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
3. Csopaki creek Specific electric conductivity of the Csopaki creek varied between 650-765 pS/cm corresponding to the alpha-oligohalobic stage. On the basis of the inorganic ionic composition the water falls to beta-hmno-type, in general Ca - Mg - HC0 3 , and in two occasions Mg - Ca HC0 3 . Similarly to the previously discussed two creeks the values of the Ca 2+- and Mg 2+and HC0 3 ~ as well as the value of the total hardness were slightly higher than the other parameters. The water of the creek is cleaner than the previous ones having better quality as the parameters of the oxygen budget and nutrient indicate good water quality. Worse water quality is only indicated by the oxygen saturation and total phosphorus content values. Higher species number was observed amongst the Rotatoria assemblages (7), the crustaceans were only represented by 3 Cladocera species. Individual numbers in 100 liters varied only between 20-76. On two occasions of sampling none of the species was present in the sample. Interestingly both for the Rotatorians and Crustaceans, mostly the euplanktonic organisms were found (Keratella cochlearis tecta, K. quadrata, K. testudo, Lecane bulla, Notholca squamula, Bosmina longirostris, Daphnia hyalina) in small individual numbers. Most of them are characteristic of slightly polluted or higher trophity waters. 4. Örvényesi creek The specific electric conductivity varied between 740-810 pS/cm corresponding to the alphaoligohalobic stage. On the basis of the inorganic ionic composition the water falls to beta-limnotype with characteristic Ca - Mg - HC0 3 composition, and in one occasion Mg - Ca - HC0 3 . Ca 2+-, Mg 2+- and HC0 3- concentrations as well as the total hardness values are identical to the Csopaki creek. Chemical oxygen demand values are indicating organic pollution. Dissolved oxygen contents and oxygen saturation values indicate, however, good water quality. The plant nutrient concentration of the creek, the nitrogen and phosphorus concentration is excessive. In spite of the high nutrient contents, the chlorophyll-a value is low (max. 8.9 pg/1). The creek is characterized the bentonic eutrophication and the tectonic algae are dominant. Rotatoria and Crustacea fauna of the creek is poor, similar to the previously described creeks. Indiviudal abundance values were ranging only 32-100 ind./100 liter. Identified species were nearly identical, some more rare species were recorded (Brachionus quadridentatus quadridentatus, Testudinella parva). On two occasions of sampling none of the species was present in the sample, similarly to the previous creek. 5. Burnót creek Specific electric conductivity values of the creek corresponded to alpha-oligohalobic, or oligo-mesohalobic stages. On the basis of the inorganic ionic composition the water falls within the beta-limno-type to the Mg - Ca - HC0 3 - S0 4 , Ca - Mg - S0 4 - HC0 3 and Mg - Ca HC0 3 " category. Inorganic ionic composition varied at all the sampling occasions, but the sulfate represented a good portion of the equivalent percentage. Dissolved oxygen value indicate good, while the oxygen saturation and COD values bad water quality. Nitrogen- and phosphorus concentrations are indicating moderately polluted creek water. 90% percentile of the chlorophyll-a content was 12.0 pg/1. Four Rotatoria species were only found in April 1998 (Brachionus angularis, Keratella cochlearis cochlearis, K. c. tecta, K. quadrata), and one Cladocera species (Macrothrix hirsuticornis) and some nauplius larvae. Abundance values were characteristically higher than of the previous streams indicating higher trophic status. In spite of the occurrence of these species, this creek cannot be classified.
