Particulate organic carbon (POC) of 161 water samples collected from 8 depths (surface to 1000 m) at 21 stations was measured. The POC concentrations ranged from 154 to 554 ¼g per litre at the surface and decreased in the upper 300 m water column. At greater depths (> 300 m), POC concentrations increased and were similar (145 to 542 ¼g1−1) to those observed at surface. Deep water POC maximum was embedded within the oxygen minimum layer and was also associated with high phosphate-phosphorus. The POC contents increased, whereas oxygen decreased as the distance away from the shore increased. Phytoplankton biomass was a major source of POC. The observed pattern of POC is discussed with respect to some physicochemical and biological factors.