Heterogeneity and photoreactivity of organic carbon from yedoma permafrost and thermokarst influenced aquatic systems in interior Alaska.

Abstract:

Yedoma permafrost soils, with their high thickness, ice content and considerable organic carbon storage are susceptible to abrupt thaw processes. However, their organic carbon pools are not well characterized, making it difficult to identify the impacts of thaw through mobilization to the surficial aquatic environment. In this study, we isolated and characterized organic carbon from lakes and soils of varying thaw and thermokarst activity in the Goldstream Creek watershed in interior AK, a watershed which is underlain by discontinuous yedoma permafrost. Isolates were characterized by solid and liquid state NMR (multiCP-MAS ¹³C and SPR-W5-WATERGATE ¹H), absorbance and fluorescence, as well as photolability. Isolated dissolved organic matter (DOM) varied across water bodies, season sampled, and water extractable organic matter (WEOM) varied among permafrost isolates, in terms of both composition and its photoreactivity. All isolates were photoreactive and photolability varied even among permafrost WEOM isolates. Results suggest shifting influence of permafrost and thaw under different hydrological flow regimes, and heterogeneity of yedoma permafrost, suggesting a complex pattern of response for surficial carbon pools to thaw in the coming years.