L. Forró szerk.: Miscellanea Zoologica Hungarica 13. 2000 (Budapest, 2000)
Gulyás, P.: Rotatoria and Crustacea plankton communities of the feed-water streams of the Lake Balaton
11. Zala River Its water quality is quite different from than of the previously assessed creeks. The specific electric conductivity 90% percentile value is 648 pS/cm, corresponding to alpha-oligohalobic stage. On the basis of the inorganic ionic composition the water is within the beta-limno-type with characteristic Mg - Ca - HC0 3 , or Ca - Mg - HC0 3 composition. The dissolved oxygen content and COD values are both indicating tolerable water quality. Nitrogen forms were represented in small volume, indicating good water quality. Opposite to this, considerable amount of orthophosphate phosphor and total phosphor was measured. The outlet water of the reservoir usually had low chlorophyll-a concentration in the range of 9.6-17.0 pg/1. Zooplankton studies revealed the occurrence of 21 Rotatoria, 9 Cladocera and 4 Copepoda species. The abundance values were 158-1732 ind./100 liters. Value above one thousand occurred only at one occasion. The number of the dominant species was low (Brachionus angularis, B. quadridentatus quadridentatus, B. q. brevispinus, Ceriodaphnia quadrangula, Chydorus sphaericus, Simocephalus vetulus, Acanthocyclops robustus f. limnetica and Eucyclops serrulatus). Rare species were hardly found (Lophocharis oxystemon, Trichocerca capucina, Acroperus harpae, Graptoleberis testudinaria). The low oxygen content and filter feeding Zooplankton community reduces the number of the algae (as indicated by the chlorophyll-a). This had an adverse effect to the establishment of large Zooplankton stands. 12. Nyugati channel Similar to the Zala River the specific electric conductivity value of the channel was low and varied between 545-695 pS/cm. This indicates beta-alpha-oligohalobic stage -alphaoligohalobic stage. On the basis of the inorganic ionic composition the water is within the beta-limno-type with Ca - HC0 3 and Ca - Mg - HC0 3 composition. The dissolved oxygen concentration, saturation value and COD contents are indicating moderate pollution level. Among the plant nutrients only the nitrate is low, while the ammonium and nitrite, as well as the phosphorus forms indicate polluted water quality. The amount of the chlorophyll-a varied from 7.4 to 63.0 pg/1. The species composition of the Rotatoria and Crustacea communities was rich with high individual abundances. Altogether 66 species were identified from which the dominance of Rotatoria was evident (44 species). Cladocera was represented by 15, while the Copepoda by 7 species. The dominant species are characteristic to the eutrophic Hungarian waters: Brachionus angularis, B. calyciflorus calyciflorus, B. c. amphiceros, B. c. anuraeiformis, Euchlanis dilatata, Filinia longiseta, F. terminális, Bosmina longirostris, Chydorus sphaericus, Acanthocyclops robustus f. limnetica, A. vernalis. These frequently formed large stands. The abundance values of the three groups varied in the range of 1311-5825 ind./lOO liter during the study. These high values are characteristic to hypertrophic fishponds. Apart from the dominant species some rare taxa were also determined: Beauchampiella eudactylota, Brachionus diversicornis homoceros, B. falcatus, B. quadridentatus cluniorbicularis, Euchlanis proximo, Hexarthra mira, Ptygura melicerta, Graptoleberis testudinaria, Pleuroxus trigonellus, Eucyclops speratus. These species are predominantely dwelling in dense aquatic vegetation in smaller water bodies. Excessive individual numbers of the zooplankton community were indicating the polytrophic stage of the Nyugati channel. 13. Zichy channel The specific conductivity value of the channel was 650-1190 pS/cm corresponding to alpha-oligohalobic-oligo-mesohalobic stage. On the basis of the inorganic ionic composition
