Seasonal and Regional Distribution of Phytoplankton in the Southern Part of the Caspian Sea

In the present study, seasonal distribution of species composition, cell abundance and biomass of phytoplankton in the southern part of the caspian sea were investigated. this survey were fulfilled in 6 transects and 26 stations. a total of 260 samples were collected during winter to autumn in 2005. totally, 163 species of phytoplankton were identified, including phyla bacillariophyta (71 species), chlorophyta (31 species), cyanophyta (27 species), pyrrophyta (21 species), and euglenophyta (13 species). the overall total average of cell abundance and biomass of phytoplankton were 56.30± 30.97 x l 0^6cells/m^3 and 221.70±75.87 mg/m^3', respectively. bacillariophyta accounted for 47% in cell abundance and pyrrophyta consisted of 53% of the phytoplankton biomass. maximum phytoplankton population was recorded ill winter due to bacillariophyta and the maximum biomass was recorded in spring due to pyrrophyta. the maximum density of bacillariophyta was in winter and autumn while maximum biomass was observed in spring due to larger size of bacillariophyta such as rhizosolenia calcar avis and nitzschia sigmoidea followed by pyrrophyta (exuviaella cordata) with high cell abundance throughout the year