Microbial communities, Greenhouse gas flux, stable isotope, and water quality from subarctic streams, Varrio, Finland (2022-2023)

Microbes play a key role in consuming and producing CH4. They harbor functional genes that encode enzymes involved in CH4 oxidation (particulate and soluble CH4 monoxygenases pmoA and mmoX) and methanogenesis (methyl coenzyme M reductase mcrA). The genetic potential for these processes can be studied by quantifying the abundance of the functional gene copies and by analyzing the community composition of CH4-related microbes. However, there is still a lack of knowledge about the ecology and distribution of these microbes within streams, e.g., which habitats hold higher genetic potential and more diverse communities. Our knowledge of the CH4-related microbiome in aquatic plants remains notably limited, particularly in lotic ecosystems. This basic knowledge is needed to understand the role of these microbes on CH4 fluxes from streams.In this study, we investigate the influence of land cover and hydrology on CH4 and CO2 emissions from subarctic streams. The main objectives of this study were to 1) quantify the fluxes and stable isotopic signatures of CH4 and CO2 emitted from two streams located in catchments dominated by either peatland or upland mineral soil, 2) to assess the influence of seasonal and interannual variation on these fluxes, and 3) to investigate the role of environmental factors (e.g., water discharge, meteorology, DOC and nutrient availability) and microbial communities (e.g., the pmoA, mmoX and mcrA genetic potential, diversity and community structure) on stream CH4 and CO2 fluxes.