DON cycling in the Eastern Canadian Arctic Archipelago from isotopic data

Holly Westbrook, M.Sc. student

The Eastern Canadian Arctic Archipelago (CAA) is a nitrogen limited region with high glacial coverage and relatively little riverine input relative to other Arctic regions. Climate change is expected to drastically alter the input of inorganic nitrogen (N) sources within the next decades with increasing river discharge and melting of permafrost and glacial sheets. In addition to inorganic N, dissolved organic N (DON) could represent a significant source of nutrients for primary producers in Arctic ecosystems, but few DON data for the Arctic region exist. A recent study in the Eurasian coastal Arctic revealed a dynamic DON cycling with riverine DON being consumed as it traveled along the shelves. In this study, we used stable isotopes to investigate DON cycling in the Eastern CAA. We analyzed the d   N of DON for more than 100 surface seawater samples covering the CAA in July-August 2019. We also measured the d   O of seawater to inform about water sources (i.e., riverine or marine). Our data suggest a clear input from riverine or glacial sources with a low d   N in the northern portion of the Eastern CAA . We will interpret our isotopic data to determine DON sources as well as production and consumption processes in the CAA which will help establish a baseline to assess future change in nutrient regime for this climate sensitive region. 

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