Changes and dynamics of headwaters chemistry on the boundary of nature protected areas: Example of upper Blanice River catchment, Czechia

Changes of biogeochemical parameters in the context of long-term trends and different rainfall-runoff conditions were examined with a special focus on various catchment characteristics. The study area is situated in the upper part of the Blanice River catchment, where more than 77% of the area belongs to a Protected Landscape Area and is unique for the most abundant population of the critically endangered freshwater pearl mussel (Margaritifera margaritifera) in Central Europe. The Mann-Kendall test revealed a decrease of nitrogen and phosphorus compounds at the catchment outlet since 2003. The principal component analysis divided nine study catchments into three main groups according to biogeochemical composition (natural, partly anthropogenically influenced, subsurface drainage). Changes of biogeochemical parameters during different runoff conditions revealed a higher release of aluminium, CODMn, dissolved organic carbon and total phosphorus during heavy precipitation event, which could have a negative effect on the vulnerable ecosystem including freshwater pearl mussel.