USING IN SITU SENSORS TO EXPLORE PATTERNS OF CARBON CYCLING AND METABOLISM IN RIVERS IMPACTED BY AGRICULTURAL AND URBAN LAND USE

Despite decades of research, major gaps remain in our understanding of human impacts on river ecosystems. For southern Alberta, one of Canada’s most heavily impacted agricultural landscapes, riverine metabolism and carbon cycling are not well quantified. We explored sub-hourly trends in pH, pCO₂, temperature, and O₂ using sensor deployments at two locations (Mosquito Creek (MCR) and Little Bow River (LBR)). Both rivers are heavily regulated for irrigation, and we hypothesized that upstream effluent inputs and agricultural impacts would enhance organic matter processing and CO₂ production at our sites.  From spring to fall, we estimated whole-river metabolism (gross primary production, GPP, and ecosystem respiration, ER) and metabolic contributions to CO₂ dynamics. MCR and LBR both had low daily discharge rates (1.15 m³ s^-1 vs. 2.38 m³ s^-1 respectively). Yet we observed large differences in mean net ecosystem production (NEP = GPP-ER), which was more balanced for MCR (-2.07 g O₂ m^-2 d^-1 ) and more heterotrophic for LBR (-12.03 g O₂ m^-2 d^-1). These metabolic differences had important consequences for CO₂ cycling, since mean pCO₂ was lower for MCR (721 ppm) than LBR (1174 ppm). In both cases, mean pCO₂ was well below average values for global rivers. Our preliminary results indicate that while metabolic patterns differ between rivers, the intense flow regulation and other factors may limit the processing of externally-derived carbon and overall CO₂ production in these ecosystems.

Primary Presenter: Ilyanna Janvier, University of Lethbridge (ilyanna.janvier@uleth.ca)

Authors:

Ilyanna Janvier, University of Lethbridge  (ilyanna.janvier@uleth.ca)

Laura Logozzo, University of Lethbridge  (laura.logozzo@uleth.ca)

Xingzi Zhou, University of Lethbridge  (xingzi.zhou@uleth.ca)

Samuel Woodman, University of Lethbridge  (samuel.woodman@uleth.ca)

Erin Hotchkiss, Virginia Polytechnic Institute and State University  (ehotchkiss@vt.edu)

Matthew Bogard, University of Lethbridge  (matthew.bogard@uleth.ca)