The microbial methane "filter" in the Arctic: resilience and response to climate change.

Increases in the atmospheric content of greenhouse gases (GHG) are one of the major challenges of the 21st century. Soil microorganisms are key players for both production and consumption of greenhouse gases including methane (CH4). Methane, the product from a cascade of microbial metabolic processes involved in the degradation of organic carbon, is a strong greenhouse gas and increased amounts in the atmosphere can have dramatic effects. Vast amounts of organic carbon mainly from plants are stored in Arctic ecosystems. It represents twice the amount of carbon in the atmosphere and a large potential for increased GHG emission caused by climate change and melting of permafrost. Increased emissions that lead to increased temperature in the atmosphere will speed up the greenhouse effect. However, methane oxidizing bacteria (MOB) in the soil consumes methane for life and growth, and may thus provide a key role in a future global warming scenario, by counteracting the emission of methane to the atmosphere. In the project, we studied the active frost-free soil layer over the permafrost, in which microbes produce and consume methane during the Arctic summer. The balance between production and consumption is affected by factors in the environment such as water, acidity, temperature and vegetation. Arctic wetlands are exposed to large grazing pressure during the summer, especially from geese. Our results show that after the removal of grazing animals by fences, the vegetation changes towards vascular plants, increased root biomass, and a drier more oxygen rich soil. As a result, less methane is produced in the soil. Multiple closely related strains of methane oxidising bacteria within the genus Methylobacter are present in the system. Correlating with the changes in oxygen and methane availability, we observed changes in the activity of the Methylobacter strains. Under both grazed and non-grazed conditions, little methane escaped to the atmosphere. In summary, this study shows that grazing leads to a higher water table and greater production of methane. However, the flexible and active microbial community that make up the biological filter for methane, responds to the changed conditions. They are able to remove methane before it is released into the atmosphere by altered activity of key members. The project has benefited from good infrastructure related to field studies and collection of samples in Ny-Ålesund, Svalbard. The project has had a complementary and active cooperation with Dr. Svetlana Dedysh, Moscow, Russia. In Russia, studies have been carried out to study the effects of reindeer grazing in areas with lichen. This is a sensitive ecosystem with a thin layer of soil where grazing had a dramatic effect as the methane oxidizing bacteria disappeared. These studies will be continued together with Dr. Dedysh and include additional northern reindeer grazing areas. The collaboration on basic studies of isolated bacteria from the environment and their genetic composition will also continue. During the project, we have benefited from complementary knowledge and infrastructure and all publications from the project are a result of this.

Microorganisms are key players both for the production and consumption of greenhouse gases (GHG) derived from a cascade of metabolic processes. The northern terrestrial hemisphere represents a stock of organic carbon and a large potential for increased GH G emission caused by climate change and melting of permafrost. Methane oxidizing bacteria (MOB) is the biological filter for the GHG methane (CH4), a final product from degradation of organic carbon in aquatic, terrestrial and gut environments. The perf ormance and the robustness of the methane oxidizing bacteria exposed to these changes will be decisive for the amount of methane emitted from terrestrial ecosystems. Few MOB species are present in Arctic peat soil and their performance and resilience in a changing climate are decisive for the efficiency of the biological soil CH4 filter. With our platform in the Arctic and Sub-Arctic ecosystems including detailed in situ community data as well as representative MOB species in culture, the project will imp rove our knowledge about these ecosystem and how the GHG budget of these vulnerable systems respond to climate change and emissions of GHG. The project is based on active collaboration with a very competent Russian microbiologist Dr. Svetlana N. Dedysh an d involves a young scientific group of people including researchers, postdoc and PhDs. An important strategic goal is to establish new and binding collaboration with Russia. The project will by this meet the NORRUSS objectives addressing improved knowled ge of climate change in the Arctic and the dynamics of climatically relevant gases in the environment. In addition the project can be expected to provide needed data in microbial ecology to climate models.