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We investigated the relationships between testate amoebae (Arcellinida, Euglyphida), vegetation and water chemistry along environmental gradients in minerotrophic peatlands (fens) in western Poland. We hypothesized that: a) hydrochemistry significantly influences structure of testate amoeba communities, and b) testate amoeba communities are more closely correlated with the hydrochemical variables (environment) than with the vegetation data. Testate amoeba communities and vegetation from 71 sample plots were investigated together with the hydro-chemistry and hydrology based on 16 environmental variables and vegetation composition. Testate amoeba communities revealed a distinctive poor-rich gradient in analysed fens. Mineral-rich habitats, which were dominated by brown mosses, were preferred by a higher number of taxa than acidic habitats, which were dominated by Sphagnum. We recorded a total of 107 testate amoebae taxa. The average species richness of testate amoebae for brown mosses was higher (20) than for Sphagnum (13). We found that testate amoebae communities were similarly correlated with vascular plants, mosses and environmental parameters. Results of direct ordination demonstrate that hydrology, pH, Mg 2+ and sodium remain the most important environmental control for the entire data set. CCA showed that in case of brown mosses hydrology, sodium and oxygen affect testate amoeba communities significantly whereas in Sphagnum only sodium emerge as most significant determining testate amoeba assemblages. IntroductionKnowledge about microorganisms is important for understanding peatland ecosystems (GIL- BERT and MITCHELL, 2006). A holistic ecosystem approach, however, is not possible because the number of variables, groups of organisms and interactions is too large to be described in one study. Relationships between soil microbes and plants have not been well explored and increasing numbers of studies are focusing on belowground interactions (WARDLE, 2006;BEVER et al., 2010). In the case of peatlands (especially rich fens), a lot of work is needed to fully explore microbial communities. Among them testate amoebae (Arcellinida, Euglyphida) are an important group of biotic indicators. These organisms live in the soil and mosses in fens and are useful for thoroughly exploring environmental gradients. Their biomass and density in wetlands depends strongly on the abundance and the level of the complicated spatial structure of the plants (MIECZAN, 2010) . They graze on other microbes, such as bacteria, algae and fungi, and play an important role in the soil microbial loop and nutrient cycle in soils (GILBERT et al., 1998;WILKINSON and MITCHELL, 2010). Furthermore, testate amoebae have been used in ecological studies of the response of terrestrial ecosystems to climate change (LAMENTOWICZ et al., 2010b;TSYGANOV et al., 2010) and also are usefull paleoindicators of hydrological changes on ombrotrophic peatlands (BOOTH, 2002) however until now most of the research have been conducted in raised bogs or Sphagnum...

Peat bog lakes represent important ecosystems in temperate and boreal zones. We investigated the seasonal dynamics of the microbial community in two small peat bog lakes, Kuźnik Olsowy and Kuźnik Bagienny, located in western Poland. Fluorescence in situ hybridization analyses revealed that the bacterial community was dominated by Proteobacteria and Actinobacteria, in addition to a substantial number of archaea. An infrared epifluorescence analysis demonstrated that aerobic anoxygenic phototrophs (AAPs) constituted a significant fraction of bacterial plankton (1-19%). All the bacterial groups exhibited large seasonal changes whose course differed between the studied lakes. While chlorophyll had its maximum during winter or early summer, AAPs peaked in summer, when the growth of this group was stimulated by higher irradiance and elevated water temperatures.

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