Melting glacier ice surfaces host active microbial communities that enhance glacial melt, contribute to biogeochemical cycling, and nourish downstream ecosystems; but these communities remain poorly characterised. This study shows regionally consistent mean microbial abundance of 10⁴ cells mL⁻¹ in surface meltwaters from ten glaciers across Europe, North America, and Greenland. Microbial abundance is correlated with suspended sediment concentration. The study forecasts that under a medium carbon emission scenario (RCP 4.5), the release of these microbes will deliver 2.9 × 10²² cells yr⁻¹ (0.65 million tonnes yr⁻¹ of cellular carbon) to downstream ecosystems over the next ~80 years.

Ian T. Stevens, Tristram D. L. Irvine-Fynn, Arwyn Edwards, Andrew C. Mitchell, Joseph M. Cook, Philip R. Porter, Tom O. Holt, Matthias Huss, Xavier Fettweis, Brian J. Moorman, Birgit Sattler, Andy J. Hodson