Warm currents affecting the spring and winter distributions of living coccolithophores in the Yellow Sea, China

Spring and winter distributions of living coccolithophores in the Yellow Sea were studied using a polarizing microscope based on two surveys in April 2010 and January 2011. Nine species were recorded, including Emiliania huxleyi and Gephyrocapsa oceanica as the predominant forms. The cell abundance of all coccolithophores in the spring was significantly higher than in the winter (p<0.01), with means of 15 387 and 2470 cells l-1, respectively. Notably, we observed a habitat selection of coccolithophores in the southeastern Yellow Sea (32–35°N, 123–125°E). This habitat was characterized by sharp temperature gradients during both seasons caused by water exchange between the shelf waters and the Yellow Sea Warm Current. Moreover, the cell abundance, standing crop and estimated fluxes of coccolithophores were abnormally high compared to other regions. The habitat preference of coccolithophores in the Yellow Sea was directly related to the hydrodynamic conditions. The unfavorable light conditions caused by the intense convective mixing were responsible for the low biomass of coccolithophores during the winter. However, the increasing temperature influenced by the warm current, in combination with water column stability, triggered the spring bloom of coccolithophores in the southern Yellow Sea.