Response of Phytoplankton Community Structure and Size- Fractionated Chlorophyll a in an Upwelling Simulation Experiment in the Western South China Sea

The South China Sea（SCS）, which is the largest marginal sea in the western tropical Pacific, plays an important role in regional climate change. However, the research on the phytoplankton community structure（PCS） response to the upwelling remains inadequate. In January 2014, the upwelling simulation experiment was performed in the western SCS. Results indicate that the nutrient-rich bottom water not only increased the total Chlorophyll a（Chl a） concentrations, but would potentially altered the PCS. Due to new nutrients added, microphytoplankton had more sensitivity response to nutrient uptake than other phytoplankton groups. The variation of nutrients induced by formation, weakening and disappearance of upwelling resulted in phytoplankton species succession from cyanophyta to bacillariophyta. It may be the leading factor of the changes in PCS and size-fractionated Chl a. The initial concentration of DIP less than 0.1 μmol L-1 could not sustain the phytoplankton growth. This indicates that phosphorus may be the limiting factor in the western SCS.