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
17. ABC channel Similar to the Ordacsehi-trench this is a heavily polluted creek, as indicated by 90% value of the specific electric conductivity (1265 pS/cm). This corresponds to the alpha-oligohalobicoligo-mesohalobic stage. On the basis of the inorganic ionic composition the water is within the beta-limno-type with Mg - HC0 3 , Mg - Ca - HC0 3 and Mg - Ca - HC0 3 - S0 4 ionic composition. The values of the oxygen budget are quite contradictory at this creek. Dissolved oxygen values indicate clean water. The detailed analysis of the saturation value fluctuations, however, does prevail values around 50% indicating moderately good quality and on three occasions significant super-saturation. All of these indicate polluted water quality. This is supplemented by the measured values of the COD content. Nitrogen forms indicate that this is a so-called "fresh pollution" as the ammonium content of the creek is significant. Nitrite and nitrate concentrations indicate good water quality. Phosphorus content was found to be high. Chlorophyll-a did show large fluctuations, varied between 3.7-84.0 pg/1. Opposite to previous creeks planktonic eutrophication was observed here. Due to the more polluted character of the water in the channel the Zooplankton community was poorer than the previous streams, only 24 Rotatoria, 8 Cladocera and 5 Copepoda species were found. Individual abundance values were between 686-7586 ind./100 liter. The large populations of Brachyonus calyciflorus calyiciflorus and Polyarthra vulgaris in June 1997 caused the latter high value, in this sample only 13 taxa were found. During the investigations smaller individual numbers were measured. Analysis of the species composition revealed that the genera of Brachionus- and Keratella are the richest. It seems that these species better tolerate organic pollution and the increased saprobic state. Therefore these are good indicators of these processes. Of the rare species the occurrence of Alona costata (Cladocera) is worth mentioning. The Rotatoria and Crustacea community of the channel is poor. Single species are representing large individual numbers. These two factors together indicate heavily polluted stream. 18. Tetves creek The specific electric conductivity varied between 730 and 950 pS/cm indicating alpha-oligohalobic conditions. On the basis of the inorganic ionic composition the water is within the betalimno-type with Mg - Ca - HC0 3 and Ca - Mg - HC0 3 ionic dominances. Dissolved oxygen content and saturation values showed similar dynamics and similar values to the ones measured in the ABC channel. In this situation the presence of similar pollutants and planktonic eutrophication is the key factor, therefore the water is heavily polluted. The same is evidenced by the measured value of the COD concentrations. No significant difference was observed between the phosphorus and nitrogen forms, all of them indicate slight pollution state. High species number Zooplankton communities were found in the stream that was classified as heavily polluted on the basis of the oxygen budget parameters. This is supported by the presence of some 31 Rotatoria, 9 Cladocera and 5 Copepoda taxa. Individual abundance values varied between 317-6979 ind./lOO liter with peaks at two occasions. Dominant species were, apart from the previously mentioned Brachionus and Keratella species, Euchlanis dilatata, Bosmina longirostris, Chydorus sphaericus, Disparalona rostrata and Eucyclops serrulatus. From saprobiological indication viewpoint it could be interesting that the latter species are always found in moderately and heavily polluted waters. In addition to the previously mentioned two species of the previous creek, these could be the indicators of organic pollution. There are some taxa not found in previous streams: Notommata sp., Polyarthra major, Trichocerca elongata, T. similis, Trichotria pocillum. The species rich Zooplankton community of this creek is particularly characterized by the occurrence of organic pollution tolerant species.
