text: Measurements of primary productivity in the ocean can be made using this ratio. The concentration of oxygen dissolved in seawater varies according to biological processes (photosynthesis and respiration) as well as physical processes (air-sea gas exchange, temperature and pressure changes, lateral mixing and vertical diffusion). Argon concentrations, by contrast, vary only by physical processes.
  This technique was first used by Craig and Hayward (1987) when they separated oxygen supersaturations into a biological and a physical component.  This O/Ar supersaturation can be defined as
  ∆(O/Ar)=(c(O )/c(Ar)) / (c(O)/(c(Ar)))  -1
  where (∆O)/Ar is the difference between O production via photosynthesis and removal via respiration, c is the concentration of dissolved gas and c is the saturated concentration of the gas in water at a specific temperature, salinity and pressure.
  Oxygen and argon concentrations can be compared using samples from water systems aboard ships using either a membrane inlet mass spectrometer (MIMS) or an equilibrator inlet mass spectrometer (EIMS).   The measurements can then be used in conjunction with air-sea gas exchange values to calculate biologically induced air-sea O fluxes and net community production.