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
the water is within the beta-limno-type with ionic composition predominantly of Mg - Ca HCO3 - S0 4 , Mg - Ca - S0 4 - HCO3 and Ca - Mg - HC0 3 - S0 4 . The concentration of dissolved oxygen indicated good water quality, into the saturation and COD content revealed highly polluted water quality in the channel. Values varied highly most probably as the function of the discharge of the channel. Concentration of plant nutrients, in spite of the presence of large macrophyta stands remained high and indicates moderate pollution level. Due to the benthic eutrophication processes the chlorophyll-a content usually remained small to medium (2.2-32.0 pg/1). Species composition of the Rotatoria and Crustacea communities was also rich in this creek (altogether 46 species), with two population peaks that had lower value than in the Nyugati channel. Individual numbers were 238-2458 for 100 liters. Similar to the previously described waterways the dominant species and rare species are listed here. Interestingly the Zooplankton of this creek was not dominated usually by the Brachionus genus, only B. angularis formed larger stands. Further dominant species were: Asplanchna priodonta (predatory), Euchalnis dilatata, Keratella quadrata, Mytilina mucronata, Polyarthra vulgaris, Alona rectangula, Chydorus sphaericus, Pleuroxus aduncus, Acanthocyclops robustus f. limnetica, Eucyclops serrulatus. It is worth mentioning that some of the listed species are not planktonic but dwell in the shoreline zone and on the biofilm communities on the higher aquatic plants. The same is true for the rare species of the creek: Brachionus falcatus, B. quadridentatus melheni, Collotheca volutata, Encentrum sp. Lecane stenroosi, Acroperus harpae, Alona costata, Chydorus latus, Kurzia latissima, Pleuroxus striatus, Diacyclops bicuspidatus. On the basis of the Zooplankton results the Zichy creek is a polluted, eutrophic stream with slow-to-stagnant water. Bentonic eutrophication is registered. 14. Keleti Bozót creek The measured specific electric conductivity value of this creek is significantly lower than the previous ones falling to the range of 580-680 pS/cm, indicating alpha-oligohalobic stage. On the basis of the inorganic ionic composition the water is within the beta-limno-type with characteristic ionic composition of Ca - Mg - HC0 3 , Mg - Ca - HC0 3 . The dissolved oxygen concentration varied widely. COD values indicated tolerable water quality and pollution. Plant nutrient content is small compared to the previous ones only the total phosphorus concentration was higher, indicating tolerable quality. Chlorophyll-a content is high in spite of the presence of large macrophyte vegetation stands (15.5-85.0 pg/1). The pollution is more moderate than in the previous creek, but the enriched nutrient content (indicated by the high chlorophyll-a concentration) resulted in excessive stands of Rotatoria and Crustacea communities. Individual abundances were high accordingly, 2143-6877 ind./100 liter. As it was mentioned earlier these values are characteristic to fishponds. Species composition is considered to be rich, 30 Rotatoria, 11 Cladocera and 8 Copepoda species were found in the plankton, among these there are euplanktonic as well as tichoplanktonic species. Dominant species were in most of the cases similar to the ones found in the Nyugati channel: Brachionus angularis, B. calyciflorus (and forms), B. quadridentatus (and forms), Euchlanis dilatata, Keratella cochlearis cochlearis, Lecane bulla, Bosmina longirostris, Ceriodaphnia quadrangula, Chydorus sphaericus, Acanthocyclops robustus f. limnetica, Eucyclops serrulatus. Of the rare species Brachionus rubens and Megafenestra aurita were not found in the previously mentioned streams, but Brachionus diversicornis homoceros, Lecane stenroosi, Paradicranophorus sp., and Ptygura melicerta were registered at one-one sampling site. Large Zooplankton
