An important part of the McMurdo Long Term Ecological Research (LTER) is monitoring of spatial and temporal patterns, and processes that control net primary production (carbon dynamics) in perennial ice-covered lakes. One of the primary losses of carbon fixed by phytoplankton is through respiration, directly by the phytoplankton themselves and secondarily through the metabolic contributions of heterotrophic organisms such as bacterioplankton and protozoa. The coupling of low metabolic activity and supersaturated gases in the water column prohibits a direct measurement of respiration.