Vulnerability of the Biological Elements of River Bed Ecosystem on Regulatory Works

The vulnerability of the system to changes is an additional factor that is often taken into account in risk analysis. Usually this assessment takes into account only two elements – probability and consequences of an event. The study attempts to assess the vulnerability of vascular aquatic plant communities to the qualitative and quantitative changes as a result of regulatory works in a river bed. The aim of the paper is to assess the possibility of using biological indicators, commonly used in assessing the status of aquatic ecosystems, as indicators of the vulnerability of analyzed communities. These are: the number of plant species, the degree of their bottom coverage, Shannon-Wiener diversity index, Pielou evenness index and ecological status. Field studies were carried out in growing seasons from 2008–2014 in small and medium-sized lowland watercourses in Lower Silesia. The field study included an inventory of vascular aquatic plants. Based on the results of the research, values of biological indicators were calculated and statistical analysis (cluster analysis and Spearman’s rank correlation) were performed. On this basis it was found that the number of aquatic plants species and diversity index may be indicators of the vulnerability of plant communities to the changes as a result of river regulation.