Spring Distribution of Ciliate Plankton in the Southeastern Yellow Sea in 2019

As planktonic ciliates have been recognized as important players in marine microbial food webs, relevant studies have been conducted in the western coastal waters of the Yellow Sea. However, little is known about ciliate distributions from the eastern coast of the Yellow Sea near the Korean Peninsula. A spring cruise in April 2019 was carried out to investigate vertical and horizontal distributions of ciliate plankton at 18 stations that form three zonal sections in the eastern area. Biological (picoplankton, nanophytoplankton, and mesozooplankton) and hydrological (water temperature and salinity) environments were also analyzed to understand relationships between the ciliate distributions and the environments. High abundance (ca. 2400 cells L-1) of a large ciliate species, Laboea strobila, was observed at the surface water of Stn. 37-5. Abundance peak of large (> 50 mu m) ciliates coincided with the peak of mesozooplankton abundance. Spatial distribution of the large ciliates was associated with nanophytoplankton distribution while a smaller (20-50 mu m) ciliate group was associated with picoplankton distribution. Therefore, the spring distribution of ciliate plankton in the southeastern coast of the Yellow Sea indicates that food size for the ciliates is one of the important factors controlling ciliate compositions as well as their abundances. Further investigations need to be carried out to understand seasonal differences of ciliate distributions in the eastern Yellow Sea.