Quantifying and characterising organic carbon and microbes in newly developed soils following glacier retreat in northern latitudes

Akhmetkaliyeva, Saule (2023) Quantifying and characterising organic carbon and microbes in newly developed soils following glacier retreat in northern latitudes. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Glacier retreat in northern latitudes expose nutrient rich glacial landscapes that may develop soils and ecosystems via accumulation of soil organic carbon (OC). Accumulation of soil derived OC was investigated in three contrasting glacial systems (Tarfala in Sweden, Vatnajökull ice cap in Iceland and Zackenberg in Greenland) in order to understand the main source of OC in soils and distribution of soil OC along downstream transects from the glacier front. Soil and sediment samples were analysed for OC concentration, bacteriohopanepolyol biomarkers (BHPs) and glycerol dialkyl glycerol tetraethers (GDGTs), groups of membrane lipids that can be used to trace major microbial groups, DNA sequencing of microbes and major elements. Soil and sediment samples from Sweden showed low OC concentrations (0 - 1.08±0.09%), while samples from Iceland (0.01 - 5.24±2.68%) and Greenland (0.01±0.01 - 4.88±3.56%) had higher values. Soils from older moraines showed highest OC concentrations (up to 8.96% in Greenland), while fluvial sediment samples from all study areas had low to no OC. BHPs and GDGTs were rare in fluvial sediments, observed in riverbank soils and most common in moraines. Distribution of soil specific BHPs and the R’soil index suggests soil development in recently deglaciated areas along downstream transects from the glacier front, followed by stabilisation in older soils in Iceland and Greenland. Microbial communities stabilised along transects, quickly adapting to the new environment. Acidobacteria, Actinobacteria, Chloroflexi, Proteobacteria, Planctomycetes and Verrucomicrobia were the most abundant phyla identified in post-glaciated terrains, while candidate phylum AD3 had surprisingly high concentration in samples from Sweden. Linking biomarkers with bacterial community showed that soil marker BHPs in samples from Sweden were mainly produced by Rhodospirillaceae or purple non-sulfur bacteria, while Bradyrhizobiaceae, Hyphomicrobiaceae and Nitrosomonadaceae were responsible for production of soil marker BHPs in Iceland and Greenland. BrGDGTs, indicative of terrestrial OC, were produced by Acidobacteria. Based on these data, it can be concluded that soil and ecosystem development in front of retreating glaciers leads to the build-up of new terrestrial OC stores and future glacier retreat in deglaciating systems in northern latitudes might increase terrestrial OC productivity.