Analysis and evolution of water quality of the upper Váh River (northern Slovakia) by long-term changes in the community structure of ciliates (Protista: Ciliophora)

Abstract

A long-term monitoring of the upper Vah River was carried out in order to evaluate evolution of water quality by means of ciliate taxocoenoses. One sampling station (Liskova) was located upstream of the pulp and paper mill in the town of Ružomberok, while two stations (Bystra and Stankovany) were situated downstream of Ružomberok. Benthic samples were collected three times a year at each station during 2004–2011. This long-term study enabled us to assemble a comprehensive checklist of ciliates recorded in the upper Vah, and to characterize and compare the ciliate communities in the investigated watercourse. The saprobic index and valency analysis of the ciliate communities allowed us to quantify organic input and to evaluate changes in the saprobity of the upper Vah. The saprobic index ranged from 2.45 to 3.66 corresponding to the quality classes II–IV. Further, there was a prevalence of the α- and β-mesosaprobic levels, but during some periods the polysaprobic level increased along with the decrease of the β-mesosaprobic level. Beside the organic pollution, toxic contaminations were also noticed several times in the studied watercourse. This was documented by a significant drop in the species diversity and abundance of ciliates as well as by various morphological malformations and movement disorders of ciliates and other microorganisms. However, the negative effect of toxic and/or organic pollution wore off relatively quickly, indicating a good self-purification capability of the river.