ISCA Journal of Biological Sciences _____ ______________________________ ______ __ _ _ ISCA J. Biological Sci. Vol. 1 ( 1 ), 30 - 34 , May (201 2 ) International Science Congress Association 30 Study on Zooplankton of Fresh Water Reservoir Nyari – II Rajkot district, Gujarat, India Goswami A.P. 1 and Mankodi, P.C. 2 1 Department of Biology , M.V.M. Science and Home Science College, Rajkot, Gujarat, INDIA 2 Department of Zoology , Faculty of Science, The M.S. University of Baroda, Vadodara, Gujarat, IN DIA Available online at: www.isca.in (Received 10 th April 201 2 , revised 18 th April 201 2 , accepted 20 th April 201 2 ) Abstract Zooplankton are the grazers on the phytoplankton and a food base for the carnivorous as well as omnivorous fishes, have been reported in percentage composition of different groups. The diversity of various types of zooplankton was studied of fresh water re servoir Nyari – II Rajkot district, Gujarat. The planktonic forms were collected from the surface of the reservoir water with plankton net of 20ĩ mesh size nylon cloth. The plankton samples were preserved for laboratory analysis. The collected samples were identified using standard references. The result revealed that the zooplankton were represented by various phyla like, protozoa, helminthes, rotifera, annelida, arthropoda etc. Arthropods have been reported maximum in number of varieties and percentage am ount in the total zooplankton followed by Rotifer in general. The range of zooplankton between 174 to 769 n/l, and average was 378.42 n/l, the minimum zooplankton was in March and maximum were in the month of October. The annual percentage composition of v arious representative groups of zooplankton revealed 7.90% protozoa, 35.32% Rotifer, 5.41% Arthropoda and Miscellaneous 2.64%. The detailed aspect of monthly variation, percentage composition and diversity of zooplankton is discussed herein. Keywords: Zooplankton, Nyari reservoir. Introduction Gujarat state is the 7 th largest state of India and comprises three distinct geographic regions. Larger area of this state is semi – arid and water scarcity prone zone 1 - 2 . Few big and several small rivers form their basin in this state. This network of small rivers and undulating terrain creates ideal conditions for water resource development projects and thus, five districts of Saurashtra region among themselves share nearly half of the reservoirs in the state. Planktonic forms are the producers in an aquatic ecosystem and also p rimary food base for nektons like fishes and other fishable organisms. In the tropical country like India, highly seasonal rainfall and heavy discharge of water during monsoons results in high flushing rate in the most of the reservoirs. Therefore, the con sistency and productiveness of biotic component is variable. Plankton by virtue of drifting habit and short turnover period constitutes major link in the trophic structure and events in the reservoir ecosystem 3 - 4 . A rich plankton community is the hallmark of Indian reservoirs that can be attributed to abiotic factors and nutrient load variability 5 . It is found that nitrates and phosphates are lacking in south Indian reservoirs this has relation with high numerical abundance of plankton in this reservoir. pH has positive relation with abundance of zooplankton 6 . Zooplankton was represented by three different group viz., protozoa, rotifera and arthropoda. Percentage compositions of these planktonic forms were indicative of its richness and possible contribution in organic productivity as well as trophic status maintenance. It is usually observed that the greater population of the rotifers appeared in waters with eutrophication state of the reservoir. The presence of copepods is indicative of pray – predator rela tionship among zooplankton 7 . Material and Methods Study Site: Study site fresh water reservoir Nyari – II is located in Rajkot district Latitude: 22 0 – 21’ – 45” N and Longitude: 70 0 – 40’ – 15 E. This perennial reservoir is rain fed as well as receives flood water through Nyari River. Primarily the water resource is identified to be utilized for irrigation and community water supply to RUDA (Rajkot Urban Development Area). This long seasonal reservoir has the catchment area of 314 sq km and water storage capacity of 88.94 FRL, which is used for capture fisheries as well as stocking of Indian Major Carps. The surface water samples were collected from different locations of the reserv oir randomly from June 2008 to May 2009 and such samples were pooled together to consider final sample for analysis. All samples were collected at trice in month during morning hours. The samples were collected by filtering 10L of water through plankton ne t of 20ĩ pore size filtering cloth and concentrated up to 100 ml. The concentrated zooplankton sample was preserved immediately with the help of 4% formalin. The samples were analyzed qualitatively under the microscope for different types of zooplanktons. The identification of zooplanktons was carried out by using keys and published literature 8 - 10 . The quantitative estimation was done by ISCA Journal of Biological Sciences ________________ ______________________________ ______ __ _ _ ISCA J. Biological Sci. Vol. 1 ( 1 ), 30 - 34 , May (201 2 ) International Science Congress Association 31 using Sedgewick – Rafter Cell and expressed as numbers per liter. Results and discussion The range of zooplankton betw een 174 to 769 n/l, and average was 378.42 n/l, the minimum zooplankton was in March and maximum were in the month of October, (table - 1). The zooplankton forms were represented in the phylum like Protozoa, Rotifera and Arthropoda, wherein Arthropoda was do minating two different sub classes of Arthropoda, i.e. Copepods (73.43%) and Cladocera (26.56%) were abundantly present in the water of this reservoir (table - 2). Correlation of physico - chemical properties with zooplankton abundance indicates positive relat ionship. All the types of zooplanktonic forms indicates marginal declined trend from June to May with no significant relationship with monthly variations ( figure - 1 A - E). Table – 2 Type compositions of Arthropods Arthropoda Months Copepods Cladocera Jun 120 40 Jul 168 71 Aug 189 57 Sep 235 106 Oct 304 133 Nov 186 72 Dec 76 20 Jan 110 33 Feb 102 25 Mar 85 18 Apr 69 42 May 161 36 Total 1805 653 % 39.74% 14.38 % However, during month of September, October and November comparatively plankton density was high that coincides with the similar condition for nutrients as well as some physico - chemical property of water 6 . The annual percentage composition of various representative groups of zooplankton revealed 7.90% protozoa, 35.32% Rotifer, 5.41% Arthropoda and Miscellaneous 2.64% (figure - 2). Annual average percentage of zooplankton from reservoir revealed different fo rms in their density attributed to water quality. Protozoan and Rotifers were less numerically however, Arthropods were comparatively more. Arthropods were represented by variety of copepods and cladocerans. Larvae and nymphs of several insects were observ ed specific seasonal variation. During post monsoon such stages were abundant. The density and diversity of zooplankton certainly get influenced by the physico - chemical properties of water 11 . (A) y = - 1.3182x + 38.485 Rē = 0.0597 0 10 20 30 40 50 60 70 80 90 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Protozoa Table – 1 Monthly variation in zooplankton density (no/liter) Month Protozoa Rotifer Arthropoda Miscellaneous Total Jun 16 71 160 11 258 Jul 32 126 239 12 409 Aug 34 160 246 7 447 Sep 44 239 341 16 640 Oct 82 241 437 9 769 Nov 34 171 258 8 471 Dec 12 79 96 6 193 Jan 17 88 143 3 251 Feb 19 131 127 21 298 Mar 12 52 103 7 174 Apr 22 81 111 10 224 May 35 165 197 10 407 Total 359 1604 2458 120 4541 % 7.90 % 35.32% 54.12 % 2.64% - ---- ISCA Journal of Biological Sciences ________________ ______________________________ ______ __ _ _ ISCA J. Biological Sci. Vol. 1 ( 1 ), 30 - 34 , May (201 2 ) International Science Congress Association 32 (B) (C) Figure - 2 P ercentage composition of various groups of zooplankton (D) (E) Further, it is a fact that the diversity of zooplankton is always less in the flowing fresh water compared to stagnant water like that of reservoirs. The presence of variety of Branchionus sp. and copepods are the indicator of influence of pollutants as we ll as domestic sewage discharges 12 - 14 , the similar pattern of presence of such Rotifers and Arthropods has been observed from the study area. Spatial and temporal variability in the different forms of zooplankton and especially arthropods has been observ ed in the study site may be attributed to effluent and domestic discharges and fresh water inflow velocity 15 . The planktonic forms of insect fauna have been recorded as several larval or nymph form of Mayfly, Dragon fly, mosquitoes etc. From the entire sam pling such insect fauna has been reported with variation in their abundance mainly dependent on seasonal conditions 16 . All the physico - chemical parameters favours growth of phytoplankton as well as aquatic weed in fresh water ponds is well established fact 17 . Similarly variation in plankton diversity and density in relation to limnological factors has been y = - 4.2587x + 161.35 Rē = 0.0587 0 50 100 150 200 250 300 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Rotifer y = - 13.497x + 292.56 Rē = 0.2151 0 100 200 300 400 500 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Arthropoda Protozo a, 7.90% Rotifer, 35.32% Arthrop oda, 54.12% Miscell aneous, 2.64% y = - 0.0839x + 10.545 Rē = 0.004 0 5 10 15 20 25 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Miscellaneous y = - 8.8287x + 207.8 Rē = 0.2017 y = - 4.6678x + 84.758 Rē = 0.2231 0 50 100 150 200 250 300 350 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Copepod Cladocera Figure – 1 (A - E): Monthly variation for various zooplankton forms ISCA Journal of Biological Sciences ________________ ______________________________ ______ __ _ _ ISCA J. Biological Sci. Vol. 1 ( 1 ), 30 - 34 , May (201 2 ) International Science Congress Association 33 observed for urban ponds also which has direct influence on nutrient content and productivity 18 . The seasonal variation in plankton community has been re corded for fresh water ponds 19 . Thus it is evident from the observations recorded in this work as well as other documented literature that water quality of aquatic reservoirs play significant role in seasonal variations in diversity and density of differen t planktonic forms. The result indicates that the maximum number of genera occurred during winter season than summer and monsoon seasons similar observations recorded by 20 - 21 . This might promote suitable food for the developmental stage hence a high density of zooplankton population was recorded in winter season. The higher density of plankton population in reservoir might be due to availability of suitable food and less predators. In the monsoon fall of zooplankton density of all the zooplankton comp onents during the study period can be attributed to the dilution effect 22 - 23 . The rotifera and cladocera were higher in winter can be linked to favourable temperature and availability of abundant food in the form of bacteria and suspended detritus 24 - 26 . Larvae and nymphs of several insects were observed at different sites with specific seasonal variation. During post monsoon such stages were abundant. Conclusion The Nyari - II reservoir is rain fed as well as receives flood water through Nyari River. Pr imarily the water resource is identified to be utilized for irrigation and community water supply. The zooplankton study was carried out to understand its relation with water quality parameters. The range of zooplankton between 174 to 769 n/l, and average was 378.42 n/l, the minimum zooplankton was in March and maximum were in the month of October. The zooplankton forms were represented in the phylum like Protozoa, Rotifera and Arthropoda. The Arthopods were dominated as two different sub classes i.e. Cop epods (73.43%) and Cladocera (26.56%). During month of September, October and November comparatively plankton density was high that coincides with the similar condition for nutrients as well as some physico - chemical property of water. The annual percentage composition of various representative groups of zooplankton revealed 7.90% protozoa, 35.32% Rotifer, 5.41% Arthropoda and Miscellaneous 2.64%. Zooplankton is one of the necessities to evaluate fresh water reservoir in respect to their ecological and fishe ries status. Acknowledgement Authors are thankful to the Head, Department of Zoology, Faculty of Science, The M. S. University of Baroda, Vadodara to provide necessary laboratory facility for this work. One of the authors Goswami A. P. is also thankful to The Principal, Shree M.V. 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