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  • 1
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 41 (1994), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Non-skeletal carbonate particles in microbial mats were studied using thin sections and scanning electron microscopy. The microbial mats form biolaminated units (so-called potential stromatolites) in salterns. This study emphasizes the coexistence of different particle forms and makes a genetic connection between the heterogeneity of the organic substrate built by bacteria and diatoms and their extracellular polymeric substances (EPS). Whereas allochthonous particles are scarce, Lanzarote microbial mats provide various autochthonous surfaces for the attachment of cells and EPS, including sheaths and capsules of cyanobacteria, frustules of diatoms, metabolic products such as gas bubbles, liquid globules and faecal pellets, as well as the carbonate precipitates themselves. Morphologically different carbonate precipitates are: (i) calcified organic clumps (peloids), (ii) particles composed of concentric aragonite and biofilm laminae (ooids and oncoids), (hi) isolated particles floating in gel-supported mats and coated by rims of fibrous cement (cortoids), (iv) particles bound by cryptocrystalline matrices or cement, resulting in aggregate grains and (v) lobate cement which fills out spaces and pores and fixes the particles. Peloids are suggested to represent faecal pellets although microbial systems also generate cell clumps by non-faecal processes. Ooid and oncoid constructions clearly record alternating processes of biofilm accumulation and aragonite encrustation. Further characteristic features of carbonate particles generated within a microbial mat are: (i) an irregular distribution ranging from isolated particles floating within the gel-like matrix to closely packed particles, (ii) the amalgamation of different particle types (e.g. peloids and ooids) in aggregate grains, (iii) the heterogeneous nature of nuclei comprising bacterial clumps, intraclasts, individual cells, cell colonies and bubbles, (iv) the enrichment of remains, casts and imprints of cells within precipitates and (v) deformation (e.g. truncated cortices) of particles.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 10 (1968), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Three stages of statistical development can be recognized in sedimentology. The first is descriptive statistics, in which the sample is the object of interest, and the second is analytical statistics, in which the population assumes major importance. A very large variety of statistical techniques is available for estimating mean values, degrees of variability, tests of differences among population means, linear relations (correlations) among the variables, and ways of evaluating areal variations (trends) in sedimentary phenomena.The third stage of statistical development is the application of stochastic process models to sedimentology, in which the objective is to discern the probabilistic elements in sedimentary processes, in part by simulation with the high-speed computer. Stochastic process models thus provide one way of examining sedimentary processes through time or over an area. In conjunction with deterministic models they provide a framework for exploring the underlying physical, chemical, and biological controls on sedimentary processes and deposits, with superimposed random fluctuations introduced by the “built–in” probabilistic mechanism.
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  • 4
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract The occurrence of Late Pleistocene dolomite crusts that occur at 64 m depth on the carbonate platform off western India is documented. Dolomite is the most predominant mineral in the crusts. In thin section, the crust consists of dolomitized microlaminae interspersed with detrital particles. Under scanning electron microscopy, these laminae are made up of tubular filaments or cellular structures of probable cyanobacterial origin. Dolomite crystals encrust or overgrow the surfaces of the microbial filaments and/or cells; progressive mineralization obliterates their morphology. Well-preserved microbial mats, sulphide minerals (pyrrhotite and marcasite) and the stable isotope composition of dolomite in the crusts indicate hypersaline and anoxic conditions during dolomite formation. The crusts are similar to dolomite stromatolites, and biogeochemical processes related to decaying microbial mats under anoxic conditions probably played an important role in dolomite precipitation. The dolomite is therefore primary and/or very early diagenetic in origin. The dolomite crusts are interpreted to be a composite of microbial dolomite overprinted by early burial organic dolomite. The results of this study suggest that a microbial model for dolomite formation may be relevant for the origin of ancient massive dolomites in marine successions characterized by cryptalgal laminites. The age of the crusts further suggests that the platform was situated at shallow subtidal depths during the Last Glacial Maximum.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 26 (1979), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In the Borrego Desert (California) and in the Sinai Desert (Israel) laminated, microbially mediated carbonate crusts have been found and analysed biologically and mineralogically, and further studied with scanning electron microscope methods combined with energy dispersive X-ray analyses. All morphological and biological features of the extant crusts justify the term ‘desert stromatolite’, a term applied to stromatolites from desert regions which form under permanent exposure to the atmosphere. These stromatolites are never covered by standing water, and running water (heavy rainfall) covers them for only a few hours during the year. Carbonate deposition is achieved principally by the cyanobacterium Pleurocapsa sp. which exhibits characteristic yet different stages of calcification. Calcification occurs in the sheaths of single cells (including baeocytes) as well as in mature colonies. The specificity for calcification in Pleurocapsa sp. is discussed.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 22 (1975), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
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  • 7
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Helgoland marine research 25 (1973), S. 347-356 
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary 1. Berbelin blue-I (N.N.′-Dimethylamino-p, p′-triphenylmethane-o″-sulphonic acid) has been examined as a reagent for the detection of manganese oxidation and manganese reduction in microbial culture media. 2. Berbelin blue in slightly acid solution may be added to media without influencing population growth of micro-organisms. The oxidation of Mn II solutions to Mn III and IV is detected by occurrence of deep blue colours. 3. In case of long-term culture experiments, it is more advisable to add Berbelin blue-I solutions only after cultivation. 4. Berbelin blue-I solutions react with manganese IV–VII in pH ranges between 3.5 and 10, thus allowing tests at desired pH values. 5. Reduction of manganese VII or manganese IV by micro-organisms may be detected by addition of Berbelin blue-I solutions after cultivation periods. White halos within dark-blue coloured media indicate reduction of Mn-IV compounds better than occurrence of white spots in slightly violet or grey media, as produced by the incorporation of manganese oxides or permanganate solutions to test media. 6. Ecological work and quantitative work on board research vessels is much easier and less dangerous with Berbelin-I solutions than withFeigl's Benzidinium reagent. 7. Berbelin blue-I may be used for quantitative determination of manganese and oxygen when measuring optical density of the colour complex at 618 nm in wide concentration ranges and working in acetate buffer.
    Notes: Kurzfassung Berbelinblau I (N.N′-Dimethylamino-p,p′-triphenylmethan-o″-sulfonsäure) ist die Leukobase eines neuen Farbstoffes und bildet mit Mn(III)-Mn(VII)-kationen einen intensiv blau gefärbten Farbstoff. Die Reaktion verläuft quantitativ, indem die Leukobase (FH) zum Farbstoff (F+) oxidiert wird. Sie entwickelt sich am günstigsten in Acetatpuffer. Eine intensive und schnelle Reaktion mit anwesenden Mangan-III-VII-kationen läuft jedoch auch im pH-Bereich zwischen 4 und pH 7 ab. Bei Verwendung von konzentrierteren Lösungen von Berbelinblau I entstehen in Anwesenheit oxidierter Stufen des Mangans gut erkennbare Farbkomponenten noch bis pH 10. Die Verwendungsfähigkeit des neuen Farbstoffes als Beimengung zu Nährböden wurde getestet. Mangan oxidierende Bakterien und Pilze wachsen auf Nährböden, in denen der Farbstoff in Konzentrationen zwischen 10−4 und 10−5 g/100 ml imprägniert wurde, ohne erkennbare Behinderung gegenüber nichtbehandelten Nährböden. Bereits früher als die Bildung von schwarzbraunen Manganoxidhydratablagerungen im Nährboden tritt eine Blauverfärbung der Kolonien ein, die Mangan oxidieren. Berbelinblau I eignet sich deshalb ausgezeichnet für die Früherkennung von Mangan oxidierenden Mikroorganismen in selektiven Nährböden. Bei einem Vergleich der Benzidinmethode nachFeigl (1958) mit dem neuen Farbstoff ergab sich ein erkennbarer Vorteil von Berbelinblau I. Das Testreagens kann dem Nährboden oder den Kulturen in schwach saurem Puffer zugeführt werden und die Isolation von Mikroorganismen ist nach Anfärbung noch ohne weiteres möglich. Kulturen und Kolonien von Mangan reduzierenden Bakterien und Pilzen lassen sich deutlich von unspezifischen Kolonien unterscheiden, wenn nach der Anfärbung mit Berbelinblau ungefärbte Höfe gezählt werden. Auch in diesem Fall ist eine Isolation ohne weiteres möglich, während dies bei der Verwendung vonFeigls Reagens in konzentrierter Essigsäure auf Schwierigkeiten stößt. Quantitative Bestimmung von Mangan (und Sauerstoff über die Winklermethode) in Nährböden und bakteriell gefälten Manganablagerungen ist ohne weiteres möglich.
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  • 9
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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