Browsing by Author "Jensen, Sydney"

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Open Access
Controls of Carbon Dioxide, Methane, and Nitrous Oxide Emissions in Natural and Constructed Agricultural Waterbodies on the Northern Great Plains
(2022-11-21) Jensen, Sydney; Webb, Jackie; Simpson, Gavin; Baulch, Helen Margaret; Finlay, Kerri
Inland waters are hotspots of greenhouse gas (GHG) emissions, and small water bodies are now well known to be particularly active in the production and consumption of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). High variability in physical, chemical, and environmental parameters affect the production of these GHG, but currently the mechanistic underpinnings are unclear, leading to high uncertainty in scaling up these fluxes. Here, we compare the relative magnitudes and controls of emissions of all three major GHG in twenty pairs of natural wetland ponds and constructed reservoirs in Canada’s largest agricultural region. While gaseous fluxes of CO2 and CH4 were comparable between the two waterbody types, CH4 ebullition was greater in wetland ponds. Carbon dioxide levels were associated primarily with metabolic indicators in both water body types, with primary productivity paramount in agricultural reservoirs, and heterotrophic metabolism a stronger correlate in wetland ponds. Methane emissions were positively driven by eutrophication in the reservoirs, while competitive inhibition by sulfur-reducing bacteria may have limited CH4 in both waterbody types. Contrary to expectations, N2O was undersaturated in both water body types, with wetlands a significantly stronger and more widespread N2O sink than were reservoirs. These results support the need for natural and constructed water bodies for regional GHG budgets and identification of GHG processing hotspots.
Open Access
Differential Controls of Greenhouse Gas (CO2, CH4, and N2O) Concentrations in Natural and Constructed Agricultural Waterbodies on the Northern Great Plains
(Wiley-Blackwell, 2023-04-18) Jensen, Sydney
Inland waters are hotspots of greenhouse gas (GHG) cycling, with small water bodies particularly active in the production and consumption of carbon dioxide (CO 2), methane (CH4), and nitrous oxide (N2O). However, wetland ponds are being replaced rapidly by small constructed reservoirs in agricultural regions, yet it is unclear whether these two water body types exhibit similar physical, chemical, and environmental controls of GHG content and fluxes. Here, we compared the content and regulatory mechanisms of all three major GHGs in 20 pairs of natural wetland ponds and constructed reservoirs in Canada's largest agricultural region. Carbon dioxide content was associated primarily with metabolic indicators in both water body types; however, primary production was paramount in reservoirs, and heterotrophic metabolism a stronger correlate in wetland ponds. Methane concentrations were correlated positively with eutrophication of the reservoirs alone, while competitive inhibition by sulfur-reducing bacteria may have limited CH 4 in both waterbody types. Contrary to expectations, N 2O was undersaturated in both water body types, with wetlands being a significantly stronger and more widespread N 2O sink. Varying regulatory processes are attributed to differences in age, depth, morphology, and water-column circulation between water body types. These results suggest that natural and constructed water bodies should be modeled separately in regional GHG budgets.
Open Access
Salinity causes widespread restriction of methane emissions from small inland waters
(Springer Science and Business Media LLC, 2024-01-24) Soued, Cynthia; Bogard, Matthew J.; Finlay, Kerri; Bortolotti, Lauren E.; Leavitt, Peter R; Badiou, Pascal; Knox, Sara H.; Jensen, Sydney; Mueller, Peka; Lee, Sung Ching; Ng, Darian; Wissel, Bjoern; Chan, Ngai Chun; Page, Bryan; Kowal, Paige
AbstractInland waters are one of the largest natural sources of methane (CH4), a potent greenhouse gas, but emissions models and estimates were developed for solute-poor ecosystems and may not apply to salt-rich inland waters. Here we combine field surveys and eddy covariance measurements to show that salinity constrains microbial CH4 cycling through complex mechanisms, restricting aquatic emissions from one of the largest global hardwater regions (the Canadian Prairies). Existing models overestimated CH4 emissions from ponds and wetlands by up to several orders of magnitude, with discrepancies linked to salinity. While not significant for rivers and larger lakes, salinity interacted with organic matter availability to shape CH4 patterns in small lentic habitats. We estimate that excluding salinity leads to overestimation of emissions from small Canadian Prairie waterbodies by at least 81% ( ~ 1 Tg yr−1 CO2 equivalent), a quantity comparable to other major national emissions sources. Our findings are consistent with patterns in other hardwater landscapes, likely leading to an overestimation of global lentic CH4 emissions. Widespread salinization of inland waters may impact CH4 cycling and should be considered in future projections of aquatic emissions.
Open Access
Seasonal variability of CO 2, CH 4 , and N2 O content and fluxes in small agricultural reservoirs of the northern Great Plains.
(Frontiers Media, 2022-10-03) Jensen, Sydney; Webb, Jackie; Simpson, Gavin L.; Baulch, Helen M.; Leavitt, Peter R
Inland waters are important global sources, and occasional sinks, of CO 2 , CH 4, and N 2 O to the atmosphere, but relatively little is known about the contribution of GHGs of constructed waterbodies, particularly small sites in agricultural regions that receive large amounts of nutrients (carbon, nitrogen, phosphorus). Here, we quantify the magnitude and controls of diffusive CO 2 , CH4 , and N 2 O fluxes from 20 agricultural reservoirs on seasonal and diel timescales. All gases exhibited consistent seasonal trends, with CO 2 concentrations highest in spring and fall and lowest in mid-summer, CH 4 highest in mid-summer, and N 2 O elevated in spring following ice-off. No discernible diel trends were observed for GHG content. Analyses of GHG covariance with potential regulatory factors were conducted using generalized additive models (GAMs) that revealed CO 2 concentrations were affected primarily by factors related to benthic respiration, including dissolved oxygen (DO), dissolved inorganic nitrogen (DIN), dissolved organic carbon (DOC), stratification strength, and water source (as δ18 O water ). In contrast, variation in CH 4 content was correlated positively with factors that favoured methanogenesis, and so varied inversely with DO, soluble reactive phosphorus (SRP), and conductivity (a proxy for sulfate content), and positively with DIN, DOC, and temperature. Finally, N 2 O concentrations were driven mainly by variation in reservoir mixing (as buoyancy frequency), and were correlated positively with DO, SRP, and DIN levels and negatively with pH and stratification strength. Estimates of mean CO 2 -eq flux during the open-water period ranged from 5,520 mmol m−2 year 1 (using GAM- predictions) to 10,445 mmol m−2 year−1 (using interpolations of seasonal data) reflecting how extreme values were extrapolated, with true annual flux rates likely falling between these two estimates.