Hidrológiai Közlöny 1997 (77. évfolyam)

16 3. ábra A C. raciborskii százalékos részesedésének időbeli változása 15 napos, a Balaton üledékével végzett csiráztatási kísérletben a fényintenzitás függvényében foszformentes BG-11 tápoldatban Light dependent spccics suceession of hetcrocyslous cyanobactcria Attila Kovács, Eszter Koncz & Lajos Vörös Balaton Limnological Research Jnstitute ofthe Hungárián Academy of Sciences, Tihany Abstract The filamcntous heterocystous cyanobactcria, wich ploriferate in summer, play significant role in the eutrophicalion of Laké Balaton. The most abundant species was the Cylindrospermopsis raciborskii but other species such as Aphanizomenon flos-aquae, A. issatschenkoi, Anabaena aphanizomenoides ete. produce alsó great biomass. These cyanobactcria in Lakc Balaton gcncrally exist in vegetatíve forms only one-three months and in the other part ofthe year they are in resting stagc, and their akinctcs accumulatc in the surface laycr ofthe sediment. Sediment suspensions from the hypcrtrophic Keszthcly-basin of the laké were incubated at difTerent light intensity (220, 150, 120, 85, 60, 30 mEinstein m"

2 sec"

1 ) in phosphorus rich and phosphorus deficient BG-11 médium. The process of germination and the subsequent growth of cyanobacteria were followed by epifluorescence microscopy. In this experiment the germination of 10 filamentous heterocystous cyanobacteria species was observed. (Fig. 1). During the experiment species composition of the cyanobactcria populations showcd significant light and phosphorus dcpendence. In the observed algal communities the contribution of C. raciborskii lo the totál algal population showed an inverse relation lo the light intensity, particularly in phosphorus deficient enviroment ( Fig. 2., 3.). By the rcsults the experiment it bccame evident, that among the filamcntous heterocystous cyanobacteria of Lakc Balaton C. raciborskii was the best compelitor for the poor phosphorus source at low light intensity.