High-Frequency Dynamics of Carbon Dioxide and Methane Fluxes in a Surface Flow Constructed Wetland as Affected by Discharge and Vegetation

English Abstract:

Constructed wetlands (CW) are built to manage runoff and matter fluxes to aquatic ecosystems from agricultural and urban environments. Free-water surface CWs with aquatic vegetation and stilling ponds resemble eutrophic aquatic ecosystems. We have studied fluxes of carbon, nutrients, and suspended solids in a CW at the mouth of an agricultural/residential watershed in Southern Finland. We will present dissolved [CO₂], [CH₄], and [O₂] in in- and out-flow measured at 10 min frequency since December 2012 and fluxes of CO₂ and CH₄ at the air-water interface measured weekly by chambers and bubble collectors in summer 2013. We will test a hypothesis that the photosynthesis of the submerged vegetation cause diurnal variations in dissolved [CO₂], [O₂], and [CH₄], consequently affecting gas fluxes at the air-water surface. We will also analyze the impact of discharge, weather, and vegetation on the seasonal gas flux dynamics in the CW. Continuous data with high temporal resolution of dissolved [CO₂] and [CH₄] can improve our understanding of aquatic metabolism and of the impacts of weather and vegetation on the aquatic C cycling.