Community structure of netz-phytoplankton in northern South China Sea in winter, 2009

Based on the cruise in northern South China Sea(SCS) from 6th January to 30th,2010,we analyzed the characteristics of netz-phytoplankton distribution and community structure in this area.The majority of species ecotype were neritic and cosmopolitan in temperate coastal seas.One hundred and fifty-fie species were identified (including variety and form) belonging to 4 phyla with 52 genera,in which 60.6% were diatoms(38 genera and 94species) and 37.4% were dinoflagellates(12 genera and 58 species).The average cell abundance of phytoplankton Bacllariophyta or Pyrrophyta was 36.46×104cells/m3,13.77×104cells/m3 or 1.39×104cells/m3,respectively.In addition,the average cell abundance of Trichodesmium thiebautii was 21.30×104 cells/m3.It was found that the coastal water of Eastern Guangdong was the area of highest phytoplankton abundance,followed by the Pearl River estuary and the coastal waters southwestward.Phytoplankton abundance decreasing from coastal area to far-shore area,the central area of the northern South China Sea was the area of lowest phytoplankton abundance.The dominant species included Thalassionema nitzschioides,Chaetoceros messanensis,Coscinodiscus spp.,Rhizosolenia robusta,and Chaetoceros spp.besides Trichodesmium thiebautii.The average diversity index(H’) and evenness(J) values were 4.50 and 0.81,respectively.The diversity level of phytoplankton community in survey area was high,the horizontal distribution of diversity index was contrary to phytoplankton cell abundance,with a low area in the inshore area.