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  • zooplankton  (3)
  • TOC  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Niche overlap between herbivorous cladocerans; the role of food quality and habitat homogeneity (1990)
    Springer
    Hydrobiologia 190 (1990), S. 61-78 
    Details
    ISSN: 1573-5117
    Keywords: zooplankton ; niche-overlap ; competition ; food quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In spite of resource limitation, five abundant species of herbivorous metazoan zooplankton in a humic lake exhibited extensive niche overlap both with regard to seasonal and spatial occurrence, time of reproductive maxima, juvenile release and food choice. Their coexistence could not be explained by modifying predation, environmental oscillations or recolonization. Laboratory bottle experiments indicated only weak interspecific interactions between the three tested species at low food levels, but negative interactions were induced at elevated food levels. Bosmina appeared as competitively inferior during enrichment with cultured algae, but as the superior species during starvation. At low nutrient levels, all species coexisted for several generations with low reproduction, in accordance with the lake situation. It was concluded that the observed niche overlaps would be promoted if; 1) Intraspecific competition is more important than interspecific competition. 2) All species are co-adapted to low nutrient availability, food is quantitatively in surplus, but qualitatively deficient (mainly recycled detritus). During such conditions, no species would be capable of obtaining a population increase until extinction of the other species. This situation may be typical of oligotrophic humic lakes, and of other localities with low predation pressure and high inputs of allochthonous particulate carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020688
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Bacteria as a source of phosphorus for zooplankton (1990)
    Springer
    Hydrobiologia 206 (1990), S. 217-223 
    Details
    ISSN: 1573-5117
    Keywords: zooplankton ; bacteria ; phosphorus ; nutrient limitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The utilization of bacterial phosphorus in zooplankton metabolism was investigated using radio-phosphorus labelled natural bacteria as food source for zooplankton in feeding experiments. Incorporation of labelled bacteria was clearly related to the species' ability to graze on bacteria, with the cladoceran Daphnia reaching the highest biomass-specific activity and the copepod Acanthodiaptomus the lowest. Within Daphnia, juveniles had a higher biomass-specific uptake of phosphorus than adults. This was presumably caused by higher growth rates of the juveniles rather than age-specific differences in the ability to feed on bacteria, supported by the observation that the juveniles had the highest specific P-content. Retention of ingested 32P from labelled particles exceeded 80%, indicating higher assimilation efficiencies on phosphorus compared with carbon. In the investigated humic lake, approximately 75% of the phosphorus in grazable particles was bound in bacterial cells, making bacteria the most important source of P to the bacterivore zooplankton species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014087
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Stoichiometric relationships among producers, consumers and nutrient cycling in pelagic ecosystems (1992)
    Springer
    Biogeochemistry 17 (1992), S. 49-67 
    Details
    ISSN: 1573-515X
    Keywords: algae ; nitrogen ; nutrient ; phosphorus ; regeneration ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Most ecosystem models consolidate members of food-webs, e.g. species, into a small number of functional components. Each of these is then described by a single state variable such as biomass. When a multivariate approach incorporating multiple substances within components is substituted for this univariate one, a ‘stoichiometric’ model is formed. Here we show that the Nitrogen:Phosphorus ratio within zooplankton herbivores varies substantially intraspecifically but not intraspecifically. By using stoichiometric theory and recent measurements of the N:P ratio within different zooplankton taxa, we calculate large differences in ratios of nutrients recycled by different zooplankton species. Finally, we demonstrate that N:P stoichiometry can successfully account for shifts in N- and P-limitation previously observed in whole-lake experiments. Species stoichiometry merges food-web dynamics with biogeochemical cycles to yield new insights.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002759
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    TOC fluctuations in a humic lake as related to catchment acidification, season and climate (1997)
    Springer
    Biogeochemistry 36 (1997), S. 139-151 
    Details
    ISSN: 1573-515X
    Keywords: humic lake ; TOC ; acidification ; climate ; carbon budget
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Studies of fluctuations in total organic carbon (TOC) were performedin both the reference basin and the acidified basin of experimental LakeSkjervatjern, in order to separate effects of various catchment and in-lakeprocesses. Nearly five years of catchment acidification did not inducesignificant changes in TOC. TOC concentrations was not related clearly toprecipitation or runoff. In both basins, there was a regular, seasonal patternwith a gradual increase in TOC concentrations from spring to late autumn.Minima in concentrations occurred during periods with frozen ground inwinter, irrespective of discharge patterns. The decrease from ∼10 mg C l-1 in autumn to 1--2 mg C l-1 in latewinter, was only seen in surface layers. Runoff was the major loss routefor surface TOC in the lake. Photo-oxidation, bacterial oxidation, andsedimentation combined yielded maximum loss rates of 3%of surface TOC d-1. Below a depth of 1 m 0.5%d-1 was lost to these same processes. The surface microlayerhad 5--10 times more TOC than the bulk water on average, and could haveeffects on gas exchange and sub-surface light. Despite the oxidation ofTOC, the short residence time of the lake and rapid replacement of TOCfrom the catchment was the major determinant of lake water TOC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005740030477
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    Paper (German National Licenses)
    Fulltext
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