Composition and Biodiversity of Rotifer Population in Godavari River

In the present investigation variation in rotifer population of Godavari river from Nashik, (M.S.) India from four different study stations were analyzed from May 2009 to April 2010. During the study period total 24 rotifer species belonging to 17 genera were found. The most quantitatively genera Brachionus were the main and significantly abundant genera, represented by 6 species. Monthly population density of rotifera showed its peak during December while least in August at study station IV. INTRODUCTION Amongst the zooplanktons rotifers ought to be wellknown. Rotifera also known as the “Wheel Animal” (rota=wheel, -fera=those that bear). Rotifers are microscopic aquatic animals of the phylum Rotifera. They play an important role in the ecosystem, and considered as a bioindicators of the habitats (Segers 2008). A few rotifers are cosmopolitan, while majority of these animals are highly adapted to a wide range of freshwater conditions (Brummett 2000). As a result, the ecological investigations on rotifers also gained importance. Hence, qualitative and quantitative studies of rotifers are of great importance. Bhat et al, (2012) studied composition and dynamics of rotifera fauna from upper basin (Bhoj Wetland) as parameter of water quality. Sitre and Zade (2012) studied biodiversity of rotifers in a freshwater lake of Nagpur city (M.S.) during different seasons of the year. Shah et al, (2013) studied rotifers of aquatic ecosystems of Kashmir Himalaya for documentation and authentication. At present there has been lack of studies regarding the biodiversity of rotifers from Godavari river. As a consequence, the aim of the present study was to collect, identify as well as to determine monthly variation of density and diversity of rotifers from surface water of Godavari river from four study stations. Materials and Methods (A) Study area Four sampling stations were selected to study the monthly composition and diversity of the rotifer population in Godavari river, Nashik, Maharashtra. Station I: At downstream of Gangapur dam, the point before the discharge of industrial effluents. The water is used for agriculture purpose only. Station II: Near Someshwar Temple, the point before the discharge of agro-industrial effluents. The water is used for agriculture, bathing and washing purposes and agriculture runoff is also released. Station III: Ramkund also known as Ganga ghat is a holy place. Various rites and rituals are performed here. Water is used for bathing and washing. The domestic waste water is mostly released before and subsequent to this point. Station IV: Ramkund Downstream just before the Tapovan area. At this point, sewage from Nashik City and some industrial waste are also released in to water. (B) Collection of samples Rotifers samples were collected for qualitative and quantitative analysis in between 7 a.m. to 10 a.m. by standard methods (APHA, 1985) from four sampling sites over a period of one year (May 2009 to April 2010). The collected samples were fixed in 4% formalin and brought to the laboratory for zooplankton analysis; counting and identification were done as per Battish (1992). For quantitative estimation Sedgwick – Rafter cell method was used. RESULTS AND DISCUSSION Table 1 represents list of rotifer species recorded in Godavari river. The pattern of rotifer analysis and monthly variation at four studied sites of Godavari river are given in table 2 and figure 1. Figure 2 represents annual mean percentage composition of rotifers at four studied stations. During the present study, 24 species of rotifers belonging to 17 genera were recorded from four studied stations. Diversity population as studies in the present investigation indicates that rotifers dominate at all considered stations of Godavari river. The Brachionus was represented by 6 different species while Filina and Keratella by 2 species. The other genera of rotifer such as, Conochilus unicornis, Hexarthra mira, Polyathra indica, Trichotria trichatris, Mytilina ventralis contributed low densities and were restricted to certain season only. The annual rotifers population was 16%, 20%, 29%, and 35% at stations I, II, III, and IV respectively.


INTRODUCTION
Amongst the zooplanktons rotifers ought to be wellknown. Rotifera also known as the "Wheel Animal" (rota=wheel, -fera=those that bear). Rotifers are microscopic aquatic animals of the phylum Rotifera. They play an important role in the ecosystem, and considered as a bioindicators of the habitats (Segers 2008). A few rotifers are cosmopolitan, while majority of these animals are highly adapted to a wide range of freshwater conditions (Brummett 2000). As a result, the ecological investigations on rotifers also gained importance. Hence, qualitative and quantitative studies of rotifers are of great importance. At present there has been lack of studies regarding the biodiversity of rotifers from Godavari river. As a consequence, the aim of the present study was to collect, identify as well as to determine monthly variation of density and diversity of rotifers from surface water of Godavari river from four study stations.

Materials and Methods (A) Study area
Four sampling stations were selected to study the monthly composition and diversity of the rotifer population in Godavari river, Nashik, Maharashtra.
Station I: At downstream of Gangapur dam, the point before the discharge of industrial effluents. The water is used for agriculture purpose only.
Station II: Near Someshwar Temple, the point before the discharge of agro-industrial effluents. The water is used for agriculture, bathing and washing purposes and agriculture runoff is also released.
Station III: Ramkund also known as Ganga ghat is a holy place. Various rites and rituals are performed here. Water is used for bathing and washing. The domestic waste water is mostly released before and subsequent to this point.
Station IV: Ramkund Downstream just before the Tapovan area. At this point, sewage from Nashik City and some industrial waste are also released in to water.
(B) Collection of samples Rotifers samples were collected for qualitative and quantitative analysis in between 7 a.m. to 10 a.m. by standard methods (APHA, 1985) from four sampling sites over a period of one year (May 2009 to April 2010). The collected samples were fixed in 4% formalin and brought to the laboratory for zooplankton analysis; counting and identification were done as per Battish (1992). For quantitative estimation Sedgwick -Rafter cell method was used. Table 1 represents list of rotifer species recorded in Godavari river. The pattern of rotifer analysis and monthly variation at four studied sites of Godavari river are given in table 2 and figure 1. Figure 2 represents annual mean percentage composition of rotifers at four studied stations.

RESULTS AND DISCUSSION
During the present study, 24 species of rotifers belonging to 17 genera were recorded from four studied stations. Diversity population as studies in the present investigation indicates that rotifers dominate at all considered stations of Godavari river. The Brachionus was represented by 6 different species while Filina and Keratella by 2 species. The other genera of rotifer such as, Conochilus unicornis, Hexarthra mira, Polyathra indica, Trichotria trichatris, Mytilina ventralis contributed low densities and were restricted to certain season only. The annual rotifers population was 16%, 20%, 29%, and 35% at stations I, II, III, and IV respectively.     In the present study highest rotifer density was observed in the month of December i.e. in winter season. This was in accordance with observations of Mukhopadyay et al, (1981), Jayadevi (1994, Shayestehfar and Abdovis (2011)

CONCLUSIONS
From the present study it is concluded that, the diversity and density of the rotifers increased in the winter and decreased during the monsoon period. The rotifer population in Godavari river is highly influenced at station III and IV as compare to station I and II. Abundance of rotifer species such as, Brachionus at Station III and IV indicates nutrient rich water body which may undergo the state of eutrophication, if not managed appropriately. Hence there is an urgent need to control the discharge of industrial and domestic sewage.