Temporal and spatial variations of nitrous oxide fluxes from the littoral zones of three alga-rich lakes in coastal Antarctica

Nitrous oxide (N2O) fluxes across air–water interface were investigated in the littoral zones of three alga-rich lakes (Lake Mochou, Lake Tuanjie and Lake Daming) in east Antarctica during the summers of 2007/2008 and 2008/2009. In the littoral zones of these three lakes, the mean N2O fluxes were 3.1 ± 6.7 μgN2O–N m−2 h−1, 2.5 ± 2.8 μgN2O–N m−2 h−1 and 7.2 ± 6.9 μgN2O–N m−2 h−1, respectively. The fluxes showed a large temporal and spatial variation in lake littoral zones. On the whole, lake littoral zones were the emission sources for atmospheric N2O although negative fluxes occurred on most of the observation sites. The mean flux significantly correlated with NO3−–N concentration in the sediments at each site, suggesting that spatial variations of N2O fluxes have a connection with NO3−–N concentration. The seasonal pattern of the flux was positively related to daily radiation and air temperature and negatively to water depth, indicating that these factors and alga activity had an important effect on N2O emissions. The summertime N2O budget across air–water interface was estimated to be 6.7 mg N2O–N m−2, 5.4 mg N2O–N m−2 and 15.6 mg N2O–N m−2 from the littoral zones of Lake Mochou, Lake Tuanjie and Lake Daming, respectively. Our results indicated that lake littoral N2O emissions could have a regional importance in coastal Antarctica.