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  • 1
    Electronic Resource
    Electronic Resource
    The eutrophic Loosdrecht Lakes: Current ecological research and restoration perspectives (1986)
    Springer
    Aquatic ecology 20 (1986), S. 61-75 
    Details
    ISSN: 1573-5125
    Keywords: eutrophication ; lake restoration ; blue-green algae ; zooplankton ; seston ; epipelon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Features of the Loodsrecht Lakes, with emphasis on the main lake, are discussed with reference to restoration. Characteristics of the present situation are: (1) very low water transparency-Secchi-disc readings around 0.3 m occur in all seasons; (2) relatively small seasonal changes in sestonic matter; (3) important input of resuspended particles into the seston; (4) predominance of filamentous blue-green algae for most of the year; (5) relative scarcity of crustacean zooplankton, while rotifers are abundant; (6) poor development of littoral communities, and absence of benthic producers. The blue-green algae maintain high population density at very low growth rates: rates of loss are low. The zooplankton grazing rate is low due to inefficient filtering, but predation of larger crustaceans by fish may also be important. Studies on epipelon indicated that loss by deposition may be largely compensated by resuspension. Starting in 1984, the external phosphorus loading was markedly reduced. Results for 1984 and 1985 indicate that complementary measures are needed in order to improve water quality. Action should be directed towards increasing the phytoplankton turnover rates. Accelerated specific growth rate can be expected to accompany lower biomass, more successful competition by other algal groups, and enhancement of grazing pressure. Considering the shallowness of the system, promotion of littoral development and return of submerged vegetation may be important in establishing a new equilibrium of the system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02291151
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Light-limited algal growth in Lake Loosdrecht: steady state studies in laboratory scale enclosures (1990)
    Springer
    Hydrobiologia 191 (1990), S. 241-248 
    Details
    ISSN: 1573-5117
    Keywords: Loosdrecht lakes ; eutrophication ; Prochlorothrix hollandica ; growth kinetics of algae ; continuous cultures ; light attenuation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytoplankton growth in the shallow, turbid Lake Loosdrecht (The Netherlands) is importantly influenced by light availability, and thus the concentrations of the various light-attenuating materials. The system is highly eutrophic and supports an algal biomass of ca. 160 mg Chl m−3. A model is proposed here which predicts algal growth in the lake as a function of the light received and subsequent attenuation in the water column by phytoplankton, tripton and background colour. The model is based on an energy balance which relates growth rate to the ‘true’ growth yield on light energy and the energy demand for cell maintenance. The coefficients for energy conversion (Y = 0.002 gDW kJ−1) and cell maintenance (µe = 0.031 day−1) were determined from steady state growth kinetics of Prochlorothrix hollandica in light-limited laboratory flow systems with the same depth as the lake and receiving summer average conditions of irradiance. Light attenuation by phytoplankton and tripton were quantified using specific attenuation coefficients: 0.011 m2 mg−1 Chl for the phytoplankton and 0.23 m2 g−1 DW for tripton. The growth studies demonstrated that Lake Loosdrecht can support a much higher algal biomass in the absence of non-algal particulate matter. The proposed model is used to predict chlorophyll a concentrations in dependence on growth rate and levels of tripton. Since approximately 75% of the sestonic dry weight in Lake Loosdrecht may be attributed to tripton, it is concluded that the algal biomass is markedly lowered by the abundance of tripton in the water column. A knowledge of the sources and fate of tripton in the lake is thus of fundamental importance in modelling phytoplankton dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026057
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Algal growth and loss rates in Lake Loosdrecht: first evaluation of the roles of light and wind on a basis of steady state kinetics (1990)
    Springer
    Hydrobiologia 191 (1990), S. 129-138 
    Details
    ISSN: 1573-5117
    Keywords: Loosdrecht lakes ; eutrophication ; underwater light ; resuspension ; wind effect ; Prochlorothrix hollandica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Loosdrecht (The Netherlands) is shallow, highly eutrophic and subject to frequent wind-induced resuspension of settled algae and detritus. The summer phytoplankton consists of filamentous prokaryotic species. Chlorophyll a levels are rather stable over the summer at a concentration of ca. 160 mg m−3; losses due to grazing and sinking are small. Epipelic chlorophyll a concentrations range from 0 to 250, but ca. 50 mg m−2 is typical. In situ rates of change of chlorophyll a in the water column were related to specific growth rates predicted by a model for light-limited growth. In the model, incident light is partitioned among algae, tripton and background colour, to determine the light available for algal growth and cell maintenance. Model coefficients were derived primarily from laboratory studies of the growth of Prochlorothrix hollandica, an abundant species in the lake in summer. Presuming constant rates of loss due to grazing and sinking, for summers 1985 and 1986 some 56% of the variation in the chlorophyll a in the lake water was explained by change in light conditions alone and 77% by light and wind-driven resuspension of epipelic chlorophyll a together. These factors had little influence on the phytoplankton biomass in 1983 and 1984; other environmental conditions, e.g. phosphorus availability, may have been important. Also, the laboratory-derived growth kinetics of P. hollandica may not have been equally suitable for modelling in the four summers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026047
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    Paper (German National Licenses)
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