L. Forró szerk.: Miscellanea Zoologica Hungarica 10. 1995 (Budapest, 1995)

Gulyás, P.: Rotatoria and Crustacea plankton of the River Danube between Bratislava and Budapest

Summary Survey of the River Danube between Bratislava and Budapest in the period of 1992-1994 included 8 sampling sites where bi-weekly sampling of the Rotatoria and Crustacea plankton communities was carried out. Occurrence of 148 species was recorded, rotatorians dominated, among which Brachionus angularis, B. calyciflorus, Filinia longiseta, Keratella cochlearis, K. cochlearis tecta, K. quadrata and Polyarthra vulgaris were found at almost every sampling site. Among the Crustacea most frequent were Acanthocyclops robustus f. limnetica and Bosmina longirostris, and copepod larvae. We have recorded many rare species, which are interesting from faunistical point of view as well. Frequently occurring Rotatoria and Crustacea species are characteristic to the planktonic communities of eutrophic stagnant and slow-flowing rivers. Species compositions of the investigated communities were the poorest at Bratislava showing a constant enrichment towards the downstream sampling sites. No significant changes were found in species composition of the community within the investigated time period. In samples taken from the middle of the river occurrence of non planktonic species was frequently observed. These organisms are rather characteristic to the littoral zone or the upper layer of the sediment. The abundance of the Rotatoria and Crustacea plankton was the highest in 1992, decreased by 1993, and has shown a further gradual decrease in 1994. The number of individuals increased longitudinally downstream, but both the rare and the dominant species were almost identical at every sampling site. Largest populations were found at Szob, Nagymaros and Budapest. Two population peaks were observed every year, from which the spring-early summer is larger followed by a smaller late summer-early fall population maximum. Increase of the abundance of the Zooplankton community downwards of the river raise the concern of the ongoing eutrophication processes. References Bancsi, I. (1986): A kerekesférgek (Rotatoria) kisliatározója I. (A guide for the identification of rotifers (Rotatoria) in Hungary I.) - In: Felföldy, L. (ed.): Vízügyi Hidrobiológia 15: 1-171. Bancsi, I. (1988): A kerekesférgek (Rotatoria) kisliatározója II. (A guide for the identification of rotifers (Rotatoria) in Hungary II.) - In: Felföldy, L. (ed.): Vízügyi Hidrobiológia 17: 173-578. Bothár, A. (1968): Untersuchungen des Donauplanktons an Entomostraca während der grossen Überschwemmung im Jahre 1965 (Danubialia Hungarica LXVIII). - Annls Univ. Sei. Budapest, Sect. Biol. 9-10: 87-98. Bothár, A. (1975): Beiträge zu den Kenntnissen der Gestaltung der Crustacea-Gemeinschaften des Planktons der Donau. - 18. Arbeitstagung der IAD, Regensburg: 181-190. Bothár, A. (1978-79): Crustacea-Planktonuntersuchungen im Donauabschnitt zwischen Szob und Nagymaros (Danubialia Hungarica LXXXVIII). - Annls Univ. Sei. Budapest, Sect. Biol. 20-21: 249-259. Bothár, A. (1985): Die qualitative und quantitative Verbreitung der planktischen Crustaceen in ungarischen Donauabschnitt von 1965-1985. - 25. Arbeitstagung der IAD, Bratislava: 283-287. Bothár, A. (1988): Results of long-term Zooplankton investigation in the River Danube, Hungary. Verb. Int. Ver. Limnol. 23: 1340-1343. Bothár, A. & Ponyi, J. E. (1968): Informatory investigations about qualitative and quantitative conditions of the Crustacean plankton of the Danube section near Alsógöd (Hungary) (Danubialia Hungarica XLVII). - Annal. Biol. Tiliany 35: 117-126.