Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 83. (Budapest 1991)

Lakatos, Gy., Ács, É. ; Buchtijarova, L. N.: Study on reed-periphyton in Lake Velence

showing an improvement in water quality and underline the processes of oligotrophication. The change in the composition of zootecton is less distinct, because zootecton responds to the alteration of plankton and phytotecton with delay, therefore the zootecton collected in Fürdető and the nearby Kárászos and Öreg-tisztás can at present be classified as Phylactolaemata-Bdelloidea-Heteroptera-type. The role of bryozoons, in the food cycle, owing to their alimentation, is worthy of mention (Job 1976, LAKATOS & BARTHA 1989, MESCHKAT 1934, SEBESTYÉN 1952). In the brown, grey and transitional water areas of the Lake Velence, the zootecton can even today be still described as Rhabditidea-Cladocera-Trichoptera community. In hairy, rich in mud periphyton, the nematodes and diatoms (e.g. Cymbella) live together, where cladocerans and caseless caddisfly larvae also find hiding place and resources of food. SUMMARY The results of the studies on periphyton carried out in 1978 and 1988 in Lake Velence indicate the changes in water quality occurring under the influence of lake restoration and provide opportunities to forecast the probable tendencies. As a result of dredging the reed stands and bank arrangements the separated water surfaces disappeared and became uniform. Thus, the special mosaic-like nature of the lake due to the hydrobiological properties has practically come to an end (except for the black-brown water of the small open spaces of the preserves). The decrease in the number of phytotecton species, and the repression and disappearance of weed, in other words, the change in the composition of living organisms in the brown water areas, is quite obvious. The larger, open water surfaces, on the one hand, are practical for holidaymaking, on the other hand, they contribute to the mixing of water which in turn becomes more homogenous continuously solving certain local problems (e. g. planktonic eutrophication). These advantageous changes in water quality in Fürdető and in its surrounding are revealed by the structural changes in phytotecton. In summing up we can confirm that conscious human intervention in Lake Velence, although it has altered the earlier mosaic-like structure of the lake and thereby decreased its hydrobiological diversity and natural values, it much contributes to a better water quality, a general demand of the public. References BARTHA, ZS. (1977): Phytoplankton investigations on Lake Velencei (Algal count and biomass). - Acta BOL Acad. Sei. Hung. 23: 1-11. EVENSON, W. E, RUSHFORTH, S. R., BROTHERSON, J. D. & FUNGLADDA, N. (1981): The effects of selected physical and chemical factors on attached diatoms in the Uintah Basin of Utah, U.S.A. -Hydrobiol. 83: 325-330. FELFÖLDY, L. (1972): A Velencei-tó vízminőségi vizsgálata. 3. részjelentés, VITUKI témabeszámoló: 131 pp. (Manuscript.) JOB, P. (1976): Intervention des populations de Plumatella fungosa (Pallas) (Bryozoaria Phylactoleme) dans l'autoepiration das eaux d'unetanget un Ruissean. - Hydrobiol. 48: 257-261. LAKATOS, GY. (1978): The phenomenon and significance of bentonic eutrophication in Lake Velencei, Hungary. -Acta Biol Debrecina 15:147-163. LAKATOS, GY. (1983): Accumulation of elements in biotecton forming on reed (Phragmites australis) in two shallow lakes in Hungary. - Proc. Int. Symp. Aquat. Macrophytes. Nijmegen: 117-122. LAKATOS, GY. (1986): A Velencei-tó nádasainak élőbevonata 1979-1984. - In: A tavak élete és vízgazdálkodása. Magyar Hidrológiai Társaság VI. Országos Vándorgyűlés I: 61-70. LAKATOS, GY. & BARTHA, ZS. (1989): Plankton- und Biotekton- Untersuchungen im Velencei-see (Ungarn). Acta Biol Debrecina 21: 37-66.