Limnological investigations of a Fish-pond supplied with sewage-water in the vicinity of Lake Balaton. II.

Ponyi, Jenő and Biró, Péter and P.-Zánkai, Nóra and Oláh, János and Tamás, Gizella and Csekei, Tibor and Kiss, György and Morvai, Tibor (1974) Limnological investigations of a Fish-pond supplied with sewage-water in the vicinity of Lake Balaton. II. A Magyar Tudományos Akadémia Tihanyi Biológiai Kutatóintézetének évkönyve, 41. pp. 235-287. ISSN 0365-3005


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1. In 1972 the size of the bacterioplankton biomass was the same as in 1971. An extremely low bacterioplankton biomass like in 1971 did not develop during the summer. The biomass varied between 1.1 and 3.7 mg dry weight/litre. 2. During the investigated period the biomass of phytoplankton, contrary to 1971, was nearly of the same quantity. No mass production of blue-green algae, like in 1971, occurred. In 1972 the biomass varied between 3.1 and 7.9 mg/1 in dry weight. 3. In the fish-pond close to the sewage inlet, the average number of alga cells was lower than a t the other points of the transversal section (10.5-12.5 million/litre). This is also characteristic of the average occurrence of the total alga species. During the investigated period at the point of sampling No. 1 we found 26 species, while a t the other areas of the pond as many as 35-39 4. Of the alga phyla Chlorophyta were represented by the highest individual and specific number. In June, except the area close to the sewage inlet, their number of cells varied between 10 and 16.5 million/litre, in the other months between 4 and 8 million/litre. Scenedesmus was of the highest importance of all algae observed. 5. Of the collecting sites on the transversal section the biomass of Rotifera was always the lowest at the inflow of the sewage water. This difference was insignificant in summer and greater in autumn. The biomass values from July to September nearly reached those on transversal section “A” in Lake Balaton (0.04 g/m3). In August the individual number per litre values somewhat surpassed those in Lake Balaton. The values in June and September were 10-15 times higher. 6. The investigations on the transversal section of the pond showed, as regards Rotifera, no horizontal distribution. At the five points of sampling the dominant species were nearly the same. 7. The biomass of cladocerans was significant only in June when varying between 0.96 and 5.20 mg/l at the different points of the pond. The biomass consisted especially of Bosmina longirostris f. cornuta. 8. In early summer the biomass of copepods was essentially lower (0.15-0.40 mg/1) than that of the cladocerans. From June, when the density of cladocerans was unimportant, that of the copepods was still considerable. 9. The fauna of Rotifera in Keleti Bozót canal differed in quality too, from that found in the pond. The tendency of seasonal change of all the total i/l values is the same as that of the pond. In the Keleti Bozót canal the Crustacea biomass was low and it gained importance only in the first half of summer (0.12 mg/l). Similar to rotifers its specific composition significantly differs from that of the pond. 10. During the months and hours of the days investigated the deoxidized sediment zone did not rise onto the water-mud interface oxygen deficit for fish was not observed. The redox potential gradient was more reduced in the district of the sewage inlet than at the other parts of the pond. 11. The biomass of macrobenthos gained importance only in June and July. The macrobenthos consisted almost exclusively of Chironomus ex gr. plumosus MEIG. larvae. 12. The biomass of meiobenthos contained four animal groups. Chironomus larvae of small size (1-4 mm) occurred in large masses only in June. Their biomass varied between 0.7 and 32.0 g/m2. The biomass of Oligochaeta was also considerable in June, but was essentially lower than th a t of the Chironomus larvae (0.6-1.1 g/m²). The biomass of nematodes was low in summer, it could be observed in larger number (0.7-10.0 g/m²) only in autumn. The biomass maximum of mud-living crustaceans developed at the beginning of the summer, their density was very low in the other months. 13. Among the fish stocked in the vegetation period of 1972 (11 239 kg) there were more grass-feeder crucian carp species than a year before. In the combined fish culture system of 1972, the first-summer-old carp was of decisive quantity (10 590 kg). Depending on the increase in the number of grass-feeder fish, the combined fish culture system yielded larger production than in 1971 (27 150 kg). The starch value of the food consumed seemed to be approximately high, 2.02 kg of food gave 1 kg production. The rate of growth of the fish also differed from that measured in 1971 which is very favourable. From spring until autumn, the deterioration of conditions for fish is characteristic which means that body length increases more rapidly than weight. The survival percentage of fish was higher in 1972 than in 1971. The carp production was significantly influenced by the abdominal dropsy in early summer the effect of which was not observed in the case of other fish.

Item Type: Article
Subjects: Q Science / természettudomány > QL Zoology / állattan
Depositing User: Edina Fejős
Date Deposited: 20 May 2024 13:56
Last Modified: 20 May 2024 13:56

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