بررسي پراكنش فيتوپلانكتون هاي حوزه جنوبي درياي خزر

The Distribution Survey of Phytoplankton in the Southern Caspian Sea

The following investigation describes some hydrology and hydrobiology projects carried out in the Southern Caspian Sea at a depth of below 100m in four investigation cruises over the Spring, Summer, Fall and Winter seasons of 1996. In accordance with the survey carried out in the Southern Caspian Sea, five Phylum of phytoplankton were identified of which the Crysophyta (diatome) has and maximum number and biomass in all seasons, its maximum and minimum biomasses were estimated as 32.8mg/m3 in Winter and 194.10 mg/m ʹ in Fall, respectively. After the Crysophyta phylum, the Pyrrophyta phylum has the highest biomass. The minimum and maximum averages of the biomasses in this Phylum were estimated as 4.8 mg/m3 in Fall, and 11.13 mg/m3 in Spring. Three Phyla, such as Cyanophyta, Cholorophyta and Euglenaphyta had a very low biomass (the annual averages were 0.6, 0.073, and 0.24mg/m3, respectively). The average biomass and density in five Phyla in the west, middle and eastern areas indicated that Cyrsophyta in the western area is more than in the two other areas. It is likely that the influx of fresh water and an increase in the need of material caused this Phylum to bloom. Pyrrophyta phylum is almost equally distributed over the three areas and Cyanophyta phylum has a higher distribution in the western but Cholorophyta and Euglenophyta in eastern coast of Iran. As a result, Crysophyta (Diatomea) phylum is the first dominant phylum and this phylum is widely distributed throughout the coasts of Iran and this phylum has a large biomass. Pyrrophyta phylum is numerically the second dominant phylum and this phylum has a maximum biomass and number greater than the three other phyla throughout the year