Long term urban impacts on the ecological status of a lowland river as determined by diatom indices

This study determined changes in the ecological status of a lowland river under the impact of an urban agglomeration after modernizing the wastewater management. For 174 years the Ner River was loaded with pollution from expanding industry. Construction of the Group Sewage Treatment Plant (GOŚ) in 1994 and its subsequent modernization should have improved the water quality. After 20 years of proper sewage treatment the ecological status of the river hasn't improved.Study sites were established on the river above and below sewage disposal from GOŚ, and the ecological status was assessed on the basis of benthic diatoms. Diatom indices: IO, GDI, IPS were calculated in order to determine the ecological status and water quality. Hierarchical cluster analysis and multivariate analysis of diatom assemblages were used to reveal differences of the study sites. It was revealed that the river is divided into two sections: the first is above the sewage disposal and the second is below it. In the first section, domina...