The Study Of Phytoplankton Sinking Rate In The Yellow Sea And Bohai Sea

Phytoplankton sinking rate in the Yellow Sea and Bohai Sea was studied during three curise carried out in autumn 2014, summer 2015 and winter 2016 based on the National Natural Science Foundation of China. These studies would provide useful insight into the process of carbon cyclig in this area.Phytoplankton sinking rates in the Yellow Sea and Bohai Sea were studied with SETCOL method, and the sinking rate of dominant phytoplankton taxa was calculated, and the phytoplankton carbon sedimentation was extimated. Phytoplankton siking rate in summer 2015 was the highest, following autumn 2014 and winter 2015. Phytoplankton sinking rate in the Yellow Sea and Bohai Sea during autumn 2014 was between -0.26 m d-1 and 2.12 m d-1,with the average of 0.35±0.09 m d-1. Phytoplankton sinking rate in the Yellow Sea and Bohai Sea during summer 2015 was ranged from -0.19 m d-1 and 1.33 m d-1, with the average of 0.45±0.10 m d-1. Phytoplankton sinking rate in the Yellow Sea and Bohai Sea during winter 2015 was between 0.01 m d-1 and 1.49 m d-1, with the average of 0.63±0.12 m d-1.Correlation analysis revealed that phytoplankton sinking rates correlated with environmental parameters such as PO43- and NO2- in autumn 2014, temperature, salinity and NO2- in summer 2015, and only temperature in winter 2015.Utermohl method was used as the standard method to study phytoplankton community here. Phytoplankton community was mainly composed of diatoms and dinoflagellates in the survey area during the three cruises. In autumn 2014 and winter 2015, phytoplankton community was mainly composed of diatoms. In summer 2015, phytoplankton community was mainly composed of diatoms and dinoflagellates. Correlation analysis revealed that the dominant phytoplankton taxa sinking rates correlated greatly with its ESD in autumn 2014 while this phenomenon was not obvious in summer and winter 2015. Phytoplankton sinking flux in summer 2015 was the higest, following with autumn 2014 and winter 2015.Phytoplankton sinking flux in the Yellow Sea and Bohai Sea was higher than that in the South Yellow Sea in the three cruises,and all showed a trend of nearshore above offshore.Phytoplankton carbon flux in the Yellow Sea and Bohai Sea during autumn 2014 was between-0.002 mg C m-2 d-1 and 184.82 mg C m-2 d-1, with the average of 15.73 mg C m-2 d-1.Phytoplankton sinking rate in the Yellow Sea and Bohai Sea during summer 2015 was ranged from 0.002 mg C m-2 d-1 and 359.07 mg C m-2 d-1, with the average of 38.00 mg C m-2 d-1.Phytoplankton carbon flux in the Yellow Sea and Bohai Sea during winter 2015 was between 0.02 mg C m-2 d-1 and 4.70 mg C m-2 d-1, with the average of 1.54 mg C m-2 d-1.These studies revealed that sinking of phytoplankton cells was an important pathway for carbon export from the upper layer to the bottom layer, which is the foundation of the investigation of carbon cycling in the Yellow Sea and Bohai Sea in the near future.