L. Forró szerk.: Miscellanea Zoologica Hungarica 10. 1995 (Budapest, 1995)
Gulyás, P., Bancsi, I.; Zsuga, V.: Rotatoria and Crustacea fauna of the Hungarian watercourses
planktonic, and littoral species were also found (e.g. Alona rectangula, Chydorus sphaericus, Disparalona rostrata, Macrocy clops fuscus). Due to the effect of the wastewaters of Zalaegerszeg the species composition of the Zooplankton community is becoming poorer. Especially the species number of the Rotatoria is reduced, the number of the microcrustaceans practically did not change. Up to the Kis-Balaton Reservoir (Zalaapáti) neither the abundance values, nor the biomass showed significant increase. Biomass varied between 0.13 - 0.38 g/m 3 that is considered to be very low value on this particular river section. Since the operation of the IJ. Phase of the Kis-Balaton Reservoir water characteristic to bogs flows at the confluence (Fenékpuszta), and therefore one cannot speak of planktonic communities of flowing water in this section. Species composition and abundance of the community is determined by the outflow water of the reservoirs. A rich community was found, as indicated by the occurrence of 35 Rotatoria, 10 Cladocera and 5 Copepoda taxa. The bog water provides poor food for filter feeding Rotatoria and microcrustacean species, therefore large populations were not formed, biomass was only between 0.44 - 1.71 g/m 3 . 43. Mosoni-Danube Altogether 87 taxa were found in the samples of the Mosoni-Danube, rotifers occurred in greatest species number (50) and abundance, while Cladocera and Copepoda were represented by 26 species. In spite of the species richness there were only a small number of rare species present in the samples. Species composition of the community showed a gradual increase and dominance of taxa characteristic to nutrient rich waters become evident downwards. Effect of the wastewaters of Mosonmagyaróvár and Győr can be traced by the increase of abundance and biomass. At these sampling locations species characteristic to eutrophic and polytrophic waters dominated in all cases, especially the rotatorian Brachionus, Keratella spp, and the cladoceran Bosmina longirostris, Moina micrura and larvae of Copepoda. Based on Zooplankton communities the Mosoni-Danube can therefore be divided into two sections. Upstream of Győr rich species composition was found, while downstream of the city increasing abundance indicated eutrophic conditions and significant deterioration of water quality. Summary Identification of the Rotatoria fauna and other planktonic Zooplankton species of the River Tisza and its tributaries, and of the Transdanubian watercourses revealed that the Zooplankton community of the watershed is largely build-up by cosmopolitan, well-adaptable species of high ecological tolerance. In the Tisza River and in its major tributaries mostly planktonic species were the dominant ones, while in smaller creeks and streams metaphyton and benthic elements are also frequently added to this species spectrum. Species richness of the Cladocera fauna only occurs in slower streams. The Copepoda fauna was characterized by the occurrence of juvenile forms, the number of adult individuals was low. During the three years 19 Rotatoria taxa new to the Hungarian fauna and several rare species (59 Rotatoria and 7 Cladocera) were recorded. On the basis of the quantitative and qualitative Zooplankton investigation the watercourses are grouped into the following categories:
