Phytoplankton in the Yangtze River Estuary and its adjacent waters in spring 2006

Based on the multidisciplinary cruise investigation in the Yangtze River estuary and its adjacent waters in May 2006,the phytoplankton species and their abundance were analyzed by the Utermhl method.In the meantime,the relationships between the dominant phytoplankton species and environmental factors were explored by Canonical Correspondence Analysis(CCA).The primary phytoplankton groups were diatoms and dinoflagellates.There were also a few species belonging to Chrysophyceae,Chlorophyceae and Cyanophyceae,respectively.The cell abundance of phytoplankton ranged from 0.76 to 6123.78 cells/mL with the average being 397.94 cells/mL.The dominant species were Prorocentrum dentatum,Skeletonema spp.,Karenia mikimotoi.The cell abundance of phytoplankton in water sample was higher than net sample on the cruise.In contrast to the net sample,P.dentatum,and K.mikimotoi.were dominant species,the cell abundance proportion of dinoflagellates was higher than diatoms in water sample.The number of dinoflagellates species and cell abundance increased distinctly.The maximum phytoplankton cell abundance was at 5 m water layer.Section distributions were briefly described by P.dentatum,S.spp.and K.mikimotoi.The Shannon diversity index and Pielou evenness index were consistently high in the southern part of the survey area,in contrast to the trend of phytoplankton cell abundance.The CCA showed that the distribution of dinoflagellates was mainly associated with water salinity and dissolved oxygen,while diatoms were mainly affected by pH value and the water nutritive contents.