محمود نفیسی بهابادی

In this research to study the abundance of blue-green algae and some environmental factors in 1385 was conducted on Parishan Lake. At first, it was identified on Eight Stations Lake and was sampled of the stations on a monthly basis. Temperature, oxygen, pH, EC and water depth were recorded. The monthly minimum and maximum mean of water temperature (54/10 -9/30 ° C), oxygen (96/3 maximum 34/7 Mg), pH (minimum 52 / 8-39 / 9 Max), EC (minimum 52 / 4. max 17/9 mg on cm), depth of the water (between drying up to 75.3 m) were determined. By using of Phytoplankton tour Hydrvbyvs 55 microns and sampled bottles at least 20 liters of water of lake monthly from each filter station and the samples with formalin 4% fixed and examined by inverted microscope. The identified Phytoplankton was including green-blue algae, chlorophytes, the diatoms and Dinoflagellate. The highest annual abundance of blue-green algae was with 8 genera and annual frequency of 26/58 percent. Blue-green algae Microcystis sex with 71/74 percent were allocated the highest frequency and Merismopeddia with 58/0 percent were allocated the lowest frequency among the blue-green algae to themselves. Other blue-green algae, including Spirulina were with 24/11 frequency, Gomphosphaeria with 97/6, Anabaena with 08/2, Chroococcus with 95/1, Oscillatoria with 85/1 and Coelosphaerium with 62/0.Most blue-green algae seen in the warm seasons of the year. Most appearances of Microcystis was in August and the hottest months of the year and was not observed in February and March. Spirulina algae and Gomphosphaeria relatively was seen in all seasons. In general, in this study it is found that by changing the physical and chemical factors especially temperature in Parishan lake, the abundance of blue-green algae changes in different seasons.