Seasonal and regional distribution of phytoplankton in the southern Caspian Sea

 Seasonal distribution of species composition, cell abundance and biomass of phytoplankton of the Caspian Sea were investigated in ۲۰۰۵. This survey were fulfilled in ۶ transects and ۲۶ stations A total of ۲۶۰ samples were collected during winter to autumn in the southern part of Caspian Sea. Totally, ۱۶۳ species of phytoplankton were identified (۷۱ species Bacillariophyta, ۳۱ species Chlorophyta, ۲۷ species Cyanophyta, ۲۱ species Pyrrophyta, and ۱۳ species Euglenophyta). Cell abundance and biomass of Bacillariophyta were high in centre, while biomass and cell abundance of Pyrrophyta were dominant in the middle as well as parts of the Sea, respectively. The overall total average of cell abundance and biomass of phytoplankton were ۵۶.۳۰± ۳۰.۹۷ ×۱۰۶cells/m۳ and ۲۲۱.۷۰±۷۵.۸۷ mg/m۳, respectively. Bacillariophyta accounted for ۴۷% in cell abundance, and Pyrrophyta consisted of ۵۳% of the phytoplankton biomass. Maximum phytoplankton population was recorded in winter due to Bacillariophyta and the maximum biomass in spring due to Pyrrophyta. The maximum density of Bacillariophyta was in winter and autumn while maximum biomass was observed in spring due to bigger size of Bacillariophyta such as Rhizosolenia calcar avis and Nitzschia sigmoidea followed by Pyrrophyta with high cell abundance throughout the year.