Effects of environment factors on the phytoplankton assemblages of the southeastern Yellow Sea in spring and summer

Abstract

This study was conducted to investigate the relationship between environment factors and phytoplankton assemblage in the southeastern Yellow Sea. Nutrient in spring showed a relative high concentration at the upper layer, compared to summer. Phytoplankton biomass in the study area was potentially controlled by nitrate concentration; Diatom was dominated at all stations in spring due to the supplied nutrient by the seasonal mixing, however, diatom dominated at the A line, and nanoflagellate was dominated at the E line in summer. This is caused by the effect of low light condition due to the upwelling event in the E line in summer. In spring, Skeletonema costatum-like usually dominated in the stations characterized by the relatively high phosphate concentration, whereas Thalassiosira. nordenskioldli usually dominated in the stations characterized by the relatively low concentration of phosphate and silicate. Leptocylindrus danicus usually dominated near the coastal area, in which the light condition showed low values by the upwelling event. In summer, small sized phytoplankton over competed with large sized phytoplankton. However, Thalassiosira prosckinae, small chained diatom species, was dominated at the A line and nanoflagellate in the E line, which may be the difference floating ability and the adaptation ability of light condition. This study suggests that the difference of phytoplanktommer. Phytoplankton biomass in the study area was potentially controlled by nitrate concentration; Diatom was dominated at all stations in spring due to the supplied nutrient by the seasonal mixing, however, diatom dominated at the A line, and nanoflagellate was dominated at the E line in summer. This is caused by the effect of low light condition due to the upwelling event in the E line in summer. In spring, Skeletonema costatum-like usually dominated in the stations characterized by the relatively high phosphate concentration, whereas Thala