Ref ID : 954
Udo Halbach; Population dynamics of rotifers and its consequences for ecotoxicology. Hydrobiologia 109:79-96, 1984
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Population dynamics of the rotifers Brachionus rubens and B. calyciflorus were studied in the field and analyzed by multivariate statistical techniques. There were some correlations, but they are difficult to interpret. Laboratory cultures under various controlled constant conditions showed sigmoid growth curves with subsequent oscillations around an equilibrium. Its level is determined by food quantity; frequencies and amplitudes of the oscillations increase with temperature. The growth curves are described by deterministic models (logistic growth function with one or two time lags) and by stochastic models (SIMULA). Both give simulations which are close to the experimental curves, even in the case of changing temperatures with variable time lags. A third descriptive model is proposed which permits predictions without causal anaylsis, on the basis of statistical properties. It is used for the development of a highly sensitive bioassay in ecotoxicology. Changes in population density reflect minute sublethal effects of toxic substances such as statistical reductions in lifespan and fertility of the individuals. Experiments suggest chronic sublethal effects which may develop over many generations: adaptation to pentachlorophenol and accumulation of detrimental effects of 4-chloroanilin. Phenol is more toxic at low than at high concentrations. Application of these finding to field conditions is discussed.