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  • 1
    Electronic Resource
    Electronic Resource
    Convergent succession of phytoplankton in microcosms with different inoculum species composition (1991)
    Springer
    Oecologia 87 (1991), S. 171-179 
    Details
    ISSN: 1432-1939
    Keywords: Phytoplankton ; Zooplankton ; Microcosm Succession ; Competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Different initial mixtures of phyto-and zooplankton from different lakes were grown under identical chemical and physical conditions in medium size (8-and 12–1) laboratory microcosm cultures until convergence of phytoplankton species composition was attained. Five such experiments with four (four experiments) or three (one experiment) microcosm cultures were run. Three experiments were performed with weak stirring which permitted sedimentary elimination of the diatoms. Two experiments were conducted with stronger stirring to prevent sedimentation. In the three “sedimentation intensive” experiments, the final phytoplankton community was composed of the filamentous chlorophyte Mougeotia thylespora together with a smaller biomass of nanoplanktic algae. In the two “sedimentation free” experiments the final phytoplankton community consisted of pennate diatoms. Both dissolved nutrient concentrations and the chemical composition of biomass suggested strong nutrient limitation of algal growth rates in the final phase of the experiments. The zooplankton communities at the end of the experiments were composed of species that were apparently unable to ingest the large, dominant algae and that presumably fed on the nanoplanktic “undergrowth” and the bacteria. There was a distinct sequence of events in all experiments: first, the large zooplankton species (Daphnia and Copepoda) were replaced by smaller ones (Chydorus, Bosmina, rotifers); second, all cultures within one experiment developed the same nutritional status (limitation by the same nutrient); and third, the taxonomic composition of phytoplankton of the different cultures within one experiment converged. The last took 7–9 weeks, with is about 2–3 times as long as the time needed in a phytoplankton competition experiment to reach the final outcome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00325254
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Demonstration of β-N-acetyl-D-glucosaminidase and β-N-acetyl-D-hexosaminidase in Drosophila Kc-cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 17 (1991), S. 3-13 
    Details
    ISSN: 0739-4462
    Keywords: intra- and extracellular enzymes ; kinetic properties ; inhibition ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Kc-cells from Drosophila melanogaster, grown under serum-free conditions, produce two β-hexosaminidases and secrete these enzymes into the medium. The two enzymes were separated by DEAE-exchange chromatography. According to their substrate specificities one enzyme is a β-N-acetyl-D-glucosaminidase (E.C.3.2.1.30), the other one a β-N-acetyl-D-hexosaminidase (E.C.3.2.1.52). The β-N-acetyl-D-glucosaminidase is predominant in the medium, the β-N-acetyl-D-hexosaminidase within the cells. The Km values for the substrates pNP-GlcNAc, pNP-GalNAc, and (GlcNAc)2 are 0.8, 16.73, and 1.67 mM for the β-N-acetyl-D-glucosaminidase and 0.24, 0.44, and 0.2 mM for the β-N-acetyl-D-hexosaminidase. Both enzymes are inhibited by the products and the β-N-acetyl-D-glucosaminidase is also inhibited stereospecifically by the substrates pNP-GlcNAc and (GlcNAc)2. Both enzymes are inhibited in a partial competitive way by acetamidolactones, the Kis being as low as 0.1 μM.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940170103
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Physical properties of β-N-acetyl-D-glucosaminidase and β-N-acetyl-D-hexosaminidase from Drosophila Kc-cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 18 (1991), S. 45-53 
    Details
    ISSN: 0739-4462
    Keywords: molecular mass ; pH and temperature optima ; thermal stability ; influence of ionic strength ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Kc-cells from Drosophila produce two different β-D-hexosaminidases, a β-N-acetyl-D-glucosaminidase (E.C.3.2.1.30) and a β-N-acetyl-D-hexosaminidase (E.C.3.2.1.52), which are also secreted into the medium. The Mr of both enzymes is about 126,000 ± 9,700; the S-values are 8.37 ± 0.44. Both enzymes have about the same pH optima at 5.5 and the same thermal stability. The temperature optima are identical (50°C) for both enzymes if p-nitrophenyl-N-acetylglucosaminide is used as a substrate. However, when p-nitrophenyl-N-acetylgalactoseaminide is used as the substrate the β-N-acetyl-D-hexosaminidase has a temperature optimum about 10°C higher. With higher salt concentrations, the activity of the β-N-acetyl-D-glucosaminidase increases, whereas β-N-acetyl-D-hexosaminidase is inhibited. Both enzymes also differ in their sensitivity to urea, the β-N-acetyl-D-hexosaminidase being less sensitive than the β-N-acetyl-D-glucosaminidase.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940180105
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    Paper (German National Licenses)
    Fulltext
  • 4
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    A Comparison of the Droop and the Monod Models of Nutrient Limited Growth Applied to Natural Populations of Phytoplankton (1991)
    British Ecological Society
    In:  Functional Ecology, 5 (4). p. 535.
    Details
    Publication Date: 2017-01-16
    Description: The extent of nutrient limitation of phytoplankton in eutrophic Pluβsee was studied by enrichment bioassays and by analysing the cellular stoichiometry of monospecific fractions obtained by size fractionation and density-gradient separation. In this lake silicate and nitrogen, but not phosphorus, at times limit the reproductive rates of phytoplankton. The dependence of nutrient-limited reproductive rates on the cellular content of the limiting nutrient (cell quota) could well be described by the Droop model. Biomass specific minimal cell quotas of nitrogen ranged from 0.014 to 0.061 mol N mol-1 C, minimal cell quotas of silicon ranged from 0.055 to 0.127 mol Si mol-1 C. The cell quotas of the non-limiting nutrients usually increased with the cell quotas of the limiting nutrient. In contrast to the Droop model, the Monod model which relies on ambient concentrations of limiting nutrients was a much poorer predictor of growth rates.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.2307/2389636
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Comparative nutrient status and competitive interactions of two Antarctic diatoms (Corethron criophilum and Thalassiosira antarctica) (1991)
    Oxford Univ. Press
    In:  Journal of Plankton Research, 13 (1). pp. 61-75.
    Details
    Publication Date: 2018-05-30
    Description: The nutrient status of two common Antarctic diatoms (Corethron criophilum and Thalassiosira cf. antarctica) was analysed by studying the growth response in enrichment bioassays and by estimates of the cell quotas of Si, N and P after size-fractionation of net plankton samples Corethron had higher biomass-specific N-quotas; Si- and P-quotas were quite similar between both species. Corethron was Si-limited in five enrichment experiments and not nutrient limited in five experiments. Thalassiosira was not nutrient limited in six experiments, N-hmited in four experiments and Si-limited in one experiment Droop-kinetics of Si-limited growth of Corethron and of N-hmited growth of Thalassiosira were obtained by combining the growth rates in the bioassays and the cell quotas from the natural populations. The minimal Si-quota of Corethron was 0 041 mol Si/mol C, the saturating cell quota was 0.158 mol Si/mol C respectively The minimal N-quota of Thalassiosira was 0 0223 mol N/mol C, the saturating cell quota was 0.208 mol N/mol C Corethron was N-saturated at cell quotas of 〉0 106 mol N/mol C; Thalassiosira was Si-saturated at cell quotas of 〈0 132 mol Si/mol C. As the better competitor for N and the poorer one for Si, Corethron became more important with increasing Si N ratios, while Thalassiosira became more important with decreasing Si:N ratios in the water
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1093/plankt/13.1.61
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Convergent succession of phytoplankton in microcosms with different inoculum species composition (1991)
    Springer
    In:  Oecologia, 87 (2). pp. 171-179.
    Details
    Publication Date: 2017-10-10
    Description: Different initial mixtures of phyto-and zooplankton from different lakes were grown under identical chemical and physical conditions in medium size (8-and 12–1) laboratory microcosm cultures until convergence of phytoplankton species composition was attained. Five such experiments with four (four experiments) or three (one experiment) microcosm cultures were run. Three experiments were performed with weak stirring which permitted sedimentary elimination of the diatoms. Two experiments were conducted with stronger stirring to prevent sedimentation. In the three ldquosedimentation intensiverdquo experiments, the final phytoplankton community was composed of the filamentous chlorophyte Mougeotia thylespora together with a smaller biomass of nanoplanktic algae. In the two ldquosedimentation freerdquo experiments the final phytoplankton community consisted of pennate diatoms. Both dissolved nutrient concentrations and the chemical composition of biomass suggested strong nutrient limitation of algal growth rates in the final phase of the experiments. The zooplankton communities at the end of the experiments were composed of species that were apparently unable to ingest the large, dominant algae and that presumably fed on the nanoplanktic ldquoundergrowthrdquo and the bacteria. There was a distinct sequence of events in all experiments: first, the large zooplankton species (Daphnia and Copepoda) were replaced by smaller ones (Chydorus, Bosmina, rotifers); second, all cultures within one experiment developed the same nutritional status (limitation by the same nutrient); and third, the taxonomic composition of phytoplankton of the different cultures within one experiment converged. The last took 7–9 weeks, with is about 2–3 times as long as the time needed in a phytoplankton competition experiment to reach the final outcome.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/BF00325254
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    The application of the Droop-model of nutrient limitation to natural phytoplankton (1991)
    In:  Verhandlungen / Internationale Vereinigung für Theoretische und Angewandte Limnologie, 24 . pp. 791-794.
    Details
    Publication Date: 2016-05-17
    Type: Article , NonPeerReviewed
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    OceanRep: Article in a Scientific Journal - without review
  • 8
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    Phytoplankton: directional succession and forced cycles (1991)
    Springer
    In:  In: The mosaic cycle concept of ecosystems. , ed. by Remmert, H. Springer, Berlin, Germany, pp. 132-146. ISBN 3-540-52502-5
    Details
    Publication Date: 2012-03-28
    Type: Book chapter , NonPeerReviewed
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    OceanRep: Book chapter
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