Dissolved organic carbon production and transport within a constructed fen watershed in the Athabasca Oil Sands Region, Alberta, Canada

Vast areas of wetlands in the Athabasca Oil Sands Region, Alberta, Canada have been disturbed for mining and other resource extraction activities. In recent years, these disturbed areas have become a focus for reclamation activities. To improve our understanding of the biogeochemical cycling of constructed ecosystems, it is important that we study the production of, as well as the inputs and outputs of dissolved organic carbon (DOC) in the system. The aim of our study was to investigate the hydrological DOC fluxes into a constructed fen in 2015 and 2016 (2- and 3-years post-construction respectively), relative to internal DOC production, and to assess the potential importance of each source for DOC export using DOC concentration and quality parameters. Our results show that while runoff added a small amount of DOC in both years, DOC concentration within the fen is driven largely by increased vegetation production, with DOC increasing in the years since construction. The measured quality indices (SUVA(254), E2/E3, FI, HIX, and beta/a) all showed that DOC present in the system is likely more recently produced and plant sourced. There was also little evidence that precipitation and runoff inputs from hillslopes impacted the quality of DOC present in the fen, while DOC export from the fen was minimal. As this constructed wetland continues to mature, it is important that monitoring of DOC continues in order to understand the trajectory of biogeochemical dynamics of the system following vegetation establishment, as well as changes under potential future climatic variations.