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
21. Endrédi creek The discharge of the creek was highly fluctuating, therefore investigations could only be conducted during 1998. Results should be considered as preliminary ones. Even the lower amount of measurement was enough to determine that water of the creek is polluted. This was evidenced by the measured high conductivity value ranging form 1120 to 1290 pS/cm. These values correspond to oligo-mesohalobic stage. On the basis of the inorganic ionic composition the water is within the beta-limno-type with ionic dominance of Ca - Mg HCO3 and Mg - Ca - HCO v Dissolved oxygen content and saturation values indicate pollution. This is supported by the values of the COD content that are characteristic of heavily polluted surface waters. The ammonium and nitrate content was less while the nitrite was slightly higher. Phosphorus concentrations indicated heavily polluted water. Zooplankton study was conducted only once here, therefore results have to be considered as preliminary ones, for faunistic purposes. Altogether 8 species were identified from which only one Proales sp. (Rotatoria) is worth mentioning while the rest of the species is characteristic to small, eutrophic surface waters. Summary On the basis of oxygen and nitrogen-, and phosphorus budget parameters among the creeks on the Northern shore the water of the Csopaki creek is slightly polluted. The Vörösberényi creek, the Lovasberényi creek, the Örvényesi creek, the Burnót creek, the Egervíz and the Tapolca creek have tolerable water quality, while the Kétöles creek is heavily polluted. Species composition of the Zooplankton communities is in general poor in these streams with low individual abundance. In many cases the samples contained drifting animals from the biotecton characteristic to meso- and eutrophic stagnant water taxa. The water quality of the Világos creek, Lesence creek, Zala River and Nyugati channel is significantly worse, indicating polluted conditions. In some cases (e.g., Világos creek, Lesence creek) oxygen budget parameters were indicating even worse conditions, of heavily polluted state. Zooplankton communities of the latter streams were ususally richer with higher abundance. In these creeks the reason for the bad water quality is the not suitable water exchange, as long-term small water periods are experienced. Water quality of the Zala River is determined by the water quality of the outlet water of the Kis-Balaton II. phase at the Fenékpuszta section. On this short section of the river the dissolved oxygen is very low with elevated phosphorus concentration. Of the creeks of the southern shore the Zichy channel, Kelet-Nyugati channel, the ABC channel and the Tetves creek are heavily polluted. Their water indicates eu- and polytrophic state as characterized by the large Zooplankton stands. On the basis of the water chemical parameters the organic pollution is high in these waters. Slow flowing regime makes the situation even worse. The water quality is slightly better, tolerable in creeks that are densely populated by macrophyte vegetation (such as the Keleti Bozót channel, Jamai creek, Nagymetszés trench, Kőró'shegyi creek). Dominant species of the Zooplankton community of these streams are characteristic to taxa occurring in eutrophic stagnant waters and fishponds. Species number of these streams is much higher than those creeks on the northern shoreline due to the elevated level of plant nutrients. Rare species are quite frequently recorded in these streams.
