Abstract:

During the austral summer of 2016—2017, CH₄, CO₂, and N₂O fluxes and selected environmental variables were measured over tundra marshes on Ardley Island in maritime Antarctica. In the presence of sunlight, a net CH₄ flux of –5.4±4.3 μg·m^–2·h^–1 was measured at the dry tundra site, while net CH4 emissions were detected at the mesic and waterlogged sites. Under sunlight conditions, maximum N₂O flux was –2.6±2.4 μg·m^–2·h^–1, and was measured at the waterlogged site; all sites showed net N₂O consumption. In the total absence of sunlight, all sites showed net CH₄ and N₂O emissions. Light and water enhance CH₄ consumption via aerobic oxidation and promote denitrification and the subsequent formation of N₂O. Under sunlight conditions, all three sites acted as CO₂ sinks. The highest net CO₂ flux and photosynthetic flux occurred at the waterlogged site (–40.1±17.6 mg·m^–2·h^–1 and –91.2±26.5 mg·m^–2·h^–1), while the highest ecosystem respiration rate occurred at the dry tundra site (73.1±17.6 μg·m^–2·h^–1). Favorable temperature and precipitation conditions during the Antarctic summer promote photosynthesis in tundra vegetation, resulting in increased CO2 uptake by marshes. Relationship between time and fluxes of the three greenhouse gases is not statistically significant (P>0.05). However, under the conditions of variable precipitation and temperature, fluctuations in N₂O and CH₄ fluxes are similar to those in CO₂. Results indicate that different light conditions, even those under the same sunlight intensity, have considerable influence on estimates of CH₄ and N₂O fluxes. Relationships between the three greenhouse gases and between the gases and various environmental factors deserve further study.

Key words: Antarctic, tundra marsh, CO₂ fluxes, CH₄ fluxes, N₂O fluxes