بررسي تنوع گونه اي و اكولوژيك فيتوپلانكتونهاي درياچه بزنگان

Species diversity and ecological studies of phytoplankton in the Bazangan Lake

Bazangan, the Khorasan largest natural lake, is located in Northeast, 120km from Mashhad with the area of 690000m^2. The purpose of this study was to characterize ecological aspects and to compare seasonal variations in species diversity of phytoplanktons in the surface water of littoral zone in the Bazangan lake. Samples were collected from eleven stations in each season during the year 2002. Some ecological factors such as pH, EC, salinity, hardness of water, nutrients and water temperature were measured. Four macroalgae and 33 phytoplankton species belonging to 5 algae groups viz. Chrysophyta (21 species), Chlorophyta (7 species), Cyanophyta (4 species) and Pyrrophyta (1 species) were identified. Diatana tenuis, Fragillaria cratonensis, Ulothrix suhtilissima and Merismopodia punctata had the most species abundance. Comparing to other groups, Chrysophyta was abundant in all seasons mostly in the spring and summer. Different numerical indices of diversity such as species richness, evenness and diversity as well as parametric families of diversity were obtained in different seasons based on the abundance data of phytoplanktons. The results showed that the highest species diversity of the phytoplanktons could be seen in the summer and autumn. The Bazangan is classified as an oligothroph and a subsaline lake.