Low biodegradability of particulate organic carbon mobilized from thaw slumps on the Peel Plateau, NT, and possible chemosynthesis and sorption effects

Abstract. Upon thaw, permafrost carbon entering streams may be mineralized into CO2 or re-sequestered into sediments. The balance between these processes is an important uncertainty in the permafrost-carbon-climate feedback. Warming and wetting in the western Canadian Arctic are accelerating thaw-driven mass wasting by permafrost thaw slumps, increasing particulate organic carbon (POC) delivered to headwater streams by orders of magnitude. Using aerobic incubations of POC from streams affected by thaw slumps we find that slump-mobilized POC undergoes minimal (~4 %) oxidation over a 1-month period and may be predominantly destined for sediment deposition. Mobilization of mineral-rich tills in this region may also protect carbon from mineralization via adsorption to minerals and promote inorganic carbon sequestration via chemolithoautotrophic processes. Region-specific assessments of permafrost carbon fates and inquiries beyond organic carbon decomposition are needed to constrain drivers of carbon cycling and climate feedbacks within stream networks affected by permafrost thaw.