Seasonal variation of phytoplankton in the southern Caspian Sea (During 2010-2011)

Ongoing ecological study of the Caspian Sea، in particular identifying the distribution and species composition، density and biomass، seasonal and regional variations in phytoplankton seems to be necessary before any study. Due to various Physic and chemical factors of rivers leading to the sea، the situation seems different topography and throughput rate initial productions in the different seasons are different. This study done in 2010-2011 through Spring، Summer، Autumn and Winter، in 32 studies from 8 transects (Astara، Anzali، Sefidrood، Tonekabon، Noshahr، Babolsar،and Bandar Turkman). In each transect، have choosen 5 stations and different depths of 5 m، 10 m، 20 m، 50 m and 100 m were sampled quarterly from the zero depth (level)، 10 m، 20 m، 50 m and 100 m were by Niskin sampler. In totally، 7 branches Bacillariophyta، Pyrrophyta، Cyanophyta، Chlorophyta، Euglenophyta، Xantophyta and Haptophyta and 182 phytoplankton species were identified. Among the 81 species of Bacillariophyta، 25 species of Pyrophyta، 33 species of Cyanophyta، 31 species of Chlorophyta، 1 specie of Chrysophyta and 1 species of Xantophyta. Studies showed that the dominant branches of phytoplankton were Pyrrophyta، Cyanophyta and Bacillariophyta and Shannon index for the various branches of phytoplankton were different.