A protozoan perspective on climate change and biosafety threats: differences in testate amoebae in lakes in forest-swamp and forest-steppe zones in Western Siberia.

The problem of increasing salinity and mineralization in natural and artificial freshwater bodies with climate warming is very relevant nowadays, as it leads to changes in the species composition of planktonic organisms. Testate amoebae are one of the responsive bioindicators that are sensitive to even minor changes in environmental conditions. In this study, a comparative analysis of the species diversity of planktonic testate amoebae was carried out in a number of lakes in the forest-steppe and forest-swamp natural zones of Western Siberia using microscopy and metabarcoding. One new species, Pseudodifflugia siemensmai sp. nov., was described. The detection frequency and the number of reads of amplicon sequence variants of potentially pathogenic testate amoebae belonging to the genera Rhogostoma and Fisculla were higher in forest-steppe lakes. Universal eukaryotic primers for the 18S rRNA gene are well suited for identifying testate amoebae from the supergroup Cercozoa but are practically not applicable for identifying Amoebozoa testaceans. The plankton of the lakes with the highest mineralization and salinity was characterized by the most specific species composition. These results should be taken into account when predicting changes in aquatic communities with further climate warming, which may also be associated with an increase in the occurrence of pathogenic testaceans that pose biosafety threats.IMPORTANCEMicroscopic and metabarcoding analyses reveal important differences in testate amoebae communities in lakes in two natural and climatic zones of Western Siberia that should be taken into account when predicting changes in aquatic communities with further climate warming, which may also be associated with an increase in the occurrence of pathogenic testaceans that pose biosafety threats.