Ross Sea Surface Water Metaproteomics

We sampled the microbial community at the sea ice edge in McMurdo Sound, Ross Sea at the same location (-77.62S, 165.41E) for four weeks (as described in Wu et al 2019, Nat. Comms.). We had four sampling dates corresponding to weeks 1 to 4: December 28 2014, January 6, 15, and 22 2015. Large volumes of water (150--250 L) were filtered from 1 m depth at the sea ice edge, and passed through three filters sequentially (3.0, 0.8, and 0.1 um, each 293 mm Supor filters). Filters with collected biomass were then placed in tubes with a sucrose-based preservative buffer (20 mM EDTA, 400 mM NaCl, 0.75 M sucrose, 50 mM Tris-HCl, pH 8.0) and stored at -80 C until sample processing. We extracted proteins after buffer exchange into a 3\% SDS solution as previously described Wu et al 2019, Nat. Comms.