This study investigates the global responses of microbial metabolism in glacier-fed streams (GFSs) to glacier shrinkage. By analyzing 154 GFSs sampled across major mountain ranges, the research reveals that these ecosystems and their benthic microbiomes are generally carbon and phosphorus limited. Threshold elemental ratios and low carbon use efficiencies (median: 0.15) from extracellular enzymatic activities support this conclusion. Space-for-time substitution analyses suggest that glacier shrinkage will increase primary production in GFSs, relieving carbon limitation. Additionally, increasing streamwater temperature is expected to stimulate microbial growth (temperature sensitivity: 0.62 eV). However, elevated phosphorus demands and reduced inputs from subglacial sources may intensify phosphorus limitation as glaciers shrink. The study highlights a "green transition" towards autotrophy in GFSs, with shifts in microbial energetics and potential broader impacts on ecosystem functioning.This study investigates the global responses of microbial metabolism in glacier-fed streams (GFSs) to glacier shrinkage. By analyzing 154 GFSs sampled across major mountain ranges, the research reveals that these ecosystems and their benthic microbiomes are generally carbon and phosphorus limited. Threshold elemental ratios and low carbon use efficiencies (median: 0.15) from extracellular enzymatic activities support this conclusion. Space-for-time substitution analyses suggest that glacier shrinkage will increase primary production in GFSs, relieving carbon limitation. Additionally, increasing streamwater temperature is expected to stimulate microbial growth (temperature sensitivity: 0.62 eV). However, elevated phosphorus demands and reduced inputs from subglacial sources may intensify phosphorus limitation as glaciers shrink. The study highlights a "green transition" towards autotrophy in GFSs, with shifts in microbial energetics and potential broader impacts on ecosystem functioning.