Phytoplankton population changes in Lake Urmia during dry and wet periods

Hypersaline environments are important natural assets of considerable economic, ecological, scientific and natural value. Management and protection of these changing ecosystems depend upon an understanding of the influence of salinity on biological productivity and community structure. The objective of the present study was to investigate the relationships between the two basic components in Urmia Lake i.e. microalgae and physico-chemical parameters, particularly salinity in order to provide a better understanding the dynamics of this unique ecosystem. 3 sampling sites were selected in north and south of Urmia lake. Samplings were carried out monthly from April 2018 to October 2019. In each site, 2 samples were taken for chemical, phytoplankton population analysis, respectively. The factors analyzed in each site were: water level, salinity, EC, TDS, pH, transparency Total phosphorus and total nitrogen (TP, TN), phytoplankton species composition and density. Statiscal analysis were performed by PAleontological STatistics (PAST) version 3.04. Totally, seven algal species were identified in Urmia Lake in this study. Bacillariophyta with 5 species was the most abundant algal group in the lake. Chlorophyta and Cyanobacteria both had 1 species, however, Dunaliella salina as the only representative of the green alga alone composed of about 99.5 percent of the total algal density of Urmia Lake. This study indicated that salinity, TDS and EC have the highest effects on the phytoplankton population structure and Dunaliella spp. Dominance in Urmia Lake. However, other factors such as TP and TN might have been masked by three main factors.