EN
Fungi occur in almost all types of waters in the world and play an important role in many processes in the environment, particularly in organic matter decomposition. During the last several decades, extensive knowledge was obtained on the ecology of aquatic fungi, but on fungal biomass in the water column less. The study was aimed at simultaneous determination of seasonal and spatial variability of aquatic fungi biomass in the river waters in relation to selected physicochemical water parameters and trophic state in the 27 lowland rivers of north-eastern Poland with length between 17 and 308 km and mean annual discharge 1 – 100 m³ s⁻¹. The chemical and mycological evaluation was provided on the basis of 64 water samples taken in the July and October 2010. The chromatographic method of determination of seston ergosterol as a specific organic compound typical for the majority of fungi, was applied. Fungi biomass was higher in summer than in autumn. The particulate organic carbon (POC) and dissolved organic carbon (DOC) concentrations had no effect on fungal biomass in the studied river, as well as forest cover of the catchment and river discharge. Statistically significant correlations of fungal biomass in the river water with concentrations of ammonium (N–NH₄⁺), Kjeldahl (NKjel), total organic (TON) and total nitrogen (TN) and dissolved (DP) and dissolved organic phosphorus (DOP) were found. The principal component analysis indicates relations between (TIN) and phosphorus (SRP) and particulate phosphorus (PP) and freshwater fungi, specially in summer when aquatic fungi are able to modify the structure of the nutrients contained in the water column.