The fluxes of Cd and PO 4 were measured during the summer using a sediment trap moored in Funka Bay. These fluxes were corrected with a phytoplankton decomposition rate constant obtained by a laboratory experiment because of decomposition of organic matter in the trap. The residence times for Cd and PO 4 in the bay were calculated by dividing their standing stocks in the water column by the corrected fluxes, on the assumption that Cd and PO 4 are at steady-state during the summer. The calculated residence times for Cd and PO 4 in the 0–40 m depth interval were 117 and 58 days in 1985, and 124 and 50 days in 1987, respectively. The residence time for Cd was approximately twice as long as that for PO 4. These values were in good accordance with the results previously obtained from the uptake rate constants of Cd and PO 4 in the bay. These results also indicate that the uptake rates of Cd and PO 4 by phytoplankton in the euphotic zone reflect the residence times for these elements.