High Arctic freshwaters as emitters of greenhouse gases

Abstract

Climate change is causing temperatures in the Arctic to rise faster than in any other region of the world. This rapid warming leads, among other effects, to the massive loss of ice masses, development of thermokarst features when permafrost thaws, intensification of the hydrological cycle, and increasing loads of nutrients and organic carbon to surface waters. Freshwaters are highly sensitive to these changes, which affect microbial community composition and diversity. Therefore, these ecosystems are good sentinels to study processes in primary ecological succession related to ecosystem processes such as productivity and greenhouse gas (GHG) emissions. With this study, we aim to contribute to a deeper understanding of the linkages between biogeochemistry and hydrology in High Arctic freshwaters. To this end, we sampled various water sources (e.g., lakes and streams) in two High Arctic catchments (Bayelva and Lovénbreen, in Svalbard in July 2021) for the analysis of GHGs (CH4, CO2, N2O), noble gases (radon-222, argon-40), major ions, stable water isotopes (δD and δ18O) and nutrients (organic C, organic -P and organic -N). We used Ar-corrected gas saturation of each GHG as a proxy of net metabolic changes, while tracers such as stable water isotopes help to disentangle water source contributions. Our first results show that lakes and streams were oversaturated in CO2 as well as N2O but slightly undersaturated in O2, suggesting higher respiration activity than primary production. Our data also indicate a strong oversaturation in CH4 in lakes, but not in streams. Moreover, we used microbial mineralization of organic matter as a proxy for GHG production. We found similar concentrations of total organic C and N in both lakes and streams and significantly higher concentrations of total P in streams than in lakes. This work furthers our knowledge of the current state of High Arctic freshwaters and helps to predict future effects of climate change impacts on GHG evasion.