Comparative investigations on the benthic fauna at two sewage inflows of Lake Balaton

Ponyi, Jenő and Oláh, János and Bíró, Péter and Bíró, Kálmán (1971) Comparative investigations on the benthic fauna at two sewage inflows of Lake Balaton. A Magyar Tudományos Akadémia Tihanyi Biológiai Kutatóintézetének évkönyve, 38. pp. 199-226. ISSN 0365-3005

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Abstract

1. Investigating the zoobenthos between August—October 1969, 92 taxa were found in the following distribution: 1 Porifera, 18 Nematoda, 1 Oligochaeta, 2 Annelida, 42 Crustacea, 2 Ephemeroptera, 16 Chironomida, 1 Ceratopogonida, 1 Psychodida, 4 Trichoptera, 1 Hemiptera, 3 Hydracarina. Isocypris arnoldi Dubowsky, Limnochironomus ex gr. tritonus Kieff., Cryptochironomus ex gr. defectus Kieff. is new to the fauna of Hungary. Species new to the fauna of Lake Balaton: Ilyocypris bradyi G. O. Sars, Cypridopsis newtoni Brady et Robertson, Cypridopsis vidua (O. F . Müller), Limnochironomus ex gr. nervosus (Staeg.), Glyptotendipes ex gr. anomalus Kieff., Cladotanytarsus ex gr. mancus (Walk.). 2. The Zoobenthos of the three collecting sites (inflow areas of the sewage-inflow at Tihany and Balatonfüred and the area in front of the Biological Research Institute) showed considerable quantitative differences as far as Nematoda, Crustacea and Insecta are concerned. The total number of individuals was the lowest in August. The decrease of populations of the different groups of animals in summer months was shown in the previous investigations. The reasons of this phenomenon are not exactly known in Lake Balaton, however, one can suppose that it is caused by the oxygen-shortage and the carnivorous members of the macrobenthos. Variable quantitative relations were observed in groups of animals collected at different sites in different months. More detailed analyses are needed to reveal the reasons of this phenomenon. 3. The summarized data obtained during the total period of investigations unanimously show definite quantitative and qualitative differences in the composition of species found at the three collecting sites. These differences may be connected with the quantitative distribution of the detritus and the propagation of detritophag organisms. The phenomenon was especially striking in the case of Crustacea being heterogeneous from point of view of feeding. 4. The degree of eutrophication seems to be different on the three collecting sites when considering the investigations on the zoobenthos. On the basis of the detritophag benthic fauna, the most advanced level of eutrophication was present at Balatonfüred, followed by the inflow area of the sewage-inflow of Tihany, whereas the lowest degree was observed in front of the Biological Research Institute.

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