Hidrológiai Közlöny 1978 (58. évfolyam)

9. szám - Dr. Herodek Sándor–dr. Tamás Gizella: A fitoplankton tömege, termelése és a Balaton eutrofizálódása. II. Szigligeti-medence 1974–1975

Dr. Herodek S.

—Dr. Tamás G.: A fitoplankton tömege Hidrológiai Közlöny 1978. 9. sz. 391 The mass, and production of pliytoplankton, and the utrophication in Lake Balaton. Part II. The Szigliget Basin, 11)74— 1975 By Dr. Herodek, S.

—dr. Tamás (Miss

), O. The composition, biomass and primary production of phytoplankton were investigated in the different basins of the lake in order to characterize the rate of eutrophication. This paper presents the results obtained at the station in the Szigliget-basin between June, 1974 and July, 1975. Water samples were taken from 25, 100, 200 and 300 cm depths. The individual number of each species was determined under an Utermöhl microscope. The biomass was calculated by the cell volume method. To each water sample of 100 ml 20 pCi Na

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1

4C0

3 was added, then the bottles were lowered to the same depths from where the samples originated. After 4 hours exposal the algae were removed by membrane filters, and their radioactivity was measured. The total carbonic acid content of the water was also determined, and the amount of carbon, fixed by photosynthesis was calculated. In the samples 124 alga species and 4 varieties were found. In summer besides Ceratium hirundinella blue-green algae and euglenophytes predominated (Table 1). In July, 1974 the wet weight of phytoplankton attained 17 g-m~

3 (Fige. 3), wich is the maximum found thus for in this lake. From October to March strong water colouration was caused by diatoms, dominated by Nitzschia acicularis. In December, 1974 in 1 litre of water 23 million algae were found. This is the highest individual number registered in Lake Balaton, and is higher by one order of magnitude than the maximum in the 1960s' (Fig. 4). The increase of algae decreased the water transparency (Table 2). As consequence of insufficient illumination the submerged macrophytes disappeared from the deeper waters. Due to the low transparency the photosynthesis of algae was restricted to the upper two metres (Table 3). In the deeper water layers there is no oxygen production, this way the decay of the plankton rain, dropping to the bottom can lead to anaerobic conditions and to the formation of toxic compounds. It is possible that this process caused the heavy fish kill in this basin in March, 1975. The primary production related to surface area unit (Fig. 1) attained its maximum [2-6 g C-m~

2-day

_

1] on August 27, 1974, but for the season high values were found in the months preceeding the fish kill, too. The annual primary production per surface area unit was 301 g C-m2. This value falls on the trophic scale of Rodhe between the eutrophic and hypertrophic ranges, while according to Hübeis' classification it belongs to the hypertrophic range (Fig. 6). In 1961 no differences were detected by the few measurements carried out at that time between the productivities of the different basins. The values obtained in the Szigliget-basin in 1974—-75 were much higher than those of 1961, and here the annual production was three times higher than off Tihany in 1972—73 (Fig. 1). In recent years the Szigliget-basin has entered into the stage of racing eutrophication. To retain there a water quality suitable for recreational uses, the plant nutrient load of this basin must be controlled in the nearest future. Macca H 0Gpa30Bamie c|)HTonjiaHKTOHa; 3BTp0<jnip0BaHne 03. EajiaTOH Jl-p XepodeK, III.

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3 (pnc. 3.), 1T0 HBJIHCTC5I HaHÖOJIblIIHM H3MepeHHbIM flO CHX nop 3HaqeHHeM AJIH BajiaTOHa. C OKTHSPH no MapT KpeMHeBbie BOAopocJiH, cpe/iH KOTopwx npeoSjiaflaji bhä Mitzschia aciculuris, Bbi3BanH CHjibHO 3aMeTiioe itBeTemie BOAbi. B aenaSpe B OÄHOM jiHTpe Boabi 06Hapy>KeH0 23 MHJiJiHOHa Boflopocjieii, MTO paHbiue HHKorAa B BaJiaTOHe He HaSjiioAa^ocb n MaKCHMyMbi uiecTH/iecjiTbix roaoB npeB30iiiJi0 Ha uejibiö nopHÄOK (pnc. 4.). BcjieacTBHe pa3MHo>KeHHn Boaopocjieö cHJibHO yMeHbWHJiacb np03paiH0CTb BOflbi (TaSji. 2.). HexBatKa COJIHCIHoro cßeTa npHBejia K HCMCSHOBCHHIO IIOABOAHOH pacTHTEJIBIIOCTH B éojiee rjiyőoKHx iacTHx 03epa. H3-3a yMeHbllieHHOii np03paiH0CTH <{)0T0CHHTe3 B0Ä0pOCJiefl npOHCXOAHJI TOJIbKO B BepXHeM 2-X MeTpOBOM c.noe BOflbi (Taóji. 3.). B őojiee rJiyöoKiix CJIOAX HeT npoH3B0ACTBa KHCJiopofla, n03T0My pa3Jio>KeHHe Bbina

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