The East China Sea (ECS) has long been considered an important monitoring site for
oceanic ecosystem changes because many water currents and river discharges constantly
influence this area. In this study, the community structure and diversity of phytoplankton
in the northern part of the ECS adjacent to Jeju Island were explored using small subunit
ribosomal RNA (SSU) pyrosequencing. We analysed samples collected from four stations
from the surface and at 30-m and 50-m depths during April and September 2011. We
observed spatial and temporal variations in the phytoplankton community. Among
phytoplankton, diatoms and dinoflagellates constituted a major portion at all stations (60
e90%). However, comparison of the April and September samples showed seasonal variation
and shifts in the dispersion of diatom and dinoflagellates among stations. Among
stations, diatoms dominated St. 1 and others were dominated by dinoflagellates.
Furthermore, phylotypes of potentially toxin-producing genera such as Karlodinium, Heterocapsa,
Gymnodinium, Gyrodinium, and Pseudo-nitzschia were dominant in this area.