Cryoconite cultivation samples
To identify the active carbon fixation microorganisms from the complex cryoconite microbial community, the DNA-SIP methods were applied with samples collected from Longxiazailongba Glacier. We thoroughly mixed 160g of sediment sample with 320 mL sterilized ultrapure water. The 13C-labeled sodium bicarbonate (NaHCO3) was added into slurries and incubated in the light at 15C. Destructive sampling was performed at three time points (20, 40, and 60 days) to obtain sufficient 20C-labeled DNA for microbial analyses.