Richness of macrophyte functional groups in relation to hydromorphological and hydrochemical factors of organic rivers in the Biebrza National Park

This study focused on the expansive area of the Biebrza National Park (BNP), with well-preserved aquatic ecosystems. The research aimed to reveal the ecological determinants of plant diversification of the BNP river network, considering water quality and hydromorphological factors. The species richness of macrophytes, considering their various functional groups, were analysed, considering different ecological groups of aquatic plants. The biodiversity estimates are based on field research results (reference sample) and extrapolated values. Field research was conducted across the entire BNP area, surveying 25 sites. The study found that the species richness largely depended on the hydromorphological quality of the habitat and was influenced by the size of the river channel and water trophic conditions, especially phosphorus richness and the ammonium form of nitrogen. The ecological reaction on species richeness was particularly evident in the case of submerged macrophytes. The average number of macrophyte taxa observed at each site was relatively high compared to other Polish rivers, but still the overall number of identified taxa and estimated species richness were smaller than other river basins in Poland. The relatively low species richness of macrophytes in the BNP area primarily resulted from the homogeneity of habitat conditions in the studied watercourses, characterised by organic types with laminar water flow and limited substrate diversity. To ensure comprehensive inventorying, continued efforts are recommended, with doubling the number of surveyed sites as the most rational approach.