Determination of Amino Acid Production Rate of a Marine Phytoplankton Population with13Cand Gas Chromatography-Mass Spectrometry

Combined13Cand gas chromatography-mass spectrometry (GC-MS) were applied to determine the rate of amino acid production of marine phytoplankton populations. The accuracy of the estimate of the13Cratio in each amino acid using the relative intensity of isotope peaks was in investigated with13C-enriched amino acid standards. Production rates of 12 amino acids of a natural phytoplankton population were determined. The gross amino acid composition of photosynthetic products is generally comparable with previous reports. Production of amino acid at night was confirmed by the increase in13Catom%; glucose appeared to supply carbon for amino acid production at night. The ratio of carbon: amino acid nitrogen in photosynthetic products showed a marked diurnal change, due mainly to the loss of glucose carbon at night and the continuing uptake of nitrogen.