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
6. Egervíz The minimal value of specific electric conductivity indicates alpha-oligohalobic and oligomesohalobic stage. On the basis of the inorganic ionic composition the water is within the betalimno-type, usually Ca - Mg - HC0 3 , or Ca - Mg - HC0 3 - S0 4 character. Ionic composition, concentrations and measured values only slightly differedfrom the values of Burnót creek. Difference was only observed in lower oxygen saturation and lower chlorophyll-a contents (90% percentile was 6.2 pg/1). The reason for this is the already mentioned benlhic eutrophication. During the investigation of the Zooplankton 15 Rotatoria, 3 Cladocera and 2 Copepoda species was registered, abundance values were always low. The dominant species was Euchlanis dilatata as species composition varied to a large extent in each sampling series. Rare species were also identified here living in the biotecton: Brachionus quadridentatus quadridentatus, Paradicranophorus hudsoni, Ptygura melicerta, Eucyclops speratus, Paracyclops affinis, Eurycercus lamellatus, Alonella nana. 7. Tapolca creek Measured values of the specific electric conductivity (980-990 pS/cm) indicate alpha-oligohalobic stage. On the basis of the inorganic ionic composition the water is within the betalimno-type with characteristic Ca - HC0 3 , Ca - Mg - HC0 3 and Ca - HC0 3 - S0 4 composition. Ionic composition is similar to the water of the Egervíz. Dissolved oxygen contents and COD parameters both indicate slightly polluted water. On the basis of nutrients, the water quality is similar. Due to the benthic eutrophication the measured chlorophyll-ű concentrations were low. No planktonic algae or Rotatoria species were observed in any of the samples in June 1997. On other occasions we have found slightly richer fauna, but this was not characteristic to the Hungarian waters. The abundances varied in the range of 40-576 ind./100 liter, which is characteristic to low production waters. Of the identified 13 species 12 Rotatoria and only one Cladocera species were present. Copepoda were not found in plankton. Some newer species were found in the biotecton community such as Mytilina mucronata, Lecane (M) lunaris and Lepadella ovalis. 8. Kétöles creek Specific electric conductivity varied between 850-1380 pS/cm. According to this the water falls the alpha-oligohalobic- oligo-mesohalobic stage. On the basis of the inorganic ionic composition the water is within the beta-limno-type with characteristic Ca - HC0 3 , and Ca - Mg HC0 3 - S0 4 content. The water quality of the creek is lower than the previous ones on the basis of the chemical parameters. Pollution is particularly evident in COD contents, while values of dissolved oxygen contents and saturation revealed good water quality. It is possible that the creek experience temporary pollution waves that are indicated by the large fluctuations of the ionic composition of the creek. Quantity of nitrogen- and phosphorus forms is high, on the basis of which the quality is tolerable. It is probable that all these indicate organic pollution, as the highest fluctuations were observed in the ammonium and nitrate concentrations. The chlorophyll-a content of the water was relatively higher than in the previous creeks. Maximums were measured during the summer period that were paralleled by the ortophosphate minimums. Amongst the so far discussed creeks the plankton communities were found to be the richest in this stream. Occurrence of 17 Rotatoria, 6 Cladocera and 5 Copepoda species were recorded. Individual abundance value for 100 liters ranged within wide numbers (92-3016 ind.). Higher
