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  • acidification  (1)
  • clear-water phase  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Lake Plessa 107 (Lusatia, Germany) – an extremely acidic shallow mining lake (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 293-299 
    Details
    ISSN: 1573-5117
    Keywords: mining lake ; acidification ; plankton ; phytobenthos ; macroinvertebrates ; food-web
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Plessa 107 is an example of the older, relatively small and often shallow mining lakes of Lusatia which only have groundwater inflow. From a morphological point of view, the lake should be polymictic with short stratified periods. But besides temperature, mixing is also determined by chemical gradients in the water column that can lead up to monomixis. The lake water shows an extreme acidification with high concentrations of calcium, iron, aluminium, manganese and sulphate. Despite low TIC and TP concentrations allowing only a low primary production in the pelagial within the oligotrophic range, anoxic conditions can occur during stratification because of Fe(II) oxidation and anoxic groundwater inflow. The phytoplankton is dominated by phytoflagellates. Chlorophyll concentrations follow a yearly pattern determined by temperature and light availability. The zooplankton consists of two rotifer species, ciliates and heliozoans. Sediment analyses show contrary depth gradients of Fe and P with a very high fraction of Fe in the upper sediment layers (up to 60% of DW) which decreases with depth. Probably due to groundwater inflow, at some sites substantial decreases in redox potential and conductivity can be observed with increasing sediment depth accompanied by increases of pH, DOC, DIC and DIP concentrations. No correlations have been found between the available phosphorus or carbon concentrations in the sediment porewater and the phytobenthic biomass. Euglena mutabilis(Euglenophyceae) and Pinnularia acoricola(Bacillariophyceae) are the dominant phytobenthic species. Lake Plessa 107 has a benthic food-web that consists of benthic algae, chironomids and corixids and a pelagic food-web which is composed of phytoflagellates, rotifers, ciliates and heliozoans. The two food-webs are not coupled because larger prey organisms such as crustaceans are missing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017038616513
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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
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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