IMIS

A core was collected from the center of each hole using a SIPRE corer. The core was removed and stored in a Ziploc bag that had been triple-rinsed with deionized water. For the samples in which meltwater was present at the time of sampling, the ice lid was removed with the SIPRE corer, and then a water sample was pumped out using a hand powered vacuum pump. A sample of sediment was removed and stored in a triple-rinsed Ziploc bag. On return to the eld laboratory, samples were stored at –20◦C until processing up to 30 days later. Samples were eventually allowed to melt out in the collection bags and water samples were drawn off using syringes, leaving the sediment behind.
Study Extent: Nineteen cryoconite holes on glaciers in Taylor Valley (McMurdo Dry Valleys, Antarctica) were sampled between 15 December 2007 and 4 January 2008.
Method step description:

1. All cryoconite samples were stored frozen at –70◦C to minimize DNA degradation. Between 25 April 2016 and 2 May 2016, the frozen cryoconite sediments were thawed at room temperature and 0.4 g was processed for DNA extraction from each technical replicate separately (47 total from 19 samples) using PowerSoil DNA Isolation Kits (MoBio Inc., Carlsbad, CA, USA), according to the manufacture’s protocol. Extracted genomic DNA was amplified in triplicate using 16S (515f-806r primers) and 18S (1391f-EukBr primers) SSU ribosomal gene markers. Amplified DNA was pooled and normalized to equimolar concentrations using SequalPrep Normalization Plate Kits (Invitrogen), and sequenced using the Illumina MiSeq V2 (2 × 250 bp chemistry) at the BioFrontiers Sequencing Core Facility at the University of Colorado at Boulder.