Phytoplankton distribution characteristics of Guangxi Beibu Gulf coast in the autumn of 2010

We investigated the abundance and species composition of phytoplankton community in the coastal water of Guangxi from 5 to 15 in September 2010.A total of 130 species belonging to 59 genera were identified.Diatoms contributed to 77.69% of the total phytoplankton species number and 94.13%of the total phytoplankton cell abundance;followed by dinoflage1lates,which accounted for 18.46%of total phytoplankton species number and 3.56%of the total phytoplankton cell abundance.Phytoplankton abundance varied from 0.43×104/L to 114.89×104/L,the average density was 15.16×104/L,the average density of diatom was 14.27×104/L,the average density of dinoflagellate was 0.54×104/L,Phytoplankton abundance had a lower value in Maowei Sea,adjacent waters of Dafengjiang and Beihai sea area,the quantitative distributions of phytoplankton,presented a reduced tendency from east to west.The dominant species were Chaetoceros pseudocurvisetuss Mangin,Thalassionema nitzschioides Grunow,Skeletonema costatum Cleve,Lauderia annulata Cleve and Rhizosolenia stolterfothii Peragallo.The Shannon-Wiener diversity indices and Pielou's evenness of phytoplankton community with a similar plane distribution were higher off the coast than on the coastal area,the phytoplankton assemblage was comparatively stabilizing.Canonical correspondence analysis(CCA) was applied to explore the relationship between phytoplankton species and environmental parameters,the results showed that phosphate concentration and the total nitrogen were the most important factors,nitrate,COD and transparency were secondary important factors,which influencing the phytoplankton species distribution patterns.