Climatic and Ecological Impact of Greenlandic Glacial Outwash Plains

Warming in the Arctic is occurring at an accelerated rate compared to the rest of the world which is partially driven by ecological and climatic feedback loops. Accelerated glacial and ice sheet retreat in Greenland drives increased development of glacial outwash plains, the climatic impact of which remains largely unknown. Receding glaciers uncover new habitats of nutrient poor sediment, formed over centuries from rock eroded by ice. Microbes are capable of colonising this oligotrophic environment which allows subsequent establishment of other organic life, such as plants. This succession event occurs spatially across the outwash plain from the newly exposed sediments by the retreating glacier, forming a deglaciated chronosequence. These chronosequences can be used to study soil development by microbes, which generate organic carbon and nitrogen pools that are essential for the growth of higher plants. Importantly, the effects of microbial colonisation, taxonomic diversity, succession, and functional potential of active taxa on greenhouse gas fluxes in outwash plains is not well understood. To address this knowledge gap, we conducted a study in South Greenland and collected sediment samples and greenhouse gas flux measurements from the Narsarsuaq glacial outwash plain. Sites were sampled along the chronosequence of the outwash plain from glacier to fjord, spanning a range of vegetated and non-vegetated areas where diurnal temperature shifts in topsoil were observed. We implemented static chambers to measure the flux of greenhouse gases in the soil, including carbon dioxide, methane and nitrous oxide, via gas chromatography analysis. Microbial interactions with these greenhouse gases will be explored through genetic approaches, providing insight into the climatic impact of glacial outwash plains. Specifically, microbial community structure and functional potential will be assessed by metagenomic analysis of the sediment samples. Further, the active taxa and functional expression of microbes will be analysed with metatranscriptomics, creating a functional profile of these communities. This genetic data will be coupled with soil physicochemical analysis of total organic carbon, total carbon, nitrogen, nitrite, nitrate, ammonium, particle size, temperature, and pH, to determine abiotic factors influencing microbial dynamics. Incorporating these techniques allows us to characterise the role of microbial communities in the biogeochemical processes of glacial outwash plains and understand the greater climatic impact of these rapidly developing environments.