Tuomela, N. | bioRxiv Science

bioRxiv2026

Northern palsa and peat ecosystem microbiomes are potentially supported by hydrogen and carbon monoxide metabolism

Northern peatland and permafrost ecosystems are facing rapid changes, with increasing temperatures, permafrost thaw and shifts in hydrology. Characterizing microbial communities and metabolic potential from the soils and associated water bodies is crucial to understanding the changes in biogeochemical cycling in these ecosystems. For this, samples were collected and sequenced from subarctic palsa and peat soils, along with samples from associated thaw ponds and streams. Metagenomics was utilized in describing the microbiome and its metabolic potential in these environments. Palsa soils hosted microbial communities that were distinct from the peatland soils, ponds and stream waters. Soils and their adjacent ponds shared taxa, and peat soils and ponds also shared taxa with the streams, unlike palsa soils which were likely more hydrologically isolated. Based on metabolic marker gene ratio for denitrification [(nirS+nirK)/nosZ], palsa soils had the strongest potential to be a source of nitrous oxide (N2O) out of all the sample types. Marker genes for hydrogen gas (H2) and carbon monoxide (CO) utilization were abundant across soil environments and metagenome assembled genomes, suggesting that trace gas oxidation is likely one of the key energy sources for microbiomes. In the palsa ponds and peat soils pmoA, marker gene for methanotrophy, was the most abundant compared to the other sample types.

microbiology↗

bioRxiv2025

Carbon and microbes from thawing palsas and peats do not reach a wider fluvial system

Climate change is altering the biogeochemical cycling of carbon and nutrients in the northern peatland and permafrost regions, which provide one of the largest terrestrial carbon storages. Lateral transfer of carbon needs to be more widely studied, especially in smaller streams and catchments, as they receive high loading of organic matter and are hotspots of carbon degradation. In this study we combined measurements of dissolved organic matter (DOM) quality and quantity with microbial community data from a small Arctic catchment. Our aim was to understand how the catchment is affected by two sub-catchments, degrading palsa permafrost mire and peatland thawing in spring. The small thaw ponds in the palsa mire were clearly distinct from the rest of the catchment and ponds in the peatland: Palsa ponds had higher DOM concentration, more aromatic DOM and distinctive microbial communities compared to the peatland ponds and the rest of the catchment. DOC export rates from the palsa and peat sites were comparable at the time of sampling, but local DOM processing was higher in the palsa site. We also detected high abundances of ultra-small Patescibacteria. Patescibacteria dominated the microbial community composition in all the sampled waters.

microbiology↗