ABSTRACT- Fresh water resources are not unlimited. The high rate of increase of human population of Nepal and the rapid rate of industrialization have created problems of disposal of waste water products. The domestic wastes, excretory materials of both human and animals and industrial effluents are discharged into the nearly lakes, rivers, reservoirs and tanks and even in the catchment area of the above water bodies. The undesirable substances are regularly mixed into the water of pond through surface run-off that degrades the water quality. Since last several years, there have been added an array of agricultural pesticides and insecticides, which are further seriously aggravating the problem of pollution both for public health and aquaculture. The detailed information of water quality and status of affected living organisms of water bodies are necessary for the implementation of any management plan. The present investigation encompasses on plankton identifying the ecological quality of Chhapakaiya pond Birgunj, Nepal. Seasonal sampling from all the sampling sites (site A, B, C, D) in winter, summer and rainy season for period of 12 months (November 2014 – October 2015) at 9:00-11: 00 AM. A total of 27 taxa from different classes of zooplankton were reported. The zooplanktons were reported to be maximum (774.4 unit/L) during summer and minimum (539.2 unit/L) during the rainy season in Chhapakaiya pond.
Key-words- Zooplankton, Biological productivity, Habitat degradation

INTRODUCTION- Water is an essential component like other biotic components (air and soil) for the sustenance of life and to maintain an ecological process of the bio-system. The world’s thirst for water is likely to become one of the most pressing resign resource issues of the 21^st Century. Biological assessment is a significant alternative for assessing the ecological quality of aquatic ecosystems since biological communities integrate the environmental effects of water chemistry of rivers and hill streams [1]. Plankton encountered in the water body reflects existed ecological characteristics and therefore, plankton organisms may be used as indicators of water quality [2]. In hill streams, a great variation in the composition of plankton occurred not only in different regions on different depths but also at different periodically time scales and seasons.
The conditions that lead to maxima and minima, as well as to minor fluctuations in abundance of phytoplankton are complex in their physical, chemical and biological characteristics. A considerable amount of research work has been done in different fresh water bodies in relation to phytoplankton [3-4].
Zooplankton is the major trophic link in a food chain and being heterotrophic organisms it plays a key role in the cycling of organic materials in an aquatic ecosystem. In addition, their diversity has assumed added importance during recent years due to the ability of certain species to indicate the deterioration in the quality of water caused by pollution or eutrophication. Monitoring the zooplankton as biological indicators could act as a forewarning, when pollution affects food chain [5-6]. The zooplankton communities, very sensitive to environmental modifications, are important indicators for evaluating the ecological status of these ecosystems [16]. They do not only form an integral part of the lentic community but also contribute significantly, the biological productivity of the fresh water ecosystem [7].
In the present study, the population density and diversity of zooplanktons are carried out to contribute further knowledge about the planktonic population of Chhapakaiya pond Birgunj, Nepal.

MATERIALS AND METHODS:
Collection of water samples and planktons- Water samples were collected in a routine manner from all sampling stations i.e. site A, site B, site C and site D. One liter polythene wide mouthed bottles are used for collecting water samples. A seasonal collection of water samples was made at intervals extending over a period of one year from the different sampling sites (site A road sites south, site B temple sites, site C resident sites and site D road and resident sites north) with an assistance of local people/fishermen. Particular attention was given in rainy period.
The zooplanktons are examined were mostly in fresh water samples while some times in fixed conditions also. Pertinent extant literature was also conducted before preparing the list.

Biological Analysis- Zooplanktons were collected along with water samples. For qualitative and quantitatively studies, plankton samples were collected by standard plankton net made of bolting silk No. 14 (120) and 25 (64).

Zooplankton Zooplanktons were quantitatively estimated by filtering 100 liters of water from the surface through t40 HD silk bolting cloth having 100mesh/cm. The samples concentrated to 100 mL were preserved in 5 % buffered formalin. Before counting the samples were throughly mixed by rotating the bottle. Subs maples were taken in triplicate on Rafter cells using a volumetric pipette. The complete area of the slide was counted from the three samples to give average number per 100 liters. The systematic identification of zooplankton was done by using standard literature books like Edmondson [9], Pennak [10], Tonapi [11], Sehgal [12], Mchael and Sharma [13], and APHA [14].
Zooplankton study was made by collecting 100 liters of water and filtering it through a bolting silk (200 mesh per linear inch) net and the concentrate was preserved in 5% formalin solution. Zooplankton count was made with “Sedgwick-Rafter Counting Cell” under a research binocular microscope. The qualitative analysis was done by identifying the zooplankton as per “Standard Methods”. Details of zooplankton structure were clarified by according Needham and Needham. The quantity of the zooplankton was calculated with help of following formula:

n = ac/1 Where,
n = number of the plankton per litre of the original water
a = average number of plankton in all counts in counting unit of 1mm³ capacity
c = volume of the original concentration in cm³
l = volume of the original water expressed in litre

STATISTICAL ANALYSIS- The data obtained were tabulated, graphically represented and subjected to statistical analysis using the computerized program (Graph Pad Prism 7.01). Simple means, standard deviations and Pearson’s correlation have been done by software and all results were found significant (p>0.05).

RESULTS- Seasonal sampling of zooplankton was done at four sites of the Chhapakaiya pond Birgunj, Nepal for one year (2014-2015). The average density of each species of zooplankton was determined for winter, summer and rainy seasons. In total 27 species of zooplankton belonging to three taxonomic groups were observed in the pond. Out of 27 species, 8 species belonged to Protozoa, 11 species to Rotifera and 8 species to Arthropoda (Table 1).

Table 1: Number of species in different groups of zooplanktons

Phylum	Group	Genera	Spps.	Percentage of species
Protozoa	Rhizopoda Mastigophora Ciliata	03 01 03	03 02 03	11.1% 7.4% 11.1%
Rotifera	Rotifera	08	11	40.7%
Arthropoda	Cladocera Copepoda Ostracoda	04 03 01	04 03 01	14.8% 11.1% 3.7%
Total	07	23	27	100%

Winter season- The average density of zooplankton observed at four sites of Chhapakaiya pond during winter season (2014-2015) are presented in Table 2. Maximum average density of 33.75org/L was observed for Diffusia sp. Among the Protozoa, Amoeba sp. Exhibited minimum density of 9.5org/L. Most of the species exhibited higher density at site ‘A’ followed by site ‘C’, site ‘D’, and site ‘B’. The average density of protozoans was recorded 129.25 org/L during winter seasons.

Table 2: Density of zooplankton (org/L) at four different sites of Chhapakaiya pond Birgunj, Nepa during winter season (2014-15)

Name of species	Site-A	Site-B	Site-C	Side-D	Avg. density
Group- I Protozoa Amoeba sp. Englypha sp. Diffusia sp. Euglena spirogyra E. gracilis Paramecium sp. Vorticella companula Epistylis anastica	16 19 37 18 23 22 22 24	7 7 29 9 6 7 13 6	10 15 32 10 19 20 14 18	5 13 37 8 17 12 10 12	9.5 13.5 33.75 11.25 16.25 15.25 14.75 15.00
Total	191.0	84.0	138.0	114.0	129.25
Group-II Rotifera Monostyla sp. Keratella sp. Brachionus quadridentatus B. Patulus B. rubens B. caudatus Filinia longiseta Lecane aculiata Polyarthra sp. Rotaria sp. Trichocerca similes	40 39 35 32 25 36 40 21 37 23 24	26 23 21 17 21 22 16 13 19 13 14	33 37 33 29 23 28 26 19 29 17 17	28 31 26 23 22 27 17 17 26 15 16	31.7 32.5 28.7 25.2 22.7 28.2 24.7 17.5 27.7 17.0 17.8
Total	352.0	205.0	239.0	202.0	217.3
Group-III Cladocera Alona sp. Basmina sp. Daphnia sp. Moina sp.	38 39 43 35	19 24 30 27	29 37 41 29	26 33 40 28	28.0 33.2 38.5 29.7
Total	155.0	100.0	136.0	127.0	126.5
Group- IV Copepoda Cyclops sp. Gammarus sp. Nauplius larvae	38 43 41	26 22 22	35 37 35	27 26 26	31.5 32.0 31.0
Total	122.0	70.0	105.0	79.0	92.5
Group-V Ostracoda Cypris sp.	43	26	35	31	33.7
Total Zooplankton	863.0	485.0	653.0	557.0	598.8

Out of 11 species of Rotifera, Keratella sp. Exhibited a higher density of 32.5 org/L followed by Monostyla sp. (31.7org/L) Brachionus quadridentatus. (28.7org/L), Filinia longiseta (24.7org/L), Rotaria sp. (17.0 org/L), Brachionus patulus (28.7 org/L) and Brachionus ruben (27.7 org/L). The average minimum density was noted for Rotaria sp. (17.0org/L). The average density of rotifers observed 217.3 org/L during the winter season of the study period.
Among the four species of Cladocera, Daphnia sp. exhibited the higher density of 38.5 org/L whereas, the minimum density (28.0org/L) was obtained for Alona sp. The higher density of cladocerans was observed at site ‘A’ (155.0 org/L) followed by ‘B’ (136.0 org/L), ‘D’ (127.0 org/L) and site ‘B’ (100.0 org/L) during winter season.
Gammarus sp. ranked first among the members of Copepoda with higher average density of 32.0 org/L, followed by Cyclops sp. (31.5 org/L) and Nauplius larvae (31.0 org/L). Most of the species of Copepoda showed higher density at site ‘A’ and site ‘C’ Ostracoda was observed by a single species, Cypris sp. with an average density of 33.7 org/L during winter season.
During the winter season of first year of study period, the total average density of zooplankton was noted 598.8 org/L. Rotifera appeared as the dominant group with higher average density of 217.3 org/L, followed by Cladocera (126.5 org/L), Protozoa (129.25 org/L), Copepoda (92.5 org/L) and Ostracoda (33.7 org/L). Members of all five groups of zooplankton were dominated at site ‘A’ (863.0 org/L) and site ‘C’ (653.0 org/L). Comparatively lesser density was recorded for all groups at site ‘B’ (485.0 org/L).

Summer season- Average density of each zooplankton observed at different sites of Chhapakaiya pond during summer season of 2014-2015 are given in Table 3. Similar trends are also observed in case of summer season in Table 3.

Table 3: Density of zooplankton (org/L) at four sites of Chhapakaiya pond Birgunj, Nepal during summer season (2014-15)

Name of species	Site-A	Site-B	Site-C	Side-D	Avg. density,/th>
Group-I Protozoa Amoeba sp. Englypha sp. Diffusia sp. Euglena spirogyra E. gracilis Paramecium sp. Vorticella companula Epistylis anastica	7 19 32 16 25 19 28 22	3 5 13 6 5 6 7 9	6 17 27 10 18 18 20	19 5 10 26 7 14 9 8 10	5.2 12.7 24.5 9.75 15.5 13.0 15.7 15.0
Total	168.0	54.0	135.0	89.0	108.5
Group-II Rotifera Monostyla sp. Keratella sp. Brachionus quadridentatus B. Patulus B. rubens B. caudatus Filinia longiseta Lecane aculiata Polyarthra sp. Rotaria sp. Trichocerca similes	49 58 62 34 39 43 40 29 37 36 38	34 25 36 23 27 26 15 17 22 21 27	46 47 56 29 26 36 29 25 31 29 30	39 36 42 27 29 31 20 23 30 27 28	42.0 41.5 49.0 28.2 32.7 34.0 26.0 23.5 30.0 28.2 30.8
Total	465.0	273.0	394.0	332.0	366.3
Group-III Cladocera Alona sp. Basmina sp. Daphnia sp. Moina sp.	40 39 49 49	27 18 36 23	29 30 48 45	28 25 47 38	31.0 28.0 45.0 38.7
Total	177.0	104.0	152.0	138.0	142.7
Group- IV Copepoda Cyclops sp. Gammarus sp. Nauplius larvae	50 45 53	28 24 44	46 38 49	39 31 48	40.7 34.5 48.5
Total	148.0	96.0	133.0	118.0	123.7
Group-V Ostracoda Cypris sp.	40	27	37	29	33.2
Total Zooplankton	998.0	554.0	851.0	706.0	774.4

Rainy season- Zooplankton density at four sites Chhapakaiya pond observed during rainy season of 2014-2015 is represented in Table 4. Similar trends also observed in case of rainy season in Table 4.

Table 4: Density of zooplankton (org/L) at four sites of Chhapakaiya pond Birgunj, Nepal during rainy season (2014-15)

Name of species	Site-A	Site-B	Site-C	Side-D	Avg. density
Group-I Protozoa Amoeba sp. Englypha sp. Diffusia sp. Euglena spirogyra E. gracilis Paramecium sp. Vorticella companula Epistylis anastica	10 10 33 20 28 16 25 29	5 5 21 11 10 9 11 21	8 8 31 13 19 13 18 27	6 9 29 12 13 11 13 26	7.25 8.0 28.5 14.0 17.5 12.2 16.7 25.7
Total	171.0	93.0	137.0	119.0	130 .0
Group-II Rotifera Monostyla sp. Keratella sp. Brachionus quadridentatus B. Patulus B. rubens B. caudatus Filinia longiseta Lecane aculiata Polyarthra sp. Rotaria sp. Trichocerca similes	27 32 38 17 24 25 36 20 21 20 22	21 27 23 13 15 9 12 12 13 9 13	25 29 37 15 19 21 31 18 19 14 18	23 28 29 13 18 14 18 13 14 10 19	24.0 29.0 31.7 14.5 19.0 17.2 24.2 15.7 16.7 13.2 18.0
Total	282.0	167.0	246.0	199.0	223.2
Group-III Cladocera Alona sp. Basmina sp. Daphnia sp. Moina sp.	22 25 25 38	16 10 9 8	19 24 24 29	18 15 16 20	18.7 16.0 18.5 26.2
Total	110.0	53.0	96.0	69.0	82.0
Group- IV Copepoda Cyclops sp. Gammarus sp. Nauplius larvae	27 28 29	11 14 13	19 22 28	16 20 21	18.2 21.0 22.7
Total	84.0	38.0	69.0	57.0	62.0
Group-V Ostracoda Cypris sp.	47	37	43	41	42.0
Total Zooplankton	694.0	388.0	591.0	485.0	539.2

DISCUSSION- Zooplankton constitutes an important source of food for fishes and benthic macro-invertebrates. These form an integral part of the lotic community and significantly contribute to the fresh water. The most influential factors which affect zooplankton abundance are those which affecting transport of organisms from source areas to the lake and the reproduction and growth of organisms [6,15]. Greenberg [16] observed that plankton density increased due to their ability to grow and reproduce and also depends upon the flow regime. A total of 27 species comprising 11 rotifers, 8 protozoans, 4 cladocerans, 3 copepods and 1 Ostracods have been observed in the Chhapakaiya pond Birgunj, Nepal during present investigation. Among the 5 major groups, rotifers showed numerical superiority over the other groups of zooplankton. This group has not only shown the more number of species but also contributed the maximum to the total density of zooplankton. Brachionus quadridentatus, B. patulus, Lecane aculiata, Keratella sp. and Monostyla sp. were contributed the main bulk of rotifers. They were found abundant during all the season.
Rotifers exhibit high turnover rates in nature. According to Adoni [17], Gannon and Stemberger [18] the density of rotifers as well as their diversity increases due to increase in eutrophication. Chaurasia [19] reported that the density of rotifers and their species diversity is highest in eutrophic conditions. Hutchinson [20] observed that family Brachionidae is of great importance in the planktonic community which is found in slight to high alkaline water. Shrivastava [21] observed the dominance of rotifers in summer. Bhowmic [22], Bilgrami and Datta Munshi [23] and Sharma [24] reported the increasement of zooplankton diversity during summer due to high photosynthetic activity and nutrient concentration.
Microplanktonic group Crustacean, Cladocerans, and Copepods are widely distributed in Nepal. Sometimes, Ostracodes inhabit the weed flora and contribute to the planktonic collections. In the present studies 4 species of Cladocerans were investigated for their density namely Alona sp., Bosmina sp., Daphnia sp. and Moina sp. were recorded in maximum quantities in most sites of Chhapakaiya pond Birgunj, Nepal. Sreenivasan et al., [25] and Unni [26] reported the domination of Moina sp. in Ganga and Narmada rivers respectively. Chakraborty et al., [27] reported Alona and Bosmina as the most dominant genera in the river Yamuna. Ray et al., [28] also observed the dominance of Alona and Moina in Jamuna and Ganga. During present investigation, copepods were represented by 3 species namely Cyclops sp. Gammarus sp. and Nauplius larvae. Nauplius larvae show maximum density among the member of Copepoda during most seasons. Verma et al., [29] and Unni [26] observed that Cyclops and Nauplius were sensitive to pollution and increase with an increase in nutrients. Ostracoda is represented by a single species, Cypris sp. and formed a minor zooplankton component. Verma et al., [29] observed that ostracods generally decrease with an increase in pollution.

CONCLUSION- The zooplankton communities, very sensitive to environmental modifications, are important indicators for evaluating the ecological status of the aquatic ecosystems. They do not only form an integral part of the lentic community but also contribute significantly, the biological productivity of the fresh water ecosystem. So, I hope this study will provide baseline information for making effective conservation programme of fisheries in this region for better and healthy resources as well as improve the livelihood of the fisherman of the country.

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How to cite this article: Yadav LBP, Singh A: Study of Zooplankton Diversity of Chhapakaiya Pond Birgunj, Nepal. Int. J. Life. Sci. Scienti. Res., 2017; 3(2): 925-931. DOI:10.21276/ijlssr.2017.3.2.9 Source of Financial Support: Nil, Conflict of interest: Nil