Phytoplankton Combination in the Southern Part of Caspian Sea

The present study was conducted in southern part of Caspian Sea, Iran. All samples were taken during 1995-1996 and 2006-2007 in 6 transects such as Lisar, Anzali, Sefidroud, Noushahr, Babolsar and Amirabad. The phytoplankton compositions were significantly changed with seasons (P<0.05). In compare to after Mnemiopsis leidyi arrival, the population of phytoplankton species were increased. Totally 195 species were identified from 5 phyla such as Bacillariophyta, Cyanophyta, Pyrrophyta, Chlorophyta and Euglenophyta. These stated 5 phyla were 91, 33, 23, 33 and 15 species, respectively. The most dominant group was Bacillariophyta; among all species, majority of them related to Thalassionema nitzchoide specie. Also, the phytoplankton species are shown significantly decreased with an increase of the depth. Maximum phytoplankton species were concentrated at the depth of less than 20 m (P<0.05). During 2006-2007 (after M. leidyi arrival), the phytoplankton are shown significant changes in diversity as seasonal variations (P<0.05). The majority of phytoplankton in southern part of Caspian Sea were Cyanophyta, Pyrrophyta and Bacillariophyta phyla.