Methane and Carbon Dioxide Flux from Ponds and Lakes of the Hudson Bay Lowlands

Book excerpt: Methane and carbon dioxide fluxes ponds and lakes in the Hudson Bay Lowland to the atmosphere from were measured from June to October 1990. The study area was located near the town of Moosonee, Ontario (51o 29' N; 80o 27' W). The study area was divided into four different sites; the Coastal Marsh, Coastal Fen, Interior Fen and the Kinosheo Lake Bog. The Kinosheo Lake bog was the furthest inland (114 km inland from the Coastal Marsh). In early July, the average daily rate of methane flux from the ponds in the Kinosheo Lake area was 20 mg CH4/m2/day, increasing to 50 mg CH4/m2/day by the end of the month. The average daily flux of carbon dioxide was 900 mg CO2/m2/day. The Coastal Fen and Interior Fen Ponds exhibited much higher fluxes of both CH4 (averaging 160 mg CH4/m2/day) and CO2 (averaging 9000 mg CO2/m2/day) than were measured at the Kinosheo Lake Bog. At all the sites the flux of CH4 and CO2 were highest in September. Differences between ponds were much greater than the differences on different dates, i.e., ponds with higher rates tended to remain higher and vice versa. All 24 ponds and lakes sampled had concentrations of CH4 and CO2 which were consistently above atmospheric equilibrium and thus were sites of net carbon loss from the Hudson Bay Lowland. Computer modelling suggests that CH4 concentration is controlled by the cfombination of wind driven gas exchange and CH4 oxidation. Carbon dioxide concentrations appear to be controlled by the combined effects of wind driven gas exchange and algal photosynthesis/respiration.