Carbon Dioxide and Methane Dynamics in a Peatland Headwater Stream: Origins, Processes and Implications

First-order streams flowing through peatlands receive, carry and transform large amounts of organic carbon, methane (CH4) carbon dioxide (CO2) but remain poorly documented. The objectives this study were to (1) identify the origins CO2 CH4 (thereafter C-GHG for greenhouse gases) in a peatland headwater stream, (2) determine environmental factors driving export emissions, (3) quantify losses from system discuss its implications. Data collected eight sampling sites along 3 km boreal stream (Eastern Canada) over growing seasons 2019 2020. studied was oversaturated pCO2 [min: 2044; max: 23,306 µatm] pCH4 [14; 17,614 µatm]. A mass balance model showed that ∼81% in-stream originated porewater seepage while remaining 17% 2% productivity oxidation, respectively. Porewater concluded be primary source CH4. Seasonal dissolved concentrations negatively correlated with water table depth, suggesting an active release carbon-rich peat during base flow. Nevertheless, greater occurred storm flow periods which acted as pulses most being shunted downstream. sum emissions at our site 8.08 gC m-2 y-1 86% released atmosphere 14% exported Our demonstrates act sources precipitation events topography control magnitude fluxes.