The distribution pattern of organisms in an aquatic ecosystems varies from minute plankton to the huge predators which is governed by the behavior and adaptability with regard to particular system in which they survive (McManus and Woodson, 2012). Generally the term plankton comprises of phytoplankton and zooplankton. Zooplankton has been derived from two Greek words “zoon” means animal and “planktos” meaning wandering. These are group of animals remaining suspended, wandering with water currents and possessing little degree of locomotion. They are microscopic animals, ranging from unicelled to multicelled; size varies from a few microns to a millimeter or even more. Besides size variations, there are differences regarding their morphological characteristic and taxonomic status as well. In aquatic ecosystems zooplankton plays a vital role in studying the faunal biodiversity. They feed on micro-algae, thereby converting the autotrophic material into animal tissue which in turn comprises the fundamental food for higher trophic levels including fishes, particularly their larvae (Pandit, 1999). Zooplankton is an important component of freshwater ecosystems (Gannon and Stemberger, 1978; Sladecek, 1983; Huys and Boxshall, 1991; Devi and Ramanibai, 2012). They regulate algal and microbial production by grazing and help in transport of energy to higher trophic levels (Pandit, 1980, 99; Dejen et al., 2004). Zooplankton are extremely receptive to changing environmental conditions, as most species have short generation time, resulting in changing their abundance, species diversity or community composition (Sharma et al., 2008).Therefore, zooplankton are considered as indicators of water quality (Pinto-Coelho et al., 2005; Rajashekhar et al., 2009; Joshi, 2011). Further, these plankters improve water quality by grazing on micro-algae and even some bacteria (Kumar et al., 2009). Freshwater zooplankton is comprised of two major groups of invertebrate animals: Rotifera and Crustacea.Digital copy of Thesis.University of Kashmri
