LIMNOLOGY OF THE TURIEC RIVER BASIN (WEST CARPATHIANS, SLOVAKIA)

Structure, dynamics and productivity of hydrocoenoses of the Turiec ri ver basin, the left-hand tributary of the upper river Vah, were studie d between the years 1986-1990. So far 616 taxa of zoobenthos have been recorded in the Turiec river basin, and out of these 442 belong to ma crozoobenthos. Infusories form the dominant group of the microzoobenth os community. From point of view of abundance and biomass, the plant s ubstratum is the richest. The rock substratum is the most stable. The least stable substratum is made up of mud - detritus, with a highly va riable index of species diversity, abundance and biomass. At the local ity Turiec - Kostany, bacterivorous and omnivorous Ciliophora species have the greatest ecological importance among the food chains of the m icrozoobenthos. Primary, transitional and secondary consumers form 73% , 10% and 17% of the Ciliophora community, respectively. In the Turiec river basin, epi-, meta- and hypohithral can be distinguished, accord ing to macrozoobenthos taxocoenoses. The highest diversity of mayflies and stoneflies was observed in ecotones. Abundance changes had the op posite course to changes in diversity. Mayflies abundance increased (s toneflies abundance decreased) in transitional zones of streams toward s the lower liver Turiec and in the hyporhithral. Production of macroz oobenthos in the hyporhithral of the river Turiec was studied. The tax a having optimal topic, thermic and trophic conditions in the river Tu riec, were characterized by a high production and P/B ratio. The resul ts confirmed the basic postulates of the river continuum concept. Ther e was an antagonistic relationships between the retention ability and the speed of transport of organic matter. Animals reacted to condition s in the water environment in a similar way. On the basis of various b iotic factors, five different groups of habitats characterized mainly by different water current and light conditions have been distinguishe d. Tile abundance of macrozoobenthos in the Turiec river basin was det ermined by discharge, by shade and by tile structure of the bottom sub stratum. The macrozoobenthos trophic guilds reflected long term trends of the habitats, although the biomass and structure of the benthic or ganic matter reflected a more immediate state of the habitat. The chan ges in the zoobenthos taxonomic groups were gradual, but they were ass ociated with sudden changes, accompanied by a significant increase in diversity, In our opinion, the joining of the river continuity concept with factors influencing zonality is important to describe the basin type, In tile hyporhithral of the river Turiec the annual dynamics of various hydrobiological parameters were traced, On the basis of these parameters different periods (i.e. early and late winter, spring, earl y and late summer, and a short autumn period) have been distinguished during the annual cycle. The retention ability and ecological stabilit y of tile low flow of the river Turiec was very low, bur the biologica l activity and transport ability of the river was very high. In the st udy of the autotrophy or heterotrophy of the water ecosystem the most suitable is to trace the ratio of production of algivores to detritivo res living in the benthic organic matter. In the river Turiec, this ra tio reached the value of 1:6:1. The proportion of production of filter s reflects the level of food dependence of aquatic animals on metaboli c processes in the water column or on the stream bottom. This group of macrozoobenthos strongly dominated in tile production of aquatic inve rtebrates. Both Facts support the river continuum concept. The annual P/B coefficient of the macrozoobenthos (7.75) was very close to the th eoretically expected coefficient of 7. 97, evaluated using various abi otic parameters.