Precise and Accurate Determination by Infrared Photometry of C02 Dynamics in Marine Ecosystems

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Abstract
Preliminary studies with an ampule analyzing unit and infrared (IR) detector showed that procedures for standardization and determination of total CO2 (.SIGMA.CO2), while often precise, lacked the accuracy required to estimate the net productivity and respiration of aquatic ecosystems during studies in which sampling over diel cycles was used. Scaling down sample and standard volumes to the .mu.l range and the use of a commercial sodium carbonate standard without dilution before and after replicate sample injections gave accurate results as shown by comparison with indirect (pH-alkalinity) .SIGMA.CO2 determinations with a SE of .+-. 3 .mu.mol in the laboratory and .+-. 6 .mu.mol at sea for 8-10 replicates. This was sufficient to detect a diurnal consumption and nocturnal production of CO2 which were inversely correlated with O2 variation in a salt marsh, an estuarine mesocosm and the Caribbean Sea.