The researchers studied phytoplankton in the Yangtze River estuary and nearby waters in spring 2006. They found that diatoms and dinoflagellates were the main types of phytoplankton present. The abundance of phytoplankton cells varied from 0.76 to 6123.78 cells/mL, with an average of 397.94 cells/mL. The dominant species were Prorocentrum dentatum, Skeletonema spp., and Karenia mikimotoi. The distribution of dinoflagellates was linked to water salinity and dissolved oxygen levels, while diatoms were influenced by pH and nutrient levels in the water. Dinoflagellates were more abundant in water samples compared to net samples, with their numbers increasing with depth. Overall, the diversity and evenness of phytoplankton species were higher in the southern part of the study area.