Abstract: The present study was undertaken in Changlu Hangu Saltworks, which is situated in Bohai Bay coastal area, China in the period of May to December in 2012. The physicochemical variables, species diversity and density of phytoplankton were determined in five sampling saltponds with salinities ranging from 5-20 SymbolpB@Bé. The results indicated that five phylum and 27 phytoplankton genera were identified, of which 18 genera belonged to Bacillariophyta. Blue green algae Oscillatoria spp. was abundant in all sampling saltponds (A1-A5), diatoms such as Thalassionema nitzschioides, Skeletonema costatum, Nitzschia spp. and Coscinodiscus spp. were dominant in the saltponds at lower salinities (A1 and A2), whilst green algae Dunaliella spp. were superior in the saltponds at higher salinities (A3-A5). The density of phytoplankton ranged 6.47×10³-5.07×106 ind·L^-1, diversity index ranged from 0.13 to 1.57,  evenness index ranged from 0.01 to 0.58, and the overall dominance index was greater than 0.5, depending on salinities and seasons. Overall, the diversity and evenness of phytoplankton in Hangu Saltworks were lower, but with apparent dominance. The diversity and biomass density in the saltponds reduced with increasing salinity and decreasing temperature.

Key words: trace element, imperatorin, Angelica dahurica, isoimperatorin, total coumarin