Phytoplankton communities and its controlling factors in summer and autumn in the southern Yellow Sea, China

The phytoplankton water samples were collected in two multidisciplinary investigations which were carried out during summer (June) and autumn (November to December) of 2011. Phytoplankton species composition and abundance data were accomplished by Utermöhl method. The phytoplankton community was dominated by diatoms and dinoflagellates in the southern Yellow Sea (YS) in summer and autumn. In summer, Paralia sulcata and Prorocentrum dentatum were the predominated species, the cell abundance ranged from 0.074 to 107.733×103 cells/L with an average of 9.057×103 cells/L. Two phytoplankton high abundance appeared in northwest part of the survey area and the Changjiang River Estuary, respectively. In autumn, Par. sulcata became the predominant species, and the phytoplankton cell abundance ranged from 1.035×103 to 8.985×103 cells/L, the average was 3.263×103 cells/L. The phytoplankton abundance in surface layer presented the homogeneous distributions. Canonical Correspondence Analysis (CCA) method was applied for discovering the relationship between environmental factors and the common found phytoplankton species. The responses of phytoplankton to nutrients were varied between summer and autumn. The abundance of most predominant species, Par. sulcata was strongly correlated to temperature and salinity in autumn, but not the case in summer.