Are there perennial and light-independent microbial processes in superglacial ecosystems? IBERS (DGES 13745)

Life thrives even on the sun-kissed surfaces of glaciers. But does life on ice survive in the darkened depths of Arctic winters and sediments? We know glacier surfaces are home to active microbial ecosystems. We know that in summer these photosynthesis-driven ecosystems fix carbon and darken ice as solar energy is converted to dark organic carbon. As a result, ecosystems on glaciers influence the fate of glaciers in our warming world. Until now, biogeochemists have assumed ecosystems on glaciers are only active when nourished with sunlight and nutrients in liquid meltwater in the brief melting season of summer. This constraint has framed our understanding of glacier surface ecology to the extent that the absence of evidence for active microbial processes on glaciers in winter has been considered evidence of their absence. But we now have year-round data which robustly challenges the assumption life is only active in summer. Our pilot data also reveals methane producers for the first time on ice surfaces. This project therefore tests the simple but powerful idea that glacier surface habitats are perennially active, resulting in unexpected sources of greenhouse gases. Our project proposes to address three interlinked major knowledge gaps in our understanding of glacier ecology. Firstly, we need to know what lives through the winter, secondly, we need to know what lives in thick accumulations of sediments on ice, and finally we need to know how the microbial life forms surviving through darkness influence carbon and nutrient cycles on glaciers. Our project's overall hypothesis is that glacier surfaces host light-independent microbial metabolic activities, thus allowing microbial activities in unexpected conditions with neglected contributions to nutrient cycles and greenhouse gas production. In this project we will go the High Arctic glaciers of Svalbard in every season to compare their microbial communities in the depths of polar night, the cold of the winter, the spring thaw and the height of summer. At each glacier we will collect samples for molecular analyses and measure microbial activities. We will conduct experiments to reveal how the microbes survive in these conditions, and how they interact with the carbon and nutrient cycles of the glaciers. We combine our fieldwork with carefully-controlled incubation experiments in cold labs in the UK, US and Norway. By doing this, we will have a clear picture for the first time of how life survives all seasons on Arctic glaciers and what this means for the ecology of Arctic glaciers as they face an uncertain future in the warming Arctic.