Hydrobiological Journal, 2013, Vol. 49, No. 4 Altitude Distribution and Structural Organization of Hydrobionts’ Communities in the Rivers of the Mountainous Part of the Tisa River Basin † S. A. Afanasyev, Ye. N. Lietitskaya & O.V. Manturova Institute of Hydrobiology National Academy of Sciences of Ukraine Kiev (Kyiv), Ukraine Paper deals with main regularities of changes of the species composition, communities’ structure and abundance of the aquatic organisms depending on altitude above the sea level in the mountainous rivers of the Upper Tisa basin. KEYWORDS: algae, bottom invertebrates, altitude, mountainous rivers. Introduction Diversity of the natural conditions in the upper Tisa basin determines significant diversity of rivers of different catchments size, direction and velocity of flow, with different qualitative and quantitative compositions of sediments, character of the bottom surface forming, morphology of the river bed and valley, temperature and gaseous characteristics. All these conditions, which deter- mine occurrence of the aquatic communities, are subjected to the altitude zonality. Actually there is no unique idea regarding structural organization of the riverine biocenoses. The most widely recognized are the Vannote’s river continuum concept [16] and the Townsend’s patch dynamic concept [14], based on different ideas on structure of the natural complexes of the riverine biota and mechanisms of its maintaining. So, the main aim of this work was to establish reg- ularities of the hydrobionts’ species composition and quantitative indexes forming in the differ- ent-type rivers of the upper Tisa basin. Material and Method Structural characteristics of the aquatic communities in the rivers of the upper Tisa basin were studied over the years 2000–2011. Typological analysis was carried out by total examination of the 16 ISSN 0018-8166 © 2013 Begell House, Inc. † Originally published in Gidrobiologicheskiy Zhurnal, 2013, Vol. 49, No. 2, pp. 17–27.