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  • 1
    Electronic Resource
    Electronic Resource
    Why ’very shallow‘ lakes are more successful opposing reduced nutrient loads (1997)
    Springer
    Hydrobiologia 342-343 (1997), S. 269-284 
    Details
    ISSN: 1573-5117
    Keywords: shallow lakes ; eu-hypertroph ; Cyanobacteria ; morphometry ; mixing ; euphotic depth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There are different approaches for classifying deep andshallowwaters using physically and ecologically derived parameters.Nevertheless, transition states make it difficult to definebordercrossing points between the two types of limnetic ecosystemsand todistinguish more precisely between different types of shallow,especially highly eutrophicated lakes. We contribute adetailedanalysis of different characteristics of shallow waters fromlakesin the Berlin/Brandenburg-region. In the catchment area of theriver Dahme in Eastern Brandenburg (Scharmützelsee-region)wefind mainly shallow and highly eutrophicated lakes, dominatedbyCyanobacteria. ’Very shallow‘ lakes of different morphometry andtopography are compared with ’medium shallow‘ or deeper lakesinthe region with similar loading characteristics for thefollowingproperties: morphometry, topography, theoretical retentiontime,mixing intensity, nutrient dynamics, external and internalloading,underwater light climate, zeu/zmix,phytoplankton development and oxygen budget. We found that’veryshallow‘ lakes in the region are more efficient in convertingtheavailable phosphorus into phytoplankton biomass because of theconstant and sufficient underwater light climate due to thefavourable relation of zeu and zmix. Weconclude that the regular mixing regime guarantees a stableandnear optimum light/dark rhythm as well as higher heterotrophicactivities, stimulating primary production up to the upperlimit ofalgal development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017012012099
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On the occurrence of clear-water phases in relation to shallowness and trophic state: a comparative study (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 251-262 
    Details
    ISSN: 1573-5117
    Keywords: clear-water phase ; cyanobacteria ; Cladocera ; shallow lakes ; seasonal succession ; PEG model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present a comparative study on the occurrence of spring clear-water phases in six eutrophic lakes (two deep, four very shallow lakes dominated by plankton, TP: 0.06–0.13 mg l-1) in the Scharmützelsee region (Germany). Our aim was to analyse the occurrence and intensity of clear-water phases in relation to shallowness and trophic state. We defined a clear-water phase by a continuous increase of Secchi depth, a corresponding decrease in algal biomass and a shift in phytoplankton species composition during the growth phase of cladoceran zooplankton. For shallow lakes, we used the increase of the euphotic depth up to maximum depth as an additional criterion. Only in two of six lakes a clear-water phase occurred. In two lakes, no spring peak of cladocerans developed. In two other lakes, a high biomass of grazing resistant cyanobacteria was not affected by cladoceran maxima. Daphnia galeatawas an important component of the grazer community in lakes with a clear-water phase, whereas lakes without a clear-water phase were dominated by Bosmina longirostris. Top-down control of grazing by fish predation is discussed as the main factor determining biomass, composition and timing of the cladoceran spring peak. The assumed relative strength of fish predation between lakes corresponds to the response in algal biomass, dominance of cyanobacteria and is inversely related to the potential grazing pressure (ratio of cladoceran and algal biomass). Bottom-up effects (food quality) and additional factors (fungal infection, flushing rate) may also influence growth and timing of cladocerans. Our results support the view that a high biomass of grazing zooplankton is essential for the occurrence of a clear-water phase, but not sufficient to explain variability between lakes. High cladoceran maxima in hypertrophic lakes indicate that food quality seems not to limit grazer biomass. Decoupling of zooplankton and phytoplankton may be the result of early and fast growth of grazing resistant algae. We conclude that shallowness and trophy may indirectly reduce the extent and predictibility of a clear-water phase by enhanced growth of cyanobacteria and increasing predation pressure at least for lakes on this TP level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017088008761
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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