Structural and functional diversity of plankton communities along lake salinity gradients

The Transbaikalia (Russia) hosts a number of shallow endorheic saline alkaline lakes. The outcome of our studies demonstrated changes in phytoplankton and zooplankton in selected lakes covering a wide salinity gradient (from 0.69 to 128.33 g/L) over a number of years. Our main goal is to assess the variability of structural and functional indicators of phytoplankton and zooplankton communities at the various salinity levels. The gradient of abiotic factors significantly determines the dynamics of planktonic community diversity, abundance, biomass, and production. High values of secondary production was ensured by nonpredators (bacteriovorous, herbivorous, and detrivorus). We found that species and functional diversity of phytoplankton and zooplankton decrease with increasing salinity, whereas their abundance, biomass, and daily secondary production did not. In phytoplankton, a shift occurred from the small-medium cell size unicellular and colonial non-flagellated forms to the large-extra large filamentous cyanobacteria and colonial algae. A shift from selective raptorial and microphagous carnivores to herbivorous copepods and cladocerans and further to more generalist filter-feeder of rotifers and anostracans was observed in zooplankton. These findings are important because they provide a meaningful view of phytoplankton-zooplankton trophic interactions and contribute to an improved understanding their functional effects on aquatic ecosystems. Our results also complement existing knowledge and provides new information about the diversity and functioning of planktonic communities in soda lakes.