Phytolankton Community Structure And Species Succession In Bloom Of Central Yellow Sea 2009

Three cruises were carried on to investigate the spring bloom processes in the Yellow Sea (33oN - 36o30'N,121oE - 124o30'E), including the lag stage, the blooming stage and the decomposition stage. Phytoplankton community structure and species succession were approached by the Uterm?hl method. Species composition, dominant species, cell abundance, community diversity, the species succession during the bloom and their relationships with the environmental factors are discussed in this thesis. The purpose of this study is to recognize the influence that the environment emphasizes on the phytoplankton and the indicating functions that the different phytoplankton species have. It can provide the fundamental data on the outbreaking the bloom, and the successing of the phytoplankton species during the bloom in the Central Yellow Sea.4 phyla and 138 species (incluing the variations and types, without the unidentified species) were found in the survey area, of which 49 genera and 94 species in Bacillariophyta, 18 genera and 36 species in Pyrrophyta, 2 genera and 2 species in Chrysophyta and 1 species in Cyanophyta. The phytoplankton was mainly composed of diatom, and dinoflagellates was also important as well. Most of the phytoplankton ecotype was temperate and coastal species, while the warm-water species and oceanic species were rarely presented. The dominant species in the background cruise were Skeletonema dohrnii, Paralia sulcata. Two blooming stations were catched in the blooming cruise, Station Z11b and Z4d. The dominant species at Station Z11b were Detonula pumila and Guinardia delicatula, while Hetercapsa sp., Skeletonema dohrnii and Prococentrum minimum were dominant at Station Z4d. The decomposition stage cruise was carried on two month after the bloom, with the dominant speces of Prorocentrum dentatum. The cell abundance varied between cruises with the maximum 267.964×10~3 cells / L at Station Z4d. The distribution of the Shannon-Wiener index was coincided with that of the Pielou evenness index more or less, and the diversity level was low in the high cell abundance areas, which contrarily with the cell abandunce distribution. The phytoplankton community structure changed step by step, and the singe-celled dinoflagelltes replaced the chain-formed diatom, and the dinoflagelltes to diatom ratio reached 0.3 at last.The nutrition concentrations passively correlated with the depth, and the stratification was clearly at the water depths upper than 30 m. The cell abundance positively correlated with the concentration of nitrate, phosphate and silicate as well as temperature and salinity at Station Z11b. In opposited to the diatom, the dinoflagelltes negatively corelated with the concentration of nitrate, phosphate and silicate. The cell abundance with the other parameter was varied in different cruise and stations. The relationship of temporal-spacial distribution of phytoplankton with environment is complex in deed, while there are different water masses in the Yellow Sea. More laboratory and filed work need to be done in order to support our conclusions.