Bacterial community structure of microbial pinnacles in ice-covered Lake Vanda, Antarctica

Abstract

ABSTRACT The McMurdo Dry Valleys are a cold and arid environment with low biomass relative to most ice-free environments. The ice-covered lakes in the valleys, however, provide a refuge for diverse microbial communities where liquid water persists year-round. Within these lakes, benthic microbial assemblages form ornate structures in the absence of burrowing and grazing organisms. In Lake Vanda, the microbial communities create pinnacles with features including tip, web, and ridge ornaments and brown, green, purple, and beige pigmented zones. Bacterial 16S rRNA gene composition differed between lake depths for all sampled features. Within each depth, community composition correlated with the relative distance into the pinnacle and there were also some significant differences between assemblages in certain zones. The bacterial community composition in the zones may reflect how they respond to environmental changes as the mat is buried, altering the internal light environment and affecting 16S rRNA gene assemblages across niches from the surface to the interior.