Exploring Ecometabolomics and Metabolomic Diversity in Response to Permafrost Thaw in Northern Sweden

Climate change is significantly affecting the equilibrium of peatlands, large C deposits that are at risk of becoming C sources. The Stordalen Mire, a thawing peat plateau in Northern Sweden, has been recently studied because it comprises characteristic habitats along the thaw gradient; Palsa (intact), Bog (partially thawed) and Fen (totally thawed). Altered climate drivers have led to changes at different scales on the peat plateau, such as shifts in vegetation, microbial community, soil organic matter composition all of which contributed to increased greenhouse production. Metabolomics provides an opportunity to detect the key molecules underlyings organism responses to abiotic environmental changes and biotic-abiotic interactions. Thus, understanding how climate and other abiotic drivers can influence metabolite assembly and metabolic pathways in organisms is critical to predict potential changes on the ecosystem processes in thawing permafrost peatlands. Water-soluble metabolites from a total of 112 samples, collected from peat (85) and porewater (27) at different depths , between June and August of 2011 and 2012 were analyzed using a 12 Tesla Bruker FT-ICR mass spectrometer. Meta-community ecology metrics were then used to analyze the FT-ICR data where metabolites were grouped based on class composition to identify the principal ecological drivers within each habitat. Furthermore, beta diversity index (NTI) was correlated with geochemical data collected from porewater and peat using Mantel test. Ordination using beta-diversity metrics showed a great influence of the habitat in sample clustering and NTI analysis indicated that deterministic processes dominated the metabolites assemblages in both peat and porewater. Analysis within habitats found that depth significantly influenced metabolite assembly in palsa habitat while, assemblages in bog seemed to be more influenced by seasonal factors. Moreover, analysis of the grouped metabolites showed that the assembly of each class of metabolites was affected differently. This study highlights the differences of metabolite assembly at different spatiotemporal scales in a thawing permafrost peatland and how changes in metabolite assembly can be related with environmental and biotic factors.