Species composition of phytoplankton and its distribution in the northern South China Sea in autumn 2004
2004年秋季南海北部浮游植物组成及其数量分布特征

Based on the cruise in the northern South China Sea from 18th September to 2nd October, 2004, the authors analyzed the characteristics of phytoplankton distribution and community structure in the surface layer. The results showed that there were 152 species belonging to 53 genera, including Bacillariophyta, Pyrrophyta, Cyanophyta and Chrysophyta. The wide-distributing dominant species were Pseudo-nitzschia delicatissima, Prorocentrum sigmoides, P. mininum, Scrippsiella trochoidea, Trichodesmium erythraeum and etc. Phytoplankton biomass fluctuated, from 0.11×106 to 23.61×106cells m-3, and decreased from coastal area to far-shore area, with the maximum and minimum appearing at stations E506 and B3, respectively. The highest species numbers was 51 species at E708 close to the Pearl River estuary. The quantities of diatom ranged from 0.02×106 to 8.13×106cells m-3 and mainly distributed in higher-salinity waters. Cyclotella spp., a kind of dimethylsulfoniopropionate (DMSP) producing species, were found at many stations. Dinoflagellate were mainly found in coastal waters with the maximum of 15.67×106cells m-3 (at station E506), thereinto, many of them were red-tide species including Scrippsiella trochoidea, Prorocentrum sigmoides, P. mininum, Gyrodinium spp. and etc. Trichodesmium erythraeum, a nitrogen-fixation species, widely distributed in the survey waters, but mainly at the eastern waters, with the maximum biomass of 1.8×107cells m-3 at station E206. Hydrological data and phytoplankton data in other layers had been analyzed contrastively. The results showed that the distribution of Trichodesmium erythraeum had relationship with the infall of Kuroshio current, and its distribution was affected by water mass and ocean current.