Over a tenth of the Earth is covered by microbially-dominated glacial ecosystems. The microbial activity on glaciers and ice sheets is postulated to have regional, potentially global, impacts on environmental biogeochemical nutrient cycling. Their activity is also believed to affect glacier surface albedo, potentially enhancing the effects of climate change in these environments. However, the magnitude and implications ofthe glacial microbial dynamics are still unknown. This PhD research aimed to elucidate the microbial dynamics within different glacier surface habitats on the Greenland Ice Sheet, together with their impacts on glacier organic matter production, nutrient export and albedo reduction. A variety of original laboratory and field studies were designed to address these aims. Microorganisms on glacier surfaces were found to be responsible for significant amounts of organic matter production, accumulation, recycling and export from glacier surfaces. The microbial communities were shown to be stable throughout a melt season, following a fast community turnover after initial snow melt. They could also be seeded by small amounts of aeolian microorganisms. The organic matter the m icrobes produced and transformed was substantial enough to reduce glacier surface albedo by -16%, equivalent to - 18 Gt yr-I of potential melt increase for the Greenland Ice Sheet, in the current climate. Furthermore, biogeochemical nutrient cycling by glacial microorganisms was successfully applied to fertilising nutrient-deprived sediment, for potential applications in countries struggling with barren soils and potentially for terraforming other planets. The results ofthis body of work thus have significant implications for predicting the impacts of climate change and anthropogenic pollution on glacial environments; future estimates of nutrient export from glaciers and the effects on downstream environments; and even for developing new soil fertilisation techniques for terrestrial and extraterrestrial use.