[A-OS19] Marine ecosystems and biogeochemical cycles: theory, observation and modeling

[AOS19-12] Impact of the deviation of phytoplankton stoichiometry from Redfield ratio on global oceanic net primary production

*Yoshio Masuda¹, Yasuhiro Yamanaka¹, Takafumi Hirata², Hideyuki Nakano³ (1.Graduate School of Environmental Earth Science, Hokkaido University, 2.Arctic Research Center, Hokkaido University, 3.Meteorological Research Institute)

Keywords:global net primary production, CN ratio, OGCM

The deviation of the carbon to nitrogen ratio (C:N) of oceanic phytoplankton from Redfield ratio is well known in field observations; however almost all marine ecosystem models are based on Redfield ratio. Incubation experiments show that C:N increases with an increase in the chlorophyll a to carbon ratio (chl:C) of phytoplankton. Recently developed FlexPFT (Flexible phytoplankton Functional Type) model proposed in Smith et al. (2016) can naturally represent the observed relation between chl:C and C:N. We introduced the FlexPFT model into a 3D ecosystem model combined with an OGCM (Oceanic General Circulation Model). We found that the global oceanic net primary production in a variable C:N case is 1.5 times larger than that in the fixed Redfield C:N case. Higher C:N in equatorial regions mainly contributes to the increase in global primary production.