Fig. 3. The measured in situ concentrations of dissolved CH4, CO2, N2O, and O2, and temperature in the water columns of non-oxygenated sites (a) A1 and (b) A2 and oxygenated sites (c) B1 and (d) B2 during winter stratification on 10 Mar. 1999. The concentrations in equilibrium with the atmosphere were 3.6 to 4.0 nM for CH4, 22 to 26 µM for CO2, and 14 to 17 nM for N2O at the measured water temperatures. Those CH4 concentrations below the detection limit are indicated with an asterisk