Distribution, Abundance and Biodiversity of Phytoplankton from Hanna Dam Lake, Isfahan, Iran

Phytoplankton are the base of production in aquatic ecosystems and have a major importance in the freshwater environment both in terms of fundamental ecology and in relation to human use of natural resources. The purpose of this research was to determine distribution, abundance and biodiversity of phytoplankton community in Hanna Dam Lake, located in Isfahan province. The sampling was carried out in mid-season from 6 fixed stations during one-year period. Abundance ranges of diatoms, Chlorophyceae, Desmids, Dinophyceae, and Cyanophyceae were estimated 405-2395, 786-6778, 0-14, and 0-70 cells/mL in spring; 1281-3879, 1987-4518, 13-173, 0-157, and 0-85 cells/mL in summer; 593-1265, 1926-4980, 0-14, 0-51, and 0-37 cells/mL in autumn; 48-264, 116-624, 0-13, 0-51, and 0-131 cells/mL in winter, respectively. Cyclotella, Cocconeis and Surirella from diatoms; Chlorella, Oocystis, and Tetraedron from Chlorophyceae were dominant in spring. In summer, Cyclotella and Surirella from diatoms; Mougeotia, Chlorella and Scenedesmus from Chlorophyceae; Closterium from Desmids; Prorocentrum from Dinophyceae; and Chroococcus from Cyanophyceae were dominant. In autumn, the dominant genera were Cyclotella and Surirella from diatoms; Mougeotia andChlorella from Chlorophyceae; Closterium from desmids; Ceratium from Dinophyceae; Chroococcus from Cyanophyceae while in winter Cocconeis and Amphora from diatoms; Chlorella and Tetraedron from Chlorophyceae; Closterium from desmids; Ceratium from Dinophyceae; Tolypothrix from Cyanophyceae were dominant. The diversity indices of Simpson, Shannon-Wiener, and Margalef were obtained at ranges of 0.40-0.72, 1.23-2.29, and 0.95-1.59 in spring; 0.59-0.77, 1.97-2.73, and 2.13-2.80 in summer; 0.50-0.71, 1.56-2.31, and 0.96-1.82 in autumn; 0.13-0.63, 0.27-1.42, and 0.10-0.97 in winter, respectively. The highest biodiversity was obtained during spring and summer. Our results showed that this lake could be classified as eutrophic lake based on water quality, abundance, composition and biodiversity of phytoplankton.