Effect of temperature and nitrogen on the changing trend in the cyanobacteria in southern part of Caspian Sea (the Stretch between Tonekabon and Amirabad)

Changes in abundance and biomass of cyanobacteria have been studied in the southern part of the Caspian Sea (the stretch between Tonekabon and Amirabad) in four seasons (spring, summer, autumn, winter) in which samples were taken from five depths of 5, 10, 20, 50 and 100 meters in the stations of Tonekabon, Noshahr, Babolsar and Amirabad. Samples were fixed with formalin (2%) before transferring to the lab for both qualitative and quantitative analyses. The results of this study showed higher abundance and biomass of cyanobacteria in euphotic layer compared to aphotic layer. Temperature, ammonium, nitrate and nitrite levels have shown significant differences.