Composition and biodegradability of dissolved organic matter in supra-permafrost groundwater and surface waters near Simpson Lagoon, Alaska

Supra-permafrost groundwater (SPGW) is an important source of terrestrial dissolved organic matter (DOM) to the Arctic Ocean, yet few studies have investigated the quality or characteristics of this DOM. We sampled fresh SPGW, run-off, and rivers near Simpson Lagoon, Alaska during spring ice break-up (mid-June), summer open water (late July), and fall freeze-up (late September - early October). We measured dissolved organic carbon (DOC) concentrations in these samples and analyzed the composition of DOM using high-resolution mass spectrometry (Fourier transform ion cyclotron resonance mass spectrometry; FT-ICR MS). To measure biodegradable dissolved organic carbon (BDOC), we conducted an aerobic incubation experiment following the methods suggested by Vonk et al. (2015). Briefly, water samples were incubated at 20C for 28 days to measure DOC loss due to remineralization by in-situ microbial communities.