Photosynthesis-irradiance relationship of phytoplankton and primary production in the vicinity of kuroshio warm core ring in spring

• Main Authors: Ken Furuya, Osamu Hasegawa, Takashi Yoshikawa, Satoru Taguchi
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1998
• Subjects: Pacific; Subarctic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1052.6040; http://oceanologia.ens.uabc.mx/%7Eadriana/Biooptica/index_files/Furuya%20et%20al_98_P-E.pdf

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.