phytoplankton population changes in lake urmia during dry and wet periods

Hypersaline environments are importantnatural assets that have significant economic,ecological, scientific and natural value.management and protection of these variableecosystems depend on understandingthe influence of salinity on biological productivityand community structure. the objectof the present study is to investigate therelationships between two basic componentsin urmia lake i.e. microalgae and physico-chemical parameters, particularly salinity level in order to provide a better understanding dynamics of this unique ecosystem. 3 sampling sites were selected in north and south of urmia lake. samplings (2 samples in each site) were carried out monthly from april 2018 to october 2019. water level, salinity, electrical conductivity (ec), total disolved solids (tds), ph, transparency, phosphate and nitrate (po4 -3 and no3 -) were analyzed. phytoplankton species composition and density were also determined. 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 green alga alone composed about 99.5 percent of total algal density of urmia lake. this study indicated that salinity, tds and ec have the highest effects on phytoplankton population structure and dunaliella spp. dominance in urmia lake. however, other factors such as po4 -3 and no3 - might have been masked by three main factors.