Distribution patterns of three Potamogeton species (P. crispus, P. nodosus and P. pectinatus) along velocity and base richness gradients from a lowland river

This study presents distribution and abundance of three Potamogeton species, namely Potamogeton crispus, P. nodosus and P. pectinatus along environmental gradients in the lowland river Wełna (NW Poland). The relationships between 13 environmental factors and the pattern aquatic vegetation distribution along river were investigated. Among ecological factors rarely undertaken in aquatic ecology the light climate was concerned. It is postulated that the Potamogeton communities in the investigated river are strongly connected with water velocity, substrate of bottom and light conditions, in particular dissolved organic matter (DOM). Elodeo-Potametum crispi and algae communities with dominant species Hildenbrandia rivularis were well developed in the places shading by trees, with high velocity and fairly clean water, mostly with stony bottom. Potametum nodosi was noted in mean values of velocity and medium water quality with high content of organic matter in the bottom substrate. The last investigated community Sparganio-Potametum interrupti was found in poor water quality with the highest values of electric conductivity. The obtained results give a new approach of the ecology and abiotic typology of rivers with macrophytes including abundance of Potamogeton species (Nature 2000 habitat, code 3260 – “Water courses of plain to montane levels with the Ranunculion fl uitantis and Callitricho-Batrachion vegetation”).