ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1573-5176
    Keywords: acetylene reducing activity ; dinitrogen fixation ; N2-fixing cyanobacteria ; ricefields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A device forin situ estimation of biological nitrogen fixation in shallow-water ricefields was developed using the acetylene-reducing assay. The device consists of a rigid transparent bottomless plastic bottle provided with an agitation system. Laboratory experiments using flooded pots inoculated withAnabaena UAM 202 indicated that agitation significantly reduced the time needed to detect the production of ethylene by eliminating the slow diffusion of acetylene and ethylene in water. A direct relationship between the abundance of cyanobacteria and the rate of acetylene reduction was observed in laboratory and field experiments. A negative correlation between the amount of combined nitrogen and the abundance of cyanobacteria was observed in the field.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1573-5176
    Keywords: ammonium ; cyanobacteria ; nitrogenase activity ; rice fields ; sugar utilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nitrogen-fixing capacity of four cyanobacterial strains was tested in relation to heterotrophic ability, tolerance to combined nitrogen and adaptive capacity to changes in light intensity and pH. Strains (Anabaena variabilis UAM 202;Calothrix marchica UAM 214;Nodularia spumigena UAM 204,Nostoc punctiforme UAM 205) were isolated from the rice-fields of Valencia (Spain).C. marchica, was the only strain able to grow and to fix dinitrogen under heterotrophic conditions, with fructose and glucose. Fructose was the best substrate supporting growth and dinitrogen fixation in mixotrophy (growth in the light under conditions where CO2 and organic carbon are assimilated simultaneously), photoheterotrophy (growth in the light on an organic compound in the absence of net CO2 fixation) and heterotrophy (growth on an organic compound in the dark). Ammonium repressed nitrogenase more than nitrate. Full repression was observed only at concentrations of combined nitrogen higher than those usually found in rice-fields. Carbohydrates had a protective effect on nitrogenase against ammonium inhibition inC. marchica. All four strains showed increased nitrogenase activity when the light intensity was increased during assays. Variations of pH normally occurring in rice fields led to no important changes in nitrogenase activity inC. marchica. This fact, together with its potential for heterotrophic growth and tolerance to combined nitrogen, make this the most suitable of the four strains for inoculation experiments in rice fields.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2013-03-20
    Description: A summer study of the vertical structure of bi-layered microbial mats was carried out on Byers Peninsula (Livingston Island, South Shetland Islands). These benthic communities had a common basic structure that consisted of two distinct layers differing in composition, morphology and colour. Our sampling focused on mats showing more layering, which thrived over moist soils and at the bottom of ponds. The photosynthetic pigments analysis performed by high-performance liquid chromatography demonstrated a major occurrence of cyanobacteria and diatoms on these mats, the former being more abundant in relative terms on the surface and composed by morphospecies grouping into orders Oscillatoriales, Nostocales and Chroococcales. The areal chlorophyll a concentrations were slightly higher in the deeper layer although not significantly. Our microscopic and chemical analyses showed that non-active biomass accumulates at the surface. Hence, the upper layers showed the sheath pigment scytonemin and higher amounts of exopolysaccharides, as a strategy to cope with environmental stress. On the other hand, the basal layer was composed of more active photosynthetic microbiota, which also revealed a more balanced stoichiometry. Here we exemplify how environmental stresses are potentially overcome by physiological mechanisms developed by microbial mats which also shape their vertical structure.
    Print ISSN: 0954-1020
    Electronic ISSN: 1365-2079
    Topics: Biology , Geography , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2013-03-20
    Description: A systematic limnological survey of water bodies of Byers Peninsula (Livingston Island, South Shetland Islands) was carried out during the summer of 2001/02. Abundances of microbial plankton were determined which allowed a delineation of the pelagic food web structure. We also report the nutrient status of these lakes. We demonstrate the occurrence of a trophic gradient that extended from upland lakes (oligotrophic) to the coastal ones (eutrophic). The study shows that a lake's morphology regulates the relative importance of the pelagic and benthic habitats, whereas nutrient loads mainly determine its trophic status. Yet, some of the variability observed could be also a legacy of the landscape. Photosynthetic pigments analyses by high-performance liquid chromatography of the lake waters revealed a major occurrence of chlorophytes, chrysophytes and diatoms. The chlorophyll a concentrations in lakes in the central plateau were consistently lower (〈 2.5 μg l-1) than coastal sites, which were one order of magnitude higher. Numbers of both bacterioplankton and autotrophic picoplankton also increased from inland to coastal sites. However, the relative role of autotrophic picoplankton in the total phytoplankton assemblage decreased with the increase in nutrients loads. Our results show that the trophic status clearly plays a significant role in structuring the pelagic communities of these lakes despite climatic constraints.
    Print ISSN: 0954-1020
    Electronic ISSN: 1365-2079
    Topics: Biology , Geography , Geosciences
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...