Temporal,regional and geochemical drivers of microbial community variation in the melt ponds of the Ross Sea region,Antarctica

To expand the understanding of the poorly described planktonic bacterial communities inhabiting Antarctic meltwater ponds, this study characterized the community composition and identified environmental drivers influencing community structure from a total of 41 meltwater ponds: 37 from the McMurdo Ice Shelf (Bratina Island) and four from a terrestrial locale (Miers Valley) during three austral summers. DNA fingerprinting coupled with in situ pH and conductivity was utilized to select ponds for in-depth nutrient and chemical analysis and high-throughput sequencing of the bacterial 16S rRNA gene V5–V6 hypervariable region. Conductivity was the strongest driver of community structure across all ponds and for all time points; however, other influential factors (pH, climatological, Hg, Fe, and PO₄) were also identified. Unique members of communities (sequences absent in at least one pond) represented a small percentage of total reads but also represented a large proportion of pond biodiversity that was strongly driven by differing environmental variables (Si, B and S). Significant temporal variation in community structure was also identified within the same ponds although major taxa remained present. Miers Valley ponds exhibit greater similarity to Bratina Island ponds rather than between each other, thereby suggesting regional movement of microorganisms. In summary, these data provide the first in-depth investigation of the intra-seasonal and regional variation of the microbial communities inhabiting these ponds and proved that a total of ten cosmopolitan OTUs were the dominant components of ponds throughout all sampling times and locations, their variable relative abundances driving the major dissimilarities in community structure.