International Journal of Aquatic Science ISSN: 2008-8019 Vol 1, No 1, 2010 () mohebbi44@yahoo.com -Review- The Brine Shrimp Artemia and hypersaline environments microalgal composition: a mutual interaction Fereidun Mohebbi Iranian Artemia Research Center, Urmia, Iran Abstract Hypersaline environments are essential, integral and dynamic part of the biosphere. Their management and protection depend on an understanding of the influence of salinity on biological productivity and community structure. The aim of this study was to review the relationships between the two basic biological components of hypersaline environments (micro-algae and Artemia) to provide a better understanding the dynamics of these unique ecosystems. Algal composition as the main food source of Artemia determines Artemia growth, reproduction rates, brood size, density, lipid index and cysts yields. Furthermore, the reproduction mode of Artemia depends on food levels, so that at the low food levels the main reproduction going into cysts. On the other hand, seasonal fluctu-ations of algal abundance influence Artemia population in temperate large hypersaline lakes such as the Great Salt Lake (USA), Urmia Lake (Iran) and Mono Lake (USA). However, Artemia grazing pressure has significant effects on microalgal density. Key Words: Artemia, hypersaline, microalgal composition, Dunaliella Introduction Hypersaline environments are important natural assets of considerable economic, ecological, scientific and natural value. These ecosystems span large areas worldwide, not only in salt production areas (solar salt works, salterns or Salinas) but also in natural lakes and lagoons, and in tidal ponds (Javor, 1989). Hypersaline environments of both marine and continental origin are essential, integral and dynamic part of the biosphere while the biogeochemical processes occurring in their unique ecosystems have considerable environmental, social and economic values (Shadrin, 2009). Interestingly, their unique physical and chemical characterization and distinctive biota set them apart from other aquatic ecosystems (Naceur et al., 2009). Hypersaline environments and biodiversity associated with such environments are affected by both human activities and natural dynamics. For example, recent climatic changes have led to increasingly intense monsoon rains in some regions and to decreasing precipitation levels in others (Das Sarma, 2007). However, increased drought in arid and semi-arid regions of the world, which most of the inland hypersaline lakes are located on, had dramatic effects on these sensitive ecosystems. In fact, inland hypersaline lakes within closed hydrologic basins are subjected to natural and induced fluctuations in size and salt concentration over both short and long term intervals (Herbst and Blinn, 1998). Hypersaline environments are generally defined as those containing salt concentrations in excess of sea water - 3.5% total dissolved salts (Das sarma and Arora, 2001). Velasco et al (2006) studied the