Summer 2016 Inuvik, Canada, seasonally ice-covered permaforst lake water and sediment microbial communities

Permafrost warming may lead to the release of methane and carbon into Arctic aquatic systems, but the role of microbial communities in cycling methane in these systems is poorly known. To examine this, six seasonally ice-covered permafrost lakes in the Mackenzie River delta, Northwest Territories, Canada (lakes 56, 87, 129, 278, 280, and 520) were sampled at five different time points across the ice thaw-to-summer period in 2016. These lakes varied in connectivity to the Mackenzie River delta and in carbon quality. In addition, three of these lakes (L56, L129, and L520) were sampled for a 2-day incubation experiment to examine rates of methane cycling, by comparing methane levels in unamended control samples versus samples amended with nutrients, bromoethanosulfonate (an inhibitor of methane production), and a combination of the two substrates, and microbial communities were examined before and after the incubation. From the water samples, tens of milliliters of water were filtered through a 0.2-micron mesh filter, and bulk community DNA was extracted with a MOBIO PowerSoil DNA Isolation Kit (from sediment samples, bulk community DNA was extracted from roughly 0.5 g sediment). The V4-V6 hypervariable region of the 16S rRNA gene was Illumina sequenced using the Earth Microbiome Project primer sequences.