Comparison of bacterial and diatom diversity patterns from waterbodies across two Antarctic Peninsula island groups

Antarctic waterbodies are biodiversity hotspots, although few studies have investigated how their microbial diversity is distributed across space. Hypothesizing that bacteria and diatoms should differ in their distributions due to unequal dispersal capacities, we here co-characterized their communities from the sediments of fifteen waterbodies across the South Shetland and James Ross archipelagos using 16S rRNA amplicon sequencing (bacterial amplicon sequence variants, ASVs) and microscopy (diatom morphotypes). We found that only bacterial community structure significantly differed across island groups, and no significant differences in alpha diversity were observed for either microbial group. Interestingly, the proportion of taxa shared between island groups was identical for both bacteria and diatoms (37 percent of all ASVs and morphotypes), and these “widespread” taxa also had the greatest relative abundances. The remaining 63 percent were unique to one island group, and of these, 34 percent of ASVs and 38 percent of morphotypes were only found in one waterbody. Though these results overall suggest that diatoms and bacteria share similar distributional patterns, and potentially dispersal capacities, future research should aim to reconcile differences in taxonomic resolution and expand the spatial representation of sampled waterbodies. Nonetheless, this work improves our understanding of Antarctic microbial biogeography and has important implications for regional conservation and management efforts.