Global warming is melting many of Earth's glaciers, increasing the production of meltwater as the glaciers expire. In the worst-case scenario, up to 85% of glaciers will be lost by 2100, which will then mean the production of meltwater will decline drastically. About a billion people depend on rivers fed by glacier meltwater for water, and nutrients in glacial meltwater fertilize crucial ecosystems. This glacial meltwater contains bacteria and their products. We have found some of these products are made to protect bacteria against their viruses, and have proof that these same products have a second job in dissolving nutrients from rocks. Earlier research tell us the meltwater bacteria, their products and the nutrients are critical for important ecosystems in the land and sea fed by glacier meltwater. But we do not know how many of these three things will be released as the glaciers die, how they will interact and what this change in the supply of bacteria, products and nutrients will mean for ecosystems fed by glaciers that will disintegrate this century. Our proposal aims to address these three gaps in our knowledge. In this project we will go to valley glaciers on Svalbard in the High Arctic, in Austria in the European Alps, and Livingston Island at the tip of the rapidly warming Antarctic Peninsula to see how microbes and their products are released from glaciers. At each location we will collect samples from the glacier surface which will tell us how the microbes grow in the ice surface and how they are released. We will conduct experiments to reveal how the "arms race" between microbes and their viruses affects the delivery of microbes, their products and nutrients in the meltwater. We will also sequence the DNA of microbes living in the ice surface and meltwater to see who is living in this very large, but poorly understood and endangered habitat. We will use our fieldwork and lab analyses to inform models of how glaciers release their microbes, and what this means for downstream habitats. By doing this we will have a clear picture for the first time of how the loss of glaciers will release microbes, and what those organisms may do as they are washed out to important environments downstream of the glaciers.