Introduction and objective:
Industrial, agricultural and construction development has brought improvements in living conditions, but have also increased the amount of pollution in the environment. Atmospheric precipitation collects pollutants from urban surfaces, which then end up in stormwater systems, contaminating surface waters. These pollutants are also linked to the similar effects of agriculture, as biogenic pollutants originate from over-fertilized crops. Contaminated surface water forces flora and fauna to adapt to new conditions, and affecting the structure and extent of ecosystems. Monitoring the environment with bio-indication methods is important because it enables identification of the areas in need of protection, in an inexpensive and environmentally harmless way. The aim of this study was to evaluate the possibility of using biocenotic indices to assess the impact of a stormwater system on the aquatic environment.

Material and methods:
Bio-indicative studies were conducted on periphyton sampled at 4 points on the Bystrzyca River in Lublin, eastern Poland, under the influence of stormwater discharge and 1 reference point localized before the stormwater system outflow. The quantitative data concerning the number of chosen algae species was analyzed using indices for the examination of community structure.

Results:
Considered the indices, i.e. taxonomic richness, Shannon, MacArthur, Menhinick and McIntosh were calculated, evaluated, and shown in various types of graphs showing the fluctuation of indices at measurement points.

Conclusions:
The use of bioindication and classic biocenotic indices allowed for the description, analysis of changes in the periphyton biocenosis under the influence of point source stormwater discharges, and linking measurements from tested samples with environmental conditions and biodiversity in the analyzed study sites and periods.