Abstract
The aim of the research was to investigate the influence of environmental factors on the structure of epilithic diatom communities in the Sava River from the source to the state border 220 km downstream. The river had numerous human influences along its course, such as municipal and industrial wastewater, agriculture, hydroelectric power plants, etc. The main objective of the research was to find out the influence of human pressure on the structure of the epilithic diatom community under winter and summer conditions. Winter and summer samples were taken at nine sites. At each sampling site, a set of abiotic factors was measured and another set of environmental parameters was evaluated. The analyses showed that nitrogen and phosphorus concentrations increased downstream. We identified 118 different species of diatoms. The most common taxa were Achnanthidium minutissimum and A. pyrenaicum. Planktonic species Cyclotella meneghiniana was only found in the samples of the lower part of the Sava, which is unusual for the epilithic community. The composition of the epilithic diatom community was significantly influenced by conductivity and water temperature, pH and distance from the source. The similarity between diatom communities closer to the source of the river was higher than between communities from the lower part of the Sava River. The values of the trophic and saprobic indices increased downstream and showed that the pollution of the river with nutrients and organic matter increases with the distance from the source. Both indices were significantly higher in winter and showed a more impaired river ecosystem during the winter.
Highlights
Periphyton is the basis for the self-purification of the aquatic ecosystem, which enables the absorption of various substances from the water and represents a fundamental component in the food chain [1,2]
The detrended correspondence analysis (DCA) shows that the differences in species composition detrended correspondence analysis (DCA) shows that the differences in species composition of theThe diatom community are greater in winter than in summer (Figure 2), when the stability and of the diatom community are greater in winter than in summer (Figure 2), when the stability and similarity of the assemblages along the course is greater
The composition of the diatom community was statistically significantly influenced by conductivity, water temperature, distance from the source and pH
Summary
Periphyton is the basis for the self-purification of the aquatic ecosystem, which enables the absorption of various substances from the water and represents a fundamental component in the food chain [1,2]. Periphytic communities are very sensitive to the deterioration as well as to amelioration of water quality, which affects algae growth [5]. Periphytic diatoms are important mediators of anthropogenic influences, since the diatoms are the most abundant group in the periphyton, especially in spring and autumn [7]. Their sorption capacity and large surface area represent a great potential for the removal of dissolved pollutants from the water. They are builders of the biofilm, as many species are firmly attached to the substrate and have an anchoring function.
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