Ongoing global warming particularly effects Arctic ecosystems with increased glacial retreat and associated changes in run-off. However, how aquatic nitrous oxide (N2O) fluxes will change in High Arctic lakes and catchments remains uncertain. As the third most important greenhouse gas and major ozone-depleting substance in the stratosphere, N2O is a crucial parameter in order to understand feedback mechanisms on climate. We will identify N2O and NO3- sources as well as production and consumption processes in lake Revvatnet, streams, glacier run-off and ponds surrounding the Polish research station at Hornsund, Svalbard using state-of-the-art molecular techniques (qPCR) and NO3- and N2O isotopic composition. This project will provide the first estimate of water-to-air transfer of N2O in high Arctic lakes and catchments in Svalbard. Considering that climate change is expected to drastically alter the input of inorganic nitrogen (N) sources, this study represents an important contribution to the understanding of the biogeochemistry of the region and to establish a baseline to assess future change in nutrient regime for this climate sensitive region.