This study was carried out in the Changjiang Estuary from 19 to 26 May 2003. Based on the data collected from 29 stations,
including two anchor stations, phytoplankton taxonomic composition, abundance, diurnal variability and spatial distribution were
examined. Eighty-seven species, including 54 species of diatoms and 16 red tide causative species, were identified. Average diversity
index (H0
) and evenness (J) values were 1.04 and 0.40, respectively. A bloom in abundance of certain phytoplankton species, especially
Prorocentrum dentatum and Skeletonema costatum, was thought to be the cause of the low diversity index and evenness values.
Total phytoplankton abundance averaged 6.75 · 105
cellsl1
, and was much higher than previous investigation carried out in the
same month in 1986. Abundance increased seaward showing a distinct spatial difference, and the dominant species varied with salinity.
Correlation between phosphorus and abundance further supported the former conclusion that phosphorus is the controlling
factor in phytoplankton growth in the Changjiang Estuary where light is not limiting. Based on the relationship between DO,
pH and abundance, it is likely that the bloom was caused by rapid in situ growth of phytoplankton with high nutrients and sufficient
light. The data also indicated that the duration of the bloom was not long and