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Funding:
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The Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project was funded by National Science Foundation grants (0838933, 0838896, 0838941, 0839142, 0839059, 0838885, 0838855, 0838763, 0839107, 0838947, 0838854, 0838764 and 1142123) from the Office of Polar Programs. Partial support was also provided by funds from NSF award 1023233 (B.C.C.), NSF award 1115245 (J.C.P.), the American Association of University Women Dissertation Fellowship (T.J.V.), the NSF’s Graduate Research Fellowship Program (1247192; A.M.A.), the Chilean Fulbright-CONICYT Scholarship (P.S), the Italian National Antarctic Program (C.B.), and fellowships from the NSF’s IGERT Program (0654336) and the Montana Space Grant Consortium (A.B.M.).
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Quality control:
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The flow cytometer (PhytoCyt from Turner Design) calibration was periodically inspected following the manufacturer instructions during the entire work.
Milli-Q as blank control, negative control and background control were also performed. All samples were pre-filtered through 30μm mesh (sterile BD Falcon 12 x 75 mm Tube with Cell Strainer Cap) to eliminate large particles. The threshold levels were used to eliminate the inherent equipment noise floor. To detect heterotrophic bacterial events, threshold levels were set on green fluorescence channel (FL1-H) at 750 and on the forward-scatter channel at 250. To detect phytoplankton events, threshold levels were set on red fluorescence channel (FL4-H) at 625 and on Forward-scatter-H (FCS-H) channel at 250. Standard validation beads (Spherotech 8- and 6-Peaks Validation Beads) were run daily and prior to running samples to validate system fluidics performance and the instrument’s level of sensitivity in detecting events. Milli-Q water was used to wash the SIP and 3 backflushes were performed between samples to prevent carry-over. All control preparations (Milli-Q blanks, background and negative controls) were measured at the same instrument settings than samples. Background controls correspond to 0.2 μm filtered stained sample to recognize the background noise inherent to samples. Negative controls are unstained sample to detect autofluorescent events. Gating strategy was use to excluded the detected background noise and negative events. In addition, serial dilution curves were carried out to verify a linear correlation of both samples.
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