engleski

Seasonal changes in trophic structure of periphytic ciliates in relation to discharge regime

In running waters discharge regime may be a major factor determinants for temporal fluctuation of the periphitic biomass. In periphyton communities ciliate density curve corresponds with that of flow record. A significant difference in population density was found between the low and high discharge periods. In stable winter and summer periods, the ciliate population density ranged from 200 to 350 Ind./cm2. In hydrologically unstable spring and autumn periods the high discharge regime with frequent periodical peaks results in an impoverishment of ciliate assemblage. The decrease in ciliate density in relation to discharge increase can be explained by the wash-off effect. In addition, calculating the Shannon index of diversity (H� ), we observed that the species diversity of ciliate assemblage decreased with an increase in water discharge. Considering the seasonal changes of four size classes analyzed in relation to discharge regime, it can be concluded that passive ciliate drift influenced by the wash -off effect correlated with increasing ciliate body size positively.

ciliated protozoa; fluvial drift; trophic structure

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