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On the red coloration of Lake Urmia

Urmia City
Urmia or (Turkish Language: اورمیه,اورمو, Urmu, Orumiyeh, Urmiye, Urmiya) is a city in Northwestern South Azerbaijan (Iranian Azerbaijan) and the capital of West Azerbaijan Province. The city lies on an altitude of 1,330 m above sea level on the Shahar Chaye river (City River). Urmia is the 10th populated city in iran and 2nd of Azerbaijanian Turks provinces after Tabriz. Urmia is the trade center for a fertile agricultural region where fruit (Specially Apple and Grape) and Tobacco are grown. An important town by the 9th cent.
The name Urmia or Urmu is thought to have come from Sumerian tongue, the earliest known civilization in the world located in southern Mesopotamia. Ur was a principle Sumerian city. Urmia, situated by a lake and surrounded by rivers, would be the cradle of water. The population of Urmia is predominantly Azerbaijanian Turks (over 90%), but with Kurdish, Assyrian and Armenian minorities.
Lake Urmia
Lake Urmia (Turkish Language: اورمیه گولو، اورمو گولو,Urmu Gölü, Urmiye Gölü,farsi ; دریاچه ارومیه Daryâcheh-ye Orumiyeh; is a salt lake in northwestern Iran, near Iran's border with Turkey. The lake is between the Iranian provinces of East Azerbaijan and West Azerbaijan, west of the southern portion of the similarly shaped Caspian Sea. It is the largest lake in the Middle East,[3] and the third largest salt water lake on earth, with a surface area of approximately 5,200 km² (2,000 mile²), 140 km (87 miles) length, 55 km (34 miles) width, and 16 m (52 ft) depth.
Ecology
Lake Urmia (Orumieh in farsi), which lies in northwestern Iran, is home to some 212 species of birds, 41 reptiles, 7 amphibians, and 27 species of mammals, including the Iranian yellow deer.
The construction of a dam on part of the lake and the recent draught has significantly decreased the annual amount of water Urmia receives. This in turn has increased the salinity of Urmiye 's water, causing the lake to lose its significance as home to thousands of migratory birds, such as flamingoes.
The lake is marked by more than a hundred small rocky islands, which are stopover points in the migrations of various kinds of wild bird life (including flamingos, pelicans, spoonbills, ibises, storks, shelducks, avocets, stilts, and gulls).
By virtue of its high levels of salinity, the lake does not sustain any fish species. Nonetheless, Lake Urmia is considered to be one of the largest natural habitats of Artemia, which serve as food source for the migratory birds such flamingos. Most of the area of the lake is considered a national park.
The lake is a major barrier between two of the most important cities in West Azerbaijan and East Azerbaijan provinces, Urmia and Tabriz. A project to build a highway across the lake was initiated in the 1970s but was abandoned after the Iranian Revolution of 1979, having finished a 15 km causeway with an unbridged gap. The project was revived in the early 2000s, and was completed in November 2008 with the opening of a 1.5 km bridge across the remaining gap. However, the high saline environment is already heavily rusting the steel on the bridge despite anti-corrosion treatment. Experts have warned that the construction of the bridge, together with a series of ecological factors, will eventually lead to the drying up of the lake, turning it into a salt marsh which will directly affect the climate of the region. Lake Urmia has been shrinking for a long time, with an annual evaporation rate of 0.6m to 1m (24 to 39 inches). The lake's salts are considered to have medical effects, especially as a cure for rheumatism. Lake Urmia is a UNESCO Biosphere Reserve and a Ramsar site.
Islands
Lake Urmia has 102 islands. For a The Turkish  names of patterns and morphology of Islands Lake Urmia of a list of their names, see this link. The second largest island, Shahi Island, is the burial place of Hulagu Khan, the grandson of Genghis Khan and the sacker of Baghdad.
Basin rivers
Aji Chay
Ghaie River
Alamlou River
Leylan River
Zarrineh River
Simineh River
Gadar River
Mahabad River
Barandouz River
Shahar River
Nazlou River
Rozeh River
Zola River
Fereidun Mohebbi*, Reza Ahmadi, Ali Mohsenpour , Latif Esmaili and Yosefali Asadpour
Iranian Artemia Research Center, Urmia, Iran 
In summer 2010, the Urmia Lake water was changed to a pinkish-purple color in several areas such as two sides of the causeway (Fig 1). To investigate on the reasons of this color change, we collected water samples for phytoplankton and some physicochemical parameters analyses from six sampling sites on the both sides of the lake causeway on August 18th 2010 (Table 1).Phytoplankton samples were immediately fixed
by 4% formaldehyde and preserved in cold,dark conditions for laboratory analysis.Phytoplankton counting and identification were
made using 5-ml settling chambers with a Nikon TS100 inverted microscope at ×400 magnification by Utermöhl (1958) method. 

The phytoplankton population of Urmia lake has mainly composed of a unicellular green alga namely Dunaliella which included about more than 90% of the whole phytoplankton density of the lake. Other phytoplanktons such as a few species of diatoms like Nitzschia and Navicula play only a minor role in phytoplankton composition of the lake (Mohebbi et al., 2009).
In the present study, Dunaliella yet contained even more abundance than previous studies in Urmia Lake (e.g. Mohebbi et al.,2009; Shoa hasani 1996) (Table 2). On the other hand, we observed    Dunaliella as two Different morphological varieties differed from each other by their colors: a green and a red colored Dunaliella which apparently the latter had higher concentrations of carotenoid pigment than the first. As  shown in table 2,however, there were no significant differences among sampling sites regarding these two morphological forms density. Therefore, though the increased red colored(morphological form)Dunaliella density may be attributed to the saturation of the lake water and other extreme conditions, but it cannot have a basic role in color  shift of the lake. As a matter of fact, although β-carotene derived from Dunaliella may be the most abundant carotenoid pigment in the hypersaline water, its dense packaging within granules inside the cells chloroplast greatly decreases its contribution to the overall light absorbance in the water. As a result, most of the pink-red color of the  hypersaline environments is caused by α-bacterioruberin and other bacterioruberin derivatives present in the family of Halobacteriaceae(Fernandez-Castillo et al., 1986).
The North Arm of Great Salt Lake, Utah,with salt concentrations above 300 g l-1 shows similar color changes (Post 1977; Baxter et al. 2005). A railroad causeway built in 1959 divided Great Salt Lake into northern and southern sections,leading to dilution of the southern section, and concentration of the northern section to nearly saturating salinity. The red color is the result of a bloom of extreme halophiles, which can reach 108 cells.ml-1 or greater concentration in the northarm (DasSarma, 2006) (Fig.2).
Solar salt ponds are established all over the world in many tropical and subtropical regions to produce salts from seawater.The seawater is evaporated by a step by step process through shallow ponds which have relatively constant salinity, so that each set of ponds contains particular microbial population which adapted to same salt concentration. At the last step of evaporation process,the salt oncentration rises to more than 300 gl-1 in crystallization ponds. In this situation, the main microbial communities are as planktonic  populations which give a pink-reddish color to water (Javor, 1989).
In fact, α-bacterioroberin and its other 50- carbon derivatives present in Archaea from Halobacteriaceae play the major role in establishing such a pink-reddish color in crystallization ponds. It can be concluded that a similar mechanism contributed in color change of brine water both at natural hypersaline waters and at man-made solar salt ponds. This is a  biological process in which Halobacteriaceae with its vast number of genera and a few recently identified bacteria involved in water color shift in NaCl saturated water.
Conclusion
Briefly, when water salinity  exceeds saturation levels, the density of halophilic bacteria increases to more than 108 cells.ml-1. Since the bacterioroberin are distributed evenly on the cell membranes in these prokaryotic  cel s, so can absorbe light more efficiently than pigments of eukaryotic Dunaliella.
Water saturation, as well as high temperatures induces a large growth in the number of halophilic bacteria in Urmia Lake. The presence of these bacteria in Urmia Lake has recently been investigated by  several authors (e.g. Amoozegar and Zahraei,2007; Arash Rad, 2000;  Asgarani et al., 2006; Bahari et al., 2009 and Rafiee et al., 2007). In conclusion,the role of prokaryotic halophilic bacteria is more than Dunaliella in red coloration of saturated water including Urmia Lake.
References
Amoozegar M.A, Zahraei. Sh (2007) Biodiversity of halophilic bacteria producing extracellular hydrolytic enzymes from Urmia Lake,II International Conference on Environmental,Industrial and Applied Microbiology,Seville(Spain), 382.
Arash Rad F, (2000) Determination of bacterial flora in the biomass of Artemia from Urmia Lake,M.Sc. Thesis, Islamic Azad University of Lahijan.
Asgarani E.,Shirzad M.,Soudi M.R. Shahmohammadi H.R. and Falsafi T.(2006) Study on the resistance of Haloferax Radiotolerans, an extreme halophilic Archa-ebacterium from Uromia Lake against Ultraviolet (UV) light and60Co Gama-Rays, Journal of Nuclear Science and Technology, 36: 13-18.
Bahari S, Zarrini Gh, Aein F, Zadeh Hosseingholi E (2009) Isolation and identification of halophilic archaea from salt crystals of Urmia Lake, 10th Iranian Congress of Microbiology,Ilam, Iran 229.
Baxter, B.K.,  C.D. Litchfield, K. Sowers, J.D. Griffith, P. Arora DasSarma & S.DasSarma. 2005. Microbial diversity of Great Salt Lake. In:Gunde-Cimerman, N., A. Oren & A. Plemenita_(eds), Adaptation to Life at High Salt Concentrations in Archaea, Bacteria, and Eukarya. Springer, Dordrecht: 9–25.
DasSarma, Sh.(2006). Extreme Halophiles Are Models for Astrobiology. Microbe, Volume 1,Number .3
Fernandez-Castillo R,Rodriguez-Valera F,Gonzalez-Ramos J, Ruiz Berraquero F (1986) Accumulation  of poly-β-hydroxybutyrate) by halobacteria. Appl Environ Microbiol 51:214–216
Javor, B., (1989), Hypersaline Environments.Microbiology and Biogeochemistry, Springer-Verlag, Berlin
Mohebbi, F., Esmaili, L.,Negarestan, H.,and Ahmadi,R.(2009).Dynamics of Phytoplankton population in Urmia Lake: Consequences  on Artemia  density. Proceeding of international sympos-ium/workshop    on biology and distribution of Artemia. Urmia, Iran.
Post, F.J. (1977. The microbial ecology of the Great Salt Lake. Microbial Ecology 3: 143–165.
Rafiee  M.R.,  Sokhansanj A., Yoosefi M.,Naghizadeh M.A. (2007)Identification of Salt-Inducible Peptide with Putative Kinase Activity in Halophilic Bacterium Virgibbacillus halodenitrificans, Journal of bioscience and Bioengineering, 104(3): 178-181.
Shoa hasani,  A. (1996). The effect of Artemia feeding on the Urmia  Lake  phytoplankton population. In M.Sc. thesis. Lahijan Islamic Azad University, pp 62-63.
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