The studies on diatom assemblages came into exit during the early 19th century (Gregory, 1854). Extensive studies on the diatom assemblages began during the 20the centuries when the Kolkwitz and Marsson (1908) give the autoecological concept of the indicator species further which improve latter by Patrick et al. (1954) and gave the synecological approach to the assessing stream condition by biological means. Such approach places the emphasis on the study of association or communities of organism rather than upon the presence or absent of certain species. Most of the studies based on synecology reflect the two basic ideas concerning community structure which were set forth by Thienemann (1939), The first of these ideas is that the more variable the conditions of life in a place, the greater the number of species in the community. The second concept is that the further the conditions of life are removed from the optimum for the majority of species, the poorer in numbers of species becomes the community but the remaining species tend to become more numerous in terms of individuals.

 Diatom assemblages was conducted in different regions of the world. (....Ref...). However, the studies were concerned largely on the distribution of diatoms in various aquatic habitats in different period and scale from the various part of the world (Riffe...). The studies on diatom community structure came in to interest when the diatoms were used as biological indicators in the 20th century. Documentation on diatom community structure has been established by ... in .. for the water quality monitoring. The studies on community structure were continued and carried out in different region of the world from various habitats. However, in most of the studies diatom assemblages were studied on the rivers, streams, lake and ponds. Diatom assemblages were intensely studied worldwide from various water bodies concerning various aspects, as assessing environmental conditions in river and streams with diatoms (Patrick 1973; Stevenson and Love, 1986; Round, 1991; Whitton et al. 1991; Coste et al. 1991; Whitten and Kelly, 1995; Rosen, 1995; Love and Pan, 1996....)

 

the approach was diatom community structure was studied with large aspect to the water quality monitoring throughout the world wide (Jorgensen, 1957; Christensen and Reimer, 1963; John & Jack, 1978; Olive and Price, 1978; Lamb and Lowe 1981, 1987; Blinn, 1993; Charles, 1985; Nautiyal and Singh, 1996; Chiang et al, 1997; Nascimento et al. 1998; Vibaste, 2001; Potapova and Patrick, 2002; Rimet et al. 2004; Soininen and Eloranta, 2004; Leira and Sabater, 2005; Walker and Pan 2006; Chathain and Harrington, 2008; Soininen and Weckstrom, 2009; Leira and Kwandrans, 2007; Sonmez and Caglar, 2011; Zhang et al. 2011; Kivrak and Uygun, 2012; Nautiyal and Mishra, 2013; Stanish et al. 2013; Vázquez and Caballero, 2013; Bere and Mangadze, 2014; Singh et al. 2014; Darling, 2015). Many investigations have been made in to the diatom community structure with reference to spatial and temporal variations (Vaultoburg and Pederson, 1994; Pan et al. 2000; Xiuning et al. 2012; Soininen et al. 2004; Mc Clatchie et al. 2015). Other studies with various prospects were as diatom community structure in relation to seasonal changes (Ohtsuka, 1996; Nı´Chatháin and Harrington 2008 ); diatom community with respect to land use (Mylvaganam and John, 1998); diatom community with changes in altitude (Nautiyal, 1998); diatom assemblages in response to light (Ikeya 2001, Lange et al 2011,); diatom assemblages  as indicators of timber harvest (Naymik 2005), diatom community in relation to the host (Jewaka et al 2013); diatom community structure from the various fish gut (Bešta et al 2015), from the ship hulls (Hunsucker et al 2015), from riparian soil  (Vachta et al 2012) and diatom community from the artificial substrate (Dalu et al. 2014).

All the above studies on the diatom community were not deal with the habitat preference. There were a little studied which deals on the diatom community structure in relation to the various habitats structure from the different part of the world. In the context of habitat diatom assemblages were investigated in both, micro-habitats such as epilithic, epipelic, epiphyitic, etc. and habitats such as river, stream, pond, lake, spring, canal etc.

Some researchers have found distinct associations of benthic diatom on different substrate in rivers, lake, streams indicating specific habitat preferences (Reavie and Smol, 1997; Round, 1993). From the microhabitats Nautiyal et al. (1996) investigated the community structure in relation to substrate (epilithic and epiphytic) and flow condition of the Himalaya river Alaknanda.  Alkananda et al. (2011) studied the microhabitat influence on the diatom distributional pattern in the lake from south India.  Kopalova et al. (2014) studies the moss inhabiting diatoms from the maritime Antarctic island.

However studies on the diatom assemblages with respective to the habitat were scare. Little studies on the diatom in relation to habitat were studied from the various parts of the world. De Vijver and Beyens (1996) studied the diatom communities from the various water bodies in Stromness Bay area of South Georgia. De Vijver et al. (2001) investigated the habitat preferences in freshwater diatom communities from the different water bodies in sub-Antarctic Iles Kerguelen. Baier T (2005) studied the diatom communities amongst the types of wetland habitats of the south-western New Zealand, El-Awamri et al. (2005) investigated diatom flora from different aquatic habitats such as river, irrigation canals, drains, springs, pools, ditches and fountains in the Greater cairo (Egypt).  Bere T (2010) investigated diatom community structure and habitat preferences along the urban pollution gradient in Monjolinho river of Brazil, Falasco and Bona (2011) studied diatom communities colonizing in different habitats (river, spring, and bog) of the Valasco Valley (in Maritime Alps Natural Park). Kova’cs et al. (2013) studied the diatom assemblages in different stream order from the Hungary.

In   India such diatom community in relation to habitat preference is still lacking however large numbers of studies on diatom community structure with various aspects from the river, stream and pond separately have been investigated (Nautiyal 1997, 2001, Nautiyal et al. 1996 a, 1997, 1999, 2000, Nautiyal et al. 2004, Ormerod et al. 1994, Jüttner et al. 1996, Ormerod et al. 1996, Rothfritz et al. 1997, Cantonati et al. 2001, Jüttner and Cox 2001).