Circum-arctic biodegradability of fluvial dissolved organic carbon: A meta-analysis

Circum-arctic frozen soils contain twice as much carbon as is currently present as greenhouse gases in the atmosphere. When frozen soils thaw, the carbon becomes available for microbial degradation. This process will generate greenhouse gases which may occur at the thaw site, but also during lateral transport in inland and coastal waters. Aquatic systems are increasingly recognized as reactive transport systems, but are generally not included in quantitative assessments of the magnitude of the permafrost carbon feedback. Carbon fluxes from lateral transport and aquatic gas emission can however be important components of the total watershed carbon budget. In this meta-analysis, part of the Research Coordination Network on Vulnerability of Permafrost Carbon, we assess the biolability of dissolved organic carbon in aquatic systems (soil leachates, streams, lakes, rivers) of the Arctic Ocean watershed, a region that is about 75% underlain by permafrost. We target dissolved organic matter as it is the most important intermediate in the global carbon cycle, fueling microbial metabolism, and it represents the major proportion (~80%) of the total organic carbon flux from Arctic watersheds. We extracted data from 15 existing literature studies. Additionally, we performed a standardized biodegradability experiment in three major Arctic watersheds. In each watershed (Yukon, Kolyma and Mackenzie River) we assessed the biodegradable fraction of the dissolved organic matter in the main river and an additional, watershed-representative, small stream, during multiple occasions in the summer season. By means of spatial data analyses we will present an estimate of aquatic processing of permafrost carbon in the Arctic Ocean watershed.