are one of the major groups of algae which originated relatively recently and evolved in the Late Jurassic/Cretaceous. This thesis presents the results of a comprehensive study of diatom lipids in cultures and in the environment and their applications in the age determination of petroleum an

  1. $\\Delta I=4$ and $\\Delta I=8$ bifurcations in rotational bands of diatomic molecules

    CERN Document Server

    Bonatsos, Dennis; Lalazissis, G A; Drenska, S B; Minkov, N; Raychev, P P; Roussev, R P; Bonatsos, Dennis

    1996-01-01

    It is shown that the recently observed $\\Delta I=4$ bifurcation seen in superdeformed nuclear bands is also occurring in rotational bands of diatomic molecules. In addition, signs of a $\\Delta I=8$ bifurcation, of the same order of magnitude as the $\\Delta I=4$ one, are observed both in superdeformed nuclear bands and rotational bands of diatomic molecules.

  2. Long-term pigment dynamics and diatom survival in dark sediment

    NARCIS (Netherlands)

    Veuger, B.; Van Oevelen, D.

    2011-01-01

    In order to investigate survival of diatoms and long-term pigment dynamics in dark sediment, we incubated samples of homogenized, sieved, tidal-flat sediment for 1 yr in darkness. Microscopic observations revealed that some diatoms survived the full year in darkness and retained their pigments. Conc

  3. Detection of immunocomplex formation by enhanced photoluminescence of antibody-functionalized diatom biosilica

    Science.gov (United States)

    Gale, Debra K.; Gutu, Timothy; Jiao, Jun; Chang, Chih-Hung; Rorrer, Gregory L.

    2009-05-01

    Diatoms are single-celled photosynthetic algae that make silica shells or "frustules" with intricate features patterned at the nano and microscales. In this study, antibody-functionalized diatom biosilica frustules serve as a biosensor platform for selective and label free antibody-antigen immunocomplex formation by enhanced photoluminescence. Biosilica frustules of 10 micron diameter were isolated from cells of the centric marine diatom Cyclotella sp. They were then mounted on glass and covalently functionalized with the model antibody Rabbit Immunoglobulin G (IgG) to yield a uniform nanostructured surface that selectively binds to its complimentary antigen, Goat anti-Rabbit IgG. Diatom frustules possess an intrinsic capacity to emit blue light when excited with a UV laser light source, a property called photoluminescence. Binding the antibody-functionalized diatom frustule with its complimentary antigen selectively enhanced the intrinsic photoluminescence intensity of the diatom frustule by a factor of three, whereas challenging the antibody-functionalized diatom frustule with a non-complimentary antigen, Goat anti-human IgG did not change the intrinsic photoluminescence intensity. The nucleophilic immunocomplex increases the photoluminescence by donating electrons to non-radiative sites on the photoluminescent diatom biosilica, thereby decreasing non-radiative electron decay and increasing radiative emission. The intensified photoluminescence intensity is correlated to the antigen, goat anti-rabbit IgG concentration, with a binding constant of 2.8 +/- 0.7x10-7 M.

  4. The fascinating diatom frustule—can it play a role for attenuation of UV radiation?

    DEFF Research Database (Denmark)

    Ellegaard, Marianne; Lenau, Torben Anker; Lundholm, Nina;

    2016-01-01

    size range as wave lengths of visible and ultraviolet (UV) light. This has prompted research into the possible role of the frustule in mediating light for the diatoms’ photosynthesis as well as into possible photonic applications of the diatom frustule. One of the possible biological roles, as well......, and applied perspective, including recent experimental data on UV transmission of diatom frustules....

  5. Biochemical and Genetic Engineering of Diatoms for Polyunsaturated Fatty Acid Biosynthesis

    Directory of Open Access Journals (Sweden)

    Hong-Ye Li

    2014-01-01

    Full Text Available The role of diatoms as a source of bioactive compounds has been recently explored. Diatom cells store a high amount of fatty acids, especially certain polyunsaturated fatty acids (PUFAs. However, many aspects of diatom metabolism and the production of PUFAs remain unclear. This review describes a number of technical strategies, such as modulation of environmental factors (temperature, light, chemical composition of culture medium and culture methods, to influence the content of PUFAs in diatoms. Genetic engineering, a newly emerging field, also plays an important role in controlling the synthesis of fatty acids in marine microalgae. Several key points in the biosynthetic pathway of PUFAs in diatoms as well as recent progresses are also a critical part and are summarized here.

  6. Calcareous nannoplankton and diatoms from the Eocene/Pliocene sediments, Fayoum depression, Egypt

    Science.gov (United States)

    Zalat, Abdelfattah A.

    1995-04-01

    Different assemblages of calcareous nannofossil and diatom taxa are detected in samples collected from sections at Shaqluf, Siela and Qaret El Faras in the Fayoum area. Five calcareous nannoplankton biozones are recorded: the Middle Eocene Discoaster tanii nodifer Zone, the Discoaster saipanensis Zone; the early, Late Eocene Chiasmolithus oamaruensis Zone; the Late Eocene Isthmolithus recurvus Zone and the Early Pliocene Reticulofenestra pseudoumbilicus Zone. Diatoms are recorded for the first time in the sections studied. The gradual changes in diatom composition from marine to brackish, ending with a well-developed, freshwater flora at the top of the Pliocene Shaqluf section, indicate changes in the palaeoecological conditions in the area during that time. In the Pliocene Siela and Qaret El Faras sections, all the identified diatom taxa belong to the freshwater assemblage together with some brackish water forms. The predominance of freshwater diatoms suggests that these taxa were introduced to the area with the sediments of the Palaeonile river during the Late Pliocene.

  7. 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...

  8. Surf zone diatoms: A review of the drivers, patterns and role in sandy beaches food chains

    Science.gov (United States)

    Odebrecht, Clarisse; Du Preez, Derek R.; Abreu, Paulo Cesar; Campbell, Eileen E.

    2014-10-01

    The accumulation of high biomass of diatoms in the surf zone is a characteristic feature of some sandy beaches where the wave energy is sufficiently high. A few species of diatoms, called surf diatoms, thrive in this harsh environment. The main processes driving the spatial and temporal distribution of surf diatoms as well as their standing biomass and growth were described twenty to thirty years ago based on studies conducted on the western coast of the United States of America and South African beaches. Since then, over fifty locations around the world have been reported to have surf diatom accumulations with most (three-quarters) of these being in the southern hemisphere. Their occurrence is controlled by physical and chemical factors, including wave energy, beach slope and length, water circulation patterns in the surf zone and the availability of nutrients to sustain the high biomass. The main forces driving the patterns of temporal variability of surf diatom accumulations are meteorological. In the short term (hours), the action of wind stress and wave energy controls the diatom accumulation. In the intermediate time scale (weeks to months), seasonal onshore winds of sufficient strength, as well as storm events are important. Furthermore, anthropogenic disturbances that influence the beach ecosystem as well as large-scale events, such as the El Niño Southern Oscillation, may lead to significant changes in surf diatom populations in the long term (inter-annual). Surf diatoms form the base of a short and very productive food chain in the inshore of the sandy beaches where they occur. However, the role of surf diatoms in the microbial food web is not clear and deserves further studies.

  9. New analytical potential energy function for doubly charged diatomic molecules

    Institute of Scientific and Technical Information of China (English)

    Wang Fan-Hou; Yang Chuan-Lu; Zhu Zheng-He; Jing Fu-Qian

    2005-01-01

    A new analytical potential function for doubly charged diatomic ions is proposed as V(R)=(∑k n=0anRn-1)exp(-ak+1R)+C/R,where an, ak+1 and C are parameters, and R is the nuclear distance. This function can be used to describe the potential curves for doubly charged diatomic ions with both potential minimum and maximum, or without any stationary point. As examples, potential functions of this form for ground states of BH2+, He22+ and HF2+ have been derived.The calculations using the theoretical method QCISD with basis set 6-311++G* have shown that the potential minimum of BH2+is at Rmin=0.147nm, the maximum at Rmax=0.185nm, and ΔE = Emax - Emin=0.062 eV; for He22+Rmin=0.0736nm, Rmax=0.105nm, and ΔE = Emax - Emin=0.71 eV. It is found that the potential curve for HF2+ is one with a singly repulsive branch. The force constants and spectroscopic data for BH2+ and He22+ have also been worked out.

  10. Underwater locomotion strategy by a benthic pennate diatom Navicula sp.

    Science.gov (United States)

    Wang, Jiadao; Cao, Shan; Du, Chuan; Chen, Darong

    2013-10-01

    The mechanism of diatom locomotion has been widely researched but still remains a hypothesis. There are several questionable points on the prevailing model proposed by Edgar, and some of the observed phenomena cannot be completely explained by this model. In this paper, we undertook detailed investigations of cell structures, locomotion, secreted mucilage, and bending deformation for a benthic pennate diatom Navicula species. According to these broad evidences, an updated locomotion model is proposed. For Navicula sp., locomotion is realized via two or more pseudopods or stalks protruded out of the frustules. The adhesion can be produced due to the pull-off of one pseudopod or stalk from the substratum through extracellular polymeric substances. And the positive pressure is generated to balance the adhesion because of the push-down of another pseudopod or stalk onto the substratum. Because of the positive pressure, friction is generated, acting as a driving force of locomotion, and the other pseudopod or stalk can detach from the substratum, resulting in the locomotion. Furthermore, this model is validated by the force evaluation and can better explain observed phenomena. This updated model would provide a novel aspect on underwater locomotion strategy, hence can be useful in terms of artificial underwater locomotion devices.

  11. Diatom vertical migration within land-fast Arctic sea ice

    Science.gov (United States)

    Aumack, C. F.; Juhl, A. R.; Krembs, C.

    2014-11-01

    Light levels inside first-year, landfast sea ice were experimentally altered by manipulating overlying snow depths. Irradiance available for ice algae growing near the ice-bottom, and under the ice, was highly dependent on snow depths ranging from 0 to > 30 cm. Importantly, algal vertical distributions also changed under different irradiances. Under thick snow (low light), the majority of algae were found several cm above the ice-seawater interface, while progressively more were found nearer the interface at locations with thinner overlying snow (higher light). Short-term field experiments suggested that ice algae were able to reposition themselves within the ice column within 3 days after manipulating snow depths. Laboratory gliding rate measurements of a cultured ice diatom suggested that it is capable of daily cm-scale movement. Vertical migration may help ice diatoms balance opposing light and nutrient resource gradients, similar to strategies used by some benthic and pelagic algae. Moreover, when ice algae congregate near the ice-seawater interface, they may be especially susceptible to loss from the ice environment. Vertical repositioning in response to changing light dynamics may be a mechanism to optimize between vertically-opposing environmental factors and help explain the connection between melting snow cover and export of biomass from sea ice.

  12. Photosystem II repair in marine diatoms with contrasting photophysiologies.

    Science.gov (United States)

    Lavaud, Johann; Six, Christophe; Campbell, Douglas A

    2016-02-01

    Skeletonema costatum and Phaeodactylum tricornutum are model marine diatoms with differing strategies for non-photochemical dissipation of excess excitation energy within photosystem II (PSII). We showed that S. costatum, with connectivity across the pigment bed serving PSII, and limited capacity for induction of sustained non-photochemical quenching (NPQ), maintained a large ratio of [PSII(Total)]/[PSII(Active)] to buffer against fluctuations in light intensity. In contrast, P. tricornutum, with a larger capacity to induce sustained NPQ, could maintain a lower [PSII(Total)]/[PSII(Active)]. Induction of NPQ was correlated with an active PSII repair cycle in both species, and inhibition of chloroplastic protein synthesis with lincomycin leads to run away over-excitation of remaining PSII(Active), particularly in S. costatum. We discuss these distinctions in relation to the differing capacities, induction and relaxation rates for NPQ, and as strain adaptations to the differential light regimes of their originating habitats. The present work further confirms the important role for the light-dependent fast regulation of photochemistry by NPQ interacting with PSII repair cycle capacity in the ecophysiology of both pennate and centric diatoms. PMID:26156125

  13. Potential role of large oceanic diatoms in new primary production

    Science.gov (United States)

    Goldman, Joel C.

    1993-01-01

    Very large phytoplankton species >50 μm in size, particularly diatoms, generally are found in background numbers throughout the euphotic zone of oceanic waters. Yet, when responding to episodic injections of new nutrients across the nutricline at the base of the euphotic zone these phototrophs may make a disproportionately large contribution to new primary production. To test this concept, we isolated a group of large diatoms from the Sargasso Sea and found that the specific growth rate of several of these species in culture was great enough at the ≈2% light level in oligotrophic waters to meet the requirements of several hypothetical scenarios in which annual rates of new production from the sum of one or more episodic blooms were equal to contemporary estimates. Two of the fast-growing species, Stephanopyxis palmeriana (Greville) Grunow and Pseudoguinardia recta von Stosch, formed giant flocculant masses while growing. Such masses could sink rapidly out of the euphotic zone or be a direct food source for invertebrates or fish higher up the food chain. Not only would a short, simple trophic system with low losses result, but the events would virtually be impossible to observe with conventional sampling.

  14. Interpretation of Diatom Assemblage Changes during the Last 30 ka and Preliminary Observations of Diatoms from D1 Deep-Drilling Samples, Lake El'gygytgyn, Siberia

    Science.gov (United States)

    Snyder, J. A.; Bryan, A.; Cherepanova, M.; Lake El'Gygytgyn Scientific Party

    2010-12-01

    Detailed diatom species assemblage determinations were conducted on samples spanning the last 30 ka of core Lz1024 collected in 2003 from Lake El’gygytgyn, northeastern Siberia. The main goals of these analyses are 1) to improve our understanding of past environmental changes in the lake during this well-studied interval 2) to provide guidance for future diatom investigations of the D1 deep drilling record collected in 2009. During MIS 2, the lake maintains a level of diatom productivity and diversity comparable to the Holocene in both plankton and periphyton. However, distinct species assemblage changes occur in both categories of diatoms associated with the transition from glacial to interglacial conditions. From 19-25 ka, omnipresent Cyclotella spp. occur with Asterionella formosa Hassall and other planktonic species suggestive of an enhanced nutrient status. In contrast, the unique large and robust diatom Pliocaenicus seczkinae Stachura-Suchoples, Genkal & Khursevich emerges as an important part of the plankton after ca. 15 ka, possibly reflecting an increase in open-water conditions. The assemblage of periphytic diatoms also changes dramatically during these intervals, suggesting changes in diatom habitats of the entire lake system. However, independent interpretation of shifts in the periphyton assemblage is difficult because of the uncertain ecological preferences for many of the abundant taxa, either unique or occurring uncommonly elsewhere. The diatoms may be responding to shifts in internal nutrient cycling in the lake associated with prolonged ice cover and lake stratification inferred during cold intervals. The deep-drilling samples, so far examined to 50 m below lake floor (1.3 million years according to preliminary age models), exhibit repeated genus-level shifts in dominant plankton and changes in abundance of both periphytic and planktonic diatoms. Some of the recent dominant taxa persist through most of the lake record while others have a more

  15. 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.

  16. Investigation of the hydrodynamic behavior of diatom aggregates using particle image Velocimetry

    Institute of Scientific and Technical Information of China (English)

    Feng Xiao; Xiaoyan Li; Kitming Lam; Dongsheng Wang

    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 colunm 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 floculation between the aggregates and other small particles including algal cells in water.

  17. Water quality assessment of the DTD canal system by diatom indices

    Directory of Open Access Journals (Sweden)

    Jakovljević Olga S.

    2014-01-01

    Full Text Available The main objective of this paper is to evaluate the water quality based on diatom indices in the study area of the Danube-Tisa-Danube (DTD canal system. We used four diatom indices: Watanabe’s index (DAIpo, biological diatom index (BDI or IBD, the trophic diatom index (TDI and index of pollution sensitivity (IPS. Benthic samples were collected in the spring and autumn 2002 and 2003 from nine sampling sites. The standard method with concentrated sulfuric acid was used for treatment of the algological samples [Krammer and Lange-Bertalot 1986] and then permanent slides of diatoms were made. The abundance was estimated by counting 400 valves of each taxa present on slide [Round 1991, 1993]. Investigation of the DTD canal system resulted in description of 145 diatom taxa. Based on the indicator values of identified taxa we calculated four diatom indices (DAIpo, BDI, TDI and IPS and estimated water quality in the study area of the DTD canal system. [[Projekat Ministarstva nauke Republike Srbije, br. TR 037009

  18. The evolution of advanced mechanical defenses and potential technological applications of diatom shells.

    Science.gov (United States)

    Hamm, Christian E

    2005-01-01

    Diatoms are unicellular algae with silicified cell walls, which exhibit a high degree of symmetry and complexity. Their diversity is extraordinarily high; estimates suggest that about 10(5) marine and limnic species may exist. Recently, it was shown that diatom frustules are mechanically resilient, statically sophisticated structures made of a tough glass-like composite. Consequently, to break the frustules, predators have to generate large forces and invest large amounts of energy. In addition, they need feeding tools (e.g., mandibles or gastric mills) which are hard, tough, and resilient enough to resist high stress and wear, which are bound to occur when they feed on biomineralized objects such as diatoms or other biomineralized protists. Indeed, many copepods feeding on diatoms possess, in analogy to the enamelcoated teeth of mammals, amazingly complex, silica-laced mandibles. The highly developed adaptations both to protect and to break diatoms indicate that selection pressure is high to optimize material properties and the geometry of the shells to achieve mechanical strength of the overall structure. This paper discusses the mechanical challenges which force the development of mechanical defenses, and the structural components of the diatom frustules which indicate that evolutionary optimization has led to mechanically sophisticated structures. Understanding the diatom frustule from the nanometer scale up to the whole shell will provide new insights to advanced combinations of nanostructured composite ceramic materials and lightweight architecture for technological applications.

  19. 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.

  20. Influence of cobalamin scarcity on diatom molecular physiology and identification of a cobalamin acquisition protein.

    Science.gov (United States)

    Bertrand, Erin M; Allen, Andrew E; Dupont, Christopher L; Norden-Krichmar, Trina M; Bai, Jing; Valas, Ruben E; Saito, Mak A

    2012-06-26

    Diatoms are responsible for ~40% of marine primary production and are key players in global carbon cycling. There is mounting evidence that diatom growth is influenced by cobalamin (vitamin B(12)) availability. This cobalt-containing micronutrient is only produced by some bacteria and archaea but is required by many diatoms and other eukaryotic phytoplankton. Despite its potential importance, little is known about mechanisms of cobalamin acquisition in diatoms or the impact of cobalamin scarcity on diatom molecular physiology. Proteomic profiling and RNA-sequencing transcriptomic analysis of the cultured diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana revealed three distinct strategies used by diatoms to cope with low cobalamin: increased cobalamin acquisition machinery, decreased cobalamin demand, and management of reduced methionine synthase activity through changes in folate and S-adenosyl methionine metabolism. One previously uncharacterized protein, cobalamin acquisition protein 1 (CBA1), was up to 160-fold more abundant under low cobalamin availability in both diatoms. Autologous overexpression of CBA1 revealed association with the outside of the cell and likely endoplasmic reticulum localization. Cobalamin uptake rates were elevated in strains overexpressing CBA1, directly linking this protein to cobalamin acquisition. CBA1 is unlike characterized cobalamin acquisition proteins and is the only currently identified algal protein known to be implicated in cobalamin uptake. The abundance and widespread distribution of transcripts encoding CBA1 in environmental samples suggests that cobalamin is an important nutritional factor for phytoplankton. Future study of CBA1 and other molecular signatures of cobalamin scarcity identified here will yield insight into the evolution of cobalamin utilization and facilitate monitoring of cobalamin starvation in oceanic diatom communities. PMID:22652568

  1. 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 (lakes, ordination analysis identified that nitrate, specific conductance, total 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 (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.

  2. 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

  3. Diatoms from the Quaternary sediments of the Nile Delta, Egypt, and their palaeoecological significance

    Science.gov (United States)

    Zalat, Abdelfattah A.

    1995-02-01

    This study represents the first contribution describing diatom taxa from the Quaternary sediments of the Nile Delta, Egypt. A total of 99 diatom species and varieties belonging to 28 genera were identified. The palaeoecological conditions during the time of deposition (pH salinity, eutrophication and dissolved silica concentration) are discussed. Deposition of the Quaternary Nile Delta sediments occurred in slightly alkaline, fresh water of oligohalobian type, which was of variable trophic status with a high dissolved silica concentration. The variations visible in the ratio of planktic to epiphytic and benthic diatoms generally reflect shallow environments with water-level changes related to climatic fluctuations.

  4. On the Occurrence of Four Diatom Taxa from Eastern India with a Taxonomic Note

    Directory of Open Access Journals (Sweden)

    Jai Prakash Keshri

    2016-01-01

    Full Text Available Diatoms were collected from the Kotulpur area of West Bengal. Four diatom taxa, namely, Eunotia minor (Kützing Grunow, Achnanthidium minutissimum (Kützing Czarnecki, Lemnicola hungarica (Grunow Round and Basson, and Navicula radiosa Kützing were observed using scanning electron microscopy (SEM and identified in light of modern diatom taxonomic trends. Except Eunotia minor, all these taxa are new records to Eastern India. A note on the taxonomy of Achnanthes pseudobiasolletiana as described by Gandhi and Eunotia serrata var. diadema (Ehr. R. M. Patrick as reported by Dwivedi and Misra has been added.

  5. Partition Functions for Diatomic Molecules in Plasmas out of Thermal Equilibrium

    Institute of Scientific and Technical Information of China (English)

    Geraldine FAURE

    2012-01-01

    Two calculation methods on the partition functions for diatomic molecules in plas- mas out of thermal equilibrium are reported. A Boltzmann distribution for the electronic, vi- brational and rotational quantum levels is assumed in the two calculation methods. The results obtained by two methods are displayed for four sorts of diatomic molecules, 02, N2, OH and NO, that are present in humid air plasmas. The calculation method of density for the electronically excited states is developed. Finally, a method to calculate the partition functions for simulating the non-normalized diatomic spectra is discussed.

  6. Spectral Analysis of Two Coupled Diatomic Rotor Molecules

    Directory of Open Access Journals (Sweden)

    Horace T. Crogman

    2014-10-01

    Full Text Available In a previous article the theory of frame transformation relation between Body Oriented Angular (BOA states and Lab Weakly Coupled states (LWC was developed to investigate simple rotor–rotor interactions. By analyzing the quantum spectrum for two coupled diatomic molecules and comparing it with spectrum and probability distribution of simple models, evidence was found that, as we move from a LWC state to a strongly coupled state, a single rotor emerges in the strong limit. In the low coupling, the spectrum was quadratic which indicates the degree of floppiness in the rotor–rotor system. However in the high coupling behavior it was found that the spectrum was linear which corresponds to a rotor deep in a well.

  7. Quantum control of vibrational excitations in a heteronuclear diatomic molecule

    Indian Academy of Sciences (India)

    Sitansh Sharma; Purshotam Sharma; Harjinder Singh

    2007-09-01

    Optimal control theory is applied to obtain infrared laser pulses for selective vibrational excitation in a heteronuclear diatomic molecule. The problem of finding the optimized field is phrased as a maximization of a cost functional which depends on the laser field. A time dependent Gaussian factor is introduced in the field prior to evaluation of the cost functional for better field shape. Conjugate gradient method21,24 is used for optimization of constructed cost functional. At each instant of time, the optimal electric field is calculated and used for the subsequent quantum dynamics, within the dipole approximation. The results are obtained using both Morse potential as well as potential energy obtained using ab initio calculations.

  8. Direct signature of light-induced conical intersections in diatomics

    CERN Document Server

    Halász, Gábor J; Cederbaum, Lorenz S

    2014-01-01

    Nonadiabatic effects are ubiquitous in physics, chemistry and biology. They are strongly amplified by conical intersections (CIs) which are degeneracies between electronic states of triatomic or larger molecules. A few years ago it has been revealed that CIs in molecular systems can be formed by laser light even in diatomics. Due to the prevailing strong nonadiabatic couplings, the existence of such laser-induced conical intersections (LICIs) may considerably change the dynamical behavior of molecular systems. By analyzing the photodissociation process of the D2+ molecule carefully, we found a robust effect in the angular distribution of the photofragments which serves as a direct signature of the LICI providing undoubted evidence for its existence.

  9. Paulsenella Chatton (Dinophyta), ectoparasites of marine diatoms: development and taxonomy

    Science.gov (United States)

    Drebes, G.; Schnepf, E.

    1988-09-01

    All members of the dinophyte Paulsenella are ectoparasites on marine planktonic diatoms. At present three species are known, two of which are described here for the first time. The taxonomy of the type species, P. chaetoceratis, is paid critical attention. The species are clearly distinguished by their host specificity and additionally by differences in morphology, especially of the trophonts. Using clonal cultures the life cycles of the three species are compared. The vegetative development may be interrupted by formation of temporary and resting cysts. In ageing cultures, stages with nuclear cyclosis occur, believed to indicate meiosis. In P. vonstoschii, the meiospores are capable of developing into resting cysts. As yet, knowledge on sexual reproduction is still incomplete.

  10. Atom-diatom scattering dynamics of spinning molecules.

    Science.gov (United States)

    Eyles, C J; Floss, J; Averbukh, I Sh; Leibscher, M

    2015-01-14

    We present full quantum mechanical scattering calculations using spinning molecules as target states for nuclear spin selective atom-diatom scattering of reactive D+H2 and F+H2 collisions. Molecules can be forced to rotate uni-directionally by chiral trains of short, non-resonant laser pulses, with different nuclear spin isomers rotating in opposite directions. The calculations we present are based on rotational wavepackets that can be created in this manner. As our simulations show, target molecules with opposite sense of rotation are predominantly scattered in opposite directions, opening routes for spatially and quantum state selective scattering of close chemical species. Moreover, two-dimensional state resolved differential cross sections reveal detailed information about the scattering mechanisms, which can be explained to a large degree by a classical vector model for scattering with spinning molecules. PMID:25591357

  11. Stable Langmuir solitons in plasma with diatomic ions

    Directory of Open Access Journals (Sweden)

    M. Dvornikov

    2013-08-01

    Full Text Available We study stable axially and spherically symmetric spatial solitons in plasma with diatomic ions. The stability of a soliton against collapse is provided by the interaction of induced electric dipole moments of ions with the rapidly oscillating electric field of a plasmoid. We derive the new cubic-quintic nonlinear Schrödinger equation, which governs the soliton dynamics and numerically solve it. Then we discuss the possibility of implementation of such plasmoids in realistic atmospheric plasma. In particular, we suggest that spherically symmetric Langmuir solitons, described in the present work, can be excited at the formation stage of long-lived atmospheric plasma structures. The implication of our model for the interpretation of the results of experiments for the plasmoids generation is discussed.

  12. Asymmetric wave transmission in a diatomic acoustic/elastic metamaterial

    Science.gov (United States)

    Li, Bing; Tan, K. T.

    2016-08-01

    Asymmetric acoustic/elastic wave transmission has recently been realized using nonlinearity, wave diffraction, or bias effects, but always at the cost of frequency distortion, direction shift, large volumes, or external energy. Based on the self-coupling of dual resonators, we propose a linear diatomic metamaterial, consisting of several small-sized unit cells, to realize large asymmetric wave transmission in low frequency domain (below 1 kHz). The asymmetric transmission mechanism is theoretically investigated, and numerically verified by both mass-spring and continuum models. This passive system does not require any frequency conversion or external energy, and the asymmetric transmission band can be theoretically predicted and mathematically controlled, which extends the design concept of unidirectional transmission devices.

  13. Thermodynamic and kinetic properties of some diatomic gases

    Science.gov (United States)

    Holbrook, Robert Thomas, III

    1997-11-01

    In this work, the thermodynamic and kinetic properties of some diatomic gases are calculated and analyzed. In chapter 1, the partition functions of the species composing a dissociating and ionizing iodine vapor, specifically those for homonuclear diatomic 127I127I molecules, 127I atoms, 127I+ ions, and free electrons, are calculated. These partition functions are subsequently used in statistical mass action equations to determine the local thermal equilibrium dissociation degree a and the ionization degree φ of the iodine vapor over the temperature range 700 DyF, HoF, and TmF. Such systems are composed of seven different species: LnF and F2 molecules (Ln≡Dy, Ho, and Tm), LnF+ molecular ions, Ln and F atoms, LnF+ atomic ions, and free electrons. Once again, the partition functions are calculated for the various species and used in statistical expressions to determine the local thermal equilibrium compositions and thermodynamic properties of the LnF-based gas mixtures for the temperature range 3000 <= T/ /le 9000 K and initial molecular number densities 1014, 1016, and 1018 cm-3. Finally, in chapter 3, the Monte Carlo trajectory method is used to study the probabilities P(Vr, b, v1, J1, v2, J2) for dissociation via collisions between two ground electronic state X1Σ(0g+) I2 molecules. The two molecules interact with an impact parameter b and a relative speed Vr. The incident molecule is in the vibrational-rotational state specified by the vibrational quantum number v1 and the rotational quantum number J1 while the target molecule is in the state specified by the quantum numbers v2 and J2.

  14. Marine diatoms sustain growth of bivalves in a Mediterranean lagoon

    Science.gov (United States)

    Pernet, Fabrice; Malet, Nathalie; Pastoureaud, Annie; Vaquer, André; Quéré, Claudie; Dubroca, Laurent

    2012-02-01

    Carbon stable isotopes and fatty acids were measured in the suspended particulate organic matter (POM) of the Thau lagoon to study its qualitative temporal changes in relation to environmental factors and to identify the food sources of bivalves over a one-yr-cycle in relation to their growth. Reciprocally, the impact of shellfish farming on POM was also studied. Oysters and mussels were sampled and measured for biometry, stable isotopes and fatty acid composition. Water samples were collected at two sites, both inside and outside of the shellfish farming area, to determine concentrations in POM, chlorophyll a (Chl a) and stable isotopes. Carbon isotopes and fatty acids in bivalves reflected seasonal changes in food sources, which varied consistently with the environment. Seasonal changes in δ13C and fatty acids in the bivalves suggested that dietary phytoplankton contribution varied according to season. Terrestrial organic matter and bacteria can contribute to the diet of bivalves during non-bloom periods. Mussels seemed to rely more on diatoms and less on terrestrial organic matter and bacteria than oysters did, particularly when phytoplankton biomass was low during the summer. Although one- and two-yr-old oysters showed similar δ13C, their fatty acid dynamics differed slightly. Periods of high growth rate in bivalves were mainly fuelled by diatoms, thus highlighting the importance of seasonal blooms of microphytoplankton during the critical period of bivalve growth and gamete production. Although there was no significant effect of shellfish farms on Chl a and POM δ13C, consistent differences indicate that stable isotopes could be used successfully to investigate the effects of bivalve aquaculture.

  15. Stability conditions of diatomic molecules in Heisenbergs picture: inspired from the stability theory of lasers

    CERN Document Server

    Jahanpanah, Jafar

    2015-01-01

    The vibrational motion equations of both homo and hetero-nuclei diatomic molecules are here derived for the first time. A diatomic molecule is first considered as a one dimensional quantum mechanics oscillator. The second and third-order Hamiltonian operators are then formed by substituting the number operator for the quantum number in the corresponding vibrational energy eigenvalues. The expectation values of relative position and linear momentum operators of two oscillating atoms are calculated by solving Heisenbergs equations of motion. Subsequently, the expectation values of potential and kinetics energy operators are evaluated in all different vibrational levels of Morse potential. On the other hand, the stability theory of optical oscillators (lasers) is exploited to determine the stability conditions of an oscillating diatomic molecule.It is peculiarly turned out that the diatomic molecules are exactly dissociated at the energy level in which their equations of motion become unstable. We also determine...

  16. 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

    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 nondisruptive system. Chlorophyll autofluorescence can be used to distinguish different photoautotrophic groups if the correct excitation light is applied. Using this principle, a nonintrusive technique was developed to study the spatial distribution of benthic cyanobacteria and diatoms. By means...... of a charge coupled device camera, diatoms and cyanobacteria could be identified by blue light (470 nm) excitation and amber light (600 nm) excitation, respectively. By this approach, diatom or cyanobacterial dominance could be easily distinguished using the blue over amber ratio. We applied this method...

  17. Study of the mechanism of diatom cell division by means of 29Si isotope tracing

    International Nuclear Information System (INIS)

    Diatoms are delicate unicellular organisms enclosed in a silica frustule, that is made up of two valves. Multiplication of the diatoms occurs by ordinary mitotic cell division. During cell division each cell produces two daughter cells, each of them keeping one of the two valves of the mother cell and producing a new valve by absorbing the silicon present in the environment. The NanoSIMS 50 allows ion imaging to be performed on diatoms in order to determine the site of fixation of silicon. The aim of this study was to observe and compare the mechanism of the construction of the new valve after cell division. To this end, different types of diatoms have been transferred in a culture medium enriched with 29Si and after several days, the distribution of the different isotopes of silicon has been determined by NanoSIMS50 imaging. The construction of new valves has been observed and the isotopic ratio has been determined

  18. Wetland Paleoecological Study of Coastal Louisiana: Surface Sediment and Diatom Calibration Dataset

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Wetland sediment data was collected from coastal Louisiana as part of a pilot study to develop a diatom-based proxy for past wetland water chemistry and the...

  19. 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.

  20. Wetland Paleoecological Study of Coastal Louisiana: Sediment Cores and Diatom Samples Dataset

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Wetland sediment data was collected from coastal Louisiana as part of a pilot study to develop a diatom-based proxy for past wetland water chemistry and the...

  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. UVB radiation modifies protein and photosynthetic pigment content, volume and ultrastructure of marine diatoms

    NARCIS (Netherlands)

    Buma, AGJ; Zemmelink, HJ; Sjollema, K; Gieskes, WWC

    1996-01-01

    Three marine diatom species (Cyclotella sp., Nitzschia closterium and Thalassiosira nordenskioldii) were exposed to a range of daily doses of ultraviolet B radiation (UVBR: 280-320 nm). The lowest UVBR treatments (

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

    Energy Technology Data Exchange (ETDEWEB)

    Rampen, S.W.

    2009-06-11

    Diatoms are one of the major groups of algae which originated relatively recently and evolved in the Late Jurassic/Cretaceous. This thesis presents the results of a comprehensive study of diatom lipids in cultures and in the environment and their applications in the age determination of petroleum and in palaeoenvironmental studies. Diatom DNA sequences were analyzed in order to relate the phylogenetic positions of diatoms to the lipid chemotaxonomy. Forty four different sterols were identified in diatoms, with 24-methylcholesta-5,24(28)-dien-3-beta-ol being most common. 24-Methylcholesta-5,22E-dien-3-beta-ol, previously described as a diatom biomarker, was only the fifth most common sterol and absent in some major diatom groups. All identified sterols have been reported in other algae, but within the diatoms, some sterols and sterol compositions seem to be specific for specific phylogenetic clusters. Sterol compositions confirmed the separate phylogenetic position of the genus Attheya, as also indicated by molecular phylogeny and microscopy. 23-Methyl and 23,24-dimethyl sterols, often associated with dinoflagellate algae, were present in a substantial number of diatoms, suggesting that diatoms may also be a major source. Their phylogenetic position suggests that these diatoms originated from a single common ancestor which evolved in the late Jurassic. In addition to 23-methyl and 23,24-dimethyl sterols, the unusual sterol gorgosterol was found in two diatom cultures of the genus Delphineis. 24-Norsterols were found in the diatom species Thalassiosira aff. antarctica and in dinoflagellate cultures. The evolutionary history of dinoflagellates and diatoms explains the stepwise increases of 24-norsterane concentrations, diagenetic products of 24-norsterols, in petroleum. Long-chain 1,14-diols and 12-hydroxy methyl alkanoates were detected in Proboscia diatoms and may be used as indicators for high-nutrient conditions and upwelling. Their distributions varied between

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

    Science.gov (United States)

    Le, Thi Duy Hanh; Bonani, Walter; Speranza, Giorgio; Sglavo, Vincenzo; Ceccato, Riccardo; Maniglio, Devid; Motta, Antonella; Migliaresi, Claudio

    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.

  5. 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.

    prior to bacteria (Skerman, 1956; O’ Neil & Wilcox, 1971). However, some studies have shown that although the presence of the bacterial film may facilitate the attachment of diatoms, it is not a pre-requisite (Horbund & Freiberger, 1970; Cooksey et al.... 1980). Further, diatom metabolic activities have been shown to provide the sole carbon and energy source for heterotrophic bacteria in films where both types of organisms are present (Murray et al. 1986). These microfilms are responsible...

  6. Solid self-emulsifying phospholipid suspension (SSEPS) with diatom as a drug carrier.

    Science.gov (United States)

    Milović, Mladen; Simović, Spomenka; Lošić, Dušan; Dashevskiy, Andriy; Ibrić, Svetlana

    2014-10-15

    We report the application of diatom as a solid carrier for water insoluble drugs applied in oral drug delivery system based on the self-emulsifying drug delivery system (SEDDS) caprylocaproyl macrogol-8 glycerides/lecithin/propylene glycol/caprylic/capric triglyceride. Diatoms are fossilized skeletons of photosynthetic algae with complex 3-dimensional (3D), porous structure consisting of amorphous silica, obtained by purification of diatomaceous earth. Different solid samples of carbamazepine (CBZ) suspension in SEDDS, called solid self-emulsifying phospholipid suspension (SSEPS), were prepared using two methods: adsorption of CBZ dispersion in SEDDS by gentle mixing with diatoms in mortar with pestle (Method A) or dispersion of diatoms in ethanol solution of CBZ and SEDDS components, followed by ethanol evaporation (Method B). Release rate of CBZ from SSEPS was significantly higher in comparison to pure drug, physical mixture of diatoms and CBZ as well as solid dispersion of pure CBZ and diatoms obtained by ethanol evaporation. The dissolution of CBZ from SSEPS sample prepared using method B was faster than from the sample prepared by the method A. Higher dissolution for sample prepared by the method B can be attributed to the partial adsorption (deeper localization) of liquid material inside the pores of diatoms. Upon storage of the samples under accelerated conditions (40°C and 70% RH) for 10 weeks no significant changes in CBZ crystallinity and dissolution was in case of SSEPS, contrary to solid dispersion with increased crystallinity, indicating that diatoms with adsorbed liquid CBZ-loaded SEPS can maintain initial CBZ characteristics. PMID:25125211

  7. The model marine diatom Thalassiosira pseudonana likely descended from a freshwater ancestor in the genus Cyclotella

    Directory of Open Access Journals (Sweden)

    Julius Matthew L

    2011-05-01

    Full Text Available Abstract Background Publication of the first diatom genome, that of Thalassiosira pseudonana, established it as a model species for experimental and genomic studies of diatoms. Virtually every ensuing study has treated T. pseudonana as a marine diatom, with genomic and experimental data valued for their insights into the ecology and evolution of diatoms in the world's oceans. Results The natural distribution of T. pseudonana spans both marine and fresh waters, and phylogenetic analyses of morphological and molecular datasets show that, 1 T. pseudonana marks an early divergence in a major freshwater radiation by diatoms, and 2 as a species, T. pseudonana is likely ancestrally freshwater. Marine strains therefore represent recent recolonizations of higher salinity habitats. In addition, the combination of a relatively nondescript form and a convoluted taxonomic history has introduced some confusion about the identity of T. pseudonana and, by extension, its phylogeny and ecology. We resolve these issues and use phylogenetic criteria to show that T. pseudonana is more appropriately classified by its original name, Cyclotella nana. Cyclotella contains a mix of marine and freshwater species and so more accurately conveys the complexities of the phylogenetic and natural histories of T. pseudonana. Conclusions The multitude of physical barriers that likely must be overcome for diatoms to successfully colonize freshwaters suggests that the physiological traits of T. pseudonana, and the genes underlying those traits, might differ from those of strictly marine diatoms. The freshwater ancestry of T. pseudonana might therefore confound generalizations about the physiological and metabolic properties of marine diatoms. The freshwater component of T. pseudonana's history merits careful consideration in the interpretation of experimental data collected for this important model species.

  8. Radiolarian and Diatom Fluxes in Two California Borderland Basins as Indices of Climate Variability

    OpenAIRE

    Weinheimer, Amy L.

    1994-01-01

    The diversity, wide ranging habitats, and endemism of diatoms and radiolarians make them useful biological indicators of physical oceanography. The unique varved sediment (yearly layers) of the Santa Monica and Santa Barbara Basins (SMB and SBB, respectively) in the Southern California Borderland permits analysis of the diatom and radiolarian record at an annual resolution. In addition to the high resolution record preserved in the sediment, present-day teleconnections suggest that climate va...

  9. Role of diatoms in the spatial-temporal distribution of intracellular nitrate in intertidal sediment.

    Directory of Open Access Journals (Sweden)

    Peter Stief

    Full Text Available 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 Wadden Sea and are potentially involved in anaerobic nitrate respiration. Intracellular nitrate (ICNO3 was present year-round in the sediment and was spatially and temporally correlated with fucoxanthin, the marker photopigment of diatoms. Pyrosequencing of SSU rRNA genes of all domains of life confirmed that ICNO3 storage was most likely due to diatoms rather than other known nitrate-storing microorganisms (i.e., large sulfur bacteria and the eukaryotic foraminifers and gromiids. Sedimentary ICNO3 concentrations reached up to 22.3 µmol dm(-3 at the sediment surface and decreased with sediment depth to negligible concentrations below 5 cm. Similarly, the ICNO3/fucoxanthin ratio and porewater nitrate (PWNO3 concentrations decreased with sediment depth, suggesting that ICNO3 of diatoms is in equilibrium with PWNO3, but is enriched relative to PWNO3 by 2-3 orders of magnitude. Cell-volume-specific ICNO3 concentrations in a diatom mat covering the sediment surface during spring were estimated at 9.3-46.7 mmol L(-1. Retrieval of 18S rRNA gene sequences related to known nitrate-storing and nitrate-ammonifying diatom species suggested that diatoms in dark and anoxic sediment layers might be involved 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.

  10. 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.

  11. Electroless Gold-Modified Diatoms as Surface-Enhanced Raman Scattering Supports

    Science.gov (United States)

    Pannico, Marianna; Rea, Ilaria; Chandrasekaran, Soundarrajan; Musto, Pellegrino; Voelcker, Nicolas H.; De Stefano, Luca

    2016-06-01

    Porous biosilica from diatom frustules is well known for its peculiar optical and mechanical properties. In this work, gold-coated diatom frustules are used as low-cost, ready available, functional support for surface-enhanced Raman scattering. Due to the morphology of the nanostructured surface and the smoothness of gold deposition via an electroless process, an enhancement factor for the p-mercaptoaniline Raman signal of the order of 105 is obtained.

  12. Tracking the sterol biosynthesis pathway of the diatom Phaeodactylum tricornutum

    OpenAIRE

    Fabris, M; Matthijs, M.; Carbonelle, S.; Moses, T.; Pollier, J.; Dasseville, R.; Baart, G.J.E.; Vyverman, W.; Goossens, A

    2014-01-01

    Diatoms are unicellular photosynthetic microalgae that play a major role in global primary production and aquatic biogeochemical cycling. Endosymbiotic events and recurrent gene transfers uniquely shaped the genome of diatoms, which contains features from several domains of life. The biosynthesis pathways of sterols, essential compounds in all eukaryotic cells, and many of the enzymes involved are evolutionarily conserved in eukaryotes. Although well characterized in most eukaryotes, the path...

  13. 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...

  14. Electroless Gold-Modified Diatoms as Surface-Enhanced Raman Scattering Supports.

    Science.gov (United States)

    Pannico, Marianna; Rea, Ilaria; Chandrasekaran, Soundarrajan; Musto, Pellegrino; Voelcker, Nicolas H; De Stefano, Luca

    2016-12-01

    Porous biosilica from diatom frustules is well known for its peculiar optical and mechanical properties. In this work, gold-coated diatom frustules are used as low-cost, ready available, functional support for surface-enhanced Raman scattering. Due to the morphology of the nanostructured surface and the smoothness of gold deposition via an electroless process, an enhancement factor for the p-mercaptoaniline Raman signal of the order of 10(5) is obtained. PMID:27356562

  15. GENERAL FEATURES OF PHOTOPROTECTION BY ENERGY DISSIPATION IN PLANKTONIC DIATOMS (BACILLARIOPHYCEAE)

    OpenAIRE

    Lavaud, Johann; Rousseau, Bernard; Etienne, Anne-Lise

    2004-01-01

    International audience; Planktonic diatoms (Bacillariophyceae) have to cope with large fluctuations of light intensity and periodic exposure to high light. After a shift to high light, photoprotective dissipation of excess energy characterized by the non-photochemical quenching of fluorescence (NPQ) and the concomitant de-epoxidation of diadinoxanthin to diatoxanthin (DT) were measured in four different planktonic marine diatoms (Bacillariophyceae): Skeletonema costatum (Greville) Cleve, Cyli...

  16. Protection of cells from salinity stress by extracellular polymeric substances in diatom biofilms

    OpenAIRE

    Steele, Deborah J.; Franklin, Daniel J.; Underwood, Graham J.C.

    2014-01-01

    Diatom biofilms are abundant in the marine environment. It is assumed (but untested) that extracellular polymeric substances (EPS), produced by diatoms, enable cells to cope with fluctuating salinity. To determine the protective role of EPS, Cylindrotheca closterium was grown in xanthan gum at salinities of 35, 50, 70 and 90 ppt. A xanthan matrix significantly increased cell viability (determined by SYTOX-Green), growth rate and population density by up to 300, 2,300 and 200%, respectively. D...

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

    Science.gov (United States)

    Mitbavkar, Smita; Anil, Arga Chandrashekar

    2007-01-01

    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 meagre. In this regard, a study was carried out by transferring natural diatom biofilms into controlled conditions in order to understand the roles of nutrients, initial cell inoculum and seasonal variation in species composition in structuring the fouling diatom community. This community exhibited seasonal variation during the monsoon, post-monsoon and pre-monsoon periods. During each of these seasons, diatom species interactions varied depending upon the species composition. It was observed that excess nutrients favoured those species with comparatively higher growth rates, thereby suppressing the growth of other co-existing species. This competitive trait was found to be effective at an appropriate cell density ratio of the competitive and target species. Understanding such pathways will be useful for modelling the interactions between diatom species in various habitats under different resource conditions.

  18. Diatom acclimation to elevated CO2 via cAMP signalling and coordinated gene expression

    Science.gov (United States)

    Hennon, Gwenn M. M.; Ashworth, Justin; Groussman, Ryan D.; Berthiaume, Chris; Morales, Rhonda L.; Baliga, Nitin S.; Orellana, Mónica V.; Armbrust, E. V.

    2015-08-01

    Diatoms are responsible for ~40% of marine primary productivity, fuelling the oceanic carbon cycle and contributing to natural carbon sequestration in the deep ocean. Diatoms rely on energetically expensive carbon concentrating mechanisms (CCMs) to fix carbon efficiently at modern levels of CO2 (refs , , ). How diatoms may respond over the short and long term to rising atmospheric CO2 remains an open question. Here we use nitrate-limited chemostats to show that the model diatom Thalassiosira pseudonana rapidly responds to increasing CO2 by differentially expressing gene clusters that regulate transcription and chromosome folding, and subsequently reduces transcription of photosynthesis and respiration gene clusters under steady-state elevated CO2. These results suggest that exposure to elevated CO2 first causes a shift in regulation, and then a metabolic rearrangement. Genes in one CO2-responsive cluster included CCM and photorespiration genes that share a putative cAMP-responsive cis-regulatory sequence, implying these genes are co-regulated in response to CO2, with cAMP as an intermediate messenger. We verified cAMP-induced downregulation of CCM gene δ-CA3 in nutrient-replete diatom cultures by inhibiting the hydrolysis of cAMP. These results indicate an important role for cAMP in downregulating CCM and photorespiration genes under elevated CO2 and provide insights into mechanisms of diatom acclimation in response to climate change.

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

    Science.gov (United States)

    D'Costa, Priya M.; Anil, Arga Chandrashekar

    2010-07-01

    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 consecutive post-monsoons (2001 and 2002) and the intervening pre-monsoon at Mumbai and Jawaharlal Nehru ports along the central west coast of India. Characteristic temporal shifts in diatom community structure were observed across the sampling periods; these were mainly driven by temperature, salinity and dissolved oxygen saturation. The nutrient-poor pre-monsoon period supported low abundance yet high species richness and diversity of diatoms. Coscinodiscus, Cyclotella, Thalassiosira, Triceratium, Pleurosigma, Skeletonema and Surirella were the most dominant genera. Both the post-monsoon periods, following dissimilar monsoon events, were dominated by Skeletonema costatum, but differed in some of the residual species . Thalassiosira and Thalassionema spp. dominated mostly during post-monsoon I whereas Triceratium and Pleurosigma spp. dominated during post-monsoon II. To understand the underlying ecological mechanisms involved in such dynamics, we focus on the dominant diatom species in post-monsoon periods, S. costatum, that contributes up to 60% to total diatom cell numbers. This research is relevant in light of the fluctuating monsoon regimes over the Asian continent, the confounding effects of anthropogenic eutrophication and the resulting cascading effects on trophic web dynamics.

  20. 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.

  1. 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.

  2. Impact of Irgarol 1051 on the larval development and metamorphosis of Balanus amphitirite Darwin, diatom, Amphora coffeaformis and natural biofilm

    Digital Repository Service at National Institute of Oceanography (India)

    Desai, D.V.

    (Daley and Hobbie 1975). Development of diatom biofilm A. coffeaformis was cultured in f/2 medium (Guillard 1975). When visible diatom films had formed in the culture flask, the biofilm was removed by brushing the culture flask with a sterile..., 2 ml aliquots of the diatom suspension was inoculated into the 24 well multiwells which were gently shaken for a period of 24 hours. The multiwell plates were then rinsed three times using autoclaved filtered seawater. The films developed without...

  3. Auxosporulation in Paralia guyana MacGillivary (Bacillariophyta and Possible New Insights into the Habit of the Earliest Diatoms.

    Directory of Open Access Journals (Sweden)

    Irena Kaczmarska

    Full Text Available Diatoms are one of the most ecologically important aquatic micro-eukaryotes. As a group unambiguously recognized as diatoms, they seem to have appeared relatively recently with a limited record of putative remains from oldest sediments. In contrast, molecular clock estimates for the earliest possible emergence of diatoms suggest a considerably older date. Depending on the analysis, Paralia and Leptocylindrus have been recovered within the basal molecular divergences of diatoms. Thus these genera may be in the position to inform on characters that the earliest diatoms possessed.Here we present auxospore development and structure of initial and post-auxospore cells in a representative of the ancient non-polar centric genus Paralia. Their initial frustules showed unusual, but not unprecedented, spore-like morphology. Similarly, initial frustules of Leptocylindrus have been long considered resting spores and a unique peculiarity of this genus. However, even though spore-like in appearance, initial cells of Paralia readily resumed mitotic divisions. In addition, Paralia post-auxospore cells underwent several rounds of mitoses in a multi-step process of building a typical, "perfect" vegetative valve. This degree of heteromorphy immediately post-auxosporulation is thus far unknown among the diatoms.A spore-related origin of diatoms has already been considered, most recently in the form of the "multiplate diploid cyst" hypothesis. Our discovery that the initial cells in some of the most ancient diatom lineages are structurally spore-like is consistent with that hypothesis because the earliest diatoms may be expected to look somewhat similar to their ancestors. We speculate that because the earliest diatoms may have appeared less diatom-like and more spore-like, they could have gone unrecognized as such in the Triassic/Jurassic sediments. If correct, diatoms may indeed be much older than the fossil record indicates, and possibly more in line with some

  4. The last glacial-interglacial cycle in Lake Ohrid (Macedonia/Albania): testing diatom response to climate

    OpenAIRE

    J. M. Reed; Cvetkoska, A.; Z. Levkov; H. Vogel; Wagner, B.

    2010-01-01

    Lake Ohrid is a site of global importance for palaeoclimate research. This study presents results of diatom analysis of a ca. 136 ka sequence, Co1202, from the northeast of the lake basin. It offers the opportunity to test diatom response across two glacial-interglacial transitions and within the Last Glacial, while setting up taxonomic protocols for future research. The results are outstanding in demonstrating the sensitivity of diatoms to climate change, providing proxy evidence for tempera...

  5. Long range intermolecular forces in triatomic systems: connecting the atom-diatom and atom-atom-atom representations

    OpenAIRE

    Cvitas, Marko T.; Soldan, Pavel; Hutson, Jeremy M.

    2005-01-01

    The long-range forces that act between three atoms are analysed in both atom-diatom and atom-atom-atom representations. Expressions for atom-diatom dispersion coefficients are obtained in terms of 3-body nonadditive coefficients. The anisotropy of atom-diatom C_6 dispersion coefficients arises primarily from nonadditive triple-dipole and quadruple-dipole forces, while pairwise-additive forces and nonadditive triple-dipole and dipole-dipole-quadrupole forces contribute significantly to atom-di...

  6. Influence of environmental and spatial factors on the distribution of surface sediment diatoms in Chaohu Lake, southeast China

    OpenAIRE

    Chen, Xu; YANG, XIANGDONG; Dong, Xuhui; Enfeng LIU

    2012-01-01

    The spatial distribution of surface sediment diatoms in Chaohu Lake (southeast China), and their relationships with environmental and spatial variables were analyzed in this study. The diatom assemblages were dominated by planktonic species. Three dominant species Cyclostephanos dubius, Aulacoseira granulata and Aulacoseira alpigenaare unevenly distributed across the lake. The distribution of surface sediment diatoms must be subject to trophic status, hydrodynamics and other spatial variables...

  7. Hydroclimatic modulation of diatom/Phaeocystis blooms in nutrient-enriched Belgian coastal waters (North Sea)

    OpenAIRE

    Breton, E.; Rousseau, V.; Parent, J.-Y.; Ozer, J.; C. Lancelot

    2006-01-01

    Statistical analysis of 14 yr (1988-2001) of intensive phytoplankton monitoring at Station 330 in the central Belgian Coastal Zone (BCZ, Southern Bight of the North Sea) indicates that the long-term diatom biomass trend and the spring dominance of Phaeocystis colonies over diatoms are determined by the combined effect of the North Atlantic Oscillation (NAO) and freshwater and continental nitrate carried by the Scheldt. The strong correlation between diatoms and the NAO index is largely explai...

  8. 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.

  9. Controlling a diatomic shape resonance with non-resonant light

    CERN Document Server

    Aganoglu, Ruzin; Friedrich, Bretislav; González-Férez, Rosario; Koch, Christiane P

    2011-01-01

    A (diatomic) shape resonance is a metastable state of a pair of colliding atoms quasi-bound by the centrifugal barrier imposed by the angular momentum involved in the collision. The temporary trapping of the atoms' scattering wavefunction corresponds to an enhanced atom pair density at low interatomic separations. This leads to larger overlap of the wavefunctions involved in a molecule formation process such as photoassociation, rendering the process more efficient. However, for an ensemble of atoms, the atom pair density will only be enhanced if the energy of the resonance comes close to the temperature of the atomic ensemble. Herein we explore the possibility of controlling the energy of a shape resonance by shifting it toward the temperature of atoms confined in a trap. The shifts are imparted by the interaction of non-resonant light with the anisotropic polarizability of the atom pair, which affects both the centrifugal barrier and the pair's rotational and vibrational levels. We find that at laser intens...

  10. Functional Relationship between a Dinoflagellate Host and Its Diatom Endosymbiont.

    Science.gov (United States)

    Hehenberger, Elisabeth; Burki, Fabien; Kolisko, Martin; Keeling, Patrick J

    2016-09-01

    While we know much about the evolutionary patterns of endosymbiotic organelle origins, we know less about how the actual process unfolded within each system. This is partly due to the massive changes endosymbiosis appears to trigger, and partly because most organelles evolved in the distant past. The dinotoms are dinoflagellates with diatom endosymbionts, and they represent a relatively recent but nevertheless obligate endosymbiotic association. We have carried out deep sequencing of both the host and endosymbiont transcriptomes from two dinotoms, Durinskia baltica and Glenodinium foliaceum, to examine how the nucleocytosolic compartments have functionally integrated. This analysis showed little or no functional reduction in either the endosymbiont or host, and no evidence for genetic integration. Rather, host and endosymbiont seem to be bound to each other via metabolites, such as photosynthate exported from the endosymbiont to the host as indicated by the presence of plastidic phosphate translocators in the host transcriptome. The host is able to synthesize starch, using plant-specific starch synthases, as a way to store imported photosynthate. PMID:27297471

  11. Purification of a diatom and its identification to Cylindrotheca closterium

    Science.gov (United States)

    Wang, Song; Zhang, Lin; Yang, Guanpin; Zhu, Baohua; Pan, Kehou

    2015-04-01

    A diatom was purified with colony selection and continuous dilution methods. It was identified to Cylindrotheca closterium according to its morphological characteristics and rbcL and 18s rRNA gene sequences. The alga was not sensitive to ampicillin and neomycin, but sensitive to chloramphenicol which inhibited its growth at concentrations ranging from 50 to 150 μg mL-1. The purified alga was easy to culture and its specific growth rate was 0.207 ± 0.002 (d-1). It was resistant to pollution and could be harvested in an easy way. It was relatively high in lipid content (20.08% ± 0.67% of dry weight) and the combined amount of its 16:0 and 16:1 (n-7), the most suitable resource of biodiesel, was as high as 64% of the total fatty acids, while the amount of polyunsaturated fatty acids reached 19.96%-20% of the total fatty acids. Thus the purified C. closterium can be cultured as a biodiesel producer or a nutrition supplement producer.

  12. Diatom attachment inhibition: limiting surface accessibility through air entrapment.

    Science.gov (United States)

    Wu, Alex H-F; Nakanishi, Kenichi; Cho, K L; Lamb, Robert

    2013-12-01

    Surfaces consisting of sub micron holes (0.420-0.765 μm) engineered into nanoparticle (12 nm) coatings were examined for marine antifouling behaviour that defines early stage settlement. Immersed surfaces were found to be resistant to a 5-hour attachment assay of Amphora coffeaeformis, a marine organism commonly found in abundance on fouled substrates such as foul-releasing paints and self-polishing coatings. Attachment inhibition was attributed to the accessibility of diatoms to the surface. This was governed by the size and morphology of trapped interfacial air pockets measured in-situ using synchrotron small angle x-ray scattering. Surfaces containing larger pores (0.765 μm) exhibited the highest resistance. Macroscopic wettability via contact angle measurements however remained at 160° and sliding angle of < 5° and was found to be independent of pore size and not indicative of early stage fouling behaviour. The balance of hierarchical nano/micro length scales was critical in defining the early stage stability of biofouling character of the interface. PMID:24706117

  13. Theory of rotational transition in atom-diatom chemical reaction

    Science.gov (United States)

    Nakamura, Masato; Nakamura, Hiroki

    1989-05-01

    Rotational transition in atom-diatom chemical reaction is theoretically studied. A new approximate theory (which we call IOS-DW approximation) is proposed on the basis of the physical idea that rotational transition in reaction is induced by the following two different mechanisms: rotationally inelastic half collision in both initial and final arrangement channels, and coordinate transformation in the reaction zone. This theory gives a fairy compact expression for the state-to-state transition probability. Introducing the additional physically reasonable assumption that reaction (particle rearrangement) takes place in a spatially localized region, we have reduced this expression into a simpler analytical form which can explicitly give overall rotational state distribution in reaction. Numerical application was made to the H+H2 reaction and demonstrated its effectiveness for the simplicity. A further simplified most naive approximation, i.e., independent events approximation was also proposed and demonstrated to work well in the test calculation of H+H2. The overall rotational state distribution is expressed simply by a product sum of the transition probabilities for the three consecutive processes in reaction: inelastic transition in the initial half collision, transition due to particle rearrangement, and inelastic transition in the final half collision.

  14. Ratchet dynamics of large polarons in asymmetric diatomic molecular chains

    Energy Technology Data Exchange (ETDEWEB)

    Brizhik, L S; Eremko, A A [Bogolyubov Institute for Theoretical Physics, 03680 Kyiv (Ukraine); Piette, B M A G; Zakrzewski, W J, E-mail: brizhik@bitp.kiev.u, E-mail: eremko@bitp.kiev.u, E-mail: B.M.A.G.Piette@durham.ac.u, E-mail: W.J.Zakrzewski@durham.ac.u [Department of Mathematical Sciences, University of Durham, Durham DH1 3LE (United Kingdom)

    2010-04-21

    We study the dynamics of large polarons in diatomic molecular chains, at zero temperature, under the influence of an external, periodic in time, electric field of zero mean value. We show that in asymmetric chains, i.e. chains with two different atoms per unit cell, a harmonic unbiased field causes a drift of such polarons. Such a drift current, known as the ratchet phenomenon, depends strongly on the parameters of the chain; in particular, on the extent of the anisotropy of the chain and on the size of the polaron. Moreover, the drift takes place only if the intensity and the period of the field exceed some critical values which also depend on the parameters of the chain. We show that this directed current of polarons is a complicated phenomenon. It takes place in dissipative systems with a broken spatial symmetry and is generated by the interplay between the Peierls-Nabarro barrier and the impact of the external field on the charged polarons. The dependence of the amplitude of the polaron oscillations, the size of the drift per period of the external field and the average velocity are determined as a function of the intensity of the field and of its frequency.

  15. Revisiting Zeno's paradox: Flying arrows for atom-diatom reactions

    CERN Document Server

    Sanz-Sanz, C; Gonzalez-Lezana, T; Roncero, O; Miret-Artes, S

    2011-01-01

    The possibility to observe quantum Zeno and anti-Zeno scenarios for atom-diatom reactive collisions is investigated for two diferent processes (F+HD and H+O_2) by means of time-dependent wave packet propagations. A novel approach is proposed in which the survival probabilities investigated are those obtained when the initial state is redefined after time intervals tau at which measurements are performed on the system. The comparison with the actual probability for the unperturbed system reveals the existence of a regime in which the decay from the initial state appears to be inhibited (the quantum Zeno effect) or accelerated (the anti-Zeno effect). In contrast with preceding interpretations, given that the time-evolving wave packet is not affected at any time ("flying arrow"), the present procedure does not require to invoke to counterintuitive hindered evolutions ("stopping arrow") to explain the results. On the contrary the consecutive update of the reference state of the system solves the apparent modern v...

  16. Hidden thin layers of toxic diatoms in a coastal bay

    Science.gov (United States)

    Timmerman, Amanda H. V.; McManus, Margaret A.; Cheriton, O. M.; Cowen, Robert K.; Greer, Adam T.; Kudela, Raphael M.; Ruttenberg, Kathleen; Sevadjian, Jeff

    2014-03-01

    Harmful algal blooms (HABs) can threaten animal and human health through the production of toxins such as domoic acid. These blooms have become more frequent and toxic over the last few decades. In this study, we investigate the role that nutrients play in a toxic, subsurface bloom of Pseudo-nitzschia in northeastern Monterey Bay, California. Profilers and towed instruments were deployed and laboratory analyses of discrete water samples were conducted to describe the physical and biogeochemical conditions of the sampling site and to characterize the bloom. The subsurface Pseudo-nitzschia bloom occurred within a well-defined layer, containing high levels of domoic acid. In situ images taken within the layer revealed diatom flocs—indicators of nutrient stress. Nutrient ratios and alkaline phosphatase activity, commonly used to determine the nutritional status of phytoplankton, suggest that the Pseudo-nitzschia cells were phosphate stressed, and we speculate that this physiological stress led to increased toxicity of the bloom. Understanding how frequently blooms such as these are characterized by nutrient stress could improve our ability to predict the occurrence of HABs. With increased anthropogenic input of nutrients, such blooms could occur more often and with greater degrees of toxicity in the future.

  17. Ultrastructure of the Periplastidial Compartment of the Diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Flori, Serena; Jouneau, Pierre-Henri; Finazzi, Giovanni; Maréchal, Eric; Falconet, Denis

    2016-06-01

    Diatoms contain a secondary plastid that derives from a red algal symbiont. This organelle is limited by four membranes. The two outermost membranes are the chloroplast endoplasmic reticulum membrane (cERM), which is continuous with the host outer nuclear envelope, and the periplastidial membrane (PPM). The two innermost membranes correspond to the outer and inner envelope membranes (oEM and iEM) of the symbiont's chloroplast. Between the PPM and oEM lies a minimized symbiont cytoplasm, the periplastidial compartment (PPC). In Phaeodactylum tricornutum, PPC-resident proteins are localized in "blob-like-structures", which remain associated with plastids after cell disruption. We analyzed disrupted Phaeodactylum cells by focused ion beam scanning electron microscopy, revealing the presence of a vesicular network (VN) in the PPC, at a location consistent with blob-like structures. Presence of a VN in the PPC was confirmed in intact cells. Additionally, direct membrane contacts were observed between the PPM and nuclear inner envelope membrane at the level of the chloroplast-nucleus isthmus. This study provides insights into the PPC ultrastructure and opens perspectives on the function of this residual cytoplasm of red algal origin. PMID:27179349

  18. Ratchet dynamics of large polarons in asymmetric diatomic molecular chains

    International Nuclear Information System (INIS)

    We study the dynamics of large polarons in diatomic molecular chains, at zero temperature, under the influence of an external, periodic in time, electric field of zero mean value. We show that in asymmetric chains, i.e. chains with two different atoms per unit cell, a harmonic unbiased field causes a drift of such polarons. Such a drift current, known as the ratchet phenomenon, depends strongly on the parameters of the chain; in particular, on the extent of the anisotropy of the chain and on the size of the polaron. Moreover, the drift takes place only if the intensity and the period of the field exceed some critical values which also depend on the parameters of the chain. We show that this directed current of polarons is a complicated phenomenon. It takes place in dissipative systems with a broken spatial symmetry and is generated by the interplay between the Peierls-Nabarro barrier and the impact of the external field on the charged polarons. The dependence of the amplitude of the polaron oscillations, the size of the drift per period of the external field and the average velocity are determined as a function of the intensity of the field and of its frequency.

  19. An efficient screening method for the isolation of heterotrophic bacteria influencing growth of diatoms under photoautotrophic conditions.

    Science.gov (United States)

    Zecher, Karsten; Jagmann, Nina; Seemann, Philipp; Philipp, Bodo

    2015-12-01

    Interactions between photoautotrophic diatoms and heterotrophic bacteria are important for the biogeochemical C-cycle in the oceans. Additionally, biofilms formed by diatoms and bacteria are the initiating step of biofouling processes, which causes high costs in shipping. Despite this ecological and economical importance, the knowledge about biochemical and molecular mechanisms underlying these interkingdom interactions is relatively small. For analyzing these mechanisms, laboratory model systems are required. In this study, an efficient screening method for isolating bacteria influencing photoautotrophic diatom growth was established. First, diatom cultures of Phaeodactylum tricornutum and Thalassiosira pseudonana were made axenic by applying β-lactam antibiotics. Second, a non-invasive method for measuring growth of multiple parallel diatom cultures by chlorophyll fluorescence was established. This method allowed semi-quantitative chlorophyll determination of cultures with up to 3 μg (chlorophyll) ml(-1). Axenic diatom cultures were then used for enriching bacteria and led to the isolation of 24 strains influencing growth of both diatom strains in various ways. For example, Rheinheimera sp. strain Tn16 inhibited growth of T. pseudonana, while it stimulated growth and cell aggregation of P. tricornutum. Thus, this screening method is appropriate for isolating heterotrophic bacteria showing different interactions with different diatom species ranging from synergistic to antagonistic. In consecutive applications, this method will be useful to screen for bacterial mutants with altered phenotypes regarding the influence on diatom growth.

  20. Vast laminated diatom mat deposits from the west low-latitude Pacific Ocean in the last glacial period

    Institute of Scientific and Technical Information of China (English)

    ZHAI Bin; LI Tie Gang; CHANG Feng Ming; CAO Qi Yuan

    2009-01-01

    Diatoms are one of the predominant contributors to global carbon fixation by accounting for over 40% of total oceanic primary production and dominate export production. They play a significant role in marine biogeochemistry cycle. The diatom mat deposits are results of vast diatoms bloom. By analysis of diatom mats in 136°00'-140°00'E, 15°00'-21°00'N, Eastern Philippines Sea, we identified the spe-cies of the diatoms as giant Ethmodiscus rex (Wallich) Hendey. AMS ~(14)C dating shows that the sedi-ments rich in diatom mats occurred during 16000-28600 a B.P., which means the bloom mainly occurred during the last glacial period, while there are no diatom mat deposits in other layers. Preliminary analysis indicates that Antarctic Intermediate Water (AAIW) expanded northward and brought silicate-rich water into the area, namely, silicon leakage processes caused the bloom of diatoms. In addition, the increase of iron input is one of the main reasons for the diatom bloom.

  1. Dominance by a canopy forming seaweed modifies resource and consumer control of bloom-forming macroalgae

    NARCIS (Netherlands)

    Eriksson, Britas Klemens; Rubach, Anja; Hillebrand, Helmut

    2007-01-01

    Degradation of ecological resources by large-scale disturbances highlights the need to demonstrate biological properties that increase resistance to change and promote the resilience of ecosystem regimes. Coastal eutrophication is a global-scale disturbance that drives ecosystem change by increasing

  2. Intraspecific Variation in Growth and Morphology of the Bloom-Forming Cyanobacterium Microcystis aeruginosa▿

    OpenAIRE

    Wilson, Alan E.; Wilson, Whitney A.; Hay, Mark E.

    2006-01-01

    In the laboratory, we documented large variation in the morphology, toxicity, and maximum population growth rates for 32 Microcystis aeruginosa strains isolated from 12 lakes. Growth rates and mean colony sizes varied significantly across strains and were positively correlated. However, growth rates were unrelated to toxin production.

  3. Ocean Acidification Accelerates the Growth of Two Bloom-Forming Macroalgae.

    Directory of Open Access Journals (Sweden)

    Craig S Young

    Full Text Available While there is growing interest in understanding how marine life will respond to future ocean acidification, many coastal ecosystems currently experience intense acidification in response to upwelling, eutrophication, or riverine discharge. Such acidification can be inhibitory to calcifying animals, but less is known regarding how non-calcifying macroalgae may respond to elevated CO2. Here, we report on experiments performed during summer through fall with North Atlantic populations of Gracilaria and Ulva that were grown in situ within a mesotrophic estuary (Shinnecock Bay, NY, USA or exposed to normal and elevated, but environmentally realistic, levels of pCO2 and/or nutrients (nitrogen and phosphorus. In nearly all experiments, the growth rates of Gracilaria were significantly increased by an average of 70% beyond in situ and control conditions when exposed to elevated levels of pCO2 (p0.05. The δ13C content of both Gracilaria and Ulva decreased two-to-three fold when grown under elevated pCO2 (p<0.001 and mixing models demonstrated these macroalgae experienced a physiological shift from near exclusive use of HCO3- to primarily CO2 use when exposed to elevated pCO2. This shift in carbon use coupled with significantly increased growth in response to elevated pCO2 suggests that photosynthesis of these algae was limited by their inorganic carbon supply. Given that eutrophication can yield elevated levels of pCO2, this study suggests that the overgrowth of macroalgae in eutrophic estuaries can be directly promoted by acidification, a process that will intensify in the coming decades.

  4. Compensatory growth of the bloom-forming dinoflagellate Prorocentrum donghaiense induced by nitrogen stress

    Directory of Open Access Journals (Sweden)

    Honghui Zhu

    2013-02-01

    Full Text Available Although the phenomenon of compensatory growth has been documented in someanimals and higher plants, little information is available on its manifestation in marinemicroalgae. We have conducted the first study on the compensatory growth of the red tide causative dinoflagellate Prorocentrumdonghaiense after its recovery from different nitrogen concentrations.The results showed that NaNO3 concentrations of 0 and 7.5 mg l-1 significantly reduced thegrowth of P. donghaiense, as compared to 37.5 and 75 mg l-1. When the microalgal cells were returned to 75 mg l-1, they exhibited subsequent compensatory growth. The most significant compensatory growth was found in those cells previously experiencing 0 mg dm3, followed by 7.5 mg dm3, indicating thatcompensatory growth depended on the extent of nitrogen stress they had been subjected to. Our results suggest thatcompensatory growth can be induced in the marine microalga P. donghaiense after its recovery from nitrogen fluctuation, and that this should be taken into consideration in the prevalence of P. donghaiense blooms in coastal waters.

  5. Ocean Acidification Accelerates the Growth of Two Bloom-Forming Macroalgae

    Science.gov (United States)

    Young, Craig S.; Gobler, Christopher J.

    2016-01-01

    While there is growing interest in understanding how marine life will respond to future ocean acidification, many coastal ecosystems currently experience intense acidification in response to upwelling, eutrophication, or riverine discharge. Such acidification can be inhibitory to calcifying animals, but less is known regarding how non-calcifying macroalgae may respond to elevated CO2. Here, we report on experiments performed during summer through fall with North Atlantic populations of Gracilaria and Ulva that were grown in situ within a mesotrophic estuary (Shinnecock Bay, NY, USA) or exposed to normal and elevated, but environmentally realistic, levels of pCO2 and/or nutrients (nitrogen and phosphorus). In nearly all experiments, the growth rates of Gracilaria were significantly increased by an average of 70% beyond in situ and control conditions when exposed to elevated levels of pCO2 (p0.05). The δ13C content of both Gracilaria and Ulva decreased two-to-three fold when grown under elevated pCO2 (p<0.001) and mixing models demonstrated these macroalgae experienced a physiological shift from near exclusive use of HCO3- to primarily CO2 use when exposed to elevated pCO2. This shift in carbon use coupled with significantly increased growth in response to elevated pCO2 suggests that photosynthesis of these algae was limited by their inorganic carbon supply. Given that eutrophication can yield elevated levels of pCO2, this study suggests that the overgrowth of macroalgae in eutrophic estuaries can be directly promoted by acidification, a process that will intensify in the coming decades. PMID:27176637

  6. Effects of Bloom-Forming Algae on Fouling of Integrated Membrane Systems in Seawater Desalination

    Science.gov (United States)

    Ladner, David Allen

    2009-01-01

    Combining low- and high-pressure membranes into an integrated membrane system is an effective treatment strategy for seawater desalination. Low-pressure microfiltration (MF) and ultrafiltration (UF) membranes remove particulate material, colloids, and high-molecular-weight organics leaving a relatively foulant-free salt solution for treatment by…

  7. Interactive effects of ocean acidification and nitrogen limitation on two bloom-forming dinoflagellate species

    NARCIS (Netherlands)

    Eberlein, T.; Van de Waal, D.B.; Brandenburg, Karen M.; John, U.; Voss, M.; Achterberg, E.P.; Rost, B.

    2016-01-01

    Global climate change involves an increase in oceanic CO2 concentrations as well as thermal stratification of the water column, thereby reducing nutrient supply from deep to surface waters. Changes in inorganic carbon (C) or nitrogen (N) availability have been shown to affect marine primary producti

  8. Diatoms as Proxies for a Fluctuating Holocene Ice Cap Margin in Hvitarvatn, Iceland

    Science.gov (United States)

    Black, J. L.; Miller, G. H.; Geirsdottir, A.

    2006-12-01

    Hvitarvatn is a glacier-dominated lake located on the eastern margin of Langjokull, Iceland's second largest ice cap. Hvitarvatn is ideally positioned to provide a continuous record of Holocene climate change as 1) glacial erosion and soft bedrock result in high lacustrine sedimentation rates, 2) diagnostic tephras of known age aid the geochronology, and 3) a relatively flat ice-cap profile responds sensitively to small climate-driven changes in the equilibrium line altitude (ELA). The erosive power of Langjokull and the efficient delivery system of these glacial sediments into Hvitarvatn are the dominant factors affecting both the nutrient and light availability in the lake. Any perturbations to the lake system, such as large fluctuations of the ice cap margin, result in a swift response in the diatom community due to the rapid growth and immigration rates of diatoms. The Holocene diatom assemblages preserved in Hvitarvatn sediments are a key proxy for recording Iceland's sensitivity to changes in North Atlantic circulation and addressing whether Iceland's large ice caps disappeared in the early Holocene, and if they did, when they re-grew. The presence of the Saksunarvatn tephra in the Hvitarvatn sediments indicates the lake was deglaciated by 10,300 yr BP. The Holocene Thermal Maximum (HTM) is represented in the lake sediments by an abundant, diverse benthic diatom population that dominated Hvitarvatn between 6000-9000 yr BP. A resurgence of ice cap activity around 6000 yr BP is reflected by a shift to a planktonic diatom assemblage composed mostly of Aulacoseira subarctica. Langjokull grew to its largest Holocene extent during the LIA and reached its maximum between 150-300 yr BP. Diatom assemblages during the LIA are largely composed of Aulacoseira islandica and Aulacoseira subarctica, reflecting extremely low light and turbid water conditions.The diatom assemblages in Hvitarvatn indicate very large environmental changes occurred during the Holocene in Iceland.

  9. 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.

  10. Effect of hydrological variability on diatom distribution in Poyang Lake, China

    Science.gov (United States)

    Qian, Kuimei; Liu, Xia; Chen, Yuwei

    2016-04-01

    Poyang Lake is the largest freshwater lake in China, and it has a seasonal flooding cycle that significantly changes the water level every year. The aim of this paper was to explain how these hydrological changes influence diatom populations in Poyang Lake. The yearly hydrological cycle can be divided into 4 phases: low water-level phase, increasing water-level phase, high water-level phase and decreasing water-level phase. Variations in the abundance of planktonic diatoms were studied using quarterly monitoring data collected from January 2009 to October 2013. Generally, diatoms were dominant in Poyang Lake and accounted for more than 50% of the total phytoplankton biomass except in July 2009 (26%) and January 2012 (35%). Aulacoseira granulata and Surirella robusta were the predominant species in all four phases, and they accounted for 25.02% to 56.89% and 5.07% to 14.78% of the total phytoplankton biomass, respectively. A redundancy analysis (RDA) showed that changes in physico-chemical parameter were related to the water level, and changes in diatom biomass were related to nitrite levels and pH. These results indicate that changes in environmental parameters related to both seasonal variations and water-level fluctuations caused variations in diatom biomass and community composition in Poyang Lake. Furthermore, extreme hydrological events can have diff erent influences on the diatom community composition in the main channel and lentic regions. This research provides data on the diatom variations in Poyang Lake and will be useful for establishing biological indicators of environmental change and protecting Poyang Lake in the future.

  11. B content and Si/C ratios from cultured diatoms (Thalassiosira pseudonana and Thalassiosira weissflogii): Relationship to seawater pH and diatom carbon acquisition

    Science.gov (United States)

    Mejía, Luz María; Isensee, Kirsten; Méndez-Vicente, Ana; Pisonero, Jorge; Shimizu, Nobumichi; González, Cristina; Monteleone, Brian; Stoll, Heather

    2013-12-01

    Despite the importance of diatoms in regulating climate and the existence of large opal-containing sediments in key air-ocean exchange areas, most geochemical proxy records are based on carbonates. Among them, Boron (B) content and isotopic composition have been widely used to reconstruct pH from foraminifera and coral fossils. We assessed the possibility of a pH/CO2 seawater concentration control on B content in diatom opal to determine whether or not frustule B concentrations could be used as a pH proxy or to clarify algae physiological responses to acidifying pH. We cultured two well-studied diatom species, Thalassiosira pseudonana and Thalassiosira weissflogii at varying pH conditions and determined Si and C quotas. Frustule B content was measured by both laser-ablation inductively coupled mass spectrometry (LA-ICPMS) and secondary ion mass spectrometry (SIMS/ion probe). For both species, frustules grown at higher pH have higher B contents and higher Si requirements per fixed C. If this trend is representative of diatom silicification in a future more acidic ocean, it could contribute to changes in the efficiency of diatom ballasting and C export, as well as changes in the contribution of diatoms relative to other phytoplankton groups in Si-limited regions. If B enters the cell through the same transporter employed for HCO3- uptake, an increased HCO3- requirement with decreasing CO2 concentrations (higher pH), and higher B(OH)4/HCO3- ratios would explain the observed increase in frustule B content with increasing pH. The mechanism of B transport from the site of uptake to the site of silica deposition is unknown, but may occur via silicon transport vesicles, in which B(OH)4- may be imported for B detoxification and/or as part of a pH regulation strategy either though Na-dependent B(OH)4-/Cl- antiport or B(OH)4-/H+ antiport. B deposition in the silica matrix may occur via substitution of a B(OH)4- for a negatively charged SiO- formed during silicification. With

  12. Application of CCA for study on modern lake diatoms and environment in the Tibetan Plateau

    Institute of Scientific and Technical Information of China (English)

    羊向东; 王苏民; 夏威岚; 李万春

    2001-01-01

    The relations between lake surface sediment diatoms and water environmental variables were revealed effectively by use of a new multivariate canonical correspondence analysis (CCA) based on 45 lakes in the Tibetan Plateau. Water depth, conductivity, Cl-, Mg2+, K+ and pH, identified from 12 contemporary water environmental variables, can significantly and independently explain the diatom distributions (p<0.05). The first two axes (λ1=0.34, λ2=0.27) capture 16.1% of the variance in the species data, and account for 57.4% of the variance in diatom-environment relationship. The deletion of redundant environmental variables and unusual samples do not influence the explanation to diatom data. The final CCA result indicates that the water depth and the salinity are the two important environmental gradients and influence the diatom distribution in the plateau lakes. The water depth correlates with axis 1, while conductivity, Cl-, Mg2+ and K+, indicating the direction of salinity changes, corr

  13. Preservation of fossil diatoms in Atlantic sediment cores: control by supply rate

    Science.gov (United States)

    Pokras, Edward M.

    1986-07-01

    Dissolution of fossil diatoms in piston cores from the North and equatorial Atlantic Ocean is generally severe only in areas of low primary productivity, and hence low fluxes of diatoms to the sea floor. In silica-rich sediments, initial dissolution increases the silica content of pore waters, which acts as a buffer against continued dissolution. Thus down-core decrease in accumulation rates reflects relative loos compared to initial supply rates, rather than absolute dissolution. Most records show either very strong or very weak impact by post-depositional dissolution. An empirical model suggest that in pelagic sediments, dissolution measurably affects diatom accumulation only when supply is below approximately 2.5 × 10 8 diatom fragments cm -2 1000 y -1, or 6.4 × 10 6 whole diatoms cm -2 1000 y -1. Other factors may also influence the preservation of siliceous microfossils; however, water depth has no discernible effect on the relative severity of opal dissolution in sediments of the abyssal Atlantic.

  14. Surface sediment diatoms from the western Pacific marginal seas and their correlation to environmental variables

    Institute of Scientific and Technical Information of China (English)

    HUANG Yue; JIANG Hui; Svante Bj(o)rck; LI Tiegang; LU Houyuan; RAN Lihua

    2009-01-01

    Diatom data of 192 surface sediment samples from the marginal seas in the western Pacific together with modern summer and winter sea surface temperature and salinity data were analyzed. The results of canonical correspondence analysis show that summer sea-surface salinity (SSS) is highly positively correlated with winter SSS and so is summer sea-surface temperature (SST) with winter SST. The correlations between SSSs and SSTs are less positively correlated, which may be due to interactions of regional current pattern and monsoon climate. The correlations between diatom species, sample sites and environmental variables concur with known diatom ecology and regional oceanographic characters. The results of forward selection of the environmental variables and associated Monte Carlo permutation tests of the statistical significance of each variable suggest that summer SSS and winter SST are the main environmental factors affecting the diatom distribution in the area and therefore preserved diatom data from down core could be used for reconstructions of summer SSS and winter SST in the region.

  15. Reproductive success of Calanus pacificus during diatom blooms in Dabob Bay, Washington

    Science.gov (United States)

    Pierson, James J.; Halsband-Lenk, Claudia; Leising, Andrew W.

    2005-11-01

    While numerous laboratory studies in the last decade have shown that diatoms can induce reproductive failure in copepods, field evidence for a negative diatom effect is equivocal. To unambiguously elucidate the effects diatoms have on copepod reproduction in situ, we undertook a study of the abundance, distribution, grazing rates, and reproductive success of Calanus pacificus in Dabob Bay, Washington, USA, during two spring bloom periods. We simultaneously measured the phytoplankton composition, abundance, and distribution. Here we present results for the reproductive success of C. pacificus using four measurements: egg production rate, clutch size, egg hatching success, and naupliar survival (to the first feeding stage). Egg production rate was positively correlated with chlorophyll a concentration, and egg hatching success and naupliar survival were usually greater than 80%. However, in February 2002 and 2003 - during blooms of diatoms of the genus Thalassiosira - either egg hatching success, naupliar survival, or both were significantly depressed compared to other times in spring and summer. These effects, combined with evidence that C. pacificus was grazing aldehyde-producing Thalassiosira at the time of their blooms, indicate that diatoms can negatively affect copepod reproduction in the field, albeit only under specific circumstances and for brief periods.

  16. Metabolic Influence of Psychrophilic Diatoms on Travertines at the Huanglong Natural Scenic District of China

    Directory of Open Access Journals (Sweden)

    Shiyong Sun

    2014-12-01

    Full Text Available Diatoms are a highly diversified group of algae that are widely distributed in aquatic ecosystems, and various species have different nutrient and temperature requirements for optimal growth. Here, we describe unusual psychrophilic diatoms of Cymbella in a travertine deposition environment in southwestern China in winter season. Travertine surfaces are colonized by these psychrophilic diatoms, which form biofilms of extracellular polysaccharide substances (EPS with active metabolic activities in extremely cold conditions. The travertine in Huanglong, is a typical single crystalline calcite with anisotropic lattice distortions of unit cell parameters along axes of a and c, and this structure is suggestive of some level of metabolic mediation on mineralization. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS results further confirmed the occurrence of biogenic distortion of the crystal lattice of travertine calcite. Overall, our results imply that the metabolic influence of psychrophilic diatoms may be particularly important for promoting formation and dissolution of travertine in extremely cold environments of Huanglong. The EPS of psychrophilic diatoms will protect travertine from HCO3− etching and provide template for forming travertine when water re-flowing, in warm season.

  17. Inland diatoms from the McMurdo Dry Valleys and James Ross Island, Antarctica

    Science.gov (United States)

    Esposito, R.M.M.; Spaulding, S.A.; McKnight, Diane M.; Van De Vijver, B.; Kopalova, K.; Lubinski, D.; Hall, B.; Whittaker, T.

    2008-01-01

    Diatom taxa present in the inland streams and lakes of the McMurdo Dry Valleys and James Ross Island, Antarctica, are presented in this paper. A total of nine taxa are illustrated, with descriptions of four new species (Luticola austroatlantica sp. nov., Luticola dolia sp. nov., Luticola laeta sp. nov., Muelleria supra sp. nov.). In the perennially ice-covered lakes of the McMurdo Dry Valleys, diatoms are confined to benthic mats within the photic zone. In streams, diatoms are attached to benthic surfaces and within the microbial mat matrix. One species, L. austroatlantica, is found on James Ross Island, of the southern Atlantic archipelago, and the McMurdo Dry Valleys. The McMurdo Dry Valley populations are at the lower range of the size spectrum for the species. Streams flow for 6-10 weeks during the austral summer, when temperatures and solar radiation allow glacial ice to melt. The diatom flora of the region is characterized by species assemblages favored under harsh conditions, with naviculoid taxa as the dominant group and several major diatom groups conspicuously absent. ?? 2008 NRC.

  18. Diatom zonation in southern Oregon tidal marshes relative to vascular plants, foraminifera, and sea level

    Science.gov (United States)

    Nelson, A.R.; Kashima, K.

    1993-01-01

    Diatom assemblages across estuarine marshes show a three-part vertical ecologic zonation of the intertidal zone similar to zonations of foraminiferal and vascular plant assemblages. Gradual changes in the compositions of all three types of assemblages reflect gradational zone boundaries, 5-40m wide. Modern mudflat, low marsh, and high marsh zones can be distinguished from one another with diatom assemblage data at three silty marshes in the middle parts of two river-dominated estuaries. The compositions of vascular plant and diatom assemblages on a transect at a sandy site near the mouth of a third estuary differ from those of the silty transects. A particularly distinct diatom subzone (the marsh border subzone) is marked by a dominance of fresh-to-brackish-water diatoms in a few samples from the upper part of the high marsh and lowest part of the upland zone on all four transects, but the vertical range of the marsh border subzone is large (c0.7m) and its range may vary from site to site depending on the amount of freshwater seepage and runoff into marshes. -from Authors

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

    Science.gov (United States)

    Wang, Meng-Jiao; Wang, Wen-Xiong

    2011-01-25

    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+)], 0.01-84nM) 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.

  20. Optimization of the replica molding process of PDMS using pennate diatoms

    Science.gov (United States)

    Hlúbiková, D.; Luís, A. T.; Vaché, V.; Ector, L.; Hoffmann, L.; Choquet, P.

    2012-11-01

    Biomimetic fabrication of nanostructured materials has recently attracted the attention of researchers as a cost-effective and easily applicable method of nanotexturing. Different techniques and materials have been used in order to replicate natural patterns, among which polydimethylsiloxane (PDMS Sylgard 184®) was recently used to replicate the micro- and nanoscale patterns from centric diatoms. In this paper, we test the reproducibility and precision of this approach using various morphologically different diatom species trying to optimize the molding parameters. The optimization process is focused on immobilization of diatoms on the glass support, which serves as a master for templating, as well as on the parameters of PDMS fabrication such as the ratio of the curing agent and elastomer, use of vacuum, curing time and temperature. The results indicate that higher ratios of curing agent and elastomer, longer curing time and lower temperature are the most favorable conditions to obtain negative diatom replicas of good quality with features of 50 nm. Although this method can give very precise results producing high-resolution molds with all micro- and nanostructures replicated, we revealed some limitations regarding the size and morphology of the species used. These results indicate that large round and flat diatom species seem to be more suitable for the cast molding.

  1. The Presence and Localization of Thioredoxins in Diatoms,Unicellular Algae of Secondary Endosymbiotic Origin

    Institute of Scientific and Technical Information of China (English)

    Till Weber; Ansgar Gruber; Peter G.Kroth

    2009-01-01

    Diatoms are unicellular algae of great ecological importance.So far,very little is known about the regulation of carbon fixation in these algae; however,there are strong indications that in diatom plastids,the ferredoxin/thioredoxin system might play a minor role in redox regulation of the photosynthetic reactions compared to land plants.Until now,it is nknown whether there are fewer or other target enzymes of thioredoxins in diatoms.Only a single potential target enzyme for thioredoxin,the plastidic fructose-l,6-bisphosphatase,has yet been identified.Nevertheless,during the an-notation of the genome of the diatom Phaeodactylum tricornutum,we identified several genes encoding different thi-oredoxins.Utilizing in vivo expression of GFP:presequence fusion proteins in P.tricornutum,we were able to show that these thioredoxins are targeted either into plastids,mitochondria,or remain in the cytosol.Surprisingly,two of the three usually cytosolic thioredoxin h proteins are apparently plastid associated and,together with a thioredoxin reductase,putatively located in the periplastidic compartment.This is one of the few indications for so far unknown enzymatic reac-tions in the space between the two pairs of diatom plastid envelope membranes.

  2. 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.

  3. Eukaryotic pathogens (Chytridiomycota and Oomycota) infecting marine microphytobenthic diatoms - a methodological comparison.

    Science.gov (United States)

    Scholz, Bettina; Küpper, Frithjof C; Vyverman, Wim; Karsten, Ulf

    2014-12-01

    Using sediment samples from the Solthörn tidal flat (southern North Sea, Germany), collected in bi-weekly intervals from June to July 2012, a range of qualitative and quantitative screening methods for oomycete and chytrid pathogens infecting benthic diatoms were evaluated. Pre-treatment of sediment samples using short ultrasound pulses and gradient centrifugation, in combination with CalcoFluor White, showed the best results in the visualization of both pathogen groups. The highest number of infected benthic diatoms was observed in mid July (5.8% of the total benthic diatom community). Most infections were caused by chytrids and, in a few cases, oomycetes (Lagenisma Drebes (host: Coscinodiscus radiatus Ehrenberg) and Ectrogella Zopf (hosts: Dimeregramma minor in Pritchard and Gyrosigma peisonis). Among the chytrids, sporangium morphology indicated the presence of five different morphotypes, infecting mainly epipelic taxa of the orders Naviculales (e.g., Navicula digitoradiata) and Achnanthales (e.g., Achnanthes brevipes Agardh). The presence of multiple pathogens in several epipelic diatom taxa suggests a significant role for fungal parasitism in affecting microphytobenthic diatom succession.

  4. Metabolic influence of psychrophilic diatoms on travertines at the Huanglong natural scenic district of China.

    Science.gov (United States)

    Sun, Shiyong; Dong, Faqin; Ehrlich, Hermann; Zhao, Xueqing; Liu, Mingxue; Dai, Qunwei; Li, Qiongfang; An, Dejun; Dong, Hailiang

    2014-12-01

    Diatoms are a highly diversified group of algae that are widely distributed in aquatic ecosystems, and various species have different nutrient and temperature requirements for optimal growth. Here, we describe unusual psychrophilic diatoms of Cymbella in a travertine deposition environment in southwestern China in winter season.Travertine surfaces are colonized by these psychrophilic diatoms, which form biofilms of extracellular polysaccharide substances (EPS) with active metabolic activities in extremely cold conditions. The travertine in Huanglong, is a typical single crystalline calcite with anisotropic lattice distortions of unit cell parameters along axes of a and c, and this structure is suggestive of some level of metabolic mediation on mineralization Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) results further confirmed the occurrence of biogenic distortion of the crystal lattice of travertine calcite.Overall, our results imply that the metabolic influence of psychrophilic diatoms may be particularly important for promoting formation and dissolution of travertine in extremely cold environments of Huanglong. The EPS of psychrophilic diatoms will protect travertine from HCO3− etching and provide template for forming travertine when water re-flowing, in warm season. PMID:25590097

  5. Allelopathic Effects of Cyanobacterial Filtrates on Baltic Diatom

    Science.gov (United States)

    Śliwińska, Sylwia; Latała, Adam

    2012-01-01

    Allelopathy may be one of the factors affecting the formation of massive and harmful algal blooms in aquatic environments. Recent studies indicate that blooms of cyanobacteria in the Baltic Sea has grown significantly in last decades, so it is important to determine the allelopathic interactions between the dominant species of cyanobacteria and microalgae. In this work we investigated the influence of allelopathic compounds on the growth of Skeletonema marinoi by addition of cell-free filtrate of the Baltic cyanobacterium Nodularia spumigena cultures grown under different temperature (15-25°C). Additionally the effects of filtrates of both an exponential and a stationary growing culture of N. spumigena were tested on diatom. These studies indicate that high temperature affected the donor species by increasing its production of allelochemicals. The highest drop of growth of analyzed diatom were observed after the addition of cell-free filtrate obtained from N. spumigena grown at 25°C and constituted 70% of their control. N. spumigena was only allelopathic in exponential growth phase, whereas the cyanobacteria filtrate from stationary phase have any effect on S. marinoi. These findings suggest that N. spumigena may reveal allelopathic activity and that the production of allelopathic substances is influenced by the temperature and growth phase of cyanobacteria. Allelopatia może być kluczowym czynnikiem wpływającym na tworzenie się masowych zakwitów sinic w wielu wodnych ekosystemach. Badania pokazują, że zakwity sinic w Morzu Bałtyckim w ostatnich dekadach znacznie się nasiliły, dlatego tak ważne jest określenie stopnia oddziaływania allelopatycznego dominujących w tym akwenie gatunków fitoplanktonu. W przeprowadzonych badaniach określono wpływ związków allelopatycznych produkowanych przez bałtycką sinicę Nodularia spumigena hodowaną w różnych temperaturach (15-25°C) na wzrost okrzemki Skeletonema marinoi. Dodatkowo w niniejszej pracy por

  6. Impact of silver nanoparticles on marine diatom Skeletonema costatum.

    Science.gov (United States)

    Huang, Jun; Cheng, Jinping; Yi, Jun

    2016-10-01

    When silver nanoparticles (AgNPs) are used commercially at a large scale, they infiltrate the environment at a rapid pace. However, the impact of large quantities of AgNPs on aquatic ecosystems is still largely unknown. In aquatic ecosystems, the phytoplanktons have a vital ecological function and, therefore, the potential impact of AgNPs on the microalgae community has elicited substantial concern. Therefore, in this study, the impacts of AgNPs on a marine diatom, the Skeletonema costatum, are investigated, with a focus on their photosynthesis and associated mechanisms. Exposure to AgNPs at a concentration of 0.5 mg l(-1) significantly induces excess intracellular reactive oxygen species (ROS, 122%) and reduces 28% of their cell viability. More importantly, exposure to AgNPs reduces the algal chlorophyll-a content. Scanning electron microscopy (SEM) was conducted, which revealed that AgNPs obstruct the light absorption of algae because they adhere to their surface. The maximum photochemical efficiency of photosystem II (Fv/Fm) demonstrates that exposure to AgNPs significantly inhibits the conversion of light energy into photosynthetic electron transport. Moreover, the genes of the photosystem II reaction center protein (D1) are significantly down-regulated (P < 0.05) upon exposure to 5 mg l(-1) AgNPs. These results suggest that the physical adhesion and effects of shading of AgNPs on algae might affect their light energy delivery system and damage the crucial protein function of PSII. The photosynthesis inhibition effect of AgNPs is largely different from Ag(+) . This study shows that AgNPs at higher concentrations might have serious consequences for the succession of the phytoplankton communities and aquatic ecosystem equilibrium. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27080522

  7. Assemblage of benthic diatoms and culturable heterotrophs in shallow-water hydrothermal vent of the D. Joao de Castro Seamount, Azores in the Atlantic Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Raghukumar, C.; Mohandass, C.; Cardigos, F.; DeCosta, P.M.; Santos, R.S.; Colaco, A.

    . In this recently described vent site, we have studied species diversity of benthic diatoms and heterotrophic microorganisms and their metal tolerance. Species diversity of benthic diatoms was marginally higher in white than the yellow zone. A higher number...

  8. 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

    anaerobic nitrogen cycling at ambient oxygen 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 oxygen 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 dinitrogen production, which may partially uncouple anaerobic nitrate turnover by diatom aggregates from direct ambient...

  9. Mussel- and Diatom-Inspired Micropattern Generation of Silica on a Solid Substrate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jungkyu K. [Kyungpook National Univ., Daegu (Korea, Republic of); Kang, Sung Min [Pukyong National Univ., Busan (Korea, Republic of)

    2013-02-15

    Biosilicification in diatoms and sponges potentially promises physiological, mild reaction conditions for controlling silica structures at the nanometer scale. Since Sumper et al. had isolated catalytic peptides (i. e., silaffins) from diatoms, a number of polymers bearing tertiary amine or ammonium groups have been used as a counterpart of silaffins to biomimetically synthesize silica structures. We demonstrated a micropattern generation of silica on the solid substrate by a mussel- and diatom-inspired approach combined with a soft lithography. This method shows several advantages to apply for a wide range of materials without harsh reaction conditions. Moreover, it could allow us to give proper functionalities on silica layers via well-defined organosilane chemistry.

  10. Probing the evolutionary history of epigenetic mechanisms: what can we learn from marine diatoms

    Directory of Open Access Journals (Sweden)

    Achal Rastogi

    2015-07-01

    Full Text Available Recent progress made on epigenetic studies revealed the conservation of epigenetic features in deep diverse branching species including Stramenopiles, plants and animals. This suggests their fundamental role in shaping species genomes across different evolutionary time scales. Diatoms are a highly successful and diverse group of phytoplankton with a fossil record of about 190 million years ago. They are distantly related from other super-groups of Eukaryotes and have retained some of the epigenetic features found in mammals and plants suggesting their ancient origin. Phaeodactylum tricornutum and Thalassiosira pseudonana, pennate and centric diatoms, respectively, emerged as model species to address questions on the evolution of epigenetic phenomena such as what has been lost, retained or has evolved in contemporary species. In the present work, we will discuss how the study of non-model or emerging model organisms, such as diatoms, helps understand the evolutionary history of epigenetic mechanisms with a particular focus on DNA methylation and histone modifications.

  11. [Evaluation of the quality of river water with diatoms (Bacillariophyceae): an experience in Tacna, Peru].

    Science.gov (United States)

    Calizaya-Anco, José; Avendaño-Cáceres, Miriam; Delgado-Vargas, Irma

    2013-03-01

    In order to evaluate the quality of the water of the Locumba river, Tacna (Peru), water samples were taken from ten stations located along the Locumba river basin, during six periods in an annual cycle. The diversity and number of diatoms was also evaluated, together with eleven physiochemical parameters in order to determine the degree of water contamination. We found that as the basin advanced down the mountain, the diversity of diatoms decreased from 2.37 bits cell-1 to 0.71 bits cell-1 and the gradient of contaminants increased. In addition to this increase, the number of species tolerant to high levels of environmental disturbance rose. An increase in all physiochemical parameters used to evaluate the degree of contamination was observed. These results suggest that diatoms can be adequate bioindicators when evaluating the quality of water in this basin. PMID:23612814

  12. Isolation and Physiological Characterization of a Novel Algicidal Virus Infecting the Marine Diatom Skeletonema costatum

    Directory of Open Access Journals (Sweden)

    JinJoo Kim

    2015-06-01

    Full Text Available Diatoms are a major component of the biological community, serving as the principal primary producers in the food web and sustaining oxygen levels in aquatic environments. Among marine planktonic diatoms, the cosmopolitan Skeletonema costatum is one of the most abundant and widespread species in the world’s oceans. Here, we report the basic characteristics of a new diatom-infecting S. costatum virus (ScosV isolated from Jaran Bay, Korea, in June 2008. ScosV is a polyhedral virus (45–50 nm in diameter that propagates in the cytoplasm of host cells and causes lysis of S. costatum cultures. The infectivity of ScosV was determined to be strain- rather than species-specific, similar to other algal viruses. The burst size and latent period were roughly estimated at 90–250 infectious units/cell and <48 h, respectively.

  13. Isolation and Physiological Characterization of a Novel Algicidal Virus Infecting the Marine Diatom Skeletonema costatum.

    Science.gov (United States)

    Kim, JinJoo; Kim, Chang-Hoon; Youn, Seok-Hyun; Choi, Tae-Jin

    2015-06-01

    Diatoms are a major component of the biological community, serving as the principal primary producers in the food web and sustaining oxygen levels in aquatic environments. Among marine planktonic diatoms, the cosmopolitan Skeletonema costatum is one of the most abundant and widespread species in the world's oceans. Here, we report the basic characteristics of a new diatom-infecting S. costatum virus (ScosV) isolated from Jaran Bay, Korea, in June 2008. ScosV is a polyhedral virus (45-50 nm in diameter) that propagates in the cytoplasm of host cells and causes lysis of S. costatum cultures. The infectivity of ScosV was determined to be strain- rather than species-specific, similar to other algal viruses. The burst size and latent period were roughly estimated at 90-250 infectious units/cell and <48 h, respectively. PMID:26060438

  14. 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...... Wadden Sea and are potentially involved in anaerobic nitrate respiration. Intracellular nitrate (ICNO3) was present year-round in the sediment and was spatially and temporally correlated with fucoxanthin, the marker photopigment of diatoms. Pyrosequencing of SSU rRNA genes of all domains of life...... 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....

  15. Application of potential constants: Empirical determination of molecular energy components for diatomic molecules—II

    Science.gov (United States)

    Ohwada, Ken

    The harmonic and anharmonic potential (force) constants which are usually available from a normal coordinate analysis for a diatomic molecule are applied to determine the molecular energy components such as the electronic kinetic energy, the total electrostatic potential energy, the electron—nuclear attraction energy, the electron—electron repulsion energy, the nuclear—nuclear repulsion energy, and the Hartree—Fock eigen-value sum. The method developed here is based on an inhomogeneous linear third-order differential equation derived from the quantum mechanical virial theorem, and a homogeneity hypothesis of the molecular energy with respect to the atomic number. To confirm the utility of the method, the calculated molecular energy components of diatomic molecules are compared with available Hartree—Fock data. It is concluded from this data that the present method is simple and useful for evaluating the molecular energy components of various diatomic molecules.

  16. Eigensolution techniques, their applications and the Fisher's information entropy of Tietz-Wei diatomic molecular potential

    CERN Document Server

    Falaye, B J; Ikhdair, S M; Hamzavi, M

    2014-01-01

    In this study, approximate analytical solution of Schr\\"odinger, Klein-Gordon and Dirac equations under the Tietz-Wei (TW) diatomic molecular potential are represented by using an approximation for the centrifugal term. We have applied three types of eigensolution techniques; the functional analysis approach (FAA), supersymmetry quantum mechanics (SUSYQM) and asymptotic iteration method (AIM) to solve Klein-Gordon Dirac and Schr\\"odinger equations, respectively. The energy eigenvalues and the corresponding eigenfunctions for these three wave equations are obtained and some numerical results and figures are reported. It has been shown that these techniques yielded exactly same results. some expectation values of the TW diatomic molecular potential within the framework of the Hellmann-Feynman theorem (HFT) have been presented. The probability distributions which characterize the quantum-mechanical states of TW diatomic molecular potential are analysed by means of complementary information measures of a probabil...

  17. Diatoms of the microphytobenthic community in a tropical intertidal sand flat influenced by monsoons: Spatial and temporal variations

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Anil, A.C.

    with the diatom abundance at the deeper sediment layers and the high tide zone, the fact that viable cells were present at these areas reveal that the diatoms adopt survival strategies, contributing significantly to the carbon budgets of such unstable habitats....

  18. Dangerous relations in the Arctic marine food web: Interactions between toxin producing Pseudo-nitzschia diatoms and Calanus copepodites

    DEFF Research Database (Denmark)

    Hardardottir, Sara; Pancic, Marina; Tammilehto, Anna;

    2015-01-01

    Diatoms of the genus Pseudo-nitzschia produce domoic acid (DA), a toxin that is vectored in the marine food web, thus causing serious problems for marine organisms and humans. In spite of this, knowledge of interactions between grazing zooplankton and diatoms is restricted. In this study, we exam...

  19. Relationship of fouling diatom number and chlorophyll-a value from Zuari estuary, Goa (west coast of India)

    Digital Repository Service at National Institute of Oceanography (India)

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

    The diatom cell biomass is expressed in terms of diatom number and chlorophyll -a value on panel of glass slide. The Chlorophyll value in a water body is indicative of the productivity. The present study was conducted to find out the relationship...

  20. Preponderance of a few diatom species among the highly diverse microphytoplankton assemblages in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Paul, J.T.; Ramaiah, N.; Gauns, M.; Fernandes, V.

    . Abundance of pennate diatoms was higher in the open Bay compared to that of centric diatoms in the more productive northern locations and the western Bay. There appears to be a basic difference between near shore flora and offshore flora. This first analysis...

  1. Uptake of phytodetritus by meiobenthos using 13C labelled diatoms and Phaeocystis in two contrasting sediments from the North Sea

    NARCIS (Netherlands)

    Franco, M.A.; Soetaert, K.E.R.; Costa, M.J.; Vincx, M.; Vanaverbeke, J.

    2008-01-01

    Meiobenthic uptake of 13C labelled diatom Skeletonema costatum and Prymnesiophyte Phaeocystis was investigated in permeable and fine grained depositional sediments from the Southern Bight of the North Sea at different sediment horizons. Both the diatom and Phaeocystis–derived organic matter (OM) cas

  2. Effects of the coexisting Baltic amphipods Monoporeia affinis and Pontoporeia femorata on the fate of a simulated spring bloom diatom

    NARCIS (Netherlands)

    Van de Bund, W.J.; Ólafsson, E.; Modig, H.; Elmgren, R.

    2001-01-01

    A laboratory experiment was performed to quantify the fate of diatom phytodetritus and how this is affected by the presence of benthic amphipods. A Baltic Sea spring bloom sedimentation event was simulated by adding C-14-labeled diatoms (Skeletonema costatum) to microcosms with varying densities of

  3. Diatom assemblages in surface sediments from the South China Sea as environmental indicators

    Institute of Scientific and Technical Information of China (English)

    WU Rui; GAO Yahui; FANG Qi; CHEN Changping; LAN Binbin; SUN Lin; LAN Dongzhao

    2013-01-01

    We studied diatom distribution from 62 samples from the uppermost 1 cm of sediment in the South China Sea (SCS),using grabs or box corers in three cruises between 2001-2007.Fifty six genera,256 species and their varieties were identified.Dominating species included Coscinodiscus africanus,Coscinodiscus nodulifer,Cyclotella stylorum,Hemidiscus cuneiformis,Melosira sulcata,Nitzschia marina,Roperia tesselata,Thalassionema nitzschioides,Thalassiosira excentrica,and Thalassiothrix longissima.Most surface sediments in the SCS were rich in diatoms,except for a few coarse samples.Average diatom abundance in the study area was 104 607 valve/g.In terms of the abundance,ecology,and spatial distribution,seven diatom zones (Zones 1-7) were recognized.Zone 1 (northern continental shelf)is affected by warm currents,SCS northern branch of the Kuroshio,and northern coastal currents; Zone 2 (northwestern continental shelf) is affected by intense coastal currents; Zone 3 (Xisha Islands sea area) is a bathyal environment with transitional water masses; Zone 4 (sea basin) is a bathyal-to-deep sea with stable and uniform central water masses in a semi-enclosed marginal sea; Zone 5 (Nansha Islands marine area) is a pelagic environment with relatively high surface temperature; Zone 6 (northern Sunda Shelf) is a tropical shelf environment; and Zone 7 (northern Kalimantan Island shelf area) is affected by warm waters from the Indian Ocean and coastal waters.The data indicate that these diatom zones are closely related to topography,hydrodynamics,temperature,nutrients and especially the salinity.Better understanding of the relationship between diatom distribution and the oceanographic factors would help in the reconstruction of the SCS in the past.

  4. 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.

  5. Metatranscriptomes reveal functional variation in diatom communities from the Antarctic Peninsula

    KAUST Repository

    Pearson, Gareth A

    2015-04-14

    Functional genomics of diatom-dominated communities fromthe Antarctic Peninsula was studied using comparative metatranscriptomics. Samples obtained from diatom-rich communities in the Bransfield Strait, the western Weddell Sea and sea ice in the Bellingshausen Sea/Wilkins Ice Shelf yielded more than 500K pyrosequencing reads that were combined to produce a global metatranscriptome assembly. Multi-gene phylogenies recovered three distinct communities, and diatom-assigned contigs further indicated little read-sharing between communities, validating an assembly-based annotation and analysis approach. Although functional analysis recovered a core of abundant shared annotations that were expressed across the three diatom communities, over 40% of annotations (but accounting for <10% of sequences) were community-specific. The two pelagic communities differed in their expression of N-metabolism and acquisition genes, which was almost absent in post-bloom conditions in the Weddell Sea community, while enrichment of transporters for ammonia and urea in Bransfield Strait diatoms suggests a physiological stance towards acquisition of reduced N-sources. The depletion of carbohydrate and energy metabolism pathways in sea ice relative to pelagic communities, together with increased light energy dissipation (via LHCSR proteins), photorespiration, and NO3 - uptake and utilization all pointed to irradiance stress and/or inorganic carbon limitation within sea ice. Ice-binding proteins and cold-shock transcription factors were also enriched in sea ice diatoms. Surprisingly, the abundance of gene transcripts for the translational machinery tracked decreasing environmental temperature across only a 4 °C range, possibly reflecting constraints on translational efficiency and protein production in cold environments. © 2015 International Society for Microbial Ecology All rights reserved.

  6. 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

  7. Caddisflies (Trichoptera) and diatoms of some springs in the vicinity of Łódź (Central Poland).

    Science.gov (United States)

    Kwiatkowska, Katarzyna; Żelazna-Wieczorek, Joanna; Ziułkiewicz, Maciej

    2016-01-01

    The distribution, species richness and ecology of Trichoptera, the diversity of benthic diatoms, and hydrochemical data in 7 springs in the vicinity of Łódź were investigated in 2011. In total, 17 Trichoptera taxa and more than 300 diatom taxa were collected from the studied springs. Trichoptera and especially diatom taxa are very sensitive indicators of ecological conditions; both showed a strong response to degradation in lowland springs. On the basis of faunal, diatom microfloral, and hydrochemical data, the typology of springs of the vicinity of Łódź is proposed. Two groups of factors (differentiating and non-differentiating) which contribute to distinguishing the studied springs are described. Additional experiments and observations were done on Trichoptera, including their life cycles, biology, and larval diet. In particular, the abundance of common diatom taxa in the guts of Silo sp. larvae was investigated. PMID:27470754

  8. Vibrationally resolved molecular frame photoelectron angular distributions of diatomic and polyatomic molecules

    International Nuclear Information System (INIS)

    Vibrationally resolved molecular frame photoelectron angular distributions (MFPADs) of fixed-in-space molecules have been evaluated for diatomic and polyatomic molecules. Calculations have been performed by using an extension of the static-exchange density functional theory formerly developed by P. Decleva [1] and coworkers and extended in order to include the nuclear motion in the Born-Oppenheimer approximation. The method proved to be very accurate for diatomic molecules [2, 3, 5], particularly at high energy of the photoelectron. In this work, we present the results obtained for the inner shell photoionization of C2H2, NH3, CH4, CF4, BF3 and SF6.

  9. Energy of one-dimensional diatomic elastic granular gas: Theory and molecular dynamics Simulation

    CERN Document Server

    Khotimah, Siti Nurul; Widayani,; Waris, Abdul

    2011-01-01

    One-dimensional ideal diatomic gas is simulated through possible types of motion of a molecule. Energy of each type of its motion is calculated from theory and numerical method. Calculation of kinetic energy of an atom in translational-vibrational motion is not analytically simple, but it can be solved by numerical method of molecular dynamic simulation. This paper justifies that kinetic energy of a diatomic molecule can be determined by two different approaches. The first is the sum of kinetic energy of each atom and second is the sum of kinetic energy of translational motion and vibrational motion.

  10. The Holocene history of the Guadiana estuary as told by diatoms and chrysophyte cysts

    OpenAIRE

    Gomes, A.; Boski, T.; Moura, Delminda; Szkornik, Katie; Connor, Simon; Witkowski, Andrzej

    2015-01-01

    In order to tell the history of the Guadiana Estuary since the Last Glacial Maximum, a core collected therein, and spanning more than 13200 cal. years B.P., was studied regarding its diatom and chrysophyte cyst fossil records. Additionally, a diatom-based transfer function was used to reconstruct paleo-salinity and paleo-duration of tidal inundation to better understand the estuary’s evolution in relation to sea-level rise and climate changes. This study identifies some important climatic eve...

  11. Planktonic diatoms of the Zuari estuary, Goa (west coast of India)

    Digital Repository Service at National Institute of Oceanography (India)

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

    . Introduction The important work on planktonic diatoms from Indian waters has been done by Subrahmanyan (1946, 1958), Gonsalves (1947), Venkataraman (1957, 1958), Misra (1962), Chennubhotla (1969), Gopala krishnan (1972), Desikachary (1977) and Nair et.... Redekar and A. B. Wagh Misra, J.N. 1962. A systematic account of some littoral marine diatoms from the west coast of India. J. Bombay Nat. Hist. Soc., 53(4): 537-568. Nair Sreekumaran, S.R., C. T. Achuthankutty V.R. Nair and V.P. Devassy 1980 Plankton...

  12. Dissociation energy of diatomic molecules -comment on the work of Kaur and Mahajan

    Science.gov (United States)

    Chandra, Suresh

    2001-04-01

    When observed spectrum of a diatomic molecule is expressed in terms of the Dunham coefficients Y00, Y10, Y20, Y01, and Y11 only, dissociation energy of the molecule is given by Y00 + Y102/(-4 Y20). Kaur and Mahajan [1] have used the Dunham coefficients Y10, Y20, Y01, and Y11, for 15 vibrational states of 12 diatomic molecules (Y00 is zero for the cases accounted for), but their dissociation energy cannot be reproduced by the expression Y102/(-4 Y20). Probable reason for the discrepancy has been discussed.

  13. Diatom responses to 20th century climate warming in lakes from the northern Urals, Russia.

    OpenAIRE

    Solovieva, N.; Jones, V. J.; Birks, H. J. B.; Appleby, P. G.; Larisa NAZAROVA

    2008-01-01

    Changes in diatom assemblages and spheroidal carbonaceous particle (SCP) profiles during the last 200 years in 210Pb-dated sediment cores from five remote arctic and sub-arctic lakes in the northern Urals were analysed. The study area covers a large territory from arctic tundra in the north to boreal forest on the western slopes of the Ural mountains in the south. pH was reconstructed using a diatom-based model. The degrees of compositional turn-over and rates-of-change were estimated numeric...

  14. Dissociation energy of diatomic molecules – comment on the work of Kaur and Mahajan

    Indian Academy of Sciences (India)

    Suresh Chandra

    2001-04-01

    When observed spectrum of a diatomic molecule is expressed in terms of the Dunham coefficients 00, 10, 20, 01, and 11 only, dissociation energy of the molecule is given by 00 + $^{2}_{10}$/(-420). Kaur and Mahajan [1] have used the Dunham coefficients 10, 20, 01, and 11, for 15 vibrational states of 12 diatomic molecules (00 is zero for the cases accounted for), but their dissociation energy cannot be reproduced by the expression $^{2}_{10}$/(-420). Probable reason for the discrepancy has been discussed.

  15. Studies on dissociation energies of diatomic molecules using vibrational spectroscopic constants

    Institute of Scientific and Technical Information of China (English)

    HOU; Shilin(侯世林); SUN; Weiguo(孙卫国)

    2003-01-01

    New analytical expression and numerical approach are suggested to calculate dissociation energies De of diatomic molecular states using an extreme value method (EVM). Studies on some electronic states of OH, BH, N2, Br2, ClF and CO molecules show that the accuracy of the EVM dissociation energies depends on the number of correct vibrational constants used in the calculations. The convergence qualities of De are suggested to be an alternative physical criterion to measure the qualities of the various sets of vibrational constants from different literature for the same diatomic state.

  16. Genome size differentiates co-occurring populations of the planktonic diatom Ditylum brightwellii (Bacillariophyta

    Directory of Open Access Journals (Sweden)

    von Dassow Peter

    2010-01-01

    Full Text Available Abstract Background Diatoms are one of the most species-rich groups of eukaryotic microbes known. Diatoms are also the only group of eukaryotic micro-algae with a diplontic life history, suggesting that the ancestral diatom switched to a life history dominated by a duplicated genome. A key mechanism of speciation among diatoms could be a propensity for additional stable genome duplications. Across eukaryotic taxa, genome size is directly correlated to cell size and inversely correlated to physiological rates. Differences in relative genome size, cell size, and acclimated growth rates were analyzed in isolates of the diatom Ditylum brightwellii. Ditylum brightwellii consists of two main populations with identical 18s rDNA sequences; one population is distributed globally at temperate latitudes and the second appears to be localized to the Pacific Northwest coast of the USA. These two populations co-occur within the Puget Sound estuary of WA, USA, although their peak abundances differ depending on local conditions. Results All isolates from the more regionally-localized population (population 2 possessed 1.94 ± 0.74 times the amount of DNA, grew more slowly, and were generally larger than isolates from the more globally distributed population (population 1. The ITS1 sequences, cell sizes, and genome sizes of isolates from New Zealand were the same as population 1 isolates from Puget Sound, but their growth rates were within the range of the slower-growing population 2 isolates. Importantly, the observed genome size difference between isolates from the two populations was stable regardless of time in culture or the changes in cell size that accompany the diatom life history. Conclusions The observed two-fold difference in genome size between the D. brightwellii populations suggests that whole genome duplication occurred within cells of population 1 ultimately giving rise to population 2 cells. The apparent regional localization of population 2 is

  17. Diatoms and Other Epibionts Associated with Olive Ridley (Lepidochelys olivacea Sea Turtles from the Pacific Coast of Costa Rica.

    Directory of Open Access Journals (Sweden)

    Roksana Majewska

    Full Text Available Although the sea turtles have long been familiar and even iconic to marine biologists, many aspects of their ecology remain unaddressed. The present study is the first of the epizoic diatom community covering the olive ridley turtle's (Lepidochelys olivacea carapace and the first describing diatoms living on sea turtles in general, with the primary objective of providing detailed information on turtle epibiotic associations. Samples of turtle carapace including the associated diatom biofilm and epizoic macro-fauna were collected from Ostional beach (9° 59´ 23.7´´ N 85° 41´ 52.6´´ W, Costa Rica, during the arribada event in October 2013. A complex diatom community was present in every sample. In total, 11 macro-faunal and 21 diatom taxa were recorded. Amongst diatoms, the most numerous were erect (Achnanthes spp., Tripterion spp. and motile (Haslea sp., Navicula spp., Nitzschia spp., Proschkinia sp. forms, followed by adnate Amphora spp., while the most common macro-faunal species was Stomatolepas elegans (Cirripedia. Diatom densities ranged from 8179 ± 750 to 27685 ± 4885 cells mm-2. Epizoic microalgae were either partly immersed or entirely encapsulated within an exopolymeric coat. The relatively low diatom species number, stable species composition and low inter-sample dissimilarities (14.4% on average may indicate a mutualistic relationship between the epibiont and the basibiont. Dispersal of sea turtle diatoms is probably highly restricted and similar studies will help to understand both diatom diversity, evolution and biogeography, and sea turtle ecology and foraging strategies.

  18. Diatom colonization on stainless steel panels in estuarine waters of Goa, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Anil, A.C.

    , over a period of one year (March '96 to February '97). Qualitative and quantitative enumeration of the diatoms from the fouling film as well as that from the water column was carried out. The surrounding waters were dominated by the centrales whereas...

  19. Genome-Scale Model Reveals Metabolic Basis of Biomass Partitioning in a Model Diatom.

    Science.gov (United States)

    Levering, Jennifer; Broddrick, Jared; Dupont, Christopher L; Peers, Graham; Beeri, Karen; Mayers, Joshua; Gallina, Alessandra A; Allen, Andrew E; Palsson, Bernhard O; Zengler, Karsten

    2016-01-01

    Diatoms are eukaryotic microalgae that contain genes from various sources, including bacteria and the secondary endosymbiotic host. Due to this unique combination of genes, diatoms are taxonomically and functionally distinct from other algae and vascular plants and confer novel metabolic capabilities. Based on the genome annotation, we performed a genome-scale metabolic network reconstruction for the marine diatom Phaeodactylum tricornutum. Due to their endosymbiotic origin, diatoms possess a complex chloroplast structure which complicates the prediction of subcellular protein localization. Based on previous work we implemented a pipeline that exploits a series of bioinformatics tools to predict protein localization. The manually curated reconstructed metabolic network iLB1027_lipid accounts for 1,027 genes associated with 4,456 reactions and 2,172 metabolites distributed across six compartments. To constrain the genome-scale model, we determined the organism specific biomass composition in terms of lipids, carbohydrates, and proteins using Fourier transform infrared spectrometry. Our simulations indicate the presence of a yet unknown glutamine-ornithine shunt that could be used to transfer reducing equivalents generated by photosynthesis to the mitochondria. The model reflects the known biochemical composition of P. tricornutum in defined culture conditions and enables metabolic engineering strategies to improve the use of P. tricornutum for biotechnological applications.

  20. Genome-Scale Model Reveals Metabolic Basis of Biomass Partitioning in a Model Diatom.

    Directory of Open Access Journals (Sweden)

    Jennifer Levering

    Full Text Available Diatoms are eukaryotic microalgae that contain genes from various sources, including bacteria and the secondary endosymbiotic host. Due to this unique combination of genes, diatoms are taxonomically and functionally distinct from other algae and vascular plants and confer novel metabolic capabilities. Based on the genome annotation, we performed a genome-scale metabolic network reconstruction for the marine diatom Phaeodactylum tricornutum. Due to their endosymbiotic origin, diatoms possess a complex chloroplast structure which complicates the prediction of subcellular protein localization. Based on previous work we implemented a pipeline that exploits a series of bioinformatics tools to predict protein localization. The manually curated reconstructed metabolic network iLB1027_lipid accounts for 1,027 genes associated with 4,456 reactions and 2,172 metabolites distributed across six compartments. To constrain the genome-scale model, we determined the organism specific biomass composition in terms of lipids, carbohydrates, and proteins using Fourier transform infrared spectrometry. Our simulations indicate the presence of a yet unknown glutamine-ornithine shunt that could be used to transfer reducing equivalents generated by photosynthesis to the mitochondria. The model reflects the known biochemical composition of P. tricornutum in defined culture conditions and enables metabolic engineering strategies to improve the use of P. tricornutum for biotechnological applications.

  1. Comparative investigation of damage induced by diatomic and monoatomic ion implantation in silicon

    NARCIS (Netherlands)

    Lohner, T.; Toth, L.; Fried, M.; Khanh, N.Q.; Yang, Gen Qing; Lu, Lin Chen; Zou, Shichang; Hanekamp, L.J.; Silfhout, van A.; Gyulai, J.

    1994-01-01

    The damaging effect of mono- and diatomic phosphorus and arsenic ions implanted into silicon was investigated by spectroscopic ellipsometry (SE) and high-depth-resolution Rutherford backscattering and channeling techniques. A comparison was made between the two methods to check the capability of ell

  2. Eddies as trigger for diatom productivity in the open-ocean Northeast Atlantic

    Science.gov (United States)

    Romero, Oscar E.; Fischer, Gerhard; Karstensen, Johannes; Cermeño, Pedro

    2016-09-01

    Anticyclonic mesoscale eddies (ACME) have been proposed as a mechanism by which new nutrients are episodically delivered into the euphotic zone, thereby enhancing new production as well as shifting phytoplankton community structure. In this paper, we report on a 34-month sediment trap experiment at the Cape Verde Ocean Observatory (CVOO; ca. 18°N, 24°E; December 2009-October 2012), occasionally influenced by ACME passages. The typically oligotrophic, weakly seasonal particle flux pattern at the CVOO is strongly modified by the appearance of a highly productive and low oxygen ACME. Out of four recorded diatom flux maxima at CVOO, three were associated with the passage of ACMEs. The recorded diatom maxima events support the view that local ACME dynamics promotes upward nutrient supply into the euphotic zone leading to a rapid response of diatoms. This response is clearly reflected by the flux seasonality: between 40% and 60% of the total annual diatom flux at the CVOO site was intercepted in a relatively short time interval (ocean, oligotrophic subtropical regions of the world ocean. Our observations are useful for testing biogeochemical ocean models and will also help in improving the knowledge of processes and mechanisms behind interannual time-series of bulk components and microorganisms in pelagic and hemipelagic ocean areas.

  3. Spatial scale and the diversity of benthic cyanobacteria and diatoms in a salina

    DEFF Research Database (Denmark)

    Nübel, U.; Garcia-Pichel, F.; Kühl, Michael;

    1999-01-01

    We characterized the richness of benthic cyanobacteria and diatoms in a salina system using traditional and molecular biological methods. After determining the different morphotypes and 16S rRNA genes present in various localities within this hypersaline system, an analysis of the increase...

  4. Risk assessment of excessive CO2 emission on diatom heavy metal consumption.

    Science.gov (United States)

    Liu, Fengjiao; Li, Shunxing; 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 CO2 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 acidificationdesalinationdesalination for Zn, acidificationdesalinationdesalination 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 CO2 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. PMID:27265731

  5. Colonization dynamics of periphytic diatoms in coastal waters of the Yellow Sea, northern China

    Institute of Scientific and Technical Information of China (English)

    Liu Yuanyuan; Zhang Wei; Xu henglong

    2014-01-01

    The colonization features of periphytic diatoms were studied in coastal waters of the Yellow Sea, northern China from May to June 2010, using glass slides as an artificial substratum. Samples were collected at a time interval of 1, 3, 7, 10, 14, 21 and 28 d from two depths of 1 and 3 m. The dynamics of diatom colonization process had a similar pattern in community structure and fitted the logistic model in growth curve at both depths. The maximum abundance and the time for reaching 50%maximum abundance (10 d) showed no significant differences (P>0.05) between two depths 1 and 3 m. although the diatom communities repre-sented similar taxonomic composition, they differed in the temporal pattern of structural parameters and in succession dynamics of dominant species between the two layers. The species richness showed significantly higher values during the colonization period more than 14 d, while the species diversity and evenness rep-resented a higher variability with significantly different values (P<0.05) at a depth of 1 m than at a deeper layer. The results suggest that the diatom colonization follows the logistic model growth curve and differs in colonization features between different depths in the coastal waters, and that the sampling strategy at 1 m is more effective to detect the ecological features for bioassessment in marine ecosystems.

  6. Aulacoseira coroniformis sp. nov., a new diatom (Bacillariophyta) species from Highland Hammock State Park, Florida

    NARCIS (Netherlands)

    Cremer, H.; Pearce, C.; Wagner-Cremer, F.

    2010-01-01

    Aulacoseira coroniformis sp. nov. is described from a short peat core recovered in Highlands Hammock State Park, Florida, U.S.A. The morphology of the new diatom species is documented by light and scanning electron micrographs and discussed in detail, including a comparison with related species in t

  7. 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.

    . All the three extracts possessed antifouling activity bu their efficacy was found to be species specific. The highest bacterial inhibition zone ranged between 3-4 mm with both the zoanthid extracts. In case of diatoms, inducement of growth was observed...

  8. 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.)

  9. Tracing decadal environmental change in ombrotrophic bogs using diatoms from herbarium collections and transfer functions

    International Nuclear Information System (INIS)

    Central European mountain bogs, among the most valuable and threatened of habitats, were exposed to intensive human impact during the 20th century. We reconstructed the subrecent water chemistry and water-table depths using diatom based transfer functions calibrated from modern sampling. Herbarium Sphagnum specimens collected during the period 1918–1998 were used as a source of historic diatom samples. We classified samples into hummocks and hollows according to the identity of dominant Sphagnum species, to reduce bias caused by uneven sampling of particular microhabitats. Our results provide clear evidence for bog pollution by grazing during the period 1918–1947 and by undocumented aerial liming in the early 90-ies. We advocate use of herbarized epibryon as a source of information on subrecent conditions in recently polluted mires. -- Highlights: •We reconstruct the subrecent ecological variables using transfer functions. •Calibration was based on long-term averages and modern diatom sampling. •Herbarized bryophytes were used as a source of historic diatom samples. •Bogs were influenced by grazing in the period 1918–1947. •We provide clear evidence of bog pollution by aerial liming in early 90-ies. -- We provide clear evidence that the recent pH/calcium gradient appeared ca 20 years ago owing to aerial liming of forests

  10. Diatom-inferred history of one of the northernmost Greenland lakes

    DEFF Research Database (Denmark)

    Ludikova, Anna; Olsen, Jesper; Kjær, Kurt H.;

    , as well as physical and geochemical proxies was used to reconstruct the Holocene history of one of the small lakes located in Peary Land, northernmost Greenland, to decipher the environmental changes of the past. The diatom record of Bliss Lake (83°35'14''N 28°21'12''W, 17 m a.s.l.) reveals three main...

  11. Ultrastructure and Membrane Traffic During Cell Division in the Marine Pennate Diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Tanaka, Atsuko; De Martino, Alessandra; Amato, Alberto; Montsant, Anton; Mathieu, Benjamin; Rostaing, Philippe; Tirichine, Leila; Bowler, Chris

    2015-11-01

    The marine pennate diatom Phaeodactylum tricornutum has become a model for diatom biology, due to its ease of culture and accessibility to reverse genetics approaches. While several features underlying the molecular mechanisms of cell division have been described, morphological analyses are less advanced than they are in other diatoms. We therefore examined cell ultrastructure changes prior to and during cytokinesis. Following chloroplast division, cleavage furrows are formed at both longitudinal ends of the cell and are accompanied by significant vesicle transport. Although neither spindle nor microtubules were observed, the nucleus appeared to be split by the furrow after duplication of the Golgi apparatus. Finally, centripetal cytokinesis was completed by fusion of the furrows. Additionally, F-actin formed a ring structure and its diameter became smaller, accompanying the ingrowing furrows. To further analyse vesicular transport during cytokinesis, we generated transgenic cells expressing yellow fluorescent protein (YFP) fusions with putative diatom orthologs of small GTPase Sec4 and t-SNARE protein SyntaxinA. Time-lapse observations revealed that SyntaxinA-YFP localization expands from both cell tips toward the center, whereas Sec4-YFP was found in the Golgi and subsequently relocalizes to the future division plane. This work provides fundamental new information about cell replication processes in P. tricornutum.

  12. 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

    within the diatom community. The outcome can be predicted by a set of simple differential equations. For a two-species system the equations reduce to the Lotka-Volterra two-species competition model. The outcome of this interference competition depends on species-specific growth rates, cell sizes...

  13. Anomalia em Coscinodiscus oculus-iridis ehrenberg, 1839 (Diatomácea

    Directory of Open Access Journals (Sweden)

    Luiz Tavares de Lyra

    1964-01-01

    Full Text Available The author describes an anomalous specimen in diatom Coscinodiscus oculus-iridis Ehr., 1839, caught from Guanabara Bat, (22º 51' 8" Lat. S. - 43º 14' 3" Long. W. G.; its dorsal face (fig. 1, is different from the ventral one, (fig. 2.

  14. Genome Sequence of Marinobacter sp. Strain MCTG268 Isolated from the Cosmopolitan Marine Diatom Skeletonema costatum.

    Science.gov (United States)

    Gutierrez, Tony; Whitman, William B; Huntemann, Marcel; Copeland, Alex; Chen, Amy; Kyrpides, Nikos; Markowitz, Victor; Pillay, Manoj; Ivanova, Natalia; Mikhailova, Natalia; Ovchinnikova, Galina; Andersen, Evan; Pati, Amrita; Stamatis, Dimitrios; Reddy, T B K; Ngan, Chew Yee; Chovatia, Mansi; Daum, Chris; Shapiro, Nicole; Cantor, Michael N; Woyke, Tanja

    2016-01-01

    Marinobacter sp. strain MCTG268 was isolated from the cosmopolitan marine diatom Skeletonema costatum and can degrade oil hydrocarbons as sole sources of carbon and energy. Here, we present the genome sequence of this strain, which is 4,449,396 bp with 4,157 genes and an average G+C content of 57.0%. PMID:27609918

  15. Genome-Scale Model Reveals Metabolic Basis of Biomass Partitioning in a Model Diatom

    Science.gov (United States)

    Broddrick, Jared; Dupont, Christopher L.; Peers, Graham; Beeri, Karen; Mayers, Joshua; Gallina, Alessandra A.; Allen, Andrew E.; Palsson, Bernhard O.; Zengler, Karsten

    2016-01-01

    Diatoms are eukaryotic microalgae that contain genes from various sources, including bacteria and the secondary endosymbiotic host. Due to this unique combination of genes, diatoms are taxonomically and functionally distinct from other algae and vascular plants and confer novel metabolic capabilities. Based on the genome annotation, we performed a genome-scale metabolic network reconstruction for the marine diatom Phaeodactylum tricornutum. Due to their endosymbiotic origin, diatoms possess a complex chloroplast structure which complicates the prediction of subcellular protein localization. Based on previous work we implemented a pipeline that exploits a series of bioinformatics tools to predict protein localization. The manually curated reconstructed metabolic network iLB1027_lipid accounts for 1,027 genes associated with 4,456 reactions and 2,172 metabolites distributed across six compartments. To constrain the genome-scale model, we determined the organism specific biomass composition in terms of lipids, carbohydrates, and proteins using Fourier transform infrared spectrometry. Our simulations indicate the presence of a yet unknown glutamine-ornithine shunt that could be used to transfer reducing equivalents generated by photosynthesis to the mitochondria. The model reflects the known biochemical composition of P. tricornutum in defined culture conditions and enables metabolic engineering strategies to improve the use of P. tricornutum for biotechnological applications. PMID:27152931

  16. The Reimer Diatom Herbarium: An important resource for teaching and research

    Science.gov (United States)

    Rushforth, S.J.; Edlund, M.B.; Spaulding, S.A.; Stoermer, E.F.

    2010-01-01

    The Reimer Diatom Herbarium (ILH) at Iowa Lakeside Laboratory (ILL), a field station of Iowa's state universities, contains 3,280 permanent diatom slides of collections made from prairie potholes, alkaline fens, acid bogs, eutrophic lakes, saline lakes, Pleistocene paleolakes, and Miocene fossil deposits near ILL. The herbarium has a focus on collections made within Dickinson County, a region with an important legacy of study by students and visiting researchers from the US, Canada, and international institutions. The herbarium is well documented by taxon and location catalogues. The taxon card catalogue contains over 2,800 records referencing 67 genera, and the location card catalogue references collection sites from 51 counties in 16 North American states. Curated slides include over 300 species identifications made, or verified, by C.W. Reimer. Most curated slides have diatom specimens identified to species, circled with a diamond objective marker, and indicated on the slide label Six holotypes are included in the herbarium and we present the first light micrograph images of these type specimens. We present documentation of the contents and current condition of the herbarium and report that it is now available to researchers for scientific study. Many of the sites represented in the Reimer Diatom Herbarium are the same locations visited each year by students and visiting researchers at ILL, resulting in an important resource for monitoring environmental change, resolving taxonomic issues, and understanding species distributions in unique habitats.

  17. DIATOMS AS INDICATORS OF ISOLATED HERBACEOUS WETLAND CONDITION IN FLORIDA, USA

    Science.gov (United States)

    Benthic, epiphytic, and phytoplanktonic diatoms, as well as soil and water physical-chemical parameters, were sampled from 70 small (~1 ha) isolated depressional herbaceous wetlands located along a gradient of human disturbance in peninsular Florida to: 1) compare assemblage str...

  18. A new four-parameter empirical potential energy function for diatomic molecules

    Indian Academy of Sciences (India)

    M Rafi; Reem Al-Tuwirqi; Hanaa Farhan; I A Khan

    2007-06-01

    A new empirical four-parameter function is proposed for the construction of potential curves of 15 stable states of diatomic molecules. The parameters are evaluated in terms of experimentally known spectroscopic constants. On comparing its performance with other functions, the proposed function is found to be simple and reliable for a wide range of molecules.

  19. Study on Non-Sequential Double Ionization of Aligned Diatomic Molecules in Strong Laser Fields

    Institute of Scientific and Technical Information of China (English)

    LI Yan; CHEN Jing; YANG Shi-Ping; LIU Jie

    2007-01-01

    We develop a semiclassical model to describe the non-sequential double ionization of aligned diatomic molecules in an intense linearly polarized field. It is found that in the tunnelling regime, the oriented molecule shows geometric effects on double ionization process when aligned parallel and perpendicular to the external Geld. Our results are qualitatively consistent with the recent experimental observations.

  20. Diatom Derived Polyunsaturated Aldehydes Do Not Structure the Planktonic Microbial Community in a Mesocosm Study

    Directory of Open Access Journals (Sweden)

    Ulf Båmstedt

    2012-03-01

    Full Text Available Several marine and freshwater diatoms produce polyunsaturated aldehydes (PUA in wound-activated processes. These metabolites are also released by intact diatom cells during algal blooms. Due to their activity in laboratory experiments, PUA are considered as potential mediators of diatom-bacteria interactions. Here, we tested the hypothesis that PUA mediate such processes in a close-to-field mesocosm experiment. Natural plankton communities enriched with Skeletonema marinoi strains that differ in their PUA production, a plankton control, and a plankton control supplemented with PUA at natural and elevated concentrations were observed. We monitored bacterial and viral abundance as well as bacterial community composition and did not observe any influence of PUA on these parameters even at elevated concentrations. We rather detected an alternation of the bacterial diversity over time and differences between the two S. marinoi strains, indicating unique dynamic bacterial communities in these algal blooms. These results suggest that factors other than PUA are of significance for interactions between diatoms and bacteria.

  1. Deglacial diatom production in the tropical North Atlantic driven by enhanced silicic acid supply

    Science.gov (United States)

    Hendry, Katharine R.; Gong, Xun; Knorr, Gregor; Pike, Jennifer; Hall, Ian R.

    2016-03-01

    Major shifts in ocean circulation are thought to be responsible for abrupt changes in temperature and atmospheric CO2 during the last deglaciation, linked to variability in meridional heat transport and deep ocean carbon storage. There is also widespread evidence for shifts in biological production during these times of deglacial CO2 rise, including enhanced diatom production in regions such as the tropical Atlantic. However, it remains unclear as to whether this diatom production was driven by enhanced wind-driven upwelling or density-driven vertical mixing, or by elevated thermocline concentrations of silicic acid supplied to the surface at a constant rate. Here, we demonstrate that silicic acid supply at depth in the NE Atlantic was enhanced during the abrupt climate events of the deglaciation. We use marine sediment archives to show that an increase in diatom production during abrupt climate shifts could only occur in regions of the NE Atlantic where the deep supply of silicic acid could reach the surface. The associated changes are indicative of enhanced regional wind-driven upwelling and/or weakened stratification due to circulation changes during phases of weakened Atlantic meridional overturning. Globally near-synchronous pulses of diatom production and enhanced thermocline concentrations of silicic acid suggest that widespread deglacial surface-driven breakdown of stratification, linked to changes in atmospheric circulation, had major consequences for biological productivity and carbon cycling.

  2. Autoradiographic investigation of diatom succession in Lake Tahoe. [Natural /sup 14/C tracer

    Energy Technology Data Exchange (ETDEWEB)

    Dozier, B. J.; Beauchamp, J. J.

    1977-01-01

    Carbon-14 grain density autoradiography was used to qualitatively assess the changes in photosynthetic activity occurring throughout the course of a year within the three dominant phytoplankton populations in Lake Tahoe. Lake Tahoe is an ultraoligotrophic subalpine monomictic lake situated at 1898 m in the Sierra-Nevada-mountains of California and Nevada. Diatoms dominate the lake phytoplankton.

  3. Seasonal and interannual dynamics of diatom assemblages in Sacrower See (NE Germany): A sediment trap study

    NARCIS (Netherlands)

    Kirilova, E.P.; Bluszcz, P.; Heiri, O.; Cremer, H.; Ohlendorf, C.; Lotter, A.F.; Zolitschka, B.

    2008-01-01

    Diatom assemblages from sediment trap samples collected during ten intervals between October 2003 and October 2005 in Sacrower See (NE Germany) were related to limnological and meteorological data. Sacrower See is a dimictic, 38 m deep, hypertrophic lowland lake (29.5 m a.s.l.). We identified distin

  4. Multisignal control of expression of the LHCX protein family in the marine diatom Phaeodactylum tricornutum.

    Science.gov (United States)

    Taddei, Lucilla; Stella, Giulio Rocco; Rogato, Alessandra; Bailleul, Benjamin; Fortunato, Antonio Emidio; Annunziata, Rossella; Sanges, Remo; Thaler, Michael; Lepetit, Bernard; Lavaud, Johann; Jaubert, Marianne; Finazzi, Giovanni; Bouly, Jean-Pierre; Falciatore, Angela

    2016-06-01

    Diatoms are phytoplanktonic organisms that grow successfully in the ocean where light conditions are highly variable. Studies of the molecular mechanisms of light acclimation in the marine diatom Phaeodactylum tricornutum show that carotenoid de-epoxidation enzymes and LHCX1, a member of the light-harvesting protein family, both contribute to dissipate excess light energy through non-photochemical quenching (NPQ). In this study, we investigate the role of the other members of the LHCX family in diatom stress responses. Our analysis of available genomic data shows that the presence of multiple LHCX genes is a conserved feature of diatom species living in different ecological niches. Moreover, an analysis of the levels of four P. tricornutum LHCX transcripts in relation to protein expression and photosynthetic activity indicates that LHCXs are differentially regulated under different light intensities and nutrient starvation, mostly modulating NPQ capacity. We conclude that multiple abiotic stress signals converge to regulate the LHCX content of cells, providing a way to fine-tune light harvesting and photoprotection. Moreover, our data indicate that the expansion of the LHCX gene family reflects functional diversification of its members which could benefit cells responding to highly variable ocean environments. PMID:27225826

  5. Energetic coupling between plastids and mitochondria drives CO2 assimilation in diatoms.

    Science.gov (United States)

    Bailleul, Benjamin; Berne, Nicolas; Murik, Omer; Petroutsos, Dimitris; Prihoda, Judit; Tanaka, Atsuko; Villanova, Valeria; Bligny, Richard; Flori, Serena; Falconet, Denis; Krieger-Liszkay, Anja; Santabarbara, Stefano; Rappaport, Fabrice; Joliot, Pierre; Tirichine, Leila; Falkowski, Paul G; Cardol, Pierre; Bowler, Chris; Finazzi, Giovanni

    2015-08-20

    Diatoms are one of the most ecologically successful classes of photosynthetic marine eukaryotes in the contemporary oceans. Over the past 30 million years, they have helped to moderate Earth's climate by absorbing carbon dioxide from the atmosphere, sequestering it via the biological carbon pump and ultimately burying organic carbon in the lithosphere. The proportion of planetary primary production by diatoms in the modern oceans is roughly equivalent to that of terrestrial rainforests. In photosynthesis, the efficient conversion of carbon dioxide into organic matter requires a tight control of the ATP/NADPH ratio which, in other photosynthetic organisms, relies principally on a range of plastid-localized ATP generating processes. Here we show that diatoms regulate ATP/NADPH through extensive energetic exchanges between plastids and mitochondria. This interaction comprises the re-routing of reducing power generated in the plastid towards mitochondria and the import of mitochondrial ATP into the plastid, and is mandatory for optimized carbon fixation and growth. We propose that the process may have contributed to the ecological success of diatoms in the ocean. PMID:26168400

  6. A diatom record of recent environmental change in Lake Duluti, northern Tanzania

    DEFF Research Database (Denmark)

    Öberg, Helena; Andersen, Thorbjørn Joest; Westerberg, Lars-Ove;

    2012-01-01

    Lake Duluti is a small, topographically closed crater lake located on the flanks of Mt Meru, northern Tanzania. Analyses of diatoms in three short sediment cores and four modern samples from Lake Duluti were used to infer past environmental changes. 210Pb and 137Cs activity profiles combined...

  7. UV- and salinity-induced oxidative effects in the marine diatom Cylindrotheca closterium during simulated emersion

    NARCIS (Netherlands)

    Rijstenbil, J.W.

    2005-01-01

    The diatom Cylindrotheca closterium was exposed to transient light- and osmotic conditions as occur during its tidal emersion. The objective was to analyze how this simulated emersion contributes to the production of active oxygen species (AOS) and via this, to oxidative cell damage. Light- and sali

  8. A Gas Chromatography Experiment for Proving the Application of Quantum Symmetry Restrictions in Homonuclear Diatomic Molecules.

    Science.gov (United States)

    Dosiere, M.

    1985-01-01

    Background information, procedures used, and typical results obtained are provided for an experiment in which gas chromatography is used to prove the application of quantum symmetry restrictions in homonuclear diatomic molecules. Comparisons between experimental results and theoretical computed values show good agreement, within one to two…

  9. Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

    Science.gov (United States)

    Abrantes, Fatima; Cermeno, Pedro; Lopes, Cristina; Romero, Oscar; Matos, Lélia; Van Iperen, Jolanda; Rufino, Marta; Magalhães, Vitor

    2016-07-01

    Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica-precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia-Canary, Benguela, Peru-Humboldt, California, and Somalia-Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production, and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. On the global scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

  10. Benthic diatom composition in isolated forested wetlands subject to drying: implications for monitoring and assessment

    Science.gov (United States)

    The development of bioindicators for wetlands, especially ephemerally hydrated depressional and isolated wetlands, can be problematic because of seasonal hydrology and target organism biology. To determine if benthic diatoms could be used as a year-round biological indicator of w...

  11. Improved understanding of Diatom stratigraphy in a varved sediment through lake monitoring and sediment trap data

    Science.gov (United States)

    Maier, Dominique Beatrice; Bigler, Christian

    2016-04-01

    Biological remains in lake sediments reflect past conditions in the lake itself and within its catchment. However, it is difficult to disentangle to which extent the environmental drivers are natural (e.g. population dynamics, climate) or human-induced (e.g. agriculture, forestry). Therefore, comprehensive lake monitoring is crucial to understand taphonomy and sediment formation, and enhances the value of the paleolimnological archive. In this study, we analyze survey data of a varved lake in northern Sweden (Nylandssjön, Nordingrå) with special focus on the diatom record. Different monitoring components are combined, i.e. (1) bi-weekly data of chemical parameters (chlorophyll a, nutrients) covering the period from 2012 to 2015, (2) physical parameters (temperature, oxygen, ice-cover) covering the period from 2000-2015, (3) high-resolution data from a sequential sediment trap covering the period from 2000-2015 and (4) annually resolved diatom data from the sediment varves. Early and intense spring mixing in 2012 translates into a short but vertically pervasive chlorophyll a band which is simultaneously recorded in the sequential trap with a high diatom peak (500 000 valves cm2 d-1). The years 2013 and 2014 show higher chlorophyll a concentrations in the water column, but diatoms do not form a peak flux (>100 000 diatoms cm2 d-1) at any time in the sediment trap, probably due to stratification patterns. The trap record from 2012 indicates a spring bloom dominating the sediment signal, but this is not repeated in 2013 and 2014. Future analyses will be directed towards linking the monitored in-lake processes to annually or even seasonally resolved environmental characteristics. The multiplicity of potential ecological and environmental drivers led us to reverse our analytical view by starting with the diatom stratigraphy in the varved sediment, continuing through the data from sediment trap and water column into the lake catchment to identify deviations (timing

  12. Objective Diagnosis of Drowning by the "Diatom Test" - A Critical Review.

    Science.gov (United States)

    Bortolotti, F; Tagliaro, F; Manetto, G

    2004-07-01

    The identification of diatoms in the body tissues to prove a death by drowning (known as the diatom test) dates back to the end of the 19th century. However, in recent decades the reliability of this method was disproved because of an alleged inaccuracy and high false positive rate; nonetheless, the matter is still highly controversial. The purpose of the present work is to offer a critical review of the subject with a specific emphasis on the technical problems. In particular, contamination of samples during autopsy and of tissue extracts during processing was recognized as the main source of false positive results. However, the possibility of diatom passive penetration into the body (particularly into lungs) during submersion cannot be excluded, especially in highly transformed cadavers. Hence, tissues that are highly secluded from the drowning medium, such as bone marrow, are preferred as samples, according to the most recent literature. Additional information on the drowning site and circumstances can be drawn from the qualitative and quantitative comparison between the diatoms found in the body tissues and those present in the drowning water. From the analytical point of view, the majority of authors digest tissues by treatment with strong acids, often after oxidation; alternatively, proteolytic enzymes are widely used. Detection is generally carried out by light microscopy, but scanning electron microscopy (SEM) shows much better resolution, which is important for the identification of the smallest diatoms or diatom fragments. In the experimental part of the work, a recent evolution of SEM, known as environmental scanning electron microscopy (ESEM) has been tested on drowning victims. The main feature of ESEM is the possibility to work on standard microscopic preparations without the need of sample coating, which allows switching between light and electron microscopy, thus taking advantage of the wide optical field of the former technique and of the high

  13. Physical processes affecting availability of dissolved silicate for diatom production in the Arabian Sea

    Science.gov (United States)

    Young, David K.; Kindle, John C.

    1994-01-01

    A passive tracer to represent dissolved silicate concentrations, with biologically realistic uptake kinetics, is successfully incorporated into a three-dimensional, eddy-resolving, ocean circulation model of the Indian Ocean. Hypotheses are tested to evaluate physical processes which potentially affect the availability of silicate for diatom production in the Arabian Sea. An alternative mechanism is offered to the idea that open ocean upwelling is primarily responsible for the high, vertical nutrient flux and consequent large-scale phytoplankton bloom in the northwestern Arabian Sea during the southwest monsoon. Model results show that dissolved silicate in surface waters available for uptake by diatoms is primarily influenced by the intensity of nearshore upwelling from soutwest monsoonal wind forcing and by the offshore advective transport of surface waters. The upwelling, which in the model occurs within 200 +/- 50 km of the coast, appears to be a result of a combination of coastal upwelling, Elkman pumping, and divergence of the coastal flow as it turns offshore. Localized intensifications of silicate concentrations appear to be hydrodynamically driven and geographically correlated to coastal topographic features. The absence of diatoms in sediments of the eastern Arabian Basin is consistent with modeled distributional patterns of dissolved silicate resulting from limited westward advection of upwelled coastal waters from the western continental margin of India and rapid uptake of available silicate by diatoms. Concentrations of modeled silicate become sufficiently low to become unavailable for diatom production in the eastern Arabian Sea, a region between 61 deg E and 70 deg E at 8 deg N on the south, with the east and west boundaries converging on the north at approximately 67 deg E, 20 deg N.

  14. Distribution patterns of benthic diatoms during summer in the Niyang River, Tibet, China

    Institute of Scientific and Technical Information of China (English)

    PEI Guofeng; LIU Guoxiang

    2011-01-01

    The aim of this study was to investigate the distribution,density,community structure and biodiversity characteristics of benthic diatoms,and to analyze whether differences in species composition and abundance exist in different regions of the Niyang River,Tibet.Among the 157 taxa observed in 15 sampling sites in the main river and tributary,most were casual species (>100),the relative abundance of the genera Achnanthes and Fragilaria was 67% of the total relative abundance.Achnanthes minutissima was the most important species and dominated the whole river reaches (average relative abundance was 30%); the average diatom densities were 7.4× 105 cell/cm2 at all sites,and increased slowly from the upper section to downriver.The significant indicator taxa with higher relative abundance were Achnanthes biasolettiana (18.0%) and Fragilaria arcus (18.2%),Fragilaria capucina var.vaucheriae (31.2%),Fragilaria construens var.venter (11.3%) and Cymbella affinis (11.0%) in the upper,tributary and mid-river sections,respectively.Achnanthes minutissima was the most abundant species (56%) in the downriver section.Biodiversity indices showed a gradual decrease from the up- to down-river section,and dominant species were more abundant in the upper and mid-river sections than in the downriver section.A two-way indictor species analysis (TWINSPAN) of diatom composition clearly showed four different groups,namely the upper,mid,lower and tributary sections.Detrended correspondence analysis (DCA)supported the results of TW1NSPAN,and the characteristics of site distribution and species composition in the Niyang River supported the spatial structure of diatom assemblages.This study indicates that bio-assessment programs utilizing benthic diatoms could clearly benefit lotic water with regional stratification.

  15. Whole transcriptome analysis of the silicon response of the diatom Thalassiosira pseudonana

    Directory of Open Access Journals (Sweden)

    Shrestha Roshan

    2012-09-01

    Full Text Available Abstract Background Silicon plays important biological roles, but the mechanisms of cellular responses to silicon are poorly understood. We report the first analysis of cell cycle arrest and recovery from silicon starvation in the diatom Thalassiosira pseudonana using whole genome microarrays. Results Three known responses to silicon were examined, 1 silicified cell wall synthesis, 2 recovery from silicon starvation, and 3 co-regulation with silicon transporter (SIT genes. In terms of diatom cell wall formation, thus far only cell surface proteins and proteins tightly associated with silica have been characterized. Our analysis has identified new genes potentially involved in silica formation, and other genes potentially involved in signaling, trafficking, protein degradation, glycosylation and transport, which provides a larger-scale picture of the processes involved. During silicon starvation, an overrepresentation of transcription and translation related genes were up-regulated, indicating that T. pseudonana is poised to rapidly recover from silicon starvation and resume cell cycle progression upon silicon replenishment. This is in contrast to other types of limitation, and provides the first molecular data explaining the well-established environmental response of diatoms to grow as blooms and to out-compete other classes of microalgae for growth. Comparison of our data with a previous diatom cell cycle analysis indicates that assignment of the cell cycle specific stage of particular cyclins and cyclin dependent kinases should be re-evaluated. Finally, genes co-varying in expression with the SITs enabled identification of a new class of diatom-specific proteins containing a unique domain, and a putative silicon efflux protein. Conclusions Analysis of the T. pseudonana microarray data has provided a wealth of new genes to investigate previously uncharacterized cellular phenomenon related to silicon metabolism, silicon’s interaction with

  16. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wang Mengjiao [State Key Laboratory in Marine Pollution, Section of Marine Ecology and Biotechnology, Division of Life Science, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon (Hong Kong); Wang Wenxiong, E-mail: wwang@ust.hk [State Key Laboratory in Marine Pollution, Section of Marine Ecology and Biotechnology, Division of Life Science, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon (Hong Kong)

    2011-01-25

    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{sup 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{sup 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{sup 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{sub 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{sup 2+}] and duration increased. This study shows that the physiological/biochemical and kinetic responses of phytoplankton upon metal exposure deserve further investigation.

  18. 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.

  19. Characterisation of transparent exopolymer particles (TEP) produced during algal bloom: A membrane treatment perspective

    KAUST Repository

    Villacorte, Loreen O.

    2013-01-01

    Algal blooms are currently a major concern of the membrane industry as it generates massive concentrations of organic matter (e.g. transparent exopolymer particles [TEP]), which can adversely affect the operation of membrane filtration systems. The goal of this study is to understand the production, composition and membrane rejection of these organic materials using different characterisation techniques. Two common species of bloom-forming freshwater and marine algae were cultivated in batch cultures for 30days and the productions of TEP and other organic matter were monitored at different growth phases. TEP production of the marine diatom, Chaetoceros affinis, produced 6-9 times more TEP than the freshwater blue-green algae, Microcystis. The organic substances produced by both algal species were dominated by biopolymeric substances such as polysaccharides (45-64%) and proteins (2-17%) while the remaining fraction comprises of low molecular weight refractory (humic-like) and/ or biogenic organic substances. MF/UF membranes mainly rejected the biopolymers but not the low molecular weight organic materials. MF membranes (0.1-0.4 lm) rejected 42-56% of biopolymers, while UF membranes (10-100 kDa) rejected 65-95% of these materials. Further analysis of rejected organic materials on the surface of the membranes revealed that polysac-charides and proteins are likely responsible for the fouling of MF/UF systems during an algal bloom situation. © 2013 Desalination Publications.

  20. The transferability of diatoms to clothing and the methods appropriate for their collection and analysis in forensic geoscience.

    Science.gov (United States)

    Scott, Kirstie R; Morgan, Ruth M; Jones, Vivienne J; Cameron, Nigel G

    2014-08-01

    Forensic geoscience is concerned with the analysis of geological materials in order to compare and exclude environmental samples from a common source, or to identify an unknown provenance in a criminal investigation. Diatom analysis is currently an underused technique within the forensic geoscience approach, which has the potential to provide an independent ecological assessment of trace evidence. This study presents empirical data to provide a preliminary evidence base in order to be able to understand the nature of diatom transfers to items of clothing, and the collection of transferred diatom trace evidence from a range of environments under experimental conditions. Three diatom extraction methods were tested on clothing that had been in contact with soil and water sites: rinsing in water (RW), rinsing in ethanol (RE), and submersion in H2O2 solution (H). Scanning electron microscopy (S.E.M.) analysis was undertaken in order to examine the degree of diatom retention on treated clothing samples. The total diatom yield and species richness data was recorded from each experimental sample in order to compare the efficacy of each method in collecting a representative sample for analysis. Similarity was explored using correspondence analysis. The results highlight the efficiency of H2O2 submersion in consistently extracting high diatom counts with representative species from clothing exposed to both aquatic and terrestrial sites. This is corroborated by S.E.M. analysis. This paper provides an important empirical evidence base for both establishing that diatoms do indeed transfer to clothing under forensic conditions in a range of environments, and in identifying that H2O2 extraction is the most efficient technique for the optimal collection of comparative samples. There is therefore potentially great value in collecting and analysing diatom components of geoforensic samples in order to aid in forensic investigation.

  1. Data from two different culture conditions of Thalassiosira weissflogii diatom and from cleaning procedures for obtaining monodisperse nanostructured biosilica.

    Science.gov (United States)

    Vona, Danilo; Urbano, Laura; Bonifacio, Maria A; De Giglio, Elvira; Cometa, Stefania; Mattioli-Belmonte, Monica; Palumbo, Fabio; Ragni, Roberta; Cicco, Stefania R; Farinola, Gianluca M

    2016-09-01

    Diatoms microalgae produce biosilica nanoporous rigid outershells called frustules that exhibit an intricate nanostructured pore pattern. In this paper two specific Thalassiosira weissflogii culture conditions and size control procedures during the diatoms growth are described. Data from white field and fluorescence microscopy, evaluation of cell densities and cell parameters (k value and R value) according to cell culture conditions are listed. Different cleaning procedures for obtaining bare frustules are described. In addition, FTIR and spectrofluorimetric analyses of cleaned biosilica are shown. The data are related to the research article "Chemically Modified Diatoms Biosilica for Bone Cell Growth with Combined Drug-Delivery and Antioxidant Properties" [1]. PMID:27331108

  2. 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

    Mineral content and physico-chemical properties of the freshwaters are the main factors affecting both algal assemblages and distributions, while presence of dissolved silicon, low water conductivity, and rocky-mountain habitats host benthic diatom assemblages of high species richness. It is shown that diatoms are sensible to the freshwater acidification (used as pH indicators in acid waters), environmental and climate changes, river organic load, and heavy metal water pollution. For this characteristic, diatoms are among the major biological markers for a variety of environmental and stratigraphic applications. In particular, qualitative and quantitative analyses (assemblage analyses) together with biotic indices as well as morphological and ultrastructure parameterisation provide tools for detailed environmental control and paleo-environmental reconstructions. Severe environmental problems are typically caused by "abandoned mine" and are consequences of the cessation of the mining activity with a lack in infrastructure maintenance. The mine waters which flow into the Gromolo Torrent are almost acidic (pH varying from 2.4 to 5) and enriched in heavy metals and SO42-. This pollution is caused by Acid Mine Drainage (AMD) processes that interest the Libiola mining area, known as a typical example of active AMD processes. The aim of this work is: 1) to characterise the local benthic diatom assemblages along the acidic mine effluents that discharge from Libiola mine, the entire Gromolo torrent course, and in the marine area off the torrent mouth; 2) to identify the main diatom biomarker taxa; 3) to highlight striking situations of equilibrium-disequilibrium in the algal communities, and 4) to point out types and frequency of some teratologies affecting specific diatom taxa as a response to environmental stressors (such as metal-metalloid enrichment). A total of 17 diatom samples was collected and examined, including some marine samples. Diatoms were collected in the

  3. MOLECULAR EVIDENCE CONFIRMS SISTER RELATIONSHIP OF ARDISSONEA, CLIMACOSPHENIA, AND TOXARIUM WITHIN THE BIPOLAR CENTRIC DIATOMS (BACILLARIOPHYTA, MEDIOPHYCEAE), AND CLADISTIC ANALYSES CONFIRM THAT EXTREMELY ELONGATED SHAPE HAS ARISEN TWICE IN THE DIATOMS(1).

    Science.gov (United States)

    Medlin, Linda K; Sato, Shinya; Mann, David G; Kooistra, Wiebe H C F

    2008-10-01

    With the use of a new kit from Qiagen to amplify total genome quantity, DNA was bulked up from two diatoms that are difficult to grow (Ardissonea and Climacosphenia), and the nuclear SSU rRNA gene was successfully amplified. Results of Bayesian analyses showed that these diatoms are sister to Toxarium and belong to the bi- and multipolar centric diatoms. The results indicate that extremely elongate shape has arisen at least twice in diatoms, in the true pennates, and in the bipolar centrics. The two lateral pattern centers of Ardissonea and Climacosphenia likely represent a modified annulus that subtends ribs internally as well as externally. Studies of sexual reproduction are needed to determine whether Ardissonea, Climacosphenia, and Toxarium achieve their elongate shape by similar means to each other and to true pennates, that is, by controlling the expansion of the auxospores by sequential addition of silicified bands (to form a properizonium or perizonium).

  4. Silica Biogenic Dissolution in Sediment of Lake Chapala, Mexico and the 'dilemma of Dissapearing Diatoms'

    Science.gov (United States)

    Zarate, P. F.; Ramirez Sanchez, H.; Israde-Alcantara, I.

    2013-12-01

    Neotectonic Lake Chapala (LC) is in the Citala Rift of western Mexico, which in association with the Tepic-Zacoalco and Colima Rifts, form the well-known neotectonic Jalisco continental triple junction (JNTJ), that is located at the western end of the Transmexican Volcanic Belt geological province (major andesitic composition) and was generated by the activity of a Pleistocene continental arc. The mean lake level is 1526 m above sea level with a mean depth of 4 m. Due to the shallowness and wind action the LC water is well mixed. The sedimentation rate (SR) throughout LC is not uniform. The SR from west to east varies from ≤2 to ≤4 mm a-1 (based on 210Pb, 137Cs and 240Pu). Terrigenous minerals of a feldspathic affinity (Si/Al ratio 2-3) dominate the infilling at Lake Chapala, with a granulometric media ranging from 10 to 50 μm in diameter. Hydrogeochemistry data is showed in Table 1. At LC there are also in-shore and off-shore geothermal manifestations of carbonate type (193 and 263 mg*L-1) and only one site with sulfated type (≥479 mg*L-1 of SO-24). Biological proxies like diatoms and pollen occur over the last 600 years B.P. at LC and provide information about the paleoenvironmental conditions in the late Holocene. Although vegetation changes cannot be interpreted with precision due to the high silica dissolution of diatoms, it is possible to make some inferences. The major diatom taxa are epiphytic, dominated by Surirella, Nitzschia, Amphora and Campylodiscus: evidence for a wide belt of submerged vegetation. Diatom remains show dissolution and ulterior fragmentation. The diatoms in the last 100 years B.P. are characterized by Stephanodiscus aff. nemanensis and Cyclostephanus, where the latter has been associated with elevated levels of eutrophication. The phenomena of silica biogenic dissolution (cf. diatom and phytolithes) in sediment of LC is preliminarly associated to alkaline values of pH (7,20-9,45), salinity and carbonate concentration.Lake Chapala

  5. Vertical migratory rhythms of benthic diatoms in a tropical intertidal sand flat: Influence of irradiance and tides

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.; Anil, A.C.

    Vertical migratory behavior of benthic diatoms is one of the adaptive strategies employed for a life in intertidal habitats. Irradiance and tides are considered to be the key factors governing vertical migration. Experiments were carried out...

  6. Lipophilic pigments from cyanobacterial (blue-green algal) and diatom mats in Hamelin Pool, Shark Bay, Western Australia

    Science.gov (United States)

    Palmisano, A. C.; Summons, R. E.; Cronin, S. E.; Des Marais, D. J.

    1989-01-01

    Lipophilic pigments were examined in microbial mat communities dominated by cyanobacteria in the intertidal zone and by diatoms in the subtidal and sublittoral zones of Hamelin Pool, Shark Bay, Western Australia. These microbial mats have evolutionary significance because of their similarity to lithfied stromatolites from the Proterozoic and Early Paleozoic eras. Fucoxanthin, diatoxanthin, diadinoxanthin, beta-carotene, and chlorophylls a and c characterized the diatom mats, whereas cyanobacterial mats contained myxoxanthophyll, zeaxanthin, echinenone, beta-carotene, chlorophyll a and, in some cases, sheath pigment. The presence of bacteriochlorophyll a within the mats suggest a close association of photosynthetic bacteria with diatoms and cyanobacteria. The high carotenoids : chlorophyll a ratios (0.84-2.44 wt/wt) in the diatom mats suggest that carotenoids served a photoprotective function in this high light environment. By contrast, cyanobacterial sheath pigment may have largely supplanted the photoprotective role of carotenoids in the intertidal mats.

  7. X-ray fluorescence mapping of mercury on suspended mineral particles and diatoms in a contaminated freshwater system

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Baohua [ORNL; Mishra, Bhoopesh [ORNL; Miller, Carrie L [ORNL; Wang, Wei [ORNL; Lai, Barry [Argonne National Laboratory (ANL); Brooks, Scott C [ORNL; Kemner, Kenneth M [Argonne National Laboratory (ANL); Liang, Liyuan [ORNL

    2014-01-01

    Mercury (Hg) bioavailability and geochemical cycling is affected by its partitioning between the aqueous and particulate phases. We applied X-ray fluorescence (XRF) microprobes to directly visualize and quantify the spatial localization of Hg and its correlations with other elements of interest on suspended particles from a Hg contaminated freshwater system. Up to 175 g/g Hg is found on suspended particles. Mercury is heterogeneously distributed among phytoplankton (e.g., diatoms) and mineral particles that are rich in iron oxides and natural organic matter (NOM), possibly as Hg-NOM-iron oxide ternary complexes. The diatom-bound Hg is mostly found on outer surfaces of the cells, suggesting passive sorption of inorganic Hg on diatoms. Our results indicate that localized sorption of Hg onto suspended particles, including diatoms and NOM-coated oxide minerals, is an important sink for Hg in natural aquatic environments.

  8. Interactions between diatom aggregates, minerals, particulate organic carbon, and dissolved organic matter: Further implications for the ballast hypothesis

    OpenAIRE

    De La Rocha, Christina,; Nowald, N.; Passow, Uta

    2008-01-01

    Correlations of particulate organic carbon (POC) and mineral fluxes into sediment traps in the deep sea have previously suggested that interactions between organic matter and minerals play a key role in organic matter flux to the deep. Here experiments were carried out in rolling tanks to observe the incorporation of suspended biogenic minerals ( calcium carbonate coccoliths or silica diatom frustules) into diatom aggregates and examine their influence on aggregate character. Addition of high...

  9. Top-down, bottom-up and physical controls on diatom-diazotroph assemblage growth in the Amazon River plume

    OpenAIRE

    M. R. Stukel; V. J. Coles; Brooks, M. T.; Hood, R.R.

    2014-01-01

    The nutrient-rich waters of the Amazon River plume (ARP) support dense blooms of diatom-diazotroph assemblages (DDAs) that introduce large quantities of new nitrogen to the planktonic ecosystem and, unlike other nitrogen-fixers, are likely to directly fuel vertical carbon flux. To investigate the factors controlling DDA blooms, we develop a five phytoplankton (cyanobacteria, diatoms, unicellular microbial diazotrophs, DDAs, and Trichodesmium), two zooplankton model and embed...

  10. Top-down, bottom-up and physical controls on diatom-diazotroph assemblage growth in the Amazon River Plume

    OpenAIRE

    M. R. Stukel; V. J. Coles; Brooks, M. T.; Hood, R.R.

    2013-01-01

    The nutrient-rich waters of the Amazon River Plume (ARP) support dense blooms of diatom-diazotroph assemblages (DDA) that introduce large quantities of new nitrogen to the planktonic ecosystem and, unlike other nitrogen-fixers, are likely to directly fuel vertical carbon flux. To investigate the factors controlling DDA blooms, we develop a five phytoplankton (cyanobacteria, diatoms, unicellular microbial diazotrophs, DDA, and Trichodesmium), two zooplankton model and embed it within a 1/6° re...

  11. Community- and population-level changes in diatom size structure in a subarctic lake over the last two centuries

    OpenAIRE

    Kerrigan, Elizabeth A.; Irwin, Andrew J; Zoe V. Finkel

    2015-01-01

    Climate change over the last two centuries has been associated with significant shifts in diatom community structure in lakes from the high arctic to temperate latitudes. To test the hypotheses that recent climate warming selects for species of smaller size within communities and a decrease in the average size of species within populations, we quantified the size of individual diatom valves from 10 depths in a sediment core covering the last ∼200 years from a pristine subarctic lake. Over the...

  12. Metabolic Analysis of Adaptation to Short-Term Changes in Culture Conditions of the Marine Diatom Thalassiosira pseudonana

    OpenAIRE

    Bromke, Mariusz A; Patrick Giavalisco; Lothar Willmitzer; Holger Hesse

    2013-01-01

    This report describes the metabolic and lipidomic profiling of 97 low-molecular weight compounds from the primary metabolism and 124 lipid compounds of the diatom Thalassiosira pseudonana. The metabolic profiles were created for diatoms perturbed for 24 hours with four different treatments: (I) removal of nitrogen, (II) lower iron concentration, (III) addition of sea salt, (IV) addition of carbonate to their growth media. Our results show that as early as 24 hours after nitrogen depletion sig...

  13. Response of Spring Diatoms to CO2 Availability in the Western North Pacific as Determined by Next-Generation Sequencing.

    Science.gov (United States)

    Endo, Hisashi; Sugie, Koji; Yoshimura, Takeshi; Suzuki, Koji

    2016-01-01

    Next-generation sequencing (NGS) technologies have enabled us to determine phytoplankton community compositions at high resolution. However, few studies have adopted this approach to assess the responses of natural phytoplankton communities to environmental change. Here, we report the impact of different CO2 levels on spring diatoms in the Oyashio region of the western North Pacific as estimated by NGS of the diatom-specific rbcL gene (DNA), which encodes the large subunit of RubisCO. We also examined the abundance and composition of rbcL transcripts (cDNA) in diatoms to assess their physiological responses to changing CO2 levels. A short-term (3-day) incubation experiment was carried out on-deck using surface Oyashio waters under different pCO2 levels (180, 350, 750, and 1000 μatm) in May 2011. During the incubation, the transcript abundance of the diatom-specific rbcL gene decreased with an increase in seawater pCO2 levels. These results suggest that CO2 fixation capacity of diatoms decreased rapidly under elevated CO2 levels. In the high CO2 treatments (750 and 1000 μatm), diversity of diatom-specific rbcL gene and its transcripts decreased relative to the control treatment (350 μatm), as well as contributions of Chaetocerataceae, Thalassiosiraceae, and Fragilariaceae to the total population, but the contributions of Bacillariaceae increased. In the low CO2 treatment, contributions of Bacillariaceae also increased together with other eukaryotes. These suggest that changes in CO2 levels can alter the community composition of spring diatoms in the Oyashio region. Overall, the NGS technology provided us a deeper understanding of the response of diatoms to changes in CO2 levels in terms of their community composition, diversity, and photosynthetic physiology.

  14. The impact of food type, temperature and starvation on larval development of Balanus amphitrite Darwin (Cirripedia: Thoracica)

    Digital Repository Service at National Institute of Oceanography (India)

    Desai, D.V.; Anil, A.C.

    The impact of diatom food species (Chaetoceros calcitrans and Skeletonema costatum), temperature and starvation on the larval development of Balanus amphitrite was evaluated. Starvation threshold levels for different ages of larvae (0- to 5-day...

  15. 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.

  16. Effect of nitrate enrichment and diatoms on the bioavailability of Fe(III) oxyhydroxide colloids in seawater.

    Science.gov (United States)

    Liu, Feng-Jiao; Huang, Bang-Qin; Li, Shun-Xing; Zheng, Feng-Ying; Huang, Xu-Guang

    2016-03-01

    The photoconversion of colloidal iron oxyhydroxides was a significant source of bioavailable iron in coastal systems. Diatoms dominate phytoplankton communities in coastal and upwelling regions. Diatoms are often exposed to eutrophication. We investigated the effects of different species of diatom, cell density, illumination period, and nitrate additions on the bioavailability of Fe(III) oxy-hydroxide colloids in seawaters. With the increase of illumination period from 1 to 4 h, the ratios of concentrations of total dissolved Fe (DFe) to colloidal iron oxyhydroxides and Fe(II) to DFe increased up to 24.3% and 23.9% for seawater without coastal diatoms, 45.6% and 30.2% for Skeletonema costatum, 44.3% and 29.7% for Thalassiosira weissflogii, respectively. The photochemical activity of coastal diatoms themselves (excluding the dissolved organic matter secreted by algae) on the species transformation of iron in seawater (including the light-induced dissolution of Fe(III) oxyhydroxide colloids and the photo-reduction of Fe(III) into Fe(II)) was confirmed for the first time. There was no significant difference of the ability of S. costatum and Thalassiosira weissflogii on the photoconversion of colloidal iron oxyhydroxides. The photoproduction of dissolved Fe(II) and DFe in the seawater with or without diatoms could be depressed by the nitrate addition. PMID:26766021

  17. A tyrosine-rich cell surface protein in the diatom Amphora coffeaeformis identified through transcriptome analysis and genetic transformation.

    Directory of Open Access Journals (Sweden)

    Matthias T Buhmann

    Full Text Available Diatoms are single-celled eukaryotic microalgae that are ubiquitously found in almost all aquatic ecosystems, and are characterized by their intricately structured SiO2 (silica-based cell walls. Diatoms with a benthic life style are capable of attaching to any natural or man-made submerged surface, thus contributing substantially to both microbial biofilm communities and economic losses through biofouling. Surface attachment of diatoms is mediated by a carbohydrate- and protein- based glue, yet no protein involved in diatom underwater adhesion has been identified so far. In the present work, we have generated a normalized transcriptome database from the model adhesion diatom Amphora coffeaeformis. Using an unconventional bioinformatics analysis we have identified five proteins that exhibit unique amino acid sequences resembling the amino acid composition of the tyrosine-rich adhesion proteins from mussel footpads. Establishing the first method for the molecular genetic transformation of A. coffeaeformis has enabled investigations into the function of one of these proteins, AC3362, through expression as YFP fusion protein. Biochemical analysis and imaging by fluorescence microscopy revealed that AC3362 is not involved in adhesion, but rather plays a role in biosynthesis and/or structural stability of the cell wall. The methods established in the present study have paved the way for further molecular studies on the mechanisms of underwater adhesion and biological silica formation in the diatom A. coffeaeformis.

  18. The {\\it ab initio} calculation of spectra of open shell diatomic molecules

    CERN Document Server

    Tennyson, Jonathan; McKemmish, Laura K; Yurchenko, Sergei N

    2016-01-01

    The spectra (rotational, rotation-vibrational or electronic) of diatomic molecules due to transitions involving only closed-shell ($^1\\Sigma$) electronic states follow very regular, simple patterns and their theoretical analysis is usually straightforward. On the other hand, open-shell electronic states lead to more complicated spectral patterns and, moreover, often appear as a manifold of closely lying electronic states, leading to perturbations with even larger complexity. This is especially true when at least one of the atoms is a transition metal. Traditionally these complex cases have been analysed using approaches based on perturbation theory, with semi-empirical parameters determined by fitting to spectral data. Recently the needs of two rather diverse scientific areas have driven the demand for improved theoretical models of open-shell diatomic systems based on an \\emph{ab initio} approach, these areas are ultracold chemistry and the astrophysics of "cool" stars, brown dwarfs and most recently extraso...

  19. Shifted Tietz-Wei oscillator for simulating the atomic interaction in diatomic molecules

    CERN Document Server

    Falaye, Babatunde J; Hamzavi, Majid

    2015-01-01

    The shifted Tietz-Wei (sTW) oscillator is as good as traditional Morse potential in simulating the atomic interaction in diatomic molecules. By using the Pekeris-type approximation to deal with the centrifugal term, we obtain the bound-state solutions of the radial Schr\\"odinger equation with this typical molecular model via the exact quantization rule (EQR). The energy spectrum for a set of diatomic molecules ($NO \\left(a^4\\Pi_i\\right)$, $NO \\left(B^2\\Pi_r\\right)$, $NO \\left(L'^2\\phi\\right)$, $NO \\left(b^4\\Sigma^{-}\\right)$, $ICl\\left(X^1\\Sigma_g^{+}\\right)$, $ICl\\left(A^3\\Pi_1\\right)$ and $ICl\\left(A'^3\\Pi_2\\right)$ for arbitrary values of $n$ and $\\ell$ quantum numbers are obtained. For the sake of completeness, we study the corresponding wavefunctions using the formula method.

  20. Oxygen isotopic ratio of the diatom siliceous valves: development of a new method in quantitative paleoclimatology

    International Nuclear Information System (INIS)

    This paper describes a new method allowing the measurement of the 18O/16O ratio of the biogenic silica oxygen, which takes into account the effects due to the organic matter and hydration water associated with this type of silica. By isotopic exchange with enriched water, we have been able to fix a treatment which eliminate all contamination and memory effects. This has permitted us to study the temperature dependance of the hydrated silica-water oxygen isotopic fractionation. As application, we present a study of the variations of the delta 18O of fossil diatoms valves along an Equatorial Pacific sediment core covering the last 20.000 years. The results demonstrate the usefulness of the delta 18O of the diatom silica for paleoclimatic investigations

  1. A new blue-pigmented hasleoid diatom, Haslea provincialis, from the Mediterranean Sea

    DEFF Research Database (Denmark)

    Gastineau, Romain; Hansen, Gert; Davidovich, Nikolai;

    2016-01-01

    Haslea provincialis Gastineau, Hansen & Mouget, sp. nov., is a new, morphologically semicryptic blue diatom discovered on the French shores of the Mediterranean Sea. Like H. ostrearia and H. karadagensis, H. provincialis shares the capacity to synthesize a marennine-like blue pigment. Sexual....... This indicates that the synthesis pathways and excretion mechanisms among the three ‘blue’ Haslea may be species-specific. Molecular taxonomy and phylogeny (based on rbcL, cox1 and SSU V4 DNA sequences) confirmed the distinct position of this species among the blue Haslea species. Haslea provincialis occurs...... in environments from which H. ostrearia has already been reported (mostly based on the presence of the blue cell vacuoles). Possible species misidentifications and the impact of the complex geological history of the Mediterranean Sea on blue diatom diversification are also discussed....

  2. Searching for a Mate: Pheromone-Directed Movement of the Benthic Diatom Seminavis robusta.

    Science.gov (United States)

    Bondoc, Karen Grace V; Lembke, Christine; Vyverman, Wim; Pohnert, Georg

    2016-08-01

    Diatoms are species-rich microalgae that often have a unique life cycle with vegetative cell size reduction followed by size restoration through sexual reproduction of two mating types (MT(+) and MT(-)). In the marine benthic diatom Seminavis robusta, mate-finding is mediated by an L-proline-derived diketopiperazine, a pheromone produced by the attracting mating type (MT(-)). Here, we investigate the movement patterns of cells of the opposite mating type (MT(+)) exposed to a pheromone gradient, using video monitoring and statistical modeling. We report that cells of the migrating mating type (MT(+)) respond to pheromone gradients by simultaneous chemotaxis and chemokinesis. Changes in movement behavior enable MT(+) cells to locate the direction of the pheromone source and to maximize their encounter rate towards it. PMID:27260155

  3. Above-Threshold Ionization and Laser-Induced Electron Diffraction in Diatomic Molecules

    CERN Document Server

    Suárez, N; Ciappina, M F; Wolter, B; Biegert, J; Lewenstein, M

    2016-01-01

    Strong field photoemission and electron recollision provide a viable route to extract electronic and nuclear dynamics from molecular targets with attosecond temporal resolution. However, since an {\\em ab-initio} treatment of even the simplest diatomic systems is beyond today's capabilities approximate qualitative descriptions are warranted. In this paper, we develop such a theoretical approach to model the photoelectrons resulting from intense laser-molecule interaction. We present a general theory for symmetric diatomic molecules in the single active electron approximation that, amongst other capabilities, allows adjusting both the internuclear separation and molecular potential in a direct and simple way. More importantly we derive an analytic approximate solution of the time dependent Schr\\"odinger equation (TDSE), based on a generalized strong field approximation (SFA) version. Using that approach we obtain expressions for electrons emitted transition amplitudes from two different molecular centres, and a...

  4. Temperature and vibrational distribution function in high-pressure diatomic gas mixture

    Science.gov (United States)

    Lou, Guofeng; Lempert, Walter R; Adamovich, Igor V; Rich, William J

    2009-03-01

    Temperatures and vibrational populations are investigated experimentally and numerically in a CO-N2-O2 gas mixture. By spatially resolved Raman Q-branch spectra measurement, the strong vibrational excitation was observed in the gas mixtures at a high gas pressure. Numerical calculation, which incorporates both major processes of molecular energy transfer and diffusion of vibrationally excited species across the spatially nonuniform excitation region, provides indepth perception of vibrational kinetics of these diatomic molecular gas mixtures and is verified by the experimental data. The results demonstrate that strong vibrational nonequilibrium for all diatomic species can be sustained by the optical pumping method with a focused CO laser in a relatively cold (300-400 K) molecular gas mixture up to one atmospheric pressure. However, the results also demand further investigations on determining accurate rates of the V-V exchange gas mixture such as for N2-O2.

  5. Global molecular identification from graphs. Neutral and ionized main-group diatomic molecules.

    Science.gov (United States)

    James, Bryan; Caviness, Ken; Geach, Jonathan; Walters, Chris; Hefferlin, Ray

    2002-01-01

    Diophantine equations and inequalities are presented for main-group closed-shell diatomic molecules. Specifying various bond types (covalent, dative, ionic, van der Waals) and multiplicities, it becomes possible to identify all possible molecules. While many of the identified species are probably unstable under normal conditions, they are interesting and present a challenge for computational or experimental analysis. Ionized molecules with net charges of -1, 1, and 2 are also identified. The analysis applies to molecules with atoms from periods 2 and 3 but can be generalized by substituting isovalent atoms. When closed-shell neutral diatomics are positioned in the chemical space (with axes enumerating the numbers of valence electrons of the free atoms), it is seen that they lie on a few parallel isoelectronic series. PMID:11855960

  6. Partition functions and equilibrium constants for diatomic molecules and atoms of astrophysical interest

    CERN Document Server

    Barklem, Paul S

    2016-01-01

    Partition functions and dissociation equilibrium constants are presented for 291 diatomic molecules for temperatures in the range from near absolute zero to 10000 K, thus providing data for many diatomic molecules of astrophysical interest at low temperature. The calculations are based on molecular spectroscopic data from the book of Huber and Herzberg with significant improvements from the literature, especially updated data for ground states of many of the most important molecules by Irikura. Dissociation energies are collated from compilations of experimental and theoretical values. Partition functions for 284 species of atoms for all elements from H to U are also presented based on data collected at NIST. The calculated data are expected to be useful for modelling a range of low density astrophysical environments, especially star-forming regions, protoplanetary disks, the interstellar medium, and planetary and cool stellar atmospheres. The input data, which will be made available electronically, also prov...

  7. Diatomácea marinha Coscinodiscus wailesii Gran et Angst(BACILLARIOPHYCEAE)

    OpenAIRE

    Ascencio, Poliana G. Marson

    2012-01-01

    A diatomácea marinha cêntrica Coscinodiscus wailesii Gran et Angst, considerada uma espécie nociva, vem despertando grande interesse ecológico. Suas florações, vêm prejudicando áreas de pesca e cultivo em diferentes regiões do mundo. Entretanto essa microalga marinha é muito pouco estudada em relação ao seu crescimento celular, composição química, produção e caracterização de polissacarídeos e ácidos graxos. Sendo assim, nesse trabalho foi realizado o isolamento e o cultivo da diatomácea C. w...

  8. Simulation of the scattering properties of a chain-forming triangular prism oceanic diatom

    Science.gov (United States)

    Sun, Bingqiang; Kattawar, George W.; Yang, Ping; Twardowski, Michael S.; Sullivan, James M.

    2016-07-01

    The optical properties of diatom chains in the ocean are studied based on a combination of the many-body iterative T-matrix (MBIT) method and an improved implementation of the ray-by-ray (RBR) geometric optics method. The MBIT, a numerically accurate method, is advantageous for scatterers with linear cells. In contrast to other popular geometric optics methods, the RBR, an approximate method, considers the interference of all outgoing rays. The two methods are verified in comparison with benchmark simulations. The simulation results of diatom chains in a wide size range can be obtained with either or both methods, and each can be applied to any optically soft particle, i.e., in the case when relative refractive index approaches unity.

  9. 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.

  10. Cadmium-Containing Carbonic Anhydrase CDCA1 in Marine Diatom Thalassiosira weissflogii

    Directory of Open Access Journals (Sweden)

    Vincenzo Alterio

    2015-03-01

    Full Text Available The Carbon Concentration Mechanism (CCM allows phytoplakton species to accumulate the dissolved inorganic carbon (DIC necessary for an efficient photosynthesis even under carbon dioxide limitation. In this mechanism of primary importance for diatoms, a key role is played by carbonic anhydrase (CA enzymes which catalyze the reversible hydration of CO2, thus taking part in the acquisition of inorganic carbon for photosynthesis. A novel CA, named CDCA1, has been recently discovered in the marine diatom Thalassiosira weissflogii. CDCA1 is a cambialistic enzyme since it naturally uses Cd2+ as catalytic metal ion, but if necessary can spontaneously exchange Cd2+ to Zn2+. Here, the biochemical and structural features of CDCA1 enzyme will be presented together with its putative biotechnological applications for the detection of metal ions in seawaters.

  11. Driven Diatomic Frenkel-Kontorova Model: Resonant Steps, Spatiotemporal Dynamics and Dynamical Phase Diagrams

    Institute of Scientific and Technical Information of China (English)

    XU Ai-Guo; ZHANG Guang-Cai; CHEN Shi-Gang; YANG Zhan-Ru; WANG Guang-Rui

    2001-01-01

    The resonant steps, spatiotemporal dynamics and dynamical phase diagrams of the driven diatomic FrenkelKontorova model are studied. The complete resonant velocity spectrum which relates only to the winding number is given. The diatomic effects result in each resonant step which is characterized by two integer pairs (k1, k2) and (k1, k′2).In the high-velocity regime thelinear response of v to F is often punctuated by the subharmonic resonances (k,1 > k2).There are two kinds of nonlinear response regimes in the high-velocity regime. A new physical interpretation to the mean-field treatment is presented. The commensurate and incommensurate structures show similar dynamical behaviors except that the latter lacks depinning transition below the Aubry transition point. The increase of m makes the critical forces increasing, the transitions smoother and the hysteresis thinner.

  12. High-efficiency nuclear transformation of the diatom Phaeodactylum tricornutum by electroporation.

    Science.gov (United States)

    Zhang, Chunye; Hu, Hanhua

    2014-08-01

    We established a high-efficiency nuclear transformation method for the diatom Phaeodactylum tricornutum using an electroporation system. Based on a universal electroporation protocol, the conditions for the introduction of exogenous DNA including electric field strength and plasmid form were optimized. Following optimization, the diatom cells could be transformed with exogenous gene easily, the maximum transformation frequency obtained was 2.8×10(-5) cells. The cotransformation of P. tricornutum with a non-selective GUS gene together with the selectable resistance gene has also been achieved using our new method and found to be very efficient (up to 60%). The electroporation procedure described in this article offers a number of advantages, including simplicity, general utility, low-cost and high efficiency. The described method also provides some clue for developing electroporation transformation system in other eukaryotic microalgae.

  13. 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 investigate...... phase (3-12 h) and a late acclimation phase (12-48 h). The initial phase is recognized by strong and rapid regulation of genes encoding proteins involved in photosynthesis, pigment metabolism and reactive oxygen species (ROS) scavenging systems. A significant increase in light protecting metabolites...... occur together with the induction of transcriptional processes involved in protection of cellular structures at this early phase. During the following phases, the metabolite profiling display a pronounced decrease in light harvesting pigments, whereas the variable fluorescence measurements show...

  14. Phytoplankton dynamics in contrasting early stage North Atlantic spring blooms: composition, succession, and potential drivers

    Directory of Open Access Journals (Sweden)

    C. J. Daniels

    2015-01-01

    Full Text Available The spring bloom is a key annual event in the phenology of pelagic ecosystems, making a major contribution to the oceanic biological carbon pump through the production and export of organic carbon. However, there is little consensus as to the main drivers of spring bloom formation, exacerbated by a lack of in situ observations of the phytoplankton community composition and its evolution during this critical period. We investigated the dynamics of the phytoplankton community structure at two contrasting sites in the Iceland and Norwegian Basins during the early stage (25 March–25 April of the 2012 North Atlantic spring bloom. The plankton composition and characteristics of the initial stages of the bloom were markedly different between the two basins. The Iceland Basin (ICB appeared well mixed to > 400 m, yet surface chlorophyll a (0.27–2.2 mg m–3 and primary production (0.06–0.66 mmol C m–3 d–1 were elevated in the upper 100 m. Although the Norwegian Basin (NWB had a persistently shallower mixed layer (< 100 m, chlorophyll a (0.58–0.93 mg m–3 and primary production (0.08–0.15 mmol C m–3 d–1 remained lower than in the ICB, with picoplankton (> 2 μm dominating chlorophyll a biomass. The ICB phytoplankton composition appeared primarily driven by the physicochemical environment, with periodic events of increased mixing restricting further increases in biomass. In contrast, the NWB phytoplankton community was potentially limited by physicochemical and/or biological factors such as grazing. Diatoms dominated the ICB, with the genus Chaetoceros (1–166 cells mL–1 being succeeded by Pseudo-nitzschia (0.2–210 cells mL–1. However, large diatoms (> 10 μm were virtually absent (< 0.5 cells mL–1 from the NWB, with only small nanno-sized (< 5 μm diatoms present (101–600 cells mL–1. We suggest micro-zooplankton grazing, potentially coupled with the lack of a seed population of bloom forming diatoms, was restricting diatom

  15. Which-pass information in the double-slit experiment of diatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Ueda, Kiyoshi, E-mail: ueda@tagen.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan)

    2010-02-01

    Analogy between the double-slit experiment in quantum optics and the photoelectron emission from diatoms is discussed in the light of availabilities of which-pass information and quantum eraser. The availability of which-pass information and the degree of the predictability may be determined by the intrinsic molecular processes involved, whereas the erasing the which-pass information relies on the observation.

  16. Efficiency of copper and cupronickel substratum to resist development of diatom biofilms

    Digital Repository Service at National Institute of Oceanography (India)

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

    (Corbett and Fishbank,1997) and hinder the operation of optical sensors used for ocean monitoring and (iii) the diatoms have been reported to be highly resistant to biocidal antifouling coatings (Callow, 1986; Jelic-Mrcelic et al,. 2006; Molino and...Wetherbee, 2008;Molino et. al., 2009; Zargiel et. al., 2011; Briand et. al., 2012) as well as found to be dominant on fouling release coatings (Casséand Swain, 2006; Molino et. al., 2009; Dobretsovand Thomason, 2011). Historically, marine biofouling...

  17. Eco-biology of marine diatoms with emphasis on the influence of physico-chemical parameters

    Digital Repository Service at National Institute of Oceanography (India)

    Mitbavkar, S.

    in the marine periphytic diatom diversity by eliminating fresh recruitment and grazing, components of the gain and loss processes respectively revealed three cases. These cases illustrated the influences of intergeneric competition (case I), simultaneous inter...-existence of diverse community ES >Growth rate of N. longissima Major players: N. delicatula, A. coffeaeformis, N. subinflata, Nitzschia closterium, N. longissima Competitive exclusion of N. longissima Case I (Intergeneric competition) Case II (Inter & intrageneric...

  18. Sequential pathology of the gills of Coho salmon with a combined diatom and microsporidian gill infection

    OpenAIRE

    Speare, David J.; Brackett, Jim; Ferguson, Hugh W.

    1989-01-01

    A large group of 40 gram Coho salmon smolts experienced 60% mortality within the first week after introduction to cages in sea-water. Histological and ultrastructural examination of sequential samples of gill tissue revealed a dramatic suppurative branchitis accompanied by extensive fusion of gill lamellae. This dramatic host response and subsequent high mortality appeared to be in response to a bloom of Corethron-like diatoms. A further complication was an extensive infection of endothelial ...

  19. Quaternary surface water temperature estimations: New diatom transfer functions for the Southern Ocean

    OpenAIRE

    Esper, Oliver; Gersonde, Rainer

    2014-01-01

    Here we present an improvement of paleotemperature reconstructions for the Southern Ocean by combining new diatom data from the Pacific sector with published Atlantic and Indian sector reference data. The statistical analysis of 336 surface sediment samples recovered from a wide area of Southern Ocean environments defines a supra-regional reference data set for quantitative summer sea surface temperature (SSST) estimations. In situ temperature measurements covering the time span from approx. ...

  20. Centennial-scale variations in diatom productivity off Peru over the last 3000 years

    Science.gov (United States)

    Fleury, Sophie; Crosta, Xavier; Schneider, Ralph; Blanz, Thomas; Ther, Olivier; Martinez, Philippe; Kim, Jung-Hyun

    2016-04-01

    The Peruvian coastal upwelling is one of the most productive systems in the global ocean, with important impacts on the carbon cycle. Primary productivity there displays strong variations at the inter-annual to decadal timescales. However, down-core investigations rarely reach sufficient temporal resolution to assess the response of productivity to climatic variations at these timescales beyond the instrumental and historical periods. We here analyzed diatom assemblages, sea-surface temperatures, nitrogen and organic carbon contents on a laminated sediment core from the Peruvian continental shelf to trace variations in regional productivity over the last 3000 years. Our record provides evidence for different climatic and oceanic conditions with more humid and less productive conditions older than 2500 Cal years BP and drier and more productive conditions younger than 2500 Cal years BP. The last 2500 years also present much stronger centennial-scale variability with the occurrence of six intervals with higher total diatom abundances and stronger percentages in upwelling-related diatom species, representative of intensified productivity, congruent to lower percentages in benthic diatoms, indicative of reduced rainfall. These six periods were synchronous to intervals of enhanced Walker circulation, suggesting a strong imprint of the Pacific zonal circulation on productivity variations off Peru. Our record also demonstrates that SSTs did not vary in phase with productivity, arguing against the idea of regional SSTs controlled by the upwelling intensity, but were rather in agreement to SST records off southern Chile, suggesting that Peruvian SSTs variations were largely controlled by oceanic currents at southern high latitudes.

  1. PRESPHOTO – a project to improve the preservation of cyanobacteria and diatom cultures

    OpenAIRE

    Deprez, Karolien; Vanormelingen, Pieter; Crahay, Charlotte; Wilmotte, Annick; Day, John G.; Vyverman, Wim

    2014-01-01

    The availability of biological material of guaranteed identity and quality in Biological Resource Centers is considered fundamental for scientific research and R&D, but depends heavily on adequate preservation methods. We present a new BRAIN-BE project on improving the preservation of two groups of photosynthetic microorganisms, cyanobacteria and diatoms, in two collections of the Belgian Co-ordinated Collections of Micro-organisms (BCCM). First, we will improve the cultivation...

  2. Production of macroaggregates from dissolved exopolymeric substances (EPS) of bacterial and diatom origin

    Digital Repository Service at National Institute of Oceanography (India)

    Bhaskar, P.V.; Grossart, H.P.; Bhosle, N.B.; Simon, M.

    -1 1 Production of macroaggregates from dissolved exopolymeric substances (EPS) of bacterial and diatom origin P V Bhaskar1*, Hans-Peter Grossart2, 3, N B Bhosle1 and Meinhard Simon2. 1National Institute of Oceanography, Dona Paula, GOA- 403 004...-cycles [14]. Moreover, the composition and quality of these aggregates influence feeding and grazing rates of filter feeders [15], bacterial re-mineralization of organic matter, and POM-DOM conversion [16, 17, 18], thereby regulating the vertical flux...

  3. Holocene evolution of diatom and silicoflagellate paleoceanography in Slocum Arm, a fjord in southeastern Alaska

    Science.gov (United States)

    Barron, John A.; Bukry, John D.; Addison, Jason A.; Ager, Thomas A.

    2016-01-01

    Diatom and silicoflagellate assemblages in cores EW0408-47JC, -47TC, -46MC (57° 34.5278′ N, 136° 3.7764′ W, 114 m water depth) taken from the outer portion of Slocum Arm, a post-glacial fjord in southeastern Alaska, reveal the paleoclimatic and paleoceanographic evolution of the eastern margin of the Gulf of Alaska (GoA) during the past 10,000 years. Between ~ 10 and 6.8 cal ka, periods of low salinity and cool water conditions alternated with brief intervals marked by the increased influx of oceanic, more saline and likely warmer waters. Increased surface water stability characterized by a middle Holocene interval between ~ 6.8 and 3.2 cal ka is typified by increased abundances of northeastern Pacific Thalassiosira spp. that are indicative of spring coastal blooms and decreased abundances of warm and higher salinity oceanic diatoms. At ~ 3.2 cal ka, an abrupt increase in both the relative contribution of oceanic diatoms and silicoflagellates suggestive of cooler upwelling conditions occurred in the -47JC record. A stepwise increase in alkenone sea surface temperature in northern GoA core EW0408-85JC and increase in southern sourced precipitation in the carbonate δ18O record of Jellybean Lake (Yukon) present evidence that this ~ 3.2 cal ka event coincided with the onset of enhanced positive Pacific Decadal Oscillation-like (PDO) conditions in the GoA. These positive PDO-like conditions persisted until ~ 1.0 cal ka and were followed by high amplitude fluctuations in the relative abundance of diatom and silicoflagellate assemblages.

  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. Diatoms : an ecoregional indicator of nutrients, organic mater and micropollutants pollution

    OpenAIRE

    Rimet, Frédéric,

    2012-01-01

    Diatoms are ubiquitous microalgae of an extreme diversity. This made them good indicators of aquatic ecosystems quality and they are used since 50 years for this purpose. Since year 2000, the European Water Framework Directive requires their use to assess the ecological quality of watercourses. A typological framework has to be used in order to compare comparable rivers between each other, that is, rivers of the same bioclimatic regions, flowing on the same geological substrate at similar alt...

  6. 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.

  7. Design of optimal laser pulses to control molecular rovibrational excitation in a heteronuclear diatomic molecule

    Indian Academy of Sciences (India)

    Sitansh Sharma; Gabriel G Balint-Kurti; Harjinder Singh

    2012-01-01

    Optimal control theory in combination with time-dependent quantum dynamics is employed to design laser pulses which can perform selective vibrational and rotational excitations in a heteronuclear diatomic system. We have applied the conjugate gradient method for the constrained optimization of a suitably designed functional incorporating the desired objectives and constraints. Laser pulses designed for several excitation processes of the molecule were able to achieve predefined dynamical goals with almost 100% yield.

  8. Identification of two Skeletonema costatum-like diatoms by fluorescence in situ hybridization

    Institute of Scientific and Technical Information of China (English)

    张宝玉; 陈国福; 王广策; 陆斗定

    2010-01-01

    A harmful algae bloom (HAB) is a dense aggregation of algae in a marine or aquatic environment that can result in significant environmental problems. To forecast the occurrence of HAB, development of a rapid and precise detection method is urgently required. In this study, two Skeletonema costatum-like diatoms (SK-1 and SK-2), were identified morphologically under a light microscope, and detected using fluorescent in situ hybridization (FISH). Strain SK-1 was isolated from a frequently HAB affected area of ...

  9. 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 - _ varied more than _ 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 _ copepods.

  10. Death-specific protein in a marine diatom regulates photosynthetic responses to iron and light availability.

    Science.gov (United States)

    Thamatrakoln, Kimberlee; Bailleul, Benjamin; Brown, Christopher M; Gorbunov, Maxim Y; Kustka, Adam B; Frada, Miguel; Joliot, Pierre A; Falkowski, Paul G; Bidle, Kay D

    2013-12-10

    Diatoms, unicellular phytoplankton that account for ∼40% of marine primary productivity, often dominate coastal and open-ocean upwelling zones. Limitation of growth and productivity by iron at low light is attributed to an elevated cellular Fe requirement for the synthesis of Fe-rich photosynthetic proteins. In the dynamic coastal environment, Fe concentrations and daily surface irradiance levels can vary by two to three orders of magnitude on short spatial and temporal scales. Although genome-wide studies are beginning to provide insight into the molecular mechanisms used by diatoms to rapidly respond to such fluxes, their functional role in mediating the Fe stress response remains uncharacterized. Here, we show, using reverse genetics, that a death-specific protein (DSP; previously named for its apparent association with cell death) in the coastal diatom Thalassiosira pseudonana (TpDSP1) localizes to the plastid and enhances growth during acute Fe limitation at subsaturating light by increasing the photosynthetic efficiency of carbon fixation. Clone lines overexpressing TpDSP1 had a lower quantum requirement for growth, increased levels of photosynthetic and carbon fixation proteins, and increased cyclic electron flow around photosystem I. Cyclic electron flow is an ATP-producing pathway essential in higher plants and chlorophytes with a heretofore unappreciated role in diatoms. However, cells under replete conditions were characterized as having markedly reduced growth and photosynthetic rates at saturating light, thereby constraining the benefits afforded by overexpression. Widespread distribution of DSP-like sequences in environmental metagenomic and metatranscriptomic datasets highlights the presence and relevance of this protein in natural phytoplankton populations in diverse oceanic regimes. PMID:24277817

  11. 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.

  12. Inelastic scattering in atom-diatomic molecule collisions. II - Effect of rotation on vibrational transition

    Science.gov (United States)

    Stallcop, J. R.

    1975-01-01

    Rotational and vibrational transitions in a diatomic molecule caused by collisions with an atom are analyzed by a semiclassical method for conditions where the rotational transitions can be handled well by the sudden approximation and the vibrational transitions belong to the adiabatic regime. The contribution to the vibrational transition probability from the correction, which takes the finite value of the spacing between rotational energy levels into account, is examined.-

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

    Directory of Open Access Journals (Sweden)

    Marianne Nymark

    Full Text Available 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 investigate the mechanisms of high light acclimation in Phaeodactylum tricornutum using an integrated approach involving global transcriptional profiling, metabolite profiling and variable fluorescence technique. Algae cultures were acclimated to low light (LL, after which the cultures were transferred to high light (HL. Molecular, metabolic and physiological responses were studied at time points 0.5 h, 3 h, 6 h, 12 h, 24 h and 48 h after transfer to HL conditions. The integrated results indicate that the acclimation mechanisms in diatoms can be divided into an initial response phase (0-0.5 h, an intermediate acclimation phase (3-12 h and a late acclimation phase (12-48 h. The initial phase is recognized by strong and rapid regulation of genes encoding proteins involved in photosynthesis, pigment metabolism and reactive oxygen species (ROS scavenging systems. A significant increase in light protecting metabolites occur together with the induction of transcriptional processes involved in protection of cellular structures at this early phase. During the following phases, the metabolite profiling display a pronounced decrease in light harvesting pigments, whereas the variable fluorescence measurements show that the photosynthetic capacity increases strongly during the late acclimation phase. We show that P. tricornutum is capable of swift and efficient execution of photoprotective mechanisms, followed by changes in the composition of the photosynthetic machinery that enable the diatoms to utilize the excess energy available in HL. Central molecular players in light protection and acclimation to high irradiance have been identified.

  14. Metal-organic frameworks reactivate deceased diatoms to be efficient CO(2) absorbents.

    Science.gov (United States)

    Liu, Dingxin; Gu, Jiajun; Liu, Qinglei; Tan, Yongwen; Li, Zhuo; Zhang, Wang; Su, Yishi; Li, Wuxia; Cui, Ajuan; Gu, Changzhi; Zhang, Di

    2014-02-26

    Diatomite combined with certain metal-organic frameworks (MOFs) is shown to be an effective CO2 absorbent, although diatomite alone is regarded as inert with respect to CO2 absorption. This finding opens the prospect of reactivating millions of tons of diatomite for CO2 absorption. It also shows for the first time that diatom frustules can act as CO2 buffers, an important link in a successive biological CO2 concentration mechanism chain that impacts on global warming.

  15. Nitric oxide mediates the stress response induced by diatom aldehydes in the sea urchin Paracentrotus lividus.

    Directory of Open Access Journals (Sweden)

    Giovanna Romano

    Full Text Available Diatoms are ubiquitous and abundant primary producers that have been traditionally considered as a beneficial food source for grazers and for the transfer of carbon through marine food webs. However, many diatom species produce polyunsaturated aldehydes that disrupt development in the offspring of grazers that feed on these unicellular algae. Here we provide evidence that production of the physiological messenger nitric oxide increases after treatment with the polyunsaturated aldehyde decadienal in embryos of the sea urchin Paracentrotus lividus. At high decadienal concentrations, nitric oxide mediates initial apoptotic events leading to loss of mitochondrial functionality through the generation of peroxynitrite. At low decadienal concentrations, nitric oxide contributes to the activation of hsp70 gene expression thereby protecting embryos against the toxic effects of this aldehyde. When nitric oxide levels were lowered by inhibiting nitric oxide synthase activity, the expression of hsp70 in swimming blastula decreased and the proportion of abnormal plutei increased. However, in later pluteus stages nitric oxide was no longer able to exert this protective function: hsp70 and nitric oxide synthase expression decreased with a consequent increase in the expression of caspase-8. Our findings that nitric oxide production increases rapidly in response to a toxic exogenous stimulus opens new perspectives on the possible role of this gas as an important messenger to environmental stress in sea urchins and for understanding the cellular mechanisms underlying toxicity during diatom blooms.

  16. Nitric oxide mediates the stress response induced by diatom aldehydes in the sea urchin Paracentrotus lividus.

    Science.gov (United States)

    Romano, Giovanna; Costantini, Maria; Buttino, Isabella; Ianora, Adrianna; Palumbo, Anna

    2011-01-01

    Diatoms are ubiquitous and abundant primary producers that have been traditionally considered as a beneficial food source for grazers and for the transfer of carbon through marine food webs. However, many diatom species produce polyunsaturated aldehydes that disrupt development in the offspring of grazers that feed on these unicellular algae. Here we provide evidence that production of the physiological messenger nitric oxide increases after treatment with the polyunsaturated aldehyde decadienal in embryos of the sea urchin Paracentrotus lividus. At high decadienal concentrations, nitric oxide mediates initial apoptotic events leading to loss of mitochondrial functionality through the generation of peroxynitrite. At low decadienal concentrations, nitric oxide contributes to the activation of hsp70 gene expression thereby protecting embryos against the toxic effects of this aldehyde. When nitric oxide levels were lowered by inhibiting nitric oxide synthase activity, the expression of hsp70 in swimming blastula decreased and the proportion of abnormal plutei increased. However, in later pluteus stages nitric oxide was no longer able to exert this protective function: hsp70 and nitric oxide synthase expression decreased with a consequent increase in the expression of caspase-8. Our findings that nitric oxide production increases rapidly in response to a toxic exogenous stimulus opens new perspectives on the possible role of this gas as an important messenger to environmental stress in sea urchins and for understanding the cellular mechanisms underlying toxicity during diatom blooms. PMID:22022485

  17. Judging diatoms by their cover: variability in local elasticity of Lithodesmium undulatum undergoing cell division.

    Directory of Open Access Journals (Sweden)

    Lee Karp-Boss

    Full Text Available Unique features of diatoms are their intricate cell covers (frustules made out of hydrated, amorphous silica. The frustule defines and maintains cell shape and protects cells against grazers and pathogens, yet it must allow for cell expansion during growth and division. Other siliceous structures have also evolved in some chain-forming species as means for holding neighboring cells together. Characterization and quantification of mechanical properties of these structures are crucial for the understanding of the relationship between form and function in diatoms, but thus far only a handful of studies have addressed this issue. We conducted micro-indentation experiments, using atomic force microscopy (AFM, to examine local variations in elastic (Young's moduli of cells and linking structures in the marine, chain-forming diatom Lithodesmium undulatum. Using a fluorescent tracer that is incorporated into new cell wall components we tested the hypothesis that new siliceous structures differ in elastic modulus from their older counterparts. Results show that the local elastic modulus is a highly dynamic property. Elastic modulus of stained regions was significantly lower than that of unstained regions, suggesting that newly formed cell wall components are generally softer than the ones inherited from the parent cells. This study provides the first evidence of differentiation in local elastic properties in the course of the cell cycle. Hardening of newly formed regions may involve incorporation of additional, possibly organic, material but further studies are needed to elucidate the processes that regulate mechanical properties of the frustule during the cell cycle.

  18. 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.

  19. Laboratory Rotational Spectroscopy of the Interstellar Diatomic Hydride Ion SH+ (X 3Σ-)

    Science.gov (United States)

    Halfen, DeWayne; Ziurys, Lucy M.

    2016-06-01

    Diatomic hydride are among the most common molecular species in the interstellar medium (ISM). The low molecular mass and thus moments of inertia cause their rotational spectra to lie principally in the submillimeter and far-infrared regions. Diatomic hydrides, both neutral (MH) and ionic (MH+) forms, are also basic building blocks of interstellar chemistry. In ionic form, they may be the “hidden” carriers of refractory elements in dense gas. They are therefore extremely good targets for space-borne and airborne platforms such as Herschel, SOFIA, and SAFIR. However, in order to detect these species in the ISM, their rotational spectra must first be measured in the laboratory. To date, there is very little high resolution data available for many hydride species, in particular the ionic form. Using submillimeter/THz direct absorption methods in the Ziurys laboratory, spectra of the interstellar diatomic hydride SH+ (X 3Σ-) have been recorded. Recent work has concerned measurement of all three fine structure components of the fundamental rotational transition N = 1 ← 0 in the range 345 - 683 GHz. SH+ was generated from H2S and argon in an AC discharge. The data have been analyzed, and spectroscopic constants for this species have been refined. SH+ is found in Photon Dominated Regions (PDRs) and X-ray Dominated Regions (XDRs) and is thought to trace energetic processes in the ISM. These current measurements confirm recent observations of this species at submillimeter/THz wavelengths with ALMA and other ground-based telescopes.

  20. Multi-layer hierarchical array fabricated with diatom frustules for highly sensitive bio-detection applications

    International Nuclear Information System (INIS)

    Diatoms have delicate porous structures which are very beneficial in improving the absorbing ability in the bio-detection field. In this study, multi-layered hierarchical arrays were fabricated by packing Nitzschia soratensis (N. soratensis) frustules into Cosinodiscus argus (C. argus) frustules to achieve advanced sensitivity in bio-detection chips. Photolithographic patterning was used to obtain N. soratensis frustule arrays, and the floating behavior of C. argus frustules was employed to control their postures for packing N. soratensis frustule array spots. The morphology of the multi-layer C. argus–N. soratensis package array was investigated by scanning electron microscopy, demonstrating that the overall and sub-structures of the diatom frustules were retained. The signal enhancing effect of multi-layer C. argus–N. soratensis packages was demonstrated by fluorescent antibody test results. The mechanism of the enhancement was also analyzed, indicating that both complex hierarchical frustule structures and optimized posture of C. argus frustules were important for improving bio-detection sensitivities. The technique for fabricating multi-layer diatom frustules arrays is also useful for making multi-functional biochips and controllable drug delivery systems. (paper)

  1. Partition functions and equilibrium constants for diatomic molecules and atoms of astrophysical interest

    Science.gov (United States)

    Barklem, P. S.; Collet, R.

    2016-04-01

    Partition functions and dissociation equilibrium constants are presented for 291 diatomic molecules for temperatures in the range from near absolute zero to 10 000 K, thus providing data for many diatomic molecules of astrophysical interest at low temperature. The calculations are based on molecular spectroscopic data from the book of Huber & Herzberg (1979, Constants of Diatomic Molecules) with significant improvements from the literature, especially updated data for ground states of many of the most important molecules by Irikura (2007, J. Phys. Chem. Ref. Data, 36, 389). Dissociation energies are collated from compilations of experimental and theoretical values. Partition functions for 284 species of atoms for all elements from H to U are also presented based on data collected at NIST. The calculated data are expected to be useful for modelling a range of low density astrophysical environments, especially star-forming regions, protoplanetary disks, the interstellar medium, and planetary and cool stellar atmospheres. The input data, which will be made available electronically, also provides a possible foundation for future improvement by the community. Full Tables 1-8 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A96

  2. Cenozoic Antarctic DiatomWare/BugCam: An aid for research and teaching

    Science.gov (United States)

    Wise, S.W.; Olney, M.; Covington, J.M.; Egerton, V.M.; Jiang, S.; Ramdeen, D.K.; ,; Schrader, H.; Sims, P.A.; Wood, A.S.; Davis, A.; Davenport, D.R.; Doepler, N.; Falcon, W.; Lopez, C.; Pressley, T.; Swedberg, O.L.; Harwood, D.M.

    2007-01-01

    Cenozoic Antarctic DiatomWare/BugCam© is an interactive, icon-driven digital-image database/software package that displays over 500 illustrated Cenozoic Antarctic diatom taxa along with original descriptions (including over 100 generic and 20 family-group descriptions). This digital catalog is designed primarily for use by micropaleontologists working in the field (at sea or on the Antarctic continent) where hard-copy literature resources are limited. This new package will also be useful for classroom/lab teaching as well as for any paleontologists making or refining taxonomic identifications at the microscope. The database (Cenozoic Antarctic DiatomWare) is displayed via a custom software program (BugCam) written in Visual Basic for use on PCs running Windows 95 or later operating systems. BugCam is a flexible image display program that utilizes an intuitive thumbnail “tree” structure for navigation through the database. The data are stored on Micrsosoft EXCEL spread sheets, hence no separate relational database program is necessary to run the package

  3. Chiral separation of a diketopiperazine pheromone from marine diatoms using supercritical fluid chromatography.

    Science.gov (United States)

    Frenkel, Johannes; Wess, Carsten; Vyverman, Wim; Pohnert, Georg

    2014-03-01

    The proline derived diketopiperazine has been identified in plants, insects and fungi with unknown function and was recently also reported as the first pheromone from a diatom. Nevertheless the stereochemistry and enantiomeric excess of this natural product remained inaccessible using direct analytical methods. Here we introduce a chiral separation of this metabolite using supercritical fluid chromatography/mass spectrometry. Several chromatographic methods for chiral analysis of the diketopiperazine from the diatom Seminavis robusta and synthetic enantiomers have been evaluated but neither gas chromatography nor high performance liquid chromatography on different chiral cyclodextrin phases were successful in separating the enantiomers. In contrast, supercritical fluid chromatography achieved baseline separation within four minutes of run time using amylose tris(3,5-dimethylphenylcarbamate) as stationary phase and 2-propanol/CO2 as mobile phase. This very rapid chromatographic method in combination with ESI mass spectrometry allowed the direct analysis of the cyclic dipeptide out of the complex sea water matrix after SPE enrichment. The method could be used to determine the enantiomeric excess of freshly released pheromone and to follow the rapid degradation observed in diatom cultures. Initially only trace amounts of c(d-Pro-d-Pro) were found besides the dominant c(l-Pro-l-Pro) in the medium. However the enantiomeric excess decreased upon pheromone degradation within few hours indicating that a preferential conversion and thus inactivation of the l-proline derived natural product takes place.

  4. Positive selection within a diatom species acts on putative protein interactions and transcriptional regulation.

    Science.gov (United States)

    Koester, Julie A; Swanson, Willie J; Armbrust, E Virginia

    2013-02-01

    Diatoms are the most species-rich group of microalgae, and their contribution to marine primary production is important on a global scale. Diatoms can form dense blooms through rapid asexual reproduction; mutations acquired and propagated during blooms likely provide the genetic, and thus phenotypic, variability upon which natural selection may act. Positive selection was tested using genome and transcriptome-wide pair-wise comparisons of homologs in three genera of diatoms (Pseudo-nitzschia, Ditylum, and Thalassiosira) that represent decreasing phylogenetic distances. The signal of positive selection was greatest between two strains of Thalassiosira pseudonana. Further testing among seven strains of T. pseudonana yielded 809 candidate genes of positive selection, which are 7% of the protein-coding genes. Orphan genes and genes encoding protein-binding domains and transcriptional regulators were enriched within the set of positively selected genes relative to the genome as a whole. Positively selected genes were linked to the potential selective pressures of nutrient limitation and sea surface temperature based on analysis of gene expression profiles and identification of positively selected genes in subsets of strains from locations with similar environmental conditions. The identification of positively selected genes presents an opportunity to test new hypotheses in natural populations and the laboratory that integrate selected genotypes in T. pseudonana with their associated phenotypes and selective forces. PMID:23097498

  5. Biomass, species composition and diversity of benthic diatoms in mangroves of the Houyu Bay, China

    Institute of Scientific and Technical Information of China (English)

    CHEN Changping; GAO Yahui; LIN Peng

    2005-01-01

    The biomass, species composition and diversity of benthic diatom assemblages in mud-flat soils in Kandelia candel (L.) Druce communities with and without vegetation were studied seasonally at the Houyu Bay in Fuding City, Fujian Province, China. A total of 103taxa were identified (including varieties). Eighty-four taxa were found in the mud-flat with vegetation and 74 taxa in the mud-fiat without vegetation, while the biomass was large in January and April and decreased from July to October. The most abundant species in the mud-flat with vegetation are Nitzschia cocconeiformis, Gyrosigma scalproides and N. Fasciculata, compared with G. Scalproides and N.obtusa var. Scalpelliformis in the mud-flat without vegetation. High H' values at 2 sites during all seasons suggest that diatom assemblages in the sediments of the Houyu Bay represent an original environment. Multi-dimensional scaling of diatom assemblages from mud-flats with and without vegetation shows that a slight seasonal change and only a single association occur in the angroves.

  6. Investigation of porous silica nanostructures in diatoms isolated from Kurichi and Sulur lakes of Coimbatore, India using field emission scanning electron microscopy.

    Science.gov (United States)

    N, Seethalakshmi; R, Selvakumar

    2015-12-01

    Diatoms are unicellular algae that possess cell wall made of silica. These diatoms play a pivotal role in synthesis of variety of silica nanostructures and have adorning morphology in nature. In the present study, we have used field emission scanning electron microscopy (FE-SEM) to investigate their morphological features like pore size, shape, and porous pattern in various diatoms isolated from Kurichi and Sulur fresh water lakes, Coimbatore, Tamil Nadu, India. Diatoms were identified as Nitzschia sp., Cyclotella meneghiniana, Coscinodiscus sp. and Cyclotella atomus based on their morphological features. The arrangement of porous nanostructures in these diatoms have been characterized. The change in the nanostructures present in the diatoms have been correlated to the contamination of water bodies. PMID:26296232

  7. Penicillin-mediated changes in viable benthic diatom assemblages – insights about the relevance of bacteria across spatial and seasonal scales.

    Digital Repository Service at National Institute of Oceanography (India)

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

    are attributed to bacterial influence. Bacteria stimulate diatoms 3 through vitamins, siderophores, cytokinins and inhibit the same through direct contact and proteases (Maruyama et al. 1986; Amin et al. 2012 and references therein). Bacteria also... samples. The mechanisms by which such changes in bacterial communities translate to diatom assemblages are numerous, as discussed by Bruckner et al. (2011). Bacteria can influence diatoms via soluble factors (for e.g., amino acids, vitamins), thereby...

  8. Ice nucleation from aqueous NaCl droplets with and without marine diatoms

    Directory of Open Access Journals (Sweden)

    P. A. Alpert

    2011-06-01

    Full Text Available Ice formation in the atmosphere by homogeneous and heterogeneous nucleation is one of the least understood processes in cloud microphysics and climate. Here we describe our investigation of the marine environment as a potential source of atmospheric IN by experimentally observing homogeneous ice nucleation from aqueous NaCl droplets and comparing against heterogeneous ice nucleation from aqueous NaCl droplets containing intact and fragmented diatoms. Homogeneous and heterogeneous ice nucleation are studied as a function of temperature and water activity, aw. Additional analyses are presented on the dependence of diatom surface area and aqueous volume on heterogeneous freezing temperatures, ice nucleation rates, ωhet, ice nucleation rate coefficients, Jhet, and differential and cumulative ice nuclei spectra, k(T and K(T, respectively. Homogeneous freezing temperatures and corresponding nucleation rate coefficients are in agreement with the water activity based homogeneous ice nucleation theory within experimental and predictive uncertainties. Our results confirm, as predicted by classical nucleation theory, that a stochastic interpretation can be used to describe the homogeneous ice nucleation process. Heterogeneous ice nucleation initiated by intact and fragmented diatoms can be adequately represented by a modified water activity based ice nucleation theory. A horizontal shift in water activity, Δaw, het = 0.2303, of the ice melting curve can describe median heterogeneous freezing temperatures. Individual freezing temperatures showed no dependence on available diatom surface area and aqueous volume. Determined at median diatom freezing temperatures for aw from 0.8 to 0.99, ωhet~0.11+0.06−0.05 s−1, Jhet~1.0+1.16−0.61×104 cm−2

  9. Evolution and Functional Diversification of Fructose Bisphosphate Aldolase Genes in Photosynthetic Marine Diatoms

    Science.gov (United States)

    Allen, Andrew E.; Moustafa, Ahmed; Montsant, Anton; Eckert, Angelika; Kroth, Peter G.; Bowler, Chris

    2012-01-01

    Diatoms and other chlorophyll-c containing, or chromalveolate, algae are among the most productive and diverse phytoplankton in the ocean. Evolutionarily, chlorophyll-c algae are linked through common, although not necessarily monophyletic, acquisition of plastid endosymbionts of red as well as most likely green algal origin. There is also strong evidence for a relatively high level of lineage-specific bacterial gene acquisition within chromalveolates. Therefore, analyses of gene content and derivation in chromalveolate taxa have indicated particularly diverse origins of their overall gene repertoire. As a single group of functionally related enzymes spanning two distinct gene families, fructose 1,6-bisphosphate aldolases (FBAs) illustrate the influence on core biochemical pathways of specific evolutionary associations among diatoms and other chromalveolates with various plastid-bearing and bacterial endosymbionts. Protein localization and activity, gene expression, and phylogenetic analyses indicate that the pennate diatom Phaeodactylum tricornutum contains five FBA genes with very little overall functional overlap. Three P. tricornutum FBAs, one class I and two class II, are plastid localized, and each appears to have a distinct evolutionary origin as well as function. Class I plastid FBA appears to have been acquired by chromalveolates from a red algal endosymbiont, whereas one copy of class II plastid FBA is likely to have originated from an ancient green algal endosymbiont. The other copy appears to be the result of a chromalveolate-specific gene duplication. Plastid FBA I and chromalveolate-specific class II plastid FBA are localized in the pyrenoid region of the chloroplast where they are associated with β-carbonic anhydrase, which is known to play a significant role in regulation of the diatom carbon concentrating mechanism. The two pyrenoid-associated FBAs are distinguished by contrasting gene expression profiles under nutrient limiting compared with

  10. 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

  11. Diatom responses to precipitation and anthropogenic disturbances in an azorean lake during the last seven centuries

    Science.gov (United States)

    Vázquez-Loureiro, David; Bao, Roberto; Gonçalves, Vitor; Rubio-Inglés, Maria J.; Sáez, Alberto; Hernández, Armand; Raposeiro, Pedro M.; Pueyo, Juan J.; Masqué, Pere; Trigo, Ricardo; Giralt, Santiago

    2015-04-01

    Sedimentary lacustrine records provide an important source of knowledge of past environmental changes at regional and local scales. Here we perform a diatom-based paleoenvironmental reconstruction, complemented with geochemical proxies, of the recent history of Lake Azul (37° 52' 21' N - 25° 46' 26' W), located in the crater caldera of Sete Cidades volcano, São Miguel Island. A 132 cm long sediment core from the offshore and deepest part of the lake was selected, from a total of fourteen cores extracted in 2011, and dated with21Pb and137Cs, as well as AMS14C. Two main litological intervals were described: at the lower part there are hard volcanic rocks interbedding silty lacustrine episodes, whereas the upper part is made up by silty mud lacustrine sediments. Eight terrestrial-nearshore levels with high values of TOC/TN ratio, low values of δ13C and high abundances of aerophilic diatoms, plus nine volcanic levels, were removed from any further analysis in order to assess changes in in-lake processes. Main environmental gradients driving the composition of the diatom assemblages were explored by a Principal Component Analysis (PCA) on the diatom relative abundance data, and four statistically significant Diatom Assemblage Zones (DAZs) were defined with a cluster analysis (CONISS). The first axis of PCA (PC1), explaining 47.3% of total variance, confronts benthic vs tychoplanktonic and euplanktonic taxa, suggesting a relationship with water depth. The second axis (PC2) explained 23.1% of total variance, showing high positive values for eutrophic taxa of the genus Aulacoseira, and negative values for oligotrophic taxa and diatoms of a broad trophic spectrum. This axis is very likely related to a trophic gradient. DAZ-1 (c. 1280 - 1400 cal yr AD), dominated by benthic taxa, is characterized by positive values of PC1 and PC2, indicating relative shallow lake conditions and a high trophic level, respectively. A transition from a benthic to a facultatively planktonic

  12. Laurentian Great Lakes phytoplankton and their water quality characteristics, including a diatom-based model for paleoreconstruction of phosphorus.

    Science.gov (United States)

    Reavie, Euan D; Heathcote, Adam J; Shaw Chraïbi, Victoria L

    2014-01-01

    Recent shifts in water quality and food web characteristics driven by anthropogenic impacts on the Laurentian Great Lakes warranted an examination of pelagic primary producers as tracers of environmental change. The distributions of the 263 common phytoplankton taxa were related to water quality variables to determine taxon-specific responses that may be useful in indicator models. A detailed checklist of taxa and their environmental optima are provided. Multivariate analyses indicated a strong relationship between total phosphorus (TP) and patterns in the diatom assemblages across the Great Lakes. Of the 118 common diatom taxa, 90 (76%) had a directional response along the TP gradient. We further evaluated a diatom-based transfer function for TP based on the weighted-average abundance of taxa, assuming unimodal distributions along the TP gradient. The r(2) between observed and inferred TP in the training dataset was 0.79. Substantial spatial and environmental autocorrelation within the training set of samples justified the need for further model validation. A randomization procedure indicated that the actual transfer function consistently performed better than functions based on reshuffled environmental data. Further, TP was minimally confounded by other environmental variables, as indicated by the relatively large amount of unique variance in the diatoms explained by TP. We demonstrated the effectiveness of the transfer function by hindcasting TP concentrations using fossil diatom assemblages in a Lake Superior sediment core. Passive, multivariate analysis of the fossil samples against the training set indicated that phosphorus was a strong determinant of historical diatom assemblages, verifying that the transfer function was suited to reconstruct past TP in Lake Superior. Collectively, these results showed that phytoplankton coefficients for water quality can be robust indicators of Great Lakes pelagic condition. The diatom-based transfer function can be used in

  13. Examination of aerial diatom flushing across watersheds in Luxembourg, Oregon and Slovakia for tracing episodic hydrological connectivity

    Directory of Open Access Journals (Sweden)

    Pfister Laurent

    2015-09-01

    Full Text Available Hydrological processes research remains a field that is severely measurement limited. While conventional tracers (geochemicals, isotopes have brought extremely valuable insights into water source and flowpaths, they nonetheless have limitations that clearly constrain their range of application. Integrating hydrology and ecology in catchment science has been repeatedly advocated as offering potential for interdisciplinary studies that are eventually to provide a holistic view of catchment functioning. In this context, aerial diatoms have been shown to have the potential for detecting of the onset/cessation of rapid water flowpaths within the hillslope-riparian zone-stream continuum. However, many open questions prevail as to aerial diatom reservoir size, depletion and recovery, as well as to their mobilisation and transport processes. Moreover, aerial diatoms remain poorly known compared to freshwater species and new species are still being discovered. Here, we ask whether aerial diatom flushing can be observed in three catchments with contrasting physiographic characteristics in Luxembourg, Oregon (USA and Slovakia. This is a prerequisite for qualifying aerial diatoms as a robust indicator of the onset/cessation of rapid water flowpaths across a wider range of physiographical contexts. One species in particular, (Hantzschia amphioxys (Ehr. Grunow, was found to be common to the three investigated catchments. Aerial diatom species were flushed, in different relative proportions, to the river network during rainfall-runoff events in all three catchments. Our take-away message from this preliminary examination is that aerial diatoms appear to have a potential for tracing episodic hydrological connectivity through a wider range of physiographic contexts and therefore serve as a complementary tool to conventional hydrological tracers.

  14. Summer Epiphytic Diatoms from Terra Nova Bay and Cape Evans (Ross Sea, Antarctica)--A Synthesis and Final Conclusions.

    Science.gov (United States)

    Majewska, Roksana; Convey, Peter; De Stefano, Mario

    2016-01-01

    Despite recent advances in polar marine biology and related fields, many aspects of the ecological interactions that are crucial for the functioning of Antarctic shallow water habitats remain poorly understood. Although epiphytic diatoms play an essential role in the Antarctic marine food web, basic information regarding their ecology, biodiversity and biogeography is largely unavailable. Here, we synthesise studies on Ross Sea epiphytic diatoms collected during 11 summer Antarctic expeditions between the years 1989/90 and 2011/12, presenting a full list of diatom taxa associated with three macroalgal species (Iridaea cordata, Phyllophora antarctica, and Plocamium cartilagineum) and their epiphytic sessile fauna. Diatom communities found during the three summer months at various depths and sampling stations differed significantly in terms of species composition, growth form structure and abundances. Densities ranged from 21 to >8000 cells mm-2, and were significantly higher on the surface of epiphytic micro-fauna than on any of the macroalgal species examined. Generally, host organisms characterized by higher morphological heterogeneity (sessile microfauna, ramified Plocamium) supported richer diatom communities than those with more uniform surfaces (Iridaea). Differences between epiphytic communities associated with different macroalgae were reflected better in species composition than in growth form structure. The latter changed significantly with season, which was related strongly to the changing ice conditions. A general trend towards an increasing number of erect forms in deeper waters and tube-dwelling diatoms in the shallowest sites (2-5 m) was also observed. This study explores further important and largely previously unknown aspects of relationships and interactions between Antarctic epiphytic diatoms and their micro- and macro-environments.

  15. The marine Eemian of the Baltic: new pollen and diatom data from Peski, Russia, and Põhja-Uhtju, Estonia

    Science.gov (United States)

    Miettinen, Arto; Rinne, Katja; Haila, Heikki; Hyvärinen, Hannu; Eronen, Matti; Delusina, Irina; Kadastik, Ene; Kalm, Volli; Gibbard, Philip

    2002-05-01

    Several relatively well-preserved last interglacial (Eemian, marine oxygen isotope substage 5e; ca. 130-116 ka) deposits containing marine diatom flora have been found in Finland. In addition to these Finnish sites, more numerous Eemian (Mikulino) marine deposits are known from the northwestern part of Russia and from Estonia.Two new clayey and silty deposits covered by till, one at Peski, Russia, and the other Põhja-Uhtju, Estonia, were studied for pollen and diatom content. At Peski, the deposit representing the Eemian interglacial is 3.8 m thick. The polyhalobous diatom flora in the Corylus and Carpinus zones indicates the maximum of the marine transgression during the climatic optimum. Later, the increasing proportion of brackish water diatom flora indicates a lowering in the relative sea-level, and finally, during a very late phase of the Eemian, the sharply increasing proportion of freshwater species indicates the isolation of the sedimentary basin from the Eemian Sea.At Põhja-Uhtju, according to the pollen, the Eemian deposit is 3.5 m thick. Diatoms occur only in a layer 1.6 m thick, which represents the period of Corylus and Carpinus zones, and thus the period of the climatic optimum. The brackish-marine diatom flora consists mainly of littoral, shallow-water species.Although Peski is situated at a higher altitude than Põhja-Uhtju at present, the diatom stratigraphy at Peski indicates deeper and more saline conditions than at Põhja-Uhtju during the Eemian. This probably is the result of variations in glacio-isostatic rebound between these sites, which can be accounted for by differences of the ice load during the final phase of the Saalian glaciation.

  16. Drivers of Change in a 7300-Year Holocene Diatom Record from the Hemi-Boreal Region of Ontario, Canada.

    Science.gov (United States)

    Beck, Kristen K; Medeiros, Andrew S; Finkelstein, Sarah A

    2016-01-01

    A Holocene lake sediment record spanning the past 7300 years from Wishart Lake in the Turkey Lakes Watershed in the Hemi-Boreal of central Ontario, Canada, was used to evaluate the potential drivers of long-term change in diatom assemblages at this site. An analysis of diatom assemblages found that benthic and epiphytic taxa dominated the mid-Holocene (7300-4000 cal yr BP), indicating shallow, oligotrophic, circum-neutral conditions, with macrophytes present. A significant shift in diatom assemblages towards more planktonic species (mainly Cyclotella sensu lato, but also several species of Aulacoseira, and Tabellaria flocculosa) occurred ~4000 cal yr BP. This change likely reflects an increase in lake level, coincident with the onset of a more strongly positive moisture balance following the drier climates of the middle Holocene, established by numerous regional paleoclimate records. Pollen-inferred regional changes in vegetation around 4000 yrs BP, including an increase in Betula and other mesic taxa, may have also promoted changes in diatom assemblages through watershed processes mediated by the chemistry of runoff. A more recent significant change in limnological conditions is marked by further increases in Cyclotella sensu lato beginning in the late 19th century, synchronous with the Ambrosia pollen rise and increases in sediment bulk density, signaling regional and local land clearance at the time of Euro-Canadian settlement (1880 AD). In contrast to the mid-Holocene increase in planktonic diatoms, the modern increase in Cyclotella sensu lato likely indicates a response to land use and vegetation change, and erosion from the watershed, rather than a further increase in water level. The results from Wishart Lake illustrate the close connection between paleoclimate change, regional vegetation, watershed processes, and diatom assemblages and also provides insight into the controls on abundance of Cyclotella sensu lato, a diatom taxonomic group which has shown

  17. 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. PMID:27289395

  18. The new data on the seasonal distribution of diatoms in the Southern Baltic coastal lakes as a basis for diatom-based transfer functions to reconstruct past environmental changes in the Baltic coastal zone

    Science.gov (United States)

    Rzodkiewicz, Monika; Szpikowska, Grażyna; Woszczyk, Michał; Suchińska, Anita; Burchardt, Lubomira; Messyasz, Beata

    2016-04-01

    Lakes ecosystems are very sensitive to climate and environment changes. In lake sediments there are preserved remains of plant and animals that lived in the lake and its surroundings in the past. The species composition of past assemblages is a basis for quantitative and qualitative reconstruction of the past environmental changes (climate changes). One of the most commonly used bio-proxy for the reconstruction of lake development are subfossil diatoms which are sensitive to lake water pH, nutrient status, salinity and temperature. In this poster we present the new data from the coastal lakes on the Southern Baltic coast. The main goal of this research was to quantify the relationships between modern diatom assemblages and present-day environmental conditions. These relationships will be used to develop diatom-based transfer functions that will be applied to future studies of environmental change on the Polish Baltic coast. Water samples for diatom and chemical analyses were collected a few times per year between 2012 and 2014 from 12 coastal lakes located along the Polish Baltic coast as well as from the Baltic Sea. We analysed the whole phytoplankton composition. However the special focus was put on diatoms. At each site, a suite of important water quality parameters was collected, including chemical (e.g., chlorides, phosphorous and sulphur) and physical (e.g., Secchi depth) variables. Diatom assemblages from each site were counted and identified to the most specific taxonomic level possible. Diatom data were compiled for comparison to corresponding environmental data and development of indicator models. The results of the analysis show seasonal changes in diatom distribution as well as the chemical and physical water propertieswhich are mainly related to saltwater ingressions to the lakes. Lake Koprowo, Lake Resko Przymorskie, Lake Bukowo and Lake Łebsko are under the constant of seawater influence, which makes them similar to lagoons. In Lake Gardno seawater

  19. Micro-phytoplankton distribution and biomass in and around a channel-based fish farm:implications for sustainable aquaculture

    Institute of Scientific and Technical Information of China (English)

    SADALLY S B; NAZURALLY N; TALEB-HOSSENKHAN N; BHAGOOLI R

    2014-01-01

    Micro-phytoplankton density, genera composition, chlorophyllaconcentration, and physico-chemical pa-rameters were investigated at five stations (S1—near the coast; S2 and S4—at the edges of the aquaculture set-up; S3—in the center of the set-up; and S5—nearby patch of corals) in and around a coastal channel-based fish farm. The highest total micro-phytoplankton density (TPD), including diatoms, dinoflagellates and cyanobacteria, was recorded at S3 ((6.28±2.00)×106 cells/L) followed by S4 ((5.87±2.81)×105 cells/L), S1 ((4.92×105±8.70×104) cells/L), S5 ((3.54×105±5.33×104) cells/L) and S2 ((2.60±1.14)×105cells/L). Chlorophyll a and nutrient concentrations were highest at S3 and were positively correlated with TPD. Among the 35 genera documented in this study,Chaetoceros spp. was the dominant diatom whilePeridinium spp. was the most dominant dinoflagellate. Very low densities of toxic bloom-forming dinoflagellates were encountered during this study. These results suggest that occurrence of non-bloom densities of micro-phytoplankton, possibly due to the natural flushing of the existing lagoonal channel at the aquaculture site, yielded in little environmental impact and can represent an appropriate sustainable approach for future aquaculture de-velopment.

  20. A diatom-based sea-ice reconstruction of the last 5000 years in Vaigat Strait, Disko Bugt, West Greenland

    Science.gov (United States)

    Sha, Longbin; Jiang, Hui; Seidenkrantz, Marit-Solveig; Luise Knudsen, Karen; Olsen, Jesper; Kuijpers, Antoon; Liu, Yanguang

    2013-04-01

    Sea ice is a major component of the climate system, because it influences the planetary albedo and the exchanges of heat, moisture and gases between the ocean and the atmosphere. Thus, sea ice is a key parameter in atmospheric and ocean models assessing future climate change. However, observed reliable data on sea-ice cover, such as satellite data, are only available as far back as 30 years with the exception of records from ship logs, which are sporadic and irregular. To obtain longer time series of Arctic SIC, microfossils such as diatoms and dinoflagellate cysts are commonly used. We have developed a diatom-based sea-ice concentration (SIC) transfer function using 72 surface samples from west of Greenland and around Iceland, and through comparison with the associated modern SIC. Canonical correspondence analysis (CCA) on surface sediment diatoms and monthly average of SIC reveals that April SIC is the most important environmental factor controlling the distribution of diatoms in the area, and permits the development of a diatom-based SIC transfer function. The consistency between reconstructed SIC based on diatoms from West Greenland core GA306-BC4 and the instrumental and documentary data during the last ~75 years demonstrates that the diatom-based SIC reconstruction is reliable for studying the palaeoceanography off West Greenland. Based on the diatom record from a 446 cm long gravity core DA06-139G, collected from Vaigat Strait in Disko Bugt (water depth 384 m), the reconstructed April SIC varies between 40 and 70% with a mean value around 55% over the last 5000 years. Relatively warm conditions with strong influence of the IC are indicated for the early part of the record (~5000-3860 cal. yr BP), corresponding in time to the latest part of the Holocene Thermal Maximum. The April SIC oscillated around the mean value between 3860 and 1510 cal. yr BP and was above mean afterwards, particularly during the time interval 1510-1120 cal. yr BP and after 650 cal. yr