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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

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J.N. Nosek and M.Cs. Bereczky; [Structure Investigations of Ciliate-Plankton Community in the Main and in a Side Arm of the River Danube by Correlation- and Path Analysis]. Arch.Protistenk 124:173-192, 1981

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Investigations were carried out in the main and in a side arm of the river Danube at God (river-km mark 1669), North Hungary. In the side arm there is a cross-barrage, which stops the flow at water levels less than 200 cm (19%). Sampling were performed weekly from March till November 1976. Simultaneously five physicochemical parameters were recorded (water level, water temperature, pH, oxygen consumption and dissolved oxygen). Changes in the community structure were followed by species-individuals diversity (using the Shannon-Weaver function) and evenness. Correlation and path analysis were applied to calculate the effect of the physicochemical parameters on the number of individuals and/or species as well as the effect of the latter two and the evenness on the diversity. With the decrease in stability of the environment the effect of the physicochemical factors on the number of individuals increased. In the case of diversity the number of species was more effective than the evenness in both biotopes. With decreasing environmental stability the relative importance of the number of species increases. On the basis of our results Tramer's (1969) conclusions on the regulation of species diversity seem to be valid only under natural or hardly disturbed conditions.