Streszczenie:

This paper attempts to assess an effect of the range of regulatory works in watercourse beds on the aquatic plant communities. The results of field studies carried out on sections transformed as a result of regulatory works and the non-altered sections were compared for this purpose. The field studies were conducted in growing seasons in years 2008-2014 on 11 small and medium-sized lowland watercourses in Lower Silesia. They included identification of aquatic plant species and estimation of the degree of bottom coverage with them. The assessment was based on analysis of changes in the values of five biological indicators such as: the number of aquatic plant species, Jaccard similarity coefficient, ecological status, Shannon-Wiener biodiversity index and Pielou`s evenness index. Comparative analyzes enabled to determine the qualitative and quantitative changes in the aquatic plant communities. However, they did not show any correlation between the analyzed biological indicators and the range of regulatory works in watercourse beds.