Netz-Phytoplankton Community in the Northern South China Sea in Summer 2009

The preliminary study of netz-phytoplankton was based on the investigation in the northern South China Sea(18°N~22°30′N,109°30′E~120°30′E)in summer 2009.4 phyla and 54 genera including 180 species(including the and form) were found in the survey area,in which diatoms were predominant and coexisted with dinoflagellates.The average cell abundance of phytoplankton was 6.02×104cells·m-3,which decreased in number from coastal area to offshore.Most of the phytoplankton ecological type was warm-water,temperate-coastal,and tropical species,while oceanic species were rarely presented.The dominant species were Thalassionema nitzschioides,Rhizosolenia styliformis,Climacodium biconcavum,Pseudosolenia calcar-avis,and Thalassionema frauenfeldii.Trichodesmium thiebautii,a nitrogen-fixation species,was widely distributed in the survey area and mainly concentrated in the northeast of Hainan coastal zone and Luzon strait,with the maximum abundance of 1.06×107cells·m-3 at station E601.Trichodesmium erythraeum was also commonly distributed.The horizontal distribution of diversity indexes was contrarily with phytoplankton cell abundance,and the diversity level of phytoplankton community in survey area was high.with a low valae in the inshore area.