Particle organic radiocarbon (POCΔ 14 C) of settling particles collected by time-series sediment traps deployed in the Western Pacific Warm Pool (WPWP) was analyzed by accelerator mass spectrometry (AMS). The (POCΔ 14 C) during period 2 (August to October), when mass fluxes were relatively high, was comparable to the Δ 14 C values (80–100‰) in corals from Tarawa (Guilderson et al., 1998). In contrast, low Δ 14 C values of POC were observed during periods 1, 3 and 4. One of the possible processes behind decreasing Δ 14 C values is river water input. Probably during periods 1, 3 and 4 the surface water at Site 1 was under the influence of the South Equatorial Current, flowing toward the west along the coastal line of New Guinea and transporting appreciable amount of solutes and suspended matter to the hemipelagic region.