عنوان مقاله [English]
To study toxic phytoplankton Nitzschia seriata (diatoms group) fluctuations, 4146 samples were collected from surface, 2,5,10,20,50 and 100 m depths during 1994-2007 in the southern part of Caspian Sea seasonally. Comparative data (1994-2007) showed that the toxic specimens (Nitzschia seriata)were not observed before 2005, but after 2005, this species appears in some of water layers in southern Caspian Sea. The average of cell abundance and biomass of these species were about 23.41× 106 ±4.25× 106 cells/m3 and 23.71±4.81 mg/m3, respectively. The annual survey of cell abundance and biomass about N.setiata showed that the maximum of cell abundance and biomass in 2005 were 39×106 cells/m3 and 39.55 mg/m3, respectively. The most of cell abundance and biomass was observed in spring 2005 and autumn 2004 and its minimum was seen in autumn of 2005 and 2004. The regional survey of this species indicated that the maximum cell abundance and biomass observed in the east region in 2005 and 2007.The middle region was lower in value than other regions (east and west). Therefore, the maximum of N.seritia frequency and bloom were recorded in east and west respectively.