International Research Journal of Environment Sciences________________________________ ISSN 2319–1414Vol. 2(5), 87-91, May (2013) Int. Res. J. Environment Sci. International Science Congress Association 87 Zooplankton Diversity and their Seasonal Variations of Bhadra Reservoir, Karnataka, IndiaShivashankar P.* and Venkataramana G.V. Department of Studies in Environmental Science, Manasagangotri, University of Mysore, Karnataka, INDIAAvailable online at: www.isca.in Received 19th April 2013, revised 27th April 2013, accepted 17th May 2013 AbstractA study on zooplankton species abundance and diversity of Bhadra reservoir, chikkamagalur district, Karnataka, India was conducted to check the status in the area and provide new insights into its ecology. Samples were collected during June 2010 to May 2011. A total of 23 species were found in this reservoir. Among these, rotifers comprise of 8 species (22.78%), Cladocera 5 (22.17%), Copepods 3 (25.13%), Ostracoda 2(14.69 %) and 5 protozoan species (13.25%). Some of the dominant zooplanktons present throughout the year. The season wise zooplankton analysis showed an average abundance of species in winter, lower in winter and maximum occurrence in summer due to the different environmental and inflow characteristic s of the water body. Keywords: Bhadra reservoir, zooplankton, diversity, rotifers.Introduction Zooplanktons are the smallest organisms present in almost all the water body and they can be observed only through microscope. They invariably form an integral component for fresh water communities and contribute significant to biological productivity. Zooplankton acts as main sources of food for many fishes and plays an important role in early detection and monitoring the pollution of water. Zooplankton community distribution depends on some of the complex factors viz, change of climatic conditions, physical and chemical parameters and vegetation cover1,2 Most of the planktonic organisms are cosmopolitan in distributionA number of studies has been carried out on the condition of ecology and freshwater bodies in various parts of India4-6 but in some parts of southern Karnataka, the ecological studies of freshwater bodies especially zooplankton studies is very scanty. So that the present investigation made an attempt to study the zooplanktons species in Bhadra Reservoir. Material and Methods Study area: Bhadra reservoir is located near Kuvempu University, Shankaraghatta, a tributary of Tungabhadra in Chikkamagalur district of Tarikere taluk in Western parts of Karnataka in South India with latitude: 13º 42'.00'' N, and longitude: 75º 38'.20'' E. Some of the benefits getting from the reservoir storage are irrigation potential of 162, 818 hectares (402,330 acres), hydropower generation, fisheries, drinking water supply and industrial use. Zooplankton sample Collection, Preservation, Identification and Density Analysis: Water samples were collected randomly in different locations of the reservoir during an early hours of the day (7am to 9am) to a period of 1 year (June 2010– May 2011) and such samples were pooled together to consider a final sample for analysis. The plankton net is made by the bolting nylon silk (mesh- size 50m) is used for collection of zooplankton and which is conical shape and reducing cone with the bottle at its end. For a precise collection of zooplankton, the plankton net is towed horizontally and obliquely (for Qualitative) in surface water of the study area and for quantitative analysis, 10 liters of water samples were filtered out through the net. After transferring the sample in air tight plastic bottles, it would keep carefully with labeling and preserved immediately using 4% formaldehyde. Later, the collected samples were brought to laboratory and analyzed qualitatively under the microscope for different types of zooplanktons and identified using various authenticated monographs7- 11After an accurate identification of each genus, the density of zooplankton was calculated as per the Lackey’s drop method. Results and Discussion The obtained zooplankton forms were represented by five groups of Phylum viz Rotifera, Cladocera, Copepoda, Ostracoda and Protozoa. Among these, Rotifera comprise of 8 species, Cladocera 5 species, Copepoda 3 species, Ostracoda 2 and protozoa 5 species. The total numbers of species recorded were 1039 of which rotifers are 245 (22.78%), Cladocerons 242 (22.17%) copepods 258 (25.13%), Ostracods 159 (14.69%) and protozoa 135 (13.25%). All the dominant group of zooplankton were present throughout the year. It is reported that five genera amongst zooplankton population of Janatal at Gwalior12. Five genera of rotifers, three genera of International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 2(5), 87-91, May (2013) Int. Res. J. Environment Sci. International Science Congress Association 88 cladocerans and ostracods and two genera each in respect of protozoans and copepods in virla reservoir, Madhya Pradeshwere observed13While analyzing seasonal dynamics of rotifers in relation to physic-chemical conditions of lotic water body made similar observations in increased densities of zooplanktons in summers and reduced densities in winters14. In summer season, the absence of inflow of the water brings stability to the water body. The availability of food is more due to production of organic matter and decomposition15. In this study the occurrence of zooplankton groups was in the following increasing order. Winter: Copepoda � Cladocera � Rotifera � Ostracoda � Protozoa Summer: Rotifera � Copepoda � Cladocera � Ostracoda � ProtozoaRainy: Cladocera � Copepoda � Rotifera � Protozoa � OstracodaRotifers: These are considered as the most important soft bodied invertebrates16 and they play a major role in aquatic food chain and major food for fishes. In rotifers zooplanktons like Brachinous calcyflorus and Brachinous caudatus found to be present throughout the year whereas cladocera was represented by Bosmina longirostris, Alona davidi davidi, Macrothrix spinosa, Simocephalus exspinosus and Diaphonosoma species According to observation the Brachionus species are very common in temperate and tropical waters16, indicates alkaline nature of water. Excess growth of rotifers in lakes and reservoirs indicates eutrophic conditions17. Presence of rotifers is also an indication of eutrophic as observed in Govind Sagar, Chhattri tank,Sawarkar Sarova and Matsya sarovar in Gwalior18, the rotifers dominance followed by copepods in Virla reservoir at Madhya Pradesh was also reported13. Cladocerons: Cladocera is an order of small crustaceans commonly they are called by “water fleas”. Around 620 species have been identified so far, with many more undescribed. It has been reported that the density and biomass of cladocerans was primarily determined by food supply In the present study, similar observations were made where cladocerans were abundant when the food supply (phytoplankton) was maximum. In the present study, similar observations were made where the cladocerans were abundant when the food supply (phytoplankton) was maximum. During summer the cladoceron population was moderate due to dense growth of rotifers and thus avoiding competition. It is found that the temperature is the primary factor affecting the occurrence and distribution of cladocerons19. Copepods: These constitutes a major zooplankton communities occurring in almost all the water bodies, which serve food for many fish and play a vital role in ecological pyramids. Nearly 120 species recorded from India20. The important factors which controlled the distribution of copepods were rainfall, river discharge and decreased phytoplankton abundance due to increased turbidity21,22. In our studies the copepods recorded were Cyclops strenuous, Cyclops scutifer and mesocyclops hyalinus. Ostracods: The ostracods are bivalve crustaceans found in both fresh and marine water. About 1700 known species are freshwater forms which inhibit a wide variety of freshwater like pool, pond swamps, streams and polluted areas. Occurance of of some species of ostracods in Dharwad district has been reported23. In the present study, only two species of ostracods were found and these are represented by Cypris species and heterocypris species. Protozoa: These are the very diverse group of unicellular eukaryotic organisms24 any of which are motile. We have recorded Aspidisca species, Didinium nasutum, Centropyxis aculeate, Coleps hirtus and Amoeba. In this particular observation the density of zooplanktons showed distinct seasonal variation. All the groups have shown their own maximum and minimum peaks in which the density of rotifers was maximum during summer (26.79 %) and minimum in rainy season (18.60%). But the densities of highest groups in rainy season were cladocerons and copepods (28.92% and 27.28 %) and cladocerons were lowest during summer season (20.08%) while copepods minimum in winter season (23.8%). However in winter season ostracods showed their maximum population (17.20 %) and minimum during rainy season (10.33%). The protozoan density was highest in rainy season (14.88 %) and low in summer (12.28 %). Similar observations were also made25-27. Conclusion The overall view in this study reveals that the fluctuation of zooplankton occurs distinctly in the study area and normally in rainy season there is a less population due to the dilution factors and its effects leads to less photosynthetic activity by primary producers. The population raises a bit higher level during winter season due to favorable environmental conditions and presence of excess of food in the form of bacteria and suspended detritus, but in summer where inflow is less to compare with other seasons resulted in stability of water body and availability of food is more due to decomposition of organic matter and the density of zooplankton might be high due to less predators. Acknowledgements Authors are grateful to Institution of Excellence (IOE-UGC) for providing financial assistance of this study and also thankful to the Department of Studies in Environmental Science, University of Mysore, Mysore- 570006 (Karnataka) for providing laboratory facilities. International Research Journal of Environment Sciences______________________________________________ ISSN 2319–1414 Vol. 2(5), 87-91, May (2013) Int. Res. J. Environment Sci. International Science Congress Association 89 Table-1 Zooplankton diversity in Bhadra Reservoir, Karnataka RotiferaCladoceraCopepodaOstracodaProtozoa Keratella tropica Bosmina longirostris Cyclops strenuus Cyrpris species Aspidisca species Brachinous calcyflorus Alona davidi davidi Mesocyclops haylinus Heterocypris sp. Didinium nasutum Brachinous caudatus Macrothrix spinosa Cyclops scutifer Centropyxis aculeate Brachinous falcatus Simocephalus exspinosus Coleps hirtus Brachinous forticula Diaphonosoma species Amoeba Brachinous rubens Lepodella species Lecane species Table-2 Seasonal variation of Zooplanktons in Bhadra Reservoir Season Rotifera Cladocera Copepoda Ostracoda Protozoa Winter 22.92(80) 23.50(82) 23.8(83) 17.20(60) 12.60(44) Summer 26.79(120) 20.08(90) 24.33(109) 16.51(74) 12.28(55) Rainy 18.60(45) 28.92(70) 27.28(66) 10.33(25) 14.88(36) Total 22.78(245) 22.17(242) 25.13(258) 14.69(159) 13.25(135)  Figure-1 Map showing Bhadra Reservoir International Research Journal of Environment Vol. 2(5), 87-91, May (2013) International Science Congress Association Percentage representation of different orders of zooplanktons in Bhadra reservoir Reference 1.Rocha O., Matsumura- Tundisi, T., Espindola, E.L.G.,Roche K.F.,and Ri etzler A.C. Ecological theory applied to reservoir zooplankton. 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