Primary productivity by ¹⁴C method, inorganic carbon estimation using pH and alkalinity, as well as organic carbon in sediment by high temperature combustion of the western Gulf of Thailand were studied in September-Gctober 1995 and October 1996. Primary production was found in the range of 0.20-0.61 gC/m²/day with the high value at the surface and decreasing with depth. However, where there was stratification in the offshore water column, the highest values of primary productivity and chlorophyll a were found near the thermocline level. The northern part of the western Gulf (latitude 11-12°N), primary productivity was higher than the other parts of the Gulf. The average flux of carbon dioxide from the atmosphere into surface water poured the whole study was 3.49 mol/m²/year. The carbon budget calculation, assuming no organic carbon contribution, revealed that dissolved inorganic carbon was exported by physical process to the South China Sea with the rate of 1.27E + 11 mol/year. Organic carbon content in the sediments was in the range of 0.15-1.28% usually with the highest value at the sediment surface and decreasing with depth in the core. Distribution of organic carbon in the surfical sediment appeared to be correlated with depth integrated primary production in the water column except at the station near Phangan Island in the western Gulf where high organic carbon was found, possibly a result of organic transport by water current.
