| Summary: | High-latitude, coastal wetland biogeochemistry is dynamic in response to climate change, and yet we do not understand, and thus cannot fully predict, how crucial aspects of these systems will change in the future. Temperatures in the Northern Hemisphere have disproportionately increased 4° Celsius (C) in 30 years causing the rate of deglaciation to increase significantly in global high-latitude river deltas. This will have a prolonged effect on local microbiome metabolism and biodiversity of the subsurface, influencing solid, liquid, and gaseous compounds in the system. Using sediment geochemical analyses, autonomous sampling techniques, and 16S rRNA (Ribosomal ribonucleic acid) gene sequencing, we have identified key processes that occur in the Copper River Delta, AK (Alaska), a model system to study high-latitude watersheds during rapid climate change. We calculated carbon accumulation rates upwards of 520 ± 60 grams (g) C per meter squared per year (m-2 yr-1) in outwash pond sediments nearest to the glaciers, which co-occurred with pronounced suboxic peaks in Iron (Fe) (III) and Manganese (Mn) (II). Sediment microbial communities across the outwash ponds are structured on the basis of total iron and manganese concentrations, proximity to glaciers, and organic matter content. Additionally, we revealed no methane accumulation in the ponds during ice-cover, despite high organic matter content. High-latitude wetland ecosystems are not only influenced by the changing climate, but also have the potential to impact carbon cycling considering high carbon burial rates. These findings show the importance of understanding changing biogeochemical processes in high-latitude wetlands, as they have the potential to influence carbon cycling.
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