Lake Vostok is a large lake located 4 km beneath the East Antarctic Ice Sheet that should be supersaturated with dissolved gases in equilibrium with clathrate present in the water column. Here we show that if the age of the lake is such that the lake water mass has been cycled over 30 times then the total dissolved gas equilibrates at about 2.5 liters (STP) of gas per kg of water; high enough to have important implications for drilling into this deep subglacial lake. Different air gases are preferentially incorporated into the clathrate and thus the molar ratios in the water column will reflect the presence of clathrate and indicate a more precise age of the lake. Preferential incorporation of CO2 into the clathrate would result in the clathrate sinking if the carbon input is 1% of the air input and the lake water is fresh water. The redox state of the lake is set by the high oxygen concentration which is 50 times more than air-equilibrated water and may be a severe biological stress.