Relationship between diatoms,dinoflagellates assemblages changes and environmental factors in Nanji Islands Sea Area,Wenzhou

An investigation was carried out from Apr.2006 to Mar.2007 at four sampling stations in Nanji Islands Sea Area.The water samples,ambient chemical,physical and meteorological data were examined.The highest and higher cell abundance of diatoms almost are in the summer(from Aug.to Dec.).Two blooms of diatoms were found,arising in Aug.and Dec.respectively.The dinoflagellates blooms just occurred in the spring.Nutrient elements needed by diatoms and dinoflagellates are different.They were higher prior to the blooms and large amounts of nutrients were assimilated as cell abundance increased.DIN nearly reached to the minimum at the maximum cell abundance of diatoms.High DIP promoted the blooms of dinoflagellates and almost fully used by the dinoflagellates blooms.The results shown that favorable water temperature and nutrient elements are the major causes of high cell abundance of phytoplankton and frequent outbreaks of blooms in Nanji islands sea area.Moreover,high cell abundance brought by the physical factors such as wind and current from Zhejiang Province coast to Nanji Islands Sea Area,play an important role in the occurrence of blooms.