Local-scale variation of soil bacterial communities in ice-free regions of maritime Antarctica

The majority of biogeographic studies in Antarctic terrestrial ecosystems have focused on macroscopic eukaryote taxa. In contrast, microbial taxa have been almost neglected or examined without sufficient spatial coverage. Here, we examined the spatial distribution of soil bacterial communities and their relation to local environmental gradients in ice-free regions of the maritime Antarctic. Soils in this region were dominated by Actinobacteria and Proteobacteria, which are typically found in Antarctic soils. Notably, candidate divisions AD3 and WPS-2, which rarely occur in other biomes, were found in high abundance in acidic surface soils. Soil pH and total organic carbon (TOC) were the primary drivers of the bacterial community structure and various geochemical variables also played important roles in structuring bacterial community composition. Bacterial communities were significantly correlated to measured environmental variables, most of which are spatially structured at the local spatial scale (0.5–8 km). This suggests that spatial heterogeneity of environmental factors is an important driver of shifts in bacterial communities. Although various sets of environmental variables were related to bacterial communities, a large proportion of community variation remained unexplained. This indicates that bacterial communities in Antarctic soils may be governed by other biotic or abiotic factors which are not typically measured in other biome studies.