Transfer of carbon dioxide and methane through the soil‐water‐atmosphere system at Mer Bleue peatland, Canada

Surface waters associated with peatlands, supersaturated with CO 2 and CH 4 with respect to the atmosphere, act as important pathways linking a large and potentially unstable global repository of C to the atmosphere. Understanding the drivers and mechanisms which control C release from peatland systems to the atmosphere will contribute to better management and modelling of terrestrial C pools. We used non‐dispersive infra‐red (NDIR) CO 2 sensors to continuously measure gas concentrations in a beaver pond at Mer Bleue peatland (Canada); measurements were made between July and August 2007. Concentrations of CO 2 in the surface water (10 cm) reached 13 mg C l −1 ( ep CO 2 72), and 26 mg C l −1 ( ep CO 2 133) at depth (60 cm). The study also showed large diurnal fluctuations in dissolved CO 2 which ranged in amplitude from ∼1·6 mg C l −1 at 10 cm to ∼0·2 mg C l −1 at 60 cm depth. CH 4 concentration and supersaturation ( ep CH 4 ) measured using headspace analysis averaged 1·47 mg C l −1 and 3252, respectively; diurnal cycling was also evident in CH 4 concentrations. Mean estimated evasion rates of CO 2 and CH 4 over the summer period were 44·92 ± 7·86 and 0·44 ± 0·25 µg C m −2 s −1 , respectively. Open water at Mer Bleue is a significant summer hotspot for greenhouse gas emissions within the catchment. Our results suggest that CO 2 concentrations during the summer in beaver ponds at Mer Bleue are strongly influenced by biological processes within the water column involving aquatic plants and algae ( in situ photosynthesis and respiration). In terms of carbon cycling, soil‐stream connectivity at this time of year is therefore relatively weak.