Saprobiological Description of Urban Watercources (The Kutum and the Tsarev Rivers) in Astrakhan

Abstract

Today, biological indication methods are recognized as highly effective, since they allow to directly assess the state of the ecosystem and its individual components. Even casual examining of hydrobionts can provide fast and reliable information on water quality. The rivers Kutum and Tsarev located on the territory of the city of Astrakhan were selected as objects of research. Samples of zooplankton collected in the fall of 2016 and 2017 served as research material. Organisms belonging to different zones of saprobity were selected as an indicator group. Calculations of weighted average saprobity were made. Both reservoirs under study have been found to belong to beta-mesosaprobic zone. At station 1 of the Kutum River and at station 1 of the Tsarev River there were registered equal values of the indicator of weighted average saprobity that correspond to oligosaprobic and beta-mesosaprobic zones. This may be explained by the change of community and by the fact that the identified organisms at these stations had a very wide tolerance to polluting factors. At station 2 of the Kutum River in 2016 and 2017 there was stated the predominance and increase in the number of bioindicators of the oligosaprobic zone, while at the other stations the organisms gravitating towards beta-mesosaprobic zone did not seriously change their indicators. As it can be inferred from the results of the saprobiological analysis of the urban watercources (the Kutum River and the Tsarev River), they are undergoing an active process of self-purification, culminating in mineralization of water (beta-mesosaprobic zone) with transition to oligosaprobic zone (almost pure water). However, the presence of indicator organisms and their predominance in plankton samples give grounds to regard the studied water bodies as moderately polluted. That is why it is recommended to lower the recreational load on the urban water bodies by reducing wastewaters discharge from the urban storm sewage system.