Preliminary Study On Living Coccolithophores And Its Associated Phytoplankton Community In The South China Sea In Summer And Winter

South China Sea (SCS), being the deepest and biggest sea adjacent to China, lies in the western part of the Pacific Ocean. Rivers flows into South China Sea, including Pearl River, Hong Ha River, Mekong River, etc. which can supply nutrients for the south china sea. However SCS is also the deepest and the biggest sea along China, the nutrients is scarce, and they can't support to form phytoplankton blooms. The phytoplankton community is an important index on understanding SCS, including the water masses, the productivity and so on. The living coccolithophores (LC) plays an important role in the production of Particle Inorganic Carbon (PIC) and Particle Organic Carbon (POC), so the species composition, community structure, the physiological and biochemical mechanism of LC were concerned in this thesis, menwhile the LC associated phytoplankton community was also reported in this thesis.According to the samples gottend by the cruises from the northern South China Sea(17°-24°,108°-122°E)in summer and winter 2009, the species composition, cell abundance, community structure, Shannon-Wiener index, Pielou index of LC and phytoplankton are reported here. The LC analysis via polarizing microscope, and identifying of uncertain taxa with the help of scanning electron microscope (SEM), the associated phytoplankton was analysed with Utermohl method.LC samples taken from 8 stations in summer and winter cruises respectively, and a total of 273 samples were analysed. There are 13 LC species belonging to 11 genera. The coccolithophores cell abundance ranged from 2.633 to 718.1 cells/L in the summer and the average cell abundance is 59.53 cells/L,while the cell abundence ranged from 3.021 to 644.1 cells/L in the winter, coupling with the average of 66.83cells/L. The Shannon-Wiener index of LC in summer and winter ranged from 0.3034 to 1.981 and 0.5107 to 2.249 respectively, and Pielou evenness index ranged from 0.3034 to 0.9998 and from 0.3340 to 0.9984. The LC cell abundance is greaterin winter than that of in summer. In the surface distribution of the LC abundance isn't remarkable in summer, while the distribution of abundance appeared prevailed in the basin than on the continental shelf in winter;In the vertical distribution, the high cell abundance usually lie in tne sub-surface. Umbellosphaera tenuis (Kamptner) Paasche, Emiliania huxleyi (Lohmann) Hay et Mohler and Gephyrocapsa oceanica Kamptner were predominant in the two cruises.The associated phytoplankton community structure in this area were also studied, and a total of 145 taxa (include unidentifying species) belonging to 68 genera in 5 phyla were recorded. The phytoplankton cell abundance ranged from 0.009 to 125.6×103cells/L in summer and the average cell abundance is 7.245×103cells/L Bacillariophyta were predominant and coexisted with Dinophyta, and some species belonging to Cyanophyta, Chlorophyta and Chrysophyta, most of phytoplankton taxa is eurythermal species and cosmopolitan species. The dominant species in turn were Thalassionema nitzschioides Grunow, Pseudo-nitzschia delicatissma (Cleve) Heiden, Pseudo-nitzschia pungens (Grunow et Cleve) Hasle, Chaetoceros sp., Detonula pumila (Castra) Schiitt, Melosira grannulata Ehrenberg, Trichodesmium thiebaultii Gomont, which belonging to Cyanophyta. The high phytoplankton cell abundance region in surface layer occurred in the Pearl River Estuary and its southern part. In the Beibu Gulf, phytoplankton cell abundance decreased from coastal zone to the center of the Gulf, and cell abundance of dinoflagellates was high in the coastal seawater of Guangdong Province. Phytoplankton cell abundance was high in surface water and decreased rapidly from surface layer to the bottom. The Shannon-Wiener index and Pielou evenness index were low in the southern part of Pearl River Estuary and the coastal water of Guangdong Province.