Bacterial community pattern along the sediment seafloor of the Arctic fjorden (Kongsfjorden, Svalbard)

The Arctic region has been the focus of increasing attention as an ecosystem that is highly sensitive to changes associated with global warming. Although it was assumed to be vulnerable to changes in climate, a limited number of studies have been conducted on the surface sediment bacteria of Arctic fjorden. This study assessed the diversity and distribution pattern of bacterial communities in eight marine sediments along the seafloor in a high Arctic fjorden (Kongsfjorden, Svalbard). A total of 822 operational taxonomic units (OTUs) were identified by Illumina MiSeq sequencing, targeting the V3–V4 hypervariable regions of the 16S rRNA gene. In these surface marine sediments, more than half of the sequences belonged to the phylum Proteobacteria, followed by Bacteroidetes, Verrucomicrobia, Actinobacteria, Chloroflexi and Lentisphaerae. The bacterial genera Marinicella, Desulfobulbus, Lutimonas, Sulfurovum and clade SEEP-SRB4 were dominant in all samples. Analysis of similarity indicated that bacterial communities were significantly different among the inner, central and outer basins (r2 = 0.5, P = 0.03 < 0.05). Canonical correspondence analysis and permutation tests revealed that location depth (r2 = 0.87, P < 0.01), temperature (r2 = 0.88, P < 0.01) and salinity (r2 = 0.88, P < 0.05) were the most significant factors that correlated with the bacterial communities in the sediments. 28 differentially abundant taxonomic clades in the inner and outer basin with an LDA score higher than 2.0 were found by the LEfSe method. The Spearman correlation heat map revealed different degrees of correlation between most major OTUs and environmental factors, while some clades have an inverse correlation with environmental factors. The spatial patterns of bacterial communities along the Kongsfjorden may offer insight into the ecological responses of prokaryotes to climate change in the Arctic ecosystem, which makes it necessary to continue with monitoring.