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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 81 (1984), S. 237-250 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The changes in the intracellular concentrations of nitrate, ammonium, free amino acids, protein, DNA, RNA and total nitrogen were measured in batch cultures of seven species of marine phytoplankton as they progressed from being nitrogen sufficient to being nitrogen starved. After several days of nitrogen starvation, either nitrate or ammonium was added to the cultures, and the measurements were continued for 10 to 36 h. By this means it was possible to assess the long-term and short-term changes in cellular nitrogen compounds and how they relate to phytoplankton nitrogen uptake and growth. Considerable species differences were observed in the amounts and kinds of nitrogen compounds which were stored and the degree to which the utilization of these compounds could support growth if the external nitrogen supply is low or variable. Despite the species variation, the results suggest that the concentrations or ratios of a number of intracellular nitrogen compounds can be used to assess the nitrogen deficiency and/or growth rate of natural phytoplankton populations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 20 (1978), S. 369-377 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract For use in trace pollutant studies a description is presented of a protected closed plankton net whose purpose is to minimize the exposure of collected samples to surface films and debris. Tests described in this paper appeared to show that the protected closed net was not necessary for the environmental conditions encountered during our field studies. However, additional calculations based on the data of other investigators strongly imply that employment of such a net in heavily polluted surface waters may be highly advantageous.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 28 (1982), S. 409-415 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The uptake of nitrate and ammonium was measured separately in uni-algal, nitrogen-deficient cultures of four species of marine phytoplankton. Nitrogen-deficient phytoplankton took up ammonium at initial rates which greatly exceeded those measured for nitrogen-sufficient phytoplankton. However, nitrate uptake by nitrogendeficient cultures was generally much slower than either nitrate or ammonium uptake by nitrogen-sufficient cultures or ammonium uptake by nitrogen-deficient cultures. Considerable species differences were observed in the degree to which nitrogen deficiency increased ammonium uptake or decreased nitrate uptake. Loss of ability to take up nitrate, but enhanced ability to take up ammonium, as a result of nitrogen deficiency may be an adaptation to the different mechanisms by which nitrate and ammonium are supplied to the euphotic zone. In areas with an intermittent supply of nitrogen, changes in the ability of some species to take up nitrogen as a result of nitrogen starvation will influence species composition and complicate interpretations of measurements of nitrogen uptake.
    Type of Medium: Electronic Resource
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