Variations in phytoplankton community could affect zooplankton biomass and lead to shifts in zooplankton composition and, accordingly, impacting food quality for fish. This study focuses on Zhejiang coastal, a crucial spawning and nursing ground, and discusses its future changes of phytoplankton community under multi-pressures based on 3-dimension biophysical and geochemical model and forcings that originated from CMIP6. Results show that under the SSP 2−4.5/5−8.5 scenario, spring bloom start date in the 2050s is projected to be earlier when compared to that in the 2010s, and similar phenomenon could be found in variations of the peak time in spring. The succession of phytoplankton from diatoms to flagellates also changes; the succession time in late-spring will occur earlier in the 2050s, especially under the high emission scenario (~ two weeks), and the proportion of diatoms in May will largely decrease (~ 20%) under this scenario. Sensitivity experiments demonstrate that under the SSP 5−8.5, the intensified riverine nutrient inputs plays a crucial role adjusting the succession time off Zhejiang coastal. As for the total phytoplankton chlorophyll a, its concentration ([Chl a]) in summer will increase in the 2050s when compared to that in the 2010s, while its changes in the absolute value in spring is relatively low. And further work highlights the importance of both climate change and intensified riverine nutrient inputs promoting the summertime biomass of phytoplankton.

phytoplankton community, climate change, riverine nutrient inputs, Zhejiang coastal, numerical model