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
0 5 10 km H 1 1 Fig. 1. Sampling sites on creeks flowing to the Lake Balaton, 1997-1998 concentration was only 5.2 ug/1. The reason for this could be the high flow velocity (turbulent stream), and the photosynthetic activity of the rich biofilm community. The nitrogen and phosphorus contents of the creek are high, indicating the presence of pollutants. The Rotatoria and Crustacea fauna of the creek is poor, as indicated by the presence of only 9 taxa. Average individual number varied between 36-99 ind./100 liter. Common species are characteristic to eutrophic waters such as (Brachionus angularis, Euchlanis dilatata, Keratella cochlearis cochlearis, Alona rectangula, Chydorus sphaericus). No rare species was found. 2. Lovasi creek The specific electric conductivity of the creek varied between 695-885 pS/cm corresponding to the alpha-oligohalobic stage. On the basis of the inorganic ionic composition the water falls within the beta-limno-type to the Mg - Ca - HC0 3 category, and in one occasion to Ca - HC0 3 class. Higher than average values of Ca 2+- and Mg 2+- as well as hydrogen-carbonate, and total hardness values were measured. Parameters of oxygen budget indicate the presence of organic pollutants that either can be easily or not easily broken down. Of the nitrogen forms the ammonium and nitrite, and phosphorus forms were contributing to the deterioration of water quality during the study. Concentrations of chlorophyll-a varied in the range of 1.5-21.0 pg/1. 10 Rotatoria and 11 Crustacea species were identified during the study period with variable individual abundance values (22-332 ind./lOO 1). Primarily the dominance of those species that are living on the submerged aquatic vegetation was observed (Euchlanis dilatata, Lepadella ovalis, Platyas patulus, P. quadricornis, Ceriodaphnia quadrangula, Leydigia leydigi, Eucyclops serrulatus, Macrocyclops albidus). Occurrence of some euplanktonic species was also recorded (Brachionus rubens, Keratella quadrata, Daphnia hyalina). The species composition and abundance of the Zooplankton community was poor of this creek.
