Phylogenetic Diversity of Prokaryotic Communities of the Upper Sediment Layers of the Kandalaksha Bay, White Sea

Abstract—

Microbial communities of the sediments of the Kandalaksha Bay (White Sea) remain insufficiently studied. While the data on the rates of some microbial processes are available, very little is known about microorganisms inhabiting these sediments. In the this study, high-throughput sequencing of variable regions of 16S rRNA genes was used to characterize the microbial communities of 47 Kandalaksha Bay sediment samples collected at 10 cm below the bottom surface. Pseudomonadota and Desulfobacterota were the most abundant phyla, comprising together about a half of all prokaryotes. Determination of the dominant genus-level taxon proved impossible. The most represented chemoorganotrophic microorganisms were uncultured Sandaracinaceae (up to 10.8%) and Woeseia (up to 7.5%). Sulfate-reducing bacteria were important community components in the studied upper sediment layers, with uncultured groups SEEP-SRB1 (up to 7.0%) and Sva0081 (up to 5.9%) being the most abundant. In some samples, the genera Sulfurovum (up to 15.5%) and Thiohalophilus (up to 7.0%) involved in the oxidation of sulfur compounds were found to be important components of the community. Among the archaeal ASVs, the genus Nitrosopumilus oxidizing ammonium to nitrite exhibited the highest relative abundance (up to 6.9% of the total number of prokaryotes). Numerous sequences identified as the 16S rRNA gene fragments of chloroplasts were found in the samples, indicating that the rate of organic matter delivery to the upper sediment layers exceeded the rate of its degradation.