Lietytska O. Benthic macroinvertebrates communities in the mountain rivers (Tisza River Basin).

The thesis presents the findings of a comprehensive study of macroinvertebrates groups, conducted for the first time in the different types of rivers in the Tisza river basin at Ukrainian and Romanian territories. It determines that the current species diversity macroinvertebrates in the Tisza basin rivers studied includes 861 species out of 28 taxonomic groups. A number of new species are identified in the thesis, and the lists of water macroinvertebrate species are extended. Spatial distribution, quantity of the different macroinvertebrates species are studied as well as consumption of oxygen by the of macroinvertebrates communities in the different sites of the mountain rivers. It is found out, that the diversity of bottom habitats to large extent determines the structure of macroinvertebrates communities. Similarity of quantitative indexes of macroinvertebrates within the sites of the same type of the rivers confirms this finding. It was identified that the trophic structure in the small rivers is more various, than in middle and large ones. With decreasing the altitude of the river flow the number of shredders decreases and the number of the animals with mixed type of nutrition and filterers, and the proportion of predators increases with the altitude. Curve "dominance - diversity" in macroinvertebrates communities change synchronously with change of bottom substrates with the change in the river types downstream. It was identified that the largest consumers of oxygen are macro invertebrate communities of small and medium-sized rivers in lowland and small hills, therefore the average values of oxygen consumption are highest for small rivers in mountains, and the lowest for large rivers in lowland and foothills. The main characteristics of the macroinvertebrates drift in mountain rivers and their role in the functioning of river systems are defined. It is identified that the drift dynamics is different in different river types: the larger the river is, and the lower is the altitude, the more smoothly increase and decrease of intensity of the drift is, its maximum is during the dark hours of the day, and minimum - during the morning hours. For the first time a quantitative assessment of the role of functional groups macroinvertebrates in flows of matter and energy in mountain rivers is done. The main natural and human pressures affecting the main characteristics of macroinvertebrates groups, determining the distribution of the species and the groups, dynamics and quantitative indicators of their habitats affiliation are analysed. For the first time, the risk of significant environmental sources of contamination on macroinvertebrates is calculated. It is identified that depending on the type of the pollution, significant environmental risks are observed 7-45 km downstream the source. Proposals to mitigate negative impacts on mountain river ecosystem are developed. The obtained characteristics of benthic macroinvertebrates hydrocenosis are indicative for the river continuum concept and necessary for assessment of integrity and restoration of the good status of the river ecosystems. They can serve as a indicator if river problems are solved in applied and fundamental hydroecology. Key words: macroinvertebrates benthic communities, structural and functional characteristics, mountain river systems, Tisza river basin.