Abstract:

In order to illustrate the community structure of phytoplankton assemblage of the Yangtze River Estuary and its adjacent waters (30.5° ~ 32.5°N，121.0° ~ 123.5°E) in autumn 2005，besides clarifying its relationship with the nutrient pulsing of the Yangtze River.Phytoplankton samples were analyzed by using Utermhl method and their relationship with the environmental factors were further discussed meanwhile.After a total of 95 phytoplankton species were identified including species variation results were obtained.Diatom was the major phytoplankton group in survey area and accounted for 93.1% in total abundance.Most of the phytoplankton ecotypes were temperate coastal species and few were warm and oceanic species.Dominant species were Skeletonema costatum，Paralia sulcata，Coscinodiscus spp.，〖WTBX〗Thalassionema nitzschioides and Thalassiosira rotula.Averaging phytoplankton abundance was 2.04 cells/mL with the maximum appeared in the southern part of the Yangtze River mouth.The distribution of Margalef，ShannonWiener and Pielou′ indexes indicated that relative high phytoplankton diversity and evenness appeared in the offshore pelagic water area.Pearson correlation showed that seawater temperature and nitrate content were the main environmental factors that controlling the phytoplankton distribution pattern in autumn.Dominant species S.costatum was negatively correlated with the temperature and positively correlated with the nitrate.

Key words: phytoplankton/assemblage structure/ , Skeletonema costatum/ Paralia sulcata〖/ the Yangtze River Estuary