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  • 1
    Electronic Resource
    Electronic Resource
    Rhythmic release of dissolved free amino acids from partly synchronized Thalassiosira rotula under nearly natural conditions (1983)
    Springer
    Marine biology 74 (1983), S. 305-312 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In outdoor tanks enclosed monocultures of Thalassiosira rotula showed partly synchronized cell divisions during exponential growth. The changes in division activity showed a characteristic frequency, which also could be found for cell length (pervalvar axis) and assimilation rate as well as for concentration changes of dissolved free amino acids (DFAA) and ammonia. Excretion of DFAA occurred preferentially during periods of reduced cell division activity, when assimilation was at a higher level. The concentration of ammonia decreased during these periods. The rates per hour of these parameters showed significant multiple correlations. The release of six individual amino acids (ala, β-ala, gly, lys, orn and ser) seemed to be controlled by the physiological status of the diatoms. These amino acids amounted to a portion of about 70–80% of the total DFAA. Uptake and release rates of DFAA nitrogen and ammonia were in the same range with maxima of about 350 ng at nitrogen dm-3 h-1 and litre. These dynamics pointed to strong fluxes of organic bound nitrogen in marine micro-heterotrophs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00403456
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Dissolved organic substances during a Phaeocystis pouchetii bloom in the German Bight (North Sea) (1985)
    Springer
    Marine biology 89 (1985), S. 311-316 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dissolved organic substances (carbohydrates, organic nitrogen, free amino acids) were measured in the German Bight (North Sea) in June, 1981. During and before this survey, sea foam was observed in the east Frisian coastal water and it accumulated on the nearby beaches to an unusually high extent. In this coastal water area, a large Phaeocystis pouchetii Lagerheim bloom and very high concentrations of dissolved organic matter were found. The above dissolved organic substances were all positively correlated to a highly significant degree with P. pouchetii cell numbers in the bloom area. An influence of salinity (or river water) on this correlation could be excluded. Thus, exudation or decomposition products of P. pouchetii were most likely the cause of the unusually high concentrations of dissolved organic matter in the bloom area off the east Frisian coast, where P. pouchetii blooms have been reported for many years. Ammonia concentrations were very low in the P. pouchetii bloom area; this and the accumulation of dissolved organic substances might lead to speculation that decomposition of dissolved organic matter by bacteria could have been reduced due to antibiotic activity of P. pouchetii.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393665
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    An automated fluorescence assay for dissolved total amino acids from marine waters in the presence of interfering material (1987)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 327 (1987), S. 518-520 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary For the determination of dissolved total amino acids from seawater a method is recommended that was based on the fluorimetric detection of primary amines with o-phthaldialdehyde (OPA). Automatic measurements are performed and calibrated with an amino acid mixture standard. Proteins which interfere with the procedure are separated by gel filtration. Ammonia which is also detected by OPA has to be determined additionally and corrected. The fluorescent response is linear over a wide range. The detection limit is in femtomol concentrations.
    Notes: Zusammenfassung Für die Bestimmung von im Meerwasser gelösten Gesamt-Aminosäuren wird eine Methode empfohlen, die auf einem fluorimetrischen Nachweis primärer Amine mit o-Phthaldialdehyd (OPA) basiert. Die Messungen erfolgen automatisch und werden gegen ein Aminosäurengemisch als Standard geeicht. Proteine, die den Nachweis stören, werden durch Gelfiltration abgetrennt. Ammonium, das ebenfalls durch OPA angezeigt wird, muß separat gemessen und korrigiert werden. Das Fluoreszenz-Signal ist über einen weiten Bereich linear. Die untere Nachweisgrenze liegt im Femtomolbereich.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00487238
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Automatic determination of total carbohydrates in sea water (1980)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 301 (1980), S. 17-19 
    Details
    ISSN: 1618-2650
    Keywords: Best. von Kohlenhydraten in Wasser ; Spektralphotometrie ; AutoAnalyzer, Meerwasser, Tryptophan-Schwefelsäure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary The recommended method is based on the l-tryptophane/sulphuric acid reaction and has been adapted for a continuous flow system with the Technicon AutoAnalyzer. A supplementary run (cold run) is required with more than 10μmol/l of nitrate. The presence of acetone or formaldehyde must be avoided. Total carbohydrates can be determined by this method within the range of 0.02–5mg/l. The relative coefficient of variation at the 1 mg/l level is 0.25 % (glucose).
    Notes: Zusammenfassung Die empfohlene Methode basiert auf der l-Tryptophan-Schwefelsäure-Reaktion und wurde dem Durchflußsystem des Technicon AutoAnalyzers angepaßt. Bei einem Nitratgehalt von mehr als 10μmol/l ist zur Feststellung einer Korrektur ein zusätzlicher »kalter« Durchlauf notwendig. Aceton oder Formaldehyd dürfen nicht anwesend sein. Die Bestimmung kann im Bereich von 0.02–5 mg/l erfolgen und weist einen relativen Variationskoeffizienten von 0.25 % bei 1 mg/l auf (Glucose).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00481265
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    Paper (German National Licenses)
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  • 5
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    Nitrogen and phosphorus in different water layers at the central station during FLEX '76 (1980)
    Bornträger
    Details
    Publication Date: 2022-06-24
    Description: The main objectives of the Fladen Ground Experiment (FLEX) 1976 were an investigation of the dynamics of the mixed layer and the development of the spring plankton bloom. A quantitative consideration of individual chemical parameters (nutrients, particulate nitrogen and phosphorus) showed it to be advantageous to divide the water column into several layers which are separated from one another by measured temperature gradients. Measurements of particulate matter (phosphorus and nitrogen) revealed two plankton blooms at the central station. The first one (21.4.-14.5.76) was much more extensive than the second one, since the limiting thermocline was at a depth of about 60 m. Silicate was consumed most rapidly during this bloom and almost completely exhausted. The second bloom (19.-30.5.76) produced concentrations of particulate matter which were almost as high as the first one but were limited in only a few meters' water depth by a secondary thermocline, which prevented an influx of nutrients. Nitrate was completely exhausted during the second bloom. A high degree of nutrient depletion in the mixed layer from 24.4.-29.4. and from 22.5.-27.5.76 make these periods appear well-suited for determination of uptake rates. These periods are characterized. by a parallel course of concentration curves in the upper water layers for all nutrients except ammonium, and by the absence of !arge short-term fluctuations. Thus, disturbances due to hydrodynamic effects were minimal. The effects of tidal changes were minimized by using daily averages of the various concentrations. However, from 9.5.-13.5.7 6 in the upper layer a relatively strong and rapid increase was observed in the concentrations of all nutrients, which can probably only be explained by hydrodynamic influences. The nitrogen and phosphorus budgets can only be approximately balanced without considering dissolved organic matter. The strong decrease in dissolved inorganic nutrients during the first plankton bloom is almost comple,tely compensated by the increase in particulate matter. Not considering hydrodynamic influences, deficits after the plankton bloom could be explained by the fact that dissolved organic substances, as weil as sedimentaty matter and zooplankton, either were not considered at all, or at least not quantitatively. The time periods from 2.-7.4. and from 21.4.-14.5.76 show no strong short-term fluctuations in the nitrogen and phosphorus budgets and appear most suitable for calculations of mass fluxes, uptake and production rates, since biological-chemical processes seem to be dominant over hydrodynamic ones during these periods.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    An attempt to determine fluxes of nitrogen and phosphorus in special time periods during FLEX '76 (1980)
    Bornträger
    Details
    Publication Date: 2022-06-24
    Description: Measurements of nutrients and the elements phosphorus and nitrogen from the central station in FLEX '76 were used to calculate mass fluxes and budgets for these elements in defined time and depth intervals. The intervals were defined using hydrodynamic and biological criteria. Within these periods rates of increase and decrease were calculated for nitrate, ammonium, phosphate, particulate nitrogen and phosphorus. These rates were also calculated for the layer above and below the main thermocline. The element budget was balanced within some of the defined intervals. This was possible by only considering biological, chemical, and vertical physical interactions at the central station. At the beginning of the phytoplankton bloom we found fluxes with a maximum of 28 ngat · l-1 · d-1 for phosphorus and 590 ngat · l-1 · d-1 for nitrogen. Interaction diagrams are shown for mass fluxes for three periods during the plankton bloom.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Release of dissolved free amino acids during a bloom of Thalassiosira rotula (1981)
    Institut für Meereskunde
    Details
    Publication Date: 2022-05-24
    Description: Three large plastic enclosures (3-4 m3) were anchored in the outer harbour of Helgoland (German Bight) and filled with natural seawater which was filtered free of algae. The enclosed water bodies were enriched with inorganic nutrients and inoculated with the diatom Thalassiosira rotula. During the growth of the algae diurnal changes in concentration of dissolved free amino acids (DFAA) occurred. The periodic concentration changes of individual amino acids with a low carbon to nitrogen ratio showed significant interrelationships with the partly synchronous devisions of the diatoms. From the exponential to the stationary phase the carbon to nitrogen ratio of DFAA shifted to higher values pointing at an adaptation of the organisms to the decreasing inorganic nitrogen source. During the bloom amino acids relatively rich in nitrogen were mainly excreted but by the end of the growth amino acids with a higher carbon content predominated. At phases of high photosynthetic activity the organisms probably reduced the high osmotic pressure by exudation of DFAA.
    Type: Article , NonPeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - without review
  • 8
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    Impact of plasma jet vacuum ultraviolet radiation on reactive oxygen species generation in bio-relevant liquids (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-11-12
    Description: Plasma medicine utilizes the combined interaction of plasma produced reactive components. These are reactive atoms, molecules, ions, metastable species, and radiation. Here, ultraviolet (UV, 100–400 nm) and, in particular, vacuum ultraviolet (VUV, 10–200 nm) radiation generated by an atmospheric pressure argon plasma jet were investigated regarding plasma emission, absorption in a humidified atmosphere and in solutions relevant for plasma medicine. The energy absorption was obtained for simple solutions like distilled water (dH 2 O) or ultrapure water and sodium chloride (NaCl) solution as well as for more complex ones, for example, Rosewell Park Memorial Institute (RPMI 1640) cell culture media. As moderate stable reactive oxygen species, hydrogen peroxide (H 2 O 2 ) was studied. Highly reactive oxygen radicals, namely, superoxide anion (O 2 •− ) and hydroxyl radicals ( • OH), were investigated by the use of electron paramagnetic resonance spectroscopy. All species amounts were detected for three different treatment cases: Plasma jet generated VUV and UV radiation, plasma jet generated UV radiation without VUV part, and complete plasma jet including all reactive components additionally to VUV and UV radiation. It was found that a considerable amount of radicals are generated by the plasma generated photoemission. From the experiments, estimation on the low hazard potential of plasma generated VUV radiation is discussed.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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