As a result of the dissertation, the species community of amphipods in the modern period was specified, the spatiotemporal features of the formation of taxocene amphipods (Crustacea, Amphipoda) and their reactions to the abiotic factors of the marine environment of the Northwestern Black Sea were firstly studied. The 39 species of amphipods belonging to 21 families and 33 genera have been found on the Ukrainian Black Sea shelf. The most frequently were representatives of familу Gammaridea (D. villosus (Sowinsky, 1894), C. olivii (Milne-Edwards, 1830), E. ischnus (Stebbing, 1898), G. subtypicus Stock, 1966, G. aequicauda (Martynov, 1931), G. insensibilis Stock, 1966, P. оbesus (G.O. Sars, 1896), P. maeoticus (Sovinskij 1894), O. crassus G.O. Sars, 1894). The greatest diversity of the various crustaceans was noted in the Odessa Marine Region – 29 species, in the Lower Danube region – 20 species, open gulfs (Yagorlytska, Tendrivskaya and Karkinitskaya) – 14 species. The largest similarity of fauna of amphipods` communities of solid substrates from the Odessa region was noted with the groupings of fouling from the Zmeiniy Island – 70 %. The largest faunal similarity was observed between the waters of the Tendrivskaya, Yagorlytska and Karkinitskaya Gulfs: 81.4 % between the Tendrivskaya and Yagorlitskaya Gulfs, 66.67 % between the Karkinitskaya and Tendrivska Gulfs and 61.54% between the Karkinitskaya and Yagorlitska Gulfs. On the solid soils of the Odessa Marine Region, amphipods are found almost constantly and are detected in 100 % of samples, 21 species have been identified. The 6 species dominate in the fouling communities: M. gryllotalpa, E. оlivii, J. оcia, M. рalmatа, S. monoculoides, C. bonellii, A. ramondi. The highest abundance of a is observed amphipods the periphytal of the solid substratum of the upper sublittoral of Zmiinyi Island and Odessa Marine Region: 34902.90±4904.60 ind.•m-2 and 4314.86±488.48 ind.•m-2, respectively. In the Odessa region, 26 species of amphipods have been identified on soft soils. Amphipods in such conditions occur in 61.43 % of cases, respectively, of the dominant species. The most common are M. gryllotalpa, A. diadema, D. spinosa – 31.44 %, 17.02 % and 15.40 %, respectively. 20 species of amphipods have been identified in the Danube Region of the Black Sea. On average, throughout the study period, amphipods were recorded in 47.80 % of samples. A. diadema was the most frequently noted and numerous and significant in the formed biomass. The species composition of amphipods in Grigorievskyi Estuary is represented by 23 species nowadays. Amphipods occur in 64.16 % of samples. During the entire study period, the average amphipod number was 686.74±139.04 ind.•m-2, the average biomass was 2.402±0.278 g∙m-2. The highest occurrence, abundance and biomass was recorded for A. diadema, M. gryllotalpa and C. bonellii. In the modern period, the amphipods of the Tiligulsly Estuary are represented by nine species. In the shallow (up to 0.5 m) zone 9 species of amphipods were found, at depths from 0.5 m to 13 m 7 species were found. G. aequicauda, M. gryllotalpa, D. spinosa, C. bonellii were the most common. In Sukhoy Estuary 18 species of amphipods have been found during investigations. Amphipods were frequently found in benthos sampled in Sukhoy Estuary – 60.98 %. No species is more common than 50 % of cases (samples). Most common were M. gryllotalpa, C. bonellii and D. spinosa – 39.02 %, 21.95 % and 14.6 %, respectively, five species out of eighteen noted only once – A. bispinosa, C. baeri, E. difformis, Р. ocia, P. longimanus. Analysis of the material showed that the number of amphipod species increases with increasing salinity: from 10 species at 8 ‰ to 16 species at 16–18 ‰ in the Odessa Marine Region, from 1 species at 4 ‰ to 19 species at 16 ‰ in the Grigorievsky Estuary and from 2 species at salinity of 4–8 ‰ to 12 species at 16–18 ‰ in the Lower Danube Region. The analysis of long-term dynamics showed that the number of amphipod species decreased in the Lower Danube Region from 2002 to 2017, at the same time other quantitative indicators (occurrence, abundance, biomass) are increasing. During the studies in the Odessa Marine Region and the Grigorievsky Estuary, there has also been a decrease in the number of species and other quantitative indicators of amphipod populations. During the year in the Danube region all quantitative indicators are the largest in the autumn season, in the Grigorivsky estuary the number of species and numbers are the largest in the summer season, while the occurrence of biomass is most significant in the spring season. On solid substrates of Odessa Marine Region, the number and biomass are more significant in the spring. The main factors affecting the distribution of amphipods are water salinity, depth and substrate.
