Characteristics of phytoplankton community in the Pearl River Estuary during saline water intrusion period
珠江河口咸潮期间浮游植物的群落特征

The authors analyzed species composition, distribution of species richness and phytoplankton density based on the data collected from two cruises carried out during saline water intrusion period from the end of 2007 to the beginning of 2008 at both spring and neap tides in the Pearl River Estuary. In addition, influence of environmental factors on phytoplankton community was discussed. Seventy-six species in total were identified, including 38 diatoms, 18 green algae, 14 dinoflagel-lates, 4 cyanobacteria and 2 euglenas. In general, the distribution of species richness decreased from inner section to outer section of the Pearl River Estuary. The species richness of phytoplankton was higher at neap tide than at spring tide, and it distributed unevenly among different water layers. The dominant species were mainly freshwater diatoms, such as Melosira granulate, Melosira granulata v. angustissima, Cyclotella sp. and Thalassiosira sp. The dominant species were very out-standing in the inner section of the Pearl River Estuary with the characteristics of uneven density distribution and low even-ness index value. The mean phytoplankton densities at spring and neap tides were 53.80×104 and 62.21×104ind.L-1, and the ranges of cell density were from 1.48×104 to 290.41×104 and from 1.52×104 to 283.62×104ind.L-1, respectively. Phyto-plankton density decreased from the inner to outer sections of the Pearl River Estuary, and the density of diatom was the highest among different groups during both spring and neap tides. The community of phytoplankton presented clear tidal pe-riodicity. Environmental factors such as salinity and nutrients played an important role in the composition and distribution of phytoplankton during saline water intrusion period in the Pearl River Estuary.