Spatial and temporal variation in greenhouse gas emissions from two open water prairie wetlands

Abstract

Prairie wetlands provide valuable habitat for waterfowl and wildlife and buffer the impacts of upland land uses. Their contribution to Canada’s greenhouse gas inventory is poorly understood. The purpose of this study was to compare the spatial and temporal variation in nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) emissions from Pond 1 at the St. Denis Wildlife Management Area, Saskatchewan and the Deep Crop Wetland (DCW) at the Manitoba Zero Tillage Research Association farm, Manitoba. Nitrous oxide flux was low on all measurements days: at Pond 1 flux ranged from -1.47 to 6.01 ng N2O-N m-2 s-1 in 2004 and -6.98 to 5.74 ng N2O-N m-2 s-1 in 2005 and flux from the DCW never exceeded 2.50 ng N2O-N m-2 s-1 in 2005. Methane flux from Pond 1 was substantially higher in 2005 (-469.10 to 3776.08 µmol CH4 m-2 d-1) than in 2004 (-251.55 to 191.55 µmol CH4 m-2 d-1). This increase in methane from Pond 1 followed a major increase in water volume in 2005 after snowmelt. Methane flux in 2005 from the open water and riparian sampling points at the DCW ranged from -13.64 to 110.47 µmol CH4 m-2 d-1 and -4.51 to 40.23 µmol CH4 m-2 d-1, respectively. Carbon dioxide flux from Pond 1 and the DCW in 2005 were very similar: open water flux ranged from -96.42 to 95.42 mmol CO2 m-2 d-1 at Pond 1 and 3.21 to 38.94 mmol CO2 m-2 d-1 at the DCW. Despite the similarity in CO2 flux, the DCW had 10- to 15-fold higher levels of macrophytes, phytoplankton and metaphyton biomass and similar levels of periphyton to Pond 1 in 2005. These biomass differences were not, however, reflected in the CO2 or CH4 flux. Pond 1 and the DCW were net sources for greenhouse gases but contributed less greenhouse gas than reports from other aquatic systems.