The Study of Circulation and Stratification in Urmia Lake
Alireza Asem1,2*, Yosefali Asadpour1, Fereshte Gasemzadeh3, Alireza Borhani Dariane4
1) Iranian Artemia Research Center (I.A.R.C), Golmankhane Port, Urmia, IRAN
2) Protectors of Urmia Lake National Park Society (NGO), Urmia, IRAN
3) Department of Biology, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, IRAN
4) Civil engineering Department, Khaje Nasir Toosi University of Technology, Tehran, IRAN
Summary:
Most lakes in temperate zone are dimictic; they stratify and circulate twice a year. These stagnations and circulations occur due to thermal and density differences. The lakes become isothermal and mix in spring and fall; stratification and stagnation occur in summer and winter. The foregoing conditions show general situations at lakes but there are other models in different geographical regions. The study of Urmia Lake salinity in three different locations (North, Southwest, middle and Southeast) shows that Urmia Lake is heterogeneous in spring but there is a circulation during the fall that homogenize the entire water column. The average salinity of Urmia Lake was 230 g/l in 1995 and 166 g/l in 1987. The salinity gradient with the depth during the stratification is insufficient to increase stability to a point where wind energy does not cause holomixis. Thus, there is one circulation in fall and the stagnation due to stratification occurs in winter, spring and summer. However this method doesn't accord with general condition also it is different with other models such as: Dimictic, Amictic, Oligomictic, Warm Monomictic, Cold Monomictic and Polymictic. The spring is onset of life cycle of Artemia in Urmia Lake; by the way physicochemical characterizations are influent in intraspecific and interspecific variations of Artemia. Thus, stratification of Urmia Lake can be important in genetic and morphometrical variations of Artemia in Urmia Lake.
