Under the sea (ice): Concentration, composition, and bioavailability of dissolved organic carbon

The Arctic region plays a key role in the global carbon cycle. The recent decline in sea ice is a major change that directly impacts organic carbon cycling. Our understanding of the sinks of organic carbon in the region is constrained by the challenge of sampling an ice-covered area. Here, we sampled seawater beneath sea ice and defined temporal and spatial variability in dissolved organic carbon (DOC) concentrations and the amount of bioavailable dissolved organic carbon (BDOC). We then used benzoyl chloride derivatization to capture metabolites, known compounds that play a key role in biological processes, to identify compounds significantly correlated with BDOC. This molecular level information on carbon cycling provides the foundation for understanding the conversion of organic carbon into inorganic forms in the Arctic.