That reminds me a bit of what's going in at Lake Nyos, Cameroon. Basically, there are two "layers" of water in the lake, and due to the lakebed giving off carb

That reminds me a bit of what's going in at Lake Nyos, Cameroon. Basically, there are two "layers" of water in the lake, and due to the lakebed giving off carbon dioxide the lower layer will become increasingly saturated. When the two layers get mixed due to something like a minor earthquake, huge quantities of carbon dioxide get released - resulting in a massive disaster. The solution here was to essentially just stick a pipe all the way down, so water could flow up and safely release the gas.The interesting part is that this is a self-sustaining process after an initial pumped startup. Something similar might be possible in other lakes, perhaps driven by a temperature difference rather than gas saturation. I doubt it'd generate enough energy to make it economically viable, though.