Some organisms can live without dependence on either oxygen OR light. The result is a whole ecosystem that depends on other inorganic compounds as a source of energy for metabolism. One such location that may be studied occurs at Blood Falls, a lake under the ice that seeps to the surface at the tongue of Taylor Glacier. This enables scientists to study the organisms without actually contacting the lake. This is a big advantage as the material seeping out can’t contaminate the lake, yet scientists may study the organisms that live there. The falls are red from Iron in the water reacting with oxygen on contact with the air.
Here is an article from Wikipedia about Blood Falls
Another article about anoxic waters. Anoxic waters are salt or fresh water completely depleted of oxygen.