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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Freshwater biology 41 (1999), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Long-term records of air temperature and ice phenology (ice duration), and phyto- and zooplankton time series (1979–1997) were used to study the effects of ice duration on the successional pattern within plankton communities during spring in a shallow polymictic lake.2. Water temperature in March was significantly lower after cold winters when compared to average or mild winters. Mean water temperature in April was not significantly different after mild, average or cold winters, but showed an overall significant negative correlation with ice duration.3. Ice duration affected the timing and the magnitude of the peak abundance of diatoms, rotifers and daphnids during spring, but had no direct effects on the timing and maximum of chlorophytes, cryptophytes, cyanobacteria, bosminids and cyclopoid copepods.4. Plankton groups which appeared first in the seasonal succession (i.e. diatoms, rotifers and daphnids) reached maximum abundance earlier after mild and average winters. The peak abundance of diatoms was negatively correlated with ice duration, whereas that of rotifers and daphnids was independent of the conditions during the preceding winter.5. Temperature alone was generally a poor predictor of the timing and magnitude of both phyto- and zooplankton maxima. Turbulence may be important in the timing and the magnitude of peaks in diatoms, while total algal biomass was the most important determinant for the timing of the rotifer maximum. The magnitude of the daphnid maxima were significantly influenced by water temperature in March and April, and by rotifer abundance. The magnitude of the bosminid maximum was correlated with food availability and predation, whereas the timing of the maximum was more closely related to water temperature in May.6. We conclude that, as a result of the low heat storage capacity of shallow lakes, the effects of winter on planktonic communities are short lived, and soon overtaken by the prevailing weather and by biotic interactions.
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  • 2
    ISSN: 1573-5117
    Keywords: rotifers ; growth rates ; life history ; reproduction ; cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The population dynamics of B. calyciflorus was investigated using a green alga, Monoraphidium minutum, and a blue-green alga Planktothrix agardhii as food sources, separately and as mixtures. Growth rate (r), egg ratio (ER), and juvenile development time (D j ) were measured in the laboratory and mortality rate and embryonic development time (D E ) were calculated. With M. minutum, Brachionus showed a typical growth curve (‘Monod-kinetics’) dependent on food concentration. In contrast B. calyciflorus did not grow well on P. agardhii. With all food concentrations the measured growth rates were about r=0. At low food concentrations r was low with both food types, but the ER of B. calyciflorus was significantly higher with P. agardhii as food source. Furthermore the relative egg volume of females carrying one egg was higher with Planktothrix than with Monoraphidium. An addition of P. agardhii to M. minutum led to increasing growth rates. Highest growth rates were found with complementary food sources. High food concentrations of M. minutum shortened the juvenile development (D J ) time, but D j was uneffected by different P. agardhii food concentrations. A mixture of both algae did not shorten D j compared with M. minutum as single food. The calculated D E was not effected by different food qualities but the calculated mortality was nearly 3 times higher with P. agardhii as food.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 358 (1997), S. 127-132 
    ISSN: 1573-5117
    Keywords: chemostat ; turbidostat ; growth rates ; processstability ; Brachionus calyciflorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A two stage turbidostat was developed according toBoraas & Bennet (1988), but with highly improvedturbidity sensors. The first stage was an algalturbidostat where algal density was regulated byturbidity measurements. Algal density was also heldconstant in the second stage (rotifer production)according to turbidity measurements. Additionally,the growth rates were monitored. The regulation system allowed an effective on-line process control.Initially, the production of rotifers in long-timestudies was variable. However, after furtherimprovements of the turbidity measurement, fluctuations in the rotifer turbidostat decreasedsignificantly.
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  • 4
    ISSN: 1573-5117
    Keywords: cladocerans ; Rotifera ; seasonal succession ; diversity ; wind velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From the end of May to November 1995 the succession of rotifers and cladocerans was investigated in Müggelsee with samples taken twice a week. Keratella cochlearis was the only rotifer which was found on every sampling day and this species also showed the highest abundances. During summer, when frequencies of strong wind events were low and water was strongly stratified, three small cladocerans were dominant (Daphnia cucullata, Chydorus sphaericus, Eubosmina coregoni). Food supply was the main limiting factor for Keratella spp. and Synchaeta spp. In autumn, however, when the intervals between strong winds were shorter, rotifers with shorter periods for population development prospered. Zooplankton diversity first increased and subsequently decreased after disturbances. The results do not support the intermediate disturbance hypothesis in its present formulation.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 408-409 (1999), S. 233-239 
    ISSN: 1573-5117
    Keywords: plankton dynamics ; lowland river ; River Continuum Concept ; Serial Discontinuity Concept
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied the plankton dynamics in the shallow, rapidly flushed lake Neuendorfer See and an adjacent reach of the river Spree. During summer/fall, zooplankton and phytoplankton densities increased exponentially in the lake and decreased exponentially in the river without major changes in species composition. Both parts of the system can be described as tubular plug flow reactors that differ markedly in the growth rates of plankton. Whereas reproduction in rotifers was constant in the whole system, the mortality was about 10 times higher in the river compared to the lake caused by the filtration activity of abundant mussels. Physiological conditions can be regarded as continuous in the river-lake system. According to trophic conditions, the river-lake system is divided in two contrasting subsystems with the lake classified as `autotrophic' and the river as `heterotrophic' and the site of discontinuity was located sharply at the lake-river transition. At very low discharges, the differences between the subsystems were reduced and intra-pelagic mechanisms became more important. A model of plankton dynamics in the river-lake system is presented.
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  • 6
    ISSN: 1573-5117
    Keywords: cladocerans ; Rotifera ; seasonal succession ; diversity ; wind velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From the end of May to November 1995 the succession of rotifers and cladocerans was investigated in Müggelsee with samples taken twice a week. Keratella cochlearis was the only rotifer which was found on every sampling day and this species also showed the highest abundances. During summer, when frequencies of strong wind events were low and water was strongly stratified, three small cladocerans were dominant (Daphnia cucullata, Chydorus sphaericus, Eubosmina coregoni). Food supply was the main limiting factor for Keratella spp. and Synchaeta spp. In autumn, however, when the intervals between strong winds were shorter, rotifers with shorter periods for population development prospered. Zooplankton diversity first increased and subsequently decreased after disturbances. The results do not support the intermediate disturbance hypothesis in its present formulation.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 107 (1983), S. 35-45 
    ISSN: 1573-5117
    Keywords: zooplankton ; rotifers ; laboratory culture ; life table ; population dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new culture method for K. cochlearis has made it possible to study isolated animals and to investigate the population dynamics of this pelagic rotifer species. The duration of principal developmental stages diminishes continuously with temperature. Decreased survival was associated with a reduced duration of individual fecundity. The age distribution of the population shifted toward younger age intervals with higher temperatures. Growth rates had an optimum at 15°C; the population dynamics, while lower for K. cochlearis than for some other rotifers, were in good agreement with field data.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 147 (1987), S. 209-213 
    ISSN: 1573-5117
    Keywords: Rotifera ; life table analysis ; r- and K- strategy ; Brachionus angularis ; Keratella cochlearis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The results indicate that the two rotifer species Brachionus angularis and Keratella cochlearis have different life history strategies. Brachionus angularis appeared to be an r-strategist, showing higher reproductive, mortality and population growth rates than K. cochlearis. Additional evidence is offered suggesting that K. cochlearis is a K-strategist. Although K. cochlearis had a lower growth rate than B. angularis, this was compensated by a lower mortality rate, especially in pre-reproductive individuals. In addition, K. cochlearis allocated energy to reproduction more efficiently than B. angularis.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 186-187 (1989), S. 363-369 
    ISSN: 1573-5117
    Keywords: rotifers ; temperature ; food concentration ; bioenergetic parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of temperature and food quality was studied on the following energy balance parameters of B. angularis: ingestion, production, growth and mortality. The ingestion rate rises to an optimum at 15 and 20 °C and decreases at 25 °C. The other rates increase continuously over the 5–25 °C range. The Q10-values of production rate are higher than those of ingestion rate. Temperature also modifies the relationship between food concentration and bioenergetic rates. They react according to a Monod function (production at all temperatures, growth at 10 °C) or decrease at high concentrations (growth at 15° and 20 °C.)
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 255-256 (1993), S. 165-170 
    ISSN: 1573-5117
    Keywords: Brachionus angularis ; chemostats ; steady-state ; transient-state ; regulation-model ; computer-simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Derived from the Monod-model and regulating principles a regulation model of the rotifer development in chemostats was developed. The model was validated in continuous cultures of Brachionus angularis both in steady-states, when undisturbed, and in transient-states after perturbations by step changes of dilution rate or input substrate concentration. Simulations of the simple model monotonically approached steady-states, but cultures show overshoots and damped oscillations before reaching this state. After introducing time-lags into the model it depends on the size of the time lag if model rotifer densities reach stable steady-state values (at low time lags) or stable limit cycles with periodic oscillations (at high time lags). At even higher time lags chaotic conditions occur in the model with final extinction of the rotifers.
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