Nematodes of Lake Balaton. IV. Seasonal qualitative and quantitative changes

Biró, Kálmán (1973) Nematodes of Lake Balaton. IV. Seasonal qualitative and quantitative changes. A Magyar Tudományos Akadémia Tihanyi Biológiai Kutatóintézetének évkönyve, 40. pp. 135-158. ISSN 0365-3005

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Abstract

In the open-water sediment of Lake Balaton the following nematodes predominated during 1966-68: Paraplectonema pedunculatum S. (20 percent), Paraphanolaimus behningi M. (20 percent), Ironus tenuicaudatus dM. (19 percent), Theristus setosus (В.) M. (17 percent), Monhystera paludicola dM. 15 percent), Their occurrence varies by seasons: during winter (between 4 and 12 °C) T. setosus and M . paludicola are the most frequent species, while during summer they are absent at some places. A rare species, Paraphanolaimus anisitsi (D.) ANDRÁSSY 1968 was also observed in the sediment of the lake. The highest number of nematodes was found in spring (May), 60-80 000 i/m², there was a gradual decrease during summer 10-20 000 i/m², then from the middle of autumn (October) there was an increase again. During winter 100 000 i/m² nematodes were observed under the ice at Tihany (“A₀” ). The regional distribution of nematodes was also variable: the highest number was at Balatonszemes (“G” ) averaging 44 000 i/m², the lowest one in the Keszthely-Bay (“M” ) averaging 23 000 i/m². The biomass of nematodes varied between 4-20 mg/m². Generally this value is nearly twice as high in spring than in summer, it is the lowest usually in early autumn (4—6 mg/m²) and th en slowly increases. The highest value of biomass was found at Balatonszemes (“G” ). On the basis of the benthic fauna, the Lake Balaton can be divided into three regions: the north-eastern basin (“A” and “E”), the Keszthely-Bay (“M” ) and the central part of the lake (“K ” and “G” ).

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