<p>This paper summarises results of a three-year research aimed at investigating the variability of chemical composition and species diversity and functional structure of planktonic communities in saline lakes of Transbaikalia (Russia). According to the ionic content, the lakes were classified either as soda (13 lakes), chloride (3 lakes), and sulphate (2 lakes) types. Water salinity ranges widely, from 0.5 to 334.5&#xa0;g L⁻¹ in soda lakes, from 8.2 to 257.8&#xa0;g L⁻¹ in chloride ones, and from 21.3 to 146.8&#xa0;g L⁻¹in sulphate lakes. In all lakes the cation Na⁺ dominated, with its concentration increasing as the salinity of the water rises. An increase in salinity, accompanied by a sequential change in the chemical types and subtypes of lakes, led to an excess of bioavailable forms of nitrogen and phosphorus. Diversity and density of phytoplankton and zooplankton depended on both to an increase in the total salt content and the anionic composition of water. Salinity constrains species composition and functional diversity and leads to changes in trophic structure and density of some aquatic organisms. We determined two assemblages of aquatic organisms: <i>Anabaenopsis knipowitschii</i> and <i>Brachionus angularis</i> preferring sulphate dominated habitats and <i>Limnospira fusiformis, Ascomorpha ecaudis,</i> and <i>Hexarthra mira</i> commonly associating with carbonate dominated habitats<i>.</i></p>