Phytoplankton Community of the Bohai Sea in Winter 2001

Features of phytoplankton community were studied based on the phytoplankton data of a 56 grid stations investigation from 10 th to 15 th January 2001 in the Bohai Sea, China. Three classes including 37 genera and 72 species (not including unidentified taxa) were common found in the survey area. The main phytoplankton group was temperate and neritic autochthonous diatom. The dominant species were Pseudo-nitzschia pungens, Eucampia zodiacus, Coscinodiscus excentricus, Paralia sulcata and Lauderia annulata etc. The preliminary result of community comparison study was that the key species of phytoplankton in this season were Pseudo-nitzschia pungens, Coscinodiscus excentricus and Paralia sulcata. The horizontal patterns of phytoplankton cell abundance were controlled by those of diatoms, which was higher in the South of the survey area than that of the North. Two concentration areas of phytoplankton cell abundance were found in Laizhou Bay and the South of the Bohai Strait. The dinoflagellate abundance was high in the estuary of the Huanghe River and the Bohai Strait. A comparison of the data with those collected in winter, 1983 shows that the dominant species composition was similar in these two data sets, but the cell abundance of these dominant species and the dominance was changed, and the cell abundance of phytoplankton was increased greatly in this study. The Margalef species richness index, Shannon-Wiener index and Evenness of phytoplankton were relatively higher in the South of the survey area than those of the North. The fuzzy evaluation of biodiversity shows that phytoplankton community biodiversity in the Bohai Sea was low in winter.