Summertime fluxes of N2O, CH4and CO2from the littoral zone of Lake Daming, East Antarctica: effects of environmental conditions

Abstract Nitrous oxide (N 2 O), methane (CH 4 ) and carbon dioxide (CO 2 ) fluxes were investigated from the algal-rich littoral zone of Lake Daming, East Antarctica during the summers of 2008/09 and 2009/10, using a static chamber technique. High N 2 O emissions occurred in the littoral zone with the mean flux range of 0.19–7.11 μmol N 2 O m -2 h -1 . The mean CH 4 fluxes ranged from 2.51–5.32 μmol CH 4 m -2 h -1 , and they were significantly affected by the lake thermal regime. There were significant differences ( P < 0.05) in CH 4 and N 2 O fluxes under the light and dark conditions, and sunlight greatly increased N 2 O emissions by stimulating the algal photosynthesis, but decreased CH 4 emissions. Overall the littoral zone represented a weak CO 2 sink with the mean flux range of -0.37–0.13 mmol CO 2 m -2 h -1 . The mean ecosystem respiration and photosynthesis rates varied from 0.47–2.90 mmol CO 2 m -2 h -1 and from -0.33 to -2.63 mmol CO 2 m -2 h -1 . The combined global warming potential (GWP) of N 2 O and CH 4 fluxes completely counteracted and surpassed CO 2 uptake by the algal photosynthesis, and high GWP-positive of N 2 O and CH 4 emissions might convert an algal-rich lake site with a net CO 2 uptake into a net radiative forcing source during the ice-free period.