Reconstruction of the main phytoplankton population off the Changjiang Estuary in the East China Sea and its assemblage shift in recent decades: From observations to simulation

Abstract

Under eutrophication background, the increasing dinoflagellates blooms relative to diatoms blooms off the Changjiang Estuary has caused much concern. We have provided sediment evidence for the first time that the time window of diatoms-to-dinoflagellates shift off the Changjiang Estuary in the East China Sea is early 1990s. Investigations to the water column revealed different surface-bottom concentration matchup patterns between peridinin (dinoflagellates) and fucoxanthin (diatoms), which suggests that the diatoms-dinoflagellates shift recorded in the sediment may have come from more dinoflagellate blooms since 1990s. Physical-biogeochemical 3D numerical simulations for the past decades suggest that the effect of increasing spring sea surface temperature and increasing N/P ratio on the diatoms-dinoflagellates shift is dominant and recessive, respectively.

Keywords: Diatoms-dinoflagellates shift; East China Sea; N/P ratio; Phytoplankton pigment; SST; Sediment core.