Summer methane ebullition from a headwater catchment in Northeastern Siberia

Abstract

Streams and rivers are active processors of terrestrial carbon and significant sources of carbon dioxide (CO 2) and methane (CH 4) to the atmosphere. Recent studies suggest that ebullition may represent a sizable yet overlooked component of the total CH 4 flux from these systems; however, there are no published CH4 ebullition estimates for streams or rivers in subarctic or arctic biomes, regions that store vast quantities of vulnerable, old organic carbon in permafrost soils. We quantified CH 4 ebullition from headwater streams in a small arctic watershed in Northeastern Siberia. Ebullitive emissions were 0.64 mmol m -2 d -1, which is lower than the global average but approximately 2 times greater than the pan-arctic diffusive CH 4 flux estimate reported in a recent synthesis of global freshwater CH 4 emissions. The high CO 2 :CH 4 of sediment bubbles (0.52) suggests that methane emissions may currently be constrained by resource competition between methanogens and microbes using more efficient metabolic strategies. Furthermore, the magnitude and frequency of ebullition events were greater as temperatures increased, suggesting that ebullition from streams could become a more prominent component of the regional CH 4 flux in a warmer future.