Taxonomic Structure of Planktonic Protist Communities inSaline and Hypersaline Continental Waters Revealedby Metabarcoding

Saline and hypersaline waters are one of the most peculiar ecosystems of our planet, characterized by extreme life conditions. Despite their worldwide distribution, the diversity and abundance of protist communities in these ecosystems remain poorly studied. Here, we analyze planktonic communities of protists sampled across 38 saline and hypersaline water environments (2-390 parts per thousand) from arid climatic zones of the South Urals and Crimea in light of environmental data using high-throughput 18S rDNA amplicon sequencing. A total of 9 eukaryotic supergroups, 34 phyla, 104 classes, 184 orders, 315 families and 548 genera have been identified. We revealed significant differences in the taxonomic structure of protist communities depending on salinity, geographic location and pH. The protist communities demonstrated linear regression of richness and diversity and growth of the percentage of unclassified Eukaryota (up to 43%) with the increase in salinity. Centrohelids demonstrated the ability to inhabit a broad range of salinities, up to 320%, which is four times higher than previously reported. Centrohelid species Pinjata ruminata and Yogsothoth sp. are assumed to be specifically adapted to salinity of 3-210%. The obtained results provide insight into the taxonomy and diversity of protists in saline and hypersaline environments and highlight the great potential for the discovery of new taxa due to the large number of unclassified 18S rDNA sequences.

Automated summary

By analyzing planktonic communities of protists in 38 saline and hypersaline water environments, we found significant differences in the taxonomic structure of these communities depending on salinity, geographic location, and pH. Centrohelids showed adaptability to different salinity environments, with the species Pinjata ruminata and Yogsothoth sp. assumed to be specifically adapted to salinity of 3-210%. These findings are important for understanding the taxonomy and diversity of protists in saline and hypersaline environments, and highlight the potential for discovering new taxa.