Vliv antropogenních aktivit na společenstva vodních organismů v horní části povodí Litavky

The degradation of the natural environment is considered to be a global problem. Due to the importance of water sources, preservation and improvement of their quality are one of priority interest of all society. This study deals with the reactions of aquatic organism groups like fish and benthic invertebrates to an anthropological effect in the Litavka basin. Researched part of Litavka is polluted by toxic heavy metals from past ceveral centuries of extensive mining and industrial smelting in its close proximity. It is also polluted by releasing wastewaters, which contain xenobiotics, trash, and decomposing organic matter. The Obecnický stream was chosen as a reference locality because it is the most similar to a clear natural habitat. It flows into the Litavka river in a spot, where the riverbed is channelised and its floodplain is occupied by toxic waste dumps. The Obecnický stream can be considered the most important water source in the upper Litavka basin regarding the current hydrological conditions. Autochthonous fish population in the upper Litavka basin suffer from several water abstractions, which change temperature and flow regimes. It was our effort, to evaluate the influences of these anthropological factors on aquatic biota, aiming to above-mentioned pollution types, and presence of the water reservoir situated on the Obecnický stream. Monitoring of organism and environmental data collecting (physically chemical parameters, NH4+ , NO2-, PO43-, bottom substrate, flow, and others) were always implemented parallelly. In the case of fish species groups, the resulting correlations show us the greatest impact of the temperature gradient and zinc concentration. We found out a negative correlation between zinc concentrations and abundances of brown trout (Salmo trutta morpha fario) and brook lamprey (Lampetra planeri). On the other hand, common minnow (Phoxinus phoxinus) was highly tolerant for this kind of pollution. The abundance of brown trouts decreased with increasing temperature and it seemed as beneficial for common minnow populations. There was also a shift in the community of invertebrates, namely total absence of three mayflies families (Ephemerellidae, Heptageniidae and Leptophlebidae), Gammaridae, the sphaerid clam Pisidium sp. and the river limpet (Ancylus fluviatilis). The inflow of the wastewaters was accompanied with considerable increase of biomass of common several cyprind species. Besides that, there was a high density of eruciform caddisflies of genus Micropterna and Halesus. Within particular benthic invertebrates, domination of dipteran insects, leeches (Hirudinea) and the freshwater waterlouse (Asellus aquaticus) was observed under the outcome of wastewaters