Аннотация:Information on the freshwater fauna of the remote arctic territories is very patchy; most of the isolated islands of the Arctic Ocean remain absolutely unexplored. The pioneer data on the species composition of microcrustaceans of Shokalsky Island (Northwest Siberia, Russia) is reported here. The initial three-year research revealed a total of 31 new for the area species of Cladocera and Copepoda, including new records for the whole northwestern Siberia. Comparing the interannual differences in faunal composition, we suggested the hypothesis of the existence of a cryptic pool of species’ resting stages, which can invade to the community in the event of favorable environmental conditions in the arctic freshwaters. We also compiled all the available data from other different parts of northern Siberia and compared fauna of Shokalsky Island with those ones to analyze the diversity and distributional patterns of copepods and cladoceran species with the connection to the climate conditions of different territories.