Temporal and spatial variations in photosynthetic parameters in the South Sea and East/Japan Sea, Korea

Abstract:

Although the photosynthetic parameters are important factors for phytoplankton ecology and simulation models of ecological dynamics in marine ecosystems, very limited data for temporal and spatial variations in in situ photosynthetic parameters are available in Korean oceans. To obtain the photosynthetic parameters, we measured carbon fixation rates of phytoplankton from six light depths (100, 50, 30, 12, 5, and 1 %) at 2 sampling sites (Hupo-Pohang and Gwangyang bay, Korea) in 2013, using a stable carbon isotope (¹³C) tracer technique. Based on the results from this study, the ranges of α (photosynthetic efficiency), β (strength of the photoinhibition) and μ (growth rate) were 0.06-0.07 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1, 3.90-21.41 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1, and 0.18-0.19 d^-1, respectively at Hupo-Pohang site in the East/Japan Sea. The values of α and β were higher in November (Average ± S.D = 0.07±0.02 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1 and 21.41±36.89 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1, respectvitly) than those (Average ± S.D = 0.06±0.05 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1 and 3.90±5.36 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1, respectively) in September, 2013. In contrast, μ value was higher in September (Average ± S.D = 0.19±0.15 d^-1) than that (Average ± S.D = 0.18±0.14 d^-1) in November. In comparison, the ranges of α, β and μ at Gwangyang bay site in the South Sea were 0.05-0.11 mg C h^-1 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1 , 3.14-93.91 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1 and 0.14-0.34 d^-1, respectively. The parameters of α and μ were highest in June (Average ± S.D = 0.11±0.05 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1, and 0.34±0.27 d^-1), and β was highest value in January (Average ± S.D = 93.31±81.47 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1). The photosynthetic parameters obtained in this study are within the ranges of α (0.08 to 0.26 mg C h^-1 (µmol quanta m^-2 s^-1) ^-1) and μ (0.42 to 1.31 d^-1) in Bedford basin previously reported by Brenda and T. Platt (1983). Overall, the values of α, β and μ were higher in the South Sea than the East/Japan Sea.