EN
The purpose of this paper is to assess how informative phytoperiphyton structural parameters are, and to assess the feasibility of using them for biological monitoring of river quality. The spatial distribution of the attached algae community was studied in some of rivers in Republic of Karelia (NW Russia). The influence of anthropogenic impacts on periphyton communities was analysed in terms of species richness, species diversity, species ecology values, biomass and chlorophyll concentration. All rivers are subjected to different kind of anthropogenic impacts in addition to natural disturbance. With regards to the species composition the differences between the urban and natural stretches of rivers are obvious. The data obtained demonstrate that the phytoperiphyton communities in urban streams are dominated by broadvalent, pollution-tolerant and even saprophilic taxa. Substantial changes in periphyton structure were often caused by an enhanced mechanical impact by storm run-off, which retarded colonisation, rather than any chemical influence. The burial of algae by sand and silt resulted in the loss of species or entire algal assemblages were observed. As result the communities are dominated by a few species with high recolonization potential.