The light-saturated maximum value (P B max ) and initial slope (α) of the photosynthesisirradiance (P-E) curve were examined in a warm streamer, a cold streamer and a warm core ring off the Sanriku area in the subarctic western North Pacific Ocean during an ADEOS/OCTS Sanriku field campaign in early May 1997. Both P B max and α were within the ranges of temperate populations. A regional difference was apparent in P B max : populations in the warm streamer tended to show higher value ranging between 1.92 and 4.74 mgC (mgChl a) -1 h -1 than those in the cold streamer and the warm core ring (1.35-2.87 mgC (mgChl a) -1 h -1 ). A depth variation was also observed in α in both the warm streamer and the warm core ring: shallow populations tended to have lower α than deep populations. The depth variations in both P B max and α resulted in a lower light intensity of the light saturation in a deeper population than that of a shallower one. These depthrelated variations in the P-E parameters were likely a manifestation of "shade-adaptation" of photosynthesis. Photoinhibition was not observed over in situ surface light intensity varying below ca 1600 µmol photon m -2 s -1 . Water-column primary productivity was biooptically estimated to be 233 to 949 mgC m -2 d -1 using vertical distributions of the P-E parameters, chlorophyll a, phytoplankton light absorption and underwater irradiance. Applicability of surface data sets for estimation of water-column productivity is discussed
