Regulation of cyanobacteria and microcystin dynamics in polymictic shallow lakes
Wiedner, Claudia; Nixdorf, Brigitte; Heinze, Rita; Wirsing, Birgit; Neumann, Uwe; Weckesser, Jürgen
published: Apr 10, 2002
ArtNo. ESP141015503002, Price: 29.00 €
A comparative study on seasonal dynamics of cyanobacteria and microcystins in relation to physical and chemical parameters was carried out in three polymictic shallow lakes. Lakes were predominated by Oscillatoriales: Planktothrix agardhii in one lake and Limnothrix spp. in the other two lakes. Considerable populations of Nostocales occurred in two of the lakes prior to mass developments of Oscillatoriales. The lake predominated by P. agardhii differed from the lakes predominated by Limnothrix spp. by higher total phosphorus concentrations and a larger surface area. Phosphorus is discussed as the crucial factor in the competition between Oscillatoriales, with P. agardhii as the stronger competitor under higher phosphorus concentrations. Both Oscillatoriales outcompeted Nostocales populations under a declining intensity of PAR (photosynthetically active radiation). The decline of PAR intensity was promoted by the cyanobacteria itself and had a positive feed back on the development of Oscillatoriales but a negative effect on the development of Nostocales populations. Furthermore, the presence and concentration of microcystin was related to the presence and biovolume of P. agardhii, respectively. No microcystins were found when only Limnothrix spp. were present.