Patterns of diversity and driving factors in microcrustacean assemblages in the lowland and mountain Arctic: comparison of the Anabar Plateau and the adjacent regions of Middle Siberia

One of the key problems of modern ecology is to analyze the structure of ecosystems in Arctic water bodies, which are sensitive to global climatic changes and anthropogenic stress. It is important to determine the general principles of the formation of aquatic communities in different polar landscapes. An attempt was made to characterize the potential influence of altitude on the dominance structure, taxonomic richness, and species composition of benthic and planktonic microcrustacean assemblages on the example of the Anabar Plateau. In parallel, a comparative analysis of assemblages’ regulation in the Lena River Delta (flat tundra), the Anabar Plateau and the Putorana Plateau (mountainous massifs) in northern Middle Siberia was conducted. A total of 96 crustacean taxa were found in the water bodies of the Anabar Plateau: 44 Copepoda, 50 Cladocera, one species each of Anostraca and Laevicaudata. Of these, 44 species are newly found in the region. Structure of the microcrustacean assemblages on the Anabar Plateau depends on mountainousness and the associated hydrochemical and hydrological characteristics of the water bodies. For zooplankton, altitude and macrophyte composition are the main determinants of the assemblage structure. For meiobenthos, altitude and water mineralization are the key environmental factors. A comprehensive analysis of the original and literature data revealed that the formation of fauna and assemblages of microcrustaceans in Arctic water bodies is a result of a complex influence of climate and landscape. The species richness of thermophilic Cladocera exhibits a notable decline with increasing latitude, in contrast to that of thermotolerant Copepoda. In lowland regions, the variability of assemblages is determined by a set of hydrological and hydrochemical factors correlating with the age of the water body. In mountains, the assemblage variability is related to altitude above sea level, which determines the main characteristics of water body.