Planktonic and reed biofilm bacterial communities of riverine habitats with different water regimes. Bacterial communities of riverine habitats

The submerged reed (Phragmites australis) stands provide surfaces for biofilm forming bacteria which play decisive role in the littoral zones of aquatic habitats. In the present study, comparative examinations were performed on the structure and composition of planktonic and reed biofilm bacterial communities from two riverine habitats with different water regimes. Water and reed biofilm samples were taken at the beginning and end of the vegetation period from the side arms of River Danube (Soroksári-Duna and Riha-tó). The environmental variables of the waters were measured by standard methods. The bacterial cell numbers were detected by DAPI staining method. The genetic diversity of bacterial communities was analyzed by DGGE. Regarding the physical and chemical variables of the water, significant differences were revealed between the studied riverine habitats contrary to the total bacterial cell counts. Based on the DGGE results, less seasonal differences were detected in the Soroksári-Duna than Riha-tó samples in connection with the changes of environmental variables. However, the structure of the bacterial communities was different in the water and reed biofilm samples. From the water samples representatives of wide-spread and typical freshwater planktonic bacteria (‘Candidatus Planktophila’, Limnohabitans, Polynucleobacter) were revealed. From the reed biofilm samples different phototrophic and plant associated bacteria were also detected.