Temporal and spatial variations of trophic status of a small lowland river

The research area was situated in Kujawskie Lakeland (central Poland), where agricultural landscape, arable lands, and improved grasslands prevail. River water samples for physico-chemical analyses were collected in the years 1999, 2006, and 2010, together with macrophyte data. All studied sites were localised in the rural landscape with insignificant impact of shading on the structure of aquatic taxa. The analysis of temporal changes in the taxonomic composition of macrophytes was performed with linear indirect PCA ordination. Evaluation of the trophic status of the Noteć River was performed using different macrophyte metrics and the chemical index of trophy. There were not significant temporal shifts of the trophic level of studied sites evaluated both using macrophyte metrics and hydrochemical index, but particular physico-chemical parameters like total phosphorus, soluble reactive phosphates, conductivity, and pH reaction showed statistically significant temporal changes. Significant difference of trophic states between sites localised below lakes and the others was observed for all years.