Temporal and spatial dynamics of phytoplankton diversity in the East China Sea near Jeju Island (Korea): A pyrosequencing-based study

•East China Sea (ECS) as important monitoring sites for oceanic ecosystem changes.•Pyrosequencing showed a great extent of phytoplankton diversity in the ECS region.•Construction of complete checklist of phytoplankton in ECS around Jeju Island.•Seasonal variation and shift in the diatom and dinoflagellates among stations.•Phylotypes of potentially toxin-producing phytoplankton were dominant in this area.

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 (60–90%). 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.