DON Cycling in the Eastern Canadian Arctic Archipelago from Isotopic Data

Abstract:

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 δ¹⁵N of DON for more than 100 surface seawater samples covering the CAA in July-August 2019. We also measured the δ¹⁸O of seawater to inform about water sources (i.e., riverine or marine). Our data suggest an input from freshwater sources with a low δ¹⁵N in Nares Strait, which is surrounded by glaciers such as the Peterman, Humboldt, and Eugenie’s Sister glaciers, as well as various rivers. 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.