UNDERLYING LITHOLOGY AND LEVEL OF DISTURBANCE DEFINES MICROBIAL DIVERSITY AND COMMUNITY COMPOSITION IN HIGH ARCTIC SOILS

Pyrosequencing and qPCR were employed to contrast microbial composition and diversity as a function of geochemical conditions and site history to understand drivers of microbial community structure in high Arctic soil systems. Specifically, 16S rRNA gene libraries were developed for nine sites across the Kongsfjord region (Svalbard) to determine α and β diversity of resident microbial communities in local soils. Seven of the soils were from undisturbed sites, representing a range of lithological conditions due to differential weathering of metamorphic carbonate and aluminosilicate rocks, whereas one soil was from a location with significant historic mining and another was from an organic-rich peatland. All soils were dominated by 10 phyla, accounting for 95 % of all sequences, with the Proteobacteria, Actinobacteria and Chloroflexi being the predominant lineages. Multivariate analysis showed total P, Ca, organic C, and N most influenced variation in overall microbial community composition, although the mining-impacted and peatland sites often were outliers relative to the other sites. For example, N-limited mineral soils were greater in Cyanobacterial sequences, whereas N-rich organic sites were lower. Further, P level significantly correlated with β diversity in Proteobacteria (the dominant phylum across the soils; p < 0.05) in the soils, except the mining-impacted site, which had much lower β diversity than predicted by P level. Finally, significant relationships (p < 0.05) were seen between α diversity estimates (Shannon and Chao) and geochemical proxies for soil mineralogical parameters (Ca and Mg); however, mining-impacted and peatland soils deviated farthest from the means. Overall, regional lithological conditions across Kongsfjord strongly correlated with soil microbial diversity and community composition, except at sites with human disturbance or anomalous sites, like the peatland, which did not reflect the broader Svalbard landscape.